Improving the Endurance of Nonvolatile Flash Memory Using Micro-Grain Poly-Silicon Floating Gate

This paper applied a grain-refinement technique to develop an alternative poly-silicon floating gate. Micro-grain poly-silicon grains were refined by using a single-wafer LPCVD processor and adding hydrogen. The SIMS analysis of micro-grain poly-silicon films revealed that hydrogen contributed to poly-silicon formation but was not incorporated into the poly-silicon films. The grain size and dopant concentration of poly-silicon affected oxide integrity. The grain size of micro-grain poly-silicon was well controlled under 15 nm by annealing with 950°C /30s N₂. A 100 k-cycle erase-program endurance test of a single-wafer LPCVD processor confirmed that the micro-grain floating gate poly-silicon with hydrogen had better endurance compared to conventional furnace poly-silicon.