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Extreme Ultra Violet (EUV) Lithography

What’s behind EUV Lithography?

Extreme ultraviolet (EUV) lithography is nearly ready for high-volume microchip manufacturing in production fabs. This method will make future technological applications possible.

But what exactly is EUV and how does it work?

What is EUV lithography?

Remember your first cell phone? Pretty much all you could do with it was to make calls, write SMS messages, and play simple games. Things have certainly changed, and nowadays most of us carry around a smartphone – effectively a compact computer – in our pocket. What most people don’t realize is that the development of lithography was one of the key factors behind this rapid transformation.

Lithography technology is used to create billions of tiny structures on silicon disks known as wafers, building up the patterns of features that make up a microchip. The more transistors you can pack onto a chip, the more powerful it will be. That’s why the manufacturers of lithography systems are constantly striving to miniaturize structures on the wafer – and that’s exactly what EUV light achieves with a wavelength of just 13.5 nanometers. Ultimately that allows our customers to fabricate faster, more powerful and more energy-efficient chips, all thanks to EUV lithography.

How does EUV lithography work?

ZEISS EUV lithography optics are at the heart of the wafer exposure machines, or wafer scanners, produced by our customer and partner ASML. In terms of how they work, scanners are similar in operation to oversized slide projectors. Lithography optics use a complex system of mirrors to focus EUV light onto the wafer through a mask. The mask is a kind of design plan containing all the features the finished microchip will need. The EUV light projects the mask pattern onto a wafer coated with photosensitive chemicals. The patterns of features are then revealed using an etching process. This process is repeated several times to build up the components on the microchip layer by layer.

What makes EUV light special is how it is absorbed by all known materials, even air. That’s why the lenses in lithography optics are equipped with vacuum chambers, as are several other parts of the wafer scanner.

Why is EUV lithography necessary?

If EUV poses so many challenges, wouldn’t it be better to simply stick with the technologies we have now? Well, imagine for a moment that you wanted to fit a large amount of text on a small piece of paper. To do that, you would need a pen with a very fine nib. Applying that concept to lithography, you could say that the earliest stages of optics development created a tool that acts like a thick marker pen. Each generation has made that nib finer, and EUV lithography optics are the finest pen we can currently make, capable of drawing structures less than 20 nanometers across.

So what’s next?

The first technological applications containing microchips produced using EUV exposure will come into the market at the end of this decade. These chips will be more powerful, and that means big benefits for everything from the Internet of Things and artificial intelligence to self-driving vehicles, big data, and a range of other developments that are currently beyond our scope of imagination. Ultimately, this development will improve people’s lives all over the world.

MILESTONES IN THE DEVELOPEMENT OF EUV AT ZEISS

2003: Micro-exposure tool (MET) shipped to the University of California (Berkeley) for functional and performance testing

2006: First alpha demo tool shipped to the IMEC research institute as the precursor to EUV optics

2009: Presentation of preliminary results of alpha demo tool testing

2012: First shipment of EUV volume production optics to ASML

EUV Facts

  • The Starlith® system from ZEISS is the first EUV light source lithography optics system in the world to enter volume production.
  • It can create structures on a wafer measuring just twenty nanometers across – some 4,000 times thinner than a human hair. Scientists are working on ways to shrink feature sizes even further.
  • The surfaces of EUV mirrors are exceptionally smooth after polishing, with a final surface roughness of less than a tenth of a nanometer – equivalent to the diameter of a hydrogen atom. That makes them the world’s most high-precision mirrors.
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