GLASS SUBSTRATE-HOLDING TOOL AND METHOD FOR PRODUCING AN EUV MASK BLANK BY EMPLOYING THE SAME

There is provided a glass substrate-holding tool which is capable of preventing a glass substrate from being displaced or coming off and of controlling the occurrence ofscratches or the deposition of foreign substances on the glass substrate caused by holding action during the production of an EUV mask blank, and a method for producingan EUV mask blank or a functional film-provided substrate for an EUV mask blank by employing the glass substrate-holding tool.A glass substrate-holding tool which is adapted to be employed during the production of a reflective mask blank for EUV lithography (EUVL), includes an electrostatic chuck configured to catch and hold a portion of a rear surface of a glasssubstrate; 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 pressedby 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 200kgf; and wherein a pressing force per unit area applied to the glass substrate by themechanical chuck is at most 25 kgf/mm2.Fig. 1