RIE etching of deep trenches in Si using CBrF 3 and SF 6 plasma

Abstract

A two step RIE etch process offers the capability to form deep trenches with ideal profiles in bulk silicon. The first step in CBrF 3 transfers the pattern of the structured tri-level system into the silicon. Because the sidewalls are not smooth and the corners at the bottom of the 4 to 6 μm deep trenches are relatively sharp, a further short etch step in SF 6 was introduced. The RIE with CBrF 3 results in an anisotropic etch of Si compared to SF 6 which leads due to the isotropic etch behaviour to smooth and slightly tapered side-walls and to a rounded bottom.