Glass substrate-holding tool and method for producing an EUV mask blank by employing the same

A glass substrate-holding tool which is adapted to be employed during the production of a reflective mask blank for EUV lithography (EUVL), comprising:

• an electrostatic chuck configured to catch and hold a portion of a rear surface of a glass substrate;
• and
• a mechanical chuck including pressing portions and configured to press portions of a film deposition surface of the glass substrate by the pressing portions so as to clamp and hold the glass substrate from a side of the film deposition surface and a side of the rear surface;
• wherein a caught and held portion of the glass substrate caught and held by the electrostatic chuck, and pressed portions of the glass substrate pressed by the mechanical chuck are located outside a quality-guaranteed region on each of the film deposition surface and the rear surface of the glass substrate;
• wherein the sum of a catching and holding force applied to the glass substrate by the electrostatic chuck and a holding force applied to the glass substrate by the mechanical chuck is at least 200 kgf;
• and
• wherein a pressing force per unit area applied to the glass substrate by the mechanical chuck is at most 25 kgf/mm2.