Patent ID: 8906248

Claim:
A method for etching features through a stack of a silicon nitride or silicon carbide layer over a silicon layer over a silicon oxide layer in a plasma processing chamber, comprising: etching the silicon nitride or silicon carbide layer in the plasma processing chamber, wherein the silicon nitride or silicon carbide layer is disposed below a silicon oxide layer, the etching comprising: flowing a silicon nitride or silicon carbide etch gas into the plasma processing chamber; forming the silicon nitride or silicon carbide etch gas into a plasma to etch the silicon nitride or silicon carbide layer; and stopping the flow of the silicon nitride or silicon carbide etch gas; etching the silicon layer positioned directly below the silicon nitride or silicon carbide in the plasma processing chamber, comprising: flowing a silicon etch gas into the plasma processing chamber that is different than the silicon nitride or silicon carbide etch gas and wherein the silicon etch gas comprises SF 6 or SiF 4 ; forming the silicon etch gas into a plasma to etch the silicon layer; and stopping the flow of the silicon etch gas; and etching the silicon oxide layer positioned below the silicon layer that is below the silicon nitride or silicon carbide layer in the plasma processing chamber, comprising: flowing a silicon oxide etch gas into the plasma processing chamber that is different than the silicon etch gas; forming the silicon oxide etch gas into a plasma to etch the silicon oxide layer; and stopping the flow of the silicon oxide etch gas, wherein the etching the silicon nitride or silicon carbide layer etches most of the silicon layer.