Transconductance degradation in thin-Oxide MOSFET's

In this work we investigate the transconductance degradation effect which occurs in thin-oxide FET's due to the finite inversion-layer capacitance and to the decrease of the electron mobility as the electric field increases. Experimental capacitance and charge measurements are performed at room and at liquid-nitrogen temperature on 10-nm oxide FET's, and the data are compared with a classical and a quantum-mechanical model extended to take into account the non-uniform doping profile in the silicon substrate. Accurate mobility determinations are performed accounting for the nonuniform distribution of the mobile charge along the channel, and a mobility expression against the average normal field is incorporated in a generalized Pao-Sah double-integral formula for the FET drain current. Design trade-offs for submicrometer FET's are finally discussed.