Hot carrier induced photon emission in silicon devices

Hot-carrier induced photon emission (luminescence) represents a powerful experimental technique to analyse in detail hot-carrier effects and degradation in MOSFETs. This technique has been the subject of a long going research at DEIS in cooperation with the Dept. of Physics in Parma, Italy. The activity covered the analysis of the bias, temperature and photon energy dependence of emission in silicon devices (p- and n-channel MOSFETs, n-i-n structures), and the correlation with other hot carrier monitors (gate and substrate currents).

The emission mechanisms have been experimentally analysed by means of CCD structures and ionized impurity assisted transitions have been shown to be of minor importance in the emission process. The impact of layers covering the emission area has also been analyzed, and demonstrated to prevent correlation between light polarization and the anysotropicity of the carrier distribution function.

Special purpose n-i-n structures, free frum the obscuring effects of additional layers, have been fabricated characterized and modeled, demonstrating that luminescence spectra indeed represent a powerful and detailed technique for the experimental verification of carrier distributions.

From the application point of view, the relationship between emission and hot carrier degradation has been studied in detail in bulk and soi MOSFETs, demonstrating that by properly accounting for photon energy, emission can represent a precise hot carrier and degradation monitor in both device types. Applications to soi characterization, still under development, are particularly promising because in this case the most common monitor (substrate current) cannot be measured without severely perturbing the device behavior. Finally, a photon emission model to compute photon spectra by post-processing Monte Carlo simulations.