NBTI-channel hot carrier effects in pMOSFETs in advanced CMOS technologies.

In this work the reliability of a 0.35 um p+ poly-gate p-MOSFET CMOS technology under conductive channel hot carrier conditions is investigated. It is found that at any bias and temperature condition applied, the degradation of sufficiently short channel length (Leff approximate to 0.14 um) devices results in a reduction in drive current due to the impact of donor type interface trap generation and positive charge formation during the stress. At these dimensions the degradation is controlled by a contribution of both Negative Bias Temperature Instability (NBTI) and Channel Hot Carrier (CHC) mechanism. We will show the role that each of these two mechanisms play in determining the shift of typical device parameters. We have found that the shift of the maximum transconductance (Gmax) is mainly controlled by the CHC damage through hot hole (HH) injection. In this case the ratio between the nwell and the drain currents (Inw/Id) is a good PIC reliability monitor contrary to what is typically observed in pMOS transistors. On the other hand, device parameters such. as the threshold voltage (Vth), that are mostly sensitive to the formation of net positive charge in the gate oxide, do experience the effect of both NBTI and CHC, and at a given Vd are controlled by the Vg bias as well (assume Vs=Vnw=0 V). In. this case Inw/Id is not a good monitor of the device reliability particularly at high temperature (T > 80 C). The comparison between the Vth shifts of high temperature symmetric NBTI and conductive Channel Hot Carrier (Vg=Vd) stresses suggests that both the NBTI and CHC mechanisms act independently, but in separate regions of the device. A methodology to decouple the two effects is also provided allowing to quantity each contribution separately at any bias and temperature condition. A conductive CHC model that takes into account the impact of both mechanisms to the device lifetime at the worst observed degradation condition (Vg=Vd) is also discussed.