Method of making masks for phase shifting lithography

摘要

An improved method of fabricating phase shifting masks for semiconductor manufacture includes protecting an opaque layer of the mask during the mask fabrication process with a toughened layer of resist. For forming a Levenson phase shifting mask, an opaque layer is deposited on a transparent substrate. The opaque layer is then patterned using a layer of resist. This layer of resist is toughened and de-sensitized to subsequent patterning and intermediate processing. A phase layer of resist is then deposited on the toughened layer of resist and patterned for etching phase shifting areas in the substrate. During the etching process the opaque layer is protected by the toughened layer of resist. Etching of the phase shifting areas on the substrate can be in stages using a voting technique.