Keithley 4200A-SCS Reference Manual page 1168

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Model 4200A-SCS Parameter Analyzer Reference Manual

Appendix D: Using a Model 82 C-V System

Determining delay time with leaky devices

When testing for delay time on devices with relatively large leakage currents, it is recommended that

you use the corrected capacitance feature, which is designed to compensate for leakage current. The

reason for doing so is illustrated in the figure below. When large leakage currents are present, the

capacitance curve will not flatten out in equilibrium, but will instead either continue to rise (positive

Q/t) or begin to decay (negative Q/t).

Using corrected capacitance results in the normal flat capacitance curve in equilibrium due to leakage

compensation. Note, however, that the curve taken with corrected capacitance will be distorted in the

non-equilibrium region, so data in that region should be considered to be invalid when using corrected

capacitance. If it is necessary to use corrected capacitance when determining delay time, it is

recommended that you make all measurements on that particular device using corrected

capacitance.

Corrected capacitance can be enabled for simultaneous C-V measurements by setting the

"LeakageCorrection" parameter to "1" (see line 12 of the

SIMCVsweep82 user module

Figure 603: Capacitance and leakage current curves of leaky device

Testing slow devices

A decaying noise curve, such as the dotted line shown in the figure in

Determining the optimal delay

(on page D-26), will result if the maximum delay time is too short for the device being tested.

This phenomenon, which is most prevalent with slow devices, occurs because the signal range is too

small. To eliminate such erroneous curves, choose a longer maximum delay time. A good starting

point for unknown devices is a 30-second maximum delay time.

4200A-901-01 Rev. C / February 2017