As flat optics become increasingly mainstream, there is high interest in improving patterning resolution, making new materials available, and lowering manufacturing costs for these components. Because of their maturity across the entire supply chain, 300 mm m offer one of the best opportunities to simultaneously achieve all of these goals. By leveraging existing tooling and knowledge from 300 mm CMOS patterning, the high-pattern resolution of immersion DUV mastering can be combined with nanoimprint lithography and etching to achieve pattern transfer to optical materials. Wafer scale CMOS metrology can also be leveraged to optimize process uniformity and repeatability. This talk will present imec’s recent developments in utilizing CMOS fab tools to pattern high-index dielectrics on 300 mm substrates.
Precise control on nanoscale pattern manufacturing is key to enable new-generation devices in numerous fields, such as bioelectronics or optics, among others. However, to meet the requirements of the industry, it is especially relevant to increase throughput and reduce processing costs. In this regard, Nano-Imprint Lithography (NIL) is an ideal candidate for manufacturing large volumes of devices with low cost-of-ownership, by replicating small features from high-quality masters. However, NIL faces some challenges, such as limited pattern transfer fidelity in large-area processing. Here, we show our NIL processing capabilities, in terms of both yield and transfer fidelity from original DUV manufactured masters, including features from few hundred to tens of nanometers. We present an exhaustive study on the pattern evolution through the complete process, including design, master fabrication, NIL and subsequent pattern transfer via etching. This study demonstrates the inclusion of NIL into our foundry-mature, CMOS-compatible process modules as well as the pattern evolution characterization that enable technology-aware modelling and designing.
Nano-Imprint lithography (NIL) is a powerful technology for low-cost, large area patterning of complex nano-features, including surface relief gratings and meta-structures for AR optical components. A full layer patterning module that includes a NIL process suited for mass manufacturing requires multiple capabilities: nano-imprint tools, materials, template fabrication, potentially pre- or post-imprint material deposition or removal and extensive metrology. Through its longstanding history in the semiconductor industry, imec has developed advanced mastering, deposition, and etch capabilities that can be paired with NIL process development for fully integrated patterning. In this talk, recent developments in integrated surface relief patterning on transparent 300 mm substrates will be presented. Because the fabrication itself is substrate agnostic, this capability can be transferred to other substrate material available at 300 mm to match the design requirements of a variety of diffractive optical components, such as refractive index tuning.
Photonic Integrated Circuits (PICs) in the visible wavelength range have been extensively used for life science applications. Silicon Nitride has been the most widely used material, as it allows to fabricate low loss waveguides with the refractive index ranging from 1.9 to 2.1. For downscaling of PICs, many investigations into Titanium Oxide (TiO2) have been studied. The refractive index of TiO2 ranges from 2.3 to 2.6. Despite a high refractive index, TiO2 tends to crystallize at temperatures above 300ºC, limiting its potential for CMOS compatible fabrication. In addition, the presence of oxygen vacancies in TiO2 results into photon absorption in the visible range, leading to high propagation losses. We investigate Niobium Oxide (Nb2O5) as an alternative waveguide material, focusing on material and optical properties for light propagation in the visible wavelength range. Physical vapor deposition of the Nb target in Oxygen atmosphere results in stoichiometric Nb2O5. On a 200mm wafer, a 90nm Nb2O5 is deposited on 2.3µm bottom clad (SiO2). The extracted refractive index is above 2.3, while the extinction coefficient is 0 for visible wavelengths. From X-ray diffraction, the as-deposited layers were amorphous, while the surface roughness was below 0.3 nm. Waveguides were patterned using 193 nm lithography and etched using chlorine based chemistry. In the visible range, optical losses for un-cladded waveguides were below 5 dB/cm, comparable to our in-house SiN platform. There were no significant changes in optical losses after 400ºC anneal, signifying its potential for improved propagation after top-cladding deposition.
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