In late March, we launched our ReviewBase, a listing of atomic layer deposition (ALD) and atomic layer etching (ALE) review articles. The ReviewBase files available in Excel and PDF formats have been downloaded more than 500 times altogether in a little over two months. As the AtomicLimits site values open access to information, the ReviewBase is now also available in .ods format. We have received valuable suggestions of missing reviews as well as numerous responses in LinkedIn and Twitter from the ALD/ALE community, suggesting that many of you, like us, find this resource useful. This post describes updates to the ReviewBase that we have been working on as well as some of our future plans.
Expansion of ALD and ALE ReviewBase
The ALD ReviewBase has been updated by adding more than 100 old and new ALD reviews. The original list was compiled based on a Web of Science (WoS) search using keyword “atomic layer deposition” restricted to “review” document type. Such a search is not perfect, however, as many of the results are not review articles and must be manually removed. Even more importantly, the search misses many relevant reviews that do not share these exact keywords. We have now conducted similar searches using search terms complementary to ALD, including “atomic layer epitaxy” (commonly used during the 1970s to 1990s – partially for processes similar to current mainstream ALD, partially for pulsed molecular beam epitaxy and vapor phase epitaxy like processing), “molecular layering” (commonly used in Russia and the Soviet Union where ALD was independently discovered under this name), and “molecular layer deposition” (a “sibling” of ALD using organic precursors).
Several of the older reviews have gathered a large number of citations. In reference to our previous “top 20 most cited” list, the most cited review that was added in this update ranks #9 with more than 600 citations to date: this is Surface Chemistry for Atomic Layer Growth (1996) by Steven George et al. Two reviews titled Atomic Layer Epitaxy that were written by Tuomo Suntola, the inventor of the method, published in 1989 and 1992, have each gathered around 500 citations. We think this a good reminder that many older reviews are still regularly cited today and are still worth reading for valuable information and insights.
Besides the WoS searches, updating the ReviewBase has been a largely manual process relying on feedback from the community as well our personal review collections. In particular, we would like to acknowledge Simon Elliott and Séan Barry for their input. We are grateful to Riikka Puurunen for her comments and suggestions as well as for pioneering openly available ALD resources, including a list of published reviews. We continue to welcome suggestions for review articles that should be added.
New ALD book chapter ReviewBase
We have also compiled and added a list of book chapters on ALD. The rather large number of such chapters, at present more than 70 on our list, is noteworthy. As book chapters are often not easily found using platforms such as WoS, we hope this will be a useful resource. To assist in accessing the book chapters, we have added a link to an e-book, if possible. If you know a chapter or link not included in the file, please send us a message.
Many of the book chapters are introductory chapters to ALD and are often great alternatives to general ALD review articles for newer as well as more experienced ALD researchers alike. Some examples that we and colleagues have found useful include chapters by Knoops et al. (2014) in Handbook of Crystal Growth, Leskelä et al. (2014) in Comprehensive Materials Processing, and van Ommen et al. (2021) in Kirk-Othmer Encyclopedia of Chemical Technology.
Besides individual chapters, a few books solely focusing on ALD are worth noting. There are three edited books that collect together chapters on Atomic Layer Deposition of Nanostructured Materials (2011, edited by Nicola Pinna and Mato Knez), Atomic Layer Deposition for Semiconductors (2014, edited by Cheol Seong Hwang), and Atomic Layer Deposition In Energy Conversion Applications (2017, edited by Julien Bachmann). Very recently, Séan Barry has written the first ALD textbook titled Chemistry of Atomic Layer Deposition.
New ASD ReviewBase
As the atomic layer deposition and etching fields evolve and expand, so do the subfields. One such a field is area-selective deposition (ASD). In ASD, besides atomic scale thickness control, limiting growth to only desired areas is of high importance. Such selectivity can be achieved between different materials or topographies. An example of the former is growing SiO2 on top of SiO2 but not on an adjacent layer of Al2O3. This can be achieved by using inhibitors, which adsorb onto the non-growth area and prevent precursors from adsorbing onto it. For a more detailed explanation, see our previous blog post.
The published reviews that are listed in a table below discuss many aspects of ASD. The most severe limitation of ASD is imperfect selectivity, meaning that growth will take place on the non-growth area after a certain delay. Efforts to revert this unwanted growth exist, such as by etching back (Mackus et al. 2019, Parsons and Clark, Yarbrough et al., Bonvalot et al.).
The inhibitors used are often relatively bulky molecules with long hydrocarbon chains, which form self-assembled monolayers (SAMs) (Mackus et al. 2014, Cao et al., Mackus et al. 2019, Yarbrough et al.). SAMs can offer good selectivity, although their size may lead to reduced coverage and thus limited selectivity when working with narrow trenches and other nanoscale patterns. This along with preference for all vapor-phase processing motivates the surging interest in a class of inhibitors known as small molecular inhibitors (SMIs) (Yarbrough et al., Bonvalot et al.).
Besides ALD, ASD can take place with other deposition techniques including chemical vapor deposition (CVD). We are looking to add ASD reviews relevant to future nanoelectronics and other applications involving nanoscale patterns.
|Mackus et al.||The use of atomic layer deposition in advanced nanopatterning||221||Nanoscale||2014|
|Cao et al.||Review Article: Catalysts design and synthesis via selective atomic layer deposition||55||J. Vac. Sci. Technol. A||2018|
|Mackus et al.||From the Bottom-Up: Toward Atomic Area-Selective Atomic Layer Deposition with High Selectivity||125||Chem. Mater.||2019|
|Cao et al.||Inherently Selective Atomic Layer Deposition and Applications||31||Chem. Mater.||2020|
|Parsons and Clark||Area-Selective Deposition: Fundamentals, Applications, and Future Outlook||67||Chem. Mater.||2020|
|Yarbrough et al.||Next generation nanopatterning using small molecule inhibitors for area-selective atomic layer deposition||5||J. Vac. Sci. Technol. A||2021|
|Bonvalot et al.||Atomic and Molecular Layer Deposition Area Selective Deposition using alternate deposition and etch super-cycle strategies||0||Dalton Trans.||2022|
A peek at the future
We hope that the atomic scale processing community finds ReviewBase an even more useful resource after our updates. We continue to welcome your suggestions and comments on how to improve it or what additional features you might find useful. If you notice a review that is missing, please notify us! We will keep updating the ReviewBase files on a regular basis, so be sure to check the site regularly if you are interested in the latest updates.
In the future, we are looking into adding additional functionalities. One such feature might be an indicator if a review is open access or not as well as including links to openly available versions in, for example, institutional repositories. Further down the line, we are looking at options to make the ReviewBase more easily updateable as well as automating the retrieval of citation counts to keep them up to date.
The full ALD and ALE reviews tables can be found here in .xlsx, .ods, and .pdf formats.
The ReviewBase has been put together by Miika Mattinen, Joost Maas, Harm Knoops, Bart Macco and Erwin Kessels. They also take care of the content management and have contributed to the ReviewBase blog posts.