Chemical vapor deposition , microelectronics processes

In the production of many microelectronic devices, continuous chemical vapor deposition (CVD) processes are used to deposit thin and exceptionally uniform silicon dioxide films on silicon wafers. One CVD process involves the reaction between silane and oxygen at a very low pressure. 

Chemical vapor deposition is distinguished from physical vapor deposition processes by the use of a chemical reaction, usually a decomposition, to create the chemical species that is deposited. An example important to the microelectronics industry is the formation of polycrystalline silicon by the decomposition of silane ... 

Reactions involving solids are very important in many technologies such as microelectronics processing, ceramics, ore refining, electrochemical deposition and etching, chemical vapor deposition and etching, and food processing. We will consider some of these applications in problems, but we first note several important examples. 

The prototype processes we consider in this chapter are chemical vapor deposition and reactive etching, and the other examples listed such as crystallization and catalytic reactions are basically simplifications of these processes. In chemical vapor deposition (CVD), gases react to form solid films in microelectronic chips and in wear protective coatings. 

Chemical vapor deposition is a key process in microelectronics fabrication for the deposition of thin films of metals, semiconductors, and insulators on solid substrates. As the name indicates, chemically reacting gases are used to synthesize the thin solid films. The use of gases distinguishes chemical vapor deposition (CVD) from physical deposition processes such as sputtering and evaporation and imparts versatility to the deposition technique. 

High-vacuum dry-processes, such as chemical vapor deposition (CVD) and molecular beam epitaxy (MBE), have made it feasible to control precisely the thickness of metal oxide thin films. In these techniques, the preparative conditions like pressure and substrate temperature can be widely varied, and the elemental composition in individual atomic layers is controllable by sequential supply of precursor gases [1]. The dense, defect-less oxide films thus prepared are frequently used as underlayers of microelectronics devices. 

Chemical vapor deposition is not restricted to the microelectronics industry. It is the key process in the fabrication of optical fibers where it enables grading of the refractive index as a function of the radial position in the fiber (JO. In the manufacturing industry the technique provides coatings with special properties such as high hardness, low friction, and high corrosion resistance. Examples of CVD reactions and processes are given in Table 1. 

Chemical vapor deposition is a key process for thin film formation in the development and manufacture of microelectronic devices. It shares many kinetic and transport phenomena with heterogeneous catalysis, but CVD reactor design has not yet reached the level of sophistication used in analyzing heterogeneous catalytic reactors. With the exception of the tubular LPCVD reactor, conventional CVD reactors may be viewed as variations on the original horizontal reactor. These reactors have complex flow fields and it is consequently difficult to control and predict the effect of operating conditions on the film thickness and composition. 

Kuo,T.-F., et al. (2001), Microwave-assisted chemical vapor deposition process for synthesizing carbon nanotubes,/. Vac. Sci. Technol. Microelectron. Nanometer Struct., 19(3), 1030-1033. 

Processing of metallic thin films by chemical vapor deposition has been rapidly developed during the past few years, mainly due to numerous potential applications in the microelectronics industry. Research groups worldwide publish in this or allied fields. Contributions come from diverse scientific domains, such as coordination and theoretical chemistry, chemical engineering, and of course materials science. Such an interest from the scientific community reveals that CVD is an attractive route for the deposition of metallic films. However, there are numerous and complex problems to solve before optintizing it. 

In chemical vapor deposition (CVD), a semiconducting or insulating solid material is formed in a reaction between a gaseous species and a species adsorbed on the surface of silicon wafers (disks about 10 cm in diameter and 1 mm thick). The coated wafers are subjected to further processing to produce the microelectronic chips in computers and most other electronic devices in use today. 

P3-23b Chemical vapor deposition (CVD) is a process used in the microelectronics industry to deposit thin films of constant thickness on silicon wafers. This process is of particular importance in the mamifactuiing of very iai-ge scale integrated circuits. One of the common coatings is Si3N4, which is produced according to the reaction... 

Another example of phase change during reaction is chemical vapor deposition (CVD), a process used to manufacture microelectronic materials. Here, gas-phase reactants are deposited (analogous to condensation) as thin films on solid surfaces (see Problem P3-25). One such reaction is the production of gallium arsenide, which is used in computer chips. 

Reif. R.. Plasma enhanced chemical vapor deposition of thin films for microelectronics processing. In Handbook of Plasma Processing Technology Fundamentals, Etching, Deposition, and Surface Interactions, (Rossnagel, S. M., Cuomo, J. J., and Westwood, W. D., Noyes, Eds.), Park Ridge, NJ, 1990. 

In general, for the deposition of thin films used in microelectronics, low-pressure processes, such as sputtering and low-pressure chemical vapor deposition (LP CVD), are preferred over the older, conventional chemical methods such as electroplating because deposition from an aqueous solution produces poorer quality films. On the other hand electrochemical and electroless metal deposition from solution are gaining renewed interest with micromachinists because of their emerging importance to LIGA. 

We shall consider three primar> examples as a means of illustrating the main concepts in this chapter. The first example is one of the reactions responsible for smog formation in the atmosphere. It consists of a single, reaction, among three species. The second example is the water gas shift reaction, and it illustrates the case of multiple reactions it consists of three reactions among six chemical species. The third example illustrates the complexity of common industrial reactions of interest, consisting of 20 reactions among 14 species. These reactions have been proposed to describe a silicon chemical vapor deposition process, which is an important step in the production of microelectronic materials. 

We now introduce the third example, which is a more complicated reaction network. The following chemistry has been proposed to describe a silicon chemical vapor deposition (CVD) reaction, which is an important process in the production of microelectronic materials. 

---