Macronix promises a 3D revolution in the world of NOR flash memory

NOR flash memory appeared a little earlier than NAND, but due to its low cost and ease of scaling, NAND became more widespread. This was largely helped by the development of 3D NAND technology, thanks to which it was possible to significantly increase the capacity of serial drives.

NOR is not dead because it has advantages over NAND – fast random access coupled with reliability, due to which it is often used in embedded and industrial solutions for storing firmware, BIOS, etc. However, the lack of multilayering seriously hampered the scaling of this type of flash memory. But the Taiwanese company Macronix, which specializes in creating niche NAND and NOR solutions, is going to change that.

3D NOR. Source: Macronix

Back in 2022, Macronix announced that it was working on creating 32-layer 3D NOR memory, which would increase the capacity compared to 2D NOR by seven times. The main market niches for this development were named embedded and industrial applications, as well as the automotive sector.

Structurally, 3D NOR consists of a multilayer “sandwich” with alternating layers of oxides and nitrides, which is pierced by so-called “plugs” – rather complex vertical structures consisting of two columns of n-type doped semiconductor with a silicon nitride spacer between them. Two such “plugs” per cell serve as the drain and source for the transistors that make up the bit-column channels. The word lines (and the gates of the aforementioned transistors) are arranged orthogonally.

Source: Macronix

The new memory is designed for 100 thousand rewrite cycles with full erasure, has an access latency of around 100 ns and a linear access speed of 400 MB/s per chip (DDR-200). It is also characterized by low power consumption (1.8 or 3 V supply), can have QSPI/Octal interfaces and meets AECQ-100 and ISO 26262 ASIL Level B reliability standards. The crystals are packaged in standard 24-BGA packages.

Previously published company materials stated plans to begin mass production of 3D NOR with capacities of 1, 2, 4 and 8 Gbit in 2024. In reality, the new products will be delayed somewhat – pilot deliveries will begin this year, and you shouldn’t expect widespread availability of chips before 2025.