Collector Mirror Lifetime Research Articles

High Power LPP-EUV Source with Long Collector Mirror Lifetime for Semiconductor High Volume Manufacturing

High Power LPP-EUV Source with Long Collector Mirror Lifetime for Semiconductor High Volume Manufacturing

Advances in EUV light sources

Abstract Extreme ultraviolet (EUV) lithography has emerged as the preferred choice for high-volume manufacturing, now that immersion ArF reaches its limits. Light source power is a key driver to achieve the throughput required for successful adoption of extreme ultraviolet lithography (EUVL). Cymer has developed a laser-produced plasma source based on a high-power CO2 drive laser exciting tin targets to emit 13.5 nm light. Five sources are currently installed at chipmaker fabs and are being used for process development. The power output of the fielded source configuration is currently 20 W, lower than required for manufacturing introduction. The technology for scaling up power is under development, focusing on increasing the conversion efficiency and collection efficiency of the source. Increasing drive laser power to 17 kW has allowed the demonstration of EUV power of nearly 50 W, with paths identified for further scaling to 100 W. An additional focus on product reliability has driven the availability up to 70%, primarily through extending the collector mirror lifetime.

Laser-Produced Plasma EUV Light Source for Microlithography

The current status of the laser produced plasma light source development for EUV lithography is presented. Our key technology is based on an RF-excited CO2 driver laser combined with a Sn droplet target, because this approach enables cost-effective high-conversion efficiency. The RF-excited CO2 laser has a MOPA (master oscillator power amplifier) configuration. It currently generates an average output power of 2.6kW at 130kHz repetition rate. Due to negligible wavefront distortion of the laser beam during amplification, a laser focus of 100μm (FWHM) has been obtained. The Sn target and magnetic ion mitigation development as well as an evaluation of the collector mirror lifetime are presented.

Effect of xenon bombardment on ruthenium-coated grazing incidence collector mirror lifetime for extreme ultraviolet lithography

The effect of energetic xenon ion bombardment on the extreme ultraviolet (EUV) reflectivity performance of mirrors is of vital importance for the performance of discharge- and laser-produced plasma extreme ultraviolet lithography sources. To study these effects, we measured absolute and relative reflectivities at the National Institute of Standards and Technology and the Interaction of Materials with Particles and Components Testing facility to quantify the effects of singly ionized Xe ion bombardment on the reflectivity of Ru EUV collector mirrors. Results show that unity sputtering is reached at Xe+ energies near 400–500eV. The Xe+-induced sputter yield decreases an order of magnitude with only a 60% decrease in energy. Incident angle-dependent data of Xe+ bombardment show that the sputter yield is weakly dependent on angle at energies near 1keV. Dynamic measurements of in situ EUV reflectivity during Xe+ irradiation show that the oxygen state of the reflecting mirror has a significant effect on reflectivity performance. For example, 13.5nm light reflecting from an oxygen-rich mirror results in over a 40% loss in reflectivity. These studies also found that the surface roughness increased only at the atomic scale (subnanometer scale) when exposed to energetic Xe+ and thus did not contribute to EUV reflectivity losses except for cases of very high fluences (>1016cm−2).

EUV radiation characteristics of a CO2 laser produced Xe plasma

A CO2 laser-driven Xe liquid jet plasma has been studied with respect to its usability as a EUV lithography light source. A short-pulse TEA-CO2 master oscillator power amplifier system (MOPA) and a pre-pulse Nd:YAG laser were used for the plasma generation. The dependence of EUV plasma parameters, e.g., conversion efficiency, plasma image, in-band and out-of-band spectra, on the delay time between the pre-pulse and the main pulse laser was investigated. A maximum conversion efficiency of 0.6% was obtained at a delay time of about 200 ns. In addition, characteristics of fast ions were measured by the time-of-flight method. The peak energy of the fast ion energy distribution decreased significantly at delay times longer than 200 ns. This result is very promising with respect to a collector mirror lifetime extension by magnetic field mitigation.

Laser-Produced Plasma Light Source Development for Extreme Ultraviolet Lithography

We present recent results of our laser-produced plasma light source development for next-generation lithography. The plasma target of the extreme ultraviolet (EUV) source system is a liquid xenon jet and the driver laser is a 600 W Nd:YAG laser operating at a repetition rate of 10 kHz. A EUV output power of 2.2 W at 13.5 nm (2% bandwidth, 2π sr) having a stability of 0.72% (1σ, 50-pulse moving average) has been achieved. Related to future collector mirror lifetime considerations, fast ions from the laser-produced plasma have been characterized by time-of-flight (TOF) measurements. Using a low repetition rate 8-ns, 100-mJ Nd:YAG laser Xe+ to Xe6+ ions were observed with Xe2+ being the main charge state. In addition, the effects of fast ions on Mo/Si multilayer mirrors have been studied using a Xe ion gun. Ion sputtering of the multilayer structure is the main damage mechanism but layer boundary mixing and surface roughness increase are also observed.