Hello everyone, this is a popular science article about the most basic raw material in the chip field, “monocrystalline silicon rod”. This is a magical rod!
Before we start, please let me say something else briefly. Some readers may find that the title of this article has an additional prefix “The World of Chips丨”.
Chips have special significance to our country and are the biggest bottleneck in our country’s science and technology field. This chip also tortures the hearts of countless readers. Everyone is looking forward to a breakthrough in my country’s chip technology, looking forward to the birth of 5nm lithography machines, looking forward to Huawei standing up and roaring at the United States, looking forward to our own entity list being filled with American companies…
Technological progress takes time. In order to allow readers who don’t know about chips to know more about chips during the long wait, and to better digest various chip-related information, I plan to write a few more articles around chips. Articles, strive to form a series. If you are interested in my articles, please follow me!
The content of the article will focus on chip design and production. Chip design includes basic knowledge, design tools, instruction sets and architecture, chip product design, etc.; chip production includes raw materials, manufacturing equipment, production, packaging and testing, etc. After reading this, you will find that photolithography machines are just a drop in the ocean of the chip industry, and the world of chips is really huge!
The content of the article strives to be understandable by liberal arts students. While reading, everyone should feel like cheering for my country’s chip industry!
Let’s get into the main text next, thank you all for your patience!
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Silicon is the third most abundant element on earth.
The first is iron, which accounts for about 32%. The interior of the earth is basically a big hot iron core;
The second is oxygen, which accounts for about 30%. It mainly exists in the earth’s crust and the air and is the basis of various compounds.
Silicon, accounting for about 15%, is mainly found in the earth’s crust and is widely found in minerals, rocks and sand in the form of compounds such as silica and various silicates.
We should remember one scientist, the Swedish chemist Jons Jakob Berzelius, who discovered silicon as an element in 1823.
There are some interesting things about silicon, here are two:
Silicon was formerly called silicon (xi sounds), which is transliterated from the English Silicon. Because it is easily confused with other chemical elements “tin” and “selenium” with the same pronunciation, our mainland changed it to silicon in 1953. Hong Kong, Macao and Taiwan also use the word “Si”, such as “Si Valley” (Silicon Valley), so don’t think it’s a typo when you see Silicon Valley.
Silicon and carbon are elements of the same family. Silicon content in the earth is 15%, while carbon belongs to others, and together with 109 other elements, it only accounts for 1.2%. However, life on earth is carbon-based, which does not make sense in terms of probability. Therefore, some people believe that life on earth originated from alien planets, which means that we humans are colonizers of the earth. Doesn’t this sound like science fiction? Of course, more scientists believe that carbon is more active than silicon and can easily form macromolecular organic matter with other elements, so the aliens’ views are just for everyone’s entertainment. There are also some scientists who firmly believe that there are indeed silicon-based life forms in the universe, the kind that do not need to breathe oxygen.
Silicon has so many uses and is an element that modern people cannot live without. Industrial silicon for smelting, organic silicon for chemical industry, polycrystalline silicon for photovoltaics, silicon powder for commercial concrete (tong ersheng), and monocrystalline silicon for chips. It can be said that silicon can be used in the hall and in the kitchen!
Semiconductor properties of silicon
Regarding the theoretical knowledge of why chips must use semiconductors, we will leave it to a follow-up article. Here we will popularize the semiconductor characteristics of silicon.
The discovery of silicon semiconductor properties was a tortuous process. After the discovery of silicon element, people’s understanding of silicon was very confused. Is silicon a metal or an insulator? People at that time had a relatively simple understanding and believed that metal was a conductor, and if it was not a metal, it must be an insulator. This debate lasted for more than 100 years, and it was finally discovered that silicon is neither a metal nor an insulator, but a semiconductor!
The semiconductor properties of silicon, academically speaking, are because when silicon atoms form crystals, they have three energy bands: conduction band, forbidden band and valence band. If there are electrons in the conduction band, they can move and conduct electricity. Unfortunately, electrons are usually in the valence band, separated from the conduction band by a forbidden band. However, under certain conditions, such as voltage, current, light, heat and other factors, the electrons jump over the forbidden band and jump to the conduction band, so they can conduct electricity.
If any readers are still unclear, let me give you another vivid example:
The price band of silicon crystal is equivalent to a country’s domestic, the forbidden band is equivalent to customs, and the conductive band is equivalent to a flight abroad. Electronics are domestic people. Usually, you cannot go abroad without a passport and visa. Customs will stop you. But once you get your passport and visa, you can go through customs and get on your flight abroad without any hassle. Passports and visas are equivalent to voltage, current, light and heat.
By the way, the electrons in the conductor are equivalent to people with foreign green cards, who can go abroad at will. The electrons in the insulator are equivalent to those in the system whose passports are collected by the organization and cannot go anywhere.
In fact, the semiconductor properties of pure silicon are not practical because its bandgap is awkward:
For low-voltage applications, such as chips, its bandgap is too wide, which means customs procedures are too cumbersome. Therefore, in practical applications, other elements must be added to adjust the forbidden band, usually boron and phosphorus, to form an impurity energy band between the forbidden band and the conduction band, which is equivalent to simplifying customs procedures and providing one-stop customs clearance.
For high-voltage applications, such as high-power devices, the forbidden band is too narrow, which is equivalent to lax customs supervision. Once there is a violation, it will be unstoppable. Therefore, a wider bandgap is needed, and the third-generation semiconductor silicon carbide and gallium arsenide came into being. My other articles have mentioned the third-generation semiconductor.
This article mainly discusses low-voltage chips for computers and mobile phones, so impurities must be added to pure silicon. To add impurities, you must first have pure monocrystalline silicon. Next, let’s talk about the production of monocrystalline silicon.
Readers who can read this, I admire you, please come on!
Monocrystalline silicon rod
Monocrystalline silicon rod
The rod in the picture above is our protagonist today—monocrystalline silicon rod.
Silicon is the purest substance that humans can extract so far. The highest purity can reach 99.99999999999999%. There is no need to count, there are 16 nines in total! It’s really like a dream! It can be said that pure silicon represents the purity of love better than diamonds!
The purity of silicon is generally represented by N, N