David W. Myers

LPP EUV source development for HVM

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.

LPP source system development for HVM

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.

Laser produced plasma light source for EUVL

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.

EUV source collector

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.

Laser produced plasma EUV sources for device development and HVM

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-100s of hours.

Laser-produced plasma source system development

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.

Laser produced plasma EUV light source for EUVL patterning at 20nm node and beyond

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..

Development of stable extreme-ultraviolet sources for use in lithography exposure systems

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.

LPP EUV source readiness for NXE 3300B

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.

Light sources for EUV lithography at the 22-nm node and beyond

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.