Finally, the San Diego based company Cymer won the race with a system that uses a CO2 laser to create EUV radiation from a 30 µm droplet of tin. While they
promoted a rather unstable 30 W source in 2007, it was 2014 when they
first showed how to get to 250 W, a number that was regarded as the breakthrough for high-volume production.
Driving up the efficiency of the EUV conversion process was a wonderful piece of applied research that made EUV lithography viable after all. To enable faster progress (and to secure its sole supplier), ASML purchased Cymer in 2012.
The eventual solution for making just enough EUV radiation for commercial viability is a machine that impresses even seasoned laser experts. It is based on the most powerful laser that was ever built in serial production: a 40 kW CO2 laser. The whole system needs a 1 MW power supply. As only the tiny fraction of 200 W of power is used for processing the wafer, cooling is a major issue.
The sole supplier of this technology is TRUMPF in Ditzingen, Germany. Trumpf owner and CTO Peter Leibinger is well aware of his company’s role: “If we fail, Moore's law will discontinue. Of course, the world doesn't depend on TRUMPF, but without TRUMPF, the chip industry couldn't do it,” he said in an
interview in 2017.
Typical CO2 lasers from TRUMPF deliver some kilowatts of continuous-wave (CW) radiation. This is just right for cutting steel. For EUV, TRUMPF developed a laser that produces 40 kW of pulsed radiation at a repetition rate of 50 kHz. The laser, with its two seeders and four amplification stages, is so large that it has to be placed on a separate floor below the EUV machine.
To keep pace with the market demand,
TRUMPF has invested heavily in an entirely new factory with 10 production bays just for these lasers. With 10 weeks to put them together, the company now has a capacity of 50 systems per year. At the time of writing, 44 systems were in the field with a total of 30 shipments expected in 2019.
Note—The resolution of the NXE:3400 systems is about 13 nm; this refers to formula (2) and the actual gate pitch. This is very different from the "nodes" often discussed the chip manufacturers. Originally, the nodes referred to the gate length of a transistor. Obviously, this can differ as a function of the process and, hence, of the manufacturer. Today, however, the node only refers to a certain process developed by a chip maker and does not correspond directly to the resolution of the optics. For example, chip makers tout 7 nm or 3 nm nodes referring to their proprietary processes using similar EUV machines.
Cooperation is the key
While more than 1000 suppliers are involved overall, the core technology is made by Trumpf, Zeiss, and ASML. They developed rather unconventional forms of cooperation in the EUV project. Peter Leibinger from Trumpf called it a “virtually merged company” with an open-book policy and an extensive exchange of people and knowhow.
Zeiss SMT has a long history with ASML, as the company produced its first lithography optics for Philips in 1983; that business was spun off in 1984 and named ASML.
Together, Zeiss and ASML conquered the market for lithography systems well before EUV. In 2010, they already had about 75% market share for lithography systems. So far, they are the sole providers of industry-grade EUV systems. To foster the relation, ASML bought a 24.9% stake in Zeiss SMT for roughly one billion Euros in November 2016. Additionally,
ASML promised to support Zeiss SMT’s R&D efforts for six years with 220 million Euros plus some investments support of 540 million Euros.
That money was much needed, as Zeiss was investing heavily in EUV. The company erected halls for manufacturing and metrology near Oberkochen, Germany; currently, it is completing preparation for the next generation of EUV optics with higher NA—another 700 million Euro investment. This includes high-vacuum chambers the size of a truck for metrology of the optical systems. The mirror surfaces that are tested in these chambers have a maximum tolerance of 0.5 nm, so they use the most precise alignment and metrology technology ever built in industry.