| 摘要 |
PURPOSE:To enable the alignment of an electron beam focus to be accurately detected quantitatively further in a short length of time by widely reducing the effect of a noise, in such means that a nonlinear element is placed on the half way of signal processing circuits. CONSTITUTION:Electrons emitted from an electron gun 101 are deflected by a deflecting coil 102 and scanning on a sample 105. The secondary electrons, reflected electrons, etc. emitted from the sample 105 are detected by a detector 106. A signal amplified by an amplifier 107 is differentiated by a differentiating circuit 108, squared by a squarer 110 via a nonlinear element 109, integrated by an integrator 111 and then displayed its value by a display element 115. If currents flowing in an objective lens 104 and stigma coil 103 are adjusted in such a manner as to obtain a maximum indicating value of the display element 115, the work of matching a focus and correcting an astigmatism can be performed. |
