| 摘要 |
PURPOSE:To speed up an operation, by executing electron beam scanning of reference mark plural number of times at a condition set into a calculator and detecting a mark position from an average value of the amount of each beam scanning. CONSTITUTION:Resistors 2X, 2Y and 3-6 are given by a calculator 1 scanning start-up point coordinates Xo and Yo and a width W of a mark scanning beam, a number of scanning times N, a scanning pitch P and a scanning speed S, etc. When a command of ''Start'' is given to a circuit 7, an electron beam 9 generates, a clock pulse corresponding to the speed S is counted by a counter 11, and an amount of beam scanning is measured. Now, if a scanning is done in X axial direction of a specimen 17 and a mark 16 is detected by a detector 18, the beam scanning is automatically repeatd N times by a circuit 19 from the next scanning start-up point (a position shifted by P in Y axial direction). The value of the counter 11 at each scanning time is multiplied by a multiplier 21, divided by calculated value (number of scanning times N) of a counter 20, and the position of the mark 16 is calculated as an average value of amounts of scanning. It is possible, by doing so, to eliminate the necessity of control of the calculator at each scanning time, and therefore, the detection can be speeded up. |
