Low-voltage hot electrons and soft-programming lifetime prediction in nonvolatile memory cells

This paper reports experiments and Monte Carlo (MC) simulations of flash memory cells at the typical bias conditions of read operations (high V/sub GS/ and low V/sub DS/) leading to the soft-programming phenomenon. Comparing experiments with simulations we first show that, differently from the previously reported case of homogeneous injection experiments, efficient energy gain mechanisms must be invoked to explain the order of magnitude of gate (I/sub G/) and substrate (I/sub B/) currents at low voltage. Second, the voltage scaling behavior of the soft-programming lifetime is analyzed and the validity of usual extrapolation techniques to evaluate this parameter is addressed.