JP2004197159A - Thin film deposition method, and cvd system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which a thin film of oxide can be deposited on the substrate to be treated without using a vacuum, and also, at a temperature lower than that in the conventional method, and to provide a CVD (Chemical Vapor Deposition) system therefor. <P>SOLUTION: The CVD system is, e.g., composed of a reaction chamber 10 capable of atmospheric control, a raw material vaporization tank 7 arranged therein with a raw material for thermal deposition reaction stored therein, a susceptor 2 holding a substrate 6 as the object for treatment to the upper direction of the raw material vaporization tank 7 so as to be close thereto, and a heater 3 controlling the temperature of the substrate 6. The substrate 6 as the object for treatment is heated, and the raw material is heated and vaporized by radiation heat from the substrate 6 to cause thermal decomposition reaction on the substrate 6, by which a thin film consisting of a product by the thermal decomposition reaction is deposited on the substrate 6. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of forming a thin film based on a CVD method, and more particularly to a method of forming a thin film of a metal oxide on a substrate to be processed at a relatively low temperature of 100 ° C. or more.
[0002]
[Prior art]
In recent years, the development of display technology and semiconductor technology has been remarkable, and in such a situation, there is a demand for a low-temperature and low-cost CVD process without using a vacuum.
[0003]
Conventionally, when an oxide thin film is formed by a CVD method, a reactive gas as a raw material is a carrier gas (an inert gas such as argon or nitrogen) so that an oxidation reaction does not proceed in a raw material vaporizer or a transport pipe. Gas) and transported to the vicinity of the substrate to be processed. However, such a conventional method requires a carrier gas, a carrier gas piping, a control system, and the like, which has been a factor of increasing the running cost for the CVD process and the manufacturing cost of the equipment used for the CVD process.
[0004]
Further, since the distance from the raw material vaporizer to the substrate to be processed is long, there is also a problem that some raw material molecules active at low temperature and fragments thereof are deactivated before reaching the substrate to be processed. Further, in the conventional method, it is impossible to raise the vaporization temperature of the raw material gas to the decomposition temperature in order to avoid blockage of the piping due to the decomposition reaction of the reaction gas in the raw material transporting pipe.
[0005]
Furthermore, the carrier gas surrounds the raw material molecules, which hinders the reaction. For example, when a thin film of ZnO (zinc oxide) is formed using a β-diketone metal complex as a raw material, the thin film is formed at a low temperature unless an apparatus having a double-tube nozzle using steam as a reaction gas is used. It is difficult to obtain ZnO highly oriented along the C axis at a low temperature (see Patent Literatures 1, 2, and 3 and Non-Patent Literature 1).
[0006]
[Patent Document 1]
JP 2002-309373 A (Claim 1)
[0007]
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-2002696939 (Claim 5)
[0008]
[Patent Document 3]
Japanese Patent Application Laid-Open Publication No. 2002-2002-069641 (Claim 1)
[0009]
[Non-patent document 1]
Kamada, Matsumoto: Journal of the Ceramic Association, 89 (1981) p. 337
[0010]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems with the conventional method of forming an oxide thin film using a CVD method, and an object of the present invention is to form an oxide thin film without using a vacuum. It is another object of the present invention to provide a method and an apparatus therefor which can be formed on a substrate to be processed at a lower temperature than before.
[0011]
[Means for Solving the Problems]
The method of forming a thin film of the present invention comprises:
The raw material for the pyrolysis reaction is stored in a raw material vaporization tank,
Above this raw material vaporization tank, the substrate to be processed is held close to the raw material vaporization tank,
Heating the substrate to be processed, heating and vaporizing the raw material by radiant heat from the substrate to be processed, causing a thermal decomposition reaction on the substrate to be processed,
Thus, a thin film made of a product of the thermal decomposition reaction is deposited on the substrate to be processed.
[0012]
According to the method of the present invention, a thin film composed of a reaction product can be deposited on a substrate to be processed at a relatively low temperature at atmospheric pressure without using a carrier gas. Therefore, according to the method of the present invention, the running cost for the CVD process and the manufacturing cost of the equipment used for it can be reduced.
[0013]
In the above method, by changing the atmosphere gas, the temperature of the substrate to be processed, the distance between the surface of the substrate to be processed and the surface of the raw material, and the thermal conductivity and heat capacity of the raw material vaporization tank, the obtained thin film can be obtained. Physical properties and morphology can be controlled.
[0014]
Further, according to the method of the present invention, a raw material vaporizer and a piping for transporting the raw material gas are not required, and only by replacing the raw material vaporization tank (that is, without cleaning the raw material vaporizer and the inside of the piping), Many types of thin films can be deposited on a substrate to be processed without containing impurities such as metal ions used in a process performed before that.
[0015]
If a metal β-diketone complex is used as the raw material, a metal oxide thin film can be deposited on the substrate by a thermal decomposition reaction without using a carrier gas.
[0016]
For example, when a β-diketone complex of zinc is used as the complex, a ZnO thin film can be deposited on the substrate by a thermal decomposition reaction without using a carrier gas.
[0017]
Further, the thin film forming apparatus of the present invention,
A reaction chamber with adjustable atmosphere,
A raw material vaporization tank that is disposed in the reaction chamber and contains a raw material for the pyrolysis reaction;
A substrate holding mechanism for holding a substrate to be processed in close proximity to the raw material vaporizing tank above the raw material vaporizing tank,
A temperature control mechanism that heats the substrate to be processed and controls the temperature thereof,
The substrate to be processed is heated, and the raw material is heated and vaporized by radiant heat from the substrate to be processed, thereby causing a thermal decomposition reaction on the substrate to be processed. The method is characterized in that a thin film composed of a product of the reaction is deposited.
[0018]
Preferably, the thin film forming apparatus of the present invention includes an elevating mechanism for adjusting a height of the raw material vaporization tank or the substrate to be processed, so that a distance between the raw material vaporization tank and the substrate to be processed can be adjusted. Further provision.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a schematic configuration of a CVD apparatus used for forming a thin film based on the method of the present invention. In the figure, 2 is a susceptor (substrate holding mechanism), 3 is a heater (temperature control mechanism), 6 is a substrate (substrate to be processed), 7 is a raw material vaporization tank, 9 is a jack (elevating mechanism), and 10 is a reaction chamber. .
[0020]
The substrate 6 and the raw material vaporization tank 7 are accommodated in a reaction chamber 10 in which the atmosphere can be adjusted. A jack 9 is provided on the bottom surface of the reaction chamber 10, and a ceramic raw material vaporization tank 7 is supported thereon via a ceramic base 8. A stage 1 with a micrometer is installed downward on the ceiling of the reaction chamber 10, and a susceptor 2 is attached to the lower surface thereof. A substrate 6 is held on the lower surface of the susceptor 2 via a flat heater 3. A temperature sensor 5 is attached to the heater 3. The temperature of the substrate 6 is controlled by the temperature controller 4 based on the output of the temperature sensor 5.
[0021]
The deposition of the thin film on the surface of the substrate 6 is performed as follows using this CVD apparatus. In the raw material vaporization tank 7, a complex to be a raw material for a thermal decomposition reaction is accommodated. The substrate 6 is held just above the raw material vaporizing tank 7 and close to the raw material vaporizing tank 7. The substrate 6 is heated, and the radiant heat from the substrate 6 heats and vaporizes the raw material in the raw material vaporization tank 7 to cause a thermal decomposition reaction on the surface of the substrate 6. As a result, a thin film made of a thermal decomposition reaction product can be deposited on the surface of the substrate 6.
[0022]
By adjusting the temperature of the substrate 6, the distance between the substrate 6 and the raw material vaporizing tank 7, or the thermal conductivity and heat capacity of the raw material vaporizing tank 7 and the pedestal 8 supporting the same, an appropriate process can be performed. Select conditions.
[0023]
Next, an example in which a ZnO thin film is formed on the substrate 6 by using the CVD apparatus shown in FIG. 1 will be described.
[0024]
In this example, zinc acetylacetonate [bis (2,4-pentanedionato) zinc, Zn (C ₅ H ₇ O ₂ ) ₂ ] was used as a complex as a raw material for the thermal decomposition reaction. As the substrate 6 to be processed, a Si single crystal and a fused quartz glass were used. Further, ceramics (made of ceramic with glaze, diameter 25 mm, depth 4.5 mm) was used for the raw material vaporization tank 7, and a porous ceramic plate (made of ceramic, thickness 12 mm) was used for the base 8. The substrate 6 is held in close proximity to the raw material vaporizing tank 7 immediately above the raw material vaporizing tank 7 under the open to the atmosphere, the substrate 6 is heated by the heater 3, and the radiant heat evaporates the raw material complex. A thin film was deposited.
[0025]
The ZnO thin film was formed under various conditions mainly using the substrate temperature (Ts) and the distance (D) between the substrate and the raw material vaporization tank as parameters. Evaluation of the obtained ZnO thin film was performed by evaluation of crystal orientation and crystal particle diameter by XRD, AFM observation, refractive index measurement by ellipsometer, UV-visible transmittance measurement, and the like.
[0026]
FIG. 2 shows the relationship between substrate temperature, deposition rate, and refractive index when a ZnO thin film is deposited on a fused silica glass substrate with the distance between the substrate and the raw material surface set to 5.0 mm.
[0027]
As shown in FIG. 2, the deposition rate of the thin film increases exponentially as the substrate temperature (Ts) increases. This is considered to correspond to the fact that the raw material is vaporized by the radiant heat of the substrate, so that the amount of vaporized raw material increases exponentially with temperature. The refractive index measured using an ellipsometer increased with the temperature until the substrate temperature (Ts) reached about 500 ° C., but turned to decrease when the temperature (Ts) exceeded 600 ° C.
[0028]
FIG. 3 shows an X-ray diffraction pattern of a ZnO thin film when ZnO was deposited on a fused silica glass substrate at a substrate temperature (Ts) of 300 ° C. with the distance between the substrate and the raw material surface set to 5.0 mm. Show. It can be seen that the ZnO thin film formed under these conditions grows with very high preferential orientation in the c-axis direction.
[0029]
FIG. 4 shows an X-ray of a ZnO thin film when ZnO is deposited on a quartz glass substrate at a substrate temperature of 150 ° C. to 600 ° C. with the distance between the substrate and the raw material surface set to 5.0 mm. 3 shows a diffraction pattern.
[0030]
It can be seen that a c-axis oriented ZnO thin film is formed at all substrate temperatures. At substrate temperatures of 300 ° C. and 150 ° C., only diffraction peaks corresponding to the 002 plane and the 004 plane of ZnO were observed, indicating that the substrate was completely oriented along the c-axis. In this figure, the peak of the X-ray intensity near 22 degrees is a halo from the quartz glass of the substrate.
[0031]
When the substrate temperature was 300 ° C. or higher, a thin film was formed even when the distance between the substrate and the material surface was increased to 10 mm, but a ZnO thin film was not formed at a deposition time of 12 hours at 150 ° C. .
[0032]
FIG. 5 shows an X-ray diffraction pattern of a ZnO thin film when ZnO was deposited on a quartz glass substrate at a distance of 2.5 mm between the substrate and the raw material surface, substrate temperatures of 100 ° C. and 150 ° C., and a deposition time of 24 hours. Show.
[0033]
At a substrate temperature of 150 ° C., only diffraction peaks corresponding to the 002 plane and the 004 plane of ZnO are observed, and it can be seen that they are completely oriented along the c-axis. At 100 ° C., the film was thin because the deposition rate was low, and only a peak corresponding to the 002 plane of ZnO was observed.
[0034]
At a substrate temperature of 100 ° C., no ZnO thin film was formed when the distance between the substrate and the material surface was 5.0 mm. Even when the substrate temperature was 70 ° C., when the distance between the substrate and the raw material surface was 2.5 mm, a ZnO thin film was formed on the substrate. However, the adhesive force to the substrate surface was very weak, and it was such that it was easily peeled off only by rubbing by hand.
[0035]
As a result of experiments using various conditions as described above, when the substrate temperature was 100 ° C. or more and 300 ° C. or less, and the distance between the substrate and the material surface was 2 mm or more and 5 mm or less, the film was highly oriented along the c-axis on the substrate. It was found that a ZnO thin film was deposited. Under the above conditions, the ratio of the c-axis: a-axis orientation could be 100: 1 or more.
[0036]
Further, it was confirmed that when the temperature of the substrate to be processed was high, the vaporization temperature of the raw material could be increased to the decomposition temperature, and a high deposition rate was obtained.
[0037]
【The invention's effect】
According to the thin film forming method of the present invention, a thin film having a high orientation can be formed at a relatively low temperature at atmospheric pressure without using a carrier gas.
[0038]
In particular, according to the thin film forming method of the present invention, since no carrier gas is used, equipment and a control system related to the carrier gas are not required, and the running cost for the CVD process and the manufacturing cost of the equipment used for the CVD process are reduced. be able to. Furthermore, since a raw material vaporizer and piping from the vaporizer to the substrate to be processed are not required, the raw material vaporization temperature can be increased, and the deposition rate of decomposition products increases as the raw material vapor pressure increases. Is also obtained.
[0039]
Further, in the method of forming a thin film of the present invention, since the substrate to be processed is disposed immediately above the raw material vaporization tank, a thin film can be uniformly formed on the surface of the substrate to be processed having a large area.
[0040]
Further, since the thin film forming method of the present invention can be performed at a relatively low temperature, it is possible to form a zinc oxide thin film on a plastic film such as PET which is widely used at present. Therefore, the present invention is effective for application to a plastic antistatic film or a flexible dye-sensitized solar cell, and reduction in manufacturing costs of surface acoustic wave devices, optical waveguides, laser oscillation devices, LEDs, electrodes for FED, and the like.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a CVD apparatus used in a method of the present invention.
FIG. 2 is a diagram showing a relationship between a substrate temperature, a deposition rate, and a refractive index when a ZnO thin film is deposited at a distance of 5.0 mm between a substrate and a raw material surface.
FIG. 3 is an X-ray diffraction pattern of a ZnO thin film formed at a distance of 5.0 mm between a substrate and a raw material surface and a substrate temperature of 300 ° C.
FIG. 4 is an X-ray diffraction pattern of a ZnO thin film formed at a distance between a substrate and a raw material surface of 5.0 mm and a substrate temperature of 150 ° C. to 600 ° C.
FIG. 5 is an X-ray diffraction pattern of a ZnO thin film formed at a distance of 2.5 mm between the substrate and the raw material surface and at a substrate temperature of 100 ° C. and 150 ° C.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Stage with a micrometer, 2 ... Susceptor (substrate holding mechanism), 3 ... Heater (temperature control mechanism), 4 ... Temperature controller, 5 ... Temperature sensor, 6 ... Substrate (substrate to be processed), 7 ... Material vaporization tank , 8 pedestal, 9 jack, 10 reaction chamber.

Claims (7)

The raw material for the pyrolysis reaction is stored in a raw material vaporization tank,
Above this raw material vaporization tank, the substrate to be processed is held close to the raw material vaporization tank,
Heating the substrate to be processed, heating and vaporizing the raw material by radiant heat from the substrate to be processed, causing a thermal decomposition reaction on the substrate to be processed,
Thus, a thin film forming method comprising depositing a thin film made of a product of a thermal decomposition reaction on the substrate to be processed. The method according to claim 1, wherein the raw material is a metal β-diketone complex, and a product of the thermal decomposition reaction is a metal oxide. The method according to claim 1, wherein the raw material is a β-diketone complex of zinc, and a product of the thermal decomposition reaction is ZnO. A reaction chamber with adjustable atmosphere,
A raw material vaporization tank that is disposed in the reaction chamber and contains a raw material for the pyrolysis reaction;
A substrate holding mechanism for holding a substrate to be processed in close proximity to the raw material vaporizing tank above the raw material vaporizing tank,
A temperature control mechanism that heats the substrate to be processed and controls the temperature thereof,
The substrate to be processed is heated, and the raw material is heated and vaporized by radiant heat from the substrate to be processed, thereby causing a thermal decomposition reaction on the substrate to be processed. A CVD apparatus for depositing a thin film made of a product of a reaction. 5. The apparatus according to claim 4, further comprising an elevating mechanism for adjusting a height of the raw material vaporizing tank or the substrate to be processed so that a distance between the raw material vaporizing tank and the substrate to be processed can be adjusted. 3. The CVD apparatus according to 1. The CVD apparatus according to claim 4, wherein the raw material is a metal β-diketone complex, and a product of the thermal decomposition reaction is a metal oxide. The CVD apparatus according to claim 4, wherein the raw material is a β-diketone complex of zinc, and a product of the thermal decomposition reaction is ZnO.

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