High energy proton damage effects in thin high resistivity FZ silicon detectors

The proposed luminosity upgrade of the Large Hadron Collider (S-LHC) will demand the inner most layers of the vertex detector to sustain fluences of about 1016 charged hadrons/cm2. Due to the high multiplicity of tracks, the required spatial resolution and the extremely harsh radiation field thin silicon detector assemblies are proposed as a possible solution for this challenge. The radiation tolerance of 50 μm thin high resistivity float zone (FZ) devices has been studied for 24 GeV/c protons in the fluence range between 4×1013 cm−2 and 8.6×1015 cm−2. For the manufacturing of such thin devices, a technology based on direct wafer bonding and deep anisotropic etching was used. Annealing measurements at 80 °C have shown that the introduction rate gC in the stable damage component is about the same as observed for oxygen enriched FZ detectors and that the fluence dependence of the reverse annealing amplitude NY exhibits a saturating function. It is also demonstrated that the annealing behavior of the reverse current related damage parameter α is independent on the fluence and the silicon material parameters. Charge collection efficiency (CCE) measurements were performed using 5.8 MeV α-particles. After fully annealing for about 31 days at 80 °C CCE was determined by extrapolation to be 66% at 1016 p/cm2.