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Surdo S, Barillaro G. Voltage- and Metal-assisted Chemical Etching of Micro and Nano Structures in Silicon: A Comprehensive Review. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2400499. [PMID: 38644330 DOI: 10.1002/smll.202400499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 03/12/2024] [Indexed: 04/23/2024]
Abstract
Sculpting silicon at the micro and nano scales has been game-changing to mold bulk silicon properties and expand, in turn, applications of silicon beyond electronics, namely, in photonics, sensing, medicine, and mechanics, to cite a few. Voltage- and metal-assisted chemical etching (ECE and MaCE, respectively) of silicon in acidic electrolytes have emerged over other micro and nanostructuring technologies thanks to their unique etching features. ECE and MaCE have enabled the fabrication of novel structures and devices not achievable otherwise, complementing those feasible with the deep reactive ion etching (DRIE) technology, the gold standard in silicon machining. Here, a comprehensive review of ECE and MaCE for silicon micro and nano machining is provided. The chemistry and physics ruling the dissolution of silicon are dissected and similarities and differences between ECE and MaCE are discussed showing that they are the two sides of the same coin. The processes governing the anisotropic etching of designed silicon micro and nanostructures are analyzed, and the modulation of etching profile over depth is discussed. The preparation of micro- and nanostructures with tailored optical, mechanical, and thermo(electrical) properties is then addressed, and their applications in photonics, (bio)sensing, (nano)medicine, and micromechanical systems are surveyed. Eventually, ECE and MaCE are benchmarked against DRIE, and future perspectives are highlighted.
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Affiliation(s)
- Salvatore Surdo
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, via G. Caruso 16, Pisa, 56122, Italy
| | - Giuseppe Barillaro
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, via G. Caruso 16, Pisa, 56122, Italy
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Adhila TK, Elangovan H, John S, Chattopadhyay K, Barshilia HC. Engineering the Microstructure of Silicon Nanowires by Controlling the Shape of the Metal Catalyst and Composition of the Etchant in a Two-Step MACE Process: An In-Depth Analysis of the Growth Mechanism. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:9388-9398. [PMID: 32687375 DOI: 10.1021/acs.langmuir.0c01164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this work, slanted, kinked, and straight silicon nanowires (SiNWs) are fabricated on Si(111) and (100) substrates using a facile two-step metal-assisted chemical etching nanofabrication technique. We systematically investigated the effect of crystallography, morphology of Ag catalyst, and composition of etchant on the etch profile of Ag catalyst on Si(111) and (100) substrates. We found that the movement of AgNPs inside the Si is determined by physiochemical events such as Ag/Ag interaction, Ag/Si contact, and diffusion kinetics. Further, from detailed TEM and micro-Raman spectroscopy analyses, we demonstrate that the metal catalyst moves in the crystallographically preferred etching direction (viz., <100>) only when the interface effect is not predominant. Further, the metal-assisted chemical etching (MACE) system is highly stable at low-concentration plating and etching solutions, but at high concentrations, the system loses its stability and becomes highly random, leading to the movement of Ag catalyst in directions other than ⟨100⟩. In addition, our studies reveal that Ag nanostructures growth on Si(111) and (100) substrates through galvanic displacement is controlled by substrate symmetry and surface bond density. Finally, we demonstrate that by using an optimized balance between the Ag morphology and concentration of the etchant, the angle in slanted SiNWs, kink position in kinked SiNWs, and aspect ratio of straight SiNWs can be controlled judiciously, leading to enhanced optical absorption in the broadband solar spectrum.
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Affiliation(s)
- T K Adhila
- Nanomaterials Research Laboratory, Surface Engineering Division, CSIR-National Aerospace Laboratories, Kodihalli, Bangalore 560 017, India
- Academy of Scientific and Innovative Research, CSIR-NAL Campus, Kodihalli, Bangalore 560 017, India
| | - Hemaprabha Elangovan
- Department of Materials Engineering, Indian Institute of Science, CV Raman Road, Bangalore 560 012, India
| | - Siju John
- Nanomaterials Research Laboratory, Surface Engineering Division, CSIR-National Aerospace Laboratories, Kodihalli, Bangalore 560 017, India
| | - Kamanio Chattopadhyay
- Department of Materials Engineering, Indian Institute of Science, CV Raman Road, Bangalore 560 012, India
| | - Harish C Barshilia
- Nanomaterials Research Laboratory, Surface Engineering Division, CSIR-National Aerospace Laboratories, Kodihalli, Bangalore 560 017, India
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Romano L, Stampanoni M. Microfabrication of X-ray Optics by Metal Assisted Chemical Etching: A Review. MICROMACHINES 2020; 11:E589. [PMID: 32545633 PMCID: PMC7344591 DOI: 10.3390/mi11060589] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 11/19/2022]
Abstract
High-aspect-ratio silicon micro- and nanostructures are technologically relevant in several applications, such as microelectronics, microelectromechanical systems, sensors, thermoelectric materials, battery anodes, solar cells, photonic devices, and X-ray optics. Microfabrication is usually achieved by dry-etch with reactive ions and KOH based wet-etch, metal assisted chemical etching (MacEtch) is emerging as a new etching technique that allows huge aspect ratio for feature size in the nanoscale. To date, a specialized review of MacEtch that considers both the fundamentals and X-ray optics applications is missing in the literature. This review aims to provide a comprehensive summary including: (i) fundamental mechanism; (ii) basics and roles to perform uniform etching in direction perpendicular to the <100> Si substrate; (iii) several examples of X-ray optics fabricated by MacEtch such as line gratings, circular gratings array, Fresnel zone plates, and other X-ray lenses; (iv) materials and methods for a full fabrication of absorbing gratings and the application in X-ray grating based interferometry; and (v) future perspectives of X-ray optics fabrication. The review provides researchers and engineers with an extensive and updated understanding of the principles and applications of MacEtch as a new technology for X-ray optics fabrication.
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Affiliation(s)
- Lucia Romano
- Institute for Biomedical Engineering, ETH Zürich, 8092 Zürich, Switzerland;
- Paul Scherrer Institut, Forschungsstrasse 111, CH-5232 Villigen, Switzerland
- CNR-IMM, Department of Physics, University of Catania, 64 via S. Sofia, 95123 Catania, Italy
| | - Marco Stampanoni
- Institute for Biomedical Engineering, ETH Zürich, 8092 Zürich, Switzerland;
- Paul Scherrer Institut, Forschungsstrasse 111, CH-5232 Villigen, Switzerland
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Romano L, Kagias M, Vila-Comamala J, Jefimovs K, Tseng LT, Guzenko VA, Stampanoni M. Metal assisted chemical etching of silicon in the gas phase: a nanofabrication platform for X-ray optics. NANOSCALE HORIZONS 2020; 5:869-879. [PMID: 32100775 DOI: 10.1039/c9nh00709a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
High aspect ratio nanostructuring requires high precision pattern transfer with highly directional etching. In this work, we demonstrate the fabrication of structures with ultra-high aspect ratios (up to 10 000 : 1) in the nanoscale regime (down to 10 nm) by platinum assisted chemical etching of silicon in the gas phase. The etching gas is created by a vapour of water diluted hydrofluoric acid and a continuous air flow, which works both as an oxidizer and as a gas carrier for reactive species. The high reactivity of platinum as a catalyst and the formation of platinum silicide to improve the stability of the catalyst pattern allow a controlled etching. The method has been successfully applied to produce straight nanowires with section size in the range of 10-100 nm and length of hundreds of micrometres, and X-ray optical elements with feature sizes down to 10 nm and etching depth in the range of tens of micrometres. This work opens the possibility of a low cost etching method for stiction-sensitive nanostructures and a large range of applications where silicon high aspect ratio nanostructures and high precision of pattern transfer are required.
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Affiliation(s)
- Lucia Romano
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
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Kim JD, Kim M, Chan C, Draeger N, Coleman JJ, Li X. CMOS-Compatible Catalyst for MacEtch: Titanium Nitride-Assisted Chemical Etching in Vapor phase for High Aspect Ratio Silicon Nanostructures. ACS APPLIED MATERIALS & INTERFACES 2019; 11:27371-27377. [PMID: 31265223 DOI: 10.1021/acsami.9b00871] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Metal-assisted chemical etching (MacEtch) is an emerging anisotropic chemical etching technique that has been used to fabricate high aspect ratio semiconductor micro- and nanostructures. Despite its advantages in unparalleled anisotropy, simplicity, versatility, and damage-free nature, the adaptation of MacEtch for silicon (Si)-based electronic device fabrication process is hindered by the use of a gold (Au)-based metal catalyst, as Au is a detrimental deep-level impurity in Si. In this report, for the first time, we demonstrate CMOS-compatible titanium nitride (TiN)-based MacEtch of Si by establishing a true vapor-phase (VP) MacEtch approach in order to overcome TiN-MacEtch-specific challenges. Whereas inverse-MacEtch is observed using conventional liquid phase MacEtch because of the limited mass transport from the strong adhesion between TiN and Si, the true VP etch leads to forward MacEtch and produces Si nanowire arrays by engraving the TiN mesh pattern in Si. The etch rate as a function of etch temperature, solution concentration, TiN dimension, and thickness is systematically characterized to uncover the underlying nature of MacEtching using this new catalyst. VP MacEtch represents a significant step toward scalability of this disruptive technology because of the high controllability of gas phase reaction dynamics. TiN-MacEtch may also have direct implications in embedded TiN-based plasmonic semiconductor structures for photonic applications.
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Affiliation(s)
- Jeong Dong Kim
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory , University of Illinois at Urbana-Champaign , Champaign , Illinois 61801 , United States
| | - Munho Kim
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory , University of Illinois at Urbana-Champaign , Champaign , Illinois 61801 , United States
| | - Clarence Chan
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory , University of Illinois at Urbana-Champaign , Champaign , Illinois 61801 , United States
| | - Nerissa Draeger
- Lam Research Corporation , Fremont , California 94538 , United States
| | - James J Coleman
- Department of Electrical Engineering and Department of Materials Science , University of Texas at Dallas , Richardson , Texas 75080 , United States
| | - Xiuling Li
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory , University of Illinois at Urbana-Champaign , Champaign , Illinois 61801 , United States
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Kolasinski KW, Unger BA, Ernst AT, Aindow M. Crystallographically Determined Etching and Its Relevance to the Metal-Assisted Catalytic Etching (MACE) of Silicon Powders. Front Chem 2019; 6:651. [PMID: 30701171 PMCID: PMC6343677 DOI: 10.3389/fchem.2018.00651] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 12/13/2018] [Indexed: 02/04/2023] Open
Abstract
Metal-assisted catalytic etching (MACE) using Ag nanoparticles as catalysts and H2O2 as oxidant has been performed on single-crystal Si wafers, single-crystal electronics grade Si powders, and polycrystalline metallurgical grade Si powders. The temperature dependence of the etch kinetics has been measured over the range 5-37°C. Etching is found to proceed preferentially in a 〈001〉 direction with an activation energy of ~0.4 eV on substrates with (001), (110), and (111) orientations. A quantitative model to explain the preference for etching in the 〈001〉 direction is developed and found to be consistent with the measured activation energies. Etching of metallurgical grade powders produces particles, the surfaces of which are covered primarily with porous silicon (por-Si) in the form of interconnected ridges. Silicon nanowires (SiNW) and bundles of SiNW can be harvested from these porous particles by ultrasonic agitation. Analysis of the forces acting between the metal nanoparticle catalyst and the Si particle demonstrates that strongly attractive electrostatic and van der Waals interactions ensure that the metal nanoparticles remain in intimate contact with the Si particles throughout the etch process. These attractive forces draw the catalyst toward the interior of the particle and explain why the powder particles are etched equivalently on all the exposed faces.
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Affiliation(s)
- Kurt W Kolasinski
- Department of Chemistry, West Chester University, West Chester, PA, United States
| | - Bret A Unger
- Department of Chemistry, West Chester University, West Chester, PA, United States
| | - Alexis T Ernst
- Department of Materials Science and Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT, United States
| | - Mark Aindow
- Department of Materials Science and Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT, United States
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Kong L, Zhao Y, Dasgupta B, Ren Y, Hippalgaonkar K, Li X, Chim WK, Chiam SY. Minimizing Isolate Catalyst Motion in Metal-Assisted Chemical Etching for Deep Trenching of Silicon Nanohole Array. ACS APPLIED MATERIALS & INTERFACES 2017; 9:20981-20990. [PMID: 28534611 DOI: 10.1021/acsami.7b04565] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The instability of isolate catalysts during metal-assisted chemical etching is a major hindrance to achieve high aspect ratio structures in the vertical and directional etching of silicon (Si). In this work, we discussed and showed how isolate catalyst motion can be influenced and controlled by the semiconductor doping type and the oxidant concentration ratio. We propose that the triggering event in deviating isolate catalyst motion is brought about by unequal etch rates across the isolate catalyst. This triggering event is indirectly affected by the oxidant concentration ratio through the etching rates. While the triggering events are stochastic, the doping concentration of silicon offers a good control in minimizing isolate catalyst motion. The doping concentration affects the porosity at the etching front, and this directly affects the van der Waals (vdWs) forces between the metal catalyst and Si during etching. A reduction in the vdWs forces resulted in a lower bending torque that can prevent the straying of the isolate catalyst from its directional etching, in the event of unequal etch rates. The key understandings in isolate catalyst motion derived from this work allowed us to demonstrate the fabrication of large area and uniformly ordered sub-500 nm nanoholes array with an unprecedented high aspect ratio of ∼12.
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Affiliation(s)
- Lingyu Kong
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , 28 Medical Drive, Singapore 117456
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
- Department of Electrical and Computer Engineering, National University of Singapore , 4 Engineering Drive 3, Singapore 117583
| | - Yunshan Zhao
- Department of Electrical and Computer Engineering, National University of Singapore , 4 Engineering Drive 3, Singapore 117583
| | - Binayak Dasgupta
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , 28 Medical Drive, Singapore 117456
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Yi Ren
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Kedar Hippalgaonkar
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Xiuling Li
- Department of Electrical and Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Wai Kin Chim
- Department of Electrical and Computer Engineering, National University of Singapore , 4 Engineering Drive 3, Singapore 117583
| | - Sing Yang Chiam
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
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Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon. Sci Rep 2016; 6:36582. [PMID: 27824123 PMCID: PMC5100464 DOI: 10.1038/srep36582] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 10/18/2016] [Indexed: 11/08/2022] Open
Abstract
In this work, we investigate the transport processes governing the metal-assisted chemical etching (MacEtch) of silicon (Si). We show that in the oxidation of Si during the MacEtch process, the transport of the hole charges can be accomplished by the diffusion of metal ions. The oxidation of Si is subsequently governed by a redox reaction between the ions and Si. This represents a fundamentally different proposition in MacEtch whereby such transport is understood to occur through hole carrier conduction followed by hole injection into (or electron extraction from) Si. Consistent with the ion transport model introduced, we showed the possibility in the dynamic redistribution of the metal atoms that resulted in the formation of pores/cracks for catalyst thin films that are ≲30 nm thick. As such, the transport of the reagents and by-products are accomplished via these pores/cracks for the thin catalyst films. For thicker films, we show a saturation in the etch rate demonstrating a transport process that is dominated by diffusion via metal/Si boundaries. The new understanding in transport processes described in this work reconcile competing models in reagents/by-products transport, and also solution ions and thin film etching, which can form the foundation of future studies in the MacEtch process.
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Romano L, Kagias M, Jefimovs K, Stampanoni M. Self-assembly nanostructured gold for high aspect ratio silicon microstructures by metal assisted chemical etching. RSC Adv 2016. [DOI: 10.1039/c5ra24947c] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Self-assembly Au nanostructures stabilize the catalyst during metal assisted chemical etching, improving the vertical profile of high aspect ratio Si dense micro-patterns on large area, such as diffraction gratings for X-ray phase contrast imaging.
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Affiliation(s)
- L. Romano
- Department of Physics and CNR-IMM
- University of Catania
- Catania
- Italy
- Swiss Light Source
| | - M. Kagias
- Swiss Light Source
- Paul Scherrer Institut PSI
- Villigen
- Switzerland
- Institute for Biomedical Engineering
| | - K. Jefimovs
- Swiss Light Source
- Paul Scherrer Institut PSI
- Villigen
- Switzerland
- Institute for Biomedical Engineering
| | - M. Stampanoni
- Swiss Light Source
- Paul Scherrer Institut PSI
- Villigen
- Switzerland
- Institute for Biomedical Engineering
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Otte MA, Solis-Tinoco V, Prieto P, Borrisé X, Lechuga LM, González MU, Sepulveda B. Tailored Height Gradients in Vertical Nanowire Arrays via Mechanical and Electronic Modulation of Metal-Assisted Chemical Etching. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2015; 11:4201-4208. [PMID: 26033973 DOI: 10.1002/smll.201500175] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 04/26/2015] [Indexed: 06/04/2023]
Abstract
In current top-down nanofabrication methodologies the design freedom is generally constrained to the two lateral dimensions, and is only limited by the resolution of the employed nanolithographic technique. However, nanostructure height, which relies on certain mask-dependent material deposition or etching techniques, is usually uniform, and on-chip variation of this parameter is difficult and generally limited to very simple patterns. Herein, a novel nanofabrication methodology is presented, which enables the generation of high aspect-ratio nanostructure arrays with height gradients in arbitrary directions by a single and fast etching process. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how nanostructure arrays with directional height gradients can be accurately tailored by: (i) the control of the mass transport through the nanohole array, (ii) the mechanical properties of the perforated metal layer, and (iii) the conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. The proposed technique, enabling 20-fold on-chip variation of nanostructure height in a spatial range of a few micrometers, offers a new tool for the creation of novel types of nano-assemblies and metamaterials with interesting technological applications in fields such as nanophotonics, nanophononics, microfluidics or biomechanics.
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Affiliation(s)
- M A Otte
- NanoBiosensors and Bioanalytical Applications Group, Institut Catala de Nanociencia i Nanotecnologia (ICN2), Consejo Superior de Investigaciones Científicas (CSIC) & CIBER-BBN, Campus UAB, Bellaterra, 08193, Barcelona, Spain
| | - V Solis-Tinoco
- NanoBiosensors and Bioanalytical Applications Group, Institut Catala de Nanociencia i Nanotecnologia (ICN2), Consejo Superior de Investigaciones Científicas (CSIC) & CIBER-BBN, Campus UAB, Bellaterra, 08193, Barcelona, Spain
| | - P Prieto
- IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, 28760, Tres Cantos, Madrid, Spain
| | - X Borrisé
- Nanolithography Laboratory, Institut Catala de Nanociencia i Nanotecnologia (ICN2) & CNM-IMB (CSIC), Campus UAB, Bellaterra, 08193, Barcelona, Spain
| | - L M Lechuga
- NanoBiosensors and Bioanalytical Applications Group, Institut Catala de Nanociencia i Nanotecnologia (ICN2), Consejo Superior de Investigaciones Científicas (CSIC) & CIBER-BBN, Campus UAB, Bellaterra, 08193, Barcelona, Spain
| | - M U González
- IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, 28760, Tres Cantos, Madrid, Spain
| | - B Sepulveda
- Magnetic Nanostructures Group, Institut Catala de Nanociencia i Nanotecnologia (ICN2), Consejo Superior de Investigaciones Científicas (CSIC), Campus UAB, Bellaterra, 08193, Barcelona, Spain
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Ouertani R, Hamdi A, Amri C, Khalifa M, Ezzaouia H. Formation of silicon nanowire packed films from metallurgical-grade silicon powder using a two-step metal-assisted chemical etching method. NANOSCALE RESEARCH LETTERS 2014; 9:574. [PMID: 25349554 PMCID: PMC4209156 DOI: 10.1186/1556-276x-9-574] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 10/01/2014] [Indexed: 06/02/2023]
Abstract
In this work, we use a two-step metal-assisted chemical etching method to produce films of silicon nanowires shaped in micrograins from metallurgical-grade polycrystalline silicon powder. The first step is an electroless plating process where the powder was dipped for few minutes in an aqueous solution of silver nitrite and hydrofluoric acid to permit Ag plating of the Si micrograins. During the second step, corresponding to silicon dissolution, we add a small quantity of hydrogen peroxide to the plating solution and we leave the samples to be etched for three various duration (30, 60, and 90 min). We try elucidating the mechanisms leading to the formation of silver clusters and silicon nanowires obtained at the end of the silver plating step and the silver-assisted silicon dissolution step, respectively. Scanning electron microscopy (SEM) micrographs revealed that the processed Si micrograins were covered with densely packed films of self-organized silicon nanowires. Some of these nanowires stand vertically, and some others tilt to the silicon micrograin facets. The thickness of the nanowire films increases from 0.2 to 10 μm with increasing etching time. Based on SEM characterizations, laser scattering estimations, X-ray diffraction (XRD) patterns, and Raman spectroscopy, we present a correlative study dealing with the effect of the silver-assisted etching process on the morphological and structural properties of the processed silicon nanowire films.
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Affiliation(s)
- Rachid Ouertani
- Laboratoire de Photovoltaïque, Centre de Recherches et des Technologies de l'Énergie, Technopôle de Borj-Cédria, BP 95, 2050 Hammam-Lif, Tunisie
| | - Abderrahmen Hamdi
- Laboratoire de Photovoltaïque, Centre de Recherches et des Technologies de l'Énergie, Technopôle de Borj-Cédria, BP 95, 2050 Hammam-Lif, Tunisie
| | - Chohdi Amri
- Laboratoire de Photovoltaïque, Centre de Recherches et des Technologies de l'Énergie, Technopôle de Borj-Cédria, BP 95, 2050 Hammam-Lif, Tunisie
| | - Marouan Khalifa
- Laboratoire de Photovoltaïque, Centre de Recherches et des Technologies de l'Énergie, Technopôle de Borj-Cédria, BP 95, 2050 Hammam-Lif, Tunisie
| | - Hatem Ezzaouia
- Laboratoire de Photovoltaïque, Centre de Recherches et des Technologies de l'Énergie, Technopôle de Borj-Cédria, BP 95, 2050 Hammam-Lif, Tunisie
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Li L, Liu Y, Zhao X, Lin Z, Wong CP. Uniform vertical trench etching on silicon with high aspect ratio by metal-assisted chemical etching using nanoporous catalysts. ACS APPLIED MATERIALS & INTERFACES 2014; 6:575-84. [PMID: 24261312 DOI: 10.1021/am4046519] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Recently, metal-assisted chemical etching (MaCE) has been proposed as a promising wet-etching method for the fabrication of micro- and nanostructures on silicon with low cost. However, uniform vertical trench etching with high aspect ratio is still of great challenge for traditional MaCE. Here we report an innovated MaCE method, which combined the use of a nanoporous gold thin film as the catalyst and a hydrofluoric acid (HF)-hydrogen peroxide (H2O2) mixture solution with a low HF-to-H2O2 concentration ratio (ρ) as the etchant. The reported method successfully fabricated vertical trenches on silicon with a width down to 2 μm and an aspect ratio of 16. The geometry of the trenches was highly uniform throughout the 3D space. The vertical etching direction was favored on both (100)- and (111)-oriented silicon substrates. The reported method was also capable of producing multiple trenches on the same substrate with individually-tunable lateral geometry. An etching mechanism including a through-catalyst mass-transport process and an electropolishing-favored charge-transport process was identified by a comparative study. The novel method fundamentally solves the problems of distortion and random movement of isolated catalysts in MaCE. The results mark a breakthrough in high-quality silicon trench-etching technology with a cost of more than 2 orders of magnitude lower than that of the currently available methods.
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Affiliation(s)
- Liyi Li
- School of Materials Science and Engineering, Georgia Institute of Technology , 771 Ferst Drive, Atlanta, Georgia 30332, United States
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