| AVS 56th International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | M. Shiratani, Kyushu University, Japan |
| Authors: | M. Shiratani, Kyushu University, Japan S. Iwashita, Kyushu University, Japan H. Miyata, Kyushu University, Japan K. Koga, Kyushu University, Japan |
| Correspondent: | Click to Email |
Formation of dust particles due to plasma-surface interaction has attracted a great deal of attention in many fields because dust particles can cause quality deterioration in semiconductor manufacturing [1, 2] and can contain a large amount of tritium in fusion devices [3], and so on. Therefore, it is important to reveal their formation mechanisms, their transport as well as their accumulation area. Up to now, we have collected carbon dust particles formed due to interaction between graphite target and helicon plasmas using in-situ and ex-situ collection methods [4], and have analyzed them. Here we report experimental results regarding carbon particle formation due to interaction between graphite and helicon plasmas and discuss their formation mechanisms.
Experiments were carried out with a helicon plasma reactor. Hydrogen or deuterium plasmas were generated by applying pulsed rf voltage of 13.56 MHz to a helicon antenna. The ion density and electron temperature obtained in the helicon discharge reactor are 4x1010-3x1012 cm-3 and 4.5-11.8 eV, respectively. Dust particles collected in the helicon plasma reactor can be classified into small spherical particles, agglomerates whose primary particles are around 10 nm in size and large irregular particles. There are many small dust particles of 1 nm-1 μm in size. The typical density ratio among them is 2x103 : 1: 3. The smaller their size is, the higher their number density is. The size regions of these dust particles are 1-500 nm for small spherical particles, 50-700 nm for agglomerates and 50 nm-6 μm for large irregular particles, respectively. The three kinds of dust particles suggest three formation mechanisms: CVD growth, agglomeration, and peeling from walls. The dust particles of 10 nm in size have the highest probability to be charged positively, whereas those above 30 nm in size are charged negatively [5]. Agglomeration between a negative large agglomerate and a positive small dust particle takes place during the discharging period.
[1] M. Shiratani, M. Kai, K. Koga, and Y. Watanabe, Thin Slid Films, 427, 1 (2003).
[2] N. Hershkowitz, IEEE TRANSACTIONS ON PLASMA SCIENCE, 26, 1610 (1998).
[3] J. Winter, Plasma Physics and Controlled Fusion, 40, 1201 (1998).
[4] K. Koga, S. Iwashita, S. Kiridoshi, M. Shiratani, N. Ashikawa, K. Nishimura, A. Sagara, A. Komori, LHD Experimental Group, Plasma and Fusion Research, in press.
[5] Y. Watanabe, M. Shiratani, H. Kawasaki, S. Singh, T. Fukuzawa, Y. Ueda, and H. Ohkura, Journal of Vacuum Science & Technology, A14, 540 (1996).