Coating apparatus – Projection or spray type
Reexamination Certificate
1999-01-26
2001-05-22
Crispino, Richard (Department: 1734)
Coating apparatus
Projection or spray type
C118S326000, C118S725000, C118S726000, C427S248100, C427S099300, C427S124000, C427S585000, C117S088000, C117S102000, C438S680000
Reexamination Certificate
active
06235112
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an apparatus and a method for forming a thin film on a substrate surface, and particularly to those for vapor-phase deposition of a thin film using a liquid reaction material having a low vapor pressure.
Heretofore, in production processes of semiconductor circuits or liquid crystal circuits, a chemical vapor deposition (CVD) method has been employed for forming various thin films. In the CVD method, plasma excitation energy or thermal energy is exerted onto material gas necessary for forming a film so as to form a thin film on a base plate or substrate. Recently, in view of demands for more integrated semiconductor circuits, as a reaction material, what is used is liquid reaction materials having a low vapor pressure, and which have good characteristics of covering steps and filling in spaces.
A method of introducing the liquid reaction material into a reaction chamber upon vaporization of the material includs a bubbling method wherein the liquid material is vaporized by passing inert gas thereinto, a baking method wherein the liquid material is vaporized directly by heating, a direct vaporization method wherein the liquid material is vaporized by introducing it along with a carrier gas to a heated and pressure-reduced space, an ultrasonic wave method wherein the liquid material is vaporized by heating mist of the material generated by ultrasonic wave vibration, and so forth.
However, by these conventional methods, a constant amount of reaction gas cannot be provided for the reasons below, and further, a large amount of low vapor pressure liquid reaction material cannot be provided, thereby causing drawbacks of decreasing film reproducibility and deposition rate.
That is, in the above bubbling method, in order to maintain the flow of vaporized liquid material at a constant rate, it is necessary to keep the temperature of the liquid material constant. However, the temperature of the liquid material gradually decreases due to the latent heat upon its vaporization by the carrier gas, and thus it is technologically difficult to maintain a temperature constant during the vaporization process.
Further, in the bubbling method and in the direct vaporization method, the amount of carrier gas needs to be increased in order to obtain a large amount of liquid material gas. However, even if the absolute amount of the liquid material gas is increased, the concentration of the liquid material gas is decreased, thereby subsequently reducing the speed of film formation.
In the baking method, in order to obtain a large amount of liquid material gas, it is necessary to heat the liquid material to a high temperature by using a large and expensive heat chamber. However, this method cannot be applied to liquid material which is prone to decompose or deteriorate with heat. Further, it is necessary to heat the entire passage of the liquid material gas in order to prevent re-liquification of the liquid material gas, and thus in view of problems in heat resistance of the devices and the cost of the apparatus, high-temperature operation may be barred to a certain extent.
Additionally, in the ultrasonic wave method, liquid material apt to decompose or deteriorate by heat cannot be used. Further, when liquid material which is difficult to vaporize is used, it is necessary to heat the liquid material for vaporization. In this case, heat resistance of the ultrasonic vibrator becomes an issue.
SUMMARY OF THE INVENTION
The present invention has exploited thin film formation using a low vapor pressure material. An objective of the present invention is to provide an apparatus for forming thin films, which is capable of supplying accurately a constant amount of liquid reaction material. Another objective of the present invention is to provide an apparatus for forming thin films, which is capable of supplying a large amount of liquid reaction material having a low vapor pressure. Still another objective of the present invention is to provide an apparatus for forming thin films, which is capable of using any type of liquid reaction material.
Namely, the present invention is to provide an apparatus for forming a thin film on a surface of a substrate, which apparatus comprises: a reaction chamber having an interior where the substrate is placed when in use; a liquid reaction material supplier for supplying a given amount of liquid reaction material for forming a thin film on the substrate; and a mist-forming device for forming mist of the liquid reaction material and spraying the liquid reaction material onto a surface of the substrate for forming a thin film thereon, said mist-forming device being disposed upstream of the reaction chamber and downstream of the liquid reaction material supplier. In the above, preferably, neither of the mist-forming device nor the liquid reaction material supplier comprises a heating device for heating the liquid reaction material. In the above, the liquid reaction material is in the form of liquid when at normal temperature and under normal pressure.
In the above, preferably, the apparatus further comprises a reaction material gas-supplying device for supplying a reaction material gas at a given flow rate, said reaction material gas-supplying device being connected to the interior of the reaction chamber, said reaction material gas being reactive with the liquid reaction material to form a thin film on the surface of the substrate.
The apparatus according to the present invention can typically be adapted to, but is not limited to, a plasma CVD apparatus and a thermal CVD apparatus.
The apparatus of the present invention is based on a method for forming a thin film on a surface of a substrate placed in an interior of a reaction chamber, which method comprises the steps of: forming mist of liquid reaction material for forming a thin film on the substrate; advancing the mist of liquid reaction material toward a surface of the substrate which has a temperature suitable for forming a thin film with the liquid reaction material; and forming a thin film on the substrate, wherein the mist is vaporized at the surface of the substrate or prior to reaching the surface of the substrate. In the above, preferably, the mist is formed by means of ultrasonic wave vibration. Further, preferably, the method further comprises supplying a reaction material gas being reactive with the liquid reaction material to form the thin film on the surface of the substrate. In this method, heat is not applied to the mist when being formed prior to entering the reaction chamber. After entering the reaction chamber and until reaching the substrate, the mist receives heat, and further, in a thermal CVD, heat continues to be applied to the mist after reaching the substrate.
According to the apparatus and method for forming thin films of the present invention, it is possible to use a large amount of liquid reaction material having a low vapor pressure while maintaining a stable flow, thereby forming thin films having high quality with high reproducibility.
Further, according to the apparatus and method for forming thin films of the present invention, it is possible to eliminate vaporization of liquid reaction material as conventionally conducted, and to use a liquid reaction material which is prone to heat decomposition or deterioration.
Still further, according to the apparatus and method for forming thin films of the present invention, it is possible to eliminate all devices or apparatuses for vaporization, thereby reducing the space for installing the apparatus and reducing the cost of installation.
REFERENCES:
patent: 4749440 (1988-06-01), Blackwood et al.
patent: 5280012 (1994-01-01), Kirlin et al.
patent: 5451260 (1995-09-01), Versteeg et al.
patent: 5620524 (1997-04-01), Fan et al.
patent: 6074487 (2000-06-01), Yoshioka et al.
ASM Japan K.K.
Crispino Richard
Knobbe Martens Olson & Bear LLP
Lorengo J. A.
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