p-Bulk silicon microstrip sensors and irradiation

Anticipating the requirement for highly radiation-tolerant silicon microstrip sensors suitable for the SLHC application, we have fabricated n-in-p microstrip sensors in p-FZ and p-MCZ industrial wafers which we then irradiated with 70 MeV protons. Studies were made of the leakage current, onset of microdischarge, body capacitance, charge collection efficiency, and n-strip isolation at the fluences of nil, 0.7×1014, and 7×1014 1-MeV neutrons equivalent (neq)/cm2. The bias and edge structure achieved holding the bias voltages up to 1000 V. The full depletion voltages were about 160, 250, and 600 V in the p-FZ and 1190, 500, and 840 V in the p-MCZ at nil, low, and high fluences, respectively. The radiation damage helped to reduce the density of electron accumulation layer. The strip isolation in the p-MCZ sensors was found to be much better than in the p-FZ sensors; even the no-isolation structure isolated the strips at nil fluence at bias voltage above 50 V. The lower density of electron accumulation layer in the p-MCZ could be attributed to an order less interface trap density in the 〈1 0 0〉 surface than that of 〈1 1 1〉, the negative potential in the inter-strip region by the bias voltage, and the possible effect of high oxygen content in the MCZ bulk.