| 摘要 |
<p>A spherical aberration corrector (10) is offered which is easy to design and which can correct spherical aberration and even six-fold astigmatism in a charged particle beam instrument. A method of spherical aberration correction is also offered. The corrector (10) has a first pair of multipole elements (A and B) for producing a first pair of three-fold symmetric fields in which three-fold astigmatisms produced mutually are canceled out and a second pair of multipole elements (C and D) for producing a second pair of three-fold symmetric fields in which three-fold astigmatisms produced mutually are canceled out. The second pair of multipole elements (C and D) produce six-fold astigmatisms angularly spaced by 30° about an optical axis (20) from six-fold astigmatisms produced by the first pair of multipole elements (A and B) .</p> |
