Selective silicon nitride plasma etching.

摘要

A two-step method of etching a silicon nitride layer carrying a surface oxygen film from a substrate in a plasma reactor including the steps of (1) a breakthrough step of employing a plasma of oxygen free etchant gases to break through and to remove the surface oxygen containing film from the surface of the silicon nitride layer, and (2) a main step of etching the newly exposed silicon nitride with etchant gases having high selectivity with respect to the silicon oxide underlying the silicon nitride. The plasma etching is performed in a plasma reactor comprising a low pressure, single wafer tool. It can be performed while employing magnetic-enhancement of the etching. The etchant gases include a halide such as a bromide and a fluoride in the breakthrough step, and an oxygen and bromine containing gas in the main step. For example the above method can be used to etch a thin SI3N4 layer (16) formed in an opening (12) provided with TEO's oxide sidewalls (18 min ) to expose the underlying SIO2layer (14).