Introduction to Semiconductor Manufacturing Toxicity

• Semiconductor manufacturing appears "clean" but only in particle-free sense
• Companies use immense amounts of toxic/carcinogenic materials
• Historical record shows reason for concern
• Major factor in manufacturing exodus from Silicon Valley

Core Manufacturing Processes and Chemical Usage

• All wafer fabrication facilities perform core processes:
  • Deposition, resist coding, light exposure, etching, resist removal, washing
  • Repeated until desired chip sophistication achieved
• Study of 2 Korean semiconductor memory facilities found:
  • Over 400 chemical ingredients used
  • 40% of 400 ingredients classified as trade secrets (couldn't be reviewed)
  • Only 10% of non-trade secret chemicals classified as human carcinogens by International Agency for Research on Cancer
• Carcinogenic chemicals (mostly sulfuric acid) make up 30% of total volume used
  • Sulfuric acid: removes photoresist, cleans wafers
  • Harmful to eyes/skin, damages teeth/lungs
  • Raises lung cancer risk up to 64% when inhaled
• Facilities use over 45,000 tons of chemicals per factory annually
• Second most used ingredient: cyclohexanone
  • Not classified as human carcinogen
  • Causes kidney/liver damage when inhaled
  • Possible central nervous system effects

Back-End Manufacturing Concerns

• Chip cutting, testing, wire bonding, molding, plating, soldering
• Two worker types with different exposure levels:
  • Operators: relatively low toxic chemical exposure
  • Maintenance workers: high concentrations during equipment disassembly
• Epoxy molding compounds used (epoxy resin, hardeners, silica)
  • Ingredients not known to be toxic
  • Molding process generates toxic byproducts: phenol, formaldehyde, benzene
  • Formaldehyde and benzene are carcinogens

Silicon Valley Historical Case Studies

• Fairchild Semiconductor pioneer case (1977-1981):
  • Used 1-1-1 trichloroethane as organic solvent
  • Stored in underground fiberglass tanks at San Jose site
  • Tanks leaked solvent into groundwater, contaminating well #13
  • Los Paseos neighborhood showed higher rates of spontaneous abortion/congenital malformation
  • Indirect evidence, uncertain timing
  • 69 women in area showed no birth issues
  • University study linked chemical to congenital heart defects in rats
  • Fairchild paid multi-million dollar settlement
• 1988 pregnancy outcomes study (Santa Clara County 1980-1985):
  • Neighboring city women drank contaminated water but suffered no unusual effects
  • Counter study noted 1988 study didn't account for showering/washing effects

Industry Health Studies Complexity

• Multiple incidents: 1979 Signetics, 1985 IBM, 1998 National Semiconductor UK, 2008 Samsung cancer cluster
• Standard statistical methods used but challenges include:
  • Small cohorts (1-5,000 workers)
  • Classification errors
  • Confounding factors everywhere
  • Difficulty proving causation from correlation

Cancer Research Findings

• Industry-cancer connection hotly debated since 1980s across UK, South Korea, Taiwan, US
• 2006 IBM workers study: no causal associations between semiconductor manufacturing and cancer
• Same data analyzed differently by Richard Clapp: elevated incidence of kidney, skin, brain/nervous system cancers
• 2010 National Semiconductor UK study: no elevated cancer rates except lung cancer (statistically significant but smoking rates unknown)

Reproductive Health Risks

• Female reproductive health special concern (majority workforce: women of child-bearing age)
• 1980 Finnish study: first to identify elevated spontaneous abortion risk among female electronics workers
• Series of studies identified elevated spontaneous abortion risk, especially in masking/photolithography processes
• Suspected chemical: ethylene glycol ether (known reprotoxin)
• Also causes lower fertility, variable menstrual cycles
• Replaced with propylene glycol monomethyl ether (neurotoxin)
• Elevated abortion risks continue despite replacement

Environmental Impact and Regulation Evolution

• 1960s-70s cavalier approach to waste handling:
  • Acids/solvents dumped into sewers flowing to San Francisco Bay
  • Toxic chemicals tossed into city dumps, pits, dry wells
  • Intel Mountain View facility: acids ate through sewer line bottoms
• 1970s environmental movement created EPA, tightened toxic waste regulations
• Modern improvements:
  • Recycling/reuse technologies essential at current scale
  • Wastewater treatment: reverse osmosis, oxidation, carbon filters
  • TSMC treats for 25 chemicals in wastewater

Current Monitoring Gaps

• Over 400 ingredients used, far more compounds produced
• Only 10% of ingredients monitored, none of byproducts from reactions like plasma
• 2018 sustainability study: varied disposal performance across US semiconductor facilities
• Legacy contamination remains: Superfund sites in Silicon Valley, RCA plant groundwater damage (1968-1992) in Taiwan

Global Manufacturing Migration

• Silicon manufacturing moved from Silicon Valley to:
  • Inside US: Arizona, Texas
  • Outside US: South Korea, Taiwan, China
• Regulators poorly positioned to monitor facilities despite best efforts
• New locations often have less resources/regulatory knowledge
• Economic importance creates powerful constituencies:
  • South Korea 2019: $93 billion chip exports (15% of total exports)
  • Taiwan similar economic dependence

Current Semiconductor Shortage Context

• Big semiconductor shortage ongoing
• Companies/consumers cannot get needed chips
• Fab construction crews rushing to break ground
• Environmental surveys/evaluations might not seem important in hurry
• TSMC passed environmental review for 2nm Shinshu facility
• Still much unknown about semiconductor manufacturing effects on environment/people