Optimized diode analysis of electrical silicon substrate properties

In this paper the reverse current characteristics of Si p-n junction diodes are analyzed in detail, in order to obtain an improved analysis of the underlying material parameters (generation and recombination lifetime, thermal activation energy). For that purpose, measurements on different geometry diodes are combined in order to separate peripheral from volume components. Using the correct depletion capacitance of the p-n junction, one can separate the diffusion from the generation component. From a study of the behavior with changing temperature, it is concluded that the peripheral generation component is due to surface generation by interface states. This is further supported by measurements on gated diodes, which yield an extra feature that is speculated to be related to the surface generation along the isolation oxide edges. For the volume generation component, widely different activation energies have been found, depending on whether an internal gettering step was applied or not. A good agreement with deep-level parameters and trap profiles obtained by deep level transient spectroscopy has been found. In the case of Czochralski material, there exists a clear correlation with the oxygen-precipitation related extended defects. Finally, it is reported that the electric field dependence of the generation current component is stronger than expected from the Poole-Frenkel effect only with an activation energy Towering which is much greater. Trap-assisted tunneling is a possible explanation.