Abstract

We use optical emission to study chemically assisted ion-beam etching. Ar-ion and Cl₂-gas beams are used separately and together to etch Al and Si. The atomic and electronic optical emission is measured with a multichannel analyzer spectroscopic system. The relationship between optical emission and etch rate is examined. We observe surface roughening caused by Ar sputtering of Al which is minimized by the addition of small amounts of O₂ to the etching chamber. This is ascribed to the smoothing out of ion-channeling effects by the amorphous oxide which grows on the surface and is itself sputtered off.¹ O₂ pressure determines the oxidation rate, while Ar pressure determines the sputter rate. As these two processes compete, the intensity of neutral Al (398.3 nm) varies, depending on whether the Ar ions are sputtering Al from Ai or Al₂O₃. Similar results are obtained for neutral Si (288.1 nm) for Si and SiO₂. The addition of the Cl₂ beam begins to alter the emission characteristics, since in addition to sputtering we expect chemical etching to form volatile Al and Si chlorides.

© 1987 Optical Society of America