Proof of concept for through silicon vias in application-specific integrated circuits for hard x-ray imaging detectors

Abstract

Application-specific integrated circuits (ASICs) are commonly used to efficiently process the signals from sensors and detectors in space. Wire bonding is a space-qualified technique of making interconnections between ASICs and their substrate packaging board for power, control, and readout of the ASICs. Wire bonding is nearly ubiquitous in modern space programs, but their exposed wires can be prone to damage during assembly and subject to electric interference during operations. Additional space around the ASICs needed for wire bonding also impedes efficient packaging of large arrays of detectors. Here, we introduce the through silicon vias (TSV) technology that replaces wire bonds and eliminates their shortcomings. We have successfully demonstrated the feasibility of implementing TSVs to existing ASIC wafers (a.k.a. a via-last process) developed for processing the x-ray signals from the x-ray imaging CdZnTe detectors on the Nuclear Spectroscopic Telescope Array small explorer telescope mission that was launched in 2012. While TSVs are common in the semiconductor industry, this is the first (to our knowledge) successful application for astrophysics imaging instrumentation. We expect that the TSV technology will simplify the detector assembly and thus will enable significant cost and schedule savings in assembly of large area CdZnTe detectors.