JPH08109471A - Production of thin film - Google Patents

Abstract

PURPOSE: To produce an optical thin film at a high speed by bombarding steam generated from a film raw material with accelerated ions and allowing the accelerated film raw material to arrive at the substrate. CONSTITUTION: The inside of a vacuum tank 1 is exhausted, and a gas of Ar or the like is introduced therein from a gas introducing port 6. A Ti sheet 3 as a film raw material is heated to about 1200 deg.C, and Ti steam is made present in the vicinity of the upper direction of the sheet 3. At the time of applying the accelerated Ar ions from an ion gun 5, Ti steam is sputtered. Then, at the time of opening a shutter 7, a Ti film is formed on a substrate 2. Thus, the film forming rate is accelerated. The adhesion and hardness of the formed film are sufficient. As the film raw material, granular SiO and MgF2 as well as the Si sheet 3 can be utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin film at a high speed, and more particularly to a method for producing an optical thin film at a high speed by using a sputtering method.

[0002]

2. Description of the Related Art Conventionally, when forming a thin film, a vacuum vapor deposition method has been widely used because of the ease of the method and the speed of film formation. This is the same when forming an optical thin film such as an antireflection film, a half mirror, or an edge filter. On the other hand, in recent years, even for optical thin films and other thin films, there is an increasing demand for coating by a sputtering method, which is advantageous in terms of automation, labor saving, and applicability to a large area substrate as compared with the vacuum deposition method. . However, the sputtering method has been slightly delayed in industrial diffusion in that the film formation rate is slower than that of the vacuum evaporation method.

An example of applying a sputtering method to an optical thin film is, for example, Japanese Patent Laid-Open No. 4-223401. According to the publication, a low-refractive-index film that hardly absorbs light can be formed by using a target such as MgF ₂ which easily absorbs light when sputtering and added Si.

[0004]

However, in the conventional technology of the related art, the film forming rate is 10 nm / min or less at the maximum even when a high frequency power of 2.8 W / cm ² is applied, and the film forming rate is slow. The drawbacks of the sputtering method have not been solved.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a thin film manufacturing method capable of forming a thin film at a high speed by a sputtering method.

[0006]

According to the present invention, in order to solve the above-mentioned problems, the temperature of a solid film raw material is raised, and the vapor generated from the film raw material is caused to collide with accelerated ions. The film raw material accelerated by being bombarded by the ions reaches the substrate to form a film on the substrate.

Further, in the present invention, the surface of the granular film raw material having a particle size of 0.1 to 10 mm is heated by plasma, and the accelerated ions are collided with the vapor generated from the film raw material to accelerate. The film raw material reaches the substrate to form a film on the substrate.

Further, in the present invention, granular MgF ₂ having a particle size of 0.1 to 10 mm is used as a target, and a high frequency power of ² W / cm ² or more is applied to the target while introducing a gas containing at least oxygen. Generate a plasma on the top, raise the temperature of the target surface by the plasma,
It was decided to form a film on the substrate by sputtering both the target and vapor from the target.

[0009]

[Action]

(Operation of claim 1) In the conventional sputtering method, when the ions collide with the target, it is necessary to break the bonds between the atoms and molecules in the target and eject the atoms and molecules from the target. Since a part of them is spent for breaking the bonds between atoms and molecules, the sputtering yield is lowered, and as a result, there is a drawback that the film forming rate is slowed down. On the other hand, in the present invention,
The solid film raw material is not directly sputtered, but the film raw material is heated to cause the ions to collide with the vapor existing above the raw material, so all the accelerated ion energy is used for sputtering. The yield is high, and as a result, the film formation rate can be significantly increased as compared with the conventional method.

(Operation of Claim 2) Further, such a state can be produced relatively easily by heating the granular film raw material with plasma. Because there are many edges in the granules, an electric field
This is because the magnetic field concentrates and is easily heated. Also, the granules are poor in heat conduction and are therefore easily heated.
If the vapor pressure rises due to local heating of the granular raw material, especially around the edges, the sputter yield will rise sharply. At this time, if the size of the granules is too small, they will rise up in the chamber and become particles, so the particle size is preferably 0.1 mm or more, and more preferably 0.5 mm or more. Also, if the granules are too large, the edges will decrease,
Particle size is 1 because the effect of concentration of electric and magnetic fields is reduced.
It should be 0 mm or less, preferably 5 mm or less. Granule size,
The shape does not have to be uniform.

(Operation of claim 3) Mg mentioned in the prior art
In the case of F ₂ sputtering, the grain size is 0.
High frequency sputtering is performed using a granular raw material of 1 to 10 mm as a target. At this time, the MgF ₂ granules are heated by the plasma generated by the high frequency, but there is a correlation between the applied power and the temperature of the target, and when the high frequency power of ² W / cm ² or more is applied, the temperature of the MgF ₂ granules is 7
Since the temperature is higher than 00 ° C. and the vapor pressure is sufficiently increased, it is advisable to perform sputtering in this state. At this time, not only the steam but also the target granular MgF
_{2 is} also sputtered at the same time, but there is no particular problem in terms of film formation rate. The relationship between the input power and the sputtering yield will be described in detail in Example 3.

For optical applications, it is desirable that light absorption is small, but when solid MgF ₂ is sputtered, most of it is dissociated into Mg and F, and F on the substrate.
The film is formed in a state of insufficient light absorption and light absorption occurs. On the other hand, the vapor generated by heating is in the state of MgF ₂ molecules, and when the accelerated ions collide with the molecules, most of the molecules reach the substrate in the molecular state without being dissociated. Light absorption is less likely to occur in the formed thin film. When not only vapor but also granular MgF ₂ is simultaneously sputtered as in the case of the present invention, some light absorption occurs. Therefore, in order to reduce the light absorption to a level where there is no practical problem, a gas containing oxygen is introduced. It is good to sputter while. At this time, oxygen combines with dissociated Mg and has an effect of reducing light absorption.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the thin film manufacturing method according to the present invention will be described below with reference to the accompanying drawings.

Example 1 A film forming apparatus used in this example is shown in FIG. A substrate 2 is placed above the vacuum chamber 1. The Ti plate 3 which is a film raw material can be heated to a desired temperature by a resistance heating method by passing an electric current from a power source 4. The ion gun 5 is directed to the plate 3, and is arranged so that ions are made to collide with the plate 3 to sputter, and the sputtered particles reach the substrate 2 to form a thin film.

After evacuating the vacuum chamber 1 to 3 × 10 ^-5 Pa, Ar gas is introduced from the gas inlet 6 to 5 × 10 ^-4 Pa. The Ti plate 3 is heated by the power source 4 to 1200 ° C. At this time, the vapor pressure of Ti is in the order of 10 ⁻⁴ Pa,
Ti vapor comes to exist near the upper part of the plate 3. Subsequently, the ion gun 5 accelerated with an accelerating voltage of 0.9 kV A
Upon irradiation with r ions, Ti vapor is sputtered. Here, when the shutter 7 is opened, a Ti film is formed on the substrate 2.

When formed by this method, the film formation rate is extremely high at 200 nm / min. Further, the adhesion and hardness of the film were sufficient.

(Comparative Example) When sputtering was performed in the same manner as in Example 1 except that no current was applied to the plate 3 and heating was performed (conventional sputtering method), the film formation rate was 8 nm / min, which was 1 nm as compared with the example. It will be less than / 20. Moreover, when the temperature of the plate 3 is raised to about 1400 ° C. without using an ion gun (conventional vacuum deposition method), the deposition rate is 100 nm.
/ Min or more, but the adhesion of the film is extremely low and not at a practical level.

(Embodiment 2) A film forming apparatus used in this embodiment is shown in FIG. A substrate 12 is installed above the vacuum chamber 11. SiO granule 13 with a particle size of 1-10 mm, which is the raw material for the film
Put the magnetron cathode 15 in a Cu dish 14
It is placed on top. The cathode 15 is connected to a DC power source 16 for sputtering. A gas inlet 17 is provided on the side surface of the vacuum chamber 11.

After evacuating the vacuum chamber 11 to 1 × 10 ^-4 Pa, O ₂ gas is introduced from the gas inlet 17 to 2 × 10 ^-1 Pa. Electric power of 400 W is supplied from the DC power supply 16 to the magnetron cathode 15 to generate plasma. This plasma heats the SiO granules 13 to about 800
C., and SiO vapor is present near the upper part of the granule 13. Here, when the shutter 18 is opened, the substrate 12
A SiO film is formed on top.

When a thin film is formed by the above method, the film formation speed is extremely high at 160 nm / min. Further, the adhesion and hardness of the film were sufficient, and the film density was high and the gas barrier property was excellent.

(Embodiment 3) FIG. 3 shows a film forming apparatus used in this embodiment. A substrate 12 is installed above the vacuum chamber 11 so that it can rotate. Membrane particle size M of 3-5 mm
The gF ₂ granules 13 are placed in a quartz dish 14 and placed on a magnetron cathode 15 having a diameter of 4 inches (about 100 mm). The cathode 15 is connected to the RF power source 20 for sputtering. Gas inlets 17 and 19 are provided on the side surface of the vacuum chamber 11.

While heating the substrate 12, which is BK optical glass, to 100 ° C. by a heater (not shown), 1 × 10
^The inside of the vacuum chamber 11 is evacuated to ^-4 Pa. Then, O ₂ gas is introduced from the gas inlet 19 to 1 × 10 ⁻¹ Pa. Power is supplied from the RF power source 20 to the magnetron cathode 15,
Generate plasma. This plasma causes MgF ₂
The granules 13 are heated and sputtered. Here, when the substrate 12 is rotated and the shutter 18 is opened, the MgF ₂ film is formed on the substrate 12.

Here, when the input power is changed, the granules 13 are
FIG. 4 shows how the surface temperature of the film changes with the film formation rate on the substrate 12. It can be seen that when the applied power is 300 W (that is, 3.8 W / cm ² ) or more, the surface temperature rises up to about 700 ° C., and the film formation rate rapidly increases. MgF ₂ granules initially increased vapor pressure at this temperature, it come to exist vapor on top of MgF ₂ granules,
This is because vapor comes to be sputtered.

As a comparative example, FIG. 5 shows the results of the same experiment using a MgF ₂ sintered body instead of the MgF ₂ granules 13. In the case of using a sintered body, unlike the case of granules, since there is no edge portion, the electric field and magnetic field do not concentrate, and even if the applied power is increased, it is difficult to heat and the temperature does not rise so much. That is, it is a state of sputtering that is usually performed, and the film formation rate is extremely low, which is not practical.

The film formed by the manufacturing method of this embodiment is
The adhesiveness to the substrate and the scratch resistance were excellent, and it was sufficiently practical. In addition, the light absorption is smaller than that of the comparative example, and especially when the input power is 400 W or more, the absorption in the visible region (wavelength 400 to 700 nm) becomes 1% or less, and CR
It can be used as an antireflection film for display elements such as T and liquid crystals and optical lenses.

The particle size of the granules used in this example is 0.
If the size is made smaller, such as 1 mm, the edge effect will be further enhanced, and even with an applied power of about ² W / cm ² , vapor will start to be generated and a film can be formed at high speed.

(Example 4) The same apparatus as in Example 3 was used. A plastic substrate was set. The substrate was not heated. O ₂ was introduced from the gas inlet 17 to 5 × 10 ⁻² Pa, then Ar was introduced from the gas inlet 19 to 5 × 10 5.
^It was introduced until it became ^-1 Pa. Sputtering is performed with an input power of 500 W, and the optical film thickness λ / is formed on the substrate in only 12 seconds.
The film of No. 4 could be formed.

The film formed in this example has a thickness of 1 to 2 in the visible range.
Although it has a light absorption of about%, the refractive index is 1.4 or less, which is excellent in the antireflection effect, and the adhesiveness and scratch resistance are sufficient.
It can be used as an antireflection film for sunglasses and goggles.

(Example 5) The same apparatus as in Example 3 was used. A La-based optical glass substrate was set. The substrate was not heated. CO ₂ was introduced from the gas inlet 19 to ₂ Pa. Sputtering was performed with an applied power of 800 W, and a film having an optical film thickness of λ / 4 could be formed on the substrate in only 3 seconds.

The film formed in this example had a light absorption of 1% or less in the visible region. Since CO ₂ with a large mass was used,
The film could be formed at a higher speed than in the above examples.

[0031]

As described above, according to the method for producing a thin film of the present invention, the solid film raw material is not directly sputtered, but the film raw material is heated and ions are made to collide with the vapor existing above the raw material. As a result, all of the accelerated ion energy is used for sputtering, so that the sputtering yield is high, and as a result, the film formation rate can be significantly increased as compared with the conventional method.

Moreover, such a state can be produced relatively easily by heating the granular film raw material with plasma.

Particularly in the case of sputtering MgF ₂ ,
When a high frequency power of ² W / cm ² or more is applied, the temperature of the MgF ₂ granules becomes 700 ° C. or more, and the vapor pressure is sufficiently increased. Therefore, if sputtering is performed in this state, high speed film formation is possible. is there.

In this case, the vapor is in the state of MgF ₂ molecules, and when the accelerated ions collide with the molecules, most of the molecules reach the substrate in the molecular state without being dissociated. Light absorption is less likely to occur in the formed thin film, and there is an effect that light absorption can be eliminated by introducing a gas containing oxygen.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a film forming apparatus used in a method of manufacturing a thin film according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a film forming apparatus used in a thin film manufacturing method according to a second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a film forming apparatus used in a thin film manufacturing method according to a third embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the surface temperature of granules and the film formation rate with respect to the input power in the method for producing a thin film of the present invention.

FIG. 5 is a graph showing the relationship between the surface temperature of granules and the film formation rate with respect to the input power in the manufacturing method of the comparative example.

[Explanation of symbols]

 1 Vacuum Tank 2 Substrate 3 Plate 4 Power Supply 5 Ion Gun 6 Gas Inlet 7 Shutter 11 Vacuum Tank 12 Substrate 13 Granule 14 Dish 15 Magnetron Cathode 16 Sputtering DC Power 17 Gas Inlet 18 Shutter 19 Gas Inlet 20 Sputtering RF Power

Claims (3)

[Claims] 1. The temperature of a solid film raw material is raised and the vapor generated from the film raw material is caused to collide with accelerated ions so that the film raw material collided by the ions and accelerated reaches a substrate. And then forming a film on the substrate. 2. The surface of a granular film raw material having a particle size of 0.1 to 10 mm is heated by plasma, and the vapor generated from the film raw material is caused to collide with accelerated ions, whereby the film raw material is produced. A method of manufacturing a thin film, which comprises reaching a substrate and forming a film on the substrate. 3. Granular MgF ₂ having a particle size of 0.1 to 10 mm
Target, and while introducing a gas containing at least oxygen, high-frequency power of ² W / cm ² or more is applied to the target to generate plasma on the target, and the temperature of the target surface is raised by the plasma, And a film is formed on the substrate by sputtering both vapor from the target.