Evaluation of Damage in Crystalline Silicon Substrate Induced by Plasma Enhanced Chemical Vapor Deposition of Amorphous Silicon Films

Abstract

We evaluated damage to crystalline silicon (c-Si) induced by plasma enhanced chemical vapor deposition (PECVD) of hydrogenated amorphous silicon (a-Si:H). The damaged layer +-on the c-Si surface under the a-Si:H film was evaluated by lifetime measurements using the photoconductance method in conjunction with step etching. This damaged layer is approximately 2.8 nm and did not disappear by annealing at 200 °C for 30 min in the air atmosphere. The image from cross-sectional transmission electron microscope (TEM) observation also shows an area of contrast on the c-Si surface approximately 2.8 nm thick, which appears to be a damaged layer. Photoluminescence (PL) measurements revealed that this damage is a non-luminescent defect. We verified that the difference in H2 flow rate during the a-Si:H deposition has an effect on the depth of the damage penetration into the c-Si. We concluded that the H atom is the main cause of the damage introduced into c-Si during a-Si:H deposition by PECVD.