JP2002047572A - Method for producing titanium oxide thin film - Google Patents

Abstract

(57) [Problem] To form a uniform titanium oxide film when forming a titanium oxide film on a substrate by a plasma CVD method. SOLUTION: A plasma generating step for generating plasma by discharging to a rare gas and an oxygen gas by a discharging means,
By reacting the plasma generated by the plasma generation step with a source gas containing titanium, a film formation step for forming a titanium oxide film on a base material,
The plasma generating step and the film forming step are performed in different places.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a titanium oxide film or the like on a substrate by using plasma.

[0002]

2. Description of the Related Art Since titanium oxide has a high refractive index,
For example, in the case of forming an antireflection film by laminating several types of films on a polymer film,
It is suitably used as a high refractive index layer in the laminated film.

Means for forming a titanium oxide film on a substrate include a vacuum deposition method, a sputtering method, and a thermal CV method.
There is a method such as wet coating by a D method or a sol-gel method. However, the vacuum deposition method using titanium or titanium oxide as a material has poor adhesion to a substrate,
In addition, the sputtering method using titanium or titanium oxide as a target has a problem that the generation rate of a titanium oxide film is extremely slow. In thermal CVD,
Since this method oxidizes and decomposes the raw material gas by the heat energy of the base material to form a thin film, it is necessary to raise the temperature of the base material. Therefore, when the base material is a polymer film, Since decomposition and oxidation occur, it is impossible to form a titanium oxide film on a polymer film by a thermal CVD method. Furthermore, when a titanium oxide film is formed by wet coating by a sol-gel method or the like, it is difficult to reduce the thickness of the titanium oxide film, make the film quality uniform, and control the film thickness.

In order to solve such a problem, it is conceivable to form a titanium oxide film on a substrate by using a so-called plasma CVD method. Here, the plasma CVD method means that atomic or molecular radical species are generated by generating plasma in a reaction chamber into which a predetermined gas is introduced, and adhere to a solid surface. In many cases, volatile molecules are further generated by a surface reaction. This is a film formation method utilizing the phenomenon of being released and taken into the solid surface.

However, even when the plasma CVD method is used, the plasma generating step for generating plasma and the film forming step for forming the titanium oxide film are performed in the same place, so that titanium oxide is used. In the case where the material gas for forming the film is an organic titanium material gas, the gas is immediately decomposed (very high reactivity) when exposed to plasma. Therefore, there is a problem that it is difficult to form a titanium oxide film uniformly on the entire surface of the substrate on which the titanium oxide film is to be formed.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to form a uniform titanium oxide film when forming a titanium oxide film on a substrate by a plasma CVD method. I do.

[0007]

According to the present invention, in order to achieve the above object, a plasma generating step for generating a plasma by discharging a rare gas and an oxygen gas by a discharging means, A plasma generated by the generation step and a source gas containing titanium are reacted with each other to form a titanium oxide film on the base material, and the plasma generation step and the film formation step Provides a method for manufacturing a titanium oxide film, which is performed in different places.

[0008] In order for a source gas containing titanium to form a film on a substrate as titanium oxide, the source gas collides (reacts) with electrons or radicals present in the plasma, so that the source gas is produced. It needs to be disassembled.
According to the present invention, the plasma generation step for generating the plasma and the film formation step for forming the titanium oxide film on the base material are performed in different places, respectively. Radicals collide with the source gas (reaction)
It is possible to reduce the chance of performing the process (reduce the density of the plasma), thereby preventing the source gas from being decomposed near the gas inlet. Therefore, a titanium oxide film can be uniformly formed on the substrate.

Here, in the first aspect of the present invention, as described in the second aspect, the discharge means uses microwaves, or as described in the third aspect, It is preferable to use an electrode.

The present invention is not particularly limited as the discharging means, and any discharging means can be used as long as it can generate plasma. Among them, a device using a microwave or a device using an electrode is preferable because it can generate plasma efficiently and can be used relatively easily.

Further, in the invention according to any one of the first to third aspects, as described in the fourth aspect, it is preferable that the raw material gas containing titanium is an organic titanium material gas.

In the present invention, as the material gas used to form the titanium oxide film, any gas containing titanium can be used. However, among them, the organic titanium material gas decomposes immediately upon exposure to plasma, and forms a titanium oxide film. Therefore, it is difficult to form a uniform film by a normal plasma CVD method. .

[0013] In the invention according to any one of the first to fourth aspects, as described in the fifth aspect, the density of the plasma used in the film forming step is 10 ⁹ /
cm ³ or less.

When the density of the plasma used in the film forming step is set to 10 ⁹ / cm ³ or less, electrons and radicals present in the plasma collide with the source gas.
It is possible to reduce the chance of performing the process (reduce the density of the plasma), thereby preventing the source gas from being decomposed near the gas inlet. Then, the titanium oxide film can be uniformly formed on the base material. The density of the plasma used in the film forming step is preferably 10 ⁷ / cm ³ or more. If the density of the plasma is smaller than 10 ⁷ / cm ³ , the source gas may not be decomposed efficiently.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be specifically described below.

The present invention is characterized in that a plasma generating step for generating plasma and a film forming step for forming a titanium oxide film on a substrate are performed in different places, respectively.
Therefore, by reducing the chance of collision (reaction) between electrons and radicals present in the plasma and the source gas (reducing the plasma density), the source gas is prevented from being decomposed near the gas inlet. This enables a titanium oxide film to be uniformly formed on a substrate.
Hereinafter, the plasma generation step and the film formation step will be described respectively.

(1) Plasma Generation Step In the present invention, the plasma generation step is a step of generating plasma by discharging a rare gas and an oxygen gas (hereinafter, referred to as a plasma generation gas) by a discharge means. .

First, the method of the present invention is not particularly limited as a rare gas as a plasma generating gas.
Any rare gas can be used, but among them, argon gas is preferable. This is because argon gas has good plasma generation efficiency and can be used relatively easily.

In the method of the present invention, the oxygen gas in the plasma generating gas is necessary for forming a titanium oxide film in a film forming step described later. Therefore, the amount of the introduced oxygen gas is related to the thickness of the titanium oxide film to be used.

The discharging means in the present invention is used for discharging to a plasma generating gas as described above. In the method of the present invention, the discharge means for generating plasma is not particularly limited, and any discharge means can be used. Examples of the discharging means that can be used in the present invention include those using electrodes or coils connected to a power supply, those using electromagnetic waves introduced from a dielectric window or the like, and the like. Above all, an electrode connected to a power source and a discharge unit using microwaves are preferable because the device is relatively simple and the plasma generation efficiency is high.

Hereinafter, an example of an apparatus for carrying out the method of the present invention for the above-mentioned plasma generation step will be specifically described.

FIG. 1 shows an example of an apparatus used in the method of the present invention. As shown in FIG. 1, a titanium oxide film manufacturing apparatus 1 has a plasma generation region 2 for generating plasma and a source gas decomposed by plasma generated in the plasma generation region 2 to form a film on a substrate. And the film formation regions 3 are located at different places.

The plasma generating region 2 has a plasma generating gas inlet 4 for introducing a rare gas and an oxygen gas,
Electrode 5 for discharging to the introduced plasma generating gas
And a plasma guide tube 6 for sending generated plasma to the film formation region.

The plasma generating gas inlet 4 is provided for introducing a plasma generating gas into the plasma generating region 2, and its shape is not limited. A mass flow controller 7 for adjusting the amount of plasma generating gas arbitrarily before the inlet 4.
It is also possible to set up. This is because by installing the mass flow controller 7, an appropriate amount of plasma generating gas can be introduced, the waste of the gas can be eliminated, and the plasma can be generated efficiently.

The electrode 5 serving as a discharging means provided in the plasma generating region 2 is for discharging plasma generating gas to generate plasma.
The method of the present invention does not particularly limit the discharge means for generating plasma as described above, and any discharge means can be used. The apparatus shown in FIG. 1 uses the electrode 5 as the discharge means. It was used.

The electrodes 5 are installed so as to face each other in the plasma generation region.
A voltage is applied. In this case, the frequency of the power supply is
Any frequency can be used, not limited to radio waves. Then, when an RF voltage is applied between the opposing electrodes 5, plasma can be generated between the two electrodes.

As the discharging means in the plasma generating region, it is possible to use a microwave as shown in FIG. 2 in addition to the above-mentioned electrodes. As shown in FIG. 2, the waveguide 20 is installed so as to be orthogonal to the flow of the plasma generation gas, and microwaves are introduced into the waveguide 20 to generate plasma around the waveguide 20. I can do it. Although not shown, it is also possible to generate a plasma by winding a coil around a plasma generation region and applying a current to the coil to apply the current to a plasma generation gas.

The plasma generated in the plasma generation region 2 passes through the plasma guide tube 6 and is inserted into the film formation region 3. In the present invention, the shape or the like of the plasma induction tube 6 is not particularly limited, and may be any as long as it connects the plasma generation region 2 and the film formation region 3. As will be described later, the plasma generated in the plasma generation region 2 naturally flows into the film formation region 3 because the film formation region 3 is at a constant pressure (reduced pressure) state (also flows into the film formation region by diffusion). .

(2) Film Forming Step Next, the film forming step in the method of the present invention will be described.

In the present invention, the film forming step is a step for forming a titanium oxide film on a base material by reacting the plasma generated in the plasma generating step with a raw material gas containing titanium. . In the present invention, the film forming step is performed in a place different from the plasma generating step.

The density of the plasma used in the film forming step is preferably 10 ⁹ / cm ³ or less, more preferably 10 ⁷ / cm ³ or more and 10 ⁹ / cm ³ or less. If the plasma density is higher than 10 ⁹ / cm ^3, electrons and radicals present in the plasma are likely to react with the raw material gas containing titanium, so that the raw material gas is decomposed near the raw material gas inlet. This is because it may be difficult to form a uniform titanium oxide film on the base material. On the other hand, if the density of the plasma is smaller than 10 ⁷ / cm ³ , the decomposition of the raw material gas is unlikely to occur, which makes it difficult to efficiently form a titanium oxide film.

Here, the plasma density in the present invention is a value measured by a probe method. The probe method is to calculate a plasma density, a potential, and the like from the IV characteristics of a small electrode inserted into the plasma. For this measurement, a triple probe monitor TPM-2000 (Japan High Frequency) was used.

The titanium used in the film forming step is
If the gas contains titanium,
Any gas may be used. Among them, organic titanium material gas
Has the property of decomposing immediately when exposed to plasma
Therefore, it is preferable to form a film by the method of the present invention.
No. As the organic titanium material gas, Ti (i-OC
_ThreeH₇)_Four(Titanium tetra i-propoxide), Ti (O
CH_Three)_Four(Titanium tetramethoxide), Ti (OC
_TwoH_Five)_Four(Titanium tetraethoxide), Ti (n-OC_Three
H₇)_Four(Titanium tetra n-propoxide), Ti (n-
OC_FourH₉)_Four(Titanium tetra n-butoxide), Ti
(T-OC_FourH₉)_Four(Titanium tetra-t-butoxide)
Titanium alkoxide; Above all, Ti
(I-OC_ThreeH₇)_Four(Titanium tetra i-propoxy
C), Ti (t-OC_FourH₉)_Four(Titanium tetra t-but
(Oxide) is preferred. These organic titanium material gases
Is converted to a gaseous state by being evaporated in a liquid vaporizer.
Is what it is.

The substrate that can be used in the method of the present invention is not particularly limited, and a titanium oxide film can be formed on any substrate. For example, it is also possible to form a titanium oxide film on a plate-like substrate (for example, metal, plastic, glass, etc.),
It is of course possible to form a titanium oxide film on a polymer film.

The polymer film usable in the present invention includes, for example, triacetyl cellulose film, diacetyl cellulose film, acetate butyrate cellulose film, polyether sulfone film, polyacrylic film, polyurethane film, polyester film, Polycarbonate films, polysulfone films, polyether films, trimethylpentene films, polyetherketone films, acrylonitrile films, methacrylonitrile films, polyethylene terephthalate films (PET films), and the like. Among them, a polyethylene terephthalate film (PET film) and a triacetyl cellulose film are particularly preferred.

When a titanium oxide film is formed on these polymer films by the method of the present invention, the thickness of the titanium oxide film becomes uniform, and the titanium oxide film has a high refractive index. The polymer film can be used as an anti-reflection film.

Hereinafter, the film forming step in the method of the present invention will be described more specifically with reference to the above-mentioned drawings.

As shown in FIG. 1, a source gas introduction pipe 8 for introducing a source gas containing titanium, an exhaust port 9, and a base material for installing a base material 10 are provided in the film formation region 3. An installation member 11 is provided, and the film formation region 3 is kept at a constant pressure (reduced pressure) by being evacuated by a vacuum pump and then filled with a source gas. Then, in the film forming region 3, the plasma generated in the plasma generating region 2 reacts with the raw material gas containing titanium introduced through the raw material gas introduction pipe 8, and the raw material gas is decomposed, and the raw material gas is decomposed. The combination of the titanium contained and the oxygen contained in the plasma forms a titanium oxide film on the substrate 10. At this time, the density of the plasma in the film formation region is higher than the density in the plasma generation region 2.
Since the density is low, the raw material gas and the plasma do not react with each other at only a certain portion to form a film, and a uniform film can be formed.

In the present invention, the shape and the like of the source gas introduction pipe 8 for introducing the source gas into the film formation region 3 as described above are not particularly limited. However,
In order to form a titanium oxide film uniformly on the substrate,
It is preferable that the source gas is uniformly filled in the entire film formation region. Therefore, it is preferable to introduce the source gas from a plurality of locations instead of introducing the source gas only from one specific location.

For the above reason, the source gas introduction pipe shown in FIG. 1 has a single tube at its root and is connected to a source tank (not shown). Has a shape that draws a circle above the substrate on which the film is to be formed, and has a plurality of holes in the tube to make the concentration of the source gas above the substrate uniform. It has become.

An exhaust port 9 is provided in the film forming area 3. This is provided to exhaust the gas (such as a raw material gas after decomposition) in the film formation region and to keep the film formation region in a constant pressure state. Therefore, a vacuum pump is installed at the end of the exhaust port. The inside of the film formation region is filled with a source gas containing titanium, plasma generated in the plasma generation region, and the like, and a preferable pressure in the film formation region is 1 Torr or less. If the pressure is higher than 1 Torr, there is a problem that the refractive index and mechanical strength of the formed titanium oxide film decrease. The partial pressure of the organic titanium compound gas is 10 ^-1 T
It is preferably at most orr. If the partial pressure of the organic titanium compound gas is higher than 10 ^-1 Torr, there is a problem that the organic titanium compound is liquefied in the reaction chamber.

As described above, the substrate 10 on which the titanium oxide film is formed is not particularly limited in the method of the present invention, and any substrate can be used. Since the specific description has been described above, it is omitted here.

The method of the present invention is not particularly limited as to the shape of the base member 11 on which the base member 10 is set, and may be any shape.
For example, when the substrate 10 is plate-shaped (metal or the like), a table-type installation member 11 can be used. When the substrate is a polymer film, the substrate 10 can be used. The material setting member may be formed in a roller shape, and the polymer film may be sequentially transported. It is also possible to control the temperature of the base member. In such a case, a titanium oxide film is formed on a base material that is particularly vulnerable to heat because the temperature of the equipment can be accurately controlled. It is particularly suitable.

As described above, in the film formation region, the oxygen contained in the plasma generated in the plasma generation region and introduced into the film formation region reacts with the titanium contained in the titanium source gas, thereby causing oxidation. A titanium film is formed on the base material. At this time, the flow ratio of oxygen and organic titanium material gas contained in the plasma (oxygen gas / organic titanium material gas)
Is desirably 10 or more and 30 or less. If the thickness is smaller than this range, the amount of carbon mixed into the film increases, and the refractive index of the formed titanium oxide film decreases. Also,
If it is larger than 30, the amount of the organic titanium material gas is too small, and it is difficult to efficiently form a titanium oxide film.

The temperature in the film formation region is as follows.
The present invention is not particularly limited, and a titanium oxide film can be formed at any temperature. However, a film formation method using plasma is generally characterized in that a film can be formed at a low temperature (not less than −10 ° C. and not more than 150 ° C.).
Since there is no particular merit, the temperature is preferably 150 ° C. or lower also in the present invention. In addition, the case where the substrate is a heat-sensitive substance such as a polymer film can be sufficiently considered. Also -10
There is little merit obtained by forming a film at a temperature lower than ℃, and it is preferable to be -10 ° C. or more even in view of cost.

In the film formation region, a base member is provided, but is not necessarily required in the method of the present invention, and is limited to a shape as shown in FIG. not.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

[0048]

The present invention will be described in more detail with reference to examples.

Example A titanium oxide film was formed on a polymer film (polyethylene terephthalate (PET) film) under the following conditions using the apparatus shown in FIG. 2 (apparatus using microwaves as discharging means). The organic titanium compound gas, vaporized by liquid vaporizer titanium tetraisopropoxide _{Ti (i-OC 3 H 7} ) 4 used,
As a plasma generating gas for generating plasma, a mixed gas of argon and oxygen gas was used.

<Conditions of Plasma Generation Region> Applied power 1 kW Titanium tetraisopropoxide gas flow rate 100 sccm Oxygen gas flow rate 1000 sccm

The gas flow unit sccm is defined as
It is dar cubic cm per minute.

<Plasma concentration in film formation region> Plasma concentration in the film formation region (arbitrary three points between the titanium tetraisopropoxide gas inlet and the base material (PET film)) under the conditions of the plasma generation region. Was measured by the probe method. The measurement results are shown below. The measurement is based on the method described above.

The concentration of plasma in the film formation region 2 × 10 ^{8 to} 9 × 10 ⁸ / cm ³

The measurement results of the titanium oxide film formed on the polyethylene terephthalate film under the above conditions are shown below.

<Results of Measurement of Titanium Oxide Film> As a result of forming a titanium oxide film under the above conditions, the average thickness was about 50 nm.
The variation of the film thickness within a diameter of about 30 cm was about ± 10%.

<Equipment Used for Titanium Oxide Film Measurement> Film Thickness Measurement Ellipsometer Model No. UVSEL ^™ Manufacturer JOBIN YVON Composition Analysis Photoelectron Spectroscopy Model ESCALAB220i-XL Manufacturer VG Scientific Refractive Index Measurement Ellipsometer Model No. UVISEL ^™ Manufacturer JOBIN YXON Structure Diffractometer Model RINT 1500 Manufacturer RIKEN ELECTRIC CO., LTD.

As described above, the variation in the film thickness can be suppressed to about ± 10%, and the titanium oxide film can be formed evenly as compared with the ordinary plasma CVD method. Was. In addition, after forming the titanium oxide film,
The polyethylene terephthalate film was in a good state without slight elongation or deformation.

(Comparative Example) As shown in FIG. 3, an apparatus 30 in which a plasma generation region and a film formation region are installed at the same place was used, and all other conditions were the same as in the first embodiment. A titanium oxide film was formed on the polymer film. The device 30 is a plasma CVD device conventionally used.
The apparatus is provided such that electrodes 31 and 31 face each other, and a source gas introduction pipe 32 for introducing a source gas is provided therebetween. The substrate 33 is provided on one of the substrates, generates plasma between the electrodes, decomposes a source gas using the plasma, and forms a titanium oxide film on the substrate 33 on the electrodes. It is.

<Plasma concentration in film forming region> Film forming region in the above comparative example (arbitrary three points between titanium tetraisopropoxide gas inlet and substrate (PET film))
Was measured by the probe method. The measurement results are shown below. The measurement is based on the method described above.

The concentration of plasma in the film formation region 2 × 10 ^{9 to} 5 × 10 ⁹ / cm ³

<Results of Measurement of Titanium Oxide Film> The titanium oxide film was formed only about 5 cm from the raw material gas inlet, and it was not possible to form a uniform film on the entire polymer film.

In addition, as described above, the plasma concentration in the film formation region is a value larger than 10 ⁹ / cm ³ , and it is clear that it is difficult to form a uniform film if the plasma concentration is too high. Was.

[0063]

According to the present invention, the plasma generating step for generating plasma and the film forming step for forming a titanium oxide film on a substrate are performed in different places, respectively.
The chance of collision (reaction) between electrons and radicals present in the plasma and the source gas can be reduced (reducing the density of the plasma), so that the source gas is decomposed near the gas inlet. Can be prevented.
Therefore, a titanium oxide film can be uniformly formed on the substrate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a schematic sectional view showing another example of an apparatus for performing the method of the present invention.

FIG. 3 is a schematic sectional view of a conventional plasma CVD apparatus (used in a comparative example).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Titanium oxide film manufacturing apparatus 2 ... Plasma generation area 3 ... Film formation area 4 ... Plasma generation gas introduction port 5 ... Electrode 6 ... Plasma guide tube 7 ... Mass flow controller 8 ... Material gas introduction pipe 9 ... Exhaust port 10 ... Group Material 11: Substrate installation member 20: Waveguide 30: Apparatus for producing titanium oxide film of comparative example 31: Electrode 32: Source gas guide tube 33: Substrate

Claims (5)

[Claims] 1. A plasma generating step for generating plasma by discharging to a rare gas and an oxygen gas by a discharging means, and reacting the plasma generated by the plasma generating step with a raw material gas containing titanium, A film forming step for forming a titanium oxide film on a base material, wherein the plasma generating step and the film forming step are performed in different places, respectively. . 2. The method for producing a titanium oxide film according to claim 1, wherein said discharging means uses microwaves. 3. The method for producing a titanium oxide film according to claim 1, wherein said discharging means uses an electrode. 4. The method for producing a titanium oxide film according to claim 1, wherein the raw material gas containing titanium is an organic titanium material gas. 5. The method for producing a titanium oxide film according to claim 1, wherein the density of the plasma used in the film forming step is 10 ⁹ / cm ³ or less.