Friday, October 17, 2014

A Short History of Atomic Layer Deposition: Tuomo Suntola's Atomic Layer Epitaxy

Chem. Vap. Dep. Article first published online: 15 OCT 2014
DOI: 10.1002/cvde.201402012

Atomic layer deposition (ALD) is a thin film growth technique based on the repeated use of separate, saturating gas-solid reactions. The principle of ALD has been discovered twice; in the 1960s under the name “molecular layering” in the Soviet Union, and in the 1970s under the name “atomic layer epitaxy” (ALE) in Finland. In 2014, it is forty years since the filing of the worldwide patent on ALE as a method for the growth of compound thin films. This essay celebrates the fortieth anniversary of ALE-ALD, briefly telling the story of ALE as shared by its Finnish inventor, Dr. Tuomo Suntola. Initially, ALE was aimed at the growth of high-quality polycrystalline ZnS thin films for electroluminescent (EL) display panels. Gradually, the material selection of ALE increased, and the application areas were extended to photovoltaics, catalysis, semiconductor devices, and beyond. Fast, production-worthy ALE reactors were imperative for industrial success. The unprejudiced creation of new technologies and products with ALE, initiated by Dr. Tuomo Suntola and led by him until early 1998, are an integral part of the Finnish industrial history, the fruits of which are seen today in numerous applications worldwide.

Sven Lindfors in 1978 next to the flow-type ALD reactor in which the successful H2S/ZnCl2 process was demonstrated.


* The author thanks Tuomo Suntola for sharing these and other details of the development of ALE and EL. It has been a great honor and privilege to work with him and to write this history. Writing this history was triggered by the parallel-running worldwide Virtual Project on the History of ALD (VPHA). Warmest thanks to Tuomo Suntola for his support for the VPHA, too. The author also acknowledges Tapio Alvesalo for checking the details related to NAPS, Dr. Marko Tuominen for the details related to ASM Microchemistry, Juhana Kostamo for the details related to Picosun, Prof. Victor Drozd for confirming the timing of Suntola's visit to Leningrad, Prof. Yukihiro Shimogaki and Prof. Markku Leskelä for identifying the second-left participant in the ALE-1 photograph, and Prof. David Cameron for polishing the language in this article. Funding by the Academy of Finland's Centre of Excellence in Atomic Layer Deposition (ALDCoE) is gratefully acknowledged.

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