Silicon deposited by low pressure chemical vapour deposition from Si 2H 6: experiments, modelling and properties

Abstract

This paper describes the study of low pressure chemical vapour deposition of silicon from disilane (Si 2H 6) in a horizontal hot-wall furnace. Special attention is devoted to the kinetic phenomena, and in particular to the thickness distribution across the wafers and across the load. Examples are given, which show that acceptable uniformities can be obtained. A simulation of these processes is also presented. For that, a two-dimensional model taking into account, in every region of the furnace, mass transport, fluid dynamics and chemical reactions in the gas phase and on the solid surfaces has been used. In particular, it shows that the much lower deposition rate obtained when silane (Si 2H 4) is the source gas is due to a much lower silylene (SiH 2) contribution. The SiH content measurements by Fourier transform IR spectroscopy show that, for similar deposition conditions (temperature and pressure), the SiH content of “SiH 4 films” is much higher than that of “Si 2H 6 films”, thus confirming than the ultimate silicon precursor is different for the two gases. The study of the crystallization properties of the amorphous films made on SiO 2 shows that they are dependent not only on the SiH content, but also on the deposition growth rate and pressure.