| 摘要 |
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.
|
