Augmented reality glassed based on waveguides with diffraction gratings are the technology of choice for many device makers. They have evolved to provide excellent picture quality and large field of view to the users. However, the field of view is a key criterion for such waveguides and to further increase it the refractive index of the used materials has to be increased. With current manufacturing methods mostly nanoimprinted permanent polymers with inorganic high refractive nanoparticles are used. Commercial materials can already achieve refractive index of n=1.9 but it seems difficult to achieve refractive indices of n=2.0 and above. On the other side the glass substrates or coating are already available with a refractive index n=2.0 and higher and thus could be utilized directly for structuring the needed diffraction gratings. In this case a pattern transfer by etching is required which should enable binary grating designs as well as slanted grating. In this work the nanoimprint lithography patterning is investigated in combination with subsequent etching processes to achieve binary or slanted nanograting in high refractive TiO2 and glasses.
Performance demands for many devices has driven feature dimensions to reduce to sub nm scale. Whilst new, and complex combinations of materials have increased the importance of interface effects at the atomic scale. Many of the macro-market dynamics such as Internet of Everything, increased volume in data traffic and energy efficiency require III-V based devices eg GaN, SiC. The combination of new materials and dimensions means that new etch solutions are required to achieve the accuracy and low damage needed for optimized device results. Low damage etching of AlGaN, GaN and SiN layers were studied using the PlasmaPro100 Cobra300 system from Oxford Instruments Plasma Technology, configured with ICP-RIE, RIE and ALE plasma etching modes. These techniques were used to etch shallow depths of between 5 and 100 nm in both SiN, AlGaN and GaN substrates and the resultant etched surface layer quality was measured using Atomic Force Microscopsy (AFM). ALE of SiN and GaN showed etch rates of 2.5 nm/min and 2 nm/min respectively. Using a conventional ICP-RIE process a GaN etch rate of 50 nm/min with a selectivity to AlGaN of 25:1 was achieved.
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