Self-aligned integrated nanostructures fabricated by UV-nanoimprint lithography
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Fabricating large-area multilevel integrated nanostructures and 3D nanoshapes are of tremendous importance for applications in the fields of nanoelectronics, nanophotonics, semiconductor memory, biosensors, and high density displays. As the dimensions of such nanostructures are driven-down by design, in order to drive-up the performance of the overall device, we run into challenges such as nanoscale overlay and level-to-level alignment during the lithography process. State-of-the-art nanolithography tools can achieve a certain level of nanoscale overlay with their optical and thermo-mechanical mechanisms. But these tools are expensive and they have a limit to the best possible nanoscale overlay achievable. In particular, if integrated nanostructures are needed on a large area such as an entire wafer (without having to step-and-repeat), or on non-conventional substrates such as flexible substrates, nanoscale alignment cannot be achieved using these tools. Jet and Flash Imprint Lithography (J-FIL) is a high-throughput, inexpensive, mechanical nanopatterning technique that uses a mold or imprint template to create nanostructures by causing a polymer resist to flow into its etched shapes by capillary action. The imprint template is typically fabricated using available lithography techniques and hence there is a limitation on the achievable nanoscale overlay. In this research, methods are developed to fabricate large-area, multilevel nanostructures and 3D nanoshapes on nanoimprint templates without the need for level-to-level alignment and nanoscale overlay. These nanoimprint templates are essential to explore large-area multilevel integrated nanostructures and 3D nanoshapes by J-FIL replication. The general methodology for fabrication of multilevel nanoimprint templates relies on a combination of nanoscale lithography, atomic layer deposition’s (ALD) atomic precision, and choice of highly etch selective materials, to ensure precise self-alignment of multiple levels in the nanoscale. Such templates fabricated in this work are named self-aligned multilevel templates (SAMTs). Five specific self-aligned multilevel fabrication techniques have been demonstrated that result in symmetric multilevel structures, bilaterally symmetric multilevel structures, nanotube structures, asymmetric multilevel structures, and asymmetric sloped structures on SAMTs. When used in conjunction with a nanoimprint lithography process, the SAMTs can enable high-throughput patterning of various nanoelectronic and nanophotonic devices using a single patterning step with perfect alignment and overlay. SAMTs further enable large area patterning, such as wafer-scale patterning and roll-to-roll patterning on flexible substrates, without compromising perfect overlay.