Interstrip Capacitance of Single Sided Silicon Detectors for ATLAS





Author: Riko Wichmann
This page was created November 30, 1995, last modified Decmber 1, 1995

The interstrip capacitance for Hamamatsu single sided microstrip detectors was measured with the method described earlier.
Since the backplane has it's own guard ring, a special backplane probe was used to apply the bias voltage to prevent shorting out the top and bottom side of the diode via the two guard rings. The (negative) bias voltage was applied to the backplane, while the bias ring was put to zero voltage. Four new detectors were measured, each of them shows the same behavior. Besides the interstrip capacitance as a function of bias voltage also an IV curve was obtained.

Detector

The detectors were new Hamamatsu AC coupled single sided silicon strip detector of 6 cm length and 6 cm width. They are n-side with a n-type bulk. The features of the detector are the following:
  1. Geometric Properties
  2. Electrical Properties
  3. Interstrip Capacitance:
The IV curve shows an almost flat behaviour up to app. 200 V where a breakdown of the diode occurs. One of the Detectors (SDX32940-1) was measured up to 300 V bias.
The depletion voltage was determined by putting a straight line through the flat part of the CV curve and through the slope at low bias voltages. The voltage, where these two lines intersect is approximately the depletion voltage.

IV and CV curves are available for all 4 test detectors:
  1. 3 neighbors connected
  2. 5 neighbors connected
  3. 8 neighbors connected

    Conclusion

    So far these detectors meet the specifications outlined in the agenda of the December 95 SCT review meeting. From the above values of the interstrip capacitance, we conclude that the first 5 neighbors make a significant contribution to the total interstrip capacitance one channels sees.

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