Transistor-limited constant voltage stress of gate dielectrics

Abstract

Conventional methodologies gauge gate oxide reliability by stressing with a low impedance voltage source. This is more severe than the stress sustained during circuit operation in which transistors are driven by other transistors. A new test configuration which better approximates circuit stress conditions, the transistor-limited constant voltage stress test, significantly reduces post-breakdown conduction (I/sub BD/) as compared to standard constant voltage stress. The smaller the current drive capability of the limiting transistor, the softer the breakdown. If I/sub BD/ of the broken dielectric is sufficiently reduced while the circuit voltage margin is not exceeded, circuits may continue to function even with a failed oxide.