Fabrication of phase-shifting lithographic masks

Abstract

A phase-shifting lithographic mask is fabricated, in one embodiment, by using a resist layer that is negative tone with respect to a (patterned) electron beam and is positive tone with respect to a (flood) mid-ultraviolet beam, with the tone of the electron beam predominating over that of the mid-ultraviolet beam. The resist layer is spun on a body comprising a patterned metallic layer located on a (transparent) quartz slab. The body is subjected from below to a flood mid-ultraviolet beam and from above to a patterned electron beam whose edges are located somewhere in the midst of the patterned opaque layer but are not coincident with any edges of the patterned opaque layer. Thus, a subsequent development of the resist layer removes those regions and only those regions of the resist layer upon which the ultraviolet beam was incident--i.e., not in the shadows cast by the patterned opaque layer--in the absence of incidence of the patterned electron beam. Then, an anisotropic etching removes to a prescribed depth the portions of the (transparent) substrate not covered by the remaining (patterned) resist layer. In other embodiments, the (patterned) electron beam is replaced by a (patterned) deep ultraviolet beam. In still other embodiments the same radiation (wavelength) can be used for the patterned beam as for the flood radiation in conjunction with a resist layer whose tone can be reversed by an intermediate processing step between irradiations with the patterned and flood beams, respectively.