Gas cluster ion beam (GCIB) etching of etch-resistant materials under acetic acid vapor was studied for development of new manufacturing process of future nonvolatile memory. Etching depths of various etch-resistant materials (Pt, Ru, Ta, CoFe) with acetic acid vapor during O2-GCIB irradiations were 1.8–10.7 times higher than those without acetic acid. Also, etching depths of Ru, Ta, CoFe by Ar-GCIB with acetic acid vapor were 2.2–16.1 times higher than those without acetic acid. Even after etching of Pt, smoothing of Pt was realized using O2-GCIB under acetic acid. From XPS and angular distribution of sputtered Pt, it was shown that PtO
x
layer was formed on Pt after O2-GCIB irradiation. PtO
x
reacted with acetic acid by GCIB bombardments; as a result, increase of etching depth was observed.
FeCo films of the type used in spin transfer torque magnetoresistive random access memory were etched by gas cluster ion beam (GCIB) irradiation with acetic acid vapor and characterized by in situ X-ray photoelectron spectroscopy. After 20 keV O2-GCIB irradiation with acetic acid vapor, etching depth enhancement (10.7×) was observed compared with the results without acetic acid vapor. The etching model of FeCo can be described as follows: (1) FeCo oxide formation with O2-GCIB irradiation, (2) acetic acid adsorption on FeCo oxide, (3) reactions between FeCo oxide and acetic acid, and (4) the desorption of volatile compounds by local and transient heating owing to O2-GCIB bombardment. Cross-sectional transmission electron microscopy, transmission electron diffraction analysis, and electron energy loss spectroscopy results showed no significant etching damage or oxidation of FeCo films after etching by O2-GCIB irradiation with acetic acid vapor. Therefore, the low-damage etching of FeCo can be performed by O2-GCIB irradiation with acetic acid vapor.
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