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.
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..
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.
Laser-produced plasma sources offer the best option for scalability 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. Experimental 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+ h of testing. The lifetime of the collector is significantly enhanced with improved coatings, supporting uninterrupted operation for several weeks.
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.
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.
The development of a successful extreme ultraviolet light source for lithography relies on the ability to
maintain collector optic cleanliness. Cleanliness is required to maintain the reflectivity of the collector optic, thus
maintaining the light power output at the intermediate focus. In this paper, an in-situ method is explored to remove
Sn from a contaminated collector optic. Hydrogen plasma is used to promote Sn etching while maintaining the
integrity of the collector optic's multi-layer structure. The removal rate of Sn is investigated as a function of various
operational parameters including chamber pressure, plasma electron density, as well as plasma electron temperature.
Initial results are presented using an external RF-plasma source. The use of the collector optic as a RF-antenna is
also investigated to optimize the etching rate of the hydrogen plasma. Initial plasma parameter measurements reveal
electron densities on the order of 1011-1012 cm-3, with electron temperatures on the order of 1-3 eV. An optimized
etch rate of ~125 nm/min off of Si was observed using 1000 W, 80 mTorr, and a flow rate of 50 sccm of H2. These
initial measurements are used as a basis for optimizing the etching rate off of the collector optic. Such results are
important in allowing the long-term usage of a single collector optic to minimize operating costs involved with
replacing the optic as well as tool downtime.
This paper describes the development of laser-produced-plasma (LPP) extreme-ultraviolet (EUV) source
architecture for advanced lithography applications in high volume manufacturing. EUV lithography is
expected to succeed 193 nm immersion technology for sub-22 nm critical layer patterning. In this paper we
discuss the most recent results from high qualification testing of sources in production. Subsystem
performance will be shown including collector protection, out-of-band (OOB) radiation measurements,
and intermediate-focus (IF) protection as well as experience in system use. This presentation reviews the
experimental results obtained on systems with a focus on the topics most critical for an HVM source.
Laser produced plasma (LPP) systems have been developed as a viable approach for the EUV scanner light sources to
support optical imaging of circuit features at sub-22nm 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. The status of first generation High Volume
Manufacturing (HVM) sources in production and at a leading semiconductor device manufacturer is discussed. The
EUV power at intermediate focus is discussed and the lastest data are presented. An electricity consumption model is
described, and our current product roadmap is shown.
This paper describes the development of laser-produced-plasma (LPP) extreme-ultraviolet (EUV) source architecture
for advanced lithography applications in high volume manufacturing. EUV lithography is expected to succeed 193nm
immersion technology for sub-22nm critical layer patterning. In this paper we discuss the most recent results from high
EUV power testing and debris mitigation testing on witness samples and normal incidence collectors. Subsystem
performance will be shown including the CO2 drive laser, debris mitigation, normal incidence collector and coatings,
droplet generation, laser-to-droplet targeting control, intermediate-focus (IF) metrology and system use and experience.
In addition, a number of smaller lab-scale experimental systems have also been constructed and tested. This
presentation reviews the experimental results obtained on systems with a focus on the topics most critical for an HVM
source.
Laser produced plasma (LPP) systems have been developed as a viable approach for the EUV scanner light source to support 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. The status of first generation High Volume Manufacturing (HVM) sources in production and of prototype source operation at a leading scanner manufacturer is discussed. The EUV power at intermediate focus is discussed and the lastest data is presented. An electricity consumption model is described, and our current product roadmap is shown.
Improved performance and specific results are reported for several test and prototype extreme ultraviolet (EUV) light sources developed 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 performance 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 measurements with ion energy analyzer and Faraday cups reveal the contributions 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.
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.
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.
This paper provides a 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. Laser produced plasma 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. Recent advances in the development of the system, its present average output power level and progress with various subcomponents is discussed. We present the latest results on peak EUV and average EUV power as well as stability of EUV output, measured in burst-mode operation at the nominal repetition rate of the light source. In addition, our progress in developing of critical components, such as normal-incidence EUV collector and liquid-target delivery system is described. We also report on dose stability, plasma position stability and EUV distribution at the output region of the source. This presentation reviews the experimental results obtained on systems with a focus on the topics most critical for an HVM source.
The capability to scale LPP power by further development of the high power CO2 drive laser in order to increase duty cycle and duration of continuous light source operation is shown. Production systems with thermal management and capable of 5 sr light collection are being assembled and tested. A description of the development of a normal-incidence ellipsoidal collector is included. Improvements in substrate quality lead to increased EUV reflectance of the mirror. Results on the generation of liquid tin droplets as target material for efficient plasma generation are also described. The droplet generator serves as a key element in the precise and spatially stable delivery of small quantities of liquid tin at high repetition rates. We describe a protection module at the intermediate focus (IF) region of the source and imaging of the EUV distribution using a sub-aperture collector and a fluorescent screen. A path to meet requirements for production scanners planned well into the next decade is also presented.
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.
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, mass-limited droplet generation, laser-to-droplet targeting control, and system use and experience. The results from full-scale prototype systems are presented. In addition, several smaller lab-scale experimental systems have also been constructed to test specific physical aspects of the light sources. This report reviews the latest experimental results obtained on these systems with a focus on the topics most critical for a source intended for use in high volume manufacturing (HVM). LPP systems have been developed for light-sources applications to enable EUV scanners for optical imaging of circuit features at nodes of 32 nm and below on the international technology roadmap for semiconductors (ITRS). LPP systems have inherent advantages over alternate source types, such as discharge produced plasmas (DPP), with respect to power scalability, source etendue, collector efficiency, and component lifetime. The capability to scale EUV power with laser repetition rate and pulse energy is shown, as well as the modular architecture for extendability. In addition, experimental results of debris mitigation techniques and witness sample lifetime testing of coated multi-layer-mirrors (MLM) are described and used to support the useful lifetime estimation of a normal incidence collector. A roadmap to meet requirements for production scanners planned well into the next decade is also presented.
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 source output power and the collector optics lifetime have been identified as critical key issues for EUV lithography. In order to meet these requirements a heated collector concept was realized for the first time. An ellipsoidal collector substrate with an outer diameter of 320 mm was coated with a laterally graded high-temperature multilayer. The interface-engineered Mo/Si multilayer coating was optimized in terms of high peak reflectivity at 13.5 nm and a working temperature of 400 °C. Barrier layers were introduced on both interfaces to block thermally induced interdiffusion processes of molybdenum and silicon to provide long-term optical stability of the multilayer at elevated temperatures. A normal-incidence reflectance of more than 40 % at 13.55 nm was measured after heating. After initial annealing at 400 °C for one hour, no degradation of the optical properties of these multilayer coatings occurred during both long-term heating tests for up to 100 hours and multiple annealing cycles. The successful realization of this high-temperature sub-aperture collector mirror represents a major step towards the implementation of the heated collector concept and illustrates the great potential of high-temperature EUV multilayer coatings.
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.
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.
Efficient conversion of laser light into EUV radiation is one of the most important problems of the laser-produced plasma (LPP) EUV source. Too low a conversion efficiency (CE) increases the amount of power the drive laser will have to deliver, which, besides the obvious laser cost increase, also increases the thermal load on all the components and can lead to increased debris generation. In order to meet the requirements for a high-volume manufacturing (HVM) tool and at the same time keep the laser power requirements within acceptable limits, a CE exceeding 2.5% is likely to be required. We present our results on optimizing conversion efficiency of LPP EUV generation. The optimization parameters include laser wavelength, target material, and laser pulse shape, energy and intensity. The final choice between parameter sets that leads to the required minimum CE is dependent on the debris mitigation solutions and the laser source available for a particular parameter set.
Now that 1000 Hz KrF excimer laser based DUV lithography tools are firmly established in production, emphasis is shifting from development towards improving the productivity and profitability of the manufacturing process, thereby reducing the cost per wafer. In this arena, laser manufacturers are competing now not only on performance but also on cost and productivity enhancements that the laser can offer to the lithography process.
The use of higher NA lenses and higher throughput of the next generation 248 nm microlithography systems sets tight requirements on the spectral properties of the laser as well as its power output and dose stability. We demonstrate that such scaling of spectral widths, power and repetition rates is possible by revisiting some of the dynamics of evolution of laser spectrum and stability of laser discharge. In the following, we present results of several optical configurations, that result in spectral widths between 1.0 and 2.0 pm (95% integrated linewidth). The optical configurations are derivatives of Cymer's standard Littrow grating and prism expander configuration. Thereby, the other parameters (beam size, coherence, etc.) are not impacted. Simultaneously, we provide results of scaling a laser to 2 kHz with a dose stability of less than plus or minus 0.5% over a 16 ms window. The resulting laser is now capable of meeting the technical requirements of the next generation microlithography scanners.
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