Observation on Defects in Poly-Si Films Prepared by RTCVD Under Nonideal Conditions

Abstract

Polycrystalline silicon (poly-Si) thin films were deposited on quartz substrates by rapid thermal chemical vapor deposition (RTCVD) under nonideal conditions. Then, crystallographic defects in the poly-Si films were investigated by using transmission electron microscopy (TEM) and optical microscopy combined with defect etching. We found that as-deposited poly-Si films contain a lot of twin crystals, including first-order, second-order, third-order, and higher-order twinned crystals. Besides twinned crystals, stacking faults, dislocations, dislocation nets, dislocation loops, extended dislocations, and dislocation line arrays were also found. Finally, the origins of the defects were analyzed, being attributed to the peculiarities of the RTCVD-quartz growth system, stress caused by lattice and thermal mismatch, a huge temperature ramp, and nonideal deposition conditions. Although our experimental results cannot represent the crystallographic quality of poly-Si films prepared by RTCVD, they at least indicate what kinds and how many defects exist in poly-Si films when deposition conditions severely deviate from the optimum.

APCVD Deposition of Si Film on SiO₂ Patterned Si (111) Substrates for Solar Cells

“…Depending on the film thickness and other parameters, the grain size should be in the order of 10-100 µm on condition that there is a good design adjustment [8]. Different ways are used to prepare large grain poly-Si active layers for solar cells [9][10][11][12]. But it is desirable to obtain a large grain poly-Si active layer without the necessity of recrystallization.…”