Gas separation: processes – Selective diffusion of gases – Selective diffusion of gases through substantially solid...
Reexamination Certificate
2000-11-30
2002-10-08
Hopkins, Robert A. (Department: 1724)
Gas separation: processes
Selective diffusion of gases
Selective diffusion of gases through substantially solid...
C095S053000, C095S055000, C096S006000
Reexamination Certificate
active
06461407
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a method and an apparatus for supplying a liquid raw material, and, particularly, to a method and an apparatus for supplying a liquid raw material from a liquid raw material container to a liquid flow control section while deaerating the raw material in semiconductor manufacturing processes and the like.
(2) Description of the Prior Art
Along with the progress of semiconductor industries in recent years, high performance and highly integrated semiconductor devices have been developed. As raw materials for metal films and insulated films, various liquid organic metal compounds have come to be used in place of conventionally used hydride gases and halide gases.
To state, for example, metal films of semiconductor devices, dimethylaluminum hydride (Al(CH
3
)
2
H) is used as a CVD raw material for an aluminum film, hexafluoroacetylacetone copper vinyltrimethylsilane ((CF
3
CO)
2
CHCu.CH
2
CHSi(CH
3
)
3
) as a CVD raw material for a copper film and bis(ethylcyclopentadienyl)ruthenium (Ru(C
5
H
4
C
2
H
5
)
2
) as a CVD raw material for a ruthenium film.
Also, to state insulated films of semiconductor devices, SiO
2
is known as a gate insulated film, Si
3
N
4
as a capacitor insulated film and PSG (Phosphorous/ silicon/ glass) and BPSG (boron/phosphorous/silicon/glass) as a layer insulated film. Moreover, tetraethoxysilicon (Si(OC
2
H
5
)
4
) is used as a CVD raw material for SiO
2
film and trimethoxyboron (B(OCH
3
)
3
), trimethoxyphosphine oxide (PO(OCH
3
)
3
) and the like are used as CVD raw materials for a PSG film and a BPSG film.
Meanwhile, various apparatuses and methods have been developed for supplying these liquid raw materials to manufacturing apparatuses of semiconductors at a desired concentration and at a desired flow rate by vaporization. For example, liquid raw material vaporizing equipment provided with a liquid flow control section for controlling the flow rate of a liquid raw material and a vaporizer for atomizing the liquid raw material, controlled by the flow control section, by ultrasonic vibration, and vaporizing the atomized material by heating is known (Japanese Patent Application Laid-Open No.5-132779). Also, a method for supplying a liquid raw material is known in which the liquid raw material whose flow rate is controlled by a liquid flow control section is mixed with a pressurized carrier gas and thereafter the flow rate of the gas is controlled to become constant (Japanese Patent Application Laid-Open No.9-111456). Further, a method for supplying a liquid raw material is known, having an apparatus which is connected to a mass flow controller and a low pressure source and removes gas dissolved in the liquid raw material (Japanese Patent Application No.6-220640).
In the liquid flow control section used in the aforementioned supply method or supply apparatus, a two- or multiple-series of corrosion resistant bellows pump which can supply a liquid raw material without pulsating current or a mass flow controller in place of a pump is used because the liquid raw material must be supplied to the vaporizer quantitatively with extremely high accuracy. Such a bellows pump and liquid mass flow controller can supply a liquid raw material to the vaporizer quantitatively with high accuracy when the liquid raw material is homogeneous. However, the liquid raw material cannot be supplied at a constant flow rate when inert gas and the like exist as fine air bubbles in the liquid raw material.
Namely, in a general supply system for liquid raw materials, a liquid raw material container is filled with inert gas such as helium, nitrogen, argon or the like and the liquid raw material is supplied to the liquid flow control section by the pressure of the inert gas in the production of a semiconductor.
In the process of producing a semiconductor, therefore, a relatively large amount of inert gas is dissolved in the liquid raw material because of its a pressurized condition in the liquid raw material container. On the other hand, the CVD apparatus is operated under reduced pressure. Hence the liquid flow control section disposed between the container and the CVD apparatus is operated under atmospheric pressure or lower pressure. The solubility of the inert gas in the liquid raw material is lowered and the dissolved inert gas frequently generates fine air bubbles by the time when the liquid raw material reaches the outlet side of the liquid flow control section. If fine air bubbles are present in the liquid raw material, this offers such a disadvantage that the liquid raw material can not be measured in a bellows pump or a mass flow controller, and the liquid raw material cannot be quantitatively supplied to semiconductor-manufacturing equipment in a vapor state with high accuracy. Also, when fine air bubbles are generated in the liquid raw material after the liquid raw material passes through the liquid flow control section, this offers such a disadvantage that the air bubbles adversely affect the uniformity of film qualities.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to solve the aforementioned problem and to provide a method and apparatus for supplying a liquid raw material, the method and apparatus making it possible to remove inert gas dissolved in the liquid raw material as aforementioned easily and efficiently before the flow rate of the liquid raw material is controlled in a liquid flow control section such as a bellows pump or a mass flow controller in a semiconductor-manufacturing process using the liquid raw material.
The inventors of the present invention have conducted earnest studies to solve the above problem and as a result, found that degassing can be attained by passing a liquid raw material, in which a first inert gas is dissolved, in the inside of a gas permeable synthetic resin tube and by passing a second inert gas having a lower permeability into the synthetic resin tube than the first inert gas to allow the first inert gas to penetrate into the outside of the synthetic resin tube while the penetration of the second inert gas into the inside of the synthetic resin tube is restrained. Thus the present invention was completed.
Specifically, the present invention resides in a method for supplying a liquid raw material wherein the liquid raw material is deaerated and supplied from a liquid raw material container to a liquid flow control section, the method comprising passing the liquid raw material, supplied from a liquid raw material container by the pressure of a first inert gas, inside of a gas permeable synthetic resin tube, passing a second inert gas having a lower permeability into the synthetic resin tube than the first inert gas along the external surface of the synthetic resin tube whereby the first inert gas dissolved in the liquid raw material is allowed to penetrate into the outside of the synthetic resin tube and then supplying the liquid raw material to the liquid flow control section.
The present invention also resides in an apparatus for supplying a liquid raw material. The apparatus is equipped with a deaerating section of liquid raw material and a liquid flow control section, the deaerating section comprising a gas permeable synthetic resin tube, an introduction port and a discharge port for introducing and discharging the liquid raw material, the both being connected to each other by the synthetic resin tube, a passage for passing the inert gas along the external surface of the synthetic resin tube and an introduction port and a discharge port for introducing and discharging the inert gas.
REFERENCES:
patent: 4917776 (1990-04-01), Taylor
patent: 5425803 (1995-06-01), van Schravendijk et al.
Asano Akira
Ishihama Yoshiyasu
Takamatsu Yukichi
Yoneyama Takeo
Hopkins Robert A.
Japan Pionics Co., Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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