Si + SiH4 Reactions and Implications for Hot-Wire CVS of a-Si:H

Richard P. Muller1, Jason K. Holt2, David G. Goodwin2, and William A. Goddard, III1
1Materials and Process Simulation Center,
2Division of Engineering and Applied Sciences,
California Institute of Technology


Gas-phase chemistry is believed to play an important role in hot-wire CVS of amorphous silicon, serving to convert the highly-reactive atomic Si produced at the wire into a less-reactive species by reaction with ambient SiH4. We use quantum chemical calculations (B3LYP/cc-pVTZ) to examine the energetics and rates of possible gas-phase reactions between Si and SiH4. The results indicate that formation of triplet disilyne (Si2H2) and molecular hydrogen is exothermic by ~2 kcal/mol with a low barrier. It does not require collisional stabilization and thus can proceed at the low pressures characteristic of hot-wire CVD. Other singlet species can also play a role but may require collisional stabilization. Possible roles for singlet or triplet disilyne in film growth will also be discussed.

Figure 1: Free Energies (at 2000 K) for reactions of Si and SiH4.

Richard P. Muller <>
Last modified: Fri Feb 25 11:32:31 2000