An electron beam maskmaker

An electron beam machine is described, in which the ¼-µm diameter beam is computer controlled to define integrated circuit and other fine patterns at their final size in response to a coordinate data input. Electron sensitive resist is exposed on metallized quartz or glass substrates. Resist development followed by metal etching enables masks to be made, either for subsequent photolithography or, more usually, for use in the electron image projector developed by J. P. Scott. The mask drawing process is entirely automatic and the emphasis is on the rapid generation of complex patterns with high precision. A two-stage deflection system enables rectangular pattern elements to be drawn at a 10-MHz stepping rate and accurately positioned throughout a 2-mm square main deflection field. Patterns are automatically positioned, to an accuracy of ±1/8 µm, relative to an array of markers predeposited on the substrate. The beam is also refocused automatically at the markers. A mechanical stage for the substrate enables 50 × 50-mm arrays of patterns to be built up. A complete mask containing detail as small as 1 µm takes 1-3 h to draw. Finer patterns can be drawn, although more slowly.