KR20230168143A - Optical element and device - Google Patents

Abstract

Provides an advantageous technology in improving optical properties against ultraviolet light.
An optical element comprising a base and an optical structure provided on the base, wherein the optical structure is located between a first dielectric layer, a second dielectric layer, the first dielectric layer and the second dielectric layer, and the first dielectric layer and the second dielectric layer. It has at least a third dielectric layer having a lower refractive index than the second dielectric layer, wherein the first dielectric layer and the second dielectric layer are films containing aluminum oxide and hydrogen, and the oxygen content in the film is [O]at%. , Let the aluminum content in the film be [Al]at%, and the hydrogen content in the film be [H]at%,
An optical element that satisfies [Al]+[O]≥50.0at% and [O]/([Al]+[H])≤1.40.

Description

Optical elements and devices {OPTICAL ELEMENT AND DEVICE}

The present invention relates to an optical element having an aluminum oxide film.

Since the aluminum oxide film transmits ultraviolet light, its use as an optical element for ultraviolet light is being considered. Patent Document 1 discloses an aluminum oxide film containing fluorine or hydroxyl groups.

Japanese Patent Publication No. 9-316631

In the technology of Patent Document 1, there is room for improvement in optical characteristics with respect to ultraviolet light. Therefore, the purpose of the present invention is to provide a technology that is advantageous in improving optical properties against ultraviolet light.

The first aspect of the means to solve the above problem is,

An optical element comprising a base and an optical structure provided on the base,

The optical structure has at least a first dielectric layer, a second dielectric layer, and a third dielectric layer located between the first dielectric layer and the second dielectric layer and having a lower refractive index than the first dielectric layer and the second dielectric layer,

The first dielectric layer and the second dielectric layer are films containing aluminum oxide and hydrogen,

Let the oxygen content in the film be [O]at%, the aluminum content in the film be [Al]at%, and the hydrogen content in the film be [H]at%,

[Al]+[O]≥50.0at%

and

It is characterized by satisfying [O]/([Al]+[H])≤1.40.

The second aspect of the means to solve the above problem is,

An optical element comprising a base and an optical structure provided on the base,

The optical structure has at least a film containing aluminum oxide, hydrogen, and fluorine, the oxygen content in the film is [O]at%, the aluminum content in the film is [Al]at%, and the film Let the hydrogen content in the film be [H]at%, and the fluorine content in the film be [F]at%,

[Al]+[O]≥50.0at%

and

[F]/[H]≤1.0

It is characterized by satisfying.

Further features of the invention will become apparent from the following description of exemplary embodiments (with reference to the accompanying drawings).

1 is a schematic diagram explaining an optical element.
Figure 2 is a diagram explaining an aluminum oxide film.
Figure 3 is a diagram explaining an aluminum oxide film.
4 is a diagram explaining an aluminum oxide film.
Figure 5 is a diagram explaining an aluminum oxide film.
Figure 6 is a diagram explaining an aluminum oxide film.
Fig. 7 is a diagram explaining an aluminum oxide film.
Fig. 8 is a diagram explaining an aluminum oxide film.
9 is a diagram explaining the device.
Figure 10 is a diagram explaining the results of the example.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in the following description and drawings, common components are assigned common symbols across a plurality of drawings.

Therefore, common configurations will be described with reference to a plurality of drawings, and descriptions of configurations assigned common symbols will be omitted as appropriate.

1 is a schematic diagram of an optical element according to this embodiment. The optical element 100 includes a base 101 and an optical structure 102 provided on the base 101. The base 101 is made of resin, glass, ceramics, metal, etc. The optical structure 102 has an aluminum oxide film 105. The optical structure 102 may have a single-layer structure, but in the example of FIG. 1, it has a multi-layer structure. The optical structure 102 of the multi-layer structure is located between the dielectric layer 103a and the dielectric layer 103b, and a dielectric layer ( 104a). The multilayer optical structure 102 may also have a dielectric layer 104b having a lower refractive index than the dielectric layer 103a and the dielectric layer 103b, and the dielectric layer 103b may be located between the dielectric layer 104a and the dielectric layer 104b. Located. The dielectric layers 103a and 103b with relatively high refractive index are collectively referred to as high refractive index layers 103, and the dielectric layers 104a and 104b with relatively low refractive index are collectively referred to as low refractive index layers 104. The optical structure 102 may be a structure in which high refractive index layers 103 and low refractive index layers 104 are alternately stacked. Here, the first type of layer and the second type of layer are alternately laminated, meaning that at least one second type of layer is located between the two first type layers and also two second type layers. It means a state in which at least one first type of layer is located in between. Therefore, in order for the first type of layer and the second type of layer to be stacked alternately, at least four layers are required.

In Figure 1 (a), among the high refractive index layers 103 and low refractive index layers 104 stacked alternately, the lowest dielectric layer 103a and the uppermost dielectric layer 103x are shown as the high refractive index phase 103. , the high refractive index phase 104 shows the lowest dielectric layer 104a and the uppermost dielectric layer 104x. There may be a dielectric layer under the dielectric layer 103a or the dielectric layer 104a, and there may be a dielectric layer on the dielectric layer 103x or the dielectric layer 104x. Here, the dielectric layers 103a, 103b, and 103x, which are the high refractive index layers 103, include, for example, an aluminum oxide film 105 shown in the conceptual diagram of FIG. 1(b). In the aluminum oxide film 105, aluminum (Al) and oxygen (O) are combined. The aluminum oxide film 105 is a film containing aluminum oxide as its main component. Additionally, the aluminum oxide film 105 may include hydrogen (H), and this hydrogen (H) may be bonded to aluminum (Al). However, hydrogen (H) bonded to oxygen (O) may be present. Figure 1 (b) shows that, for Al ₂ O ₃ , which is the stoichiometric composition of aluminum oxide, one of the two oxygens (O) that can be bonded to one aluminum (Al) is missing, and the missing oxygen (O ) Instead, it represents a model in which hydrogen (H) is bonded to aluminum (Al). The aluminum oxide film 105 may include this model, but may also include models different from this model. Additionally, the aluminum oxide film 105 may contain fluorine (F), and the fluorine (F) may be bonded to aluminum (Al). Additionally, the aluminum oxide film 105 of this embodiment may contain argon (Ar).

Let the aluminum content in the aluminum oxide film 105 be [Al]at%, and the oxygen content in the aluminum oxide film 105 be [O]at%. Additionally, let the hydrogen content in the aluminum oxide film 105 be [H]at%, and the fluorine content in the aluminum oxide film 105 be [F]at%. Additionally, let the argon content in the aluminum oxide film 105 be [Ar]at%. Here, “at%” means “atomic percentage” and is the ratio of the number of specific atoms to the total number of atoms in the composition of the object.

Since the aluminum oxide film 105 contains oxygen and aluminum, [Al] > 0 and [O] > 0 are satisfied, and [H] > 0, [F] > 0, and [Ar] > 0 are satisfied. . For example, when the aluminum oxide film 105 does not contain fluorine, the fluorine content [F] = 0 at%.

When the aluminum oxide film 105 does not contain argon, the argon content [Ar] = 0 at%. As described above, in the aluminum oxide film 105 containing aluminum oxide as the main component, [Al] + [O] ≥ 50.0 at%. That the aluminum oxide film 105 is a film containing aluminum oxide as a main component means that the sum of the aluminum content [Al] and the oxygen content [O] in the aluminum oxide film 105 is 50.0 at% or more.

In the aluminum oxide film 105, the content of elements other than aluminum, oxygen, hydrogen, fluorine, and argon may be less than 0.1 at%. The sum of the oxygen content [O], the aluminum content [Al], the hydrogen content [H], the fluorine content [F], and the argon content [Ar] may be 99.0 at% or more, and may be 99.9 It may be at% or more. That is, [Al]+[O]+[H]+[F]+[Ar]≥99.0at% may be used, and [Al]+[O]+[H]+[F]+[Ar]≥99.9at%. % is also acceptable.

The dielectric layer 103a, 103b, and dielectric layer 103x do not need to have completely the same composition and film thickness, but as long as they have the characteristics of the aluminum oxide film 105 described below, the dielectric layer 103a and the dielectric layer 103x The composition and film thickness of (103b) and the dielectric layer (103x) may be different from each other.

Materials used for the low refractive index layer 104 include materials or mixtures containing aluminum fluoride (AlF ₃ ), magnesium fluoride (MgF ₂ ), and silicon oxide (SiO ₂ ) as main components. In addition, the material is not limited to these, and may be a material or a mixture containing sodium fluoride (NaF), lithium fluoride (LiF), calcium fluoride (CaF ₂ ), and yttrium fluoride (YF ₃ ) as main components. In addition, inclusion as a main component does not require the inclusion of a secondary component, and the low refractive index layer 104 may be composed only of the materials listed here as the main component of the low refractive index layer 104.

Of course, the low refractive index layer 104 may contain subcomponents such as hydrogen, carbon, nitrogen, oxygen, fluorine, and argon in addition to the materials listed here as the main components of the low refractive index layer 104.

As shown in FIG. 1, the optical structure 102 is made by alternately stacking high refractive index layers 103 and low refractive index layers 104 in order from the base 101 side, and the outermost layer is the low refractive index layer 104. It is a composition. However, the configuration may be changed depending on the purpose of the optical element. For example, a configuration may be used in which low refractive index layers 104 and high refractive index layers 103 are alternately stacked from the base 101 side, and the outermost layer is the low refractive index layer 104, and the outermost layer is the high refractive index layer. The structure may be the layer 103. Additionally, a protective layer may be provided and the protective layer may be the outermost layer. An adhesion layer may be provided between the base 101 and the optical structure 102. When providing an adhesion layer, silicon oxide, aluminum oxide, aluminum fluoride, magnesium fluoride, or materials or mixtures containing these as main components are suitable from the viewpoint of adhesion to the base 101. Additionally, it is not essential for the optical structure 102 to have an alternating stacked structure in which low refractive index layers 104 and high refractive index layers 103 are alternately stacked. It is not essential to have a multilayer structure including the high refractive index layer 103 and the low refractive index layer 104, and it may have a single layer structure of only one layer of the high refractive index layer 103. There may be an additional layer between the dielectric layer 103a and the base 101, and this layer is not limited to the dielectric layer, but may be a metal layer containing a single metal or alloy. In a reflective optical element, a metal layer between the dielectric layer 103a and the base 101 may be used as a reflective layer.

The plurality of high refractive index layers 103 (aluminum oxide films 105) of the optical structure 102 do not all need to be identical. The composition of the plurality of aluminum oxide films 105 may be different within the range described later. Among the plurality of high refractive index layers 103, some of them may be made of lanthanum fluoride (LaF ₃ ) and the remainder may be made of other materials, such as aluminum oxide film 105 . The low refractive index layer 104 of the optical structure 102 does not necessarily need to be all the same. For example, of the plurality of low refractive index layers 104, other materials may be used, such as aluminum fluoride for a portion and magnesium fluoride for the remainder.

Typically, the aluminum oxide film 105 is preferably used as the high refractive index layer 103, but the aluminum oxide film 105 is used as the low refractive index layer 104, and the aluminum oxide film 105 is used as the high refractive index layer 103. A film with a higher refractive index than the film 105 can also be used.

The base 101 may be made of optical glass such as calcium fluoride crystal or quartz glass, which has low absorption of light at the design wavelength (for example, 193 nm). In a reflective optical element, it is not essential for the base 101 to transmit ultraviolet light. Additionally, the base 101 can be of various shapes, such as a flat shape or a curved shape, depending on the purpose or type of the optical element (eg, lens, mirror, film, prism, etc.). In a lens or mirror, the surface of the base 101 on the side of the aluminum oxide film 105 is a concave or convex surface.

The optical structure 102 may have a reflective structure. At this time, the physical film thickness of the high refractive index layer 103 and the low refractive index layer 104 may be optimized in order to maximize reflection characteristics at the design wavelength (eg, 193 nm) or design wavelength range. When only the optical structure 102 has a reflective structure, in order to obtain a high reflectance, the high refractive index layer 103 and the low refractive index layer 104 may be composed of a total of 30 or more layers. Additionally, a reflective layer such as aluminum may be formed between the base 101 and the optical structure 102. In this case, forming a reflective layer has the advantage of reducing the number of layers of the optical structure 102 to less than 30 layers. The outermost layer is preferably a high refractive index layer 103 in order to obtain a high reflectance. Of course, the outermost layer does not necessarily have to be the high refractive index layer 103, and may be the low refractive index layer 104. For example, if the low refractive index layer 104 is a material that can suppress the influence of moisture in the atmosphere more than the high refractive index layer 103, the outermost layer may be the low refractive index layer 104. The outermost layer can be freely selected depending on the required performance. In this way, the number of layers and the material of the optical structure 102 are determined taking into account the reflectivity, the influence of moisture in the atmosphere, and further the influence of the laser. In addition, it is determined by considering the intended use, such as a reflective mirror or a half mirror.

The optical structure 102 may have an anti-reflection structure. In the anti-reflection structure, the physical film thickness of the high refractive index layer 103 and the low refractive index layer 104 may be optimized to minimize reflection characteristics at the design wavelength or design wavelength range. At this time, the optical structure 102 having an anti-reflection structure may be optimized so that the reflectance in the base 101 is smaller than when the optical structure 102 does not have the optical structure 102. When the optical structure 102 is composed of one layer, a material having a refractive index smaller than that of the base 101 can be used. For example, when the optical structure 102 is composed of a single layer of the aluminum oxide film 105, if the refractive index of the aluminum oxide film 105 is NH and the refractive index of the base 101 is NS, the relationship NH < NS there is.

When the anti-reflection structure of the optical structure 102 is formed in multiple layers, the refractive index of the base 101 is not limited to the relationship of NH<NS. Additionally, when the anti-reflection structure is formed in multiple layers, it is preferable that the outermost layer be the low refractive index layer 104 to suppress reflection.

An optical device including the optical element 100 includes holding parts that hold the optical element 100 . This holding part may hold a plurality of optical elements including the optical element 100. The holding part may be a light barrel.

The optical device provided with the optical element 100 may be provided with a light source that generates ultraviolet light. When ultraviolet light generated from this light source is irradiated to the aluminum oxide film 105, the aluminum oxide film 105 may have low absorption and/or high refractive index with respect to the ultraviolet light. It is more suitable when the wavelength of this ultraviolet light is less than 200 nm.

FIG. 2 is a schematic diagram of an example of a film forming apparatus 200 used for forming an aluminum oxide film 105. The film forming apparatus 200 of this example is a film forming apparatus 200 using a sputtering method. The film forming apparatus 200 has a vacuum chamber 201 as an airtight container, and an exhaust system 202 for exhausting the inside of the vacuum chamber 201. In addition, an argon gas introduction port 204, an oxygen gas introduction port 205, a hydrogen gas introduction port 206, and a fluorine-based gas introduction port 207 are provided so that the gas required for film formation can be introduced into the vacuum chamber 201. It is available. The gas introduced from the fluorine-based gas introduction port 207 is fluorine (F ₂ ), carbon tetrafluoride (CF ₄ ), nitrogen trifluoride (NF ₃ ), hydrogen fluoride (HF), silicon tetrafluoride (SiF ₄ ), and hydrochloride. It is at least one type of gas containing fluoroolefin. Additionally, in addition to the vacuum chamber 201, a sputtering target 211, a backing plate 212, a magnet mechanism 208, and a gas holding mechanism 209 are provided. By holding the base 101 of the optical element in the base holding mechanism 209 and applying power from the power source 203, film formation can be performed by the reactive sputtering method. At this time, the base holding mechanism 209 determines the relative positional relationship between the sputtering target 211 and the film forming surface of the base 101 using a drive mechanism (not shown) to distribute the film thickness within the surface of the base 101. Adjust in advance so that is constant.

A method for forming the aluminum oxide film 105 will be described.

In order to form the aluminum oxide film 105 (high refractive index layer 103), film formation is performed by a reactive sputtering method in the following procedure. For example, a vacuum chamber 201 is formed using a base 101 made of quartz glass processed into the shape of a predetermined optical element and a sputtering target 211 made of, for example, 9-inch metal aluminum (purity 99.9 wt% or more). ) set within. At this time, the distance between the base 101 and the sputtering target 211 is, for example, 200 mm. Then, using the exhaust system 202, the inside of the vacuum chamber 201 is exhausted until the pressure reaches a vacuum degree of about 5×10 ^-5 Pa. Afterwards, argon gas is supplied from the argon gas introduction port 204, oxygen gas is supplied from the oxygen gas introduction port 205, hydrogen gas is supplied from the hydrogen gas introduction port 206, and fluorine-based gas is supplied from the fluorine-based gas introduction port 207. Introduce fluorine gas. Plasma discharge is performed while supplying gas from each port. That is, a power of 10 W/cm ² is applied from the power source 203 to the sputtering target 211 to generate a plasma discharge, and an aluminum oxide film containing hydrogen and fluorine is formed on the base 101 to a thickness of about 100 nm. . Additionally, the thickness of each layer is not necessarily limited to about 100 nm, and is appropriately set depending on the wavelength of light handled by the optical element and the number of layers constituting the optical structure. The physical film thickness of the aluminum oxide film 105 in the optical element is, for example, 8 to 1000 nm. The 1000 nm thick aluminum oxide film 105 may be formed by stacking 10 aluminum oxide layers with a thickness of 100 nm without any other layers in between.

The aluminum oxide film 105 may be crystalline or amorphous, but is preferably amorphous. An amorphous aluminum oxide film is advantageous in reducing the surface roughness of the aluminum oxide film compared to a crystalline aluminum oxide film. Amorphous (or amorphous) means that no clear diffraction peak is detected when X-rays or electron beams are irradiated to the film of the measurement object at a small incident angle of about 0.5 degrees and the diffraction pattern is observed. In other words, a halo pattern is observed. says that Therefore, amorphous as used herein does not necessarily exclude a state containing material in a microcrystalline state.

The crystallinity of the film can be controlled by the film formation pressure, the arrangement of the gas 101 and the sputtering target 211, and the gas supply flow rate. It is desirable to set the film formation conditions in advance so that the aluminum oxide film 105 formed by the film formation apparatus 200 is amorphous.

Description of the formation of the low refractive index layer 104 is omitted because known film forming methods can be used. In the film forming apparatus 200 shown in FIG. 2, there is only one sputtering target 211, but when forming a multilayer film, two or more sputtering targets 211 are placed in the vacuum chamber 201, and each sputtering target 211 is made of a different material. You can do it. At this time, a shutter may be placed near the surface of the sputtering target to suppress adhesion of different materials to the surface during film formation of other materials.

Evaluation of the hydrogen content [H]at% in the aluminum oxide film 105 is performed by irradiating the aluminum oxide film 105 with a high-energy ion beam, for example, on the order of MeV, and using hydrogen forward scattering spectrometry (HFS). ) can be done by the method.

Evaluation of elements other than hydrogen in the aluminum oxide film 10 can be performed by irradiating a high-energy ion beam of the MeV order and using the method of Rutherford Backscattering Spectrometry (RBS).

Using these results, the aluminum content [Al]at%, oxygen content [O]at%, hydrogen content [H]at%, and fluorine content [F]at% in the aluminum oxide film 105. %, the argon content [Ar]at% can be obtained.

Reflectance and transmittance can be measured using a spectrophotometer in the wavelength range of 180 nm to 250 nm and at a light incident angle of 10 degrees. From the measurement results, the light absorption rate can be calculated using the following formula.

A=1-T-R

However, A represents the light absorption rate representing the ratio of absorption to the incident light intensity, T represents the transmittance representing the ratio of transmission to the incident light intensity, and R represents the reflectance representing the ratio of reflection to the incident light intensity. Additionally, the light absorption rate A has the following relationship with the extinction coefficient k.

A=1-exp(-4πkx/λ)

Here, x is the distance within the thin film and λ is the wavelength of light. The extinction coefficient k can be calculated from the above equation, and the light absorption of the aluminum oxide film 105 can be evaluated.

The refractive index can be calculated by analyzing the measured reflectance using FilmWizardTM, an optical thin film analysis and design software manufactured by Sciencetific Computing International. Here, the extinction coefficient for light of λ = 193 nm and the refractive index for light of 193 nm are calculated.

The surface roughness of the aluminum oxide film 105 can be measured within a range of 1 μm × 1 μm using an AFM (Atomic Force Microscope), and the root mean square roughness (RMS) can be calculated in nm.

An example in which samples 00 to 18 of the aluminum oxide film 105 were produced by changing the film formation conditions will be described.

In samples 00 to 06, an aluminum oxide film was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced from the argon gas introduction port 204 at a flow rate of 150 sccm, oxygen gas was introduced from the oxygen gas introduction port 205 at a flow rate of 50 sccm, and hydrogen gas was introduced from the hydrogen gas introduction port 206 to form a film. The flow rate of hydrogen introduced from the hydrogen gas introduction port 206 was varied within the range of 0 to 100 sccm to produce an aluminum oxide film.

In sample 00, an aluminum oxide film containing hydrogen was produced using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, and hydrogen gas was introduced from each port at a flow rate of 0 sccm to form a film.

In Sample 06, an aluminum oxide film containing hydrogen was produced using the film forming apparatus 200 in FIG. 2. Argon gas was introduced from each port at a flow rate of 150 sccm, oxygen gas was flowed at 50 sccm, and hydrogen gas was formed at a flow rate of 50 sccm.

In Sample 07, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 20 sccm, and fluorine gas at a flow rate of 4.0 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 20.0 at%, the fluorine content [F] was 11.0 at%, the oxygen content [O] was 42.5 at%, the aluminum content [Al] was 26.2%, and the argon content [Ar]. was 0.3at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 6.3E-3.

In Sample 08, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 50 sccm, and fluorine gas at a flow rate of 4.5 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 17.9 at%, the fluorine content [F] was 14.9 at%, the oxygen content [O] was 39.9 at%, the aluminum content [Al] was 26.7%, and the argon content [Ar]. was 0.6at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 2.0E-3.

In Sample 09, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 50 sccm, and fluorine gas at a flow rate of 5.0 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 21.5 at%, the fluorine content [F] was 15.9 at%, the oxygen content [O] was 35.7 at%, the aluminum content [Al] was 26.5%, and the argon content [Ar]. was 0.4at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 1.8E-3.

In Sample 10, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 70 sccm, and fluorine gas at a flow rate of 3.5 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 26.9 at%, the fluorine content [F] was 8.2 at%, the oxygen content [O] was 39.1 at%, the aluminum content [Al] was 25.7%, and the argon content [Ar]. was 0.1at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 2.7E-3.

In Sample 11, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 50 sccm, and fluorine gas at a flow rate of 4.0 sccm from each port to form a film. The hydrogen content [H] in the produced aluminum oxide film was 24.2 at%, the fluorine content [F] was 11.0 at%, the oxygen content [O] was 39.3 at%, the aluminum content [Al] was 25.1%, and the argon content [Ar]. was 0.4at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 2.3E-3.

In Sample 12, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 100 sccm, and fluorine gas at a flow rate of 1.0 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 29.2 at%, the fluorine content [F] was 1.5 at%, the oxygen content [O] was 43.6 at%, the aluminum content [Al] was 25.5%, and the argon content [Ar]. was 0.2at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 1.9E-3.

In Sample 13, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 30 sccm, and fluorine gas at a flow rate of 2.5 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 21.0 at%, the fluorine content [F] was 8.0 at%, the oxygen content [O] was 45.7 at%, the aluminum content [Al] was 24.9%, and the argon content [Ar]. was 0.4at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 7.0E-4.

In Sample 14, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 70 sccm, and fluorine gas at a flow rate of 0.5 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 27.3 at%, the fluorine content [F] was 0.8 at%, the oxygen content [O] was 46.5 at%, the aluminum content [Al] was 25.1%, and the argon content [Ar]. was 0.3at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 6.8E-4.

In Sample 15, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 50 sccm, and fluorine gas at a flow rate of 1.0 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 24.8 at%, the fluorine content [F] was 1.7 at%, the oxygen content [O] was 47.9 at%, the aluminum content [Al] was 25.4%, and the argon content [Ar]. was 0.2at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 4.7E-4.

In Sample 16, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 50 sccm, and fluorine gas at a flow rate of 0.5 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 24.4 at%, the fluorine content [F] was 0.7 at%, the oxygen content [O] was 49.8 at%, the aluminum content [Al] was 24.8%, and the argon content [Ar]. was 0.3at%.

In Sample 17, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 50 sccm, and fluorine gas at a flow rate of 2.0 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 24.0 at%, the fluorine content [F] was 4.5 at%, the oxygen content [O] was 46.0 at%, the aluminum content [Al] was 25.2%, and the argon content [Ar]. was 0.3at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 3.3E-4.

In Sample 18, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using the film forming apparatus 200 in FIG. 2. Argon gas was introduced at a flow rate of 150 sccm, oxygen gas at a flow rate of 50 sccm, hydrogen gas at a flow rate of 50 sccm, and fluorine gas at a flow rate of 3.0 sccm from each port to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 24.0 at%, the fluorine content [F] was 5.5 at%, the oxygen content [O] was 44.8 at%, the aluminum content [Al] was 25.1%, and the argon content [Ar]. was 0.6at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 1.3E-4.

In Sample 19, an aluminum oxide film containing hydrogen and fluorine was produced on a quartz glass substrate using a film formation apparatus using a sputtering method similar to the film formation apparatus 200 in FIG. 2.

The film forming apparatus used here differs from the film forming apparatus 200 in the type of gas introduced. Argon gas was introduced at a flow rate of 20 sccm, oxygen gas was introduced at a flow rate of 150 sccm, H ₂ O gas was introduced at a flow rate of 4 sccm, and CF ₄ gas was introduced from each port at a flow rate of 2 sccm to form a film. In the produced aluminum oxide film, the hydrogen content [H] was 2.3 at%, the fluorine content [F] was 4.3 at%, the oxygen content [O] was 56.9 at%, the aluminum content [Al] was 36.2%, and the argon content [Ar]. was 0.3at%. Additionally, the extinction coefficient at a wavelength of 193 nm was 3.1E-3.

When crystallinity was evaluated for each sample, all were amorphous regardless of the magnitude of the extinction coefficient.

In each sample, the content of argon was confirmed in the aluminum oxide film, but this was because the aluminum oxide film was produced using a sputtering method in which argon is introduced and film formation is performed.

Table 1 summarizes the data for each sample. Table 1 also shows the refractive index for a wavelength of 193 nm. Additionally, in Table 1, optical properties are comprehensively evaluated and classified into evaluations I to V. Evaluation I has an extinction coefficient greater than Sample 19 and a refractive index higher than Sample 19. Evaluation II has an extinction coefficient smaller than Sample 19 and a refractive index higher than Sample 00. Evaluation III is that the extinction coefficient is lower than that of Sample 19 and the refractive index is lower than that of Sample 19. Evaluations IV and V have an extinction coefficient smaller than Sample 19 and a refractive index higher than Sample 19. Evaluation V means that the extinction coefficient is less than 1.0E-03. Additionally, Samples 13 to 18 corresponding to Evaluation V have a refractive index higher than Sample 00, but this point does not need to be a standard for Evaluation V. Samples 00 and 19, which were also used as evaluation standards, were designated as evaluation X and Y, respectively.

Based on Table 1, conditions A to E that are desirable to satisfy for [Al], [O], [H], [F], and [Ar] are explained.

Condition A1… [Al]≤39.0at%

Condition A1 means that [Al] is significantly lower than the Al content of 40.0 at% in the stoichiometric composition of aluminum oxide, Al ₂ O ₃ . At least samples 01 to 19 satisfy condition A2.

Condition A2… [Al]≤35.0at%

At least samples 01 to 18 satisfy condition A2.

Condition A3… [Al]≤30.0at%

At least samples 02 to 18 meet condition A3.

Condition A4… [Al]≤25.4at%

At least samples 13 to 18 meet condition A4. Sample 15 corresponds to [Al]=25.4at%.

Condition A5… [Al]≥20.0at%

Condition A5 means that [Al] is more than half of the Al content of 40.0 at% in the stoichiometric composition of aluminum oxide, Al ₂ O ₃ . At least samples 01 to 18 meet condition A5.

Condition A6… [Al]≥24.8at%

At least samples 01 to 18 meet condition A6. Sample 16 corresponds to [Al]=24.8at%.

Condition B1… [O]≤59.0at%

Condition B1 means that [O] is significantly lower than the O content of 60.0 at% in the stoichiometric composition of aluminum oxide, Al ₂ O ₃ . It is thought that an aluminum oxide film with a hydrogen content [H] of 0 at% would ideally have a stoichiometric composition of Al ₂ O ₃ and an oxygen content [O] of 60.0 at%. However, in Table 1, the [O] of sample 00 is ] is smaller than 60.0at%. This is presumed to be because oxygen defects occurred in the aluminum oxide film. The same applies to other samples 01 to 19, and at least samples 01 to 18 satisfy condition A5.

Condition B2… [O]≤55.5at%

At least samples 01 to 18 satisfy condition B2.

Condition B3… [O]≤53.5at%

At least samples 02 to 18 meet condition B3.

Condition B4… [O]≤49.8at%

At least samples 13 to 18 meet condition B3. Sample 16 corresponds to [O]=49.8at%.

Condition B5… [O]≥30.0at%

Condition B5 means that [O] is more than half of the 60.0 at% O content in the stoichiometric composition Al ₂ O ₃ of aluminum oxide. At least samples 01 to 18 meet condition B5.

Condition B6… [O]≥44.8at%

At least samples 13 to 18 meet condition B6. Sample 18 corresponds to [O]=44.8at%.

Condition C1… [H]≥1.0at%

At least samples 01 to 18 satisfy condition C1. Even considering the inevitable mixing of hydrogen, it is difficult to think of sample 00 satisfying condition C0.

Condition C2… [H]≥5.0at%

[H] = 5.0at% is the intermediate value between [H] in sample 00 and [H] in sample 01. At least samples 01 to 18 meet condition C2.

Condition C3… [H]≥10.0at%

At least samples 01 to 18 satisfy condition C3.

Condition C4… [H]≥20.0at%

At least samples 02 to 18 meet condition C4.

Condition C5… [H]≤40.0at%

At least samples 01 to 18 meet condition C5.

Condition C6… [H]≤30.0at%

At least samples 01 to 18 meet condition C6.

Condition D1… [F]≥0.1at%

At least samples 07 to 18 meet condition D1. Even considering the inevitable mixing of fluorine, it is difficult to imagine that samples 00 to 06 satisfy condition D1.

Condition D2… [F]≥0.5at%

At least samples 07 to 19 meet condition D2.

Condition D3… [F]≤20.0at%

At least samples 01 to 18 meet condition D3.

Condition D4… [F]≤10.0at%

At least samples 01 to 18 meet condition D4.

Condition D5… [F]≤8.0at%

At least samples 01 to 18 meet condition D5.

Condition E1… [Ar]≥0.1at%

At least samples 01 to 18 satisfy condition E1.

Condition E2… [Ar]≤1.0at%

At least samples 01 to 18 satisfy condition E1.

The hydrogen content [H] in the produced aluminum oxide film was measured, and the relationship between the hydrogen content [H] in the obtained aluminum oxide film and the extinction coefficient k at a wavelength of 193 nm is shown in Fig. 3(a).

The result was that as the hydrogen content [H] in the aluminum oxide film increased, the extinction coefficient decreased, that is, the absorption of light with a wavelength of 193 nm decreased. Additionally, the results showed that as the hydrogen content [H] in the aluminum oxide film increased, the refractive index increased.

When the hydrogen content [H] was 10.0 at% or more, the extinction coefficient was 2E-2 or less, and the effect of reducing the extinction coefficient was confirmed. It was confirmed that at a hydrogen content [H] greater than 20.0 at%, the extinction coefficient decreases rapidly and becomes smaller than 1E-2. A small extinction coefficient was achieved up to 29.2 at%, which is the maximum hydrogen content [H] in the aluminum oxide film.

From the results in Table 1, for samples 07 to 18, a graph showing the relationship between the oxygen content [O] in the aluminum oxide film and the extinction coefficient is shown in Fig. 3(b). If the oxygen content [O] of the aluminum oxide film 105 is large, the extinction coefficient becomes small. Therefore, the oxygen content [O] in the aluminum oxide film also has a correlation with the optical properties of the aluminum oxide film 105. From Figure 3(b), when the oxygen content [O] is greater than 44.8 at%, an aluminum oxide film with a very small extinction coefficient can be obtained.

Also, from Table 1, it can be seen that as the hydrogen content [H] increases, the oxygen content [O] decreases, and the effect of the extinction coefficient becoming smaller when the oxygen content [O] is 55.2 at%, and in the area less than 51.9 at% The extinction coefficient was significantly reduced.

In Samples 13 to 18, aluminum oxide films with different hydrogen and fluorine contents were produced, but the extinction coefficient at a wavelength of 193 nm was small in all cases, and good aluminum oxide films were obtained.

The spectrum of the extinction coefficient of the aluminum oxide film produced as Sample 16 is shown in Figure 4. At the ArF wavelength of 193 nm, the extinction coefficient was as small as 4.7E-4, and an aluminum oxide film with low absorption was obtained. Additionally, even when irradiated with an ArF excimer laser, the occurrence of absorption was suppressed.

The spectrum of the extinction coefficient of the aluminum oxide film produced from Sample 06 and Samples 15 to 18 is shown in Figure 5(a). It can be seen that in the wavelength range of less than 200 nm, the reduction in the extinction coefficient becomes significant. From Figure 5(a), it can be seen that the extinction coefficients of Sample 06, which does not contain fluorine, and Samples 15 to 18, which contain fluorine, are small. Here, the wavelength at which the extinction coefficient is 4E-4 is taken as the reference wavelength. The reference wavelength can be considered the absorption edge wavelength. From Figure 5(a), the reference wavelength of sample 06 (fluorine content [F] 0 at%) is 194 nm. Likewise, the reference wavelength of sample 16 ([F] = 0.7at%) is 193nm, the reference wavelength of sample 15 ([F] = 1.7at%) is 193nm, and the reference wavelength of sample 17 ([F] = 4.5at%) The standard wavelength of sample 18 ([F] = 5.5 at%) was 191 nm and 190 nm. In this way, it can be seen that in samples 15 to 18, the reference wavelength is shifted toward a shorter wavelength compared to sample 06.

In order to make it easier to understand that the reference wavelength is shifted to the short wavelength side, the relationship between the fluorine content [F] and the reference wavelength is shown in Fig. 5(b). From Figure 5(b), it can be seen that when the fluorine content is greater than 0 at%, the reference wavelength is shifted toward the short wavelength side. This is presumed to be because the inherent band gap of aluminum oxide is expanded by containing fluorine. The reference wavelength is determined depending on the material's inherent bandgap size. It is thought that when fluorine is contained in the aluminum oxide film, a new bond is created between aluminum and fluorine, thereby expanding the band gap. The band gap of aluminum fluoride (AlF ₃ ), which does not contain oxygen, is 11 eV, which is larger than the band gap of aluminum oxide of 7 eV. Therefore, it is thought that by containing fluorine in the aluminum oxide film and generating a new bond between aluminum and fluorine, a bond similar to that of aluminum fluoride can be formed, thereby widening the band gap. This effect can be obtained by containing fluorine in the aluminum oxide film, and the effect can be obtained at a fluorine content [F] of 0.1 at% or more. A more preferable fluorine content [F] is 0.7 at% or more, which makes the absorption edge shorter than 193 nm.

Additionally, from Table 1, it can be seen that Samples 13 to 18 have a higher refractive index than Samples 07 to 12 and are suitable as a high refractive index material when forming a multilayer film. When aluminum oxide is used as a high refractive index material, it is preferable that the refractive index is higher. From the viewpoint of refractive index, the fluorine content [F] is preferably 8.0 at% or less.

Additionally, in order to determine the influence of hydrogen content [H] and fluorine content [F] on the aluminum oxide film, the inventors focused on the roughness of the surface of the aluminum oxide film and measured the roughness with AFM. For Samples 13 to 18 and Samples 07 to 12, Table 1 shows the hydrogen content [H], fluorine content [F], extinction coefficient, and roughness contained in the aluminum oxide film.

From Table 1, it can be seen that there is a relationship between the extinction coefficient and the illuminance. The greater the extinction coefficient, the greater the illuminance. This indicates that light scattering occurs on the surface of the aluminum oxide film.

The extinction coefficient is calculated from the light absorption rate A, but the light absorption rate A is

A=1-T-R

It is calculated from the equation. When the roughness of the surface of the aluminum oxide film is large, scattering occurs on the surface of the aluminum oxide film, so the transmittance T becomes small. Therefore, although light is not actually absorbed in the film, apparently, the light absorption rate A increases and the extinction coefficient increases.

To determine the cause of the increase in roughness, the surface of Sample 11 was observed with AFM. The observation results are shown in Figure 6. On the surface of the aluminum oxide of Sample 11, the presence of protrusions with a height of 10 nm or more was confirmed. Also, in Figure 6, the tip of the protrusion is flattened, but this is because flattening is observed beyond the measurement range of 10 nm. In reality, the protrusion is 10 nm or more in height. Similar observations were made for Samples 07 to 12, and these protrusions were easily observed in all of them. Additionally, upon observation of Samples 13 to 18, it was difficult to confirm the presence of such protrusions.

In both cases where the hydrogen content [H] is small or large, the extinction coefficient is sometimes small and sometimes large. The same applies to the fluorine content [F].

In Table 1, simply focusing on the various contents [Al], [O], [H], [F], and [Ar] is insufficient to determine a clear relationship between the contents and the extinction coefficient or refractive index. do. So, the sum or ratio of two of [Al], [O], [H], and [F], or the sum of two of [Al], [O], [H], and [F] and one other ratio, The review was conducted using this as an indicator. The results are shown in Tables 2 and 3. Please refer to Table 1 for various evaluations for each sample.

Based on Table 2, conditions F to M that are desirable to be satisfied for [Al], [O], [H], [F], and [Ar] in order to improve the optical properties of the aluminum oxide film 105 Explain.

Condition F1… [Al]+[O]≥50.0at%

Condition F1 means that the main component of the aluminum oxide film 105 is aluminum oxide. At least samples 01 to 18 satisfy condition F1.

Condition F2… [Al]+[O]≥69.9at%

At least samples 01 to 06 and 13 to 18 satisfy condition F2.

Condition F3… [Al]+[O]≤99.0at%

At least samples 01 to 18 satisfy condition F3.

Condition F4… [Al]+[O]≤90.0at%

At least samples 01 to 18 satisfy condition F4.

Condition F5… [Al]+[O]≤74.6at%

At least samples 07 to 18 meet condition F5.

Condition G1… [Al]+[H]≥40.0at%

At least samples 01 to 18 satisfy condition G1. Condition G1 means that when [H] > 0, [Al] + [H] is the Al content of 40.0 at% or more in the stoichiometric composition Al ₂ O ₃ of aluminum oxide.

Condition G2… [Al]+[H]≥42.0at%

At least samples 01 to 18 satisfy condition G2.

Condition G3… [Al]+[H]≥45.9at%

At least samples 04 to 06 and 13 to 18 satisfy condition G3.

Condition G4… [Al]+[H]≤60.0at%

At least samples 01 to 18 meet condition G4.

Condition G5… [Al]+[H]≤52.4at%

At least samples 13 to 18 meet condition G5.

Condition H1… [O]+[H]≤75.0at%

At least samples 01 to 18 satisfy condition H1.

Condition H2… [O]+[H]≥60.0at%

At least samples 01 to 06 and 10 to 18 satisfy condition H2. Condition H2 means that when [H] > 0, [O] + [H] is the O content of 60.0 at% or more in the stoichiometric composition Al ₂ O ₃ of aluminum oxide.

Condition H3… [O]+[H]≥63.0at%

At least samples 01 to 06 and 10 to 18 satisfy condition H3.

Condition H4… [O]+[H]≥66.7at%

At least samples 13 to 18 meet condition H4.

Condition I1… [O]/[Al]≥1.30

At least samples 01 to 18 satisfy condition I1.

Condition I2… [O]/[Al]≥1.60

At least samples 01 to 07 and 12 to 18 satisfy condition I2. Condition I2 means that [O]/[Al] is significantly larger than the ratio (1.50) of the O content of 60.0 at% and the Al content of 40.0 at% in the stoichiometric composition of aluminum oxide, Al ₂ O ₃ do.

Condition I3… [O]/[Al]≥1.75

At least samples 04 to 06 and 13 to 18 satisfy condition I3.

Condition I4… [O]/[Al]≤2.10

At least samples 01 to 18 satisfy condition I4.

Condition J1… [H]/[Al]≥0.25

At least samples 01 to 18 satisfy condition J1.

Condition J2… [H]/[Al]≥0.50

At least samples 02 to 18 satisfy condition J2.

Condition J3… [H]/[Al]≥0.75

At least samples 03 to 18 satisfy condition J3.

Condition J4… [H]/[Al]≤1.25

At least samples 01 to 18 satisfy condition J4.

Condition J5… [H]/[Al]≤1.10

At least samples 13 to 18 meet condition J5.

Condition K1… [H]/[O]≥0.10

At least samples 01 to 18 satisfy condition K1.

Condition K2… [H]/[O]≥0.25

At least samples 02 to 18 satisfy condition K2.

Condition K3… [H]/[O]≥0.46

At least samples 10 to 18 meet condition K3.

Condition K4… [H]/[O]≤0.75

At least samples 01 to 18 satisfy condition K4.

Condition K5… [H]/[O]≤0.59

At least samples 13 to 18 meet condition K5.

Condition L1… [O]/([Al]+[H])≤1.40

At least samples 01 to 18 satisfy condition L1. Condition L1 is that [O]/([Al]+[H]) is the ratio of the O content of 60.0 at% and the Al content of 40.0 at% in the stoichiometric composition of aluminum oxide Al ₂ O ₃ (1.50) It means something significantly smaller than that.

Condition L2… [O]/([Al]+[H])≤1.10

At least samples 02 to 18 satisfy condition L2.

Condition L3… [O]/([Al]+[H])≤1.01

At least samples 07 to 18 satisfy condition L3.

Condition L4… [O]/([Al]+[H])≥0.70

At least samples 01 to 18 satisfy condition L4.

Condition L5… [O]/([Al]+[H])≥0.89

At least samples 13 to 18 satisfy condition L5.

Condition M1… ([O]+[H])/[Al]≥1.60

At least samples 01 to 18 satisfy condition M1. Condition M1 is ([O]+[H])/[Al], which is the stoichiometric composition of aluminum oxide, the ratio of the O content of 60.0 at% and the Al content of 40.0 at% in Al ₂ O ₃ (1.50) It means something significantly bigger than that.

Condition M2… ([O]+[H])/[Al]≥1.90

At least samples 01 to 18 satisfy condition M2.

Condition M3… ([O]+[H])/[Al]≥2.68

At least samples 13 to 18 satisfy condition M3.

Condition M4… ([O]+[H])/[Al]≤3.00

At least samples 01 to 18 satisfy condition M4.

Condition N1… [H]/([Al]+[O])≥0.10

At least samples 01 to 18 satisfy condition N1.

Condition N2… [H]/([Al]+[O])≤0.40

At least samples 13 to 18 meet condition N2.

The present inventors assume a model in which hydrogen fills lattice defects (oxygen defects) generated in the aluminum oxide film. The defect-free aluminum oxide film is considered to have a stoichiometric composition of Al ₂ O ₃ , and the atomic ratio of aluminum and oxygen in the Al ₂ O ₃ film is 2:3, that is, [O]/[Al]=1.50. In Table 2, conditions I, L, and M are related to this, but conditions L and M, in which [H] is directly related, are examined.

In Figure 7 (a), the relationship between condition L, that is, [O]/([Al] + [H]) and the extinction coefficient is shown, and in Figure 7 (b), condition L, that is, [O]/( It shows the relationship between [Al]+[H]) and the refractive index. As can be understood from Fig. 7(a), the sample for which an extinction coefficient lower than Evaluation Y (sample 19) is obtained satisfies conditions L1 and L2. In addition, as can be understood from FIG. 7(b), the sample for which a higher refractive index than evaluation Y (sample 19) was obtained satisfies condition L1.

Next, focus on the condition M, which is the ratio of the sum of the hydrogen content [H] and oxygen content [O] in the aluminum oxide film and the aluminum content [Al] ([O]+[H])/[Al]. In samples 01 to 19 of evaluations I to V, it is greater than ([O]+[H])/[Al]=1.50 ([H]=0) obtained from the stoichiometric composition of Al ₂ O ₃ and satisfies condition M1. and also satisfies the condition M2 of ([O]+[H])/[Al]≥1.90.

It is presumed that the reason why the extinction coefficient and refractive index depend on the conditions L and M is because hydrogen not only fills lattice defects occurring in the aluminum oxide film, but also hydrogen is trapped between the lattices. It is thought that absorption occurring in the aluminum oxide film is suppressed by these and the extinction coefficient is reduced. In condition M1, the effect of the extinction coefficient being smaller than sample 00 can be confirmed. In addition, it can be seen that when condition M3 is satisfied, the extinction coefficient is significantly reduced. It is assumed that this effect will become more noticeable as the amount of hydrogen captured between lattices increases.

Similarly, in the other conditions J, K, and N, which are expressed as a ratio of at least one of hydrogen, aluminum, and oxygen, a significant difference is seen between Samples 00 to 18 and Sample 19.

Rather than hydrogen (H) being bonded to aluminum (Al) through oxygen (O) like hydroxyl (OH), hydrogen (H) is bonded directly to aluminum (Al), resulting in low absorption and/or high refractive index. I think it is advantageous for anger. Samples 01 to 18 were formed using hydrogen gas (H ₂ gas), so hydrogen (H) is easily bonded to aluminum (Al), and sample 19 was formed using H ₂ O gas, so hydroxyl groups (OH ) is easily bonded to aluminum (Al). It is thought that oxygen (O) that must be supplied by oxygen gas (O ₂ ) generates defects, and hydrogen or hydroxyl groups are placed in the defects and bonded to aluminum (Al). Here, based on FIG. 3, consider increasing the hydrogen content. When hydrogen is placed in an oxygen defect, the fluctuation of [O] is small and the increase in [H] is large, so when the hydrogen content increases, [H]/[O] increases, and [O]/[ H] tends to decrease. On the other hand, when a hydroxyl group is placed in an oxygen defect, both [O] and [H] increase, so the fluctuations in [H]/[O] and [O]/[H] are small. This is thought to be shown in conditions K, L, and N.

Based on Table 3, conditions O to W that are desirable to be satisfied for [Al], [O], [H], [F], and [Ar] in order to improve the optical properties of the aluminum oxide film 105. Explain.

Condition O1… [O]+[F]≤60.0at%

At least samples 01 to 18 satisfy condition O1. Condition O1 means that when [F] > 0, [O] + [F] is the O content of 60.0 at% or less in the stoichiometric composition Al ₂ O ₃ of aluminum oxide.

Condition O2… [O]+[F]≤56.0at%

At least samples 01 to 18 satisfy condition O2.

Condition O3… [O]+[F]≥45.0at%

At least samples 07 to 18 satisfy condition O3.

Condition P1… [H]+[F]≥10.0at%

At least samples 01 to 18 satisfy condition P1.

Condition P2… [H]+[F]≥20.0at%

At least samples 02 to 18 satisfy condition P2.

Condition P3… [H]+[F]≤40.0at%

At least samples 01 to 18 satisfy condition P3.

Condition P4… [H]+[F]≤30.0at%

At least samples 13 to 18 meet condition P4.

Condition Q1… [Al]+[F]≤42.4at%

At least samples 01 to 18 satisfy condition Q1.

Condition Q2… [Al]+[F]≤40.0at%

At least samples 10 to 18 satisfy condition Q2. Condition Q2 means that when [F] > 0, [Al] + [F] is the Al content of 40.0 at% or less in the stoichiometric composition Al ₂ O ₃ of aluminum oxide.

Condition Q3… [Al]+[F]≤32.9at%

At least samples 13 to 18 satisfy condition Q3.

Condition Q4… [Al]+[F]≥25.5at%

At least samples 01 to 18 satisfy condition Q4.

Condition R1… [F]/[H]≤1.00

At least samples 01 to 18 satisfy condition R1.

Condition R2… [F]/[H]≤0.50

At least samples 01 to 18 satisfy condition R2.

Condition R3… [F]/[H]≥0.01

At least samples 07 to 18 satisfy condition R3.

Condition R4… [F]/[H]≥0.03

At least samples 07 to 18 satisfy condition R4.

Condition S1… ([O]+[F])/[Al]≥1.60

At least samples 01 to 18 satisfy condition S1. Condition S1 is ([O]+[F])/[Al], which is the stoichiometric composition of aluminum oxide, the ratio of the O content of 60.0 at% and the Al content of 40.0 at% in Al ₂ O ₃ (1.50) It means something significantly bigger than that.

Condition S2… ([O]+[F])/[Al]≥1.75

At least samples 07 to 18 satisfy condition S2.

Condition S3… ([O]+[F])/[Al]≥1.88

At least samples 13 to 18 meet condition S3.

Condition S4… ([O]+[F])/[Al]≤2.20

At least samples 01 to 18 satisfy condition S4.

Condition S5… ([O]+[F])/[Al]≤2.04

At least samples 14 to 18 meet condition S5.

Condition T1… ([H]+[F])/[Al]≥0.25

At least samples 01 to 18 satisfy condition T1.

Condition T2… ([H]+[F])/[Al]≥1.00

At least samples 07 to 18 satisfy condition T2.

Condition T3… ([H]+[F])/[Al]≤1.50

At least samples 07 to 18 satisfy condition T3.

Condition T4… [H]/([Al]+[F])≤1.18

At least samples 13 to 18 satisfy condition T4.

Condition U1… [H]/([Al]+[F])≥0.25

At least samples 07 to 18 satisfy condition U1.

Condition U2… [H]/([Al]+[F])≥0.50

At least samples 07 to 18 satisfy condition U1.

Condition U3… [H]/([Al]+[F])≥0.75

At least samples 13 to 18 satisfy condition U3.

Condition U4… [H]/([Al]+[F])≤1.25

At least samples 01 to 18 satisfy condition U4.

Condition U5… [H]/([Al]+[F])≤1.10

At least samples 07 to 18 satisfy condition U5.

Condition V1… ([H]+[F])/[O]≥0.18

At least samples 01 to 18 satisfy condition V1.

Condition V2… ([H]+[F])/[O]≥0.50

At least samples 07 to 18 satisfy condition V2.

Condition V3… ([H]+[F])/[O]≤1.05

At least samples 01 to 18 satisfy condition V3.

Condition V4… ([H]+[F])/[O]≤0.66

At least samples 13 to 18 meet condition V4.

Condition W1… [H]/([O]+[F])≥0.10

At least samples 01 to 18 satisfy condition W1.

Condition W2… [H]/([O]+[F])≥0.39

At least samples 09 to 18 satisfy condition W2.

Condition W3… [H]/([O]+[F])≥0.48

At least samples 10 to 12 and 14 to 18 satisfy condition W3.

Condition W4… [H]/([O]+[F])≤0.66

At least samples 01 to 18 satisfy condition W4.

Condition W5… [H]/([O]+[F])≤0.58

At least samples 13 to 18 meet condition W5.

Figure 8 shows the relationship between hydrogen content [H] and fluorine content [F]. In Figure 8, the relationship with the evaluation results is shown with the hydrogen content [H] on the horizontal axis and the fluorine content [F] on the vertical axis. From Figure 8, it can be seen that there is a correlation between the hydrogen content [H] and the fluorine content [F] and the evaluation. The inventors estimate that when fluorine is contained in the aluminum oxide film, a new bond occurs between aluminum and fluorine within the aluminum oxide molecule, and shortening the reference wavelength (absorption end wavelength) has been realized. Even if the fluorine content [F] is relatively small, the low water absorption effect can be sufficiently obtained. However, even if the fluorine content [F] is larger, the low water absorption effect does not increase as much, or rather decreases. Additionally, an increase in the fluorine content [F] may result in low refractive index. On the other hand, as shown in FIG. 3, the larger the hydrogen content [H], the more advantageous it is for low absorption and high refractive index. And, the smaller the condition R, [F]/[H], the better the evaluation tends to be. As mentioned above, it is assumed that the production of aluminum fluoride is involved. It can be seen that evaluation Y does not satisfy condition R1, while evaluation III, IV, and V satisfy condition R1. In addition, it can be seen that evaluation III does not satisfy condition R2, while evaluation IV and V satisfies condition R2. In addition, while evaluations III and IV do not satisfy condition P4, those that satisfy condition P4 are evaluated as V.

In addition, here, evaluation IV and evaluation V are judged with an extinction coefficient of 1.0E-3 as the boundary.

When the hydrogen content [H] is large, the extinction coefficient becomes smaller than 1.0E-3 when the fluorine content [F] is small. Furthermore, when the hydrogen content [H] is small, the extinction coefficient is smaller than 1.0E-3 even if the fluorine content [F] is high to some extent. As shown in Figure 8, the relationship between the hydrogen content [H] and the fluorine content [F] for which the extinction coefficient is smaller than 1.0E-3 is such that the sum of the hydrogen content [H] and the fluorine content [F] is 30.0at%≤ In this case, a good aluminum oxide film 105 can be obtained.

By observing the surface of the aluminum oxide film, it was found that one of the reasons for the extinction coefficient being higher in Samples 07 to 12 than in Samples 13 to 18 was the presence of protrusions. It is presumed that this protrusion exists as a lump of aluminum fluoride. It is believed that when the supply amount of fluorine gas increases, aluminum fluoride molecules are formed and the protrusions observed in FIG. 6 are generated. Additionally, hydrogen is thought to have the effect of promoting the formation of aluminum fluoride. The aluminum oxide film of this embodiment is formed by a reactive sputtering method in which sputtering is performed by supplying a reactive gas. Hydrogen gas and fluorine gas are supplied during film formation, but if the amount of hydrogen gas supplied is large, the formation of aluminum fluoride in the gas phase is promoted. On the other hand, it is thought that if the supply amount of hydrogen gas is small, the formation of aluminum fluoride in the gas phase can be suppressed. If the amount of hydrogen gas introduced is small, the formation of protrusions is suppressed even if the amount of fluorine gas supplied is somewhat large, and an aluminum oxide film with a small extinction coefficient is realized. On the other hand, as the supply amount of hydrogen gas increases, the extinction coefficient is thought to increase because the formation of aluminum fluoride is promoted and protrusions are formed even if the amount of fluorine gas is small. Similarly, for the other conditions T, U, and W, expressed as the ratio of fluorine to hydrogen, a significant difference is visible between samples 00 to 18 and sample 19.

Similarly, in other conditions S, T, and V, which are expressed in the ratio of at least one of fluorine, aluminum, and oxygen, a significant difference is seen between Samples 00 to 18 and Sample 19.

The optical element 100 can be manufactured using the aluminum oxide film 105 that satisfies one or more of the above-described conditions A to W so that any of the optical properties of evaluations I to V can be obtained.

The optical element 100 can be applied to various optical devices EQP. Examples of optical equipment EQPs equipped with the optical element 100 include camera lenses, telescopes, projectors, exposure devices, and measuring instruments. In particular, it is suitable for optical devices equipped with a light source, such as projectors, exposure devices, and measuring instruments. This is because the laminated film 20 of the optical element 100 can be designed to match the wavelength of the light source so that the optical element 100 transmits and/or reflects light from the light source. The light from the light source may be any of infrared light, visible light, and ultraviolet light, but since the optical element of this embodiment has low absorption of ultraviolet light, it is suitable when the light source is ultraviolet light.

Figure 9 shows a schematic diagram of an exposure device as an example of an optical device EQP. The optical device EQP, which is an exposure device, includes a light source 1 and mirrors 2 and 3 that constitute an illumination optical system. In addition, the optical device EQP includes a reticle stage 5 on which the reticle 4 is mounted, a projection optical system 6 on which the pattern of the reticle 4 is projected, and a substrate stage 8 on which the substrate 7 is mounted. Equipped with The exposure light 9 from the light source 1 is reflected by the mirrors 2 and 3 of the illumination optical system and is guided to the reticle 4, and the exposure light 9 accompanying the pattern of the reticle 4 is transmitted to the projection optical system ( Light is collected at 6) and projected onto the substrate 7. The pattern formed on the reticle 4 by the light source 1 and the optical element 100 is projected onto the substrate 7. Photoresist is applied to the substrate 7, and the photoresist is exposed by exposure light 9.

The substrate 7 may be a semiconductor wafer or a glass substrate for FPD (flat panel display). The exposure light of the exposure apparatus is typically ultraviolet light. The wavelength of the exposure light is 436 nm for a g-line light source, and approximately 365 nm for an i-line light source. The wavelength of the exposure light is about 248 nm for a KrF excimer laser light source, about 193 nm for an ArF excimer laser light source, about 157 nm for an F2 excimer laser light source, and 10 to 20 nm for an EUV (extreme ultraviolet) light source. As explained using FIG. 5, this embodiment can significantly reduce absorption in a wavelength range of less than 200 nm, and is therefore suitable for using a light source containing light in a wavelength range of less than 200 nm. Here, an example in which the optical element 100 is used as the mirrors 2 and 3 of the illumination optical system is shown, but the optical element 100 may also be used as the lens of the projection optical system. Additionally, the projection optical system may be comprised of a mirror, and the optical element 100 may be employed as this mirror. The projection optical system may be a reduced projection type, an equal projection type, or an enlarged projection type. Although the transmissive reticle 4 is illustrated here, a reflective reticle 4 may also be used. The projection optical system may be a refractive type using a lens or a reflective type using a mirror. The optical element 100 may be used as a mirror of a reflective reduction projection optical system included in an exposure apparatus equipped with an EUV light source.

In recent years, exposure equipment has been studied to increase the intensity of light reaching a photosensitive substrate to expose the substrate in a short period of time, thereby improving the production capacity of the exposure equipment. Therefore, the light source of the exposure apparatus tends to have a high output. By improving the optical properties of a plurality of aluminum oxide films in response to the light of a high-output ArF excimer laser, the production capacity of the exposure apparatus is greatly improved.

[Example]

In Examples 1 and 2, a specific example of manufacturing an optical structure characterized by having a reflective structure on the surface of a reflective optical element will be described. On the quartz glass base 101, a total of 40 layers of high refractive index layers 103 and low refractive index layers 104 can be stacked alternately, forming the optical structure 102.

In Example 1, sample 16 in Table 1 was used as the high refractive index layer 103, and in example 2, sample 11 was used as the high refractive index layer 103. As the low refractive index layer 104, aluminum fluoride was used. Considering each refractive index and the purpose of use of the optical element 100, the configuration of the optical structure was determined by optimizing the physical film thickness of each layer in order to maximize reflection characteristics at a wavelength of 193 nm. Table 4 shows the layer structure of the optical element of Example 1, and Table 5 shows the layer structure of the optical element of Example 2.

Figure 10(a) shows the reflection characteristics of the reflective optical elements of Examples 1 and 2. The reflectance of the reflective optical element was measured in the wavelength range of 180 nm to 250 nm and at a light incident angle of 45 degrees. In Example 1, the reflectance at 193 nm was 98% or more, which was a good result. In Example 2, the reflectance at 193 nm was 96.4%. Example 1 was able to realize a higher reflectance than Example 2.

In Examples 3 and 4, a specific example of manufacturing an optical structure characterized by having a reflective structure on the surface of a reflective optical element will be described. On the quartz glass base 101, a total of 7 layers of high refractive index layers 103 and low refractive index layers 104 can be stacked alternately, forming the optical structure 102. In Example 1, sample 16 in Table 1 was used as the high refractive index layer 103, and in example 2, sample 11 was used as the high refractive index layer 103. As the low refractive index layer 104, aluminum fluoride was used. Considering each refractive index and the purpose of use of the optical element 100, the configuration of the optical structure was determined by optimizing the physical film thickness of each layer to maximize transmission characteristics at a wavelength of 193 nm. Table 6 shows the layer structure of the optical element of Example 3, and Table 7 shows the layer structure of the optical element of Example 4. The reflectance of the transmissive optical element was measured in the wavelength range of 180 nm to 250 nm and at a light incident angle of 45 degrees. In Example 3, the transmittance at 193 nm was 99% or more, which was a good result. In Example 2, the transmittance at 193 nm was 98.8%.

Figure 10(b) shows the transmission characteristics of the transmission type optical elements of Examples 3 and 4. The transmittance of the transmissive optical element was measured at a light incident angle of 10 degrees. In Example 3, the transmittance at 193 nm was 99% or more, which was a good result. In Example 4, the transmittance at 193 nm was 98.8%. Example 3 was able to realize a higher transmittance than Example 2.

The embodiments described above can be changed appropriately without departing from the technical idea. For example, multiple embodiments can be combined. Additionally, some details of at least one embodiment can be deleted or replaced. Additionally, new matters can be added to at least one embodiment.

In addition, the disclosure of this specification includes not only what is explicitly described in this specification, but also all matters that can be understood from this specification and the drawings attached to this specification. Additionally, the disclosure content of this specification includes the complement of individual concepts described in this specification. In other words, if there is a description in this specification to the effect that, for example, “A is B,” for example, even if the description in the case of “A is not B” is omitted, this specification is said to have disclosed the case that “A is not B.” can do. This is because, in the case where it is written to the effect that “A is B,” the premise is that the case where “A is not B” is being considered.

According to the present disclosure, it is possible to provide an advantageous technology in improving optical properties with respect to ultraviolet light.

Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be interpreted in the broadest manner to encompass all such modifications and equivalent structures and functions.

This application claims priority from Japanese Patent Application No. 2022-091133, filed on June 3, 2022, which is incorporated herein by reference in its entirety.

Claims (31)

An optical element comprising a base and an optical structure provided on the base,
The optical structure has at least a first dielectric layer, a second dielectric layer, and a third dielectric layer located between the first dielectric layer and the second dielectric layer and having a lower refractive index than the first dielectric layer and the second dielectric layer,
The first dielectric layer and the second dielectric layer are films containing aluminum oxide and hydrogen,
Let the oxygen content in the film be [O]at%, the aluminum content in the film be [Al]at%, and the hydrogen content in the film be [H]at%.
[Al]+[O]≥50.0at%
and
[O]/([Al]+[H])≤1.40
An optical element that satisfies the above. According to paragraph 1,
([O]+[H])/[Al]≥1.90
An optical element that satisfies the above. According to paragraph 1,
[H]/[O]≥0.10
An optical element that satisfies the above. According to paragraph 1,
[H]/([Al]+[O])≥0.10
An optical element that satisfies the above. According to paragraph 1,
Let the fluorine content in the above film be [F]at%,
([O]+[F])/[Al]≥1.60
An optical element that satisfies the above. According to paragraph 1,
[H]/[Al]≥0.25
An optical element that satisfies the requirements. According to paragraph 1,
[O]/[Al]≥1.75
[H]/[Al]≥0.75
[H]/[O]≥0.46
[O]/([Al]+[H])≤1.10
([O]+[H])/[Al]≥2.68
An optical element that satisfies at least one of the following. According to paragraph 1,
[H]≥10.0at%
[Al]≤35.0at%
[O]≤55.5at%
[Al]+[O]≤90.0at%
[Al]+[H]≥40.0at%
[O]+[H]≥60.0at%
An optical element that satisfies at least one of the following. According to paragraph 1,
[H]≥20.0at%
and
[H]≤30.0at%
An optical element that satisfies the requirements. According to paragraph 1,
[H]/[O]≤0.75
[H]/[Al]≤1.25
[O]/([Al]+[H])≥0.70
([O]+[H])/[Al]≤3.00
[H]/([Al]+[O])≤0.40
An optical element that satisfies at least one of the following. An optical element comprising a base and an optical structure provided on the base,
The optical structure has at least a film containing aluminum oxide, hydrogen, and fluorine,
The oxygen content in the film is [O]at%, the aluminum content in the film is [Al]at%, the hydrogen content in the film is [H]at%, and the aluminum content in the film is [H]at%. Let the fluorine content be [F]at%,
[Al]+[O]≥50.0at%
and
[F]/[H]≤1.0
Optical elements that meet the requirements. According to clause 11,
[H]/([Al]+[F])≥0.25
An optical element that satisfies the requirements. According to clause 11,
[H]/([O]+[F])≥0.10
An optical element that satisfies the above. According to clause 11,
([H]+[F])/[Al]≥0.25
An optical element that satisfies the requirements. According to clause 11,
([H]+[F])/[Al]≥1.00
and
([H]+[F])/[Al]≤1.50
Optical elements that meet the requirements. According to clause 11,
[F]/[H]≤0.50
An optical element that satisfies the above. According to clause 11,
([H]+[F])/[O]≥0.50
An optical element that satisfies the above. According to clause 11,
[H]+[F]≥20.0at%
and
[H]+[F]≤30.0at%
An optical element that satisfies the requirements. According to clause 11,
[O]+[F]≤60.0at%
[Al]+[F]≤40.0at%
An optical element that satisfies at least one of the following. According to clause 11,
([O]+[F])/[Al]≥1.75
An optical element that satisfies the requirements. According to clause 11,
The optical structure has at least a first dielectric layer, a second dielectric layer, and a third dielectric layer located between the first dielectric layer and the second dielectric layer and having a lower refractive index than the first dielectric layer and the second dielectric layer,
An optical element wherein the first dielectric layer and the second dielectric layer are the films. According to any one of claims 1 to 21,
An optical element, wherein the optical structure has an anti-reflection structure. According to any one of claims 1 to 21,
An optical element, wherein the optical structure has a reflective structure. According to any one of claims 1 to 21,
An optical element, wherein the surface on the film side of the substrate is a concave surface or a convex surface. According to any one of claims 1 to 21,
An optical element, wherein the optical element is a lens, mirror or prism. According to any one of claims 1 to 21,
An optical element wherein the main component of the gas is silicon oxide or calcium fluoride. The optical element according to any one of claims 1 to 21,
An apparatus characterized by comprising a holding part that holds the optical element. The optical element according to any one of claims 1 to 21,
A device comprising a light source that generates ultraviolet light to irradiate the film. According to clause 28,
A device wherein the wavelength of the ultraviolet light is less than 200 nm. According to clause 29,
A reticle stage equipped with a reticle,
Provided with a substrate stage for mounting a substrate,
A device in which ultraviolet light generated by the light source is irradiated to the substrate through the reticle and the optical element. According to clause 29,
The film contains argon, the oxygen content in the film, the aluminum content in the film, the hydrogen content in the film, the fluorine content in the film, and the film. A device in which the sum of argon content is 99.0 at% or more.

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