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’sCandGunder the considerations of oxide charges, doping concentration, device dimension, and AC signal frequency(ω)was proposed. A relation ofC-CD∝ ω -0.5was found, whereCDis 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 forQₒₓ/q=7.5× 10¹⁰ cm⁻², the MIS capacitor with substrate doping concentrationNA=1× 10¹⁵ cm⁻³exhibits a long lateral AC signal decay length of52~μ mat 1 kHz under the inversion region. The findings of this work are fundamental and are helpful for device engineering.