Silicon: Can Europe supply itself with the important raw material?
In our series we take a look at how far Germany and Europe could move away from import dependency. What about silicon - sand is everywhere, isn't it?
Silicon wafers with a diameter of 12 inches (30 centimetres).
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The use of silicon is closely linked to the number 9. The semimetal only develops the desired properties when it is produced extremely cleanly. The silicon for a photovoltaic cell should consist of 99.9999 percent silicon atoms. In comparison, a precious gold bar of 24 carat is extremely impure. It only has a purity level of 99.99 percent. But when silicon is used in microelectronics for semiconductors or computer chips, the requirements increase by a factor of a thousand: the chip industry demands a purity of 99.9999999 per cent. This means that there may only be less than one harmful foreign atom per billion parts of silicon.
These figures explain why the search for silicon is not as easy as the composition of the Earth's crust would suggest. Silicon is the second most abundant element (by mass) after oxygen. Nevertheless, there are only a few deposits that can be used for high-tech applications. The sand in the Sahara, for example, is not suitable for extracting silicon because of its composition and the size of the individual grains. Geologists are mainly looking for quartz deposits (chemical: silicon dioxide), which should be as pure as possible.
Shenzhen, Yantian Port
(Bild: zhangyang13576997233 / Shutterstock.com)
The past months have painfully shown that dependence on resources comes at a high price. But can the wheel still be turned back? So let's take a look at the supply situation.
How far Europe could supply itself with strategically important raw materials and what that means for industry is what we want to explore with a raw materials article series.
- New Series: De-Globalisation - How Independent Can Europe Be?
- De-globalisation: Can Europe supply itself with lithium?
- Rare earths and platinum group metals: Can Europe be self-sufficient?
- De-globalisation: Can Europe supply itself with steel and aluminium?
- De-globalisation: Can Europe supply itself with copper?
- Cobalt: Can Europe supply itself with the important raw material?
- De-globalisation: dependence on China remains despite new battery factories
- De-globalisation: How the signs stand for a European solar industry
"High-quality quartz sands are widespread in Germany and are source materials for the production of a wide variety of building materials as well as industrial goods," reports the Federal Institute for Geosciences and Natural Resources (BGR). Germany and Europe can be self-sufficient in the production of glass fibre-reinforced plastics, powerful drinking water filters, abrasive materials, glass containers or discs. Nowadays, glass containers consist on average of 60 per cent recycled waste glass. "Quartz raw materials that can be used to produce pure silicon, on the other hand, are much rarer and are largely imported," the BGR report says.
How silicon is extracted
The semimetal silicon is extracted in two steps. The first step is similar to iron production from iron ore. The silicon is usually released from the silicon oxides with coking coal in the electric arc furnace, which sinks in liquid form in the reactor as raw silicon. But even here, the nature of the oxides is crucial. Quartz sands are so dense because of their small grain sizes that the air cannot circulate sufficiently. The process works best with quartz pebbles or gravels, which at the same time must have a very high silicon oxide content.
The world market for raw silicon is dominated by China, which produces about 70 per cent of the semimetal. But significant quantities are also produced in Norway and Iceland. According to the BGR, the only German silicon smelter south of Passau obtains its raw materials from Bavaria, Austria and the Czech Republic. The main customers are the aluminium industry (alloys) and chemical companies as manufacturers of pure silicon.
The raw silicon must be further purified for high-tech applications such as solar cells, which is how polycrystalline silicon, or polysilicon for short, is produced. In the process, the semimetal is allowed to react with hydrogen chloride to produce liquid trichlorosilane, which is easier to purify via distillation. The trichlorosilane can be decomposed again using various processes, resulting in the separation of high-purity silicon.
Dependence is less due to the silicon itself
According to industry estimates, 80 per cent of the global market is in the hands of a few Chinese suppliers, who provide the raw material for conventional photovoltaic systems, for example. It could increase to 90 per cent by 2024. Germany, however, has so far been able to keep up in this growing market. The company Wacker Chemie is one of the largest producers of polysilicon worldwide. It could presumably cover European demand in high quality. The fact that Germany is dependent on foreign countries for mass-market photovoltaics is therefore less due to the raw materials than to the production, which takes place almost exclusively in Asia. But the market for solar modules is changing. In 2018, 96 percent of the solar cell modules delivered were made of polysilicon. In the meantime, monocrystalline silicon and thin-film cells are playing a growing role.
Silicon recycling
The recycling of discarded photovoltaics is still in its infancy. The first solar modules installed are just reaching the end of their service life. In 2030, however, about 20 million individual modules will be available for recycling each year in Germany.
For semiconductor technology, the market is different again. The polysilicon has to be cleaned again with a very expensive technology so that it can be used in control units, data memories and computers. A ring-shaped induction heater melts a narrow section of a silicon rod, the impurities dissolve in this liquid silicon, the melting zone with the unwanted components moves along the rod to its end. What remains is high-purity silicon with 99.9999999 per cent.
Europe is largely dependent on imports. Only four of the top 35 companies in the semiconductor industry are located in Europe. Within the EU, there is an urgent need for investment in a modern semiconductor ecosystem, according to an assessment by the Bundestag's scientific service. The EU Commission wants to provide eleven billion euros for chip development and production in Europe. In addition, member states are to be allowed to support the construction of chip factories through high subsidies.
The production process requires a lot of know-how, far more than just in the field of silicon production. Meanwhile, many countries assess this knowledge as strategically valuable for their own security. This also applies to Germany. Federal Minister of Economics Habeck therefore banned the takeover of the Munich-based company Siltronic by the Taiwanese competitor Globalwafers at the beginning of 2022. Siltronic produces wafers from hyperpure silicon, the basic material for semiconductor chips.
(jle)
