ICP-MS Analysis of Silicon Feedstock Materials

Balazs NanoAnalysis, 46409 Landing Parkway – Fremont CA 94538

Inter Solar Europe 2012

Hugh Gotts, Ph.D.

2 The MicroContamination Experts

Inductively Couple Plasma (ICP)■ ICP

Co-developed by Stanley Greenfield in England and Velmer Fassel in USA

■ PropertiesHigh excitation/ionization, and electron temperatureAr plasma at 10000 KHigh-density plasma with electron density >1 E16 cm-3

■ ApplicationsExcitation source for optical emission spectroscopy(ICP-OES)Ionization source for elemental mass spectrometry(ICP-MS)

■ AdvantagesEfficient atomization and ionizationMinimum matrix effectSimple spectra with much less spectral interferenceWide linear dynamic range: 7 - 9 orders of magnitudesSystems are available in most modern chemical laboratories

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Bulk Analysis via ICP-MS

System calibration is performed with traceable standards (NIST)A large sampling mass (more representative sample)High sensitivityAnalysis is independent of surface conditions and physical properties of silicon such as density, texture, strength …Data can be verified by analysis of prepared samples on multiple analyzers

Chemical Digestion& Treatments

Why results are accurate?

Analytical Balance

ICP Plasma

Silicon

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Application Example

Analysis of TM’s in High Silicon Content Matrix

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ICP Mass Spectrometry (ICP-MS)

ICP-MS Ion Source

Quadrupole Based ICP-MS (Q ICP-MS)

Collision Cell ICP-MS (CC ICP-MS)

Dynamic Reaction Cell (DRC ICP-MS)

Time of Flight ICP-MS (TOF-ICP-MS)

High Resolution Magnetic Sector Based ICP-MS (HR SF ICP-MS)

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Collision Cell ICP-MS

0

200000

400000

600000

800000

1000000

1200000

1400000

1600000

0 0.2 0.4 0.6 0.8 1

Collision Gas Flow Rate (mL/min)

ICP

-MS

Sign

al (c

/s)

Ar+ (m/z 40)

ArO (m/z 56)

Gas + Ar+ → Gas+ + Ar

Gas + Ca+ ≠

Gas + ArO+ → Gas+ + ArO

Gas + Fe+ ≠

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High Resolution ICP-MS

Si+ (m/z 27.97693)

N2+ (m/z 28.00614)

CO+ (m/z 27.99491)

Base-line separation of Si (m/z 28) from CO

(m/z 28) and N2 m/z 28

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ICP-MS DL Comparison with Other Techniques

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Method Use to Prepare and Analyze Material

Weigh samples to 4 significant figuresDigest pre-weighed sample using 1:1 mixture of HF:HNO3 added drop-wiseSilicon evaporation utilizing excess HF to remove Si backgroundDilution Sample Sample Analysis

Calibration of ICP-MS utilizing a multi-element Standard covering theexpected concentration range

Element list taken from SEMI PV17-0611

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Summary: Elemental Spiking of Silicon Feedstock Material

1 lot of granular material, sub-sampled into 8 portionsEach portion individually spiked with NIST traceable multi-element standardEach portion individually digested, evaporated, and re-dissolved

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Inter-Laboratory Results Comparison

1 lot of granular material, divided into 3 sub-lots (3 labs)Each laboratory digested, evaporated, and re-dissolved replicate samplesLaboratories utilized NIST traceable multi-element standards

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Summary

Today’s activities in PV industries are directed towards high performance, reliability, and low cost.

■ Silicon Feedstock Material Analysis via ICP-MSAllows determination of metallic contaminants at important concentrationsTraceable standards (NIST) and spike recoveries validate resultsSimultaneous preparation of multiple samples results in high throughputReasonable correlations are achieved between laboratories

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Thank you for your attention

End of presentation Hugh Gotts, Ph.D.

hugh.gotts@airliquide.com

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