Undoped silicon dioxide as etch mask for patterning of doped silicon dioxide

Abstract

Disclosed is a process of using undoped silicon dioxide as an etch mask for selectively etching doped silicon dioxide for forming a designated topographical structure. In one embodiment, a doped silicon dioxide layer is formed over a semiconductor substrate. An undoped silicon dioxide layer is formed and patterned over the doped silicon dioxide layer. Doped silicon dioxide is selectively removed from the doped silicon dioxide layer through the pattern by use of a plasma etch or another suitable etch that removes doped silicon dioxide at a rate greater than that of undoped silicon dioxide. The process may be used to form contacts to the semiconductor substrate. The process may also be used to form a structure with a lower and an upper series of parallel gate stacks, where the gate stacks have upper surfaces consisting essentially of undoped silicon dioxide.