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May 1978

Volume 15, Issue 3, pp. 837-1199


Improved integrated circuit failure analysis using SEM video processing

A. J. Gonzales and M. W. Powell

J. Vac. Sci. Technol. 15, 837 (1978); http://dx.doi.org/10.1116/1.569608 (4 pages)

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Video processing of voltage contrast information from the scanning electron microscope is used to reduce unnecessary information in order to enhance voltage contrast effects and pattern recognition. A video comparator is employed to sample the video information of any two portions of the device operating cycle. The comparator output is the algebraic difference of the two samplings thereby producing an image of areas that have changed between samplings. Unchanged areas appear gray, whereas bright and dark areas indicate shifts towards a more negative or positive potential. By suppressing static areas, small detail and logical patterns are easily distinguished even at low magnification. Synchronization of the comparator samplings to the device operation cycle isolates specific IC logic functions. The comparator which operates at video frequencies is extended to give a time resolution of one nanosecond by the addition of SEM stroboscopic techniques.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.60.-q Optoelectronic devices

New concepts for electron–ion beam and electron–electron beam memories

C. G. Kirkpatrick, J. F. Norton, H. G. Parks, and G. E. Possin

J. Vac. Sci. Technol. 15, 841 (1978); http://dx.doi.org/10.1116/1.569609 (4 pages) | Cited 2 times

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Abstract Unavailable
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29.27.-a Beams in particle accelerators
89.20.Ff Computer science and technology
85.30.Hi Surface barrier, boundary, and point contact devices

Fine‐focus ion beams with field ionization

J. Orloff and L. W. Swanson

J. Vac. Sci. Technol. 15, 845 (1978); http://dx.doi.org/10.1116/1.569610 (4 pages) | Cited 9 times

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The applicability of the field ionization source for microprobe use is under investigation with a differentially pumped high‐pressure source and an electrostatic optical column. Resolution of 6500 Å with greater than 50 pA hydrogen current and approximately 2000 Å with 20 pA Ar current have been achieved, using polycrystalline Ir emitters. Single‐crystal 〈110〉 Ir emitters can be built up in a manner similar to 〈100〉 oriented W to reproducibly yield high current on axis with good angular confinement of the ion beam, as opposed to the poor confinement and difficult‐to‐reproduce results obtained with polycrystalline Ir.
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79.70.+q Field emission, ionization, evaporation, and desorption
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Design of electron‐beam scanning systems using the moving objective lens

H. Ohiwa

J. Vac. Sci. Technol. 15, 849 (1978); http://dx.doi.org/10.1116/1.569611 (4 pages) | Cited 1 time

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Some considerations and results of designing air‐core scanning systems comprising round lenses and saddle‐type deflection coils are presented. If the deflection coils are cosine distributed, the third‐order deflection aberrations are similar to those of a round magnetic lens. This round‐lens‐type deflection aberrations can be eliminated or reduced by using the Moving Objective Lens (MOL) and predeflection. As is seen from the first‐order Taylor‐series expansion, a round lens whose potential is ϕ (x,y,z) can be moved in the x direction by superposing the deflection field ∂ϕ/∂x. Such a MOL is placed before the image plane and a predeflection coil placed at the object position deflects the beam into the center of the moved lens. Then, a particular aberration such as coma or astigmatism can be eliminated by properly arranging this predeflection. In particular, if coma is eliminated by the predeflection, astigmatism and field curvature are at the stationary point with respect to the predeflection, which is of importance from the design tolerance point of view. A practical scanning system which may be used in microfabrication has been designed. The deflection coils used are half‐inch vidicon printed coils which are of best geometrical precision available. A found system produces at the corner of 5×5 mm deflection field with 0.005 rad semiaperture and 1 in 104 beam‐voltage ripple, a total aberration disk of 0.35 μm, of which field curvature is 0.30 μm and chromatic aberrations are 0.10 μm.
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41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Averaging of electron‐beam aberrations

John L. Mauer

J. Vac. Sci. Technol. 15, 853 (1978); http://dx.doi.org/10.1116/1.569612 (4 pages)

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The design of the imaging and deflection components in an electron probe is directly related to the resolution required in the target plane. The resolution has an especially strong effect on the design when the probe is to be scanned over a large area. The theoretical models of such systems commonly calculate the properties of single trajectories through the column, and from these properties the worst‐case aberrations are inferred. But such calculations, though more convenient than direct measurement, are often misleading. In most applications, the average properties of an electron beam have more physical meaning than the relatively few electrons with worst‐case trajectories. The calculation of single electron trajectories can be applied to the actual electron‐optical system by modeling the actual illumination of the electron beam and averaging over this illumination to get certain specific properties of the beam. The illumination is described by probability distributions over the beam parameters; these distributions are related to the electron source through the optical transfer functions of the column. Intervening apertures also affect the boundary conditions of the distributions. This method can be applied o a shaped electron probe. The dislocation and blurring of the shaped spot can be calculated from the single electron trajectories in the final imaging and deflection system by taking into account the correlation of the various aberrations. Changes in beam energy or lens excitation cause beam dislocation and blurring different from what has usually been reported.
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41.75.Fr Electron and positron beams

Electrostatic einzel lenses with reduced spherical aberration for use in field‐emission guns

G. H. N. Riddle

J. Vac. Sci. Technol. 15, 857 (1978); http://dx.doi.org/10.1116/1.569613 (4 pages) | Cited 20 times

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Focusing properties and aberration coefficients are calculated for electrostatic einzel lenses suitable for use as preaccelerator lenses in field‐emission electron guns. Various lens shapes are analyzed, and asymmetric designs with conical central electrodes are found to have reduced spherical aberration. A lens shape with optimized geometry is found to have a spherical aberration coefficient of less than six times the working distance from the lens to the focal point. This lens has a bored conical central electrode located close to a thin first electrode. Calculations indicate that a field‐emission gun using such a lens should be able to provide a 0.24 μA beam from a 1100 Å effective source size into an emission half‐angle of 2.4×10−2 rad. At lower emission angles the source size would be limited by chromatic rather than spherical aberration.
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41.75.Fr Electron and positron beams

Systematic transformations of the asymptotic aberration coefficients of round electrostatic lenses (1)

C. E. Kuyatt

J. Vac. Sci. Technol. 15, 861 (1978); http://dx.doi.org/10.1116/1.569614 (4 pages)

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In previous work we formulated the third‐order asymptotic aberration coefficients of round (axially symmetric) electrostatic lenses in a form independent of object and aperture positions, and expressions for the six quantities which are sufficient to specify completely the aberration properties of the lenses were derived in the form of integrals involving derivatives of the axial potential through the fourth order. Because actual calculations involved numerical differentiation of the axial potentials, integrations by parts were used to transform the integrals to two new forms with axial derivatives of lower degree. Many other forms of the aberration integrals can be obtained by further integrations by parts, but the transformations are laborious and it is not easy to predict the forms which are possible nor to determine the sequence of operations which will yield a desired result. However, using a method originally developed by Seman and extended by Hawkes, a completely general formula has been derived from which all of the possible forms of the asymptotic integrals can be obtained simply. A few of these possible forms are derived and discussed.
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29.27.-a Beams in particle accelerators
07.77.-n Atomic, molecular, and charged-particle sources and detectors
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Focusing and dispersing properties of a stigmatic crossed‐field energy analyzer

A. Galejs and C. E. Kuyatt

J. Vac. Sci. Technol. 15, 865 (1978); http://dx.doi.org/10.1116/1.569615 (3 pages) | Cited 2 times

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The electron‐optical properties of a stigmatic crossed‐field energy analyzer (double‐focusing Wien filter) have been obtained from exact trajectory calculations. The results are given in the form of focusing and dispersing coefficients to the second order. These coefficients enable the device designer or potential user to calculate the total beam transfer and evaluate the resulting beam quality without additional ray tracing. The specific device for which calculations are made employs a uniform electric field and a toroidal magnetic field. This analyzer is of special interest in our laboratory because it can be constructed with a very small stray magnetic field, and in addition to its dispersive properties it also rotates the spin of a polarized electron beam.
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41.75.Fr Electron and positron beams

Focusing of electron beams by laser‐beam fields

S. Yadavalli

J. Vac. Sci. Technol. 15, 868 (1978); http://dx.doi.org/10.1116/1.569616 (4 pages)

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Employing the paraxial electron‐trajectory equation of a cylindrical electron (beam) the theory of the focusing action of an enveloping annular laser beam is presented and discussed. Analogies between schemes employing laser‐beam fields to focus electron beams and methods involving conventional ’’strong’’ and ’’quadrupole’’ focusing of electron beams are indicated. Some advantages and limitations of the suggested focusing method are pointed out. Also, some approximate numerical estimates regarding the parameters of a cylindrical electron beam and a (focusing) surrounding annular laser beam are obtained for a typical example.
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41.75.Fr Electron and positron beams
42.62.-b Laser applications

Dynamic beam shaping

Jacques Trotel

J. Vac. Sci. Technol. 15, 872 (1978); http://dx.doi.org/10.1116/1.569617 (2 pages) | Cited 1 time

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Abstract Unavailable
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79.20.Ds Laser-beam impact phenomena

Electron‐beam lithographic pattern generation system

A. M. Patlach, P. R. Jaskar, and T. W. Studwell

J. Vac. Sci. Technol. 15, 874 (1978); http://dx.doi.org/10.1116/1.569618 (4 pages) | Cited 1 time

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An electron‐beam lithographic system has been evolving over the past few years at the IBM Research Laboratory in Yorktown Heights, New York. Several versions are now operational in the Yorktown Laboratory, and one in the IBM San Jose Laboratory. Many novel features which create a high degree of automation have been incorporated into each of these systems. This paper describes a pattern generator which was designed to allow a highly compact word syntax for transmission of stored mask information from a small computer, while the computer concurrently controls other system functions. The pattern generator is arranged to write shapes a minimum of data transfer. After initialization, only the origin and size of the first shape need be specified to begin execution. Then, if any parameters pertaining to a shape remain unchanged for the following shape, only the changes need be transmitted to cause the fill routine to operate. Predefined shapes (rectangles, parallelograms, triangles,...) are microcoded into the Generator and are directly invoked during the writing of a mask. A feature which provides still greater flexibility allows dynamic loading a microcode defining cells containing shapes whose perimeter may be irregular or curved. In addition, all these features may be written in an orientable array by giving a few machine instructions. This allows the repetition of millions of similar shapes with but a few transmitted words. The organization of the pattern generator is described, as well as integration with the remainder of the system to provide high‐speed addressing of a 16K×16K array of points.
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41.75.Fr Electron and positron beams
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Deflection distortion in scanning electron‐beam systems

T. H. P. Chang and R. Viswanathan

J. Vac. Sci. Technol. 15, 878 (1978); http://dx.doi.org/10.1116/1.569619 (5 pages) | Cited 2 times

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A simple method for the measurement of deflection distortions in a scanning electron‐beam system using a ’’Stripe Scan’’ technique is described. This technique allows real‐time measurements to be performed at high accuracy. Results obtained by this technique have been compared to those obtained by a laser interferometer measuring system and good agreements have been achieved. The effects on distortion of various factors in VSI, a vector scan electron‐beam lithographic system, have been evaluated and the results will be described.
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41.75.Fr Electron and positron beams

Design of a variable‐aperture projection and scanning system for electron beam

Eiichi Goto, Takashi Soma, and Masanori Idesawa

J. Vac. Sci. Technol. 15, 883 (1978); http://dx.doi.org/10.1116/1.569620 (4 pages) | Cited 2 times

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Results of design calculations of a variable‐aperture projection and scanning exposure system is presented. Use is made of newly developed aberration formulas for the focus deflection system, which can handle systems consisting of a set of focus and deflection coils with superimposed fields and of deflection coils arranged in rotated angular positions, taking into account the finiteness of the object. The aberration of less than 0.2 μm and the incident angle less than 1 mrad with the normal, at the corners of a 5×5 mm deflection field, is expected for the 25 μm (maximum) square and 3 mrad semi‐angle probe, in the linear MOL deflector, with object to image distange of 100 mm, consisting of only an axially symmetric lens and five linear deflectors without dynamic corrections.
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41.75.Fr Electron and positron beams

Variable spot shaping for electron‐beam lithography

H. C. Pfeiffer

J. Vac. Sci. Technol. 15, 887 (1978); http://dx.doi.org/10.1116/1.569621 (4 pages) | Cited 13 times

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Spot size and shape can be changed rapidly, without loss of resolution and current density, by use of the probe‐forming electron‐beam system described here. The variable‐shaped spot (VSS) method is an extension of the fixed‐shaped‐beam concept. It further increases the exposure rate, projecting up to 100 or more image points in parallel, and provides more flexible pattern generation. The beam spot at the target is tailored to fit each pattern segment while it steps from one segment to the next. Spots are shaped by projecting two square apertures simultaneously, and by laterally shifting the image of the first aperture electrostatically with respect to the second. The compound image is subsequently demagnified and projected onto the target. The feasibility of this VSS method has been demonstrated experimentally.
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41.75.Fr Electron and positron beams
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Double‐aperture method of producing variably shaped writing spots for electron lithography

M. G. R. Thomson, R. J. Collier, and D. R. Herriott

J. Vac. Sci. Technol. 15, 891 (1978); http://dx.doi.org/10.1116/1.569622 (5 pages) | Cited 1 time

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Edge definition in an electron‐beam lithography instrument may be improved by imaging an illuminated aperture instead of a Gaussian electron source, but such a system suffers from either slow throughput or large minimum feature size. A system has been constructed here in which an image of one aperture is projected onto a second, and both are imaged onto the writing surface. By changing the relative positions with an electrostatic deflection system, the size and shape of the writing spot may be changed within a few nanoseconds. Two square apertures can be used to give a writing spot of rectangular cross section with variable dimensions. Such an arrangement can be used directly in vector scan, and an example of a scheme for raster scan is described. Alternatively, an aperture of complicated shape is used so that the writing spot resembles four independent spots adjacent to each other. By using suitable electrostatic deflection, any combination of the four can be blanked off at any one time. A system employing this technique has been constructed, and simple patterns written on silicon wafers demonstrate a factor of four increase in speed over the Bell Laboratories EBES lithography instrument.
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41.75.Fr Electron and positron beams
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Design aspects of a scanning electron‐beam‐microfabrication instrument having 10×10 mm field coverage, normal substrate incidence, and high throughput

G. A. C. Jones and G. Owen

J. Vac. Sci. Technol. 15, 896 (1978); http://dx.doi.org/10.1116/1.569623 (5 pages)

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A microfabrication instrument with a field size of 10×10 mm is being developed so that masks for large devices can be exposed without having to stitch together a number of small fields. A satisfactory probe size has already been achieved using a postlens deflection system which has written 10 000 lines per field. Normal substrate incidence will be incorporated in order to eliminate positional errors due to electron optical distortion and to maintain a high writing speed despite the large scanned area. It is proposed that the positional errors be reduced by the application of a polynomial correction function containing terms corresponding to each of the possible deflection distortions. These errors may either be precorrected by a digital computer during data handling for the vector scan generator, or corrected in ’’real time’’ during exposure by suitable analogue modification of the scan currents. The fundamental writing speed of the magnetic deflection system is limited by the self‐inductance and self‐capacitance of the scan coils. It is shown how the number of turns wound on the coils may be optimized to obtain the maximum writing speed, subject to the constraints imposed by the output characteristics of the scan amplifiers and the allowable power dissipation in the scan coils.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.75.Fr Electron and positron beams

Method of optimizing registration signals for electron‐beam microfabrication

W. Stickel

J. Vac. Sci. Technol. 15, 901 (1978); http://dx.doi.org/10.1116/1.569624 (5 pages) | Cited 4 times

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This paper discusses a way by which registration signals for pattern overlay in a given process environment can be optimized by emphasizing signal transitions and by exploiting an enhancement effect: The slope of signal transitions increases significantly when the separation of adjacent mark edges (mark width) is such that the corresponding complementary signals interfere. The signal‐to‐noise ratio can be improved even further because more edges can be confined within a given scan window than with conventional configurations with no signal overlap. Experimental results indicate an overall improvement factor of at least 4. The observed enhancement effect is understood on the basis of a simple qualitative model.
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41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling

High‐precision automatic alignment procedure for vector scan e‐beam lithography

D. Stephani and E. Fröschle

J. Vac. Sci. Technol. 15, 906 (1978); http://dx.doi.org/10.1116/1.569625 (3 pages) | Cited 1 time

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The described automatic alignment procedure permits an alignment of two successive exposure levels of better than ±50 nm in a deflection field of 600 μm at a beam current of 5×10−10 A within an average time of 3 s even without using a laser interferometer controlled stage.
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41.75.Fr Electron and positron beams
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Digitally positioned mechanical stage

J. Pasiecznik and J. W. Reeds

J. Vac. Sci. Technol. 15, 909 (1978); http://dx.doi.org/10.1116/1.569626 (4 pages)

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A computer‐controlled, servo‐driven, vacuum X–Y stage has been built for electron‐beam microfabrication. The stage travel is 5×5 cm. Slew speed is 0.75 cm/s. Balance time is less than 1 s for small motions. Repeatability of positioning has been determined to be 0.01 μm. Accuracy is 0.01 μm plus 0.005 μm/cm of stage travel (laser interferometer error). Backlash between the stage and the drive servo motors has been eliminated by utilizing special friction drive ’’lead screws’’ in place of conventional threaded lead screws and Mylar drive belts in place of gears. Bellows seals on the stage drive shafts are equipped with an auxiliary vacuum pump to reduce air pressure loading on the servo drive system. Stage position is sensed by means of a two‐axis He–Ne laser interferometer which reflects the sensing laser beams from a precision optical ’’true square’’ mounted on the stage. For each axis, a digital servo stores a 24‐bit position command generated by a computer, and compares this desired position with the actual position sensed by the laser interferometer. If the digital position error exceeds 12 bits, a maximum output to the servo motor causes it to move at slewing velocity. When the error is less than 12 bits, a digital‐to‐analog converter generates an analog signal proportional to the digital errors and feeds it to the servo motor. A zero speed detector circuit and an error tolerance comparator indicate when the stage is stopped within preset accuracy requirements. The tolerance comparator output may also be used to correct the electron beam position if it is desired to begin exposure before the stage has settled. Servo damping is provided by means of tachometer generator coupled to the servo motor.
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06.60.Sx Positioning and alignment; manipulating, remote handling
41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Quality assurance procedures for MEBES

Barry Lieberman

J. Vac. Sci. Technol. 15, 913 (1978); http://dx.doi.org/10.1116/1.569627 (4 pages)

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MEBES is the first commercially available electron‐beam‐lithography system intended for production use. This paper describes the techniques that are employed to perform final system calibration and to evaluate system performace. These techniques simultaneously provide a quantitative and systematic method for demonstrating the machine’s ability to meet specifications.
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41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling

High‐contrast registration marks for electron‐beam pattern exposure on (100) silicon

Y. Iida and T. E. Everhart

J. Vac. Sci. Technol. 15, 917 (1978); http://dx.doi.org/10.1116/1.569628 (4 pages) | Cited 3 times

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Secondary‐electron signals have been measured from 10‐μm‐square registration marks as a function of electron‐beam energy (10∠30 keV). These marks are anisotropically etched holes in (100) silicon which may or may not be covered with SiO2. The uncovered holes are sharp enough to measure electron‐beam diameters less than 100 Å. PMMA coating (4000 Å) on the uncovered registration holes reduces signal contrast at 25 kV, incident beam energy from 0.87 to 0.79, and from 0.78 to 0.76 for the mark covered with a SiO2 layer, where perfect contrast is unity. The signal‐transition distance from substrate to hole, ϵ20%–80%, for the mark with a SiO2 cover is degraded to approximately 0.6 μm. However, it is experimentally possible to register vernier patterns to at least ±0.25 μm accuracy, with SiO2‐covered holes used as registration marks.
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41.75.Fr Electron and positron beams
61.80.Fe Electron and positron radiation effects
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Abstract: Field emitter electron‐beam exposure system

Göran Stille and Börje Åstrand

J. Vac. Sci. Technol. 15, 921 (1978); http://dx.doi.org/10.1116/1.569629 (1 page)

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Abstract Unavailable
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Highly stable single‐crystal LaB6 cathode for conventional electron microprobe instruments

R. Shimizu, T. Shinike, S. Ichimura, S. Kawaii, and T. Tanaka

J. Vac. Sci. Technol. 15, 922 (1978); http://dx.doi.org/10.1116/1.569676 (5 pages) | Cited 7 times

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The performance of single‐crystal LaB6 cathode was examined by measuring the brightness and current stability under the same conditions as for the conventional W hairpin cathode. The LaB6 cathode was mounted in Vogel‐type electron gun assembly of an electron probe microanalyser JAX‐3 specifically modified for this purpose. The result shows that the present LaB6 cathode provides not only high brightness of 2×105 A/cm2 str. at 20 kV, but also high‐current stability better than 1×10−3 Ah−1 in standard operation without any specific aid for current stabilization. Thus an order of magnitude increase in both the brightness and service lifetime can easily be obtained provided that the vacuum of the system is adequate, namely better than 1×10−5 Torr (1.33×10−3 Pa). This substantial improvement of the present single‐crystal LaB6 cathode over the conventional W hairpin was also confirmed in a practical way by use in a commercial‐type scanning Auger electron microscope, JAMP III.
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79.40.+z Thermionic emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
29.25.Bx Electron sources

Control of pattern dimensions in electron lithography

H. Sewell

J. Vac. Sci. Technol. 15, 927 (1978); http://dx.doi.org/10.1116/1.569677 (4 pages) | Cited 7 times

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In electron lithographic processes pattern dimensions are distorted by ’’proximity’’ and ’’size’’ effects due to the action of backscattered electrons. This presents the mask designer with the problem of controlling these dimensions during the mask fabrication process so that the required patterns can be produced on the final substrate. This paper describes the processing of a resolution pattern, minimum geometry 0.5 μm, as it passes through the various stages of mask fabrication to the final stage where it is replicated in an electron image projector. The results show the pattern changes that take place, first at the electron‐beam pattern generation stage, second at the mask etching stage, and third at the mask projection stage.
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41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Self‐consistent proximity effect correction technique for resist exposure (SPECTRE)

Mihir Parikh

J. Vac. Sci. Technol. 15, 931 (1978); http://dx.doi.org/10.1116/1.569678 (3 pages) | Cited 16 times

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Submicron electron‐beam lithography for the direct exposure of wafers and for the fabrication of masks cannot be successful until the incident electron exposure can be properly adjusted to compensate the proximity effects. A self‐consistent proximity effect correction technique for resist exposure (SPECTRE) has been developed to compute, for any given pattern, the corrections to the incident electron exposure which must be applied in order to obtain ’’uniform’’ absorbed (incident plus backscattered) exposure in the resist. Mathematically, the solution is unique for any given proximity function. SPECTRE has been successfully implemented on practical pattern data. Experimentally, simultaneous delineation of pattern geometries from 1/4 to 2 μm has been achieved by an automatic application of SPECTRE.
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41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Electron‐beam exposure profiles in polymer films for metallic film mask fabrication

Tadao Kato, Toshihiko Yahara, Hidefumi Nakata, Kenji Murata, and Koichi Nagami

J. Vac. Sci. Technol. 15, 934 (1978); http://dx.doi.org/10.1116/1.569679 (4 pages) | Cited 1 time

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The effect of the metallic thin film on energy dissipation profiles in a resist polymer film on a metallic film‐clad glass plate as in mask fabrication was investigated experimentally and by Monte Carlo calculations which take an exact account of the above boundary condition for a specific geometry. The thicknesses of the polymer film and metallic films are 8000 Å and 500–800 Å, respectively. Various metals such as Al, Cr, Mo, and Ta are used as mask materials. Both experimental and theoretical results show that the width of the developed profile increases with an increasing atomic number of the metallic film element depending on exposure density as expected due to increasing backscattering from the metallic film. It is concluded that even a very thin metallic film has an appreciable effect on the profile and its effect is exaggerated either by a large dose or by a strong development.
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68.60.-p Physical properties of thin films, nonelectronic
61.80.Fe Electron and positron radiation effects

Negative electron resists for direct fabrication of devices

L. F. Thompson, L. E. Stillwagon, and E. M. Doerries

J. Vac. Sci. Technol. 15, 938 (1978); http://dx.doi.org/10.1116/1.569680 (6 pages) | Cited 14 times

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The Bell Laboratories electron‐beam exposure system (EBES) is currently being used to fabricate master masks and experimental devices using a negative resist based on poly(glycidyl methacrylate‐co‐ethyl acrylate) (COP) and a positive resist, poly(butene‐1‐sulfone) (PBS). COP was designed to have a sensitivity of 2–4×10−7 C cm−2 and good wet chemical etching resistance for a variety of thin‐film conductors and insulators. The resolution obtained with a 0.6‐μm initial COP film exposed with EBES and processed on a routine line is 2.0 μm. These characteristics are satisfactory for current requirements; soon however, machine improvements, smaller device geometries, and new processing procedures are going to place increasing demands on resist systems. In addition to resolution requirements, it is desirable to have a resist which is resistant to ion beam milling, plasma etching, or other dry etching techniques. Each of these requirements will be discussed in detail. This paper summarizes the results of the synthesis and initial lithographic evaluation of several potential negative electron resist systems. These resists were designed to have higher resolution and improved dry etching resistance than the negative resist, COP. Specifically copolymers of glycidyl methacrylate and/or glycidyl acrylate with styrene, and phenyl methacrylate will be discussed.
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41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling
61.80.Fe Electron and positron radiation effects

Sol–gel behavior and image formation in poly(glycidyl methacrylate) and its copolymers with ethyl acrylate

E. D. Feit, M. E. Wurtz, and G. W. Kammlott

J. Vac. Sci. Technol. 15, 944 (1978); http://dx.doi.org/10.1116/1.569681 (4 pages) | Cited 11 times

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For the formation of rather large features (≳5 μm on a side) in poly(glycidyl methacrylate) and its copolymers with ethyl acrylate, the lithographic response can be characterized by a gel‐point energy and a contrast. The gel‐point occurs at 6.8 eV absorbed energy per molecule of homopolymer or of its effective equivalent in the copolymer. The contrasts of these negative resists are dynamic properties, but depend in part on the polymer’s dispersitivity, at least to a value 2.3. As features are progressively reduced, the gel‐point advances to higher dose and the contrast increases. These new parameters correlate poorly with the molecular parameters of the polymers; they depend instead on developer‐induced swelling of the image, on competitive wetting of the support layer by the developer and the polymer and on gel‐rupture by forced development.
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36.20.-r Macromolecules and polymer molecules
82.70.Gg Gels and sols

Chrome mask fabrication with electron‐beam‐lithographic system

C. H. Ting, R. L. Anderson, D. Y. Saiki, and A. J. Kraft

J. Vac. Sci. Technol. 15, 948 (1978); http://dx.doi.org/10.1116/1.569682 (5 pages)

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An automated electron‐beam‐lithographic system, Vector Scan‐I, was designed to fabricate devices beyond the optical limit. When the resolution requirement is only moderate, i.e., approximately one micron, VS‐1 can be used to fabricate chrome masks for conventional optical processing. VS‐1‐fabricated chrome masks have better pattern definition and extremely fast turnaround time. Furthermore, the VS‐1 electron‐beam system can generate pattern sizes from a given design to fit different experimental needs. The capability of accommodating many different designs on a single mask greatly reduces the device fabrication effort. Examples of chrome masks fabricated by the VS‐1 electron‐beam system will be described. These masks are routinely used for fabricating magnetic bubble devices. Large chips can be obtained by stitching several fields together.
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41.75.Fr Electron and positron beams
42.30.Va Image forming and processing

Inspection for defects of a mask containing one‐ to submicrometer patterns using a scanning electron microscope and feature extraction method

Y. Goto, Y. Furukawa, and T. Inagaki

J. Vac. Sci. Technol. 15, 953 (1978); http://dx.doi.org/10.1116/1.569683 (4 pages)

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The automatic inspection for defect of x‐ray patterns using a scanning electron microscope and feature extraction is proposed. A new algorithm in feature extraction method for the automatic inspection is contrived. After confirming the feasibility of the algorithm by computer simulation, this inspection method is applied to the SEM image of an actual x‐ray mask containing a few‐micrometer patterns and the defect of 0.5 μm in size can be extracted successfully. It is found that this new method is a very suitable one for the automatic inspection for the defect of x‐ray masks containing one‐ to submicrometer patterns.
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07.85.-m X- and γ-ray instruments
41.75.Fr Electron and positron beams
81.70.-q Methods of materials testing and analysis

Two‐phase high‐density charge coupled devices fabricated by electron‐beam lithography

P. K. Chatterjee, H. S. Fu, A. F. Tasch, T. C. Holloway, and T. G. Blocker

J. Vac. Sci. Technol. 15, 957 (1978); http://dx.doi.org/10.1116/1.569684 (3 pages)

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One hundred and twenty‐eight‐bit, two‐phase, high‐density CCD linear shift registers with double‐level polysilicon overlapping gate electrodes have been fabricated using electron‐beam lithography for all levels of pattern delineation. The polysilicon gate electrodes are 0.15 mil long and the channel widths on two shift registers are 0.25 and 0.06 mil. The critical registration accuracy is ±1500 Å. These represent cell sizes of 0.1 mil2 corresponding to packing densities of 10–20 million bits/in. Charge transfer efficiency with VΦ=10 V and without fat zero is at least 0.9997 for 0.05 mil2 shift register. The low, uniform leakage current (1.5–4 nA/cm2) observed in CCD’s fabricated by electron‐beam lithography compares favorably with those fabricated using optical lithography and larger geometry sizes. This indicates that no significant electron beam induced residual damage is present in these CCD structures.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
41.75.Fr Electron and positron beams
61.80.Fe Electron and positron radiation effects

Direct, electron lithographic fabrication of silicon devices and circuits

L. D. Yau and L. R. Thibault

J. Vac. Sci. Technol. 15, 960 (1978); http://dx.doi.org/10.1116/1.569685 (5 pages) | Cited 4 times

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The Bell Laboratories Electron Beam Exposure System (EBES) together with sensitive electron resists have been used to produce low‐noise microwave bipolar transistors with features of one‐micron and n‐channel MOS circuits, such as 4096‐bit random access memories with minimum dimensions of two microns. Both negative and positive resists were used. The negative resist was poly (glycidyl methacrylate‐co‐ethyl acrylate) (COP), and the positive resist was poly (butene‐1‐sulfone) (PBS). In some cases, the device processing required modification to accomodate the properties of the electron resist used. The transfer of the resist patterns into the circuit material employed wet and dry etching processes. Unlike other electron‐beam lithographic systems which require chip‐by‐chip realignment procedure, EBES realigns the wafer at three points only. The results show a level to level registration of wihin 1/4 μm.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.30.Pq Bipolar transistors

Electron‐beam fabrication of submicron gates for GaAs FET’s

T. G. Blocker, H. M. Macksey, and F. H. Doerbeck

J. Vac. Sci. Technol. 15, 965 (1978); http://dx.doi.org/10.1116/1.569686 (4 pages) | Cited 1 time

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High‐performance GaAs FET’s with nominal gate lengths of 0.5, 0.75, and 1.0 μm have been fabricated with electron‐beam‐lithography techniques. A hybrid process was developed which only required e‐beam definition of the critical gate level and was otherwise compatible with the fabrication process developed for conventional optically defined gates. The source–drain metallization mask was modified to include alignment marks for the gate level and the source–drain metallization was augmented to give marks after alloying with acceptable secondary electron contrast against the GaAs background: ±2000 Å registration was routinely achieved over the 80×80 mil2 field. A test pattern which could be examined optically with rapid turnaround to determine the proper exposures for the various gate lengths was employed. The pattern evaluation was confirmed by resist exposure studies in conjunction with SEM examination. Evaluation of the test pattern together with corrections for the GaAs substrate backscatter and proximity effect allowed control of the gate lengths to ±10% over the entire slice. The gates were tapered at the mesa edge to prevent constriction of the resist over the step. The resist used was polymethyl methacrylate (PMMA) with a nominal thickness of 7500 Å and the developed pattern served as the lift‐off mask for 4000–5000 Å of aluminum gate metallization. The nominal slice size used for these runs was slightly greater than 1 cm2 (420×420 mil2) and up to 588 devices were patterned in a single pumpdown. The exposure time required per slice, including stage step and alignment, was six minutes. Both small signal and power GaAs FET’s have been fabricated with e‐beam defined gates. Small signal devices with 0.75μm gate lengths had 2.0 dB minimum noise figures with 10 dB gain at 9 GHz. Power devices with 4800‐μm total gate width and 1‐μm gate length had up to 4.1 W output power at 8 GHz with 4 dB gain.
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85.30.Tv Field effect devices
41.75.Fr Electron and positron beams
61.80.Fe Electron and positron radiation effects

Fabrication of integrated injection logic using e‐beam lithography

S. A. Evans, J. L. Bartelt, B. J. Sloan, and G. L. Varnell

J. Vac. Sci. Technol. 15, 969 (1978); http://dx.doi.org/10.1116/1.569687 (4 pages) | Cited 1 time

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Integrated injection logic (I2L) gates have been fabricated using electron‐beam lithography, ion implanatation, and advanced I2L design technology. Minimum line widths of 1.25 μm were used to delineate structures five times smaller in area than obtained with conventional design rules. Improved geometry control was achieved by using shallow diffusions and thin epi (∠1.2 μm). PBS positive resist was used to pattern and etch oxides and TI309 negative resist was used to mask etching of Al/Si and Al/Cu metallizations. Thick PMMA was used as an implant mask for 300‐keV p− intrinsic base implant. Chip‐by‐chip alignment of 2.5×2.5 mm2 fields yielded level to level registration accuracy of 0.2–0.4 μm. Using a 25‐stage ring oscillator as a test vehicle, gate delays of ∠6 ns at 100 μA/gate have been measured on 5‐collector, n+ guard ring device structures. These devices also yielded a speed–power product five times lower than that of similar conventionally sized devices.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
41.75.Fr Electron and positron beams

Abstract: Use of submicron electron‐beam lithography for fabricating 4K CCD memory arrays

R. C. Henderson, T. Reiner, and P. J. Coppen

J. Vac. Sci. Technol. 15, 973 (1978); http://dx.doi.org/10.1116/1.569688 (1 page)

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Abstract Unavailable
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
41.75.Fr Electron and positron beams

Design of a medium‐power x‐ray‐lithography system

Gregory P. Hughes

J. Vac. Sci. Technol. 15, 974 (1978); http://dx.doi.org/10.1116/1.569689 (3 pages)

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A medium‐power x‐ray‐lithography system has been developed. The system includes an inexpensive stationary water‐cooled x‐ray source and a modified Cobilt aligner system. The exposure system is capable of printing 1‐μm lines with an edge accuity of 2000 Å over a 5‐cm‐diam wafer. The alignment is compatable with this tolerance of line definition. The x‐ray source uses a defocused electron beam on a water‐cooled anode. For cooling purposes the anode is a thin copper plate with an evaporated aluminum film. The 10‐kV electron beam creates a ∠1‐cm‐diam x‐ray source able to handle more than 1 kW of power without detrimental effects on the aluminum film. The system uses an electrostatic shield to prevent over heating a 25‐μm‐thick beryllium vacuum window by stray electron bambardment. The x rays pass through the beryllium window into a helium atmosphere where they expose the wafer through the x‐ray mask. The wafer is printed with the mask in contact to avoid alignment problems arising from wafer warpage. In this geometry the pattern to wafer distance is kept constant at 3 μm or less which allows the use of the large x‐ray source and thus, the high x‐ray flux.
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07.85.-m X- and γ-ray instruments
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Synchrotron radiation research: Recent developments

I. Lindau and H. Winick

J. Vac. Sci. Technol. 15, 977 (1978); http://dx.doi.org/10.1116/1.569690 (7 pages)

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Synchrotron radiation as a new tool within photon beam technology was described in the 13th Symposium on Electron, Ion, and Photon Beam Technology in Colorado Spings in May 1975. In this paper, we give a review of the developments since that time of the use of synchrotron radiation at SSRP (Stanford Synchrotron Radiation Project). The unique properties of synchrotron radiation have during the last two years been applied to an ever increasing number of research problems within x‐ray absorption, diffraction, fluorescence, and scattering, within surface science, atomic, and molecular spectroscopy. The research capabilities at SSRP have been expanded and new instrumentation with, for instance, focusing x‐ray optics has been developed. In particular, we want to discuss the current prospects and plans for expansion of the research facilities at SSRP.
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78.70.-g Interactions of particles and radiation with matter
82.80.Dx Analytical methods involving electronic spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
79.60.-i Photoemission and photoelectron spectra
29.20.db Storage rings and colliders

Alignment of x‐ray lithography masks using a new interferometric technique—Experimental results

Stewart Austin, Henry I. Smith, and D. C. Flanders

J. Vac. Sci. Technol. 15, 984 (1978); http://dx.doi.org/10.1116/1.569691 (3 pages) | Cited 2 times

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A new interferometric alignment technique has been developed that is compatible with both photolithography and x‐ray lithography, and should be capable of a superposition precision of the order of 100 . The operational features of the technique and experimental results are described. With gratings of 10‐μm spatial period a superposition precision ?1000 Å has been demonstrated, and with gratings of 1.2‐μm spatial period a superposition precision of about 200 Å has been achieved.
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07.85.-m X- and γ-ray instruments
85.40.Bh Computer-aided design of microcircuits; layout and modeling
07.60.Ly Interferometers

X‐ray exposure system using finely position adjusting apparatus

S. Yamazaki, S. Nakayama, T. Hayasaka, and S. Ishihara

J. Vac. Sci. Technol. 15, 987 (1978); http://dx.doi.org/10.1116/1.569692 (5 pages)

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An apparatus for finely adjusting the three‐dimensional position of a workpiece and the application of this apparatus to high power x‐ray lithography are presented. The relative positioning apparatus has been designed, using electrodynamic transducers for the x, y, and z directions and an electrostrictive transducer for rotary direction (ϑ). Motions in each direction are supported by a resilient plate. The relative position of mask and wafer has been detected by applying a mechanical vibration to the wafer, with an accuracy of less than ±0.1 μm. The fine positioning mechanisms have displayed excellent performance with high accuracies. As a first step to constructing a working apparatus, a prototype exposure system was built using pattern replication in an atmospheric environment, comprised of a positioning system and a high‐power x‐ray source with a rotary Al target operated at more than 20‐kW electron‐beam input power. The characteristic x ray has been irradiated on a wafer through a contractile vacuum pipe. Using an exposure test, the system functions have been confirmed as a fine pattern replicating system.
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07.85.-m X- and γ-ray instruments
85.40.Bh Computer-aided design of microcircuits; layout and modeling

X‐ray lithography by synchrotron radiation of INS–ES

H. Aritome, T. Nishimura, H. Kotani, S. Matsui, O. Nakagawa, and S. Namba

J. Vac. Sci. Technol. 15, 992 (1978); http://dx.doi.org/10.1116/1.569693 (3 pages)

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Synchrotron radiation from the electron‐synchrotron INS‐ES at the University of Tokyo has been used for x‐ray lithography. Several mask patterns, such as the bubble pattern and the holographic grating pattern, are duplicated. Masks used are 0.4 μm‐thick gold on 3‐μm silicon. At an electron energy of 1.1 GeV the direct‐total beam of synchrotron radiation can be used for mask replication. By using the grating‐mask pattern with 692‐nm period made by the holographic method, the grating pattern with a large height‐to‐width ratio is obtained. This result clearly demonstrates the high collimation of the x‐ray beam from the synchrotron.
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07.85.-m X- and γ-ray instruments
42.30.Va Image forming and processing

Polyimide membrane x‐ray lithography masks—Fabrication and distortion measurements

D. C. Flanders and Henry I. Smith

J. Vac. Sci. Technol. 15, 995 (1978); http://dx.doi.org/10.1116/1.569694 (3 pages) | Cited 7 times

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A process for fabricating polyimide membrane x‐ray lithography masks is described in detail. Thin membranes of polyimide are formed by spinning polyamic acid on Corning 0211, or other glass substrates, and polymerizing in situ. The glass substrate acts as a holder and an efficient heat sink during formation of gold absorber patterns on top of the polyimide, a procedure that usually includes ion beam etching. A support ring is then bonded to the polyimide, and the glass etched in dilute HF. Optically smooth polyimide membranes with thicknesses from 0.5 to 5 μm are readily achieved. Measurements of the distortion of polyimide membrane x‐ray lithography masks have been made using a holographic moiré method and a method based on measuring the spread in the angle of diffraction from gold‐grating patterns. These indicated a distortion less than two parts in 105 over the central 7.5‐mm‐diam area of a 19‐mm‐diam membrane.
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07.85.-m X- and γ-ray instruments
85.40.Bh Computer-aided design of microcircuits; layout and modeling
42.40.My Applications

Fabrication of micro‐ and submicron‐bubble memory devices by a mask transfer technique with subsequent getter‐ion etching

T. Funayama, K. Yanagida, N. Nakayama, K. Komeno, and T. Inagaki

J. Vac. Sci. Technol. 15, 998 (1978); http://dx.doi.org/10.1116/1.569695 (3 pages)

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In order to fabricate magnetic bubble memory circuits of high bit density using x‐ray lithography, it is necessary to form accurate gold absorber patterns for x‐ray masks and accurate permalloy patterns for the bubble memory circuits. The combined processes of mask transfer technique and getter‐ion etching instead of conventional ion etching in pure argon gas were used to make patterns in these metal films. Pattern width accuracies within ±0.1 μm and the angles of edge slope up to 70° were obtained by using these processes. Our new method was applied to the microfabrication of gold x‐ray mask patterns and permalloy patterns of the circuits for magnetic bubbles of diameters 0.95 and 1.5 μm.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
07.85.-m X- and γ-ray instruments
85.70.Ay Magnetic device characterization, design, and modeling
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Surface relief gratings of 3200‐Å‐period fabrication techniques and influence on thin‐film growth

D. C. Flanders and Henry I. Smith

J. Vac. Sci. Technol. 15, 1001 (1978); http://dx.doi.org/10.1116/1.569722 (3 pages) | Cited 3 times

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As part of a project to study the effects of surface relief steps on thin‐film nucleation and growth, a technology for fabricating 1000‐Å‐linewidth surface relief gratings with control of sidewall profiles to a resolution of the order of 100 Å is under development. Laser holographic lithography and ion beam etching are used to produce gold gratings on 0.9‐μm‐thick polyimide membrane masks. Next, these masks are replicated using CuL or CK x‐ray lithography, thereby producing high aspect ratio relief gratings in PMMA having well‐defined vertical sidewalls. Surface relief structures are then produced on substrates by liftoff, ion beam etching, or reactive ion etching using the PMMA relief gratings. Such structures were decorated with gold nuclei using ion beam sputter deposition. The decoration experiments indicated a periodic variation in nuclei density and showed that the smoothness of the grating edges is of the order of 100 Å.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.65.-b Surface treatments

Simulation of x‐ray resist line edge profiles

A. R. Neureuther

J. Vac. Sci. Technol. 15, 1004 (1978); http://dx.doi.org/10.1116/1.569723 (5 pages) | Cited 3 times

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X‐ray resist line edge profiles are explored as a function of exposure, mask, and resist properties. The study is based on an exposure‐scission and development‐etching model of positive resists. Development rate curves for two actual and three hypothetical resists are used. The simulation is implemented by using a string of points to follow the contour of the developer–resist interface as a function of development time. Control of the resist profile suitable for liftoff of 0.4‐μm lines is explored in the context of low flux levels for a high throughput production environment. High aspect ratio lines (3:1) and profiles degradation due to mask edge effects for Alkα and CuL exposures are considered.
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07.85.-m X- and γ-ray instruments
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Influence of photoelectrons on the exposure of resists by x rays

E. Hundt and P. Tischer

J. Vac. Sci. Technol. 15, 1009 (1978); http://dx.doi.org/10.1116/1.569724 (3 pages) | Cited 3 times

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Sensitivity and contrast ratio of PMMA resist were measured for Ti‐K radiation (λ=0.27 nm). We found a constant rate of solubility during development for exposed as well as for unexposed resists. This means that the process of solution is limited by diffusion and that the resist layer is homogeneously irradiated. Looking at the influence of substrate on exposure we found that the exposure time for gold substrate was only half of that with silicon substrate. This is, to a small part, due to x‐ray fluorescence and mainly to photoelectrons. We also looked at the profiles of structures during development process and found that the resist behavior was similar for great areas as for fine structures.
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79.60.-i Photoemission and photoelectron spectra
85.40.Bh Computer-aided design of microcircuits; layout and modeling
07.85.-m X- and γ-ray instruments
61.80.Cb X-ray effects

Optical manipulation of resist profile in conformable printing

B. J. Lin

J. Vac. Sci. Technol. 15, 1012 (1978); http://dx.doi.org/10.1116/1.569725 (4 pages)

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Differences between the developed photoresist profile and the optical image in the resist is a function of exposure and development conditions. Because of absorption of light in the photoresist and lateral etching by the developer, an overcut profile in the developed image of positive resists is inevitable, even if the distribution of the exposing light is perfectly verical. Intentional overexposure followed with quick development, or the use of highly reflective substrates only minimizes the overcut. This paper describes an approach using a rotating plane wave making a predetermined angle with the optical axis to expose a mask–wafer assembly. This type of illumination produces an undercut optical image which compensates for the absorption and lateral etching effects. It also reduces the coherence in the illumination to give better images. The angle of inclination as well as the exposure–development parameters can be adjusted to manipulate the angle of cutting. Analytical intensity distribution based on geometric optics is given to provide an insight to the dependence of the cutting angle to the beam angle and the exposure–development parameters. PMMA in the deep‐uv wavelength region and AZ1350J in the near‐uv region are used to demonstrate the variation of the cutting angle and the liftoff process.
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42.70.Gi Light-sensitive materials
07.68.+m Photography, photographic instruments; xerography
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Recent progress on the electron image projector

J. P. Scott

J. Vac. Sci. Technol. 15, 1016 (1978); http://dx.doi.org/10.1116/1.569726 (6 pages) | Cited 3 times

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Three main aspects of the 1:1 electron image projector are considered; the economics, the ultimate resolution, and an electrostatic chuck. It is shown that the image projector is economic if more than four exposures per mask can be made; the resolution limitation due to the system is shown to be 200–300 Å, but is in practive limited by electron scattering. The effect of electron scattering can be overcome by altering dimensions in patterns down to 1 μm, but isolated windows of 0.5 μm require ’two‐mode’ masks. The electrostatic chuck is shown to provide an adequate pressure to hold slices flat, and adequate heat sinking.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
41.75.Fr Electron and positron beams

Imaging and alignment tests on an electron projection system

W. R. Livesay

J. Vac. Sci. Technol. 15, 1022 (1978); http://dx.doi.org/10.1116/1.569727 (6 pages) | Cited 2 times

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Improvements to an Electron Projection System are described which eliminate many of the reported disadvantages to this type of system. The performance of a field‐compensating electrostatic chuck that remedies pattern distortion caused by the wafer (anode) is described in conjunction with imaging and alignment tests on 75‐mm‐diam wafers. Proximity effects and reimpacting backscattered electron flooding are shown to be minimized by reduction of the electron exposure energy thereby eliminating the need for pattern compensation in the mask. Line and space patterns with 0.5‐μm dimensions were exposed and resolved without compensation for exposure dosage of larger patterns. Overlay registration results are given for two‐layer alignment tests using e‐beam‐fabricated masks to expose 75‐mm‐diam wafers.
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85.60.-q Optoelectronic devices

Projection ion lithography with aperture lenses

Bernard A. Free and George A. Meadows

J. Vac. Sci. Technol. 15, 1028 (1978); http://dx.doi.org/10.1116/1.569728 (4 pages)

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This paper reports on experiments in projection ion lithography in which multiple demagnified images have been etched directly into a substrate through an aperture lens array, without using a resist or proximity mask. The ion source is an 8‐cm‐beam‐diam, Kaufman‐type mercury ion thruster, which accelerates ions through a grid of perforated plates, and then neutralizes the resultant beamlets by injecting electrons at ground potential. The neutralized ion beam is allowed to pass through a suitable mask and thence onto an array of apertures of a few tens of microns in diameter. Ions impinging on the apertures are accelerated through a field produced by imposing a negative potential on a substrate placed just downstream of the aperture array. An image of the mask is etched in the substrate directly below each aperture. The substrate is a polished metal disk which has been sputter coated with a number of alternating layers of chromium and copper, each about 500 Å thick. Etching of these layers quickly produces an easily visible contour map which accurately depicts variations in the etch rate over the substrate surface. It is necessary to generate random motion of the substrate relative to the ion source to prevent projection of a superimposed image of the ion source grid system. To date, mask elements of the order of 2–3 mm in diameter have been used to produce multiple images demagnified by about 20–30× with resolution better than 10 μm. Suitable equipment is now being fabricated to permit exploration of the submicron region.
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Diode‐array‐targeted CRT scan converter: Some operational limitations and failure mechanisms

George Hashizume, John S. Moore, and Larry D. Riley

J. Vac. Sci. Technol. 15, 1032 (1978); http://dx.doi.org/10.1116/1.569729 (3 pages)

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Some operational limitations of a high‐speed, dual‐gun, diode‐array‐targeted CRT scan converter when used as a transient signal acquisition unit and A/D converter are discussed with respect to trace blooming and target burning at slow trace velocities and/or excessive writing gun beam current. The blooming charactertistics of three target types are described. It is shown that a five times reduction in trace blooming can be obtained, but only with a resultant loss of a factor of four in writing sensitivity. Residual trace retention phenomena (burning) are analyzed. X‐ray generation in the silicon by the 10‐kV writing beam is shown to cause the damage and experimental data is offered to verify this effect and determine the x‐ray dose.
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41.75.Fr Electron and positron beams
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Matrix lens electron‐beam recording systems

H. G. Parks

J. Vac. Sci. Technol. 15, 1035 (1978); http://dx.doi.org/10.1116/1.569730 (4 pages)

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State‐of‐the‐art achievements of matrix lens recording systems are presented in this paper. Also the primary beam limiting aberrations and physical constraints of matrix lens electron‐beam recording systems are discussed. A new concept in matrix lens optics, known as the short focus plus relay with improved performance over conventional matrix lens systems is presented. Analytical projections of the beam current and spot size for this configuration are shown indicating significant performance improvements in matrix lens capabilities. Preliminary experimental data for the short focus plus relay matrix optics is presented.
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41.75.Fr Electron and positron beams
07.07.Hj Display and recording equipment, oscilloscopes, TV cameras, etc.

Modeling charge storage in electron‐beam‐accessed MOS memories

Howard K. Rockstad

J. Vac. Sci. Technol. 15, 1039 (1978); http://dx.doi.org/10.1116/1.569731 (4 pages) | Cited 1 time

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MOS capacitors have been subjected to 10‐kV elecron irradiation at different gate biases, resulting in charge storage in the oxide. C–V translations vs bias are given for various accumulated electron doses extending from 10−4 to 0.1 C/cm2. To explain the essential features of the data, a single‐layer model for the charge distribution is proposed. The model comprises several stages which depend upon the irradiation bias. For the first stage, a characteristic charge layer thickness is independent of bias; this thickness varies from less than 300 Å early in the radiation history to over 800 Å for an accumulated dose of 0.1 C/cm2. A critical interfacial electric field and a trap density are incorporated in the model to directly account for other features of the data.
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61.80.Fe Electron and positron radiation effects
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.De Semiconductor-device characterization, design, and modeling

Resolution of MOS one‐transistor, dynamic RAM bit failures using SEM stroboscopic techniques

A. J. Gonzales and M. W. Powell

J. Vac. Sci. Technol. 15, 1043 (1978); http://dx.doi.org/10.1116/1.569732 (4 pages)

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Stroboscopic techniques are used to allow the scanning electron microscope (SEM) to function as an electronic probe with a spatial resolution of 0.2 μm2 and a time resolution of 0.3 ns. The causes of ’’row’’ and ’’single‐bit’’ failures in the one‐transistor, dynamic random‐access‐memory (RAM) are resolved using the SEM electronic probe technique.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
89.20.Ff Computer science and technology
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Radiation effects of electron‐beam metal depositions on IGFET’s

B. El‐Kareh and A. F. Puttlitz

J. Vac. Sci. Technol. 15, 1047 (1978); http://dx.doi.org/10.1116/1.569733 (6 pages) | Cited 5 times

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Electron‐beam radiation effects on n‐channel IGFET parameters were studied. This paper summarizes the resulting surface‐ and dielectric‐radiation effects obtained with a series of experiments incorporating e‐gun metal deposition on MOS, MNOS, and SNOS structures. The results are compared with those using resistance‐heated metal deposition for various thin‐film compositions between the metal and silicon surfaces. A comparison is also made with the effects of controlled direct e‐beam irradiation of the structures. The efficiency of quartz and aluminum thin films over MNOS structures, in reducing e‐gun radiation effects, is evaluated for double‐level metallurgy structures. The effect of different thermal‐annealing conditions for offsetting the radiation effects is determined. It is concluded that e‐gun metallization causes large negative voltage shifts in MOS, MNOS, and SNOS devices. While MOS threshold shifts are fully ’’annealable’’, residual MNOS and SNOS VT shifts are observed after an anneal of 350°/450°C. Thin films of quartz and aluminum over MOS and MNOS structures effectively reduce radiation effects. Other IGFET parameters are not substantially affected by e‐gun radiation.
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61.80.Fe Electron and positron radiation effects
85.30.Tv Field effect devices
81.40.Rs Electrical and magnetic properties related to treatment conditions

Imaging conditions for electron‐beam micromachining

Leendert A. Fontijn

J. Vac. Sci. Technol. 15, 1053 (1978); http://dx.doi.org/10.1116/1.569734 (3 pages) | Cited 1 time

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In electron‐beam micromachining the highest attainable power density in the substrate material is required for material removal. The application of the Zr/W(100) thermal field emitter combines the advantages of a low electron energy for a minimum electron penetration range in the substrate and a high current density in the final spot. The range of final electron spot sizes considered is from 10 to 100 nm. The spot size on‐axis, as well as off‐axis when scanning the beam, is mainly limited by chromatic aberration. A considerable improvement of the power density, up to about 108 W/cm2 at 3 kV, is obtained by using a high beam current collection efficiency and a symmetrical imaging system of unit magnification. Therefore, a power density of more than 1013 W/cm3 for most of the substrate materials results, allowing operation times of less than 1 μs per image element. A proposed illumination system for electron‐beam micromaching with a working distance of 4 mm is outlined. The intention is to replace the electron optics of a SEM by the proposed illumination system for micromaching purposes.
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06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)
41.75.Fr Electron and positron beams

Mechanism of cavity formation in unfired ceramic by electron‐beam machining

Brian H. Desilets

J. Vac. Sci. Technol. 15, 1056 (1978); http://dx.doi.org/10.1116/1.569735 (4 pages)

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A high‐energy electron beam striking an unfired ceramic penetrates into the material to a maximum depth. Energy is given off along the path of penetration, but this energy transfer is a maximum at about 30% of the maximum penetration depth. Very shortly after the electron beam strikes the material, the organic binder vaporizes and forms a high‐pressure, high‐temperature gas pocket at the location of maximum‐energy transfer. This gas pocket expands by melting the binder around its periphery until it penetrates the surface in an explosive action, drawing with it the solids and liquids and forming a cavity. This process continues until the beam is turned off. When the beam is turned off a heat‐affected zone remains in the cavity wall. The heat dissipates into the bulk material, causing a temperature rise. This rise in temperature is calculated, and experimental results verifying the calculations are presented.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.80.Fe Electron and positron radiation effects

Kinetic focusing requirements for precision e‐beam machining of unfired ceramic material

M. A. Sturans and W. W. Koste

J. Vac. Sci. Technol. 15, 1060 (1978); http://dx.doi.org/10.1116/1.569736 (4 pages)

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Unfired ceramic and other substances containing organic materials generate relatively large quantities of ionized gases during e‐beam thermal machining and, thus, cause beam defocus. The defocus problem is discussed theoretically and demonstrated experimentally. A practical solution for keeping the beam in focus is suggested. It is shown that high‐speed machining is possible by the application of a ’’kinetic focus’’ current function to a kinetic‐focus lens.
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06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)
41.75.Fr Electron and positron beams

Proximity effect in beam‐addressed metal‐oxide semiconductor memory

M. Parikh and M. Heritage

J. Vac. Sci. Technol. 15, 1064 (1978); http://dx.doi.org/10.1116/1.569737 (3 pages)

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Electron scattering in a semiconductor target of a an electron‐beam‐addressed MOS memory can result in proximity effects between a number of adjoining memory locations (bits). As bit spacings decrease, there can be significant unintended charge accumulation in regions unirradiated by the electron beam. This can set a limit to usable bit packing density in the memory.
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79.20.Kz Other electron-impact emission phenomena
89.20.Ff Computer science and technology
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Fe Electron and positron radiation effects

PR‐30 ion implantation system

J. G. McCallum, G. I. Robertson, A. F. Rodde, B. Weissman, and N. Williams

J. Vac. Sci. Technol. 15, 1067 (1978); http://dx.doi.org/10.1116/1.569738 (3 pages) | Cited 1 time

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The PR‐30 uses a 30‐kV high throughput ion implanation system developed for the production line. It was designed to improve dose uniformity and control by replacing predeposition furnaces with acceptably fast ion implantation. The PR‐30 uses rotating mechanical scan, in which 30 3‐in. (7.6 cm) wafers are implanted simultaneously, to achieve high throughput at low as well as high doses. A doubly focusing magnet provides species selection and is the sole focusing element, and a high‐current ion source allows short implant time. Typical ion beam currents are 1 mA of B+ and 5 mA of P+, As+, and Sb+. The pumping system gives a total batch change time of under three minutes which maintains high throughputs at low doses. Throughputs of 3‐in. wafers at a dose of 1×1015/cm2 are 200/h for B+, and 450/h for the other species. The combination of a mechanical scanning mechanism, the doubly focusing magnet, and no accelerator section enables the machine to be compact. The beam line is vertical with the target at the top, and the required floor space is 6×7 ft (1.8×2.1 m) excluding instrumentation. The machine is fully automatic. A single button initiates the implant and a punched card defines the dose. All other functions and sequences are under computer control. PR‐30’s have been used in production in the Western Electric manufacturing locations since 1974, and have significantly improved the yield of silicon devices.
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61.72.U- Doping and impurity implantation
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
61.80.Jh Ion radiation effects

Development of the ERC cold‐cathode ion source for use on the PR‐30 ion‐implantation system

H. M. B. Bird and J. P. Flemming

J. Vac. Sci. Technol. 15, 1070 (1978); http://dx.doi.org/10.1116/1.569739 (6 pages) | Cited 2 times

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The ERC cold‐cathode ion source has been in routine production use on several PR‐30 systems for the past three years. This source has been further developed to improve target current, lifetime, and stability. The ion‐optical lens has been changed from circular to elliptical geometry in order to provide an asymmetric beam for entry into the PR‐30 analyzing magnet. This measure, as well as the use of higher extraction voltages, provides higher beam currents on the PR‐30 target wafers. Beam steering in the nondispersive direction has been provided to correct the effects of minor machine misalignments, further enhancing target current. The discharge chamber has been modified to increase source lifetime. A new gas‐feed control system and a new method of oven temperature control have been devised to provide good source and ion beam stability. The source operates with only occasional attention by unskilled personnel, and has been used principally for boron and arsenic implants. Target currents of 1‐mA boron and 4‐mA arsenic can be obtained routinely. Lifetimes are of the order of 40–80 h, depending on ion species. The source has also been used to provide 5‐mA phosphorus, 4‐mA argon, 3‐mA helium and neon, and 0.3‐mA nickel and palladium ion beams.
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61.72.U- Doping and impurity implantation
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

High‐current ion source for use on the PR‐30 implanter

N. Williams

J. Vac. Sci. Technol. 15, 1076 (1978); http://dx.doi.org/10.1116/1.569740 (4 pages) | Cited 1 time

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An ion source of the Freeman type has been extensively reworked and tailored for the routine production of dopant species on the PR‐30 ion implantation machine. The modified source is presently used on several such machines within the Bell System, routinely producing intense beams of B+, P+, As+, and Sb+. Typical PR‐30 target currents for the above species are 1, 5, 6, and 5 mA, respectively, with peak currents about 20% higher than these figures. With the possible exception of B+, these beam current intensities are the highest presently available for implantation applications. Further studies on improved B+ production are being pursued. BF3 gas is used as a feed for B+ production and solid charges are used for P+, As+, and Sb+, ususally without a carrier gas, so as to maintain maximum beam purity. The source lifetime is typically 30–60 h at the above current levels and is limited by filament sputtering. Operation of the source is relatively facile and good beam stability can be obtained.
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
61.72.U- Doping and impurity implantation

PR‐200 ion implantation system

H. M. B. Bird, J. H. Jackson, B. Weissman, and N. Williams

J. Vac. Sci. Technol. 15, 1080 (1978); http://dx.doi.org/10.1116/1.569741 (6 pages)

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PR‐200 is a 200‐kV, general‐purpose, high‐throughput ion‐implantation system which was installed on Western Electric’s production line at Reading, PA in mid‐1975. The ’’front end’’ is a commercial Lintott mass separator to which has been added a high‐current version of the Lintott–Harwell hot‐cathode ion source. The front end produces 11B currents of 1 mA and 31P, 75As, and 121Sb currents of 3 mA. The ’’rear end’’ is an acceleration and rotating scan target stage based upon the PR‐500 technology which was developed at this laboratory. Careful matching of the front‐end slit‐beam ion optics to the rear‐end circular‐beam optics produces high currents on target, up to 1 mA of 11B and 2.5 mA or 31P, 75As, and 121Sb. These currents, combined with fast turnaround time (5–7 min) and rotating mechanical scan, permit more than 100 3‐in. wafers/h to be implated with wafer nonuniformities (1 σu) less than 0.5% and a total product nonuniformity (1 σT) less than 2.0%. The target stage floats at high voltage, and is pumped through insulating columns by a vacuum system at ground potential. Additional pumping speed is obtained by a titanium sublimation pump inside the target stage. The pumpdown sequence is automated and the implant sequence is under minicomputer control, permitting operation of the system by unskilled personnel. Communication between the high‐voltage target stage and ground potential is accomplished with a four‐light‐beam telemetry system. Two light beams are dedicated to the rotating‐scan implant and dose control, and two other light beams communicate a variety of analog, digital, and status information.
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61.72.U- Doping and impurity implantation
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
61.80.Jh Ion radiation effects

Implantation temperature for III–V compound semiconductors

K. Gamo, M. Takai, H. Yagita, N. Takada, K. Masuda, S. Namba, and A. Mizobuchi

J. Vac. Sci. Technol. 15, 1086 (1978); http://dx.doi.org/10.1116/1.569742 (3 pages) | Cited 7 times

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Ion implantation in various III–V compound semiconductors (BP, InSb, GaP, and GaAs) has been investigated to reveal the effect of implantation temperature on the general implantation behaviors of III–V compounds. Lattice location of implanted ions and defects were measured by means of He ion‐channeling techniques as a function of implantation temperature. For all of the crystals studied, it was found that no amorphous layer was formed above the critical temperature (Tc), and that Tc is linearly corrlated to a melting point of a crystal. High substitutational fraction of implanted ions and low defect density were obtained by an implanatation above Tc.
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61.72.U- Doping and impurity implantation
61.80.Jh Ion radiation effects

Annealing and rolling behaviors of concentration profiles of Cr and Cu implanted into mild steel

M. Iwaki, S. Namba, K. Yoshida, N. Soda, T. Sato, and K. Yukawa

J. Vac. Sci. Technol. 15, 1089 (1978); http://dx.doi.org/10.1116/1.569743 (4 pages)

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Concentration profiles of 52Cr and 63Cu implanted in mild steel have been measured by means of ion microprobe analysis in order to investigate annealing and rolling behaviors of implanted ions. Ion implantation has been performed with the dose of 1017 ions/cm2 at the energy of 150 keV. The concentration profile of as‐implanted Cu exhibits the deeper penetration and its peak exists at the shallower region, compared with the depth distribution predicted by the LSS theory. The Cu maximum concentration after annealing decreases. It also decreases, being rolled, and its depth approaches near the surface. The concentration profile of as‐implanted Cr has two peaks, of which the presence can not be predicted by the LSS theory. Chromium concentrations after annealing at 700°C decrease. The profile in the specimen rolled after ion implantation shows an exponential decrease inwards from the surface. These results are explained by sputtering, enhanced diffusion, thermodynamic, and rolling effects.
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61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Argon plasma bridge neutralizer operation with a 10‐cm‐beam‐diameter ion etching source

Paul D. Reader, Dennis P. White, and Gerald C. Isaacson

J. Vac. Sci. Technol. 15, 1093 (1978); http://dx.doi.org/10.1116/1.569516 (3 pages) | Cited 6 times

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The plasma bridge neutralizer operating on argon offers a long‐life, contamination‐free method of neutralizing the ion beams of industrial etching and deposition sources. The neutralizer described herein is capable of neutralizing the 200‐mA beam produced by the 10‐cm‐diameter ion source used for these tests. Beam plasma potential and electron temperature are essentially the same as those from an immersed thermionic emitter neutralizer. Lifetimes 3 to 5 times as great as immersed wires were obtained with the plasma bridge neutralizer in similar reactive environments.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors

Microfabrication in LiNbO3 by ion‐bombardment‐enhanced etching

M. Kawabe, M. Kubota, K. Masuda, and S. Namba

J. Vac. Sci. Technol. 15, 1096 (1978); http://dx.doi.org/10.1116/1.569517 (3 pages) | Cited 6 times

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Ion‐bombardment‐enhanced etching is suggested as an useful microfabrication technique for LiNbO3. Diluted HF was found to be a good selective etchant for a layer damaged by Ar+ and N+. This method is compared with another microfabrication method, ion beam etching. The accuracy of the pattern width by this method is better than that ion beam etching and the slope of the grooved wall is very steep. The etched depths of the layer damaged by 60‐keV Ar+ at the dose of 3×1015/cm2 and N+ at the dose of 2×1016/cm2 are 70 and 145 nm, respectively. The depth is controllable by changing the ion energy and dose.
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61.80.Jh Ion radiation effects
42.82.-m Integrated optics
42.79.Gn Optical waveguides and couplers
81.65.-b Surface treatments

Controlled vapor growth of small particles of Pd and Fe on thin Al2O3 substrates

Helmut Poppa, Eal H. Lee, and R. Dale Moorhead

J. Vac. Sci. Technol. 15, 1100 (1978); http://dx.doi.org/10.1116/1.569518 (5 pages) | Cited 2 times

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An exploratory study, dealing with the preparation of well‐defined particulate metal deposits that can be used in model studies of catalytic reactions, was performed. Small metal particles of Fe and Pd were grown in situ in an electron microscope by vapor deposition onto different phases of electron transparent alumina substrates. The results show that characteristic properties of the deposits, such as particle density, size distribution, habit, and orientation, are strongly dependent on the cleanliness, phase, and crystallographic orientation of the alumina substrate; also, the deposition conditions can be chosen in such a way as to reproducibly manipulate the overall deposit structure.
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68.55.-a Thin film structure and morphology

Study of planarized sputter‐deposited SiO2

C. Y. Ting), V. J. Vivalda, and H. G. Schaefer

J. Vac. Sci. Technol. 15, 1105 (1978); http://dx.doi.org/10.1116/1.569519 (8 pages) | Cited 15 times

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A theoretical model is proposed to explain the mechanism of the formation of sputter‐deposited ’’planarized glass’’; a phenomenon which describes the topography change during sputter glass deposition on top of a metal strip when sufficient bias is applied to the substrate target, and the sputter‐deposited ’’standard glass’’ when little or not bias is applied to the substrate target. By assuming that the deposition rate is independent of the substrate topology, and that the removal rate is a function of the slope angle of the substrate surface, it is able to explain the various experimental phenomena observed for both ’’planarized glass’’ and ’’standard glass’’. A delineation scheme is adopted to support the model by displaying the glass contour step‐by‐step in formation of both kinds of sputter‐deposited glass.
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73.61.Ng Insulators
77.55.-g Dielectric thin films
81.90.+c Other topics in materials science (restricted to new topics in section 81)
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)

Deposition of aluminum on Kapton laminates by electron‐beam evaporation

Dudley M. Sherman

J. Vac. Sci. Technol. 15, 1113 (1978); http://dx.doi.org/10.1116/1.569520 (4 pages)

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Aluminum films 10 μm thick have been deposited on the Kapton surface of a laminated substrate consisting of Kapton–Kapton–aluminum foil bonded with a thermosetting adhesive. The processing of the substrates before deposition necessary to obtain reasonably short deposition cycle times and a minimal amount of deposition system contamination was developed. The laminated substrates required bakeouts both at atmosphere and in high vacuum prior to deposition to permit evaporation at a pressure of 0.1 mPa (1×10−6 Torr). The deposited films exhibited a high specular reflectance, resistivity within 5% of that of bulk aluminum, and a strong (111) fiber texture.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys
78.66.Bz Metals and metallic alloys

Electrical resistivity of vaccum‐deposited molybdenum films

Hideo Oikawa and Takaakira Tsuchiya

J. Vac. Sci. Technol. 15, 1117 (1978); http://dx.doi.org/10.1116/1.569521 (6 pages) | Cited 13 times

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The electrical resistivity ρ of Mo films evaporated by an electron‐beam gun onto SiO2/Si substrates has been studied in relation to the film structure and purity. The resistivity was profoundly influenced by the substrate temperature during deposition Ts but was almost independent of film thickness d if d exceeded 1000 Å. When the films were heat treated at above 700°C, ρ decreased as the grain size increased. These results can be explained if one assumes that the resistivity is due to grain‐boundary scattering. The reflection coeficient of the electrons at grain boundaries R depends on Ts, but shows no change with heat treatments at temperatures up to about 1000°C(R =0.41/0.21 for Ts=300/600°C). It is shown that R is proportional to oxygen content in the grain boundaries.
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73.61.At Metal and metallic alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Rs Electrical and magnetic properties related to treatment conditions

Comparison of Auger signals measured using differential and integral Auger spectra from C and O adsorbed on W

Kazuo Ishikawa and Yasushi Tomida

J. Vac. Sci. Technol. 15, 1123 (1978); http://dx.doi.org/10.1116/1.569522 (6 pages) | Cited 6 times

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Comparison was made experimentally with carbon and oxygen atoms on tungsten between the widely used peak‐to‐peak height measurements in dEN (E)/dE mode spectra, A, and the rarely used Auger peak heights and areas in EN (E) mode spectra, H and S, respectively, as measures of the signal in Auger electron spectroscopy. The proportionality between A and S was found to hold or not depending on whether chemical changes of the elements did not or did occur, respectively. As a quantitative example, carbide was found to have A‐values about 3.5 times larger than graphite for the same atomic concentration. For carbon, the H‐values gave better indications of concentration than A. An example is presented in which the observation of an A vs S relation provides a means to detect the chemical change of specimens more sensitively than by observing Auger peak shapes.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Chemical characterization of WC–Co composite materials by AES and ISS (1) Processing

L. L. Tongson, J. V. Biggers, J. M. Bind, G. O. Dayton, and B. E. Knox

J. Vac. Sci. Technol. 15, 1129 (1978); http://dx.doi.org/10.1116/1.569523 (4 pages) | Cited 1 time

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Technological innovations in the processing of WC–Co composite materials were developed recently in this laboratory. The cobalt binder is precipitated from solution onto WC grains initially. The application of low‐energy ion scattering spectrometry (ISS) and Auger electron spectrometry (AES) in optimizing processing modes is discussed. A method is presented for comparing the initial distribution of the binder in the starting materials by correlating the surface compositions determined by ISS and AES with bulk measurements determined by x‐ray fluorescence.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.05.Mh Cermets, ceramic and refractory composites

Surface analysis of WC–Co composite materials (2) Quantitative Auger electron spectrometry

L. L. Tongson, J. V. Biggers, G. O. Dayton, J. M. Bind, and B. E. Knox

J. Vac. Sci. Technol. 15, 1133 (1978); http://dx.doi.org/10.1116/1.569524 (6 pages) | Cited 3 times

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The unique sensitivity of Auger electron spectrometry (AES) to combined carbon has been exploited in measuring the surface compositions of hot‐pressed, conventionally sintered and mixed powders of WC–Co composite materials. AES sensitivity factors for tungsten and carbon (in WC) relative to cobalt were determined. The concentrations of the major elements in hot‐pressed samples measured with AES using the relative sensitivity method were compared to those obtained independently by electron microprobe (EMP) and x‐ray fluorescence (XRF) techniques. Corollary studies using ion scattering spectrometry (ISS) showed the absence of (1) matrix effects in the AES measurements, (2) preferential sputtering during ion bombardment, and (3) deposition of the easier‐to‐sputter component (cobalt) onto WC.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.05.Mh Cermets, ceramic and refractory composites

Quantitative AES of stainless‐steel samples with computer evaluation

W. Färber

J. Vac. Sci. Technol. 15, 1139 (1978); http://dx.doi.org/10.1116/1.569525 (4 pages) | Cited 2 times

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A series of different stainless‐steel samples has been investigated. The Auger spectra were evaluated quantitatively using a computer program. This computer program, called AUA, is a least‐squares fit program and has stored the spectra of elemental standards and their Auger yields. In the present form the program includes 19 different elements (Si, P, S, Cl, Mo, K, C, Ca, N, Ti, V, Cr, O, Mn, Fe, Co, Ni, Cu, and Al) and is used for the investigation of stainless‐steel samples. The structure of the program is explained and a number of examples demonstrates the reliability of the method and the magnitude of the errors. The resulting sample composition is given both in atomic and in weight percent. The expansion to a higher number of elements and thereby the application of the program AUA to other samples is possible.
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81.05.Bx Metals, semimetals, and alloys
89.20.Bb Industrial and technological research and development
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Atomic structure of the annealed Ge(111) surface

Marc Taubenblatt, Edward So, Philip Sih, Antoine Kahn, and Peter Mark

J. Vac. Sci. Technol. 15, 1143 (1978); http://dx.doi.org/10.1116/1.569526 (3 pages)

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A model for the atomic structure of the annealed Ge(111) 2×8 surface is proposed on the basis of intensity measurements in which the fractional order beams are attributed to a ripplelike distortion of (at least) the top two double layers in a manner consistent with charge density wave (Peierls) instabilities or compresive stress deformations derived from distributed rehybridization. The distortion is similar to that suggested for the annealed Si(111) 7×7 surface from a similar analysis. The superlattice is actually an 8×8 unit cell; the observed 2×8 reconstruction follows from selected structure factor cancellations owing to the specific topography of the distortion.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.66.Bi Elemental solids
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Hydrogen and deuterium permeation in copper alloys, copper–gold brazing alloys, gold, and the in situ growth of stable oxide permeation barriers

David R. Begeal

J. Vac. Sci. Technol. 15, 1146 (1978); http://dx.doi.org/10.1116/1.569527 (9 pages) | Cited 7 times

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The deuterium permeation through several copper alloys has been measured over a temperature range of 550 to 830 K using the membrane technique. In some cases, the hydrogen permeability was also measured. The results were divided into three categories: common alloys, gold alloys, and stable oxide forming alloys. Common alloys which showed typical bulk metallic diffusion with litle change in the permeation activation energy as compared to copper (77 kJ/mol for D2) were: (additions are in weight percent) 5% Sn, 2.3% U, 0.15% Zr, 4% Sn+4% Pb+4% Zn, 3% Si, and 7% Al+2% Fe. Compared to copper, the D2 permeability at 573 K was reduced by factors of 2.0, 2.7, 4.5, 5.3, 5.9, and 7.0, respectively. A series of gold–copper alloys including pure gold, 80% Au, 50% Au, 49% Au, and 35% Au also showed typical bulk metallic diffusion with a trend of decreasing permeability (increasing activation energies for permeation) with increasing gold content. There were also pronounced inflections or shifts in the permeability at ∠370°C, or about the order–disorder transition for Cu3Au and CuAu, for the 80% and 50% alloys. Two alloys did not exhibit bulk metallic permeation behavior and the permeabiltiy was in fact controlled by surface oxide layers. It was found that a layer of beryllium oxide could be formed on Cu+2% Be and a layer of aluminum oxide could be formed on Cu+7% Al+2% Si. As compared to 0.25 mm‐thick copper, the deuterium permeability at 500°C was reduced by a factor of ∠250 for Cu–Be and ∠1000 for Cu–Al–Si. The activation energies for deuterium permeation were 98 kJ/mol and 132 kJ/mol, respectively. The mechanism for the oxide growth is the high‐temperature hydrogen reduction of nearby less stable oxides, simultaneous with oxidation of the active metal, Be or Al, by trace amounts of water in the hydrogen. Ion microprobe mass analysis identified the oxide layers as containing beryllium or aluminum but not containing copper. The trend of activation energies found lends support to a theoretical model that relates the activation energy for diffusion to the shear modulus of the host oxide and the molecular radius of the diffusing molecule.
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66.30.J- Diffusion of impurities
64.60.Cn Order-disorder transformations
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Solar energy conversion using semiconducting photoanodes

W. A. Gerrard and L. M. Rouse

J. Vac. Sci. Technol. 15, 1155 (1978); http://dx.doi.org/10.1116/1.569528 (11 pages) | Cited 1 time

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In recent years, interest in the use of photoelectrochemical devices for solar energy conversion has grown dramatically. The major advantage over more conventional solar cells (e.g., the silicon p–n junction) is the ease with which the device can be constructed, since the interface between the semiconductor and electrolyte is not subject to such problems as lattice mismatch. Prior to 1969 it was thought that semiconductors invariably degraded when illuminated in an aqueous environment. Such corrosion problems have been overcome by using more rugged semiconductors and adding stabilizing redox ions (e.g.,S2−/S2−2) to the electrolyte. The understanding of semiconductor–electrolyte interfaces has been greatly enhanced by the ability to study stable systems. It is now clear that the conversion efficiency of such devices is a function of the quality of the Schottky barrier at the interface, the band gap and electron affinity of the semiconductor, and the redox level in the electrolyte that it acts upon. Another advantage over the silicon solar‐cell is the ability to store solar energy by the direct production of chemicals (e.g., H2). At present the best conversion efficiencies that have been observed have been of the order of 7%–9% (AM 2 sunlight). While this is poor compared to that which can be obtained with silicon solar‐cells, cheap thin‐film semiconductor techniques could make such devices extremely competitive in terms of economics.
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84.60.Jt Photoelectric conversion
85.30.Hi Surface barrier, boundary, and point contact devices
82.47.-a Applied electrochemistry
85.60.Dw Photodiodes; phototransistors; photoresistors

Studies on arrays of Josephson tunnel junction interferometers

Ronald F. Broom and Theodor O. Mohr

J. Vac. Sci. Technol. 15, 1166 (1978); http://dx.doi.org/10.1116/1.569529 (9 pages) | Cited 3 times

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Josephson‐junction interferometers have previously been proposed as memory devices in which information is stored as a single flux quantum, (SFQ). To investigate the feasibility of making large arrays of SFQ cells suitable for the memory of a cryogenic computer, arrays containing 80 interferometers have been made and measured. The prime objective was to determine the distribution of the dc Josephson current i1 within the arays and to compare it with the design value required for successful operation of all cells in high density arrays. The results show that a substantial fraction of the arrays has standard deviations in i1 less than the maximum allowable, thus demonstrating for the first time that such a memory can be made with present technology. The fabrication, measurement technique and a detailed analysis of the current distributions on the arrays are presented.
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74.50.+r Tunneling phenomena; Josephson effects
89.20.Ff Computer science and technology
85.25.-j Superconducting devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

In situ conditioning for proton storage ring vacuum systems

D. Blechschmidt

J. Vac. Sci. Technol. 15, 1175 (1978); http://dx.doi.org/10.1116/1.569530 (7 pages)

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Average pressure and vacuum‐stability limit as expected in the presence of a proton beam were measured after in situ treatments such as bakeout under various conditions, argon glow‐discharge cleaning and sputter deposition of titanium. Measurements were carried out for test pipes made of stainless steel (untreated, electropolished, or cooled to 77 K), pure titanium and aluminum alloy. The measurement method used to obtain the vacuum‐stability limit in the laboratory and in a prototype system is described. The results can be applied also to other systems of different geometry by use of scaling laws. In situ conditioning generally has a stronger influence on vacuum performance than a particular choice of material. Bakeout gives low average pressures and rather good vacuum stability. Glow discharges also increase the vacuum stability but have only a small effect on the static pressure. Coating the beam‐pipe wall with titanium by in situ sputtering provides large linear pumping, thus a lower pressure and an extremely good vacuum stability.
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29.20.db Storage rings and colliders
07.30.Hd Vacuum testing methods; leak detectors
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Rate at which molecules strike a surface or orifice in a vacuum system

D. Edwards

J. Vac. Sci. Technol. 15, 1182 (1978); http://dx.doi.org/10.1116/1.569531 (4 pages)

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It is shown for a spherical vacuum chamber with system pressure in the molecular flow region, that the rate per unit area at which molecules strike a surface or orifice is, in general, not 1/4 nva but depends on the molecule–wall scattering function, the classical result (1/4 nva) being obtained for a cosine wall scattering function.
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05.20.Dd Kinetic theory

Pressure measurements in a cryogenic environment

D. Edwards and P. Limon

J. Vac. Sci. Technol. 15, 1186 (1978); http://dx.doi.org/10.1116/1.569532 (3 pages) | Cited 3 times

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A technique is presented which allows the measurement of He and H2 pressures in a cold system (∠4 K) with instrumentation at room temperature. It is applied to vacuum measurements of a section of a beam tube to be used in a proton accelerator application. The primary result is that with the beam tube at 4.7 K the helium pressure is less than 10−11 Torr and the H2 pressure is negligible.
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07.30.Hd Vacuum testing methods; leak detectors
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
29.20.-c Accelerators