Coating apparatus – Gas or vapor deposition – Crucible or evaporator structure
Reexamination Certificate
1999-04-28
2001-08-21
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
Crucible or evaporator structure
C261S142000, C118S7230VE
Reexamination Certificate
active
06277201
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a CVD (Chemical Vapor Deposition) apparatus to form a thin film on a semiconductor substrate by a CVD method using liquid reaction materials having a low vapor pressure. Particularly, it relates to the CVD apparatus with a liquid-source vaporization system that supplies a flow-controlled liquid reaction material after its vaporization.
2. Description of the Related Art
Up to this time, the CVD method has been widely adopted as a thin film formation method for a semiconductor apparatus. The CVD method is a method to form a thin film on a substrate by importing several types of gases selected according to the type of film to be formed into the reaction chamber and causing a chemical reaction by applying thermal energy or plasma excitation energy. In recent years, liquid reaction materials with low vapor pressure have attracted more attention for the reasons that they are excellent in covering and filling gaps or steps.
For example, Japan Patent Laid-open No.5-132779 discloses an apparatus that vaporizes a liquid reaction material to supply it to the reaction chamber. In this case, the liquid reaction material, the flow rate of which is controlled by a liquid flow rate controller, is atomized by an ultrasonic vibrator (circular vibrator depth-direction resonance type ultrasonic vibrator) placed in the atomization means, and then heated and vaporized with a heater.
However, according to the apparatus disclosed by Japan Patent Laid-open No. 5-132779, after the completion of the thin film formation processing, a liquid reaction material remains behind inside the ultrasonic vibrator, the casing of the atomization means, etc. The liquid reaction material residual within the ultrasonic vibrator drips and accumulates in the casing, and is soon atomized. The liquid reaction material gases remaining in the casing are denatured or degenerated through further heat. This will create the source of particle generation and will contaminate semiconductor substrates in the subsequent thin film formation process.
In particular, because Ta (OC
2
H
5
)
5
which is one of the liquid reaction materials is decomposed at approximately 150° C. (302° F.), there is a high risk of creating a source of particle generation, if it remains in the casing.
Accordingly, an objective of the present invention is to provide a CVD apparatus equipped with a liquid-source vaporization system that does not leave any liquid reaction material within the system.
Another objective of the present invention is to provide a CVD apparatus with improved productivity by minimizing particle contamination.
In addition, another objective of the present invention is to provide a CVD apparatus equipped with a liquid-source vaporization system, which can perform cleaning work easily and quickly.
Furthermore, another objective of the present invention is to provide a CVD apparatus quipped with a liquid-source vaporization system, which can use various types of liquid reaction materials, regardless of their characteristics.
SUMMARY OF THE INVENTION
To achieve the above-mentioned objectives, the CVD apparatus of the present invention comprises the following elements:
In one embodiment, the CVD apparatus for forming a thin film on a surface of a semiconductor substrate under reduced pressure, comprises: (a) a reaction chamber; (b) a vacuum device connected to the reaction chamber for vacuuming and exhausting the reaction chamber; (c) a susceptor that maintains the semiconductor substrate inside the reaction chamber; (d) a reaction gas supplier (e.g., showerhead) that supplies a reaction gas to the surface of the semiconductor substrate set on the susceptor; and (e) a liquid-source vaporization system connected to the reaction gas supplier which is disposed upstream of the reaction gas supplier and is used for atomizing and vaporizing the liquid reaction material at a given flow rate prior to its entry into the reaction chamber, said liquid-source vaporization system comprising: (i) an atomizer connected to a liquid reaction material supply source, said atomizer atomizing the liquid reaction material from the supply source; and (ii) a vaporizer connected to the atomizer downstream thereof, said vaporizer vaporizing the atomized reaction material.
In another embodiment, the liquid-source vaporization system further comprises a cleaning device connected to the atomizer and the vaporizer, which evacuates the liquid reaction material remaining inside the atomizer and the vaporizer by generating a pressure difference between the outlet of the vaporizer and the inlet of the atomizer. In another embodiment, the liquid-source vaporization system further comprises a liquid flow controller for controlling the liquid flow rate of the liquid reaction material supplied to the atomizer. Further, in another embodiment, the atomizer atomizes the liquid reaction material by ultrasonic vibration, although atomization can be achieved by a high-pressure jet nozzle, for example. In anther embodiment, the vaporizer vaporizes the atomized reaction material by heating, although vaporization can be achieved by reducing the pressure, for example.
According to the CVD apparatus of the present invention, because the residual liquid material within the liquid-source vaporization system is completely eliminated, the particle contamination problem caused by the degeneration of the residual liquid material has been resolved. In addition, because the vaporizer is provided separately from the reaction chamber, contamination inside the reaction chamber, which is caused by particles generated by the vaporizer, can be minimized. Furthermore, because the CVD apparatus has a simple structure and it is easy to operate, it can shorten the time required for cleaning and enhance throughput. Furthermore, various types of liquid materials including liquid materials that can be vaporized at relatively low temperatures (e.g., 20° C. or lower) can be used. For example, the liquid material includes TEOS, SiH(OC
2
H
5
)
3
, SiH(CH
3
)
3
, Si(OCH
3
)
4
, and TEFS/FSi(OC
2
H
5
)
3
. Further, in the present invention, the reaction gas includes O
2
, O
3
, O
2
+O
3
, NO
2
, N
2
O
4
, N
2
O, and the formed thin film includes SiO and SiOF.
Here specifically, the cleaning device is connected to the atomization means and comprises (1) a cleaning-chemical supplier to supply cleaning chemicals into the vaporizer through the atomizer, and (2) an evacuater to evacuate the liquid reaction material left within the atomizer and the vaporizer.
More suitably, the cleaning-chemical supplier can include a mass flow controller and at least one valve, and the evacuater can include a trap device, an exhaust device, and at least one valve. Furthermore, the exhaust device can serve as a vacuum exhaust device that exhausts the reaction chamber. More suitably, the trap device can include a gas cooling device. More specifically, the atomizer is of a horn type. More suitably, the vaporizer can include a carrier gas supplier for supplying carrier gas.
The CVD apparatus according to the invention may further comprise a gas supplier connected to the showerhead to supply into the reaction chamber at least one gas selected from the group consisting of a reaction gas, a carrier gas, and a purge gas.
REFERENCES:
patent: 5097800 (1992-03-01), Shaw et al.
patent: 5362328 (1994-11-01), Gardiner et al.
patent: 5476547 (1995-12-01), Mikoshiba et al.
patent: 5690743 (1997-11-01), Murakami et al.
patent: 5730804 (1998-03-01), Gomi et al.
patent: 5835677 (1998-11-01), Li et al.
patent: 6036783 (2000-03-01), Fukunaga et al.
patent: 5-132779 (1993-05-01), None
ASM Japan K.K.
Knobbe Martens Olson & Bear LLP
MacArthur Sylvia R.
Mills Gregory
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