Sensitive Trace Element Analytics

© Fraunhofer CSP

The ICP-MS is loaded with samples.

We provide comprehensive chemical analytics for customers from the photovoltaics sector. The core sector of our R&D services is ultra-trace analytics in all relevant materials: silicon, silane, CIGS, quartz crucibles, sawing slurry, etc. We provide the determination of total concentrations as low as the ppt range as well as the sensitive chemical characterization of surfaces and interfaces. Regardless of whether it's about metals, doping substances, organic contaminations or surface energies – all methods are tuned to the special purity requirements of semiconductor materials.

Depending on our customer's preferences, we offer both plain analytical services as well the identification of causes and complex problem solutions.

Services

  • Ultra-trace analytics in bulk materials: quantitative determination of contaminations and doping agents
  • Surface and interface analytics: quantitative determination of inorganic/organic contaminations as well as surface energy
  • Development of adjusted analytical methods, for example, for process monitoring and quality control
  • Training and consultation in trace element analytics
  • Rent-a-Scientist

Examples

© Fraunhofer CSP

Experimental CZ silicon crystal and vertical concentration profile of impurities (example: aluminum).

Ultra Trace Analysis in Solids

A high purity of the starting materials is an elementary condition for high-power solar cells and semiconductor components. This is opposed by the pressure on the costs for the manufacturing processes. The highly sensitive, quantitative determination of contaminating elements in feedstock, crystals and wafers may help to assure the material quality necessary and optimize the energy-intensive processes.

© Fraunhofer CSP

Flow chart of the layer-specific element analysis.

Layer-specific Element Analysis

Processing steps like sawing, cracking and grinding produce surface contaminations which might also migrate deeper into the bulk material. A sensitive layer-specific element analysis can help to find out where the impurities are localized and how efficient cleaning might proceed. The analysis of wafers, chunks, granulate or powder samples is done by means of layer-specific etching and subsequent ICP-MS analysis.

  • Wahl, S., Meyer, S., Hagendorf, C., Localization of inorganic impurities in silicon samples by sequential etching and ICP-MS detection, 6th International Conference on Silicon Photovoltaics, SiliconPV 2016 (on Sciencedirect)
     

© Fraunhofer CSP

Surface tension determined after contact angle analysis.

Characterization of Wafer Surfaces

Regardless of the semiconductor type involved, inorganic and organic contaminations on the wafer's surface have a negative impact on the subsequent processing steps and the final function of the component. The quantitative determination of the physicochemical surface properties enables a reliable product and process monitoring. Apart from the surface TOC (total organic carbon) analysis in order to achieve an integral quantification of the organic contaminants and contact angle mapping to determine the homogeneity of the surface energy, we can determine metallic contaminations sensitively and quantitatively by applying SE (surface extraction) ICP-MS.

© Fraunhofer CSP

Molecular structure of hexachlorodisilane (HCDS).

Sensitive Trace Analysis in Hexachlorodisilane

Nowadays hexachlorodisilane (HCDS) is applied in microelectronics as a precursor especially for the deposition of silicon nitride and silicon oxinitride films. It is used instead of monomeric precursors whenever low temperatures are demanded for CVD deposition processes. Concomitantly, the purity requirements increase, especially with regard to the metallic contaminations which might induce damage in the active regions of the circuit structure by way of diffusion. The Fraunhofer CSP is able to carry out sensitive and reliable HCDS analyses with detection limits that are distinctly below 1pbb and applicable to most elements.

© Fraunhofer CSP

Quantitative Elementanalyse in CIGS-Solarzellen.

Quantitative Element Analysis in CIGS Solar Cells

Quantitative element analysis is also interesting for manufacturers of CIGS solar cells. For quality control or process optimization, both the matrix elements of the TCO, buffer and absorber layers and the trace elements contained therein can be analyzed layer-selectively. This is done by serial removal of the individual layers with suitable etching solutions and subsequent quantitative determination of the element concentration in the solutions using ICP-OES or ICP-MS. The method is suitable for all substrate types and it has been shown that the results are comparable with reference methods such as ToF-SIMS or XRF.

K. Kaufmann, S. Wahl, S. Meyer, E. Jarzembowski, C. Hagendorf : Quantitative Analysis of Matrix Elements and Sodium in Photovoltaic Cu(In, Ga)Se2 Thin Films by the Use of Time-of-Flight Secondary Ion Mass Spectrometry; 31st European Photovoltaic Solar Energy Conference and Exhibition 2015.