July 4, 2011 – New Way Air Bearings, manufacturer of porous media air bearing products, announced it has been issued United States patent 7,908,885-B2 for its non-contact porous air bearing and glass flattening device.
According to the patent, this invention is directed to a system and
method for supporting thin work pieces, particularly glass, for more
precise inspection, coating, patterning, and other processes without
contacting the work piece.
The common technique with semiconductors was to put the substrate on a
vacuum chuck. This is also how the flat panel display industry
started out. But as FPD glass substrates grew larger – about Generation 6
– this technology became impractical. In the chuck method there were
two primary flatness error sources: the flatness of the chucks
supporting the glass, including any contamination between chuck and
glass, and the thickness of the glass itself.
By floating the glass through a precision zone the area that requires
precision is dramatically reduced from the area of the entire vacuum
chuck to the area directly under the process.
New Way Air Bearings was a pioneer in the development of non-contact
glass handling components for processing and inspection, with commercial
sales in Japan as early as 1999. Throughout the next decade, New Way
honed its technology leadership with the release of new products
enabling substrate stability to plus/minus one nanometer.
But the error of the thickness variation remained.
“Even high-quality FPD glass is subject to
thickness variations, reducing processing and inspection accuracy,”
noted New Way chairman and CTO Drew Devitt, who is also credited as the
inventor of this New Way patent. “But this new technology stands
conventional thinking on its head. It uses a combination of air pressure
and vacuum from above to control and flatten the glass substrate,
enabling a much higher degree of processing accuracy, all without
contact.”
FPD glass has an inherent thickness variation of five to seven microns. When it
is sucked down to a flat vacuum chuck, all five to seven microns of this
variation will appear as surface-flatness error. By positioning the
vacuum preloaded air bearing array on the same side as the precision
process being applied to the glass, the natural thickness errors in the
glass or substrate may be removed or minimized.
New Way uses its porous media air bearing technology to evenly
distribute air pressure through millions of sub-micron sized holes
across the air bar surface with the capacity to carry thousands of
kilograms of load. Simultaneously, a set of vacuum holes and grooves
provide tens of kilograms of atmospheric force, which evenly pushes and
flattens the glass up against the air film, and holds it in a very safe
place. The result is a non-contact precision zone which presents the
flattest possible glass surface to the process.
Glass thickness variation errors have started to become a limiting
factor for the higher-resolution types of lithography required for
higher definition displays. This new approach reduces the requirement
for depth-of-field capability in the tool, and enables higher-resolution
lithography, while also greatly minimizing the structural loop between
the optics and the glass.
This technique also allows for:
• Viscous shear cleaning* of the surface immediately before the process,
• Isolation of process gases* or containment of particulates from ablation processes, and
• Glass conditioning* with relation to temperature, humidity, and oxygen levels in the bonding layer pre-coating.
*Protected by separate patents.
Today’s Generation 10 glass is 2850 by 3050 mm, or 8.7 square meters.
And a structural loop which must include components above and below the
glass is problematic.
“The second significant advantage of our new patent is the reduction in
size of the overall structural loop,” Devitt continued. “Many
contemporary FPD processing lines still feature a multi-ton granite
base, a giant gantry with two large granite columns, a huge stage
mechanism, and the processing equipment or inspection cameras
themselves. This structural loop can be 10 meters or longer.”
“In this new embodiment, with the glass moving just 10 microns below the
processing or inspection equipment, the structural loop can be just a
small fraction of a meter. This avoids errors from thermal and vibration
sources in the machine.”
“Of course this new technology will be particularly useful and effective
in the manufacture of flat panel displays,” said Nick Hackett, New Way
president and CEO. “Already our Air Bars have helped to increase FPD
manufacturing yields which, in turn, have helped to bring down the cost
of flat panel TVs and computer monitors industry-wide. This new patented
technology will enable the even more highly-precise processing and
inspection that will be required in the future.”
“We’re starting to see similar requirements in the solar manufacturing
industry, particularly for thin-film PV applications with a need for
very precise, non-contact substrate handling,” Hackett added. “We
anticipate that this technology offers a viable solution there as well.”
Related links
New Way Air Bearings
How to make a flat panel display
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