Date Visited: October 2, 1991
Report Author: T. Credelle
Mr. Hirano is a senior staff member in charge of TFT LCD development at IBM Japan. We spoke with him for two hours and had a tour of the IBM development line. He presented a historical perspective of the IBM/Toshiba relationship and how it was working to develop AMLCDs for office automation use by the two companies.
In late 1985, IBM decided to invest in AMLCDs for future products; they chose Toshiba for a partner and entered into a two-year joint development agreement in 1986. The first year, IBM engineers worked at Toshiba to learn the technology while building a development line for large substrates at IBM Yamato Labs (PC division R&D and hard drive R&D). The second year, Toshiba engineers came to IBM to work on the new line and to develop a 14.25-inch color AMLCD based on the jointly- developed a-Si technology. The clean room is a laminar down- flow clean room (Class 100, 1,000 and 10,000); the total area is approximately 1000 m2. It used the best equipment at the time, although Hirano said that some of the equipment is now a little out-of-date. Lines were established for TFT, color filters, and panel assembly. He called panel assembly an "agriculture" as opposed to "industry." He said that even if "the best seeds" were sown, there was no guarantee of a "good crop." In March of 1988 the 14-inch panel was completed (720 x 550 color quads RGBW, 0.2 mm subpixel). The partners made a total of 20 panels.
A decision was then made to continue the joint development and to also invest in a factory. In the interim, a pilot line was established at Himeji by Toshiba. The factory is a 50/50 deal, with each company getting 50% of the output. Display module design is separate, since it is dependent on the portable computer design and other applications. The first products will be 512-color AMLCDs, but they are evaluating 4-bit designs. IBM/Toshiba will demonstrate a 13.8-inch, 1152 x 900 pixel color LCD at JES and Comdex. Mr. Hirano claimed that he was told that the pilot line was achieving approximately 50% yield. The DTI factory is now operating; he did not say what the yield or production capacity would be. He did say it would be the largest such facility in Japan (60 m x 90 m x 31 m high, 4 stories).
Gray scale--IBM is working on 6- and 8-bit versions.
Panel size--IBM thinks 16 inches is feasible and will replace 20-inch monitors.
Penetration into CRT market--estimates 50% by 2000.
Aperture ratio--will be improved from current 30-40% to >60%.
Mobility--IBM and Toshiba are working on higher mobility a-Si.
Poly-Si--IBM doesn't believe it will be successful for large sizes; interconnection to external drivers is more economical than building poly-Si.
Integrated drivers--it should be possible to do some kind of auxiliary driver circuit in a-Si.
Backlight--looking at improved designs and are working with suppliers of lamps to improve brightness. He mentioned an experiment where brightness was weighted higher in the center; it looked brighter than a comparable unit with uniform brightness and did not look nonuniform.
Costs--costs will be gradually reduced through small improvements (the "Japanese way"); and through process equipment improvements.
Ferroelectric LCDs--might be competition for AMLCD but gray scale and manufacturability are a problem (plus/minus 0.05 micron).
We had a brief glimpse of the development line. The line consists of single pieces of equipment in most cases. The photo lab uses a Nikon stepper with a 100 mm field; IBM jointly developed its own spinner with an equipment manufacturer for resist coating. The PCVD has six chambers (four active). The sputtering system has three active chambers. Two laser repair systems are in use, one for cutting and one for adding material. Color filters are made by IBM. Backlights, TAB packaging, and so forth are also done at IBM Yamato. A lot of attention was paid to safety, with an excellent monitoring system. They have had no accidents.
We did not see any working panels because they were at Comdex and JES.