PURPOSE: To improve the efficiency and uniformity of implanting against discharge, by implanting continuously if interruption of ion beam is shorter than allowable time width while blocking the beam path if it has exceeded over the allowable time width and enabling uniform re-implant simultaneously with recovery.
CONSTITUTION: The implanting current from a disc 3 is detected by a current amplifier 10 while the implanting current error is detected by a comparator 11. Upon occurence of discharge, the output signal from the comparator 11 is applied on an error time width control circuit 12 comprising signal delay circuit 13 and AND gate 14, and when it has exceeded over the allowable time width of the implanting uniformity an output signal is produced from said circuit 12. The output from the control circuit 12 will set FF circuits 15, 16 to close a shield board 17 to shield the beam 2 while to turn a switch 18 thus to stop up/down driving. At the same time the output signal from the control circuit 12 will set the radius (R) position upon occurence of an error in a memory register 20.
SAKUMICHI KUNIYUKI
YAMADA SEIICHI
