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Over 85 EUV scanners are installed at customer factories and being used in high volume manufacturing (HVM) of leading semiconductor devices. The latest generation of EUV sources are operating at 250W with 92% availability, while meeting all performance requirements. Future EUV scanners are projected to require even higher power to meet throughput requirements. In this paper, we provide an overview of a the latest advances in the laboratory for tin laser-produced-plasma (LPP) extreme-ultraviolet (EUV) sources at 13.5nm enabling HVM at the N5 node and beyond, highlighting crucial EUV source technology developments needed to meet future requirements for EUV power and stability. This includes the performance of subsystems designed for critical source functions such as collector protection and continuous tin droplet supply.

This year, we expect EUV lithography to succeed 193 nm immersion multi-patterning technology for sub-10 nm critical layer patterning. In order to be successful, the EUV lithography source has to de...

Over 50 EUV scanners are installed at customer factories and being used in high volume manufacturing (HVM) of leading semiconductor devices. The latest generation of EUV sources are operating at 250W while meeting all other requirements. Future EUV scanners are projected to require more stable EUV and higher powers >600W to meet throughput requirements. In this paper, we provide an overview of a the latest advances in the laboratory for tin laser-produced-plasma (LPP) extreme-ultraviolet (EUV) sources at 13.5nm enabling HVM at the N5 node and beyond, highlighting crucial EUV source technology developments needed to meet future requirements for EUV power and stability. This includes the performance of subsystems such as the Collector and the Droplet Generator.

A hydrogen plasma cleaning technique to clean Sn (tin) off EUV collector optics is studied in detail. The cleaning process uses hydrogen radicals and ions (formed in the hydrogen plasma) to interact with Sn-coated surfaces, forming SnH 4 and being pumped away. This technique has been used to clean a 300mm-diameter stainless steel dummy collector optic, and EUV reflectivity of multilayer mirror samples was restored after etching Sn from them. Previous experiments have shown etch rates of greater than 10 nm/min over a 2 inch diameter circular plasma area with an SWP launcher. An etch experiment was conducted with a sweep over sample bias to investigate the influence of hydrogen ions. Radial etch rates for each hydrogen ion energy were measured using profilometry. Langmuir probe and radical measurements were also taken. Langmuir probe measurements of the surface wave plasma show a two temperature distribution for electrons: a bulk temperature of 2.3 eV and some population at 8.6 eV. The bulk electron density was measured to be 2.7e11 cm -3 . Radical probe measurements give the hydrogen radical density at 1.96e15 cm -3 . A COMSOL model of this experiment was also built and simulation results will be presented. In this work, experiments elucidating the fundamental processes of tin removal are conducted by varying pressure, power, surface temperature and gas flow rate. The ion bombardment reduces the number of radicals needed to etch a single tin atom to the range of -. The linear SWP antenna yields plasma densities on the order of and radical densities on the order of , allowing for greater utilization of ion etch enhancement. Etch rates of up to 200 nm/min have been achieved. The surface temperature of the samples is an important factor in the etching process such that decrease of the surface temperature increases the etch rates and decreases the hydrogen desorption rates. In addition, a kinetic etch model is developed to explain the behavior of the etch rates as function of the surface temperature. Furthermore, results from experiments performed in Illinois NXE:3100 chamber will be discussed.

A novel method of modeling Sn (tin) scattering through H2 (molecular hydrogen) is examined. Density-functional theory (DFT) software from the Amsterdam Modeling Suite was used to determine the interaction energy of Sn and H2 at varying spacing and orientations. This data was used to generate a function that describes the average interaction energy with respect to distance between the two species for neutral Sn as well as selected Sn ionized states. These resulting functions were inserted into RustBCA, a binary collision approximation code for ion-material interactions. The scattering of a Sn beam through H2 was modeled for each newly generated potential, along with well-known potentials such as ZBL and Moliere for comparison. Legacy software, such as TRIM, is not capable of modeling scattering using potentials that contain attractive components. The potentials generated with DFT have attractive components, so this analysis is only possible now using RustBCA. This method can give more accurate results than previous work. A model using the ZBL potential wherein a neutral Sn beam of 10 keV scattered through 15 cm of H2 left 87.8% of the Sn atoms within 41.4 millisteradians of the primary axis and an average energy of 816.3 eV ± 8.71 eV. The same model with a DFT-generated potential gives a much narrower particle distribution with higher average energies. This modeling work will also be compared against ongoing experimental measurements of Sn ions through H2 for further comparison.

Multiple ASML NXE:3400C scanners are installed at customer factories and being used in high volume manufacturing (HVM) of leading semiconductor devices. The latest generation of NXE:3400C sources has improved performance and availability by implementing a modular vessel concept and an automated tin supply system. In this paper, we provide an overview of 13.5 nm tin laser-produced-plasma (LPP) extreme-ultraviolet (EUV) sources enabling HVM at the N5 node and beyond. The field performance of sources operating at 250 watts power including the performance of subsystems such as the Collector and the Droplet Generator will be shown. Progress in the development of key technologies for power scaling towards 420W will be described.

Extreme ultraviolet (EUV) lithography is expected to succeed in 193-nm immersion multi-patterning technology for sub-10-nm critical layer patterning. In order to be successful, EUV lithography has to demonstrate that it can satisfy the industry requirements in the following critical areas: power, dose stability, etendue, spectral content, and lifetime. Currently, development of second-generation laser-produced plasma (LPP) light sources for the ASML’s NXE:3300B EUV scanner is complete, and first units are installed and operational at chipmaker customers. We describe different aspects and performance characteristics of the sources, dose stability results, power scaling, and availability data for EUV sources and also report new development results.

In this paper, we provide an overview of state-of-the-art technologies for incoherent laser-produced tin plasma extreme-ultraviolet (EUV) sources at 13.5nm with performance enabling high volume semiconductor manufacturing (HVM). The key elements to development of a stable and reliable source that also meet HVM throughput requirements and the technical challenges for further scaling EUV power to increase productivity are described. Improvements in availability of droplet generation and the performance of critical subsystems that contribute to EUV collection optics lifetime toward the one tera-pulse level, are shown. We describe current research activities and provide a perspective for EUV sources towards the future ASML Scanners.

We provide an overview of laser-produced-plasma (LPP) extreme-ultraviolet (EUV) source performance to enable high volume manufacturing and improvements in various technologies for scaling output power of the source. Several companies have multiple systems and are ramping toward production, we will show current output and availability of sources and describe their readiness for HVM. We will show improvements to source architecture that facilitated the increase of EUV power to 250W, and the technical challenges for power scaling of key source parameters and subsystems. The performance of critical subsystems such as the Droplet Generator and Collector protection will be shown, with emphasis on stability and lifetime. Finally, we will describe current research activities and provide a perspective for LPP EUV sources towards 500W.

In this paper, we provide an overview of various technologies for scaling tin laser-produced-plasma (LPP) extremeultraviolet (EUV) source performance to enable high volume manufacturing (HVM). We will show improvements to source architecture that facilitated the increase of EUV power from 100W to 250W, and the technical challenges for power scaling of key source parameters and subsystems. The performance of critical subsystems such as the Droplet Generator and Collector protection will be shown, with emphasis on stability and lifetime. Finally, we will describe current research activities and provide a perspective for LPP EUV sources towards 500W.

In this paper, we provide an overview of various challenges and their solutions for scaling laser-produced-plasma (LPP) extreme-ultraviolet (EUV) source performance to enable high volume manufacturing. We will discuss improvements to source architecture that facilitated the increase of EUV power from 100W to >200W, and the technical challenges for power scaling of key source parameters and subsystems. Finally, we will describe current power-scaling research activities and provide a forward looking perspective for LPP EUV sources towards 500W.

We present highlights from plasma simulations performed in collaboration with Lawrence Livermore National Labs. This modeling is performed to advance the rate of learning about optimal EUV generation for laser produced plasmas and to provide insights where experimental results are not currently available. The goal is to identify key physical processes necessary for an accurate and predictive model capable of simulating a wide range of conditions. This modeling will help to drive source performance scaling in support of the EUV Lithography roadmap. The model simulates pre-pulse laser interaction with the tin droplet and follows the droplet expansion into the main pulse target zone. Next, the interaction of the expanded droplet with the main laser pulse is simulated. We demonstrate the predictive nature of the code and provide comparison with experimental results.

NXE:3300B scanners have been operational at customer sites since almost two years, and the NXE:3350B, the 4th generation EUV system, has started shipping at the end of 2015. All these exposure tools operate using MOPA pre-pulse source technology, which enabled significant productivity scaling, demonstrated at customers and at ASML. Having achieved the required throughput to support device development, the main priority of the ASML EUV program has shifted towards improving stability and availability. Continuous progresses in defectivity reduction and in the realization of a reticle pellicle are taking place at increased speed. Today’s overlay and imaging results are in line with the requirements of 7nm logic devices; Matched Machine overlay to ArF immersion below 2.5 nm and full wafer CDU performance of less than 1.0nm are regularly achieved. The realization of an intensity loss-less illuminator and improvements in resist formulation are significant progress towards enabling the use of EUV technology for 5nm logic devices at full productivity. This paper will present an overview of the status of the ASML EUV program and product roadmap by reviewing the current performance and on-going developments in productivity, imaging, overlay and mask defectivity reduction.

Cymer-ASML is committed to develop high power EUV source technology based on CO 2 laser-produced-plasma (LPP) for use in EUV lithography for high-volume-manufacturing of semiconductors. Stable dose controlled EUV power at intermediate focus (IF) has been successfully developed using a CO 2 laser of high intensity, short pulse duration, high repetition, and high average power. Figure 1 shows 185 W at Intermediate Focus (IF) dose-controlled EUV source power and dose stability over a one hour demonstration. EUV pulse energy up to 5 mJ with 22% overhead is created at 50 kHz. Dose error is all smaller than 1%. This enables 100% good dies exposure.

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 (LPP) EUV systems have been considered as a viable and scalable approach for the EUV scanners at sub-32nm and beyond nodes on the ITRS roadmap. High EUV power and reduction of chamber contaminations inside EUV vacuum chambers or to EUV scanner optics are two main concerns for the LPP EUV source system development. In this paper, a review of Cymer LPP EUV development progress will be provided along with productization status for LPP EUV sources with performance goals targeted to meet specific requirements from leading scanner manufacturers. The latest results on high EUV power generation, debris mitigation and clean transmission of EUV light through the intermediate focus will be described. Finally, a development roadmap to achieve high LPP EUV source power will be illustrated.

This paper describes the development of a LPP EUV source using a CO"2 laser with tin droplet targets. Burst power of 100W and average power of 25W has been achieved. Collector mirrors have been fabricated with >50% reflectivity and show stable EUV images. Multiple debris mitigation techniques preserve mirror reflectivity. Manufacturing of the first production systems is in progress.

Extreme ultra-violet (EUV) lithography is considered to be the most viable candidate to replace DUV to fulfill Moore's Law for 22nm generation and beyond. In this manuscript, we will show that LPP is the preferred choice for high volume manufacturing due to its scaling capability, enabled by high efficiency in both EUV light production and collection. The LPP EUV source development history and current status are described in this work, including EUV power progress, highly reliable Tin droplet generator, advanced debris mitigation technology and other technology advantages. Future EUV source roadmap provides a detailed schedule and technology requirements for high volume manufacturing EUV sources for the 22nm generation and beyond.

This paper describes the development and evolution of the critical architecture for a laser-produced-plasma (LPP) extreme-ultraviolet (EUV) source for advanced lithography applications in high volume manufacturing (HVM). In this paper we discuss the most recent results from high power sources in the field and testing on our laboratory based development systems, and describe the requirements and technical challenges related to successful implementation of those technologies on production sources. System performance is shown, focusing on pre-pulse operation with high conversion efficiency (CE) and with dose control to ensure high die yield. Finally, experimental results evaluating technologies for generating stable EUV power output for a high volume manufacturing (HVM) LPP source will be reviewed.

Multiple NXE:3300 are operational at customer sites. These systems, equipped with a Numerical Aperture (NA) of 0.33, are being used by semiconductor manufacturers to support device development. Full Wafer Critical Dimension Uniformity (CDU) of 1.0 nm for 16nm dense lines and 1.1 nm for 20nm isolated space and stable matched overlay performance with ArF immersion scanner of less than 4nm provide the required lithographic performance for these device development activities. Steady progresses in source power have been achieved in the last 12 months, with 100Watts (W) EUV power capability demonstrated on multiple machines. Power levels up to 90W have been achieved on a customer machine, while 110W capability has been demonstrated in the ASML factory. Most NXE:3300 installed at customers have demonstrated the capability to expose 500 wafers per day, and one field system upgraded to the 80W configuration has proven capable of exposing 1,000 wafers per day. Scanner defectivity keeps being reduced by a 10x factor each year, while the first exposures obtained with full size EUV pellicles show no appreciable difference in CDU when compared to exposures done without pellicle. The 4th generation EUV system, the NXE: 3350, is being qualified in the ASML factory.

The first NXE3300B systems have been qualified and shipped to customers. The NXE:3300B is ASML’s third generation EUV system and has an NA of 0.33. It succeeds the NXE:3100 system (NA of 0.25), which has allowed customers to gain valuable EUV experience. Good overlay and imaging performance has been shown on the NXE:3300B system in line with 22nm device requirements. Full wafer CDU performance of Source power is the major challenge to overcome in order to achieve cost-effectiveness in EUV and enable introduction into High Volume Manufacturing. With the development of the MOPA+prepulse operation of the source, steps in power have been made, and with automated control the sources have been prepared to be used in a preproduction fab environment. Flexible pupil formation is under development for the NXE:3300B which will extend the usage of the system in HVM, and the resolution for the full system performance can be extended to 16nm. Further improvements in defectivity performance have been made, while in parallel full-scale pellicles are being developed. In this paper we will discuss the current NXE:3300B performance, its future enhancements and the recent progress in EUV source performance.

This paper describes the development of a laser-produced-plasma (LPP) extreme-ultraviolet (EUV) source for advanced lithography applications in high volume manufacturing. EUV lithography is expected to succeed 193nm immersion double patterning technology for sub- 20nm critical layer patterning. In this paper we discuss the most recent results from high power testing on our development systems targeted at the 250W configuration, and describe the requirements and technical challenges related to successful implementation of these technologies. Subsystem performance will be shown including Conversion Efficiency (CE), dose control, collector protection and out-of-band (OOB) radiation measurements. This presentation reviews the experimental results obtained on systems with a focus on the topics most critical for a 250W HVM LPP source.

Laser produced plasma (LPP) light sources have been developed as the primary approach for EUV scanner imaging of circuit features in sub-20nm devices in high volume manufacturing (HVM). This paper provides a review of development progress and readiness status for the LPP extreme-ultra-violet (EUV) source. We present the latest performance results from second generation sources, including Prepulse operation for high power, collector protection for long lifetime and low cost of ownership, and dose stability for high yield. Increased EUV power is provided by a more powerful drive laser and the use of Prepulse operation for higher conversion efficiciency. Advanced automation and controls have been developed to provide the power and energy stability performance required during production fab operation. We will also discuss lifetesting of the collector in Prepulse mode and show the ability of the debris mitigation systems to keep the collector multi-layer coating free from damage and maintain high reflectivity.

The presence of Sn on the collector optic of an extreme ultraviolet (EUV) light lithography tool continues to be a concern for source manufacturers. A mere nanometers deposition results in reduction of EUV light reflectivity to unacceptable levels. It has been shown previously that hydrogen radical etching of Sn provides a promising technique for in-situ cleaning of the collector optic. One concern in this technique is the redeposition by radicalized SnH4 breaking apart after making contact with a surface. To address this concern, large scale etching measurements were made using a metallic antenna as the substrate. Optimized etch rates approaching 7.5±1 nm/min have been achieved with a flow rate of 500 sccm at a pressure of 80 mTorr. The effect of variations in the Sn cleaning environment will be investigated with respect to temperature increases as well as air, oxygen, and methane contamination gasses. Furthermore, the effect of Sn located away from the cleaning location will also be presented.

Laser produced plasma (LPP) systems have been developed as the primary approach for use in EUV scanner light sources for optical imaging of circuit features at 20nm nodes and beyond. This paper provides a review of development progress and productization status for LPP extreme-ultra-violet (EUV) sources with performance goals targeted to meet specific requirements from ASML. We present the latest results on power generation and collector protection for sources in the field operating at 10W nominal power and in San Diego operating in MOPA (Master Oscillator Power Amplifier) Prepulse mode at higher powers. Semiconductor industry standards for reliability and source availability data are provided. In these proceedings we show results demonstrating validation of MOPA Prepulse operation at high dose-controlled power: 40 W average power with closed-loop active dose control meeting the requirement for dose stability, 55 W average power with closed-loop active dose control, and early collector protection tests to 4 billion pulses without loss of reflectivity.

This paper describes the development of a laser-produced-plasma (LPP) extreme-ultraviolet (EUV) source for advanced lithography applications in high volume manufacturing. EUV lithography is expected to succeed 193nm immersion double patterning technology for sub-20nm critical layer patterning. In this paper we discuss the most recent results from high power testing on our development systems in San Diego, and describe the requirements and technical challenges related to successful implementation of these technologies. Subsystem performance will be shown including the CO2 drive laser, droplet generation, laser-to-droplet targeting control, intermediate-focus (IF) metrology, out-of-band (OOB) radiation measurements and system use and experience. In addition, a multitude of smaller lab-scale experimental systems have also been constructed and tested..

The usable power of high-power EUV light sources at 13.5 nm and also the lifetime of source and collector optics are currently considered to be the largest challenges encountered during the transition of EUV lithography from the current beta-tool status to high-volume manufacturing. Fraunhofer IOF Jena has developed cost-effective refurbishment technologies of multilayer-based near normal incidence collector mirrors for high-power laser-produced plasma sources. Presently, the collector mirror lifetime exceeds 80 billion laser pulses which correspond to a lifetime of several months during continuous use of the source. Together with their partners Cymer is currently carrying out a focused program to improve the collector lifetime. New multilayer coatings together with new in-situ cleaning strategies during source operation are key technology development strategies to get closer to the ultimate target of about one year collector lifetime. The paper discusses different LPP collector refurbishment strategies and presents the recent status on collector refurbishment techniques.

Through a number of experimental studies carried out on various experimental test stands we are characterizing the scaling of EUV power and collector lifetime. The current performance of the first generation of EUV sources to support EUV lithography scanners is at 20 W power and 70% availability. CO2 drive laser power of up to 17 kW has been reached, while average EUV power of nearly 50 W was demonstrated on an HVM I source with a laser pre-pulse at our facilities. The burst EUV power on this source was in excess of 90 W at 10% to 20% duty cycle and closer to 60 W at 80% duty cycle since the full set of automated controls has not yet been implemented on this source. Once the automation of the laser-droplet position controls is implemented on our pre-pulse system, the average source power is expected to reach power levels on the order of 100 W. Further scaling of source power through operation at repetition rates higher than 50 kHz was also shown to be possible. Through improved gas management, better coatings and parallel testing of collector samples, we have significantly extended the useful life of the source collector mirrors.

Laser produced plasma (LPP) systems have been developed as the primary approach for the EUV scanner light source for optical imaging of circuit features at sub-22nm and beyond nodes on the ITRS roadmap. This paper provides a review of development progress and productization status for LPP extreme-ultra-violet (EUV) sources with performance goals targeted to meet specific requirements from leading scanner manufacturers. We present the latest results on exposure power generation, collection, and clean transmission of EUV through the intermediate focus. Semiconductor industry standards for reliability and source availability data are provided. We report on measurements taken using a 5sr normal incidence collector on a production system. The lifetime of the collector mirror is a critical parameter in the development of extreme ultra-violet LPP lithography sources. Deposition of target material as well as sputtering or implantation of incident particles can reduce the reflectivity of the mirror coating during exposure. Debris mitigation techniques are used to inhibit damage from occuring, the protection results of these techniques will be shown over multi-100's of hours.

One of the main challenges in extreme ultraviolet lithography (EUVL) is the development of a method for cleaning collector optics without inhibiting cost-effectiveness. Cost-effectiveness of EUV methods can be increased by in-situ processes for removing debris placed on the collector optic. This paper focuses on the use of a hydrogen plasma to remove Sn, a common EUV fuel, from Si surfaces. Sn was deposited on both large and small Si samples via magnetron sputtering, and optimized hydrogen plasma selectively etched the Sn. Deposition uniformity and thickness are measured, as are Sn etch rates and cleaning uniformity. Positive results indicate the potential of this method for use in cleaning EUV mirrors.

This paper is devoted to the development of laser produced plasma (LPP) EUV source architecture for advanced lithography applications in high volume manufacturing of integrated circuits. The paper describes the development status of subsystems most critical to the performance to meet scanner manufacturer requirements for power and debris mitigation. Spatial and temporal distributions of the radiation delivered to the illuminator of the scanner are important parameters of the production EUV tool, this paper reports on these parameters measured at the nominal repetition rate of the EUV source. The lifetime of the collector mirror is a critical parameter in the development of extreme ultra-violet LPP lithography sources. Deposition of target material and contaminants as well as sputtering and implantation of incident particles can reduce the reflectivity of the mirror coating substantially over time during exposure even though debris mitigation schemes are being employed. We report on progress of life-test experiments of exposed 1.6sr collectors using a Sn LPP EUV light source. The erosion of MLM coating is caused mostly by the high-energy ions generated from the plasma. In this manuscript the ion distribution measured at small (14 degree) and medium (45 degree) angles to the laser beam are presented. The measurements show that the chosen combination of the CO2 laser and Sn droplet targets is characterized by fairly uniform angular ion energy distribution. The maximum ion energy generated from the plasma is in the range of 3-3.5 keV for all incident angles of the collector. The measured maximum energy of the ions is significantly less than that measured and simulated for plasmas generated by short wavelength lasers (1 μm). The separation of ions with different charge states was observed when a retarding potential was applied to the Faraday Cup detector.

Extreme ultraviolet (EUV) technology has been recognized as the major lithography technology for 22 nm HP and beyond to fulfill Moore's Law, which predicts that circuit dimensions shrink 70% every 2~3 years in order to achieve cost down and obtain greater functionality per unit area. EUV source power is one of the key factors in determining the cost-effectiveness of EUVL compared to other lithography technologies, like double patterning. Only when EUV power can achieve a certain level, the cost of EUV lithography under high volume manufacturing (HVM) can become much more competitive than that of double patterning techniques. In this paper, the performance of the first production Cymer high power laser produced plasma (LPP) EUV source integrated with a 5 sr multi-layer mirror (MLM) collector and fully integrated debris mitigation will be shown. The latest results on power generation, stable and efficient collection, and clean transmission of EUV light through the intermediate focus will be presented. The lifetime of the MLM collector is a critical parameter in the development of extreme ultraviolet LPP lithography sources. Debris mitigation techniques are used to inhibit reflectivity degradation from deposition of target material, sputtering of the multilayer coating, and implantation of incident particles, which can reduce the efficiency of the MLM collector during exposure. The far field images of MLM collector are recorded by intermediate focus metrology with a CCD camera to determine the reflectivity status of the MLM collector during exposure. The results of these debris mitigation techniques are compared through multiple-hour EUV exposure. Testing shows cleanliness at the source-scanner interface acceptable to the limit of detection.

Laser produced plasma (LPP) systems have been developed as a viable approach for the EUV scanner light source for optical imaging of circuit features at sub-32nm and beyond nodes on the ITRS roadmap. This paper provides a review of development progress and productization status for LPP extreme-ultra-violet (EUV) sources with performance goals targeted to meet specific requirements from leading scanner manufacturers. We present the latest results on power generation, stable and efficient collection, and clean transmission of EUV light through the intermediate focus. We report on measurements taken using a 5sr collector optic on a production system. Power transmitted to intermediate focus (IF) is shown. The lifetime of the collector mirror is a critical parameter in the development of extreme ultraviolet LPP lithography sources. Deposition of target material as well as sputtering of the multilayer coating or implantation of incident particles can reduce the reflectivity of the mirror coating during exposure. Debris mitigation techniques are used to inhibit damage from occuring, the results of these techniques are shown. We also report on the fabrication of 5sr collectors and MLM coating reflectivity, and on Sn droplet generators with droplet size down to 30μm diameter.

The need for improved lithography resolution has driven the development of light sources with ever shorter wavelength. Excimer lasers have extended the exposure wavelength down to 193nm. Further resolution extension will require the introduction of Extreme UV (EUV) light source technology at 13.5nm. The traditional light source driver at each technology node has been higher power which enables increased productivity. More recently, improved light source stability, driven by tighter CD and overlay budgets for Double Patterning processes, has become more important and developments in this area will be described. The leading challenge for insertion of EUVL is source power and lifetime, which are both necessary to ensure cost effective operation. The first Laser Produced Plasma (LPP) production source using a high power CO2 laser and tin droplet targets is described. High conversion efficiency has enabled high EUV power performance. Continuous operation up to 18 hours, with stable power output, has been demonstrated. High collection efficiency is obtained using a large (5sr) multilayer mirror collector optic. The first integrated source will be delivered to support scanners for process development and insertion of EUVL at the 22nm node. A roadmap for future generations of LPP sources with scalable power will be outlined.

This paper describes the development of laser produced plasma (LPP) technology as an EUV source for advanced scanner lithography applications in high volume manufacturing. EUV lithography is expected to succeed 193 nm immersion technology for critical layer patterning below 32 nm beginning with beta generation scanners in 2009. This paper describes the development status of subsystems most critical to the performance to meet joint scanner manufacturer requirements and semiconductor industry standards for reliability and economic targets for cost of ownership. The intensity and power of the drive laser are critical parameters in the development of extreme ultraviolet LPP lithography sources. The conversion efficiency (CE) of laser light into EUV light is strongly dependent on the intensity of the laser energy on the target material at the point of interaction. The total EUV light generated then scales directly with the total incident laser power. The progress on the development of a short pulse, high power CO2 laser for EUV applications is reported. The lifetime of the collector mirror is a critical parameter in the development of extreme ultra-violet LPP lithography sources. The deposition of target materials and contaminants, as well as sputtering of the collector multilayer coating and implantation of incident particles can reduce the reflectivity of the mirror substantially over the exposure time even though debris mitigation schemes are being employed. The results of measurements of high energy ions generated by a short-pulse CO2 laser on a laser-produced plasma EUV light source with Sn target are presented. Droplet generation is a key element of the LPP source being developed at Cymer for EUV lithography applications. The main purpose of this device is to deliver small quantities of liquid target material as droplets to the laser focus. The EUV light in such configuration is obtained as a result of creating a highly ionized plasma from the material of the droplets. Liquid tin is the material of choice to be used as a target due to the relatively high CE of the laser energy into in-band EUV radiation. Results obtained with the droplet generator and technical challenges related to successful implementation of the device are discussed.

The source output power and lifetime, including the collector optics lifetime, are among the key issues for EUV lithography systems. In order to meet the requirements for the EUV collector mirror, both the reflectivity and the long-term thermal stability of its multilayer coating have been enhanced considerably during recent development efforts. Sub-aperture ellipsoidal mirrors of different substrate materials with outer diameters of about 320 mm were coated with laterally graded high-temperature multilayers. The interface-engineered Mo/Si multilayer mirror (MLM) coatings were optimized in terms of high peak reflectivity at 13.5 nm and working temperatures above 400°C. Thin barrier layers were introduced on both interfaces to block thermally induced interdiffusion processes of molybdenum and silicon and to provide long-term optical stability of the coating at elevated temperatures. A normal-incidence reflectance of R ~ 60 % at 13.5 nm was measured on Si wafer samples after heating up to 600°C. No degradation of the optical properties of these multilayer coatings occurred during both long-term heating tests and multiple annealing cycles. On highly polished collector substrates with improved surface roughness a reflectance for s-polarized light exceeding peak values of R = 57 % was obtained. With optimized layer gradient the degree of wavelength matching was improved, as well, resulting in peak reflectivity values above 56 % throughout the clear aperture for a series of measurement points across the mirror. The corresponding area-weighted 2% in-band average reflectance for this collector mirror coating exceeds 52 % for unpolarized light.

A comprehensive review of the development activities being undertaken at Cymer in the development of a CO2 laser produced plasma (LPP) light source for EUV lithography is provided. A new and effective debris mitigation technique which greatly reduces the Ion Flux generated during exposure is also demonstrated.

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.

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.

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.

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.

Laser-produced plasma sources offer the best option for scal- ability to support high-throughput lithography. Challenges associated with the complexity of such a source are being addressed in a pilot program where sources have been built and integrated with extreme-ultraviolet (EUV) scanners. Up to now, five pilot sources have been installed at R&D facilities of chip manufacturers. Two pilot sources are dedicated to product development at our facility, where good dose stability has been demonstrated up to levels of 32 W of average EUV power. Experi- mental tests on a separate experimental system using a laser prepulse to optimize the plasma conditions or EUV conversion show power levels equivalent to approximately 160 W within a low duty-cycle burst, before dose control is applied. The overall stability of the source relies on the generation of Sn droplet targets and large EUV collector mirrors. Stability of the Sn droplet stream is well below 1 μm root mean square during 100 þ h of testing. The lifetime of the collector is significantly enhanced with improved coatings, supporting uninterrupted operation for several weeks. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.JMM.11.2.021110)

Improved performance and specific results are reported for several test and prototype extreme ultraviolet EUV light sources devel- oped for next-generation lithography. High repetition rate and high-power CO2 laser-produced plasma sources operating on tin droplet targets are described. Details of laser architecture, source chambers and system operation are given. Stable output power, efficient light collection, and clean EUV transmission could be achieved for hours of operation. We review progress during integration of light sources with collector mirrors reaching EUV power levels at intermediate focus of 60 W and 45 W, respectively, with duty cycles of 25% and 40%. Far-field EUV images of the collected light were recorded to monitor the source output perfor- mance during extended tests of collector longevity and debris protection with system operation time exceeding 50 h. Development results on EUV spectra, out-of-band OOB radiation, and ion debris obtained with dedicated metrology setups are also described. Angle-resolved mea- surements with ion energy analyzer and Faraday cups reveal the contri- butions of individual ion charge states in related spectra. Our laser- produced EUV light source technology has now reached a level of maturity in full integration where prototype sources can be delivered and pilot line introduction can be prepared. © 2009 Society of Photo-Optical Instru