Post on 23-Dec-2015
Unique ESH Considerations in Compound Semiconductor Operations
Presented by:
Kerrie A. Romanow
MROE Environmental
Risk Managementand Occupational
Copyright EORM®, Inc. 2001
Introduction
Focus is major differences between silicon and Compound Semiconductor operationsApplication BenefitsProductsHazardous Production MaterialsHealth and Safety Considerations– MBE, MOCVD
Environmental Considerations– Wastewater, Gallium Recycling
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Why Compound Semiconductor?
Circuits are fasterConsume less powerMore resistant to ionizing radiationWider temperature limitsCan support both electronic and photonic applications
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Compound Semiconductor Products
Solid State DevicesOptical CommunicationsLight Emitting Diodes (LEDs)Automobile Instrument displaysCellular PhonesMilitary Applications
(Can cost 10-20 times as much as silicon chips!)
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Compound Semiconductor Products
Type Attributes Product
LEDs White, Blue and other color displays
Auto Panels, Cellular Displays, Display Lighting
ICs High performance with low power demand
PDAs, PCS phones
Power AmplifiersRF Devices
Low power requirements Cell Phones, TVs
Photovoltaics Newly advancing technologies
Solar cells
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Compound Semi Process
Wafer Preparation– Crystal Growth– Slicing– Lap and Polish
Epitaxy– Molecular Beam Epitaxy (MBE)– MOCVD (OMVPE)– Liquid Phase Epitaxy (LPE)
Wafer FabricationFinal Test and Packaging
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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
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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
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Unique ESH ConsiderationsWafer Preparation
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
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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
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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
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Unique ESH ConsiderationsEpitaxy
Commercial Applications typically revolve around three major types of expitaxy– Molecular Beam Epitaxy (MBE)– MOCVD (OMVPE)– 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
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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
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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
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Unique ESH ConsiderationsWafer Fabrication
Similar to silicon wafer fabricationTypical Hazardous Materials
Liquids• N-Methyl Pyrrolidine (NMP)• Bromine• HF• Nitric Acid• Solvents
Gases• Arsine• Chlorine• Hydrogen Bromide• Boron Trichloride• Ammonia• Phosphine• Silane• Hydrogen
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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 levelWastewater requirements – State and Local requirements will apply
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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
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Work Practices/Controls – Tool Maintenance
Maintain material wetUse drop clothes to ease cleanupPlace tool parts in closed containers or fume hoodUse HEPA vacuum near point of dust generation– HEPA vacuum must be dedicated for arsenic use
and appropriately labeled
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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
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Work Practices/Controls – Tool Maintenance
Regulated Area– Only authorized persons may enter– Appropriate signage
DANGERARSENIC
CANCER HAZARDAUTHORIZED PERSONNEL ONLY
NO SMOKING OR EATINGRESPIRATOR REQUIRED
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Work Practices/Controls – PPE
PPE– Tyvek– Head covers– Gloves– Eye protection
Exit Protocols– HEPA vacuum clothing– Shower– Change clothes
Wash Hands After Handling– Prevent moving material
to other areas where gallium arsenide may dry and present inhalation hazard
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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
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Wastewater
Type Attributes ConcernsCoagulation/ Filtration (C/F)
Combined with AWN can be very effective
Effective for arsenic removal
Ferric sulfate provided good performance
High or low pH can affect efficiency
Generates arsenic-contaminated sludge
Lime Softening (LS) Optimal for pH range > 10.5
Low pH of most semiconductor waste streams makes this unsuitable
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Wastewater
Type Attributes ConcernsReverse Osmosis (RO) Removal efficiencies >
95% at ideal psiIncreased demand for
raw water
Ion Exchange with Brine Recycle
Works well even with sulfate levels to 200mg/L
Brine regeneration could be reused to 20 times with addition of salt
Based on recent research at University of Houston
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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!
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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
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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
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Summary
Compound semiconductor operations present many unique ESH challenges– Hazardous materials– Arsenic exposure– Wastewater treatment– Gallium recycling