Plasma composition for selective high-k etch

Abstract

A method for the selective removal of a high-k layer such as HfOover silicon or silicon dioxide is provided. More specifically, a method for etching high-k selectively over silicon and silicon dioxide and a plasma composition for performing the selective etch process is provided. Using a BClplasma with well defined concentrations of nitrogen makes it possible to etch high-k with at a reasonable etch rate while silicon and silicon dioxide have an etch rate of almost zero. The BClcomprising plasmas have preferred additions of 10 up to 13% nitrogen. Adding a well defined concentration of nitrogen to the BCl/Nplasma gives the unexpected deposition of a Boron-Nitrogen (BxNy) comprising film onto the silicon and silicon dioxide which is not deposited onto the high-k material. Due to the deposition of the Boron-Nitrogen (BxNy) comprising film, the etch rate of silicon and silicon dioxide is dropped down to zero. The Boron-Nitrogen (BxNy) comprising film can be removed during the etching process using the right substrate bias (leading to ion bombardment) or after the etching process by a simple water rinse since the Boron-Nitrogen (BxNy) comprising film is water soluble.