| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS1-TuM |
| Session: | Plasma Diagnostics, Sensors and Control 1 |
| Presenter: | T. Suzuki, Nagoya University, Japan |
| Authors: | T. Suzuki, Nagoya University, Japan A. Malinowski, Nagoya University, Japan K. Takeda, Nagoya University, Japan H. Kondo, Nagoya University, Japan K. Ishikawa, Nagoya University, Japan Y. Setsuhara, Osaka University, Japan M. Shiratani, Kyushu University, Japan M. Sekine, Nagoya University, Japan M. Hori, Nagoya University, Japan |
| Correspondent: | Click to Email |
A precise shape control at less than 1 nm scale is demanded in large-scaled-integrated-circuits (LSI) fabrication of the 10-nm half pitch and beyond. In realization of super-fine plasma etching process, surface reactions of ions and radicals play important role because they determine etched feature [1]. Thus control of actual plasma parameters such as substrate temperature, radical density, and electron density is required. It has been proved that the radical density is changed as a result of emission into bulk plasma both of etching products and adsorbed species on chamber wall. However, investigation of influence of inner wall condition on bulk radical density has not been studied yet. Thus, in this study we focused on gaseous radical density in H2/N2 plasmas, and investigated temporal changes subsequently after different kind of plasmas where inner wall condition could be changed.
Measurements of gaseous radical densities have been carried out by the Vacuum Ultra Violet Absorption Spectroscopy (VUVAS) equipped with a micro-discharge hollow cathode lamp (MHCL) [2]. In this case we measured transition lines for Lyman α at 121.6 nm for H atoms and 4P5/2-4S03/2, 4P3/2-4S03/2 and 4P1/2-4S03/2 at 120.0 nm for N atoms. H2/N2 plasma was generated in a 100-MHz capacitively coupled plasma (CCP) reactor with H2/N2 gas mixture ratio of 75/25. Applied power was 400W (100 MHz) for upper electrode, and 200W (2 MHz) for bottom electrode respectively. The gaseous radical densities for the H2/N2 plasmas were monitored subsequently after different plasmas, (a) seasoning condition of H2/N2 plasma, (b) O2 plasma, and (c) air exposure.
First, temporal changes for N radical density in the H2/N2 plasma subsequently, after the various plasma exposures were compared. In case of (a) seasoning, the N density was stable. On the other hand, the N radical densities were much varied after (b) O2 plasma, and (c) air exposure. Notably, the density just after H2/N2 plasma ignition reached value which is more than twice higher when compared to stabilized value for (a) seasoning. Interpretation can be given as etched products or process gases were adsorbed on inner wall surface at the previous process, and then those species were desorbed from the wall into bulk plasmas in the subsequent processes. In accordance with organic low-k etching using H2/N2 plasmas, when a ratio of H radical and N radical (H/(H+N)) was changed more than 15% against an optimal original value, a shape of etched feature is resulted in modifications with scales of 10 nm [1].
[1] M. C. Sung et al, J. Appl. Phys. 107, 113310 (2010).
[2] S. Takashima et al, J. Vac. Sci. Technol. A 19, 599 (2001).