Cross-Temperature Effects of Program and Read Operations in 2D and 3D NAND Flash Memories

Abstract

The cross-temperature effect in NAND Flash memories has always been a concern since the early developments of the planar technology. The sensing of the data at a temperature different from that used during programming is a source of a large number of failed bits, leading to unrecoverable data corruption even using well-known error correction codes. In this work, we show that this issue is still present in 3D NAND Flash technology, though with different peculiarities due to the different materials used for the channel in the memory cells. The characterization of the fail bits count distributions as a function of the temperature combinations of program and read will expose that the most critical condition is that where program temperature is higher than the read one, therefore requiring special care at system-level to handle the increased errors number (i.e., using secondary correction mechanisms like soft decoding or read retry).