Patent ID: 8584054

Claim:
A photomask manufacturing apparatus, comprising: a first generating unit configured to generate a pattern dimensional map of a photomask in which a mask pattern is formed on a transparent substrate, the pattern dimensional map being generated by measuring a mask in plane distribution of dimensions of the pattern; a second generating unit configured to generate a transmittance correction coefficient map by dividing a formation region of the pattern into a plurality of subregions and determining a transmittance correction coefficient for each subregion in accordance with a size of a pattern of said each subregion; a third generating unit configured to generate a transmittance correction value map by calculating a transmittance correction value of said each subregion on the basis of the pattern dimensional map and the transmittance correction coefficient map; and a changing unit configured to change a transmittance of the transparent substrate corresponding to said each subregion on the basis of the transmittance correction value map.