First Demonstration of Ruthenium and Molybdenum Word lines Integrated into 40nm Pitch 3D-NAND Memory Devices

We demonstrate the integration of Ruthenium (Ru) and Molybdenum (Mo) as Word Line (WL) metals in a record 40nm pitch 3D-NAND device through an optimized Replacement Metal Gate (RMG) process. The optimized RMG process minimizes oxide regrowth which affects WL fill capability in reduced pitches. Ru and Mo gates show better resistivity (ρ) and memory characteristics compared to the currently used Tungsten WL. We demonstrate good channel control and program/erase (P/E) characteristics down to 20nm WL. Best P/E is obtained for Mo with 2nm HfOx liner after a post metallization anneal (PMA) at 750°C for 20mins, while devices with Ru WL show better retention.