unique esh considerations in compound semiconductor operations presented by: kerrie a. romanow

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


Why Compound Semiconductor?

Circuits are fasterConsume less powerMore resistant to ionizing radiationWider temperature limitsCan support both electronic and photonic applications


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!)


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


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


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



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



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 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 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 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



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 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 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


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


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

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



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



Regulated Area– Only authorized persons may enter– Appropriate signage

DANGERARSENIC

CANCER HAZARDAUTHORIZED PERSONNEL ONLY

NO SMOKING OR EATINGRESPIRATOR REQUIRED


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


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


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


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


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 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 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


Summary

Compound semiconductor operations present many unique ESH challenges– Hazardous materials– Arsenic exposure– Wastewater treatment– Gallium recycling

unique esh considerations in compound semiconductor operations presented by: kerrie a. romanow

Documents

copyright eorm

gallium recycling slide

packaging slide

romanow slide

lesser role wafer preparation

foundry type process

safety considerations

vertical growth growth