Patent ID: 7879250

Claim:
A method of performing a plasma etch process on a workpiece surface of a workpiece comprising a surface material to be etched, comprising: placing the workpiece on a workpiece support in a chamber of the plasma reactor; introducing through a ceiling gas disperser a first process gas comprising an etchant species capable of causing etching of said surface material in a plasma, said ceiling gas disperser comprising mutually concentric inner and outer gas dispersers; generating a plasma in said chamber by coupling RF power into said chamber; controlling etch rate distribution across said workpiece surface by adjusting respective flow rates of said first process gas through respective ones of said inner and outer gas dispersers; reducing etch rate at an edge periphery of said workpiece surface relative to etch rate across a remainder of said workpiece surface by injecting a polymerizing gas through a workpiece support gas disperser provided on said workpiece support and facing said edge periphery, said workpiece support gas disperser defining a polymerizing gas injection pattern directed toward said edge periphery of said workpiece surface and confined generally to said edge periphery.