JP6982951B2 - Silicon substrate with functional film for infrared rays - Google Patents

Description

The present disclosure relates to a silicon substrate with a functional film for infrared rays, which is formed by laminating a plurality of thin films on a silicon substrate.

Conventionally, a substrate with a functional film having an antireflection function and an antireflection function by laminating thin films having different refractive indexes on the substrate has been known. Such a substrate with a functional film is known to be formed by laminating a thin film on the substrate by using a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method, or an ion plating method. (See Patent Document 1).

For example, in such a substrate with a functional film, a silicon substrate may be used when manufacturing a substrate with a functional film for infrared rays (for infrared light). The silicon substrate is cheaper in cost than other substrates (for example, germanium substrate, chalcogenide substrate, etc.) used in manufacturing a substrate with a functional film for infrared rays.

For example, in the manufacture of a substrate with a functional film for infrared rays, when a silicon substrate is used and a thin film is to be laminated on the surface of the silicon substrate, the adhesion between the silicon substrate and the thin film is weak, so that the thin film is formed from the silicon substrate. Is easy to peel off. Therefore, a method has been proposed in which the surface of a silicon substrate is irradiated with an ion beam to form a modified layer on the surface of the silicon substrate to improve the adhesion between the silicon substrate and the thin film (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2007-271860 Japanese Unexamined Patent Publication No. 7-20302

However, in the manufacture of a silicon substrate with a functional film for infrared rays, in order to improve the adhesion between the silicon substrate and the thin film, the method of irradiating the surface of the silicon substrate with an ion beam requires expensive equipment for irradiating the ion beam. It was required separately, and it was difficult to easily laminate a thin film on a silicon substrate.

In view of the above problems, it is a technical subject of the present disclosure to provide a silicon substrate with a functional film for infrared rays, which has an optical function for infrared rays and has good durability.

In order to solve the above problems, the present disclosure is characterized by having the following configurations.

(1) The silicon substrate with a functional film for infrared rays according to the first aspect of the present disclosure is a silicon substrate with a functional film for infrared rays formed by laminating a plurality of thin films on the silicon substrate, and is at least the silicon substrate. On one surface, the adhesion layer, which is a Si layer formed on the silicon substrate by thin film deposition, and the functional film layer on the adhesion layer are the first layer from the silicon substrate side. It is characterized in that it is formed in the order of the functional film layer and the layer next to the adhesion layer.

It is a schematic diagram which shows the laminated structure of the silicon substrate with the functional film for infrared rays in this embodiment.

Hereinafter, the silicon substrate with a functional film for infrared rays according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a laminated structure of a silicon substrate with a functional film for infrared rays in the present embodiment.

For example, in the present embodiment, the silicon substrate with a functional film for infrared rays is a silicon substrate with a functional film for infrared rays, which is formed by laminating a plurality of thin films on the silicon substrate. For example, the silicon substrate 1 with a functional film for infrared rays is formed of a silicon substrate (Si substrate) 2, an adhesion layer 3, and a functional film layer 4. For example, in the present embodiment, the adhesion layer 3 is formed on the silicon substrate 2 on at least one surface of the silicon substrate 2. Further, for example, the functional film layer 4 is formed on the adhesion layer 3. That is, for example, the adhesion layer 3 and the functional film layer 4 are laminated in order from the silicon substrate 2 side on one surface of the silicon substrate 2.

The silicon substrate 1 with a functional film for infrared rays in the present embodiment will be described by taking as an example a configuration in which the adhesion layer 3 and the functional film layer 4 are formed on one surface of the silicon substrate 2. Not limited to this. For example, the silicon substrate 1 with a functional film for infrared rays may have a configuration in which the adhesion layer 3 and the functional film layer 4 are formed on both sides of the silicon substrate 2. In this embodiment, the case where the antireflection film layer is used as the functional film layer 4 in the silicon substrate 1 with the functional film for infrared rays will be described as an example. That is, in the following description, among the silicon substrates with a functional film for infrared rays, a silicon substrate with an antireflection film for infrared rays will be described as an example.

For example, in the present embodiment, the silicon substrate 1 with a functional film for infrared rays is configured to have a high transmittance in an infrared wavelength region of 2 μm or more. Of course, the infrared wavelength region is not limited to the above configuration. Any infrared wavelength region can be set as the infrared wavelength region for increasing the transmittance. For example, the infrared wavelength region for increasing the transmittance may be an infrared wavelength region in the vicinity of 2 μm to 15 μm. The material and optical film thickness of the functional film layer 4 are appropriately set according to the infrared wavelength region for increasing the transmittance. In the following description, a silicon substrate with a functional film for infrared rays, which increases the transmittance in the infrared wavelength region near 10 μm, will be described as an example.

For example, in the present embodiment, the silicon substrate 2 is a silicon substrate having a refractive index of 3.4. In this embodiment, a configuration using a silicon substrate 2 having a refractive index of 3.4 will be described as an example, but the present invention is not limited to this. For example, a silicon substrate 2 having a different refractive index may be used. For example, in this embodiment, the silicon substrate 2 has a thickness of 0.5 mm. Of course, a configuration in which silicon substrates 2 having different thicknesses are used may be used. In addition, for example, the silicon substrate 2 in this embodiment is not limited to a plate shape, and includes a film substrate. Further, for example, the silicon substrate 2 in the present embodiment includes an optical member such as a lens.

For example, the adhesion layer 3 is a layer formed to improve the adhesion between the silicon substrate 2 and the functional film layer 4. For example, the adhesion layer 3 is made of Si (silicon). For example, in the present embodiment, the adhesion layer 3 is Si having a refractive index of 3.4. In this embodiment, a configuration using Si having a refractive index of 3.4 as the adhesion layer 3 will be described as an example, but the present invention is not limited to this. For example, the adhesion layer 3 may be configured in which Si having a different refractive index is used. The adhesion layer 3 is not limited to Si. For example, as the adhesion layer 3 _{, metal oxides such as SiO, ZrO 2} , TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , Al ₂ O ₃ , HfO ₂ , Y ₂ O ₃ , and CeO ₂ can also be used. .. Further, for example, as the adhesion layer 3 _{, fluorides such as YF 3} , LaF ₃ , MgF ₂ , CeF ₃ , and YbF ₃ can also be used. Further, for example, as the adhesion layer 3, a mixture in which at least two or more of the above-mentioned substances are mixed can also be used.

For example, as the material of the adhesion layer 3, a material that is transparent in the infrared wavelength region that increases the transmittance or that absorbs less light in the infrared wavelength region that increases the transmittance is selected. Is considered preferable. Of course, even if the light absorption in the infrared wavelength region that increases the transmittance is large, it can be applied by reducing the film thickness. When the silicon substrate 1 with a functional film for infrared rays is configured to have a high transmittance in the infrared wavelength region near 7 μm to 15 μm, it is preferable to select Si having higher transparency. ..

For example, the physical film thickness of the adhesion layer 3 may be a film thickness having an effect of having high adhesion to the silicon substrate 2 and high adhesion to the functional film layer 4. For example, the physical film thickness of the adhesion layer 3 is preferably 1 nm or more and 400 nm or less, and more preferably 10 nm or more and 100 nm or less. For example, if the physical film thickness is less than 1 nm, the adhesion is deteriorated and the functional film layer 4 is easily peeled from the silicon substrate 2. Further, for example, when the physical film thickness exceeds 400 nm, the transmittance in the infrared wavelength region is lowered, so that the antireflection function tends to be lowered. That is, Si has a property of absorbing light in the infrared wavelength region. Therefore, it is more preferable that the optical film thickness of Si is small (thin) because it is difficult for light in the infrared wavelength region to be absorbed. In the present embodiment, the physical film thickness of the adhesion layer 3 is 30 nm. For example, the physical film thickness is a generally-called film thickness calculated by measuring the film thickness with a ruler. The optical film thickness is calculated by multiplying the physical film thickness by the refractive index of the substance.

For example, the functional film layer 4 has a structure in which materials having different refractive indexes are laminated, and an antireflection function can be obtained by adjusting the physical film thickness, the refractive index, and the like. Therefore, the functional film layer 4 can be configured by laminating a plurality of thin film layers. The film thickness of the functional film layer 4 is appropriately set according to the infrared wavelength region for increasing the transmittance. For example, the optical film thickness (multiplication of the physical film thickness and the refractive index) of the functional film layer 4 is set by λ / 4 (λ is the center wavelength of the infrared wavelength region that increases the transmittance).

For example, in the present embodiment, the functional film layer 4 is an antireflection film layer. For example, in the present embodiment, the functional film layer 4 is composed of a multilayer film in which thin films having different refractive indexes are laminated. More specifically, for example, in the present embodiment, the functional film layer 4 is formed of a first thin film layer 5 and a second thin film layer 6.

For example, the first thin film layer 5 is a thin film layer made of a material (low refractive index material) having a refractive index lower than that of the silicon substrate 2. In the present embodiment, the case where the first thin film layer 5 is made of a material having a refractive index lower than that of the silicon substrate 2 is described as an example, but the present invention is not limited to this. For example, the first thin film layer 5 may be a thin film layer made of a material having a refractive index lower than that of the second thin film layer 6. For example, examples of the low refraction material include zinc sulfide (ZnS), yttrium fluoride layer (YF ₃ layer), silica dioxide layer (SiO ₂ layer) and the like. In this embodiment, a ZnS layer (refractive index 2.3) is used as the first thin film layer 5. Of course, the refractive index of ZnS is not limited to 2.3, and may be another refractive index. For example, in the present embodiment, the physical film thickness of the first thin film layer 5 is preferably 100 nm or more and 2000 nm or less, and more preferably 300 nm or more and 1500 nm or less. Even if the physical film thickness is thicker or thinner, it is difficult to have an antireflection function. In the present embodiment, the physical film thickness of the first thin film layer 5 is 1100 nm.

For example, the second thin film layer 6 is a thin film layer made of a material (high refractive index material) having a refractive index higher than that of the silicon substrate 2. In the present embodiment, the case where the second thin film layer 6 is made of a material having a refractive index higher than that of the silicon substrate 2 is described as an example, but the present invention is not limited to this. For example, the second thin film layer 6 may be a thin film layer made of a material having a refractive index higher than that of the first thin film layer 5. For example, examples of the high refractive material include germanium (Ge) and titanium dioxide (TIO ₂ ). In this embodiment, a Ge layer (refractive index 4.0) is used as the second thin film layer 6. Of course, the refractive index of Ge is not limited to 4.0, and may be another refractive index. For example, in the present embodiment, the physical film thickness of the second thin film layer 6 is preferably 50 nm or more and 1500 nm or less, and more preferably 100 nm or more and 1000 nm or less. Even if the physical film thickness is thicker or thinner, it is difficult to have an antireflection function. In the present embodiment, the physical film thickness of the second thin film layer 6 is 650 nm.

For example, in the functional film layer 4 of the present embodiment, the outermost final layer from the silicon substrate 2 is the first thin film layer 5 made of a low refraction material. That is, the second thin film layer 6 and the first thin film layer 5 are laminated in this order from the silicon substrate 2 side. The outermost final layer from the silicon substrate 2 may be a different thin film. For example, the outermost final layer from the silicon substrate 2 may be a second thin film layer 6 made of a high refractive material. In this case, it is preferable that the functional film layer 4 is formed with a film thickness that does not affect the antireflection function.

In the present embodiment, the functional film layer 4 has been described by taking as an example a configuration composed of a multilayer film in which a plurality of thin films are laminated, but the present invention is not limited thereto. For example, the functional film layer 4 may be configured to be composed of at least one or more thin films. In this case, for example, the functional film layer 4 may be composed of only the first thin film layer 5 (for example, ZnS layer or the like) made of a material having a lower refraction than the silicon substrate 2.

In the present embodiment, the case where the functional film layer 4 is formed of two layers, the first thin film layer 5 and the second thin film layer 6, is described as an example, but the present invention is limited to this. Not done. For example, the functional film layer 4 has a configuration in which a plurality of thin films of the material of the first thin film layer 5 and the material of the second thin film layer 5 are alternately and repeatedly laminated (for example, four layers (Ge) from the silicon substrate 2 side. Layer, ZnS layer, Ge layer, ZnS layer stacked in this order), 7 layers (ZnS layer, Ge layer, ZnS layer, Ge layer, ZnS layer, Ge layer, ZnS layer stacked in this order), 8 layers Configuration, etc.) may be used.

In the present embodiment, the case where the functional film layer 4 is formed by using two different materials is described as an example, but the present invention is not limited to this. For example, the functional film layer 4 may form a thin film layer made of a different material in addition to the material of the first thin film layer 5 and the material of the second thin film layer 5.

In the present embodiment, the functional film layer 4 has been described by taking as an example an antireflection film layer having an antireflection function, but the present invention is not limited thereto. For example, the functional membrane layer 4 may have other functions. For example, the functional film layer 4 may have functions such as augmentation reflection, edge filter, beam split, band pass, and the like.

As a method for forming each of the thin film layers (adhesion layer 3, functional film layer 4) shown above on the silicon substrate 2, the physical vapor deposition method (PVD) includes a vacuum vapor deposition method, a sputtering method, and an ion play method. The ting method and the like can be mentioned. Moreover, as a chemical vapor deposition method (CVD), a chemical vapor deposition method and the like can be mentioned. All of these film forming methods can be used as the present embodiment, but since deformation of the silicon substrate 2 due to heat is conceivable in a method involving high temperature during film formation, the formation of a multilayer film on the silicon substrate 2 is possible. As the film, a vacuum vapor deposition method or a sputtering method that does not require high heat is preferably used.

As described above, for example, in the present embodiment, even when the functional film layer is formed on the silicon substrate by providing the adhesion layer made of Si between the silicon substrate and the functional film layer. It is possible to suppress the peeling of the functional film layer from the silicon substrate and obtain a silicon substrate with a functional film for infrared rays having good durability. That is, even when a silicon substrate with a functional film for infrared rays is used, which is inexpensive in terms of cost, it is easy to obtain a silicon substrate with a functional film for infrared rays which has an optical function for infrared rays and has good durability. Obtainable.

Further, for example, in the present embodiment, the antireflection film layer is provided as the functional film layer, and the adhesion layer made of Si is provided between the silicon substrate and the antireflection film layer, whereby the antireflection film layer is provided on the silicon substrate. Even in the case of forming the above, it is possible to suppress the peeling of the antireflection film layer from the silicon substrate and obtain a silicon substrate with a functional film for infrared rays having good durability.

Hereinafter, the present disclosure will be specifically described with reference to the present examples and comparative examples, but the present disclosure is not limited to the following examples. Hereinafter, in Examples 1 and 2, on one surface of the silicon substrate, an adhesion layer made of Si on the silicon substrate and a functional film layer on the adhesion layer (in the case of this example, an antireflection film layer). ) And were formed in order from the silicon substrate side, and the adhesion and functionality of the obtained silicon substrate with a functional film for infrared rays were evaluated. In Examples 3 to 4, on both sides of the silicon substrate, an adhesion layer made of Si on the silicon substrate and a functional film layer on the adhesion layer are formed in order from the silicon substrate side, and the obtained infrared rays are used. The adhesion and functionality of the silicon substrate with a functional film were evaluated.

In Comparative Examples 1 and 2, a functional film layer was formed on one surface of the silicon substrate, and the adhesion and functionality of the obtained silicon substrate with a functional film for infrared rays were evaluated.

<Example 1>
In Example 1, Si granules, Ge granules, and ZnS granules are prepared as a vapor deposition source, and Si is used as an adhesion layer, Ge is used as a first reflective film layer (thin film layer) having a high refractive index, and low refractive index is obtained by vacuum vapor deposition. ZnS was laminated on the silicon substrate in order from the silicon substrate side as the second reflective film layer (thin film layer), to obtain a silicon substrate with an antireflection film. That is, an antireflection film layer was formed by Ge as the first reflective film layer having a high refractive index and ZnS as the second reflective film layer having a low refractive index. Here, as the silicon substrate, a silicon plate having a thickness of 0.5 mm was used. The film thickness of the adhesion layer made of Si was 30 nm in terms of physical film thickness. The film thickness of the first reflective film layer made of Ge was 650 nm in terms of physical film thickness. The film thickness of the second reflective film layer made of ZnS was set to 1100 nm in terms of physical film thickness. The transmittance of the obtained silicon substrate with antireflection film was measured with an infrared spectrophotometer (Perkin Elme Inc. Frontier). The evaluation criteria are evaluation ○ when the transmittance is higher than the transmittance (51%) of the silicon substrate before the antireflection film layer is attached, and the transmittance (51%) or less of the silicon substrate without the antireflection film. If it was, the evaluation was ×. In addition, an adhesion test was conducted on a silicon substrate with an antireflection film to evaluate the adhesion between the antireflection film layer and the silicon substrate. In the adhesion test, an adhesive tape (Nichiban Co., Ltd. Tape No. 405) was strongly attached to a silicon substrate with an antireflection film, and the adhesive tape (Nichiban Co., Ltd. Tape No. 405) was quickly peeled off to confirm whether or not the antireflection film was peeled off. This operation was repeated 3 times, and when the antireflection film layer was not peeled off, the evaluation was ◯, and when even a part of the antireflection film layer was peeled off, the evaluation was ×. Similar evaluations were made for Example 2 and Comparative Examples 1 and 2 below. The evaluation results are shown in Table 1.

<Example 2>
Instead of forming the antireflection film layer with the first reflective film layer made of Ge and the second reflective film layer made of ZnS, the antireflection film layer was formed only with ZnS as the first reflective film layer having a low refractive index. Made a silicon substrate with an antireflection film in the same manner as in Example 1. The film thickness of the first reflective film layer made of ZnS was set to 1100 nm in terms of physical film thickness.

<Comparative Example 1>
A silicon substrate with an antireflection film was produced in the same manner as in Example 1 except that an adhesion layer was not formed between the silicon substrate and the antireflection film layer.

<Comparative Example 2>
A silicon substrate with an antireflection film was produced in the same manner as in Example 2 except that an adhesion layer was not formed between the silicon substrate and the antireflection film layer.

（結果）
以上、表１で示されるように、シリコン基板と反射防止膜層との間にＳｉからなる密着層を設けた赤外線用機能性膜付シリコン基板の密着性が、シリコン基板と反射防止膜層との間にＳｉからなる密着層を設けない場合の密着性と比較して向上する。また、Ｓｉからなる密着層を用いた場合に、密着層の上に積層される薄膜層が高屈折材料又は低屈折材料のいずれの材料であっても、密着性を向上させることができる。

(result)
As described above, as shown in Table 1, the adhesion of the silicon substrate with the functional film for infrared rays provided with the adhesion layer made of Si between the silicon substrate and the antireflection film layer is the adhesion between the silicon substrate and the antireflection film layer. This is improved as compared with the case where the adhesion layer made of Si is not provided between the two. Further, when the adhesive layer made of Si is used, the adhesiveness can be improved regardless of whether the thin film layer laminated on the adhesive layer is a high-refractive material or a low-refractive material.

In this way, by providing the adhesion layer made of Si between the silicon substrate and the antireflection film layer, the antireflection film layer is peeled off from the silicon substrate even when the antireflection film layer is formed on the silicon substrate. It is possible to obtain a silicon substrate with a functional film for infrared rays having good durability.

Claims (3)

A silicon substrate with a functional film for infrared rays, which is formed by laminating multiple thin films on a silicon substrate.
On at least one surface of the silicon substrate, an adhesion layer which is a Si layer formed on the silicon substrate by vapor deposition and a functional film layer on the adhesion layer are the first layer from the silicon substrate side. A silicon substrate with a functional film for infrared rays, wherein the contact layer and the functional film layer are formed in the next layer of the contact layer in this order. In the silicon substrate with a functional film for infrared rays according to claim 1.
The functional film layer is a silicon substrate with a functional film for infrared rays, which is an antireflection film layer. In the silicon substrate with a functional film for infrared rays according to claim 1 or 2.
The functional film layer is silicon with a functional film for infrared rays, wherein the final layer outermost from the silicon substrate is a first thin film layer made of a material having a refractive index lower than that of the silicon substrate. substrate.

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