Method and apparatus for etching carbon-doped organic silicate glass

A method for etching a carbon-doped Organic Silicate Glass (OSG) insulating layer on a semiconductor device, as disclosed herein, includes introducing into a processing chamber a substrate with a carbon-doped OSG insulating layer and an overlying mask layer having an aperture. A plasma is then developed within the chamber from an oxidizing gas and a high selectivity gas. The high selectivity gas is preferably either a bromine containing gases, or a chlorine containing gases, or both. The ratio of oxidizing gas to high selectivity gas is preferably no less than 4:1. In addition, an inert carrier gas may be also provided. The plasma is then used to etch the organic silicate glass insulating layer through the mask layer, thereby forming a via in the organic silicate glass insulating layer wherein an underlying silicon nitride barrier layer remains essentially intact.