Light of the future: How does EUV lithography work?

New light for digitalization: Without EUV lithography, modern microchips would be inconceivable – and without optics from ZEISS, there would be no EUV lithography.

Microchips are manufactured using the lithography process. This means that the structures desired on the chip are first transferred from a mask onto a light-sensitive layer – as in the projection of a slide. In the next step, the exposed structures are chemically fixed and then the unexposed areas are washed out. This process is repeated up to a hundred times with different masks, gradually creating an increasingly complex three-dimensional structure of tiny electrical components such as transistors and conductor tracks – a functioning microchip.

To increase the computing power of a chip, engineers are packing more and more transistors onto the wafers. The microchips in the Apollo 11 moon capsule had only about 1,000 transistors; today, the central chip of a humble smartphone has more than 57 billion transistors. Gordon Moore, co-founder of Intel, predicted this continuous increase in performance as early as 1965. The "Moore's Law" he postulated states that the performance of each current chip generation doubles every two years – this increase being driven by the miniaturization of chip structures. A prediction that has become the benchmark for the semiconductor industry.

The size of the chips has not grown over time – but the number of transistors has. This has been made possible by the increasing efficiency of the lithography process, which exposes ever finer structures onto the wafers. The quality of these structures depends on many factors, such as the mask (or to stay in the picture: the slide), the mechanics and optics used – but above all the light used. The shorter the wavelength, the smaller the exposed structures.

The use of EUV light requires an immense technical effort – from the light source to the entire optics used to the mechatronics. The EUV light is generated within a globally unique light source. A tiny drop of tin is hit by a laser beam in a vacuum, causing it to swell. After this so-called pre-pulse, the subsequent main pulse heats the tin to 200,000°C (approx. 360,000°F), transforming it into a hot plasma that is almost forty times hotter than the surface of the sun. The ignited tin plasma then emits the desired EUV radiation – this process is repeated 50,000 times a second. The laser used for this is the most powerful pulsed industrial laser in the world – ten times more powerful than all currently available systems used for steel cutting.