Charge Trap Flash

Charge Trap Flash (CTF) is a semiconductor memory technology used in creating non-volatile NOR and NAND flash memory. The technology differs from the more conventional Floating Gate MOSFET technology in that it uses a silicon nitride film to store electrons rather than the doped polycrystalline silicon typical of a floating gate structure. This approach allows memory manufacturers to reduce manufacturing costs five ways:

1. Fewer process steps are required to form a charge storage node
2. Smaller process geometries can be used (therefore reducing chip size and cost)
3. Multiple bits can be stored on a single flash memory cell.
4. Improved reliability
5. Higher yield since the charge trap is less susceptible to point defects in the tunnel oxide layer

Advanced Micro Devices (AMD) and its partner Fujitsu pioneered the production of charge-trapping flash memory in 2002 with the introduction of the GL NOR flash memory family, and the same business, now operating under the Spansion name, has produced charge trapping devices in high volume since that time. Charge trapping flash accounted for 30% of 2008’s $2.5 billion NOR flash market. Saifun Semiconductor, who licensed a large charge trapping technology portfolio to several companies, was acquired by Spansion in March 2008.

Although the charge trapping concept has been known since 1967, it wasn't until 2002 that AMD and Fujitsu produced high-volume charge-trapping flash memories.