| abstract |
The invention is embodied in a method of processing ansemiconductor workpiece in a plasma reactor chamber,nincluding supplying a polymer and etchant precursor gasncontaining at least carbon and fluorine into the chamber atna first flow rate sufficient of itself to maintain a gasnpressure in the chamber in a low pressure range below aboutn20mT, supplying a relatively non-reactive gas into thenchamber at second flow rate sufficient about one half ornmore of the total gas flow rate into the chamber, inncombination with the first flow rate of the precursor gas,nto maintain the gas pressure in the chamber in a highnpressure range above 20mT, and applying plasma source powerninto the chamber to form a high ion density plasma having annion density in excess of 10 10 ions per cubic centimeter. Innone application of the invention, the workpiece includes annoxygen-containing overlayer to be etched by the process andna non-oxygen-containing underlayer to be protected fromnetching, the precursor gas dissociating in the plasma intonfluorine-containing etchant species which etch the oxygen-containingnlayer and carbon-containing polymer species whichnaccumulate on the non-oxygen-containing underlayer.nAlternatively, the high pressure range may be defined as anpressure at which the skin depth of the inductive fieldnexceeds 1/10 of the gap between the inductive antenna andnthe workpiece. |