Showing papers on "Chemical vapor deposition published in 1981"

Laser chemical vapor deposition: A technique for selective area deposition

Abstract: Laser chemical vapor deposition (LCVD) uses a focused laser beam to locally heat the substrate and drive the CVD deposition reacton. Several different deposition reactions and substrates have been examined as a function of intensity and irradiation time using a CO2 laser source: Ni on SiO2, TiO2 on SiO2, TiC on SiO2, and TiC on stainless steel. LCVD film thicknesses range from <100 A to ≳20 μm. Deposition rates of mm/min have been observed for LCVD Ni and 20 μm/min for LCVD TiO2. The diameter of the deposited films is dependent on irradiation conditions and can be as small as one tenth of the laser beam diameter. The LCVD films exhibit excellent physical properties such as adherence, conductivity, hardness, and smoothness.

Mechanisms of Plasma‐Enhanced Silicon Nitride Deposition Using SiH4 / N 2 Mixture

Abstract: The mechanism of plasma‐enhanced vapor deposition of silicon nitride is studied by varying process parameters, such as substrate temperature, rf power, reactant gas ratio, and total pressure. The film composition (Si, N, O, and H) is determined by electron microprobe and infrared analysis. From these analyses, it is established that the film composition is determined not only by the reactant gas ratio, but also by a combined function of the rf power and total pressure in terms of , with a system‐dependent factor. The dependence of film composition on can be related to the radical generation processes. The substrate temperature is found to affect the film composition as well. Greater substrate temperature produces films with less hydrogen and more nitrogen, and hence, higher density. The film dielectric property and plasma etching rate are both studied and found to be dependent on the film composition. Finally, a three‐step deposition mechanism, namely, radical generation, radical adsorption, and adatom rearrangement, is proposed to explain the reaction scheme, and an ion incorporation mechanism is proposed to explain the change of film physical properties.

Epitaxial Growth of Aluminum Nitride on Sapphire Using Metalorganic Chemical Vapor Deposition

Abstract: Epitaxial aluminum nitride (AlN) films were grown on the basal planes of sapphire substrates using metalorganic chemical vapor deposition (MO-CVD), and the following results were obtained. (1) The substrate temperature and the trimethylaluminum (TMA) concentration dependences of the growth rate suggested that the growth process is limited by mass transport. (2) The crystalline perfection of epitaxial films is strongly affected not only by the substrate temperature but also by the gas flow pattern. (3) Single-crystal AlN films which include no misoriented grains can be grown epitaxially at ~1200°C under carefully-controlled gas flow patterns. (4) Crystalline imperfection is caused mainly by (1 01)-oriented grains which correspond to the hillocks observed in the surface morphology.

Kinetics and mechanism of amorphous hydrogenated silicon growth by homogeneous chemical vapor deposition

Abstract: A new method of amorphous hydrogenated silicon (a‐Si:H) chemical vapor deposition is presented in which SiH4 is homogeneously decomposed at high temperature and pressure to produce films on low‐temperature substrates having up to 30‐at. % H and properties very similar to plasma‐deposited material. Kinetic studies provide a film growth activation energy of 54 kcal/mole, confirming that SiH2 is the primary gas phase intermediate. A mechanism based on SiH2 chemistry is presented to account for the rapid surface reactions leading to a‐Si:H growth and its possible relevance to the plasma deposition process is emphasized.

The use of beam shaping to achieve large-grain cw laser-recrystallized polysilicon on amorphous substrates

Abstract: Laser beam shaping has been used to increase the grain size of laser‐recrystallized polycrystalline silicon on amorphous substrates. Using a slanted liquid‐solid interface, rectangular grains as large as 45×50 μm have been grown in 0.5‐μm‐thick chemical vapor deposited polysilicon on quartz substrates. Improved surface smoothness of recrystallized material has also been achieved using this procedure.

Laser induced chemical vapor deposition of carbon

Abstract: Initial results on laser‐induced chemical vapor deposition using the visible radiation of an Ar+ laser are presented. Due to the smaller wavelength of Ar+ laser radiation in comparison to the infrared radiation of a CO2 laser used in earlier experiments, much finer patterns could be produced. The influence of laser irradiance on the deposition rate and widths of patterns was investigated.

Electrical properties of SiO2 and Si3N4 dielectric layers on InP

Abstract: Plasma‐enhanced chemical vapor deposition techniques using SiH4 and N2O have been employed to deposit SiO2 insulating layers on n‐type InP substrates. Si3N4 layers have been deposited employing the reaction between SiH4 and NH3. Metal‐insulator‐semiconductor capacitors have been fabricated from these structures and their interfacial properties have been measured using capacitance‐voltage techniques. The amount of surface potential modulation achieved using SiO2 layers is process dependent and varied from 0.4 to 1.2 V. The modulation observed using Si3N4 layers was consistently about 0.6 V. The amount of trapped interfacial charge in the SiO2 layers is shown to be given by a fixed charge plus a charge directly proportional to the electric field in the oxide. A compilation of data for SiO2 layers on other semiconductors, including silicon, illustrates that this is apparently a universally‐observed phenomenon. It is shown that this charging behavior gives the familiar u‐shaped density of states curve. As an alternative to the present method of characterizing interfacial charging behavior, an interfacial quality factor ΔQss/ΔQsc is proposed that is independent of the semiconductor band gap or impurity level.

Studies of surface, thin film and interface properties by automatic spectroscopic ellipsometry

Abstract: This paper qualitatively describes the principles and presents some applications of the rapidly developing technique of automatic spectroscopic ellipsometry, as applied to the analysis of the properties of surfaces and interfaces of materials in bulk or thin film form. Examples include composition and density measurements of polycrystalline and amorphous Si films, the determination of the best‐quality surfaces of bulk materials, oxidation of Si, optical profiling of microscopic surface roughness, determination of interface widths in semiconductor–oxide systems and CVD heterostructures, and nucleation of a‐Si films.

Aluminum Nitride Epitaxially Grown on Silicon: Orientation Relationships

Abstract: Epitaxial aluminum nitride (AlN) films have been grown on (111), (110) and (100)-oriented Si substrates using metalorganic chemical vapor deposition (MO-CVD). We found that (0001)-oriented AlN films were grown on the above three planes of Si substrates.

Optical properties of low‐pressure chemically vapor deposited silicon over the energy range 3.0–6.0 eV

Abstract: The optical properties of undoped and P‐doped silicon prepared by low‐pressure chemical vapor deposition were measured by spectroscopic ellipsometry over the energy range 3.0–6.0 eV. A marked effect of material microstructure is observed. Approximate values of the density deficit and of the volume fractions of crystalline and amorphous material are estimated as components of the microstructure by comparing measured spectra to those synthesized from constituent spectra in the Bruggeman effective‐medium approximation.

Heteroepitaxy of vacuum‐evaporated Ge films on single‐crystal Si

Abstract: Heteroepitaxial Ge films on 〈100〉 and 〈111〉 Si substrates have been prepared by vacuum evaporation. The films were deposited in moderate vacuum (10−6 Torr) at a rate of ∼10 A/sec, with the substrates heated to 350–750 °C. The crystalline perfection of the films depends on both substrate orientation and temperature. The best films were obtained on 〈100〉 Si substrates heated to 550 °C. Heteroepitaxial GaAs layers of excellent crystal quality have been grown by chemical vapor deposition on such Ge films. GaAs shallow‐homojunction solar cells with conversion efficiencies up to 12% at AM1 have been successfully fabricated.

Hydrogen elimination during the glow‐discharge deposition of a‐Si:H alloys

Abstract: A model of the deposition of a‐Si:H films by silane glow discharge is presented. Three steps are involved: SiH2 addition, H2 elimination, and cross linking. The model is based upon SiH2 gas‐phase chemistry and explains the dependence of hydrogen content of a‐Si:H upon substrate temperature.

Method for LPCVD co-deposition of metal and silicon to form metal silicide

Abstract: A low temperature LPCVD process for co-depositing metal and silicon to form metal silicide on a surface such as the surface of a semiconductor integrated circuit wherein the metal is selected from the group consisting of tungsten, molybdenum, tantalum and niobium. A reactor which contains the surface is maintained at a temperature of about 500°-700° C. The reactor is purged by the successive steps of introducing an inert gas into the reactor, introducing a reducing atmosphere into the reactor and introducing hydrogen chloride gas into the reactor. Silane is then introduced into the reactor such that a base layer of polysilicon is formed on the surface. Then, while maintaining silane introduction to the reactor, metal chloride vapor is simultaneously introduced into the reactor such that metal and silicon are co-deposited on the polysilicon as metal silicide.

Laser photodeposition of refractory metals

Abstract: We report the deposition of the refractory metals chromium, molybdenum, and tungsten through the laser‐induced gas‐phase photolysis of their respective hexacarbonyls A copper, hollow cathode laser was used at ultraviolet wavelengths matched to peaks in the absorption spectra of the carbonyl molecules Localized room‐temperature metal deposition was achieved by focusing the beam into a cell containing the carbonyl gas and helium as a buffer No major differences were noted for deposition on a polished silicon wafer, a thermally oxidized silicon wafer, and a quartz flat

Optical absorption studies on tin oxide films

Abstract: Transparent electrically conducting SnO2 films were prepared by the chemical vapour deposition technique. The films were deposited at substrate temperatures of 400, 450 and 500 degrees C by stannous chloride oxidation. The optical absorption studies, using unpolarised light, indicated that the deposition temperature is an important parameter influencing the optical properties of the films. The absorption edge for the films occurs at about 3.7 eV. The films also indicated direct transitions at about 3.95 eV and indirect transitions at about 3.27 eV.

AlGaAs grown by metalorganic chemical vapor deposition for visible laser

Abstract: Doping efficiency of selenium hydride (for Se donors) to GaAs in metalorganic chemical vapor deposition was shown to be high and near unity, whereas that of sulfur hydride (for S donors) was nearly two orders lower. The difference was even greater with the addition of aluminum to grow AlxGa1−xAs. Doping efficiency of diethyl zinc (for Zn acceptors) was shown to be three to four orders lower than of Se. A higher partial flow ratio of arsenic to column III elements was necessary to grow high‐quality layers of AlxGa1−xAs with larger x. Room‐temperature cw operation of AlxGa1−xAs/AlyGa1−yAs double heterostructure visible (760–780 nm) lasers grown by MOCVD has been achieved. The planar lasers, with an oxide‐insulated stripe structure 10 μm wide and 250 μm long showed a cw threshold current from 150 to 300 mA.

Epitaxial growth of Ge on 〈100〉 Si by a simple chemical vapor deposition technique

Abstract: The heteroepitaxial growth of Ge on Si substrates by means of a simple chemical vapor deposition (CVD) method is presented. The epitaxial Ge layers were formed by the decomposition of GeH4 in a H2 ambient at substrate temperatures of 500–900 °C. Smooth surface morphologies and high crystalline quality are obtained in the epitaxial Ge layers. Electrical properties of the Ge films and the resulting p‐Ge/n‐Si heterojunctions were determined. This technique provides a Ge growth method that is compatible with the current CVD processes used in the growth of GaAs.