Partnerships in environmentally benign semiconductor manufacturing

03/01/1997

Partnerships in environmentally benign semiconductor manufacturing

C.R. (Bob) Helms, Stanford University, Stanford, CA

In the ideal world of environmentally benign semiconductor manufacturing, industry recovers, recycles, and reuses all material resources with a minimal consumption of energy. Truly environmentally benign semiconductor manufacturing must

integrate the complete cycle from raw materials and energy to final product disposal (Fig. 1) [1].

Environmentally benign solutions include reducing the use of hazardous and environmentally harmful materials (source reduction), recycling, and reuse (reclamation). The preferred method is clearly source reduction, in which environmentally damaging or toxic materials (such as CFCs) are replaced with environmentally benign alternatives. The trend toward source reduction leads to a focus on "designing for the environment," where reducing or eliminating harmful substances in electronic product manufacturing is planned right from the beginning. The opportunities to apply environmentally benign concepts in the semiconductor industry are enormous (Fig. 2), considering the significant quantities of water, energy, and hazardous chemicals used in all stages of manufacturing.

One overall driver of future manufacturing developments is the reduction in cost/bit or other performance metrics. Any sacrifice in productivity that may be required for environmentally benign solutions will be difficult to implement. This consideration is all the more important as lower cost/bit becomes more difficult to achieve [2]. Environmentally benign manufacturing must also deliver superior yield, throughput, cycle time, and overall cost of ownership. Environmentally benign processes and tools have the potential to provide a significant cost/bit reduction in and of themselves through the reduction in consumables use and process simplification.

Effective solutions to environmentally benign semiconductor manufacturing should begin with a breadth of activity in research, development, design, and engineering, with participation of multiple disciplines, such as chemistry, chemical engineering, electrical engineering, and mechanical engineering. Such a vertically integrated, cross-functional approach has the potential for effective timely solution coupled with a horizontally integrated multidisciplinary approach.

Figure 1. Environmental life cycle for semiconductors indicating opportunities for source reduction as a first priority and recycle and reuse for an integrated solution with minimal environmental impact.

Research center

The NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing was established April 15, 1996, to perform the cross-functional, multidisciplinary work necessary to make the US semiconductor industry a leader in this field. Funded by a partnership between the National Science Foundation, the Semiconductor Research Corp., SEMATECH, numerous semiconductor manufacturers and suppliers, and universities, the Center provides a unique multidisciplinary culture to educate a new breed of engineering leaders, producing critical science and technology for environmentally benign semiconductor manufacturing (see table).

Headquartered at the University of Arizona, the Center is directed by professor Farhang Shadman of the Chemical Engineering Department. The Arizona site conducts studies in water use and conservation, chemical mechanical polishing, and factory science. Stanford University, overall industrial liaison for the Center, researches front end processes and tools, especially related to aqueous chemical use reduction. Activities at MIT, led by Center associate director Rafael Reif of MIT`s Electrical Engineering & Computer Science Department, concentrate on interconnect processes and tools, especially related to the reduction of global warming gases. Some of the work in this area is being conducted at the University of California, Berkeley. Each major research area has participants from more than one university, with multiple industry participation as well.

This concept is implemented and managed through the World Wide Web and extensive use of video and teleconferences. The portability of this program gives graduate students access to the resources of all the universities and many of the industrial companies involved.

Integrated water use reduction and recycle

SEMATECH organized a program to develop technologies to minimize water use, particularly related to ultrapure water (UPW), and to deliver better overall performance to the IC manufacturing community in the form of increased throughput, process/tool simplification and reliability, and reduced cost. Activities were vertically integrated across the IC manufacturing industry, national labs, wet tool suppliers, and universities. The program, in many ways the forerunner to the NSF/NRC Center, applied horizontal integration from fundamental surface chemistry to large scale DI pilot plant development.

Two groups are developing solutions for water reduction. The University of Arizona group, consisting of Shadman and Sandia National labs under Dr. Bob Donovan, is targeting UPW recycling with the help of major DI plant suppliers and major IC manufacturers. Another group, Stanford University and Sandia, in collaboration with wet tool suppliers and IC manufacturers, is developing point-of-use water reduction at the wet tool level. Stanford is working to reduce not only the water supplied to the fab but also the overall requirements on delivery as well as recycling. Both the Sandia and Stanford activities rely on coordinated technology transfer to the IC manufacturers and wet tool suppliers: The IC manufacturers optimize their wet tool processes for both water consumption and performance metrics, while the wet tool suppliers factor equipment and process improvements into their designs.

In one example, a team from the Stanford group with Russ Parker from Hewlett-Packard used wet tool process optimization to reduce water use by a factor of five. The cross-functional approach identified and eliminated what could have been a major program show-stopper. Point-of-use reduction leads to reduced water use and to inferior quality of the recycle streams, adversely affecting operations. Researchers identified this issue early in the program and called for integrated development of recycle and point-of-use reduction.

The NSF/SRC Engineering Research Center will continue to provide a pre-competitive arena for long range strategic research in this area. The SEMATECH program will continue to disseminate its technological findings to IC manufacturers and equipment suppliers through SEMI and SEMATECH. These developments have a natural feedback path into the educational infrastructure, where they can be included in the curriculum of the Center.

Figure 2. Modules for an advanced integrated circuit process a) early in the process flow and b) near the end for an advanced integrated circuit process. The vertical arrows indicate processes where significant quantities of water, energy, and hazardous chemicals are used.

Future activities

The potential exists for a significant cost/bit reduction through environmentally benign semiconductor manufacturing, as well as for significant benefits to the overall semiconductor manufacturing industry in the regulatory and political arena. The semiconductor industry is already planning to build and expand more focus centers like the NSF/SRC Engineering Research Center with cross-functional, vertical and multidisciplinary, horizontal integrated participation. The Center`s progress in research, development, education, and manufacturing could serve as a model for the future and assist other industries with their environmental, safety, and health issues.

References

1. C.R. Helms, J. Shaw, "Topical Workshop Report on the Electronics Industry," Basic Research Needs for Environmentally Responsive Technologies for the Future, P.M. Eisenberger, ed., Princeton University Materials Institute, p. 15 (1996).

2. P.E. Ross, "Moore`s Second Law," Forbes, p. 116 (March 25, 1995).

For information on companies participating with the NSF/SRC Center, contact Don Herr at at ph 419/941-9431, e-mail [email protected], or Bob Helms.

C.R. (Bob) Helms is professor of electrical engineering and director of solid state industrial affiliates at the Department of Electrical Engineering at Stanford University, Stanford, CA 94305; ph 415/723-0406 or e-mail [email protected]. Helms is also founding associate director of the Center for Environmentally Benign Semiconductor Manufacturing.