X-ray or gamma ray systems or devices – Specific application – Lithography
Patent
1991-09-30
1993-02-16
Church, Craig E.
X-ray or gamma ray systems or devices
Specific application
Lithography
378 34, G21K 500
Patent
active
051877260
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.
REFERENCES:
patent: 4360586 (1982-11-01), Flanders et al.
patent: 4890309 (1989-12-01), Smith et al.
Y. C. Ku, et al., "Use of a Pi-Phase Shifting X-Ray Mask to Increase the Intensity Slope at Feature Edges," J. Vac. Sci. Technol. B, vol. 6, No. 1, Jan./Feb. 1988, pp. 150-153.
Jerry Z. Y. Guo, et al., "Verification of Partially Coherent Light Diffraction Models in X-Ray Lithography," presented at EIPB 1991 Symposium on May 30, 1991.
Church Craig E.
Wisconsin Alumni Research Foundation
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