Optimizing Cv Measurement Accuracy; Basic Cv Test Procedure; Typical Cv Curves - Keithley 7174A Instruction Manual

3.2.3 Optimizing CV measurement accuracy

For accurate CV measurements, each Model 590 CV mea-
surement pathway must be corrected using the procedure
outlined in the Model 590 Instruction Manual. The pathways
to each DUT must be cable corrected separately.
Also, for best quasistatic CV results, the corrected capaci-
tance feature of the Model 595 should be used. Corrected
capacitance compensates for any leakage currents present in
the cables, switching matrix, or test fixture. However, care
must be taken when using corrected capacitance to ensure
that the device remains in equilibrium throughout the test
sweep to avoid distorting the CV curves.
In order to minimize the effects of the switching network on
quasistatic CV measurements, cables to the Model 595 and
DUT should be kept as short as possible.

3.2.4 Basic CV test procedure

The fundamental CV test procedure is outlined below. Keep
in mind that this procedure does not address many consider-
ations and aspects of CV testing, which is fairly complex.
The procedure given is for the stand alone system in Figure
3-1. Detailed instrument operating information may be
found in the pertinent instruction manuals.
1. Connect the HP-GL plotter to the IEEE-488 bus connec-
tor of the Model 595 only.
2. Set up the Model 595 for the expected CV sweep.
3. Close the crosspoints necessary to connect the Model
595 to the device under test, as summarized in Table 3-1.
For example, to test device #1, close A1 and B2.
4. Place the probes down on the wafer test dots.
5. Run a quasistatic sweep on the selected device and gen-
erate a CV curve.
6. Open the crosspoints that are presently closed.
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7. Set up the Model 590 for the expected CV sweep.
8. Close the crosspoints necessary to connect the Model
590 to the device under test. For example, to test device
#1, close G1 and H2.
9. Run a high-frequency test sweep on the device to store
the CV data in the Model 590 buffer.
10. Disconnect the plotter from the Model 595 and connect
it to the Model 590.
11. Generate a plot from the data in the Model 590 buffer.
12. Repeat steps 2 through 11 for the remaining devices, as
required.
Table 3-1
CV test crosspoint summary
Closed crosspoints
Wafer # Quasistatic (595)
1 A1, B2
2 A3, B4
3 A5, B6
4 A7, B8
5 A9, B10
6 A11, B12

3.2.5 Typical CV curves

Figure 3-3 and Figure 3-4 shows typical CV curves as
generated by the Model 595 and 590 respectively. The
quasistatic curve shows a fair amount of symmetry, while the
high-frequency curve is
asymmetrical nature of the high-frequency curve results
from the inability of minority carries to follow the high-
frequency test signal.
Applications
High frequency (590)
G1, H2
G3, H4
G5, H6
G7, H8
G9, H10
G11, H12
highly asymmetrical. The
3-3