Low temperature Si₂H₆ Si epitaxy in-situ doped with AsH₃/SiH₄

Abstract

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° C. The growth rates observed for temperatures at or below 750° 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° 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 × 10¹⁸/cm³ and 2 × 10¹⁸/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° 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 concentraton in the gas phase.