A collector subsystem has been designed, built, and tested. The subsystem consists of a 320mm diameter ellipsoidal collector coated with a graded multilayer, mounting mechanics, thermal management capability, and a collector protection system. The EUV light emission can be collected with a solid angle of 1.6 sr. Collector substrates have been developed with the goal of offering both optical surface quality to support high multilayer mirror (MLM) reflectivity and material compatibility for long-term operation in the EUV source system. An interface-engineered MLM coating capable of maintaining high normal-incidence peak reflectivity at 13.5 nm during continuous operation at 400 °C has been developed. The thermal management of the system has been engineered and tested to maintain uniform substrate temperature during operation. Lastly, protection techniques have been developed to provide the collector with a long operational lifetime. Performance data for the entire subsystem are presented. The collector was installed in the source chamber of a laser-produced-plasma EUV source during system integration experiments using a tin droplet target. First results of the collected EUV output at the intermediate focus measured with a power meter and a fluorescence-converter-based imaging system are discussed.
We report on the approach for a high-power high-beam-quality drive laser system that is used for a laser-produced plasma (LPP) EUV source. Cymer has conducted research on a number of solutions for a multi-kW drive laser system that satisfy high volume production requirements. Types of lasers to be presented include XeF at 351 nm and CO2 at 10.6 micron. We report on a high efficiency XeF amplifier with a 3rd harmonic Nd:YLF master oscillator operated in the 6 to 8 kHz range and a CO2 laser system with Q-switched cavity dumped master oscillator and RF pumped fast axial flow amplifiers operated in the 10 to 100 kHz range. CO2 laser short pulse gain and optical isolation techniques are reported. Optical performance data and design features of the drive laser system are discussed, as well as a path to achieve output power scaling to meet high volume manufacturing (HVM) requirements and beyond. Additionally, the electrical efficiency as a component of cost of operation is presented. Development of a drive laser with sufficient output power, high beam quality, and economical cost of operation is critical to the successful implementation of a laser-produced-plasma (LPP) EUV source for HVM applications. Cymer has conducted research on a number of solutions to this critical need. We report our progress on development of a high power system with two gas-discharge power amplifiers to produce high output power with high beam quality. We provide optical performance data and design features of the drive laser as well as a path to output power scaling to meet HVM requirements. Development of a drive laser for LPP EUV source is a challenging task. It requires multi-kW laser output power with short pulse duration and diffraction limited beam quality. In addition, this system needs to be very reliable and cost-efficient to satisfy industry requirements for high volume integrated circuit manufacturing. Feasibility studies of high power laser solutions that utilize proven laser technologies in high power optical gain modules and deliver required beam properties have been performed and are reported.
This paper provides a detailed review of development progress for a laser-produced-plasma (LPP) extreme-ultra-violet (EUV) source with performance goals targeted to meet joint requirements from all leading scanner manufacturers. We present the latest results on drive laser power and efficiency, source fuel, conversion efficiency, debris mitigation techniques, multi-layer-mirror coatings, collector efficiency, intermediate-focus (IF) metrology, mass-limited droplet generation, laser-to-droplet targeting control, and system use and experience. Results from several full-scale prototype systems are discussed. In addition, a multitude of smaller lab-scale experimental systems have also been constructed and tested. This paper reviews the latest experimental results obtained on these systems with a focus on the topics most critical for an HVM source. Laser produced plasma systems have been researched as probable light source candidates for an EUV scanner for optical imaging of circuit features at 32nm and beyond nodes on the ITRS roadmap. LPP systems have inherent advantages over alternative source types, such as Discharge Produced Plasma (DPP), with respect to power scalability, etendue, collector efficiency, and component lifetime. The capability to scale LPP power with repetition rate and modular design is shown. A path to meet requirements for production scanners planned well into the next decade is presented. This paper includes current testing results using a 320mm diameter near-normal-incidence elliptical collector, the first to be tested in a full-scale LPP system. With the collector in-situ, intermediate focus (IF) metrology capability is enabled, and data is presented that describes the quality of light at IF.
Metrology concepts and related results are discussed for characterization of extreme ultraviolet (EUV) light sources based on laser-produced plasmas using metal foil and droplet targets. Specific designs of narrow-band EUV detectors employing multilayer mirrors and broadband detectors for droplet steering are described. Spatially resolved plasma imaging using in-band EUV pinhole cameras is discussed. A grazing-incidence flat-field EUV spectrometer is described that has been employed for spectroscopy in the 6 nm - 22 nm range. In addition, spectroscopic data of out-of-band radiation in the ultraviolet and visible spectral regions are presented. Results obtained for different wavelengths of the incident laser radiation and for both tin- and lithium foil- and droplet- targets are discussed.
The EUV light source has been characterized as the top-priority critical issue facing the viability of EUV lithography. Cymer's extensive EUV source development efforts have focused both on the technical feasibility of various approaches as well as the critical issue of commercial feasibility to reach high volume manufacturing (HVM) requirements. We present a comprehensive summary of performance data from a state-of-the-art operational EUV source that thoroughly characterizes technical issues such as conversion efficiency, source material delivery, collector coatings, protection techniques and the path to higher and higher EUV power. Additionally, we present analysis of this performance data when compared to HVM requirements. Finally, we also briefly investigate the associated implications of the cost of consumables (COC) for a production EUV light source.
We describe an application of multiple target tracking (MTT) to microneurography, with the purpose of estimating conduction velocity changes and recovery constants of human nerve C-fibers. In this paper, the focus is on the detection and the tracking of the nerve action potentials (APs). The subsequent parameter estimation is described only briefly. Results from an application of the tracking system on real data recorded inhuman subjects are presented. Action potentials form C-fibers were recorded with a thin needle electrode inserted into the peroneal nerve of awake human subjects. The APs were detected by a matched filter constituting a maximum likelihood constant false alarm rate detector. By utilizing the multiple hypothesis tracking method, the detected APs in each trace were associated to individual nerve fibers by their typical conduction latencies in response to electrical stimulation in the skin. The measurements were 1D, and the APs were spaced in time with intersecting, piecewise continuous, trajectories. The amplitude of the APs was varying slowly over time for each C-fiber and was in general different for different fibers. It was therefore incorporated into the tracking algorithm to improve its performance.
Until now active or passive Q-switching have been used to achieve highly energetic laser pulses. Both these pulsing techniques have advantages as well as drawbacks. Passive Q- switching is extremely simple and need no electronic driving, but the emitted pulse has a large time jitter (100 ns to 1 ms) between the emitted pulses, which is detrimental in many applications. Active Q-switching on the other hand require advanced high voltage drive electronics which consume a substantial amount of electrical power, but the emitted pulse train is normally clean and well-behaved. In this paper we propose and demonstrate a novel Q-switched diode-pumped solid- state laser design, which combines the advantages of active and passive Q-switching, resulting in low time jitter as well as simple drive electronics with low power consumption. The plane-plane diode pumped laser consisted of a 0.5 mm long 3% Nd3+:YVO4 crystal acting as the gain medium, with the first mirror directly coated on the input face. The laser chip was followed by the active modulator, a 2 mm long z-cut LiNbO3 crystal, which in turn was followed by the saturable absorber, a 0.6 mm thick Cr4+:YAG crystal, and the output mirror. All elements were optically bonded together and the total cavity length including mirrors was 3.5 mm. The monolithic laser has a low jitter, here limited by our driving electronics to 85 ps, at a switching voltage of 300 V, compared to the V(pi ) of 5.2 kV. The pulse length is only 3 ns when the laser operates in combined Q-switched mode and 12 ns when passively Q-switched. In addition, multiple pulses caused by the active modulator is suppressed by the saturable absorber.