Sensitive differential method for the extraction of the mobility variation in uniformly degraded MOS transistors

A new method for the exploitation of the characteristics of uniformly degraded MOS transistors is proposed. The method, which is based on a first order differential analysis of the shift observed in the I_d(V_g) transfer characteristics after stress, enables an accurate determination both of the threshold voltage shift and of the mobility variation to be accurately obtained as a function of stress (e.g. injection dose). The method has been tested on Fowler-Nordheim stressed MOSFETs and this enabled the authors to demonstrate that the mobility is not a monotonous function of the interface charge created after stress, and, therefore, that no unique value for the Coulomb scattering coefficient can be extracted