Analog micro-optics fabrication by use of a binary phase grating mask

In this paper, we present a new photo-mask technology capable of forming a continuous relief micro-optic profile on thick photo-resist. This technique eliminates many of the drawbacks of gray-scale and half-tone masking technology. An optical stepper is used to fabricate binary phase gratings of pi phase depth on a transparent quartz reticle. When the phase reticle is used in the stepper an analog intensity profile is created on the wafer. The period is constrained allowing for control of the 0th order in the stepper. The duty cycle of the phase gratings can be varied in such a way to provide the proper analog intensity profile for a wide range of micro-optics on the photo-resist. The design, analysis, and fabrication procedures of this technique will be discussed.