Methods of fabricating phase shift masks by controlling exposure doses

A method of fabricating a phase shift mask having wider phase shifting trenches than non-phase shifting openings, comprising the steps of:

• forming a radiation blocking layer on a phase shift mask substrate;
• forming a first photoresist layer on the radiation blocking layer;
• exposing first portions of the first photoresist layer at a first exposure dose;
• exposing second portions of the first photoresist layer at a second exposure dose that is greater than the first exposure dose wherein the second portions are nonoverlapping with the first portions;
• developing the first photoresist layer;
• patterning the radiation blocking layer using the first photoresist layer as an etch mask to thereby produce first apertures in the radiation blocking layer beneath the first portions of the first photoresist layer and second apertures in the radiation blocking layer beneath the second portions of the first photoresist layer, the first apertures forming non-phase shifting openings on the phase shift mask substrate;
• removing the first photoresist layer;
• forming a second photoresist layer on the radiation blocking layer including in the first and second apertures;
• patterning the second photoresist layer to expose the phase shift mask substrate beneath the second apertures;
• and
• etching the exposed phase shift mask substrate beneath the second apertures, using the second photoresist layer as an etch mask, to thereby produce phase shifting trenches in the phase shift mask substrate that are wider than the non-phase shifting openings in the phase shift mask substrate.

A method of fabricating a phase shift mask having wider phase shifting trenches than non-phase shifting openings, comprising the steps of:

• forming a radiation blocking layer on a phase shift mask substrate;
• forming a first photoresist layer on the radiation blocking layer;
• exposing first portions of the first photoresist layer at a first exposure dose;
• further exposing second selected ones of the first portions of the first photoresist layer at a second exposure dose;
• developing the first photoresist layer;
• patterning the radiation blocking layer using the first photoresist layer as an etch mask to thereby form second apertures in the radiation blocking layer beneath the second selected ones of the first portions of the first photoresist layer and first apertures in the radiation blocking layer beneath the first portions of the first photoresist layer other than the second selected ones, the first apertures forming non-phase shifting openings on the phase shift mask substrate;
• removing the first photoresist layer;
• forming a second photoresist layer on the radiation blocking layer including in the first and second apertures;
• patterning the second photoresist layer to expose the phase shift mask substrate beneath the second apertures;
• and
• etching the exposed phase shift mask substrate beneath the second apertures, using the second photoresist as an etch mask, to thereby produce phase shifting trenches in the phase shift mask substrate that are wider than the non-phase shifting openings in the phase shift mask substrate.