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UBC Theses and Dissertations

Differential testing of CMOS integrated circuits Syal, Ashish


As CMOS technologies scale down, background leakage current increases inexorably, primarily due to device sub-threshold leakage. As a result, conventional single-threshold pass/fail IDDQ testing may no longer be valid for deep sub-micron technology. A number of alternatives to single threshold IDDQ testing have been proposed. A testing technique to complement IDDQ testing that has shown promise is thermal signature testing. The validity of using temperature as a test observable was investigated. After establishing this, the use of differential thermal sensing as a possible way of detecting bridging faults in CMOS gates was studied. Differential sensing provides high sensitivity to temperature changes generated by internal changes of the power distribution due to defects and immunity to ambient temperature changes. Different topologies for such sensors have been proposed targeting bipolar and BiCMOS. The novelty of the work is that these were the first such sensors to have been developed in CMOS technology. The thermal sensors were designed, simulated, fabricated and the chips that came back were tested. Three different types of sensors were designed and developed. They have the advantage that the performance of the CUT is unaffected by the sensors, as there is no direct electrical loading of the circuit due to them. Since these sensors do not directly load the circuit under test, they allow a non-intrusive methodology for testing. Also the sensors allow for on-line and off-line test, and diagnosis capabilities.

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