A method etching features through a stack of a silicon nitride layer over a silicon layer over a silicon oxide layer in a plasma processing chamber is provided. The silicon nitride layer is etched in the plasma processing chamber, comprising; flowing a silicon nitride etch gas; forming the silicon nitride etch gas into a plasma to etch the silicon nitride layer, and stopping the flow of the silicon nitride etch gas. The silicon layer is, comprising flowing a silicon etch gas, wherein the silicon etch gas comprises SF6 or SiF4, forming the silicon etch gas into a, and stopping the flow of the silicon etch gas. The silicon oxide layer is etched in the plasma processing chamber, comprising flowing a silicon oxide etch gas, forming the silicon oxide etch gas into a plasma, and stopping the flow of the silicon oxide etch gas.