High Catalytic Activity of Palladium for Metal-Enhanced Hydrofluoric Acid Etching of Silicon

Yae, Shinji; Tashiro, Masayuki; Hirano, Tatsuya; Abe, Makoto; Fukumuro, Naoki; Matsuda, Hitoshi

doi:10.1149/1.2982567

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…15,18 In this paper, we describe the unique behavior of Pd on HF etching of Si and micropattern formation. 19…”

mentioning

confidence: 99%

High Catalytic Activity of Palladium for Metal-Enhanced HF Etching of Silicon

Yae¹,

Tashiro²,

Abe³

et al. 2010

J. Electrochem. Soc.

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Metal-enhanced HF etching of Si is an electroless method used to produce porous Si. Such etching generally uses not only metal-modified Si but also an oxidizing agent, such as hydrogen peroxide or metal ions. Pd exhibits high activity in enhancing the HF etching of Si without an oxidizing agent even under dissolved-oxygen-free and dark conditions. Electrolessly deposited Pd particles on n-type Si enhance the HF etching of Si but produce no porous layer. Patterned Pd films localize the etching under the boundary of the Pd deposited areas, and thus Pd can produce a microetch pattern on Si with a simple immersion in the HF solution. This etching reaction is explained by electron injection into the conduction band of Si due to the Pd-enhanced anodic oxidization of Si with water and the cathodic hydrogen evolution on Pd with the injected electrons.Porous silicon ͑Si͒ is usually prepared by electrochemical etching under an anodic bias in a fluoride-containing solution. 1-3 Metalenhanced HF etching of Si has attracted considerable attention as a new electroless method that can produce porous Si by immersing metal-modified Si in an HF solution without bias. 4-15 Such etching generally uses not only metal-modified Si but also an oxidizing agent, such as hydrogen peroxide, 5,10,12-14 peroxodisulfate, 8 permanganate, 8 or metal ions. 7 We reported the preparation process 6,9,11,15 of porous Si using metal-particle-enhanced HF etching of Si without a particular oxidizing agent as well as its application for solar cells 6,9,16 and metal nanorod formation. 17 This etching generally proceeds by a local galvanic cell mechanism requiring photoillumination or dissolved oxygen. Palladium ͑Pd͒ exhibits high activity in enhancing etching under dissolved-oxygen-free and dark conditions. 15,18 In this paper, we describe the unique behavior of Pd on HF etching of Si and micropattern formation. 19 ExperimentalSingle-crystalline n-type Si wafers ͓Yamanaka Semiconductor, CZ ͑100͒, ca. 1 ⍀ cm͔ were cut into pieces ͑1 ϫ 1 cm͒, washed with acetone, and etched with CP-4A ͑a mixture of HF, nitric acid, acetic acid, and water͒ and a 7.3 M ͑M = mol dm −3 ͒ HF solution. Metal particles were deposited on Si wafers by electroless displacement deposition from a 1 mM metal-salt ͑PdCl 2 or H 2 PtCl 6 ͒ solution containing 0.15 M HF. 20 Pd thin films were deposited onto n-Si wafers by the electron-beam evaporation method. The thicknesses of the deposited films were measured using a quartz crystal microbalance ͑ULVAC, CRTM-5000͒ adjusted by gravimetry. The Pd films were patterned by attaching a mask ͑85 m square holes and 40 m space͒ to the n-Si wafers during deposition. The metaldeposited n-Si wafers were immersed in a 7.3 M HF aqueous solution at 298 K under dark conditions. The etching time was 24 h unless otherwise specified. Argon gas ͑Ͼ99.9999% purity, Taiyo Nippon Sanso, grade-1͒ bubbling was applied to the HF solution before and during etching to remove the dissolved oxygen from the solution. The average etch rate of Si was measured using a gravi...

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“…15,18 In this paper, we describe the unique behavior of Pd on HF etching of Si and micropattern formation. 19…”

mentioning

confidence: 99%

High Catalytic Activity of Palladium for Metal-Enhanced HF Etching of Silicon

Yae¹,

Tashiro²,

Abe³

et al. 2010

J. Electrochem. Soc.

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“…Pt formed both a porous layer and helical etch track pores on 10 Ω·cm p-type wafers; the latter was attributed to the multifaceted crystalline shape of the Pt particles. Pd was found to be more convoluted than others as it catalyzed etching even without an oxidant and resulted in electropolishing of Si. − HL-MACE with Cu never produced defined etch track pores , and Si NWs, except in the case of electrochemical etching under applied bias . This is due to the low electronegativity and reduction potential of Cu compared to those of other metals, which prevents efficient deposition and leads to enhanced dissolution during etching.…”

Section: Introductionmentioning

confidence: 99%

Low-Load Metal-Assisted Catalytic Etching Produces Scalable Porosity in Si Powders

Tamarov

Kiviluoto

Swanson

et al. 2020

ACS Appl. Mater. Interfaces

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The recently discovered low-load metal-assisted catalytic etching (LL-MACE) creates nanostructured Si with controllable and variable characteristics that distinguish this technique from the conventional high-load variant. LL-MACE employs 150 times less metal catalyst and produces porous Si instead of Si nanowires. In this work, we demonstrate that some of the features of LL-MACE cannot be explained by the present understanding of MACE. With mechanistic insight derived from extensive experimentation, it is demonstrated that (1) the method allows the use of not only Ag, Pd, Pt, and Au as metal catalysts but also Cu and (2) judicious combinations of process parameters such as the type of metal, Si doping levels, and etching temperatures facilitate control over yield (0.065–88%), pore size (3–100 nm), specific surface area (20–310 m2·g–1), and specific pore volume (0.05–1.05 cm3·g–1). The porous structure of the product depends on the space-charge layer, which is controlled by the Si doping and the chemical identity of the deposited metal. The porous structure was also dependent on the dynamic structure of the deposited metal. A distinctive comet-like structure of metal nanoparticles was observed after etching with Cu, Ag, Pd, and, in some cases, Pt; this structure consisted of 10–50 nm main particles surrounded by smaller (<5 nm) nanoparticles. With good scalability and precise control of structural properties, LL-MACE facilitates Si applications in photovoltaics, energy storage, biomedicine, and water purification.

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“…This deposition reaction consists of a local cathodic formation of metal and a local anodic dissolution of Si. This deposition method has been studied for application of the defect detection of Si wafers (5,6) and catalytic-fine-metal-particleformation for photoelectrochemical solar cells (4, 7-10), metal-particle-assisted HF etching of Si (7,8,(10)(11)(12), and autocatalytic electroless plating (12)(13)(14). We previously reported that the particle density of metals varied widely from 10 6 (Pt) to 10 11 (Au) cm -2 , depending on the kind of metal (Pt, Ag, Au, Cu, Pd, and Rh) (3).…”

Section: Introductionmentioning

confidence: 99%

Influence of Si Surface Condition on Electroless Displacement Deposition of Pt Particles

et al. 2011

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The displacement reaction, which is the immersion of Si wafers into a metal-salt solution containing HF, has been applied to prepare catalytic fine metal particles for metal-assisted HF etching, photoelectrochemical solar cells, and autocatalytic plating. The particle density of Pt particles deposited by displacement reaction on n-Si was different based on the solution used for Si chemical oxidation prior to the deposition. Particle density correlates not with the electrical state density at the SiO x /Si interface but with the contact angle of pure water and the microroughness of the oxidized n-Si surface. A model of the deposition process of Pt particles on an oxidized n-Si surface is proposed.

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High Catalytic Activity of Palladium for Metal-Enhanced Hydrofluoric Acid Etching of Silicon

Cited by 6 publications

References 15 publications

High Catalytic Activity of Palladium for Metal-Enhanced HF Etching of Silicon

High Catalytic Activity of Palladium for Metal-Enhanced HF Etching of Silicon

Low-Load Metal-Assisted Catalytic Etching Produces Scalable Porosity in Si Powders

Influence of Si Surface Condition on Electroless Displacement Deposition of Pt Particles

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