Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

Rola, Krzysztof; Zubel, Irena

doi:10.1007/s00542-012-1675-x

Cited by 45 publications

(32 citation statements)

References 31 publications

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“…The solutions were modified with alcohols (with one or more hydroxyl group). The alcohols with one hydroxyl group were represented by isopropyl alcohol (IPA); the other alcohols of this group had been already presented in our earlier studies 18 . More attention was devoted to diols (pentanediol and hexanediol), which have much larger atomic mass than isopropanol and contain two active OH -groups in their molecules.…”

Section: Methodsmentioning

confidence: 99%

Behavior of tensioactive compounds in the solutions for silicon anisotropic etching

2013

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In this work, results of measurements of surface tension of KOH and TMAH solutions containing alcohol additives were used to assess the behavior of the alcohols during silicon anisotropic etching. Surface tension of KOH and TMAH solutions containing additives of alcohols with one or more hydroxyl groups as well as etching rates and surface roughness of Si(100) and Si(110) surfaces etched in these solutions were analyzed. An improvement in roughness of both the planes was observed after addition of the alcohols to the KOH and TMAH solutions, however reduction of etching rates of Si(110) planes occurred only in KOH solutions. Based on surface tension measurements, it was stated that reduction of etching rates results from selective adsorption of the surface active compound on Si surfaces, which is possible due to adsorption layer formed on the solution surface of KOH etchant. The adsorption layer does not appear in TMAH + alcohols solutions, which accounts for a different behavior of TMAH-based etchants.

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Section: Methodsmentioning

confidence: 99%

Behavior of tensioactive compounds in the solutions for silicon anisotropic etching

2013

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“…Isopropyl Alcohol (IPA) is a widely known molecule that modulates the etching rate of specific crystallographic planes in KOH wet etching processes. Various authors have suggested that IPA acts as a mask, limiting the access of KOH particles to the surface of the Silicon sample [12,13]. However, no chemical reaction seems to be formed between IPA and silicon atoms, thus acting as a mere modulation agent, rather than an etching stop agent [14].…”

Section: Introductionmentioning

confidence: 99%

“…From the proposed models, this abundance of IPA affects the formation of a linear monolayer of alcohol molecules at the surface of the sample [12,13]. Therefore, the final structure at which a silicon wafer is etched is intrinsically dependent on both the crystallographic orientation of the wafer and the type of chemicals used in the etching solution.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Wet Etching of Silicon through Isopropanol Alcohol Evaporation

et al. 2015

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Abstract:In this paper, Isopropanol (IPA) availability during the anisotropic etching of silicon in Potassium Hydroxide (KOH) solutions was investigated. Squares of 8 to 40 µm were patterned to (100) oriented silicon wafers through DWL (Direct Writing Laser) photolithography. The wet etching process was performed inside an open HDPE (High Density Polyethylene) flask with ultrasonic agitation. IPA volume and evaporation was studied in a dynamic etching process, and subsequent influence on the silicon etching was inspected. For the tested conditions, evaporation rates for water vapor and IPA were determined as approximately 0.0417 mL/min and 0.175 mL/min, respectively. Results demonstrate that IPA availability, and not concentration, plays an important role in the definition of the final structure. Transversal SEM (Scanning Electron Microscopy) analysis demonstrates a correlation between microloading effects (as a consequence of structure spacing) and the angle formed towards the (100) plane.

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“…Saturation of the solution with butyl alcohols not only yields striped {110} planes, but also roughens the (100) surface [13]- [15]. Although the smoothness of (110) surface is improved at low alcohols concentrations (below the saturation level), the (100) surface is covered with pyramidal hillocks [16], [17]. Furthermore, controlling the composition of the non-saturated solution is difficult due to the evaporation of alcohol at elevated temperatures during the etching process.…”

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Triton Surfactant as an Additive to KOH Silicon Etchant

Rola

Zubel

2013

J. Microelectromech. Syst.

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Anisotropic etching of Si (100) and (110) planes in alkaline solutions containing the nonionic surfactant is studied in this paper. Triton X-100 surfactant, normally used for the modification of TMAH (tetramethylammonium hydroxide) etchant, is added to KOH (potassium hydroxide) solution. As a result, the (100) and (110) etch rates are significantly reduced and the etch rate ratio R(100)/R(110) >1 is obtained. The influence of KOH concentration (at 10 and 100 ppm (v/v) of the surfactant) on the etching process is also investigated. Low roughness of (110) surface is achieved in the 2 M KOH solution containing Triton. The smooth {110} sidewall planes inclined at 45°toward the (100) substrate are fabricated by etching in the KOH + Triton solution. The 45°{110} sidewalls are potentially attractive as MEMS micromirrors for optical beam reflection at an angle of 90°. The low etch rate of (100) plane is kind of a disadvantage of the fabrication method, but it can be fairly overcome by elevating the process temperature and stirring the etching solution.[ 2012-0371]Index Terms-Anisotropic etching, potassium hydroxide (KOH), silicon, surfactant, Triton X-100.

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Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

Cited by 45 publications

References 31 publications

Behavior of tensioactive compounds in the solutions for silicon anisotropic etching

Behavior of tensioactive compounds in the solutions for silicon anisotropic etching

Dynamic Wet Etching of Silicon through Isopropanol Alcohol Evaporation

Triton Surfactant as an Additive to KOH Silicon Etchant

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