Oral-History:Takuo Sugano

About Takuo Sugano

Takuo Sugano

Takuo Sugano became interested in science as a child, and entered the University of Tokyo in 1950 for a BS in electrical engineering. He was inspired by the recent invention of the transistor to spend his career studying semiconductors. Among other things, his research has included germanium bipolar transistors, electron transport through the surface inversion layer (the channel of the MOS transistor), silicon dioxide films, silicon oxidization, etc. He has co-edited a book, Competitive Edge: Semiconductor Industry in the US and Japan, intended to keep commercial competition from turning into national rivalry. He spent most his career as a professor at the University of Tokyo, and since his mandatory requirement at age 60 has split his time between Toyo University and the government-sponsored Institute of Physical and Chemical Research. He has received the Purple Ribbon Prize from the Japanese government for his contributions to solid-state electronics. He has been active in the IEEE since a student, has been involved in such IEEE conferences as the VLS1 Technology Symposium and the IEEE Electron Devices Society, and has been involved as an Associate Editor of the IEEE Transactions of Electron Devices in trying to turn manuscripts by Japanese scientists into acceptable English. He notes a very heavy orientation by Japanese scientists to reading English-language journals and producing English-language papers. He also notes, favorably, IEEE’s recent efforts to expand its scope to bioscience, biotechnology, neurocomputing, etc.

About the Interview

TAKUO SUGANO: An Interview Conducted by Robert Colburn, IEEE History Center, 15 July 2000

Interview # 401 for the IEEE History Center, The Institute of Electrical and Electronics Engineering, Inc.

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It is recommended that this oral history be cited as follows:

Takuo Sugano, an oral history conducted in 2000 by Robert Colburn, IEEE History Center, Piscataway, NJ, USA.

Interview

Interview: Takuo Sugano

Interviewer: Robert Colburn

Date: 15 July 2000

Place: Toyo University, Tokyo, Japan

Electrical engineering education and initial involvement with the IEEE

Colburn:

Dr. Sugano, if I could take you through the early stages of your career and how you became interested in electrical engineering, and how you became interested in the IEEE.

Sugano:

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Even at the elementary school as well as in junior and high schools I was interested in science, especially physics. Fortunately I met a very good teacher of physics when I was a senior in high school, so I was motivated and stimulated to study physics.

As for college level education the University of Tokyo, from which I received my Bachelor Degree, was admitting students to the science division as a group. This division is not divided to departments. After one and a half years, the students were required to apply to a department of the schools, and screened by their academic achievements during the period of one and a half year. I applied to Department of Electrical Engineering and was admitted to the Department.

During my stay at the University of Tokyo I took a freshman course in quantum physics as well as a course in classical physics and mathematics. Fortunately, the invention of transistors was announced in 1948. Actually, I know, the invention of transistors was done in 1947, but it was published in Letter Section of Physical Reviews in 1948.

I entered the University of Tokyo at 1950. That is two years later the invention of transistors, which was really very important and had a big impact on electrical engineering. Operating principle of the transistors is based on the quantum mechanical properties of material, and, I believed, transistors would explore a new field in electrical engineering. So I decided to study the science and technology related to semiconductor. Fortunately in those days professors at the Department of Electrical Engineering started to work in this field, so there were students in graduate Ph.D. studies involved into the research or transistors. I worked on the science and technology related to geranium bipolar transistors. This is the story how I became interested in semiconductor electronics.

In this country, too, we have a professional institute like the IEEE. However in 1950s our professional societies didn’t have any publications in English; all publications were in Japanese. Also the huge amount of information about the semiconductor science and technology was coming from the United States. So I applied to be a student member of the IEEE to get the technological information, and also I published my paper for the first time in the Proceedings of the IRE. That is a main part of my Ph.D. thesis. Since then I have been involved in the activities of the IEEE.

Role of IEEE in Japan; service as IEEE Regional Director

Colburn:

In what ways do you feel that the IEEE has been important to Japanese affairs?

Sugano:

The motivation for most of Japanese to be a member of the IEEE is to receive the technical information from the IEEE publications, and to present their work at IEEE meetings and publish their papers in IEEE publications in order exchange their knowledge and experience with scientists and engineers in US and other countries. So probably you see many Japanese are active in technical societies. Japanese contributions to the IEEE Regional Activities have not been so significant. However, I am pleased to serve on the IEEE as a Regional Director.

I am the second Director elected from Japan. The first one was Dr. Tsuneo Nakahara for 1995-1996. Before him there was no Japanese Regional Director. Most of the Japanese are active in the technical societies, as I said previously.

Colburn:

But not regional?

Sugano:

Neither regional nor corporate activity with a few exceptions.

Research

Colburn:

After you began publishing as a student and went on to work with the IEEE, what were some of the things that you worked on and researched?

Sugano:

You mean the subjects of my research?

Colburn:

Yes.

Sugano:

After germanium bipolar transistors?

Colburn:

Right.

Sugano:

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I was offered a position of assistant professor at the University of Tokyo in 1959, and three years later I visited Stanford University as a visiting research associate for one year. My stay was supported by the research fund at Stanford University. To get such a forceful position, I distributed a copy of my publication in the Proceedings of the IRE, which I mentioned previously. Fortunately, Professor John L. Moll gave me the position. I stayed at Stanford University for one year.

After I returned to the University of Tokyo again, my interest was rather shifted to physics of semiconductors rather than devices. Also in 1960, the invention of MOS transistors was announced. From a physical point of view, the early interest in semiconductor surface was related to surface recombination of minority carriers, whose research I had been involved in since I was a graduate student. Since the invention of MOS transistors I became interested in the electron transport through the surface inversion layer, so-called the channel of MOS transistor.

After I worked on the surface quantization of electrons, especially on the galvanomagnetic effects on electron transport in silicon surface inversion layer, my interests returned again to device performance of MOS devices, and also the semiconductor technology. My research interest was concentrated on silicon-silicon dioxide systems. Firstly I started the structural study of thermally grown silicon dioxide on silicon substrate. Silicon dioxide films thermally grown on silicon substrates are generally known to be amorphous. But by doping antimony or arsenic to silicon dioxide, it was observed that local crystallization was enhanced. This was found in course of research carried out to understand the physical mechanism of immobilization of sodium and other alkaline atoms in silicon dioxide by phosphorus doping. Also I was interested in geometrical morphology of the interface between silicon and silicon dioxide, because I was doing research into electron scattering by surface roughness, and worked on the microscopic study of the interface roughness.

Then I worked on the technology to get a very stable silicon dioxide film and was particularly interested in oxidation of silicon in extremely dry atmosphere. I tried to eliminate the inclusion of hydroxyl into silicon dioxide during the oxidation process. I found a very interesting relationship between the moisture content in oxidizing ambient and the density of hole traps, which are oxygen vacancies, in silicon dioxide and electron traps. I found the density of hole traps and the density of electron traps are just in tradeoff. By reducing the moisture content in oxidizing atmosphere the density of hole traps increases but the density of electron traps decreases, vice versa. That was very interesting observation.

Concurrently I worked on metal- insulator- three/five compound semiconductors systems, too. The thermal oxidation process could not be used to fabricate this system, because the arsenic and other group V elements evaporate during the oxidation process. I believe there are a lot of vacancies of arsenic or other group V elements generated at the near surface region of the substrate. In consequence I tried to oxidize the gallium arsenide at low temperatures, namely anodic oxidation in oxygen plasma. That was a successful technique. I presented my work on gallium arsenide MOS transistors in the IEEE International Electron Devices Meeting, and published it in the IEEE Transactions of Electron Devices.

I applied this plasma organization technique to silicon, too, to oxidize silicon at lower temperature. I succeeded in getting a very small so-called bird-beak like structure. You know the bird-beak like structure which appeared in so-called LOCOS, local oxidation of silicon. I succeeded in shortening the bird-beak like structure by anodic oxidation of the silicon in oxygen plasma. This was very interesting achievement.

The other one, we elaborated, was the transmutation of silicon by thermal neutron. This is rather common technique to get a uniform doping of phosphorus. To get phosphorus doping by such transmutation, irradiated silicon substrates should be annealed at temperature higher than around 800 degrees centigrade. However, before such thermal annealing, irradiated silicon substrates include a lot of defects and consequently the resistivity of silicon substrate is extremely high. So that I wanted to use such a higher receptivity silicon as a substrate for high speed MOS transistors. Of course, the thermal oxidation technique cannot be used, because high temperature process such as at 800 or 900 degrees centigrade is needed to oxidize the silicon. So I oxidized the silicon surface by anodic oxidation in oxygen plasma. I succeeded in making MOS transistors on semi-insulating silicon substrate irradiated by thermal neutron.Here I must thank my colleagues, including research assistant, graduate students and visiting scholars in my group, for their collaboration. Without their collaboration, I could not have achieved those works.

IEEE and the relationship between Japanese and American seminconductor industries

Colburn:

Yes indeed. I see that you’ve also been active in a number of different IEEE conferences. Would you talk about some of those conferences?

Sugano:

My very first association with IEEE conference was the International Solid- States Circuits Conference. During my stay at Stanford University, I recognized the high technical activity of integrated circuits in the United States. But the activity of ICs in Japan was very premature. In 1950s Sony was selling portable radio sets to the United States, so my friends in the United States were very much interested in the technical activity of Japanese industries related to consumer electronics. I was invited to the Program Committee , the highest seat. That was my first affiliation with IEEE conference. I have been on the Committee for many, many years.

In late ‘70s DRAMs, produced by Fujitsu, were accepted by Hewlett Packard. That was the first export of Japanese industrial semiconductor products rather than consumer products to the United States. It came as a big shock to the US semiconductor industry and aroused public interest.

Colburn:

We are looking at the book Competitive Edge: Semiconductor Industry in the US and Japan edited by Daniel Okimoto, Takuo Sugano, Franklin B. Weinstein.

Sugano:

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You see, this is a publication from the joint research with a group of Stanford University and Japanese group. Professor Linvill at Stanford University was very much worried about misperception and the misunderstanding about the competition between Americans and Japanese. At that time someone was joking that it is called as “competition” between American and Japanese semiconductor industry in California, but in Hawaii probably they say “conflict” between them and in Tokyo they could say “war” [laughter]. We studied this issue from the view-point of political science.

IEEE committees and publications

Sugano:

I was asked to chair the Japanese group. That was a very interesting experience for me. During this work, we recognized that mutual understanding between Americans and Japanese is very, very important to keep a good, friendly relationship between them. So the IEEE and Japan Society of Applied Physics jointly organized VLSI Technology Symposium for this purpose. This year we had the twentieth Symposium in Hawaii. The Symposium place is alternated between Honolulu and Kyoto, and the Symposium will be held in Kyoto next year.

From the very early stage I have been deeply involved in the VLSI Symposium Committee. I am chairing now the Japanese Symposium Committee. Also I have been deeply involved in the activity of the IEEE Electron Devices Society. I was invited to be an Administrative Committee Member of the Electron Devices Society. I have been serving on the Committee for almost ten years. Furthermore I was invited to be an Associate Editor of the IEEE Transactions of Electron Devices. Yes, that’s a priority.

Many Japanese scientists wanted to publish their papers in the IEEE Transactions, however, there were two problems in those days. One is to whom they should submit their manuscripts. That is a problem. The second one is that unfortunately the English of most of the manuscripts should be refined. However, to refine the English sometimes the editor needed to have discussions with the authors. I was told that the associate editors of the IEEE Transactions of Electron Devices had real difficulty to understand what the Japanese authors wanted to say. So I was asked to be an Associate Editor of the IEEE Transactions on the Electron Devices in Japan to make a good bridging between Japanese authors and American Editor. I have been serving as an Associate Editor of IEEE Transactions of Electron Devices for more than ten years.

You see a list of my publications. When I left the University Tokyo eight years ago, because the age limit at the University of Tokyo was sixty, I prepared this publication list. Sixty is too young to retire, so I decided to join this university, Toyo University. Probably you will see from my publication list that most of my publications are in English in the IEEE Transactions on Electron Devices and other American journals. If you’re interested in, you may keep this copy.

Colburn:

Thank you very, very much.

Government appointments and honors

Sugano:

So most of the publications are in English. Recently many Japanese scientists are publishing their work in English, probably more than ninety-nine percent. After I left the University of Tokyo, I had a joint assignment with the Institute of Physical and Chemical Research. That is the research institute that is fully supported by the government, but not a government laboratory.

Colburn:

Is it the Ministry of Trade?

Sugano:

No, it isn’t. It’s the Agency of Science and Technology. I was serving as a Group Director for the Frontier Materials Research and also a Team Leader for the Nano-Electronics Materials Research. I was under this program for eight years. During these eight years, my team, which was an excellent research team, published so many papers. This is a bundle of the papers. As you can see, all of the publications, except a very few, are in English. This is an indication of the general, very common attitude of Japanese scientists.

Colburn:

Is there a problem for most of them, or is there a cause for dissatisfaction to have to publish in English?

Sugano:

No, I don’t think so. Twenty years ago when I was invited to be an Associated Editor of the IEEE Transactions, I would say they were rather frustrated, because they were not so much familiar with reparation of their manuscripts in English. But now publishing the work in English is very popular in this country. So I don’t think the scientists are frustrated or dissatisfied. No problem at all.

Colburn:

It says here you won the Purple Ribbon Prize from the Japanese Government.

Sugano:

This is a great honor. The Japanese Government awarded me this Purple Ribbon Prize for my contribution to solid -state electronics for many years. I started my Ph.D. work in 1954. Just six years or seven years later the invention of transistors came around. I am just one of the pioneers of semiconductor device research in this country, so Japanese government appreciated my contribution to initiate the research in this field, and also for my academic activity, both domestic and international. I was very pleased to receive the Prize. I very much appreciate the activity of the IEEE. The IEEE gave scientists and engineers all over the world a huge amount of technical information, and also a good opportunity to exchange knowledge and experience between them.

IEEE research and membership benefits

Sugano:

I know that the IEEE is not only the academic society but also the IEEE is offering the members services such as life insurance or lobbying, which are particularly beneficial to IEEE members in the United States. The Japanese scientists and engineers, or probably scientists in other countries, are not receiving such benefits from the IEEE. The Japanese are not so much concerned with this difference because we have a relatively good social security program, for instance, the health care plan that is enforced by law. However, scientists and engineers in other Asian countries, I have recognized as Region 10 Director, they have been requesting to receive the same benefits as in the US, or benefits similar to those of the US members. In any case I am enjoying the IEEE membership as a Life Fellow.

Colburn:

You’ve done a lot of very good work for the institute, and we appreciate it.

Sugano:

It’s my great pleasure. Major Japanese professional societies, such as the Japan Society of Applied Physics and the Institute of Electronics, Information and Communication Engineers, have established cooperative relationship with the IEEE. We are really delighted to collaborate with the IEEE.

Colburn:

It seems to be working well.

Sugano:

We’re really satisfied with the activity of the IEEE.

Colburn:

That is good to hear. Is there anything else that you want to tell me, either about the industry, yourself, your research, the IEEE, or anything else?

Sugano:

I was very much impressed with the positive efforts of the IEEE to include or to expand their scope to bioscience and technology. That is very impressive for me. Bioscience and -technology are emerging fields. Electronics is used as technique to study the biological phenomenon, and also from biological science and technology, we can get the idea to explore new fields of electronics, like neuro- computing.

The IEEE is expanding its scope. That’s very good. Previously there was the AIEE and the IRE, which were unified to form the IEEE, and now the IEEE is expanding its scope to bioscience. Excellent work!

Colburn:

I thank you again for your time.

Sugano:

It’s my pleasure. Thank you very much for coming.