Path Delay Measurement with Correction for Temperature And Voltage Variations

Path delay measurement in field is useful for not only detection of delay-related faults but also prediction of aging-induced delay faults. In order to utilize the delay measurement results for fault detection and fault prediction, the measured delay must be corrected because the circuit delay is varied in field due to environment such as temperature or voltage variations. This paper proposes a method of BIST-based path delay measurement in which the influence of environmental variations is eliminated. An on-chip sensor measures temperature and voltage during delay measurement. Using information from the temperature and voltage sensor and pre-computed temperature and voltage sensitivities of the circuit delay, the measured delay value is corrected to a delay value that would be obtained under a fixed temperature and voltage. Evaluation for a test chip with 65nm CMOS technology implementing the proposed method shows that errors of measured delays brought by environmental variations could be reduced from 2419 to 211 ps in the range of 30 to 80 °C and 1.05 to 1.35 V. This paper also discusses application and feasibility for degradation detection of the proposed method.