How to effectively characterize transistor leakage during volume production with minimal test time.
A method of estimating the subthershold component of MOSFET off-state current (Ioffs) using low-cost, low-resolution fast parallel parametric test is introduced. This method measures the subthreshold slope and uses it to estimate Ioffs. Measurements of individual transistors show a very good agreement between measured Ioffs and Ioffs estimated using our approach. For a simple pad-efficient transistor array test-structure, where unselected devices can add additional noise to the subthreshold measurements, the sum of extracted Ioffs for all transistors in an array is strongly correlated to the measured array Ioffs, even though it does not match the measured array Ioffs. The strong correlation is used to derive calibration factors which are then used to estimate individual transistor Ioffs from array test structures. This allows statistical characterization of transistor leakage during volume production with minimal test time overhead. The applications of statistical off-state leakage characterization to diagnose IDDQ yield problems during production are also described.
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