Silicon is the cornerstone of semiconductor industry, and sand is an important raw material for extracting silicon. Has the rapid development of semiconductor industry in the past half century resulted in over-exploitation of sand? Will the depletion of sand resources lead to the development crisis of semiconductor industry?
On the above issues, the Science and Technology Daily reporter interviewed relevant experts in the industry.
Because of the large stock, it is easy to purify and stand out.
Sand is a rich material in the earth's crust. Silicon is the second largest element in the earth's crust, accounting for about 25% of the total crustal mass. There are two main types of sand: natural sand and mechanized sand. Natural sand can also be divided into river sand, sea sand and mountain sand.
So why is silicon the basic material for making semiconductor devices?
"this is mainly due to the stable chemical properties of silicon and its excellent semiconductor properties. Secondly, the reserves of silicon are extremely rich, and the abundance in the crust is as high as 27.72%." Chang Shuai, an associate researcher at Beijing Institute of Technology Institute of Materials, said in an interview with Science and Technology Daily that in addition, monosylsilicon production technology is very mature, related semiconductor manufacturing processes based on silicon chips, such as doping, lithography and so on, have also been popularized, and the manufacturing cost is relatively controllable.
Qin Rong, deputy general manager of Qinghai New Energy Branch, also pointed out in an interview with Sci-tech Daily that the reason why silicon has become the "soul" raw material of semiconductor industry is mainly determined by the chemical properties of silicon.
"in industrial production, it is easy to purify silicon and can achieve 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 to a certain extent.cellphoneThe pricing of end products such as computers. In the past, laptops often cost tens of thousands of yuan, but now you can buy a well-equipped computer for only a few thousand yuan. " Qin Rong said.
How does it go to change sand into silicon?
First, silicon should be extracted from silica-rich sand with carbon and converted into silicon material with purity of more than 98 percent by carbon powder reduction, also known as industrial silicon, Chang said. However, 98% industrial silicon can not be used in chip manufacturing, and some chemical processes need to be used to further purify industrial silicon. The purified silicon belongs to polysilicon or amorphous silicon. Although the purity of silicon is up to standard, it can not be directly used in the first-line production of precision semiconductor devices because of the confusion of its internal atomic arrangement. Therefore, it is necessary to make monosylsilicon into silicon material with purity up to standard by some methods. In the actual production operation, the staff mainly converts polysilicon or amorphous silicon into single silicon ingot by Czochralski method or zone melting method.
"in short, only high purity monosylsilicon can be used as a production material." Chang Shuai said.
Silicon used in semiconductor industry is very limited
Sand is second only to air, water, the world's largest demand for natural resources, but also an indispensable basic raw material for human production.
Statistics show that the annual output of global sand is about 50 billion tons. According to an article in the British Journal Nature, this amount is higher than the natural regeneration rate. By the middle of this century, demand may exceed supply. Not long ago, a report from the United Nations Environment Programme (UNEP) showed that in the past 20 years, human demand for sand has tripled with changes in consumption patterns, population growth, urbanization and infrastructure development.
So, is the global sand stock enough for the future development of the semiconductor industry? Will the decrease of sand stock lead to an increase in the price of raw materials in the semiconductor industry?
Chang Shuai believes that there is not much correlation between the rapid development of the semiconductor industry and excessive gravel mining. "In fact, the shortage of sand reported in Nature is most likely to occur in the construction industry, because there are certain standards for building sand, sand in 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 led to the exploitation and consumption rate of river sand in the world exceeding the natural recovery rate. He said.
Chang Shuai also pointed out that the main source of silicon materials used in semiconductor industry is not river sand, but all kinds of silicon-bearing ores, such as vein quartz, quartz gravel and so on. These ores have very large reserves on the earth, and the consumption of silicon materials in semiconductor, a highly sophisticated chemical industry, is much smaller than that in the construction industry, so the problem of "insufficient sand" will not become a bottleneck in the development of the semiconductor industry.
"The annual production capacity of polycrystalline silicon is about 640,000 tons, only 30,000 tons are used to make chips, and silicon materials for semiconductors account for only 5% of the total output of silicon materials. Semiconductor industry uses very little silicon, even if the sand is really not enough, it is difficult to trigger the overall rise in raw material prices. Qin Rong said that in fact, semiconductor is only a small application area in the whole application of silicon materials. A large number of silicon materials, such as solar grade silicon and silicone, are used in construction, transportation, chemical industry, textile, food, medical and other fields.
"A lot of things in our daily lives are applied to silicon elements, such as optical fiber for communication, pesticides, shampoo, cosmetics and so on, but we pay little attention to it." Qin Rong said.
There is no substitute for silicon at present.
Although in the short term, there is no need to worry that less sand will have a significant impact on the semiconductor industry, but we will also have a vague concern: if one day sand is really gone, is there a new raw material that can replace silicon?
In this regard, Qin Rong and Chang Shuai both believe that it is still difficult to find alternative raw materials at the present level of technology.
"there is no new substance to replace silicon at present." Qin Rong said that Moore's Law, the first law of information technology, says the number of components that can be accommodated on integrated circuits roughly doubles every 18 months. "it is impossible to increase the number of components without restriction, and the number of components that can be integrated per unit area will reach the limit, after which new technologies will inevitably emerge, but it is not known when they will appear, so semiconductor device manufacturing will continue to follow the existing process, and silicon will still be the main manufacturing material." She said.
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, which have less cost considerations and higher technical reliability requirements, silicon substitutes may be available. In most areas, however, switching to other materials by replacing existing "affordable" silicon is likely to lead to a sharp rise in the cost of electronic information products.
Chang Shuai's point of view supports the above statement. He believes that in the field of materials, although scientists have carried out various studies on new materials to replace silicon materials, these studies mainly focus on remedying some inherent defects of silicon materials, such as the carrier mobility of silicon materials is not fast enough, transparency and poor luminescence, which limit its semiconductivity. Applications in some fields.
"for all kinds of new materials, whether early gallium arsenide or hot graphene, or all kinds of organic semiconductor materials, they are restricted by tedious process or high cost in practical application, and can not shake the dominant position of silicon materials. Moreover, although some materials may outperform silicon in some aspects, there are some shortcomings in one way or another. Perhaps in the near future, when material technology breaks through, these shortcomings will be overcome, then the replacement of silicon materials will really appear. " Chang Shuai said.