CVD Processes and Equipment

The book is divided into three major parts. The first covers a theoretical examination of the CVD process, a description of the major chemical reactions and a review of the CVD systems and equipment used in research and production, including the advanced subprocesses such as plasma, laser, and photon CVD. 

Describe the various processes and equipment used in R D and production such as thermal CVD, plasma CVD, photo CVD, MOCVD, and others. 

Zilko, J. L., Metallo-Organic CVD Technology and Equipment, in Handbook of Thin-Film Deposition Processes and Techniques, (K. K. Shuegraf, ed.), Noyes Publications, Park Ridge, NJ (1988)... 

In previous sections we introduced the basic elements for a conventional CVD system this section introduces some special CVD processes and their equipments. 

The author is fortunate to have the opportunity, as a consultant, to review and study CVD processes, equipment, materials and applications for a wide cross-section of the industry, in the fields of optics, optoelectronics, metallurgy and others. He is in a position to retain an overall viewpoint difficult to obtain otherwise. 

The U.S. electronics industry appears to be ahead of, or on a par with, Japanese industry in most areas of current techniques for the deposition and processing of thin films—chemical vapor deposition (CVD), MOCVD, and MBE. There are differences in some areas, thongh, that may be cracial to future technologies. For example, the Japanese effort in low-pressure microwave plasma research is impressive and surpasses the U.S. effort in some respects. The Japanese are ahead of their U.S. counterparts in the design and manufacture of deposition equipment as well. 

There are numerous materials, both metallic and ceramic, that are produced via CVD processes, including some exciting new applications such as CVD diamond, but they all involve deposition on some substrate, making them fundamentally composite materials. There are equally numerous modifications to the basic CVD processes, leading to such exotic-sounding processes as vapor-phase epitaxy (VPE), atomic-layer epitaxy (ALE), chemical-beam epitaxy (CBE), plasma-enhanced CVD (PECVD), laser-assisted CVD (LACVD), and metal-organic compound CVD (MOCVD). We will discuss the specifics of CVD processing equipment and more CVD materials in Chapter 7. 

This chapter introduces new equipment design and a CVD process methodology. The chapter then gives details of the most commonly used subsystems followed by some special applications of CVD processes. 

The MOCVD process does not involve a new type of CVD reactor. The reactor used is basically a thermal CVD rector. Metallo-organic compounds are used as precursors usually in conjunction with other reactants to reduce the operating temperature required in a thermal CVD reactor. The precursors and equipment costs are high for MOCDV reactors. As a result MOCVD is used when high-quality coating is required. These reactors are typically open-type reactors that operate in the Torr to atmospheric pressure range. 

These processes, CVD, PVD, and thermal spray have reached the stage of large industrial production with a constant R D effort, particularly in the development of new source materials with greater purity, the refinement of processii parameters, and the improvement of the equipment. In the next sections, the processes are reviewed as they pertained to the refractory carbides and nitrides. This review can only touch on the major aspects of these extended and complex technologies and the references should be consulted for further information. 

An important recent trend is the tendency for the two processes, CVD andPVD, to merge. For instance, CVD now makes extensive use of plasma (a physical phenomenon) and reactive PVD (evaporation or sputtering) occurs in a chemical environment. Much ofthenew equipment reflects this process integration in the concept of cluster tools which may incorporate CVD, etching, sputtering, and ion implantation in one piece of equipment. 

The Cluster Tool Concept. A recent trend in semiconductor equipment is the integration of two or more functions, such as CVD, PVD, etching, stripping, or rapid thermal processing, in one piece of equipment the so-called cluster tool. A continuous vacuum can be maintained, a feature which reduces the handling and contamination problems, increases the overall throughput, improves the process control, and generally lowers the cost. 

Copper is intrinsically a better metal than aluminum for the metallization of IC s. Latest developments in MOCVD show that it can be readily deposited without major changes in existing processing equipment. Diffusion problems are minimized and it appears that present barrier materials, such as titanium nitride or titanium-tungsten alloys, should provide adequate diffusion barriers for the copper-silicon couple, certainly up to the highest temperatures presently used in IC s processing (see Ch. 6). The development of CVD copper for semiconductor metallization is on a considerable scale at this time.Clt ]... 

The major optical coating process remains evaporation. However, sputtering, solgel, and CVD are making inroads because of the better properties they provide.fi l At this time, it is not clear which coating process will prove best but CVD, because of the excellent bond and hardness of the deposited materials and the relatively moderate cost of the equipment, is a good candidate. 

Applications. CVD ceramic powders such as SiC and Si3N4 are used to produce ceramic bodies for a wide variety of applications, either experimentally or in production. These include structural applications in high temperature or corrosive environments where metals are not suitable, in such areas as reciprocating engines, gas turbines, turbochargers, bearings, machinery, and process equipment. 

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