A sense amplifier based bulk built-in current sensor for detecting laser-induced currents

Abstract

Soft errors can occur when integrated circuits (ICs) are subjected to hostile conditions in space, the upper atmosphere, or even on Earth. For more than four decades, researchers have been studying similar phenomena. Among the different existing effects, Single-Event Effects (SEEs) caused by ionizing particles may cause the affected circuit to behave incorrectly. Since then, significant study has been devoted to the understanding and mitigation of SEEs in order to cope with the repercussions of such events. In this context, pulsed lasers were used to simulate SEEs at the experimenter’s bench. However, pulsed lasers can be used to introduce defects (as a result of SEEs) into the computations of security-dedicated Integrated circuits in order to get the secret information they may store. Fortunately, additional strategies developed by the experts in the radiation community to minimize SEEs may be adopted to better deal with the issue of laser fault-injection. Monitoring the currents that occur with SEEs was a fruitful concept. The notion of Bulk Built-in Current Sensors (BBICS) was designed to monitor transient currents generated in the bulk of Integrated circuits when struck by ionizing particles or a pulsed laser. This thesis work presents a novel approach to detect laser induced faults. This method uses a combination of sense amplifiers that evaluates the sampled substrate current in a time-interleaved manner. The proposed method can detect low-energy laser injection in the nanosecond range that does not always necessarily result in Single Event Transient (SET) / Single Event Upset (SEU). A current as low as 20 uA sustained for 10ns under typical operating conditions can be detected. It can also detect high-energy laser injection in the picosecond range that would result in SET or SEU. The design shows a leakage of 42 nA and consumes 41 nW/MHz at worst case. The simulations and analysis are being performed at 1.08 V using CMOS 65nm Low Standby Power (LSTP) process.