Oxygen content of substrates and tunnel oxide quality: an in-line systematic analysis

An experimental study is presented concerning the impact of several substrate parameters on the reliability of thin oxides in an actual device process. Our results show that some bulk properties have a relevent impact on wafer performances. For instance, the reliability of thin oxide is found to be sensitive to variations of initial interstitial oxygen concentration within a rather narrow range. Epitaxial substrates give the best performances, provided suitable extrinsic gettering is used. On the contrary the behavior of thin oxides is found not to be very sensitive to the status (in terms of light point defects) of the water surface at the beginning of the device process.