Patent ID: 7645707

Claim:
A method for etching a dielectric layer, wherein the dielectric layer is a silicon oxide based dielectric layer, over a substrate and disposed below a photoresist mask, comprising: placing the substrate in a plasma processing chamber; providing an etchant gas comprising a fluorine component, O 2 , and a sulfur component gas comprising at least one of H 2 S and a compound containing at least one carbon sulfur bond into the plasma chamber, wherein the etchant gas has an etchant gas flow and the sulfur component gas has a sulfur component flow, wherein the sulfur component flow is between 0.1-10% of the etchant gas flow, wherein the fluorine component is at least one of a hydrofluorocarbon and a fluorocarbon; forming a plasma from the etchant gas; and etching features with a height to weight aspect ratio of at least 5:1 into the dielectric layer through the photoresist mask with the plasma from the etchant gas, wherein the etchant gas reduces bowing in the critical dimension of the etched features.