Selective etching of silicon nitride over silicon oxide using ClF(3)/H(2) remote plasma

Precise and selective removal of silicon nitride (SiN(x)) over silicon oxide (SiO(y)) in a oxide/nitride stack is crucial for a current three dimensional NOT-AND type flash memory fabrication process. In this study, fast and selective isotropic etching of SiN(x) over SiO(y) has been investigated using a ClF(3)/H(2) remote plasma in an inductively coupled plasma system. The SiN(x) etch rate over 80 nm/min with the etch selectivity (SiN(x) over SiO(y)) of ~ 130 was observed under a ClF(3) remote plasma at a room temperature. Furthermore, the addition of H(2) to the ClF(3) resulted in an increase of etching selectivity over 200 while lowering the etch rate of both oxide and nitride due to the reduction of F radicals in the plasma. The time dependent-etch characteristics of ClF(3), ClF(3) & H(2) remote plasma showed little loading effect during the etching of silicon nitride on oxide/nitride stack wafer with similar etch rate with that of blank nitride wafer.