Effect of A Double Metal Layer on the Performance of CMS Silicon Sensors: A Preliminary Study

The luminosity upgrade of the Large Hadron Collider (LHC) at CERN after 2020 requires the upgrade of the Compact Muon Solenoid (CMS) detector. The silicon strip detectors in the CMS Tracker must be able to handle the larger number of particles that come with higher energies and luminosities. One of the solutions for the high occupancy is to increase the granularity of the sensor. A second metal layer on the sensor would allow the integration of the Pitch Adapter (PA), which currently lies on the detector module, into the sensor design and make the detector design more flexible. This could also help reduce the material budget of the CMS tracker since the traditional PA is made of metal routing on top of a glass substrate. The CMS Tracker Collaboration is investigating the feasibility of the double metal scheme as one possible option and, as such, has designed some small test sensors. The test sensors have regions with, and without, double metal routing. The results from the electrical characterization and charge collection measurement of these sensors will be reported.