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Since its breakthrough, the liquid crystal technology has continued to gain momentum and the LCD is
today the dominating display type used in desktop monitors, television sets, mobile phones as well as other
mobile devices.
To improve production efficiency and enable larger screen sizes, the LCD industry has step by step
increased the size of the mother glass used in the LCD manufacturing process. Initially the mother glass
was only around 0.1 m2 large, but with each generation the size has increased and with generation 10 the
area reaches close to 10 m2.
The increase in mother glass size has in turn led to an increase in the size of the photomasks used - currently the largest masks are around 1.6 × 1.8 meters. A key mask performance criterion is the absence of
"mura" - small systematic errors captured only by the very sensitive human eye. To eliminate such
systematic errors, special techniques have been developed by Micronic Mydata. Some mura suppressing
techniques are described in this paper.
Today, the race towards larger glass sizes has come to a halt and a new race - towards higher resolution
and better image quality - is ongoing. The display mask is therefore going through a change that resembles
what the semiconductor mask went through some time ago: OPC features are introduced, CD requirements
are increasing sharply and multi tone masks (MTMs) are widely used. Supporting this development,
Micronic Mydata has introduced a number of compensation methods in the writer, such as Z-correction,
CD map and distortion control. In addition, Micronic Mydata MMS15000, the world's most precise large
area metrology tool, has played an important role in improving mask placement quality and is briefly
described in this paper.
Furthermore, proposed specifications and system architecture concept for a new generation mask writers - able to fulfill future image quality requirements - is presented in this paper. This new system would use an
AOD/AOM writing engine and be capable of resolving 0.6 micron features.
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