Nanofabrication of an On-Chip Direct Write Evaporator for Scanning Near-Field 3D Deposition

In order to realize the next generation of electronic devices, it is desirable to be able to create nano and mesoscale dimensioned patterns in three dimensions with scalability, robustness, and ease of fabrication. Current lithography techniques are inherently two-dimensional in approach, and subtractive in nature (i.e. involving the blocking out patterns then removal or addition of material on a wafer). As a result many successive steps of lithography and wafer processing are necessary for creating three-dimensional heterostructures on a wafer and makes the technique non-ideal for future cheap, 3D integrated structures. Furthermore, many steps of wafer processing require the use of materials that will not be part of the final product, so a process that eliminates these intermediary steps will have the added benefit of reducing waste for sustainable manufacturing. Our research has involved the design and fabrication of a miniaturized on-chip physical or chemical vapor deposition system (henceforth called a Direct Write Evaporator, DWE) with nozzle dimensions in the nanoscale to mesoscale, to precisely deliver evaporant to a substrate’s surface. When the nozzle is small and close to the surface, it creates a localized deposition spot that can be moved around to directly write patterns. The direct write system is then completed by mounting the DWE onto a near field x-y-z scanning stage with nanometer scale “write” resolution.<br/>We have designed and developed a cleanroom based process flow which utilizes a series of plasma etch steps for the fabrication of the DWE using a silicon-on-insulator substrate as a starting material. The main components in this DWE are the nozzle and the reservoir. The DWE device is ~ 1 mm in overall dimensions and contains a nozzle of a few hundred nanometer diameter at the tip of a patterned annular needle that transports an evaporant from the reservoir to the substrate. The DWE is mounted on a 3-axis piezoelectric scanning stage and incorporated into a vacuum deposition chamber. In this presentation we will describe the fabrication of the DWEs, and show the results of our initial direct deposition/writing experiments at the nanoscale.