EHS Division

Addressing Safety Concerns in Photovoltaic Manufacturing: A Supply Chain Perspective

American Society of Safety Engineers (ASSE)

Greater San Jose Chapter

December 8, 2009Aaron Zude / Sanjay Baliga

SEMI EHS DivisionSan Jose

Proposed Agenda• Photovoltaics (PV) Basics

• Economics of PVs

• Overview of PV Manufacturing

• Overview of Safety Hazards [ Chemical | Mechanical | Facilities | Product ]

• SEMI’s PV EHS Activities

• Questions

Presentation Overview

What are Photovoltaics (PVs)?• Arrays of cells containing a material that converts

solar radiation into direct current electricity

• Made up of semiconductive materials

• First introduced into commercial production in the 1950s

• Renewable energy source (low / zero carbon energy)

• Often cited as a primary mechanism to address global climate change

Basics of Photovoltaics

What is the outlook for PVs?• EXCELLENT

• Decreasing manufacturing costs (increasing scale)

• Increasing power generation efficiency (innovation)

• Approaching grid parity (versus other sources of electricity) at about $0.10/kWt

• Grid Parity means you pay the same price for PV generated electricity as for fossil fuel or other generated electricity

PV Economic Outlook

What is the outlook for PVs?• Can be decentralized (good for rural areas with no grid

availability)

• Low / zero carbon substitute in a carbon constrained world

• Increasing complexity of applications

• Ecosystem of innovation (application of Moore’s Law-like efficiency gains for PV)

PV Economic Outlook

PV Economic Outlook

Doubling of capacity every 2 years.

Doubling of capacity every 2 years.

Different Approaches to Manufacturing PVs• Use of various semiconductive materials (Si, CdTe,

CIGS, etc)

• Use of various manufacturing techniques (Poly-Si, Crystal-Si, Thin Film, etc)

• Use of various end product form factors (cell, module, ribbon, etc)

Overview of PV Manufacturing

Overview of PV Manufacturing

Overview of PV Manufacturing

Overview of PV Manufacturing

Thin-FilmsThin-Films

~3 GW Total Production ~3 GW Total Production in 2007in 2007

• 90% crystalline silicon90% crystalline silicon• 10% thin-films 10% thin-films

120 MW in 2007 1200 MW in 2010

Major PV Manufacturing Steps

Example of PV Fabrication Plant

c-Si Operation

MBPV: 80 MW cell line

Acid Texturing

PVD

PSG

Dryer Dryer Firing Furnace

LCL

P-Doper

Dryer Dryer

Diffusion

Diffusion

Doper

Doper

Cell

Sort

er

Lase

r

Lase

rSP-1 SP-2 SP-3

Acid Texturing

PVD

PSG

Dryer Dryer Firing Furnace

LCL

High Line throughput & yieldTotally in-line process with no manual

intervention

Example of PV Fabrication Plant

Thin Film a-Si 40 MW

Different Types of Hazards• Chemical [ includes industrial hygiene ]

• Mechanical

• Facilities [ includes electrical hazards ]

• Product [ includes installation and end of life ]

Overview of Safety Hazards

Chemical Hazards Overview(Not A Complete List)

Substance Use

Arsine (AsH3) Dopant

Boron Trifluoride (BF3) or trimethyl boron Dopant

Trimethyl Boron (TMB) Dopant

Diborane (B2H6) Dopant

Phosphine (PH3) Dopant

Cadmium Compounds CdTe, CIGS/CdS

Tin Oxide, Zinc Oxide (sputtered),

or Diethyl Zinc (DEZ) precursor.

Top glass transparent conductive oxide (TCO) film

Germane Tandem TFPV

IPA & Acetone Wetting agents, solvents

Sodium Hydroxide (NaOH) & Potassium Hydroxide (KOH)

Surface roughness, stripping

Hydrochloric Acid (HCl), Phosphoric Acid Cleaning agent – c-Si

Hydrogen Fluoride (HF) Etchant – c-Si

Fluorine (F2) Chamber clean

Hydrogen Selenide CIGS selenization

Hydrogen Controls film growth

Phosphorous Oxytrichloride (POCl3) Diffusion

NF3, SF6, CF4, C2F6, O2, N20 Chamber clean, surface texturing, PSG removal

Ammonia (NH3) Silicon nitride deposition

Silane, trisilane a-Si deposition, SiNx deposition, c-Si production

Simplified Process-flow DiagramsMining to System Manufacturing Stages

(mono-, ribbon-, and multi-Si PVs, and (b) thinfilm CdTe PVs)

Source: “Emissions from Photovoltaic Life Cycles”, Vasilis M. Fthenakis, Hyung Chul Kim, and Erik Alsema

What is Silane?• Compressed pyrophoric gas

• Leaks of silane can oxidize in air without obvious signs of ignition

• Leaks can also result in flames, with the severity depending on the leak hole size, ventilation and containment

• “Poppers” can occur when a small amount of silane leaks into space between valve and cap during storage & transit

• When a silane leak is contained and concentration exceeds 4.5% then delayed ignition and bulk autoignition occurs

Silane Safety

Silane Incidents• Major incidents have occurred during Silane use in

the semiconductor industry• Release and detonation of gas cabinet

• Release and detonation of duct

• Release and fire

• Explosion of cylinder

• Reaction of solid by-products

• Pressure relief device leak

• Aluminum cylinder rupture

Silane Safety

PV Industry Silane Explosion, Changsha China, August 2009

• During installation of a full 10 kg cylinder into a 2 cylinder gas cabinet, there was a release of silane from the cylinder that was online. Flames impinged directly onto the cylinder from the pigtail. This heated the cylinder for some period of time and it ruptured

• An immediate evacuation occurred, probably preventing serious injury or fatalities. Silane then ignited and detonated blowing out windows on all sides of the 3 storey 1,000 m2 metal frame building. Metal walls on the process side were blown out. There was no fire afterwards

• 35 cylinders of silane in the area were knocked over by the blast. Two started to leak. One leak was sealed by facility personnel. The second leak could not be stopped and was placed in a field 1000 m away by the fire department

Silane Safety

Summary of Mechanical Hazards• Physical pinch, crush, entanglement, and cut hazards

• Exposure to the broken glass

• Ergonomic, trip and slip hazards

• Noise

• LASERS

• Machine guarding

• Robotics

• Soldering

• Glass handling

Mechanical Hazards

Summary of Facilities Hazards• Facility fitup

• Building design (materials of construction, exiting, access, etc.)

• Tool Installation

• Tool commissioning

• Management of change

Facilities Hazards

Summary of Facilities Hazards• Bulk specialty gases & distribution

• Process effluent management

• Electrical & Arc Flash

• Use of combustible plastics

• Waste management

• Electrical Safety (hazardous voltages, energies)

Facilities Hazards

Summary of Product Hazards• Solar farm fires (frames)

• Electrical shock potential to emergency responders

• Products of combustion during fire?

• Installation hazards

• End of life product hazards (CaTe hazards)

Product Hazards

Concerns over PV safety issues• PV technology is rapidly evolving, bringing in new

materials (or new uses of existing materials) whose EHS characteristics may not be fully known or appreciated.

• New manufacturing locations are being brought on-line at a rapid pace, sometimes at the expense of best known construction design and tool fit-up and hook-up ESH principles.

Industry Responses

Concerns over PV safety issues• There is no single “platform” for globally sharing

technical information, best practices and other resources among those assigned PV EHS responsibilities.

• Regional EHS laws and standards that address PV EHS concerns are oftentimes not in place or are developing.

• Regional infrastructure is oftentimes not in place or is developing.

• Regional geographic conditions preclude the application of EHS best practices.

Industry Responses

What is SEMI doing to address these safety concerns?

• Tradeshow workshops

• Webcasting

• Partnering with others (SEIA, EPIA, SESHA, etc)

• Peer knowledge-sharing (Safety Grapevine / SemiNeedle)

• Technical standards (S2 for PVs)

SEMI EHS Division Activities

To Join The PV EHS Group:1. Visit www.semineedle.com2. Choose the “Sites” tab3. Click on “PV EHS” site4. Select “Request to Join”

What can ASSE members do?• Actively participate in EHS seminars such as this

• Consider participating in the SemiNeedle PV EHS Group

• Understand and apply semiconductor-related EHS guidelines, standards and best known methods (BKM’s) to your operations as appropriate

• Share BKM’s and lessons learned

• Obtain outside assistance, if needed, to conduct hazards analysis techniques on materials or processes of concern

• Develop “Alternate Methods and Materials” when geographic or other conditions preclude application of guidelines, standards or BKM’s

Potential ASSE PV Safety Activities

Thank You

Please contact:• Aaron Zude (Senior Director), azude@semi.org

• Sanjay Baliga (Senior Manager), sbaliga@semi.org

Questions