Abstract: A large-size substrate adapted for light exposure is of a plate shape having a diagonal length or diameter of 500-2,000 mm, a thickness of 1-20 mm, and a peripheral surface with a roughness Ra of 0.05-0.4 ?m. The number of particles released from the substrate periphery during cleaning is minimized, leading to an improved yield in the cleaning step. The substrate can be manually handled, achieving an improvement in substrate quality without a need for a handling mechanism.

Abstract: A large-size glass substrate, from which a photomask substrate is formed, is prepared by processing a large-size glass substrate stock by (1) a flattening removal quantity based on height data of the substrate stock in the vertical attitude plus a deformation-corrective removal quantity. The deformation-corrective removal quantity is calculated from (2) a deflection of the substrate stock by its own weight in the horizontal attitude, (3) a deformation of the photomask substrate caused by chucking in an exposure apparatus, and (4) an accuracy distortion of a platen for supporting a mother glass.

Abstract: A large-size glass substrate, from which a photomask substrate is formed, is prepared by processing a large-size glass substrate stock by (1) a flattening removal quantity based on height data of the substrate stock in the vertical attitude plus a deformation-corrective removal quantity. The deformation-corrective removal quantity is calculated from (2) a deflection of the substrate stock by its own weight in the horizontal attitude, (3) a deformation of the photomask substrate caused by chucking in an exposure apparatus, and (4) an accuracy distortion of a platen for supporting a mother glass.

Abstract: A large-size substrate having improved flatness is prepared by measuring the flatness of one surface or opposite surfaces of a large-size substrate having a diagonal length of at least 500 mm, and partially removing raised portions on the one surface or opposite surfaces of the substrate by means of a processing tool on the basis of the measured data. The processing tool is adapted to blast a slurry of microparticulates in water carried on compressed air against the substrate.

Abstract: A large-size substrate having improved flatness is prepared by measuring the flatness of one surface or opposite surfaces of a large-size substrate having a diagonal length of at least 500 mm, and partially removing raised portions on the one surface or opposite surfaces of the substrate by means of a processing tool on the basis of the measured data. The processing tool is adapted to blast a slurry of microparticulates in water carried on compressed air against the substrate.

Abstract: A large-size substrate adapted for light exposure is of a plate shape having a diagonal length or diameter of 500-2,000 mm, a thickness of 1-20 mm, and a peripheral surface with a roughness Ra of 0.05-0.4 ?m. The number of particles released from the substrate periphery during cleaning is minimized, leading to an improved yield in the cleaning step. The substrate can be manually handled, achieving an improvement in substrate quality without a need for a handling mechanism.