It might not be fully unexpected but after launching our online ALD database a few months ago, but now we have now also put together an online database on Atomic Layer Etching (ALE). So here it is! Similar to the ALD database, you can also access it through a link at the top of the Atomic Limits blog.
It is very similar…
You can click on an element to find ALE processes reported for the materials containing that element (just scroll down the page) or you can just search the database through the search-function. Articles can easily be accessed through the web links given. You can also update it with missing or new ALE processes as the database relies on crowdsourcing. So please help us to keep it up to date! Processes will be added after a quick evaluation by the content hosts. You can also leave comments and even make an instant figure (png-format) of the periodic table you are looking at. This can be helpful, for example if you want to use the Periodic Table in a presentation. And feel free to do so, since we distribute the image under Creative Commons BY 4.0 license:
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Also note that both the ALD and ALE database have a DOI: 10.6100/alddatabase and 10.6100/aledatabase for easy referencing.
…but also slightly different
A difference with the ALD database is that the ALE database lists two types of ALE processes per element. The reason is that ALE comes basically in two flavors: there exist anisotropic ALE processes and isotropic ALE processes. In anisotropic ALE processes one typically uses energetic ion or neutral beams to etch materials anisotropically, i.e., the etch is directional in the direction perpendicular to the surface with preferably no lateral etching. Or in other words, one has only vertical etching and no horizontal etching. In isotropic ALE processes one etches features from all sides with the same etch rate, i.e., there is difference between vertical and horizontal etching. Both processes are illustrated in the figure below. The figure also shows the cross-section of 3D features etched, e.g., a finFET structure being etched anisotropically and a gate-all-around FET (GAA-FET) structure being etched isotropically.
The fact that ALE has two flavors was discussed in the review by Kanarik and co-workers (Kanarik et al., J. Vac. Sci. Technol. A 33, 020802 (2015)) also emphasized in a publication from Intel (Carver et al., ECS J. Solid State Sci. and Technol., 4 (6) N5005 (2015)) in the JSS Focus Issue on Atomic Layer Etching and Cleaning. In that same special issue, we also underlined it in our publication (Faraz et al., ECS J. Solid State Sci. and Technol., 4 (6) N5023 (2015)) by addressing the similarities between ALD and ALE. In that paper we highlighted that one usually does not want to have any directionality in ALD (instead, the excellent conformality is one of the key merits of ALD) while this is different in ALE. In ALE one either wants perfect directionality (anistropic etching) or no directionality at all (isotropic etching).
Please don’t hesitate to send us your comments on the database. We are willing to improve it if we see fit. And once again, please make sure that you add missing and newly developed processes. To keep the database up to date, we rely on you. And please enjoy!