PHOTORESIST STUDY REVEALS EXPOSURE TIME MORE CRITICAL THAN LIGHT INTENSITY.

The reciprocity between exposure time and light intensity for three commercially available photoresists is examined. All three resists exhibit a reciprocity failure in the sense that as intensity is decreased at a constant exposure level, the rate of increase in exposure time is less than the rate of decrease of intensity. This result implies that photoprinting process improvements such as increased light intensity and transmittance of the printing tool will not produce a fully reciprocal reduction in scan time. It likewise follows that printers which linearly adjust exposure time to account for variations in light intensity will not maintain a constant exposure level. In fact, for the resist tested, this technique for controlling the exposure level offers only a slight advantage over using a constant exposure time.