HF-chemical etching of the oxide layer near a SiO2/Si(111) interface

The HF-chemical etching process near the SiO2/Si(111) interface (<1 nm) is investigated by scanning reflection electron microscopy and microprobe Auge r electron spectroscopy. The HF etching of the SiO2 layer thermally grown o n an atomically flat Si(111)- 7x7 surface progresses in a layer-by-layer ma nner, and then the final layer of oxide (similar to 0.3 nm) is removed in a two-dimensional void expansion with the H-terminated Si surface. This very uniform HF etching is thought to reflect the structural anisotropy of the SiO2 layer formed near the SiO2/Si(111) interface. (C) 1998 American Instit ute of Physics. [S0003-6951(98)04752-4].