| 摘要 |
PURPOSE:To obtain an accurate dosage even in a low current ion implantation, by integrating the difference between a cathode current to produce an electron cloud and an anode current to find the dosage during the ion implantation period. CONSTITUTION:A dense electron cloud is generated in front of a wafer 16, ion beams 26 are fed through the electron cloud to be neutralized perfectly, and an impurity is implanted to the wafer 16 in the neutralized condition. Therefore, since the cathode current IA is the sum of the electron flow used to neutralize the ion beams 26 and the anode current IB, the difference I indicates the electron flow to carry the ion beams 26, by finding I=IA-IB at a differential amplifier 30. Therefore, the I is integrated at an integrator 32 during the implantation process, and the integrated value shows the dosage of the impurity implanted to the wafer 16.
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