Patent Number: 051877260
Section: abstract

Phase shift masks for X-ray lithography include a carrier with a phase shift feature formed thereon having at least one sharply defined sidewall which is upright with respect to the surface of the carrier. The height of the feature on the phase shift mask is selected such that it provides a phase shift of substantially one-half wavelength of a selected band of the X-rays passed therethrough with respect to the X-rays that are passed through the carrier where there is no phase shift material. The phase shift mask is positioned closely above a target composed of a photoresist on a substrate, and X-rays are then passed therethrough, preferably being provided by synchrotron radiation. The collimated X-rays passed through the mask into the photoresist expose those areas of the photoresist away from the upright sidewalls sufficiently to cause those to be removed by developer, whereas the regions under the upright sidewalls have the X-ray intensity canceled by diffraction effects such that that the region under the sidewall is left in place on the substrate after developing. Very thin walled structures, in the range of 50 nanometers, can be formed in this manner by X-ray lithography.