the most advanced in terms of research on control methods. is was likely one of the reasons Japan became a leader in the semiconductor industry, according to Dr. Fujii.“Particulate matter was controlled in the same way in each country. But particulates aren’t the only contami-nants in cleanrooms. Chemical sub-stances emerged as a problem around 1990. In Japan, research papers on the importance of chemical substance con-trol began to appear in the 1980s. e idea existed in Japan that controlling contamination also required account-ing for the eects of not just the chemi-cal substances in the air, but, in certain cases, those of oxygen and ionic species. I think this perspective was one of the factors that helped make Japan the world’s leader in the semiconductor industry.”A 10% increase in yield makes all the dierence in making semiconduc-tors price competitive. e prevailing view is that Japan won the price wars through contamination control.What’s the future of particle counters?More than 40 years have passed since Rion began selling the KC-01, the rst airborne particle counter manufac-tured in Japan. How will particle count-ers evolve in the future? “The measurement of atmospheric particles is likely to transition to the number counting method,” says Dr. Fujii. e number counting method is a method for measuring the number of particles by particle size.“Right now, atmospheric monitor-ing is based on the mass method to measure the mass of the particles col-lected. But in the future, I think we’ll aspiration of the air being measured. He also stressed the need for a liquid-borne particle counter. “I think they accelerat-ed eorts to develop a liquid-borne par-ticle counter because particles suspended in liquids directly aect the contamination of the subject.”Particle counters: Essential clean-room instrumentsAs mentioned at the beginning of this article, particle counters are an essential technology for cleanrooms. “A particle counter is the optimal instrument for measuring environmental concentra-tions in a ltered room,” Dr. Fujii con-tinues. “It’s also much easier to inspect for pinholes, which are defects in a lter, using a particle counter. It would be next to impossible to evaluate and man-age a cleanroom without particle counters.”In the 1980s, some years aer the release of the KC-01, the Japanese semi-conductor industry began to dominate the world. And cleanrooms are vital for semiconductor production. What was the role of particle counters back then? We asked Dr. Fujii.“Aer Rion released its simultane-ous multi-particle size measuring parti-cle counter, many companies began selling their own simultaneous multi-particle size measuring particle counters at lower prices. e price com-petition for particle counters became fierce, and the technology quickly became one that could be used any-where. It became quite commonplace to use particle counters for cleanroom contamination control.”Particle counters had, so to speak, become commonplace.Contamination control focused on lters and control methods. Japan was see demand for measuring particle size distributions as well. So we’ll likely transition to the number counting method, just as we do now for measur-ing lter performance. Particle counters aren’t very good at measuring atmo-spheric particles due to the high con-centration of particles, but I think these measurements will become increasingly important.”As for remote measurement, Dr. Fujii wonders if it would be possible to apply lidar, which is currently used for atmospheric observations, to measure-ments of the general environment. Lidar entails generating laser beams to capture the light reected from partic-ulate matter.“Several obstacles lie in the path of applying lidar for measurements of the general environment. We might have a dicult time guring out how to over-come them, but given the importance of performing in situ measurements, we may want to consider this a candidate for such measurements.”Market share of semiconductors(64 K DRAM) in the early 1980sIn the early 1980s, Japanese companies like Hitachi and Fujitsu held approx-imately 70% of the 64 K DRAM (Dy-namic Random Access Memory) market share. (Source: December 1981 issue of Fortune magazine)Circuit diagram for KC-01 and photo of the main unitOn the left is a circuit diagram of the KC-01 that enabled simultane-ous multiple particle size measure-ments. On the right is a photo-graph of the KC-01 main unit. The circuit diagram was copied using the so-called blueprint method, which is all but forgotten today.Hitachi40%Motorola20%Fujitsu20%NEC6%TI7%OthersOthersJapan 69.5%USA 30.5%5
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