Low-temperature epitaxial growth of in-situ heavily b-doped Si_(1-x)Ge_x films using ultraclean LPCVD

摘要

In-situ heavy doping of B into Si_(1-x)Ge_x epitaxial films on the Si(100) substrate have been investigated at 550 deg C in a SiH_4(6.0Pa)-GeH_4(0.1-6.0Pa)-B_2H_6(1.25x10~(-5)-3.75x10~(-2)Pa)-H_2(17-24Pa) gas mixture by using an ultraclean hot-wall low-pressure CVD system. The deposition rate increased with increasing GeH_4 partial pressure, and it decreased with increasing B_2H_6 partial pressure only at the higher GeH_4 partial pressure. As the B_2H_6 partial pressure increased, the Ge fraction scarcely changed although the alttice constant of the film decreased. These characteristics can be explained by the suppression of both the SiH_4 and GeH_4 adsorption/reactions in a similar degree due to B_2H_6 adsorption on the Si-Ge and/or Ge-Ge bond sites. The B concentration in the film increased proportionally up to 10~(22)cm~(-3) with increasing B_2H_6 partial pressure.