Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Patent
1997-09-30
1999-12-28
Berman, Jack I.
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
25049223, 250396ML, H01J 37302, H01J 37153
Patent
active
060084987
ABSTRACT:
The imaging characteristics of focal-point position, image rotation, and magnification of a projection system of a charged-particle-beam image-transfer apparatus are corrected by correction lenses positioned between a first projection lens and a second projection lens. The driving currents of the correction lenses are determined by solving a system of three linear equations with three unknowns, whose coefficients are the correction amounts for the three imaging characteristics of the projection system produced by the three correction lenses when they are driven by the unit Ampere-turn, and the target correction amounts for the three imaging characteristics. More correction lenses can be employed than imaging characteristics to be corrected, with Ampere-turn values selected from among those that satisfy the corresponding equations. Also, the driving currents of one or more projection lenses can be varied to allow the projection lenses to operate as correction lenses. Also, three correction lenses can be provided for each of three characteristics to be corrected. The correction for each characteristic can be performed individually, so as to avoid substantial change in the other two characteristics, and this may be done iteratively to approach the ideal correction.
REFERENCES:
patent: 4400622 (1983-08-01), Takeuchi et al.
patent: 4544847 (1985-10-01), Taylor
Lischke et al., "High Resolution Electron Lithography Aided By Micro Imaging, Part 2: Realization of a 1:4 Projector Including Experimental Findings," Optik 54:325-341 (1978) (in the German language, with an English Translation attached).
Berman Jack I.
Nikon Corporation
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