Overcome the End of Life of 3D Flash Memory by Recovery Annealing, Aiming for Carbon Neutrality in Semiconductor Manufacturing

In this work, we report a novel approach using thermal annealing to recover the degradation of cell characteristics due to program/erase (P/E) cycling in 3D flash memory. To achieve an effective recovery, the threshold voltage (Vth) of the cell during thermal annealing should be close to the neutral Vth level, at which defects in the tunnel dielectric layer (TNL) generated by P/E cycling are electrically empty. Optimized annealing temperatures and times, specifically 3 hours (h) at 200 °C or 7 h at 150 °C, effectively recover the degradation of the cell characteristics caused by 10k P/E cycling. Furthermore, the recovery effect of annealing is valid even after repeating 10k P/E cycling and recovery annealing at least 5 times. Optimized recovery annealing can achieve reuse of 3D flash memory that have reached their end-of-life (EOL), contributing to sustainability by reducing CO2 emissions during product manufacturing.