Characterisation of silicon sensor materials and designs for the CMS Tracker Upgrade

During the high luminosity phase of the LHC (HL-LHC, starting around 2020) the inner tracking system of CMS will be exposed to harsher conditions than the current system was designed for. Therefore a new tracker is planned to cope with higher radiation levels and higher occupancies. Within the strip sensor developments of CMS a comparative survey of silicon materials and technologies is being performed in order to identify the baseline material for the future tracker. Hence, a variety of materials (float-zone, magnetic Czochralski and epitaxially grown silicon with thicknesses from 50μm to 320μm as p- and n-type) has been processed at one company (Hamamatsu Photonics K.K.), irradiated (proton, neutron and mixed irradiations up to 1:5 1015 neq=cm2 and beyond) and tested under identical conditions. The wafer layout includes a variety of devices to investigate different aspects of sensor properties like simple diodes, test-structures, small strip sensors and a strip sensor array with varying strip pitch and strip width. This paper presents the current status and results of this campaign.