Non-Visual Defect Inspection: The Tech of Tomorrow?

The chip industry is conservative when it comes to adopting new metrology and inspection. Will it ultimately see NVD inspection as a wunderkind, or an also-ran?

Remember when it first became obvious that the semiconductor manufacturing industry was going to expect lithography to resolve features smaller than the wavelength of light used in the litho tools themselves?

Semi EngineeringThanks to techniques such as the use of phase shift photomasks, sub-wavelength lithography is standard in chip fabs today. It might even be viewed as “old hat,” although still an expensive old hat.

Whether non-visual defect (NVD) inspection follows a similar trend remains to be seen. This is perhaps especially true in light of the history of metrology and inspection technology. Chipmakers always have been loathe to spend money on these often expensive tools and processes unless it proves indispensable in production. That explains why historical adoption rates of today’s standard metrology and inspection tools tend to have long ramps.

Still, it’s clear that as the industry begins to get serious about the forthcoming 14nm and 10nm nodes, NVDs, such as sub-monolayer residues and contaminants, have the potential to become increasingly problematic. One could argue they already are. But the key words here are non-visual and sub-monolayer, as in “sub-atomic.”

Chip manufacturing in the age of the electron

Generally speaking, device shrinks have proven problematic for years now. That’s nothing new and hasn’t been at least since R&D got underway for the 0.13-micron node. But things are getting really, really tiny now, not to mention complex—so much so that the industry is going to have to start worrying about specific electrons and Heisenberg.

“It hasn’t been uncommon with the 28nm and the 20nm transition where you get a device and everything looks great, but it doesn’t work right. You have, maybe for lack of a better term, a current flow problem,” said Dean Freeman, a semiconductor equipment analyst with Gartner Inc.

Freeman wasn’t talking about NVDs specifically, but commenting more generally on the challenges the industry faces at the 14nm and 10nm nodes and beyond, as the end of Moore’s Law creeps up on the horizon, along with exotic things like single-electron transistors.

The industry is probably going to see more problems like the one he described above, along with the need to be able to detect things that aren’t immediately understood. “We’re getting to the point where our modern measurements are getting past Heisenberg’s uncertainty principle,” Freeman said.

“One of the things people have to realize is, it’s just a lot more difficult to manufacture, even at sub-30nm, than people first thought,” said Bob Johnson, another analyst with Gartner who specializes in the metrology and defect inspection market segments. He noted that even a juggernaut such as Intel, with its deep pockets and advanced R&D efforts, was later than expected with its first sub-22nm chip.

In today’s advanced manufacturing fab line, a defect “can be something as subtle as something like two lines too close together that generate a certain amount of heat, which then throws off a timing circuit,” Johnson said.

As for NVDs, are they going to become more of a problem? Will the industry need NVD inspection tools on production lines, beyond the R&D and pilot lines? It’s too early to say just yet. Nevertheless there is some interesting and even compelling data out there.

So how do you see an NVD?

So if a defect is non-visual, i.e., you can’t see it because it doesn’t reflect or otherwise scatter light, how do you detect it? How do you “see” sub-monolayer contamination?

Currently there is only one company on the market offering NVD inspection tools to the chip industry: Qcept Technologies Inc. At the heart of Qcept’s tools is the concept of a vibrating Kelvin probe, a vibrating capacitor device that measures changes in the work function or potential in surface chemistry — without contacting the surface. Rather than vibrating a probe tip over a wafer surface, Qcept’s ChemetriQ scans the entire surface of a wafer, measuring differentials in work function. Its tools can scan a 300mm wafer in four minutes, according to the company.

Spun out of the Georgia Institute of Technology, the company announced its first beta site projects in 2011, one at a leading-edge logic fab and the other at a leading-edge memory fab; both involved inspection of 3X-nm production wafers. Since then it has placed systems at five of the top six chipmakers as determined by sales (not including fabless companies, naturally).

One of those chipmakers is South Korea’s Samsung Electronics. Samsung and Qcept published a joint paper earlier this year detailing the company’s use of Qcept’s ChemetriQ tool to identify a post-wet clean residue that was ultimately causing pitting defects in a later gate oxide process. The residue defect correlated with a known yield problem at end of line (EOL) test. Notably, while Samsung said it suspected the defect was occurring at the front-end of line gate module process, there was no matching defect pattern identified during optical inspection. The company used ChemetriQ inspection at several process steps in the gate and spacer module process, including post-gate lithography, post-gate etch and clean, post-spacer deposition and post-spacer etch and ash clean.

The resulting inspection data detected spots of increased work function in areas of the wafer that corresponded with the location of die failing at EOL test. Ultimately NVD inspection illustrated that the way a batch clean tool was handling the wafer was leaving unwanted residue on part of the wafer; among the most promising solutions was switching to a linear, single-wafer clean tool which enabled a more uniform post-clean surface and a significant yield increase at final test, according to Samsung.

Problems like the one discussed in the Samsung paper are not uncommon, according to Qcept. The company has had customers with 20 to 30 percent yield problems at end of line with no corresponding defect data, according to Robert Newcomb, executive vice president at Qcept. That’s where a lot of the time NVD inspection helps find the additional yield, when there is no corresponding optical defect inspection data, he said.

In October the company published a paper with Applied Materials Inc.’s Asia Product Development Center in Singapore and the Institute of Microelectronics in Singapore in which the companies used Qcept’s inspection technology to detect surface contamination within a chemical mechanical polarization (CMP) process used to reveal through-silicon vias (TSVs). The fact that Applied Materials turned to Qcept for CMP process development help perhaps speaks volumes, particularly given that Applied has its own optical defect inspection division — detecting NVDs is clearly a new thing.

While residues are one category of NVD, another is process-induced charge, according to Newcomb. “We have found that charge can result in yield failure and yield defectivity in many ways — electrostatic charge, discharge in the wafer — it can blow out the gate oxide fabbed three weeks ago,” he said. “Charge can result in electrochemical defects too.”

Charge problems tend to result from wet process steps, Newcomb noted. “Any process where you are doing a wet process to the surface of the wafer with different chemistries can result in these charge events,” he said. It is one area in which Qcept’s customers are focusing on in particular.

Wafer cleaning is incidentally one of the most common and repeated steps in a fab line. Some 200 steps can be involved with surface prep and cleaning with the fabrication of a complex device. Given the increasing use of exotic materials in semiconductor fabrication, that number is likely to grow at future nodes. “From that perspective, for wet cleans and surface prep, it’s more than just particles,” Newcomb said.

Future inspection tech or perfect future inspection tech?

Nevertheless, to say NVDs are a widespread phenomenon, or will be, or rather that NVD inspection is the wave of the inspection future — it’s too early to make that call. As Gartner’s Johnson noted, 30% yield problems at advanced nodes is hardly unusual. In fact some of the large complex die that appeared at 28nm node were rumored to have production yields in the 40% range.

Again, when it comes to metrology and inspection, chipmakers are loathe to spend money on the tools and add the steps in production. Any time there is a new metrology technology, it goes into the R&D area first before it gets adopted in production. Chipmakers have to be convinced that the problems illustrated in R&D are problems that are not just solved then and there, and instead must be monitored in production, Johnson said. And what if NVDs do prove a recurring problem in the production fab? “Then you would have to put some (NVD) inspection steps at critical points in the fab,” he said.

Johnson noted there have been promising metrology and inspection technologies in the past that failed to find their way into mainstream production, such as integrated metrology. In that case it proved too expensive and not absolutely necessary.

On the other hand, there is the example of optical critical dimension (CD) metrology technology. It had a long road to adoption. Like NVD inspection tech today, at the time optical CD inspection was a brand-new technology and it took the industry a while to figure out how to use it. Today, however, it’s an important part of the fab line and the metrology tool market.

As for NVD inspection technology and Qcept, time will tell. But it would seem that at least for the likes of Applied and Samsung, the evidence thus far is compelling.

Editor’s Note: As explained at length elsewhere on this site this is a news story written by me for another publication. This originally appeared on Semiconductor Engineering; it holds the copyright, of course.

… So What’s All the August Fuss About?

Alas, Electronic News, we hardly knew ye: RIP.Up until now, unless someone was directly involved in backend macro defect inspection – spotting errant particles that can cause yield problems, with macro defined as particles of 0.5 microns or larger – they might not have heard of August Technology.

Based in Minneapolis, the tool vendor saw revenues of approximately $67 million in 2004, based on figures in its Q3 earnings report and its guidance for Q4 (the company hasn’t posted Q4 or year-end figures yet). Founded in 1992, the company has focused on automated defect inspection systems, finding most of its success in backend or final manufacturing applications.

Only recently has the company made moves into front-end manufacturing defect inspection, touting itself as the only company to offer “all wafer” inspection – front-side, backside and edge inspection. But its management has publicly acknowledged that it faces an up hill battle and stiff competition in getting into the front-end market, which means courting IDMs and other chipmakers around the globe.

With approximately 17.8 million shares, KLA-Tencor Inc.,’s offer to acquire August comes out to approximately $204.7 million. Not a ridiculous offer for a company that had $67 million in revenues last year and outpaced the equipment market in terms of growth rate. But it is certainly a healthy one, to say the least.

And it places August at the center of a three-way tug of war between KLA-Tencor and smaller rivals Rudolph Technologies and Nanometrics – a four-way struggle if one includes August shareholders, which have filed suit to stop August and Nanometrics’ plans to merge.

Why the fuss? Well it’s obvious one doesn’t need a macro defect inspection tool to see why August is suddenly the belle of the inspection and metrology ball.

What You Want, Baby I Got …
D-E-F-E-C-T: Find Out What it Means to Me

It’s a well-recognized trend in process technology that inspection and metrology are becoming of critical importance as design parameters, and consequently process windows, shrink. The particle defect, once something that could often be ignored, has become a common yield killer here in the deep submicron era.

So being able to spot defects and figure out where they are coming from is what all the fuss is about, and why August suddenly can pick and choose among multiple suitors.

“They’ve obviously got a very nice macro defect inspection technology people seem to want,” observed Bob Johnson, a principle analyst with market researcher Gartner Dataquest. Johnson specializes in the metrology and related markets.

For it’s part, KLA-Tencor suggested that the merger would be complementary; while it is the leader in process control and yield management in front-end apps, August is known for its inspection technology in the advanced packaging/wafer level packaging market, but has been making moves toward the front-end market.

“We have the highest regard for August Technology and its employees, and believe that the acquisition of August Technology by KLA-Tencor serves the best interests of our respective shareholders and customers,” Ken Schroeder, KLA-Tencor’s president and CEO, said in a statement.

Furthermore, sources involved in the inspection market have observed that KLA-Tencor, while it dominates many of the markets it serves, hasn’t been as successful in its forays into particle inspection.

As Dataquest’s Johnson noted, KLA-Tencor’s merger bid may not necessarily be a defensive move; given its size and dominance in other areas of the market place, it would have little to fear from a combined August/Nanometrics or August/Rudolph. But the merger would eliminate a potential competitor in the inspection space, and would add a product line complementary to its own, one with a proven track record in the industry.

Rudolph, on the other hand, may have been playing defense when it threw its merger monkey wrench into the August/Nanometrics deal, Johnson theorized. Rudolph has already begun making moves in the front-end defect inspection market as well, and may have reacted in an attempt to block the rise of another competitor.

Of course the merger would also give Rudolph that successful product line of August’s that everyone seems to covet.

As for Nanometrics, known primarily for its integrated metrology technology, it would have opened up a whole new market for the company; indeed in a conference call with analysts on the day the August/Nanometrics deal was announced, both sides touted the fact that there was no product overlap between the two companies.

“I think we all realize that inspection and metrology are cousins, sort of sister capabilities, if you will,” said Jeff O’Dell, August CEO, during an August/Nanometrics conference call in late January. “And August has done a little bit of work in metrology specifically around the bump inspection side. And … we all know that Nanometrics is taking a look at some inspection on the macro end for good reasons because our customers independently were leading us in those directions.

“So just from a pure customer standpoint, the product lines right out of the box, because they are different in terms of special metrology have, I think, that appeal from a single supplier,” O’Dell said.

So what is August looking for? Why does a company with a now obviously hot technology need a merger? It would seem to be global infrastructure and access. Both Nanometrics CEO John Heaton and August CFO Stan Piekos touched on the idea during the companies’ joint call that companies need to have global infrastructure if they are to remain competitive in the future, and that both companies would be strengthened in this respect by a merger.

Plus the two serve complimentary regional markets, said Piekos.

“In the case of Nanometrics, their largest foreign operations are in Japan,” Piekos said. “And there, they compliment us nicely because that’s one of our weaker areas. We still serve the Japanese market with a distributor network. And now that we’re moving in to the front end, we see a need to enhance our marketing distribution and marketing channels in Japan.

“August, on the hand …we started in final manufacturing or backend. We have a strong position in Taiwan, and elsewhere in the southeast. And we believe the Taiwanese position can help Nano as they expand,” Piekos concluded.

“So Tell Me, Bachelor No. 4 …”

And so the August merger saga continues, with new wrinkles seeming to occur on an almost daily basis now. The one thing everyone in the metrology and inspection market is wondering is when KLA-Tencor’s biggest rival – in terms of size, if not necessarily market penetration – Applied Materials Inc., is going to make its own public bid for August.

Editor’s Note: As explained at length elsewhere on this site, this is a news story written by me that originally appeared on the now-defunct Electronic News’ website, which is long gone. It’s former sister pub Electronic Design News (EDN) currently holds the copyright to all Electronic News copy (to the best of my knowledge). You can still see a copy of this story at EDN.

Outsourcing Has Its Dark Side

Nanometrics Opts for Vertical Integration Instead

Alas, Electronic News (the print edition): we hardly knew ye!

The metrology company is bucking the trend and has become more vertically integrated to guarantee its ability to ramp whenever the industry recovers. A key part of its strategy is being able to deliver its metrology tools quickly and at the same time being able to directly ensure quality.

When the next upturn does come, having its own in-house machine shop will be a competitive advantage for Nanometrics over its larger competitors, according to its CEO John Heaton.

John Heaton, Nanometrics CEO“My only advantage as a small company is to do something quickly, better, faster, cheaper,” Heaton explained. In the past, Nanometrics would have to compete during an upturn for time at local machine shops that also served much larger companies, such as KLA-Tencor Inc., a competitor, and Applied Materials, a customer.

Needless to say, the larger companies often took priority. Furthermore, there was such a rush during 2000 among the entire supply chain that the company had quality-control problems with its suppliers. Thus Nanometrics has brought its own machine shop, anodizing shop and related parts of the business in-house.

But there is more to the strategy than guaranteeing quality and the ability to ramp production. Many of the machine shops used by process technology OEMs were hit hard by the two-year economic downturn. A number of them have closed their doors, which could dramatically impact the ability to ramp for the companies that have relied on them in the past, Heaton said.

“No one is talking about that right now. We believe we will have a competitive advantage,” he added.

Nanometrics’ size and its business model lend themselves to vertical integration. The company has been an early proponent of integrated metrology in an industry that is just beginning to seriously come around to the idea. The company has based its technology on integrated metrology modules, and then migrated that technology to its stand-alone platforms, rather than the other way around.

“We start with a clean sheet of paper and say how do we take our technology and redesign it?” said Peter Gise, Nanometrics’ senior marketing manager.

That has meant the key components of its systems are small, compact systems, which are not particularly challenging for an in-house machine shop to produce quickly while maintaining quality. And by bringing the manufacturing in-house, it keeps the cost of the finished integrated metrology modules down by eliminating a step in the supply chain, he said.

“We believe integrated metrology is the way to go,” Gise said. But this is not to suggest that the company has forsaken its off-line tool base. “We haven’t exactly bet the farm because we still have off-line tools,” he added. But the concept is gaining traction in both OEM and end-user customers. “In three to five years ? it’s really going to take hold,” he said.

With chip production lot sizes decreasing along with feature sizes and cycle times, process parameters are becoming increasingly tighter, and defects more critical. Using feed-forward and feedback of metrology data to control process excursions during production runs is becoming an increasingly popular idea among chipmakers, Gise said. As a result, Nanometrics has begun expanding beyond its traditional thin-film measurement to metrology applications for lithography, planarization, deposition, etch, and copper and low-k films.

This past week the company rolled out the Nano CLP-9010, a laser profiler that nondestructively monitors the metal loss between an isolated copper feature and the surrounding dielectric region. The module is designed to integrate within a metal chemical mechanical planarization tool. It is a new technology for Nanometrics, and an application driven by and large by its OEM customers, Heaton said. Interest in the new module was nearly instantaneous, he said, adding that the company started receiving calls from customers within hours of the news release.

Editor’s Note: As explained at length elsewhere on this site, this is a news story written by me that originally appeared on the now-defunct Electronic News’ website, which is long gone. It’s former sister pub Electronic Design News (EDN) currently holds the copyright to all Electronic News copy (to the best of my knowledge). You can still see a copy of this story at EDN.

Japan Inc. Rethinks Its Semi Strategy

Tough Economic Times Force Changes at Equipment Companies

TOKYO —  It is evident here at Semicon that Japan’s continued economic woes are changing the way Japanese equipment companies do business.

Alas, Electronic News (the print edition): we hardly knew ye!Even in the midst of a lengthy recession, executives and analysts cling to evidence of a recovery for the latter quarters of 2002. Yet, even if this takes place, the days of Japan Inc. and its us vs. them mentality are over, and the Japanese readily acknowledge and accept this.

Perhaps the most visible aspect of this phenomenon is Canon Inc.’s embrace of two-year-old Austin metrology start-up nLine Corp. Canon announced that its sales and distribution subsidiary, Canon Sales Co., would function as a sales partner for nLine, selling its newly unveiled direct digital holography Fathom tool in Japan.

Canon Sales is the distributor for a number of third-party tools in Japan, not just Canon’s own semiconductor equipment, explained Hiroshi Shibuya, director and group executive for Canon’s semiconductor equipment sales. Many companies approach Canon’s sales arm to represent them in Japan, but they must meet very strict criteria, Shibuya said. But he found nLine’s technology impressive, suggesting that it has strong potential, and he felt that the two companies would be able to establish a mutual trust between them, he said.

Kyodai Brothers perform outside Tokyo at SEMI Japan 2001
Tradition meets Tech: The Kyodai brothers of Michinoku, Japan, played the shamisen at the opening of Semicon Japan outside of Tokyo. The Kyodai brothers are well known throughout Japan.

While it’s too early to declare a trend, perhaps, the agreement is not without precedent. At last year’s Semicon Japan, Japanese OEM giant Tokyo Electron Ltd. (TEL) announced that it would handle sales and support throughout the world for start-up NuTool Inc. and its copper electrochemical mechanical deposition tool and technology. The move raised a lot of eyebrows in the industry, but TEL heartily endorsed the Silicon Valley start-up. Tetsuro Higashi, TEL president and CEO, said that NuTool’s technology would permit the Japanese OEM to penetrate the market for interconnect process technology.

The idea of Canon’s and TEL’s embrace of American companies and technology would have seemed laughably ridiculous not too many years ago, when Japanese automobiles and electronics dominated America and there was talk that the United States would exit the chip industry all together.

Now, the roles have been reversed. Japan is struggling to move away from the troubled DRAM-dependent semiconductor business model and expand into other areas—system LSI, as opposed to system-on-a-chip, is the current buzzword on this side of the Pacific.

Canon and TEL aren’t the only ones looking west. Specialty etch tool OEM Tegal Corp. announced at the show joint development partnerships with three Japanese microelectronic companies. They look to Tegal for manufacturing process expertise in order to enter the market for nonvolatile memory.

Meanwhile, U.S.-based OEMs August Technology, Ultratech Stepper and Kulicke & Soffa, and European OEM Unaxis Balzers announced that they were joining Japanese tech and OEM companies Dainippon Screen Manufacturing, Ebara and Casio Computer Co. in the newly created Advanced Packaging and Interconnect Alliance (APiA). APiA wants to accelerate the development and implementation of commercially viable advanced packaging technologies.

Semi Japan 2001 in Chiba, outside Tokyo
While participation may be down, particularly among other Asian countries, many exhibitors expressed surprise at the number of Japanese customers at Semicon Japan particularly interested in advanced technologies, even though there is little, if any talk of equipment purchases at the current time.

Many of the OEM executives involved in these partnerships noted that as chip technology becomes more complex, it becomes more costly to invest. While Tegal’s Japanese subsidiary has been established in Japan for 16 years, its new partnerships weren’t struck solely on Tegal’s reputation. The Japanese economy has been hurting for so long that it has created opportunities for foreign companies to become more involved in the domestic Japanese semiconductor business, said Jim McKibben, VP of worldwide marketing and sales for Petaluma, Calif.-based Tegal.

This trend may be most dramatically evident in Japan, but the phenomenon isn’t limited to this side of the Pacific, suggested Mike Parodi, Tegal chairman, president and CEO. “I see a change in the complexion of the industry … It’s driving relationships that wouldn’t have occurred before,” he said.

The business climate has changed so much here, that some U.S. OEM executives are openly wondering what will happen to the Japanese chipmakers during the next upturn. With investment in technology seemingly at an all-time low in tech-hungry Japan, they question if the Japanese will be able to compete with the global market, or if they will eventually be forced to exit not just DRAM, but the chip market altogether.

Editor’s Note: As explained at length elsewhere on this site, this is a news story written by me that originally appeared on the now-defunct Electronic News’ website, which is long gone. It’s former sister pub Electronic Design News (EDN) currently holds the copyright to all Electronic News copy (to the best of my knowledge). You can still see a copy of this story at EDN.