EUVL

Even for someone who has been in this industry since the days of the TI Datamath 4-function calculator and the TMS1100 4-bit microcontroller (yes, that’s been a LONG time – the movie Grease premiered the same year!), it is sometimes hard to grasp the scope and complexity of what happens in today’s leading-edge semiconductor gigafabs. In fact, the only way to comprehend the enormous volume of transactions that occur is to consider what happens in a single minute – this is illustrated in the infographic we have labeled “The Gigafab Minute.”* It’s amazing enough to think that a single factory can start 100,000 wafers every month on their cyclical journey through 1500 process steps… and have 99%+ of them emerge 4 months later to be delivered to packaging houses and then on to waiting customers. It’s quite another to realize that all of this happens continuously (24 x 7) and automatically. “How is this possible?” you ask.Well, a big part of the solution is the body of SEMI standards which have evolved since the early 80s to keep pace with the ever-changing demands of the industry. From an automation standpoint, many of these standards deal with the communications between manufacturing equipment and the factory information and control systems that are essential for managing these complex, hyper-competitive global enterprises.A significant characteristic of these standards is that they have been carefully designed to be “additive.” This means that new generations of SEMI’s communications standards do not supplant or obsolete the previous generations, but rather provide new capabilities in an incremental fashion. To appreciate the importance of this in actual practice, consider how the GEM, GEM300, and EDA/Interface A standards support the transactions that occur in a single Gigafab Minute.Starting at 1:00 o’clock on the infographic and moving clockwise, you first notice that 2.31 wafers enter the line. Of course, these are actually released in 25-wafer 300mm FOUPs (Front-Opening Unified Pod), but 100K wafers per month translates to 2.31 per minute. Since these factories run continuously, once the line is full, it stays full. And with an average total cycle time of 4 months, this means that there are 400K wafers of WIP (work in process) in he factory at any given time. This number, and the total number of equipment (5000+), drive the rest of the calculations.GEM (Generic Equipment Model) – SEMI E30, etc.The GEM messaging standards were initially defined in the early 90s to support the factory scheduling and dispatching applications that decide what lots should go to what equipment, the automated material handling systems that deliver and pick-up material to/from the equipment accordingly, the recipe management systems that ensure each process step is executed properly, and the MES (Manufacturing Execution System) transactions that maintain the fidelity of the factory system’s “digital twin.”Every minute of every day, GEM messages support and chronicle the following activities: 240 process steps are completed (i.e., 240 25-wafer lots are processed), 300 recipes are downloaded along with a set of run-specific adjustable control parameters, and 600 FOUPs are moved from one place to another (equipment, stockers, under-track storage, etc.). For each of these activities, the factory’s MES is notified instantaneously.GEM300 – SEMI E40, E87, E90, E94, E157With the advent of 300mm manufacturing in the mid-to-late 90s, a global team of volunteer system engineers from the leading chip makers defined the GEM300 standards to support fully automated manufacturing operations. Starting at 5:00 o’clock on the infographic, the number of transactions per minute jumps almost 3 orders of magnitude, from the monitoring of 900 control jobs across 4000 process tools to the tracking of 360,000 individual recipe step change events. This level of event granularity is essential for the latest generation of FDC (Fault Detection and Classification) applications, because precise data framing is a key prerequisite for minimizing the false alarm rate while still preventing serious process excursions. In this context, more than 6000 recipe-, product- and chamber-specific fault models may be evaluated every minute.Simultaneously, the applications that monitor instantaneous throughput to prevent “productivity excursions” and identify systemic “wait time waste” situations depend on detailed intra-tool wafer movement events. In a fab with hundreds of multi-chamber, single-wafer processes, 75,000 or more of these events occur every minute. EDA (Equipment Data Acquisition) – SEMI E120, E125, E132, E134, E164, etc.Rounding out the SEMI standards in our example gigafab is the suite of EDA standards which complement the command and control functions of GEM/GEM300 with flexible, high-performance, model-based data collection. The EDA standards enable the on-demand collection of the volume and variety of “big data” required from the equipment to support the advanced analysis, machine learning, and other AI (Artificial Intelligence) applications that are becoming increasingly prevalent in leading semiconductor manufacturers. As EUV (Extreme Ultraviolet) lithography moves from pilot production to high-volume manufacturing at the 7nm process node and beyond, the litho process area will become a major source of process data by itself, generating 10 GB of data every minute. This is in addition to the 100 GB of data collected from other process areas. The End ResultThe final wedge (12:00 o’clock) in our infographic highlights the real objective – which is producing the millions of integrated circuits that fuel our global economy and provide the technologies that are an integral part of our modern way of life. Assuming a nominal die size of 50 square mm (typical of an 8 GB DRAM), the 2.31 wafers we started at 1:00 o’clock result in almost 3200 individual chips. But none of this would be possible without the pervasive factory automation technology we now take for granted. So, as you finish reading this posting on whatever device you happen to be using, take a micro-moment to acknowledge and thank the hundreds of standards volunteers whose insights and efforts made this a reality!You may not be responsible for running a gigafab anytime soon, but the SEMI standards used in this setting are no less applicable to any Smart Manufacturing environment. Give us a call if you’d like to know more about how these technologies can benefit your operations for many years to come.Alan Weber is Vice President, New Product Innovations, at Cimetrix Incorporated. Previously he served on the Board of Directors for eight years before joining the company as a full-time employee in 2011. Alan has been a part of the semiconductor and manufacturing automation industries for over 40 years. He holds bachelor’s and master’s degrees in Electrical Engineering from Rice University. For more information on SEMI Standards, please click here.

The Advanced Lithography TechXPOT at this year’s SEMICON West will explore progress in extreme ultraviolet lithography (EUVL), its economic viability for high-volume manufacturing (HVM) and other lithography solutions that will address the march to 5nm and onward to 3nm.As a prelude to the event, SEMI asked Neeraj Khanna, Global Head of the Patterning Customer Engagement Team at KLA-Tencor, a speaker at the TechXPOT, for insights about the readiness of inspection and metrology tools for EUVL applications at 5nm and 3nm. For a full list of speakers and program agenda, visit http://www.semiconwest.org/programs-catalog/lithography-5nm-and-below.Neeraj Khanna, Global Head of the Patterning Customer Engagement Team at KLA-TencorSEMI: In general, how would you characterize the readiness of inspection and metrology tools intended for EUVL applications at 5nm and 3nm? In particular, what are some of the remaining research and development challenges that need to be addressed for each of these nodes?Neeraj Khanna: KLA-Tencor is working closely with its customers to qualify and ramp EUV. Our suite of inspection, metrology and data analytic solutions are being implemented to enable EUV infrastructure readiness including, for example, new reticle and resist qualification, scanner qualification, and EUV ramp preparation. These EUV integration activities require process control systems that support a wide range of applications, including hotspot discovery, lithography modeling, focus/dose process window qualification, reticle print check, mask blank inspection, and process and tool monitoring.As with any major technology inflection, it is critical to understand sources of process variation to enable ramp at optimal yield. For example, stochastics result in random pattern variations, which have a major impact on EUV yield. To manage stochastics, IC manufacturers are deploying process control solutions that support fast modeling of stochastic variations coupled with high-sensitivity, high-coverage wafer defect inspection. Another example is a methodology called hybrid scanner utilization whereby, when EUV scanners are implemented in production, they will only be used for a few layers, while all other layers will be patterned with 193i scanners. This technique requires tighter control and monitoring of overlay budgets.SEMI: How are you able to achieve this tighter control and monitoring?NK: To understand why hybrid scanner utilization requires tighter control and monitoring of overlay budgets, it’s important to outline how this differs from current scanner implementation. For critical layers in current process flows using 193i lithography, pattern layers for a given wafer are printed using the same stage/chuck on the same scanner. The overlay performance achieved using this lithography strategy is called dedicated chuck overlay (DCO). Use of a dedicated scanner and chuck for lithography reduces inter-scanner and inter-chuck distortion effects, resulting in DCO overlay error of less than 1nm. When EUVL is first implemented in production, it will be used for a few layers – likely, cut masks and contacts with eventual migration to metal 1 layers. All other layers will be patterned with 193i scanners. This hybrid scanner operation eliminates any possibility of using a dedicated scanner and dedicated chuck to support tight overlay performance specifications. Instead, fabs will be forced to optimize mix-and-match overlay (MMO), with the overlay performance obtained using different scanners for printing different layers on a given wafer.With overlay specifications for advanced DRAM and logic at ~2.5nm, fabs will need to implement strict 193i-to-EUV scanner matching strategies or risk consuming 60 to100 percent of the overlay budget on just MMO. To achieve tighter overlay control and monitoring required for MMO, fabs need to implement dense, in-field overlay error measurements that feed into scanner fleet management systems. KLA-Tencor’s ATL™ overlay metrology system supports a high measurement speed and the use of small in-die targets, enabling dense in-field overlay measurements with high accuracy. Our 5D Analyzer® data analytic and management system includes scanner fleet management capability that enables automatic product-based corrections to minimize MMO error, helping fabs reduce the risk to yield loss associated with a 193i-EUV mixed scanner implementation. SEMI: What other challenges do you see coming to the fore at 5nm and 3nm?NK: Overall, the 5nm and beyond design nodes will face challenges associated with new lithography technology, potential new device structures and smaller pattern pitches. IC manufacturers will require process control solutions that not only identify process windows, but also monitor patterning parameters and defectivity at multiple points to identify process shifts. To monitor dynamic processes at these advanced nodes, inspection and metrology tools will need to have both sensitivity to critical parameters/defects and robustness to process variation in order to provide IC engineers with smart feedback for efficient control of their processes.SEMI: Could you elaborate on what will be required to monitor patterning parameters and defectivity at multiple points? How different will the techniques be at 5nm/3nm vs. at say, 7nm or 10nm?NK: As an example of monitoring at multiple points, consider the transition to EUV lithography. With EUV, the cost per scan goes up dramatically. Thus, IC manufacturers will monitor parameters at multiple points to maximize yield and minimize risk: EUV reticle qualification requires inspection and metrology throughout the entire flow from mask blank manufacturing, to the mask shop, to the IC fab. For the advanced design nodes associated with EUV, wafer qualification requires monitoring and control of wafer defectivity, shape and geometry throughout the wafer manufacturing process. It also requires control of fab incoming wafer qualification while ensuring that fab-wide processes are meeting defect and shape standards necessary for printing smaller feature sizes. EUV resist characterization and qualification requires comprehensive lithography simulation, wafer defect inspection, and film thickness and uniformity measurements to help reduce development time and prepare the litho stacks for production ramp. As EUV scanners are ramping, fabs are faced with finding any unknown particle sources within the new scanner chambers. This situation is driving the need for tighter and more frequent PWP (particles per wafer pass) chamber monitors to ensure scanner cleanliness. In addition, EUV scanner qualification requires reticle front and backside particle checks, and hotspot discovery and process window qualification using optical wafer defect inspection and e-beam review. EUV process monitoring encompasses overlay error monitoring, focus/dose monitoring, critical dimension (CD) and 3D device shape monitoring, and continuous process window monitoring. EUV inline defect monitoring and tool monitoring is important for reducing baseline defectivity in the litho cell for faster ramp, and for early identification of litho excursions in production. A critical part of this monitoring strategy is inline after develop inspection (ADI) monitoring, which is defect inspection on patterned wafers after printing and development of the resist ADI. Inline ADI innovations that find yield-critical defects allow fabs to reduce process issues, prevent at-risk wafers early in the process, and enable rework when excursions are found in production. As with past technology transitions, the implementation of multiple monitoring steps as part of a comprehensive process control strategy will be critical for a fab’s successful ramp of EUV.Debra Vogler, SEMI

What’s next for smarter, more connected electronics manufacturing - Part 2The fast-maturing infrastructure now enabling applications for big data and artificial intelligence means disruptive change not just at individual companies but also in data connections among companies across the microelectronics manufacturing value chain. SEMI checked in with some leading players on the changes they see coming in the next several years for this article series. The trade group is expanding its programming on smart manufacturing to address these industry-wide developments at SEMICON West, July 10-12 in San Francisco.“The ramp of EUV, and the smaller geometries and smaller process margins, will drive an exponential increase in the amount of metrology data to manage,” says Neal Callan, ASML vice president, Silicon Valley. Callan notes that moving to multibeam e-beam inspection will increase data volume from megabytes per second to gigabytes per second and from thousands of data points to millions of data points. “The process is so tight and the margin so small that stochastic variation, or noise, becomes more dominant – at least it’s noise until we can learn to understand and control it. And understanding and controlling this variation will be key to delivering 5nm patterning,” he says.Single-beam e-beam inspection is already driving large increases in data as engineers extend the slow technology to broad, high-speed defect metrology applications by more intelligently instructing the system where to look for problems. Callan says ASML is now using the scanner data on wafer focus, alignment and leveling. The company is also using the computational lithography model from the design to identify the smallest process windows in the pattern that are most likely to see problems. The model then quantifies the number and significance of those instances.“The collection of all this diverse data means that tools will need to be plug-and-play so all tool data is instantly available to all systems and software,” says Doug Suerich, PEER Group product evangelist. “We need tools that can be discovered automatically by the network so it can start slurping up data immediately. The adoption of the Interface A (EDA) standard is accelerating and fabs are starting to ask for it. The proliferation of sensors also needs to self-discover. If you are going to add thousands of new sensors into a facility, you can’t afford a time-consuming integration process.”“We are now seeing that engineers are greedy for more data – if they can get the data, it’s becoming a need-to-have,” adds Tom Ho, BISTel America president. “Getting more data from more sensors, from the sensors on the tool that are not being fully utilized, and from untapped data sources like vibration is another big coming opportunity.” Process complexity drives demand for feed-forward between silos with computational models ASML co-optimizes its scanner process with etch and reticle process steps. Source: ASML In addition to the drive for trace-back of data, the increasing complexity of interrelated processes is also driving demand for feed-forward of data. “Feed-forward is becoming more important,” notes Ho. He points to the example of 3D NAND features, now getting so deep that identifying the layer being measured is a challenge unless the signal at the step before can be recognized. “We need partnerships with our peers to understand how to take advantage of the sensors they use, integrate them with our data, and then feed-forward corrections to the other systems,” concurs Callan. “To drive the best CD uniformity and overlay, we need to co-optimize litho and etch,” agrees Henk Niesing, ASML director of product management. He notes that the company is working with etcher makers to measure the overlay and CD, decompose the finger prints, and then use models to steer automated control that best adjusts both the scanner and the etcher. ASML is also working with Zeiss on co-optimization between the scanner and the reticle to make even higher-order corrections by locally modifying the reticle.These higher-order corrections, applied on each exposed field, drive the need for even more data, and at higher speed but without higher cost, notes Jan Mulkens, ASML senior fellow. These corrections increase demand for computational metrology, which combines various metrology sources with physics and deep learning models trained on real data to predict and control process results in real time. “We’re working on computational metrology to ideally use all the knobs we have in the fab,” he says. So far this effort has largely involved linking data between two companies. More consistent data formats would enable data exchange to be extended to more companies. “The software versions also need to be managed for upgrades so they still match after one party updates the system on its tool,” notes Niesing. Speakers on these issues of smart manufacturing and data handling at SEMICON West include Active Layer Parametrics, Applied Materials, Applied Research Photonics, ASML, Cimetrix, Coventor, ECI Technologies, Edwards Vacuum, Final Phase Systems, GE Digital, Infineon, Jabil, Lam Research, Osaro, Otosense, PEER Group, Rockwell Automation, Rudolph Technologies, Schneider Electric, Seagate, Seimens, Stanford University, TEL, TIBCO Software. See semiconwest.org.What’s next for smarter, more connected electronics manufacturing - Part 1What’s next for smarter, more connected electronics manufacturing - Part 3Paul Doe, SEMI

The Advanced Lithography TechXPOT at this year’s SEMICON West will explore progress in extreme ultraviolet lithography (EUVL), its economic viability for high-volume manufacturing (HVM) and other lithography solutions that will address the march to 5nm and onward to 3nm.As a prelude to the event, SEMI asked Mary Ann Hockey, director for Advanced Emerging Lithography at Brewer Science Inc., and a speaker at the TechXPOT, for insights into the status of directed self-assembly (DSA) as it applies to the industry’s march to patterning for the 3nm node and beyond. For a full list of speakers and program agenda, visit http://www.semiconwest.org/programs-catalog/lithography-5nm-and-below.Mary Ann Hockey, director for Advanced Emerging Lithography at Brewer Science Inc.SEMI: What is the current status of materials development for DSA?Hockey: We are currently working with strategic customers to implement high-quality DSA chemical material solutions. We are both addressing near-term implementation of standard PS-b-PMMA block copolymers (28-30nm Lo) by leveraging our strategic partnership with Arkema, France, and building a library of high-chi block copolymers for long-term device requirements (Figure 1). SEMI: How do those developments prepare the technology for 5nm, 3nm or beyond?Hockey: We have engaged the strategy of engineering a library of novel high-chi block copolymer (BCP) platforms for next-generation DSA technology requirements of 3-5nm devices. One key objective is a global focus on easing implementation into a manufacturing environment. This objective requires large process windows for guided alignment (accommodating pitch and guide size target variability), minimizing BCP microphase anneal times (short anneal time supports high throughput), and streamlining the total number of process steps required for volume production (Figure 2).SEMI: How will industry’s use of DSA be intertwined with immersion lithography?Hockey: We envision immersion lithography as the foundation enabler with strategic use of optical lithography for generating consistent critical dimension (CD) sizes of DSA guides/templates for low cost of ownership.SEMI: What about the combination of DSA and extreme ultraviolet lithography (EUVL) to fabricate devices at 5nm, 3nm, and beyond?Hockey: EUVL and DSA can potentially work in harmony to support next-generation device technology. DSA can be made with the capability of lithography rectification or enhancing EUVL photoresist sidewalls and targeting low line-edge roughness and line-width roughness (LER/LWR) values.Debra Vogler, SEMI

This year’s Advanced Lithography TechXPOT at SEMICON West will explore the progress on extreme ultra-violet lithography (EUVL) and its economic viability for high-volume manufacturing (HVM), as well as other lithography solutions that can address the march to 5nm and onward to 3nm. Several session speakers offered their insights into the readiness of EUVL for 5nm and how other lithography solutions will enable 3nm. See the full list of speakers and program agenda at http://www.semiconwest.org/programs-catalog/lithography-5nm-and-below.Diverging viewpoints on EUVL readiness for 5nmMike Lercel, Director of Strategic Marketing at ASMLASML expects its first customer to start volume manufacturing with EUV at the 7nm logic node and the mid-10nm DRAM node in the 2018/2019 timeframe. “EUV will replace the most difficult layers that require multiple patterning, and many layers will continue to be allocated to immersion tools for the foreseeable future,” said Lercel. “For the 5nm logic node, more layers are expected to migrate to EUV.”Three ASML customers have early-access versions of the next-generation TWINSCAN NXT:2000i for the development of advanced logic and DRAM nodes. “This system delivers 2.0nm cross-matched on-product overlay, achieved through several hardware advancements,” noted Lercel. “It is also significant because this mix-and-match use with EUV features a significantly different hardware platform.” TWINSCAN NXT:2000i features a new alignment sensor and improved wafer table flatness, endurance, and clamping mechanism to enhance matching to EUV.ASML has achieved good industrialization progress of its pellicle, with tests confirming that pellicles can withstand 245W source power and an offline power lifetime test indicating 400W capability. Compared to the 7nm logic node, the requirements for EUV masks will become tighter at 5nm, but Lercel noted that ASML sees good progress with the industry infrastructure to support 5nm in areas such as reducing mask blank defects. “We will continue to improve pellicle transmission for enhanced throughput, but there are no fundamental changes in pellicle requirements for 5-3nm logic nodes. We see no infrastructure showstoppers for the introduction of EUVL at the 5nm node.”Stephen Renwick, Director of Imaging Physics at Nikon Research Corporation of AmericaRenwick said that the 7nm logic node is expected to be fabbed mostly using 193i lithography. “EUV will struggle to be ready for 5nm, limited by yield issues caused by stochastic effects in the resist,” said Renwick. “Ready or not, though, it will be used.” Renwick suggests that introducing multiple-patterning with EUV may be needed but would increase costs. “193i lithography will continue to be used with quadruple-patterning and in combination with other techniques – there is no single solution.”Figure 1. Normalized cost/layer vs. lithography method. SOURCE: Nikon Research Corporation of America When choosing between immersion lithography and EUV for different customer segments at 5nm, Renwick noted that the cost depends on the layer. “Some time ago, we calculated that the costs of either 193i triple-patterning or 193i SADP with two cuts were roughly equal to single-patterning with EUV,” explained Renwick (Figure 1). “That agreed with chipmakers' public estimates and meant that the choice of lithography method depended more on the performance tradeoffs involved, such as 193i's better line-edge roughness. At the 5nm node, we are probably faced with quad-patterning from 193i, double-patterning from existing EUV tools, or single-patterning from as-yet undelivered high-numerical aperture (NA) EUV tools.” Renwick believes that the competition between low-NA EUV double-patterning and 193i quad-patterning will be similar to the current situation (i.e., comparison of 193i triple-patterning or 193i SADP with two cuts vs. single-patterning with EUV), but for high-NA EUV tools he believes it's too early to say.Other challenges Renwick sees on the horizon for EUVL at 5nm are stochastic effects in EUV resists. “They cause yield problems on contact arrays and unacceptable line-edge roughness on line/space patterns,” said Renwick. “It's unlikely that these effects will go away without increasing the litho dose, which will further challenge throughput performance.” He also questions whether EUV pellicles, though under development, will be “ready for prime time.”Harry Levinson, Sr. Director of Strategic Lithography Technology and Sr. Fellow at GLOBALFOUNDRIESLevinson said additional fundamental engineering work is needed to ready EUV lithography for 5nm. “Among the top problems are stochastics-induced resist defects, which increase significantly as dimensions shrink below those for 7nm,” explained Levinson (Figure 2). “Higher exposure doses will be required to address these issues related to stochastics at 5nm, which will require higher source output” (than 7nm).Levinson said there will be greater motivation to use EUVL at the 5nm node vs. at 7nm to offset the large number of exposures associated with 193nm immersion multiple-patterning solutions. “The primary application of EUV lithography at 7nm will be for contact, via and cut layers,” Levinson noted. “It will be important to enable EUVL for metal masks at the 5nm node, which increases the need for an ample supply of very low defect EUV mask blanks.” Levinson added that the 7nm node is already stressing defect inspection capabilities, and no actinic defect inspection system is yet available for patterned masks. “This situation becomes more problematic with widespread application of EUVL to metal layers.” Mask development for 5nmChristopher C. Progler, CTO Strategic Planning at PhotronicsProgler said that the basic infrastructure for delivering EUV masks is available, especially for dark field layers and near in nodes. “The interconnected or more open frame patterns will need refinements to the processes and two to three nodes out will need certain new infrastructure,” said Progler. Overall, the main challenges for initial insertion are about creating a cost-effective and rapid-turn EUV mask process, he said. “The industry can certainly deliver EUV masks in some form. It is more a question of doing it efficiently and productively to match the stated value proposition of EUV over other lithographic methods. We don’t want a pick two of ‘cost, cycle time, capability’ sort of mask solution.” More specifically, Progler explained that after the initial EUV mask development for 5nm focused on contacts and block layers, the major push for N5 switched to delivering single-exposure EUV metal patterning as early as possible. “This has opened some new challenges for masks given the resolution, critical pattern density and tight pitch defect requirements of the re-aggregated single-layer metal mask designs,” said Progler. “For example, on the resolution side, we are accelerating the insertion of higher dose photoresists and also driving patterning module improvements in CD control, mask LER and sidewall angle.” Progler added that at N5, the mask 3D structure itself – including the sidewall – will have a greater impact on lithography because it is tied to stochastic error rates on the wafer.“Reliable, wide-area metrology for some of these 2D and 3D mask parameters is currently hard to come by. We may see an evolution of the blank structure at some point in N5, including hard mask options for pattern stability and expect earlier insertion of EUV mask process correction with model-based hot spot detection and rule checking as well. We also hope mask-scanner dedication is not needed, but there are some indications process sensitivity may push us earlier in this direction.” He added that to reduce metal layer defects, more attention needs to be devoted to advanced repair and model-based validation. “We are, unfortunately, still in a situation of blurry vision and high native defect counts alongside possible in situ contamination during mask changes.” Figure 2. Resist stochastics-induced defects. Graph courtesy of Peter DeBisschop, imec; SOURCE: GLOBALFOUNDRIES Progler pointed out that, with the advent at 5nm, metal masks will require some level of actinic blank inspection for yield, increasing the cost of an already expensive mask technology. “So, unless we want to contend with double and triple photomasks’ starts to deliver a single metal layer, it will be very important to tighten the multi-sensor inspection, defect abatement, and repair loops,” said Progler. He does see some clouds forming around high-volume manufacturing pellicles for metal layers. “This remains an open question, mainly for thermal and materials reasons, not to mention cost and cycle time,” Progler said. “We may be pessimistic, but we do not see an HVM pellicle solution converging in the required timeframe, which means leaning even more on a wafer-level inspection in the validation loop.” He believes that streamlining validation will be a differentiator. “I can imagine one losing most of the EUV cycle time benefits by endlessly circling masks around if this is not done well.” How does the industry get to 3nm? ASML plans to ship its first high-NA EUV prototope/pilot systems between 2020 and 2023 to support 3-2nm process development. “System designs are now being finalized and the platform is starting to come to life,” said Lercel. ASML supplier ZEISS is building a high-NA cleanroom for optics production. ASML believes that EUV, high-NA and DUV systems will be used together at the most advanced nodes and is designing to account for this mixed environment. “As chipmakers drive toward smaller geometries in the most advanced nodes like 3nm, they face unprecedented challenges in devices and materials. This will make the process control requirements even more challenging.” ASML is tackling these challenges with its YieldStar metrology platform, e-beam metrology (HMI) and computational lithography solutions that are designed to expand the process window, enhance process control, and improve patterning defect detection. “This ‘Holistic Lithography’ approach will become increasingly important to ensure throughput and yield at the most advanced nodes.”Levinson said that the issues he projects for 5nm will need to be addressed further at 3nm. “The challenges associated with resists at 3nm dimensions are such that it isn’t clear that chemically amplified resists will be capable of meeting requirements,” said Levinson. “If true, we would be seeing the most significant change in resist platforms in a quarter of a century. Potentially cost-reducing technologies such as directed self-assembly (DSA) are always welcome, but EUVL will be the lithographic workhorse through the 3nm node, and likely beyond.”At 3nm, mask makers will confront the realities of higher EUV NA tools. “We will need to implement thinner mask absorbers, new films, and perhaps hard masks,” Progler said. “This puts us in a new materials regime for masks, and history has shown us the mask industry takes a long time to refine processes and tools for new mask materials.” He explained that the small scale of the mask ecosystem and the small number of large suppliers available to address the challenges accounts for this lengthy time frame. Still, looking ahead, Progler noted that Photronics has already done a few studies on the impact of proposed half-field, high NA anamorphic optics on masks. "We uncovered some challenges that need to be addressed, particularly at boundaries and within the overall mask flow,” said Progler. As mask resolution continues to scale down, the industry will need fundamentally higher resolution mask making and inspection processes, requiring next-generation multi-beam mask writing and electron beam inspection, he explained.At 3nm and below, Progler noted that the metrology needs for masks, while not as severe as that for wafers at these nodes, will test the mask equipment infrastructure in ways that could challenge the relatively small mask industry. “Of course, EUV multi-patterning comes into play as well, and with that, the SRAF sizes will drop below 20nm, requiring an asymmetric compensation over a much wider influence area than the OPC people are used to considering.” With EUV multi-patterning, Progler explained that it will be increasingly important to match or pair EUV masks and to consider how 3D effects and stochastics will drive new technology to enable new requirements for high-speed metrology and simulation components. “All the justifiable hand-wringing over EPE with ArF multi-patterning today gets introduced to the EUV scene when masks are ganged together to make a single device layer,” said Progler.Debra Vogler, SEMI