Uniform Metal-Assisted Chemical Etching for Ultra-High-Aspect-Ratio Microstructures on Silicon

Li, Liyi; Tuan, Chia-Chi; Zhang, Cheng; Chen, Yun; Lian, Gang

doi:10.1109/jmems.2018.2881510

Cited by 20 publications

(21 citation statements)

References 36 publications

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“…30,31 On the other hand, uniform high aspect ratios have been reported for a nanoporous Au catalyst in conditions of low HF and high H 2 O 2 concentration. 32,33 Under these conditions the etching is more isotropic, 34 the tops of the trenches appear wider with respect to the bottom compromising the fidelity of the pattern in the lateral dimension, so the process is not suitable for high aspect ratio nanostructures.…”

Section: Pt Catalyst Pattern For Nanowire Fabricationmentioning

confidence: 99%

“…The use of an interconnected pattern has been demonstrated to effectively reduce the off-vertical catalyst movement. 29,32,33 De-wetting occurs when a thin film on a solid substrate is heated, inducing clustering of the film. 41 The film structure morphology (feature size, roughness, pores distribution) and the pattern evolution strongly depend on the film/substrate parameters (film material, film thickness, substrate material, defects) and the experimental conditions (deposition rate, annealing temperature, annealing environment etc.).…”

Section: Pt Catalyst Pattern For Nanowire Fabricationmentioning

confidence: 99%

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Metal assisted chemical etching of silicon in the gas phase: a nanofabrication platform for X-ray optics

et al. 2020

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Section: Pt Catalyst Pattern For Nanowire Fabricationmentioning

confidence: 99%

Section: Pt Catalyst Pattern For Nanowire Fabricationmentioning

confidence: 99%

Metal assisted chemical etching of silicon in the gas phase: a nanofabrication platform for X-ray optics

et al. 2020

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“…movement. [16][17][18] The nanopore morphology allows the MacEtch reactants to pass through the catalyst spacing, significantly improving the mass transport and uniformity, which ensures a highly uniform etch rate over the catalyst area.…”

Section: Platinum Thermal Dewettingmentioning

confidence: 99%

High‐Aspect‐Ratio Grating Microfabrication by Platinum‐Assisted Chemical Etching and Gold Electroplating

et al. 2020

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Diffractive optics play a key role in hard X‐rays imaging for which many scientific, technological, and biomedical applications exist. Herein, high‐aspect‐ratio microfabrication of gratings for X‐ray interferometry is demonstrated using Pt as a catalyst for the metal assisted chemical etching of Si in a solution of HF and H2O2. The Pt layer is thermally treated to realize a porous catalyst layer that stabilizes the etching of a pattern with a pitch size from 4.8 to 20 μm in the direction perpendicular to the <100> Si substrate and an aspect ratio up to 60:1. The superior etching performance of Pt as a catalyst and its stability in a solution with high HF content are reported in direct comparison with the Au catalyst for the same grating parameters. The Si structure is then used as a template for filling with Au, as a high absorbing X‐ray material. The Pt catalyst layer is used as a conductive seed for Au electroplating. The quality of the overall process is assessed by obtaining a visibility map using 30 μm‐thick Au grating in an X‐ray interferometric setup at 20 keV.

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“…Gold catalyst suffers of bad adhesion on silicon substrates, yet a detrimental pattern peel-off has been reported during MacEtch in conditions of high HF concentration [50,65]. On the other hand, uniform high aspect ratio has been reported for nanoporous Au catalyst in conditions of low HF and high H 2 O 2 concentration [39,66]. In these conditions, the etching is more isotropic [63], the top of the trenches appear wider with respect to the bottom compromising the fidelity of the pattern transfer in the lateral dimension, so the process is not suitable for high aspect ratio structures.…”

Section: Catalystmentioning

confidence: 99%

“…Porous catalyst film is reported [2,63,66,67] to improve the etching performances of micro-scaled Si trenches structures with interconnected catalyst pattern. The porous morphology of the film allows the MacEtch reactants to pass through the catalyst spacing, significantly improving the mass transport and uniformity, which ensures a highly uniform etch rate over all the catalyst area.…”

Section: Catalystmentioning

confidence: 99%

Microfabrication of X-ray Optics by Metal Assisted Chemical Etching: A Review

Romano

Stampanoni

2020

Micromachines

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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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Uniform Metal-Assisted Chemical Etching for Ultra-High-Aspect-Ratio Microstructures on Silicon

Cited by 20 publications

References 36 publications

Metal assisted chemical etching of silicon in the gas phase: a nanofabrication platform for X-ray optics

Metal assisted chemical etching of silicon in the gas phase: a nanofabrication platform for X-ray optics

High‐Aspect‐Ratio Grating Microfabrication by Platinum‐Assisted Chemical Etching and Gold Electroplating

Microfabrication of X-ray Optics by Metal Assisted Chemical Etching: A Review

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