Development of metal-assisted chemical etching as a 3D nanofabrication platform

dc.contributor.advisor Wong, C. P.
dc.contributor.author Hildreth, Owen James
dc.contributor.committeeMember Kohl, Paul
dc.contributor.committeeMember Nadler, Jason
dc.contributor.committeeMember Summers, Christopher
dc.contributor.committeeMember Yushin, Gleb
dc.contributor.department Materials Science and Engineering
dc.date.accessioned 2013-09-20T12:00:14Z
dc.date.available 2013-09-20T12:00:14Z
dc.date.issued 2012-05-07
dc.description.abstract The considerable interest in nanomaterials and nanotechnology over the last decade is attributed to Industry's desire for lower cost, more sophisticated devices and the opportunity that nanotechnology 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 perfect 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 of arbitrary shape, with smooth walls, and at low cost. This in part is due to two important limitations of current nanofabrication methods. First, 3D geometry is difficult if not impossible to fabricate, often 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, nano-fluidics, nano-imprint lithography, and more. Summary To overcome these limitations, this study developed a novel and efficient method to etch complex 2D and 3D geometry in silicon with controllable sub-micron to nano-sized features with aspect ratios in excess of 500:1. This study utilized Metal-assisted Chemical Etching (MaCE) of silicon in conjunction with shape-controlled catalysts to fabricate structures such as 3D cycloids, spirals, sloping channels, and out-of-plane rotational structures. This study focused on taking MaCE from a method to fabricate small pores and silicon nanowires using metal catalyst nanoparticles and discontinuous thin films, to a powerful etching technology that utilizes shaped catalysts to fabricate complex, 3D geometry using a single lithography/etch cycle. The effect of catalyst geometry, etchant composition, and external pinning structures was examined to establish how etching path can be controlled through catalyst shape. The ability to control the rotation angle for out-of-plane rotational structures was established to show a linear dependence on catalyst arm length and an inverse relationship with arm width. A plastic deformation model of these structures established a minimum pressure gradient across the catalyst of 0.4 - 0.6 MPa. To establish the cause of catalyst motion in MaCE, the pressure gradient data was combined with force-displacement curves and results from specialized EBL patterns to show that DVLO encompassed forces are the most likely cause of catalyst motion. Lastly, MaCE fabricated templates were combined with electroless deposition of Pd to demonstrate the bottom-up filling of MaCE with sub-20 nm feature resolution. These structures were also used to establish the relationship between rotation angle of spiraling star-shaped catalysts and their center core diameter. Summary In summary, a new method to fabricate 3D nanostructures by top-down etching and bottom-up filling was established along with control over etching path, rotation angle, and etch depth. Out-of-plane rotational catalysts were designed and a new model for catalyst motion proposed. This research is expected to further the advancement of MaCE as platform for 3D nanofabrication with potential applications in thru-silicon-vias, photonics, nano-imprint lithography, and more.
dc.description.degree Ph.D.
dc.identifier.uri http://hdl.handle.net/1853/49011
dc.language.iso en_US
dc.publisher Georgia Institute of Technology
dc.subject Metal-assisted chemical etching
dc.subject Silicon
dc.subject Nanofabrication
dc.subject Nanotechnology
dc.subject Etching
dc.subject MaCE
dc.subject Electroless
dc.subject Filling
dc.subject.lcsh Thin films
dc.subject.lcsh Nanoimprint lithography
dc.subject.lcsh Nanolithography
dc.subject.lcsh Nanomanufacturing
dc.title Development of metal-assisted chemical etching as a 3D nanofabrication platform
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Wong, C. P.
local.contributor.corporatename School of Materials Science and Engineering
local.contributor.corporatename College of Engineering
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relation.isOrgUnitOfPublication 21b5a45b-0b8a-4b69-a36b-6556f8426a35
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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