The purity of the reduced silicon is mostly 98% to 99.9%, which is called metallurgical grade silicon (MG-Si). Metallurgical grade silicon, also known as industrial silicon, chemical silicon, crystalline silicon or metallic silicon, is mainly used as an additive for non-ferrous alloys, as an alloying agent for silicon steel, and as a deoxidizer for smelting special steel and non-ferrous alloys. After a series of process treatments, industrial silicon can be drawn into monocrystalline silicon for use in the electronics industry and for the production of organic silicon in the chemical industry. Therefore, it is called magic metal and has a wide range of uses. The industrial silicon produced in China was originally metallurgical silicon. The production of industrial silicon has been mainly developed since the mid-1990s. In recent years, the output and export of chemical silicon in China have grown rapidly. In recent years, from a global perspective, the main exporters of industrial silicon are China, Norway, Brazil, South Africa, etc.; the countries that import industrial silicon are mainly Japan, Western Europe, North America and some countries in Southeast Asia. Since 2000, China’s annual industrial silicon output has reached more than 400,000 tons, accounting for about one-third of the world’s total industrial silicon output. The annual export volume has exceeded 300,000 tons, and it has been exported to more than 50 countries and regions. At present, China’s industrial silicon production capacity, output and export growth rank first in the world. Most of the industrial silicon produced in China is exported, and it is the world’s largest industrial silicon exporter, except for exports to Japan, South Korea, and some countries in Southeast Asia. It also exports to some countries in North America, Western Europe and North Africa.
The purity of metallic silicon is usually expressed as the percentage of the content of the three main impurities, iron, aluminum, and calcium. If the content of iron, aluminum, and calcium are 0.4%, 0.3%, and 0.2%, it is called 432. The content of calcium in these three impurities is usually less than one thousandth, just add a “0” in front of this position. For example, the content of iron, aluminum, and calcium are respectively: 0.2%, 0.2%, and 0.03%, converted into One part per million (10-6), the content of iron, aluminum, and calcium is 2000×10-6, 2000×10-6, 300×10-6, and the unit of polysilicon impurity concentration is generally expressed by 10-6, and 1×10-6 is 6N . In the metal silicon industry, three elements are mainly concerned: iron, aluminum, and calcium. If the sum of the three elements is less than 1%, it can be called 99% metallic silicon. If the sum of the content of these three elements is less than 0.1%, it can be called 3N metallic silicon. The physical method of polysilicon is directly purified by metallic silicon. This habit, because boron and phosphorus play a key role in the production of solar cells, so boron and phosphorus must be added. Of course, carbon, oxygen, nitrogen, hydrogen and other elements also play an important role. If the sum of these elements is less than 1×10-6, it can be called 6N; if the sum of these elements is less than 10×10-6, it is called 5N. Of course, there are also questions here: Do other elements also need to be removed? In fact, it is rare to use a figure obtained by subtracting the sum of 108 elements outside of silicon by 100% to express the purity of silicon. Therefore, we can also express the content of a certain element separately. At present, with a precision of 10-6, the most common instrument for measuring element content is the inductively coupled plasma emission spectrometer (ICP-AES). If the accuracy is higher, you can use the inductively coupled plasma mass spectrometer (ICP-MS). When the impurity content is expressed by 10-6, there is a difference between the concentration calculated by weight (mass) and the one-millionth calculated by atomic density. The latter means that there are several impurity atoms per million silicon atoms. For the same material, there is a certain correspondence between one part per million calculated by weight (mass) and one part million calculated by atomic density, and its ratio is the ratio of the atomic weight of silicon atoms and impurity atoms. same. For example, the atomic weight of silicon is 28 and the atomic weight of boron is 11. If the concentration of boron is calculated by weight (mass) as 4×10-6, the corresponding value calculated by atomic density is 4×10-6x28÷11=10.2×10-6
The production scene of metal silicon and metal silicon products are shown in Figure 1 and Figure 2.
Ubora wa silicon ya chini ni 98% hadi 99.9%, ambayo inaitwa silicon ya daraja la metallurgical (MGS). Silicon ya kiwango cha metallurgical, pia inajulikana kama silicon ya viwanda, silicon ya kemikali, silicon ya kioo au silicon ya chuma, hutumiwa hasa kama nyongeza ya alloys zisizo za chuma, kama wakala wa alloying kwa chuma cha silicon, na kama deoxidizer kwa kutengeneza chuma maalum na alloys zisizo za chuma. Baada ya mfululizo wa matibabu ya mchakato, silicon ya viwanda inaweza kuchukuliwa katika silicon monocrystalline kwa ajili ya matumizi katika sekta ya elektroniki na kwa ajili ya uzalishaji wa silicon kikaboni katika sekta ya kemikali. Kwa hiyo, inaitwa chuma cha kichawi na inatumiwa kwa njia mbalimbali. Silicon ya viwanda iliyotengenezwa nchini China awali ilikuwa silicon ya metallurgical. Kwa mfano, silicon ya viwanda imekuwa ikitengenezwa kwa kasi zaidi tangu miaka ya 1990. Katika miaka ya hivi karibuni, uzalishaji na mauzo ya nje ya silicon kemikali katika China wamekua kwa kasi. Katika miaka ya hivi karibuni, kutoka mtazamo wa kimataifa, wauzaji wakuu wa silicon ya viwanda ni China, Norway, Brazil, Afrika Kusini, nk. Nchi zinazopeleka silicon kwa viwanda ni Japan, Ulaya Magharibi, Amerika ya Kaskazini na baadhi ya nchi za Asia ya Kusini Mashariki. Tangu mwaka 2000, China inazalisha zaidi ya tani 400,000 za silicon kila mwaka, na ni theluthi moja ya jumla ya silicon ulimwenguni. Kiasi cha kila mwaka cha mauzo ya nje imezidi tani 300,000, na imeuzwa kwa nchi zaidi ya 50 na mikoa. Kwa sasa, China viwanda silicon uzalishaji uwezo, pato na mauzo ya nje ukuaji nafasi ya kwanza katika dunia. Silicon ya viwanda inazalishwa nchini China ni zaidi ya mauzo ya nje, na ni nchi ya kwanza duniani ya kuuza nje silicon ya viwanda, isipokuwa kwa mauzo ya nje ya Japan, Korea Kusini, na baadhi ya nchi katika Asia ya Kusini. Pia inasafirisha kwa baadhi ya nchi katika Amerika ya Kaskazini, Ulaya Magharibi na Afrika Kaskazini. Usafi wa silicon ya chuma kwa kawaida huonyeshwa kama asilimia ya maudhui ya uchafu kuu tatu, chuma, alumini, na kalsiamu. Ikiwa kiwango cha chuma, alumini na kalsiamu ni 0.4%, 0.3%, na 0.2%, inaitwa 432. Kwa kawaida, kiasi cha kalsiamu katika uchafu huu wa tatu ni chini ya sehemu moja ya elfu, tu kuongeza <unk> 0 <unk> mbele ya nafasi hii. Kwa mfano, kiwango cha chuma, alumini na kalsiamu ni 0.2%, 0.2%, na 0.03%, iliyobadilishwa kuwa sehemu moja kwa milioni (10-6), kiwango cha chuma, alumini na kalsiamu ni 2000×106 na 300×106 na kitengo cha mkusanyiko wa uchafu wa polysilicon kwa ujumla huonyeshwa na 106, na 1×106 ni 6N. Katika sekta ya chuma silicon, elementi tatu ni hasa wasiwasi: chuma, alumini, na kalsiamu. Ikiwa jumla ya vipengele hivyo vitatu ni chini ya 1%, inaweza kuitwa silicon ya chuma ya 99%. Ikiwa jumla ya vipengele hivyo vitatu ni chini ya 0.1%, inaweza kuitwa silicon ya chuma ya 3N. Njia ya kimwili ya polysilicon ni moja kwa moja kusafishwa na silicon chuma. Kwa sababu boroni na fosforasi ni muhimu katika uzalishaji wa seli za jua, boroni na fosforasi lazima ziongezwe. Bila shaka, kaboni, oksijeni, nitrojeni, hidrojeni na elementi nyinginezo pia zina fungu muhimu. Ikiwa jumla ya vipengele hivyo ni chini ya 1 × 10 6 inaweza kuitwa 6N, ikiwa jumla ya vipengele hivyo ni chini ya 10 × 10 6 inaweza kuitwa 5N. Bila shaka, kuna maswali pia hapa: Je, mambo mengine pia yanahitaji kuondolewa? Kwa kweli, ni nadra kutumia takwimu inayopatikana kwa kuondoa jumla ya elementi 108 nje ya silicon kwa 100% ili kuelezea usafi wa silicon. Kwa hiyo, tunaweza pia kuelezea maudhui ya kipengele fulani kando. Kwa sasa, kwa usahihi wa 10-6, chombo cha kawaida cha kupima maudhui ya elementi ni inductively coupled plasma emission spectrometer (ICP-AES). Kwa mfano, kwa ajili ya uchunguzi wa maambukizi ya chembechembe, unaweza kutumia inductively coupled plasma mass spectrometer (ICMS). Wakati maudhui ya uchafuzi ni kuonyeshwa kwa 10-6, kuna tofauti kati ya mkusanyiko mahesabu kwa uzito (wingi) na moja ya milioni mahesabu kwa wiani atomiki. Ya mwisho inamaanisha kwamba kuna atomu kadhaa za uchafu kwa kila atomu milioni ya silicon. Kwa nyenzo moja, kuna uwiano fulani kati ya sehemu moja kwa milioni, kulingana na uzito (wingi), na sehemu moja kwa milioni, kulingana na wiani wa atomu, na uwiano ni uwiano wa uzito wa atomu ya silicon na atomu ya uchafu. sawa. Kwa mfano, uzito wa atomu ya silicon ni 28 na uzito wa atomu ya boroni ni 11. Kwa mfano, ikiwa kiwango cha boroni kinahesabiwa kwa uzito (wingi) kama 4 × 10 6 (mfano wa chuma cha silicon), basi thamani inayolingana na wiani wa atomiki ni 4 × 10 6 × 28 × 11 = 10.2 × 10 6 (mfano wa chuma cha silicon na bidhaa za chuma cha silicon).