Direct Patterning of Quartz Substrates by Laser Ablation Using VUV Anti-Stokes Raman Pulses
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DIRECT PATTERNING OF QUARTZ SUBSTRATES BY LASER ABLATION USING VUV ANTI-STOKES RAMAN PULSES K. SUGIOKA*, S. WADA*, H. TASHIRO*, K. TOYODA*, T. SAKAI**, H. TAKAI**, H. MORIWAKI***, AND A. NAKAMURA*** *RIKEN, The Institute of Physical and ChemicalResearch, Wako, Saitama 351-01, Japan **Tokyo Denki University, 2-2, Kanda-Nishi-Cho, Chiyoda-Ku, Tokyo 101, Japan ***Science University of Tokyo, 1-3, Kagurazaka, Shinjuku-Ku, Tokyo 162, Japan
ABSTRACT
High speed microfabrication of quartz substrates by laser ablation using vacuum ultraviolet (VUV) laser beams is described. The VUV light is generated by anti-Stokes stimulated Raman scattering of fourth harmonics of Q-switched Nd:YAG laser. The well-defined patterns with a cross-sectional profile of rectangular shape are formed by using a contact mask. The role of short wavelength components of the VUV laser beams in the process is discussed. INTRODUCTION Micropatterning of quartz substrates is of great interest to various fields, since the materials is of use for integrated optical devices, liquid crystal displays, optical position sensors, and so on. One of the promising technique for the fabrication is laser ablation, by which direct etching of various polymers has been reported 1 -3. However, ablation of the quartz is in general difficult because of transparence in a wavelength range longer than 190 nm and of high i
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Nd :YAG (40o))
f = 100 Mmm at 160 nm Vacuum Chamber Raman Cell
f =533 mm~ at 266 nm
f = 400 mm at 170 nm
Exhaust Mesh Mask Quartz Substrate
FIG. 1. Schematic diagram of the experimental setup for the ablation using VUV laser. Mat. Res. Soc. Symp. Proc. Vol. 285. 01993 Materials Research Society
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binding energy of Si-O bonds of about 8 eV. The high quality and high speed fabrication is required for industrial application. The use of vacuum ultraviolet (VUV) laser with high photon energy may solve such problems. In the present paper, photoablation of synthetic quartz substrates by irradiation of VUV laser beams is demonstrated. The widely spread discrete lines of VUV lights are generated by anti-Stokes stimulated Raman scattering of fourth harmonics of Q-switched Nd: YAG laser. 4 The short wavelength components below 150 nm of the VUV laser beams play the most important role to induce the photochemical reaction and to enhance the ablation rate. EXPERIMENTAL PROCEDURES
Figure 1 shows a schematic diagram of the experimental setup for the ablation. The fourth harmonics of Q-switched Nd:YAG laser beam with a 266 nm wavelength and a 8 ns pulse duration was focused into the 100-cm-long Raman cell filled with H2 gas of 4.5 kg/cm 2 . The VUV light pulses scattered from the Raman cell was directed perpendicularly to the quartz substrates, which have no absorption in a wavelength range longer that 190 nm, in a vacuum of less than 8x10- 5 Torr. For the patterning, a Ni mesh with 20x20 gtm 2 apertures was used as a contact mask. The irradiated area at the sample surface and the repetition rate of the laser pulses were about 1 mmcb in diameter and 1 Hz, r
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