Tunable process for selectively etching oxide using fluoropropylene and a hydrofluorocarbon

A process of etching an oxide layer formed on a substrate and comprising silicon and oxygen overlying a non-oxide layer comprising silicon but substantially less oxygen than in said oxide layer, comprising the steps of:

• placing said substrate into a plasma reaction chamber;
• a first step of admitting into said chamber a first etching gas;
• exciting said first etching gas into a plasma;
• a second step of admitting into said chamber a second etching gas comprising fluoropropylene and a hydrofluorocarbon, wherein said first etching gas provides in etching said oxide layer less selectivity to said non-oxide layer than does said second etching gas;
• and
• exciting said second etching gas into a plasma.

A process for etching in a substrate a hole through a layer of silicon oxide and stopping on an underlying layer of silicon nitride, comprising the steps of:

• placing said substrate into a plasma reaction chamber;
• admitting a first etching gas into said chamber;
• exciting said first etching gas into a plasma to etch said hole part way through said oxide layer;
• admitting a second etching gas into chamber, said second etching gas comprising fluoropropylene, a hydrofluorocarbon, and argon;
• and
• exciting said second etching gas into a plasma to etch said hole through said oxide layer and down to said nitride layer.