Si-PIN X-Ray detector technology

PIN diodes and other test structures have been fabricated on both n- and p-type, high-resistivity, Floating-Zone (FZ) silicon substrates. Different alternative extrinsic-gettering techniques have been adopted to the purpose of meeting the required specification of a detector leakage current density lower than 1 nA/cm2. Phosphorus-doped polysilicon gettering provided the best results on n-type Si with a leakage current density lower than 0.2 nA/cm2 at 100 um depletion width. On the contrary, devices made on p-type substrates exhibited a leakage current density two orders of magnitude higher. A proper control of the oxide charge at the silicon-silicon dioxide interface was found to be crucial in obtaining a predictable behavior of PIN diode detectors. Some degradation of the reverse leakage current has been observed after device dicing and bonding.