  Physically unclonable functions (PUFs) are increasingly adopted for low-cost
and secure secret key and chip ID generations for embedded and IoT devices.
Achieving 100% reproducible keys across wide temperature and voltage variations
over the lifetime of a device is critical and conventionally requires large
masking or Error Correction Code (ECC) overhead to guarantee. This paper
presents an Automatic Self Checking and Healing (ASCH) stabilization technique
for a state-of-the-art PUF cell design based on sub-threshold inverter chains.
The ASCH system successfully removes all unstable PUF cells without the need
for expensive temperature sweeps during unstable bit detection. By accurately
finding all unstable bits without expensive temperature sweeps to find all
unstable bits, ASCH achieves ultra-low bit error rate (BER), thus significantly
reducing the costs of using ECC and enrollment. Our ASCH can operate in two
modes, a static mode (S-ASCH) with a conventional pre-enrolled unstable bit
mask and a dynamic mode (D-ASCH) that further eliminates the need for
non-volatile memories (NVMs) for storing masks. The proposed ASCH-PUF is
fabricated and evaluated in 65nm CMOS. The ASCH system achieves "0" Bit Error
Rate (BER, < 1.77E-9) across temperature variations of -20{\deg}C to
125{\deg}C, and voltage variations of 0.7V to 1.4V, by masking 31% and 35% of
all fabricated PUF bits in S-ASCH and D-ASCH mode respectively. The prototype
achieves a measured throughput of 11.4 Gbps with 0.057 fJ/b core energy
efficiency at 1.2V, 25{\deg}C.
