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Trichlorosilane (TCS)

About Trichlorosilane

Trichlorosilane (SiHCl3) is a colorless liquid containing silicon, hydrogen, and chlorine. It is the key intermediate compound used to produce extremely pure polysilicon, from which computer chips and solar cells are made.

The key difference between solar grade and electronic grade polysilicon is the purity requirement. The purity requirement for electronic grade polysilicon is the highest and typically 99.999...% (in thirteen 9s) pure or more, while solar grade polysilicon tends to be at least 99.999...% (in six 9s) pure.

In 2000, the semiconductor industry consumed over 90% of the world's silicon supply while the solar industry consumed approximately 10%. In 2006, the solar industry consumed more than 50% of the world's available supply of polysilicon for the first time ever. This historic shift illustrates the growing size and importance of the solar industry.

According to Semiconductor Equipment and Materials International (SEMI), polysilicon producers shipped about 12,600 metric tons (MT) of their products in the fourth quarter of 2008; a 7% growth from the previous quarter. SEMI also reported that, overall, polysilicon producers shipped about 43,900 MT of polysilicon in 2008. Companies that provided figures were DC Chemical, Hemlock Semiconductor, MEMC Electronic Materials, REC Silicon, Tokuyama and Wacker Chemie, which are among the largest polysilicon producers in the world.

Another important fact that is relatively unknown is the quantity of Trichlorosilane needed to produce polysilicon. The ratio is 6.25 to 1. In other words, 6.25 MT of Trichlorosilane is required to produce only 1 MT of polysilicon.

The entry barrier for the solar business varies depending where on the PV value chain someone wishes to become involved. Becoming a Trichlorosilane or polysilicon producer will require special permitting, large capital investment and several years of planning and construction. It is much easier to become involved at the other end of the PV value chain (downstream) as it does not require a large amount of capital and the business can quickly be operational. Because of the above situation, companies involved in the Trichlorosilane and polysilicon production tend to achieve the highest profit, followed by solar cell manufacturers.

At SunSi, we believe that the best place to be involved on the PV value chain is exactly where we are -- as a Trichlorosilane producer.


Making Trichlorosilane (TCS)

The process of producing Trichlorosilane begins by mining for relatively pure silicon dioxide (sand or quartz). The next step is to separate the silicon from the oxygen. This is achieved by heating sand grains containing silicon dioxide with carbon at very high temperature. At the end of this stage, the silicon or metallurgical grade silicon (MGS) is about 97% pure.

In order to reach a purity level suitable for semiconductor devices and solar applications, the MGS goes through a purification process, which involves the reaction of MGS with hydrogen chloride. This reaction will finally form Trichlorosilane.

The distillation process, the final step in producing high quality Trichlorosilane, is all about bringing impurities below the part-per-billion (ppb) level. Liquefied Trichlorosilane at room temperature is purified by the distillation process until the impurity levels are acceptable.

SunSi Energies... the only "pure play" public company in the world
focused on TCS production!