Anomalous Hot-Carrier-Induced Increase in Saturation-Region Drain Current in n-Type Lateral Diffused Metal–Oxide–Semiconductor Transistors

Anomalous increase in saturation-region drain current I_d(sat) but serious on-resistance degradation (decrease in linear-region drain current) is observed in n-type high-voltage lateral diffused MOS transistors stressed under medium gate voltage V_g. However, I_d(sat) is degraded for the devices stressed under low and high V_g. Experimental data reveal that two competing mechanisms are responsible for the shift of I_d(sat). One is the interface state N_it formation in the N^- drift region. The other is the N_it formation in the channel region. The former mechanism leads to the anomalous increase in I_d(sat), whereas the latter mechanism causes the to decrease. Experimental data and technology computer-aided-design simulations confirm that the impact ionization rate of the device is enhanced if significant N_it formation in the N^- drift region is present. According to the results presented in this paper, significant formation in the drift region is identified to be the main mechanism responsible for the anomalous increase in I_d(sat).