| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThA |
| Session: | Plasma Chemistry and Plasma Surface Interactions |
| Presenter: | Kazuhiro Karahashi, Osaka University, Japan |
| Authors: | K. Karahashi, Osaka University, Japan T. Seki, Kyoto University, Japan J. Matsuo, Kyoto University, Japan K. Mizotani, Osaka University, Japan K. Kinoshita, Osaka University, Japan S. Hamaguchi, Osaka University, Japan |
| Correspondent: | Click to Email |
Dry etching of magnetic thin films is a critical issue in the fabrication of magnetic random access memories (MRAMs). Currently argon (Ar) ion milling seems the only etching technique available in the manufacturing processes. However Ar ion milling is incapable of achieving anisotropic and selective etching of magnetic films and therefore extensive research is underway to establish highly selective anisotropic reactive ion etching (RIE) processes for magnetic thin films [1]. The formation of volatile metal carbonyl compounds produced by reactions of a metal surface with incident CO molecules may be used as a chemical etching process but such reaction probabilities are known to be very small. In this study we propose gas cluster beam processes as a means to etch magnetic metal surfaces. Gas clusters can provide a large number of reactant molecules to the metal surface at low incident energies and are expected to cause multiple collision processes at impact [2]. Especially we have examined surface reactions of Ni thin films by CO neutral clusters as well as energetic CO ion clusters. First we studied Ni etching reaction by incident CO cluster ion irradiation with typical single cluster ion energy being Ecluster = 20 keV (and a single CO molecule ion incident energy being ECO= 11 eV). It was found that amorphous carbon deposition occurred on Ni surfaces and the beam did not etch the Ni films. These results suggest that each CO cluster is broken apart to CO molecules at impact by the excessive kinetic energy. Such excess kinetic energy prevents the formation of carbonyl compounds. Second, we examined interactions between low-energy incident CO neutral clusters (Ecluster = 300 eV, ECO= 60 meV) with Ni surfaces. NiCO (Mass 86), which are fragments of nickel carbonyl compound [Ni(CO)4], were detected with a quadrupole mass spectrometer equipped in the chamber of the beam system. These results suggest that carbonyl formation reaction occurred by CO neutral cluster irradiation. Currently the probability of such carbonyl-formation reaction seems low and we shall discuss how the carbonyl-formation reaction rate on a metal surface can be increased. This work was supported by the Semiconductor Technology Academic Research Center (STARC)
References
[1]K. Kinoshita et al., Jpn. J. Appl. Phys. 49(2010) 208JB02.
[2]I. Yamada, J. Matsuo, et al., Mater. Sci. Eng. A, 253(2005) 249.