Effect of additives on preparation of vertical holes in Si substrate using metal-assisted chemical etching

Shimizu, Tomohiro; Niwa, Ryosuke; Ito, Tetsuo; Shingubara, Shoso

doi:10.7567/1347-4065/ab0ff5

Cited by 7 publications

(14 citation statements)

References 32 publications

(40 reference statements)

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“…Similarly, PEG (polyethylene glycol) can be added into etchant, which has led to vertical etching with rather large (approximate diameter of 10 µm) Au catalyst disc; otherwise, the Au catalyst is easily bent due to unequal etch rate between edge and center, leading to the formation of holes having bent bottom. [126] Another useful additive for MaCE is chloride, such as HCl and NaCl. [127,128] These chlorides can easily dissociate into ions, and those ions interfere with reactive species in the MaCE.…”

Section: Etch Additivesmentioning

confidence: 99%

“…[331] Similarly, one can apply porous entity, either substrate or metal stamp, to fabricate macroscale Si features successfully by MaCE. One can make lithographically defined nanoscale (≈200 nm in diameter) pores array in larger (≈10 µm) metal layer, [126,332] which facilitate mass transport of etchant/ by-products during MaCE for the fabrication of macroscale Si features, as shown in Figure 6d. Also, porous network of metal catalyst mold, prepared by sintering of metal powder at high temperature and pressure, can be used for the MaCE; in this case, the porous mold can supply paths for mass transport of etchant/by-products.…”

Section: Mass Transport In Macementioning

confidence: 99%

“…During the MaCE for the fabrication of macroscale Si features, it is inevitable that there remain unwanted micro/nanostructures on the etched Si surface when a porous, permeable metal catalyst is used. [125,126,131,326,330,332,336] Pores in metal catalyst layer can be widened during MaCE, and can lead to the mechanical rupture of catalyst in the extreme case. Then, the unwanted Si structures can be generated where there are widened pores, often called sprouts.…”

Section: Generation and Removal Of Unwanted Micro/ Nanostructuresmentioning

confidence: 99%

“…The readers can refer to the works on the modeling of h + distribution in MaCE. [134,327,340] Various etch additives, such as ethanol, [124,145,326,333] isopropyl alcohol, [125] and polyethylene glycol (PEG), [126] are helpful in reducing the attack of Si top surface. These additives reduce the surface tension of etching solution, which enhance the uniform wetting of etchant and facilitate the removal of generated H 2 gas.…”

Section: Rough Porosified Si Surfacementioning

confidence: 99%

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Structuring of Si into Multiple Scales by Metal‐Assisted Chemical Etching

Srivastava

Khang

2021

Advanced Materials

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classified into two common approaches: bottom-up chemical synthesis, such as vapor-liquid-solid growth, [16][17][18][19][20] and topdown fabrication schemes. [21][22][23] This review will focus on the top-down fabrication of Si structures using a wet chemical etching technique aided with a metal catalyst, called metal-assisted chemical etching (MaCE). [24][25][26][27][28][29][30][31][32] In comparison with top down fabrication methods based on dry etching using a reactive plasma in vacuum, MaCE is less expensive and less complex. [33][34][35] MaCE is a nano-scale reductionoxidation (redox) process that usually occurs in aqueous solution where the sample to be etched is in contact with the etchant. MaCE is a simple, cost-effective, and versatile method to produce Si nanostructures; due to these attractive features, there have been many good review articles published on the process. [36][37][38][39][40][41][42] With two-decades of research of the MaCE and its innovative variations, recent studies have focused on the various applications of Si nanostructures prepared by MaCE, including photovoltaics, [43,44] thermoelectrics and piezoelectric nanogenerators, [45] energy storage, [46][47][48] nanophotonics and optoelectronics, [49] and biosensors and biomedical applications. [50][51][52] In this review, we provide an overview of the recent advances in MaCE processes and their novel applications. To differentiate this review from previous review articles, the main emphasis is on the recently developed novel MaCE processes and the macroscale structuring of Si by MaCE. We begin the review by describing new MaCE processes, particularly catalysts for MaCE. In contrast to well-known noble metal catalysts, such as Ag, Au, and Pt, carbon-based catalysts, such as graphene, graphene oxide, and carbon nanotubes, have been successfully applied as catalysts for MaCE. In addition, TiN has been found to be a catalyst for MaCE, making the whole process CMOS-compatible. Different types of etch additives, such as various alcohols and chlorides, have also been discussed, which enhance etch uniformity by increasing the wettability of etchants and suppressing the random diffusion of excessive (holes) h + by trapping them for better etch control. Recent novel variations of the MaCE process have been introduced, such as MaCE with externally applied electric or magnetic fields. The external field has a profound effect on the output of MaCE, by controlling the etch directionality and etch rate. In addition, MaCE can be combined with unconventional patterning techniques, StructuringSi, ranging from nanoscale to macroscale feature dimensions, is essential for many applications. Metal-assisted chemical etching (MaCE) has been developed as a simple, low-cost, and scalable method to produce structures across widely different dimensions. The process involves various parameters, such as catalyst, substrate doping type and level, crystallography, etchant formulation, and etch additives. Careful optimization of these parameters is the key to the succe...

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Section: Etch Additivesmentioning

confidence: 99%

Section: Mass Transport In Macementioning

confidence: 99%

Section: Generation and Removal Of Unwanted Micro/ Nanostructuresmentioning

confidence: 99%

Section: Rough Porosified Si Surfacementioning

confidence: 99%

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Structuring of Si into Multiple Scales by Metal‐Assisted Chemical Etching

Srivastava

Khang

2021

Advanced Materials

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show abstract

“…As examples of the applications, Si nanohole arrays and Si nanowires produced by the metal-assisted etching have been applied to anti-reection for solar cells, 5,7,8 anode materials of lithium-ion batteries, 9 and thermoelectric conversion materials, 10 taking advantages of its low reectivity, large specic surface area and large space to accommodate volume expansion, and low thermal conductivity. Fabrication of high-aspectratio structures has been studied for the production of micro electro mechanical systems (MEMS), 11 through-silicon via (TSV), 12,13 and X-ray diffractive optics 14,15 as well as for wafer dicing. 16 Complex 3D structures, e.g.…”

Section: Introductionmentioning

confidence: 99%