On the 20th of May, the atomic layer deposition and etching for quantum technologies workshop took place at the Eindhoven University of Technology. The event was a great success—if we may say so ourselves—and sparked valuable exchanges between the ALD/ALE and quantum communities. In this blog post, we reflect on the day and highlight the key discussions and takeaways.
The workshop was organized as part of the Atomic Scale Processing for Quantum Technologies project, funded by the Dutch Research Council (NWO). It was also partly sponsored by Oxford Instruments Plasma Technology to highlight the 20 years of collaboration with the Eindhoven University of Technology. The audience was a nice mix of people from universities, institutes, start-ups and other companies. We started with two introductory talks that served as a ”101” on ALD/ALE and quantum computing. The first was given by Erwin Kessels from Eindhoven University of Technology and the second was given by Gary Steele from Delft University of Technology. The other speakers focused on their respective quantum devices, exploring how ALD/ALE is—or could be—integrated into their process flows. In addition to the presentations, the day featured poster pitches, poster sessions, and engaging discussions throughout. The event concluded with a joint discussion on key challenges and the potential for mutual benefit between the two fields.
Some numbers:
- Approximately 70 participants attended, with 30% joining from abroad—mainly from Germany, Belgium, and the UK.
- The audience consisted for 70% of representatives from universities and research institutes, and for 30% of people from start-ups and industry.
- The program featured a total of 9 presentations spread throughout the day.
- 10 poster pitches covered a wide range of topics, from single-photon detectors based on ALD films to the development of ALE processes for smoothing device structures.
Main takeaways:
- Inferring cryogenic performance from room-temperature measurements remains a major challenge—materials that appear promising at 300 K can underperform at 10 mK, and vice versa.
- Interface quality is critical to quantum device performance, as most losses originate at interfaces. Each step—from film deposition to device fabrication—must be carefully evaluated for its effect on interface integrity.
- ALD and ALE offer significant opportunities in quantum technologies due to their inherent advantages: excellent conformality, uniformity, precise thickness control, and damage removal capabilities.
- Strengthening collaboration between the materials science and quantum communities is essential. Real progress toward practical quantum computing will depend on integrating expertise from across disciplines.
During the workshop, a Mentimeter poll was conducted to gather input from attendees on several key questions. The top three answers for each are summarized in the table below. Some of these points are explored further in the main insights, but the overall message is clear: ALD and ALE show strong potential—particularly in terms of scalability, reproducibility, and interface/surface quality. This highlights the importance for the ALD/ALE community to prioritize wafer-scale processing where possible, and to place increased emphasis on surface quality using advanced characterization techniques such as AFM, XPS, SEM/TEM, and FTIR.
| What is the main challenge in quantum device fabrication? | Which steps in quantum device fabrication could benefit from ALD/ALE? | What advancements in ALD/ALE are key for integration in quantum device fabrication? |
|---|---|---|
| Quality of interfaces/surfaces | Deposition of superconductors and dielectrics | Faster processes |
| Uniformity/scalability | Steps to reduce roughness | Improved etch selectivity |
| Materials quality control | All steps | New processes (extension of material set, novel etch recipes, …) |
Main insights from our workshop
With this workshop, our goal was to gather perspectives from attendees on the current status and future opportunities for ALD/ALE in quantum technologies. To support this, Mara Liebregts (a student from TU/e) conducted interviews throughout the day. Below, we highlight several key themes that emerged—both from these conversations and from the presentations. We welcome continued dialogue on these topics, so feel free to share your thoughts in the comments section below!
‘’New breakthroughs will be obtained by bridging communities’’. The importance of collaborations between both communities was mentioned many times throughout the day. The quantum computing community is working towards large-scale systems through device design, error correction, and material development. Meanwhile, ALD and ALE are gaining popularity for their high-quality interfaces and scalability. This was highlighted during the presentations by Nicholas Chittock from Oxford Instruments Plasma Technology and Bas van Asten from the Kavli Institute (Delft), who described the many examples and possibilities in tailoring ALD/ALE to quantum applications. These speakers emphasized that while many materials and processes from the electronics field can be leveraged, quantum applications often come with unique requirements and constraints. They highlighted the importance of close collaboration between the ALD/ALE and quantum communities to build a skilled workforce capable of developing materials with the appropriate properties and assessing their performance in quantum devices. Partnerships with simulation-focused research groups could further accelerate progress by helping to identify process conditions that yield the desired material characteristics—and by addressing the fundamental question: “What material properties are actually needed for quantum technologies?” Naturally, the answer depends on the specific device. For instance, the requirements for a superconducting layer used in single-photon detectors differ from those for a superconducting qubit. While certain properties—such as surface roughness, material density, and oxygen impurity levels—can offer some indication of expected quantum performance, predicting device behavior based solely on room-temperature characterization remains a major challenge. This leads us directly to our next key insight.
‘’Room-temperature properties do not translate well to cryogenic performance’’. This was exemplified by Timo Willigers from TNO, who showed DC leakage properties for the dielectrics Al2O3 and SiNx, where the conclusions on which layer performed better changed when going from room temperature to cryogenic temperatures. Hence, characterization at cryogenic temperatures is key, which is maybe one of the major differences with current electronic devices. This calls for quick feedback loops from process development to characterization at room temperature and cryogenic temperature to device fabrication and characterization. However, the accessibility of testing equipment is a challenge, as cryogenic measurement set-ups are often fully utilized and getting sufficient time on this equipment is often difficult. While predicting the cryo-properties of devices from room-temperature measurements is still a challenge at the moment, some quality indicators can be used. One of these quality indicators is the surface roughness, that can be used as one of the fingerprints for the interface quality.
‘’Interfaces are the main source of losses’’. When discussing the losses emerging from interfaces in (superconducting) qubits, Gary Steele from the Delft University of Technology explained that they could be swept under the rug in the early stages of the technology, but “when you start looking under the rug you find out they are everywhere.’’ Gary identified the defects leading to losses at interfaces as one of the biggest, or even the biggest, challenge in the continued development of superconducting qubits. This point was echoed during the talks of Christos Zachariadis from QuantWare and Nicholas Chittock from Oxford instruments, and also applies to spin qubits, as highlighted by Timo Willigers from TNO. Wet etching is currently the method used to remove some of the interfacial defects, but it can leave impurities, lacks selectivity, is performed in atmosphere and is still not sufficient for certain interfaces. The potential of ALE and its smoothening effect, already introduced in our previous blogpost, was brought up throughout the day. The different routes to help tackle this problem and the many questions raised are closely linked to the two previous sections of this blogpost. There is a need to facilitate a feedback loop between ALD/ALE processes and their impact on quantum devices, implying again that collaboration is key. Finally, it was a general agreement that all the interfaces could benefit from ALD/ALE, and this demonstrates the high number of opportunities of those two techniques in quantum device fabrication.
‘’There is a myriad of opportunities to apply ALD and ALE in quantum technologies’’. The several presentations and discussions of this workshop highlighted the many possibilities to incorporate ALD and ALE in a quantum device fabrication. ALD is even already applied for some fabrication steps. For example, QuantWare already uses superconducting nitrides deposited by ALD to fabricate resonators and to deposit a superconducting layer conformally in a through-silicon-vias (TSVs). TNO uses ALD to deposit dielectric layers in their spin qubits devices, and is interested in exploring alternative dielectrics by ALD. At the University of Glasgow, superconducting nitrides are prepared by ALD for single photon detectors because of the unmatched thickness control ALD provides. ALE is starting to get attention thanks to its potential to improve interface quality, as this is a bottleneck for the improvement of many quantum devices. Furthermore, the combination of ALE and ALD, for example as a cleaning process followed by a capping layer to protect a quantum device, was one of the promising future pathways discussed during the workshop.
We enjoyed the insightful discussions throughout the day and were happy to receive positive feedback from the attendees. We would like to thank all attendees and everyone who made this event possible, especially the speakers, for the success of the workshop. We hope that this event will help to trigger and deepen research collaborations between both communities.
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