Photonic crystals are being extensively investigated due to their capability of controlling the properties of light by confining photons in one, two and three dimensions. The sensitivity of optical properties of photonic crystals to the changes in refractive index at one or more lattice sites makes them potential building blocks of high-sensitivity biosensors. Fabrication of photonic crystals, including crucial steps such as lithography and plasma etching, is very challenging due to the nanoscale features. ICP-RIE is one of the preferred etching techniques because of its good control over the aspect ratio, high etch rates, low surface damage and many other advantages. This work deals with the optimization of ICP etching of Si and GaN, which can be used to fabricate photonic crystals operating at near infrared and visible wavelengths, respectively. Etch recipes have been optimized to obtain fast etch rates, smooth surfaces, vertical profiles and high selectivities over various mask materials. A two-step pattern transfer technique has been developed to transfer photolithographic patterns to Si and GaN substrates by using an intermediate hard mask such as Cr, Ni and SiO2. The effects of different hard masks on the etch profiles of Si were studied. The developed etching and pattern transfer techniques were used to fabricate 1-micron hole arrays in SiO2 and Si for microfludic fluorescence measurement.
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