| 摘要 |
PURPOSE:To eliminate an uneven image drawing due to a wavy surface of a sample by detecting the height variation of the sample surface, converting it into an electrical signal, and controlling the focal length of electron lenses according to the signal. CONSTITUTION:The electron beam radiated from an electron gun 1 is passed through the openings in plates 2 and 5 and electron lenses 3 and 6, and converged on a sample 7. Supposing that the surface of the sample 7, which is imaginarily divided into small sectional regions, is positioned at a reference plane, and the small sectional region to be lithographed is deviated from the reference plane by a height DELTAH. The DELTAH is obtained from a coordinate-measuring system consisting of a laser interferometer 26, detector 21, mark signal generator 22 and computer 10. An electrical signal representing the height variation DELTAH is generated from the computer 10. According to the signal, an correcting current from a correcting current generating and holding circuit 25 is applied to a correcting electron lens 27. This permits the cross section of the electron beam at the small sectional region to be equal in size to that at the reference plane. |
