Semiconductor Nanofabrication Via Metal-assisted Chemical Etching

Semiconductor Nanofabrication Via Metal-assisted Chemical Etching
Author: Thomas S. Wilhelm
Publisher:
Total Pages: 240
Release: 2019
Genre: Catalysis
ISBN:

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"The increasing demand for complex devices that utilize three-dimensional nanostructures has incentivized the development of adaptable and versatile semiconductor nanofabrication strategies. Without the introduction and refinement of methodologies to overcome traditional processing constraints, nanofabrication sequences risk becoming obstacles that impede device evolution. Crystallographic wet-chemical etching (e.g., Si in KOH) has historically been sufficient to produce textured Si surfaces with smooth sidewalls, though it lacks the ability to yield high aspect-ratio features. Physical and chemical plasma etching (e.g., reactive-ion etching) evolved to allow for the creation of vertical structures within integrated circuits; however, the high energy ion bombardment associated with dry etching can cause lattice and sidewall damage that is detrimental to device performance, particularly as structures progress within the micro- and nano-scale regimes. Metal-assisted chemical etching (MacEtch) provides an alternative processing scheme that is both solution-based and highly anisotropic. This fabrication method relies on a suitable catalyst (e.g., Au, Ag, Pt, or Pd) to induce semiconductor etching in a solution containing an oxidant and an etchant. The etching would otherwise be inert without the presence of the catalyst. The MacEtch process is modelled after a galvanic cell, with cathodic and anodic half reactions occurring at the solution/catalyst and catalyst/semiconductor interfaces, respectively. The metal catalyzes the reduction of oxidant species at the cathode, thereby generating charge carriers (i.e., holes) that are locally injected into the semiconductor at the anode. The solution interacts with the ionized substrate, which creates an oxide that is preferentially attacked by the etchant. Thus, MacEtch offers a nanofabrication alternative that combines the advantages of both wet- and dry-etching, while also overcoming many of their accompanying limitations. This provides a tunable semiconductor processing platform using controlled top-down catalytic etching, affording engineers greater processing control and versatility over conventional methodologies. Here, Au-enhanced MacEtch of the ternary alloys InGaP and AlGaAs is demonstrated for the first time, and processes are detailed for the formation of suspended III-V nanofoils and ordered nanopillar arrays. Next, a lithography-free and entirely solution-based method is outlined for the fabrication of black GaAs with solar-weighted reflectance of ~4%. Finally, a comparison between Au- and CNT-enhanced Si MacEtch is presented towards CMOS-compatibility using catalysts that do not introduce deep level traps. Sample preparation and etching conditions are shown to be adaptable to yield an a priori structural design, through a modification of injected hole distributions. Critical process parameters that guide the MacEtch mechanisms are considered at length, including heteroepitaxial effects, ternary material composition, etching temperature, and catalyst type, size, and deposition technique. This work extends the range of MacEtch materials and its fundamental mechanics for fabrication of micro- and nano-structures with applications in optoelectronics, photovoltaics, and nanoelectronics."--Abstract.

Micro- and Nano-Fabrication by Metal Assisted Chemical Etching

Micro- and Nano-Fabrication by Metal Assisted Chemical Etching
Author: Lucia Romano
Publisher: MDPI
Total Pages: 106
Release: 2021-01-13
Genre: Technology & Engineering
ISBN: 303943845X

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Metal-assisted chemical etching (MacEtch) has recently emerged as a new etching technique capable of fabricating high aspect ratio nano- and microstructures in a few semiconductors substrates—Si, Ge, poly-Si, GaAs, and SiC—and using different catalysts—Ag, Au, Pt, Pd, Cu, Ni, and Rh. Several shapes have been demonstrated with a high anisotropy and feature size in the nanoscale—nanoporous films, nanowires, 3D objects, and trenches, which are useful components of photonic devices, microfluidic devices, bio-medical devices, batteries, Vias, MEMS, X-ray optics, etc. With no limitations of large-areas and low-cost processing, MacEtch can open up new opportunities for several applications where high precision nano- and microfabrication is required. This can make semiconductor manufacturing more accessible to researchers in various fields, and accelerate innovation in electronics, bio-medical engineering, energy, and photonics. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel methodological developments in MacEtch, and its use for various applications.

Micro- and Nano-Fabrication by Metal Assisted Chemical Etching

Micro- and Nano-Fabrication by Metal Assisted Chemical Etching
Author: Lucia Romano
Publisher:
Total Pages: 106
Release: 2021
Genre:
ISBN: 9783039438464

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Metal-assisted chemical etching (MacEtch) has recently emerged as a new etching technique capable of fabricating high aspect ratio nano- and microstructures in a few semiconductors substrates--Si, Ge, poly-Si, GaAs, and SiC--and using different catalysts--Ag, Au, Pt, Pd, Cu, Ni, and Rh. Several shapes have been demonstrated with a high anisotropy and feature size in the nanoscale--nanoporous films, nanowires, 3D objects, and trenches, which are useful components of photonic devices, microfluidic devices, bio-medical devices, batteries, Vias, MEMS, X-ray optics, etc. With no limitations of large-areas and low-cost processing, MacEtch can open up new opportunities for several applications where high precision nano- and microfabrication is required. This can make semiconductor manufacturing more accessible to researchers in various fields, and accelerate innovation in electronics, bio-medical engineering, energy, and photonics. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel methodological developments in MacEtch, and its use for various applications.

Materials for Advanced Packaging

Materials for Advanced Packaging
Author: Daniel Lu
Publisher: Springer
Total Pages: 974
Release: 2016-11-18
Genre: Technology & Engineering
ISBN: 3319450980

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Significant progress has been made in advanced packaging in recent years. Several new packaging techniques have been developed and new packaging materials have been introduced. This book provides a comprehensive overview of the recent developments in this industry, particularly in the areas of microelectronics, optoelectronics, digital health, and bio-medical applications. The book discusses established techniques, as well as emerging technologies, in order to provide readers with the most up-to-date developments in advanced packaging.

Development of Metal-assisted Chemical Etching as a 3D Nanofabrication Platform

Development of Metal-assisted Chemical Etching as a 3D Nanofabrication Platform
Author: Owen James Hildreth
Publisher:
Total Pages:
Release: 2012
Genre: Nanoimprint lithography
ISBN:

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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.

Effect of Thermal Oxide Film on Scalable Fabrication of Silicon Nanowire Arrays Using Metal Assisted Chemical Etching

Effect of Thermal Oxide Film on Scalable Fabrication of Silicon Nanowire Arrays Using Metal Assisted Chemical Etching
Author: Mariana Castaneda
Publisher:
Total Pages: 92
Release: 2020
Genre:
ISBN:

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Over the last several decades, the demand for real-time data processing and storage has exponentially increased and pushed the semiconductor field to its fabrication limits. Traditional methods of semiconductor nanomanufacturing, like lithography and reactive ion etching (RIE), suffer from feature resolution and etch taper limits for devices comprising sub-10 nm nanofabrication nodes. Methods like the ones mentioned above are both expensive and difficult to manufacture to keep up with continued scaling requirements of semiconductor fabrication. This thesis presents a fabrication method and metrology characterization of silicon nanowire arrays using a Metal Assisted Chemical Etching (MACE) approach. MACE is a simple, low-cost fabrication technique that allows for high aspect ratio silicon nanostructures to be successfully fabricated without sacrificing geometry fidelity, making it a promising etching method for large-scale semiconductor manufacturing. In this research, small-scale MACE was demonstrated on silicon coupons with an initial process window of 0 nm - 100 nm oxide thickness. Then, a down-selected process window of 10 nm - 50 nm oxide thickness was successfully reproduced on a full-wafer scale (100 mm diameter silicon wafers) at different etchant solution concentrations. The oxide layer serves as a sacrificial layer between the silicon and resist to allow a consistent etching starting point, thus improving the etch depth uniformity and aspect ratios of silicon nanowires. The silicon nanowires were characterized using local scanning electron microscopy (SEM) images by mapping the areas of the wafer as North, South, East, and West to measure critical dimensions such as height and diameter, as well as to observe phenomena such as nanowire collapse

The Fabrication of Silicon Nanostructures Using Metal-assisted Chemical Etching and Their Applications in Biomedicine

The Fabrication of Silicon Nanostructures Using Metal-assisted Chemical Etching and Their Applications in Biomedicine
Author: Hashim Ziad Alhmoud
Publisher:
Total Pages: 225
Release: 2015
Genre: Biomedical materials
ISBN:

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The main aim of this thesis was to develop novel nano-scale silicon structures with useful functions for biomedicine. Metal-assisted chemical etching (MACE) of silicon offered low fabrication cost, ease of implementation, and an inherent compatibility with various patterning technologies. For these reasons, MACE was used as the primary platform of fabrication for this work. Furthermore, nanostructure patterning was mainly carried out via self-assembled nanosphere lithography, which is a low-cost and reliable method for patterning surfaces on the sub-micrometer scale.

Photovoltaic Manufacturing

Photovoltaic Manufacturing
Author: Monika Freunek Muller
Publisher: John Wiley & Sons
Total Pages: 154
Release: 2021-08-16
Genre: Science
ISBN: 1119242010

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PHOTOVOLTAIC MANUFACTURING This book covers the state-of-the-art and the fundamentals of silicon wafer solar cells manufacturing, written by world-class researchers and experts in the field. High quality and economic photovoltaic manufacturing is central to realizing reliable photovoltaic power supplies at reasonable cost. While photovoltaic silicon wafer manufacturing is at a mature, industrial and mass production stage, knowing and applying the fundamentals in solar manufacturing is essential to anyone working in this field. This is the first book on photovoltaic wet processing for silicon wafers, both mono- and multi-crystalline. The comprehensive book provides information for process, equipment, and device engineers and researchers in the solar manufacturing field. The authors of the chapters are world-class researchers and experts in their field of endeavor. The fundamentals of wet processing chemistry are introduced, covering etching, texturing, cleaning and metrology. New developments, innovative approaches, as well as current challenges are presented. Benefits of reading the book include: The book includes a detailed discussion of the important new development of black silicon, which is considered to have started a new wave in photovoltaics and become the new standard while substantially lowering the cost. Photovoltaics are central to any country’s “New Green Deal” and this book shows how to manufacture competitively. The book’s central goal is to show photovoltaic manufacturing can be done with enhanced quality and lowering costs. Audience Engineers, chemists, physicists, process technologists, in both academia and industry, that work with photovoltaics and their manufacture.