Patent ID: 7754394
Filing Date: 2010-07-13
Classification: G03F

Abstract:
1. A method of making a photomask using a two-step opaque layer etching process which comprises: providing a transparent substrate; depositing an opaque layer on the transparent substrate; depositing a resist layer on the opaque layer; imaging and developing a resist mask pattern in the resist layer which exposes portions of the opaque layer; etching the exposed portions of the opaque layer using a first etchant in a main etch first step that etches both the opaque layer and the resist layer and forms a patterned opaque layer; etching any residual opaque layer in an overetch second step using a second etchant that etches both the opaque layer and the resist layer, whereby the second etchant needs to be more selective to etching the resist layer than the opaque layer; and removing the resist layer and forming the photomask; wherein the first etchant has a selectivity of the amount of opaque layer removed to the amount of resist layer removed of about 0.4 to 1 and the second etchant has a selectivity of the amount of opaque layer removed to the amount of resist layer removed of about 0.3 to 0.75.