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EUVL Materials Readiness for HVM

Friday, June 2nd, 2017

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By Ed Korczynski, Sr. Technology Editor

Extreme-Ultra-Violet Lithography (EUVL)—based on ~13.5nm wavelength EM waves bouncing off mirrors in a vacuum—will finally be used in commercial IC fabrication by Intel, Samsung, and TSMC starting in 2018. In a recent quarterly earning calls ASML reported a backlog of orders for 21 EUVL tools. At the 2017 SPIE Advanced Lithography conference, presentations detailed how the source and mask and resist all are near targets for next year, while the mask pellicle still needs work. Actinic metrology for mask inspection still remains a known expensive issue to solve.

Figure 1 shows minimal pitch line/space grids and contact-hole arrays patterned with EUVL at global R&D hub IMEC in Belgium, as presented at the recent 2017 IMEC Technology Forum. While there is no way with photolithography to escape the trade-offs of the Resolution/Line-Width-Roughness/Sensitivity (RLS) triangle, patterning at the leading edge of possible pitches requires application-specific etch integration. The bottom row of SEMs in this figure all show dramatic improvements in LWR through atomic-scale etch and deposition treatments to patterned sidewalls.

Fig.1: SEM plan-view images of minimum pitch Resolution and Line-Width-Roughness and Sensitivity (RLS) for both Chemically-Amplified Resist (CAR) and Non-Chemically-Amplified Resist (NCAR, meaning metal-oxide solution from Inpria) formulations, showing that excessive LWR can be smoothed by various post-lithography deposition/etch treatments. (Source: IMEC)

ASML has recently claimed that as an indication of continued maturity, ASML’s NXE:33×0 steppers have now collectively surpassed one million processed wafers to date, and only correctly exposed wafers were included in the count. During the company’s 1Q17 earnings call, it was reported that three additional orders for NXE:3400B steppers were received in Q1 adding  to a total of 21 in backlog, worth nearly US$2.5B.

At $117M each NXE:3400B, assuming 10 years useful life it costs $32,000 each day and assuming 18 productive hours/day and 80 wafers/hour then it costs $22 per wafer-pass just for tool depreciation. In comparison, a $40M argon-fluoride immersion (ArFi) stepper over ten years with 21 available hours/day and 240 wafers/hour costs $2.2 per wafer-pass for depreciation. EUVL will always be an expensive high-value-add technology, even though a single EUVL exposure can replace 4-5 ArFi exposures.

Fabs that delay use of EUVL at the leading edge of device scaling will instead have to buy and facilitize many more ArFi tools, demanding more fab space and more optical lithography gases. SemiMD spoke with Paul Stockman, Linde Electronics’ Head of Market Development, about the global supply of specialty neon and xenon gas blends:  “Xenon is only a ppm level component of the neon-blend for Kr and Ar lasers, so there should be no concerns with Xenon supply for the industry. In our modeling we’ve realized the impact of multi-patterning on gas demand, and we’ve assumed that the industry would need multi-patterning in our forecasts.” said Stockman.

“From the Linde perspective, we manage supply carefully to meet anticipated customer demand,” reminded Stockman. “We recently added 40 million liters of neon capacity in the US, and continue to add significant supply with partners so that we can serve our customers regardless of the EUV scenario.” (Editor’s note: reported by SemiMD here.)

At SPIE Advanced Lithography 2017, SemiMD discussed multi-patterning process flows with Uday Mitra and Regina Freed of Applied Materials. “We need a lot of materials engineering now,” explained Freed. “We need new gap-fills and hard-masks, and we may need new materials for selective deposition. Regarding the etch, we need extreme selectivity with no damage, and ability to get into the smallest features to take out just one atomic layer at a time.”

Reminding us that IC fabs must be risk-averse when considering technology options, Mitra (formerly with Intel) commented, “You don’t do a technology change and a wafer size change at the same time. That’s how you risk manage, and you can imagine with something like EUVL that customers will first use it for limited patterning and check it out.”

Figure 2 lists the major issues in pattern-transfer using plasma etch tools, along with the process variables that must be controlled to ensure proper pattern fidelity. Applied Materials’ Sym3 etch chamber features hardware that provides pulsed energy at dual frequencies along with low residence time of reactant byproducts to allow for precise tuning of process parameters no matter what chemistry is needed.

Fig.2: Patterning issues and associated etch process variables which can be used for control thereof. (Source: Applied Materials)

Andrew Grenville, CEO of resist supplier Inpria, in an exclusive interview with SemiMD, commented on the infrastructure readiness for EUVL volume production. “We are building up our pilot line facility in Corvallis, Oregon. The timing for that is next year, and we are putting in place plans to continue to scale up the new materials at the same times as the quality control systems such as functional QC.” The end-users ask for quality control checks of more parameters, putting a burden on suppliers to invest in more metrology tools and even develop new measurement techniques. Inpria’s resist is based on SnOx nanoparticles, which provide for excellent etch resistance even with layers as thin as 20nm, but required the development of a new technique to measure ppb levels of trace metals in the presence of high tin signals.

“We believe that there is continued opportunity for improvement in the overall patterning performance based on the ancillaries, particularly in simplifying the under-layers. One of the core principles of our material is that we’re putting the ‘resist’ back in the resist,” enthused Grenville. “We can show the etch contrast of our material can really improve the Line-Width Roughness of the patterns because of what you can do in etch, and it’s not merely smoothing the resist. We can substantially improve the outcome by engineering the stack and the etch recipe using completely different chemistry than could be used with chemically-amplified resist.”

The 2017 EUVL Workshop (2017 International Workshop on EUV Lithography) will be held June 12-15 at The Center for X-ray Optics (CXRO) at Lawrence Berkeley National Laboratory in Berkeley, CA. This workshop, now in its tenth year, is focused on the fundamental science of EUV Lithography (EUVL). Travel and hotel information as well as on-line registration is available at https://euvlitho.com/.

[DISCLOSURE:  Ed Korczynski is also Sr. Analyst for TECHCET responsible for the Critical Materials Report (CMR) on Photoresists, Extensions & Ancillaries.]

—E.K.

Edge Placement Error Control in Multi-Patterning

Thursday, March 2nd, 2017

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By Ed Korczynski, Sr. Technical Editor

SPIE Advanced Lithography remains the technical conference where the leading edge of minimum resolution patterning is explored, even though photolithography is now only part of the story. Leading OEMs continue to impress the industry with more productive ArFi steppers, but the photoresist suppliers and the purveyors of vacuum deposition and etch tools now provide most of the new value-add. Tri-layer-resist (TLR) stacks, specialty hard-masks and anti-reflective coatings (ARC), and complex thin-film depositions and etches all combine to create application-specific lithography solutions tuned to each critical mask.

Multi-patterning using complementary lithography—using argon-fluoride immersion (ArFi) steppers to pattern 1D line arrays plus extreme ultra-violet (EUV) tools to do line cuts—is under development at all leading edge fabs today. Figure 1 shows that edge placement error (EPE) in lines, cut layers, and vias/contacts between two orthogonal patterned layers can result in shorts and opens. Consequently, EPE control is critical for yield within any multi-patterning process flow, including litho-etch-litho-etch (LELE), self-aligned double-patterning (SADP) and self-aligned quadruple-patterning (SAQP).

Fig.1: Plan view schematic of 10nm half-pitch vertical lines overlaid with lower horizontal lines, showing the potential for edge-placement error (EPE). (Source: Y. Borodovsky, SPIE)

Happening the day before the official start of SPIE-AL, Nikon’s LithoVision event featured a talk by Intel Fellow and director of lithography hardware solutions Mark Phillips on the big picture of how the industry may continue to pattern smaller IC device features. Regarding the timing of Intel’s planned use of EUV litho technology, Phillips re-iterated that, “It’s highly desirable for the 7nm node, but we’ll only use it when it’s ready. However, EUVL will remain expensive even at full productivity, so 193i and multi-patterning will continue to be used. In particular we’ll need continued improvement in the 193i tools to meet overlay.”

Yuichi Shibazaki— Nikon Fellow and the main architect of the current generation of Nikon steppers—explained that the current generation of 193i steppers, featuring throughputs of >200 wafers per hour, have already been optimized to the point of diminishing returns. “In order to improve a small amount of performance it requires a lot of expense. So just improving tool performance may not decrease chip costs.” Nikon’s latest productivity offering is a converted alignment station as a stand-alone tool, intended to measure every product wafer before lithography to allow for feed-forward tuning of any stepper; cost and cost-of-ownership may be disclosed after the first beta-site tool reaches a customer by the end of this year.

“The 193 immersion technology continues to make steady progress, but there are not as many new game-changing developments,” confided Michael Lercel, Director of Strategic Marketing for ASML in an exclusive interview with SemiMD. “A major theme of several SPIE papers is on EPE, which traditionally we looked at as dependent upon CD and overlay. Now we’re looking at EPE in patterning more holistically, with need to control the complexity with different error-variables. The more information we can get the more we can control.”

At LithoVision this year, John Sturtevant—SPIE Fellow, and director of RET product development in the Design to Silicon Division at Mentor Graphics—discussed the challenges of controlling variability in multi-layer patterning. “A key challenge is predicting and then mitigating total EPE control,” reminded Sturtevant. “We’ve always paid attention to it, but the budgets that are available today are smaller than ever. Edge-placement is very important ” At the leading edge, there are multiple steps within the basic litho flow that induce proximity/local-neighbor effects which must be accounted for in EDA:  mask making, photoresist exposure, post-exposure bake (PEB), pattern development, and CD-SEM inspection (wherein there is non-zero resist shrinkage).

Due to the inherent physics of EUV lithography, as well as the atomic-scale non-uniformities in the reflective mirrors focusing onto the wafer, EUV exposure tools show significant variation in exposure uniformities. “For any given slit position there can be significant differences between tools. In practice we have used a single model of OPC for all slit locations in all scanners in the fab, and that paradigm may have to change,” said Sturtevant. “It’s possible that because the variation across the scanner is as much as the variation across the slit, it could mean we’ll need scanner-specific cross-slit computational lithography.” More than 3nm variation has been seen across 4 EUVL steppers, and the possible need for tool-specific optical proximity correction (OPC) and source-mask optimization (SMO) would be horrible for managing masks in HVM.

Thin Films Extend Patterning Resolution

Applied Materials has led the industry in thin-film depositions and etches for decades, and the company’s production proven processing platforms are being used more and more to extend the resolution of lithography. For SADP and SAQP MP, there are tunable unit-processes established for sidewall-spacer depositions, and chemical downstream etching chambers for mandrel pull with extreme material selectivity. CVD of dielectric and metallic hard-masks when combined with highly anisotropic plasma etching allows for device-specific and mask-specific pattern transfers that can reduce the line width/edge roughness (LWR/LER) originally present in the photoresist. Figure 2 from the SPIE-AL presentation “Impact of Materials Engineering on Edge Placement Error” by Regina Freed, Ying Zhang, and Uday Mitra of Applied Materials, shows LER reduction from 3.4 to 1.3 nm is possible after etch. The company’s Sym3 chamber features very high gas conductance to prevent etch byproducts from dissociation and re-deposition on resist sidewalls.

Fig.2: 3D schematics (top) and plan view SEM images (bottom) showing that control of plasma parameters can tune the byproducts of etch processes to significantly reduce the line-width roughness (LWR) of minimally scaled lines. (Source: Applied Materials)

TEL’s new SAQP spacer-on-spacer process builds on the work shown last year, using oxide as first spacer and TiO2 as second spacer. Now TEL is exploring silicon as the mandrel, then silicon-nitride as the first spacer, and titanium-oxide as second spacer. This new flow can be tuned so that all-dry etch in a single plasma etch chamber can be used for the final mandrel pull and pattern transfer steps.

Coventor’s 3D modeling software allows companies to do process integration experiments in virtual space, allowing for estimation of yield-losses in pattern transfer due to variations in side-wall profiles and LER. A simulation of 9 SRAM cells with 54 transistors shows that photoresist sidewall taper angle determines both the size and the variability of the final fins. The final capacitance of low-k dielectric in dual-damascene copper metal interconnects can be simulated as a function of the initial photoresist profile in a SAQP flow.

—E.K.

What’s the Next-Gen Litho Tech? Maybe All of Them

Thursday, February 25th, 2016

By Jeff Dorsch, Contributing Editor

The annual SPIE Advanced Lithography symposium in San Jose, Calif., hasn’t offered a clear winner in the next-generation lithography race. It’s becoming clearer, however, that 193i immersion and extreme-ultraviolet lithography will co-exist in the future, while directed self-assembly, nanoimprint lithography, and maybe even electron-beam direct-write technology will fit into the picture, too.

At the same time, plasma deposition and etching processes are assuming a greater interdependence with 193i, especially when it comes to multiple patterning, such as self-aligned double patterning, self-aligned quadruple patterning, and self-aligned octuple patterning (yes, there is such a thing!).

“We’ve got to go down to the sub-nanometer level,” Richard Gottscho, Lam Research’s executive vice president of global products, said Monday morning in his plenary presentation at the conference. “We must reduce the variability in multiple patterning,” he added.

Gottscho touted the benefits of atomic level processing in continuing to shrink IC dimensions. Atomic level deposition has been in volume production for a decade or more, he noted, and atomic level etching is emerging as an increasingly useful technology.

When it comes to EUV, “it’s a matter of when, not if,” the Lam executive commented. “EUV will be complementary with 193i.”

Anthony Yen, director of nanopatterning technology in the Infrastructure Division of Taiwan Semiconductor Manufacturing, followed Gottscho in the plenary session. “The fat lady hasn’t sung yet, but she’s on the stage,” he said of EUV.

Harry Levinson, senior director of GlobalFoundries, gave the opening plenary presentation, with the topic of “Evolution in the Concentration of Activities in Lithography.” He was asked after his presentation, “When is the end?” Levinson replied, “We’re definitely not going to get sub-atomic.”

With that limit in mind, dozens of papers were presented this week on what may happen before the semiconductor industry hits the sub-atomic wall.

There were seven conferences within the symposium, on specific subjects, along with a day of classes, an interactive poster session, and a two-day exhibition.

The Alternative Lithographic Technologies conference was heavy on directed self-assembly and nanoimprint lithography papers, while also offering glimpses at patterning with tilted ion implantation and multiphoton laser ablation lithography.

“Patterning is the battleground,” said David Fried, Coventor’s chief technology officer, semiconductor, in an interview at the SPIE conference. He described directed self-assembly as “an enabler for optical lithography.”

Mattan Kamon of Coventor presented a paper on Wednesday afternoon on “Virtual fabrication using directed self-assembly for process optimization in a 14nm DRAM node.”

DSA could be used in conjunction with SAQP or LELELELE, according to Fried. While some lithography experts remain leery or skeptical about using DSA in high-volume manufacturing, the Coventor CTO is a proponent of the technology’s potential.

“Unit process models in DSA are not far-fetched,” he said. “I think they’re pretty close.  The challenges of EUV are well understood. DSA challenges are a little less clear. There’s no ‘one solution fits all’ with DSA.” Fried added, “There are places where DSA can still win.”

Franklin Kalk, executive vice president of technology for Toppan Photomasks, is open to the idea of DSA and imprint lithography joining EUV and immersion in the lithography mix. “It will be some combination,” he said in an interview, while adding, “It’s a dog’s breakfast of technologies. Don’t ever count anything out.”

Richard Wise, Lam’s technical managing director in the company’s Patterning, Global Products Groups CTO Office, said EUV, when ready, will likely be complementary with multipatterning for 7 nanometer.

Self-aligning quadruple patterning, for example, was once considered “insanity” in the industry, yet it is a proven production technology now, he said.

While EUV technology is “very focused on one company,” ASML Holding, there is a consensus at SPIE that EUV’s moment is at hand, Wise said. Intel’s endorsement of the technology and dedication to advancing it speaks volumes of EUV’s potential, he asserted.

“Lam’s always excelled in lot-to-lot control,” an area of significant concern, Wise said, especially with all of this week’s talk about process variability.

What will be the final verdict on the future of lithography technology? Stay tuned.

Canon, Toshiba Join eBeam Initiative Group

Wednesday, February 24th, 2016

By Jeff Dorsch, Contributing Editor

The eBeam Initiative announced that Canon and Toshiba are new members of the industry organization, which seeks to promote the use of electron-beam technology in semiconductor manufacturing and design.

Canon Nanotechnologies and Toshiba are closely collaborating on the development of nanoimprint lithography technology. Both companies presented papers on Tuesday morning at the SPIE Advanced Lithography conference in the session devoted to “Nanoimprint Lithography Production Readiness.”

The eBeam Initiative additionally announced that it will expand its education efforts in 2016 to support the development of extreme-ultraviolet lithography, multi-beam mask writing, and nanoimprint lithography, all of which employ e-beam techniques in producing photomasks, or master templates in the case of NIL.

“People believe multi-beam is going to happen,” said Aki Fujimura, chief executive officer of D2S, the managing company sponsor of the e-beam group. He cited the group’s annual survey of industry figures, who last year predicted multi-beam mask-writing tools would be used in high-volume manufacturing for critical-layer photomasks by the end of 2018. This industry acknowledgement of advances in multi-beam mask writing “gives confidence,” Fujimura said at the eBeam Initiative’s annual luncheon at the SPIE Advanced Lithography symposium.

More than 100 luncheon attendees heard presentations by representatives of Dai Nippon Printing, the photomask manufacturer; imec, the research and development organization based in Belgium; and NuFlare Technology, a supplier of e-beam mask writers, mask inspection systems, and epitaxial reactors.

Naoya Hayoshi of DNP reported on the basics of NIL, which he said faces “some challenges, as in mask making.”

Praveen Raghavan of imec spoke about the organization’s development of test chips with 5-nanometer features. One was made with self-aligned quadruple patterning, using a 193i immersion scanner, while the other was fabricated with an EUV scanner.

The EUV technology offers “significant wafer cost benefit and enables 2D BEOL,” Raghavan said.

NuFlare’s Hiroshi Matsumoto spoke about the company’s forthcoming MBM-1000 multi-beam mask-writing system, an alpha version of which is currently in operation at the NuFlare facilities in Yokohama, Japan. NuFlare plans to offer a HVM version of the MBM-1000 by the end of this year, he said, with delivery in the fourth quarter of 2017.

The MBM-1000 is targeted at production of 5nm chips, while its successor, the MBM-2000, will address fabrication of 3nm ICs, according to Matsumoto. The MBM-2000 will be released in 2019, he said.

Optimism Reigns at SPIE Lithography Conference, Despite Challenges

Tuesday, February 23rd, 2016

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By Jeff Dorsch, Contributing Editor

Semiconductor manufacturing and design is growing increasingly complicated and just plain hard. Everyone knows that. The bad news is it’s only going to get worse.

Relax, there are many smart people gathered in San Jose, Calif., this week for the SPIE Advanced Lithography Symposium to discuss the challenges and figure out how to surmount them.

The changes required in lithography and related technologies to continue IC scaling promise to be painful and costly. Mitigating the pain and the cost is a common theme at the SPIE conference.

The annual SPIE Advanced Lithography conference is often dominated by discussions on the state of extreme-ultraviolet lithography (EUVL). In presentations on Sunday and Monday, the theme was generally the same as 2015 – EUV is making progress, yet it’s still not ready for high-volume semiconductor manufacturing.

Intel Fellow Mark Phillips said the technology has seen “two years of solid progress,” speaking Sunday at Nikon’s LithoVision 2016 event. He added, “There’s no change in Intel’s position: We’ll use EUV only when it’s ready.”

Anthony Yen of Taiwan Semiconductor Manufacturing covered the 30-year history of EUV development in his Monday morning presentation at the SPIE conference. Asked during the question-and-answer session following the presentation on when the world’s largest silicon foundry will use EUV, Yen stuck to the official company line of implementing EUV in production for the 7-nanometer process node, after some involvement at 10nm.

Seong-Sam Kim of Samsung Electronics also sees EUV realizing its long-aborning potential at 7nm, a node at which “argon fluoride multipatterning will hit the wall.” He touted the 80-watt power source Samsung has achieved with its NXE-3300 scanner from ASML Holding, saying it had maintained that level over more than eight months.

Intel’s Britt Turkot reported 200W source power “has been achieved recently,” and said the tin droplet generator in its ASML scanner has been significantly improved, increasing its typical lifetime by three times. EUV has demonstrated “solid progress,” she said, including ASML’s development of a membrane pellicle for EUV reticles.

While work with the ASML scanner on Intel’s 14nm pilot fab line has been “encouraging,” Turkot said, she added, “We do need to keep the momentum going.” Intel sees EUV entering into volume production with 7nm chips, according to Turkot. “It will be used when it’s ready,” she said.

EUV technology has shown “good progress” in productivity, while its availability and cost considerations have “a long way to go,” Turkot concluded, adding, “We need an actinic solution for the long term.”

An industry consensus has emerged that EUV will be used with ArF 193i immersion lithography in the near future, and this trend is likely to continue for some time, according to executives at the SPIE conference. There may also be wider adoption of directed self-assembly (DSA) and nanoimprint lithography technology, among other alternative lithography technologies.

Mark Phillips of Intel pointed to complementary implementation of EUV and 193i. “We must use EUV carefully,” he said. “We need to replace three-plus 193i masks.” Phillips added, “EUV can’t be applied everywhere affordably. 193i will continue to be used whenever possible.”

Nikon executives touted the capabilities of their new NSR-S631E ArF immersion scanner, introduced just before the SPIE conference. The new scanner can turn out 250 wafers per hour, and can be pushed to 270 wph with certain options, according to Nikon’s Ryoichi Kawaguchi.

Yuichi Shibazaki of Nikon said the company will next year introduce the S63xE scanner, improving on S631E.

For all the challenges of transitioning to 7nm and beyond, executives at SPIE remain optimistic about solving the issues of 193i multipatterning, DSA, and EUV. Harry Levinson of GlobalFoundries said in response to a question, “The ultimate resource is the human mind.”

Blog review March 9, 2015

Monday, March 9th, 2015

Pete Singer is delighted to announce the keynotes and other speakers for The ConFab 2015, to be held May 19-22 at The Encore at The Wynn in Las Vegas. The line-up includes Ali Sebt, President and CEO of Renesas America, Paolo Gargini, Chairman of the ITRS and Subramani Kengeri, Vice President, Global Design Solutions at GLOBALFOUNDRIES.

Mark Simmons, Product Marketing Manager, Calibre Manufacturing Group, Mentor Graphics writes about cutting fab costs and turn-around time with smart, automated resource management. He notes that the competition for market share is brutal for both the pure-play and independent device manufacturer (IDM) foundries. Success involves tuning a lot of knobs and dials. One of the important knobs is the ability to continually meet or exceed aggressive time-to-market schedules.

Paul Stockman, Commercialization Manager, Linde Electronics blogs that there is an increasing demand for and focus on sustainable manufacturing that will contribute to a greening of semiconductors. This greening must be robust and responsive to change and cannot constrain the individual processes or operation of a fab.

Applied Materials’ Max McDaniel writes on the quest for more durable displays. He says the same innovators who created such amazingly thin, light and highly functional smartphones (with the help of Applied Materials display technology) are already developing durability improvements that may eliminate the need for protective covers.

Batteries? We don’t need no stinking batteries, says Ed Korczynski. We’re still used to thinking that low-power chips for “mobile” or “Internet-of-Things (IoT)” applications will be battery powered…but the near ubiquity of lithium-ion cells powering batteries could be threatened by capacitors and energy-harvesting circuits connected to photovoltaic/thermoelectric/piezoelectric micro-power sources.

With the 2015 SPIE Advanced Lithography (AL) conference around the corner, some people have asked me what remaining EUVL challenges need to be addressed to ensure it will be ready for mass production later this year or next.  Vivek Bakshi of EUV Litho, Inc. provides thoughts on this topic and what he expects to hear at the conference.

Phil Garrou continues his look at presentations from the Grenoble SEMI 3D Summit which took place in January, focusing on an interesting presentation by ATREG consultants on the future of Assembly & Test.

On Tuesday, January 20, President Obama once again stood before a joint session of Congress to deliver a State of the Union Address.  With the newly seated Republican-controlled Congress and his Cabinet present, the President discussed topics ranging from the current state of the economy to foreign affairs and his ideas on how to move the nation forward.  Jamie Girard of SEMI was pleased to hear that the President supported multiple policy goals including expansion of free trade, corporate tax reform, support for basic science research and development and others.

SPIE Advanced Lithography conference concludes

Friday, February 27th, 2015

By Jeff Dorsch, contributing editor

Exposures, and reducing their cost, were a theme running through the 2015 SPIE Advanced Lithography Symposium this week in San Jose, Calif., the center of Silicon Valley.

Doubts about the continued viability of Moore’s Law abound as the 50th anniversary of Gordon Moore’s historic article for Electronics magazine draws near. Lithographers are under immense industry pressure to lower the operating costs of lithography cells in the fab while increasing wafer throughput.

“Enabling,” “productivity,” and “stability” were watchwords frequently repeated throughout the conference. The various merits (and occasional demerits) of electron-beam, extreme-ultraviolet, 193i immersion and nanoimprint lithography technologies were debated and touted over four days.

One of the technical sessions closing out Wednesday at the San Jose Convention Center was devoted to papers on “Multibeam Lithography,” especially e-beam direct-write technology, which has been seen as “pie in the sky” for many years, yet seems closer to realization than before.

Hans Loeschner of IMS Nanofabrication described how his company’s e-beam tool has progressed from alpha to beta status this year, and predicted it would be ready for production applications in 2016. Altera, CEA-Leti, and MAPPER Lithography presented a total of three papers on MAPPER’s FLX-1200 e-beam direct-write system, saying it is better able to make chips with 20-nanometer features than an immersion lithography system.

The eBeam Initiative held its annual luncheon at SPIE Advanced Lithography on Tuesday, emphasizing how multibeam mask writing, model-based mask data preparation, and complex inverse lithography technology can enable continued density scaling at the 10-nanometer process node.

“We have reached a point with traditional rules-based designs where the rules are so conservative and the implementation costs are so high that the semiconductor industry has started to lose the economic benefits of scaling to smaller design nodes for system-on-chip designs,” D2S CEO Aki Fujimura said in a statement. “A simulation-based approach combining complex ILT, MB-MDP and existing variable shaped beam mask writers in parallel with the impending emergence of multibeam mask writing are providing platforms to enable the semiconductor industry to reverse this trend and reactivate the density benefits associated with Moore’s Law.”

EUV, another technology that has had a long gestation, was the subject of a conference track over all four days, with photomask and photoresist issues being discussed in several sessions.

The news that Taiwan Semiconductor Manufacturing was able to process 1,022 wafers in 24 hours with ASML Holding’s NXE:3300B scanner was the talk of the SPIE conference on Tuesday, the first day of the two-day exhibition, which had about 60 companies occupying booths. ASML didn’t declare an end to development of its EUV systems, saying there is more work to be done. This includes development of a pellicle for the scanner’s reticles and working with resist suppliers on formulas for EUV resists.

While improvements in all types of lithographies were discussed at the conference, there was increased interest in directed self-assembly, which employs polymers to get molecules to arrange themselves in lines and spaces with a patterning guide. Advances in reducing the defectivity of DSA were reported by imec, Merck, and Tokyo Electron.

Global interest in DSA over the past four years has accelerated due to “other things getting delayed,” said Tom Ferry of Synopsys. Among other initiatives, the electronic design automation software and services company was talking about how its S-Litho molecular simulator, S-Litho shape optimizer, and Proteus ILT guide patterning tool can help enable DSA research and development, design, and manufacturing.

The Belgium-based imec was a big contributor to conference presentations, with a first author on 18 papers and posters, and a co-author of 25 publications.

While EUV garnered headlines during SPIE Advanced Lithography, the Cymer subsidiary of ASML was at the conference to talk about its third-generation XLR 700ix light source for deep-ultraviolet lithography systems. Ted Cacouris of Cymer said, “10 nanometer is basically done with DUV. It could go to 7 nanometer; immersion could be extended. It could be complementary to EUV.”

Cymer also announced its DynaPulse program, an upgrade for its OnPulse subscription service for maintenance and repair of light sources. In 2012, prior to the company’s acquisition by ASML, Cymer derived nearly 70 percent of its light-source revenue from the OnPulse service program.

It’s been an interesting week, with about 2,400 attendees from around the world gathering for the premier lithography conference of the year. They will convene again a year from now to learn what’s new in lithography.

Learning to live with negative tone

Friday, February 27th, 2015

By Jeff Dorsch, contributing editor

In lithography for manufacturing semiconductors, a negative tone can be a positive attribute.

Negative-tone photoresists can be used in electron-beam, extreme-ultraviolet, and immersion lithography to improve contrast prior to the etching process. Multiple papers and posters on the topic were presented at this week’s SPIE Advanced Lithography Symposium in San Jose, Calif.

Tuesday morning at the conference saw an entire session devoted to “Negative Tone Materials.” Other papers on the subject were scattered throughout technical sessions covering EUV resists.

Negative-tone resists are especially useful in argon fluoride immersion lithography, according to George Bailey of Synopsys. Contrast loss can result in rounding off of features, and negative-tone resist can aid in keeping features sharp through etch, he noted.

“The technology has been around for a long time,” said Tom Ferry of Synopsys. “First there was negative resist, then positive resist.”

Directed Self Assembly Hot Topic at SPIE

Wednesday, February 25th, 2015

By Jeff Dorsch, contributing editor

At this week’s SPIE Advanced Lithography Symposium in San Jose, Calif., the hottest three-letter acronym is less EUV and more DSA, as in directed self-assembly.

Extreme-ultraviolet lithography continues to command much attention, yet this conference is awash in papers about DSA, which dominates the “Alternative Lithographic Technologies” track of technical sessions. The two-day poster sessions feature 15 posters about DSA. Thursday’s conference sessions include three separate sessions devoted to “DSA Design for Manufacturability” and one for “DSA Modeling.”

With semiconductor industry anxiety rising at the prospect of quadruple-patterning and the slow yet steady progress of EUV technology, directed self-assembly is being hailed and recognized as a way to simplify chip manufacturing at the low end of the nanoscale era.

Before the conference got under way, imec reported on making significant progress in DSA technology, specifically reducing the defectivity associated with the process. Working with Tokyo Electron Ltd. (TEL) and Merck, which acquired AZ Electronic Materials last year, imec has come up with a DSA solution for a via patterning process that they say is compatible with the 7-nanometer process node. The partners are targeting the manufacture of DRAMs using 193nm immersion scanners.

“Over the past few years, we have realized a reduction of DSA defectivity by a factor 10 every six months,” imec’s An Steegen said in a statement. “Together, with Merck and Tokyo Electron, providing state-of-the-art DSA materials and processing equipment, we are looking ahead at two different promising DSA processes that will further improve defectivity values in the coming months. Our processes show the potential to achieve single-digit defectivity values in the near future without any technical roadblocks lying ahead.”

Kurt Ronse of imec describes DSA as utilizing two polymers to get molecules to array in lines or spaces. The issue has been to avoid the creation of holes that don’t fit the guided pattern, resulting in defects.

“All the big [chip] companies are having their internal developments on DSA,” Ronse said at SPIE. “All the memory companies are interested; Micron is in our program.”

While DSA is being implemented with 193 immersion equipment at the outset, there is the possibility of working with EUV scanners in the future, according to Ronse, and imec has an extensive EUV research and development program, he noted.

DSA started to emerge as a technology of note at the 2011 SPIE Advanced Lithography conference, Ronse said, which resulted in imec initiating its program in the field. There has been a significant amount of progress in the past two years, he added.

The momentum behind DSA R&D led to the establishment of the 1st International Symposium on DSA, scheduled for October 26-27, 2015, in Leuven, Belgium. Partnering with imec on the conference are CEA-Leti, EIDEC, and Sematech.

DSA – it’s one TLA you’ll hear a lot about in the years to come.

Proponents of EUV, immersion lithography face off at SPIE

Wednesday, February 25th, 2015

By Jeff Dorsch, contributing editor

The two main camps in optical lithography are arrayed for battle at the SPIE Advanced Lithography Symposium in San Jose, Calif.

Extreme-ultraviolet lithography, on one side, is represented by ASML Holding, its Cymer subsidiary, and ASML’s EUV customers, notably Intel, Samsung Electronics, and Taiwan Semiconductor Manufacturing.

On the other side is 193i immersion lithography, represented by Nikon and its customers, which also include Intel and other leading chipmakers.

There are other lithography technologies being discussed at the conference, of course. They are bit players in the drama, so to speak, although there is a lot of discussion and buzz about directed self-assembly technology this week.

ASML broke big news on Tuesday morning, reporting that Taiwan Semiconductor Manufacturing was able to expose more than 1,000 wafers in one day this year with ASML’s NXE:3300B EUV system. “During a recent test run on an NXE:3300B EUV system we exposed 1,022 wafers in 24 hours with sustained power of over 90 watts,” Anthony Yen, TSMC’s director of research and development, said at SPIE.

While ASML was obviously and justifiably proud of this milestone, after achieving its 2014 goal of producing 500 wafers per day, it cautioned that more development remains for EUV technology.

“The test run at TSMC demonstrates the capability of the NXE:3300B scanner, and moves us closer to our stated target of sustained output of 1,000 wafers per day in 2015,” ASML’s Hans Meiling, vice president service and product marketing EUV, said in a statement. “We must continue to increase source power, improve system availability, and show this result at multiple customers over multiple days.”

The day before, Cymer announced the first shipment of its XLR 700ix light source, which is said to improver scanner throughput and process stability for manufacturing chips with 14-nanometer features. The company also debuted DynaPulse as an upgrade option for its OnPulse customers. The XLR 700ix and DynaPulse together are said to offer better on-wafer critical dimension uniformity and provide stable on-wafer performance.

Another revelation at SPIE is that SK Hynix has been working with the NXE:3300, too, and is pleased with the system’s capabilities. According to Chang-Moon Lim, who spoke Monday morning, SK Hynix was recently able to expose 1,670 wafers over three days, with uptime of 86.3 percent over that period.

“Progress has been significant on various aspects, which should not be overshadowed by the delay of [light] sources,” he said of ASML’s EUV systems.

The Korean chipmaker is exploring how it could work without pellicles on the EUV reticle, Lim noted. ASML has been developing a pellicle, made with polycrystalline silicon, in cooperation with Intel and others.

Nikon Precision and other Nikon subsidiaries didn’t issue any press releases at SPIE. The companies presented much information at Sunday’s LithoVision 2015 event, held at the City National Civic auditorium, across the street from the San Jose Convention Center, where SPIE Advanced Lithography is staged.

On offer at the Nikon conference was the claimed superiority of 193i immersion lithography equipment to EUV systems for the 14nm, 7nm and future process nodes. Donis Flagello, Nikon Research Corp. of America’s president, CEO, and chief operating officer, emphasized that message on Tuesday morning with an invited paper on “Evolving optical lithography without EUV.”

Nikon’s champion machine is the NSR-S630D immersion scanner, which was touted throughout the LithoVision event. The system is capable of exposing 250 wafers per hour, according to Nikon’s Yuichi Shibazaki.

Ryoichi Kawaguchi of Nikon told attendees, “EUV lithography needs more stability and improvement.” He also brought up the topic of manufacturing on 450-millimeter wafers, which has mostly gone ignored in the lithography competition. Nikon will ship a 450mm system this spring to the Global 450 Consortium in Albany, N.Y., Kawaguchi said. The bigger substrates could provide “an alternative option to reduce cost,” he added.

Erik Byers of Micron Technology observed, “EUV is not a panacea.”

Which lithography technology will prevail in high-volume manufacturing? The question may not be definitively answered for some time.

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