Preparation of micropatterns with profile heights up to 30 microns from silica sols

Martin Mennig; A. Gier; Herbert Krug; Helmut K. Schmidt

doi:10.1117/12.284142

2 October 1997 Preparation of micropatterns with profile heights up to 30 microns from silica sols

Martin Mennig, A. Gier, Herbert Krug, Helmut K. Schmidt

Proceedings Volume 3136, Sol-Gel Optics IV; (1997) https://doi.org/10.1117/12.284142
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

A new synthesis and processing route for SiO₂ glass like micropatterns with heights up to 30 micrometer by gel embossing and thermal densification has been developed. For this reason an organically modified nanoparticulate sol prepared by acid catalysis of methyl- and phenyl- triethoxysilane and tetraethyl orthosilicate in combination with colloidal silica sol was used. Sol coatings with thicknesses up to 15 micrometer are obtained by dipping of float glass substrates. After a predrying step of about 60 s micropatterns are obtained using a pressure of only 2.5 mN/mm². Due to this low pressure, flexible and low cost silicon rubber stampers can be used. The gelation time of the sol can be extended from 5 d to 16 days and the working time for embossing can be extended from 60 s up to 100 s by a partial replacement of methyl silane by phenyl silane from 0 to 20 mole %. After embossing and drying at 50 degrees Celsius the patterned layer was densified at temperatures up to 500 degrees Celsius to 95% density as indicated by refractive index measurements. It is assumed that the densification process is strongly promoted by the used colloidal silica nano particles. The linear shrinkage of the micropatterns is limited to about 25% due to the high solid content of the sol and the high green density of the layers. Since the structures are densified at temperatures far below T_g sharp edged patterns can be obtained as shown by high resolution secondary electron microscopy. The capability of this technique is demonstrated by the fabrication of light trapping structures with pyramides of 7 micrometer in height and 10 micrometer in width on an area of 20 multiplied by 20 mm² and micro lens arrays of lenses with 30 micrometer in height and 600 micrometer in diameter on an area of 20 multiplied by 30 mm².

Citation Download Citation

Martin Mennig, A. Gier, Herbert Krug, and Helmut K. Schmidt "Preparation of micropatterns with profile heights up to 30 microns from silica sols", Proc. SPIE 3136, Sol-Gel Optics IV, (2 October 1997); https://doi.org/10.1117/12.284142

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