Journal of Vacuum Science & Technology B, Vol.12, No.3, 1390-1393, 1994
Arsenic Gas-Phase Doping of Polysilicon
Polysilicon layers have been doped with high uniform concentrations of arsenic in short processing times using gas-phase doping. The polysilicon layers were doped at total system pressures from 1 to 760 Torr with arsine or tertiarybutylarsine (TBA) as gas-phase dopant sources. An arsenic concentration as high as >4 X 10(20) atm/cm3 in 100 nm polysilicon layers was measured after a 60 s diffusion in 2.4% arsine in He at 1000-degrees-C at 760 Torr. Using tertiarybutylarsine (TBA) at 3 Torr, a sheet resistance of 2.5 kOMEGA/square was measured in a 100 nm polysilicon layer after 12 min at 900-degrees-C. Doping at temperatures as low as 770-degrees-C also gave high arsenic concentrations. Finally, a 6 mum deep DRAM trench capacitor was uniformly doped with arsenic to a concentration of 8 X 10(19) atm/cm3 using gas-phase doping and a two-step polysilicon deposition process.