Original title:We're running out of sand!Don't worry, it's not the main thing we use to make chips

Original link:http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2019-09/18/content_431001.htm?div=0

　　In mobile phones, computers, smart watches and other electronic devices, chips are the most core components。The chip is also the most integrated component in the semiconductor industry, and the silicon material used in its production is mainly derived from sand。

　　Recently, the British "Nature" magazine reported that the current speed of mining sand and gravel has exceeded the speed of its natural recovery。As a result, the demand for sand on Earth may soon exceed the supply。For a time, the news of "sand is almost gone" triggered hot discussion on the Internet。

　　Silicon is the cornerstone of the semiconductor industry, and sand is an important raw material for extracting silicon。For nearly half a century, the rapid development of the semiconductor industry has caused excessive mining of sand？Whether the depletion of sand resources will lead to the development crisis of the semiconductor industry？

　　On the above issues, science and Technology Daily reporter interviewed relevant experts in the industry。

　　Stand out with large stock and easy purification

　　Sand is a relatively rich substance in the Earth's crust, and the element silicon contained in the sand is the second largest component element in the earth's crust, accounting for about 25% of the total mass of the crust。There are two main types of sand: natural sand and mechanical sand, natural sand can be divided into river sand, sea sand and mountain sand。

　　So why is silicon the building block for semiconductor devices？

　　"This is mainly because silicon is chemically stable and has excellent semiconductor properties;Secondly, the reserves of silicon are extremely rich, with an abundance of up to 27 percent in the Earth's crust.72%。Chang Shuai, an associate researcher at the School of Materials, Beijing Institute of Technology, said in an interview with Science and Technology Daily that in addition, monocrystalline silicon production technology is now very mature, and related silicon-based semiconductor manufacturing processes such as doping and lithography have also been popular, and manufacturing costs are relatively controllable。

　　Yellow River upstream hydropower Development Co., Ltd. is a company engaged in silicon material manufacturing, its Qinghai new energy branch deputy general manager Qin Rong in an interview with Science and Technology Daily reporter also pointed out that the reason why silicon has become the semiconductor industry's "soul" raw materials, mainly determined by the chemical properties of silicon。

　　"In industrial production, it is relatively easy to purify silicon and achieve very high purity。With the characteristics of large stock and easy purification, the manufacturing cost of silicon materials is getting lower and lower, which also reduces the pricing of terminal products such as mobile phones and computers to a certain extent。In the past, laptops cost tens of thousands of yuan, but now you can buy a well-configured computer for only a few thousand yuan。"Qin Rong said。

　　What process does it take for sand to become silicon？

　　First of all, carbon is used to extract silicon from silica rich sand, and through the reduction of charcoal powder, the silica in the sand is converted into a silicon material with a purity of more than 98%, which is also known as industrial silicon。However, industrial silicon with 98% purity can not be used for chip manufacturing, and some chemical processes need to be applied to further purify industrial silicon。The purified silicon belongs to polysilicon or amorphous silicon, and although the purity of the silicon is up to the standard, it still cannot be directly applied to the first-line production of precision semiconductor devices due to the chaotic arrangement of atoms inside it。Therefore, it is necessary to make monocrystalline silicon by some methods。In the actual production operation, the staff mainly converts polysilicon or amorphous silicon into monocrystalline silicon ingot by direct-pull method or zone-melting method。

　　"In short, only high-purity monocrystalline silicon can be used as a production material。"Chang Shuai said。

　　The semiconductor industry uses very limited amounts of silicon

　　Sand is the world's largest demand for natural resources after air and water, and it is also an essential basic raw material for human production activities。

　　Statistics show that the current global annual production of sand is about 50 billion tons。The British "Nature" journal article pointed out that this amount is higher than the natural regeneration rate。By the middle of the century, demand may exceed supply。Recently, a report from the United Nations Environment Programme showed that in the last 20 years, with the change of consumption patterns, population growth, urbanization and infrastructure development, human demand for sand has tripled。

　　So, whether the global sand stock is enough for the future development of the semiconductor industry？Will the dwindling sand stock trigger an increase in raw material prices for the semiconductor industry？

　　Chang Shuai believes that there is not much correlation between the rapid development of the semiconductor industry and the excessive mining of gravel。"In fact, the shortage of sand reported by Nature is most likely to occur in the construction industry, because there are certain standards for construction sand, sand in the desert or sea sand generally do not meet the requirements, only river sand is suitable.。In addition, the rapid development of the construction industry in recent years has caused the rate of river sand mining and consumption around the world to exceed the natural recovery rate。”他说。

　　Chang Shuai also proposed that the silicon material used in the semiconductor industry is not the main source of river sand, but a variety of silicon-containing ores, such as gangue quartz and quartz gravel。The reserves of these ores in the Earth are very large, and the consumption of silicon materials in the semiconductor industry is much smaller than that in the construction industry, so the problem of "not enough sand" will not become a bottleneck in the development of the semiconductor industry。

　　"The global annual polysilicon capacity is about 640,000 tons, and only 30,000 tons are used to make chips;Silicon materials for semiconductors account for only 5% of the total production of silicon materials。The semiconductor industry uses very little silicon, and even if there is not enough sand, it is difficult to trigger an overall increase in raw material prices。Qin Rong said that in fact, in the entire application of silicon materials, semiconductors are only a small application field, a large number of silicon materials, such as solar grade silicon, silicone, etc., are used in construction, transportation, chemical, textile, food, medical and other fields。

　　"Many things in our daily life will be applied to silicon, such as optical fiber for communication, pesticides, shampoo, cosmetics, etc., but we rarely pay attention to it.。"Qin Rong said。

　　There is currently no substitute for silicon

　　Although less sand will have a significant impact on the semiconductor industry in the short term, there is also a looming concern about whether there is a new raw material that can replace silicon if sand is really gone one day？

　　In this regard, Qin Rong and Chang Shuai both believe that with today's level of technology, it is difficult to find alternative raw materials。

　　"There are no new substances that can replace silicon。According to Qin Rong, Moore's Law, the "first law of information technology," states that the number of components that can be accommodated on an integrated circuit approximately doubles every 18 months。"The number of components can not grow without limit, the number of integrated components per unit area will reach the limit, and then there will inevitably be new technologies, but when can appear unknown, so semiconductor device manufacturing will still follow the existing process, silicon will still be the main manufacturing material?。”她说。

　　In addition to technical factors, cost is the biggest consideration when looking for alternative materials。

　　Qin Rong believes that in the space, military and other fields with less cost consideration and higher technical reliability requirements, silicon materials may be affordable alternatives。But in most areas, replacing the existing "cheap" silicon with other materials is likely to cause the cost of electronic information products to skyrocket。

　　Chang Shuai's opinion supports the above statement。He thinks，Currently in the field of materials，Scientists have carried out various studies on new materials to replace silicon materials，But these studies are mostly centered around making up for some inherent flaws in silicon materials，For example, the carrier mobility of silicon materials is not fast enough, and the transparency and luminescence are poor，These disadvantages limit its application in some fields of semiconductors。

　　"For a variety of new materials, whether it is the early gallium arsenide or the current hot graphene, or a variety of organic semiconductor materials, they are subject to cumbersome processes or high costs in practical applications, and can not shake the dominance of silicon materials.。And while some materials may be able to outperform silicon in one way or another, they have shortcomings in other ways。Perhaps in the near future, when the material technology is breakthrough, these shortcomings are overcome, then the replacement of silicon materials will really appear。"Chang Shuai said。