SK Hynix has completed production validation for its 375‑layer 3D NAND and will convert existing lines at its Cheongju M15 fab – currently making 176L, 238L, and 321L – to volume production by the end of this year. The original target was 400 layers, but channel hole etching constraints led to the 375‑layer design. The company plans 480‑layer and 604‑layer products in future generations.

The key innovation: replacing some tungsten with molybdenum (Mo) in word lines. Tungsten’s higher resistance and need for barrier layers become problematic at ultra‑high stacks; molybdenum offers lower resistance, faster read/write, and no barrier layer, improving storage density. However, Mo precursors are solid at room temperature, requiring specialized high‑temperature equipment.

Samsung, which has used molybdenum since its 286‑layer NAND (April 2024), employs Lam Research’s single‑wafer tools. SK Hynix will use TEL’s furnace‑type tools , processing hundreds of wafers at once – better for cost, footprint, and material consumption.

Air Liquide, Entegris, and Merck will supply Mo materials; SK Specialty may join via Air Liquide’s supply system.

SK Hynix is no longer adding raw NAND capacity but shifting to higher‑layer, higher‑efficiency production to improve bit cost.

ICgoodFind : SK Hynix’s 375‑layer switch to molybdenum word lines signals a material‑driven performance leap, with efficiency now prioritized over mere layer count.