AN ELECTRON-BEAM INSPECTION SYSTEM FOR X-RAY MASK PRODUCTION

SEMSpec is a scanning electron-beam inspection system designed for high-resolution die-to-die inspections of conductive x-ray masks, wafer prints, or stencil masks in a production environment. The inspection sensitivity can be varied from 97% detection of 50-nm defects, at a rate of 27 min cm-2, to 97% detection of 250-nm defects at 1 min cm-2. A thermal-field-emission source produces a Gaussian profile electron beam that is moved by electrostatic deflectors over the continuously moving substrate that is being inspected. Secondary electrons from the substrate are collected in a high-speed detector and the resulting digitized image data is stored in a specialized memory system. Pairs of images to be compared are continuously transferred from the memory to a high-speed defect processor for analysis. Defect reports from the defect processor are analyzed during inspection and stored for subsequent review. We describe the overall system including the electron-beam column with its six-emitter field-emission gun, the deflection system, the secondary-electron detector, the linear-motor drive stage, the control system, the robotic mask handler, and the image-data flow from the high-speed image acquisition subsystem through the analysis system. The electron-beam column is described in detail in a companion paper [W. D. Meisburger, A. A. Desai, and A. D. Brodie, J. Vac. Sci. Technol. B 9, 3010 (1991)]. All functions of the highly automated system-including vacuum control, mask loading, electron-beam column setup, and inspection-can be operated from the system control computer.