Environmental Impacts of Manufacturing

1. Environmental Impacts of Manufacturing Stephen P. Beaudoin Arizona State University  1999 Arizona Board of Regents for The University of Arizona

2. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing $1,000,000 Questions • How does one assess environmental “soundness” of exisiting processes? • Waste Audit • How does one assess environmental consequences of processes? • Environmental Impact Assessment (EIA) • How does one assess and compare environmental impacts of real and proposed/improved processes? • Life Cycle Analysis (LCA)

3. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Waste Audits - Objectives • Develop understanding of the actual operating processes in a facility or unit operation • Identify regions where waste is generated • Guide to environmental optimization of process • 6 steps

4. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Waste Audits (cont’d) • 1) List all unit operations in process of interest • CMP unit operations: • DI water preparation • slurry mixing • chemical mixing • polish tool • buff tool • wafer transport line • brush cleaning tool • megasonic tank • SRD (spin rinse dryer)

5. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Waste Audits (cont’d) • 2) Construct process flow diagrams • easy for case of CMP and post-CMP cleaning • 3) Determine resource usage • raw materials/feeds used in each process/unit operation • analysis of process specifications and actual process data • many subtle materials (air, water) • startup wastes

6. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Waste Audits (cont’d) • 4) Determine storage/handling losses • invoices can be compared to actual operating data • spillage, spoilage, bad feed wastes identified • 5) Quantify levels of waste reuse • easy for CMP (none) • 6) Quantify process outputs • products, wastes

7. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Waste Audits (cont’d) • Results • awareness of wastes, both obvious and hidden, in process • ability to optimize process to minimize environmental impact • Questions: waste audit of CMP/post-CMP train • Where do wastes come from in CMP/post-CMP cleaning? • What could have the highest impact for reducing waste? • Would process performance be affected? • Which change could reduce the waste with the least impact?

8. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Environmental Impact Assessment • Prioritization of concerns for environmental impacts of processes and appropriate planning to minimize impacts • Required by law in U.S. for many new manufacturing projects • mandated contents • interpreted and enforced by courts • government approves or disapproves project • public can challenge in court • 4 stages

9. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Environmental Impact Assessment (cont’d) • 1) Process screening - determines which aspects of existing or planned process must be evaluated • a process step that generates slurry waste may be more important that one that generates DI water waste • 2) Scoping - determines key issues to be considered • CMP generates basic wastewater • immediate concern: effect of pH on natural waters or treatment loop • long-term concern: effects of neutralization wastes

10. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Environmental Impact Assessment (cont’d) • 3) Statement Preparation - the impact of each waste is assessed • soil, water, air, wildlife, and people considered • evaluated over appropriate time scales • 4) External review - the community evaluates the EIA • independent review by local community, government, academia • ensures that the statement is accurate, objective • all EIA’s must be reviewed

11. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Environmental Impact Assessment (cont’d) • Mandated contents of EIA: • state of present environmental condition • features of project • effects of project • ways to minimize effects • residual impacts of project • Must be comprehensible to the general public

12. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Environmental Impact Assessment (cont’d) • Criteria for choosing projects that require EIA’s: • Lists: certain types of projects always require EIAs • Project thresholds: exceeding threshold values of project cost, production, or land use can mandate EIA • Sensitive area criteria - based on ability of environment to handle project and wastes • Matrix criteria - all project activities and impacts listed on a matrix • activities: site investigation, preparation, construction, operation and maintenance, future and related activities • impacts: physical, chemical, ecological, aesthetic, social

13. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Environmental Impact Assessment (cont’d) • Sensitive area criteria - based on ability of environment to handle project and wastes • Matrix criteria - all project activities and impacts listed on a matrix • activities: site investigation, preparation, construction, operation and maintenance, future and related activities • impacts: physical, chemical, ecological, aesthetic, social

14. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Life Cycle Analysis • Evaluation of entire life of a product • cycle = material acquisition to final product disposal • Tool to identify and evaluate opportunities to reduce environmental impacts of products, processes, packaging, materials, and activities • Important in ISO 14000, Product Stewardship • 7 steps

15. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Life Cycle Analysis (cont’d) • 1) Define scope and purpose of process • 2) Set system boundaries • primary systems: activities that directly contribute to making, using or disposing of a product • secondary systems: auxiliary processes that contribute to making or doing something in the primary sequence • Good use of LCA - to assess environmental impacts of changes in CMP processing methods • Question: What is a primary, secondary and ternary process for CMP?

16. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Life Cycle Analysis (cont’d) • 3) Inventory checklist • outlines all decision areas to be considered in the analysis • Guides data collection and analysis • Decision areas: • purpose, system boundaries, geographic scope, types of data used, data collection or synthesis methods, data quality measures, presentation of results

17. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Life Cycle Analysis (cont’d) • 4) Peer review • guarantees validity of study • internal or external reviewers • financially supported by EPA • possible comment areas: • scope/boundaries methodology, data acquisition/compilation methodology, validity of assumptions and results, method of communication of results

18. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Life Cycle Analysis (cont’d) • 5) Gather data • depending on scope and boundaries, may have to go all the way to raw materials acquisition for each chemical used in process • remember to include data on materials required to maintain and use your product, and on the final fate of your product • 6) Normalize data • all data must be evaluated on a common scale (per wafer, per machine per wafer, per hour, per liter slurry...)

19. NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Life Cycle Analysis (cont’d) • 7) Generate mathematical model of process • allows effects of changes in operating techniques to be compared in terms of their environmental impacts • Question: outline the LCA for an oxide polishing process

20. Summary: Life Cycle Analysis • By following the analysis presented, we now have a tool that can be used to evaluate the true impact of a process • can choose the best process from an environmental perspective • avoid transferring wastes from one medium to another