From WikiChip
Difference between revisions of "electronic-grade silicon"

(→‎Purification)
 
(6 intermediate revisions by 3 users not shown)
Line 1: Line 1:
−
{{title|Electronic-Grade Silicon (EGS)}}
+
{{title|Electronic-Grade Silicon (EGS)}}{{wafer tech}}
 
'''Electronic-grade silicon''' ('''EGS''' or '''EG-Si''') or '''semiconductor-grade silicon''' ('''SGS''') is a highly-purified version of the [[metallurgical-grade silicon]] with extremely low impurities suitable for microelectronic device applications. Electronic-grade silicon is the raw material used for the [[crystal growth|growth of single-crystal silicon]] in the manufacturing of [[silicon wafers]]. From MGS to EGS, the impurities go from the order of parts per million to the low parts per billion.
 
'''Electronic-grade silicon''' ('''EGS''' or '''EG-Si''') or '''semiconductor-grade silicon''' ('''SGS''') is a highly-purified version of the [[metallurgical-grade silicon]] with extremely low impurities suitable for microelectronic device applications. Electronic-grade silicon is the raw material used for the [[crystal growth|growth of single-crystal silicon]] in the manufacturing of [[silicon wafers]]. From MGS to EGS, the impurities go from the order of parts per million to the low parts per billion.
 +
 +
Creating EGS is expensive and is thus only usually justified for integrated circuits. For other applications such as solar cells and liquid crystal displays, EGS is cost prohibitive, making [[upgraded metallurgical-grade silicon]] (UMG-Si) a much more attractive alternative.
  
 
== Overview ==
 
== Overview ==
Line 43: Line 45:
 
|}
 
|}
  
−
== Purification ==
+
 
−
The most common way to further purify metallurgical-grade silicon into electronic-grade silicon is by converting it into a liquid volatile silicon such as monosilane (SiH<sub>4</sub>),  dichlorosilane (SiH<sub>2</sub>Cl<sub>2</sub>), and trichlorosilane (SiHCl<sub>3</sub>). The most common method is converting the silicon to [[trichlorosilane]] (TCS), a volatile liquid at room temperature that can easily be purified through subsequent distillation. Trichlorosilane can also be stored in standard carbon steel tanks, making storage and handling very convenient. Conversion is done by reacting it with anhydrous [[hydrogen chloride]] at 300 °C in a fluidized bed reactor to form polychlorinated silanes.
+
 
 +
=== Trichlorosilane ===
 +
The most common method is using [[trichlorosilane]] (TCS), a volatile liquid at room temperature that can easily be purified through subsequent distillation. Trichlorosilane can also be stored in standard carbon steel tanks, making storage and handling very convenient. Conversion is done by reacting it with anhydrous [[hydrogen chloride]] at 300 °C in a fluidized bed reactor to form polychlorinated silanes.
  
 
:MGS + 3HCl → SiHCl<sub>3</sub> + H<sub>2</sub>
 
:MGS + 3HCl → SiHCl<sub>3</sub> + H<sub>2</sub>
  
 
Note that in addition to TCS, Hydrogen is also produced. TCS boils at 31.8 °C and is liquid at room temperature meaning impurities can easily be removed through fractional distillation to produce extremely high purity liquid. The liquid TCS is then converted into solid polysilicon through the [[Siemens process]] which results in electronic-grade silicon with purity level as high as 9N or even 10N (99.99999999998%). The process results in TCS decomposing with the pure silicon being deposited on the highly-pure silicon slim rods located inside the reactor.
 
Note that in addition to TCS, Hydrogen is also produced. TCS boils at 31.8 °C and is liquid at room temperature meaning impurities can easily be removed through fractional distillation to produce extremely high purity liquid. The liquid TCS is then converted into solid polysilicon through the [[Siemens process]] which results in electronic-grade silicon with purity level as high as 9N or even 10N (99.99999999998%). The process results in TCS decomposing with the pure silicon being deposited on the highly-pure silicon slim rods located inside the reactor.
 +
 +
=== Monosilane ===
 +
{{empty section}}

Latest revision as of 06:21, 4 December 2020

Ingot Production
Wafer Processing
v · d · e

Electronic-grade silicon (EGS or EG-Si) or semiconductor-grade silicon (SGS) is a highly-purified version of the metallurgical-grade silicon with extremely low impurities suitable for microelectronic device applications. Electronic-grade silicon is the raw material used for the growth of single-crystal silicon in the manufacturing of silicon wafers. From MGS to EGS, the impurities go from the order of parts per million to the low parts per billion.

Creating EGS is expensive and is thus only usually justified for integrated circuits. For other applications such as solar cells and liquid crystal displays, EGS is cost prohibitive, making upgraded metallurgical-grade silicon (UMG-Si) a much more attractive alternative.

Overview[edit]

While pure silicon (referred to as metallurgical-grade silicon) is of very good quality, it is still unsuitable for electronic device fabrication. Even impurities in the order of parts per million or less have significant impact on carrier mobility, reliability, and other aspects of the microelectronic device.

Impurity Concentrations in MG-Si (ppm)
Element Concentration   Element Concentration
Al 1000-5000 B 35-50
P 20-50 Ca 250-600
Cr 50-200 Cu 15-60
Fe 1600-6500 Mn 50-100
Mo 2-20 Ni 20-100
Ti 150-300 V 50-250
Zr 20-30

Metallurgical-grade silicon must be furthered purified to levels of usually less than a part per billion in order to be called electronic-grade silicon which can be used in subsequent fabrication steps.

Impurity Concentrations in EG-Si (ppb)
Element Concentration   Element Concentration
B ≤ 0.1 C 50-1000
Cr ≤ 0.01 Co ≤ 0.01
Cu ≤ 0.1 Fe 0.1 - 1
Ni 0.1 - 0.5 O 100-500
P ≤ 0.5 Zn ≤ 0.1


Trichlorosilane[edit]

The most common method is using trichlorosilane (TCS), a volatile liquid at room temperature that can easily be purified through subsequent distillation. Trichlorosilane can also be stored in standard carbon steel tanks, making storage and handling very convenient. Conversion is done by reacting it with anhydrous hydrogen chloride at 300 °C in a fluidized bed reactor to form polychlorinated silanes.

MGS + 3HCl → SiHCl3 + H2

Note that in addition to TCS, Hydrogen is also produced. TCS boils at 31.8 °C and is liquid at room temperature meaning impurities can easily be removed through fractional distillation to produce extremely high purity liquid. The liquid TCS is then converted into solid polysilicon through the Siemens process which results in electronic-grade silicon with purity level as high as 9N or even 10N (99.99999999998%). The process results in TCS decomposing with the pure silicon being deposited on the highly-pure silicon slim rods located inside the reactor.

Monosilane[edit]

New text document.svg This section is empty; you can help add the missing info by editing this page.
Retrieved from "https://en.wikichip.org/w/index.php?title=electronic-grade_silicon&oldid=98227"