SIKA Flow & Temperature Sensors are Utilized by TRUMPF Laser Systems in the Semiconductor Industry

SIKA Vortex Flow Sensors (VVX15) and Pt1000 Temperature Sensors are utilized by TRUMPF Laser Systems to improve reliability, performance, and efficiency of laser technology. The computing speed of semiconductor chips is determined by technical progress. It depends on how small the conductor tracks can be made on chips. The smaller the tracks, the more circuits can fit on one chip. So far, the computer speed has doubled every two years (Moore’s Law).

Together with the Advanced Semiconductor Materials Lithography (ASML) Company in the Netherlands, our customer TRUMPF from Ditzingen Germany has developed a unique system. This system makes it possible, using Zeiss lithography optics, to significantly reduce the size of the conductor tracks on wafers and to penetrate into the nanometer (nm) range. For example: A human hair is approx. 60,000 nm (0.06 mm) thick, a conductor track on such a chip is <10 nm, an unimaginable 0.00001 mm! These systems are very expensive for the owner/operator; the TRUMPF component alone costs around 100 million euros / $114 million USD. More than ten TRUMPF systems are now sold through ASML worldwide every year. I

n the new process, the wafers are coated with a lithographic lacquer which are exposed to Extremely short-wave UV (EUV) using very precise Zeiss optics. The EUV radiation comes from “TRUMPF Laser Amplifier“ (see right).

Zeiss optics are internationally unique and are so precise that conductor tracks can be imaged in nanometer dimensions. During the subsequent etching process on the wafer, the exposed layer remains as a conductor track a few nanometers wide.

f the light were significantly longer than 13.5 nm, there would be no conductor tracks in the nanometer range.

So one absolutely needs the monochromatic EUV light with the exact wavelength for this process.

TRUMPF Ditzingen has been developing the EUV light source and the optical beam guidance system since 2010, and was awarded the German Innovation Prize for it in November 2020. There is no other manufacturer in the world who can produce this EUV light reliably and with the required power output except for TRUMPF.

How is this EUV light actually made? In the TRUMPF Laser EUV light source (Fig. 1), a generator lets drops of tin fall into a vacuum chamber (3). A pulsed high-power laser then hits (1) the tin drops rushing past (2) 50,000 times per second. The tin atoms are ionized, creating a very hot plasma. A collector mirror captures the EUV radiation emitted in all directions by the plasma, bundles it, and transfers it to the lithography system (4) for exposure of the wafer (5).

SIKA Vortex Flow Sensors (VVX15) and Pt1000 Temperature Sensors are built into these TRUMPF EUV systems.
Due to its special outer contour, the Pt1000 is mounted in a TRUMPF plug-in adapter T-piece. 

There are also SIKA Pt1000 screw-in sensors in stainless steel.

The SIKA VVX15 is integrated into the TRUMPF hydraulic module and adapted to the hydraulic conditions.

Our long-term relationship contacts with the client TRUMPF brought success!
Our sales representative Martin Knopf has been in contact with the ASML-TRUMPF working group in Ditzingen Germany since 2015. At that time, the first TRUMPF EUV systems were built in a provisional “temporary” building. As a result, there were repeated contacts with this project team and a meeting was scheduled in September 2017, which Mr. Knopf and Mr. Dietrich attended. A flow sensor was originally sourced for a water-cooling circuit distributor for the optical focusing unit. This circuit was previously monitored by a piston guard from a competitor in the market and was not satisfactory. The reason: The piston guard with a spring return often jammed because the cooling water also contained dissolved copper, which stuck to the moving parts of the piston guard. 

Additionally, they were looking for a flow sensor without moving parts to monitor the cooling circuit of other optical elements. So, SIKA was selected for the testing of a SIKA VVX15 Vortex Flow Meter. 

After these tests, TRUMPF quickly recognized that the SIKA VVX15 Vortex Flow Meter was a very precise flow sensor that, when properly installed, delivers extremely reliable measurement results. SIKA temperature sensors (Pt1000) have been utilized by TRUMPF for over 5 years and are successfully used in laser optics as class B screw-in sensors for monitoring temperature control.

The success story continues. In 2019 we were able to offer TRUMPF another benefit. In what context?

Exact SIKA sensors enable the monitoring of the TRUMPF laser optics!
One problem with the latest generation of EUV light is the gradual contamination of the laser optics (surfaces of copper mirrors), which are directly connected to the above-described EUV light source, in a high vacuum. When the tin droplets are bombarded in the plasma chamber, tin, which does not turn into plasma, regularly comes in contact with the optics. As a result of normal molecular migration, the optics gradually acquire a very fine layer of tin. This is not desired, and in the long run, leads to a reduction in the output of the EUV light source yield. It is said that the optics “get dirty.”

As a result of contamination of the optics, the mirror surface becomes slightly hotter over time which reduces the system performance. The challenge is to determine the optics’ temperature, which increases over time, and compare it to a fresh system without “dirty optics”. This is done by suitable measurement of the continuously increasing energy input in the cooling medium. The cooling medium cools the mirrors on the back. This energy input is calculated by a very precise flow measurement and temperature difference measurement. 

Two SIKA temperature sensors and a VVX15 vortex flow sensor are required for this application. The two SIKA temperature sensors, Pt1000 class A, are installed in front of and behind the respective mirror cooling circuit and the vortex flow sensor type VVX15 in the measuring section. The latter determines the heated cooling water volume per unit time. With the SIKA sensors, TRUMPF is able to precisely monitor the efficiency of the EUV systems. This enables TRUMPF to make reliable statements about the required maintenance of the laser optics and to pass them on to ASML.

This, in turn, is a great advantage for TRUMPF and ASML, in terms of superior system performance. True to the motto:

Clever SIKA solutions for our customers‘ market success!
 — Martin Knopf, Ralf Dietrich 

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