A new model for dielectric breakdown mechanism of silicon nitride metal-insulator-metal structures

For the further advance of Si RF devices and also GaAs/GaN MMIC devices, highly reliable and low leakage MIM structure with thick silicon nitride (SiN) film has to be realized on the basis of deeper understandings on its degradation and breakdown mechanisms. Therefore, a comprehensive study has been performed on the TDDB mechanism of MIM structures with SiN films having various thicknesses fabricated by three different deposition conditions and, then, a new TDDB model, the constant ΔE model, has been proposed. The constant Qbd (charge to breakdown) hypothesis which is assumed in the generally accepted √E-model for SiN films is not valid. In contrast, the field shift until the breakdown (ΔE) monitored by the I-V characteristics is constant independent of the stress voltage, stress method - constant voltage or constant current stress-, temperature, SiN film thickness, and also the deposition condition. Furthermore, the analysis on the deposition condition dependence has revealed that the dielectric breakdown does not occur when ΔE reaches the threshold only at the cathode side. To induce breakdown, ΔE at the anode side or at both sides must reach the threshold. The voltage dependence of TDDB lifetime is also discussed.