We present the conceptualization and preliminary deposition results of a unique silicon-based gas-phase direct-write system for additive manufacturing of electronic devices or interconnects. This system utilizes localized vapor delivery to deposit thin films using traditional physical vapor deposition or chemical vapor deposition precursors rather than novel inks or other liquid precursors commonly used in direct-write applications. It is therefore free from limitations caused by the use of liquid inks such as clogging, drying effects and contamination from dissolving agents. We developed a silicon-based microevaporator which contains of a mm-scale reservoir which can either be filled with solid evaporant and heated for physical vapor deposition (PVD) or connected to gas-feedthroughs to be used for chemical vapor deposition (CVD). The reservoir is connected to a nanoscale nozzle which allows for the delivery of precursor locally to the substrate surface. The nozzle is centered on a 100 um tall, 50 um across protruding tip which allows for close positioning of the nozzle to the substrate surface without crashing and decreases the thermal crosstalk between microevaporator and substrate. Source-to-substrate distance is important since the evaporant emerges in a cone-like shape from the nozzle as described by Knudsen's cosine law, and we confirmed by Monte Carlo simulations that the exiting flux spread depends strongly on distance from nozzle. As a rule of thumb, source-to-substrate distances should be kept to around the same as the nozzle diameter in order to obtain optimal resolution, so we find that the distance control challenge is more pressing for smaller nozzles. We present results from successfully fabricated nozzles with diameters down to 300 nm and demonstrate deposition of ~1 um features by PVD. We show that we are on a direct path towards shrinking this dimension by at least an order of magnitude. Since the nozzle is fabricated on silicon, the system is readily adaptable to improvements such as fabricating sub-10 nm nozzles and adding nozzle-tip sensors. This system could be a powerful platform not only for engineering the next generation of devices and high-density interconnects, but also for bettering our understanding of the science of thin film deposition, such as the atomistic processes during the early stages of thin film growth, as the relevant scale in manufacturing continues to shrink down to the atomic level.
