Electron beam writing techniques for fabricating highly accurate X-ray masks

The problems in electron beam writing for the membrane-process were investigated; the resist thickness on the thinned membrane was adequately uniform (3 sigma=0.44%), and the resultant pattern size error was negligible. Deformation due to mask chucking onto the electron beam (EB) cassette was small enough to allow production of acceptable gigabit ULSI devices. We also confirmed that the SiC membrane is durable enough for tile task of membrane-process, even with thermal impact of EB energy 40 times larger than that used in conventional writing. Moreover, the improvement of pattern size accuracy by using multiple writing was investigated in detail under various conditions of the beam step size, the writing time and tile resist sensitivity. The pattern width deviation was improved from 20 ro to 13% for 0.15 mu m line-and-space patterns by multiple writing, and was little dependent on the beam step size and the resist sensitivity.