Solid-phase epitaxy of amorphous silicon films by in situ postannealing using RPCVD

Abstract

Solid-phase epitaxy (SPE) of in situ As-doped amorphous Si (a-Si) deposited on SiO 2/Si 3N 4 patterned Si (1 0 0) wafers by reduced pressure chemical vapour deposition (RPCVD) using a H 2–Si 2H 6 gas system was investigated. The SPE was performed by applying in situ postannealing directly after deposition process. On the one hand, we studied the lateral SPE (L-SPE) length of As-doped Si on mask and their crystal quality by TEM/SEM characterisation for various postannealing temperatures (700–1000 °C for 60 s). We observed increase in L-SPE growth and decrease of dislocation density for higher postannealing temperatures. On the other hand, L-SPE length was also investigated for different postannealing times (0–120 min at 575 °C) and As concentrations. At these conditions the L-SPE length has increased with increasing postannealing time. For both, higher and lower annealing temperature region, crystallization has been inhibited for higher As concentrations. After modifying As-doping level, we were able to crystallize up to 500 nm of a-Si on mask to epi-Si by combination of 575 °C and 1000 °C postannealing.