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 I_d(_sat) 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 N_it formation in the N^- drift region is identified to be the main mechanism responsible for the anomalous increase in I_d(_sat).