JP2006030530A - Optical device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a refractive index of a silicon oxide for general use as a low-refractive index material while maintaining the performance to environment of the refractive index. <P>SOLUTION: With respect to an optical filter like an anti-reflection filter, a structure is given wherein layers (a first layer, a third layer, and a fifth layer) containing SiO<SB>2</SB>as a main component and Ta<SB>2</SB>O<SB>5</SB>(a second layer and a fourth layer) are alternately laminated, and at least one of SiO<SB>2</SB>layers is caused to contain boron, whereby the refractive index can be reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical device formed of at least one thin film and a manufacturing method thereof.

  Conventionally, a thin film laminated type optical filter represented by an antireflection filter and a wavelength selection filter has been manufactured mainly by a vacuum deposition method such as an electron beam deposition method because of its mass productivity and simplicity of an apparatus. Some of the antireflection filters used for display panels and window glass are manufactured by a coating sintering method or the like. In any of these methods, various efforts are being made to improve the characteristics, improve the productivity, or stabilize the quality of the antireflection filter. Hereinafter, these techniques will be described.

  Conventionally, in order to form an antireflection filter, it is common to laminate a plurality of materials. However, in the invention described in Patent Document 1, the refractive index is changed in the film forming process while the main components are the same. I am doing so. Thereby, for example, in the vacuum deposition method, it is not necessary to switch the evaporation material, and an antireflection filter can be easily formed.

  The invention described in Patent Document 1 is an antireflection film in which a hard coat layer, an antireflection layer, and an antifouling layer are sequentially formed on one side of a plastic film. It is formed from (x = 0.8 to 1.5) layer and SiOy (y = 1.6 to 2.0) layer and satisfies the following conditions.

  The SiOx (x = 0.8 to 1.5) layer of the antireflection layer is a non-uniform layer in which the x value changes continuously in the layer direction, and the x value is closer to the hard coat layer. , It becomes smaller as it goes to the SiOy layer.

  The thickness of the antireflection layer is 50 to 250 nm, and the ratio of the thickness of the SiOx layer to the SiOy layer is 1: 0.5 to 8.

  Further, Patent Document 1 has the following description.

  The formation method of the SiOx (x = 0.8 to 1.5) layer and the SiOy (y = 1.6 to 2.0) layer of the antireflection film is an induction heating type or resistance heating type vacuum deposition method. Can be used. Moreover, since the SiOx (x = 0.8 to 1.5) layer and the SiOy (y = 1.6 to 2.0) layer which are antireflection layers can be formed by a vacuum deposition method, Only one kind of SiO is sufficient, and a plurality of materials are not required. Therefore, workability in the manufacturing process of forming the antireflection layer is improved.

  In the invention described in Patent Document 1, a SiOx (x = 0.8 to 1.5) layer having a desired refractive index and a SiOy (y = 1.6 to 2.0) are formed on the hard coat layer of the antireflection film. ) To form the layer, use SiO as the deposition material, introduce oxygen into the vacuum soda of the vacuum deposition machine, adjust the amount of oxygen introduced to stabilize the properties as the antireflection layer, and vacuum While keeping the degree constant, deposition is performed while reacting SiO and oxygen.

  In order to form a SiOx (x = 0.8 to 1.5) layer, an appropriate amount of oxygen is introduced in accordance with the x value, and reacted with SiO as a deposition material to have a refractive index of 1.54. A ~ 2.1 SiOx layer is formed. At this time, if the oxygen partial pressure occupying the degree of vacuum is too high, the reaction rate between oxygen and SiO is increased, the x value is larger than 1.5, and a desired refractive index cannot be obtained because it approaches 2, which is not preferable. . On the other hand, if the oxygen partial pressure in the degree of vacuum is too low, SiO decomposition proceeds too much, and the x value becomes smaller than 0.8, so that the transmitted light yellowness becomes high. If the x value of the SiOx layer is 0.8 to 1.5, the desired refractive index is 1.54 to 2.1. Therefore, the x value is preferably 0.8 to 1.5.

  In order to form a SiOy (y = 1.6 to 2.0) layer, an appropriate amount of oxygen is introduced according to the y value and reacted with SiO as a vapor deposition material so that the refractive index is 1. A SiOy layer of .4 to 1.6 is formed. At this time, if the oxygen partial pressure occupying the degree of vacuum is too high, the SiOy layer is not dense, and the adhesion with the SiOx layer and the antifouling layer is lowered, which is not preferable. On the other hand, if the oxygen partial pressure occupying the degree of vacuum is too low, the reaction rate between oxygen and SiO is lowered, and the y value is smaller than 1.6, so that a desired refractive index cannot be obtained, which is not preferable. If the y value of the SiOy layer is 1.6 to 2.0, the desired refractive index is 1.4 to 1.52. Therefore, the y value is preferably 1.6 to 2.0.

  The above is the outline of the invention described in Patent Document 1, and it can be said that the cost reduction and productivity improvement are mainly achieved by reducing the number of materials.

  Next, the invention described in Patent Document 2 will be described. The invention described in Patent Document 2 relates to a method for manufacturing a sputtering target, and the main purpose is to change the sputtering method from RF sputtering to DC sputtering without changing the physical properties of the formed thin film as compared with the conventional example. It is to make.

  The invention described in Patent Document 2 is a target used when an interference film for an optical recording disk is formed by a DC sputtering method, includes a chalcogenide and glass, and has an electric resistance value of 0.001 to 0.00. The present invention relates to a sputtering target for an interference film of an optical recording medium of 1 Ω · cm. This target is used when an interference film for an optical recording disk is formed by a DC sputtering method.

  Further, Patent Document 2 has the following description.

  The target constituents include chalcogenide and glass as the main matrix material. Examples of chalcogenides include zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), lead sulfide (PbS), lead selenide (PbSe), lead telluride (PbTe), and calcium sulfide (CaS). And magnesium sulfide (MgS). Among these, it is preferable to use zinc sulfide.

A chalcogenide may be used alone or in combination of two or more. Examples of the glass include silicon oxide (SiO ₂ ), germanium oxide (GeO ₂ ), tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), tellurium oxide (TeO ₂ ), and the like. Among these, it is preferable to use silicon oxide. Glass may be used alone or in combination of two or more. Chalcogenides and glass usually exist in a stoichiometric composition, but may be somewhat deviated from the stoichiometric composition.

  The mixing ratio of the chalcogenide and the glass is preferably 10 to 30 mol%, particularly preferably 15 to 25 mol% of the glass. If the glass content is too high, the refractive index becomes too small when the interference film of the optical recording disk is used, and it becomes difficult to obtain high C / N, and it is difficult to obtain good characteristics. On the other hand, if the glass content is too small, when it is used as an interference film of an optical recording disk, the reliability with respect to repeated recording and erasing is lowered, and it becomes difficult to obtain good characteristics.

  The sputtering target of the invention described in Patent Document 2 has an electric resistance value of 0.001 to 0.1 Ω · cm, preferably 0.003 to 0.02 Ω · cm. Conventionally, a mixture of chalcogenide and glass used as an interference film material is an insulator, and could only be formed by RF sputtering, but it is suitable for mass production by reducing the electrical resistance in this way. It is possible to form a film by the DC sputtering method.

The above is the outline of the invention described in Patent Document 2.
JP 2002-6107 A JP 2000-64035 A

  However, there are some problems in the conventional technology.

  In the invention described in Patent Document 1, it can be considered that it is very advantageous in manufacturing that the refractive index can be controlled with one material. However, when a higher-performance optical filter is required, there is a possibility that the refractive index in the range of 1.4 to 2.1 cannot be used. In addition, it seems that there is a problem in terms of reliability because the refractive index is changed by largely sliding from the original stoichiometric ratio of silicon dioxide.

  Deviation from the stoichiometric ratio means that there are many defects in the thin film. For example, there is a problem that the refractive index changes with time due to the intrusion of moisture into the vacancy defect and the characteristics of the antireflection filter change accordingly. Moreover, although the refractive index is defined by the flow rate of oxygen gas introduced during the process, there seems to be a problem in its stability and reproducibility.

  In the invention described in Patent Document 2, when the invention is applied to an optical thin film, it is insufficient in terms of transmittance and reflectance. In addition, the method according to the invention described in Patent Document 2 is considered to be effective for an opaque film such as an interference film of an optical disk according to the embodiment. However, in the antireflection filter in the visible light region according to the present invention, It becomes an absorption film and cannot be used. In addition, it is important to define the ratio of the additive element so that the function of the optical thin film can be expressed.

  In view of the prior art, the present invention can reduce the refractive index of silicon oxide, which is generally used as a low refractive index material, while maintaining the refractive index with respect to environmental performance. An object of the present invention is to provide an optical device that can be used, and a method for manufacturing the same.

In order to achieve the above object, the invention according to claim 1 is provided with at least one layer containing silicon oxide as a main component and containing boron. By adding a small amount of boron that does not deviate significantly from the stoichiometric ratio, the oxide of silicon generally used in low-refractive-index materials (for example, silicon dioxide: SiO ₂ ) The refractive index can be lowered.

  According to a second aspect of the present invention, in the optical device according to the first aspect, the layers mainly composed of an oxide of silicon and the layers mainly composed of an oxide of tantalum, titanium, or niobium are alternately provided. With this structure, high antireflection characteristics can be exhibited in combination with a low refractive index silicon oxide.

  The invention according to claim 3 is the optical device according to claim 1 or 2, comprising at least one layer mainly composed of silicon oxide having a refractive index of 1.44 or less, With this configuration, the degree of freedom in designing the filter can be expanded without using magnesium fluoride that is generally used as a low refractive index material.

  The invention according to claim 4 is the optical device according to claim 1, 2 or 3, comprising five layers of thin films, each layer having a thickness of 10 nanometers to 200 nanometers, An optical device having a total of 150 nanometers to 400 nanometers, mainly comprising a layer mainly composed of the silicon oxide and any one of the tantalum, titanium, and niobium oxides from the material side serving as a substrate. The layers as components are alternately laminated, and this configuration makes it suitable as a structure of an optical device formed on a general glass substrate having a refractive index of about 1.5.

  Invention of Claim 5 is a method of manufacturing the optical device according to any one of Claims 1 to 4, which is mainly composed of silicon, contains boron, and has a resistivity of 0.1 to 10Ω. Using a target material that is cm, introduce argon gas and oxygen gas into the vacuum chamber, and apply a direct current or alternating current voltage to the target material to oxidize silicon on the substrate disposed in the vacuum chamber. By forming a thin film containing an oxide as a main component and containing boron by sputtering, a small amount of boron element is added to the thin film containing a silicon oxide as a main component so as not to destroy the stoichiometric ratio. be able to.

  According to the present invention, the refractive index can be lowered by adding a small amount of boron to the silicon oxide so as not to destroy the stoichiometric ratio. This makes it possible to design a filter that can keep the reflectance low without using magnesium fluoride.

  Further, by forming a film using the sputtering target containing boron, boron can be easily added without lowering the transmittance of the silicon oxide. In addition, by adding boron to a silicon target, DC sputtering can be performed, although conventionally only RF sputtering was possible. As a result, the equipment cost can be greatly simplified, resulting in cost reduction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an antireflection filter according to an embodiment of the present invention, and FIG. 2 is a diagram showing a specific example of the refractive index and film thickness of constituent materials in the antireflection filter.

In FIG. 1, BK-7 (manufactured by Sumita Optical Glass) was used as the material of the substrate 1. A total of five layers of SiO ₂ (first layer, third layer, fifth layer) and Ta ₂ O ₅ (second layer, fourth layer) were alternately laminated on the substrate 1. In this embodiment, boron is contained in at least one layer of SiO ₂ .

FIG. 3A is a diagram showing a reflection spectrum of the antireflection filter of the comparative example having the configuration shown in FIG. 2 and containing no boron in the SiO ₂ layer. In this case, as can be seen from FIG. 3A, the maximum value of the reflectance in the wavelength region of 400 to 650 nm is about 0.6%.

On the other hand, FIG. 3B is a diagram showing a reflection spectrum of the antireflection filter in the present embodiment having the configuration shown in FIG. 2 and containing boron in all three layers of SiO ₂ . Note that the refractive index of the SiO ₂ layer in this example is 1.45. FIG. 3B shows that the maximum reflectance in the wavelength region of 400 to 650 nm is improved to about 0.3%.

In addition, the effect of suppressing the reflectance can be obtained by not using all three layers of SiO ₂ as a low-refractive index layer containing boron but by using at least one layer as a low-refractive index SiO ₂ containing boron. It is done.

  FIG. 4 is a cross-sectional view schematically showing a sputtering apparatus used for manufacturing an antireflection filter according to the present invention, wherein 1 is a substrate also shown in FIG. 1, 2 is a boron-doped silicon target, 3 is a DC power source, 4 Is a gas introduction pipe.

In FIG. 4, a target 2 containing boron having a resistivity of 10 Ω · cm is placed in a vacuum chamber (not shown), a substrate 1 is placed at a position facing the target 2, and a gas introduction pipe 4 Then, argon gas and oxygen gas to oxidize the material to form an oxide thin film are introduced 100 sccm each (argon flow rate: oxygen flow rate = 1: 1), and power is supplied from the DC power source 3 to the target 2. The film was formed by sputtering. By this method, a SiO ₂ thin film containing boron having a refractive index of 1.45 could be formed. Further, a Ta ₂ O ₅ thin film could be formed by performing sputtering in the same manner as described above using Ta as a target.

As described above, the antireflection filter according to the present embodiment is an oxide of silicon that is generally used as a low refractive index material in an antireflection filter that is conventionally formed of a combination of a low refractive index material and a high refractive index material. The refractive index can be lowered by adding a small amount of boron to an object (for example, silicon dioxide: SiO ₂ ). It is important that the amount of boron to be added is such that the main component, silicon oxide, does not deviate significantly from the stoichiometric ratio. Further, it is not necessary to add boron to all the layers mainly composed of silicon oxide constituting the antireflection filter, and an effect can be obtained by adding boron to at least one layer.

  In addition to the tantalum used in the above embodiment, any one of titanium and niobium oxide can be used as the high refractive index material, and in combination with a low refractive index silicon oxide, high antireflection Express characteristics.

In addition, by making the refractive index of a layer mainly composed of silicon oxide, which is a low refractive index layer in an antireflection filter, 1.44 or less, magnesium fluoride generally used as a low refractive index material can be used. 1 and 2, the anti-reflection filter is composed of five layers of thin film, and the physical thickness per layer is 10 nanometers or more. 200 nanometers, the total thickness of the five layers is 150 nanometers to 400 nanometers, and a layer mainly composed of an oxide of silicon from the material side to be the substrate, and tantalum, titanium, niobium Suitable as an antireflection filter structure formed on a general glass substrate having a refractive index of about 1.5 by alternately laminating one of oxides as a main component. Configuration and become.

  INDUSTRIAL APPLICABILITY The present invention is applied as an antireflection filter for improving the characteristics of various optical elements such as lenses used in a camera, and a method for producing the same. In particular, a low-refractive-index silicon oxide containing boron is A thin film having a difference in refractive index can be prepared using a base material, and can be applied to the formation of a core portion and a cladding portion of an optical waveguide in addition to an optical filter typified by an antireflection film.

Sectional drawing which shows the antireflection filter which is embodiment of this invention The figure which shows the specific example of the refractive index and film thickness of the constituent material in an antireflection filter (A) is a diagram showing the reflection spectrum of the anti-reflection filter of a comparative example not Boron is included in a layer of SiO _2, the reflection spectrum in (b) in this embodiment containing a boron three layers of SiO ₂ Illustration Sectional drawing which shows typically the sputtering device used for manufacture of the antireflection filter concerning this invention

Explanation of symbols

1 Substrate 2 Boron-doped silicon target 3 DC power supply 4 Gas introduction piping

Claims (5)

  An optical device comprising at least one layer mainly composed of an oxide of silicon and containing boron.   2. The optical device according to claim 1, wherein the layer mainly composed of an oxide of silicon and the layer mainly composed of an oxide of tantalum, titanium, or niobium are alternately stacked.   3. The optical device according to claim 1, further comprising at least one layer mainly composed of an oxide of silicon having a refractive index of 1.44 or less.   It is an optical device composed of five thin films, each layer having a thickness of 10 to 200 nanometers, and the total thickness of the five layers is 150 to 400 nanometers. The layers mainly composed of the oxide of silicon and the layers mainly composed of the oxide of tantalum, titanium, or niobium are alternately stacked. The optical device described.   A method for producing an optical device according to any one of claims 1 to 4, wherein a target material containing silicon as a main component and containing boron and having a resistivity of 0.1 to 10 Ω · cm is used. Argon gas and oxygen gas are introduced into the vacuum chamber, and a direct current or alternating current voltage is applied to the target material, so that a silicon oxide as a main component and boron are formed on a substrate disposed in the vacuum chamber. A method for producing an optical device, comprising forming a thin film containing the thin film by a sputtering method.

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