The success of modern electronics is due to the innovation of super-efficient and reliable devices of miniscule size. The technology that has made this possible is Atomic Layer Deposition (ALD), invented by the Finnish Doctor of Technology, Tuomo Suntola. His first ALD-related patent was filed in 1974 and is now over 40 years old. Dr. Suntola is still actively involved with ALD as a Board member of the Finnish ALD technology company, Picosun. He is also one of the owners of the company.
Tuomo Suntola graduated as a Master of Science in Electrical Engineering in 1967, and four years later, at the age of 28, he defended his doctoral dissertation. In his dissertation he studied thin films, but ALD, however, was yet to come.
Suntola realized that in order to manufacture high quality thin films, the quality demanded must of necessity be an integral part of the manufacturing process. He also understood, that a prerequisite for the strictly controllable electrical qualities of the film was a highly ordered film material. To produce this kind of film, the processing conditions had to be tightly controlled. No-one had been able to achieve this by that time.
The crucial step happened in 1974, when Instrumentarium, a company manufacturing medical equipment, recruited Suntola to set up a new R&D-team for them. Instrumentarium is today a part of the General Electric Group. Suntola had at that time already invented a very successful Humicap® humidity sensor for Vaisala Oy. Instrumentarium’s CEO, Aulis Hauhia, decided that he wanted the young scientist to lead a team that would invent “something new”.
After some studies and research, Suntola presented the company management with the idea of an electroluminescent display. Flat panel displays were wanted, but no-one had been able to solve the technological issues related to their production. The electrical breakdown strength of the material used in the displays had to be on top level, because a material layer only one thousandth part of a millimeter thick had to be able to withstand voltages over 200 V connected over it. The display had large area, and its material had to be absolutely pinhole-free. CEO Hauhia showed his courage and said, in English: “I am still confused but at a higher level. Let’s go ahead.”
It was some time after Suntola’s appointment and he was sitting in a still unfurnished, empty laboratory. The following is how he described the birth of ALD to Professor Riikka Puurunen, who has written about the history of the technology:
“We still had an empty laboratory with just tables and chairs and a Periodic Table of the Elements hanging on the wall. Looking at the Periodic Table, and thinking of the overall symmetry in nature, I had the idea of “serving” the complementary elements of a compound sequentially, one at a time, onto a surface. Monoatomic layers may be obtained if complementary elements make a stronger bond with each other than they do with atoms of their own kind”.
Conditions had to be created, under which only one atomic layer would stick to a surface. The first compound with which Suntola tested his idea, was zinc sulphide. The test film was grown in autumn 1974. Suntola called his method Atomic Layer Epitaxy (ALE). The term originates from the Greek epi – meaning ’above’ and taxis – ’orderly’. ALE only changed to ALD in 1998. After the first tests, however, Suntola still had a lot of secret work to complete. Nevertheless, the possibilities of the innovation started to take shape. This was much more than just hospital technology and Suntola’s team of researchers moved in 1978 to work for Lohja Oy, a company manufacturing consumer electronics.
The results were finally ready to publish in a Society of Information Displays (SID) conference in San Diego in 1980. The innovation received tremendous attention. Lohja Oy received over 3000 product enquiries, but lost its momentum because the production line was not ready. Displays manufactured by Lohja Oy were not able to reach the market until three years later, by which time liquid crystal displays (LCD) had started to become more popular and, little by little, electroluminescent displays were left only for special applications.
In 1990 Lohja Oy sold its display manufacturing to its competitor Planar. Tuomo Suntola was by then already working for another employer, the Finnish national oil company Neste. Neste was interested in new energy sources, including solar energy, and ALE films were thought to be suitable for harnessing it.
Specifically for this purpose, a company called Mikrokemia Oy (Microchemistry Oy) was established in 1987, and Suntola was named as its Managing Director. This big national company offered the resources for further development of ALE. The technology was studied with the aim of manufacturing solar cells, but this time, the results were not up to expectations. The cells achieved a high efficiency rating, but the manufacturing process was not scalable.
New possibilities started to emerge, however. Semiconductors were an obvious application, since that is where Suntola’s background lay.
In the late 1990’s preparations were underway for a merger of two national energy corporations: Fortum was founded in 1998, and the next year it sold Mikrokemia to a Dutch company ASM. Suntola could have followed, but he did not want to and he stayed at Fortum as a Research Fellow. Suntola’s closest workmate, the late Sven Lindfors (d. 2017), an equipment builder with an “incredibly constructive eye”, also elected to stay with Fortum, and in 1997 he founded a dormant company called Picosun Oy. That was where ALD know-how, with all the tacit knowledge, would accumulate.
In the year 2004 Sven Lindfors managed to inspire Kustaa Poutiainen to join his company, and this is how the current Picosun started its operations. Suntola joined the company after a couple of years, first as an advisor, but soon as one of the owners and a Board member – a position which he still holds.
In the year 2007 a remarkable product launch happened, when Intel presented, the first time, a metal-oxide-semiconductor (MOS) transistor equipped with an ALD film. Now the semiconductor industry started to really utilize the possibilities offered by ALD. The number of publications about ALD skyrocketed, and soon ALD equipment were a necessity to the whole semiconductor industry. The results we see every day for example in our modern smartphones.
ALD equipment manufacturers of today have to be agile and possess a strong forward vision, since other branches of industry have also woken up to the possibilities offered by ALD. This is especially true in the health industries, where the first ALD applications are already in production, and which may soon take huge leaps forward with the technology. The possibilities are limited only by man’s imagination. LED manufacturing needs ALD. Internet-of-things can’t develop without it. ALD is used even in quality watches and as protective coatings on collector coins. New applications emerge all the time. ALD is true high-tech, where invisible films only a few atomic layers thick create huge possibilities for the whole of mankind. All this was made possible by a young Doctor Tuomo Suntola working in a company whose management had the courage to trust innovation and systematic work.