Process for etching a multi-layer substrate

A process for plasma etching a multi-layer substrate in an etching device having a plasma etch deposition area to form a etched pattern therein, comprising:

• providing said multi-layer substrate having a plurality of layers comprising a silicon dioxide layer formed on an underlying silicon or metal silicide layer;
• forming on a major surface of the silicon dioxide layer a carbon-containing, etch mask defining a plurality of openings in a predetermined pattern, said plurality of openings exposing a plurality of areas of a major surface of the silicon dioxide layer;
• selectively plasma etching the plurality of exposed areas of the major surface of the silicon dioxide layer, selective to said silicon or metal silicide layer, with a carbon-free chemical etchant feed gas system comprising a halogen-containing chemical etching material and a hydrogen-containing material, at a relatively higher etch rate of the silicon dioxide than the underlying layer, selective to said underlying silicon or metal silicide layer, the hydrogen-containing material reacting with the halogen-containing material and the carbon-containing, chemical etchant protective patterned layer to form in situ a polyhalocarbon material reacting with oxygen which is released from the silicon dioxide layer to form gaseous by-products which are readily removed from the multi-layer substrate thereby exposing the surface of the silicon dioxide layer for continued etching of the silicon dioxide layer by said chemical etchant system;
• and
• exposing the silicon or metal silicide layer and, due to an absence of an oxygen source in the underlying silicon or metal silicon layer to react with said polyhalocarbon material being formed, retarding the etching process in said silicon or metal silicide layer by depositing said polyhalocarbon material on said silicon or metal silicide layer, thereby etching selectively said silicon dioxide layer so that the selectivity of the SiO.sub.2 etch to the Si or metal silicide layer is maximized.