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Unique ESH Considerations in Compound Semiconductor Operations. Presented by: Kerrie A. Romanow. Introduction. Focus is major differences between silicon and Compound Semiconductor operations Application Benefits Products Hazardous Production Materials Health and Safety Considerations

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unique esh considerations in compound semiconductor operations

Unique ESH Considerations in Compound Semiconductor Operations

Presented by:

Kerrie A. Romanow

  • Focus is major differences between silicon and Compound Semiconductor operations
  • Application Benefits
  • Products
  • Hazardous Production Materials
  • Health and Safety Considerations
    • MBE, MOCVD
  • Environmental Considerations
    • Wastewater, Gallium Recycling
why compound semiconductor
Why Compound Semiconductor?
  • Circuits are faster
  • Consume less power
  • More resistant to ionizing radiation
  • Wider temperature limits
  • Can support both electronic and photonic applications
compound semiconductor products
Compound Semiconductor Products
  • Solid State Devices
  • Optical Communications
  • Light Emitting Diodes (LEDs)
  • Automobile Instrument displays
  • Cellular Phones
  • Military Applications

(Can cost 10-20 times as much as silicon chips!)

compound semi process
Compound Semi Process
  • Wafer Preparation
    • Crystal Growth
    • Slicing
    • Lap and Polish
  • Epitaxy
    • Molecular Beam Epitaxy (MBE)
    • Liquid Phase Epitaxy (LPE)
  • Wafer Fabrication
  • Final Test and Packaging
unique esh considerations wafer preparation
Unique ESH ConsiderationsWafer Preparation
  • Commercial applications typically revolve around two major substrate preparation processes
    • Gallium Arsenide
    • Indium Phosphide
      • Gallium Phosphide – Note: is also a substrate process but plays a lesser role
  • Wafer preparation is similar to a “Foundry type” process
unique esh considerations wafer preparation8
Unique ESH ConsiderationsWafer Preparation
  • Example Process: GaAs Wafer Processing
    • Charge Preparation
      • Formation of Polycrystalline GaAs
    • Crystal Growth
      • Horizontal or Vertical Growth
        • Growth of a GaAs Ingot
    • X-ray Diffraction
      • Verification of crystalline orientation
    • Slicing
      • Ingot slicing to produce GaAs wafer
    • Polishing
      • Surface preparation of GaAs wafer
unique esh considerations wafer preparation9
Arsenic Handling and Control

Control of particulates

Production handling

Maintenance intervention (Preventive and corrective)

Particulate deposits on tools

Facilities systems, ie., exhaust ducting/scrubbers etc

Establishment of regulated areas may be required

Single point failure protection of heated processes to prevent exposure due to a furnace or crystal grower failure

Flammable Handling

Flammable Solid Handling

Indium Phosphide (as well as Gallium Phosphide processing)

Flammable Gas Handling

Large volumes of Hydrogen used in support of quartz ampoule sealing

Flammable Liquid Use

Methanol applications for solvent cleaning of wafers

Unique ESH ConsiderationsWafer Preparation
unique esh considerations gallium arsenide
Unique ESH ConsiderationsGallium Arsenide
  • Gallium Arsenide (GaAs)
    • Toxicological information derived from arsenic
      • Inhalation of GaAs (respirable particulate) can result in dissolution and exposure to Arsenic – cross the lung lining into the blood stream
    • Inorganic arsenic
      • Regulated as a human carcinogen
      • TLV: 0.01 (As) mg/m3 or 10 ug/m3
    • Gallium = low toxicity
      • Controls for Arsenic address Gallium considerations
unique esh considerations indium phosphide
Unique ESH ConsiderationsIndium Phosphide
  • Indium Phosphide (InP)
    • Health Effects
      • Liver, Heart, Kidney, Blood, Respiratory Damage
      • Inhalation May Cause Respiratory Damage
    • TLV Application: 0.01 mg/m3 as Indium
    • Special considerations
      • Can react with water vapor and acids to form phosphine
      • Flammable solid control required during wafer processing
    • InP is displacing silicon in leading edge applications
unique esh considerations epitaxy
Unique ESH ConsiderationsEpitaxy
  • Commercial Applications typically revolve around three major types of expitaxy
    • Molecular Beam Epitaxy (MBE)
    • Liquid Phase Epitaxy (LPE)
  • Compound semiconductor epitaxy hazards have some similarity silicon CVD particularly the low k and extremely low k dielectric applications
    • CVD type gases combining with organometallics
unique esh considerations epitaxy13
Unique ESH ConsiderationsEpitaxy
  • Example Process: MBE GaAs Epitaxy
    • Heating of Liquid gallium or solid arsenic
    • Performed at very low pressures
    • Effuse both Ga and As through orifice aimed at wafer
    • Layer of epitaxial alloy grown on wafer
      • Very long epitaxy growth cycle
unique esh considerations epitaxy14
Unique ESH ConsiderationsEpitaxy
  • Unique ESH Concerns – MBE Epitaxy
    • Gallium Arsenide Handling and Control
      • Control of particulates
        • Maintenance intervention (Preventive and corrective)
          • Particulate deposits on tools
          • Facilities systems, ie., exhaust ducting/scrubbers etc
      • High potential for regulated areas
      • New MBE applications for 150mm wafers have large enclosures that require maintenance
        • Potential confined space considerations
unique esh considerations wafer fabrication
Unique ESH ConsiderationsWafer Fabrication
  • Similar to silicon wafer fabrication
  • Typical Hazardous Materials
  • Gases
  • Arsine
  • Chlorine
  • Hydrogen Bromide
  • Boron Trichloride
  • Ammonia
  • Phosphine
  • Silane
  • Hydrogen
  • Liquids
  • N-Methyl Pyrrolidine (NMP)
  • Bromine
  • HF
  • Nitric Acid
  • Solvents
key regulations
Key Regulations
  • Hazard Communication (29 CFR 1910.1200)
  • Inorganic Arsenic Standard: Federal (29 CFR 1910.018) and California (8 CCR 5214) regulations provide guidelines and set safety standards for employees working with inorganic arsenic at levels above the action level
  • Wastewater requirements – State and Local requirements will apply
training priorities
Training Priorities
  • Production Personnel
    • Haz Comm and Arsenic Standard awareness
  • Emergency Response Personnel
    • Critical Scenarios
    • Decontamination procedures
  • Maintenance Staff and Contract Workers
    • Arsenic control procedures
    • Waste handling
    • PPE
work practices controls tool maintenance
Work Practices/Controls – Tool Maintenance
  • Maintain material wet
  • Use drop clothes to ease cleanup
  • Place tool parts in closed containers or fume hood
  • Use HEPA vacuum near point of dust generation
    • HEPA vacuum must be dedicated for arsenic use and appropriately labeled
work practices controls tool maintenance19
Work Practices/Controls – Tool Maintenance
  • Clean all local surfaces near openings
    • Wipe down with DI water
    • Dispose of wipes as hazardous waste
  • Clean incidental equipment
    • Pens, tools, spray bottles, etc.
  • IH Sampling
    • 8 CCR 5214(e)(3)(B) requires sampling if area meets or exceeds PEL
    • Sampling can cease when 2 consecutive determinations, a least 7 days apart, are below action level
work practices controls tool maintenance20
Work Practices/Controls – Tool Maintenance
  • Regulated Area
    • Only authorized persons may enter
    • Appropriate signage







work practices controls ppe


Head covers


Eye protection

Exit Protocols

HEPA vacuum clothing


Change clothes

Wash Hands After Handling

Prevent moving material to other areas where gallium arsenide may dry and present inhalation hazard

Work Practices/Controls – PPE
environmental considerations
Environmental Considerations
  • Arsenic in Wastewater Streams
    • EPA discharge restriction tightened from 50 ug/L to 10 ug/L
    • Increasing demand for arsenic removal is creating more treatment options
  • Gallium Recycling
gallium recycling
Gallium Recycling
  • Background
    • Gallium produces as byproduct of treating bauxite, zinc processing residue
    • 2000 demand grew, prices rose
    • Japanese consumption increased 30% last year to 148 metric tons
      • 73 metric tons obtained through scrap recycling!
gallium recycling26
Gallium Recycling
  • Recycling Process
    • Material is crushed
    • Dissolved in hot acidic solution
    • Neutralized with caustic
      • Precipitates gallium as gallium hydroxide
    • Gallium hydroxide filtered and washed
    • Filter cake redissolved in caustic and electrolyzed
    • 99.9-99.99% gallium recovered
gallium recycling27
Gallium Recycling
  • Implementing a Ga Recycling Program:
    • Identify vendor
      • Germany, Japan, UK, US(Utah and Oklahoma)
      • Many options for gold recycling
        • Strip gold and other precious metals
        • Forward to gallium recycler
    • Establish protocols
    • Train employees
  • Compound semiconductor operations present many unique ESH challenges
    • Hazardous materials
    • Arsenic exposure
    • Wastewater treatment
    • Gallium recycling