| The contribution of metallic precipitates to recombination and to generation currents in electronic devices fabricated using Si has been modeled for two types of structures: that of pn junctions and that of MOS capacitors, with the precipitate located in the charge depletion region of the appropriate structure. The physical mechanism responsible for the electrical activity of the metallic precipitate is attributed to the Schottky junction property between the precipitate and the Si matrix material. For the pn junction case, it is found that, in steady state, the precipitate changes from a highly effective carrier recombination center to a carrier generation center when the junction bias is changed from forward to reverse biasing conditions. Based on the physical model, numerical simulation results showed that the precipitates behave electrically like classical Shockley-Read-Hall (SRH) recombination/generation centers but with a large activity, and a method for determining the equivalent SRH center density is proposed. For the MOS capacitor case, the precipitate serves as a highly effective carrier generation center when the capacitor is switched from the accumulation mode to the deep depletion mode. As a practical case, the electrical activity of the copper silicide precipitate is investigated and a few measuring techniques are analyzed for potential electrical characterization of the device contaminated with copper precipitates. |
