Importance

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Abstract

An improved method for fabricating phase shifting masks suitable for semiconductor manufacture is provided. A photolithographic mask blank comprising a transparent substrate having an opaque layer of a standard thickness is provided. Using a photoresist mask, the opaque layer is patterned and etched with openings to form opaque light blockers. The substrate under the openings is then etched to a predetermined depth using the same photoresist mask or the opaque layer as a hard mask. A phase shift material, such as silicon dioxide, is then deposited over the opaque light blockers and into the openings to form rim phase shifters on the sidewalls of the light blockers and light transmission areas in the openings. The depth of the etch into the substrate and the thickness of the opaque layer determines the amount of the phase shift. These parameters are controlled to achieve a phase shift of 180.degree. or odd multiple thereof.

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First Claim