High - Speed, Reliable Ssd Developed For Real - Time Data Processing



High-speed, Reliable SSD Developed for Real-time Data ProcessingA Japanese research group developed a technology to improve the operating speed and reliability of semiconductor storage device (SSD) by six and five times, respectively.
The group is led by Ken Takeuchi, a professor at the Department of Electrical, Electronic and Communication Engineering, Faculty of Science and Engineering of Chuo University.



The new technology realizes a high operating speed and reliability with low-cost TLC (3bits/cell) NAND flash memory by compensating for the interference from surrounding memory cells and adjusting a readout level in accordance with the deterioration of memory cells. It can be applied to IoT technologies including autonomous driving and Industry 4.0, the group said.

The details of the technology were announced at International Solid-State Circuits Conference (ISSCC) 2015, which runs from Feb 23 to 26, 2015, in San Francisco, the US, under the title "Enterprise Grade 6x Fast Read and 5x Highly Reliable SSD with TLC NAND Flash Memory for Big Data Storage" (lecture number: 7.7).

In technological fields where real-time processing is important such as IoT, there are needs for storage devices that can process, store and manage data at high speeds. However, it is difficult to realize high performance and reliability at the same time with conventional SSDs. For example, when a powerful error-correcting technique is used for improving data reliability, readout performance will deteriorate, making it take longer to read out data from a memory device.

Readout level dynamically adjusted

This time, the research group solved this issue mainly by developing three technologies. The first technology is "Quick LDPC," which compensates for the interference from surrounding memory cells by referring to pre-recorded table information.

The second technology is "Dynamic Vth Optimization," which is a highly sensitive readout method that reads out data with optimal conditions regardless of the deterioration of memory. It dynamically adjusts a readout level in accordance with the memory's threshold voltage, which is dynamically changed by the injection of electrons into memory cells and leakage from the cells.

The third technology is "Auto Data Recovery," which makes (1) the error effect of mistakenly injecting electrons into memory cells being read and (2) the error effect of leaking electrons from memory cells retaining data cancel out each other to improve reliability.

With those technologies, even when an error occurs to NAND flash memory, it can be corrected with a high speed and reliability.