Subbandgap Optical Differential Body-Factor Technique and Characterization of Interface States in SOI MOSFETs

A distribution of interface states
$(D_{\rm it})$
in SOI MOSFETs has been characterized by a subbandgap optical differential body-factor (SODBoF) technique. We adopted a subbandgap
$(E_{\rm ph} < E_{g})$
optical source as a virtual gate on the body-contactless SOI MOSFETs under the subthreshold
$(V_{\rm GS} < V_{T})$
current–voltage characteristics. Employing a differentiation to the body factor, any possible error from the threshold voltage is also suppressed. We applied the SODBoF technique to n- and p-channel SOI MOSFETs on the same wafer and verified the result. Extracted traps over the bandgap ranges
$D_{\rm it} = \hbox{10}^{10} {-} \hbox{10}^{11}\ \hbox{cm}^{-2}\cdot \hbox{eV}^{-1}$
with a typical U-shape.