Enhancing Chip Security With Physical Unclonable Functions And Self-Destruction

Physical Unclonable Functions (PUFs) are the current state of the art solution to hardware security. A silicon-based PUF exploits local manufacturing variations to produce a secure encryption key that is repeatable, intrinsic, random, unique, and low-cost. In many ways, a PUF can be considered a unique digital ‘fingerprint’ for chip identification and authentication. In this dissertation we cover the properties and industry standard metrics for assessing a PUF. Results in this dissertation, are supported by hardware measurement data from multiple silicon test chips implemented in GLOBALFOUNDRIES 12-nm, TSMC 5-nm, and TSMC 3-nm Fin Field-Effect Transistor (FinFET) Complementary Metal Oxide Semiconductor (CMOS) technologies.We will target three main areas of research: PUF topologies, PUF stability, and PUF feature extensions. Regarding PUF topologies, we will provide an overview of the most common PUF topologies that exist in the industry and provide a comparison to our innovative Pre-Amplifier PUF. In general, the most challenging aspect of a PUF design is to achieve a repeatable and stable key across a wide set of test conditions. For PUF stability, we detail and compare multiple techniques that have been proposed and highlight the single test condition stable bit identification technique that we have developed and utilized to achieve as low as a “zero” Bit Error Rate (BER) in silicon testing. Further, we propose accelerated aging techniques that eliminate the need for storing stable bitcell locations, while still achieving a “zero” BER. PUF feature extensions represent one of the highlights of our research. We demonstrate the first ever silicon-proven methods and structures for a self-destructible PUF that can corrupt and physically destroy the underlying data used to generate the PUF encryption key, blocking future authentication attempts. This tamper response is done by exploiting well-known semiconductor reliability failure mechanisms. In our work, we propose a simultaneous electromigration (EM), and time-dependent dielectric breakdown (TDDB) directed to the PUF array data. The result is an irreversible corruption of the secure encryption key to enhance chip security. Outside of using self-destruct as a tamper response, we propose techniques to utilize these concepts to thwart counterfeit integrated circuits that try to emulate or duplicate the original chip functionality. As an End of Life (EOL) recycling step, PUF self-destruct can be used to safely disable chip functions and corrupt sensitive data.