Statistical modeling of dynamic random access memory data retention characteristics

A statistical model to investigate the distribution of dynamic random access memory data retention times is proposed. The model assumes that the retention time is determined by a junction leakage current generated at carrier traps by a Shockley-Read-Hall process, and that the trap levels are randomly distributed not only among the memory cells but also within a cell. Monte Carlo results based on the model were in excellent agreement with experimental results, which confirmed the validity of the model. An analytical expression of the retention time distribution was also derived, and proved a good approximation near the 50% cumulative probability. Based on the model, variation in the retention time distributions among samples was found to be related to different trap-level distributions at the SiO₂/Si interface.