SanDisk and Toshiba look to develop 3D memory

Flash memory chip maker SanDisk has teamed up with Toshiba to develop and manufacture re-writeable 3D memory.

Both companies will contribute and cross license technology related to 3D memory chip development and production to the project, and Toshiba will pay licensing fees to SanDisk as part of the venture, according to SanDisk.

The venture could ultimately result in a new kind of memory technology to take over from NAND flash memory, SanDisk's main chip product, which is used to store photos, songs and other data in iPods, iPhones, digital cameras and other devices.

The concept of 3D memory chips is not new. The technology was developed years ago as a way to lower costs and store information longer, as long as 100-years by some claims, which is far longer than NAND flash memory.

Matrix Semiconductor developed a 3D memory chip design several years ago by stacking memory arrays vertically instead of horizontally, which they said would lower costs. The company worked with Taiwan Semiconductor Manufacturing (TSMC) to produce the chips, but they never caught on widely.

SanDisk bought Matrix in 2005. One key difference between the SanDisk/Toshiba joint venture and Matrix is that Matrix's chips were not rewriteable. Whatever data was loaded on the chips, stayed there.

SanDisk and Toshiba want to make rewriteable 3D memory chips that can be reused over and over again.

A few years ago, Toshiba developed a rewriteable 3D flash memory chip called BiCS (Bit Cost Memory) in which it stacked arrays vertically. The company has created working samples of the chips, but they are also not yet commonplace.

SanDisk and Toshiba plan to combine their intellectual property and engineering talents to further develop 3D memory chips and production technology. The companies did not disclose the cost of the venture nor licensing fees involved.

Don't expect to see 3D memory chips on the market anytime soon. Gregory Wong, president of researcher Forward Insights, believes it will take three to four years for the companies to develop a 3D memory product that can compete with NAND flash memory,

One trouble with 3D memory is the chips can be difficult to manufacture at high yields, Wong says.

3D rewriteable memory consists of stacked vertical diode arrays, and currently only chips with four layers of stacked memory cells are in volume production using leading-edge technology, he says. Matrix demonstrated an eight-level stack in 2003 using much less advanced production technology, a 250-nanometre process versus an 80nm process for four-layer stacked memory.

"Producing eight level memory stacks at leading edge technology is another matter," said Wong.