Patent ID: 7135410

Claim:
A method for etching a feature in an etch layer through a mask over a substrate, comprising: placing the substrate in a process chamber; providing a first etch plasma composition to the process chamber, wherein the first etch plasma composition begins etch a feature in the etch layer; providing a second etch plasma composition, wherein the second etch plasma composition continues to etch the feature in the etch layer; and providing a third etch plasma composition, wherein the third etch plasma composition continues to etch the feature in to etch layer, wherein the third etch plasma composition is more aggressive with respect to etch stop than the second etch plasma composition and the second etch plasma composition is more aggressive with respect to etch stop than the first etch plasma composition, and wherein the first etch plasma is more selective than the second etch plasma and the second etch plasma is more selective than the third etch plasma.