Two-Pattern ∆IDDQ Test for Recycled IC Detection

Increasing numbers of used and recycled integrated circuits (ICs) being fraudulently marketed as new, is a serious concern for government and industry because these chips can pose serious reliability problems. This paper presents a novel approach to detect recycled chips already in circulation in the market by measuring I
_DDQ
, the quiescent (steady state) current from power supply. The measured I
_DDQ
is the leakage from off transistors, and decreases as the circuit ages due to the increase in the magnitude of the transistor threshold voltages caused by negative/positive bias temperature instability (NBTI/PBTI). To eliminate the influence of chip-to-chip process variation, we use a normalized difference, ΔI, from measurements at two input test patterns. Focusing on NBTI, in one pattern I
_DDQ
is controlled by a large number of minimally stressed PMOS transistors and in the other it is controlled by an equal number of heavily stressed PMOS transistors. The new approach requires no hardware addition or modification to the design. A standard IC tester can be used to measure I
_DDQ
and identify these recycled parts. Our simulation results show that we can detect recycled ICs that have been used for as little as six months.