Epitaxial growth of Si and SiGe at temperatures lower than 500 °C with disilane and germane

Abstract

We have investigated the feasibility of growing in a 300mm industrial reduced pressure chemical vapor deposition tool Si and SiGe layers at 500°C and lower thanks to disilane (Si2H6) and germane (GeH4). We have first of all evidenced the beneficial impact of the disilane partial pressure P(Si2H6) on the silicon growth rate (GR). Increasing P(Si2H6) by 5 (through a growth pressure increase or a H2 mass-flow reduction) enabled us to increase by more than 2 the Si GR. We were thus able to lower the Si growth temperature threshold (for which GR≥1nm·min−1) from 475°C down to 460°C only. Islands were present on the surface of the resulting Si layers, however. We have then studied the SiGe growth kinetics at 2666Pa (20Torr) with a H2 mass-flow divided by 5. Intrinsic SiGe growth rates were 3 times higher than Si GR in the 450°C–500°C temperature range. This is due to the catalysis of H desorption from the surface by Ge surface atoms, freeing sites for growth. A slight Ge concentration increase (from 37.5% up to 40.5%) together with a significant surface roughening was otherwise evidenced when increasing the growth temperature from 450°C up to 500°C. We have then evaluated the impact of the GeH4 mass-flow on the 450°C growth kinetics of SiGe. An almost linear increase of the SiGe growth rate (from 1 up to 3nm·min−1) together with a sub-linear increase of the Ge content x (from 22% up to 38%) occurred when increasing the GeH4 flow.