In the calculation of series resistance Rs of an MOS capacitor should we take C and G from strong accumulation only? In that case we will get only one value for Rs for any given frequency and Rs will be independent of gate voltage.Or should we take C and G corresponding to each value of gate voltage ? In that case we will have a gate voltage dependent Rs. Keithley application notes No. 2896 says: G=measured conductance and C= measured parallel model capacitance from strong accumulation - they don't explicitly say whether G is from strong accumulation or not. Can anybody familiar with this topic clear the doubt?
I would expect Rs to be gate voltage dependent, since the nondepleted semiconductor contributes to the series resistance. The best way seems to measure an impedance spectrum for each gate voltage value and extract the correct Rs from a suitable equivalent circuit. Note, that the equivalent circuit should be different for accumulation (one parallel RC combination) and depletion (two parallel RC combinations in series).
For linear regime Rs is C and G dependent. Hence, for switching regime two values of this parameter are sufficient and may be considered independent C and G (this is only an approximation).
Dear Mercea Pop,
Very much obliged to you. Could you pl. elaborate a little bit more ?
By two values in the switching regime do you mean from VT to strong inversion
one value for C and one value for G ? Or do you mean one set of value for C and G in Accumulation and another set for region beyond VT in the case of HF measurements?
Not much is found in any papers or texts. Could you suggest some papers to get the woring details of calculation of Rs?
Regards.
The above suggested impedance spectroscopy is an optimal method to analyze different components of the equivalent circuits of semiconductor devices, in particular, series resistance. You should deal with the spectral distribution of the real component of the measured impedance of the MOS structure under investigation in order to extract information about its series resistance, since it does not influence on the imaginary part of the measured impedance. If you measure the spectral distributions of the impedance at different gate voltages you can get the voltage dependence of the series resistance (if it is observed). Some additional information can be found the attached papers. Good luck!
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