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Nov 1979

Volume 16, Issue 6, pp. 1610-2116


High‐resolution, ion‐beam processes for microstructure fabrication

R. L. Seliger, R. L. Kubena, R. D. Olney, J. W. Ward, and V. Wang

J. Vac. Sci. Technol. 16, 1610 (1979); http://dx.doi.org/10.1116/1.570253 (3 pages) | Cited 25 times

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Ion beams have increased usefulness for high‐resolution microstructure fabrication if they are patterned to small dimensions before they strike a target. First, results are presented of maskless micromachining, doping, and resist exposure with a scanning focused gallium ion beam of sub‐1000‐Å diameter. Secondly, an ion‐beam‐transmission mask is described, and results are presented showing 1X replicated mask patterns with 0.6‐μm features that were exposed in PMMA resist by irradiating the mask with a conventional size 150‐kV proton beam. The potentials of ion‐beam lithography using masks and focused ion beams are discussed.
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
07.68.+m Photography, photographic instruments; xerography
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Abstract: Etching in reactive plasmas

J. W. Coburn and H. F. Winters

J. Vac. Sci. Technol. 16, 1613 (1979); http://dx.doi.org/10.1116/1.570254 (2 pages) | Cited 2 times

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Abstract Unavailable
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81.65.-b Surface treatments
52.75.-d Plasma devices
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

X‐ray lithography at ∠100 Å linewidths using x‐ray masks fabricated by shadowing techniques

D. C. Flanders

J. Vac. Sci. Technol. 16, 1615 (1979); http://dx.doi.org/10.1116/1.570255 (5 pages) | Cited 13 times

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A new technique for fabricating high contrast x‐ray masks with precisely controlled linewidths of less than 100 Å is described. The technique is based on the deposition at an oblique angle (shadowing) of x‐ray absorber material onto relief structures of triangular or square cross section in a polyimide plastic membrane. Precise linewidth control is possible because shadowing angle, absorber thickness,and relief structure can be precisely determined. The smooth and well‐controlled triangular cross‐section structures required are produced in silicon by anisotropic chemical etching and then transferred to polyimide by molding. The square structures are made by reactive‐ion‐etching of SiO2 with CHF3 and are transferred to polyimide by molding. Results of a numerical model of carbon K (45 Å) x‐ray exposures in PMMA of shadowed triangular profile masks are presented which indicate that linewidth control of ±50 Å should be possible for submicrometer period grating. Scanning electron micrographs of PMMA gratings of 1 μm, 3200 Å and 1968 Å period with linewidths as small as 400 Å are shown. The successful replication of ∠200 Å linewidth patterns in PMMA using the carbon K x‐ray and shadowed square cross‐section masks is reported.
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07.68.+m Photography, photographic instruments; xerography
07.85.-m X- and γ-ray instruments
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments

High resolution, steep profile resist patterns

J. M. Moran and D. Maydan

J. Vac. Sci. Technol. 16, 1620 (1979); http://dx.doi.org/10.1116/1.570256 (5 pages) | Cited 27 times

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High resolution and steep profile patterns have been generated in a 2.6 μm thick organic layer which conforms to the steps on a wafer surface and is planar on its top. This thick organic layer (a photoresist in the present experiments) is covered with an intermediate layer of SiO2 and a top, thin layer of x‐ray or photoresist. After exposure and development of the top resist layer, the intermediate layer is etched by CHF3 reactive ion etching. The thick organic layer is then etched by O2 reactive ion etching. Submicron resolution with essentially vertical walls in the thick organic material was achieved. The technique is also applicable to photo and electron lithography. It reduces the need for thick resist patterns for the lithography step and, at the same time, ensures high resolution combined with good step coverage.
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07.68.+m Photography, photographic instruments; xerography
07.85.-m X- and γ-ray instruments
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments

Abstract: Ion beam fabrication of 400 Å, high aspect‐ratio lines in poly methyl methacrylate (PMMA)

L. Karapiperis and C. A. Lee

J. Vac. Sci. Technol. 16, 1625 (1979); http://dx.doi.org/10.1116/1.570257 (1 page)

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Abstract Unavailable
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
07.68.+m Photography, photographic instruments; xerography
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

X‐ray zone plates fabricated using electron‐beam and x‐ray lithography

D. C. Shaver, D. C. Flanders, N. M. Ceglio, and Henry I. Smith

J. Vac. Sci. Technol. 16, 1626 (1979); http://dx.doi.org/10.1116/1.570258 (5 pages) | Cited 13 times

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Fresnel zone plate patterns, free of spherical aberration, with diameters of up to 0.63 mm and linewidths as small as 1000 Å were fabricated on polyimide membrane x‐ray masks using scanning electron beam lithography. Distortion of the electron beam scan raster was reduced to ?2500 Å over a 2×2 mm field by applying deflection corrections, while viewing the distortion using a Moiré method. CK x‐ray lithography was used to replicate the zone plate pattern in thick PMMA over a 100 Å thick plating base on a glass substrate. Zones plates in 1.3 μm thick gold were fabricated by plating, and made free‐standing by removal of the plating base and the supporting glass substrate. Zone plates were tested as imaging elements with visible light and soft x‐rays.
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41.75.Fr Electron and positron beams
42.79.Ci Filters, zone plates, and polarizers
07.68.+m Photography, photographic instruments; xerography
07.85.-m X- and γ-ray instruments

New hybrid (e‐beam/x‐ray) exposure technique for high aspect ratio microstructure fabrication

M. Hatzakis, D. Hofer, and T. H. P. Chang

J. Vac. Sci. Technol. 16, 1631 (1979); http://dx.doi.org/10.1116/1.570259 (4 pages) | Cited 3 times

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A new lithographic technique will be described in this paper which makes it possible to increase the height‐to‐width (aspect) ratio of electron‐beam‐exposed patterns in the resist layer, without significantly increasing proximity effects. The technique consists of applying two resist layers on the substrate, separated by a thin metal film. The pattern is electron‐beam exposed on the top resist layer, and after development, a thin (2000–3000 Å) gold or other x‐ray absorbing material is used to form an in situ x‐ray mask to expose a much thicker bottom resist layer in an x‐ray exposure system. It is shown that with this technique, lines of 0.25‐μm wide with vertical walls, can be obtained in 2‐μm‐thick PMMA resist or an aspect ratio of eight can be easily achieved. It is also shown that the in situ mask can be registered to a previous level on the workpiece with accuracy better than 0.1 μm.
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07.68.+m Photography, photographic instruments; xerography
41.75.Fr Electron and positron beams
07.85.-m X- and γ-ray instruments
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

High speed CMOS/SOS IC’s fabricated using x‐ray lithography

H. L. Stover, F. L. Hause, and D. McGreivy

J. Vac. Sci. Technol. 16, 1635 (1979); http://dx.doi.org/10.1116/1.570260 (5 pages)

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High‐speed CMOS/SOS IC’s with 1 μm design rules have been fabricated using x‐ray lithography and the negative resist COP at eight mask levels. The fabrication processes four ion‐implantation steps and two plasma etching steps. The CMOS/SOS LSI test chip contains ring oscillators with gate lengths of 1, 2, 3, 4, 5, and 7.5 μm. Speed–power data from the ring oscillators are presented; time delay per stage as low as 185 ps was measured for the devices with 1 μm gate lengths. The x‐ray source design and the mask technology are reviewed. Scanning electron micrographs of resist patterns and replicated thin‐film patterns are presented to show characteristic edge definition and stop coverage of narrow lines. Preliminary reliability testing of finished IC’s is reported; data from thermal stress tests (105 rads from a 60Co source) are compared to similar data from devices fabricated using photolithography. We conclude that x‐ray lithography is a viable technology for fineline LSI.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
07.68.+m Photography, photographic instruments; xerography
07.85.-m X- and γ-ray instruments
81.65.-b Surface treatments

Graphoepitaxy of silicon on fused silica using surface micropatterns and laser crystallization

M. W. Geis, D. C. Flanders, Henry I. Smith, and D. A. Antoniadis

J. Vac. Sci. Technol. 16, 1640 (1979); http://dx.doi.org/10.1116/1.570261 (4 pages) | Cited 12 times

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Uniform crystallographic orientation of silicon films, 500 nm thick, has been achieved on amorphous fused silica substrates by laser crystallization of amorphous silicon deposited over surface‐relief gratings etched into the substrates by reactive ion etching. The gratings had a square‐wave cross section with a 3.8 μm spatial period, a 100–nm depth and corner radii of about 5 nm. The 〈100〉 directions in the silicon were parallel to the grating to within ±18°, and perpendicular to the substrate plane to within ±2.5°. A simple model for the graphoepitaxy process is presented. Sheet resistivity of phosphorous doped graphoepitaxial silicon was 2.5 times larger than that of bulk silicon of the same doping. Graphoepitaxy is a new application of microstructure fabrication that may lead to new combinations of substrates and overlayer films, and perhaps to three‐dimensionally integrated electronic devices and other novel configurations.
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68.55.-a Thin film structure and morphology
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Rs Electrical and magnetic properties related to treatment conditions

Practical results of EL2

G. J. Giuffre, J. F. Marquis, H. C. Pfeiffer, and W. Stickel

J. Vac. Sci. Technol. 16, 1644 (1979); http://dx.doi.org/10.1116/1.570262 (5 pages)

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Samples of resist images and device structures are presented, which demonstrate system performance aspects of pattern image fidelity and overlay accuracy of the variable‐shape spot (VSS) lithography tool EL2. Test pattern exposure giving qualitative, but more comprehensive information about image fidelity, are compared to quantitative results of resolution measurements with the knife‐edge scanning technique. The preeminent resolution limiting electron‐optical aberrations determined by complex electron–electron interactions, are explained and put in perspective. Several EL2 systems have been equipped with VSS columns tailored to applications ranging from submicron lithography to 2 μm minimum images over fields of deflection up to 8×8 mm2. Images obtained in test patterns correspond to 10 000 fabricated lines per field. It is shown how the pattern overlay accuracy is determined. The results quoted satisfy technology requirements within an error level of three times the standard deviation.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Direct e‐beam fabrication of 256 BIT bipolar RAMS

J. Reynolds, J. L. Bartelt, R. Williamson, and G. L. Varnell

J. Vac. Sci. Technol. 16, 1649 (1979); http://dx.doi.org/10.1116/1.570263 (5 pages) | Cited 1 time

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A vector scan laser‐controlled e‐beam direct writing system (EBMIII) has been utilized to fabricate the 745201A bipolar RAM in a pilot production area. This device is a standard TTL, 256‐bit bipolar RAM using a single level metal, junction‐isolated, Schottky‐clamped bipolar process with 5‐m design rules. Two high speed electron resists, one positive (TI‐313) and one negative (TI‐309), were used in this pilot production demonstration along with a new selective plasma etching process. The completed units were screened and tested according to military specifications and compared to devices processed with conventional photoresist. The results of these stringent tests verified that e‐beam lithographic processing does not degrade the performance of this type of device.
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41.75.Fr Electron and positron beams
85.40.Bh Computer-aided design of microcircuits; layout and modeling
07.68.+m Photography, photographic instruments; xerography
07.07.Tw Servo and control equipment; robots

Short channel n‐MOS devices via combined e‐beam and photolithographic processing

R. C. Henderson and J. G. Nash

J. Vac. Sci. Technol. 16, 1654 (1979); http://dx.doi.org/10.1116/1.570264 (4 pages)

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A new silicon device processing sequence has been developed to permit fabricating n–MOS circuits with silicon gate lengths 1 μm or less. The processing sequence permits using photolithography to define the larger structures, while using e‐beam direct writing to define the critical size features. The compatible process sequence uses positive resists for all pattern definition steps. A low turn‐on voltage is achieved by a phosphorus ion implantation step which counter dopes the p‐type substrate and provides a self‐aligned channel. The e‐beam patterns are registered to the optical patterns using tantalum alignment marks protected with a capping layer of CVD oxide plus polysilicon. Diagnostic devices have been fabricated which demonstrate the capability of the new approach.
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85.30.-z Semiconductor devices
41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography

Radiation effects in MOS devices caused by x‐ray and e‐beam lithography

M. Peckerar, R. Fulton, P. Blaise, D. Brown, and R. Whitlock

J. Vac. Sci. Technol. 16, 1658 (1979); http://dx.doi.org/10.1116/1.570265 (4 pages) | Cited 5 times

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In this study we have found that electron–beam and x‐ray irradiations of metal (or polysilicon) ‐oxide‐semiconductor devices performed at typical PBS or PMMA exposure levels create temperature‐bias‐stress (TBS) instability. Experimental results can be most reasonably explained by assuming that exposure to both of these types of ionizing radiation causes mobilization of positive charge in the insulator. The positive charge is forced closer to the semiconductor–gate‐oxide interface during the positive bias phase of the TBS test. This damage mechanism was found in HCl, H2/O2, and dry grown oxides. HCl oxides exhibited the effect the least of the three oxide types studied. N2 anneals performed at 500° and 900°C, and H2 anneals performed at 500°C (all for 30 min) did not substantially reduce TBS instability. A 900°C anneal in H2 for 30 min did create a marked reduction in the TBS‐induced instability.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Cb X-ray effects
61.80.Fe Electron and positron radiation effects
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

New e‐beam‐defined memory structures

M. R. Oliver, H. D. Mercer, R. H. Havemann, R. J. Stein, R. K. Hester, T. G. Blocker, and R. L. Easley

J. Vac. Sci. Technol. 16, 1662 (1979); http://dx.doi.org/10.1116/1.570266 (3 pages)

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High density CCD memory structures often employ a SPS (serial–parallel–serial) structure. However, for two‐phase CCD’s a standard SPS array does not optimize storage well size for a given area per bit. Two structures that have an optimized well size have been conceived. Both take advantage of the fact that the optimum two‐phase CCD cell (two barriers, two wells, and associated channel stop) is not square but rectangular. The exact aspect ratio is a function of the specific process design rules. Test structures of both concepts, called the SSPS (serpentine SPS) and the CSA (common serial array), have been fabricated using e‐beam lithography. The initial test structures area per cell are 28 and 32 μm2. The fabrication process, which has eight e‐beam lithography levels, is discussed. The CCD structure is built with an n‐type buried channel using two polysilicon levels. Ion implants define the barriers, wells, and channel stops in the array. Barriers and wells are self‐aligned to electrode edges, as are diode regions to gate edges. Polysilicon and aluminum levels are etched by plasma. The preparation of e‐beam alignment marks prior to device processing is discussed, and the extra steps required to maintain alignment mark integrity are described. The operation of the fabricated arrays is given and specific characteristics of clocking in the common serial array are presented. The advantages of these arrays for memory applications are summarized.
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41.75.Fr Electron and positron beams
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
07.68.+m Photography, photographic instruments; xerography
61.72.U- Doping and impurity implantation

High resolution bubble patterns obtained by electron image projection

T. W. Bril and J. T. Snijders

J. Vac. Sci. Technol. 16, 1665 (1979); http://dx.doi.org/10.1116/1.570267 (3 pages)

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The packing density in magnetic bubble circuits is increasing very rapidly. When the smallest dimensions in these circuits are 1 μm or less a successor for the optical lithography becomes necessary. For this purpose an electron image projector is a proper candidate. To study the reliability of the technique for making bubble patterns with this projector a single mask 8 kbit shift register has been realized. The NiFe elements are structured via a Ti lift‐off procedure and subsequent reactive sputter etching of the NiFe. The lift‐off technology is, among other things favorable owing to the slightly negative slope in the PMMA‐resist. A high sputter etch rate ratio between NiFe and Ti during the reactive sputter etching process makes a very thin Ti masking layer feasible. It is shown that bubble devices with smallest features of 1 μm can be made. Uniformity over 2 in. slices is good. Proximity effects are of minor importance.
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41.75.Fr Electron and positron beams
75.70.Kw Domain structure (including magnetic bubbles and vortices)
79.20.Kz Other electron-impact emission phenomena
81.05.Bx Metals, semimetals, and alloys

Abstract: Electron‐beam‐microfabricated GaAs flip‐flop circuit

F. S. Ozdemir, P. T. Greiling, B. N. Sun, R. F. Lohr, and C. F. Krummm

J. Vac. Sci. Technol. 16, 1668 (1979); http://dx.doi.org/10.1116/1.570268 (1 page)

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Abstract Unavailable
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85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Tv Field effect devices
41.75.Fr Electron and positron beams
61.72.U- Doping and impurity implantation

Hybrid e‐beam/deep UV exposure using portable conformable masking (PCM) technique

B. J. Lin and T. H. P. Chang

J. Vac. Sci. Technol. 16, 1669 (1979); http://dx.doi.org/10.1116/1.570269 (3 pages) | Cited 10 times

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A thin dichroic resist or an opaque metal is directly applied to a deep‐UV resist and is delineated with an e‐Beam exposure tool conventionally. This intimately contacted pattern now serves as a portable mask that can be carried with the wafer to a deep‐UV blanket exposure station for delineation of the deep‐UV resist to produce high aspect ratio images with controlled profiles. In particular, AZ1350J/PMMA and AZ1350J/aluminum/PMMA systems are discussed. Sample results showing submicrometer PMMA images in thicknesses ranging from 1.6 to 1.9 μm using a 0.2 μm thick AZ PCM and 0.3‐μm‐thick aluminum PCM are presented.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

Triple slit scheme for high current variable‐shaped beam forming

Masanori Idesawa, Eiichi Goto, Takashi Soma, and Tateaki Sasaki

J. Vac. Sci. Technol. 16, 1672 (1979); http://dx.doi.org/10.1116/1.570270 (4 pages)

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Variable‐shaped beam schemes are very promising for advanced VLSI pattern generation. Some of them are made up of two beam shaping apertures, beam shaping deflectors, and projection lenses. In such devices, exposure speed is proportional to the total beam current finally projected onto the target. When the beam current is increased in this scheme, beam blurring caused by space charge effect becomes greater as the beam current increases. The observed beam blurring becomes much greater on the edges corresponding to the sides of the first beam shaping aperture than on those of the second one. A new beam shaping scheme is proposed for reducing this blurring. In this scheme, auxiliary beam shaping means are provided in the upper stream of the previously developed beam shaping system. The beam is preshaped by the new scheme so as to reduce the beam current between the first and the second beam shaping apertures by an amount which is the sum of the finally required and marginal portions, and a clearer beam shape can be formed on the target. Furthermore, to shorten the path length of electrons for reducing the above blurring, a construction method for an octupole electrostatic deflector is developed. In this method, newly designed isolating and supporting mechanisms for electrodes are adopted so as to minimize the size of the deflectors, which are sufficiently minute to be placed in the electron lens and to shorten the path length of electorn beam.
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41.75.Fr Electron and positron beams
07.77.-n Atomic, molecular, and charged-particle sources and detectors
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Boersch effect in electron‐optical instruments

W. Knauer

J. Vac. Sci. Technol. 16, 1676 (1979); http://dx.doi.org/10.1116/1.570271 (4 pages) | Cited 2 times

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This paper analyzes energy broadening in electron and ion beam. Unlike earlier treatments, the present theory takes into consideration thermal and crossover motions jointly, and it includes changes in relative transverse motion where beams converge or diverge. Expressions are presented for energy broadening in cylindrical beams, diverging beams, and beam crossovers. Calculated broadening levels are compared with experimental values given in the literature. Application of the analysis to electron‐beam configurations in which chromatic aberrations predominate leads to relations for the maximum current density as a function of spot size. It is shown that, for field‐emitting sources, which are imaged into the target, the peak current density is independent of spot size, while, for aperture imaging columns, the maximum current density varies inversely with spot edge resolution.
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41.75.Fr Electron and positron beams
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
42.15.Fr Aberrations

Electron‐beam broadening effects caused by discreteness of space charge

T. Groves, D. L. Hammond, and H. Kuo

J. Vac. Sci. Technol. 16, 1680 (1979); http://dx.doi.org/10.1116/1.570272 (6 pages) | Cited 13 times

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The importance of mutual repulsion of beam electrons is investigated for conditions relevant to electron beam lithography. A Monte Carlo calculation has been performed which evaluates the spot size for a given beam current and column geometry. The results show that the beam broadening due to mutual repulsion significantly limits the current density obtainable. Experimental results are presented, and the agreement with theory is excellent. For a column 21.5 cm long operating with a 3 mrad aperture semi‐angle, the spot size was measured as .14 μm at 100 nA, and .30 μm at 1 μA of beam current. The theory predicts that an optimum spot size exists that is proportional to the 1/4 power of the lens spherical aberration coefficient, and to the 3/4 power of the beam current.
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41.75.Fr Electron and positron beams
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
02.50.Ng Distribution theory and Monte Carlo studies

Optimization of electron probe forming systems with respect to aberrations and vertical beam landing

Dieter P. Kern

J. Vac. Sci. Technol. 16, 1686 (1979); http://dx.doi.org/10.1116/1.570273 (6 pages)

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A systematic presentation of aberrations in probe forming systems with rotationally invariant focusing and deflection fields is given, and the effect of these aberrations on the intensity distribution in the final sopt is investigated using wave‐optical and geometrical‐optical methods. The functional principle of methods for minimizing aberrations as well as their practical application to typical configurations like single post‐lense deflection, double pre‐lens deflection and Moving Objective Lens (MOL) is presented. Finally the trade‐off between minimization of aberrations and reduction of the landing angle of the beam is shown in a configuration combining pre‐ and post‐lens deflection.
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41.75.Fr Electron and positron beams
42.15.Fr Aberrations
02.30.Xx Calculus of variations
02.30.Yy Control theory

Köhler illumination and brightness measurement with lanthanum hexaboride cathodes

Alec N. Broers

J. Vac. Sci. Technol. 16, 1692 (1979); http://dx.doi.org/10.1116/1.570274 (7 pages) | Cited 2 times

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An aperture illumination system such as a Köhler system offers the ability to illuminate an electron probe system with the peak brightness from an electron source. It also provides an object with an ideal step‐function current distribution. This paper describes results obtained using Köhler illumination on a short focal length final lens SEM. Application of the SEM to brightness measurement is discussed at some length. Examples of overall probe performance for scanning transmission electron microscopy, low‐loss surface microscopy, and microfabrication are also given.
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41.75.Fr Electron and positron beams
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
29.25.Bx Electron sources

Application of a thermal field emission source for high resolution, high current e‐beam microprobes

D. Tuggle, L. W. Swanson, and J. Orloff

J. Vac. Sci. Technol. 16, 1699 (1979); http://dx.doi.org/10.1116/1.570275 (5 pages) | Cited 4 times

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A thermal field emission electron source has been incorporated into a microprobe with two magnetic lenses to produce a 0.10 μm beam spot with 0.11 μA current at 12 kV and a working distance of 13 cm, in agreement with calculated performance assuming a source angular intensity of 1 mA sr−1. The power density and brightness of the beam on the target were 1.6×107 W cm−2 and 5.5×107 A cm−2 sr−1 respectively. The emitter used was 〈100〉 oriented W coated with Zr, operated at 1800 K. Probe current fluctuations (〈ΔI2〉)1/2/IP =0.23% in the frequency interval 1–5000 Hz were measured at the target with I=30 nA. The microprobe was used to construct a scanning Auger microscope which produced submicron resolution Auger elemental maps with scan times of 5 min or less.
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41.75.Fr Electron and positron beams
79.70.+q Field emission, ionization, evaporation, and desorption
79.40.+z Thermionic emission
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Operational experience with zirconiated T–F emitters

J. E. Wolfe

J. Vac. Sci. Technol. 16, 1704 (1979); http://dx.doi.org/10.1116/1.570276 (5 pages) | Cited 4 times

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Additional experience with this type of cathode has added considerable knowledge relative to its characteristics since a report was given by Swanson in 1975 at this conference. The beam current stability is better than ±0.5% at pressures in the region of 10−8 Torr. The source brightness is 109 A/cm2/sr. The operating point is typically 107 V/cm electric field, 1800 K and 105A/cm2. Life tests have indicated life times of 5000 h or greater may be expected at the above operating point and 10−8 Torr vacuum. The virtual source size for our geometry and operating point has been calculated and measured at about 100 Å for an acceptance half angle of 0.015 rad. The zirconiated cathode is also highly recommended for thermionic and Schottky aided thermionic applications. It is more stable and longer lived than LaB6.
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79.70.+q Field emission, ionization, evaporation, and desorption
79.40.+z Thermionic emission
84.47.+w Vacuum tubes
41.75.Fr Electron and positron beams

Abstract: Electron cathode design using heat flow optimization

C. K. Crawford

J. Vac. Sci. Technol. 16, 1709 (1979); http://dx.doi.org/10.1116/1.570277 (1 page)

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Abstract Unavailable
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84.47.+w Vacuum tubes
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
07.50.-e Electrical and electronic instruments and components

Distortion correction and deflection calibration by means of laser interferometry in an electron‐beam exposure system

Shojiro Asai, Hiroyuki Inomata, Akira Yanagisawa, Eiji Takeda, Ichiro Miwa, and Minpei Fukinami

J. Vac. Sci. Technol. 16, 1710 (1979); http://dx.doi.org/10.1116/1.570278 (5 pages) | Cited 1 time

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In order to assure accuracy in an electron‐beam exposure system, it is necessary to correct for deflection distortion relative to the standard axes of the system. Distortion up to the third order is measured and corrected on‐line in a vector‐scan system, which uses a laser interferometry positioned stage, a fiducial mark, and a digital–analog correction circuit. The programmed precedure involves moving the stage to positions which form 5×5 or 9×9 lattice points in a region about 2 mm square. At each stage position, the beam is scanned to find the fiducial mark at a position in the scan field, by detecting backscattered electrons. Mark searching is done twice at each position, with two, predetermined, linearly independent settings of the correction circuit. A set of linear equations is solved using the least‐square method, to find out the distortion coefficient as well as the correction setting to compensate for the distortion. The above routine takes about 2–3 min including the stage motion, mark search, and calculation. It has been proven that distortion can be corrected to within ±0.1 μm ensuring the field stitching accuracy. It has also turned out that this method is useful in investigating the nature of the deflection subsystem.
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41.75.Fr Electron and positron beams
07.07.Tw Servo and control equipment; robots
07.60.Ly Interferometers
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Resolution test specimen for evaluating the performance of electron deflection systems

G. Owen

J. Vac. Sci. Technol. 16, 1715 (1979); http://dx.doi.org/10.1116/1.570279 (4 pages)

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A resolution test pattern is described which was developed to evaluate the performance of a large field deflection system incorporating dynamic astigmatism correction. The spot diameters of interest ranged from 1 to 10 μm and a convenient, rapid, repeatable measurement method was required. A further requirement was that the test specimen should respond to an astigmatic spot, and give a clear indication of the magnitude and direction of the astigmatism, so that stigmator corrections could be quickly determined. Because of these requirements conventional test specimens such as metallic grids could not be used, and so a special test specimen was designed. This consists of a series of concentric octagonal gold rings, fabricated on a silicon substrate. The width of the rings varies uniformly from 0.9 to 7.0 μm, and the diameter of the complete test specimen is 140 μm. Three principal applications have been investigated. Firstly, the magnitude and direction of deflection astigmatism have been measured by raster scanning the tangential and saggital line foci over the test specimen. Secondly, spot diameters habe been estimated by raster scanning over the test specimen, and noting the radius of the octagon at which contrast reversal occurs: this is dependent on the spot diameter. Thirdly, to make quantitative spot diameter measurements, the test specimen has been scanned in a line and the resulting video signal displayed as an ’’A’’ trace on an oscilloscope: modulation of the waveform is a measure of the diameter of the spot in the direction of scanned line.
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41.75.Fr Electron and positron beams
07.07.-a General equipment
42.30.-d Imaging and optical processing
42.15.Fr Aberrations

Low profile electron collector system

M. J. Penberth and B. A. Wallman

J. Vac. Sci. Technol. 16, 1719 (1979); http://dx.doi.org/10.1116/1.570280 (4 pages) | Cited 1 time

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The design of the exposure region of an Electron‐Beam Microfabrication System is usually a compromise between beam formation, deflection, and registration signal collection. In systems where a post final lens deflection assembly is used, this region is inevitably restricted in space and access for signal collection becomes difficult. Annular planar detectors of the silicon semiconductor diode type have been used in these situations but are restricted in their range of electron energy response and noise performance. An attractive alternative is the channel plate electron multiplier which can be configured into a compact annular assembly with low profile (6 mm). Additionally, it is sensitive to low energy secondary, and high energy backscattered electrons and can be made selectively sensitive to the higher energy electrons alone by suitable biasing. In the design implementation described, an annular channel plate is provided with a signal collection plate and electronic drive scheme to decouple the output signal from the relative high bias potential needed on the plate. The system has proved useful in viewing a variety of registration features in the EBMF 2 Microfabricator ranging from high contrast metallic marks used in drift correction to low contrast etch pits in silicon covered with electron resist for direct slice writing.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
84.47.+w Vacuum tubes

Accuracy requirements for adjusting variable‐shaped beam systems for the production of submicron patterns

H. J. Binder and P. Hahmann

J. Vac. Sci. Technol. 16, 1723 (1979); http://dx.doi.org/10.1116/1.570281 (3 pages) | Cited 1 time

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This paper deals mainly with accuracy requirements for adjusting the probe format in the variable shaped beam exposure system ZBA 10. The calibration of the probe format has to be performed in four steps: adjustment of the diaphragm edges with respect to parallelism and orthogonality, alignment of the coordinate system fixed by the diaphragm edges relative to the probe; deflection directions on the object; and calibration of the probe size. The admissible tolerance for each of the format setting parameters is smaller than 30 nm. This order of magnitude of the deviations can be measured and corrected by means of the highly magnifying projection system and the special probe format calibration program.
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41.75.Fr Electron and positron beams
07.07.Tw Servo and control equipment; robots
07.60.Ly Interferometers
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Proximity effect dependence on substrate material

Nao‐aki Aizaki

J. Vac. Sci. Technol. 16, 1726 (1979); http://dx.doi.org/10.1116/1.570282 (8 pages) | Cited 7 times

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The dependence of the proximity effect, which deforms electron‐beam exposed patterns, on the substrate material has been investigated theoretically and experimentally. Substrates examined are Si, SiO2, Cr, Mo, Au and their double layers, which are used in LSI fabrication process with a direct writing technique. The proximity effect is approximated as the sum of absorbed energy distributions in a resist layer, which are calculated separately with respect to electron re‐incidence number (Ns) from substrate into resist. A Monte Carlo simulation for electron scattering trajectories was used to obtain the spatial distributions of absorbed energy in a resist. The incident beam extent influence was examined. A new evaluation technique was used to obtain the exposed intensity distributions. The absorbed energy distributions, constituting the modeled proximity effect, are in good agreement with experimental results. The absorbed energy distribution for Ns=0 with a Gaussian incident beam is approximated by the function Coexp(−r/σ0). The distribution for Ns?1, expected in the case of a high atomic weight substrate, is approximated by the function Csubexp(−r/σsub).
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41.75.Fr Electron and positron beams
79.20.Kz Other electron-impact emission phenomena
07.68.+m Photography, photographic instruments; xerography

Experimental and theoretical study of cross‐sectional profiles of resist patterns in electron‐beam lithography

K. Murata, E. Nomura, K. Nagami, T. Kato, and H. Nakata

J. Vac. Sci. Technol. 16, 1734 (1979); http://dx.doi.org/10.1116/1.570283 (5 pages) | Cited 5 times

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Experimental and theoretical study was carried out on cross sectional profiles of resist patterns for line and area exposures. Experimental work was performed using an electron beam exposure system, where a PMMA film of 6000 Å thickness was used as an electron resist and the incident electron energy was 20 keV. The electron‐beam probe size was measured from a line spectrum of the secondary electron signal when the probe was scanned over a fine gold wire. The diameter of the probe was 5500 Å. The developer was a 1:1 solution of MIBK and IPA. The time evolution of the cross sectional profile was obtained from the SEM observation at various development times. Theoretical evaluation of the time evolution was conducted by a combination of Monte Carlo calculation of electron scattering and a well‐known equation for the solubility rate. Monte Carlo calculation was performed with a new model based on the Spencer and Fano theory for electron energy loss. For assumed parameters in the solubility rate equation a reasonable agreement between experiment and theory was obtained in the results of the time evolution of the cross sectional profiles. Also a difference between the Monte Carlo results through use of new and old models is discussed for a typical case of an exposure pattern.
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41.75.Fr Electron and positron beams
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
34.80.-i Electron and positron scattering
07.68.+m Photography, photographic instruments; xerography

Monte‐Carlo calculations of backscattered electrons at registration marks

D. Stephani

J. Vac. Sci. Technol. 16, 1739 (1979); http://dx.doi.org/10.1116/1.570284 (4 pages) | Cited 3 times

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Using the Monte–Carlo model given by Kyser and Murata image formation by backscattered electrons of three types of registration marks has been simulated. The marks considered consist of surface transitions in a silicon substrate, i.e., a step of 1 μm, a groove with vertical walls of 1 μm depth and 2 μm width and the inversion a bar of the same size with vertical walls. The primary electron beam was assumed to have an energy of 20 keV and a Gaussian distribution with FWHM of 0.1 μm. It has been found from the calculations, that the image of the three marks is primarily formed by the changing number of backscattered electrons. The contribution of the changing exit energy is of negligible influence. The contrast obtained in the image of the three marks decreases with increasing take off angle of the backscattered electrons. Furthermore, it is shown that a summing signal is superior to any difference signal, both derived with respect to the azimuthal angle.
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85.30.-z Semiconductor devices
79.20.Kz Other electron-impact emission phenomena
81.65.-b Surface treatments
02.50.Ng Distribution theory and Monte Carlo studies

High resolution electron‐beam lithography on thin films

I. Adesida, T. E. Everhart, and R. Shimizu

J. Vac. Sci. Technol. 16, 1743 (1979); http://dx.doi.org/10.1116/1.570285 (6 pages) | Cited 8 times

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The influence of electron scattering on the resolution of electron‐beam lithography has been studied. Theoretically, we have used two different Monte‐Carlo approaches to study the spatial extent of energy dissipation in a thin film of electron sensitive polymer film coated on various thicknesses of silicon substrates. The two Monte‐Carlo approaches are the conventional continuous‐slowing‐down approximation approach and the direct simulation approach in which individual inelastic scattering is taken into account. Experimentally, we have exposed lithographic patterns on the structures mentioned above. Agreement between both Monte‐Carlo approaches and experiment is satisfactory. Results show that higher resolution in electron beam lithography can be achieved by using thin electron sensitive resist layers and thin substrates. Improvement in proximity effect is also obtained for thin structures.
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81.65.-b Surface treatments
79.20.Kz Other electron-impact emission phenomena
02.50.Ng Distribution theory and Monte Carlo studies

Impact of electron scattering on linewidth control in electron‐beam lithography

J. S. Greeneich

J. Vac. Sci. Technol. 16, 1749 (1979); http://dx.doi.org/10.1116/1.570286 (5 pages) | Cited 4 times

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The importance of electron‐scattering on pattern fidelity in electron‐beam lithography is examined using computer simulation of the exposure and development of resist images. It is found that electron scattering can be treated in terms of an effective Gaussian half‐width which is the quadrature sum of the incident Gaussian half‐width and the characteristic width for forward‐scattered electrons. Linewidth control is improved by reducing the effective half‐width; this is accomplished by using higher beam energies, thinner resists and smaller spot sizes. Developer simulation shows that using 2 pixels per minimum linewidth with a spot size equal to half the pixel size gives better developed images than the more conventional writing strategy which uses four pixels per minimum linewidth and a spot size equal to the pixel size.
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81.65.-b Surface treatments
79.20.Kz Other electron-impact emission phenomena
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities
07.68.+m Photography, photographic instruments; xerography

Line profiles in thick electron resist layers and proximity effect correction

J. C. H. Phang and H. Ahmed

J. Vac. Sci. Technol. 16, 1754 (1979); http://dx.doi.org/10.1116/1.570287 (5 pages) | Cited 5 times

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A theoretical and experimental investigation of the developed profile shape in thick resist layers is described. The profiles that are exposed by a single line scan at various incident doses and by two adjacent scans with increasing separations between the scans are compared with a threshold solubility model and a development model. Near the neck of the profiles, the predictions of the theoretical models are in good agreement with experiments. In the resist substrate interface regions, the development model is satisfactory but the threshold solubility model is found to be inadequate. A proximity effect correction method is also described in which the edge of the exposed pattern is monitored to obtain accurate pattern fidelity. Experimental results using this method of correction are presented.
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81.65.-b Surface treatments
79.20.Kz Other electron-impact emission phenomena
02.50.Ng Distribution theory and Monte Carlo studies

Voltage dependence of proximity effects in electron beam lithography

D. F. Kyser and C. H. Ting

J. Vac. Sci. Technol. 16, 1759 (1979); http://dx.doi.org/10.1116/1.570288 (5 pages) | Cited 5 times

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Intra line and inter line proximity effects and their dependence on beam voltage are explored via computer simulation of electron scattering, energy deposition, and subsequent development in electron‐beam lithography processes. For thin resist films (?1 μm) on silicon substrates,the simulation predicts that smaller linewidths and gaps can be achieved without proximity correction at 10 kV, compared to 20 kV. Experimental confirmation of the predictions is presented.
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81.65.-b Surface treatments
79.20.Kz Other electron-impact emission phenomena
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities
02.50.Ng Distribution theory and Monte Carlo studies

Fast computation method for exposure intensity and pattern correction in electron‐beam lithography

Atsushi Kikuchi, Akio Kanamaru, Nobumichi Okazaki, Yasuaki Nakane, and Kunihiko Tsuboi

J. Vac. Sci. Technol. 16, 1764 (1979); http://dx.doi.org/10.1116/1.570289 (3 pages)

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A fast computation method to correct for the proximity effect in electron‐beam lithography is studied for practical uses. Formerly, to compute the proximity effect a double integral of two Gaussian distribution functions was applied. To save computation time and memory size, a simplified computation using the error function is discussed. In this solution the proximity effect correction is determined by two real multiplications, four subtractions and one addition. Not only beam intensity but also a pattern element size is considered in every pattern. A large pattern is divided into small sections. In this method, the computation time is proportional to the number of elements. It takes 105 minutes to compute 10 000 test pattern elements with a minicomputer. The experiment proves that the corrected pattern can be exposed as designed. This procedure has proven effective to design VLSI by using a minicomputer.
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81.65.-b Surface treatments
79.20.Kz Other electron-impact emission phenomena
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Modeling ion milling

A. R. Neureuther, C. Y. Liu, and C. H. Ting

J. Vac. Sci. Technol. 16, 1767 (1979); http://dx.doi.org/10.1116/1.570290 (5 pages) | Cited 13 times

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A string segment motion algorithm is presented and used in conjunction with SEM observation of line edge profiles to study phenomena in ion milling which result from the angular dependence of etch rates. The algorithm allows samples to be rotated and includes shadowing, automatic faceting,and special boundary conditions at interior and exterior corners. The accuracy of the algorithm is demonstrated by comparison with known mathematical results. Simulation is used to study how the shape of the angular etch rate curve and the modification of the local etch rate at corners affect the line edge profiles. Comparisons with experimental results are made to check the algorithm assumptions and applicability. The comparisons include preferentially etched Si, a soft Au mask on a hard NiFe substrate and a hard Ti mask on a soft Au substrate.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
02.60.Cb Numerical simulation; solution of equations

Simulation of dry etched line edge profiles

John L. Reynolds, Andrew R. Neureuther, and William G. Oldham

J. Vac. Sci. Technol. 16, 1772 (1979); http://dx.doi.org/10.1116/1.570291 (4 pages) | Cited 6 times

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Computer simulation of dry etching is used to explore line edge profiles obtained in IC processing. The model divides the process into isotropic or chemically reactive etching and directional or ion illuminated etching. The algorithm simulates the time evolution of the two dimensional profile by advancing nodes on a string according to the local anisotropic and isotropic rates. The accuracy of the model and its applicability to IC processing are illustrated through comparison with known mathematical cases and experimental results. Experiment and simulation are used to explore the residue left at a step with anisotropic etching and the amount of under cut necessary in producing stepped arsenic implanted polysilicon layers.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.90.+z Other topics in physics of plasmas and electric discharges (restricted to new topics in section 52)

Cumms 11: An electron‐beam‐fabricating machine with accurate registration for direct fabrication and mask making

G. A. C. Jones and H. Ahmed

J. Vac. Sci. Technol. 16, 1776 (1979); http://dx.doi.org/10.1116/1.570292 (4 pages) | Cited 2 times

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A scanning electron‐beam lithograph machine (CUMMS 11) is described, which utilizes a novel back wafer registration technique (BWR). The registration method uses two axially coincident electron beams—one of which addresses the back of the wafer and is used for registration, the other addresses the top chip surface and is used for pattern writing. By reading a matrix array of BWR marks the system recognizes wafer distortions and provides compensation in subsequent pattern writing. An extension of this process allows stitching of subfields for writing large area chips. Since the system is symmetrical with the writing and registration occurrring on the same axis, temperature drifts are insignificant. Also several electronic drifts are self‐compensating. Also several electronic drifts are self‐compensating. The BWR method is ideally suited to use with shaped electron beam writing optics and may also be used for registration in ion‐beam writing or selected area electron‐beam annealing systems.
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07.68.+m Photography, photographic instruments; xerography
41.75.Fr Electron and positron beams
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Variable spot‐shaped e‐beam lithographic tool

E. V. Weber and R. D. Moore

J. Vac. Sci. Technol. 16, 1780 (1979); http://dx.doi.org/10.1116/1.570293 (3 pages) | Cited 1 time

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The EL2 system was developed as a direct wafer writing e beam tool to be used for product and process development. EL2 is a high thruput, high resolution, fully automated tool that utilizes the variable spot shape technique as well as other design innovations. This paper will review the system architecture, design approach, system specifications, and results obtained with this system. The systems utilize a variable spot shaped column with a maximum spot size ranging from 2×2 μm to 4×4 μm adjustable in increments of 0.1 and 0.2 μm, respectively. Gun brightness and column alignment are maintained by a group of servos which maintain proper operating conditions. The spot is positioned via a raster deflection which can be up to 8 mm. A calibration technique is employed to insure deflection accuracy over long time periods. Overlay is achieved by scanning alignment marks in the four corners of fields and processing the backscattered electron signals to determine field adjustments. EL2 is capable of exposing over 10 wafers (2.25 in) per hour with 1.25‐μm linewidths and 0.3‐μm overlay (30). This is accomplished with 10‐μC resist sensitivity and machine availability of about 80%.
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07.68.+m Photography, photographic instruments; xerography
41.75.Fr Electron and positron beams
07.07.Tw Servo and control equipment; robots

Variable spot shape control electronics

O. C. Woodard, C. T. Ho, M. S. Michail, A. W. Muir, and M. C. Williams

J. Vac. Sci. Technol. 16, 1783 (1979); http://dx.doi.org/10.1116/1.570294 (4 pages)

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The electronics, calibration, and registration techniques required to dynamically control electron beam spot size, position, and blanking on a spot‐by‐spot basis to write and overlay integrated circuit patterns are described in this paper. Pattern data which has been converted from a graphic language format to a compressed raster format is supplied to the Digital Control Unit (DCU) where it is expanded to provide control data at a 460 per spot rate to the Analog unit. The analog unit provides deflection voltages to the electron beam column which control retangular spot size and position to a resolution of 0.125 μm in X and Y over an 8 mm field, or 0.0625 μm over a 4 mm field. Pattern accuracy is assured by an automated deflection calibration system. A calibration grid placed underneath the beam is scanned using the same beam deflection pattern and field as that used for writing. Backscatter electrons from the grid are detected and the resultant signal processed to determine the deflection error at 900 points over the field. Corrections are applied to the deflection and the grid is rescanned. This process is repeated until the errors are within specified limits. Overlay of patterns is assured by registering to fiducial marks incorporated into the pattern to be overlayed. Four marks, one in each corner of the pattern, are scanned prior to writing. The resulting backscatter electron signals are processed to determine the errors in the four corners of the field. Corrections are claculated and applied as the pattern is written. Calibration techniques, registration techniques, and circuit performance criteria required to achieve 0.6 um pattern overlay over an 8 mm field are presented.
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07.68.+m Photography, photographic instruments; xerography
41.75.Fr Electron and positron beams
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
07.07.Tw Servo and control equipment; robots

High‐speed, low‐overhead electron beam direct slice writing system

G.L. Varnell, D. F. Spicer, J. Hebley, R. Robbins, C. Carpenter, and M. Malone

J. Vac. Sci. Technol. 16, 1787 (1979); http://dx.doi.org/10.1116/1.570295 (7 pages) | Cited 1 time

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Electron beam writing systems have been primarily used for photomask and reticle fabrication because of the limited throughput ahievable. A vector‐scan beam writing system (EBSP) has been developed with a 1–1.25 μm resolution capability and ±0.25 μm pattern overlay accuracy and a potential throughput capability of 14 3‐in. slices/h for 1–1.25 μm minimum pattern geometries and 20 3‐in. slices/h for 2.5 μm minimum pattern geometries. This paper discusses the throughput factors for vector‐scan e‐beam systems and describes the new developments and improvements to tne major subsystems of the earlier photomask machine (EBM II) which were necessary to achieve this order of magnitude improvement in throughput.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
07.07.Tw Servo and control equipment; robots

High speed electron optics for direct slice writing

H.T. Pearce‐Percy, D.F. Spicer, M. Abbot, C. Winborn, and G.L. Varnell

J. Vac. Sci. Technol. 16, 1794 (1979); http://dx.doi.org/10.1116/1.570296 (6 pages) | Cited 1 time

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A high throughput vector‐scan direct slice writing electron beam lithography machine has been developed. This paper describes the electron optical and the deflection amplifier designs. A double deflection system was chosen because it had high deflection sensitivity, possessed a true pivot point, and the beam remained close to the axis. The design of the deflection and lens system was accomplished using specially developed computer programs. The deflection amplifier and coil system was optimized to give a flat frequency response to 10 MHz. Careful choice of materials eliminated eddy current effects. The system can draw 1.25 μm lines across a 6.35 mm square field. Distortion after correction is typically ±3 μm over the same field.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Multifunction computer configuration for microlithography

J.C. Potosky and J.P. Reekstin

J. Vac. Sci. Technol. 16, 1800 (1979); http://dx.doi.org/10.1116/1.570297 (3 pages)

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A multiple function, multiple processor computer system has been implemented as the basis for the electron beam microfabrication facility at Rockwell International’s Electronics Research Center. The configuration of a master mini‐mainframe interfaced to several satellite miniprocessors provides for the simultaneous operation of two Electron‐Beam Microfabricators, pattern data format conversion, graphical pattern editing, and conntinued software development. Expansion of the facility with additional microfabricators requires only a buss interface and a low level 16 bit processor. At present, the system consists of a Digital Equipment Corporation PDP 11/35 CPU which acts as the master processor. PDP 11/34’s act as satellites controlling the microfabricators. An RSX–11M operating system is used with DECNET in the foreground. Microfabricator control programs and pattern data are loaded down to the satellite processors from disk storage on the master computer. Pattern data is manipulated via programs residing in the background. Software development also takes place in the background and is accessed from a remote terminal. Additional peripherals include nine track magnetic tape, paper tape, and large screen graphic display CRT’s.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Data compaction and vector scan e‐beam system performance improvement using a novel algorithm for recognition of pattern step and repeats

W.D. Grobman and T.W. Studwell

J. Vac. Sci. Technol. 16, 1803 (1979); http://dx.doi.org/10.1116/1.570298 (6 pages)

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Many classes of circuit pattern designs contain regular repeats of individual shapes. However, design manipulations (such as personalization), or electron‐beam postprocessor functions (such as partitioning and dose assignment for proximity effect correction, overlap elimination, etc.) often destroy some of the pattern regularity, leaving smaller repetitive subpatterns. We describe a novel heuristic for efficiently ’’recognizing’’ these pattern repetitions at the end of design and postprocessing. Consequently, one can achieve pattern data compaction by large factors, using a hardware step‐and‐repeat function of the vector scan pattern generator, which is discussed in detail. In order for the step‐and‐repeat recognition and compaction to be useful, this pattern recognition problem must be solved by a very efficient algorithm, due to the large number of shapes involved. We have developed an algorithm which requires an amount of CPU time which is only linear in the number of shapes in the design, requiring less than one ms/shape on an IBM model 168 computer. We will describe the algorithm in detail and demonstrate its ability to economically compact data sets for LSI by up to an order of magnitude or more.
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07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities
29.27.-a Beams in particle accelerators
07.68.+m Photography, photographic instruments; xerography

Data compaction method for raster–scan exposure system

Masahiko Sumi, Fumitaka Chiba, and Masaharu Ninomiya

J. Vac. Sci. Technol. 16, 1809 (1979); http://dx.doi.org/10.1116/1.570299 (5 pages)

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A data compaction method and a data processing system developed for raster–scan exposure system are presented. The purpose of the method is to enhance flexibility in pattern size and to increase writing speed of a raster–scan system. The data format for compaction and the data transmission scheme are given. The encoding and decoding procedures are described. Data quantity of advanced LSI patterns is examined and it is shown that data compaction ratio of 1/7 to 1/70 is attained. Writing speed of 40 MHz is also achieved. By this method, reticle pattern as large as 105×105 dots and composite patterns are successfully delineated.
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07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation
07.07.Tw Servo and control equipment; robots
07.68.+m Photography, photographic instruments; xerography
41.75.Fr Electron and positron beams

Abstract: Reticle generation by electron‐beam lithography

D. W. Berrian, J. A. Doherty, and E. C. Horvath

J. Vac. Sci. Technol. 16, 1814 (1979); http://dx.doi.org/10.1116/1.570300 (1 page)

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Abstract Unavailable
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
07.05.-t Computers in experimental physics

Advances in high precision sample positioning stages for electron‐beam microfabrication and metrology

J. Pasiecznik, J.W. Reeds, and R.D. Fralick

J. Vac. Sci. Technol. 16, 1815 (1979); http://dx.doi.org/10.1116/1.570301 (4 pages)

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An improved computer controlled X–Y stage has been built for electron‐beam microfabrication and metrology. The stage servo drives and the laser stage position sensors are mounted directly to the stage vacuum chamber to provide maximum rigidity. An ’’L’’ shaped chromium carbide mirror provides a reference with 1/4 arc‐s accuracy for the stage position sensing laser, while allowing the sample to be in the plane of the laser beams to eliminate position sensing errors due to pitch and yaw of the stage. A reference chip is mounted on the stage in the plane of the sample to aid in initial focus and registration. For precision manual control of the stage a digital joystick is used. Nonlinear shaping networks on a standard linear taper joystick enable the operator to easily position the stage to 0.01 μm and still be able to move at full slew speed (1 cm/s). For each axis, V–F converters are used to convert the analog output of the shaping network to a digital pulse train which feeds a 24 bit closed loop servosystem. A digital tach is used for damping. Rate feedback is derived from the laser interferometer system rather than the conventional generator coupled to the servomotor. High torque motors are used for improved acceleration and dynamic braking. Servomotor‐to‐stage‐drive coupling incorporates a friction lead screw to eliminate backlash. Under computer control, repeatability of positioning has been determined to be 0.01 μm. Accuracy is 0.01 μm/cm plus 0.005 μm/cm of stage travel (laser interferometer error).
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07.07.Tw Servo and control equipment; robots
41.75.Fr Electron and positron beams
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
42.62.-b Laser applications

Vibration analysis using the stripe scan method of a laser interferometer controlled X–Y table in an electron‐beam system

A.D. Wilson and T. Studwell

J. Vac. Sci. Technol. 16, 1819 (1979); http://dx.doi.org/10.1116/1.570302 (5 pages)

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The writing time of an electron‐beam lithography system can be reduced by compensating for table vibrations and other position errors using error feedback from a laser intererometer to the electron beam. The beam may then write while the table is moving because the laser interferometer corrects for vibration of the table and mirror system. However, this may not represent the substrate motion because of relative movement between mirror and substrate. A stripe scan technique is used to identify these problems and to evaluate the sample securing system. The amplitude and frequency of vibration are easily determined as well as the correct value of laser interferometer servofeedback gain.
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41.75.Fr Electron and positron beams
07.07.Tw Servo and control equipment; robots
42.62.-b Laser applications

Electron beam exposure system

Qiu Pei‐yong and Wang Jian‐kun

J. Vac. Sci. Technol. 16, 1824 (1979); http://dx.doi.org/10.1116/1.570303 (3 pages)

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An electron‐beam exposing system, utilizing a computer generated pattern and used for microcircuit fabrication of high packing density, is described.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities
42.62.-b Laser applications

Aligned multilayer structure generation by electron microprojection

J. Frosien, B. Lischke, and K. Anger

J. Vac. Sci. Technol. 16, 1827 (1979); http://dx.doi.org/10.1116/1.570304 (3 pages) | Cited 2 times

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Electron microprojection allows the fast transfer of structures with high resolution. Using a projector with a 1:4 image scale, a resolution of 0.3 μm across an 8×8 mm image field is experimentally obtained. The development of a novel alignment technique assures the superposition of several mask levels with an alignment accuracy better than 0.1 μm.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
81.65.-b Surface treatments

Developments in electron image projection

R. Ward

J. Vac. Sci. Technol. 16, 1830 (1979); http://dx.doi.org/10.1116/1.570305 (4 pages) | Cited 1 time

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Unity magnification electron image projection shows considerable promise in lithography of VLSI the developments discussed are an extension to the alignment system to correct magnification, an automatic alignment technique for magnetic bubble circuits and an improved electrostatic chuck.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography

Electron Beam Proximity Printing: Mask life investigations

H. Bohlen, J. Greschner, and P. Nehmiz

J. Vac. Sci. Technol. 16, 1834 (1979); http://dx.doi.org/10.1116/1.570306 (4 pages)

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Electron‐beam Step and Repeat Proximity Printing is a lithographic method for replicating repetitive mask patterns directly onto wafers. Shadow projection of the mask pattern using intense EB illumination gives very short exposure times. The self‐supporting masks have chip size, i.e., the masks have to sustain a great number of exposures to make the EB Proximity Printer an economic exposure tool.
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41.75.Fr Electron and positron beams
07.68.+m Photography, photographic instruments; xerography
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

Abstract: Pulsed electron‐beam processing of material surfaces

A. C. Greenwald, A. R. Kirkpatrick, R. G. Little, and J. A. Minnucci

J. Vac. Sci. Technol. 16, 1838 (1979); http://dx.doi.org/10.1116/1.570307 (2 pages)

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Abstract Unavailable
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41.75.Fr Electron and positron beams
61.72.U- Doping and impurity implantation
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.-a Thin film structure and morphology

Direct device fabrication by selected area e‐beam annealing

R. A. McMahon and H. Ahmed

J. Vac. Sci. Technol. 16, 1840 (1979); http://dx.doi.org/10.1116/1.570308 (3 pages) | Cited 6 times

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A flexible scanning electron‐beam system for annealing ion‐implanted semiconductors or partially processed devices, direct device fabrication, or other high flux thermal processing is described. A maximum beam current of 3 mA in a 40 μm spot is available at accelerating voltages of up to 30 kV. Microprocessor controlled scanning over a 10 mm square field is available in this system. Resistor structures and diode arrays fabricated by e‐beam annealing of ion‐implanted layers show an edge resolution of 40 μm between unannealed and annealed regions. The diodes have characteristics close to those predicted for ideal structures and may be fabricated in arrays to make integrated devices such as vidicon targets.
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41.75.Fr Electron and positron beams
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.80.Jh Ion radiation effects
07.07.Tw Servo and control equipment; robots

Scanning electron beam annealing with a modified SEM

K. N. Ratnakumar, R. F. W. Pease, D. J. Bartelink, and N. M. Johnson

J. Vac. Sci. Technol. 16, 1843 (1979); http://dx.doi.org/10.1116/1.570309 (4 pages) | Cited 3 times

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A commercial scanning electron microscope, modified for high current operation, has been successfully used to anneal arsenic implanted silicon. The measured parameters of the electron–beam are shown to fit a model for localized heating, taking into account source‐dispersal due to beam penetration, and to explain the experimentally observed window for annealing without melting. Recrystallization of the annealed layers is shown by the sharp electron‐channeling patterns obtained. Spreading‐resistance and junction depth measurements indicate complete electrical activation of the implanted species without any measurable redistribution. The potential for localized annealing through a finely focused scanning electron–beam is illustrated by the fabrication of conducting region of submicron dimensions surrounded by high resistivity amorphous silicon.
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41.75.Fr Electron and positron beams
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.72.U- Doping and impurity implantation
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Modeling of beam voltage effects in electron‐beam annealing

A. Neukermans and W. Saperstein

J. Vac. Sci. Technol. 16, 1847 (1979); http://dx.doi.org/10.1116/1.570310 (6 pages) | Cited 7 times

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Beam penetration effects can be important if accurate estimates are to be made of the temperature rise in electron beam annealing of silicon. This is because the electron penetration is typically much larger than the thickness of the layer to be annealed. Depth deposition curves and radial energy spread functions are calculated in silicon for beam energies of 5, 10, 15, 20, and 30 keV. Using the image method, the results are applied to calculate temperature profiles for planar beams of infinite extent and for finite beams with Gaussian cross section.
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41.75.Fr Electron and positron beams
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
44.30.+v Heat flow in porous media
02.50.Ng Distribution theory and Monte Carlo studies

Improvement of voltage contrast in the scanning electron probe by floating the ground level of a device

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

J. Vac. Sci. Technol. 16, 1853 (1979); http://dx.doi.org/10.1116/1.570311 (3 pages)

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A simple way to improve the voltage contrast in an SEM and its application are described. The electron beam probe is an effective medium for function testing and fault analysis of semiconductor devices. The voltage contrast is caused by the retarding fields above the specimen surfaces. It often happens, however, that good contrast cannot be obtained in the area of negative surface voltage of a semiconductor device, because of its narrow dynamic range. It is proposed that the voltage contrast for the negative voltage range of a device is improved by floating the ground level of the device above the ground level of the measurement system. The secondary electron signal in our SEM was entirely saturated. Adopting the floating method, the secondary electron signal becomes linear against the surface voltage down to −8 V. This effect is applied to the logic function test of a semiconductor device operating in both the positive and negative voltage ranges. Changes in voltage contrast image corresponding to the change of the logic function status are effectively extracted by a subtraction method.
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41.75.Fr Electron and positron beams
07.50.-e Electrical and electronic instruments and components
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
85.30.-z Semiconductor devices

Study on voltage contrast in SEM

Y. C. Lin and T. E. Everhart

J. Vac. Sci. Technol. 16, 1856 (1979); http://dx.doi.org/10.1116/1.570312 (5 pages) | Cited 3 times

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Voltage contrast in the SEM is a contactless technique for the study of potentials and potential distributions. Its applications include the examination of static and dynamic voltage signals on semiconductor devices, the direct observation of grain boundaries on polycrystalline semiconductors, and the detection of acoustic wave signals on a piezoelectric material. The quality of a recorded micrograph and the minimum detectable voltage are both limited by the noise level associated with the electron–beam and the detector system. In general, the electron–beam current must be increased to apoint at which the noise level in the collected signal is acceptable. A relationship between the minimum detectable voltage and the beam current has been established for any specific recording condition. The theory assumes a Maxwellian energy distribution of the secondary electrons. Furthermore, the collector system is assumed to act like a simple energy filter which accepts only secondary electrons having an energy higher than Ef. The theoretical results also indicate that the highest detection sensitivity can be achieved when the collector system is designed so tht Ef is around 2.6 eV for an ’’average’’ metal. A relationship between the electron beam current and the expanded SNR caused by a voltage difference has been obtained experimentally. There was a satisfactory agreement between theoretical predictions and experimental results. The experiment was conducted in an SEM which is equipped with a standard scintillator–photomultiplier detector.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.75.Fr Electron and positron beams
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
85.30.-z Semiconductor devices

Inspection of complete VLSI chips with a high resolution image recording system and large area SEM

V. R. M. Rao and W. C. Nixon

J. Vac. Sci. Technol. 16, 1861 (1979); http://dx.doi.org/10.1116/1.570313 (3 pages)

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This paper presents results that have been obtained from an electron‐beam recording system that has been coupled to a large area coverage SEM and used for the inspection of VLSI chips with areas up to 5×5 mm. The recording system is capable of copying 10 000×10 000 picture points over negative areas of 50×50 mm in 50 s. In order to utilize fully the resolution capability of the recording system the SEM must also have a similar performance. To this end and SEM with post‐final lens single deflection has been used to generate 10 000×10 000 picture point images of VLSI chips. These images have been copied onto photographic film using the scanning recording system. The advantages of the recording system lie in its ability to copy the images of complete chips with micron and submicron feature sizes directly onto photographic film in a single scan and in the relative ease with which the system can be linked to an SEM.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
41.75.Fr Electron and positron beams
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.68.+m Photography, photographic instruments; xerography

Emission characteristics of gallium and bismuth liquid metal field ion sources

L. W. Swanson, G. A. Schwind, A. E. Bell, and J. E. Brady

J. Vac. Sci. Technol. 16, 1864 (1979); http://dx.doi.org/10.1116/1.570314 (4 pages) | Cited 34 times

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Emission characteristics such as energy distribution, angular intensity distribution, noise current, and temperature effects have been measured and compared for liquid bismuth and liquid gallium ion sources. The full width half maximum (FWHM) at low currents (IT?1 μA) was ?4.5 eV for gallium at ?300 K and ?9 eV for bismuth at ∠600 K. For both gallium and bismuth the FWHM increased monotonically with current. Gallium beam angular intensity at IT?1 μA was 15 μA/sr increasing to ?65 μA/sr at 30 μA emission current while for bismuth the angular intensity increased from ? 12 μA/sr to ?35 μA/sr as the emission current increased from 1 μA to ∠30 μA. A large increase in beam angular divergence was observed as IT was increased over the range 1–30 μA for bismuth. An unusually low noise current almost entirely accounted for by shot noise was exhibited by both the bismuth and the gallium ion sources. These results point towards a strongly space charge limited emission process.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
79.70.+q Field emission, ionization, evaporation, and desorption

Abstract: Ionization mechanism of gallium on a tungsten field emitter

R. J. Culbertson, G. H. Robertson, and T. Sakurai

J. Vac. Sci. Technol. 16, 1868 (1979); http://dx.doi.org/10.1116/1.570315 (3 pages) | Cited 10 times

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Abstract Unavailable
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
79.70.+q Field emission, ionization, evaporation, and desorption
79.40.+z Thermionic emission

Liquid gold ion source

A. Wagner and T. M. Hall

J. Vac. Sci. Technol. 16, 1871 (1979); http://dx.doi.org/10.1116/1.570316 (4 pages) | Cited 37 times

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The fabrication procedure for a liquid gold ion source is described. The source consists of a tungsten needle wetted with liquid gold. Stable gold ion currents of 1 to 100 μA have been reliably obtained. Factors affecting the ion emission characteristics including needle geometry, surface structure, and temperature are discussed.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
79.70.+q Field emission, ionization, evaporation, and desorption
06.60.-c Laboratory procedures
07.30.-t Vacuum apparatus

H2 and rare gas field ion source with high angular current

Gary R. Hanson and Benjamin M. Siegel

J. Vac. Sci. Technol. 16, 1875 (1979); http://dx.doi.org/10.1116/1.570317 (4 pages) | Cited 10 times

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We have built and carried out initial tests on a field ion source that has been designed to operate at very low temperatures with a physisorbed surface supply to the ionization region. This mode has been found to give beams of high angular current density and is expected to have low energy spread in the beam. Presently we have measured dI/dΩ?10 to 60/sr with a probable energy spread of ?l eV. The UHV system allows processing of the field emitter under clean, high vacuum conditions. A liquid He cooled finger maintains the tip at controlled temperatures from that of liquid He to room temperature. The tip is mounted on a sapphire block to provide both excellent thermal conduction and electrical insulation to ?30 kV. Differential pumping allows a high supply pressure of H2, He, Ar, etc. in the region of the tip (≳ 10−2 Torr) and a low pressure in the rest of the system. Observation on the characteristics of the field ionization pattern are made under varying conditions of pressure, temperature, field and tip processing, and orientation by using a channel electron multiplier array and phosphor screen (CEMA). An alignable aperture defines the angular divergence.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
79.70.+q Field emission, ionization, evaporation, and desorption
07.30.-t Vacuum apparatus

Applications of a Kaufman ion source to low energy ion erosion studies

D. J. Sharp, J. K. G. Panitz, and D. M. Mattox

J. Vac. Sci. Technol. 16, 1879 (1979); http://dx.doi.org/10.1116/1.570318 (4 pages) | Cited 1 time

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The erosion of materials by low energy ions is of concern in fusion reactors since high Z impurities in the plasma cause radiation cooling. Ion bombardment of the fusion reactor chamber walls arises from ions of fuel (D, T) material, gaseous impurities (O, C), and impurities from eroded components (Fe, Co, Ni, C, Mo, etc.) being accelerated across the wall sheath potential (0.1 to 1 KeV). A Kaufman type ion source has been characterized for use with hydrogen, and subsequently used to determine the relative erosion rates of bulk Mo, C, Cu, coating of TiB2, B4C, Be, VBe12 and other materials. Ions of hydrogen (Z=1), argon (Z=18), and xenon (Z=54) at acceleration potentials of 250, 500, and 1000 V have been used to determine erosion yields.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
81.65.-b Surface treatments

Ion projection system for IC production

G. Stengl, R. Kaitna, H. Löschner, P. Wolf, and R. Sacher

J. Vac. Sci. Technol. 16, 1883 (1979); http://dx.doi.org/10.1116/1.570319 (3 pages) | Cited 6 times

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An ion projection system suitable for production of IC’s is described. Self‐supporting metal masks are imaged with a demagnification of 10 : 1 onto a wafer. The resolution of the system is below 1 μm. Direct structuring of oxide and metal layers without any resist, pattern transposition with thin inorganic resists (40 nm) into semiconductor layers and pattern generation in organic resists is described. Exposure times per chip in the order of magnitude of seconds for all these materials are achieved.
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
07.68.+m Photography, photographic instruments; xerography
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Reactive sputter etching and reactive ion milling—selectivity, dimensional control, and reduction of MOS–interface degradation

B. Meusemann

J. Vac. Sci. Technol. 16, 1886 (1979); http://dx.doi.org/10.1116/1.570320 (3 pages) | Cited 2 times

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Recent results on the application of reactive etching techniques in semiconductor device technology are reported. The two systems used are a rf diode system and a dc ion milling system both fed with Ar and various Freon‐type gases. The two processes are compared with regard to selectivity, dimensional control and edge profiles. Further results show that, if CF4 and CHF3 instead of Ar are applied in the etching processes, the redeposition of sputtered materials as well as the degradation of the MOS–interface properties can be largely reduced. From our experiments we conclude that neither reactive sputter etching nor dc reactive ion milling can be favored, their potentials however exceed tunnel reactor plasma etching as well as Ar sputter etching and Ar ion milling.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.65.-b Surface treatments
85.30.-z Semiconductor devices

Ion beam exposure characteristics of resists

T. M. Hall, A. Wagner, and L. F. Thompson

J. Vac. Sci. Technol. 16, 1889 (1979); http://dx.doi.org/10.1116/1.570321 (4 pages) | Cited 9 times

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The exposure characteristics of six polymer resists to 1.5 MeV H+, He+, and O+ ions and 20 keV electrons were measured. The deposited energy per unit volume required to expose a resist was found to vary by up to a factor of ten between electrons and O+ ions. A model was developed which accounts for the variation in terms of the energy distribution around the particle track in conjunction with whether the resist requires the activation of a single site or two adjacent sites to produce exposure.
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
07.68.+m Photography, photographic instruments; xerography
41.75.Fr Electron and positron beams

Considerations of ion channeling for semiconductor microstructure fabrication

D. R. Myers, R. G. Wilson, and J. Comas

J. Vac. Sci. Technol. 16, 1893 (1979); http://dx.doi.org/10.1116/1.570322 (4 pages) | Cited 3 times

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The performance of semiconductor devices becomes increasingly sensitive to details of the depth distribution of dopants as device dimensions are reduced. In this paper, limitations on the control of dopant distributions resulting from implantation into single‐crystal silicon due to ion channeling are examined for a range of ion atomic numbers and energies characteristic of semiconductor device fabrication. Implantation profiles were obtained by 1 MHz differential capacitance–voltage profiling and by secondary ion mass spectroscopy for silicon substrates implanted at angles from accurately channeled alignment to ’’random equivalent’’ orientation. The critical angle as calculated from an existing computer fit to the Moliere continuum potential was used to scale the angular dependence of the implantation profiles. Ion channeling is seen to have important consequences not only for the deeply penetrating regions of the dopant profile but for the near‐surface profile as well. The results of this study indicate that to minimize the extent of unintentional channeling, alignment of the ion beam to the nearest low‐index crystallographic direction must be at angles exceeding twice the critical angle and that the angle required can exceed the commonly used seven degree tilt angle, especially for ions of large atomic number at low energy.
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61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.U- Doping and impurity implantation
85.30.-z Semiconductor devices

Ion‐beam lithography for IC fabrication with submicrometer features

D. B. Rensch, R. L. Seliger, G. Csanky, R. D. Olney, and H. L. Stover

J. Vac. Sci. Technol. 16, 1897 (1979); http://dx.doi.org/10.1116/1.570323 (4 pages) | Cited 5 times

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We report an entirely new pattern‐replication technique for IC fabrication. It has demonstrated submicrometer (<0.5 μm) resolution and it has the capability of large throughput (wafer‐levels/h). It utilizes high‐energy protons as the exposing radiation through a mask placed in proximity to a wafer covered with resist. We call this new technique ’’ion‐beam lithography’’ (IBL). System parameters and measurements relevant to the use of IBL as a production technology are discussed and SEM micrographs of submicrometer patterns in PMMA are presented. The technique is similar to x‐ray lithography, in that a pattern is produced in a thin resist film after exposing it to radiation through a mask. High‐energy protons have the same advantage as x rays in eliminating wavelength diffraction problems which limit the resolution of photolithography. Also, a gap (∠15–25 μm) is permitted between the mask and wafer. Ions have an advantage over x rays in that penumbral distortion is avoided by using highly collimated ion beams which are available with present state of the art; ions are collimated using conventional ion‐optical techniques, whereas use of a distant ’’point’’ source is the only feasible scheme for collimation of x rays.
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41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
07.68.+m Photography, photographic instruments; xerography
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Combined ion beam deposition and etching for thin film studies

J. M. E. Harper and R. J. Gambino

J. Vac. Sci. Technol. 16, 1901 (1979); http://dx.doi.org/10.1116/1.570324 (5 pages) | Cited 15 times

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A dual ion beam system is used to deposit thin films in the presence of ion bombardment. This technique provides a measurement of sputter yields of elements in alloy films. Material is deposited by ion beam sputtering using a high current focused beam, while a second ion beam bombards the growing film. The film composition is modified by preferential resputtering of the high sputter yield component, analogous to the effect of substrate bias in diode sputtering. The advantage of the ion‐beam technique is that ion energies, currents and angles may be directly measured and controlled. We have studied the sputter yield ratio of Gd to Co in binary Gd–Co films deposited with simultaneous ion bombardment by an argon beam of typically 500 eV ion energy. Gd is preferentially resputtered with a yield ratio which increases from 2 to 6 with increasing Co concentration in the film. This dependence of yield ratio on film composition is consistent with a model in which surface binding energy dominates the sputter yields.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.05.Bx Metals, semimetals, and alloys
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Directional oxygen‐ion‐beam etching of carbonaceous materials

P. D. DeGraff and D. C. Flanders

J. Vac. Sci. Technol. 16, 1906 (1979); http://dx.doi.org/10.1116/1.570325 (3 pages) | Cited 4 times

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The results of a comparative study of reactive ion etching in oxygen and oxygen ion beam etching of carbonaceous materials is presented. Scanning electron micrographs are shown of 1600 Å linewidth surface relief structures with vertical sidewalls etched into polyimide, and vitreous carbon. The directional nature of oxygen ion beam etching is demonstrated by the etching of a 3200 Å period grating structure into a polyimide substrate at 45°. It is proposed that the etching of carbonaceous materials in oxygen is an excellent model system for studying etching of materials in reactive gases because of its relative simplicity compared to the more commonly used processes employing fluorocarbon gases.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Interface modification of refractory metal–silicon structures by ion implantation

K. L. Wang, F. Bacon, and R. F. Reihl

J. Vac. Sci. Technol. 16, 1909 (1979); http://dx.doi.org/10.1116/1.570326 (4 pages) | Cited 2 times

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A systematic study of the modifications of the transition metal–silicon interface by ion implantation was carried out. Interface mixing was observed to be a general result in samples implanted at temperatures of 78, 297, and 423 K. Elemental depth distributions obtained using Auger electron spectroscopy combined with ion sputtering illustrated composition plateaus near the interface of the ion‐implanted structures. Additionally, high energy resolution Auger analyses of the silicon LVV transition for the implanted samples showed an energy shift and a change of the spectrum relative to the elemental silicon. The Auger‐analysis results suggest that compound (silicide) formation can be induced by ion‐implantation into transition metal–Si structures, even in cases where high temperatures are normally required for thermal reaction. The implications for potential applications to very large‐scale integration of electronic devices are discussed.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.72.U- Doping and impurity implantation
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Channeled ion implantation through metallic films

Kohki Hikosaka, Hiroshi Ishiwara, and Seijiro Furukawa

J. Vac. Sci. Technol. 16, 1913 (1979); http://dx.doi.org/10.1116/1.570327 (4 pages) | Cited 2 times

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Channeled ion implantation through metallic films is studied in such metal‐silicides as Pd2Si, NiSi2, and PtSi grown on single crystalline Si. The annealing conditions of crystal growth and the characteristics of radiation damage in those silicides are obtained by using the backscattering and channeling techniques. Electrical measurements have denonstrated that the amount of impurity ions (P+ and B+) introduced by the channeled ion implantation into a Si substrate in the Pd2Si–Si system is, at least, several times greater than that by a random implantation at the same energy, in case when the film thickness is more than 1.5 times thicker than the average projected range in the random implantation.
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61.72.U- Doping and impurity implantation
61.85.+p Channeling phenomena (blocking, energy loss, etc.)