Samsung develops 40 nm Flash, faster than NOR

In an attempt to regain the technical lead in NAND flash, Samsung Electronics Co. Ltd. today (Monday, September 11, 2006) claimed that it has developed a prototype memory device which will displace high density NOR flash in the next ten years.

South Korea's Samsung said it has made the industry's first 32 gigabit NAND flash device using a 40 nanometer process. According to the company, the first 40 nm, 32-Gb(it) chip, can be used in memory cards with densities of up to 64-gigabytes (GBs).
For instance, it will enable memory card manufacturers to assemble 64 GB SD or Compact Flash cards - which could store 64GB card. The chip can store over 64 hours of DVD resolution movies (40 movies) or 16,000 MP3 music files (1,340 hours).

Key to the capacity increase is a new approach that Samsung calls "Charge Trap Flash (CTF)" architecture. This technology is said to reduce "inter-cell noise levels" in the device, according to its manufacturer. "In each 32-Gbit device, the control gate in the CTF is only 20 percent as large as a conventional control gate, in a typical floating gate structure," Samsung said.

Emphasizing on the significance of the Charge Trap Flash architecture, the company added that "With CTF, there is no floating gate. Instead, the data is temporarily placed in a 'holding chamber' of the non-conductive layer of the flash memory composed of silicon nitride (SiN). This results in a higher level of reliability and better control of the storage current."

NOR flash memories can be used as execute-in-place memory, meaning it behaves as a read only memory (ROM) mapped to a certain address. It is used when data is only read from flash memory, such as memory chips that contain fixed operating systems, may run into natural limits earlier than NAND.

On the other hand, NAND flash memories cannot provide execute-in-place due to their different construction principles. The technology is used today in applications where data needs to be written to the flash chip. For example, the technology is used in digital cameras, USB sticks and MP3 players such as Apple's Ipod Nano.

Now, Samsung believes that a new technology could replace NOR within a decade, and the company bets that it will be Phase-change Random Access Memory (PRAM). This non-volatile PRAM can re-write without erasing existing data and that will make it 30 times faster than NOR, and offers ten times the number of read/write cycles, Samsung asserts.

Compared to the currently available NAND flash, which was launched by Toshiba in 1989, the chip uses a metal single-gate structure that is extraordinarily smaller than the usual poly-silicon dual-gate. Samsung affirmed that the technology will permit the manufacturing of 256 GB chips in 20 nm, while dual-gate flash chips will top out at 16 GB and around 50 nm.

The first prototype developed by the company has a cell size 0.0467micron square. Samsung claims that PRAM offers a "virtually unlimited scalability." First devices based on the technology are expected to be appearing as 512 megabit chips sometime in 2008. With these devices, Samsung seems to be attempting to regain the technical lead in NAND.