Modeling of phosphorus deactivation in polysilicon for simulation of memory process in nanometer era

In this study, experiments were performed to investigate phosphorus deactivation in polysilicon and a deactivation model was proposed to improve the simulation of nanometer memory devices. Decay of carrier concentration was observed during low-temperature annealing in polysilicon films formed by different methods. However, the decay rate decreased with time and the carrier concentration almost saturated after long-term annealing. The grain size of polysilicon did not significantly affect the decay of carrier concentration. A clustering model was proposed to simulate the deactivation. The model assumes that the cluster formation rate dominates the dependence of the deactivation process on temperature. Direct reactions between neighboring phosphorus atoms was suggested to explain the rapid deactivation with a high initial activation level. The impact of deactivation on the electrostatics of memory devices was demonstrated by simulation using the proposed clustering model.

► We studied phosphorus deactivation in polysilicon at temperatures below 700 °C.
► The deactivation at low temperatures is not sensitive to the grain size.
► The deactivation is governed by reaction kinetics, not solid solubility.
► A deactivation model was developed for memory process simulation.