In-Situ Testing of Electron Beam Lithographic Masks
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
Electron beam (EB)-transmission masks are tested for dust particles or other mask defects by projecting an electron shadow image of mask subsections onto an electron detector array incorporating some 105 individual detectors in an integrated charge transfer device (CTD). Fig. 1 shows an electron beam 1 with a cross-section of approximately 1 x 1 mm exposing a subarea 2 of transmission mask 3; the shadow image impinges on electron detector array 4, whose surface corresponds to the beam cross-section. The detectors in array 4 have an electron-sensitive surface of some 0.5 x 0.5 micrometer and are arranged in a matrix at a mutual spacing of some 4 micrometers; a multi-hole metallic diaphragm defines the detector pattern. Electrons entering the detector openings generate electrical charges in the CTD beneath the diaphragm.