Plasma etching with a microwave cavity plasma disk source

Abstract

A tunable resonant-cavity microwave plasma disk source is applied to etching very large scale integrated circuit compatible profiles in crystalline silicon. Anisotropic etching downstream from the plasma is demonstrated without the use of large, potentially damaging wafer biases. Etch rate and degree of anisotropy are determined as a function of process chamber pressure, microwave power, and wafer bias. Etch rates from 200 to 490 Å/min and degrees of anisotropy approaching 0.9 are obtained for pressures from 0.3 to 2 mTorr. Microwave power is varied from 150 to 200 W, and the wafer bias is varied from −10 to −50 V with a flowing mixture of 16 standard cm3/min (sccm)of CF4 and 4 sccm O2. Results are discussed in terms of simple microwave plasma etching theory and previously reported plasma characteristics.