(NIST: Gaithersburg, Maryland) -- Using an ultra-fast method of measuring how a transistor switches from the “off” to the “on” state, researchers at the National Institute of Standards and Technology recently reported that they have uncovered an unusual phenomenon that may affect how manufacturers estimate the lifetime of future nanoscale electronics.

The transistor is one of the basic building blocks of modern electronics, and the life expectancy or reliability of a transistor is often projected based on the response to an accelerated stress condition. Changes in the transistor’s threshold voltage (the point at which it switches on) are typically monitored during these lifetime projections. The threshold voltage of certain types of transistors (p-type) is known to shift during accelerated stresses involving negative voltages and elevated temperatures, a characteristic known as “negative bias temperature instability” (NBTI). This threshold voltage shift recovers to varying degrees once the stress has ended. This “recovery” makes the task of measuring the threshold voltage shift very challenging and greatly complicates the prediction of a transistor’s lifetime.

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