Technology Used in FPD Lithography Equipment
The LCD panels used in large-screen LCD televisions are created with technology that exposes minute pixel circuits on large-scale glass substrates, Canon's Flat Panel Display(FPD) lithography equipment makes possible the single-exposure production of widescreen TVs up to 57 inches in size. Canon is the leading manufacturer of this equipment.
Large Concave Mirror
Manufacturing High-Precision Mirrors with the World's Largest Diameter*1
Canon's FPD lithography equipment employs a mirror-scanning method that makes use of a mirror-based projection optical system. The system offers such merits as a simple configuration facilitating increases in substrate size, a wide exposure field, no chromatic aberration, which can occur with lenses, and no image performance degradation.
Pattern exposure processes for LCD panels are carried out with a precision of several μm.*2 The projection mirror used in the system also requires high precision. Large concave mirrors in particular, with a large diameter to realize an exposure width capable of exposing large panels seamlessly in a single pass, enable significant increases in productivity.
By making use of extremely high-precision processing technologies, Canon has succeeded in developing the world's largest diameter concave mirror, a 1,514 mm 8th-generation*3 ultra-high precision concave mirror with a surface processing accuracy of 0.015 μm. The mirror makes possible a resolving power of 3 μm across the entire exposure field.
- *1 World's largest diameter
Among semiconductorexposure equipment and FPD Lithography Equipment as of October 2010
- *2 Micrometer (μm) : 1 μm = one millionth of a meter.
- *3 8th-generation
Ongoing changes in the size of glass substrates are represented as "generations." The larger the substrate, the better suited it is for producing large panels. Productivity also increases as a single substrate yields multiple panels, so the number of generations has risen rapidly. At present, the 8th-generation is being mass produced, but development is already being conducted with an eye to the next generation.
Exposing Large Scale Substrates at a Speed of 750 mm per Second
Canon's latest FPD lithography equipment measures 9 m (W) x 11.6 m (D) x 5.8 m (H). The main body of the unit weighs 100 tons, with the moving mask stage weighing 1 ton and the substrate stage weighing 4 tons, making the aligner Canon's largest product.
As the size of LCD substrates increases, the weight of the moveable parts has also increased. Because increased weight tends to impair the performance of the stages, Canon selects materials with a low specific gravity and strong rigidity in order to develop ultra-large stages that reduce overall weight while maintaining component strength.
The substrate stage and mask stage are each maintained by air bearings and are driven by non-contact linear motors. The comparatively light mask stage follows the comparatively heavy substrate stage for completely synchronized "master slave control." The drive performance of the substrate stage realizes an extremely high level of precision, achieving a speed of 750 mm per second in just 0.5 seconds upon moving, and comes to a complete stop in a mere 0.2 seconds upon arriving at the stop position. Both stages utilize positional measuring technology using a laser interferometer to control position and speed.
The high-performance and high-speed operation of the ultra-large stage allows it to attain a high throughput of 323 panels per hour for 55-inch wide panels.