| 摘要 |
PURPOSE:To coincide the center of ion beam scanning width automatically with the center of mask opening by converting the measurement in current measuring section into digital signals 0, 1 and coinciding the output time of adjoining digital signal 0 from one dimensional direction to the other. CONSTITUTION:At first, the scanning voltage is applied only onto the X-direction scanning plate 9 to measure the beam current at current measuring section 6. The measurement is converted into digital signals 17, 18 of 0 and 1 in automatic-threshold circuit 13 where a control circuit 14 will compare the output times t1, t2 of adjoining 0 digital signal 17 to output a control signal to the scanning power source control section 12 upon coincidence of the comparison results. Then a scanning power source 11 is operated to equalize t1 and t2. Thereafter, scanning voltage is applied onto Y-direction scanning plate 10 to equalize t1, t2 in this scanning direction. Consequently, the center of scanning width of ion beam 2 can be coincided automatically and accurately with the center of mask opening 4 or the center of wafer 3. |
