Top quality silicon needs top quality analysis

Danish Technological Institute helps Topsil GlobalWafers A/S prove their silicon quality with topography

Topsil GlobalWafers A/S is a world-leading supplier of ultrapure silicon, which is used to make energy-efficient power components used in wind turbines, high-speed trains, and motors. Topsil GlobalWafers A/S is always looking for ways to ensure that they are providing a top product to their customers so they asked the question: Can we increase our confidence that there are no crystal deviations that could negatively impact the properties of our material?

The quality of the silicon is impacted by deviations in the crystal structure of the material. Some deviations do not impact the properties of the material, like vacancies, however other deviations do negatively impact the properties of the material, like interstitial atoms. Vacancies are spots in the material where a silicon atom should be present in the crystal lattice but is not. Interstitials are atoms located on positions in the crystal lattice which are empty in the perfect silicon crystal. If a silicon wafer has interstitial atoms, the material can be conductive instead of an insulator and therefore cannot be used safely in the intended device. Topsil GlobalWafers A/S provides ultrapure silicon with no interstitials as measured by standard methods. Standard methods, however, measure the electrical properties of the material and not the structure.

X-ray topography is a diffraction imaging technique that will result in contrast difference in the images when deviations in a single crystal are present, including crystalline vacancies and interstitial atoms. Topography requires a quality of X-rays that are only available at a large-scale facility called a synchrotron, which can be hard to get access to. There are more than 50 synchrotrons around the world, each with different capabilities and specialties, so knowing which synchrotron to go to and how to start the process can be a big challenge. As a synchrotron mediator, the Danish Technological Institute can help to navigate the world of synchrotrons from experiment design to measurements and data treatment.

Therefore, Topsil GlobalWafers A/S collaborated with the Danish Technological Institute to easily get X-ray topography analysis done for their ultrapure silicon (seen in top image). Ane Baden, project leader at Topsil, said that by working with the Danish Technological Institute, they were able to “get started on using synchrotrons to investigate our material in more detail. It can be a hurdle to get started with synchrotron analysis, since the required knowledge of the different facilities sites’ capability, the required documentation around the sample(s) and how to interpretate the data can be overwhelmingly and time consuming for a company."

Working with the Danish technological Institute eased the process, potential errors from lack of experience were avoided, and they decreased the process time from idea to result. Topsil GlobalWafers A/S now has another tool for investigating interstitials, vacancies and perfect silicon on a wafer on a more detailed level than previously available.

- Ane Baden, Topsil GlobalWafers A/S

This work was made possible with the use of the ESRF (European Synchrotron Radiation Facility) and the help of the Danish Technological Institute.