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Semiconductor Industry Leadership in Global Climate Protection
(7/1/2001) Future Fab Intl. Issue 10
By Scott C Bartos, US Environmental Protection Agency
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Introduction

The US Environmental Protection Agency (EPA) is proud to support semiconductor industry efforts to reduce greenhouse gas emissions. EPA and its semiconductor industry partners (see Table 1) are collaborating on climate friendly business strategies and communicating these environmental objectives to their suppliers and customers alike. EPA’s semiconductor industry partners are contributing to climate protection in three key areas:

  • Reducing direct emissions of high global warming potential (GWP) chemicals
  • Supporting climate friendly business investment
  • Reducing indirect emissions of carbon dioxide by improving manufacturing energy efficiency.
Table 1. PFC Emission reduction partnership for the semiconductor industry.
Advanced Micro Devices Micron Technology
American Microsystems Motorola
Burr-Brown National Security Agency
Cherry Semiconductor National Semiconductor
Dominion Semiconductor NEC Electronics
Eastman Kodak Philips Electronics
Hewlett-Packard Rockwell Semiconductor Systems
Intel STMicroelectronics
International Business Machines Sony Semiconductor
LSI Logic Texas Instruments
Lucent Technologies  

Beginning in 1994, EPA has developed voluntary industry initiatives seeking to cost-effectively reduce greenhouse gas emissions. While the majority of greenhouse gas emissions are carbon dioxide, emissions of high GWP gases (HFCs, PFCs, and SF6) are growing much faster than all other greenhouse gas types. The rapidly increasing concentrations of these persistent chemicals will have a lasting impact on the climate. It is important that all industry sectors reduce emissions where technically feasible and cost-effective (see Figures 1, 2, and 3).


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Figure 1.


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Figure 2. Percentage growth in US greenhouse gas emissions from 1990 to 1998.


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Figure 3. Relative contributions of US HFC, PFC and SF6 emission sources in 1998.

While Figure 3 shows that semiconductor manufacturing is currently the smallest US source of high GWP emissions, it, along with ODS substitutes, is the only source expected to grow significantly over the next ten years (see Figure 4).


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Figure 4. Estimated annual US PFC Emissions from Semiconductor Manufacturing (MMTCE) by Linewidth (Business WITHOUT Action).

EPA’s Climate Protection Division works with five major US industries that use and/or emit the most potent greenhouse gases, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6):

  • Electric utilities (SF6)
  • Aluminum producers (PFCs)
  • HCFC-22 producers (HFC-23)
  • Magnesium producers and casters (SF6)
  • Semiconductor manufacturers (HFCs, PFCs and SF6).

The PFC Emission Reduction Partnership for the Semiconductor Industry

With the support of the Semiconductor Industry Association (SIA), EPA’s Climate Protection Division created the PFC Emission Reduction Partnership for the Semiconductor Industry (Semiconductor Industry Partnership) to address emissions of long-lived greenhouse gases. The swiftly growing demand for more complex semiconductor devices is expected to result in increased use and emissions of high GWP gases. Current semiconductor manufacturing processes require the use of fluorinated compounds including PFCs, HFCs, NF3, and SF6, collectively termed perfluorocompounds (PFCs) for ease of use. These chemicals are used primarily to plasma etch thin films and to dry clean chemical vapor deposition (CVD) tool chambers. Under normal operating conditions, 20 to 80 percent of the PFCs pass through the manufacturing tool chambers unreacted and is released to the air. These chemicals persist for up to tens of thousands of years in the atmosphere and are much more potent greenhouse gases than CO2 (see Table 2). EPA’s semiconductor industry partners are using a pollution prevention approach to evaluate and implement PFC emission reduction technologies.

Table 2. Fluorinated compounds used to manufacture semiconductors.
Compound Atmospheric Lifetime (years) Global Warming Potential[1] (100-year time horizon)*
CO2 - 1
CF4 50,000 6,500
C2F6 10,000 9,200
CHF3 264 11,700
C3F8 2,600 7,000
c-C4F8 3,200 8,700
NF3** 740 8,000
SF6 3,200 23,900
* IPCC, 1995
** Maroulis, P et al, November 1994

The Semiconductor Industry Partnership catalyzed international industry action to reduce emissions of long-lived PFCs. The partnership understands that in the highly competitive global marketplace for semiconductors, broad international industry participation and information sharing are critical to successfully achieving its environmental goals.

Japan’s Ministry of International Trade and Industry (MITI) and U.S. EPA organized a “Pathfinder Meeting” on PFC emissions in 1996. This important meeting concluded with a new voluntary agreement between the Electronics Industry Association of Japan (EIAJ) and MITI to reduce PFC emissions. With commitments from US and Japanese manufacturers in place, voluntary initiatives were building momentum globally. By the time EPA and MITI hosted the first international conference on PFC emissions control in 1998[2], semiconductor manufacturers in Europe and Korea had also established voluntarily initiatives to reduce PFC emissions.

The World Semiconductor Council (WSC), whose members include the national semiconductor industry associations of the United States, Japan, Europe, Korea, and Taiwan[3] identified PFC emission reduction as the industry’s top environmental priority in 1998 (see Table 3). In an unprecedented display of global industry cooperation, the WSC successfully balanced the business and environmental objectives of a diverse group of global semiconductor manufacturers representing more than 90 percent of world production to establish an international emissions reduction goal. In April 1999, WSC members announced a goal of reducing PFC emissions by at least 10 percent below the 1995 baseline level by year-end 2010[4]. This type of responsibly aggressive goal setting assures international governments, industry suppliers, and the public of the industry’s commitment to protect the climate. EPA has presented its prestigious Climate Protection Award to the following organizations in recognition of their industry leadership and unique technical contributions towards reducing greenhouse gas emissions:

  • IBM (1998)
  • World Semiconductor Council (1998)
  • Applied Materials (1999)
  • Motorola (1999)
  • STMicroelectronics (1999)
  • Intel (2000)
  • Novellus Systems (2000).

The technical aggressiveness represented by the WSC’s reduction goal of 10 percent below the 1995 baseline by 2010 is obvious from emissions modeling. Figure 4 is derived from a top-down model of average PFC emissions from semiconductor manufacturing that accounts for the evolution of more complex devices (see Appendix A). This chart illustrates an estimate of the US industry’s rapidly expanding use and emission of the high GWP gases under a “business without action” scenario contrasted with a “business with action” target should all US semiconductor manufacturers achieve the WSC’s reduction goal. Achieving the “business with action” reduction goal, the US would prevent greenhouse gas emissions equivalent to 16 million metric tons of carbon (MMTCE) in 2010 alone, achieving climate protection equivalent to removing more than 12 million cars from the roads.

Table 3. PFC leadership timeline.
1980s PFCs identified as effective dry etch and cleaning chemicals
1990s PFCs identified as potent greenhouse gases
1996 US EPA launches voluntary PFC emission reduction partnership with semiconductor industry
EPA and MITI organize Japan PFC Pathfinder Meeting
Japan and Europe establish voluntary partnerships
1998 industry Japan announces PFC emission reduction goals for electronics
EPA and MITI host 1st Global Semiconductor Industry Conference on PFC Emissions Control, Monterey, California
World Semiconductor Council (WSC) designates PFC emissions as top environmental challenge
Korea establishes voluntary partnership
IBM announces first corporate emission reduction goal
1999 Taiwan establishes voluntary partnership
WSC commits to global emission reduction goal
2000 EPA and US partners seek to renew voluntary pledges to reduce PFC emissions

Climate-Friendly Business Opportunities

Modern integrated circuits are enabling a wealth of climate-friendly business opportunities and practices evident in the explosion of electronic commerce, telecommuting, and an ever-expanding menu of ENERGY STAR® products for the home and office. These energy-efficient technologies reduce indirect emissions of carbon dioxide and other air pollutants by reducing the demand on power plants and transportation sources that combust fossil fuels. In addition to this environmental benefit, computer and communications networks continue to reduce the time and expense of day-to-day business transactions. The integration of energy-efficient technologies helped to increase the US Gross National Product by 35 percent from 1973 to 1986 while maintaining fairly constant energy demand[5]. Joseph Romm, Executive Director of the Center for Energy and Climate Solutions, predicts a growing Internet economy and the expansion of “frictionless” electronic commerce will generate further energy intensity improvements of 1.5–2.0% per year through 2007[6].

Semiconductors are the information “nerve-centers” for many of today’s most energy-efficient appliances, vehicles, buildings, and industrial processes. The World Resources Institute’s (WRI) 1998 study, Taking a Byte Out of Carbon, begins to reveal the tremendous potential benefit the electronics and communications sectors can provide to climate protection. WRI’s analysis of fourteen corporations shows how advanced electronic processors, controls, and sensors improve product performance, reduce operating costs, and prevent atmospheric pollution. For example, Intel Corporation has developed an efficient power management system for personal computers. Known as Instantly Available Personal Computer technology, it allows a computer to enter an energy conservation mode using less than 5 watts of power when not in use and still remain connected to information networks. Instantly Available computers maintain constant and immediate access to computing functions and information and are not burdened by traditional re-booting[7]. Intel’s latest power management system uses less energy than traditional power management technology, thus reducing both greenhouse gas emissions and operating costs. The innovative technology will also provide Intel’s products with a distinct performance advantage in a very competitive market.

EPA and Department of Energy’s (DOE) innovative ENERGY STAR® labeling program provides another example of how semiconductors are supporting growth in climate-friendly business opportunities. The ENERGY STAR® identifies home and office electronics that optimize power management systems, thereby minimizing indirect CO2 emissions and cost of ownership. EPA established its energy efficiency label with computer manufacturers in 1992 and has gone on to successfully organize voluntary performance specifications with a wide range of electronics manufacturers whose products include copiers, fax machines, printers, scanners, TVs, VCRs, DVD and audio devices. At the heart of every ENERGY STAR® product is a semiconductor microprocessor that efficiently manages power consumption.

Efficient power management and superior product performance go hand-in-hand, especially when one examines the rapidly growing portable electronic device market including portable telephones, personal digital assistants (PDAs), and laptop computers. Customer demand for smaller, more energy efficient (ie, longer operating time between battery charging) portable devices are driving development of power management functionality. ENERGY STAR® promotes the transfer of the most efficient power management technologies to both home and office products. The program continues to grow and keep pace with the rapidly expanding electronics industry. Today’s ENERGY STAR® monitors use less than 5 watts of power in sleep mode and in July 2000, the ENERGY STAR® power specification for computers was lowered from 30 watts to less than 15 watts. Over the life of the ENERGY STAR® products sold to date, American consumers will save $16 billion while protecting the environment by avoiding greenhouse gas emissions equivalent to 33 million metric tonnes of carbon (MMTCE).

Improving Manufacturing Energy Efficiency

Beyond providing one of the technologies that is driving improvements in economic productivity and energy efficiency, semiconductor producers are also striving to improve the efficiency of their own manufacturing processes. The industry has specified climate protection in both its near and long term environmental health and safety goals. The Semiconductor Industry Association (SIA) has identified perfluorocompound (PFC) emission reduction and improving manufacturing energy efficiency as key environmental objectives[8]. Several leading manufacturers have begun to implement comprehensive climate protection initiatives by announcing aggressive atmospheric pollution prevention goals.

IBM Corporation and ST Microelectronics are implementing business plans that include comprehensive greenhouse gas emission reduction targets. IBM was the first major producer of semiconductors to announce this type of environmental goal. IBM has pledged to reduce energy use by 4 percent per year and reduce direct emissions of PFCs by 40 percent by year-end 2002, using 1995 as a baseline year. Reducing its energy consumption by 4 percent in 1997, IBM avoided emissions of more than 184,000 tons of carbon dioxide and saved $14.8 million in operating expenses[9].

ST Microelectronics announced a corporate environmental policy with a strong focus on climate protection in 1999. ST is striving to operate at a “carbon neutral” basis by 2010 by acquiring energy from renewable and alternative sources (eg, wind, photovoltaics, combined heat and power, and fuel cells), reducing direct emissions of PFCs, and offsetting greenhouse gas emissions with carbon sequestration projects (eg, reforestation). ST’s Environmental Decalogue establishes the following climate protection goals:

  • reduce total energy consumption by at least 5 percent per year
  • reduce total emissions of CO2 from energy consumption by a factor of 10 by 2010 (versus 1990 baseline)
  • increase utilization of renewable energy sources so they represent at least 5 percent of ST’s total energy supplies by year-end 2010
  • offset remaining CO2 emissions from energy consumption through reforestation or other means
  • reduce PFC emissions by at least a factor of 10 in 2008 versus 1995[10].

Contributions of Equipment and Material Suppliers

The semiconductor industry’s clearly defined environmental commitment acts to assure equipment and material suppliers that a robust market exists for environmentally-friendly manufacturing processes and products. Many semiconductor industry suppliers are working closely with EPA’s manufacturing partners to identify and evaluate PFC emission reduction technologies. As outlined in EPA’s Memorandum of Understanding, the industry is using a pollution prevention approach to identify the most cost-effective and environmentally-friendly reduction opportunities. The industry’s hierarchy of emission reduction technologies and examples of available technologies is:

  • Optimize manufacturing processes to minimize PFC emissions, for example Novellus Systems’ in situ NF3 CVD chamber clean recipes and Applied Materials’ Remote NF3 Plasma CVD Clean Technology.
  • Identify and implement more environmentally-benign alternative process chemicals, for example 3M’s C3F8 alternative to C2F6 for CVD chamber cleaning.
  • Capture and beneficial re-use of PFC gases, for example Air Liquide’s and Air Products’ membrane separation technologies and Praxair’s cryogenic separation technology.
  • Destroy PFCs avoiding release to the atmosphere, for example Litmas Blue’s plasma abatement device, Hitachi’s catalytic oxidation device, and BOC Edwards’ thermal oxidation device.

Semiconductor industry suppliers have made tremendous progress in a short amount of time and the menu of emission reduction technologies continues to grow. EPA is currently supporting the evaluation of another promising plasma abatement device being developed at Texas A&M University and tested at Motorola.

The equipment suppliers’ leading trade association, Semiconductor Equipment and Materials International (SEMI), supports the manufacturers’ environmental goals encouraging the supplier community to design products that minimize energy consumption and operate without PFCs where technically feasible[11]. The semiconductor manufacturers’ close working relationship with its suppliers has generated industry optimism and allowed semiconductor producers worldwide to confidently establish aggressive climate protection goals.

Future Opportunities

Opportunities for the semiconductor industry to contribute to climate protection will increase with the expansion of advanced information and communications technologies. Consumer demand for mobile devices will continue to grow as third generation cellular products lead to more available and robust Internet and video services. More efficient 300mm wafer processes will lead to lower semiconductor production costs (per die basis) and reduced energy intensity. Copper interconnects and low-k dielectric material will allow integrated circuits to continue to shrink in size, reduce PFC use by reducing the number of layers by 30 percent or more versus traditional aluminum interconnects, operate at lower temperatures, and use less energy.

A related and rapidly growing electronics industry sector uses and emits high GWP chemicals in its manufacturing processes. Manufacturing thin film transistor liquid crystal displays (TFT-LCD), the largest portion of the flat panel display (FPD) market, employs NF3-based plasma clean steps similar to those used in semiconductor manufacturing tools. With demand for TFT-LCD units (in laptop, handheld, and desktop applications) expected to grow greater than 20 percent annually through 2005[12], there is a tremendous opportunity for semiconductor manufacturers to share their knowledge and experience of emission reduction strategies. An international PFC emission reduction meeting planned for December 2000 by EIAJ and SEMI should provide an important forum in which to begin this technology transfer.

The US semiconductor industry is working together with EPA to chart a business strategy that thoroughly integrates climate protection. Close cooperation between semiconductor manufacturers and their equipment and material suppliers continues to produce increasingly energy-efficient and environmentally-friendly manufacturing tools and processes. EPA is especially proud of the collaborative working relationship that has been achieved and recognizes that these types of cooperative initiatives provide quick)and effective environmental protection.

APPENDIX A: Methodology Used to Project US PFC Emissions (Business WITHOUT action) from Semiconductor Manufacturing

This section briefly describes the method for estimating baseline US PFC emissions from semiconductor manufacturing for the period 1995 to 2010, which is shown in Figure 4. Central to our method is application of a PFC emissions factor (expressed in units of silicon consumption) and a forecast of US silicon consumption by wafer size and feature size.

The emission factor,·EÒ, is a weighted average, with the average taken over all PFC gases and all etching and CVD cleaning processes. The emissions factor was developed from estimates of total PFC emissions (units of MMTCE) that are available to the US EPA through the PFC Emission Reduction Partnership for the Semiconductor Industry. These annually reported emissions were divided by the corresponding amount of silicon consumed by the Partnership (in units of million square inches of silicon for various wafer sizes, including test wafers). Annual silicon consumption by the Partnership was estimated using publicly available information about the Partnership’s fabrication capacity in the US (by wafer size), share of worldwide average capacity utilization, and average test wafer usage in manufacturing.

The emission factor ·EÒ, however, does not account for increasing chip complexity, which is the term given to the increase in device layers that occurs as linewidths (or feature sizes) become smaller. To account for this increasing chip complexity, we defined an emission factor per average unit area of silicon consumed per average layer according to the equation

where ·eÒ is the average emissions per unit area of silicon consumed per average layer and ni is the nominal number of layers used in device fabrication for technology node i (ie, 0.35 mm, 0.25 mm, 0.18 mm, etc). Using the estimate of ·EÒ previously described and values of ni obtained from the Industry Roadmap for each technology node, we calculated ·eÒ. The sum is taken over all feature sizes in use for the years 1995–1998 using publicly available information.

Estimates of ·EÒ and ·eÒ were obtained for the years 1995, 1996, 1997, and 1998 using reports of the Partnership’s PFC emissions and consumption of silicon. The values for ·eÒ for the four years were then averaged into a single number, which was assumed to remain unchanged and used to calculate the baseline emissions.

The model uses estimates of actual worldwide silicon consumption and of forecasts of worldwide silicon consumption by the semiconductor industry that VLSI Research, Inc publishes. The forecasts cover a 5-year period and are updated annually. To calculate the US share of worldwide silicon consumption forecasts (by wafer size and feature size) we used a publicly available database of worldwide fabrication facilities. The VLSI Research reports also contain historically experienced compound average growth rates (CAGR) of silicon consumption and historically observed profiles for the technological progression to smaller linewidths. We assumed that the overall (10-year) average CAGR for silicon consumption by wafer size would be maintained to 2010. We also assumed that the worldwide profiles for progressing to smaller linewidths would mimic the observed contemporary profiles reported by VLSI Research until 2010, adjusting the profiles for linewidths 0.25 mm and smaller for the recently reported trend that the progression to smaller linewidths across the industry is accelerating. We obtained the schedule for the progression to smaller feature sizes and the corresponding nominal number of layers from the 1998 Updated Industry Roadmap.


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Figure 5. ENERGY STAR® Product Label.

US “business without action” emissions were estimated by multiplying the projected consumption of silicon for each linewidth by both the average emissions factor per layer per unit area of silicon consumed and the nominal number of layers for each linewidth. In the projections presented in Figure 4, we have also accounted for the ongoing switch to copper interconnects. Using best available information, it is assumed that the nominal number of layers is reduced by 30 percent when copper is used instead of aluminum. It is also assumed that US manufacturers will phase-in copper interconnect processes starting with linewidths between 0.16 and 0.2 mm at phase-in rates of 20 percent, and increasing to 35, 50, 65, and 80 percent for linewidths equal to 0.15 mm, 0.13 mm, 0.10 mm, and 0.07 m, respectively.

References

[1] Global warming potential values act to quantify the potential integrated climate forcing of various greenhouse gases relative to CO2.

[2] US EPA and Japan’s MITI (April 1998). Global Semiconductor Industry Conference on PFC Emissions Control. Monterey, California USA.

[3] WSC member organizations are the US Semiconductor Industry Association (SIA), Electronic Industries Association of Japan (EIAJ), European Electronic Component Manufacturers Association (EECA), Korea Semiconductor Industry Association (KSIA), and the Taiwan Semiconductor Industry Association (TSIA).

[4] SIA Press Release, http://www.semichips.org/news/archives/pr06181999_19.htm, 1999.

[5] US Department of Energy, Scenarios of US Carbon Reductions. Prepared for the Office of Energy Efficiency and Renewable Energy, September 22 1997.

[6] Romm, J, The Internet Economy and Global Warming. The Global Environment and Technology Foundation, December 1999.

[7] World Resources Institute, Taking a Byte Out of Carbon, 1998.

[8] Semiconductor Industry Association, International Technology Roadmap for Semiconductors, Environmental, Safety, and Health, 1999.

[9] IBM Corporation, Application for EPA Climate Protection Award, 1998.

[10] ST Microelectronics, http://eu.st.com/stonline/company/environm/index.htm. Environmental Decalogue, 1999.

[11] Semiconductor Equipment and Materials International, S2-0200, Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment, 2000.

[12] Young, R, “FPD Market Overview and Forecast” in Proceedings of the SEMICON West 2000 Flat Panel Display Strategic Market Seminar, San Francisco, CA, 2000.

 
 
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