US Patent 9673058 Method for etching features in dielectric layers

A method for etching features in a silicon oxide containing etch layer disposed below a patterned mask in a chamber is provided. An etch gas comprising a tungsten containing gas is flowed into the chamber. The etch gas comprising the tungsten containing gas is formed into a plasma. The silicon oxide etch layer is exposed to the plasma formed from the etch gas comprising the tungsten containing gas. Features are etched in the silicon oxide etch layer while exposed to the plasma formed from the etch gas comprising the tungsten containing gas.