JP2001192823A - Method for depositing film on substrate, and article obtained by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the conventional problem that a method for depositing an anti-reflection coating of single-layer structure, capable of reducing the reflectivity of a substrate, is not yet provided. SOLUTION: A substrate is set on the circumferential face of a cylindrical substrate holder turnable on its axis. Two sputter cathodes are set in such a way that their faces on which targets are stuck become parallel to the circumferential face of the cylindrical substrate holder respectively. The targets are sputtered, and simultaneously, the substrate is allowed to pass in front of the targets plural number of times to undergo the deposition of film containing the components of the targets on the surface of the substrate. The targets stuck on the cathodes are constituted of materials different in refractive index, respectively, and these targets are sputtered while concurrently changing the applied voltage so that film composition varies practically continuously in the film thickness direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a surface of a substrate by a sputtering method and an article obtained by the method. More specifically, the present invention relates to a method for efficiently coating a film having a composition gradient in a thickness direction and an article obtained by the method.

[0002]

2. Description of the Related Art Conventionally, in order to provide an optical function, particularly an antireflection function, to a substrate, an antireflection film is coated on the surface of the substrate by a vacuum film forming method (e.g., a vapor deposition method or a sputtering method). ing. In order to provide a more sophisticated antireflection function to a substrate, precise film thickness control is required. For this reason, a vacuum film forming method that is excellent in film thickness controllability of a film to be coated is a chemical film forming method ( Sol-gel method). The antireflection film is a laminate in which high-refractive-index films and low-refractive-index films are alternately laminated.

[0003]

However, in order to coat a substrate having a high-performance antireflection function on a substrate by a vacuum film forming method, it is necessary to laminate a film having a high refractive index and a film having a low refractive index. That is, it is necessary to coat multiple films of different components. High performance (low reflection)
In order to obtain a proper film, a large film forming apparatus is required, and there is a problem that the cost of coating the antireflection film increases. In addition, in order to coat the substrate with the multilayer film, it is necessary to switch the type of the film, and there is a problem that the tact time of the coating becomes long.

An object of the present invention is to provide a method for coating a substrate with a high-performance (low-reflection) coating without requiring a large-scale film forming apparatus. That is, an object of the present invention is to provide a method for coating a film that reduces the reflectance of the surface of the substrate over a wide wavelength range without taking a laminated structure of the film coated on the substrate.

[0005]

According to a first aspect of the present invention, a cylindrical substrate holder rotatable around a substrate is set on a circumferential surface of the cylindrical substrate holder, and two or more sputtering cathodes are attached to their target attachment surfaces. The target is sputtered, and the substrate is passed through the front surface of the target a plurality of times to be parallel to the circumferential surface of the cylindrical substrate holder and in the direction of rotation of the substrate. In the method of coating a target, the targets attached to the target are targets having different compositions, and sputtering is performed such that the film composition changes substantially continuously in the thickness direction of the coating. This is a method of coating a substrate with a coating.

According to the first aspect, the resulting coating has a composition gradient in the thickness direction. Therefore, a portion of the coating that comes into contact with the substrate can be a film having a good adhesive property, and the surface of the coating can be a film having a high abrasion resistance. This allows the substrate to be coated with a film having both adhesion to the substrate and abrasion resistance. Further, by giving a composition gradient so that the refractive index changes in the thickness direction of the coating, a so-called antireflection coating that reduces the surface reflectance of the substrate can be obtained. That is, an anti-reflection film capable of reducing the reflectance over a wide wavelength range with a single-layer structure can be applied to the substrate.

A second aspect of the present invention is characterized in that, in the first aspect, the film composition is changed in the thickness direction of the film by changing the electric power applied to each cathode during the coating.

According to the second aspect, the composition gradient of the coating can be easily provided. By applying the power applied to each cathode by a pre-programmed control mechanism, a coating having a composition gradient can be automatically coated with good reproducibility. In the present invention, 1
The membrane to be coated when passing through two cathodes is determined by the power applied to the cathode and the number of revolutions of the substrate holder.

A third aspect of the present invention is characterized in that, in the second aspect, the thickness of the coating by passing once through the front surface of each target is set to 2 nm or less. The coating is applied to a substrate set in a rotating cylindrical substrate holder. The coating is performed when the substrate passes through the front surface of the target, and it is preferable that the thickness of the coating when the substrate is coated once after passing through each cathode is 2 nm or less.

When the thickness of the coating by the above-mentioned passage exceeds 2 nm and becomes thicker, the layer structure of the coating becomes clear, and even if the refractive index of the coating as a whole gives a composition gradient from the substrate side to the film surface, This is not preferable because the effect of lowering the surface reflectance of the substrate is reduced. From this perspective,
The above value is preferably 2 nm or less. Rather than having a layered structure, the coating is more preferably comprised of a mixture of low and high refractive index materials and coated so that the layered structure is not clearly visible.

A fourth aspect of the present invention is characterized in that, in the third aspect, the thickness of the coating by passing once through the front surface of each target is 0.2 nm or more. If the thickness of the coating is smaller than 0.2 nm after passing once in front of each target, the coating takes a long time and the economical disadvantage is disadvantageous. This is because the possibility of causing damage to the rotation mechanism of the base holder increases, which is not preferable.

According to a fifth aspect of the present invention, the power applied to the cathode is changed based on the measured value of the reflectance or the transmittance of the coating in the coating. As a result, the composition gradient in the thickness direction of the coating film can be determined accurately and with good reproducibility.

[0013] Claim 6 is an article coated with a film having a composition gradient in the thickness direction obtained in any one of claims 1 to 5. For example, a film having excellent adhesion and abrasion resistance can be obtained by including a large amount of an adhesion improving component on the substrate side and a large amount of a component having good abrasion resistance near the surface of the coating.

According to a seventh aspect, in the sixth aspect, the substrate is a transparent glass, and the coating has a composition gradient so that the refractive index decreases as the distance from the substrate increases, and the coating has an antireflection function. .

In the present invention, three or more cathodes can be provided. When three cathodes are installed, a target having the same composition is attached to two of the cathodes, and a target having a different composition from the target attached to the two cathodes is attached to the other cathode. Can be simultaneously sputtered while adjusting the power applied to the respective cathodes, so that the coating has a refractive index gradient caused by the composition gradient.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described for an article in which a glass plate is coated with an antireflection film whose refractive index changes continuously in the thickness direction. FIG. 1 is a sectional view of an embodiment of an article coated with an antireflection film of the present invention. In the article 1 of the present invention, a surface of a glass plate 2 is coated with a coating 3 having a refractive index gradient in a thickness direction. The portion of the coating 3 in contact with the substrate 2 is substantially made of titanium dioxide (TiO 2).
₂ ), wherein the surface of the coating 3 is substantially silicon dioxide (SiO ₂ ). The coating has a different composition in the thickness direction,
The refractive index decreases from the substrate side toward the surface. The refractive index on the side closer to the substrate is larger than the refractive index of the substrate, and the refractive index at the surface of the coating is smaller than the refractive index of the substrate.

FIGS. 2 and 3 are schematic sectional views of one embodiment of a sputtering apparatus that can be used in the present invention. The carousel type sputtering apparatus 10 is cylindrical and has a circumferential wall 10a, a bottom 10b and an upper
With c, the atmosphere in which the inside is depressurized can be adjusted. This atmosphere is achieved by operating a vacuum pump (not shown) connected to the vacuum exhaust port 16 attached to the bottom and a gas supply mechanism connected to the sputtering gas inlet 17.

The cathodes 11A, 11B are provided on the circumferential wall 10a.
Is installed, and targets 12A, 12B
(Consisting of a material different from 11A). Electric power is applied to each of the cathodes 11A and 11B from the sputtering power supplies 13A and 13B, and the targets are simultaneously sputtered in an atmosphere containing argon. The substrate holder 14 on which the substrate 19 is set is rotated about the rotation shaft 15, and the surface of the rotating substrate is covered with the targets 12A and 12B.

For example, the target 12A is made of quartz glass for covering a low refractive index film (SiO ₂ film), and the target 12B is made of titanium metal for covering a high refractive index film (TiO ₂ film).

A method for changing the power applied to the cathode for changing the composition of the coating will be described in detail. To attach titanium metal to the cathode 11A and quartz glass to the cathode 11B so that the ratio of titanium oxide to silicon dioxide in the coating is 2: 1, the rate of coating the metal with oxygen reactivity is silicon dioxide. The applied power may be adjusted so as to be twice the coating rate. By changing each power during the film formation, the composition of the film is changed in the film thickness direction. For sputtering of the target, DC magnetron sputtering, high-frequency magnetron sputtering, or the like can be used.

FIG. 4 shows a control method for continuously changing the power applied to each cathode during coating.
As shown in (1), while controlling the transmittance or the reflectance of the coating on the rotating substrate surface using the optical transmittance monitor or the optical reflectance monitor 18, the control is performed by the control system connected to the arithmetic unit. A method can be used. According to this method, the coating rate can be controlled to a predetermined target rate, and fluctuations in optical characteristics can be kept small.

The power applied to each cathode is 2
The substrate passes once through the front surface of the two targets and the film thickness is 2n.
It is preferable to control so as to be not more than m. When the thickness exceeds 1 nm, the layered structure becomes clear and becomes optically recognized as a thin film of each single component, which is not preferable. As a specific method for reducing the film thickness to be coated to 2 nm or less each time the substrate passes once over the target, a method of reducing the power applied to the target or increasing the rotation speed of the substrate is used.

Hereinafter, the present invention will be described with reference to Examples. The substrate used was a transparent glass plate (refractive index 1.5
2) was used. The transmittance of this transparent glass plate alone is about 9
The surface reflectance (one-sided reflectance) was about 4%.

Example 1 A carousel type sputtering apparatus shown in FIG. 2 was used. Titanium metal is attached as the target 12A, DC reactive sputtering with a mixed gas of oxygen and argon is applied, and quartz glass is attached as the target 12B.
Simultaneously, high frequency sputtering was performed. At this time, the rotation speed of the substrate was 10 rpm, and the film having a thickness of 0.5 nm was coated by passing through each target once. The portion of the coating near the substrate side was a titanium dioxide film, and the portion near the surface of the coating was a silicon dioxide film, and the power was adjusted so that the composition changed for a while. That is, the composition of the coating is xSiO _2- (1-x)
X was changed from 0 to 1 with TiO ₂ (0 ≦ x ≦ 1). The glass plate coated with the obtained film was taken out, and its optical characteristics were measured. As a result, the reflectance at a wavelength of 550 nm was 0.2%. This is about one twentieth of the reflectivity of the glass plate itself of 4%. That is, the reflectivity of the surface was significantly reduced. 450 nm, 650 n
m, the reflectance was almost the same, and it was confirmed that an antireflection function was provided in a wide wavelength range.

Example 2 The target of 12B was changed to silicon nitride, and the composition of the coating was SiOxNy (0 ≦ x ≦ 2: x = 0 at the beginning of coating, y = 1, and ending at the end of coating) in the same manner as in Example 1. x = 2, Y =
0), and the power applied to the cathode in the thickness direction of the film was adjusted to have a composition gradient. A sample coated with the obtained film was taken out and the reflectance was measured. The reflectance at a wavelength of 550 nm was 0.3%, and it was confirmed that an antireflection function was provided. 450n
The reflectance was almost the same at m and 650 nm, and it was confirmed that an antireflection function was provided in a wide wavelength range.

[0026]

According to the present invention, targets to be attached to two or more sputtering cathodes are simultaneously sputtered as targets having two different compositions. At this time, since the sputtering is performed so that the film composition changes substantially continuously in the thickness direction of the film, a film having a composition gradient in the thickness direction can be efficiently coated.

Further, since a film whose refractive index changes in the thickness direction can be formed, a film which reduces the reflectance on the surface of the substrate can be formed.

Further, since the film having an antireflection function obtained by the present invention is composed of a single layer, there is no occurrence of interfacial peeling in a multilayer structure.

Further, since the coating having a composition gradient in the thickness direction of the present invention has a single-layer structure instead of a multilayer structure, a large-scale vacuum film-forming apparatus is not required, and a small-sized film forming apparatus according to the size of the substrate is required. A membrane device can be used. This can reduce the cost of the apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of an article coated with a coating having a composition gradient according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a schematic plan view of a sputtering apparatus used for carrying out the present invention.

FIG. 4 is a sectional view taken along the line BB of FIG. 3;

[Explanation of symbols]

 1: Article of the present invention 2: Glass plate 3: Film having a refractive index gradient in the thickness direction 10: Sputtering device 10a: Circumferential portion, 10b: Bottom portion, 10c: Top portion 11A, 11B: Cathode 12A, 12B: Target 13A, 13B: Sputtering power supply 14: Substrate holder 15: Rotating shaft 16: Vacuum exhaust port 17: Sputtering gas inlet 18: Reflectance monitor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Katsuhisa Enjoji 3-5-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka F-term in Nippon Sheet Glass Co., Ltd. 4K029 AA09 BA46 BA48 BA54 BB01 BB02 BC00 BC08 CA05 CA06 DC03 DC05 DC16 DC34 DC35 EA01 EA09 JA02

Claims (7)

[Claims] 1. A substrate is set on a circumferential surface of a cylindrical substrate holder rotatable around an axis, and two or more sputtering cathodes are attached to their respective target mounting surfaces on the circumferential surface of the cylindrical substrate holder. A method in which the target is sputtered, and the substrate is passed through the front surface of the target a plurality of times, and the coating containing the target component is coated on the substrate. A method of coating a substrate with a coating, wherein targets to be attached are targets having different compositions, and the targets are subjected to sputtering so that the film composition changes substantially continuously in the thickness direction of the coating. 2. The method according to claim 1, wherein the change in the film composition in the thickness direction of the film is performed by changing the electric power in the film applied to each cathode. 3. The method according to claim 2, wherein the thickness of the coating by a single pass through the front surface of each of the targets is less than 2 nm. 4. The method according to claim 3, wherein the thickness of the coating by passing once through the front surface of each of the targets is 0.2 nm or more. 5. The method according to claim 2, wherein the power applied to the cathode is varied based on a measurement of the reflectance or transmittance of the substrate being coated. 6. An article coated with a coating having a composition gradient in the thickness direction by the method according to claim 1. 7. The article according to claim 6, wherein the substrate is a transparent glass, and the coating has a composition gradient such that the refractive index decreases as the distance from the substrate in the thickness direction increases. Article to be.