Model 4200A-SCS Prober and External Instrument Control Section 6: Using a Model 82 C-V System
4200A-913-01 Rev. A December 2020 6-23
Formulas for cvsweep test (stvs project)
Gate voltage:
VGS = -VSub
Serial resistance calculated by high frequency CV:
RS = AT(MAVG(G_OR_R,5)/(WF*MAVG(CHF,5)),MAXPOS(MAVG(CHF,5))))^2/
((1+(AT(MAVG(G_OR_R,5)/(WF*MAVG(CHF,5)),MAXPOS(MAVG(CHF,5))))^2)
*(AT(MAVG(G_OR_R,5),MAXPOS(MAVG(CHF,5)))))
Intermediate parameter for calculation of CC:
AR = G_OR_R-(G_OR_R^2+(WF*CHF)^2)*RS
Corrected high frequency capacitance by compensating serial resistance:
CC = ((G_OR_R^2+(WF*CHF)^2))*CHF/(AR^2+(WF*CHF)^2)
Offset for high frequency capacitance (entered by user):
HOFFSET = 0
595 delay time:
DELAY = 0.15
Gain for calculated high frequency capacitance that is calculated:
HGAIN = AT(MAVG(CQS,5)/MAVG(CC,5),MAXPOS(MAVG(CC,5)))
Adjusted high frequency capacitance by using HGAIN and HOFFSET:
CHADJ = HGAIN*CC+ HOFFSET
595 step voltage:
VSTEP = 0.02
Average slop of leakage current neglecting the contribution of mobile ion:
LEAKSLP = LINEFITSLP(VGS, QT, 49, 200)
49 and 200 are indexes on QT array to fit the slope.
Gain for quasistatic capacitance (entered by user):
QGAIN = 1
Adjusted quasistatic capacitance by using QGAIN and QOFFSET:
CQADJ = QGAIN*CQS+QOFFSET
Mobile ion density:
NM = AVG((CQADJ- CHADJ)*ABS(DELTA(VGS))*(LASTPOS(DELTA(VGS))-
FIRSTPOS(DELTA(VGS)))/Q/AREA
Choosing the right parameters
This section describes how to choose the correct parameters for:
• Simultaneous C-V measurement
• The delay time to ensure that the device remains in equilibrium in the inversion region during a
sweep
• Controlling errors at the source
Optimal C-V measurement parameters
Simultaneous C-V measurement is a complicated matter. Besides system considerations, you should
carefully choose the measurement parameters. Refer to the following discussion for considerations
when selecting these parameters.
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