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Proceedings Paper

Silica nano-ablation using laser plasma soft x-rays
Author(s): Tetsuya Makimura; Shuichi Torii; Hiroyuki Niino; Kouichi Murakami
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Paper Abstract

We have investigated nano-ablation of silica glass and ablation process using focused laser plasma soft Xrays. Laser plasma soft X-rays were generated by irradiation of a Ta target with Nd:YAG laser light. The soft X-rays were focused on silica glass plates using an ellipsoidal mirror at fluences up to 1 J/cm2. In order to fabricate nano-trenches, a silica glass plate was irradiated with laser plasma soft X-rays through the windows of a line and space mask. We demonstrated fabrication of nano-trenches with a width of 50 nm. It should be noted that the feature size is more precise than that estimated from the thermal diffusion length for the 10-ns X-rays (i.e. 80 nm). Furthermore, the ablated area has a depth of 470 nm and a roughness of 1 nm after ten shots of irradiation. Thus, the X-ray irradiation technique have a significant feature of direct nanomachining. The ablation occurs at fluences F beyond a ablation threshould Fth and ablation depth per pulse D obeys the law D = 1/α ln(F/Fth), where α is an effective absorption coefficient. These results suggest that absorbed energy is accumulated in the absorbed region without energy diffusion until ablation occurs. In addition, time-resolved mass spectroscopy revealed that silica glass is broken into atomic ions and atomic neutrals during ablation. Because Si+ and O+ ions have kinetic energies of 10-30 eV, non-thermal process such as Coulomb explosion may be driving force behind the ablation. Such non-thermal process enables us to fabricate nano-structures on silica glass.

Paper Details

Date Published: 18 May 2009
PDF: 15 pages
Proc. SPIE 7361, Damage to VUV, EUV, and X-Ray Optics II, 73610B (18 May 2009); doi: 10.1117/12.822289
Show Author Affiliations
Tetsuya Makimura, Univ. of Tsukuba (Japan)
Shuichi Torii, Univ. of Tsukuba (Japan)
Hiroyuki Niino, National Institute of Advanced Industrial Science and Technology (Japan)
Kouichi Murakami, Univ. of Tsukuba (Japan)

Published in SPIE Proceedings Vol. 7361:
Damage to VUV, EUV, and X-Ray Optics II
Libor Juha; Saša Bajt; Ryszard Sobierajski, Editor(s)

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