Projection Photolithography for Use in the Fabrication of Microcircuits

A new photographic technique for use in the construction of photo and process masks will be discussed. The projection writing technique has been used to produce various masks which are comparable in characteristics and quality to those currently being made via contact and other photographic techniques within the microelectronic industry. The zero velocity writing method has produced process mask patterns with line boundary definition of less than 5 microns. Rectangular comers of photo masks projected light images having rounded comers with radii of less than 10 microns. Exposure time intervals of 2.0 to 4.0 seconds were used to produce useful process mask patterns. Projection writing techniques were used to produce complex micro-circuit-type photo masks using one-step reduction factors of 4.0 to 22.0. Writing velocities of 6.0 to 0.25 millimeters per second produced useful photo mask forms upon high resolution Kodak plates. Minimum dimensional tolerance obtained in experimental writing was +0.005 inches. Analysis shows that dimensional tolerances of +5.0 microns are possible to achieve for the one-step writing method.