Properties of in Situ Doped Amorphous and Polycrystalline Silicon Deposited by Chemical Vapor Deposition from Tertiarybutylarsine and Tertiarybutylphosph INE

Abstract

ABSTRACTTcrtiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) were evaluated as n-type dopant precursors for low pressure chemical vapor deposition (LPCVD) of in situ doped amorphous and polycrystalline silicon from silanc. The deposition kinetics, film composition, and electrical properties obtained with TBA and TBP dopant precursors are compared to that obtained when using arsine and phosphine as dopant precursors. Compared to the hydride dopant sources, TBA and TBP provide increased safety due to their sub-atmospheric vapor pressure (≃ 200 Torr at 26°C) and lower toxicity. Using mixtures of TBA and TBP with silane and hydrogen, high quality films of arsenic and phosphorus in situ doped amorphous and polycrystalline silicon were obtained. Dopant incorporation levels ranged from 5×1019 to l.5×1021 cm−3 as measured by SIMS. The deposition rate of polycrystallinc films deposited from TBA and TBP was enhanced by a factor of-≃-3X compared to the hydride dopants for the same mole fraction of dopant precursor. The minimum resistivitics of 5.0 and 1.4 mΩ-cm were obtained, following a 1000°C, 30 second rapid thermal anneal, for ≃500Å thick films on SiO2 deposited with TBA and TBP respectively. A drawback of TBA and TBP is the incorporation of ≃1.0 atomic percent carbon which is > 15X higher than obtained when using the hydride dopant sources. Carbon was observed under all deposition conditions examined.