| The CMS experiment which is currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) will contain a pixel detector that provides in its final configuration three space points per track close to the interaction point of the colliding beams. The readout chip is expected to survive a particle fluence of 6 x 1014 neq/cm2 and therefore all components of the hybrid pixel detector have to perform well up to at least this fluence. This requires the silicon to operate partially depleted after irradiation and therefore "n in n" concept has been chosen. In order to perform IV tests on wafers to certify the quality of sensors and to hold accidentally unconnected pixels close to ground potential a resistive path between the pixels has been implemented by openings in the p -stop implants surrounding every pixel cell. Prototypes of such sensors have been produced by two different companies and their properties have been extensively tested before and after irradiation. Their behavior under irradiation and aging has been characterized. A new type of design for detectors, semi 3D, for future experiments has also been studied and discussed. |
