Maskless Ion Beam Assisted Etching of Si Using Chlorine Gas

Characteristics of maskless ion beam assisted etching of Si have been investigated as a function of chlorine gas pressure. Focused Ga ion beam was irradiated on a Si substrate in chlorine gas atmosphere at a pressure ranging from 0 to 24 mTorr. The etching rate exhibited a maximum at a pressure of 8 mTorr, the value of which was about 5 times larger than the physical sputter etching rate, and decreased at higher chlorine gas pressure. At a pressure of 8 mTorr, the chlorine atom arrival rate was about 4 times larger than the Si removal rate. This ratio suggests that Si is mainly removed by forming volatile SiCl4.