Evolving environmental requirements for lithographic manufacturing.
As the semiconductor industry migrates to extreme ultraviolet (EUV) lithography, the requirements to reduce airborne molecular contamination, control temperature and humidity have become increasingly stringent.
EUV Lithography
To make silicon features measuring a few nanometers, a new generation of lithography machines uses extreme ultraviolet (EUV) light at a wavelength of 13.5 nm.
With more than 100,000 components, an EUV lithography system is one of the most complex machines ever built. It is powered by a powerful laser system and weighs 180 tons. This level of complexity requires extreme control of all environmental variables.
Lithography in semiconductor industry
Praecis Environment Cleanroom, ISO Class 6.
Enclosure dimensions: 3 x 3 s 2.5 m.
ATCU-9, HEPA filter ceiling, PVC strip curtains
Dust particles in the air can settle on semiconductor wafers and lithographic masks causing defects in the lithography process. The growing demand to reduce airborne contamination forces semiconductor manufacturers to lower the ISO classes of their cleanrooms. Particle filters and air exchanges achieve the desired particle count.
To ensure process stability, environmental factors including temperature and humidity must also be tightly controlled,
A typical semiconductor lithography cleanroom is ISO Class 5 - 7 with temperature variation controlled to 20 ° C ± 0.01 ° C and humidity to 45% ± 5%. Even with a temperature variation of 0.1 ºC significant errors may occur. However, by maintaining the temperature variation to ± 0.01 ºC, the precision of a typical lithography operation can improve by an order of magnitude.