Comprehensive evaluation of early retention (fast charge loss within a few seconds) characteristics in tube-type 3-D NAND flash memory

A fast charge loss within a few seconds, which is referred to as early retention, was observed in tube-type 2y word-line stacked 3-D NAND flash memory for the first time, and the origin of the early retention was comprehensively evaluated. Using a fast-response pulse I-V system, the early retention characteristics from microseconds to seconds were thoroughly investigated, and the correlations with various program and erase levels were examined using solid and checkerboard patterns. Our findings indicate that the early retention mainly originates from the lateral charge loss through the shared charge trap layers and suggest that the program and erase levels should be balanced and optimized to reduce the early retention.