An in-process monitor for n-channel MOSFET hot carrier lifetimes

A rapid test that can detect changes in the hot carrier reliability of n-channel MOSFETs due to process induced damage to the oxide/interface was developed. The test consists of a short snapback stress phase, followed by a 5-s electron injection phase. Results are shown to be strongly correlated with variations in hot carrier reliability due to oxide damage during upper-level processing steps. The test assumes that basic MOSFET structural parameters such as doping profiles and channel lengths do not vary significantly. This type of test is particularly useful as an inline monitor in wafer fabrication, enabling the rapid detection of process induced damage effects on hot carrier lifetime. The use of 1/f noise signals as a monitor for hot carrier resistance was also investigated. It was shown that the 1/f noise signal of an unstressed MOSFET was not correlated with its hot carrier robustness.< >