For Brad Van Eck and the other members of the Integrated Measurement Association (IMA), the benefits of incorporating metrology in semiconductor processes are beyond question. Their next steps are figuring out the most efficient methods, and then convincing the authors of the International Technology Roadmap for Semiconductors (ITRS) to incorporate IMA's suggestions into the upcoming revised document.

ILLUSTRATION BY JAMES SCHLESINGER

IMA hopes to take several steps toward that goal this month. The ad hoc group has a three-hour public meeting scheduled for the San Francisco Marriott on July 13, the eve of Semicon West. The meeting coincides with the first public review of the next ITRS, which is also scheduled to take place at the annual trade show in San Francisco and San Jose.

"What we have done is try to organize a meeting at Semicon West to take a look at where the roadmap is right now and ask, 'Is it covering APC and integrated metrology efficiently?'" says Van Eck, vice president of the organization. He will chair a metrology session.

Even though Van Eck joshes that the members of the not-for-profit organization are "zealots," he and other IMA members are as serious about their work as a $1-million particulate hit on an in-process lot of 12-inchers.

"The ITRS can never use the term 'APC' too often," says Van Eck. The e-manufacturing manager of International Sematech pauses and adds, "That's a joke. But we believe there's enough interest behind integrated metrology and advanced process control (APC) that we can bring a broader audience into the process by holding these meetings and by consulting all the input and bringing it to the 'TWG'," the roadmap's term for its international technology working groups.

Lise Laurin, who will oversee an interconnect breakout session, hopes participants in the IMA confab will be able to form an overarching concept to "solve some of the issues that are in the current roadmap. We're also looking at some of the things we need to know in order to develop what the industry really needs.

"So the goal of this meeting is to get people involved in thinking about these things and talking to each other so we have a kind of common front, and then have representatives join the TWGs to bring this combined thought process to the roadmap," adds Laurin, a product manager at IBEX Process Technology, a company specializing in APC systems. The other corporate members are AMD, KLA-Tencor, International Sematech, MKS Instruments, Nanophotonics, and Verity Instruments.

What processes could benefit from in-line measurement? Well, for a first easy guess, look no further than a very pricey aspect of device production, asserts James Moyne. "After a certain date, all litho tools will require integrated metrology," insists the director of APC technology at Brooks Automation. "Lithography, as we all know, is the most expensive operation in the fab in terms of production. It's a well-known fact that, in the APC arena, return on investment for lithography using APC is higher than in any other process.

"There are two types of advanced process control: CD control and overlay control, and both of those require integrated metrology," says Moyne, who is chairing a lithography breakout session. "You do integrated metrology and measure it and model it based on run-to-run control. It's become more and more clear as we get to smaller and smaller nodes that you cannot improve the equipment design. You've got to do CD control."

Van Eck, who also holds the chairmanship of the AEC/APC Conference, agrees that lithography most definitely can benefit from integrated metrology because it helps with registration, linewidth, and defects. The in situ method could also be used on track systems or in the stepper.

Interconnect is another process that would see good returns, he says. "In interconnect, you're putting down thin films and etching them. If you could measure the thickness of your films in real time and actually stop deposition when you get to the right thickness, opposed to where you get to the end of 15 seconds, you'd have a process with a tighter tolerance."

Citing another example, Van Eck says placing sensors in process tools is another key step. "When RF power is going south in interconnect, and you had better software to detect those problems, you could save scrap."

On "the next level up for APC," factory integration is an additional target of the IMA proselytizers, Van Eck points out. The factory integration TWG is "very concerned with how you integrate all the pieces running in a fab. APC is valuable in that arena as well, because you need to take data from all the tools and compare them."

Taking deposition as a component, for example, he says, "You find out that you are unable to deposit the right thickness at one step. You transfer that information to the etcher so that now the etcher knows to etch a thicker film. This may have no impact whatsoever on the quality of the resulting chip, but if you know that [information] ahead of time, you'd have a much smoother running factory."

Laurin believes that the ITRS TWG participants can pay more attention than they have in the past to the benefits of in-line measurement. She says that some solutions "are being ignored" by default without impetus from outside sources. Van Eck disagrees, however, and says that the factory integration TWG, for example, "is very, very supportive."

Metrology TWG members are strong backers as well, he insists. "What we want to do is get a lot more eyeballs looking at [integrated measurement] than just the TWGs." The hope is that IMA can pinpoint a potential solution to a particular roadblock in the roadmap, Van Eck says.

The Sematech program manager emphasizes that IMA acts as a special interest group of sort and falls outside the roadmap's official purview. "This is volunteer activity that we're doing, and even though informally the ITRS people know about it, it is not an official arm of the ITRS." IMA has contacted the roadmap's organizers and "told them we intend to do this. We fully understand that all we can do is come and attend the TWG meetings and make recommendations. We can't dictate anything."

IMA's efforts, however, have borne some fruit. In 2002, the organization developed the first integrated measurement standards for submission to the SEMI Standards ballot process. The meeting at Semicon West is IMA's third in its series of workshops.

Van Eck says the direction of the July meeting in San Francisco depends entirely on who shows up. "Once we get to the meeting, we're going to break into groups, depending on who attends. If there's a whole bunch of litho people there, we'll discuss litho issues. If there are a whole bunch of factory integration people there, we'll send those into a corner to discuss things. We won't know 'til we get there."

Asked how many participants he expects to turn up at the hotel, Van Eck recalls an IMA meeting held at the SPIE conference earlier this year. "In a similar setting at SPIE, there were 50–60 people. It was standing room only. We're hoping for those kinds of numbers at Semicon West. We sent out the notice to quite a few people."

Laurin hopes the organization's message spreads beyond the confines of meeting rooms and the pages of magazines such as MICRO. "When I joined IMA about four years ago, that was my first comment: 'You're preaching to the choir.' It's the process engineers that need to hear what our solutions are.'"