Flash memories degrade over time as the oxide gets damaged and loses its ability to hold charge. It’s apparently well known that this damage can be annealed out, but that takes time and/or temperature. You can’t heat the chip over 400 °C, so you have to anneal for minutes for nominal results.
As described in an IEDM paper, Macronix modified their cell to allow a high current in the vicinity of the cell. By running that current for milliseconds, it could create local heating above 800 °C. This resulted in endurance over 100,000,000 cycles with good retention.
Alongside the MRAM papers, it strikes me as a familiar thing because Crocus also uses a local heater for thermally-assisted switching of their MRAM cells, although the temperatures aren’t nearly as high. I don’t know if this is truly a case of cross-pollination, but it feels like it.
If you have the IEDM proceedings, more detail is available in paper #9.1.