Hydrofluoric acid plays an important role in industry, but its dangers cannot be ignored. Its use is essential for many industrial processes, including slimming technology, but there is always the possibility of a safety accident. In response, alternative etchants are being developed, and it’s worth discussing whether these technological innovations can be both safe and efficient.
A long time ago, a hydrofluoric acid spill claimed the lives of five workers and caused the evacuation of nearby residents for over a month. The incident sent shockwaves throughout society and served as a wake-up call to the dangers of chemicals. Also, a recent spill of 100 liters of hydrofluoric acid at a chemical plant caused widespread concern. This incident horrified many people and sparked calls for governments and companies to more thoroughly examine the issue of chemical safety management. There have been many other small and large hydrofluoric acid spills that have scared people.
Hydrofluoric acid refers to hydrogen fluoride (HF), a substance that is essential in industrial applications, but also has very dangerous properties. The fluorine ion (F-) in hydrofluoric acid is particularly dangerous compared to other halogen ions. Because of their small size, they easily penetrate skin tissue and are quickly absorbed into the body. Once absorbed, they react with calcium or magnesium ions in the body to form insoluble salts, which can disrupt the body’s electrolyte balance and cause bone damage and severe pain. As a result, workers exposed to hydrofluoric acid suffer extreme pain, sometimes even death. In plants, hydrofluoric acid gas absorbed into plant tissues can be metabolized poorly, causing leaves to turn yellow and die.
Despite these safety concerns, hydrofluoric acid is often used in industry due to its highly corrosive nature. The more hydrofluoric acid is used across industries, the greater the risk of accidents. There are several industries that use hydrofluoric acid, including glass processing, Teflon production, and micromachining of silicon wafers, with silicon micromachining accounting for the largest portion of the Korean industry. In particular, hydrofluoric acid is indispensable in the semiconductor industry, and the solution used to process silicon contains hydrofluoric acid. By adjusting the concentration of hydrofluoric acid, the speed at which the silicon is shaved can be controlled, enabling precise machining in the process.
One type of silicon micromachining technique using hydrofluoric acid is slimming. Slimming refers to the process of reducing the thickness of the glass substrate used in LCDs and AMOLEDs, which is a process in which a thinner display element is obtained by chemical polishing (etching) of the glass substrate after the process of processing the original glass substrate to the panel display element is completed. The recent rapid growth of the mobile smart device market has led to the need for slimmer display panels. This is a testament to the fact that technology is constantly evolving to meet consumer demands.
There are several slimming technologies, depending on the placement of the glass substrate and the type of process, one of which is the dip method. The advantage of the dip method is that it can be easily mass-produced in batches that can accommodate multiple substrates, making it highly competitive in price. However, the disadvantages of the dip method include the possibility of a large number of quality incidents due to the processing of multiple sheets at once, difficulty in automation for large glass substrates, and high consumption of etchant (the solution used for slimming). For this reason, the dip method has been criticized for its efficiency, but it has limitations in terms of safety and quality.
The next method is the side vertical spray (side spray or spray). The advantages of this method are that it is easy to apply to large substrates, has a simple facility structure, and can be easily automated in existing factories. However, the disadvantage is that it is not suitable for mass production due to the small number of pieces that can be processed at a time. In addition, since it is sprayed on the surface of the glass substrate, it is subjected to a large external force and generates a large amount of toxic gas. These disadvantages are directly related to environmental issues, which is why the development of environmentally friendly technologies has been emphasized in recent years.
The third is the horizontal spray down method. Horizontal spraying can be mass-produced and is suitable for stand-alone facilities. The advantages of horizontal spraying are that it is easy to control the thickness and can be monitored. However, when applied to large substrates, it has disadvantages such as unevenness within the glass substrate, long process time, and toxic gas generation. As a result, horizontal spraying is considered to be less environmentally safe, and quality control is difficult, especially when processing large substrates.
In recent years, slimming methods have evolved from dip, which prioritizes productivity, to vertical spray, which prioritizes quality. Not only the semiconductor industry, but the entire industry is showing a trend of prioritizing quality over quantity. In this context, various technical measures are being taken to reduce the risk of hydrofluoric acid, and efforts are being made to develop harmless etchants instead of hydrofluoric acid. These technological developments are seen as an important alternative to hydrofluoric acid spills and are expected to provide a safer working environment.
If these alternatives are indeed developed and commercialized, the hope is that we will no longer see hydrofluoric acid spills in the news. Ultimately, as the industry evolves, new safe technologies will improve our quality of life.
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