Microcircuit photomasks from automatic techniques

A new method for rapidly constructing photographic masks which are required in the fabrication of microelectronic circuits is described. The method employs an optical projection technique to obtain a precisely defined pencil of light which is used for "writing" on a high resolution photographic plate. The photomask geometry is exposed in a raster-like format by accurate servo-controlled translation of the high resolution plate with respect to the projected light beam and by relay controlled automatic shuttering employed in conjunction with the operation of the servosystem. The automatic projection method provides an inherent optical reduction factor of 2 to 22 times and has permitted one-step fabrication of master photomasks having image characteristic tolerances and definitions as follows: vertical positional of ±50.0 microns, horizontal positional of ±10.0 microns, vertical edge of less than 2.5 microns, and horizontal edge of less than 25.0 microns. Writing speeds of 2.0 to 80.0 mils per second were used to produce line widths from 6.0 to 100.0 microns.