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Huh, I just realized that I have no idea about two fundamental questions re: semiconductor fabrication. 1) Do fabs make their own silicon wafers? 2) Are silicon

by daeken 6y ago

Huh, I just realized that I have no idea about two fundamental questions re: semiconductor fabrication. 1) Do fabs make their own silicon wafers? 2) Are silicon crystals for wafers made from sand relatively directly, or is it broken down and then reformed? I can't think of it and my google-fu is failing me, but I know there's a simple compound that reacts with water to create (relatively) pure silicon dioxide, so I'm wondering if that -- or something like it -- is used.

pjc50 6y ago
https://en.wikipedia.org/wiki/Czochralski_method https://en.wikipedia.org/wiki/Czochralski_method The sand isn't particularly important. What matters is the huge amount of etchants and dopants used on it. It's more important to have somewhere you can dump a load of used carbon tetrachloride. Quite a lot of the US's old fabs are now Superfund sites.
selimthegrim 6y ago
Silane?
marcosdumay 6y ago
> Do fabs make their own silicon wafers? (Did you mean ) The answer to that oscillates from "yes" to "no" all the time. Last time I saw, only the highest tech ones did that by themselves. > Are silicon crystals for wafers made from sand relatively directly, or is it broken down and then reformed? I don't completely understand that question. But silicon crystals are composed of pure silicon, while sand is composed of silicon oxide. On the cases where silicon is refined from sand (there are many kinds of silicon oxide), people reduce it with carbon in a furnace, like they do with iron. After refined it goes into further purification and in some cases a different process that solidifies it into a single crystal. So there is a lot of processing.
bcaa7f3a8bbc 6y ago
Silicon refinery and wafer production are highly specialized industrial divisions. Most fabs don't produce their own wafers, although some of the biggest players have their own subsidiaries. * TSMC / WaferTech subsidiary https://en.wikipedia.org/wiki/TSMC#WaferTech_subsidiary https://en.wikipedia.org/wiki/TSMC#WaferTech_subsidiary WaferTech, a subsidiary of TSMC, is a pure-play semiconductor foundry located in Camas, Washington, USA. It is the second largest pure-play foundry in the United States. The facility employs 1100 workers.[citation needed] The largest is GlobalFoundries Fab 8 in Malta, NY, which employes over 3,000 workers with over 278,709 m2 (3,000,000 sq ft) under rooftop. WaferTech was established in June 1996 as a joint venture with TSMC, Altera, Analog Devices, and ISSI as key partners. The four companies along with minor individual investors invested US$1.2 billion into this venture, which was at the time the single largest startup investment in the state of Washington. The company started production in July 1998 in its 200 mm (8 in) semiconductor fabrication plant. Its first product was a 0.35 micrometer part for Altera. TSMC bought out the joint venture partners in 2000 and acquired full control, and currently operates it as a fully owned subsidiary. --- Even before you start making wafer, you need to have pure silicon, which requires a massive industrial refinery operation. See: * Silicon Production https://en.wikipedia.org/wiki/Silicon#Production https://en.wikipedia.org/wiki/Silicon#Production Silicon of 96–99% purity is made by reducing quartzite or sand with highly pure coke. However, even greater purity is needed for semiconductor applications, and this is produced from the reduction of tetrachlorosilane (silicon tetrachloride) or trichlorosilane. The former is made by chlorinating scrap silicon and the latter is a byproduct of silicone production. These compounds are volatile and hence can be purified by repeated fractional distillation, followed by reduction to elemental silicon with very pure zinc metal as the reducing agent. The spongy pieces of silicon thus produced are melted and then grown to form cylindrical single crystals, before being purified by zone refining. Other routes use the thermal decomposition of silane or tetraiodosilane (SiI4). Another process used is the reduction of sodium hexafluorosilicate, a common waste product of the phosphate fertilizer industry, by metallic sodium: this is highly exothermic and hence requires no outside fuel source. Hyperfine silicon is made at a higher purity than almost every other material: transistor production requires impurity levels in silicon crystals less than 1 part per 1010, and in special cases impurity levels below 1 part per 1012 are needed and attained. Then... * Czochralski method https://en.wikipedia.org/wiki/Czochralski_method https://en.wikipedia.org/wiki/Czochralski_method High-purity, semiconductor-grade silicon (only a few parts per million of impurities) is melted in a crucible at 1,425 °C (2,597 °F; 1,698 K), usually made of quartz. Dopant impurity atoms such as boron or phosphorus can be added to the molten silicon in precise amounts to dope the silicon, thus changing it into p-type or n-type silicon, with different electronic properties. A precisely oriented rod-mounted seed crystal is dipped into the molten silicon. The seed crystal's rod is slowly pulled upwards and rotated simultaneously. By precisely controlling the temperature gradients, rate of pulling and speed of rotation, it is possible to extract a large, single-crystal, cylindrical ingot from the melt. Occurrence of unwanted instabilities in the melt can be avoided by investigating and visualizing the temperature and velocity fields during the crystal growth process. This process is normally performed in an inert atmosphere, such as argon, in an inert chamber, such as quartz.
korethr 6y ago
Answering your second question, Silicon wafers are made from from an ingot of monocrystaline silicon[1], as the fault line formed from the boundary between two crystals could interfere with circuit operation. Said ingots are often made with the Czochralski method, wherein a seed crystal is dipped into a crucible of molten silicon and slowly pulled upward. The silicon required for this process is nine-9s purity, so there'd be a number of steps beforehand to convert sand or even relatively pure silicon dioxide to such highly-pure silicon. Given the carefully-controlled conditions required, it's an expensive process. Whether fabs in-house their wafer production or farm it out to a supporting firm, I don't know. I could see it going both ways. I'd not be surprised if Intel or TSMC had their own in-house wafer or ingot production. But, there's more fabs than just Intel and TSMC, so I'd guess the smaller operations would get their wafers from a company that specializes in creating them. 1. https://en.wikipedia.org/wiki/Monocrystalline_silicon https://en.wikipedia.org/wiki/Monocrystalline_silicon 2. https://en.wikipedia.org/wiki/Czochralski_method https://en.wikipedia.org/wiki/Czochralski_method

by daeken 6y ago

pjc50 6y ago

https://en.wikipedia.org/wiki/Czochralski_method https://en.wikipedia.org/wiki/Czochralski_method The sand isn't particularly important. What matters is the huge amount of etchants and dopants used on it. It's more important to have somewhere you can dump a load of used carbon tetrachloride. Quite a lot of the US's old fabs are now Superfund sites.

selimthegrim 6y ago

Silane?

marcosdumay 6y ago

> Do fabs make their own silicon wafers? (Did you mean ) The answer to that oscillates from "yes" to "no" all the time. Last time I saw, only the highest tech ones did that by themselves. > Are silicon crystals for wafers made from sand relatively directly, or is it broken down and then reformed? I don't completely understand that question. But silicon crystals are composed of pure silicon, while sand is composed of silicon oxide. On the cases where silicon is refined from sand (there are many kinds of silicon oxide), people reduce it with carbon in a furnace, like they do with iron. After refined it goes into further purification and in some cases a different process that solidifies it into a single crystal. So there is a lot of processing.

bcaa7f3a8bbc 6y ago

Silicon refinery and wafer production are highly specialized industrial divisions. Most fabs don't produce their own wafers, although some of the biggest players have their own subsidiaries. * TSMC / WaferTech subsidiary https://en.wikipedia.org/wiki/TSMC#WaferTech_subsidiary https://en.wikipedia.org/wiki/TSMC#WaferTech_subsidiary WaferTech, a subsidiary of TSMC, is a pure-play semiconductor foundry located in Camas, Washington, USA. It is the second largest pure-play foundry in the United States. The facility employs 1100 workers.[citation needed] The largest is GlobalFoundries Fab 8 in Malta, NY, which employes over 3,000 workers with over 278,709 m2 (3,000,000 sq ft) under rooftop. WaferTech was established in June 1996 as a joint venture with TSMC, Altera, Analog Devices, and ISSI as key partners. The four companies along with minor individual investors invested US$1.2 billion into this venture, which was at the time the single largest startup investment in the state of Washington. The company started production in July 1998 in its 200 mm (8 in) semiconductor fabrication plant. Its first product was a 0.35 micrometer part for Altera. TSMC bought out the joint venture partners in 2000 and acquired full control, and currently operates it as a fully owned subsidiary. --- Even before you start making wafer, you need to have pure silicon, which requires a massive industrial refinery operation. See: * Silicon Production https://en.wikipedia.org/wiki/Silicon#Production https://en.wikipedia.org/wiki/Silicon#Production Silicon of 96–99% purity is made by reducing quartzite or sand with highly pure coke. However, even greater purity is needed for semiconductor applications, and this is produced from the reduction of tetrachlorosilane (silicon tetrachloride) or trichlorosilane. The former is made by chlorinating scrap silicon and the latter is a byproduct of silicone production. These compounds are volatile and hence can be purified by repeated fractional distillation, followed by reduction to elemental silicon with very pure zinc metal as the reducing agent. The spongy pieces of silicon thus produced are melted and then grown to form cylindrical single crystals, before being purified by zone refining. Other routes use the thermal decomposition of silane or tetraiodosilane (SiI4). Another process used is the reduction of sodium hexafluorosilicate, a common waste product of the phosphate fertilizer industry, by metallic sodium: this is highly exothermic and hence requires no outside fuel source. Hyperfine silicon is made at a higher purity than almost every other material: transistor production requires impurity levels in silicon crystals less than 1 part per 1010, and in special cases impurity levels below 1 part per 1012 are needed and attained. Then... * Czochralski method https://en.wikipedia.org/wiki/Czochralski_method https://en.wikipedia.org/wiki/Czochralski_method High-purity, semiconductor-grade silicon (only a few parts per million of impurities) is melted in a crucible at 1,425 °C (2,597 °F; 1,698 K), usually made of quartz. Dopant impurity atoms such as boron or phosphorus can be added to the molten silicon in precise amounts to dope the silicon, thus changing it into p-type or n-type silicon, with different electronic properties. A precisely oriented rod-mounted seed crystal is dipped into the molten silicon. The seed crystal's rod is slowly pulled upwards and rotated simultaneously. By precisely controlling the temperature gradients, rate of pulling and speed of rotation, it is possible to extract a large, single-crystal, cylindrical ingot from the melt. Occurrence of unwanted instabilities in the melt can be avoided by investigating and visualizing the temperature and velocity fields during the crystal growth process. This process is normally performed in an inert atmosphere, such as argon, in an inert chamber, such as quartz.

korethr 6y ago

Answering your second question, Silicon wafers are made from from an ingot of monocrystaline silicon[1], as the fault line formed from the boundary between two crystals could interfere with circuit operation. Said ingots are often made with the Czochralski method, wherein a seed crystal is dipped into a crucible of molten silicon and slowly pulled upward. The silicon required for this process is nine-9s purity, so there'd be a number of steps beforehand to convert sand or even relatively pure silicon dioxide to such highly-pure silicon. Given the carefully-controlled conditions required, it's an expensive process. Whether fabs in-house their wafer production or farm it out to a supporting firm, I don't know. I could see it going both ways. I'd not be surprised if Intel or TSMC had their own in-house wafer or ingot production. But, there's more fabs than just Intel and TSMC, so I'd guess the smaller operations would get their wafers from a company that specializes in creating them. 1. https://en.wikipedia.org/wiki/Monocrystalline_silicon https://en.wikipedia.org/wiki/Monocrystalline_silicon 2. https://en.wikipedia.org/wiki/Czochralski_method https://en.wikipedia.org/wiki/Czochralski_method