Progress in Research and Development of Hydrofluoric Acid Production Methods and Processes (Review)

Introduction to Hydrofluoric Acid
Hydrofluoric acid (HF) is an aqueous solution of hydrogen fluoride (HF) gas, which is a colorless, transparent liquid with a strong irritant odor and extremely corrosive properties. Due to its ability to corrode glass, it is known as "bone water" in industry and is a crucial but extremely dangerous chemical.
Hydrofluoric acid is the basic raw material of the fluorine chemical industry and is widely used in important fields of the national economy. The semiconductor industry is one of the most advanced applications of hydrofluoric acid. The use of its ability to dissolve silicon dioxide for cleaning and etching in the chip manufacturing process is a key material that determines chip performance.
Basic production methods of hydrofluoric acid
The mainstream industrial method: The most commonly used method currently is the "fluorite+concentrated sulfuric acid" method.
Raw materials: Fluorite (calcium fluoride CaF ₂) and concentrated sulfuric acid H ₂ SO ₄
Typical reaction: CaF ₂+H ₂ SO ₄ → 2 HF+CaSO ₄
After condensing and purifying the generated HF, dissolve it in water to obtain hydrofluoric acid. Further dehydration and distillation can yield anhydrous hydrogen fluoride.
Progress in Production Process Research and Development
1. High purity, semiconductor applications
The demand for "ultra-high purity hydrofluoric acid" and "anhydrous hydrofluoric acid" in the semiconductor application field is increasing day by day. Therefore, purification processes that can minimize metal impurities, silicon, and particulate matter content are constantly being improved.
Electronic material manufacturers are developing ultra-high purity processes that combine rectification, ion exchange, and filtration technologies, and are continuously committed to achieving purity levels of 7N or higher.
2. Recycling and utilization of etching solution and wastewater treatment
In recent years, "recycling and reuse" has become a major trend.
The technology of separating, recovering, and reusing acidic components from hydrofluoric acid (HF) wastewater used in semiconductor and glass cleaning processes has been put into practical application and used to achieve zero wastewater discharge and fluorine resource recovery in processing plants.
A system for regenerating hydrofluoric acid during glass cleaning, which can restore the etching ability of hydrofluoric acid and reduce the generation of waste acid, aiming to achieve "zero waste" of fluorine.
In addition, "fluorine adsorbents" for selective adsorption and recovery of hydrofluoric acid have also been developed, aiming to achieve the recycling and utilization of hydrofluoric acid.
3. Using by-product fluorosilicic acid to produce hydrogen fluoride
In order to reduce dependence on fluorite, the process of producing anhydrous hydrogen fluoride using the by-product "fluorosilicic acid (H ₂ SiF ₆)" from phosphate fertilizer production has received attention.
The typical processing method is as follows:
Neutralize H ₂ SiF ₆ with alkali (such as metal carbonate) to generate fluoride salts, such as NaF ₂.
React the fluoride salt with other components to selectively precipitate (e.g., generate Na∝ AlF ₆).
Then, the generated fluoride is treated with acid, similar to the treatment method of fluorite, to regenerate HF.
Research focus:
Design a process for removing phosphorus and metal impurities from H ₂ SiF ₆
Separate SiO ₂ derived components while maintaining high fluoride yield
Integrated process for purifying fluoride to high purity and returning it to the HF production line
4. Recovering fluorine from exhaust gas
Development of "Dry Waste Gas Treatment Technology": While dry treating fluorine-containing waste gas from semiconductor factories and other sources, fluorine is recovered and extracted from waste gas containing NF ∝ and HF for reuse.

Research and development direction summary: Although the synthesis reaction of hydrofluoric acid itself has not undergone significant changes, progress has been made in related processes and sustainability
Future research and development direction
The following ideas are considered to have research and development prospects:
1. Scale up and cost evaluation of waste acid regeneration process
2. Verify whether the quality of HF derived from by-products such as H ₂ SiF ₆ can reach semiconductor level
3. Optimize the combination of dry exhaust gas treatment and wet scrubbers
4. Closed loop design connecting high-purity HF production line and recycling production line