Constant current charge-to-breakdown: Still a valid tool to study the reliability of MOS structures?

It is shown that the conventional interpretation of constant current Q/sub BD/ to evaluate the influence of process variations on the reliability of MOS structures can lead to erroneous conclusions. For a fixed thickness, the comparison of Q/sub BD/-distributions of all processes that affect the breakdown statistics becomes even meaningless. For ultra-thin oxides, the impact of different processing conditions requires constant gate voltage instead of constant current density Q/sub BD/-tests.