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Ammonium fluoride is a critical component of buffered oxide etch (BOE), a wet etchant used in microfabrication. It acts as the buffering agent in a solution of concentrated HF , creating an etchant with a more controllable rate of etching (than that of simple concentrated HF solutions).
Hydrogen fluoride does not boil until 20 °C in contrast to the heavier hydrogen halides, which boil between −85 °C (−120 °F) and −35 °C (−30 °F). [6] [7] [8] This hydrogen bonding between HF molecules gives rise to high viscosity in the liquid phase and lower than expected pressure in the gas phase.
Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water.Solutions of HF are colorless, acidic and highly corrosive.A common concentration is 49% (48–52%) but there are also stronger solutions (e.g. 70%) and pure HF has a boiling point near room temperature.
The Sb–F bonds are 2.02 Å within the eight-membered Sb 4 F 4 ring; the remaining fluoride ligands radiating from the four Sb centers are shorter at 1.82 Å. [7] The related species PF 5 and AsF 5 are monomeric in the solid and liquid states, probably due to the smaller sizes of the central atom, which limits their coordination number.
Ammonium bifluoride, as its name indicates, contains an ammonium cation ([NH 4] +), and a bifluoride (or hydrogen difluoride) anion ([HF 2] −).The triatomic bifluoride anion features a strong three-center four-electron bond (specifically, a symmetrical hydrogen bond) with a bond energy greater than 155 kJ/mol, [2] and an H-F length of 114 pm. [3]
Tetra-n-butylammonium fluoride, commonly abbreviated to TBAF and n-Bu 4 NF, is a quaternary ammonium salt with the chemical formula (CH 3 CH 2 CH 2 CH 2) 4 N + F −. It is commercially available as the white solid trihydrate and as a solution in tetrahydrofuran. TBAF is used as a source of fluoride ion in organic solvents. [1]
Buffered oxide etch (BOE), also known as buffered HF or BHF, is a wet etchant used in microfabrication.It is a mixture of a buffering agent, such as ammonium fluoride NH 4 F, and hydrofluoric acid (HF).
Because the fluoride anion is highly basic, many alkali metal fluorides form bifluorides with the formula MHF 2. Sodium and potassium bifluorides are significant to the chemical industry. [ 2 ] Among other monofluorides, only silver(I) [ 3 ] and thallium(I) [ 4 ] fluorides are well-characterized.