Methods for reducing plasma-induced charging damage

A method for protecting a semiconductor substrate from charging damage while etching through a selected portion of a conductive layer above said substrate, the etching being performed in a plasma in a plasma chamber, the charging damage being formed from a plasma induced current through said substrate, comprising:

• providing said semiconductor substrate, said semiconductor substrate having a surface, said surface having a gate oxide region covered by a thin gate oxide layer, a field oxide region covered by a field oxide layer, and a first region, said field oxide region being located between said gate oxide region and said first region, said conductive layer covering said substrate and laying over said thin gate oxide, over said field oxide and over said first region of said surface of said substrate;
• providing an etch mask over said conductive layer, said etch mask protecting said conductive layer over said thin gate oxide region, said etch mask having an opening exposing said selected portion of said conductive layer, said selected portion of said conductive layer extending over said first region and over a portion of said field oxide region;
• performing a bulk etch partially through said selected portion of said conductive layer using a high density plasma and terminating the bulk etch while a remainder of said selected portion of said conductive layer remains to be etched;
• and
• performing a clearing etch through said remainder of said selected portion of said conductive layer using a low density plasma, thus exposing said first region of said surface of said substrate to said plasma while using said low density plasma, the density of said low density plasma being substantially minimized to reduce said charging damage by reducing said plasma-induced current flowing from said conductive layer through one of said thin gate oxide region and through said substrate to said first region of said surface of said substrate.

A method of etching through a conductive layer disposed underneath a mask layer and above a substrate, said method comprising:

• performing a bulk etch step comprising etching a first portion of said conductive layer through said mask layer using a plasma with a first plasma density;
• wherein said bulk etch step is terminated while a remainder of the conductive layer remains to be etched;
• performing a clearing etch step comprising etching through the remainder of the conductive layer using a plasma with a second plasma density;
• wherein the second density is substantially minimized relative to the first density to reduce charging damage caused by a current flowing from the conductive layer to the underlying substrate.