Operating characteristics of radiation-hardened silicon pixel detectors for the CMS experiment

The Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) will have forward silicon pixel detectors as its innermost tracking device. The pixel devices will be exposed to the harsh radiation environment of the LHC. Prototype silicon pixel detectors have been designed to meet the specification of the CMS experiment. No guard ring is required on the n⁺ side, and guard rings on the p⁺ side are always kept active before and after type inversion. The whole n⁺ side is grounded and connected to readout chips, which greatly simplifies detector assembling and improves the stability of bump-bonded readout chips on the n⁺ side. Operating characteristics such as the leakage current, the full depletion voltage, and the potential distributions over guard rings were tested using standard techniques. The tests are discussed in this paper.