Patent ID: 6962879

Claim:
A process for etching a silicon nitride layer with selectivity to an underlying and/or overlying dielectric layer, comprising: introducing a semiconductor substrate into a plasma etching reactor, wherein the plasma reactor comprises a dual frequency parallel plate plasma reactor having a showerhead electrode and a bottom electrode on which the substrate is supported, the bottom electrode being supplied RF energy at two different frequencies or the showerhead electrode being supplied RF energy at a first frequency and the bottom electrode being supplied RF energy at a second frequency which is different from the first frequency, the semiconductor substrate having a layer of silicon nitride and the layer of silicon nitride having an underlying and/or overlying dielectric layer; supplying etching gas to the plasma etching reactor and energizing the etching gas into a plasma state, the etching gas including CH 3 F and O 2 supplied to the plasma etching reactor at a flow rate ratio of O 2 to CH 3 F of 0.65 to 1.5; etching exposed portions of the silicon nitride layer with the plasma so as to etch openings in the silicon nitride layer with the plasma while providing an etch rate selectivity of the etching rate of the silicon nitride layer to the etching rate of the dielectric layer of at least about 10.