Iddq Testing

IDDQ Testing is a test methodology that measures the quiescent (steady-state) power supply current — of a CMOS IC when it is in a stable, non-switching state. A defect-free CMOS circuit should draw near-zero static current; elevated IDDQ indicates a defect.

What Is IDDQ Testing?

• Principle: In defect-free CMOS, the only current path from VDD to GND is through leakage. This should be nanoamps.
• Defect Indicator: A gate oxide short, bridging fault, or stuck-open fault creates a direct current path -> microamps or milliamps.
• Procedure: Apply a test vector -> Wait for circuit to settle -> Measure $I_{DDQ}$.

Why It Matters

• Bridging Fault Detection: IDDQ is the gold standard for detecting resistive shorts that logic testing misses.
• Reliability Screening: Chips with elevated IDDQ (even if they pass logic tests) are likely to fail in the field (latent defects).
• Challenge: As process nodes shrink (7nm, 5nm), background leakage increases, making defect-induced current harder to distinguish.

IDDQ Testing is the blood pressure check for chips — detecting hidden internal defects by measuring abnormal power consumption at rest.