Vol.2 No.3 2009

Research paper−194−Synthesiology - English edition Vol.2 No.3 pp.194-205 (Dec. 2009) To realize this dream of normally-off electronic equipment requires development of non-volatile electronics technology for the main memory (DRAM and SRAM) and for the logic unit of computers. As the first stage of research and development aiming at normally-off electronics, AIST is doing R & D to achieve the first of those two requirements, a large-capacity, high-speed and highly-reliable non-volatile computer memory. Here, high reliability mainly refers to rewrite durability. To replace the DRAM and SRAM that serve as the main memory of computers, it is necessary to attain the practically limitless write endurance of 1015 rewrite cycles without failure. Incidentally, the write endurance of the flash memory used in current external storage devices is only 104 to 106 rewrite cycles, and so is not usable as main memory. The ferro-electric memory devices (FeRAM), typical non-volatile memory devices that are already on the market, have a write endurance of 108 rewrite cycles, still inadequate to serve as computer main memory. The phase change memory (called PRAM or PCRAM) devices currently under development as non-volatile memory also have limited rewrite times. Spintronics technology (explained below), on the other hand, enables the development of non-volatile memory that has unlimited rewrite times.The main non-volatile, large-capacity external storage device currently in use is the hard disk drive (HDD) (Fig. 1). In the future, SSDTerm 3 based on flash memory is expected to replace the HDD in small-capacity and high-end applications, but the HDD is expected to remain the primary device for large capacity and low cost storage applications that have a large market for some time into the future. However, high power 1 Introduction1.1 The need for non-volatile electronicsCurrent electronic memory devices are built around a core of silicon LSI technology and are basically “volatile,” which means that recorded data is erased when the power supply is cut off. That happens because the DRAMTerm 1 general-purpose high-capacity memory and SRAMTerm 2 high-speed memory used by computers and IT home electronics use volatile recording techniques, and the logic unit in the CPUs and other such electronic devices are also all volatile (Fig. 1). Generally, electronic equipment has very long input “standby time.” When creating documents with personal computers, for example, the computer is idle for most of the time from one key input to the next key input, and is not doing any work at all. Even during such “standby” times, however, the power to the electronic equipment remains on and power is consumed. The volatility of electronic equipment means that the power cannot be turned off. If the electronic devices that constitute computers and IT appliances could be made “non-volatile” (i.e., memory is retained even when power is disconnected), then basic designs in which the power could be turned on or off instantly, as needed, (“quick-on”) or in which the basic state is “normally off” and the power is turned on only when computation is being performed would be possible (Fig. 1). “Normally off”, in particular, is a new concept that is completely the opposite of the current electronics concept of power on as the basic state and holds out the promise of ultimate green IT equipment that consumes almost no power.- Toward developing ultimate green IT devices -Shinji Yuasa*, Hitoshi Kubota, Akio Fukushima,Kay Yakushiji, Taro Nagahama, Yoshishige Suzuki and Koji AndoNanoelectronics Research Institute, AIST Tsukuba Central 2, 1-1-1 Umezono, Tsukuba 305-8568, Japan *E-mail : Original manuscript received May 11, 2009, Revisions received June 30, 2009, Accepted July 1, 2009We have been promoting Full Research to develop ultimate green IT devices based on non-volatile electronics. A core technology of non-volatile electronics is a non-volatile memory possessing features such as large capacity, high-speed operation, and high endurance. To develop such an ultimate non-volatile memory, we developed a novel high-performance magnetic tunnel junction device based on magnesium oxide (MgO) and its mass-manufacturing technology. These technologies have already been commercialized for the production of the magnetic heads of ultra-high density hard disk drives (HDD). Now we are also performing intensive R & D activities for developing the ultimate non-volatile memory called Spin-RAM.Creating non-volatile electronics by spintronics technologyKeywords : Spintronics, magnetoresistance, hard disk drive (HDD), MRAM, Spin-RAM, non-volatile electronics, green IT[Translation from Synthesiology, Vol.2, No.3, p.211-222 (2009)]


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