The proposed research seeks to understand the fundamental mechanisms involved in catalyst motion in Metal-assisted Chemical Etching of Silicon(MaCE). MaCE is a new, novel method to etch complex 2D and 3D shapes such as subsurface cycloids and 3D spiraling structures while maintaining tight feature resolutions on the order of 1 nm even with aspect ratios > 50:1. These capabilities are enabled by the fact that the metal catalyst that defines the etching profile travels into the silicon as the silicon is etched by a galvanic reaction across the catalyst, resulting in etching profile is tightly maintained over the entire etch length along with the ability to etch 3D structures by controlling catalyst motion.
While the stoichiometric chemistry of MaCE has been reasonably established, the fundamental kinetics and forces involved in particle motion have remain unknown and unstudied. The proposed research will examine how etchant composition, catalyst shape, catalyst composition and external fields affect the kinetics and forces of MaCE to determine etching rate, resolution, morphology and direction. Also, analytical and computational models of the electric fields, forces, catalyst motion and etching morphology will be developed. The kinetic and morphological effects of new catalyst materials will be examined and incorporated into the models. This research will provide a greater understanding on how the kinetics of MaCE along with the catalyst particle shape interact to create 3D nanostructures with the ultimate goal of providing precise control over etching direction.
The considerable interest in nanomaterials and nanotechnology over the last decade is attributed to both the desire by industry for lower cost, more sophisticated devices and the opportunity that nano-technology presents for scientists to explore the fundamental properties of nature at near atomic levels. In pursuit of these goals, researchers around the world have worked to both prefect existing technologies and also develop new nano-fabrication methods; however, no technique exists that is capable of producing complex, 2D and 3D nano-sized features with high aspect ratios, smooth walls, and at low cost. Current nanofabrication methods face two important limitations. First, 3D geometry is difficult if not impossible to fabricate requiring multiple lithography steps that are both expensive and do not scale well to industrial level fabrication requirements. Second, as feature sizes shrink into the nano-domain, it becomes increasingly difficult to accurately maintain those features over large depths and heights. The ability to produce these structures affordably and with high precision is critically important to a number of existing and emerging technologies such as metamaterials for high-band with communication devices, nano-fluidics for advanced bio-on-a-chip devices to detect cancer and other disease at low cost, nano-imprint lithography for rapid, low cost fabrication, and more.
The proposed research seeks to develop the fundamental understand of MaCE as a new method to create 2D and 3D nanostructures with high feature fidelity even at high aspect ratios and a low cost. Scientists around the world are looking to use nanomaterials to reduce the environmental impact of human activities and the proposed research will help enable the technology needed to achieve this goal.
