Department of Computer Science and Electrical Engineering

Simulation and Measurement of gate-todrain, Cgd and

gate-to substrate Capacitance, Cgb, in MOSFETs

Chih-Chang Lin

Abstract:
In order to understanding the C-V characteristics of capacitances in MOSFETs, a thorough understanding of the device physics is required.  In this thesis, introduction to MOS-capacitor is presented in terms of band diagram which is very beneficial in understanding the three regions of operation of MOSFETs, accumulation, depletion and inversion.  To explain the physical aspect of MOSFETs, Meyer’s and the charge-based models are covered briefly in the modelling of the capacitances.  Although flaws exist, Meyer’s model is still quite accurate for predicting capacitances in long channel devices.  For this reason, Meyer’s model is used to analyse the C-V characteristics of the long channel MOSFET.  Some aspects which effect capacitances are also mentioned and their effects on the intrinsic capacitances analysed.

While the method of measuring the capacitance is covered in detailed, the resulting capacitance of MOSFET in the three operating regions are also cross checked with calculated value derived from the models. It is found that the measured value of capacitances correlate with those calculated very well indeed.

However, due to misinterpretation and lack of information of the device, the results from the simulation using the two-dimensional simulation program, MEDICI, is not conclusive.  The possible error in the simulation is described in detail with supporting semiconductor physics.  Unfortunately, no new results will be presented from these corrections in this thesis.
 

Complete thesis:
Thesis.pdf

Additional material:
Conference Paper:  Conference.pdf

Reference materials:  Reference.pdf

Measurement programs
Gate-to-Drain Cpacitance measurement: Cgd.bas
Gate-to-Substrate Cpacitance measurement: Cgb.bas

Simulation programs
MEDICI Simulation Program for both Cgd and Cgb:  Simulate.inp
 

About the Author...

Dept of Computer Science and Electrical Engineering / Chih-Chang Lin / lin@csee.uq.edu.au  /  last mod 15/10/99