Wafer charging during ion implantation and its effect on the degradation of thin oxide of mos device

Wafer charging during Ion Implantation was studied using two measurement methods: (1) the capacitive probe measurement of the surface potential on the Si wafer covered with 1 /spl mu/m thick photoresist and (2) the C-V (capacitance-voltage) measurement to evaluate the degradation of the thin oxide of MOS structure fabricated on the wafer. The wafers loaded on rotating disc were implanted with 35keV As+ at the beam currents of 1 to 10mA. The probe measurement showed that the charge-up phenomenon was to a large extent governed by the behavior of the secondary electrons. From the C-V measurement, the effects of ion beam density and of the photoresist coverage were discussed. It was shown that the four charge sources contributed to the degradation of the oxides: the irradiated ions, the secondary electrons emitted from a gate electrode, the charges accumulated on the photoresist around the gate electrode and the secondary electrons emitted from the disc.