Plasma-induced charging damage in p(+)-polysilicon PMOSFETs

This paper reports plasma-induced charging damage in p(+)-polysilicon PMOSFETs as a function of amount of boron penetration. Plasma charging effect is amplified using contact antenna structures with ratios of 10, 100 and 1K. The antenna is connected to the gate of a 25 mu m/0.8 mu m PMOSFET from a matched pair to minimized device performance deviation due to process non-uniformity. It is found that initial device characteristics, such as threshold voltage, transconductance and subthreshold swing, are degraded in the antenna devices as compared to the control devices and this degradation is aggravated with the amount of boron penetration. The percentage degradation in maximum transconductance of the antenna devices is proportional to its increase in peak charge pumping current, suggesting that the degraded interface property is responsible far the reduced G(m). It is believed that boron-penetration causes latent defects in gate oxides and thereby increases charge trapping and interface states generation during stress, resulting in an enhancement of plasma damages in the p(+)-polysilicon PMOSFETs.