Physically Unclonable Function With a Rough Silicon Channel MOSFET

Abstract

To achieve a physical unclonable function (PUF) in a MOSFET, variations in the threshold voltage ( V-T ) were intentionally induced by engineering surface roughness in a silicon channel through wet etching. The roughened surface produces fluctuations in gate oxide thickness and variability in crystal orientation, deviating from the (100) surface with a large number of interface traps. This results in a variation in V-T . A binary bit state was encoded by using a high or low V-T in each MOSFET, representing a "0" or "1" state. Three representative PUF metrics, namely uniformity, interchip Hamming distance (HD inter ), and intrachip Hamming distance (HD intra ), were evaluated. PUF keys with intentionally produced random surface roughness exhibited nearly ideal PUF metric values, even after a lapse of 300 days without any passivation for device protection.