Physically unclonable functions for embeded security based on lithographic variation

Physically unclonable functions (PUF) are designed on integrated circuits (IC) to generate unique signatures that can be used for chip authentication. PUFs primarily rely on manufacturing process variations to create distinction between chips. In this paper, we present novel PUF circuits designed to exploit inherent fluctuations in physical layout due to photolithography process. Variations arising from proximity effects, density effects, etch effects, and non-rectangularity of transistors is leveraged to implement lithography-based physically unclonable functions (litho-PUFs). We show that the uniqueness level of these PUFs are adjustable and are typically much higher than traditional ring-oscillator or tri-state buffer based approaches.