I. Introduction
Hydrogen has long been suspected of playing a key role in radiation-induced charge buildup in MOS devices [1]–[4]. Indeed, the amount of hydrogen present in ambient gases used during device fabrication has been correlated (at least qualitatively) to the concentration of radiation-induced interface traps post processing [5]. Exposure of devices to hydrogen post processing has also been shown to lead to increased interface-trap buildup. In 1988, it was shown that hydrogen (0.3 to 0.6% ) trapped in hermetically sealed ceramic packages can increase radiation-induced charge buildup in MOS devices [6]. More recently, it was shown that hydrogen trapped in hermetically sealed packages can also degrade the total dose response of bipolar linear devices [7]–[9]. These works suggest that hydrogen can readily diffuse into device oxides affecting radiation-induced charge buildup. Because hydrogen diffusion is a thermally activated time dependent process, long-term exposure to hydrogen present in device packages may lead to unexpected radiation-induced degradation before the system lifetime has been achieved. This is supported by recent work that showed increased interface-trap charge buildup in MOS devices stored for 17 years in non-hermetically sealed packages. The increase in interface-trap charge was suggested to be due to the absorption of water molecules in the devices [10]. Clearly, hydrogenous species can have a significant impact on device radiation hardness and devices exposed to hydrogen over long periods of time may be susceptible to increased radiation-induced degradation [10], [11] that may not be detected during hardness assurance qualification testing.