ETCHING APPARATUS FOR SEMICONDUTOR FABRICATION

Method of operating an apparatus which allows etching different substrate etch areas of a substrate having different pattern densities at essentially the same etch rate. The apparatus includes (a) a chamber; (b) an anode and a cathode in the chamber; and (c) a bias power system coupled to the cathode, wherein the cathode includes multiple cathode segments. The operation method is as follows. A substrate to be etched is placed between the anode and cathode, wherein the substrate includes N substrate etch areas, and the N substrate etch areas are directly above the N cathode segments. N bias powers are determined which when being applied to the N cathode segments during an etching of the substrate, will result in essentially a same etch rate for the N substrate etch areas. Then, the bias power system is used to apply the N bias powers the N cathode segments.