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ESH Challenges Facing the Semiconductor Industry

WalterWorth, Sematech

The semiconductor industry is undergoing major changes as it moves to the 65-nm node and beyond. It is finding that simple scaling to smaller feature sizes is no longer adequate for maintaining Moore's Law. In fact, to manufacture chips at advanced technology nodes, the industry must make revolutionary changes in the way it operates.

Figure 1: Comparative values for five categories of waste (2001–2004).

New materials are emerging for fabricating advanced gate stacks in front-end processing and low-k dielectric and barrier layers in interconnects. To implement these materials, new processes such as atomic layer deposition are being introduced into high-volume manufacturing. The steppers required for extreme ultraviolet lithography applications will be quite different from current lithography tools because they use mirrors instead of lenses, operate under ultrahigh vacuum, and use wavelengths in the soft x-ray range.

In the Environmental, Safety, and Health (ESH) area, the International Sematech Manufacturing Initiative sees four major challenges:

• Collecting sufficient ESH data for the timely assessment of new materials and processes.

• Expanding ESH regulations.

• Solving ergonomic issues resulting from tool complexity and larger wafer sizes.

• Conserving resources, especially those related to tool energy use.

Lack of Data. While worldwide concern over chemicals and their potential health and environmental effects has accelerated over the last decade, too little toxicity data are often available to enable researchers to make adequate hazard assessments. The lack of data results from the industry's short product lifetimes, chemical suppliers' intellectual property issues, and the aggressive time-to-market requirements for surviving in a competitive environment. In addition, many source chemicals used to manufacture chips are unique to the IC industry, making it difficult to justify costly toxicity testing based on limited sales.

Regulations. Governments, especially in Europe, are increasingly developing regulations to control the use of new and existing manufacturing chemicals. For example, the European Union is proposing a chemical policy known as REACH (registration, evaluation, and authorization of chemicals) to provide a single regulatory framework applicable to both existing and new substances. The proposed regulation, which is expected to go into effect in 2006, is 1400 pages long and contains 137 articles and 17 annexes.

A more immediate challenge is the proposed European ban on the use of perfluorooctane sulfonate (PFOS), a critical component of photoresists and antireflective coatings. However, because PFOS works better than any other potential alternatives, its replacement in 248- and 193-nm lithography applications is problematic. It is estimated that the development, qualification, and implementation of new resists can take more than 15 years and cost $200 million per resist system.

Ergonometry. Ergonomics and tool serviceability have emerged as chief concerns in 300-mm fabs because of the increased weight, complexity, and size of many common tool components, such as chamber lids, robotics, and process targets. Many components weigh more than the limit set by OSHA for one-person handling, requiring the use of two or more technicians and/or hoists and gantries. Additionally, as tool complexity has increased, common tool elements have become more awkward or less accessible, making them more difficult to service. These problems will likely escalate when the industry shifts to the use of 450-mm wafers in 2012.

Conservation. Resource conservation has and will continue to challenge the semiconductor industry. While considerable progress has been made over the years to reduce water and chemical consumption, energy conservation has been more elusive. However, the industry is seriously considering designing tools that can go into idle or sleep mode when not in use—a significant opportunity for energy savings. Since more than 50% of a typical fab's energy consumption results from vacuum pumps, pump suppliers have developed more-energy-efficient and variable-speed pumps. That capability, together with the pump's ability to go into idle mode, should make future fabs much more energy efficient.

While these ESH challenges are daunting, the ingenuity demonstrated by the semiconductor industry over the years indicates that they will be addressed successfully.

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