Study of plasma-surface interactions during overetch of polycrystalline silicon gate etching with high-density HBr/O-2 plasmas

Plasma-surface interactions occurring during overetch of polycrystalline si licon (poly-Si) gate etching with high-density HBr/O-2 plasmas have been in vestigated by x-ray photoelectron spectroscopy (XPS) and transmission elect ron microscopy (TEM). The temporal variation of the gate oxide thickness me asured by XPS indicates that both deposition of etch by-products SiBrxOy an d oxidation of Si substrate underlying thin SiO2 occur during exposure to H Br/O-2 plasmas. In particular, significant deposition of SiBrxOy, presumabl y coming from reactor walls, was observed at the beginning of the overetch step. Furthermore, TEM observations revealed that the profile evolution of oxide-masked poly-Si gates during overetch is limited by a sidewall deposit ion layer, which acts as an oxide mask for etching of poly-Si. (C) 2001 Ame rican Institute of Physics.