The Chemistry of Wet Etching

Knotter, D. Martin

doi:10.1002/9781118071748.ch3

Cited by 14 publications

(20 citation statements)

References 41 publications

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“…A closer look at the chemistry of fluoride solutions also showed that there are opportunities to shift equilibrium to equal extraction of zeolite framework cations. 17,18 The present study will explore these opportunities further and develop a method to indiscriminately etch zeolite crystals with fluoride anions and its use in the preparation of hierarchical zeolites without changing their framework composition.…”

Section: Introductionmentioning

confidence: 99%

Chemical Equilibrium Controlled Etching of MFI-Type Zeolite and Its Influence on Zeolite Structure, Acidity, and Catalytic Activity

et al. 2013

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Chemical etching with fluoride ions is a new approach for secondary porosity engineering of aluminosilicate zeolite frameworks. We show that diluted HF solutions extract preferentially aluminum from zeolite frameworks. The Brønsted acidity of ZSM-5 treated in such a way decreases, while its structure is unaffected after an HF treatment. With higher HF concentrations, the number of undissociated HF molecules and the concentration of HF2 – ions, extracting indiscriminately Al and Si, increase. The addition of NH4F shifts the chemical equilibria to produce more HF2 –, avoiding the use of highly concentrated HF solutions; it also suppresses HF dissociation. The etching selectivity of such solutions is concentration-independent and extracts indiscriminately both framework Si and Al. Zeolite dissolution in NH4F-HF solutions starts preferentially at small intergrowth domains and goes deeply in the crystals without a substantial increase of the external surface area. Macropores are produced without altering zeolite acidity. Hierarchical materials obtained by these two approaches are characterized extensively by complementary methods and the catalytic impact illustrated in the m-xylene conversion.

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Section: Introductionmentioning

confidence: 99%

Chemical Equilibrium Controlled Etching of MFI-Type Zeolite and Its Influence on Zeolite Structure, Acidity, and Catalytic Activity

et al. 2013

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“…From the results described in Figures –, an Si 3 N 4 etching mechanism in superheated water with carboxylic acid is proposed. As shown in Figure , NH 2 detaches relatively quickly from the Si 3 N 4 surface in carboxylic-acid-containing superheated water, and a dangling bond is formed on the Si atom on the Si 3 N 4 surface . Then, a nucleophilic carboxylate ion (RCOO – ) approaches positively charged Si and forms an Si–OOCR bond.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Silicon nitride (Si 3 N 4 ) is widely used as an insulating or sacrificial layer in various electronic devices. − Removal of the Si 3 N 4 thin film is often needed and has generally been performed in phosphoric acid (H 3 PO 4 ) solution at a high temperature. − It has been reported that Si 3 N 4 is etched by the nucleophilic attack of H 2 PO 4 – and H 2 O present in the H 3 PO 4 solution . However, because a high temperature and high concentration of acidic solution are required to remove Si 3 N 4 , environment, health, and safety (EHS) issues may occur.…”

Section: Introductionmentioning

confidence: 99%

Addition of Carboxylic Acids to Superheated Water for the Environmentally Benign Removal of Silicon Nitrides

Son

Park

Lim

2021

ACS Sustainable Chem. Eng.

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The conventional Si 3 N 4 etching process using H 3 PO 4 or HF may cause environment, health, and safety issues. In this study, by adding ionic compounds and carboxylic acids to superheated water, the etching of Si 3 N 4 was demonstrated without the use of H 3 PO 4 and HF. In ionic-compound-containing superheated water, the etching rate of Si 3 N 4 (R Si 3 N 4 ) showed a strong dependence on the OH − concentration: R Si 3 N 4 ≈ 170[OH − ] 0.12 . However, the material loss of the Si substrate is inevitable because of the high OH − concentration in aqueous solution. The addition of carboxylic acid to superheated water also increased the etching rate of Si 3 N 4 . In carboxylic-acid-containing superheated water, the etching rate of Si 3 N 4 was dependent on the concentration of the carboxylate ion, RCOO − , rather than the OH − concentration: R Si 3 N 4 ≈ 351[RCOO − ] 0.49 = 7.6 × 10 −4 [OH − ] −0.49 . It is suggested that RCOO − breaks the Si−N bond of Si 3 N 4 and forms Si−(OOCR) n in an S N 2-like reaction. Finally, Si 3 N 4 is etched in the form of Si(OH) 4 in the superheated water containing carboxylic acids. In addition, this new aqueous process significantly reduced the material loss of the Si substrate that can occur during the etching of Si 3 N 4 . Since the use of H 3 PO 4 or HF is avoided entirely, the ecofriendly Si 3 N 4 etching process described in this study may reduce the potential environmental and safety problems associated with the conventional Si 3 N 4 etching process.

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“…(2) The aqueous KOH solution, which is known for etching SiO2 [39], can dissolve silicon with the reaction scheme shown in Eq. 3 [40].…”

Section: Kmno Mno2 + 2k2o + 3 O2mentioning

confidence: 99%

Low-Profile Interconnects via Laser-Induced Forward Transfer

2018

JLMN

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Laser-induced backside wet etching (LIBWE) is a method for the precise etching and structuring of SiO2. In this study, LIBWE is performed by using ultrashort laser pulses with a pulse duration of τ = 500 fs and a wavelength of λ = 515 nm. Saturated aqueous KMnO4 solution is the absorbing liquid for the LIBWE process. The observed etching rate is approximately 10-3 nm/pulse, which is substantially lower than that in previous reports; it increases with increasing laser fluence. The initial etching rate decreases with higher pulse numbers until it approaches a stable value. After the LIBWE, the generated etching pits are partially covered by MnOx layers with thicknesses of tens of nanometers. However, at the etched SiO2 surface, two different laser-induced periodic surface structures (LIPSS) are found. In the center of the etching pits, LIPSS with a period of λHSFL ≈ (52 ± 2) nm are observed, whereas in the outer areas, LIPSS with a period of λLSFL ≈ (390 ± 20) nm are found. The etching mechanism for the LIBWE of SiO2 with aqueous KMnO4 solution is proposed to comprise laser-based heating, decomposition of KMnO4, and chemical etching of the SiO2 surface by the produced KOH.

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The Chemistry of Wet Etching

Cited by 14 publications

References 41 publications

Chemical Equilibrium Controlled Etching of MFI-Type Zeolite and Its Influence on Zeolite Structure, Acidity, and Catalytic Activity

Chemical Equilibrium Controlled Etching of MFI-Type Zeolite and Its Influence on Zeolite Structure, Acidity, and Catalytic Activity

Addition of Carboxylic Acids to Superheated Water for the Environmentally Benign Removal of Silicon Nitrides

Low-Profile Interconnects via Laser-Induced Forward Transfer

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