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Jan 1984

Volume 2, Issue 1, pp. 1-90


Tunability of bipolar conductivity in GaAs doping superlattices

H. Künzel, A. Fischer, and K. Ploog

J. Vac. Sci. Technol. B 2, 1 (1984); http://dx.doi.org/10.1116/1.582907 (9 pages) | Cited 2 times

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In GaAs doping superlattices the conductivity parallel to the constituent layers is tunable over wide ranges by injection or extraction of free carriers via selective electrodes. The transport simultaneously involves electrons in the n layers and holes in the p layers. The tunability of bipolar conductivity depending on temperature in the range 10 to 300 K and on the design parameters of the superlattice configuration is analyzed in detail. The carrier concentrations and mobilities as a function of bias Unp are determined independently from Hall effect measurements. The observed tunability of carrier concentration is in good agreement with calculations based on a simplified semiclassical approach. The carrier mobility is found to be strongly influenced by the carrier concentration and correspondingly by the effective thickness of the constituent superlattice layers. This behavior is analyzed in terms of the classical size effect. Only a minor influence of the temperature on the carrier mobility is detected. The temperature dependence of the carrier concentration is solely determined by the temperature dependence of the threshold voltage. The present detailed investigation is of importance for application of GaAs doping superlattices in bulk multijunction field effect transistors.
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73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
72.80.Ey III-V and II-VI semiconductors
68.55.-a Thin film structure and morphology
72.20.Pa Thermoelectric and thermomagnetic effects

Electronic transport properties of TiSi2 thin films

V. Malhotra, T. L. Martin, and J. E. Mahan

J. Vac. Sci. Technol. B 2, 10 (1984); http://dx.doi.org/10.1116/1.582905 (6 pages) | Cited 21 times

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High purity, single‐phase TiSi2 thin films were prepared by deposition of titanium onto polycrystalline silicon layers followed by furnace annealing. Measurements of the temperature dependence of resistivity show that the material behaves as a classical metallic conductor, with an intrinsic resistivity proportional to temperature and having a room temperature value of ∼11μΩ cm. Geometrical magnetoresistance measurements on Corbino disk samples give a ‘‘representative’’mobility value (∼60 cm2/V‐s at room temperature) that mirrors the temperature dependence of resistivity. The very small Hall effect, taken together with a sizeable physical magnetoresistance, indicates the material is predominantly an electron conductor with a spectrum of mobility values for carriers on the Fermi surface because an isotropic, two‐band model cannot quantitatively account for the data.
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73.61.Ng Insulators

Hydrogenic impurity states in a quantum well wire

Johnson Lee and Harold N. Spector

J. Vac. Sci. Technol. B 2, 16 (1984); http://dx.doi.org/10.1116/1.582906 (5 pages) | Cited 20 times

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A variational calculation of hydrogenic impurity binding energies in quantum well wires has been performed. The binding of the hydrogenic impurity has been calculated as a function of the transverse dimensions of the wire. It is found that the binding energy of the hydrogenic impurity increases as the ratio of the Bohr radius of the impurity in a bulk semiconductor to the transverse dimension of the wire increases. To test the sensitivity of the binding energies to the trial wave function we have used in our calculations, we use a wave function of the same type to calculate the binding energy of hydrogenic impurities confined in a quasi‐two‐dimensional quantum well as a function of well width and compare our results for the binding energies to the results obtained by Bastard [Phys. Rev. B 24, 4714 (1981)].
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78.40.Fy Semiconductors

Atom‐probe study of silicide formation at Ni/Si interfaces

Osamu Nishikawa, Mezame Shibata, Toshihiko Yoshimura, and Eiichi Nomura

J. Vac. Sci. Technol. B 2, 21 (1984); http://dx.doi.org/10.1116/1.582908 (3 pages) | Cited 6 times

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Nickel was deposited on Si substrates and the feasibility of studying the formation process of Ni silicides with the atom‐probe mass spectrometer was examined by atomic layer‐by‐layer mass analysis of the specimen from the deposited layer to the substrate through the interface. The epitaxially grown silicide with a well ordered cubic structure was observed when the specimen was heated above 800 K. The main part of the Ni–Si mixed layer formed at room temperature was Ni‐rich Ni2Si regardless of substrate materials, Ni or Si. At high temperatures the Ni concentration in the mixed layer depends on the substrate materials. The result indicates that the silicide composition is regulated by the diffusivity of Ni into Si at low temperatures and by the relative quantities of Ni and Si at high temperatures. A clear interface between the silicide and the Si substrate was formed at around 800 K.
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68.55.-a Thin film structure and morphology
07.75.+h Mass spectrometers

Lattice‐matched single‐crystalline dielectric films (BaxSr1−xF2) on InP(001) grown by molecular‐beam epitaxy

C. W. Tu, T. T. Sheng, A. T. Macrander, J. M. Phillips, and H. J. Guggenheim

J. Vac. Sci. Technol. B 2, 24 (1984); http://dx.doi.org/10.1116/1.582909 (3 pages) | Cited 5 times

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We report lattice‐matched single‐crystalline dielectric films on a III–V compound semiconductor InP(001) substrate by molecular‐beam epitaxial growth of BaxSr1−xF2. We used two methods to grow mixed fluoride films: two separate beams of BaF2 and SrF2 as well as a single beam of BaxSr1−xF2. In situ reflection high energy electron diffraction shows the parallel epitaxial relationship, BaxSr1−xF2(001)∥InP(001) and BaxSr1−xF2[110]∥InP[110]. The films were studied by double‐crystal x‐ray diffractometry for lattice parameters and Rutherford backscattering/channeling for compositions and crystallinity. Transmission electron microscopy shows that the films are single crystalline. Preliminary electrical results are also mentioned. Lattice‐matched single‐crystalline dielectric films can be important for epitaxial metal–insulator–semiconductor as well as semiconductor–insulator–semiconductor structures in a variety of device applications.
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68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
68.60.-p Physical properties of thin films, nonelectronic

CF4/silicon surface reactions: Evidence for parallel etching mechanisms from modulated ion beam studies

S. C. McNevin and G. E. Becker

J. Vac. Sci. Technol. B 2, 27 (1984); http://dx.doi.org/10.1116/1.582910 (7 pages) | Cited 6 times

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This paper reports the use of a modulated ion beam system to probe the reaction dynamics occurring in an ion/surface interaction which results in the removal of material from a solid. A modulated ion gun (15 μs rise time) was used to provide pulses of incident ions (primarily CF+3) at a Si surface. The resulting products were detected by a mass spectrometer and signals have been observed at mass 28 (Si), mass 47 (SiF), mass 66 (SiF2), and mass 85 (SiF3, principal cracking fraction of SiF4). A comparison of the amount of signal with the measured cracking pattern of SiF4 indicated that a substantial fraction of the Si left the surface with fewer than four fluorine atoms. By performing the experiments in two different sample positions, we have confirmed that complications due to collisions between the product molecules and the vacuum system walls have been eliminated. The time evolution of these product signals following the start of the ion beam pulse has been measured with signal averaging. The results are consistent with a model where mass 47 (SiF) and mass 66 (SiF2) are produced with ∼1 eV energy in a fast process. Roughly 70% of the Si is removed in this manner. In contrast, mass 28 (Si) and mass 85 (SiF3 and SiF4 cracking fraction) have an appreciably slower time dependence and a model which partially fits this observation assumes that these species are produced at the same time as SiF and SiF2 but have thermal (0.02 eV) energies and thus take longer to reach the mass spectrometer. The observed time dependence is even slower than this model predicts, however, which indicates the possibility of a surface residence time delay due to the formation of a surface complex prior to the desorption of the products.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.65.-b Surface treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Oxygen ion beam etching for pattern transfer

H. Gokan, M. Itoh, and S. Esho

J. Vac. Sci. Technol. B 2, 34 (1984); http://dx.doi.org/10.1116/1.582911 (4 pages) | Cited 10 times

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Oxygen ion beam etching for resist materials has been studied. Etch rates of resists depend on oxygen pressure and on acceleration ion energy. The oxygen pressure dependence of etch rates is attributed to the effect of ion assisted neutral oxygen molecules. The neutral oxygen contribution leads to high etch selectivity for resist materials over metals; a selectivity more than 50 is obtained for AZ1350J over Au at 100 eV acceleration energy condition. The oxygen ion beam etching is applied to the pattern transfer for the multilevel resist technique. Hard baked AZ1350J, titanium, and PMMA are applied for a bottom layer, a middle layer, and a top imaging resist layer material, respectively. Under low acceleration energy conditions, an undercut profile is observed in the transferred patterns due to large ion beam divergence. At 500 eV, patterns having square cross sections are obtained. However, with the increase in gap aspect ratio (etch depth over gap width), a slight widening of etched channels at their midpoint (barrel shaped channel) is observed.
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81.65.-b Surface treatments

Reactive ion beam etching: Dissociation of molecular ions upon impact

Ch. Steinbrüchel

J. Vac. Sci. Technol. B 2, 38 (1984); http://dx.doi.org/10.1116/1.582912 (7 pages) | Cited 9 times

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This paper reports on etch yield measurements on Au films by ion beams generated from Ar, Ne, O2, N2, CF4, and C2F6 in a Kaufman‐type ion gun for ion energies between 0.2 and 1.4 keV. Ions and neutral species emanating from the gun are characterized by mass spectrometry. For CF4 and C2F6 the ion composition is a strong function of the magnetic field in the gun, CF+3 being the major ion only for CF4 at low magnetic field. The physical etch yield of CF+3 is found to be close to that of Ne+, not Ar+. The results on the dependence of the etch yields on ion mass, ion energy, and incident angle can be correlated quantitatively by assuming complete dissociation of molecular ions upon impact on the substrate. The same model is also shown to explain the data by Tachi et al. on etching Si by mass‐selected ions of the form CF+x and BF+x. The implications of these results for plasma and reactive ion etching are discussed.
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81.05.Bx Metals, semimetals, and alloys
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.20.Hf Product distribution

Direct transfer of resist grating patterns onto InP by reactive‐ion etching using CCl4/O2

Kazuo Hirata, Osamu Mikami, and Tadashi Saitoh

J. Vac. Sci. Technol. B 2, 45 (1984); http://dx.doi.org/10.1116/1.582913 (4 pages) | Cited 1 time

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A reactive‐ion‐etching technique for direct transfer of resist grating patterns onto InP surfaces was developed. A mixture of CCl4 and O2 at a pressure of 1–5×10−3 Torr enabled a high etching rate of about 850 Å/min for InP. The etch rate ratio of InP to AZ‐1350 resist was 3.5‐1. Fine grating patterns with periodicity of 4700 Å were successfully transferred to InP and a corrugation depth of about 2000 Å was obtained.
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81.65.-b Surface treatments
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Silicon nitride film deposition by hot‐wall plasma‐enhanced CVD for GaAs LSI

Yasunobu Ishii, Tatsuo Aoki, and Shintaro Miyazawa

J. Vac. Sci. Technol. B 2, 49 (1984); http://dx.doi.org/10.1116/1.582914 (5 pages) | Cited 1 time

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Silicon nitride film deposition by a hot‐wall plasma‐enhanced chemical vapor deposition (CVD) was investigated for application to GaAs large scale integrated circuits (LSI) fabrication. Silicon nitride film properties related to deposition parameters were described. The in situ plasma‐precleaning effect on adhesion to GaAs was also investigated. Annealing effects on silicon nitride films were considered as a GaAs annealing cap material for the postimplantation annealing. It was concluded that a hot‐wall plasma‐enhanced CVD together with argon‐plasma precleaning was preferable to achieve reliable silicon nitride film deposition for GaAs devices. The optimum deposition conditions were NH3/SiH4 gas flow ratio of 6 to 9 at 380 °C substrate temperature under 2 Torr pressure.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
75.20.Ck Nonmetals
85.40.Xx Hybrid microelectronics; thick films
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Contact resistance monitor for silicon integrated circuits

T. J. Faith, R. S. Irven, L. H. Reed, J. J. O’Neill, M. C. Jones, and B. B. Levin

J. Vac. Sci. Technol. B 2, 54 (1984); http://dx.doi.org/10.1116/1.582915 (4 pages)

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Chronic problems have been experienced in integrated circuit fabrication lines in the formation of Ohmic contacts between Al–Si interconnect metallization and device (bulk or epi) silicon. One of the reasons for such problems has been the absence of a simple and reliable method for predicting, immediately after metal deposition, whether or not the contact resistances in the finished circuits will be satisfactory. This paper describes and demonstrates such a method for (Al–1% Si)/(phosphorus‐implanted) n+ Si contacts.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Dose control with high power ion beams on photoresist masked targets

K. Steeples

J. Vac. Sci. Technol. B 2, 58 (1984); http://dx.doi.org/10.1116/1.582916 (5 pages)

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The effects associated with implanting high power ion beams into photoresist masked silicon wafers have been investigated. Outgassing from the photoresist mask can result in significant dose control errors when Faradays with conventional electrostatic suppression schemes are used. Sheet resistivity measurements show that these errors can be reduced by a factor of 3 when a magnetic suppression technique is employed. With magnetic suppression of secondary charged particles from target impact with an arsenic primary ion beam dose control accuracy is better than 2%, even under severe outgassing conditions. A semiempirical model confirms the sheet resistivity results.
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81.65.-b Surface treatments
61.72.U- Doping and impurity implantation
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Submicron pattern replication using a high contrast mask and two‐layer resist in x‐ray lithography

Yasunao Saitoh, Hideo Yoshihara, Iwao Watanabe, and Satoshi Nakayama

J. Vac. Sci. Technol. B 2, 63 (1984); http://dx.doi.org/10.1116/1.582917 (5 pages) | Cited 1 time

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The effects of photoelectrons and Auger electrons from the x‐ray mask on contrast and resolution were experimentally investigated in the replication of submicron resist patterns in x‐ray lithography. A resist thinner than 550 Å was exposed by electrons generated from a Si–N membrane. The effect of electrons from the Au absorber is observed even with a 1 μm thick Au absorber pattern, because of the continuous radiation spectrum generated, producing wavelengths shorter than those of the characteristic radiation. A polymer film coating on the Au absorber pattern increases the contrast of the mask, because electrons from the x‐ray mask are absorbed by the polymer film. The unwanted exposure of a resist by electrons from a Si wafer was also studied. On the basis of these results, we proposed a new two‐layer resist process. In this way, a submicron resist pattern can easily be realized by using a high contrast mask and a two‐layer resist.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
79.60.Bm Clean metal, semiconductor, and insulator surfaces

High contrast x‐ray mask preparation

Toshiro Ono and Akira Ozawa

J. Vac. Sci. Technol. B 2, 68 (1984); http://dx.doi.org/10.1116/1.582918 (5 pages)

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Fabricating a high contrast and highly accurate gold absorber pattern has been considered for an x‐ray mask. In this method, the polyimide patterns etched by O2‐reactive ion etching are used for the plating mask. In electron beam pattern generation, few electrons are backscattered from the polyimide film. Those from the electroplating base are trapped in the polyimide film, which improves the electron beam resolution. In O2‐reactive ion etching of the polyimide film, an accurate pattern without etch residue is obtained by using the carbon target. The titanium adhesion layer for the plating base is etched off by CBrF3‐reactive ion etching without undercut. A gold pattern with 0.5 μm in width and 1.0 μm in thickness can be obtained within 0.1 μm accuracy by a combination of these technologies.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
81.05.Bx Metals, semimetals, and alloys
07.85.-m X- and γ-ray instruments
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Promising cathode materials for high brightness electron beams

Shigeaki Zaima, Hiroshi Adachi, and Yukio Shibata

J. Vac. Sci. Technol. B 2, 73 (1984); http://dx.doi.org/10.1116/1.582919 (6 pages) | Cited 4 times

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Materials for high brightness cathodes are evaluated by defining a figure of merit, which is based on the Richardson–Dushman equation. By calculating the figure of merit of borides, carbides, nitrides, and some refractory metals, it is concluded that carbides of transition metals such as TiC, ZrC, TaC, and HfC are promising for high brightness cathodes.
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73.30.+y Surface double layers, Schottky barriers, and work functions
79.70.+q Field emission, ionization, evaporation, and desorption
79.40.+z Thermionic emission

The common anion rule: An electrochemical contribution

Jacques Gautron and Jean‐Lou Sculfort

J. Vac. Sci. Technol. B 2, 79 (1984); http://dx.doi.org/10.1116/1.582920 (3 pages)

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The electrochemical behavior of III–V ternary GaxIn1‐xP alloys (with 0≤x≤1) is studied in aqueous and nonaqueous media (sodium iodide liquid ammoniate). The energy position, referenced through an electrochemical scale, of the maximum level of the valence band for each of these compounds is nearly constant. These results still show that this position depends mainly on the anion P, through its electronegativity, in accordance with the so‐called common anion rule found with semiconductor–metal junctions.
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82.45.-h Electrochemistry and electrophoresis
73.40.Mr Semiconductor-electrolyte contacts

A method for eliminating hillocks in integrated‐circuit metallizations

K. C. Cadien and D. L. Losee

J. Vac. Sci. Technol. B 2, 82 (1984); http://dx.doi.org/10.1116/1.582921 (2 pages) | Cited 4 times

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In a novel method for eliminating hillocks in integrated‐circuit metallizations, a sandwich layer is grown between the Al film and the underlying SiO2. This layer must have a thermal expansion coefficient between those of SiO2 and Al. The technique is demonstrated with WSi2 as the sandwich layer.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
68.55.-a Thin film structure and morphology
65.40.De Thermal expansion; thermomechanical effects
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Sputtering of silicon nitride with hydrogen ions

P. C. Zalm and L. J. Beckers

J. Vac. Sci. Technol. B 2, 84 (1984); http://dx.doi.org/10.1116/1.582922 (2 pages)

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The possibility of using hydrogen as a substitute for halogen gases in dry etching processes is discussed. Etch rates for Si, SiO2, and Si3N4 are compared.(AIP)
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.20.Hf Product distribution
81.65.-b Surface treatments

Reactive ion etching of GaAs in a chlorine plasma

E. L. Hu and R. E. Howard

J. Vac. Sci. Technol. B 2, 85 (1984); http://dx.doi.org/10.1116/1.582923 (4 pages) | Cited 9 times

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Chlorine was used to carry out the reactive ion etching (RIE) of GaAs. At 5 mTorr pressure and 270 V bias, it was found to etch at a rate >1 μ/min, and produced features having vertical sidewalls and a clean substrate surface. The mechanism of chlorine RIE of GaAs was studied by examining etch rates and profiles obtained using gases of different mixtures of chlorine and argon. The results are consonant with proposed mechanisms of GaAs etching by chlorine in both the plasma and reactive ion beam etching regimes.
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81.65.-b Surface treatments

Erratum: Focused ion beam microlithography using an etch‐stop process in gallium‐doped silicon [J. Vac. Sci. Technol. B 1, 1056 (1983)]

P. H. La Marche, R. Levi‐Setti, and Y. L. Wang

J. Vac. Sci. Technol. B 2, 89 (1984); http://dx.doi.org/10.1116/1.582924 (1 page)

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Abstract Unavailable
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.U- Doping and impurity implantation
99.10.Cd Errata

Book Review: Laser annealing of semiconductors

David Biegelsen

J. Vac. Sci. Technol. B 2, 90 (1984); http://dx.doi.org/10.1116/1.582925 (1 page) | Cited 1 time

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Abstract Unavailable
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01.30.mm Textbooks for graduates and researchers
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
79.20.Ds Laser-beam impact phenomena
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