Electrical characteristics of ion-implanted p-channel MOS transistors

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Abstract
11B+ ions of 1011−1012/cm2 were implanted through gate oxides of 800–2000 Å into the channel regions of p‐channel MOS transistors. For 50‐keV implantation, the dose dependence of threshold voltage could be explained by Swanson and Meindl's theory. In the case of implantation above 100 keV, slight deviation of the threshold voltage from the theoretical values was observed. Corresponding to this, the gate‐oxide‐thickness dependence of the threshold voltage was slightly deviated from the theoretical values in the range of less than 1300 Å. For more than 1500 Å, the measured threshold voltages coincided with calculated values. The energy dependence of the dose limit for ``ability to turn on‐off'' showed good agreement with the curve calculated on the basis of Swanson and Meindl's theory within this experimental error. Source‐drain current in the saturation region was slightly increased with increasing dose at least up to 5 × 1011/cm2, presumably due to the carrier compensation (band bending) and increase of the mobility. No significant change due to the implantation was observed in the breakdown voltages within the examined dose and energy ranges. Device stability was confirmed by the positive or negative BT treatments (125°C, 100 h and 300°C, 60 min). Again, no significant instabilities resulting from the implantation process was detected in this experiment.