ISSCC: Toshiba, Unity claim breakthroughs

Japan's Toshiba will disclose a new ''breakthrough'' SRAM technology. The new technology is said to overcome the high failure rate that has been the main challenge in achieving a practical, low-voltage SRAM.

Toshiba has devised a test SRAM chip fabricated with 32-nm, high-k/metal gate process technology. This in turn has reduced the voltage for stable operation from the 1-Volt typical for conventional SRAM to 0.7-Volt.

The technology solves a major issue. Voltage scaling of cutting-edge system LSI has been a challenge, because embedded SRAM lose stability in the memory function at low voltage, according to Toshiba. The memory cell transistors of SRAM are smaller than those of other logic circuits, which makes SRAM operation susceptible to transistor variability at low voltage.

Toshiba claims it has overcome this problem with a new method that employs ''read-assist and write-assist techniques and secures the function of a low voltage SRAM.'' Read-assist and write-assist techniques are recognized as a means to stabilize SRAM functionality by optimizing bit-line and word-line level during read and write operation.

Toshiba's solution employs a ''negative voltage generator with bit-line-capacitance replica, which adaptively optimizes the negative level to the SRAM capacity.''

It is said to reduce memory cell failure rate by four orders of magnitude at 0.7-V. ''Moreover, the circuit design can be applied to the memory compiler, software that automatically configures SRAM, contributing to shorter design lead times and bringing an effective solution to the LSI development process,'' according to Toshiba (Tokyo).

As expected, Unity Semiconductor will describe a technology that company founder and CEO Darrell Rinerson has been working on since 2002--Conductive-Metal-Oxide (CMOx) memory.

One analyst is bullish about the technology. ''They will announce that they have produced a 64-Mbit multi-layer and multi-level device. It is designed to function like a NAND component (although 5x faster writes) and can easily scale below 20-nm and should be capable of densities two times greater than the advanced NAND introduced by IM Flash Technologies LLC last week,'' said Alan Niebel, president of Web-Feet Research Inc.

Last week, Intel Corp. and Micron Technology Inc. regained the process technology lead in NAND flash, by rolling out the first in a family of 25-nm devices. The device is made by IM Flash, a joint NAND venture.

CMOx uses a cross-point 3-D structure (multi-layers) that with the multi-level charge state enables it to have an effective cell size of 0.25F².

''This high capacity translates to much lower costs than NAND. Although, it is potentially a 'NAND killer,' the two technologies will be made concurrently for the next seven years as NAND extends its life and CMOx ramps up volume production,'' Niebel said. ''This year CMOx may be partnered with one or more NAND manufacturers to bring it into commercial production by late next year.''