Patent ID: 7081411

Claim:
A method for etching a through via on a wafer of semiconductor material, wherein the wafer has a front side surface and a backside surface, comprising: applying a layer of photoresist material to the backside surface of the wafer; exposing the layer of photoresist to a light source, wherein the developed photoresist is removed to form at least one via in the remaining photoresist layer; baking the remaining photoresist layer in order to harden the remaining photoresist layer, wherein the baking of the remaining photoresist layer comprises a first heating step wherein the remaining photoresist layer is heated at a temperature of about 130° C. to about 135° C. for about one hour, and a second heating step wherein the remaining photoresist layer is heated at a temperature of about 180° C. to about 190° C. for about one hour, and wherein the use of the first heating step and the second heating step avoids thermal shock of the photoresist layer; and gas plasma etching the semiconductor material adjacent to the at least one via to form a through via between the backside surface and the front side surface of the wafer.