JPH08253322A - Production of titanium oxide thin membrane - Google Patents

Abstract

PURPOSE: To rapidly synthesize a titanium oxide thin membrane by using a low temperature plasma. CONSTITUTION: This titanium oxide thin membrane is accumulated on a substrate by supplying a titanium compound expressed by the general formula Ti (OR)4 (R is a lower alkyl group) in a gaseous state to an atmospheric pressure glow discharge beam plasma generated by using an inert gas as a main gas. Hydrogen gas may be supplied simultaneously with the titanium compound. The high quality titanium oxide thin membrane is synthesized without exerting an adverse effect to the substrate, since it is possible to perform the synthesis at a low temperature by this method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for depositing a uniform and high-quality titanium oxide thin film on various substrates to a desired thickness simply and in the air in a short time.

[0002]

2. Description of the Related Art Titanium oxide thin films are not only effective as capacitors, insulating films and passivation films in the field of LSI, but also wear resistance, impact resistance, and resistance to various gases.
It is effective in imparting corrosion resistance and heat resistance, and is also used for decorative purposes. Furthermore, recently, a photobactericidal effect has been found, and attention is being paid to its application to medicine.

As a method for obtaining such a titanium oxide thin film, from a conventional method of melting TiO ₂ powder, followed by molding and cooling, a recent method such as a sputtering method, a chemical vapor deposition method, a sol-gel method or the like. Has been developed and has made remarkable progress. In particular, the latter new method is extremely excellent as a method for forming a thin film uniformly and with high purity on a desired substrate.

Of these, the conventional chemical vapor deposition method using plasma is considered to be effective as a method for forming a titanium oxide thin film, but since this method is performed at a high temperature, the damage to the substrate is large and the substrate Are limited to those with high heat resistance. In order to avoid this, a method of performing low temperature plasma is also known, but it is necessary to perform plasma processing on the plasma generator and the substrate in a vacuum system, and in addition to requiring a large-scale device and peripheral equipment, As a result, it is difficult to continuously process the substrate. Further, in the sol-gel method, it takes time to dry the gel, pinholes and cracks are generated when the medium is volatilized, and pores remain,
It is difficult to obtain a precise thin film.

The present invention is intended to improve the above-mentioned circumstances. Titanium oxide capable of depositing a homogeneous and high-quality titanium oxide thin film on a variety of substrates in the atmosphere to a desired thickness easily and in a short time. It is an object to provide a method for manufacturing a thin film.

[0006]

Means and Action for Solving the Problems The present inventors have
As a result of earnest studies to achieve the above main body, the following general formula (1) Ti (OR) ₄ ··· was applied to an atmospheric pressure glow discharge beam plasma generated by using an inert gas such as helium gas or argon gas as a main gas. .. (1) (where R represents a lower alkyl group) is supplied in a gaseous state, and titanium oxide is produced from this titanium compound by atmospheric pressure glow discharge beam plasma to form a titanium oxide thin film on the substrate. When formed, the titanium oxide thin film was deposited on various substrates with good adhesion, and it was found that this titanium oxide thin film is a homogeneous and high quality product without pinholes, cracks, etc. It came to.

The present invention will be described in more detail below. In the method for producing a titanium oxide thin film according to the present invention, an atmospheric pressure glow discharge beam plasma generated by using an inert gas as a main gas is used for the following general formula (1) Ti (OR). ₄ (1) (R represents a lower alkyl group) is supplied in a gaseous state to deposit a titanium oxide thin film on the substrate.

Here, the present invention forms a titanium oxide thin film from a titanium compound by atmospheric pressure glow discharge beam plasma. As an atmospheric pressure glow discharge beam plasma apparatus, Japanese Patent Laid-Open No. 4-212253 by Koinuma et al.
JP-A-4-242924, Appl. Phys.
Lett. 60 (7), 17, Feb. , 1992, and the device shown in FIG. 1 described later can be used, for example.

In this case, in the present invention, the main gas is passed through the apparatus, the high frequency oscillator is energized to generate plasma, and titanium compound vapor entrained in the carrier gas is supplied to the inside of the plasma flame if necessary. To react with. Further, if necessary, hydrogen gas can be introduced as a reaction gas.

The output of the high frequency oscillator varies depending on the shape of the plasma torch, the size of the plasma flame, and the type of main gas, but is about 50 to 15 for a plasma flame with a diameter of 5 mm.
It is desirable to perform in the range of 0W. If it is lower than this, plasma is not generated. If it is higher than this, not only is it uneconomical, but it may lead to damage to the electrodes.

In the present invention, the main gas is helium,
Argon is preferably used. The supply amount of the main gas varies depending on the shape of the plasma torch, the size of the plasma flame, and the type of the main gas, but is usually preferably 200 to 500 sccm for a plasma flame having a diameter of 5 mm.
When it is low, the plasma may not be generated.

On the other hand, as the titanium compound, those represented by the following general formula (1) Ti (OR) ₄ ... (1) are used.

Here, R is a lower alkyl group.

Since the titanium compound is supplied in a gaseous state, a titanium compound which is gaseous at room temperature or a liquid or solid which has a vapor pressure at room temperature is preferable. In this case, compounds that easily volatilize are more preferable.

As such a titanium compound, tetramethoxytitanium, tetraethoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium, etc. are preferably used, and among them, tetraethoxytitanium having a high vapor pressure is most preferably used.

In order to improve the quality of the titanium thin film, it is necessary to make the starting titanium compound highly pure, and these titanium compounds can generally be highly purified by a distillation operation.

The amount of titanium compound gas supplied varies depending on the shape of the plasma torch, the size of the plasma flame, and the type of main gas, but it is 0.
In the range of 01 to 2 sccm, preferably 0.02 to 0.1
A sccm range is desirable. If it is lower than this, the deposition efficiency is lowered and the productivity is inferior, and if it is higher than this, titanium oxide particles adhere to each other to form a coarse and porous film surface, which is not preferable.

As a supply method, as shown in FIG. 1, a method in which the vapor pressure of the titanium compound at that temperature is sent to the plasma generator while bubbling the carrier gas is preferably adopted. At this time, it is possible to adjust the supply amount of the titanium compound gas by adjusting the amount of the carrier gas.

The gasified gas is supplied to the atmospheric pressure glow discharge beam plasma apparatus, and the gasified into plasma is deposited as titanium oxide on the substrate in the atmosphere. This operation need only continue the process for the required time to the desired thickness.

The deposition rate of the titanium oxide thin film depends on the supply rate of the titanium compound gas, but in order to obtain a uniform and dense titanium oxide thin film, the deposition rate is 20 to 200 Å per second, particularly 50 to 100 Å. Preferably.

In the present invention, it is recommended to supply hydrogen gas together with the supply of the titanium compound. The introduction of this hydrogen gas is important for making the titanium oxide thin film more uniform and of high quality.

The amount of hydrogen gas introduced is preferably in the range of 0 to 300 times the volume of the vapor of the titanium compound, especially 5
The range of 0 to 100 times is preferable. A titanium oxide thin film can be produced without supplying hydrogen gas, but if the supply amount of hydrogen gas is low, the deposition rate increases, but on the other hand, it causes an increase in carbon content and a decrease in hardness. 30 times or more is desirable. Further, if the supply amount of hydrogen is too large, the effect of adding hydrogen will not be exhibited, and the plasma flame will become unstable.

In the present invention, a carrier gas can be used as described above. The carrier gas is used for the purpose of supplying the titanium compound, and it is also possible to use an inert gas such as nitrogen in addition to helium and argon which are main gases and hydrogen gas which is a reaction gas.

The amount of aeration of the carrier gas varies depending on the vapor pressure of the titanium compound, so the range cannot be limited, but
The minimum amount required to supply the titanium compound gas is sufficient.

The type of substrate on which the titanium oxide thin film is deposited and formed according to the present invention is not particularly limited. For example, a metal substrate such as single crystal silicon, aluminum or stainless steel,
Examples thereof include ceramic substrates such as silicon nitride, alumina, and boron nitride, carbonaceous substrates such as graphite, and organic resins such as polyethylene, polypropylene, polyester, polyamide, polyimide, phenol resin, and polyurethane.

In this case, since the temperature of the substrate during the plasma treatment rises to about 200 ° C., it is possible to use the substrate stable in the atmosphere at a temperature of 200 ° C. or higher as it is.
Further, it is necessary to treat a substrate that is melted or decomposed at a temperature of 200 ° C. in the atmosphere, and is further oxidized and burned, for example, an organic substrate such as polyethylene or polypropylene, while cooling.

[0027]

The method for producing a titanium oxide thin film using atmospheric pressure glow discharge beam plasma according to the present invention allows deposition on a substrate in the atmosphere, so that a large-scale apparatus or complicated peripheral equipment can be used. Since it has no need and has a high deposition rate, it has an excellent feature that it has extremely high productivity, and continuous processing of a substrate is also possible. Also, since it is possible to deposit at relatively low temperatures, a wide variety of substrates can be selected,
It can also be used for imparting abrasion resistance, impact resistance, corrosion resistance, heat resistance, etc. of a substrate, or for decoration or sterilization. In particular, by using a high-purity titanium compound, the titanium oxide thin film according to the present invention can be manufactured to be a homogeneous and high-purity thin film of high quality without generation of pinholes or cracks or residual pores, and damage to the substrate. It is a manufacturing method that does not give it, and is also effective for applications such as electronic materials that require high quality.

[0028]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to the following examples.

Example 1 Using the apparatus shown in FIG. 1, S
A titanium oxide thin film was formed on an i single crystal substrate. First, a high-frequency oscillator (13.56M) was introduced while allowing argon gas (main gas) to flow from the argon gas cylinder 4 to the plasma generator 3 having the anode 1 and the cathode 2, respectively.
(Hz) 5 power was supplied to adjust the power to 105 W, and plasma was generated. In the figure, 6 is an insulator and 7 is a spacer.

Next, here, He gas cylinders 8 to 10
A He gas of sccm was bubbled through a bubbler 10 containing tetraisopropoxytitanium 9 to ventilate vapors of tetraisopropoxytitanium or tetraethoxytitanium, and 5 sccm of hydrogen gas was vented from a hydrogen gas cylinder 11. In this case, the ventilation amount of tetraisopropoxy titanium vapor was 0.05 sccm as a result of calculation from the vapor pressure.
Met.

The silicon single crystal substrate 12 was placed at a distance of 2 mm from the tip of the plasma generator 3 and held for 1 minute to deposit a titanium oxide thin film on the substrate 12. The deposited titanium oxide thin film had good adhesion and could not be easily peeled off.

The results of observation of this titanium oxide thin film by an electron micrograph (magnification: 60,000 times) are shown in FIG.
From this result, it was confirmed that the titanium oxide thin film was homogeneous and dense.

The thickness of the titanium oxide thin film is measured by a surface roughness meter (D
When measured by ektak3030), it was deposited to a thickness of 0.9 μm, and the deposition rate was 150 Å / sec.

The Raman spectrum of the titanium oxide thin film thus obtained is shown in FIG. The Raman spectrum of titanium oxide in the anatase phase is in good agreement with this.

When the ratio of titanium to oxygen and the carbon content were measured by X-ray photoelectron spectroscopy, the titanium / oxygen ratio was 1.9, which was almost the same as TiO ₂ and the carbon content was 0. The value was as low as 0.98%.

Furthermore, the deposited film has a high refractive index (2.5).
With.

Tetraethoxytitanate
The film formed using [Ti (O—C ₂ H ₅ ) ₄ ] changes its structure from anatase type to rutile type film by hydrogenation at a substrate temperature of 400 ° C. or higher. (The film is Amorphou
s)

The withstand voltage is 6.5 × 10 ⁵ V / cm for the anatase type film and 1.0 × 10 ⁶ V / cm for the rutile type film by hydrogenation when the leakage current j = 10 ⁻⁶ A / cm ^−2. Met.

The anatase film had a dielectric constant of 13.6, and the hydrogenated rutile film had a considerably high dielectric constant of 48.3.

From the ultraviolet absorption characteristics of the TiO ₂ film, bio-related applications are also expected (light sterilization effect).

Example 2 Ice water was poured into an aluminum container to which polypropylene of 50 μm was adhered, and a titanium oxide thin film was deposited for 10 seconds in the same manner as in Example 1. The titanium oxide thin film did not impair flexibility and had good adhesion.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for generating an atmospheric pressure glow discharge beam plasma.

FIG. 2 is an electron micrograph of a titanium oxide thin film deposited on a silicon single crystal substrate.

FIG. 3 is a graph showing a change in Raman spectrum due to a change in deposition temperature of a titanium oxide thin film deposited on a silicon single crystal substrate. Raw material {Tetraethoxy
_{titanate [Ti (O-C 2} H 5) 4]

FIG. 4 is a graph showing a change in Raman spectrum of a titanium oxide thin film deposited on a silicon single crystal substrate due to hydrogenation. Raw material {Tetraethoxyti
_{tanate [Ti (O-C 2} H 5) 4] substrate temperature 55
0 ° C

FIG. 5 is a graph showing a deposition amount of a titanium oxide thin film per minute depending on a change in deposition temperature.

FIG. 6 is a graph showing the hydrogenation effect of the withstand voltage characteristic.

FIG. 7 is a graph showing the effect of hydrogen addition on dielectric properties.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H01L 21/316 H01L 21/316 X // C07F 7/28 C07F 7/28 B

Claims (2)

[Claims] 1. An atmospheric pressure glow discharge beam plasma generated by using an inert gas as a main gas is represented by the following general formula (1) Ti (OR) ₄ ... (1) (R represents a lower alkyl group). A method for producing a titanium oxide thin film, comprising depositing a titanium oxide thin film on a substrate by supplying the indicated titanium compound in a gaseous form. 2. The method according to claim 1, wherein hydrogen gas is simultaneously supplied together with the titanium compound.