3D NAND

# Manufacturing Sequence: Stack Deposition

## 10. 10. Manufacturing Sequence Stack Deposition

Before a single channel hole is etched, a 3D NAND die begins as a flat stack of alternating thin films, deposited one layer at a time across the entire wafer — the oxide/sacrificial-nitride pairs described in the previous step, repeated as many times as the design calls for layers. This deposition stage is comparatively forgiving: each layer is a uniform blanket film across the wafer, with no per-layer patterning or alignment required at this point, so adding more layers to the design is, at this stage of the process, mostly a matter of running the same deposition step more times. That simplicity is precisely why layer count became such an attractive scaling lever compared to shrinking a lithographic feature: depositing twice as many uniform blanket layers is a comparatively linear cost, whereas shrinking a lithographic feature by the same relative amount, as planar NAND found, runs into genuinely hard physical walls. The difficulty in 3D NAND manufacturing is not depositing the stack — it is everything that has to happen to that stack afterward, starting with the channel-hole etch covered in the next step, which does not get easier as the stack gets taller.