A multi-bit/cell PUF using analog breakdown positions in CMOS
Kai-Hsin Chuang, E. Bury, R. Degraeve, B. Kaczer, T. Kallstenius, G. Groeseneken, D. Linten, Ingrid M.R. Verbauwhede · 2018
A physically unclonable function (PUF) utilizing the analog positioning of breakdown spots in CMOS transistors is presented. In contrast to digital positioning based on a three-transistor cell [3], this new approach has the capability of generating multiple bits from a more compact two-transistor cell. The basic properties and reliability aspects of this PUF are studied based on the test chips fabricated in a commercial 40nm CMOS technology. The breakdown positions in high density arrays have been characterized, proving that indeed multiple bits can be generated from a single nFET. Through consecutive measurements, the long-term stability is found to be reduced, due to shrinking of readout window, especially when more bits are generated. Finally, high temperature also negatively impact the stability, indicating that the analog BD-PUF is a lesser promising candidate for PUF application than the previously presented binarized design.