Process optimization of silicon-on-sapphire vapor-phase epitaxy

Thin (300-600 nm) heteroepitaxial silicon layers were deposited on R-plane sapphire wafers via hydride-chloride CVD technique using SiH
₄
and SiCl
₄
gas-vapor mixture with PH
₃
doping gas diluted by H
₂
. Obtained layers were studied with AFM, XRD, SEM, UV scattering and surface PV methods. Influence of SiH
₄
:SiCl
₄
volume ratio on process and layer parameters was investigated. It was found that the growth rate of Si layer was increased when the volume concentration of SiCl
₄
increased (at 900-1000 °C). Therewith the separate increase of SiH
₄
and SiCl
₄
volume ratio in gas-vapor mixture leads to a change of surface microrelief and Si-sapphire interface parameters. It was determined that the RMS (Rq) roughness of Si surface and microrelief height were decreased when the SiH
₄
:SiCl
₄
volume ratio in gas-vapor mixture changed from 8:1 to 4:1. XRD and SEM analysis of layers confirmed the improvement of the structure with increasing SiCl
₄
volume concentration.