Interface and bulk trap generation in metal-oxide-semiconductor capacitors

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Abstract
The effects of electron-hole pair recombination near the silicon/silicon dioxide interface of aluminum-gate metal-oxide-semiconductor capacitors have been studied. For the first time, electron-heating-induced trap generation and interface state creation is separated from those defects created through electron-hole pair recombination. The midgap interface state density is observed to increase linearly with the number of recombination events and approaches saturation in the mid 1011 eV−1 cm−2 range for trapped hole densities greater than about 1012 cm−2. However, the total integrated interface state density, although showing a similar net increase to that of the midgap interface state density, does not saturate for the largest trapped hole densities introduced in this work. For hot-electron-induced defects, a dramatic increase in the interface state generation rate is observed for average electric fields above a threshold of 1.5×106 V cm−1. An increase in the electron trapping rate above the heating threshold is also detected at both the cathode and anode interfaces. The rate is found to be approximately 10−5 traps or interface states generated per injected electron for average electric fields below the heating threshold, while above the threshold this rate increases by an order of magnitude. These rates were measured for injected electron fluences as low as 10−3 C cm−2. These high trapping and interface state generation rates are believed to be due to the high concentration of hydrogen (or hydrogen-related species) in these films.