Controlled synthesis of 3d nanostructures using Proximity-field nanoPatterning lithography and graded temperature ALD

The combination of Proximity-field nanoPatterning (PnP) and graded temperature ALD has enabled the synthesis of robust three dimensional nanostructures. The PnP process uses a simple elastomeric optical phase mask to generate a complex three dimensional interference pattern in photopolymer ¹. Once the photopolymer structure has been obtained, it is subsequently used as a template for graded temperature ALD. The graded temperature ALD chemistry is used to coat and lock-in the designed nanostructure without melting the template. This process generates a thermally robust nanostructure for further, higher temperature, ALD surface treatments. The ALD chemistry is performed at various (increasing) temperatures to secure the nanostructure and to reduce the macroscopic stress of the structure as higher temperature depositions are performed. Three methods for nanostructure characterization have been useful in interrogating these structures: quartz crystal microbalance (QCM), optical interference, and focused ion beam scanning electron microscopy (FIB-SEM). This paper will cover the fabrication process for generating PnP nanostructures. Details of the graded temperature ALD chemical process for AI₂O₃ will be covered. Also, structural characterizations using SEM and optical interference will be used to quantify the degree of deposition and the thermal stability of these interesting structures.