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Taiwan's ITRI innovates in emerging memory research

Posted: 01 Jan 2006 ?? ?Print Version ?Bookmark and Share

Keywords:karen kou? itri? erso? electronics research and service organization? industrial technology research institute?

The manufacture of memory products in Taiwan reached $6.835 billion in 2004, accounting for about 20 percent of the worldwide market. This positions Taiwan as an important global memory product supplier. However, the island's reliance on technology transfer from foreign countries has resulted in the relatively weak R&D capability of local dram makers. As process technologies move into the deep-submicron era, Taiwan makers are realizing that they will have to develop proprietary technologies to stay competitive in the long run.

Catering to local DRAM makers' needs, the Electronics Research and Service Organization (ERSO) of the Industrial Technology Research Institute (ITRI) is focusing on emerging memory technologies such as magnetoresistive RAM (mram), phase-change memory (PCM) and metal-insulator-metal (MIM) structures.

Major semiconductor makers, including Samsung, Infineon, IBM and Intel, are investing in research for MRAM and PCM products. However, commercialization of these memory modules has not been seen thus far. As for DRAM, the more urgent issue is leakage problems when moving into 70nm.

Ming-Jinn Tsai, director of the nanoelectronics technology division at ERSO, explained that capacitors, which are constructed with silicon-insulator-silicon (SIS) structures, are the basic elements in DRAM that save charges. As process technologies shrink, it becomes more difficult to keep the capacitor value high enough to save charges correctly. He said that to maintain appropriate capacitor values in a smaller area, high-k materials have to be used as insulators.

"Thicker insulators will cause leakage current due to the lower band offset between insulator and silicon. As a result, we should use another material such as metal to replace silicon," Tsai said.

To solve problems caused by smaller geometries, the most effective way is to adopt a MIM capacitor structure to replace the existing SIS structure. Tsai said that, starting with the 65nm node, MIM structures must be adopted for DRAM fabrication. "To establish MIM technology in the island, ITRI launched a two-year project in January 2005. We started with 65nm and then extended to 45nm and 32nm nodes," said Tsai.

"We were involved in high-k material research for the CMOS process before, but the project was stopped after a year," Tsai said. He admitted that the research capabilities of Taiwan foundry players outpace that of ITRI. Hoping to regain its important role in Taiwan's semiconductor industry, ITRI believes that they are in a good position to focus on emerging memory technologies.

"Although Taiwan's DRAM makers have their technology resources, none has successfully solved the high-k material problems yet. Hence, they are happy to co-develop with us," Tsai added.

Tsai plans to complete the development of high-k materials for 65nm by end of the year. Focusing on the interface between metal and insulator, Tsai disclosed that they filed seven to eight patents on this area last year.

At present, Al2O3 and HfO2 are the most frequently used high-k materials with dielectric values of 9 and 25, respectively. In the long term, ITRI plans to develop materials with dielectric values higher than 30 in a bid to guarantee the technology can continue to extend to 45nm and 32nm. ITRI is also developing other materials in addition to TiN.

ITRI has been developing MRAM technology for three years. "MRAM will have a niche market in the future. We have worked with TSMC for about three years. It is likely that we will move the into pilot production stage very soon," Tsai said.

- Karen Kou

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