Patent ID: 8592106

Claim:
A method of manufacturing a mask blank substrate for use in a photomask to be chucked on a mask stage of an exposure apparatus, comprising: a step of measuring a before-chucking main surface shape in an actual measurement region of a main surface of a substrate; a step of obtaining, through simulation, an after-chucking main surface shape of the substrate when the photomask manufactured from the substrate is set in the exposure apparatus, based on the before-chucking main surface shape of the substrate and a shape of the mask stage; a step of performing correction for the substrate by calculating a first approximate curve approximate to a cross-sectional shape along a first direction in a correction region of the after-chucking main surface shape, calculating an approximate curved surface from the first approximate curve, and subtracting the approximate curved surface from the after-chucking main surface shape, thereby calculating an after-correction main surface shape; and a step of selecting the substrate in which the after-correction main surface shape has a flatness of a predetermined threshold value or less in the correction region.