Safety and Health Topics > Semiconductors > Silicon
> Substrate Manufacture: Polycrystalline Silicon Production
Substrate Manufacture:
Polycrystalline Silicon Production
To manufacture polycrystalline silicon, ultra-pure silicon is produced from raw quartzite (silica sand) that is melted and reduced to silicon in an electric arc furnace at over 1900ºC.
This metallurgical-grade silicon is drawn from the furnace and blown with oxygen or an oxygen-chloride mixture to
reduce the levels of impurities to achieve approximately 99% pure silicon. Next, the silicon is reacted with
hydrogen chloride gas in the presence of a copper-containing catalyst to form trichlorosilane (SiHCl3).
The trichlorosilane is reduced to very pure silicon by reacting it with hydrogen at high temperatures (about 1100ºC).
This "electronic grade" silicon has less than 1 ppb of impurities.
Potential Hazards
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Silica (crystalline) |
Potential Hazard
- Possible employee exposure to crystalline silica used as a raw material.
Inhalation of silica can lead to chronic, accelerated or acute silicosis and is associated
with bronchitis and tuberculosis. Some studies also indicate an association with lung
cancer. Exposures to silicon dust may also occur; controls are
similar to those used for crystalline silica.
Possible Solutions
- Identify silica hazards and perform appropriate exposure evaluations.
- Identify and evaluate all potential exposure scenarios, for example: startup, operations, maintenance, cleaning, emergencies, and so forth.
- See 1910.1000, Table
Z-3, which contains permissible exposure limits for crystalline silica.
- Sampling for Special
Analyses. OSHA Technical Manual (TED 1-0.15A), Section II - Chapter 1,
Appendix II:1-5 (1999, January 20), 44 pages. Includes sampling information for crystalline
silica.
- Provide appropriate ventilation to reduce silica concentration levels in the air.
- Maintain adequate housekeeping to remove unwanted silica dust and reduce
concentration levels.
- Use respiratory protection [1910.134] when necessary to further reduce exposure and protect employees.
Additional Information
OSHA Safety and Health Topic pages:
OSHA eTools:
 Silica
eTool. OSHA (1998, October). A downloadable
version is also available. The Silica eTool is an expert training and information aid. It includes current information
that will assist businesses and workers in identifying potential silica hazards in their workplaces by choosing appropriate
sampling and analytical techniques, comparing monitoring results with the silica exposure limits, and selecting appropriate
short and long-term control options.
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Hydrogen Chloride Gas |
Potential Hazard
- Possible employee exposure to hydrogen chloride gas. Hydrogen chloride is
irritating and corrosive to the eyes, skin, and mucous membranes. Exposure to high
concentrations can cause laryngitis, bronchitis, and pulmonary edema.
Possible Solutions
- Identify hydrogen chloride hazards and perform appropriate exposure
evaluations.
- Identify and evaluate all potential exposure scenarios, for example: startup, operations, maintenance, cleaning, emergencies, and so forth.
- See 1910.1000, Table
Z-1, which contains permissible exposure limits for hydrogen chloride.
- The Workplace
Monitoring and Measurement section of the Hydrogen
Chloride Health Guidelines page includes additional sampling and analysis information.
- Provide appropriate ventilation to reduce hydrogen chloride concentration
levels in the air.
- Provide PPE [1910
Subpart I] as appropriate to prevent eye and skin contact with hydrogen chloride.
- Use respiratory protection [1910.134]
when necessary to further reduce exposure and protect employees.
Additional Information
OSHA Safety and Health Topic pages:
OSHA Health Guidelines page:
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