15 July 2016

Picosun and University of Helsinki develop photo-assisted ALD

Atomic layer deposition (ALD) thin-film technology firm Picosun Oy of Espoo, Finland, says that it is now providing equipment and solutions for the commercial utilization of photo-assisted ALD.

Photo-ALD is said to enable novel ALD processes, area-selective film deposition, low deposition temperatures, savings on precursor chemical consumption and costs, and lower environmental impact of the ALD processing.

Photo-assisted ALD uses light to enable ALD film growth. Whereas in regular ALD a film grows from two gaseous precursors that react on the coated surface one by one, in photo-ALD only one chemical is needed – light takes care of the rest.

In photo-assisted ALD, the coated surface is exposed to alternate pulses of precursor vapor and flashes of high-intensity light. The energy of light makes the precursor molecules on the surface chemically convert into the desired coating material. Alternatively, two precursors can be used but the other becomes reactive only when illuminated. When only one precursor is required, both costs and the environmental effect of the process are lower. In conventional ALD relying fully on gaseous precursors, area-selective film growth is particularly difficult to achieve and often requires additional processing steps for deposition and etching of passivation layers. Light, on the other hand, is easy to block from the areas that need to be left uncoated, and sharply defined patterns can be created without direct contact to the substrate or exposure to chemicals directing the film growth. Also, when the energy of light replaces the energy of heat (the driving force of conventional thermal ALD), processing can be performed at much lower temperatures than in regular ALD.

"The photo-ALD method has been investigated only marginally this far, mostly because of the lack of proper equipment," notes professor Mikko Ritala of Finland's University of Helsinki. "Now, using Picosun's photo-ALD tools we have been able to develop this technology and related chemistry for several key ALD processes. Potential applications can be found in MEMS (micro-electro-mechanical systems), sensors and other advanced microelectronics (for example, selective ALD to keep the chip contact areas clean), and solar cell manufacturing," he adds.

"Picosun's ambition is to take ALD where it has never gone before, to enable novel, disruptive industrial solutions and cutting-edge new products," says Picosun's managing director Juhana Kostamo. "Our photo-ALD system has enabled great results at our long-term collaboration partner University of Helsinki," he adds. "It is fascinating to introduce this technology to our industrial partners to help them find new ways to solve their manufacturing challenges."

See related items:

Picosun establishes joint industrial ALD research lab at Taiwan's NCTU

Picosun launches 150-200mm wafer batch ALD system for LEDs, MEMS and power devices

Tags: ALD

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