We developed an original thermally stimulated exoelectron emission spectroscopy method (TSEE) of measurements of the activation energy Φ of electron (hole) traps in ultrathin Si_3N_4 films. The temperature spectra of TSEE of 50A silicon nitride films demonstrate several peaks: three low temperature peaks (T_1 = 373K, T_2 = 423K, T_3 = 498K) and a high temperature maximum at T_4 ～ 750K. The obtained values of the energy activation are Φ_1 = 0.82 eV, Φ_2 = 0.93 eV, Φ + 1.09 eV, and Φ_4 = 1.73 eV. TSEE results are shown to be consistent with Φ estimates obtained from microFLASH two bit per cell memory transistor measurements. Electrons stored at traps with Φ_4 = 1.73 eV explain excellent microFlash retention properties. We believe that deep traps in Silicon Nitride are Hydrogen containing centers, while Hydrogen hopping is the route cause of observed material degradation in course of TSEE measurements.
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