A simple and physical drain avalanche hot carrier lifetime model has been proposed. The model is based on a mechanism of interface trap generation caused by recombination of hot electrons and hot holes. The lifetime is modeled as. The formula is different from the conventional -sub model in that the exponent of is 2, which results from the assumed mechanism of the two-carrier recombination. It is shown that the mechanism gives a physical basis of the empirical -sub model for NMOSFETs. The proposed model has been validated experimentally both for NMOSFETs and for PMOSFETs. Model parameters extracted from experimental data show that carrier critical energies for creating damage are lower than the interface potential barriers. It is supposed that oxide band edge tailing enables low-energy carriers to create the damage. The channel hot electron condition becomes the worst case in short channel NMOSFETs, because gate voltage dependence of the maximum channel electric field decreases.
Hot-carrier-induced photoemission of subquarter-micron n-MOSFETs is analyzed using a specially designed test structure, which has a wide channel width of 2.0 mm for sufficient photoemission intensity. Since the test structure consists of parallel-connected unit MOSFETs and photoemission images are uniform, it can be estimated that measured spectra are the same as those from unit MOSFETs. The relation between photon counts and photon energy suggests that photon energy has a Boltzman distribution; exp( ). The electron temperature calculated from photon emission spectrum takes minimum value at the channel length of 0.23 m. If is related to the device reliability, it suggests the possibility that the device structure optimized for a certain channel length may not be optimum for other channel length devices.
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