Schottky Barrier Catalysis Mechanism in Metal-Assisted Chemical Etching of Silicon

Lai, Ruby A.; Hymel, Thomas M.; Narasimhan, V.; Cui, Yi

doi:10.1021/acsami.6b01020

Cited by 107 publications

(148 citation statements)

References 32 publications

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“…Si covered by the noble metal catalyst etches significantly faster than uncovered Si, transferring the pattern of the deposited metal catalyst to the underlying Si. MACE proceeds through electrochemical and mass transport reactions predicated on the reduction of H 2 O 2 at the metal surface and extraction of electrons from underlying Si, thus injecting holes, at the Si–metal interface to create electron‐poor depletion regions in Si that are more susceptible to etching by HF …”

Section: Resultsmentioning

confidence: 99%

Interfacial Contact is Required for Metal‐Assisted Plasma Etching of Silicon

Sun

Almquist

2018

Adv Materials Inter

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For decades, fabrication of semiconductor devices has utilized well-established etching techniques to create complex nanostructures in silicon. The most common dry process is reactive ion etching which fabricates nanostructures through the selective removal of unmasked silicon. Generalized enhancements of etching have been reported with mask-enhanced etching with Al, Cr, Cu, and Ag masks, but there is a lack of reports exploring the ability of metallic films to catalytically enhance the local etching of silicon in plasmas. Here, metal-assisted plasma etching (MAPE) is performed using patterned nanometers-thick gold films to catalyze the etching of silicon in an SF6/O2 mixed plasma, selectively increasing the rate of etching by over 1000%. The catalytic enhancement of etching requires direct Si-metal interfacial contact, similar to metal-assisted chemical etching (MACE), but is different in terms of the etching mechanism. The mechanism of MAPE is explored by characterizing the degree of enhancement as a function of Au catalyst configuration and relative oxygen feed concentration, along with the catalytic activities of other common MACE metals including Ag, Pt, and Cu.

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Section: Resultsmentioning

confidence: 99%

Interfacial Contact is Required for Metal‐Assisted Plasma Etching of Silicon

Sun

Almquist

2018

Adv Materials Inter

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“…A similar mechanism was most likely responsible for the formation of macroporous Si with deep pores at lower χ values, except that the higher current densities at the pore end resulted in oxide formation and subsequent hole diffusion [31], resulting in the shallow macropores at the top surface. Such hole diffusion is expected to be particularly significant for highly doped p-type Si because of the positive Schottky barrier height that pulls injected holes away from the metal–Si interface [40]. It is also possible that the relatively high [H 2 O 2 ] to [HF] ratio led to significant Ag dissolution, which in turn resulted in the low density of deep pores in the Si substrate.…”

Section: Resultsmentioning

confidence: 99%

Unraveling the Morphological Evolution and Etching Kinetics of Porous Silicon Nanowires During Metal-Assisted Chemical Etching

et al. 2017

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Many potential applications of porous silicon nanowires (SiNWs) fabricated with metal-assisted chemical etching are highly dependent on the precise control of morphology for device optimization. However, the effects of key etching parameters, such as the amount of deposited metal catalyst, HF–oxidant molar ratio (χ), and solvent concentration, on the morphology and etching kinetics of the SiNWs still have not been fully explored. Here, the changes in the nanostructure and etch rate of degenerately doped p-type silicon in a HF–H2O2–H2O etching system with electrolessly deposited silver catalyst are systematically investigated. The surface morphology is found to evolve from a microporous and cratered structure to a uniform array of SiNWs at sufficiently high χ values. The etch rates at the nanostructure base and tip are correlated with the primary etching induced by Ag and the secondary etching induced by metal ions and diffused holes, respectively. The H2O concentration also affects the χ window where SiNWs form and the etch rates, mainly by modulating the reactant dilution and diffusion rate. By controlling the secondary etching and reactant diffusion via χ and H2O concentration, respectively, the fabrication of highly doped SiNWs with independent control of porosity from length is successfully demonstrated, which can be potentially utilized to improve the performance of SiNW-based devices.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-2156-z) contains supplementary material, which is available to authorized users.

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“…The typical MacEtch process starts by patterning catalysts composed of noble metals (Au, Pt, Pd, Ag, Cu, Ni, etc. ) or graphene on a semiconductor substrate or epitaxial structure. The catalyst layer can be patterned into any arbitrary geometry such as a mesh, dots, or trenches with micro‐ or nano‐scale dimensions .…”

Section: Introductionmentioning

confidence: 99%

Scaling the Aspect Ratio of Nanoscale Closely Packed Silicon Vias by MacEtch: Kinetics of Carrier Generation and Mass Transport

Kim

Mohseni

Balasundaram

et al. 2017

Adv Funct Materials

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Metal-assisted chemical etching (MacEtch) has shown tremendous success as an anisotropic wet etching method to produce ultrahigh aspect ratio semiconductor nanowire arrays, where a metal mesh pattern serves as the catalyst. However, producing vertical via arrays using MacEtch, which requires a pattern of discrete metal disks as the catalyst, has often been challenging because of the detouring of individual catalyst disks off the vertical path while descending, especially at submicron scales. Here, the realization of ordered, vertical, and high aspect ratio silicon via arrays by MacEtch is reported, with diameters scaled from 900 all the way down to sub-100 nm. Systematic variation of the diameter and pitch of the metal catalyst pattern and the etching solution composition allows the extraction of a physical model that, for the first time, clearly reveals the roles of the two fundamental kinetic mechanisms in MacEtch, carrier generation and mass transport. Ordered submicron diameter silicon via arrays with record aspect ratio are produced, which can directly impact the through-silicon-via technology, high density storage, photonic crystal membrane, and other related applications.

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Schottky Barrier Catalysis Mechanism in Metal-Assisted Chemical Etching of Silicon

Cited by 107 publications

References 32 publications

Interfacial Contact is Required for Metal‐Assisted Plasma Etching of Silicon

Interfacial Contact is Required for Metal‐Assisted Plasma Etching of Silicon

Unraveling the Morphological Evolution and Etching Kinetics of Porous Silicon Nanowires During Metal-Assisted Chemical Etching

Scaling the Aspect Ratio of Nanoscale Closely Packed Silicon Vias by MacEtch: Kinetics of Carrier Generation and Mass Transport

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