| AVS 65th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS+EM+TF-ThA |
| Session: | Atomic Layer Processing: Integration of ALD and ALE |
| Presenter: | Abdulrahman Basher, Osaka University, Japan |
| Authors: | A.H. Basher, Osaka University, Japan M. Isobe, Osaka University, Japan T. Ito, Osaka University, Japan K. Karahashi, Osaka University, Japan M. Kiuchi, National Institute of Advanced Industrial Science and Technology (AIST), Japan T. Takeuchi, Nara Women's University, Japan S. Hamaguchi, Osaka University, Japan |
| Correspondent: | Click to Email |
Atomic layer etching (ALE) is one of the most promising technologies and a prospective solution to various technical problems in nanometer-scale device fabrication processes. ALE consists of a series of processing cycles and, in each cycle, a transition step to form a reactive thin layer on the material surface is followed by a removal step to take off only this modified layer. For a metallic film, the formation of volatile organic metal complexes may be used to establish low-damage ALE processes. In this study, to explore the possibility of establishing new etching processes for the manufacturing of magnetoresistive random access memories (MRAMs), we examine possible etching reactions of magnetic materials with organic molecules. In this study, we select Ni as a sample of ferromagnetic materials. An earlier studies [1,2] indicated that hexafluoroacetylacetone (hfac) may be used for etching of Ni due to the possible formation of nickel(II) hexafluoroacetylacetonate Ni(hfac)2 . According to [2], if a Ni surface is oxidized and then exposed to gas-phase hfac, Ni(hfac)2 are formed when the substrate temperature is increased. It is pointed out that, without the oxidation process, Ni(hfac)2 is not formed under similar conditions. Therefore, the expected single cycle of Ni ALE by gas-phase hfac is as follows; a Ni surface is first exposed to oxygen and then to hfac. This step is then followed by the increase of substrate temperature. In this study, however, the goal of this study is to understand the interaction mechanisms between hfac and a Ni or NiO surface and we use the first principles calculation to examine the interaction of a hfac molecule with a Ni or NiO surface atoms. The simulation results based on Gaussian 09 that we have obtained so far suggest that the transfer of a proton from an enol hfac molecule to the Ni or NiO surface generates its deprotonated anion, whose oxygen atoms strongly interact with a positively charged Ni atom on the surface and thus form a precursor of a highly volatile metal complex. Difference in charge distribution between Ni and NiO surfaces affects the likelihood of the formation of such precursors. Surface roughness may also affect such surface reactions.
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[1] Chen J. K., Altieri N. D., Kim T., Chen E., Lill T., Shen M., and Chang J. P., " Direction etch of magnetic and noble metals. II. Organic chemical vapor etch," J. Vacuum Sci. & Tech. A35, 05C305 (2017).
[2] Nigg H. L. and Masel R. I., " Surface reaction pathways of 1,1,1,5,5,5-hexafluoro-2,4-pentandione on clean and pre-oxidized Ni(110) surface," J. Vacuum Sci. & Tech. A17, 3477 (1999)