The Development of silicon detectors for the CMS experiment and future experiments

A hybrid pixel detector will be installed as the inner most layer of the tracking system of the CMS experiment, currently under construction at the Large Hardron Collider (LHC) at CERN (Geneva, Switzerland) to provide high resolution tracking and vertex identification. Due to the severe radiation environment of the LHC, the performance of the sensors must be carefully evaluated up to a fluence of 6 × 1014 1-MeV equivalent neutrons per square centimeter. The sensors were fabricated "n on n", which means highly segmented n+ implants with 150 × 100 μm2 pitch are in n-type bulk material and p+ implants are used to isolate pixels. The electrical properties of these sensors has been studied. Studies of charge collection efficiency were carried out with a 1064 nm wavelength laser. Comparisons of charge collection efficiency among different sensor designs is presented. In addition, present and future possibilities for the production of thin silicon detectors are discussed. The electrical characteristics and the performance of thin silicon sensors with thickness of 150 μm, 200 μm, 300 μm respectively have been studied. We show that thin silicon sensors are intrinsically more radiation hard than thicker sensors since there is less bulk, and hence less bulk damage in the former.