CMOS-Mems Physical Unclonable Functions Based on Unbalanced Bimodal Frequency Combs

This work demonstrates for the first time micromechanical physical unclonable functions (PUFs) that leverage the unbalanced bimodal frequency combs of the internal-resonating MEMS resonator. In particular, this work utilizes the nonlinear CMOS-MEMS resonator that previously demonstrated the true random number generation (TRNG) based on the saddle-node on an invariant circle (SNIC) bifurcation point and operates it away from bifurcation, allowing stable frequency comb generation. Here, the frequency comb patterns serve as the process-variation-derived response upon a challenge determined by a particular driving frequency value, together forming a challenge-response pair. Digitizing the amplitude of the frequency comb with 16 bits for the highest 8 comb teeth generates a total of 16 × 8 = 128 PUF bits for a particular driving frequency with a single resonator. This device advances CMOS-MEMS technology into a new application area of MEMS-based PUF security.