Self-assembly nanostructured gold for high aspect ratio silicon microstructures by metal assisted chemical etching

Romano, Lucia; Kagias, Matias; Jefimovs, Konstantins; Stampanoni, Marco

doi:10.1039/c5ra24947c

Cited by 39 publications

(60 citation statements)

References 26 publications

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“…While measurements of the uniformity of the etch were not performed for these samples, no significant visual nonuniformity was observed during or after the etch process apart from sparse circular shapes due to H 2 bubble formation during the etch. Bubbles have been reported to cause localized etch nonuniformity 23 and we observed the same effect. These areas were avoided for SEM evaluation of the samples by cleaving in regions not impacted by bubble formation on the sample.…”

Section: Macetch Processsupporting

confidence: 77%

“…The most noticeable aspect is that small isolated metal islands etch in generally unpredictable directions while larger islands and interconnected web-like patterns etch nearly perpendicular to the surface. This effect was also observed by Romano et al 23 while investigating the suitability of porous gold films for micromachining silicon.…”

Section: Macetch Processsupporting

confidence: 62%

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Fabrication of ultrahigh aspect ratio silicon nanostructures using self-assembled gold metal-assisted chemical etching

Duran

Sarangan

2017

J. Micro/Nanolith. MEMS MOEMS

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Abstract. We report the critical factors that control the geometry of silicon nanostructures produced by metalassisted chemical etching (MacEtch) using self-assembled islands from an ultrathin film of gold. We have conducted a systematic study of the process parameters that control the geometry of the metal structures and the resulting etched nanostructures. Compared to prior reports, which have focused on the crystal orientation and solution stoichiometry, our study finds that the anisotropy of the etched nanostructures is primarily controlled by the deposited metal geometry, while solution stoichiometry and crystal orientation play relatively minor roles.Using an optimized self-assembled geometry and etch process, we demonstrate what we believe is the highest aspect ratio to date (greater than 5000∶1) for high density top-down etched silicon nanostructures. These structures, which we refer to as silicon nanowalls, are in the size regime where quantum confinement effects could potentially be exploited for next-generation optoelectronic components and devices. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Macetch Processsupporting

confidence: 77%

Section: Macetch Processsupporting

confidence: 62%

Fabrication of ultrahigh aspect ratio silicon nanostructures using self-assembled gold metal-assisted chemical etching

Duran

Sarangan

2017

J. Micro/Nanolith. MEMS MOEMS

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“…P-type <100> 4 inches Si wafers with resistivity of 1-30 cm were used in this work. The details of conventional UV photolithographic process with positive photoresist, the Au thin film deposition (101 nm) and lift-off, are reported elsewhere [20]. We fabricated several Au grating patterns with pitch size of p = 2.4, 4.8, 6 and 23 µm and duty cycle of 0.5.…”

Section: Methodsmentioning

confidence: 99%

“…Both etch rate and roughness of etched surface depend on the alcohol concentration in the etching solution, which is connected with the adsorption phenomena on the etched surface. Isopropanol (IPA) [20] and ethanol [5] have been used as surfactant in MacEtch solutions. While systematic observations about KOH and TMAH etching as a function of IPA concentration and models based on surface tension measurements were reported, a similar study is missing for MacEtch process.…”

Section: Introductionmentioning

confidence: 99%

“…We used the previously reported self-assembly nanostructuring of the metal film [20] to improve the metal pattern stability during the etching in order to realize high-quality vertical Si microstructures in the microscale regime. Si grating microstructures with high aspect ratio and pitch size in the range of 2.4 -23 µm have been successfully realized with very smooth surface so to be used as X-ray optics components [16].…”

Section: Introductionmentioning

confidence: 99%

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Effect of isopropanol on gold assisted chemical etching of silicon microstructures

Romano

Vila‐Comamala

Jefimovs

et al. 2017

Microelectronic Engineering

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Wet etching is an essential and complex step in semiconductor device processing. Metal-Assisted Chemical Etching (MacEtch) is fundamentally a wet but anisotropic etching method. In the MacEtch technique, there are still a number of unresolved challenges preventing the optimal fabrication of highaspect-ratio semiconductor micro-and nanostructures, such as undesired etching, uncontrolled catalyst movement, non-uniformity and micro-porosity in the metal-free areas. Here, an optimized MacEtch process using with a nanostructured Au catalyst is proposed for fabrication of Si high aspect ratio microstructures. The addition of isopropanol as surfactant in the HF-H 2 O 2 water solution improves the uniformity and the control of the H 2 gas release. An additional KOH etching removes eventually the unwanted nanowires left by the MacEtch through the nanoporous catalyst film. We demonstrate the benefits of the isopropanol addition for reducing the etching rate and the nanoporosity of etched structures with a monothonical decrease as a function of the isopropanol concentration.

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Cantilever with High Aspect Ratio Nanopillars on Its Top Surface for Moisture Detection in Electronic Products

et al. 2017

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This work reports the patterning silicon pillars by metal‐assisted chemical etching (MACE) process as a post process on a silicon cantilever for a moisture detection. Although the cantilever is very fragile, the patterning of the pillar structures on the cantilever has been successfully demonstrated. The cantilever coated with a material absorbing water (such as polyimide and mesoporous silica) can use as a humidity sensor. Its bending is due to the surface stress change from water molecule absorption. However, the bending of the cantilever is usually at a small value. Here, the silicon cantilever with high aspect ratio pillars on its surface is proposed, which is expected for a larger bending of the cantilever during the water molecule absorption. The moisture detection utilizes the principle that the pillars stack together based upon the condensation behavior of a water vapor on their surfaces.

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Self-assembly nanostructured gold for high aspect ratio silicon microstructures by metal assisted chemical etching

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.

Cited by 39 publications

References 26 publications

Fabrication of ultrahigh aspect ratio silicon nanostructures using self-assembled gold metal-assisted chemical etching

Fabrication of ultrahigh aspect ratio silicon nanostructures using self-assembled gold metal-assisted chemical etching

Effect of isopropanol on gold assisted chemical etching of silicon microstructures

Cantilever with High Aspect Ratio Nanopillars on Its Top Surface for Moisture Detection in Electronic Products

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