NAND Flash vs NOR Flash: Differences between them
Tags: electron, flash, component
Published: 2023-10-13 10:11:35

## What is NOR Flash?
Flash memory, particularly NAND and NOR flash, is the most used type of storage [integrated circuit(IC)](https://www.ersaelectronics.com/c/integrated-circuits-ics). Volatile storage ICs and non-volatile storage ICs are the two primary subcategories of semiconductor storage chips. The most common non-volatile storage ICs are flash ICs, which are further divided into NOR Flash and NAND Flash. With the advancement of the technique, serial Flash has been able to fulfill the speed and data read/write requirements of general systems. NOR Flash has a relatively simple and inexpensive serial structure. NOR Flash is divided into parallel (parallel) and serial (SPI) variants. Since Serial Flash has been able to meet the primary system requirements for speed and data reading and writing, SPI NOR Flash can essentially be considered as NOR Flash.

## How does NOR Flash work?
The core element of NOR flash memory is the FGMOS (Floating Gate Metal Oxide Semiconductor Field Effect Transistors). Every [transistor](https://www.ersaelectronics.com/c/transistors) contains a region known as the Floating Gate. This region has the ability to either trap or release the electrons it contains. These electrons are captured when the transistor is turned on. Since each transistor can represent either 0 or 1, they are referred to as memory cells. The electronic device known as a transistor is used to switch or amplify electrical impulses. It is one of the fundamental components of contemporary electronics. It has at least three terminals for connecting to an electronic circuit and is made of semiconductor material.

## Structure and Working Principle of NOR flash
A three-terminal device with a source, drain, and gate serves as the memory cell in both NOR flash and NAND flash. Similar to a field-effect transistor, this three-terminal device uses voltage to regulate the on/off states of the source and drain while consuming very little current at the gate. The middle layer of the floating gate's nitride, which serves as a charge potential well and may store charge, is sandwiched between two layers of silicon dioxide material. Breakdown is avoided because the upper and bottom oxide layers are thicker than 50.
The act of writing data to the memory cell involves injecting charge into the charge potential well. Hot electron injection, which charges the floating gate through the source (NOR uses this technique to write data), and F-N tunneling effect, which charges the floating gate through the silicon base (NAND uses this technique to write data), are the two methods available.
It is important to note that both forms of Flash must first have their charges to the floating gates discharged by the F-N tunneling effect in order to erase the previous data before recording new data.

## What is NAND Flash?
In 1989, Toshiba introduced the NAND flash structure, which was praised for its reduced cost per bit, faster performance, and simple upgradeability via a disk-like interface. It is less expensive to create Flash using NAND Flash since it reads in the form of discrete chunks, typically 512 bytes at a time, as opposed to using memory's random read technology.
Because users cannot run the code directly on NAND Flash, many development boards include a little NOR Flash in addition to NAND Flash to perform the initialization code.

## How does NAND Flash work?
Millions of MOSFET-based charge trap memory cells are used in NAND Flash memory. Nanotechnology is used to create these cells. Electrons in Charge Trap Flash Memory (CTF) cells can either be released or trapped. Since each cell could only previously represent one bit, either a 0 or a 1, this caused.
The three crucial components of CTF are the Gate, the Channel, and the Charge Trap. These are all divided using a dielectric substance. Because it has the ability to either store or release the electrons it retains, the element is known as a charge trap. The cell symbolizes 1 when there are no trapped electrons and 0 when there are. A single contemporary CFT may be more valuable than an older CFT. To accomplish this, the Charge Trap component stores a range of charge levels. For instance, we require 8 distinct charges or voltages to represent 8 different values.

## Structure and Working Principle of NAND flash
The smallest erasable units of a NAND device, 128kB blocks, are used to create NAND Flash arrays. Set all bits to "1" (and all bytes to "FFh") to erase a block. Programming is required to convert the "1" deleted bits to "0" The byte is the smallest unit of computer code. A few types of NOR flash memory provide read and write operations. NAND cannot do both read and write operations, although it may be at the system level by "shadowing" the data. The BIOS has been loaded from the slower-speed ROM to the faster-speed RAM using this technique in personal computers for many years.