Epitaxial silicon reactors

The effect of heating this axisymmetric arrangement from the outside is to create a very uniform temperature environment for each wafer, By this means, thermally-induced slip is virtually eliminated. 

At the pressures at which this system is run, deposition is diffusion controlled. Therefore, the flow patterns set up and boundary layer thicknesses are important to the goal of uniform deposition on all wafers. As noted in Chapter 3, the narrowing flow passage in the flow direction compensates for reactant depletion. 

As wafers get larger, fewer wafers per load can be handled. For example, the susceptor can have 10 faces with 4 wafers per face for 3 wafers, for a total of 40 wafers per load. For 5 wafers, the susceptor will have 5 faces and 2 wafers per face, for a total of 10. This loss of capacity can only be compensated for by building a larger reactor or by purchasing two systems. 

These systems have been the work horses for the less demanding epi applications. In general, epi thickness uniformity has not been as good as the radiative systems, but the biggest difficulty has been that they often produce wafers with significant slip defects. As noted earlier in Chapter 3, recent design modifications have tended to minimize these problems. 

Finally, clean room floor space is expensive, so this system has been designed so that the entire reactor can be outside the clean room, with one face occupying wall space only. 

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For epitaxial silicon wafers, product design focuses on optimizing the geometry of the plasma-enhanced, chemical-vapor-deposition (PECVD) reactor. To increase productivity, and maintain acceptable thickness uniformity, on the order of 5%, a simple optimization strategy locates a design that completes the deposition in 62 s. Then, for a standard manufacturing process, the economics are driven by the wafer costs, which are provided by a vendor at 206/wafer. At a sales price of 260/epitaxial wafer, the investor s rate of return is 18.3% and the return on investment is 25.3%. 

Without a doubt, a complete picture of the dynamics of dissociative chemisorption and the relevant parameters which govern these mechanisms would be incredibly useful in studying and improving industrially relevant catalysis and surface reaction processes. For example, the dissociation of methane on a supported metal catalyst surface is the rate limiting step in the steam reforming of natural gas, an initial step in the production of many different industrial chemicals [1]. Precursor-mediated dissociation has been shown to play a dominant role in epitaxial silicon growth from disilane, a process employed to produce transistors and various microelectronic devices [2]. An examination of the Boltzmann distribution of kinetic energies for a gas at typical industrial catalytic reactor conditions (T 1000 K)... 

Oh, L Takoukis, C.G. Neudeck, G.W. Mathematical modeling of epitaxial silicon growth in pancake chemical vapor deposition reactors. J. Electrochem. Soc. 1991, B8, 554-567. 

In this process, the substrate is placed inside a reactor supplied by different gases [21], The principle of the process is that a chemical reaction takes place between the source gases producing a solid material which condenses on all surfaces inside the reactor. CVD is widely used in the semiconductor industry to deposit various materials such as polycrystalline, amorphous, and epitaxial silicon, carbon fiber, filaments, carbon nanotubes, Si02, silicon-germanium, tungsten, silicon nitride, silicon oxynitride, titanium nitride, and various high-k dielectrics. 

CVD reactors operate at sufficiently high pressures and large characteristic dimensions (e.g., wafer spacing) such that Kn (Knudsen number) << 1, and a continuum description is appropriate. Exceptions are the recent vacuum CVD processes for Si (22, 23) and compound semiconductors (156, 157, 169) that work in the transition to the free molecular flow regime, that is, Kn > 1. Figure 7 gives an example of SiH4 trajectories in nearly free molecular flow (Kn 10) in a very low pressure CVD system for silicon epitaxy that is similar to that described by Meyerson et al. (22, 23 Meyerson and Jensen, manuscript in preparation). Wall collisions dominate, and be-... 

In the case of in-situ doping during epitaxy, a small amount of dopant gas is introduced into the reactor at the same time as the silicon precursor. The... 

Using a commercial MW-PCVD reactor equipped with a substrate bias, nucleation and growth of epitaxially orientated diamond films can be achieved on silicon substrates by applying a three-step procedure consisting typically of ... 

Epi Reactor A thermally programmable chamber in which epitaxial growth of silicon chips is carried out... 

It is an outstanding material for epitaxial deposition. Its silicon content by weight is greater than either trichlorosilane or silicon tetrachloride. Dichlorosilane deposits silicon more efficiently and at lower temperatures than the other chlorosilanes in epitaxial reactors. Dichlorosilane significantly lowers the processing time from that required with silane for deposition of thick layers at reduced temperatures. 

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