Mobility issues in double-gate SOI MOSFETs: Characterization and analysis

The carrier mobility in ultra-thin SOI transistors was measured at the front channel, back channel and in double gate mode (DG). A model for generalizing the mobility extraction method, based on the F-function, is proposed. In DG-mode the apparent mobility is the sum of front and back channel mobilities only if the two channels are independent (partially depleted or relatively thick fully depleted MOSFETs). In ultrathin transistors, the coupling effect should be accounted for achieving a balanced DG-mode. An outstanding apparent mobility enhancement in DG-mode is measured which cannot be explained by a 2-channels model. This result gives clear evidence of the benefit of volume inversion.