LOW-TEMPERATURE SI2H6 SI EPITAXY INSITU DOPED WITH ASH3/SIH4

The use of disilane (Si2H6) as a silicon source for epitaxial deposition was investigated for both very low pressure chemical vapor deposition (thermal CVD) and plasma enhanced chemical vapor deposition (PECVD) from 600 to 800-degrees-C. The growth rates observed for temperatures at or below 750-degrees-C were at least an order of magnitude higher than those observed for silane (SiH4) using similar deposition conditions. An argon plasma was used to sputter clean the silicon surface, in-situ, immediately before the deposition. It was found that a low dc bias on the substrate during the argon sputter cleaning process helped remove carbon and oxide from the surface of the silicon substrate. A 16 min Ar sputter clean at 650-degrees-C, 2.5 W rf power, and -50 V dc bias resulted in a carbon and oxygen concentration at the epilayer-substrate of less than 4 x 10(18)cm/cm3 and 2 x 10(18)/cm3, respectively. In situ arsenic doping during disilane epitaxial growth was carried out by thermal CVD and PECVD using arsine (AsH3) diluted in silane (SiH4) at 800-degrees-C. The results were compared to similar experiments using only SiH4 as the silicon source. Up to 500 ppm of arsine was diluted in the reactant gas and it was found that the Si2H6 growth rates were insensitive to the arsine concentration in the gas phase.