Diffusion Chemical Vapor Deposition

Nomura M, Ono K, Gopalakiishnan S, Sugawara T, Nakao SI. Preparation of a stable silica membrane by a counter diffusion chemical vapor deposition method. J Memb Sci. 2005 251(l-2) 151-58. 

Fabrication methods that are generaby used to make these junctions are diffusion, ion implantation, chemical vapor deposition (CVD), vacuum deposition, and bquid-phase deposition for homojunctions CVD, vacuum deposition, and bquid-phase deposition for heterojunctions and vacuum deposition for Schottky and MIS junctions. 

Researchers in Japan have determined that copper interconnects deposited by metallo-organic chemical vapor deposition (MOCVD), then followed by chemical mechanical polishing, provides sub-quarter-micron interconnects and can be achieved on a production basis. Titanium nitride and borophosphosilicate glass provide effective barriers against copper diffusion.PL[H]... 

Chemical Vapor Deposition- Deposition of silicon oxide films is accomplished by CVD equipment. Either plasma CVD or ozone oxidation is used. Blanket tungsten films are also deposited by CVD equipment to create contact and via plugs. Polysilicon and silicon nitride films are deposited in hot-wall furnaces. TiN diffusion barrier films are deposited by either sputtering or CVD, the latter giving superior step coverage. 

Due to the fact that industrial composites are made up of combinations of metals, polymers, and ceramics, the kinetic processes involved in the formation, transformation, and degradation of composites are often the same as those of the individual components. Most of the processes we have described to this point have involved condensed phases—liquids or solids—but there are two gas-phase processes, widely utilized for composite formation, that require some individualized attention. Chemical vapor deposition (CVD) and chemical vapor infiltration (CVI) involve the reaction of gas phase species with a solid substrate to form a heterogeneous, solid-phase composite. Because this discussion must necessarily involve some of the concepts of transport phenomena, namely diffusion, you may wish to refresh your memory from your transport course, or refer to the specific topics in Chapter 4 as they come up in the course of this description. 

Materials processing, via approaches like chemical vapor deposition (CVD), are important applications of chemically reacting flow. Such processes are used widely, for example, in the production of silicon-based semiconductors, compound semiconductors, optoelectronics, photovoltaics, or other thin-film electronic materials. Quite often materials processing is done in reactors with reactive gases at less than atmospheric pressure. In this case, owing to the fact that reducing pressure increases diffusive transport compared to inertial transport, the flows tend to remain laminar. 

Certain numerical algorithms can benefit from the equation in a form that has the dependent variable Ft directly in the diffusive terms on the right-hand side. Moreover, for flows that have relatively small mean-molecular-weight gradients, the second term may be negligible. Examples of this situation would be if there is an inert carrier gas that dominates the species composition. It is not unusual in chemical-vapor-deposition processes for... 

A further consequence of the upstream diffusion to the burner face could be heterogeneous reaction at the burner. Such reaction is likely on metal faces that may have catalytic activity. In this case the mass balance as stated in Eq. 16.99 must be altered by the incorporation of the surface reaction rate. In addition to the burner face in a flame configuration, an analogous situation is encountered in a stagnation-flow chemical-vapor-deposition reactor (as illustrated in Fig. 17.1). Here again, as flow rates are decreased or pressure is lowered, the enhanced diffusion tends to promote species to diffuse upstream toward the inlet manifold. 

While our primary interest in this text is internal flow, there are certain similarities with the classic aerodynamics-motivated external flows. Broadly speaking, the stagnation flows discussed in Chapter 6 are classified as boundary layers where the outer flow that establishes the stagnation flow has a principal flow direction that is normal to the solid surface. Outside the boundary layer, there is typically an outer region in which viscous effects are negligible. Even in confined flows (e.g., a stagnation-flow chemical-vapor-deposition reactor), it is the existence of an inviscid outer region that is responsible for some of the relatively simple correlations of diffusive behavior in the boundary layer, like heat and mass transfer to the deposition surface. 

A wide variety of names are used in the electronic industry for various types of reactors, but two broad classifications of reactors based on the means by which the molecular species are delivered to the substrate are useful direct line-of-sight impingement and diffusive-convective mass transfer. The term chemical vapor deposition (CVD) has been used generally to describe... 

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