Product specifications

4
The outer conductor of coaxial cables
works as a shield to minimize stray
capacitance between center conduc-
tors and circuit common. The outer
conductors should be extended as
close as possible to measurement
device without contacting anything
(i.e., should be floating). Note that
they work as guard terminals in case
of dc measurements, that are to mini-
mize leakage current.
Cable Calibration and Compensation
For accurate capacitance measure-
ments, perform the following three
steps shown in Figure 6.
• Open/Short Calibration of
Agilent 16048D/E Test Lead
Perform open/short calibration at
the end of the Agilent 16048D/E
Test Lead on the Agilent 4284A’s
front panel. To perform short cali-
bration, use the Agilent 42091A
Short Termination adapter to
connect high and low terminals
together as shown in Figure 7. For
open calibration, attach the test
leads to the CV1 and CV2 input
terminals of E5250A. All matrix
switch relays should be open.
Open/short calibration can be
done to the end of the 4-wire con-
nection (16048D/E). If a matrix
switch and cables are used, they
are not calibrated by open/short
calibration. In general, load cali-
bration should be additionally
performed in such a case. But,
for wafer measurements, it is very
difficult to have stable and accu-
rate load, so you should perform
compensation as described next
instead of load calibration.
• E5250A/Output Cables Compensation
Specify cable length of the Agilent
16494A Triaxial Cable and Agilent
P/N 8120-4461 Coaxial Cable in
the capacitance compensation
routine. Its usage is described
later.
Instead of load calibration, the
routine compensates the measure-
ment error generated by residuals
in the matrix switch modules and
output cables. As long as you use
recommended cable, you can easily
compensate the error by specifying
the cable length.
• Probe Card/Needles Offset
Capacitance Subtraction
Perform a measurement of offset
capacitance caused by probe card
or probe needles. This cannot be
compensated by E5250A’s com-
pensation calculation, so it should
be actually measured and sub-
tracted from device capacitance
value. Don’t connect measurement
device during offset capacitance
measurement.
4284A 20 Hz - 1 MHz
PRECISION LCR METER
Agilent 4284A LCR Meter
Agilent E5250A Matrix Switch
Agilent 16495F/G
Connector Plate
Probe card/
needles
Agilent 8120-4461
Coax Cable
Agilent 16494A
Triax Cable
Offsec C
Subtraction
Open/Short
Calibration
E5250A Compensation
Agilent 16048D/E
Test Lead
Figure 6. Compensation theory
4284A 20 Hz - 1 MHz
PRECISION LCR METER
4284A 20 Hz - 1 MHz
PRECISION LCR METER
Short Calibration
Open Calibration
4284A
16048D/E
16048D/E
4284A
42091A
E5250A
1250-2405
CV1
CV2
Figure 7. Open/short calibration
Figure 8. Agilent 4284A configuration setup