Effects of temperature and HCl flow on the SiGe growth kinetics in reduced pressure–chemical vapor deposition

Abstract

Using a reduced pressure chemical vapor deposition cluster tool, we have studied at 20 Torr the growth kinetics of SiGe using a dichlorosilane+germane+hydrochloric acid chemistry. Adding HCl leads at 700 °C to a significant increase in the germanium content x of SiGe layers. Adopting a x2/(1−x)=n(F(GeH4)/F(SiH2Cl2)) dependence of x on the F(GeH4)/F(SiH2Cl2) mass flow ratio, this translates into an n value linearly increasing with the HCl mass flow from n=0.66 (no HCl) up to n=2.24 (F(HCl)/F(H2)=0.00625). The SiGe growth rate increases strongly with an increasing GeH4 flow. This is attributed to an increased hydrogen desorption caused by the presence of Ge atoms on the growing surface that frees nucleation sites for the incoming Ge and Si atoms. Meanwhile, adding HCl leads to a strong, linear reduction of the SiGe growth rate with the HCl mass flow. As expected, the Ge concentration decreases significantly as the growth temperature increases from 650 to 750 °C. The associated n parameter depends exponentially on the reverse absolute temperature, with an “activation energy” of the order of −15 kcal mol−1. At the same time, the SiGe growth rate increases strongly as the growth temperature increases, with an activation energy dropping from 47 down to 12 kcal mol−1 as the Ge content in the film goes up (from 0% up to 27% at 700 °C).