Front-end electronics of double SOI X-ray imaging sensors

Abstract

We have developed monolithic CMOS pixel sensor using fully-depleted (FD) silicon-on-insulator (SOI) pixel process technology. The SOI substrates consist of high-resistivity silicon with p-n junctions and low-resistivity silicon layers for forming SOI-CMOS circuitry. Tungsten vias are used to make connections between p-n junctions in the silicon substrate and the first metal layers in the top-layer circuitry. Using this sensor construction, high sensor gain in small pixel areas can be achieved. In 2014, a high-resolution, integrated SOI pixel sensor, called INTPIX8, was developed with two types of substrates: a float-zone, p-type layer on a single SOI (SSOI) wafer and a Czochralski, p-type layer on a double SOI (DSOI) wafer. The X-ray spectra were obtained using Am-241 radiation source. The SSOI-based and DSOI-based sensors exhibited different levels of sensor gain and there were no large differences in the noise levels between them.