Takashi Matsuura, Yasuhiko Honda and Junichi Murota

Laboratory for Electronic Intelligent Systems
Research Institute of Electrical Communication, Tohoku University
2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
matsu@riec.tohoku.ac.jp

Self-limited atomic-layer etching of Si and Ge were realized by ultraclean chlorine adsorption with alternated irradiation of low energy Ar+ ions [1-3]. However, silicon nitride, where the bond strength between Si and N is stronger, was difficult to be etched by the same method. We propose the Role-Share Etching method for atomic-layer etching of compound materials, where one kind of the surface atoms is removed selectively by the first condition, and the remaining kind of the surface atoms is removed selectively by the second condition. In the case of silicon nitride, excited hydrogen in an Ar plasma was firstly supplied with the shutter closed so that the direct incidence of ions from the ECR plasma generating chamber was suppressed. Depending on the plasma condition, removal of a saturated amount of 1-3 atomic-layers of nitrogen was observed by XPS analyses. Secondly, after removing 1 atomic-layer of nitrogen under a typical condition, the shutter was opened and an (Ar+ H+) ion mixture was let irradiated the wafer. Removal of the remaining outermost silicon atoms was observed. By cyclic procedure of these processes, we demonstrated that 1, 2 and 3 atomic-layers of silicon nitride were etched in sequence by the role share method.

This study was partially supported by the Research for the Future Program (No. JSPS-RFTF97P00202), the Nippon Sheet Glass Foundation, and the Corning Research Grant.

[1] T.Matsuura, J.Murota, Y.Sawada and T.Ohmi, Appl.Phys.Lett. 63 2803, (1993).
[2] K.Suzue, T.Matsuura, J.Murota, Y.Sawada and T.Ohmi, Appl.Surf.Sci. 82-83, 422 (1994).
[3] T.Sugiyama, T.Matsuura and J.Murota, Appl.Surf.Sci. 112 187 (1997).