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With NIST support, yield-enhancing software program is finally ready for the fab floor

Fab purchasing managers can finally get their hands on a manufacturing software program touted as a yield-enhancing breakthrough by its developers. The advanced process control, or APC, framework is commercially available through a licensing agreement with ObjectSpace Fab Solutions of Austin, TX. APC is a souped-up manufacturing execution system (MES) that promises major benefits for semiconductor manufacturers.

Developed with partial funding from NIST's Advanced Technology Program (ATP), the leapfrog program coordinates various types of MES, process control equipment, and fab tools. The software instantaneously detects and classifies process faults. It also makes changes from one wafer run to another by adapting recipes to fit shifting process requirements.

The software was born from a collaboration among Advanced Micro Devices (AMD) in Austin, Minneapolis-based Honeywell, and Sematech. Honeywell manufactures control systems for pharmaceutical manufacturing as well as for oil and gas refining. The partners worked 27 months on the ATP project, which received $4.97 million from NIST and $5.1 million from the other partners.

Claimed benefits include an 83% reduction in photolithography reworks, a 27% reduction in the standard deviation of the rate of material removal during wafer polishing, and a 48% reduction in microprocessor speed variability. The program addresses yield "by achieving much better process uniformity," notes Alan Weber, vice president of the Fab Solutions division of ObjectSpace. The software enhances yields by modeling processes beforehand and using feedback to "accommodate for drift or for variations in input materials with the actual process targets."

By reducing variability in linewidths the project partners were able to increase microprocessor clock speeds by 15 MHz without yield losses, enabling AMD to market microprocessors with clock speeds much faster than traditional processes allow. Users of the program can make run-to-run changes up to four times faster than before, with fewer engineers needed. In addition controllers can be enhanced in days or even hours, instead of weeks or months.

Weber cited still another way that the software "turns the yield knob," as he puts it. "If you look at yield as good wafers divided by total wafers, then the productivity improvements you get by running fewer test wafers or running a tool close to capacity can also translate to yield. Most people would call that wafer yield or die yield." Weber says the APC framework works best with processes such as lithography, overlay control, and exposure dosage. "Another process that has been well applied to it is the CMP process, because it is one that is becoming more and more critical" as multilevel interconnect processing grows.

Another yield-related benefit, he notes, is the program's ability to determine when a piece of equipment may fail. "If you can predict when a tool is going to go bad and stop it from creating bad parts, you can translate that into yield also."

The main factor hindering adoption of APC till now has been the high cost of integrating static, single-task controllers into existing manufacturing systems, according to the project's partners. Combining their complementary fields of expertise, the partners sped up the development of a flexible toolset that can be installed quickly throughout the fab with little need for customization.

Weber says a client needs only to "buy the package" from ObjectSpace Fab Solutions, which will install it. "It requires system integration with whatever technology the end-user has for collecting process data. We talk with whatever piece of software that talks to the tool." He adds that future releases of the software will "have more ease-of-use filters, more built-in models, and canned strategies, plus more adapters for the popular commercial third-party tools."

Weber says his firm has a "fairly healthy backlog of initial orders" from three customers. Pilot systems are installed at Motorola and IBM. ObjectSpace has sent proposals "to six other tier-one companies in the United States, Japan, South Korea, and Taiwan."

ObjectSpace Fab Solutions is exhibiting at Semicon West 99 in San Francisco and is sponsoring a half-day seminar during the trade show's technical symposium. "I would say the adoption process is moving along nicely," says Weber. The software is in the SEMI standards process. The next ballot round is scheduled to take place during Semicon West because, says Weber, there were enough changes recommended during the last ballot round this past March to push the final balloting to the end of 1999. The changes "had to do with architectural issues and making sure multiple suppliers were accommodated," Weber says.

According to Tom Hill, the ATP project manager for Honeywell, the success of the project gives U.S. chipmakers up to a two-year jump on their foreign counterparts in using APC. The program has been identified in previous versions of the National Technology Roadmap for Semiconductors, now an international effort, as integral to enabling the industry to maintain its historical productivity growth rate of 25% to 30%, project leaders say.

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