Lenses & mirrors

The complex optical systems in our machines reduce the image printed on a wafer to the nanometer level


Each one must be correctly positioned to within a nanometer to ensure image quality. ASML’s innovation in lens design allows chipmakers to reduce the size of features on a microchip. Since the late 1980s, all our lithography systems have featured optics from our strategic partner ZEISS.

Numerical aperture

Lens development to improve resolution means increasing the numerical aperture (NA), a measure of how much light the lens system can collect and focus. One way to do that is by integrating higher-precision lenses and mirrors into extended optical systems. The highest NA optical systems today are over 1.2 meters high and weigh more than a metric ton. Used in DUV lithography, they have an NA of 1.35.

Immersion lithography

In 2003, ASML made an important step forward in numerical aperture. We developed immersion lithography, which allows chipmakers to print even smaller features by projecting light through a layer of water between the lens and the wafer. The water increases the numerical aperture of the systems' optics.


The sheer complexity of today’s lithography optics makes delivering high-quality optical systems a massive engineering challenge. But it also brings a unique opportunity to control every exposure with immense precision. Thousands of actuators allow the exact position and orientation of individual lens and mirror elements to be minutely adjusted to ensure the perfect image on the wafer every time.