Gas Cluster Ion Beam Etching under Acetic Acid Vapor for Etch-Resistant Material

Abstract

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.

The new mechanism of sputtering with cluster ion beams

“…According to the authors [3,4] just lateral sputtering is the dominating process in surface smoothing. Up to now, extensive information on this smoothing effect for various materials under irradiation by cluster ions of inert and chemically active gases has been accumulated [5,6]. At the same time, it should be noted that insufficient attention was paid to investigations of angular distributions of sputtered particles.…”

In situ X-ray photoelectron spectroscopy study of gas cluster ion beam etching of FeCo film

“…In our previous paper, we reported that the etching depth of FeCo was 2.2 times deeper under Ar-GCIB irradiation with acetic acid vapor than under that without acetic acid vapor. 19) Furthermore, after O 2 -GCIB irradiation with acetic acid vapor, the etching depth was 10.7 times deeper than that without acetic acid vapor. This result showed that FeCo films can be etched effectively by O 2 -GCIB irradiation with acetic acid vapor.…”

“…We reported in our previous paper that various metals, including FeCo, can be etched by gas cluster ion beam (GCIB) irradiation with acetic acid vapor. 19,20) Moreover, the magnetic properties of FeCo films are not degraded after Ar-GCIB irradiation. 21) The GCIB consists of several thousands of gas atoms or molecules.…”

Etch residue removal of CoFeB using CO/NH3 reactive ion beam for spin transfer torque-magnetic random access memory device

“…[11][12][13][14] Recently, several research groups have investigated additional techniques to reduce the nonvolatile etch residue and to increase the etch selectivity during etching of MTJ materials using noncorrosive gases by employing substrate heating and bias power pulsing in conventional inductively coupled plasma (ICP). [15][16][17][18] The etch residue on the sidewall was decreased while the etch rates of the MTJ materials were increased with increasing the substrate temperature up to 120 C. 19 In the etching of MTJ materials using bias power pulsing, the etch selectivity over the hard mask increased and the nonvolatile etch residues on the etched CoFeB surface were decreased as compared to etching using continuous wave plasmas. Even though these techniques have improved the etch characteristics of the MTJ materials, some of the etch residues still remain on the surface and the sidewall of the etched features.…”