A study of SRAM PUFs reliability using the Static Noise Margin

Abstract:
The use of SRAM cells as key elements in a Physical Unclonable Function (PUF) has been widely reported. An essential characteristic the SRAM cell must feature for a reliable PUF is stability, i.e., it must power up consistently to the same value. Different techniques to measure this stability (and thus improve the PUF reliability) have been reported, such as the Multiple Evaluation method and, more recently, the Maximum Trip Supply Voltage method, the latter using the Data Retention Voltage (DRV) concept. While experimental results have been reported, this paper sheds some light from a different perspective: simulation. In this sense, and using wellknown concepts like butterfly curves, static noise margin and voltage-transfer curves, an analysis is provided on why and how stability originates in the cell. Moreover, by simulating the butterfly curve behavior when the supply voltage scales down, it is possible to correlate DRV with stability, thereby confirming the correct theoretical foundation of the MTSV method.