Method of forming multiple layer attenuating phase shifting masks

摘要

This invention describes a new method of forming a double layer attenuating phase shifting mask. A first pattern is formed in a layer of attenuating phase shifting material and an alignment pattern is formed in a layer of opaque material. A first resist is used to form the first pattern. A pellicle is used to restrict the deposition of a second resist to the alignment region of the mask only and as a result neither the first resist nor the second resist must withstand dry etching steps. The first resist is removed before the step of forming the first pattern in the attenuating phase shifting material and cleaning before this step is carried out is thereby improved.