FACILITY REPORT

Transferring technology to industrial partners at LETI's Grenoble Center

In the world of sports, Grenoble is best known as the site of the 1968 Winter Olympics, a small, very pleasant French city close to some of the favorite ski resorts in the Alps. But in the world of scientific and technological research, Grenoble is an important destination. More than 13,000 scientists, engineers, and other technical support staff live and work in the area, which makes Grenoble the second-leading French city for research, trailing only Paris. Internationally recognized facilities such as the National Center for Scientific Research, the European Synchrotron, the European Laboratory for Molecular Biology, and the Center for Nuclear Studies top the list of important research institutions centered in the Rhônes-Alpes city.

Semiconductor and related microelectronics research plays a major role in Grenoble's technical community. Tenth-ranked chipmaker SGS-Thomson has one of its main fabs in nearby Crolles, a facility where manufacturing and advanced R&D take place within the same walls. The Joint Research and Development Center is run jointly by SGS-Thomson and the France Telecom's National Research Center for Telecommunications (CNET), with additional personnel from Philips Semiconductor. The R&D pilot line at the fab runs about 5000 wafers per week and is focused primarily on advanced CMOS and BiCMOS technologies.

A key participant in the development of these advanced semiconductor manufacturing processes is another Grenoble-based research center, LETI, the Electronics, Technology, and Instrumentation Laboratory. Operating under the auspices of the Advanced Technology Direction of the French Atomic Energy Commission (CEA), LETI is partnered with CNET and SGS-Thomson in a regional consortium, the Grenoble Submicron Silicon Initiative (GRESSI). The group was created in 1991 and boasts an annual budget of $60 million and a staff of 200 researchers, according to Jean Therme, director of GRESSI and LETI microelectronics department manager.

"A major part of the activity at LETI is done in common contract with the industrial partners," explains Therme, who was sent to LETI 10 years ago by SGS-Thomson to work on collaborative efforts. He adds that the global chipmaker has about 50 of its people working at the laboratory. LETI itself has about 900 employees in Grenoble and at a second, larger site in Saclay near Paris. The Grenoble campus includes 8500 square meters of cleanroom space.

Therme says his department is staffed by 210 people, divided into 40 employees in facilities, 120 in process development, and 50 in process integration. The LETI microelectronics mission focuses on three areas: R&D of advanced process modules for deep submicron semiconductor technology; process integration and validation on demonstration circuits; and development of methods for physical characterization, device testing, and reliability. The main programs are the GRESSI work on CMOS and nonvolatile memories, silicon-on-insulator (SOI) technologies, and the exotic realm of sub-0.1-µm research, including Coulomb blockade devices. "One of LETI's next challenges," notes microelectronics program manager Jean-Charles Guibert, "is to transform this exotic project into a well-structured development program."

Spinning Off Technology

LETI's goal is anything but research for research's sake. "Our main goal is to transfer technology to industrial partners, large and small," emphasizes Therme. "If no company exists to handle a new technology, then spin-off companies are started." He says this spin-off approach is rare in Europe, adding that LETI is the only French research center with this policy. Companies spun off from LETI include field emission display (FED) pioneer Pixtech, integrated read-write head manufacturer Silmag, and Soitec, a leader in the burgeoning SOI market. Soitec still makes its Unibond wafers inside the LETI fab, although the company's new facility near Grenoble is slated to begin production in the third quarter of 1998. People are also an important component of the technology transfer process. Therme claims that "more jobs have been created outside of LETI than have been on the inside," with more than 1000 workers employed by these spin-off companies by the end of this year.

LETI's evaluations of new equipment and suppliers, like this Opal CD-SEM, are relayed to its industrial partners.

Inside one of the cleanrooms in Building 41, LETI's 8-inch fab, a new spin-off named INCAM Solutions is working on a novel wafer-handling approach developed in conjunction with Air Liquide. Team members believe this wafer environment control technology will fulfill future requirements for large wafer sizes and geometries of <0.25-µm by providing a molecular contamination-free IC processing environment with flexible manufacturing capabilities. The full version of this new company's acronymic name is Individual Nitrogen Conditioning for Advanced Manufacturing, but company R&D manager Michel Morin wants people to forget the long title: "It's just INCAM, like SMIF."

The INCAM Solutions isolation technology features a module-based design with integrated ultrapure gas purging, which provides individual nitrogen conditioning—what Morin calls "a perfect purge of a single wafer"—with individual front-door opening. "The concept takes a conventional cassette and just splits it.... We believe a basic module is needed for some functioning of the cassette," says Morin. The individual INCAM modules, just a few centimeters thick, are then stacked to create a "new-style cassette" that could hold reticles and glass substrates as well as wafers.

"We provide solutions for all wafer stages—storage, transportation, and transfer to the processing equipment," explains the INCAM manager. Ultraclean wafer storage is achieved by the previously mentioned individual continuous nitrogen purge; transportation is performed in a sealed container made from permeation- and carbon-free, quartzlike materials; and transfer is done with fully integrated, MESC compatible equipment interfacing technology. "I think this is a very advanced concept," Morin stresses. "We are not promoting it for current applications because wafer logistics are not really advanced enough to integrate the concept." Prototype 200-mm modules are being alpha tested at LETI, with 300-mm models available by the end of the year. Production of the 200- and 300-mm models should start by mid-1998.

Research in SOI wafer bonding and deep-UV lithography are two other areas where LETI researchers are dealing with the challenge of molecular contamination. For the SOI Unibond Smart Cut bonding process to be successful, contaminants must be completely removed from between the layers or they could show up later in the process, explains department manager Therme.

Green-colored boxes store wafers for copper metallization work.

Philippe Spinelli, principal scientist in lithography and metrology at LETI, says the new 248-nm photoresists are still too sensitive to fugitive amine contaminants found in the Class 1 cleanroom. Rather than investing in the expensive chemical filters on the market and some of the esoteric analytical tools, Spinelli and his team have invested in new-generation resist processes that show sufficient delay time stability. Their improvisational abilities are apparent in a related project, however: Spinelli's team has devised an advanced "hybrid" lithographic method combining a state-of-the-art ASM Lithography stepper (for geometries of about 0.18 µm or better) and a Leica E-beam direct writer (for sizes down to 0.013 µm).

Role of Joint-Development Pacts

Procuring brand-new tools like the ASML stepper is critical to LETI's success, according to Therme. To get access to the latest technology, LETI has entered into joint-development pacts with suppliers since 1993. "This is the only way we've found to work with the most advanced equipment: it's a problem to get advanced tools in Europe otherwise," he says. The list of equipment companies includes many industry leaders, such as Applied Materials, TEL, Lam, Eaton, Hitachi, MRC, Tencor, Shipley, SubMicron Systems, and Semitool as well as French companies such as CMP tool supplier PRESI and gas and chemicals giant Air Liquide.

"We try to evaluate new equipment and new suppliers, comparing them with existing tools," notes Therme. This information is relayed by LETI to SGS-Thomson and other partners, where it is used in decisions on corporate tool purchasing. "If you want to succeed in the transfer of technology, you have to use the same equipment as the industrial partners," he believes. While this reporter was visiting the facility, researchers were busy seeing how well the existing Hitachi critical dimension scanning electron microscope tools stacked up with a newly arrived CD-SEM from Opal.

LETI's analytical and metrological tool set, installed in a combination of small characterization areas and a dedicated cleanroom, is impressive. Many customers use these resources in the same way they might engage the services of a private analytical lab company, explains Therme. The technologies employed include inductively coupled plasma mass spectrometry, atomic force microscopy, total reflection x-ray fluorescence, Auger electron spectrometry, minority lifetime scanning, bare and patterned wafer scanning, and surface charge profiling. The ion mobility spectrometer, an increasingly important tool in the analysis of hydrocarbons in fabs, is also available.

Adjacent to the main analytical cleanroom is a newly renovated area for copper metallization work. Therme says it is isolated from the rest of the fab to avoid cross contamination, with different garments and green storage boxes to separate wafers processed there. He points out LETI has achieved the same yields with copper interconnects compared with their conventional aluminum line, adding that photoresist strip and etch are not needed for the copper processes, thanks to the Damascene structure. Much attention is paid to contamination monitoring and postprocess cleaning in conjunction with copper use.

One of LETI's strongest research fields is wafer cleaning. Current areas of study include post-CMP cleaning, both oxide and tungsten; pre—wafer bonding cleans; hydrocarbon removal; and contact hole or prebarrier layer cleans. One project with joint development partner EKC is investigating new wet cleaning chemistries, used for relatively short process times and at low temperatures, which help eliminate chlorine contamination after metal stripping.

Another project that features an economical alternative to conventional RCA cleaning using existing wet bench technology—diluted dynamic clean, or DDC—has been developed at LETI in conjunction with SubMicron Systems. Christophe Wyon, an associate of team leader Francois Tardif, says the DDC module takes up less space, can achieve a higher throughput, and expends smaller amounts of chemicals and water than equipment utilizing the RCA clean. A diluted chemical mix of 1% HF and 1% HCl used at room temperature is the basis of the new cleaning process, which can be employed for oxide, metallic, and particle removal in addition to other applications.

Time-to-Market Strategy

GRESSI announced last November the first wafers made using a 0.25-µm CMOS process, with the initial customer design prototypes of these integrated circuits now being delivered. This is in line with the consortium's roadmap, which calls for an aggressive time-to-market strategy for process module development and transfer. GRESSI is already transferring 0.18-µm process modules to SGS-Thomson, the third such transfer in the last five years. LETI's successful recent track record proves that public research made relevant to the technological needs of industry can overcome many obstacles.

For more info about LETI's microelectronics activities, contact program manager Jean-Charles Guibert at +33 4 76 88 35 81 or via E-mail at jcguibert@cea.fr

Photos by Jean-Luc Sponga/Studio Pygmée

MicroHome | Search | Current Issue | MicroArchives
Buyers Guide | Media Kit