<i>In situ</i> observation of hydrogenated amorphous silicon surfaces in electron cyclotron resonance hydrogen plasma annealing

Abstract

The surface reactions of hydrogenated amorphous silicon (a-Si:H) films exposed to electron cyclotron resonance (ECR) H2 plasma, which is called ECR H2 plasma annealing, has been investigated by in situ polarization modulation infrared reflection absorption spectroscopy (PM-IR-RAS). The surfaces of a-Si:H films were exposed to ECR H2 plasmas at various substrate temperatures. To distinguish the roles of ionic species and atomic hydrogens, permanent magnets were employed to shut out charged species incident on the substrate. The surface reactions of a-Si:H films exposed to only atomic hydrogens were observed by in situ PM-IR-RAS and the results were compared with those exposed to ECR H2 plasmas. It was found that atomic hydrogens reacted with the Si–H2 and (SiH2)n bonds in the vicinity of the surfaces and did not etch the bulk of the films at room temperature. Moreover, it was suggested that atomic hydrogens penetrated into the bulk of a-Si:H film and promoted the Si-network modification as the substrate temperature increased. On the other hand, it was found that ionic hydrogens with the energy of 50 eV had energy enough to etch a-Si:H films.