Showing papers on "Chemical vapor deposition published in 1986"

Infrared spectroscopic study of SiOx films produced by plasma enhanced chemical vapor deposition

Abstract: We have studied the local atomic structure of silicon suboxide (SiOx, x<2) thin films using infrared (IR) spectroscopy. The films were prepared by plasma enhanced chemical vapor deposition (PECVD) of silane (SiH4) and nitrous oxide (N2O) mixtures, which were then diluted with He. The IR spectra were found to vary significantly with the degree of He dilution. Films grown with no He showed SiN, NH, and SiH bonding groups in addition to the three characteristic vibrations of the Si–O–Si linkage. The addition of He reduced the strength of the SiN, NH, and SiH absorption bands, and resulted in systematic increases in the frequency of the Si–O–Si asymmetric stretching vibration. The frequency of this Si–O–Si stretching vibration scales linearly with the oxygen concentration from approximately 940 cm−1 in oxygen doped amorphous silicon to 1075 cm−1 in stoichiometric noncrystalline SiO2. A deposition temperature of 350 °C and a He dilution of 50% gave a film composition close to SiO1.9. We propose a model for the...

Aluminum or phosphorus co-doping effects on the fluorescence and structural properties of neodymium-doped silica glass

Abstract: To utilize the excellent properties of silica (SiO2) glass for a glass laser host, neodymium‐aluminum (Nd–Al) and neodymium‐phosphorous (Nd–P) co‐doped SiO2 glasses were studied. They were prepared by plasma‐torch chemical vapor deposition (CVD). It was found that a doping level less than ten times the number of Nd for the Al co‐dopant and less than about fifteen times for the P co‐dopant was enough to remove undesirable fluorescence properties of Nd‐doped SiO2 glasses and make them suitable for laser application. The clustering Nd ions disperse well in a glass matrix and lasing fluorescence increases. The effects of the Al dopant on the density and Raman spectra were also studied to obtain structural information. On the basis of glass science and solution chemistry, the marked effects of both dopants were explained by the following model. Nd ions can be well incorporated into a SiO2 glass network through co‐dopant oxide forming a solvation shell around the Nd ions. This model leads to an expansible metho...

Low‐temperature silicon epitaxy by ultrahigh vacuum/chemical vapor deposition

Abstract: We have successfully demonstrated the use of a novel chemical vapor deposition technique, ultrahigh vacuum/chemical vapor deposition, to deposit homoepitaxial silicon layers of high crystalline perfection at low temperatures (T≥750 °C). Rutherford backscattering and transmission electron microscopy showed the transition to epitaxial silicon growth took place in the range 700–750 °C, and secondary ion mass spectrometry showed typical oxygen and carbon levels to be near the detection limits of the technique 1016–1017 cm−3. In addition, abrupt dopant transitions have been demonstrated, with B levels dropping four orders of magnitude, 1019–1015 B/cm3, in the first 1000 angstroms of an intrinsic epilayer.

A review of the present state of art in hard coatings grown from the vapor phase

Abstract: Hard‐coating materials range from ultrahard materials such as ‘‘diamondlike carbon’’ through refractory compounds to alloys. However, transition‐metal carbides and nitrides have achieved by far the highest level of commercial success. Titanium nitride and titanium carbide are the most studied and used. In this paper a review of the hard coating literature is given and includes in addition to nitrides and carbides also oxides, borides, mixed compounds, metals and alloys, and ‘‘diamondlike’’ carbon coatings. Only coatings grown from the vapor phase are discussed. Some considerations involved in selecting coating/substrate combinations as well as basic concepts of hardness and hardness measurements are also given. For example, it is shown that in order to measure the hardness of the coatings correctly the ratio between the film thickness and the depth of the indentation has to exceed a critical value, which depends on the coating/substrate combination. For TiN on steel, the coating thickness has to be a fact...

On structure and properties of sputtered Ti and Al based hard compound films

Abstract: After investigating basic correlations between process and film characteristics in previous works new multicomponent hard coatings, on the basis of Ti–Al and Ti–Zr, have been deposited by magnetron sputtering. These ternary and quaternary nitrides are crystallizing in a face centered cubic TiN lattice with reduced or enlarged lattice parameters depending on the amount and the radius of foreign atoms. Improved wear behavior compared to chemical vapor deposition (CVD) TiN coatings has been stated with (Ti,Al)N, (Ti,Zr)N, and (Ti,Al,V)N coatings. According to these results the development of the coating material itself will be of major interest in the future.

Low‐temperature deposition of high‐quality silicon dioxide by plasma‐enhanced chemical vapor deposition

Abstract: Thin films of high‐quality silicon dioxide have been deposited at low temperatures by plasma‐enhanced chemical vapor deposition. A deposition rate much lower than that used in conventional plasma‐enhanced processes is found to be crucial in obtaining material with reproducible, good properties. Controlled, slow deposition is achieved by using very low flow rates of reactive gases, together with a much higher flow of inert carrier gas to ensure uniformity. Films deposited at usual high deposition rates (∼500 A/min) exhibit irreproducible and poor electrical properties and are porous. Those deposited slowly (∼60 A/min) have very reproducible properties, are relatively dense and exhibit very good electrical integrity. Oxides deposited using a substrate temperature of 350 °C compare favorably with those deposited at 700°C using atmospheric‐pressure chemical vapor deposition and can be deposited routinely over a wide range of oxide thickness. Deposition at 275 °C results in similar properties but with increase...

Deposition of silicon dioxide and silicon nitride by remote plasma enhanced chemical vapor deposition

Abstract: We have developed a low temperature process for the deposition of thin films of silicon dioxide and silicon nitride. The process consists of four steps: (a) excitation of an oxygen or nitrogen‐containing molecule in an RF plasma; (b) transport of the excited oxygen or nitrogen species out of the plasma region; (c) mixing of the transported excited species with silane (or disilane) out of the plasma region to form precursor species; and (d) a CVD reaction at a heated substrate to form the desired thin film. We call this process remote plasma enhanced CVD (RPECVD). Silicon rich oxide films have been grown at substrate temperatures (Ts) between 100 and 350 °C using an excited O2/He mixture. Two different ‘‘silicon nitrides’’ have been deposited depending on the excited gas, NH3 or an N2/He mixture, and Ts. Using either nitrogen source and Ts greater than 450 °C, we obtain near stoichiometric films of Si3N4. On the other hand, films grown from NH3 and deposited with Ts of about 50 to 100 °C are silicon diimid...

Atomic layer epitaxy

Abstract: Atomic layer epitaxy (ALE) is not so much a new technique for the preparation of thin films as a novel modification to existing methods of vapor‐phase epitaxy, whether physical [e.g., evaporation, at one limit molecular‐beam epitaxy (MBE)] or chemical [e.g., chloride epitaxy or metalorganic chemical vapor deposition (MOCVD)]. It is a self‐regulatory process which, in its simplest form, produces one complete molecular layer of a compound per operational cycle, with a greater thickness being obtained by repeated cycling. There is no growth rate in ALE as in other crystal growth processes. So far ALE has been applied to rather few materials, but, in principle, it could have a quite general application. It has been used to prepare single‐crystal overlayers of CdTe, (Cd,Mn)Te, GaAs and AlAs, a number of polycrystalline films and highly efficient electroluminescent thin‐film displays based on ZnS:Mn. It could also offer particular advantages for the preparation of ultrathin films of precisely controlled thickne...

A Mathematical Model of Silicon Chemical Vapor Deposition Further Refinements and the Effects of Thermal Diffusion

Abstract: We describe a mathematical model of the coupled gas‐phase chemical kinetics and fluid mechanics in a chemical vapor deposition (CVD) reactor. This paper presents refinements to our earlier model of the CVD of silicon from silane. The model predicts gas‐phase temperature and velocity fields, concentration fields for seventeen chemical species, and deposition rates. The major new features are a multicomponent transport model including thermal diffusion and a new formulation of the boundary conditions that describe deposition. A significant result is that thermal diffusion is predicted to make an important contribution to species density profiles and generally to reduce deposition rates.

Synthesis of Diamond Thin Films by Thermal CVD Using Organic Compounds

Abstract: Diamond thin films have been formed by thermal chemical vapor deposition (thermal CVD) using the organic compounds such as CH3OH, C2H5OH, CH3COCH3 C2H5OC2H5, and (CH3)3N. The films are grown on the silicon substrates with high growth rate (8?10 ?m/h) under the pressure ranging 1?800 Torr. This growth rate is ten or several ten times faster than the CVD method using hydrocarbons such as CH4 and C2H2. The films have good crystallinity and high quality in the sense of electron diffraction and Raman spectrum. The Vicker's hardness of the film is about 10000 kg/mm2 and the gravity of that is about 3.52 g/cm3.

Film formation mechanisms in the plasma deposition of hydrogenated amorphous silicon

Abstract: By studying the step coverage of plasma‐deposited amorphous silicon and germanium on patterned substrates, we find that the film formation process under device‐quality deposition conditions has a substantial component that behaves like a surface rate‐limited chemical vapor deposition process, while conditions producing defective material are associated with a much more physical‐vapor‐deposition‐like process. An explanation involving surface reactions of SiHx radicals is proposed.

Interlayer dielectric process

Abstract: A method for producing a film over a topologically non-planar surface of a material which has a sputter etch rate which is higher in a direction parallel to the plane of the wafer than in a direction perpendicular to the plane of the wafer. Key steps in the process include first, depositing the material by plasma enhanced chemical vapor deposition while simultaneously sputter etching it. Then second, sputter etching the material. Using this two step process, a substantially conformal or sloped film is produced by repeating the steps consecutively until the desired thickness is obtained. The film can then be substantially planarized if desired, by an extended sputter etch to selectively remove material having a sloped surface rather than a flat surface, since the etch rate is higher parallel to the plane of the wafer than perpendicular to the wafer. If a thicker planar surface is desired, additional material can then be deposited by steps of simultaneous plasma chemical vapor deposition and sputter etch, or by consecutive steps of simultaneous plasma deposition and sputter etch followed by sputter etching.

Solventless polyimide films by vapor deposition

Abstract: Vapor deposition polymerization (VDP) has been employed for the preparation of polyamic acid/imide films using a conventional thin film evaporator with a novel source design. The process utilizes the coevaporation of the dianhydride and diamine precursors. Control of source effusion rates permit film stoichiometry to be held to better than 1 mol %. Infrared, electron spectroscopy for chemical analysis (ESCA), and thermogravimetric analysis (TGA) results are consistent with the interpretation that the VDP films produced are polyamic acid curable to polyimide. The weight average molecular weight of the polyimide as determined by low angle light scattering (LALS) technique is 13 000, in agreement with the value estimated from the measured percent elongation at break point. Lift‐off tests showed that vapor deposited polyimide is more resistant to hydrolitic attack at the silicon interface than spin coated Dupont RC5878. Dielectric constant (e=2.91) and dissipation factor (tan δ=0.008) are lower than those rep...

Sealed cavity semiconductor pressure transducers and method of producing the same

Abstract: Sealed cavity structures suitable for use as pressure transducers are formed on a single surface of a semiconductor substrate (20) by, for example, deposit of a polycrystalline silicon layer (32) from silane gas over a relatively large silicon dioxide post (22) and smaller silicon dioxide ridges (27) leading outwardly from the post. The polysilicon layer is masked and etched to expose the outer edges of the ridges and the entire structure is then immersed in an etchant which etches the silicon dioxide forming the ridges and the post but not the substrate (20) or the deposited polysilicon layer (32). A cavity structure results in which channels (35) are left in place of the ridges and extend from communication with the atmosphere to the cavity (36) left in place of the post. The cavity (36) may be sealed off from the external atmosphere by a second vapor deposition of polysilicon or silicon nitride, which fills up and seals off the channels (35), or by exposing the substrate and the structure thereon to an oxidizing ambient which results in growth of silicon dioxide in the channels sufficient to seal off the channels. Deflection of the membrane spanning the cavity occurring as a result of pressure changes, may be detected, for example, by piezoresistive devices formed on the membrane.

Catalytic Chemical Vapor Deposition (CTC–CVD) Method Producing High Quality Hydrogenated Amorphous Silicon

Abstract: A new method of producing high quality hydrogenated amorphous silicon (a-Si:H) films is presented. An SiH4. and H2 gas mixture is decomposed without using any plasmas or photochemical excitation, but using only thermal and catalytic reactions between deposition-gas and a heated tungsten catalyzer. Photoconductivity of films produced by this methodreaches 10-3 (Ωcm)-1 and photosensitivity exceeds 105 for illumination of AM-1 light of 100 mW/cm2.

New selective deposition technology by electron-beam induced surface reaction

Abstract: A new selective deposition technology using electron beam induced surface reaction has been demonstrated. Electron beam induced W and Cr patterns were deposited by using WF6, WCl6, and Cr(C6H6)2 as sources, respectively. W and Cr depositions were confirmed by analysis using Auger electron spectroscopy (AES) and x‐ray microanalysis (XMA). It was observed, with W deposition using the WF6 source, that the W pattern was deposited at below ∼50 °C substrate temperature, but that the substrate was etched at above ∼50 °C substrate temperature. The deposition rate increased with decreasing substrate temperature, and the etching rate increased with increasing substrate temperature. The deposited thickness was proportional to electron beam dose. A 0.15‐μm‐linewidth Cr pattern was deposited at 5×10−7 C/cm (3.3×10−2 C/cm2) dose by using a modified scanning electron microscope (SEM) system. These results indicate that this technology will be applicable to fabricate nanometer‐structure devices.

Doping reaction of PH3 and B2H6 with Si(100)

Abstract: The reaction of phosphine PH3 and diborane B2H6 on Si(100) surfaces was studied by surface analytical techniques in relation to the in situ doping process in the chemical vapor deposition of silicon. Phosphine chemisorbs readily either nondissociatively at room temperature or dissociatively with the formation of silicon–hydrogen bonds at higher temperatures. Hydrogen can be desorbed at temperatures above 400 °C to generate a phosphorus layer. Phosphorus is not effective in shifting the Fermi level until the coverage reaches 2×1014/cm2. A maximum shift of 0.45 eV toward the conduction band was observed. In contrast, diborane has a very small sticking coefficient and the way to deposit boron is to decompose diborane directly on the silicon surface at temperatures above 600 °C. Boron at coverages less than 2×1014/cm2 is very effective in shifting the Fermi level toward the valence band and a maximum change of 0.4 eV was observed.

Vapor deposition of semiconductor material

Abstract: Precursor gaseous mixtures from which to glow discharge deposit wide and narrow band gap semiconductor alloy material, said material characterized by improved photoconductivity and stability and improved resistance to photodegradation. There is also specifically disclosed a method of fabricating a narrow band gap semiconductor which method does not suffer from the effects of differential depletion of the components of the precursor gaseous mixture.

Investigation of the growth kinetics of glow-discharge hydrogenated amorphous silicon using a radical separation technique

Abstract: The deposition kinetics of hydrogenated amorphous silicon (a‐Si:H) from a SiH4 glow‐discharge plasma have been investigated by examining the diffusion of SiH3 monoradicals in the discharge‐free space within a triode reactor. This experiment suggests that the SiH3 radicals are responsible for about 37% of the total deposition rate of a‐Si:H in a conventional SiH4 glow‐discharge process. The contribution of other radicals and atoms to the deposition rate is also discussed through the analysis of reaction‐rate constants.

Silicon nitride and silicon diimide grown by remote plasma enhanced chemical vapor deposition

Abstract: We discuss the deposition of silicon nitride (Si3N4) and silicon diimide [Si(NH)2] thin films by remote plasma enhanced chemical vapor deposition (RPECVD). We show that the use of two different nitrogen source gases N2 and NH3 leads to qualitatively different local bonding in the deposited films. We present studies of the local chemical bonding as a function of the substrate temperature (Ts) and the dilution of the nitrogen containing species with the rare gases Ar and He. We show that diluting the N2 with He by a factor of about 10 to 1 increases the growth rate for thin film formation by a factor of more than 3. Dilution of NH3 with He, reduces the deposition rate and also the amount of bonded hydrogen.

Plasma‐enhanced growth and composition of silicon oxynitride films

Abstract: Silicon oxynitride films with varying oxygen/nitrogen ratio were grown from SiH4, N2O, and NH3 by means of a plasma‐enchanced chemical vapor deposition process. The elemental composition of the deposited films was measured by a variety of high‐energy ion beam techniques. To determine the chemical structure we used Fourier transform infrared absorption spectroscopy and electron‐spin resonance. Ellipsometric data and values for mechanical stress are also reported. We show that the entire range of compositions from silicon oxide to silicon nitride can be covered by applying two different processes and by adjusting the N2O/NH3 gas flow ratio of the respective processes. It is suggested that the N2O/SiH4 gas flow ratio is the major deposition characterization parameter, which also controls the chemical structure as far as the hydrogen bonding configuration is concerned. We found that the films contain significant amounts of excess silicon and that the mechanical stress in the oxynitrides is lower than in plasm...