Inorganic CVD

In the last several years, polymer thin film deposition using chemical vapor deposition (CVD) has become increasingly popular. CVD of polymers offers numerous unique advantages over other polymer synthesis techniques and has been exploited for a multitude of applications in microelectronics, optical devices, biomedical industry, corrosion resistant and protective coatings, and even in the automobile industry. CVD of polymers (also referred to as chemical vapor polymerization, CVP, or sometimes Vapor Deposition Polymerization, VDP) differs from inorganic CVD (such as for metallic or ceramic thin films) and must be developed and optimized... 

Normally, this silyl ether formation reaction is base catalyzed and requires the addition of, for example, an amine, to proceed unless the reagent contains its own base, as is the case with HMDS. The use of HMDS to chemically passivate the hydrophilic surface is notable in another way in that it yields only a gaseous reaction product, ammonia. Other similar adhesion promoters include trimethyl-silyldiethylamine (TMSDEA), which can be more effective but also less stable than HMDS. Wafers with inorganic CVD BARCs, such as Si OyNj, Si Ny, etc., are also typically primed for similar reasons. 

CVI is a special CVD process in which the gaseous reactants penetrate (or infiltrate) a porous structure which acts as a substrate and which can be an inorganic open foam or a fibrous mat or weave. The deposition occurs on the fiber (or the foam) and the structure isgradually densified to form a composite.The chemistry and thermodynamics of CVT are essentially the same as CVD but the kinetics is different, since the reactants have to diffuse inward through the porous structure and the by-products have to diffuse out.f l Thus, maximum penetration and degree of densification are attained in the kinetically limited low-temperature regime. 

Kern, W., and Ban V., CVD of Inorganic Thin Films, in Thin-Film Processes, (J. Vossen and W. Kern, eds ). Academic Press, New York (1978)... 

Woolfson,R. G., Application Specific Electronic Materials by Ion Implantation and CVD,"HighPerformance Inorganic ThinFilm Coatings Conf, GAMI, Gorham, ME 04038 (Oct. 1968)... 

CVD is used in the industrial production of inorganic structural fibers such as boron and silicon carbide. Boron fibers are, in... 

Properties. CVD boron fibers have high strength, high modulus, and low density. Their properties are summarized and compared with SiC fibers and other inorganic fibers in Table 19.2 (data supplied by the manufacturers). 

The approaches used for preparation of inorganic nanomaterials can be divided into two broad categories solution-phase colloidal synthesis and gas-phase synthesis. Metal and semiconductor nanoparticles are usually synthesized via solution-phase colloidal techniques,4,913 whereas high-temperature gas-phase processes like chemical vapor deposition (CVD), pulsed laser deposition (PLD), and vapor transfer are widely used for synthesis of high-quality semiconductor nanowires and carbon nanotubes.6,7 Such division reflects only the current research bias, as promising routes to metallic nanoparticles are also available based on vapor condensation14 and colloidal syntheses of high-quality semiconductor nanowires.15... 

The conductors, semiconductors, and superconductors that have been discussed are materials that can be prepared via some type of CVD process. In order to prepare each material, a precursor is required. The precursor chemistry of these materials is based heavily on organometallic and inorganic chemistry. Numerous ligand platforms have been investigated for use in the preparation of suitable CVD precursors. 

Chemical vapor deposition (CVD) is a process whereby a thin solid film is synthesized from the gaseous phase by a chemical reaction. It is this reactive process that distinguishes CVD from physical deposition processes, such as evaporation, sputtering, and sublimation.8 This process is well known and is used to generate inorganic thin films of high purity and quality as well as form polyimides by a step-polymerization process.9-11 Vapor deposition polymerization (VDP) is the method in which the chemical reaction in question is the polymerization of a reactive species generated in the gas phase by thermal (or radiative) activation. 

Another participant in the French nuclear program, Le Carbone-Lorraine, developed inorganic membranes by combining their know-how in the field of membranes with their expertise in carbon. They developed tubular UF and MF membranes using a tubular carbon support (inner diameter 6 mm, outer diameter 10 mm). The carbon support is made of carbon fibers coated with and bonded by CVD carbon, the separating layers also being made of carbon. These membranes have been marketed since 1988. 

We present results for two standard tin oxide precursors, DMTC and MBTC, as well as for tin tetrachloride. The latter compoimd is included in the analysis to provide perspective on the thermal stabihty of the inorganic system relative to the organometalhc ones. All chemical equihbrium calculations were performed with the EQUIL-code from the CHEMKIN-suite [ 100], using the thermochemical data discussed in the previous sections. The temperature range selected was 298-1023 K, the concentration of tin precursor was kept at 2 mol %, while the concentrations of oxygen and water were held at 20 mol % and 5 mol %, respectively. The total pressure was 1 atm. These conditions are similar to those used in commercial tin oxide CVD processes. Note that in the following discussion of reaction mechanisms, all heats of reaction (AHg) are given at 298 K. 

The CVD method can form a polymethylsiloxane layer of 0.6-0.8 nm on the inorganic particles (Table 12.1.2). Especially, the polysiloxane-modified titanium oxide has been used for the additives to cosmetics. Moreover, residual Si-H group grafted on the particles reacted with unsaturated organic compounds in the presence of Speier catalyst (47), H2PtCl6, to be functionalized by organic pendant group [Reaction (11 ). ... 

Scheme 12.1.7 Polymerization of polysiloxane in the modification of inorganic particles by a CVD method using 2,4,6,8-tetramethylcyclotetrasiloxane. (From Ref. 46.)...

There is much current interest in volatile compounds of some of the metallic elements which may be useful for CVD of thin films of electronic or structural materials.1 Among the presently utilized precursors for metal oxide-containing films, the /i-diketonate family has been employed by numerous researchers.2 A previous volume of Inorganic Synthesis described the general... 

---