Pure-Metal Replacement Gate for Reliable 30 nm Pitch Scaled 3D NAND Flash

We demonstrate the integration of Molybdenum as "a pure metal gate" in a record 30 nm z-pitch 3D NAND device by adopting a barrierless replacement metal gate (RMG) process. We also propose and demonstrate an in-memory-hole high-k (HK) liner to extend the 3D NAND Flash roadmap. In the new structure, the HK liner is placed inside the memory hole instead of the word-line (WL) cavity, thereby freeing up room for WL metal and enabling vertical scalability. Mo conductivity improves with a H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -only post metallization anneal. We report good channel control down to 15 nm Mo WL thickness. Superior retention is obtained for devices with Mo in combination with 2 nm HfO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> liner. No impact of z-pitch scaling on reliability down to 30 nm pitch.