| 摘要 |
PROBLEM TO BE SOLVED: To expose a semiconductor substrate with higher precision by making the total time from the input of an external trigger to the light emission of the laser beam always constant even when respective constitution elements of a pulse power source have temperature variations. SOLUTION: A current sensor 32 measures a charging current flowing to a charging capacitor C<SB>0</SB>and the quantity Qc<SB>n</SB>of electric charges accumulated in the charging capacitor C<SB>0</SB>is computed from the time integrated value. The electric charge quantity Qc<SB>n</SB>is inputted to a controller 31 and the reciprocal b/(aQc<SB>n</SB>) (where (a) is the reciprocal of the charging capacitor and (b) is a proportion coefficient) is computed by the input of the electric charge quantity Qc<SB>n</SB>. A compensation characteristic is set in the controller 31. The compensation characteristic is shown by the relation between a compensation time Tc and the variable b/(aQc). When the external trigger TR is inputted, the variable b/(aQc) begins to vary. The variable b/(aQc) decreases over time and a correction trigger TRL is outputted when the reciprocal b/(aQc<SB>n</SB>) of the compound electric charge quantity is reached. This time is the compensation time Tc. Thus, the sum of a delay time Td and the compensation time Tc is made constant. COPYRIGHT: (C)2003,JPO
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