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The 7th (2007) Yamazaki-Teiichi Prize Winner Semiconductor & Semiconductor Device

Pioneering Work of Sub-50 nm MOSFET Research and Development

winner Winner
Hiroshi Iwai
History
Apr. 1972 Graduated from the Department of Electronic Engineering, The University of Tokyo
Apr. 1973 Joined Tokyo Shibaura Electric Co., Ltd.
Apr. 1997 Chief Specialisit , Microelectronics Engineering Lab. , Toshiba Corporation
Apr. 1999 Professor, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology
Nov. 2007 Professor, Frontier Research Center, Tokyo Institute of Technology
Present

winner Winner
Hisayo S. Momose
History
Mar. 1984 Received M.S. Degree from Ochanomizu University, Graduate School of Science
Apr. 1984 Joined Toshiba Corporation
Feb. 2006 Received the degree of Dr. of Engineering from Tokyo Institute of Technology
Apr. 2006 Specialist , Center for Semiconductor Research & Development, Toshiba Corporation
Present

winner Winner
Tatsuya Ohguro
History
Mar. 1989 Received M.S. Degree from Hokkaido University, Graduate School of Science,
Apr. 1989 Joined Toshiba Corporation
Apr. 2006 Senior Specialist, Center for Semiconductor Research &Development, Toshiba
Oct. 2006 Concurrently acting as Visiting Professor, Hiroshima University
Present

Reason for award

In the early 1990s, Dr. Iwai et al. engaged in joint research and development to break through what had been taken for common sense around the world at that time -- that 0.1μm is the limit of miniaturization for large-scale integrated circuits (LSIs) -- to succeed in the trial manufacture of MOSFET with a gate length of 40nm. Thereafter, LSI miniaturization proceeded steadily, as it has to the present. The historical result that Dr. Iwai et al. achieved in the early 1990s continues to be highly regarded worldwide as one driving force that has accelerated advancements in LSIs. Today, with the LSI being an indispensable element of numerous electronic devices and infocommunications systems, the extreme importance of the results of this research and development can be understood in regard to the immense contribution it has made to both industry and society. Dr. Iwai et al. engaged in creative research and development on subjects pertaining to the limits of LSI miniaturization, such as the following. At the time, there were basic doubts about whether sub-50nm MOSFET would operate at room temperature, with no clear answers. Concerning this problem, the prizewinners conducted strict Monte Carlo Simulation to confirm MOSFET operation at room temperature at gate lengths down to 25nm. At the same time, they discovered guidelines for the basic design of LSIs composed of sub-50nm MOSFETs. In terms of phenomena obstructing MOSFET miniaturization, there had been concern over the effect of tunneling current from gate insulating film. To overcome this problem, the prizewinners developed low-defect, ultrathin SiO2 film formation technology using rapid thermal oxidation (RTO). In addition, at the time, the level of technology for optical lithography, a basic technology for manufacturing miniature structure for LSIs, was insufficient for advanced research. The prizewinners solved this problem by adopting resist narrowing method using oxygen plasma. Although the method for forming a source and drain area below a junction depth of 20nm and the low resistance of electrodes were major problems, the prizewinners solved them by selecting NiSi electrode materials and applying a high-concentration diffusion method that used rapid thermal annealing (RTA). Although diffusion from the P+ polycrystalline gate electrode to the Si substrate through boron (B)- SiO2 film was another challenge, through rapid thermal nitridation (RTN), they converted SiO2 insulating film to SiON film and succeeded in suppressing that phenomenon. Surmounting numerous technological barriers in these ways, the prizewinners' success in the trial manufacture of MOSFETs with sub-50nm gate length and in the development of this element technology have made major contributions to the continued advancement of the LSI technical field since that time. Their work has been highly regarded around the world, and Japan can take pride in their outstanding results. In this way, for the results of their creative research and development of a high technical level and the immense contribution to society and the LSI industry made, Hiroshi Iwai, Hisayo S. Momose and Tatsuya Ohguro have been awarded the Yamazaki-Teiichi Prize in Semiconductors & Semiconductor Devices.

Background of research and development

Large-scale integrated circuits (LSIs) have now come to be indispensable as a core component to assist and regulate people's activities. In an aging society with a declining birthrate, devices with the ability to take on human intellectual endeavors, such as nursing-care robots are important. For this reason, LSIs with even higher performance and reduced power consumption are required. In addition, LSIs play a major role in energy saving, which is an urgent environmental protection issue of global scale. Henceforth, it is expected that LSIs will become increasingly important to Japan as strategic high technology.
Although CMOS LSIs are standard for LSIs, they are composed of metal-oxide semiconductor field-effect transistors (MOSFETs), the miniaturization of which is crucial to improving performance and reducing power consumption. However, there are limits to the miniaturization of gate length, which determines MOSFET performance: miniaturization beyond 50nm had been deemed impossible for many years. To break through this barrier and actualize LSIs with improved performance and reduced energy consumption, various original technologies have been considered necessary, but the situation continued to be one in which clues to them proved elusive.

Achievements

Since the late 1980s, the prizewinners have been investigating various directions for realizing a sub-50nm MOSFET. First, they used Monte Carlo simulation to verify room-temperature operation of planar MOSFETs down to 25nm and clarified the specific structures and dimensions. They developed and introduced processes for miniaturizing gates and making source and drain junctions shallow that far surpassed the limits of the process technology of the time to actually prepare sub-50nm MOSFETs, for which they confirmed that transistor characteristics were normal at room temperature. They also demonstrated that fluctuations in those characteristics would be able to withstand future mass production.
Concerning gate insulating film under 2.5nm, the thinning of which had been considered difficult owing to direct tunneling current, they confirmed normal and high-performance transistor operation with miniature MOSFETs. Demonstrating the principles of operation, they utilized this technology to actualize the world's highest performance at the time. In addition, they clearly demonstrated that the thin film that introduced rapid thermal oxidation (RTO) technology was highly reliable, having excellent uniformity, no defects and no problems in actual operation. Moreover, they introduced nickel monosilicide (NiSi) as a low-resistance material to salicide structure for the first time. Along with making ultrashallow silicide source and drain junctions possible, they succeeded in controlling the narrow-line effect. In addition, they proposed applying the miniature MOSFETs to RF circuits, and led the world in demonstrating the effectiveness of RF CMOS.
The above constitutes breakthrough technology that the prizewinners developed originally and that is used widely in products throughout the world as technology indispensable to leading CMOS LSIs.
Moreover, for 3D devices of the future, the prizewinners presented directions for improving MOSFET mobility with channel plane orientation under gate thin film. For the continued thinning of gate insulating film, they conducted trailblazing research on La2O3 types and other rare earth oxide films as high-K insulating film to succeed the HfSiON films, which is now at the early stage of commercialization. Demonstrating the superiority of these films, they cleared the path for the future. These technologies also constitute major research results that will link to commercialization henceforth.


Meaning of the achievements

The research and development that the prizewinners conducted constitutes technology indispensable for continuing the ongoing effort to realize the high performance and low power consumption of the CMOS LSI, which is the brain that supports and regulates the activities of today's society, beyond sub-50nm. Although sub-50nm had been considered impossible on the roadmap, the prizewinners revealed a clear path at a time when pessimism about future miniaturization research and development had spread throughout the world's semiconductor industry, giving their results huge social and economic impact

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