Wayne J. Dunstan

Performance optimization of MOPA pre-pulse LPP light source

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.

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.

Active spectral control of DUV light sources for OPE minimization

The variation of CD with pitch, or Optical Proximity Effect (OPE), in an imaging system shows a behavior that is characteristic of the imaging and process conditions and is sensitive to variations in those conditions. Maintaining stable process conditions can improve the effectiveness of mask Optical Proximity Correction (OPC). One of the factors which affects the OPE is the spectral bandwidth of the light source. To date, passive bandwidth stabilization techniques have been effective in meeting OPE control requirements. However, future tighter OPE specifications will require advanced bandwidth control techniques. This paper describes developments in active stabilization of bandwidth in Cymer XLA and 7010 lasers. State of the art on board metrology, used to accurately measure E95 bandwidth, has enabled a new array of active control solutions to be deployed. Advanced spectral engineering techniques, including sophisticated control algorithms, are used to stabilize and regulate the bandwidth of the light source while maintaining other key performance specifications.

Increased availability of lithography light sources using advanced gas management

Increasing throughput demands on leading edge scanners are requiring greatly improved light source availability. This translates directly to minimizing downtime and maximizing productive time, as defined in the SEMI E10 standard. One positive contributor to improving productive time is the minimization of the light source stoppage for entire Halogen gas replenishment. This paper describes availability improvements of Cymer XLA and 7000 series light sources by using advanced gas management schemes to minimize entire gas replenishment impact to productive time. Recent augmented gas control algorithms have demonstrated multiple times extension of gas life through advanced gas replenishment methods and higher performance estimators. Along with these improvements to gas management, major efforts in light source fault reduction, module lifetime extension and optimization of module replacement, will provide significantly increased combined light source\scanner availability.

Performance Demonstration of Significant Availability Improvement in Lithography Light Sources using GLX Control System

Increasing productivity demands on leading-edge scanners require greatly improved light source availability. This translates directly to minimizing downtime and maximizing productive time, as defined in the SEMI E10 standard. Focused efforts to achieve these goals are ongoing and Cymer has demonstrated significant improvements on production light sources. This paper describes significant availability improvements of Cymer light sources enabled by a new advanced gas management scheme called Gas Lifetime eXtensioTM (GLTM) control system. Using GLX, we have demonstrated the capability of extending the pulse-based interval between full gas replenishments to 1 billion pulses on our XLA light sources, as well as significant extension in the time-based interval between refills. This represents a factor of 10X increase in the maximum interval between full gas replenishments, which equates to potential gain of up to 2% in productive time over a year for systems operating at high utilization. In this paper, we provide performance data on extended (1 billion pulse) laser operation without full gas replenishment under multiple actual practical production environments demonstrating the ability to achieve long gas lives with very stable optical performance from the laser system. In particular, we have demonstrated that GLX can provide excellent stability in key optical performance parameters, such as bandwidth, over extended gas lives. Further, these stability benefits can be realized under both high and low pulse accumulation scenarios. In addition, we briefly discuss the potential for future gas management enhancements that will provide even longer term system performance stability and corresponding reductions in tool downtime.

CO2/Sn LPP EUV sources for device development and HVM

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.

Lithography line productivity impact using Cymer GLX technology

Leading-edge scanners in fabs worldwide have particularly high system utilization and require peak levels of system throughput and availability. Laser gas exchanges typically occur daily on these systems (or every 100M pulses or less), with each exchange lasting up to 20 minutes. This downtime has a direct negative effect on availability, and if it is reduced, the productivity of the litho cell increases. This paper will outline the immediate success fabs have experienced after equipping scanners with Cymers Gas Lifetime eXtension (GLXTM) technology, which increases scanner availability by extending the time between excimer laser gas exchanges by a factor of more than 10. To date, more than 100 leading-edge scanners feature Cymers GLX technology, which has improved light source availability by more than 1.5 percent. Moreover, multiple chipmakers report more than 2 percent improvement in litho cell productivity due to GLX, corresponding to 2000 wafers/month increase for a 100,000 wafers/month fab. The increase in measured productivity is the leveraged benefit of reducing process interruptions around the refill cycle GLX technology extends the shot-based interval between gas refills to 1 billion pulses for Cymers XLA light sources, and provides excellent stability in key optical performance parameters, such as bandwidth and dose stability over the entire gas life. This paper will provide extensive performance data during extended light source operation on litho cells equipped with GLX technology, and multiple use scenarios will be examined, including usage at memory and logic fabs. The paper will also discuss the performance of GLX2TM technology which further extends the maximum time between light source gas exchanges from 1B pulses to 2B pulses, and reduces downtime associated with gas refills by a factor of 20. The stability and productivity benefits of this new technology can be realized under all light source utilization scenarios. With GLX2, the refill interval at high utilization chipmakers is 3 weeks, and 4-8 weeks at lower utilization customers. Metrics illustrating the success of each of these capabilities will be presented. The second-generation of GLX technology was launched in July 2008 after chipmakers responded favorably to GLX performance metrics.

High power EUV LPP

Laser produced plasma (LPP) systems are the leading approach for extreme-ultra-violet (EUV) lithography of circuit features at sub-20nm nodes. This paper reviews technology and development progress for high-power sources optimized for EUV lithography. Article not available.

Lithography light source fault detection

High productivity is a key requirement for todays advanced lithography exposure tools. Achieving targets for wafers per day output requires consistently high throughput and availability. One of the keys to high availability is minimizing unscheduled downtime of the litho cell, including the scanner, track and light source. From the earliest eximer laser light sources, Cymer has collected extensive performance data during operation of the source, and this data has been used to identify the root causes of downtime and failures on the system. Recently, new techniques have been developed for more extensive analysis of this data to characterize the onset of typical end-of-life behavior of components within the light source and allow greater predictive capability for identifying both the type of upcoming service that will be required and when it will be required. The new techniques described in this paper are based on two core elements of Cymers light source data management architecture. The first is enhanced performance logging features added to newer-generation light source software that captures detailed performance data; and the second is Cymer OnLine (COL) which facilitates collection and transmission of light source data. Extensive analysis of the performance data collected using this architecture has demonstrated that many light source issues exhibit recognizable patterns in their symptoms. These patterns are amenable to automated identification using a Cymer-developed model-based fault detection system, thereby alleviating the need for detailed manual review of all light source performance information. Automated recognition of these patterns also augments our ability to predict the performance trending of light sources. Such automated analysis provides several efficiency improvements for light source troubleshooting by providing more content-rich standardized summaries of light source performance, along with reduced time-to-identification for previously classified faults. Automation provides the ability to generate metrics based on a single light source, or multiple light sources. However, perhaps the most significant advantage is that these recognized patterns are often correlated to known root cause, where known corrective actions can be implemented, and this can therefore minimize the time that the light source needs to be offline for maintenance. In this paper, we will show examples of how this new tool and methodology, through an increased level of automation in analysis, is able to reduce fault identification time, reduce time for root cause determination for previously experienced issues, and enhance our light source performance predictability.