Observation of GeO_2 agglomeration in the oxidized polycrystalline-Si_(1-x) Ge_x films by electron beam irradiation

摘要

We have observed the morphological and compositional changes that occurred in oxidized poly-Si_(1-x)Ge_x film during the electron-beam irradiation in the transmission electron microscope (TEM). Poly-Si_(1-x)Ge_x films with various compositions and about 1000A in thickness were deposited on oxidized Si wafers (with 1000 A thick thermal SiO_2). The oxidations were carried out in a conventional tube furnace at 800℃. Cross sectional samples of oxidized poly-Si_(1-x)Ge_x films were exposed to electron-beam irradiation with kinetic energy of 300keV in the TEM. Before irradiation, the oxide layer was composed of a mixture of SiO_2 and GeO_2 phases. However, during the electron-beam irradiation, significant changes in microstructure and elemental distribution occurred. For the oxidized poly-Si_(0.6)Ge_(0.4) films, the agglomeration of GeO_2 was observed at the surface region. In the case of the oxidized poly-Si_(0.4)Ge_(0.6), films, in contrast, the crystallization of GeO_2 occurred in the oxide layer. Ge lattice fringes and twinning were observed in the oxide layer.