Single-stepper soft x-ray source for step-and-scan tools

Melvin A. Piestrup; Michael W. Powell; Stanley Mrowka; Louis W. Lombardo; Michael B. Chase; J. Theodore Cremer; Xavier K. Maruyama

doi:10.1117/12.275774

7 July 1997 Single-stepper soft x-ray source for step-and-scan tools

Melvin A. Piestrup, Michael W. Powell, Stanley Mrowka, Louis W. Lombardo, Michael B. Chase, J. Theodore Cremer, Xavier K. Maruyama

Author Affiliations +

Proceedings Volume 3048, Emerging Lithographic Technologies; (1997) https://doi.org/10.1117/12.275774
Event: Microlithography '97, 1997, Santa Clara, CA, United States

Abstract

As a synchrotron equivalent, this paper presents a single- stepper, soft-x-ray source which offers high brightness, high collimation (less than 20 mr global and less than 2 mr local), modest operating vacuum, excellent spectrum and moderate cost. The x-rays are generated by a process called transition radiation (TR). Electrons of moderate energy (e.g. 17 - 100 MeV) pass through thin-metal foils producing a forward- directed cone of x-rays whose photon energies can be between 0.5 and 3 keV. The optimum radiator consists of many thin- metal foils, e.g. beryllium, which are separated by vacuum. The x-ray wavelength an be optimized for highest photoresist sensitivity, e.g. 1.4 nm. A computer simulation shows that for beam-shaping (slit formation) and collimation, a single grazing-angle optic transforms the radiator cone into a slit (5 mm by 26 mm) in the 1X wafer image plane, having an energy density of 15 - 60 mJ/cm². This slit is then scanned for dose uniformity. In a proof-of-principle experiment, an apparatus utilizing a Au-coated grazing-angle optic was used to focus transition radiation to a slit (7 mm by 16 mm) in the image plane at 631 mm from the optic and 881 mm from the TR radiator. Intensity variation across the longitudinal direction (approximately 10 mm) of the slit was less than 5%.

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Melvin A. Piestrup, Michael W. Powell, Stanley Mrowka, Louis W. Lombardo, Michael B. Chase, J. Theodore Cremer, and Xavier K. Maruyama "Single-stepper soft x-ray source for step-and-scan tools", Proc. SPIE 3048, Emerging Lithographic Technologies, (7 July 1997); https://doi.org/10.1117/12.275774

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KEYWORDS

Mirrors

X-rays

Reflectivity

Electron beams

Lithography

Photomasks

X-ray optics

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