In this presentation, the authors will review the next generation light source with improvement in speckle reduction for improved device performance yield in next generation device nodes. Further improvements in local critical dimension uniformity (LCDU) from improvement optics that significantly reduces speckle. Overall system availability continues to increase due to significant improvements in module lifetimes which continue to contribute to productivity improvements. We continue to focus on reducing the environmental impact through the reduction and eventual elimination of helium gas which reduces supply issue risks. Lastly, we continue to focus on technology improvements that reduces energy consumption to reduce cost and ecological impact.
Over the years, lithography engineers have continued to focus on CD control, overlay and process capability to meet node requirements for yield and device performance. The use of ArFi lithography for advanced process nodes demands challenging patterning budget improvements in the sub-nm range.1 In 3D NAND devices, the height differences between the cell and periphery create issues with the ability to adequately image and maintain a useable process window in both regions. Previous work by Fukuda2 developed a multi-exposure technique at multi-focus positions to image contact holes with adequate DOF. Lalovic3 demonstrated a fixed 2 wavelength technique to improve DOF called RELAX. ASML introduced EFESE Rx, a method of tilting the stage during exposure to create multiple focus positions and finally Lalovic4 introduced a broadband laser solution to provide additional DOF. All of these techniques suffered from a number of problems that limited usability.
In this work the authors will introduce a new method to increase DOF through alternating wavelength’s from an ArFi light source. This technique, called MFI (multi-focal imaging), can be tuned specifically to provide the required amount of wavelength separation for a specific DOF need.
Two focal positions are created that are averaged over the exposure field. The authors will review this wavelength “dithering” approach which can be turned on and off, thus eliminating any potential scanner calibration issues. Initial simulation studies with a fixed source and mask indicated increased DOF with wavelength separation. These DOF improvements have been confirmed with on-wafer single-exposure data. The Tachyon MFI aware engine flow will be reviewed using several customer use cases that have been analyzed to demonstrate maximum DOF and ILS vs wavelength separation. The authors will also review the optimization of new pupils and OPC solutions that are unique with each wavelength separation case and maximize process capability. The presentation will close with a product availability timeline and roadmap.
DUV ArF immersion lithography requires patterning budget improvements in the range of 1/10 nm especially for interconnect layers for advanced process nodes. As every angstrom counts, the Cymer XLR 860ix light source has been developed to deliver the performance required for multiple patterning processes across all sectors: DRAM, 3D NAND, and logic. This paper will describe how imaging margins can be increased by optimizing light source bandwidth settings. Advancements include new hardware and software that enable industry leading bandwidth performance and control. In addition, on-wafer measurements were collected showing the progressive improvements gained with lowering bandwidth on an existing mask.
As system availability is a key enabler for chipmakers, the introduction of this new DUV light source includes improvements that continue to improve productivity by increasing service intervals by >30% while also providing sustainability enhancements.
In response to significant neon supply constraints, Cymer has responded with a multi-part plan to support its customers. Cymer’s primary objective is to ensure that reliable system performance is maintained while minimizing gas consumption. Gas algorithms were optimized to ensure stable performance across all operating conditions.
The Cymer neon support plan contains four elements: 1. Gas reduction program to reduce neon by >50% while maintaining existing performance levels and availability; 2. short-term containment solutions for immediate relief. 3. qualification of additional gas suppliers; and 4. long-term recycling/reclaim opportunity. The Cymer neon reduction program has shown excellent results as demonstrated through the comparison on standard gas use versus the new >50% reduced neon performance for ArF immersion light sources. Testing included stressful conditions such as repetition rate, duty cycle and energy target changes. No performance degradation has been observed over typical gas lives.
As chipmakers continue to reduce feature sizes and shrink CDs on the wafer to meet customer needs, Cymer continues developing light sources that enable advanced lithography, and introducing innovations to improve productivity, wafer yield, and cost of ownership. In particular, the ETC controller provides improved spectral bandwidth and wavelength stability, which enables superior CD control and wafer yield for the chipmaker. This controller is a key technology in Cymer’s XLR 700ix and DynaPulseTM products. Last year we reported that the XLR 600ix incorporates new controller technology called ETC for improvements in spectral bandwidth and wavelength stability. The Authors will present metrics demonstrating the performance and stability of systems that have been installed at chipmaker sites over the last year.
Semiconductor market demand for improved performance at lower cost continues to drive enhancements in excimer light source technologies. Multi-patterning lithography solutions to extend deep-UV (DUV) immersion have driven requirements such as higher throughput and higher efficiencies to maximize the utilization of leading-edge lithography equipment. Three key light source parameters have direct influence on patterning performance – energy, wavelength and bandwidth stability – and they have been the primary areas of continuous improvement. With 14nm node development, a number of studies have shown the direct influence of bandwidth stability on CD uniformity for certain patterns and geometries, leading to the desire for further improvements in this area. More recent studies also examined the impact of bandwidth on 10nm logic node patterning [1]. Alongside these drivers, increasing cost per patterning layer continues to demand further improvements in operating costs and efficiencies from the lithography tools, and the light source can offer further gains in these areas as well. This paper introduces several light source technologies that are embodied in a next-generation light source, the Cymer XLR® 700ix, which is an extension of the ring laser architecture introduced 8 years ago. These technologies enable a significant improvement in bandwidth stability as well as notable reductions in operating costs through more efficient gas management algorithms and lower facilities costs.
As chipmakers continue to reduce feature sizes and shrink CDs on the wafer to meet customer
needs, Cymer continues developing light sources that enable advanced lithography, and
introducing innovations to improve productivity, wafer yield, and cost of ownership. In
particular, the architecture provides dose control and improved spectral bandwidth stability,
both of which enables superior CD control and wafer yield for the chipmaker.
The XLR 660ix incorporates new controller technology called ETC for improvements in spectral
bandwidth stability, energy dose stability, and wavelength stability. This translates to improved
CD control and higher wafer yields. The authors will discuss the impact that these
improvements will have in advanced lithography applications.
Semiconductor market demand for improved performance at lower cost continues to drive enhancements in excimer
light source technologies. Increased output power, reduced variability in key light source parameters, and improved
beam stability are required of the light source to support immersion lithography, multi-patterning, and 450mm wafer
applications in high volume semiconductor manufacturing. To support future scanner needs, Cymer conducted a
technology demonstration program to evaluate the design elements for a 120W ArFi light source. The program was
based on the 90W XLR 600ix platform, and included rapid power switching between 90W and 120W modes to
potentially support lot-to-lot changes in desired power. The 120W requirements also included improved beam
stability in an exposure window conditionally reduced by 20%. The 120W output power is achieved by efficiency
gains in system design, keeping system input power at the same level as the 90W XLR 600ix. To assess system to
system variability, detailed system testing was conducted from 90W – 120W with reproducible results.
Reducing lithography pattern variability has become a critical enabler of ArF immersion scaling and is required to ensure consistent lithography process yield for sub-30nm device technologies. As DUV multi-patterning requirements continue to shrink, it is imperative that all sources of lithography variability are controlled throughout the product life-cycle, from technology development to high volume manufacturing. Recent developments of new ArF light-source metrology and monitoring capabilities have been introduced in order to improve lithography patterning control.[1] These technologies enable performance monitoring of new light-source properties, relating to illumination stability, and enable new reporting and analysis of in-line performance.
Demand for increased semiconductor device performance at low cost continues to drive the requirements for shrinking the geometry of features printed on silicon wafers. Argon fluoride (ArF) excimer laser systems operating at 193 nm and producing high output power played a key role in patterning of the most advanced features for high volume deep ultraviolet (DUV) lithography over the last decade. Lithographic patterning has progressed from ArF dry to ArF immersion (ArFi) to double and multiple patterning applications, with increasingly tight requirements for the quality of light at 193 nm and improved system reliability. This drove the transition from single chamber laser systems to dual chamber systems with ring cavity amplifier architectures. We are presenting a flexible 90-120W ArFi excimer laser system, developed for high volume multiple patterning manufacturing as well as 450mm wafer applications. Light source design is based on dual-chamber architecture with ring cavity power amplifier.
In order to improve process control of the lithography process, enhanced On-board metrology, measuring of the light
source beam parameters with software solutions for monitoring, reporting and analyzing the light source's performance
has been introduced.
Multiple lasers in the field were monitored after installing of a new On-board metrology product called SmartPulse. It
was found that changes in beam parameters can be significantly reduced at major module change service events when
new service procedures and On-board metrology were used, while significant beam parameter shift and illumination
pupil changes were observed when On-board metrology was not available at service events, causing lengthy scanner
illumination pupil recalibration.
SmartPulseTM software from Cymer Inc. was used to monitor the variation of light source performance parameters,
including critical beam parameters, at wafer level resolution. Wafer CD was correlated to the recorded beam parameters
for about a month of operation, and both wafer CD and beam parameters showed stable performance when the light
source was operating at optimal conditions.
At high-utilization lithography sites, laser light source gas replenishments and gas maintenance operations typically
require between 9 and 16 hours per year, during which the light source is unavailable for production. Reducing this
downtime is important for increasing the productivity of the lithography cell. Light sources also require intermittent gas
maintenance that must be performed manually and therefore can be subject to variability in duration and repeatability.
This paper will outline the targeted improvements in availability achieved by equipping the light source with Cymer's
iGLXTM Gas Management System. The iGLX System extends the pulse-based interval between gas refills to 4 billion
pulses for Cymer's XLA-series and XLR-series light sources, while maintaining existing performance. Additionally, the
iGLX System automates some gas maintenance events that were previously manual, improving their speed and reducing
variability. This paper will provide some performance data during extended light source operation on lithography cells
equipped with the iGLX System.
For high-utilization lithography cells, the iGLX System can reduce gas maintenance related downtime by up to 75%,
increasing light source availability up to 12 hours per year. Total halogen gas usage can also be reduced by up to 16%,
and manual gas maintenance events can be eliminated.
The iGLX System has been installed on multiple high-volume scanner systems, which experienced these improvements
immediately, and are continuing to operate nominally. As the iGLX System is deployed in volume, additional
availability improvements can be realized by more readily synchronizing other lithography line maintenance events with
gas replenishment events.
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