Characterisation of the HEXITEC[formula omitted] X-ray spectroscopic imaging detector incorporating through-silicon via (TSV) technology

Abstract

In this paper a new version of the HEXITEC spectroscopic imaging technology is presented. The HEXITEC4S ASIC maintains the same pixel electronics but, unlike the previous design, contains no I/O pads on the top surface of the ASIC. The I/O pads, used for control and readout, are now produced on the bottom metal layer of the ASIC and are accessed using a deep through-silicon via process (TSV) developed by TMicro (Japan). Wire bonding then takes place on a redistribution layer produced on the rear surface of the ASIC. The use of this TSV processing means that devices are four-side-buttable and can be used to produce detectors from multiple modules with minimal dead area. TSV processing was completed on two wafers of HEXITEC4S devices and probe testing demonstrated a working ASIC yield of 75% and 43% for the two wafers. In order to test the performance of detectors, a 100 mm diameter wafer of spectroscopic grade GaAs:Cr was fabricated by Tomsk State University (Russia). The wafer consisted of HEXITEC4S and standard HEXITEC devices which allows the performance of the TSV detectors to be compared to those of the standard system using sensor material with near-identical properties. A comparison of the spectroscopic performance of these devices demonstrated a relatively minor difference between the HEXITEC4S and HEXITEC devices with FWHM@60keV measured to be 4.1 keV and 4.5 keV respectively. These results demonstrate that this deep TSV processing for the redistribution of the detector I/O can be successfully used to produce flat panels of HEXITEC detectors with minimal dead area between modules.