Computing the Carbon Footprint Supply Chain for the Semiconductor Industry: A Learning Tool. Yasser Dessouky, Minnie H. Patel, and Tweesak Kaosamphan Industrial & Systems Engineering Charles W. Davidson College of Engineering, San Jose State University One Washington Square, San Jose, CA 95192-0085, USA Yasser.desssouky@sjsu.edu, minnie.patel@sjsu.edu Abstract Because of increasing environmental concerns and because the semiconductor industry is very energy intensive, there is a need for this industry to become more environmentally friendly and energy efficient. The semiconductor industry provides several challenges due to the complexity of the manufacture of integrated circuits and the role of globalization in their production. This paper proposes a user-friendly carbon footprint model to raise student awareness and knowledge about the effect that changes in manufacturing technologies and transportation modes can have on the carbon footprint of the supply chain for the semiconductor industry. On becoming familiar with the carbon footprint model, students will be better able to develop green solutions that address customers needs in an increasingly global marketplace. Keywords: Supply Chain, Carbon Footprint, Semiconductor Manufacturing Introduction San Jose State University (SJSU) trains engineers to meet the needs of the local industry base. It is estimated that 10 percent of California s engineering graduates come from San José State University. The American Electronics Association survey states that 1,500 of the top 2,500 electronics companies (60 percent) are within 30 miles of SJSU. Establishments and employment in green technology and services are growing in Silicon Valley (Joint Venture Silicon Valley Network, 2009). Today we have Generation Net students in our engineering schools. Generation Net students differ from previous generation of college students: they prefer learning that is experiential (learning by doing rather than being told what to do), highly visual (as compared to text based), and interactive (Chubin et al., 2008). The semiconductor industry is very energy intensive, and hence there is a need to make it more energy efficient and environment friendly. The semiconductor industry provides several challenges due to the complexity of the manufacture of integrated circuits and the role of globalization in their production. For this industry, it is common to find that each stage in the supply chain takes place in a different company and country. For example, wafer fabrication may occur in Taiwan, and then be transported to the United States for testing and sorting, and then move to Singapore for assembling and packaging. The importance of the semiconductor industry to the Silicon Valley provides San José State University (SJSU) with a tremendous opportunity to develop an educational experience. By experimenting with different manufacturing technologies and transportation modes for the semiconductor industry, students will be able to examine the effect of these changes on the carbon footprint of the supply chain. The goal of the proposed model is to help engineering students develop an understanding of the effect of manufacturing technologies and transportation modes on the carbon footprint of the supply chain for the semiconductor industry and its environmental impact. Most of the energy we use today comes from fossil fuels, such as coal, natural gas, and petroleum. In order to produce energy, fossil fuels are processed by combustion. This releases pollution, such as carbon monoxide and sulfur dioxide, which contributes to acid rain and global warming. Worldwide 95% of energy is generated from fossil fuels. The energy consumption per capita is the highest in North America. A change is urgently required in our energy policy and will need to include options for renewable energy and an emphasis on sustainability. As yet, no government has legislated that goods and services be labeled to show the carbon emitted during their production, distribution, and disposal. However, we expect that such legislation will be required in the nottoo-distant future, and retailers and manufacturers are already preparing for its arrival (Barrett, 2008). In today s global environment, many manufacturing companies have global supply chains to meet customer demands and remain competitive. Beamon (1998) defines supply chains as an integrated process wherein a number of business entities (i.e., suppliers, manufacturers, distributors, and retailers) work together in an 187
effort to: (1) acquire raw materials, (2) convert these raw materials into specified final products, and (3) deliver these final products to retailers. This chain is typically characterized by a forward flow of materials and a backward flow of information. The traditional view of optimizing supply chains is based on minimizing costs to partners in the supply chain and/or maximizing service to the customers. However, as consumers are becoming more environmentally aware, companies are also recognizing a need to optimize their supply chains based on carbon emissions. Other factors driving companies to reduce carbon emissions in their supply chain are the existing and possible new government regulations and the recent significant increases of direct energy costs. Numerous research papers have been published relating to green supply chains. Srivastava (2007) identified major works on green supply-chain management research. He analyzed those which integrated environmental thinking and identified gaps, issues, and opportunities for further study and research. The areas that have collectively begun to contribute to a more systematic knowledge base are quality, operations strategy, supply-chain management, and product and process technologies. In the short term, these areas will continue to be important. However, more integrative contributions are needed in the long term, including intra- and inter-firm diffusion of best practices, green technology transfer, and environmental performance measurement. Five factors that have a direct impact on green management implementation are materials, processes, packaging, working environment, and a waste system for the green supply chain in the electronics industry (Udomleartprasert, 2004). The changing nature of global trade requires companies to examine frequently their supply chain structure to ensure optimum efficiency and to consider the impact of this structure on the amount of carbon dioxide emitted. Thus, there is a need to develop a tool to measure the amount of carbon emissions produced from a complete supply chain. Carbon Trust (2009) defines the carbon footprint of a supply chain as follows: The carbon footprint of a product is the carbon dioxide emitted across the supply chain for a single unit of that product. For example, the carbon footprint of a can of food is the total amount of carbon emissions from production, transportation, consumption, and disposal of the single can of food. Carbon Trust is a private company set up by the United Kingdom Government to develop business solutions to accelerate the transition to a low carbon economy. Although there are many online tools to calculate individual/household carbon footprints such as Carbon Footprint (2009), Takepart.com (2009), and US EPA (2009) (to list a few), there are no standard measures to compute the carbon footprint of a supply chain. A study by Weber et al. (2007) on carbon emissions embodied in importation, transport, and retail of electronics in the United States suggests that the supply chain, transport, and retail all make significant contributions to the net CO 2 emissions associated with electronics. This study estimates the electronics portion of CO 2 emissions entering the United States has risen from 11-16% (100-320 Mmt) in 1997 to 17-26% (350-770 Mmt) in 2004. Ramudhin et al. (2008) have developed an integer programming model that allows the evaluation of different strategic decision alternatives, such as supplier and subcontractor selection, product allocation, capacity utilization, and transportation configuration, together with their impact in terms of their carbon footprint. Carbon Trust (2006) have presented a report with two case studies showing the financial and environmental gain for reducing carbon emissions across a supply chain. The studies were conducted for Walkers, a snack food company, and Trinity Mirror, a newspaper publisher. Instead of examining carbon emission reductions only within a company, they examined the emissions across the whole supply chain, and showed there were saving opportunities worth 28,000 tons of CO 2 and 2.7 million British pounds annually. Currently, most of the studies to reduce the carbon footprint across a supply chain have been performed in Europe. Furthermore, to the knowledge of the authors, no study has been performed to compute and reduce the carbon footprint across the supply chain for the semiconductor industry. There are, however reports of semiconductor fabrication plants (fabs) going green (Singer, 2007). A typical semiconductor fab may use as much electricity in a year as 10,000 homes (170,000 mega watts) and up to 3 million gallons of water per day. These new green fabs are designed to reduce electricity and water use. Proposed Modeling Tool 188
The semiconductor industry provides several challenges due to the complexity of the manufacture of integrated circuits and the role of globalization in their production. Figure 1 shows the different stages for the processing of an integrated circuit. A brief description of the stages is presented below. It is common to find that each stage in the supply chain takes place in a different company and country For example, wafer fabrication may occur in Taiwan, and then transported to United States for testing and sorting, and then to Singapore for assemble and packaging, and so on. Thus, the carbon dioxide emitted via and thus transporting the product during its production is a major factor in the computation of its carbon footprint. Furthermore, the production of integrated circuits consumes a lot of energy, and the circuits themselves generate energy. Hence, understanding and quantifying the carbon footprint of the supply chain for this industry can present significant opportunities for reducing their emissions. Semiconductor Processes Preparation Fabrication Test and Sort Customer Final Test Assembly and Packaging Figure 1. Overview of the Semiconductor Processing Stages Preparation is the process where the virgin silicon is transferred into wafers that consist of many little integrated circuits. A layer of silicon dioxide (SiO 2 ) glass is grown or deposited on the wafer. It will be patterned and etched to mask the silicon. The fabrication of the wafer is shown in Figure 2, and is composed of several highly complex processes that require sophisticated technology and equipment. In the assembly stage, a wafer will be cut into many little dice. Each die is then individually packaged to protect the chips and to provide connections from the chips to the products for which they are designed. The last step in the process is final testing that includes a temperature test, stress test, voltage test, and functionality test. Each product has unique design specifications depending on its application. For example, chips for a NASA satellite require temperature tolerance from minus 500 C to 500 C. The chip is then packaged into chip containers before shipping to the customer. Figure 2. Fabrication Process Stage 189
The carbon footprint model considers the emissions that are produced from the complete supply chain for the manufacture of an integrated circuit. At each stage, the amount of CO 2 emitted is computed for a particular technology/process. This is a function of but not limited to the energy consumed by specific technology, the number of iterations/repetitions required, batch size of the wafer, weight of the wafer, cycle time of single iteration, and floor space required. The carbon dioxide emitted via transporting the product is a function of the mode of transportation, the distance traveled, batch size, and weight of the wafer. The supply chain carbon footprint is computed from the summation of the CO 2 emitted from each stage and from the CO 2 emitted for transporting the production. Table 2 shows a sample model that students can use as a learning tool to calculate the carbon footprint. The model is divided into three sections: the manufacturing process, the facility, and the transportation. The amount of CO 2 emitted for each section would be automatically computed by the model based on the input provided by the student. The model is a user-friendly learning tool based on the foundation as shown in Table 2. CO 2 Emission per Processes Repetition Run Time (hour) Batch Size (wafers) Energy Consume (kwh) kwh per 1 Cleaning 8 0.83 25 3 0.8 1.08 2 Oxidation 9 1.5 100 45 6.08 8.20 3 Photo lithography 10 1.1 25 102 44.88 60.59 4 Etching 29 1 25 118 136.88 184.79 5 Ion implantation 8 1 25 22 7.04 9.50 Thin film deposition 9 3 100 18 4.86 6.56 6 7 Test and sort 1 0.17 50 2 0.01 0.01 8 Dicing 1 0.5 1 0.48 0.24 0.32 9 Wire bond 18000 0.625 1 0.000267 3.00 4.06 10 Encapsulation 12 5 2 0.2 6 8.10 11 Final test 1 0.75 2 10 3.75 5.06 Facilities Energy Consumed kwh/sq ft/yr Energy Consumed (kwh/year) per Year produced HVAC System Area of Clean Room (sq ft.) kwh per Front-End 93,800 1,000 93,800,000 316,000 296.84 Back-End 102,000 1,000 102,000,000 316,000 322.78 Transport ation Transport mode Distance (km) Batch Size (wafers) CO 2 Emission (kgs) CO 2 Emission (pounds) Pure wafer Seattle to San José truck 1,132 10,000 789.77 Fab San José to Singapore air 13,632 3,500 4,362.24 9,596.93 Test & Sort Singapore to Malaysia truck 300 3,500 209.30 Assembly Malaysia to San & José Packaging air 13,680 3,500 4,377.6 9,630.72 Table 2. A Sample Model to Compute CO 2 emissions for the Semiconductor Industry 190
An estimated cost for the complete supply chain will also be computed again as a function of the technology and transportation costs for the manufacture of the integrated circuit. Example cost considerations will include overall facility construction, equipment purchase & installation, annual operation and maintenance of facility and equipment, fixed (i.e. mode) and variable (i.e. mileage) costs for transporting the product. Hence, this model can be used by students to study the impact by changing a parameter in the supply chain on the amount of CO 2 emitted relative to the cost of manufacturing the chip. This model allows the students to experiment and perform tradeoff studies to explore means to reduce carbon emissions while at the same maintaining cost feasibility. The proposed model is implemented as a spreadsheet application. Output Graphs by the Tool The tool will also have the capability to generate graphs that display the amount of CO 2 computed, as shown in Figure 4. Figure 4a. Sample Graph Displaying CO 2 Emitted in Front-End Figure 4b. Sample Graph Displaying CO 2 Emitted in Back-End Figure 4c. Sample Graph Displaying Overall Amount of CO 2 Emitted Conclusion By using the proposed model, students will be able to see the impact on the environment when changes are made in manufacturing technologies and transportation modes of the supply chain for the semiconductor industry while maintaining cost feasibility. Emerging environmental issues of semiconductor manufacturing will be emphasized in the engineering student s learning environment. Students will be able to see that the manufacturing is very energy intensive and will be motivated to evaluate environmentally friendly processes that can offer significant reductions in the emission of greenhouse gases. With rising fuel prices, it is becoming increasingly important for engineers to design systems, components, and processes that are not only economical but also environmentally friendly. In addition, consumers of 191
today s market demand more and more green products. On becoming familiar with the concepts of green engineering students will be better able to develop green solutions that address customers needs in an increasingly global marketplace. The semiconductor industry is very energy intensive, and hence there is a need to make it more energy efficient and environment friendly. The importance of the semiconductor industry to the Silicon Valley provides SJSU with a tremendous opportunity to develop a model that quantifies the carbon footprint of the supply chain for this industry. References Barrett, R. (2008). An Activity-Based Approach to Measuring and Minimizing the Carbon Footprint. Retrieved May 7, 2009, from http://www.oneworld-community.com/carbon%20footprint%20whitepaper.pdf Beamon, B. M. (1998). Supply chain design and analysis: Models and methods. International Journal of Production Economics, 55(2), pp. 281-294. Chubin, D., Donaldson, K., Olds, B., and Fleming, L. (2008). Education generation net: Can U.S. engineering woo and win the competition for talent? Journal of engineering education, July, pp. 245-257. Carbon Footprint Ltd. Carbon Footprint Calculator. Retrieved May 7, 2009, from http://www.carbonfootprint.com/calculator.aspx Carbon Trust. (2006). Carbon Footprints in the Supply Chain: The Next Step for Business. Retrieved May 7, 2009, from http://www.yhub.org.uk/resources/climate%20change%20micro%20site/carbonsupply%20chain.pdf Carbon Trust. (2009). Glossary to Carbon Footprinting. Retreived May 7, 2009, from http://www.carbontrust.co.uk/solutions/carbonfootprinting/carbon_footprinting_glossary.htm. Carbon Trust Footprint Microsite (2006a), http://www.carbonconversation.co.uk/noflash.html Joint Venture Silicon Valley Network. Retrieved May 7, 2009 from http://www.jointventure.org/publications/index/2008index/2008%20silicon%20valley%20index.pdf. Ramudhin, A., Chaabane, A., Kharoune, M., and Paquet, M. (2008). Carbon market sensitive green supply chain network design. IEEE International Conference on Industrial Engineering and Engineering Management, pp 1093-1097. Singer, P. (2007). The greening of the semiconductor industry. Semiconductor International. Retrieved May 7, 2009, from http://www.semiconductor.net/article/ca6505603.html Srivastava, S. K. (2007). Green supply-chain management: A state-of-the-art literature review. International Journal of Management Reviews, 9(1), pp 53-80. TakePart.com. Calculate your Impact. Retrieved May 7, 2009, from http://www.climatecrisis.net/takeaction/carboncalculator/ Udomleartprasert, P. (2004). Roadmap to green supply chain electronics: design for manufacturing implementation and management. Proceedings of 2004 International IEEE Conference on the Asian Green Electronics, pp 169-173. U.S. EPA. Personal Emissions Calculator. Retrieved May 7, 2009, from http://www.epa.gov/climatechange/emissions/ind_calculator.html Weber, C. L., Matthews, H. S., Corbett, J. J., and Williams, E. (2007). Carbon emissions embodied in importation, transport and retail of electronics in the U.S.: A growing global issue. Proceedings of the 2007 IEEE International Symposium on Electronics and Environment, pp 174-179. 192