The bias voltage is always applied to the backplane of the detector (or in case of DSSD to the side, which is not connected to the terminal of the LCR meter). To measure the interstrip capacitance, we bond together 3 neighboring strips on each side of the strip we want to measure. The three nearest neighbors contribute approximately 95% of the total interstrip capacitance (see reference below). The next strip over on each side of this bonded area is connected via probes to the shield of the terminal probes to isolate the measured area from the rest of the detector. The probe, which is connected to the high terminal, we normally put down on the center strip, while the probe of the low terminal is put down on the neighboring strips, which are bonded together. We found that interchanging the role of low and high terminal does not effect our results. The shields of these two probes are connected to each other with a short cable (and are also connect to the shield-probe).
Before putting the two terminal probes down, we perform a short correction by shorting out the two probe tips. The open correction is performed with the high probe down and the low probe up. Refer to the user manual of your LCR meter for details.
While sweeping through the bias voltage, we take capacitance measurements for different frequencies of the signal which the LCR meter applies. Only the highest frequency sees the whole length of the detector, since the RC network of the detector has a frequency dependent impedance. An accurate value for the interstrip capacitance is obtained (in our measurements) for the 1 MHz signal.
The example plot shows the CV curves for a n-side test structure. Measurements were taken for frequencies of 1 kHz, 10 kHz, 100 kHz and 1 MHz. The values for the two highest frequencies are very close together and therefore indicate, that the whole length of the detector is seen by those signal. With higher bias voltages, the depletion layer of the detector grows from the n-side to the backplane, which is recorded in the decrease of the interstrip capacitance with increasing bias voltage.
These measurements were also performed for 6 cm and 12 cm detectors used in the H8 beam test for ATLAS and for the new Hamamatsu SSD for ATLAS:
