This page describes, how body capacitance measurements on silicon microstrip detectors between the backplane and metal strips are performed at the SCIPP labs. For this kind of measurement we use HP 4284 A Precision LCR meter.

The bias voltage is always applied to the backplane of the detector (in the picture, we show the setup for a p-type detector and therefore apply a negative voltage to the backplane). To measure the body capacitance, we bond together 16 neighboring strips so that we can neglect any contribution from interstrip capacitance. One probe connected to the high terminal of the LCR meter is brought down to the 16 bonded strips while the low terminal is connected to the backplane using a large (compared to the body capacitance) capacitor to decouple the DC bias voltage form the LCR meter. The shields of the two LCR meter terminal are connected to each other with a short cable as close to the detector as possible.




Before connecting the two terminals to the detector, we perform a short correction by shorting them out using the cable length for the actual measurement. The open correction is performed with the high terminal connected 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 lowest 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 body capacitance is obtained (in our measurements) for the 1 kHz signal.