In this work we present a novel method for improving the high-temperature performance of silicon photomultipliers (SiPMs) via focused ion beam (FIB) modification of individual microcells. The literature suggests that most of the dark count rate (DCR) in a SiPM is contributed by a small percentage (<5%) of microcells. By using a FIB to electrically deactivate this relatively small number of microcells, we believe we can greatly reduce the overall DCR of the SiPM at the expense of a small reduction in overall photodetection efficiency, thereby improving its high temperature performance. In this report we describe our methods for characterizing the SiPM to determine which individual microcells contribute the most to the DCR, preparing the SiPM for FIB, and modifying the SiPM using the FIB to deactivate the identified microcells.
This work outlines a case study of charge-induced damage to SOI wafers that caused gate leakage in discrete transistors and static leakage in packaged integrated circuits (ICs). The consequential yield fallout occurred primarily at wafer center. Electrical, optical, and laser-based failure analysis techniques were used to characterize the damage and determine root cause of electrical failure. The failure mechanism was localized to a rinse step during chemical mechanical planarization (CMP). Furthermore, both current-voltage (IV) sweeps and characteristic spatial patterns generated by thermally-induced voltage alteration (TIVA) were used to capture the trends on both packaged ICs and SOI wafers for this type of charge-induced damage; this.led to quick identification of another source of charge-induced damage that affected the post-fab yield.
We present a new, non-destructive electrical technique, Power Spectrum Analysis (PSA). PSA as described here uses off-normal biasing, an unconventional way of powering microelectronics devices. PSA with off-normal biasing can be used to detect subtle differences between microelectronic devices. These differences, in many cases, cannot be detected by conventional electrical testing. In this paper, we highlight PSA applications related to aging and counterfeit detection.