LZH’s Spatial ALD system uniformly coats complex shaped optics

28 Mar 2022

Deposition process achieves higher deposition rates than before, with apps in automotive, lighting, and AR-VR sectors.

With its newly-developed “Spatial ALD” deposition system, Laser Zentrum Hannover can now also uniformly coat complex-shaped optics. The innovative system achieves higher deposition rates than previously possible. LZH says this capability is of interest, among others, for applications in automotive lighting and VR/AR sectors.

ALD (atomic layer deposition) technology can produce very thin, high-quality coatings. So far, the ALD process has been used primarily to produce thin functional layers in the semiconductor industry, for example.

The new Spatial ALD system, which was developed in cooperation with the company Beneq, which is headquartered in Espoo, Finland, has made economically viable another application that is in high demand in industry, say the partners.

The scientists in the Optics Integration Group at LZH can use the method to produce layer systems of uniform thickness much faster than before, for example on strongly curved and structured optics. Previously used methods, such as electron beam evaporation or ion beam sputtering, are severely limited in this respect, says LZH.

The Spatial ALD system achieves high deposition rates in the production of ultra-thin coating systems for optics and enables the uniform coating of complexly shaped surfaces. This is of interest, for example, in the fields of automotive lighting or augmented reality (AR)/virtual reality (VR), where three-dimensionally shaped lighting elements are essential.

As the system is plasma-based, it can operate with low temperatures – below 100 degrees Celsius – making it particularly suitable for coating temperature-sensitive polymer optics, which are often used for displays.

Rotation principle for high rate deposition

The “rotation” system was developed by the Finnish company Beneq, a noted player in ALD technology, in collaboration with LZH. The ALD process is based on self-limiting chemical reactions between gaseous precursors and substrate surfaces.

In conventional systems, commonly used at present, the process reactions are carried out one after the other, which necessitates a time-consuming gas exchange of the entire reaction chamber. The approach is different in the LZH Spatial ALD system: Here, the process cycles take place spatially separated. The system has four individual process chambers separated by pressure and nitrogen; in each of these, an ALD reaction step is completed.

The substrates then rotate into the next chamber. In this way, the scientists have achieved deposition rates that were previously only possible with other coating processes. LZH says this approach “makes the process particularly economical and at the same time enables high throughput in optical coating.”

The development team presented their first research results with the new system in a conference contribution at this year's Photonics West. They are also currently working in the EUROSTARS collaborative project INTEGRA to coat optical diffraction gratings using the Spatial ALD system.