NOR, NAND’s poor relation in nonvolatile memory, could be getting a capacity jump with Macronix’s 3D technology.
Taiwan-based Macronix provides niche NAND and NOR and ROM products and led the NOR market in 2020 with a 24 percent share over Infineon (15 percent) and Micron (5 percent). The NOR market had a 15 percent CAGR last year. Unlike NAND, where the 3D revolution has resulted in vastly increased chip capacity using 200+ layers, NOR had remained in the planar, 2D era.
NOR flash has faster read time than NAND but slower write speed – ~100ns vs TLC NAND’s ~100us – and larger cell size. It is often used for storing application code in systems that need fast app load times, such as smartphones. Macronix said it was working on a 32-layer 3D NOR product back in 2022. Such a product could significantly increase NOR die capacity.
Macronix marketing VP Anthony Le told the EE Journal that Macronix was developing a 32-layer 3D NOR product with up seven times greater density than planar 2D NOR. Its target market was the non-volatile memory product one in the embedded, industrial and automotive areas.
We understand that the starting point for this 3D NOR is a semiconductor AND circuit with bit (cell) level access and a gate-all-around design. It fabricates a multi-layer structure of oxide and nitride layers, etching holes between them and then filling the holes with tree so-called plugs; two N+ doped and one silicon nitride (SiN) insulator column between them with a split channel taking up the rest of the hole space.The two N+ doped plugs act as the source and drain-connected bitline channels for the stacked transistors in the structure. They are orthogonal to the word lines.
It provided a 3D AND diagram showing this in late 2020:
It showed an updated version of this 3D NVM diagram at the 2023 FMS event and is using the same diagram for its FMS 2024 teaser webpage. Macronix will update attendees on its 3D NOR progress at this Santa CXlara event.
It has already been sampling 1, 2, 4 and 8Gb 3D NOR product as a 2023 chart shows:
We understand that its latest 3D NOR product features:
- 32-layer 3D NOR – single-die of 1Gb, 2Gb or 4Gb
- 100,000 program/erase cycles – similar to existing 2D NOR devices
- AECQ-100 (automotive standard) reliability and ISO 26262 ASIL (Automotive Safety Integrity l Level) B compliance
- Latency of ~100ns
- 400MB/sec throughput (200MHz DDR)
- Low power draw – either 3V or 1.8V
- QSPI and Octal interfaces
- Backwards compatibility with 24BGA-package flash
We expect this product to be sampled later this year with possible general availability in 2025.
