Electron beam tester

Claim 1

An electron beam tester for scanning a sample with an electron beam emitted from an electron beam unit, to form a secondary electron image, and matching wiring patterns of the secondary electron image with wiring patterns prepared from computer aided design (CAD) data, comprising: edge position detection means for detecting the positions Xi (i=1 to n) of edges in the CAD wiring patterns extending in parallel with an axis Y of a rectangular coordinate system defined on the CAD data; secondary electron image storage means for storing the secondary electron image; projected luminance forming means for forming projected luminance B(X) by accumulating luminance of the secondary electron image along an axis Y of a rectangular coordinate system defined on the secondary electron image; edge likelihood detection means for detecting edge likelihood E(X) of the wiring patterns of the secondary electron image according to the projected luminance B(X); pattern matching level computation means for computing a pattern matching level V according to the degree of correlation between the edge positions Xi (i=1 to n) and the edge likelihood E(X); and error detection means for changing the edge position Xi (i=1 to n) of the CAD wiring patterns in the range of Xi-ai≦Xi≦Xi+bi, wherein a and b are variables for defined edge detection regions, depending on secondary electron image magnification accuracy being corrected by shifting the edge position by an amount which is proportional to a difference between an X-coordinate of the edge and an X-coordinate of the center of the SEM image before correction, sampling position accuracy being corrected by shifting all edge positions by an equal amount, and fluctuation in a width of wiring being corrected by shifting the edge position by an equal amount along with an outward normal line, to find a maximum pattern matching level and then a secondary electron image magnification error and a sample positioning error corresponding to the maximum pattern matching level.