Quasi‐atomic layer etching of silicon with surface chlorination and removal using Ar or He plasmas

A comparative study of argon (Ar) and helium (He) plasmas is conducted in quasi‐atomic layer etching (ALE) processes for silicon (Si). The ALE window is identified to be between 35 and 55 V for Ar and 25–45 V for He, with an etch per cycle of 6.0 Å/cycle for Ar and 7.5 Å/cycle for He. Thirty percent thicker chlorination layers are observed with Cl2/He ALE than with Cl2/Ar ALE in the chlorination step. The penetration depth of He ions is twice that of Ar ions, with a standard deviation of 4.5 times greater. This study demonstrates that He ions in the removal steps considerably affect the subsequent modification steps in Si ALE.