Random Work-Function-Induced Threshold Voltage Fluctuation in Metal-Gate MOS Devices by Monte Carlo Simulation

In this paper, we estimate the effect of random work function (WK) on the threshold voltage fluctuation (σ
V
_th
) of 16-nm-gate metal-oxide-semiconductor field-effect transistors (MOSFETs) with metal-gate materials. To examine the random WK induced σ
V
_th
, nanosized metal grains with different gate materials are considered in a large-scale statistical simulation. An analytical expression of the WK induced σ
V
_th
is proposed based on the Monte Carlo simulation results which can outlook different extents of fluctuation resulting from various metal gates and benefit the device fabrication. Devices with a two-layer metal-gate are further studied for fluctuation suppression; the finding of this paper indicates the first layer of the gate structure plays the most significant role in the suppression of the WK induced σ
V
_th
, compared with the second layer. This paper provides an insight into random work-function-induced threshold voltage fluctuation, which can, in turn, be used to assess metal gate characteristics of MOSFETs.