Hydrofluoric Acid Etching
Hydrofluoric Acid Etching - Related Videos
09:15
Light Enhanced Hydrofluoric Acid Passivation: A Sensitive Technique for Detecting Bulk Silicon Defects
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Cited by 6 •
2016
A RT liquid surface passivation technique to investigate the recombination activity of bulk silicon defects is described. For the technique to be successful, three critical steps are required: (i) chemical cleaning and etching of silicon, (ii) immersion of silicon in 15% hydrofluoric acid and (iii) illumination for 1 min.
03:27
Mixtures of Acids
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2020
The pH of a solution containing an acid can be determined using its acid dissociation constant and its initial concentration. If a solution contains two different acids, then its pH can be determined using one of several methods depending upon the relative strength of the acids and their dissociation constants. A Mixture of a Strong Acid and a Weak Acid In a mixture of a strong acid and a weak acid, the strong acid dissociates completely and becomes a source of almost all the hydronium ions...
03:05
Acid Strength and Molecular Structure
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2020
Binary Acids and Bases In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with increasing...
03:38
Polyprotic Acids
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2020
Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are: Monoprotic acids: Reactions with water HCl (aq) + H2O (l) ⟶ H3O+ (aq) + Cl− (aq) HNO3 (aq) + H2O (l) ⟶ H3O+ (aq) + NO3− (aq) HCN (aq) + H2O (l) ⇌ H3O+ (aq) + CN− (aq) Even though it contains four hydrogen...
11:19
Safe Handling of Mineral Acids
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2023
Source: Robert M. Rioux & Taslima A. Zaman, Pennsylvania State University, University Park, PA A mineral acid (or inorganic acid) is defined as a water-soluble acid derived from inorganic minerals by chemical reaction as opposed to organic acids (e.g. acetic acid, formic acid). Examples of mineral acids include: • Boric acid (CAS No.10043-35-3) • Chromic acid (CAS No.1333-82-0) • Hydrochloric acid (CAS No.7647-01-0) • Hydrofluoric acid (CAS No. 7664-39-3) • Nitric acid (CAS No. 7697-37-2) •...
FAQs
At the molecular level, hydrofluoric acid etching attacks the Si–O bonds that give silicon dioxide and glass their structure. The reaction forms soluble fluoride species, allowing material to be removed rather than merely displaced. This chemical pathway supports controlled clearing of oxide regions during microscale fabrication and other engineering surface treatments.
Etch rate and uniformity are governed by several interacting conditions rather than acid concentration alone. Changes in concentration, temperature, agitation, exposure time, or surface composition can alter how quickly and evenly material is removed. Engineers therefore treat these variables as a coordinated process window when precise features or consistent oxide clearing are required.
Surface composition determines where the treatment can act effectively. Silicon dioxide and glass are prominent targets, so regions containing these materials can be cleared while other surface areas may respond differently. This material dependence matters when engineers need selective oxide removal, controlled texturing, or a prepared surface without treating every component identically.
An engineering workflow begins by identifying the intended material removal and the composition of the surface being treated. The process then sets acid concentration, temperature, agitation, and exposure time, followed by controlled exposure within specialized equipment and containment. Maintaining these conditions helps produce the intended removal and uniformity while supporting required handling procedures.
Applications include semiconductor patterning, microelectromechanical systems fabrication, glass texturing, and surface preparation for bonding or coating. In each case, the value comes from controlling where oxide or glass is removed and how uniformly the surface changes. This selectivity supports microscale features as well as engineered surface conditions for later processing.
Because hydrofluoric acid is extremely toxic and corrosive, the process requires specialized equipment, containment, and handling procedures rather than ordinary open laboratory treatment. These safeguards are part of process design, not an afterthought. They enable engineers to manage exposure while controlling the concentration, temperature, agitation, and time needed for reproducible surface modification.