Toshiba to use MRAM in HDD

Aug 17, 2011 17:32 Masahide Kimura, Nikkei Electronics

"MRAMs will make it possible to take further advantage of NAND flash memories and HDDs, whose access performances are low," said Kiyoshi Kobayashi, president of Toshiba's Semiconductor and Storage Products Company.

He made this statement Aug 10, 2011, at a corporate strategy meeting when he was explaining the MRAM (STT-MRAM) technology that Toshiba is developing with Hynix Semiconductor Inc.

Currently, memory systems have a hierarchical structure of "SRAM-DRAM-NAND-HDD." And, for servers and storage systems, Toshiba is planning to propose a new memory system by adding MRAM between DRAM and NAND, aiming to improve the low access performances of NAND flash memories and HDDs by using high-speed MRAM.

"NAND and HDD will become more convenient for system makers," Kobayashi said.

The number of times that MRAM can be rewritten will be 1015, he said. Though it seems possible to use MRAM as working memory with this number, he said, "MRAMs have a structure where electric currents are applied to tunnel insulating films. So, defects will certainly be generated, and it is impossible to be infinitely rewritable."

Therefore, Toshiba seems to be planning to use MRAMs as cache memories for making it easier to use existing storage memories such as NAND and HDD rather than to replace the entire working memory. However, the company has not completely given up the ambition of replacing working memory with MRAM because the cell area of MRAM is expected to become equivalent to that of DRAM.

Also, Toshiba considers that equipment needed to manufacture MRAMs is not much different from existing equipment.

"For example, equipment like ALD does not change, but the material used for forming films differs depending on magnetic body and so forth," Kobayashi said.

As a challenge related to manufacturing technologies, he cited the difficulty of etching, saying, "We need a bias etching technology that has a higher energy than a normal RIE (reactive ion etching) technology." Therefore, it is necessary to change the power supply system, etc of the etching equipment, he said.

Commenting on Samsung Electronics Co Ltd's acquisition of Grandis Inc, an IP vendor for STT-MRAM, Kobayashi said that he welcomes it because Samsung's full-fledged entry into the MRAM business will activate the market due to multiple suppliers.

"We have been engaged in the development of MRAM without making any connection to Grandis," he said. "We have ten years of experience and twenty years of experience if the preceding era of HDD is included."