Novel silicon stripixel detectors on high resistivity p-type magnetic Czochralski silicon wafers for US-ATLAS upgrade

A new Si detector system based on a number of novel aspects of detector structure and detector material is proposed here for the US ATLAS Upgrade Project. The novel aspects in this Si detector system include: 1) a novel Si stripixel detector structure developed at BNL will be used, which provides 2d position sensitivity with single-sided process; 2) high resistivity magnetic Czochralski (MCZ) Si wafer will be used, which provides naturally high concentration of oxygen for improved radiation hardness to charged particles; and 3) p-type MCZ substrates are used, for which single-sided process is retained and fast electron collection is presented, and which experiences no space charge sign inversion to ensure partial depletion mode operation at extremely high radiation fluences. In the first detector design layout, strip pitches in both y and u directions have been fixed at 80 μm, with a stereo angle of 4.6° between them. The strip length is 3 cm and the detector chip size is 2.56 cm × 6.0 cm, with 2 halves of 2.56 cm × 3.0 cm sensitive areas without dead space between them. Both y and u strips will be read out by the sides perpendicular to the strips. Simulations on detector processing as well as the electric properties before and after radiation by charged particles up to 1.0×10¹⁶ n_eq (1 MeV neutron equivalent)/cm² have been done. Simulation results show that up to 2.0×10¹⁵ n_eq/cm² of charged particle irradiation, the highest fluence for the inter-medium region for strip detector in the SLHC, the new detector with a thickness of 200 μm can still be fully depleted at a bias of 400 volts.