25 Facts About NAND flash

NAND or NOR flash memory is often used to store configuration data in numerous digital products, a task previously made possible by EEPROM or battery-powered static RAM.

NOR-based NAND flash has long erase and write times, but provides full address and data buses, allowing random access to any memory location.

NAND flash has achieved significant levels of memory density as a result of several major technologies that were commercialized during the late 2000s to early 2010s.

Degradation or wear of the oxides is the reason why NAND flash memory has limited endurance, and data retention goes down with increasing degradation, since the oxides lose their electrically insulating characteristics as they degrade.

NOR NAND flash continues to be the technology of choice for embedded applications requiring a discrete non-volatile memory device.

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NAND flash uses tunnel injection for writing and tunnel release for erasing.

Hierarchical structure of NAND flash starts at a cell level which establishes strings, then pages, blocks, planes and ultimately a die.

Architecture of NAND flash means that data can be read and programmed in pages, typically between 4 KiB and 16 KiB in size, but can only be erased at the level of entire blocks consisting of multiple pages.

V-NAND flash was first commercially manufactured by Samsung Electronics in 2013.

Growth of a group of V-NAND flash cells begins with an alternating stack of conducting polysilicon layers and insulating silicon dioxide layers.

One limitation of NAND flash memory is that, it can be erased only a block at a time.

In other words, NAND flash memory offers random-access read and programming operations but does not offer arbitrary random-access rewrite or erase operations.

Some file systems designed for NAND flash devices make use of this rewrite capability, for example Yaffs1, to represent sector metadata.

For NAND flash memory, reading and programming are page-wise, and unlocking and erasing are block-wise.

NAND flash devices require bad block management by the device driver software or by a separate controller chip.

NAND flash is best suited to systems requiring high capacity data storage.

NOR and NAND flash get their names from the structure of the interconnections between memory cells.

Industrial NAND flash are in demand due to their capacity, longer endurance and reliability in sensitive environments.

The capacity scaling of NAND flash chips used to follow Moore's law because they are manufactured with many of the same integrated circuits techniques and equipment.

Since the introduction of 3D NAND flash, scaling is no longer necessarily associated with Moore's law since ever smaller transistors are no longer used.

Serial NAND flash is a small, low-power NAND flash memory that provides only serial access to the data - rather than addressing individual bytes, the user reads or writes large contiguous groups of bytes in the address space serially.

When incorporated into an embedded system, serial NAND flash requires fewer wires on the PCB than parallel NAND flash memories, since it transmits and receives data one bit at a time.

Since this type of SPI NAND flash lacks an internal SRAM buffer, the complete page must be read out and modified before being written back, making it slow to manage.

Typical applications for serial NAND flash include storing firmware for hard drives, Ethernet network interface adapters, DSL modems, etc.

The cost per gigabyte of NAND flash memory remains significantly higher than that of hard disks.

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