A differential OTP memory based highly unique and reliable PUF at 180 nm technology node

Abstract

A random binary code-based unique chip identity is essential for the security of Internet-of-Things devices. Physically Unclonable Function (PUF) exploits intrinsic physical randomness in devices to generate an unbiased random binary code. Earlier, a PUF was demonstrated using a large area (10 µm × 10 µm) HfO2-based OTPM (One-Time Programmable Memory) where perfectly unbiased random bit generation was shown using differential breakdown operation. However, the use of conventional materials (e.g. PECVD SiO2) and scalability across mature nodes (10 μm–0.18 μm) are attractive for the IoT application of PUF. In this paper, we present a highly scalable PECVD SiO2 breakdown based differential OTPM PUF implemented in a 180 nm CMOS foundry. The experimental results on approximately 1700 tested differential OTPM PUF show that the random string generated is unique. i.e. mean Inter-Hamming distance of 50%. The generated string has excellent reproducibility i.e. ideal Intra-Hamming distance of 0% and no bit flip, even at 250 °C for 6 h. Excellent scalability (from area 26 µm × 26 µm to 0.26 µm × 0.26 µm) is observed. The PUF passes a variety of NIST tests successfully.