Analysis: What Happened and Why for the Semiconductor Industry.
A gigantic explosion at a semiconductor factory stunned the electronic grid last month. This article discusses what happened and its consequences for the semiconductor industry.
The explosion occurred at the Mitsubishi Materials Yokkaichi plant in Yokkaichi, Mie Prefecture, at about 2 p.m. on Jan. 9. Five people were killed and 12 others were injured, some seriously.
Mitsubishi Materials issued press releases (reference 1 and reference 2) in the days following the explosion. The company attributed the explosion to the removal of the heat exchanger from the hydrogen purification apparatus following a routine cleaning process. The explosion occurred when the cover of the appliance was opened after the pre-wash was completed. The company found that there had been no further damage to the surrounding machinery, leading it to conclude that the heat exchanger itself was the cause of the explosion; The exact cause is still under investigation.
The heat exchanger, coated with trichlorosilane (HCi3Si) for maintenance and inspection work, was cleaned with water just prior to the incident. The explosion was so strong that it ripped off the lid, 1 meter in diameter and weighing 440 pounds, 10 meters.
Mitsubishi Materials President Yao Hiroshi, during his New Year’s speech (reference 3) on Jan. 6—three days before the explosion—identified “CSR, health and safety” as one of the four major challenges for the company. “The safety of employees should be addressed at high priority. We will continue to increase the awareness on safety to ensure compliance with the basic rules towards realizing the aim to achieve ‘zero accidents’ in the plant.”
Mitsubishi shut down the plant in the wake of the accident. No date has been given for its planned reopening.
Nissin Chemical is part of the Shin-Etsu group Chemical. Se estimates that Japan’s Shin-Etsu and SUMCO are part of the global silicon wafer market in terms of share. In fact, it was this global leadership position that propelled Mitsubishi Materials to become a supplier to SUMCO. .
According to Nikkei Sangyo Shimbun, the production capacity of polycrystalline silicon at the Yokkaichi plant is approximately 2,800 tons per year, of which 70% of the capacity produced is supplied to SUMCO. The newspaper reported that supplies had fallen to about 70%.
In the polycrystalline silicon market, Germany’s Wacker and the U. S. -based Hemlock make up the largest share of the global supply, followed by Japan’s Tokuyama, which holds around 20% of the market share. Tokuyama’s production capacity is 9,200 tons per year. However, this volume dropped to around 6,200 tonnes after Tokuyama started a new solar mobile factory in Malaysia last year (reference 4). Although the exact percentage of Tokuyama’s polycrystalline silicon semiconductor production is unknown, Mitsubishi Materials’ 2,800 tons turns out to be a small figure. Based on this figure alone, and assuming an immediate recovery of Mitsubishi Materials’ production capacity, the impact on the semiconductor industry would not be as severe.
The stock market tells a different story. Mitsubishi Materials cost 376 yen based on the January 9 percentage. It fell to 370 yen the next day and fell another 3. 7% to 362 yen on Jan. 14. SUMCO’s stock value was 916 yen on Jan. 9, falling to 894 yen. yen on January 10 and 864 yen on January 14.
The shortage of polycrystalline silicon is suddenly big news. Some observers have pointed out that silicon is the most abundant element on the planet after oxygen. In descending order of abundance, they are O, Si, Al, Fe, Ca, Na, K, and Mg.
But it’s not just the abundance of silicon that matters. The parent material of crystalline silicon is silicon oxide (SiO2). SiO2 is reduced by hydrogen to produce low purity metallic silicon. Then, it is changed to trichlorosilane, a distillation procedure to increase purity. Polysilicon is ultimately produced through additional relief via hydrogen. Therefore, it is not just the shortage of polysilicon that matters, but also the ability to mass produce polysilicon. This factor must be carefully monitored.
The Japanese edition of this article can be found here.
After the massive price run up of poly-Si in late 2008 (US$450/kg) oodles of poly manufacturers charged into the business. This drove the price down to something close to US$16/kg in recent months. There is plenty of poly-Si capacity in the world. Plants have shutdown everywhere due to the extroadinarily low price and can be brought online as needed. The bigger issue is the exhaust products from TCS and DCS (SiHCl3 and SiH2Cl2). The polysiloxanes formed in the exhaust from these precursors are highly flammable and explosive. They only require some mechanical energy to light them off. Everybody who knows about Si epitaxy or bulk poly-Si growth is well acquainted with the hazards of the exhaust system. Only the public is in the dark. Note that the description by Mitsubishi does not clearly identify the metasatable polysiloxanes in the exahust as the cause, nor does it even mention them. TCS itself is flammable. But the partially oxidized polysiloxanes are “da bomb”.
Trichlorosilane (HCl3Si) is highly reactive with water. It generates hydrogen, a flammable gas, and hydrogen chloride, a corrosive gas. During a fire, it can also generate a phosgeneous poisonous gas. It also reacts violently with alcohols, acids or bases, oxidants, and amines. Every trichlorosilane MSDS has those warnings. A spark when you lift the lid?Perhaps because of the lifting device used (440-pound cap)?