A Board-Level Prognostic Monitor Circuit Design For Gate Dielectric TDDB

With the scaling of IC devices into90nm, the thickness of Gate dielectric has reduced to lessthan2nm, which means several layers of atom. In the case of the supply voltage and the gatedielectric oxide layer thickness can’t be reduced in proportion, electric field strength of the gateoxide dielectric layer is increasing. Therefore, TDDB has been one of the main failure mechanismsof ICs.At present, the PHM technology of electronic products has been widely recognized. In terms ofcost savings and avoiding failure, it has an overwhelming advantage. There are three main PHMtechnology methods for electronic products:"canaries" method, the failure precursor monitoringreasoning method and environmental monitoring method. In this paper, we design the prognosticcircuit to monitor TDDB of MOS transistors based on "canaries" method, including Non-overlapping clock module，stress voltage module, reduced voltage module and output module.Non-overlapping clock module provides overlapping clock signal for stress voltages module. Stressvoltage module uses a novel charge pump, which can not only generate high voltage stress, and alsoavoid other transistors in the prognostic cell under stressing. Therefore, the charge pump proposed inthis study has high reliability. The stress voltage generated loads to MOS testing capacitor andoutput module through reduced voltage module. MOS test capacitor is under the effect of stress toaccelerate TDDB failure. So it can be successful to warn TDDB failure.The prognostic circuit is simulated by SMIC0.18um CMOS process. It shows that beforeTDDB failure occurs, output is high voltage. Once the prognostic cell is break-down and failure, itsoutput turns, and an alarm signal would be given. The prognostic circuit designed has simplestructure, high reliability and can be easily integrated into single chip. Thus, the prognostic circuitcan not only avoid a fatal failure of integrated circuit caused by TDDB, but also guarantee thereliability of electronic products and lay a good foundation for development of PHM technology inintegrated circuit.