Mechanics of Catalyst Motion during Metal Assisted Chemical Etching of Silicon

Lai, Chang Quan; He, Cheng; Choi, W. K.; Thompson, Carl V.

doi:10.1021/jp407561k

Cited by 62 publications

(77 citation statements)

References 31 publications

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“…While the effects on ion movements through such applied bias is yet unclear, our work shows clearly why there is no substantial increase in etching since the charge transfer is a redox driven reaction. The redox driven reaction is also consistent with the interpretation of the role of van der Waals forces between the catalyst and semiconductor that is largely accepted545556. The ion transport and redox reaction model is more congruent with such interface forces as efficient charge injection will require a solid state contact instead.…”

Section: Resultssupporting

confidence: 80%

Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

Kong

Dasgupta

Ren

et al. 2016

Sci Rep

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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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Section: Resultssupporting

confidence: 80%

Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

Kong

Dasgupta

Ren

et al. 2016

Sci Rep

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“…As the particle size and surface contact area decrease, the forces imparted by these byproducts begin to compete with van der Waals forces that keep the metal particle in contact with the substrate. 27 The data in Fig. 8 numerically show a threshold size requirement for achieving highly anisotropic etching.…”

Section: Characterization Of the Macetch Processmentioning

confidence: 92%

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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“…Based on the analysis of previous reports, 27,29,30 Metal Assisted Chemical Etching (MACE) of Si in HF takes place when electronic holes (h + ) are injected into the Si near the metal-Si interface (Fig. 2a).…”

Section: A Establishing the Schottky Barrier Heightsmentioning

confidence: 99%

“…Any differences between the two dimensions cannot be easily resolved with SEM, like in the case of MACE Si nanowires 1,29,43,44 . Any differences between the two dimensions cannot be easily resolved with SEM, like in the case of MACE Si nanowires 1,29,43,44 .…”

Section: B P-type Si (P-si) Substratesmentioning

confidence: 99%

“…26,27 Indeed, researchers have acknowledged that a comprehensive study combining the electronic and chemical aspects of MACE is required to fully understand the etching mechanism. Au is stable in HF and does not dissolve and re-deposit during the etching processes 28,29 (See Supplementary Information Section I). Si substrates were coated with perforated Au films and subjected to anodic etching in a HF solution.…”

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confidence: 99%

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Metal assisted anodic etching of silicon

et al. 2015

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Metal assisted anodic etching (MAAE) of Si in HF, without H2O2, is demonstrated. Si wafers were coated with Au films, and the Au films were patterned with an array of holes. A Pt mesh was used as the cathode while the anodic contact was made through either the patterned Au film or the back side of the Si wafer. Experiments were carried out on P-type, N-type, P(+)-type and N(+)-type Si wafers and a wide range of nanostructure morphologies were observed, including solid Si nanowires, porous Si nanowires, a porous Si layer without Si nanowires, and porous Si nanowires on a thick porous Si layer. Formation of wires was the result of selective etching at the Au-Si interface. It was found that when the anodic contact was made through P-type or P(+)-type Si, regular anodic etching due to electronic hole injection leads to formation of porous silicon simultaneously with metal assisted anodic etching. When the anodic contact was made through N-type or N(+)-type Si, generation of electronic holes through processes such as impact ionization and tunnelling-assisted surface generation were required for etching. In addition, it was found that metal assisted anodic etching of Si with the anodic contact made through the patterned Au film essentially reproduces the phenomenology of metal assisted chemical etching (MACE), in which holes are generated through metal assisted reduction of H2O2 rather than current flow. These results clarify the linked roles of electrical and chemical processes that occur during electrochemical etching of Si.

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Mechanics of Catalyst Motion during Metal Assisted Chemical Etching of Silicon

Cited by 62 publications

References 31 publications

Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

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

Metal assisted anodic etching of silicon

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