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History of Atomic Layer Depositon (ALD)

The thin film electroluminescent (TFEL) displays: the initial driving force for ALD invention and development

Atomic Layer Deposition (or Atomic Layer Epitaxy as it was called) was introduced in 1974 by Dr. Tuomo Suntola and co-workers. The method was developed to improve the quality of  ZnS-films used in electroluminescent displays. It turned out that ALD produced not only better phosphor layer but also outstanding dielectric layers. The first display was lit in display board in Helsinki Airport in 1982. Since then more than 2 million EL-displays have been produced (about 200.000 m2 (20 ha)).

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The research project was started at Instrumentarium (now a part of General Electric) followed by powerful and

enduring investment by Lohja (Finlux) Oy. The operation became part of Planar Systems Inc, a US based company in 1990. The manufacturing site is located in Espoo.

ALD tools in TFEL display production at Planar

This substantial r&d project, which took more than 10 years from the idea to commercial production, initiated also research activities in the Helsinki area universities. A spin-off company  from Lohja/Finlux Microchemistry Ltd. was founded in 1987 together with Neste Oy, a domestic oil company. Microchemsitry’s tasks were to introduce ALD to other applications like thin film solar modules and catalysts. It was also to become the ice breaker for the vital ALD equipment manufacturing branch of industry in Finland.


ALD process research in universities

The research on ALD processes was started at Helsinki University of Technology in 1982 by Prof. Niinistö. The work was started in cooperation with Lohja/Finlux. The main focus was to develop processes and materials to be used in TFEL displays to produce also other colors than yellow. 

The Department of Chemistry at Helsinki University started its own ALD research activities in 1991 by Prof Markku Leskelä. They have worked in close co-operation with industry and research organizations in Finland and abroad. Their modern lab is located in Kumpula campus.

These two groups are regarded as the top ALD research labs in the world. They have published about 300 scientific papers and 17 Ph.D. have received their degrees from these labs.


ALD Processing Equipment

The first ALD growth trials were made using UHV systems but a LP-CVD type ALD reactor was developed in the late 1970ies and patented in 1980. The ALD processing equipment were build by Lohja Oy mainly for their own use.  

The situation changed when Microchemistry was founded in 1987 by a Finnish oil company Neste Oy and Lohja Oy. It was an r&d company developing ALD thin film solar cells and new types of heterogeneous ALD-catalysts for its parent company Neste. To be able to carry out these activities, a new small scale ALD reactor was developed. This reactor type was also sold to the partner university groups in early 90is. A large area ALD reactor was developed for the real size solar modules.

The first customers of Microchemistry came from EL –community in Korea, Japan and Germany. The tasks of Microchemistry were refocused in 1997 and it concentrated only in ALD equipment manufacturing. To respond

the increasing interest from the semiconductor industry Microchemistry merged into ASM, an international manufacturer of semiconductor processing equipment, in 1999.

One of the largest ALD equipment was built at Lohja/Finlux in 1985

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IC-industry has foreseen in its roadmap that e.g. they must replace silicon based dielectrics and  introduce new materials in the CMOS process to be able to produce circuits with less than 100 nm line widths. The inherited properties of ALD films like excellent step coverage, top quality dielectrics and easiness to control film growth with accuracy of 0.1 nm were the key factors to start the work with ALD films.

ALD were also introduced by Microchemistry to other applications like thin film heads in hard disk read heads in 1999. ALD very rapidly overtook sputtering as an Al2O3 deposition method in this application.

ASM Microchemistry was split in 2001 and its production and sales functions were moved to Phoenix, Arizona. ASM Microchemistry became and it still is the ALD process r&d lab of ASM. ASM America continues manufacturing of ALD processing equipment for semiconductor applications like gate dielectric and copper barrier/seed.

Since 2001 a couple of new companies have started ALD equipment manufacturing: Picosun 2003 and Beneq in 2005. They both have roots in Microchemistry, Picosun even in Lohja/Finlux, currently Planar. Also Planar entered in this market in 2003.

 


ALD-coating services

ALD coating services is the newest field of offered ALD products. These services use existing films and processes, which are used in new applications. There can be an r&d feature in this service.

 

 

 

 

Deposition of thin film samples has been and is an essential part of the equipment transaction process. However, it was not until in early 2000 when this service has been provided independently. The number of these service providers is increasing rapidly.

 

Contract ALD-coating services offer a cost effective way to carry out depositions in different quantities. It can be done from small scale in the initial r&d phase to large scale in out-sourced production of ALD-films.