A novel SRAM PUF stability improvement method using ionization irradiation

Abstract

As one of the fundamental elements of the fingerprints of integrated circuit chips, static random-access memory based physical unclonable function (SRAM PUF) has been regarded as an attractive option for hardware security circuits. Commercial SRAM chips could be used as PUF chips for low cost systems. However, the mismatches existing in most commercial SRAM chips are quite small, which could result in poor stability of SRAM PUF. To address this issue, this paper proposes a novel SRAM PUF stability improvement method using total ionization dose (TID) effect for commercial SRAM chips. The principles of this new method are presented in detail and verified by simulations. Thereafter, the TID experiments are carried out on one kind of commercial SRAM chips and validate that this novel method could reduce the intra-chip hamming distance (HD_intra) by two orders of magnitude within the ionizing dose range of 40–100 Krad (SiO2), which is a significant stability improvement. Furthermore, considering the trade-offs of other performance factors, 40 Krad (SiO2) has been regarded as the recommended ionizing dose, which not only makes the stability and uniformity of SRAM PUF attain almost ideal values but also keeps the radiation-induced damage within a limited level.