Date Visited: October 8, 1991
Report Author: A. Firester
MRS Asia, Inc.:
Our hosts were extremely hospitable and open in our technical discussions. Our agenda was as follows:
Several DaiNippon Screen (DNS) corporate facts are summarized below:
Annual sales: $1,067M (1991)
Employees: ~ 3,000
Two major business sectors:
In the equipment video, the following equipment technologies were highlighted:
ALL PRODUCTS ARE MANUFACTURED IN CLEAN ROOMS!
Class 100 R&D and process training facility
DNS actively promotes equipment standards for complete in-line processing systems.
Specification is determined jointly by DNS and manufacturer. DNS recommends roll type for high throughput and spin type for total particle reduction.
Roller Type - leaves backside particles in 5-7 mm edge band where substrate contacts conveyor system. With air knife dry and roller brushing, 100-300 particles greater than/equal 1 micron in central 280 mm x 280 mm area. With air knife dry and disk brushing, it is similar to spin system and leaves 30 particles > 1 microns 300 mm x 380 mm. Particle elimination ratio is > 95%.
New improvements in cleaning might be dry cleaning processes, but these are not necessary.
Spin coating is better than roll coating. Roll coater (conveyor) is 4x faster than spinner.
Maximum spin size is 350 mm x 450 mm, but DNS has data only up to 320 x 400. DNS believes spin machines up to 700 mm x 700 mm are possible.
Spin coater specs:
DNS currently has no edge-cleaning process for rectangular substrates. They are working on this problem. Back rinse is not a problem.
At the time of our visit, DNS was developing a new type of high-uniformity roller coater, which was to be exhibited at Semicon Japan. For 1.2-1.5 microns thick coating, 5% uniformity is achieved with no defects. Contact is a most serious issue, especially for color filter production. DNS has great expectations that this technology will dramatically reduce the cost of color filters! This roller coater can be used for post-resist coating as well. In this case, uniformity is dramatically improved.
A DNS comment on slot coating is that it is low throughput.
Since substrates can only be handled by the edges, sag becomes a problem as substrates get bigger and thinner. Glass edge finish is very important for particle control. DNS believes that cassettes should be eliminated as much as possible since considerable particle generation occurs during cassette transport and handling. DNS estimates a maximum of 25 substrates/cassette based on the maximum weight that an operator can easily handle.
See above section on Coaters for information on new type of roll coating
Pigment dispersion color filter production is very promising. Production is just starting in Japan. Problem is coating.
Today, cost of color filters produced by dyeing is twice that of pigment type assuming equal yields. Future color filter costs will be reduced by 5x.
1 substrate/minute - active matrix
4-6 substrates/minute - STN (proximity printing)
It is possible to run some equipment with only load/unload in clean room. (No equipment was mentioned that is designed for this operation.)
24-hour operation (3 shifts) requires 1 day/month preventive maintenance.
Some TFT manufacturers are considering mix-and-match photolith.
DNS does not manufacture LC assembly equipment.
DNS estimates the cost to build a TFT line to be 10-20 billion yen for fabrication equipment only.
In order to enter the manufacturing area, we had to be fully gowned (booties, coveralls, and hood). Entrance was via an air shower. However, the manufacturing area was designed to be Class 10,000, although DNS stated it achieves Class 3,000.
DNS equipment is fully built and assembled by subcontractors. It is then shipped to DNS for check-out and final adjustment.
We observed two in-line photoresist coaters in final check-out. These machines were designed for cassette-to-cassette operation with substrates about 300 mm x 400 mm in size. The machines cost roughly $1 million each. Their configuration was as follows:
We were also shown their R&D laboratory. This was designed to be Class 100, but achieves Class 10 to 50 under the hoods.