EUV lithography-2

Throughput is a big issue of EUV.
Why?

1.Reflective optics has finite reflectivity about 70% at 16.5nm(EUV wavelength).
2.There are more than 11 reflection surfaces from light source to waver.

So very small light power pump into waver.
One solution is to enhance the reflection of multi-layer coating, and another is to increase the power of light source.

There are two methods to produce EUV 16.5nm light:
1.DPP (Discharge-produced plasma)
2.LPP (Laser-produced plasma)

LPP proves its ability to produce higher power of EUV, being adopted more commonly now.
EUV is generated when a high-power RF pumped laser pulse(CO2 laser >10kW) hits droplets of tin metal (Sn ~ 30um diameter).It can scale the output power along with the laser's repetition rate(now: 50kHz) and pulse energy.

Multi-layer coated ellipsoidal collector mirror will refocus the EUV form plasma to intermediate focus, and then reflective mirror will converge into waver.

About company:
Cymer is the leading supporter of EUV and partner of ASML.

Although Cymer produce EUV with 100W output now, 250W is expected at full production.

By the way
EUV is very advanced laser technique. If you know the principles of laser, you will very surprising by the production method of EUV light source. There are many issues in the control of droplet and pulse of laser, and more the wavefront measurement plays important role in the quality of light source.