Developer of atomic layer deposition Tuomo Suntola receives Millennium Technology Prize

Thin-film deposition improves the performance of microelectronics. The pioneers of the field come from the University of Helsinki’s Department of Chemistry. Maarit Mäkelä’s upcoming public defence will introduce atomic layer deposition (ALD) processes for silver and gold.

The 2018 Millennium Technology Prize has been awarded to Tuomo Suntola, the developer of the atomic layer deposition (ALD) method. Developed by Suntola in the mid-1970s, ALD is a method in which a substrate, such as a silicon wafer, is repeatedly coated with layers of atoms. This nanotechnology method is used globally to manufacture thin films with a thickness of just a few atoms for microprocessors and memory circuits.

The University of Helsinki is home to the pioneers leading the field into the future: professors Markku Leskelä and Mikko Ritala with their teams. They have been working on atomic layer deposition for nearly 30 years.

“The world’s most prolific ALD research group at the University of Helsinki congratulates Tuomo Suntola on the Millennium Technology Prize,” says a happy Mikko Ritala from the University’s Materials Chemistry research programme, when he hears that the recognition has been granted to a colleague in the same field.

The University of Helsinki’s ALD experts are among the most prolific publishers in the field

The ALD method is used to coat complex three-dimensional structures precisely, one atomic layer at a time. New atomic layer deposition processes and materials are being developed at the University of Helsinki, contributing to the global library of ALD innovations and expanding the potential applications of the technology.

The Centre of Excellence in Atomic Layer Deposition, which operated at the University of Helsinki between 2012 and 2017, is currently drafting a concluding report on the work of the group. The results are impressive, as the global “all-time top list” of scientists in the field in terms of publications is dominated by Markku Leskelä with 329 articles and Mikko Ritala with 327 published articles in the field. Both professors also have the esteemed ISI Highly Cited Researcher status in the field of materials research.

“We are focusing on the development of new ALD chemistry, i.e., precursors and processes. By studying the reaction mechanisms, we also want to advance our collective understanding of chemistry,” says Ritala of thin-film research at the University.

Recently, chemists have been studying two-dimensional materials similar to graphene, such as MoS2, ReS2 and SnS2, for which ALD processes have already been developed.

“Graphene, which won its researchers the 2010 Nobel Prize, and the graphene-like compounds which have become a topic of interest alongside it, have a two-dimensional structure and, consequently, certain unique properties. They are expected to enable increasingly advanced and also entirely new products in electronics, energy production and storage as well as catalyst applications,” explains Ritala.

Maarit Mäkelä grows gold and silver

Another example of the latest research is Maarit Mäkelä’s dissertation, which she will present in her public doctoral defence on 4 June. Her dissertation work involved the development of ALD processes for silver and gold.

The literature review of Mäkelä’s dissertation indicates that there are only a few ALD processes suitable for creating gold and silver thin films. This is because most silver and gold compounds do not tolerate high temperatures. In the ALD method, a thin film is “grown” in a heated reaction chamber, and a fundamental requirement is that the metal precursor not disintegrate in reaction to the heat in its gas phase or on the substrate.

“Gold is a very challenging metal in terms of ALD chemistry, and developing a functional gold process seemed like an insurmountable challenge. Thanks to Timo Hatanpää’s determined and innovative precursor development and Maarit Mäkelä’s deposition research, they were ultimately able to find an atomic layer deposition process suitable for gold,” says Mikko Ritala, who supervised the dissertations of both scholars.

The new processes will have applications in the future, believes Mäkelä.

“For example, in my dissertation research, we deposited silver on titanium substrates. Similar titanium surfaces could in theory be used in tooth implants attached to the jaw bone. The purpose of the silver coating was to prevent bacteria from growing on the titanium surface, which it did. Such a silver coating could then reduce infections and, consequently, the need for antibiotics,” says Maarit Mäkelä.

When the silver coating is created with an ALD method, it is possible to precisely control its thickness, and the coating follows all the shapes of the substrate exactly.

Basic research and applications for the semiconductor industry

It’s fair to say Markku Leskelä and Mikko Ritala are international pioneers of ALD research. The research groups they lead are developing chemical production methods for materials which are particularly needed in microelectronics. However, potential applications range from corrosion prevention to energy technologies and medicine.

They are combining thin-film and surface technologies on the nanolevel, synthesising precursor molecules and organising the molecules on the surfaces. It is difficult to analyse extremely thin films, which has made the close cooperation with the accelerator laboratory led by professors Juhani Keinonen and Jyrki Räisänen particularly important.

Applications of ALD technology are internationally interesting, and research findings gained at the University have become industry practice, strengthening the position of the Finnish thin-film deposition industry in international competition. Key companies in the field include ASM Microchemistry, Picosun and Beneq, each of which employs several University of Helsinki alumni.

“We are currently in our 15th year of cooperation with ASM, and are currently planning the next five-year contract. We are developing new ALD processes for them as well, and they then sell them incorporated into their devices to the semiconductor industry around the world,” says Mikko Ritala.

ASM Microchemistry Oy, a tenant of the University of Helsinki’s Kumpula Campus since 2004, has expanded, and opened a new laboratory facility on Pietari Kalmin katu last autumn, in connection with their existing facilities. The principal clients of the company are the business units of the Netherlands-based parent corporation ASM International N.V., which develop and sell thin-film manufacturing equipment.

“The main benefit to the University from this cooperation has been nearly 15 years of long-term research funding. ASM Microchemistry is funding several doctoral students,” says Ritala.

President of Finland Sauli Niinistö awarded the eighth Millennium Technology Prize in Helsinki on 22 May 2018. The prize amount is €1 million. The sum is granted by Technology Academy Finland.

In 2012, the Millennium Technology Prize was given to open-source pioneer Linus Torvalds, a University of Helsinki alumnus. He shared the prize with stem-cell researcher Shinya Yamanaka.

Further information about the prize and award process:

Päivi Törmä, chair of the international Selection Committee for the Millennium Technology Prize, paivi.torma@aalto.fi

Ari Ahonen, CEO, Technology Academy Finland TAF, ari.ahonen@taf.fi

Developer of atomic layer deposition Tuomo Suntola receives Millennium Technology Prize

The University of Helsinki’s ALD experts are among the most prolific publishers in the field

Maarit Mäkelä grows gold and silver

Basic research and applications for the semiconductor industry

Read more about ALD expertise at the University of Helsinki