Forced and Natural Convection Effects on the Shape Evolution of Cavities during Wet Chemical Etching

Shin, Chee Burm; Economou, Demetre J.

doi:10.1149/1.2085623

Cited by 51 publications

(53 citation statements)

References 6 publications

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“…WCE has been modeled using asymptotic solution [5], moving grid (MG) approach [6][7][8][9][10][11] and level-set method [12][13][14]. One-dimensional [10] and two-dimensional [5][6][7][8][9]11] diffusion-controlled [5][6][7][8][9] and reactioncontrolled [6,[8][9][10][11] etching were examined.…”

Section: Introductionmentioning

confidence: 99%

“…One-dimensional [10] and two-dimensional [5][6][7][8][9]11] diffusion-controlled [5][6][7][8][9] and reactioncontrolled [6,[8][9][10][11] etching were examined. The effects of natural and forced convection were studied by Shin and Economou [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…As a result of the mesh velocities, a diffusion problem becomes a convection-diffusion problem and a convection term must be included in the governing equation [6,11]. Further, an unstructured mesh or a body-fitted grid system is needed to model multidimensional WCE [6,8,9,11].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A fixed-grid approach for diffusion- and reaction-controlled wet chemical etching

Rath¹,

Chai²,

Lam³

et al. 2005

International Journal of Heat and Mass Transfer

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A fixed-grid approach for diffusion- and reaction-controlled wet chemical etching

Rath¹,

Chai²,

Lam³

et al. 2005

International Journal of Heat and Mass Transfer

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“…If the fluid has a uniform density in the etch-hole, the flow problem can be solved independently of the concentration problem. Several papers were written based on finite-element or finite-volume approaches [2,9,11,12,13,24,25,26] for the computation of the fluid flow in an etched cavity. In [23] a boundary-element method is used.…”

Section: Introductionmentioning

confidence: 99%

Mass transport in a partially covered fluid-filled cavity

Driesen¹,

Kuerten²,

Kuiken³

2000

International Journal of Heat and Mass Transfer

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Abstract. A method of computing the concentration field of dissolved material inside an etch-hole is presented. Using a number of assumptions, approximate convectiondiffusion equations are formulated, and analytical descriptions for the concentration in different parts of the domain are obtained. By coupling these descriptions the concentration field can be computed. The assumptions and the results are validated by comparison with solutions based on a finite-volume method. Results of the boundary-layer method are given for two characteristic etch-hole geometries. The described boundarylayer method is efficient in terms of computational time and memory, because it does not require the construction of a computational grid in the interior of the domain. This advantage will be exploited in a future paper where the method will be used to simulate wet-chemical etching.

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“…The observed leveling and brightening effect is caused by the mass transfer limitation of the dissolution process 18 and is frequently linked to the formation of oxide or salt films along the surface. 19 Which type of mass transfer dominates the dissolution process -whether it is diffusion, natural or forced convection -thus has a marked influence on the resulting shape profiles [20][21][22][23][24][25][26] and depends on the hydrodynamic conditions in the electrochemical cell.…”

mentioning

confidence: 99%

Through-Mask Electrochemical Micromachining of Aluminum in Phosphoric Acid

Baldhoff

Nock

Marshall

2017

J. Electrochem. Soc.

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Aluminum micro-channels have been machined in phosphoric acid via mass-transfer limited electrochemical dissolution through photoresist masks. The results of shape evolution experiments using a rotating disk electrode are presented in terms of the dimensions, shape profile and uniformity of the machined micro-channels. The influences of applied potential, cumulative passed charge and hydrodynamic conditions on the shape evolution process are discussed. Experimental results are compared with a shape evolution model assuming the rate of aluminum removal is solely controlled by diffusive mass transfer. The degree of agreement between experimental and simulated results depends mainly on the hydrodynamic conditions in the electrochemical cell and indicates a shift from purely diffusive to mixed convective-diffusive mass transfer. Through-Mask Electrochemical Micromachining (TMEMM) is an unconventional machining process, in which a metal substrate is made the anode in an electrochemical cell and thereby dissolved.1,2 Localized material removal is achieved by covering the substrate with an insulating mask. The use of common photolithography processes for the creation of the mask enables the fabrication of micrometer-sized structures. Thereby, TMEMM can be used in two ways to fabricate microfluidic devices: firstly, cavities and channels can be machined into the substrate surface and secondly, through-holes and slits can be machined into metal foils or shims.1 Compared to classical wet chemical and dry etching processes, TMEMM offers higher rates of material removal, better control of surface finish, more selective machining of substrates and enhanced process safety. [3][4][5] In addition, combining photolithography with electrochemical dissolution processes is expected to enable the fabrication of a large number of microfluidic devices in parallel and at low cost. 6Aluminum is widely used as a construction material for the manufacture of microfluidic devices such as micro-heat exchangers, 7 microreactors 8 and micro-fuel cells. 9 Other areas of interest are the fabrication of intricate parts in optical, electronic, automotive and aerospace systems. 10,11 Its chief advantages compared to other materials used in these fields are its high thermal conductivity, low electrical resistivity, easy machinability and low density. In addition, it is possible to modify the surface structure of aluminum substrates via the formation of highly ordered, porous oxide films along the surface. 12,13 It has been demonstrated, that these films can be subsequently used to incorporate noble metal catalysts along the surface of micro-channels within a micro-reactor. [14][15][16] Electrochemical dissolution of aluminum in phosphoric acid is known to produce reflective aluminum surfaces with sub-micrometer surface roughness at sufficiently high electrolyte concentration and temperature.17 This property makes it attractive for TMEMM of micrometer-sized structures made from aluminum. The observed leveling and brightening effect is caused by the m...

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Forced and Natural Convection Effects on the Shape Evolution of Cavities during Wet Chemical Etching

Abstract: This work was supported by EPRI Contract No. RP8001-4. The authors would like to thank F. Goodman of EPRI and G. Fiegl of UniSil for the helpful discussions and the growth of MCZ samples.

Cited by 51 publications

References 6 publications

A fixed-grid approach for diffusion- and reaction-controlled wet chemical etching

A fixed-grid approach for diffusion- and reaction-controlled wet chemical etching

Mass transport in a partially covered fluid-filled cavity

Through-Mask Electrochemical Micromachining of Aluminum in Phosphoric Acid

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