Method of phase shift mask fabrication comprising a tapered edge and phase conflict resolution

A method for forming a phase shifting photomask comprising:

• forming opaque features on a transparent substrate to form a mask pattern;
• determining areas of phase conflict in the mask pattern;
• forming phase shifters proximate to selected edges of the opaque features in phase conflict areas of the mask pattern using design rules of a computer aided design program to locate the phase shifters, said phase shifters comprising a phase shift layer deposited on the substrate;
• each said phase shifter including a tapered edge formed with a slope such that the tapered edge does not print on a target in a subsequent lithographic process.

A method for forming a phase shifting photomask comprising:

• providing a transparent substrate;
• forming a mask pattern on the substrate comprising opaque features;
• determining areas of phase conflict in the mask pattern;
• etching phase shifters in the substrate in areas of phase conflict using design rules of a computer aided design program to locate the phase shifters, said design rules locating the phase shifters along selected edges of the opaque features;
• each said phase shifter including a tapered edge spaced from its selected edge by a distance and extending into the substrate with a slope selected to not print during a lithographic process using the photomask.

A method for forming a phase shifting photomask comprising:

• determining a mask pattern having geometrical features including generally vertically oriented features and generally horizontally oriented features;
• determining areas of phase conflict in the mask pattern;
• forming an opaque layer on a transparent substrate and patterning the opaque layer to form a pattern of opaque features corresponding to the geometrical features;
• and
• forming phase shifters for selected edges of the opaque features in the areas of phase conflict, said phase shifters placed on the mask pattern using design rules of a computer aided design program, and with each of said phase shifters including a tapered edge formed with a slope such that the tapered edge does not print on a target in a subsequent lithographic process;
• said design rules specifying that the phase shifters are to be formed along first selected edges of the vertically oriented features in areas of phase conflict and along second selected edges of the horizontally oriented features in areas of phase conflict.