40 years of atomic layer deposition

[From Materials Views] Forty years ago, Dr. Tuomo Suntola and his group demonstrated the growth of ZnS thin films in alternating, saturating gas-solid reactions. This initiated the development of atomic layer deposition (ALD) in Finland and gradually led to industrial and academic activities worldwide. Riikka L. Puurunen VTT Technical Research Centre of Finland has now written an essay covering this invention, as well as the developments that preceded and followed it, in Chemical Vapor Deposition. 

The ALE essay is part of the “40 Years of ALD in Finland: Photos, Stories” (FinALD40) exhibition organised by the Academy of Finland’s Centre of Excellence in Atomic Layer Deposition (ALDCoE), with Dr. Puurunen and Dr. Jaakko Niinistö (University of Helsinki, UH) as the main organisers. The exhibition material also describes how ALD research was initiated at Helsinki University of Technology (HUT, currently Aalto University) and at UH, contains photographs from over the years, lists Finnish academic theses related to ALD as well as organisations currently active with ALD in Finland, and contains stories on precursor development at HUT, an obituary, and a story of the successful ZyALD™ precursor.

The image is a reconstruction of the very first ALE-ALD experiment (made by Riikka Puurunen, in collaboration with Suntola).

The FinALD40 exhibition material was released in the internet on November 29, 2014, exactly forty years after filing the first ALE patent. The internet edition contains a preface written by Prof. Markku Leskelä (UH) and a reconstruction of the very first ALE experiment as the cover image. The material can be accessed through the ALDCoE webpages at http://www.aldcoe.fi/events/finald40.html and through the webpage of the Virtual Project on the History of ALD (VPHA), http://www.vph-ald.com.

Levitech BV sells two Levitrack ALD systems to Japanese high-performance solar cell manufacturer

As reported by Levitech BV, a leading supplier of advanced process equipment for the manufacturing of solar cells, announced today that it has sold two Levitrack Atomic Layer Deposition (ALD) systems to Japan, the first multiple system order for ALD equipment in the world. A major multinational, which includes solar cell manufacturing among its many concerns, will use the Levitracks for high-volume production and the development of next-generation, high-efficiency crystalline solar cells.

“The further success of the Levitrack, with two being sold to a prestigious client, is confirmation that our mass production solutions for fast ALD deposition deliver the right product to meet the needs of mass-production manufacturers”, stated Jaap Beijersbergen, CEO of Levitech. “The system will be used for PERC cells - with efficiencies exceeding 20 per cent - as well as multi-crystalline and n-type products.”

Since its introduction in 2010, the Levitrack has consistently demonstrated its advanced passivation capabilities at world-leading manufacturers and institutes in both Europe and Asia.
“We know that aluminum oxide film provides excellent cell passivation and increased cell efficiencies, especially when deposited in uniform and dense layers, a particular feature of the ALD technique. In the Levitrack these qualities are combined with an efficient and effective platform for delivery,” said Beijersbergen.

“This customer chose the Levitrack system based on its significant productivity, cost-of- ownership and process advantages over competitive PECVD and other ALD systems for aluminum oxide (Al2O3) applications.”

Hanwha Q Cells to evaluate SoLayTec InPassion technology

Dutch research spinoff SoLayTec has announced that Hanwha Q Cells has begun evaluating its atomic layer deposition (ALD) technology. The InPassion ALD can be deployed for PERC upgrades and n-type cell production.

“Last month in November SoLayTec announced it sold its first production machine in the U.S. for a 100MW n-type bi-facial cell line. Now also Hanwha Q CELLS decided to start the evaluation of the InPassion ALD system from SoLayTec for its high efficiency cell concepts in Thalheim (Germany).”

SoLayTec’s Görtzen says that the company’s goal is to demonstrate that the InPassion ALD process has a higher potential than the plasma-enhanced chemical vapor deposition (PECVD) approach.

“The biggest advantages of our spatial ALD tool compared to PECVD are a better step coverage, a stable uniformity and a layer thickness requirement of only 5 nm Al2O3,” said Görtzen. “Furthermore, if in the ALD cell process flow a direct PECVD is used for the SiN capping layer an integrated annealing process can be implemented, resulting in better cell performance compared to PECVD AlOx.”

Read more: http://www.pv-magazine.com/news/details/beitrag/hanwha-q-cells-to-evaluate-solaytec-inpassion-technology_100017741/#ixzz3OmOeCWkJ

ALD ZrO2 protects Photonic crystal nanolaser biosensor for DNA detection

As reported by AIP.org : A simple method to sense DNA, as well as potential biomarker proteins of cancer or other diseases such as Alzheimer's, may soon be within reach thanks to the work of a team of Yokohama National Univ. researchers in Japan.

As the team reports in Applied Physics Letters, they created a photonic crystal nanolaser biosensor capable of detecting the adsorption of biomolecules based on the laser's wavelength shift.

Equally impressive, the nanolaser biosensor enables detection of the surface charge from its laser emission intensity, which in turn can also be used to sense the adsorption of biomolecules. Using laser intensity to detect biomolecules is potentially less expensive than the fluorescent tagging or spectroscopy techniques typically used in biosensors because it is a simpler procedure.

When the team first set out to explore photonic crystal nanolaser sensors, they weren't focusing on the intensity of the laser emission because it's sensitive to the quality of the fabricated laser and, frankly, they didn't expect it to show sensing signals.

"In the beginning we focused on wavelength behavior, but quickly noticed that [the laser emission] intensity is influenced by both pH and polymers," noted Toshihiko Baba, a professor in Yokohama National Univ.'s Dept. of Electrical and Computer Engineering. "Our results were very reproducible and, interestingly, we found that the behaviors of the wavelength and intensity are independent." 

The team was surprised by these results, which they discovered when they deposited a protective film of thin zirconium dioxide (ZrO2) over the device using atomic layer deposition, and then tried sensing in liquids of high or low pH and liquids containing charged polymers. The coating was necessary to protect the nanolaser from damage and unwanted wavelength drift.

The nanolaser device can sense surface charge because the surface charge changes the occupancy rate of electrons at the surface states in the semiconductor of the nanolaser, Baba explained. "This modifies the semiconductor's emission efficiency." 

Full story: http://www.rdmag.com/news/2015/01/photonic-crystal-nanolaser-biosensor-simplifies-dna-detection

Simultaneous detection of refractive index and surface charges in nanolaser biosensors

Keisuke Watanabe, Yoji Kishi, Shoji Hachuda, Takumi Watanabe, Mai Sakemoto, Yoshiaki Nishijima and Toshihiko Baba

Appl. Phys. Lett. 106, 021106 (2015)

Abstract:

The emission intensity of a GaInAsP photonic crystal nanolaser is affected by the pH of the solution, in which the nanolaser is immersed. This phenomenon can be explained by the change in the redox potential, which modifies the filling of electrons at surface states of the semiconductor and hence the nonradiative surface recombination. This phenomenon allows the nanolaser to simultaneously and independently detect the refractive index and electric charges near the surface on the basis of the variation in emission wavelength and intensity, respectively. This paper demonstrates this function through alternate deposition of charged polyelectrolytes and hybridization of deoxyribonucleic acids.

New Savannah G2 Atomic Layer Deposition System Launched by Ultratech Cambridge NanoTech

Ultratech, Inc., a leading supplier of ALD systems, as well as lithography, laser-processing and inspection systems used to manufacture semiconductor devices and high-brightness LEDs (HB-LEDs), today introduced the Ultratech Cambridge NanoTech Savannah G2 atomic layer deposition (ALD) system. Since its introduction in 2004, the Savannah product line has become the industry-leading commercial ALD system used for research and development activities.

The Savannah G2 platform incorporates a wide range of advanced field-upgradable options intended to aid serious researchers in expanding their portfolio of available ALD films, as well as allow them to characterize the films in real time. Among the Savannah G2's array of options, a unique low vapor precursor delivery system has been developed to enable the growth of novel materials including single- and multi-component films from Perovskite, Yttrium, Lithium, and the rare earth families. Additional options such as ellipsometry, Quartz Crystal Microbalance (QCM), and mass spectrometry allow for the simultaneous growth of ALD films and the real-time characterization of the deposition process, all of which are indispensible capabilities for process development and optimization activities.

Ultratech Cambridge NanoTech Vice President of Research and Engineering Ganesh Sundaram noted, "With 400 ALD systems in the field, Ultratech Cambridge NanoTech's tools have been used in over 800 published papers in peer-reviewed journals. As a result, universities and government institutions, as well as corporate research and development centers, are using our ALD systems to break ground on some of the most interesting applications for thin film use. Today, the Savannah G2 system represents a highly extendable ALD platform, engineered to meet the needs of both routine and extremely challenging ALD thin-film research and development for today's and tomorrow's requirements."