| AVS 58th Annual International Symposium and Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS-ThM |
| Session: | Neutral Beam and Low Damage Processing |
| Presenter: | Tomohiro Kubota, Tohoku University and BEANS Project, Japan |
| Authors: | T. Kubota, Tohoku University and BEANS Project, Japan A. Wada, Tohoku University, Japan S. Ohtsuka, Mizuho Information & Research Institute, Inc., Japan K. Ono, Mizuho Information & Research Institute, Inc., Japan H. Ohtake, Tohoku University, Japan S. Ueki, BEANS Project, Japan Y. Nishimori, BEANS Project, Japan G. Hashiguchi, Shizuoka University and BEANS Project, Japan S. Samukawa, Tohoku University, Japan |
| Correspondent: | Click to Email |
Plasma etching is widely used for fabricating semiconductor electronic devices and microelectromechanical systems (MEMS), but plasma etching is known to cause damages due to the charge-up and UV irradiation. To overcome plasma-induced damages, we have developed a neutral beam source with very high neutralization efficiency. The neutral beam source achieved high neutralization efficiency by using negative ions from pulse-time modulation plasma, and UV irradiation was drastically reduced. To apply this neutral beam source to mass production, we have developed a large-diameter neutral beam (NB) source by using an 8-inch-diameter inductively coupled plasma etcher (Panasonic Factory Solutions Co., Ltd. E620) as an ion source. In the previous study, the beam flux of argon NB was more than 1 mA/cm2 in equivalent current density and the neutralization efficiency was more than 99%. Vertical Si etching using F2 gas chemistry was also achieved. Also, beam was successfully accelerated by bias applied to the aperture plate [1].
In this study we investigated high-aspect-ratio silicon etching. At first, angular distribution of NB was measured. As a result, Gauss-function-like distribution was observed and the width of the distribution was determined by aspect ratio of the aperture. On the other hands, angular distribution of incoming ions from plasma to the aperture was almost uniform. Also, plasma parameters such as source power and gas flow rate did not affect the distribution. From these results, it is supposed that aperture plays a dominating role in generation of collimated NB. Then, silicon etching by chlorine (Cl2) NB was performed using apertures with aspect ratio of 10 and 20. By using the aperture with aspect ratio of 10, almost vertical sidewall with a slight positive taper of 6 degree was achieved. The aperture with aspect ratio of 20 led to almost vertical etching. Silicon trench etching with aspect ratio of about 22 was achieved using the aperture and chlorine NB.
A part of this work was supported by the New Energy and Industrial Technology Development Organization (NEDO). This work is partly supported by Formation of Innovation Center for Fusion of Advanced Technologies, Special Coordination Funds for Promoting Science and Technology, Ministry of Education, Culture, Sports, Science and Technology.
[1] T. Kubota et al., J. Vac. Sci. Technol. A 28(5), 1169 (2010).