Terahertz resistance scan functionality
“Measure what is measurable, and make measurable what is not so.” – Galileo Galilei
THz resistance scan is a new measurement tool developed by Sunlab in close collaboration with Protemics GmbH. The measurement is based on THz near-field technology which is already used in several micro-electronic applications. In the quest for high-efficiency solar cells, highly doped emitter structures have become smaller and smaller. For example, narrow selective emitters or IBC solar cells fingers are now widely used, and it is important to know if the features have the correct dimensions and resistance value with high precision.
THz resistance scan allows to reveal sheet resistances for structures as small as 10-20 micrometers, combined with a high measurement speed up to 3 ms per measurement point. The THz PV measurement is contactless and shows the sheet resistance distribution over a full 156×156 solar cell. Sunlab started the development of this tool two year ago and is now ready to offer this technology to the PV market.
Sunlab offers a measurement service: you can send us your samples and we will send you a full measurement report. This way you can find out if this method is working for your research and development. We are also offering for sale a full THz resistance scan instrument on your request.
If you are interested or want to join our development, please contact us.
- Silicon wafer quality
- Selective emitter sheet resistance mapping
- Near edge sheet resistance determination
Oxygen-related defect detection in silicon wafers
The THz-resistance scan technology of Sunlab is able to detect oxygen-related defects in silicon wafers, for example oxidation-induced stacking faults (OISF).
OISF is notorious for reducing solar cell performance significantly. The effect due to OISF is often noticed when the solar cell is already processed. With the THz resistance scan the OISF can be detected in the early steps of the solar cell process.
The figure above shows a THz-scan of a wafer with OISF rings.
Sheet resistance measurement of selective emitter structures
Selective emitter technology boosts performance of the solar cell. With the THz-resistance scan the sheet resistance of the selective emitter structures can be determined.
Acurate determination of the selective emitter sheet resistance is critical for solar cell research and fabrication. With the THz-resistance scan you are able to acurately determine the sheet resistance at very high resolution.
The figure above shows a THz-scan of a sample with selective emitter structure.
Near edge sheet resistance determination
As solar cell technology is excelling forward, the margins for process errors are narrowing. The THz-resistance scanner is able to acurately determine the sheet resistance close to the edge of the wafer as shown in the sample.
This opens the opportunity for enhanced process control.
The figure above shows a THz-scan of the wafer corner after diffusion.