| 摘要 |
This invention constitutes a method of fabricating a phase-shifting photolithographic mask reticle having identical light transmittance characteristic in all transparent regions. The method is applicable to those types of phase-shifting reticles that are fabricated by masking alternating transparent regions with photoresist and subjecting the exposed transparent regions to a plasma etch until the thicknesses of the transparent reticle material has been relieved to a degree sufficient to effect diffraction cancellation between neighboring transparent regions. This invention solves the problem of unequal transmittance characteristics of plasma etched transparent regions and unetched transparent regions by subjecting the reticle to a second plasma etch once the photoresist has been removed. Thus, both the transparent regions that were initially etched and the transparent regions that were initially unetched are subjected to an etch. Both types of regions are relieved further, thus maintaining the phase-shifted relationship between the two types of transparent regions, and also equalizing the transmittance characteristics of both types of transparent regions.
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