Silicon is the foundation of semiconductor industry. Taiwan controls the global semiconductor industry. So we should ask one more question: Where does silicon come from?
"One Sand, One World" is not suitable for use in semiconductor industry, because silicon, which makes Taiwan dominate the world, is from the most inconspicuous sand. Silicon elements exist in nature in the form of silicon dioxide (SiO₂) and have a very high content on the earth, which can be seen on sand beaches. Although ordinary sand can also be used to improve silicon, in order to pursue higher purity, modern semiconductor industries mainly use "quartz sand" with extremely high silicon purity is also called "silica sand". This material mainly comes from winding wool and quartz minerals. Its silicon content is as high as 95%, not only has less complexity, but also has more suitable physical structures for melting and crystallization growth.
1. From sand to high-purity polycrystalline silicon: "Crystals" like brown sugar to white sugarAlthough natural quartz sand can be obtained in a large number in a specific area, it is rare to become a semiconductor industry as large as Taiwan, because the subsequent processes are not simple at all. Three processes are required to go through from quartz sand to silicon.
The silicon in silicon dioxide is very tightly combined with oxygen atoms and cannot be used directly. It must be restored at a high temperature first. This process is usually carried out in large arc furnaces, producing a reduction reaction with silicon dioxide, carbon (such as coal and wood chips) at high temperatures up to 1800°C:
SiO₂ + 2C → Si + 2CO↑
The obtained product is called metallurgical silicon (MG-Si), with a purity of about 98-99%. It can be used in industrial construction materials, such as elbow steel and aluminum silicon alloys. Millions of metallurgical silicon are produced every year around the world, of which less than 1%, and will enter the next stage.
In order to reach a world with a pureness of more than 99%, this batch of MG-Si will first react with hydrogen chloride and transform into trichlorosilane (SiHCl₃). This liquid silicon enters the process of the Siemens Process and heats to 1,100°C in a clock-shaped device. Then, the dielectric texture is dissipated through distillation, and the trichlorosilane is gasified and reduced, and the concentration is formed in the reaction furnace to form a high-purity polysilicon (Polysilicon) with a solidity of up to 11N, which is 99.9999999999999, a total of 11 one 9.
▲ Ximen method: Si + 3HCl → SiHCl₃ + H₂ (Source: Rfassbind, Public domain, via Wikimedia Commons)
This is like the process of refining brown sugar into white sugar step by step. This pure technology is of great importance, because pureness will directly affect the "yield" and stability of subsequent chip processes. However, the appearance of the polycrystalline silicon is still slightly rough at this time and has not yet reached the flatness that can be used to make the wafer, so we still need to enter the next key step.
2. Pull out the single crystal silicon rod after "Crystal": "Swirl Pull" like making cotton candyHigh-purity polycrystalline silicon not only has no external appearance, but also has no internal structure. Therefore, the next step is to convert it into Monocrystalline Silicon, which is a silicon material with a unified structure arranged without grain boundaries.
This process is called the Czochralski Process, also called the direct or trolling method. The specific method is to put polycrystalline silicon into the crucible and melt it at high temperature, and then slowly insert a "crystal rod" made of single crystal silicon into the molten silicon, while controlling the rotation and upward speed. In this way, the silicon atoms will start crystallizing according to the arrangement of crystals, gradually forming a "single crystal silicon rod".
▲ Chaiklasky method. (source: Twisp, Public domain, via Wikimedia Commons)
This process is a bit like making marshmallows: the sugar cube is pulled and stacked in the turn. This "single crystal silicon rod" pulled from silicon will be cut into pieces as thin as paper. This is the familiar silicon wafer (wafer) that we are familiar with, transformed into the core foundation of smart phones, computers and various computing components.
Currently, silicon wafer manufacturing technology is mainly controlled by Japanese companies, including Shin-Etsu Chemical, Sumco and Taiwan's Global Wafers. Shin-Etsu Chemical has controlled more than 30% of the global market and is the main raw material supplier for OEM factories such as Taiwan.
Starting from an inconspicuous sand, it has been lifted through high temperature, purified layer, precision crystallization and cutting, and finally became the world's most advanced processor base. Each silicon wafer contains tens of billions of transistors, supporting the computing needs of mobile phones, computers, drivers, and AI servers. It has also made Taiwan arriving as the world's most important "silicon island" and mastering the world's scientific and technological industry. A world of sand and a world, a flower is a paradise. Now Taiwan’s semiconductor industry has become a ray of blooming flowers.