Our Problem
In 2022, the United States Congress passed a bipartisan bill in order to boost domestic semiconductor manufacturing. This legislation allocated over $50 billion to fund the construction and expansion of semiconductor fabrication plants (fabs) and other related entities (e.g., suppliers). Currently, only 12% of chips used in the US are manufactured domestically. This is largely due to the inability to produce advanced chips at the necessary volume required to meet demand. Furthermore, foreign competitors are making significant investments in this industry. The CHIPS and Science Act seeks to support the construction, expansion, or modernization of domestic semiconductor fabrication facilities to enhance domestic capacity and close the gap with foreign competitors (1).
Figure 1: Share of global semiconductor manufacturing by country or region. Image from The Washington Post (2).
Semiconductor chip manufacturing is a highly technical process used to produce integrated circuits (ICs) for various electronics. The process begins with silicon, which is purified and formed into wafers. Photolithography transfers circuit patterns onto the wafer using ultraviolet light, followed by etching to remove unwanted material. Doping, a process where impurities are added to the silicon, alters electrical properties. Advanced techniques like extreme ultraviolet (EUV) lithography are now standard in fabricating smaller transistors. The chips undergo multiple inspections, testing, and packaging before deployment in devices such as smartphones and computers (3,4).
Figure 2: Overview of the process of semiconductor manufacturing illustrating water use, and chemical output.
Key to this manufacturing process is water, which is used for cleaning and cooling at multiple stages in the manufacturing process. A 2022 article in Semiconductor Digest reported that “our industry consumes… as much as 264 billion gallons [of water] per year, a resource likely to become more scarce in a changing climate.” This article goes on to report that “an individual fab[ricator] can use tens of millions of gallons of water per day” (5). To meet this demand, which will continue to grow as microprocessor demand rises, studies indicate that the industry must increasingly rely on the use of reclaimed water from both internal and external sources (6,7).
Figure 3: Projected growth in the semiconductor industry. Image from World Semiconductor Trade Statistics (8)
A critical challenge in semiconductor manufacturing is managing hazardous materials and contaminated water from the manufacturing process. We interviewed Kassey Rydberg, Associate Vice President of Environmental Health and Safety at NY CREATES, an organization dedicated to promoting manufacturing and fostering innovation in semiconductor manufacturing. Ms. Rydberg emphasized that chemicals like hydrofluoric acid are integral to production but pose significant safety risks. The industry implements rigorous safety protocols and has developed waste treatment systems to manage the waste but at a significant cost.
Monitoring pH is crucial to the waste management plans of fabs, as acids and bases are used in the process at multiple points in the fabrication process. pH is continuously monitored to ensure compliance with regulations, but this process is a challenge at the scale of water use in a fab, which may produce millions of gallons of wastewater daily. The need to remove impurities and neutralize pH also creates sustainability challenges for fabs, as it is difficult to purify wastewater sufficiently to allow its reuse (7)
Our Solution
Our project aims to produce a pH-responsive system that detects acidic or alkaline pH and produces molecules that will neutralize the solution. We identified a riboswitch from the E. coli Alx locus that responds to alkaline pH (9). Riboswitches are RNA segments that bind to a ligand and control the transcription or translation of a downstream gene (10). We also identified the pASR promoter, an acid-responsive promoter present in Enterobacteria (11). These genetic elements could be used to construct circuits that drive the expression of acid- and base-producing genes to achieve neutralization. We selected two enzyme systems, lactate dehydrogenase, and the putrescine biosynthesis pathway for inclusion in our device. These systems will produce acid or base as needed to neutralize the wastewater. They were chosen for the simplicity of the pathway, as well as the fact that pathway substrates are already present in E. coli cells, eliminating the need for special nutritional supplementation for our host chassis.
Figure 5: Diagram of our strategy for pH adjustment
We want to ensure that our project is responsible and good for the world. In the course of researching semiconductor manufacturing, we came to realize that information regarding the nature of materials used in semiconductor fabrication and waste produced during this process is difficult to obtain and understand. This is a barrier to engaging stakeholders,and ensuring responsible practices in the industry. Policy and regulations governing the reporting and monitoring of waste from fabs have therefore not kept pace with industry practices, and this complicates efforts to characterize and evaluate the environmental impact of the industry (14), We utilized community-right-to-know laws, freedom of information requests, governmental repository searches, and civic engagement practices, that complement and literature searches, sample analysis, and expert interviews to explore these issues and to improve stakeholder engagement. The story of the experience of our Human Practices work also aims to suggest directions in which we might begin to reconceptualize the relationship between Science and Human Practices work, to further expand and enhance the social value of what synthetic biology can create.
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References
1. “FACT SHEET: CHIPS and Science Act Will Lower Costs, Create Jobs, Strengthen Supply Chains, and Counter China.” The White House, The Government of the United States of America, 9 Aug. 2022, www.whitehouse.gov/briefing-room/statements-releases/2022/08/09/fact-sheet-chips-and-science-act-will-lower-costs-create-jobs-strengthen-supply-chains-and-counter-china/.
2. Whalen, Jeanne. “A New Era of Industrial Policy Kicks off with Signing of the Chips Act.” The Washington Post, 9 Aug. 2022. https://www.washingtonpost.com/us-policy/2022/08/09/micron-40-billion-us-subsidies/
3. Levinson, Harry J., and Timothy A. Brunner. “Current challenges and opportunities for EUV lithography.” International Conference on Extreme Ultraviolet Lithography 2018, vol. 9048, 24 Oct. 2018, p. 2, doi.org/10.1117/12.2502791.
4. Doering, Robert, and Yoshio Nishi. Handbook of Semiconductor Manufacturing Technology. CRC Press, 2017.
5. Davis, Shannon. “Water Supply Challenges for the Semiconductor Industry.” Semiconductor Digest, 24 Oct. 2022, www.semiconductor-digest.com/water-supply-challenges-for-the-semiconductor-industry/.
6. Wang, Qi, et al. “Water Strategies and Practices for Sustainable Development in the Semiconductor Industry.” Water Cycle, vol. 4 (2023,) 12-16. doi.org/10.1016/j.watcyc.2022.12.001
7. Jeonghoo Sim a, et al. “A Review of Semiconductor Wastewater Treatment Processes: Current Status, Challenges, and Future Trends.” Journal of Cleaner Production, vol. 429 (2023) 139570. doi.org/10.1016/j.jclepro.2023.139570.
8. “Chip Sales Rise in 2022, Especially to Auto, Industrial, Consumer Markets.” SIA: The Semiconductor Industry Association, Semiconductor Industry Association, 27 Mar. 2023,https://www.semiconductors.org/chip-sales-rise-in-2022-especially-to-auto-industrial-consumer-markets/. Accessed 25 Sept. 2024.
9. Bingham, R J et al. “Alkaline induction of a novel gene locus, alx, in Escherichia coli.” Journal of bacteriology vol. 172,4 (1990): 2184-6.doi:10.1128/jb.172.4.2184-2186.1990
10. Garst, Andrew D et al. “Riboswitches: structures and mechanisms.” Cold Spring Harbor perspectives in biology vol. 3,6 a003533. 1 Jun. 2011, doi:10.1101/cshperspect.a003533
11. Seputiene, Vaida et al. “Transcriptional analysis of the acid-inducible asr gene in enterobacteria.” Research in microbiology vol. 155,7 (2004): 535-42. doi:10.1016/j.resmic.2004.03.010
12. Mazurek, Jan. “How Fabulous Fablessness? Environmental Challenges of Economic Restructuring in the Semiconductor Industry.” Greener Management International, no. 32, 2000, pp. 57–69. JSTOR,http://www.jstor.org/stable/greemanainte.32.57. Accessed 28 Sept. 2024.