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

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 degrees 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 H-2 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.