Thin photodiodes for a neutron scintillator silicon-well detector

In the development of new neutron imaging applications, it is crucial to ac hieve a detector combining high spatial resolution, fast response, and high detection efficiency. To achieve such features, we have proposed a new des ign for position sensitive radiation sensors, which we called the micromach ined Si-well scintillator pixel detector. It consists of an array of scinti llator crystals encapsulated in silicon wells with photodiodes at the botto m. In the following, we describe such a detector, which makes use of a powd er of Li-6(6)158 Gd(BO3)(3)(Ce3+). The first experiments obtained with a pr ototype detector using a thermal neutron beam show the presence of a signal above the detector noise tail. In addition, to improve the characteristics of the well-type silicon sensor, we have investigated the deep reactive io n etching on silicon-on-insulator wafers. The process to etch 700-mum-wide vertical wells into a 500-mum-thick silicon wafer has been optimized. Test detectors with 10-mum-thick photodiodes at the bottom have been fabricated by means of this process.