Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Patent
1995-12-27
1997-04-08
Capossela, Ronald C.
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
62905, F25J 300
Patent
active
056177402
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of producing ultra high purity monosilane and apparatus therefor, and particularly to an ultra high purity monosilane producing method which comprises liquefying and rectifying a feed monosilane gas, thereby producing high pressure monosilane gas and high pressure monosilane liquid, each having an ultra high purity, which are free from hydrogen having a boiling point lower than that of monosilane and chlorides having boiling points higher than that of monosilane, and an apparatus therefor.
BACKGROUND OF THE INVENTION
Monosilane gas is generally indispensable for the manufacture of ultra LSIs, solar batteries, photosensitive materials and the like.
A known method for producing monosilane gas is that disclosed in the official gazette of Japanese Patent Publication No. 3,806/1989.
Such monosilane gas preferably should have a high purity, for instance, of 99.9999% or more. However, a preferred method for producing such high purity monosilane gas and a preferred unit therefor have not yet been developed.
The present invention is intended to achieve the aforementioned purpose.
SUMMARY OF THE INVENTION
The ultra high purity monosilane producing method according to the present invention is characterized by comprising: pressurizing, cooling down and gas-liquid separating a feed monosilane gas; introducing the separated gas to the middle stage of a lower rectification column and rectifying the pressurized gas in the lower rectification column; introducing the gas resulted from this rectification to the middle stage of an upper rectification column and rectifying the same gas there; and taking out a high pressure monosilane gas product or liquid monosilane product having an ultra high purity which is resulted from this rectification, from the bottom portion of said upper rectification column.
The ultra high purity monosilane producing method according to the present invention is characterized by further comprising: a step of warming the liquid reservoired in the bottom portion of said lower rectification column by means of a reboiler, whereby low boiling point components contained in said liquid are gasified so as to be recovered to the lower rectification column.
The ultra high purity monosilane producing unit according to the present invention is characterized by comprising: a lower rectification column with a reboiler-condenser disposed in its top portion and a condenser for cooling use disposed below the reboiler condenser; an upper rectification column with a condenser for cooling use disposed in its top portion, the bottom portion of the upper column being opposite the reboiler-condenser of said lower rectification column; means for cooling each of said condensers for cooling use; means for pressurizing, cooling down, and gas-liquid separating a feed monosilane gas; means for introducing the pressurized feed gas obtained by the above means into said lower rectification column; and means for introducing the gas rectified in said lower rectification column into said upper rectification column; wherein a high pressure gaseous monosilane product or liquid monosilane product having an ultra high purity is taken out of the bottom portion of said upper rectification column.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the present invention will be referring to the Figure which is an illustrative view of an installation for carrying out the ultra high purity monosilane producing method and unit according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, an impure monosilane gas is used as a feed.
The composition of a feed monosilane gas used in the embodiment of the present invention and the boiling points of its components are as shown in Table 1.
TABLE 1 ______________________________________
Composition of Feed Boiling Points
Monosilane Gas % (.degree.C. at 1 atm)
______________________________________
Hydrogen (H.sub.2) 16.0 -252.9
Monosilane (SiH.sub.4)
69.2 -111.5
Monochloros
REFERENCES:
patent: 4755201 (1988-07-01), Eschwey et al.
patent: 5499506 (1996-03-01), Nagamura et al.
Nagamura Takashi
Tomita Shinji
Capossela Ronald C.
L'air Liquide, Societe Anonyme Pour L'Etude Et L'Exploitation De
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