Comprehensive Study of Inversion Capacitance in Metal-Insulator-Semiconductor Capacitor With Existing Oxide Charges

The impact of oxide charges on the metal-insulator-semiconductor (MIS) device’s capacitance
$({C})$
and conductance
$({G})$
was studied in this work. A model to calculate MIS device’s
${C}$
and
${G}$
under the considerations of oxide charges, doping concentration, device dimension, and AC signal frequency
$(\omega)$
was proposed. A relation of
${C}-{C}_{\textrm {D}}\propto \omega ^{-0.5}$
was found, where
${C}_{\textrm {D}}$
is the depletion capacitance under the electrode. The relation is examined by the experimental and the TCAD simulation. The capacitance of a MIS device with oxide charges can be calculated according to the proposed model and is well-matched with the TCAD simulation under light to moderate doping concentration. For heavily doped substrates, the modeling deviates from the simulation results because of quantum confinement and concentration-dependent mobility. However, the trend of the capacitance value is still able to be estimated by our modeling. From the modeling, it was found that for
$Q_{\textrm {ox}}/\textrm {q}=7.5\times 10^{10} \textrm {cm}^{\textrm {-2}}$
, the MIS capacitor with substrate doping concentration
$N_{\textrm {A}}=1\times 10^{15} \textrm {cm}^{\textrm {-3}}$
exhibits a long lateral AC signal decay length of
$52~\mu \text{m}$
at 1 kHz under the inversion region. The findings of this work are fundamental and are helpful for device engineering.