Photomask evaluation based on lithographic simulation using sidewall angle of photomask pattern
View Patent ↗According to an aspect of the invention, there is provided a photomask evaluation method including, acquiring a pattern image of a photomask, generating sidewall angle data on the sidewall angle of a pattern from the pattern image, extracting a pattern outline from the pattern image to generate outline data, and running a lithographic simulation on the basis of the outline data and the sidewall angle data to calculate an exposure margin.
1. A photomask evaluation method comprising:
acquiring a pattern image of a photomask;
generating sidewall angle data on the sidewall angle of a pattern from the pattern image;
extracting a pattern outline from the pattern image to generate outline data;
correcting a pattern outline position of the outline data on the basis of the sidewall angle data; and
running a lithographic simulation on the basis of the corrected outline data to calculate an exposure margin.
2. The photomask evaluation method according to claim 1 , wherein the sidewall angle data is generated on the basis of an intensity profile of a white line forming the pattern outline in the pattern image obtained by a scanning electron microscope.
3. The photomask evaluation method according to claim 1 , wherein the exposure margin indicates both or one of an exposure dose range and a depth of focus necessary to obtain a desired pattern dimension.
4. The photomask evaluation method according to claim 1 , wherein the exposure margin indicates a pattern dimension obtained by an optimum exposure dose and an optimum focal position.
5. A photomask evaluation apparatus comprising:
a scanning electron microscope for acquiring a pattern image of a photomask;
a pattern sidewall angle analyzing unit for generating sidewall angle data on the sidewall angle of a pattern from the pattern image acquired by the scanning electron microscope;
a pattern outline extracting unit for extracting a pattern outline from the pattern image acquired by the scanning electron microscope to generate outline data;
an outline data correcting unit for correcting, on the basis of the sidewall angle data generated by the pattern sidewall angle analyzing unit, a pattern outline position of the outline data generated by the pattern outline extracting unit; and
a lithographic simulator which runs a lithographic simulation on the basis of the outline data corrected by the outline data correcting unit to calculate an exposure margin.
6. The photomask evaluation apparatus according to claim 5 , wherein the pattern sidewall angle analyzing unit generates sidewall angle data on the basis of an intensity profile of a white line forming a pattern outline in the pattern image obtained by the scanning electron microscope.