Quantization Effects on the Gate Capacitance of a Doubles Gate MOSFET

Abstract

The MOS technology is continuously scaling down for high performance and therefore the quantum physics becomes necessary to explain the behavior of today’s MOSFETs. In this thesis work, we investigate the quantization effects on the gate capacitance of a double gate MOSFET using a self-consistent solution of poisson’s and schrödinger’s equations of the industry standard simulation tool silvaco. To find the quantization effect we vary the electron and hole effective masses and also the channel thickness. For electron, when we start to reduce the effective mass from a nominal value the quantization effects become noticeable at mc<0.1mo and the eigen energy spacing increases significantly which decreases the capacitance value. And the C-V curves become step like in inversion. For hole, when we reduce the hole effective mass, quantization effects become noticeable at mv<0.1mo and separation between eigen energies increases significantly which leads to decrease the capacitance. For both hole and electron quantization we notice that the channel inversion switches from surface inversion to volume inversion as the effective mass goes below 0.1mo. And finally we reduce the channel thickness for two different effective masses of electron and hole. Here we don’t see any step in C-V curve but we see a different phenomenon. When we put mc = mv = 0.5mo and change the channel thickness from 10 nm to 2 nm, the bottom of the C-V curve shifts left and the minimum capacitance is reduced. However, when we put mc = mv = 0.05mo and change the channel thickness from 10 nm to 2 nm, in addition to the shift of the bottom in C-V curve, the capacitance values in accumulation and inversion are also changed.