Samsung Electronics Exploring Recycled Hydrofluoric Acid
06-03-2021 | By Robin Mitchell
Recently, Samsung Electronics announced that it has developed a system for recycling hydrofluoric acid for its semiconductor production lines. What is Hydrofluoric acid's purpose in the semiconductor industry, why has Samsung had to develop a recycling system, and how will this change the semiconductor industry?
What is hydrofluoric acid used for in the semiconductor industry?
Hydrofluoric acid is a chemical that is made up of Hydrogen and Fluorine. When in solution, HF is a hazardous acid to biological matter due to its penetrative properties. If HF comes into contact with skin, the resulting acid doesn't show signs of burns immediately, but instead sinks into the body and causes deep tissue corrosion.
HF is also a major component in the semiconductor industry thanks to its ability to dissolve glass. Silicon wafers are oxidised to create layers of silicon-diode which is an excellent electrical insulator. Furthermore, the growing of oxide layers on silicon allows for carefully controlled layer height, and such layers can reliably be grown to tens of nanometers in thickness.
Once an oxide layer is grown on a wafer, areas need to be removed to make electrical connections with the underlying silicon material. To do this, a layer of etch-resist (which does not dissolve in HF), is spun-coated onto the wafer, and the etch-resist (which is UV curable), has a design patterned to it. Once cleaned, areas which need to have their oxide layer removed are exposed, and submerging the wafer in HL will see these areas etched away.
Japan Bans the Export of Key Semiconductor Compounds
So, HF is clearly of major importance to the semiconductor industry, and as such semiconductor foundries tend to take measures to ensure their supplies of HF and other key compounds. However, back in July 2019, the Japanese government announced that it would ban the export of key compounds for semiconductors including HF to South Korea.
Such news would normally be of little importance until you discover that South Korea is one of the world’s biggest producers of semiconductors. Japan produces 90% of the worlds semiconductor consumables including HF. But why would Japan enforce such a ban on South Korea?
According to Reuters, the ban's cause extends from a court ruling in South Korea that identified Japanese companies who took part in forced labour during WW2, and ordered that those companies must pay compensation as a result. Japan stated that the matter was already settled in 1962, but South Korea has declined this response. As such, Japan decided to fight back and impose the export ban on South Korea's chemicals are heavily dependent on.
Samsung Develops HF Recycling for Semiconductors
The semiconductor industry is arguably the living embodiment of precision; billions of transistors less than 10nm all carefully spaced with no flaws all working in unison. To make such devices, every step of the production process is carefully monitored, and any consumables, whether it be a silicon wafer or a cleaning compound, must be of the highest purity.
As such, you rarely see (if at all), any recycling of components, compounds, or materials. If a piece of silicon does not work, it is binned and crushed into sand. It won’t likely be used to remake a silicon wafer or the chemicals used to make it recycled.
However, the shortage of HF caused by Japan on South Korea has seen Samsung turn to alternative methods to ensure it can continue semiconductors' manufacture. Recently, Samsung announced that it has developed a system for recycling HF acid, which can be reused in the semiconductor production process, reducing the overall quantity of clean HF purchased.
The system developed by Samsung Electronics reuses the HF used in the wafer back surface cleaning process. While the exact process behind the recycling process has not been detailed, Samsung have stated that they have been able to reuse up to 80 percent of the recycled material, and has been proven to work for up to 1,500 products. The recycled HF is to undergo testing on a main production system now, and if successful could see Samsung reduce the quantity of HF purchased by 87%.
Recycling for the Semiconductor Industry
If recycling of compounds and materials can be achieved, the semiconductor industry would undergo a massive change. The end-products produced themselves will not be different, nor will they necessarily be any cheaper, but they will be significantly more environmentally friendly.
The semiconductor industry produces many extremely toxic compounds and by-products which need to be taken care of carefully. Furthermore, the semiconductor industry requires many rare materials that can require mining operations on unimaginable scales which causes significant environmental and social damage.
Thus, recycling and reusing minerals could see less mining operations required, better conditions for poorer areas of the world (as these are disproportionately affected by mining), and a cleaner environment.
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