New aspects and mechanism of kink effect in static back-gate transconductance characteristics in fully-depleted SOI MOSFETs on high-dose SIMOX wafers

An extraordinary kink phenomenon in static back-gate transconductance characteristics of fully-depleted SOI MOSFETs has been experimentally investigated and characterized for the first time. This kink phenomenon has been observed in both NMOS and PMOS on high-dose SIMOX wafers under steady-state conditions at room temperature. It was also found that the back-gate characteristics for both NMOS and PMOS show anomalous shift phenomenon in drain current-back gate voltage (I/sub D/-V/sub G2/) curve at the back-gate voltage corresponding to the kink phenomenon. This kink phenomenon has been attributed to the presence of energetically-localized trap states at SOI/BOX interface. In order to clarify the energy level of the trap states at SOI/BOX interface corresponding to the kink, we have developed a new formula of surface potential in thin-film SOI MOS devices, in which the potential drop across semiconductor-substrate is taken into account. By using this new formula, me have demonstrated that high-dose SIMOX wafers have donor-like electron trap states at /spl sim/0.33 eV above the Si midgap with the density of /spl sim/N6.0/spl sim/10/sup 12/ cm/sup -2/ eV/sup -1/ and donor-like hole trap states at /spl sim/0.35 eV below the Si midgap with density of /spl sim/1.5/spl times/10/sup 12/ cm/sup -2/ eV/sup -1/ at SOI/BOX interface.