The microchips in the Apollo 11 lunar capsule had only about 1,000 transistors; today, thanks to EUV, the central chip of a smartphone has more than 57 billion transistors.
A ray of hope for the future
Over time, increasingly shorter wavelength light sources have therefore been used for microchip lithography. While a wavelength of 193 to 365 nanometers is still used for many commercially available microchips, 13.5 nanometers are already used for high-performance chips (for instance, for graphics cards or high-end smartphones). At 13.5 nanometers, we enter the range of extreme ultraviolet radiation that is invisible to the human eye – hence the name EUV lithography. This technology increases transistor density enormously compared to current microchips. This is because the conductor paths created in this way are only a few nanometers wide. By comparison, a human hair is about 70,000 nanometers wide.
EUV technology in the semiconductor industry
High-precision optics with two functional modules
Without air and glass
Because EUV radiation is absorbed by air and glass, ZEISS has designed an optical system specifically for EUV lithography that operates in a vacuum and uses only mirrors. The entire system is about one and a half meters high, weighs about 3.5 tons and consists of more than 35,000 individual parts. The high-precision optics enable near-perfect imaging and are divided into two functional modules: the illumination system and the projection optics. The illumination system has the task of illuminating the mask as uniformly as possible from adjustable directions. For this purpose, a large mirror (the so-called collector) collects the EUV light emitted by the tin plasma and shapes it via the next mirrors in a beam path to precisely fit the mask. With the projection optics, the extremely small mask structures are precisely projected onto the photoresist-coated wafer via further mirrors. In the end, billions of individual transistors the size of a fingertip are created.
The optical and mechatronic requirements for this system are enormous. The mirrors are masterpieces of optics: If they were scaled to the size of Germany, the highest unevenness would be just a tenth of a millimeter high. With these requirements, these are the most precise mirrors in the world – and it takes months to produce an EUV mirror. Another extreme requirement is that the mirrors reflect EUV light with as little loss as possible. This is achieved by a layer system consisting of more than 100 atomically precise individual layers, each only a few nanometers thick.
The heart of EUV technology beats in Oberkochen
Does all this sound complicated? It is. Mark Phillips, Intel Fellow and Director of Lithography, sums it up: "The EUV scanner is the most technically advanced tool of any kind that's ever been made." And indeed, an ASML EUV lithography system is as big as a school bus, weighs around 200 tons, and consists of hundreds of thousands of individual parts. Research for what is now EUV lithography began more than 25 years ago. During this time, more than 2,000 ZEISS patents have been applied for that are related to EUV. The market launch was a huge success: EUV microchips are now installed in all leading smartphones. What's more: powerful and energy-efficient EUV chips enable life-saving medical technology, support autonomous driving and form the backbone of high-performance computers, smart cities and artificial intelligence.
The way to new shores leads over narrow paths
Together with our strategic partner ASML for the system architecture, ZEISS is already working on the next EUV generation High-NA – which will enable even more powerful microchips. From today's perspective, their areas of application are visionary. Whatever is to come: ZEISS is working on pushing the boundaries of what is technically feasible.