Anti-reflective multilayer substrate, its fabrication method, and fabrication program

Abstract

This invention provides a non-reflective multilayer substrate in which the material, film thickness, and stacking order of each layer of a multilayer film stacked on an opaque base substrate are determined and the film thickness is adjusted, as well as a method for fabricating a non-reflective multilayer substrate using coordinates on a complex plane. [Solution] A multilayer substrate in which dielectric layers and light-absorbing layers are laminated on an opaque base substrate, and the thickness of each layer is adjusted so that the reflectivity becomes zero at a predetermined wavelength. Also, a method for producing an anti-reflective film by laminating a multilayer film on a base substrate, comprising: 1) a coordinateization step in which the complex reflection coefficient of the base substrate before lamination is shown in coordinates on the complex plane; 2) a trajectory creation step in which the change in the complex reflection coefficient as each layer is formed, starting from the coordinates and in the order of lamination of the multilayer film, is represented as a trajectory on the complex plane; and 3) a film thickness adjustment step in which the film thickness of each layer is adjusted based on the material and lamination order of each layer of the multilayer film, so that the end of the trajectory represented in the trajectory creation step is located at or near the origin on the complex plane.

Description

[Technical Field]

[0001] This invention relates to a non-reflective multilayer substrate for enhancing contrast in optical microscope images, a method for manufacturing the same, and a manufacturing program. [Background technology]

[0002] In the fields of electronic devices, chemistry, and biology, there is a need for technologies to detect ultrathin films, several nanometers thick, formed on the surface of substrates, as well as fine particles attached to surfaces. Generally, nanoscale surface measurement and analysis are time-consuming, requiring significant time for both measurement and sample analysis. Depending on the measurement method, vacuum evacuation may be necessary, or microscopic measurement may not be possible. Nanoscale surface measurement is not easy, and analysis is complex. Traditionally, evaluation has been performed using methods such as X-ray and infrared spectroscopy. Therefore, there is a demand for non-scanning and non-destructive microimaging using a general-purpose optical microscope and camera.

[0003] One method for performing nanoscale surface measurement and analysis involves placing a sample on a non-reflective substrate and observing it with a standard optical microscope and camera. A non-reflective substrate is a substrate whose reflectivity is nearly zero at a specific wavelength, and it has a multilayer structure in which one or more thin films are stacked on the substrate. When an ultrathin film with a nanoscale thickness is formed on a non-reflective substrate, the optical path difference increases in the areas where the ultrathin film is formed, causing the reflection spectrum to shift to longer wavelengths. As a result, a difference in color is created on the substrate due to the difference in reflectivity between areas with and without the ultrathin film, allowing for observation of the ultrathin film at the atomic level simply by photographing the sample with a camera connected to an optical microscope, without the user having to be aware of anything. Furthermore, since it is possible to detect not only ultrathin films but also nanoparticles and proteins adsorbed on the substrate surface, it is expected to be useful in the development of electronic devices and solar cells, as well as in biosensors. This method has the advantage of being usable without modifying a general-purpose optical microscope. Furthermore, since the light detected by the camera in this measurement is not weak light, a commercially available digital camera can be used, eliminating the need for high-performance cameras such as cooled cameras. Additionally, a darkroom is not required, making it a method with low equipment installation costs and offering significant ripple effects across various fields.

[0004] However, nanoscale surface measurements and analyses require a flat, non-reflective substrate, and the material of the outermost surface of the non-reflective substrate is often determined by the sample to be observed. For example, thiol-based organic molecules readily adsorb to the surface of Au thin films, and organic monolayers formed on the surface of Au thin films are used in bioscience and electronic devices. Therefore, observing these requires a non-reflective multilayer substrate with an Au thin film on its surface. Similarly, observing silane-based organic molecular films requires a non-reflective multilayer substrate with an SiO2 surface.

[0005] While anti-reflective multilayer substrates with a thin Au film on the surface have been developed to date, anti-reflective multilayer substrates for microscopic observation with oxides such as SiO2 films on the surface, which have high utility value, have not yet been obtained. Similarly, anti-reflective multilayer substrates with highly functional polymers as the top layer are also considered effective for nanoscale observation, but their development has not progressed to date. Therefore, there is a need for the development of anti-reflective multilayer substrates for observation with diverse surface materials that can be obtained through a simple film deposition process.

[0006] One of the technical reasons why the development of anti-reflective multilayer substrates for observation has not progressed is that a specialized optical design method for anti-reflective substrates for observation with optical microscopes has not been established, and optical design has so far been carried out through trial and error. A widely known technology related to this is anti-reflective coating (AR coating) applied to glass and lenses, which is in practical use, but simply applying these to anti-reflective multilayer substrates for observation is insufficient. Generally, AR coating is applied to transparent glass, but to apply it to anti-reflective multilayer substrates for observation, a coating on an opaque substrate is required. Furthermore, there is no optical design method that allows an arbitrary material to be used as the top layer.

[0007] To make the reflectivity of a substrate zero at a certain wavelength, it is necessary to layer thin films of various materials at appropriate thicknesses onto a thick base substrate and then apply an AR coating. The reflectivity when multiple thin films are layered on a substrate is expressed using the complex reflection coefficient (ρ) |ρ| 2 It is widely known that this ρ can be calculated using matrices. In this technique, the complex reflection coefficient (ρ) is plotted on the complex plane to perform optical design.

[0008] The following documents describe substrates with AR coatings. Patent documents 1 and 2 disclose supports for sample observation having AR coatings. However, these mainly disclose techniques using single-layer coatings, and do not describe design methods for making an arbitrary material the outermost surface. Furthermore, while patent document 3 describes using the complex reflection coefficient (ρ) when determining the thickness of the AR coating on a substrate, it also does not describe a design method for making an arbitrary material the outermost surface. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2016-538570 [Patent Document 2] Special Publication No. 2016-535325 [Patent Document 3] Special Publication No. 2003-506735 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] As described above, when samples such as ultrathin films or microparticles are placed on the surface of an anti-reflective substrate, a difference in reflectivity occurs between the areas where the sample is present and those where it is not. Therefore, when observed with a general optical microscope, the sample can be detected with high sensitivity. However, there is no established method for effectively designing anti-reflective substrates for use with optical microscopes. In particular, for observing surfaces at the atomic level using anti-reflective multilayer substrates, the material of the top layer of the anti-reflective multilayer substrate is important, but until now, an optical design method for having any material on the surface has not been established. Furthermore, in order to improve the flatness of the anti-reflective substrate, it is desirable to perform optical design that also takes into account the actual film deposition process, and it is necessary to develop an optical design method specifically for anti-reflective multilayer substrates for observation.

[0011] The reflectance when multiple thin films are formed on a substrate is expressed using the complex reflection coefficient (ρ) |ρ| 2 Since this can be calculated, it is sufficient if ρ=0 after applying the AR coating to the substrate, but it has been difficult to optically design a substrate that satisfies ρ=0 in the past. Since ρ is a complex number of |ρ|≦1, it can be represented on the complex plane (the |ρ|≦1 drawn on the complex plane is called a reflection circle).

[0012] Therefore, the inventors focused on the trajectory of the complex reflection coefficient (ρ) drawn in the reflection circle diagram when the top layer of the thin film is gradually stacked, assuming that each thin film of the multilayer film is stacked gradually. They designed the AR coating of the multilayer film so that the end of the trajectory is at or around the origin (ρ=0), and fabricated an anti-reflective multilayer substrate. The present invention aims to provide a non-reflective multilayer substrate in which the material and stacking order of each layer of a multilayer film stacked on an opaque base substrate are determined and the film thickness is adjusted, as well as a manufacturing method and a manufacturing program for producing a non-reflective multilayer substrate using coordinates on a complex plane. [Means for solving the problem]

[0013] To solve the above problems, the non-reflective multilayer substrate according to the first aspect of the present invention is a multilayer substrate having a dielectric portion in which two or more dielectric layers are laminated on an opaque base substrate, and having a dielectric layer as the uppermost layer, wherein the thickness of each layer is adjusted so that the reflectivity becomes zero at a predetermined wavelength. According to the first aspect of the non-reflective multilayer substrate, a multilayer substrate is provided in which dielectric layers are laminated on an opaque base substrate, and a non-reflective multilayer substrate with zero reflectivity at a predetermined wavelength can be provided. Under certain conditions, a structure with only a few layers of dielectric is sufficient, which has the advantage of simplifying the film deposition process.

[0014] Here, an opaque base substrate is a substrate made of metal or semiconductor, such as Si, Ag, Al, or Ni. A dielectric layer is a layer made of dielectric material, that is, a layer made of material that does not absorb light of the target wavelength (as will be explained later in the explanation of the calculation model for multilayer substrates, a material where k=0 in N=n-ik), and includes oxide layers and polymer layers. A dielectric portion refers to a part made up of one or more dielectric layers. Furthermore, the predetermined wavelength at which reflectance becomes zero can be selected not only from wavelengths of visible light (400nm to 800nm), but also from wavelengths of ultraviolet light (200nm to 400nm) and near-infrared light (800nm ​​to 2500nm).

[0015] In particular, the uppermost dielectric layer is preferably an oxide or polymer layer. Examples of oxides include SiO2, Al2O3, ITO, ZnO, SnO2, and NiO x It is selected from the group of In-Ga-ZnO4. Specifically, the anti-reflective multilayer substrate in the first aspect consists of a SiN layer on an opaque base substrate, which is a Si substrate. x It has two layers, one made of SiO2 and the other of which has the SiO2 layer on top.

[0016] A non-reflective multilayer substrate according to a second aspect of the present invention is a multilayer substrate having a dielectric portion in which one or more dielectric layers are laminated on an opaque base substrate, and a light-absorbing portion in which one or more light-absorbing layers are laminated on the dielectric portion, and having a light-absorbing layer as the uppermost layer, wherein the thickness of each layer is adjusted so that the reflectance becomes zero at a predetermined wavelength. According to the second aspect of the non-reflective multilayer substrate, a multilayer substrate is provided in which a dielectric layer and a light-absorbing layer are laminated on an opaque base substrate, and a non-reflective multilayer substrate with zero reflectivity at a predetermined wavelength can be provided. The top layer can be made into a light-absorbing layer with a simple configuration, and the introduction of thin buffer layers and adhesive layers, which are often important in the film deposition process, can be easily carried out. In addition, there is the advantage that the wavelength at which reflectivity becomes zero can be controlled by adjusting the film thickness of each layer of the dielectric portion.

[0017] Here, the light-absorbing layer refers to a layer composed of a light-absorbing material that absorbs the target light (a material with N=n-ik and k≠0, as will be explained later in the explanation of the calculation model for multilayer substrates), and includes metals and semiconductors. It also includes polymers with k≠0, such as polymers containing nanomaterials. Furthermore, the light-absorbing portion refers to a part composed of one or more light-absorbing layers. Specifically, in the second aspect of the anti-reflective multilayer substrate, the base substrate is made of Ag or Al or a metal with a reflectivity of 50% or more, the dielectric portion is made of SiO2, and the light-absorbing portion is made of a thin adhesive layer of Cr or Ti and an uppermost layer of Au. Alternatively, by introducing an organic molecular film having a functional group containing S (sulfur) as the adhesive layer instead of the thin adhesive layer of metal, a high-quality Au layer can be deposited on the dielectric portion. In particular, it is preferable that the functional group is a thiol group, and it is preferable that the organic molecular film is MPTMS (3-Mercaptopropyltrimethoxysilane). MPTMS has a thiol group (-SH group), and the thiol group bonds with the uppermost Au film, improving adhesion. Furthermore, by annealing the adhesive layer of the organic molecular film and the uppermost Au layer, the crystallinity of the uppermost layer is improved, and an anti-reflective multilayer substrate with high heat resistance can be constructed. Similarly, the structure can be constructed by replacing the top layer of Au film with a metal that chemically bonds with thiol groups, such as Ag, Cu, Pt, Pd, Ni, Ir, Rd, or Rh. Furthermore, it is possible to make the top layer a dielectric layer by stacking one or more dielectric layers having a thickness that is an integer multiple of the optical thickness at half a wavelength on top of the top light-absorbing layer. Making the top layer a dielectric was also explained in the first aspect of the anti-reflective multilayer substrate, but there is a problem that the materials that can be used to construct an anti-reflective multilayer substrate in the first aspect are theoretically limited. However, in this second aspect of the anti-reflective multilayer substrate, any dielectric layer can be made the top layer.

[0018] A non-reflective multilayer substrate according to a third aspect of the present invention is a multilayer substrate having a first dielectric portion in which one or more dielectric layers are laminated on an opaque base substrate, a light-absorbing portion in which one or more light-absorbing layers are laminated on the first dielectric portion, a second dielectric portion in which one or more dielectric layers are laminated on the light-absorbing portion, and a dielectric layer on the uppermost layer, wherein the thickness of each layer is adjusted so that the reflectivity becomes zero at a predetermined wavelength. According to the third aspect of the anti-reflective multilayer substrate, a multilayer substrate is provided in which each light-absorbing layer is sandwiched between two dielectric layers on an opaque base substrate, and an anti-reflective multilayer substrate with zero reflectivity at a predetermined wavelength can be provided. Making the top layer an arbitrary dielectric has already been explained in the second aspect of the anti-reflective multilayer substrate, but in the third aspect of the anti-reflective multilayer substrate, the number of layers can be reduced, which may simplify the film deposition process or allow for thinner film thicknesses for each layer.

[0019] Next, the method for manufacturing the anti-reflective multilayer substrate of the present invention will be described. The present invention relates to a method for producing an anti-reflective multilayer substrate, which involves laminating a multilayer film on an opaque base substrate to produce an anti-reflective film, as described in the first to third aspects of the present invention, or a method for laminating a multilayer film on a base substrate of any material to produce an anti-reflective film, comprising the following steps 1) to 3). 1) A coordinateization step in which the complex reflection coefficient of the base substrate before lamination is shown in coordinates on the complex plane. 2) A trajectory representation step in which the change in the complex reflection coefficient as each layer is formed, starting from a coordinate system and following the stacking order of the multilayer film, is represented as a trajectory on the complex plane. 3) A film thickness adjustment step in which the film thickness of each layer of the multilayer film is adjusted based on the material and stacking order of each layer, such that the end of the trajectory represented in the trajectory calculation step is located at or near the origin on the complex plane.

[0020] According to the method for fabricating a non-reflective multilayer substrate of the present invention, it is possible to perform optical design of a multilayer substrate that satisfies ρ=0, which was difficult with conventional methods. By placing a sample such as an ultrathin film or fine particles on the surface of the fabricated non-reflective multilayer substrate and observing it with a general optical microscope and camera, non-scanning and non-destructive real-time microimaging becomes possible under atmospheric pressure. Here, the base substrate refers to the substrate that serves as the base before the multilayer film is stacked, and includes, for example, Si substrates, Al substrates, Cu substrates, Cr substrates, Ti substrates, Ni substrates, Ag substrates, etc. Note that commercially available Al substrates other than single-crystal Si substrates have a large surface roughness, so a sufficiently thick, flat thin film is formed on a flat substrate such as a single-crystal Si substrate or a thermally oxidized Si substrate and used. For example, a 500 nm Al thin film is stacked on a thermally oxidized Si substrate and used. Furthermore, expressing the complex reflection coefficient in coordinates on the complex plane means that the horizontal axis is the real axis and the vertical axis is the imaginary axis, and the complex reflection coefficient is associated with coordinates on the complex plane. First, in the coordinateization step of 1) above, the complex reflection coefficient of the base substrate is expressed in coordinates on the complex plane.

[0021] In the trajectory tracing step described in 2) above, the coordinates of the complex reflection coefficient of the base substrate are used as the starting point. The change in the complex reflection coefficient is represented as a trajectory on the complex plane, assuming that each layer is gradually deposited on the base substrate in the order in which the AR coating is applied to the multilayer film. The change, that is, the distance and position of the coordinates on the complex plane, differs depending on the type of material of each layer and the order in which they are deposited. However, starting from the coordinates of the complex reflection coefficient of the base substrate, it is drawn continuously as a single line on the complex plane until the top layer is deposited.

[0022] The adjustment step described in 3) above involves adjusting the film thickness of each layer of the multilayer film based on the material and stacking order of each layer, so that the end of the trajectory represented on the complex plane is located at or near the origin on the complex plane. This allows for the optical design of a multilayer substrate that satisfies ρ=0. If ρ=0 cannot be achieved by adjusting the film thickness of each layer alone, some materials or the stacking order should be reconsidered. Furthermore, when a dielectric thin film that does not absorb light is incorporated into a multilayer structure, its trajectory is an arc in the reflection circle diagram, and it is drawn clockwise. On the other hand, light-absorbing materials tend to move to the second quadrant depending on their thickness. Thus, the trajectory of each layer can be predicted to some extent, making it easy to adjust the material and film thickness of each layer by referring to the trajectory in the reflection circle diagram.

[0023] In a non-reflective multilayer substrate where the multilayer film consists of p-layers, the trajectory of the p-layer portion is crucial for designing a non-reflective multilayer substrate with the top layer being a p-layer and the material of the p-layer being arbitrary. The endpoint of this trajectory must be ρ=0. That is, the trajectory of a specific material passing through ρ=0 is important, and in this invention, this trajectory is mathematically formulated and drawn on a reflection circle diagram. This trajectory is uniquely determined and does not depend on the structure of the substrate coated with the (p-1) layer below the p-layer. Therefore, by connecting the endpoint when the (p-1) layer is stacked to the trajectory of the target material passing through ρ=0, a non-reflective multilayer substrate with an arbitrary material on its surface can be designed. In other words, by appropriately selecting the material and thickness of each layer of a multilayer substrate having a (p-1) layer, the endpoint coordinates at the stage when the (p-1) layer is coated are controlled.

[0024] The anti-reflective multilayer substrate manufacturing program of the present invention, similar to the anti-reflective multilayer substrate manufacturing method of the present invention, is a program for manufacturing an anti-reflective film by laminating a multilayer film on an opaque base substrate, or a program for manufacturing an anti-reflective film by laminating a multilayer film on a base substrate of any material, and is intended to cause a computer to execute each of the following steps A) to E). A) An input step in which the wavelength of light, information about the base substrate, and information about the multilayer film to be stacked on the base substrate are input. B) A coordinateization step in which the complex reflection coefficient of the base substrate before lamination is shown in coordinates on the complex plane. C) A trajectory representation step in which the change in the complex reflection coefficient as each layer is formed, starting from a coordinate and following the stacking order of the multilayer film, is represented as a trajectory on the complex plane. D) A film thickness adjustment step in which the film thickness of each layer of the multilayer film is adjusted based on the material and stacking order of each layer, such that the end of the trajectory represented in the trajectory calculation step is located at or near the origin on the complex plane. E) Output step to output the film thickness of each layer.

[0025] Specifically, the input step A) above involves inputting the target wavelength of non-reflective light, the material of the base substrate, the material, stacking order and types of the multilayer film, and the target film thickness range into the computer. In the coordinate generation step B), the trajectory generation step C), and the film thickness adjustment step D) described above, the complex plane, the coordinates on the complex plane and the trajectory of each layer, and the film thickness of each layer based on the length of the trajectory of each layer may be displayed on the computer screen. Alternatively, in the coordinate-setting step B), the trajectory-setting step C), and the film thickness adjustment step D), when displaying the trajectories of each layer on a complex plane on a computer screen, in addition to the trajectories, the film thickness of each layer based on the length of the trajectory of each layer may also be displayed on the computer screen as additional information regarding the process of stacking each layer. In the film thickness adjustment step D) above, the film thickness of each layer may be optimized using a nonlinear equation such that the end of the trajectory represented in the trajectory calculation step is located at or near the origin on the complex plane. The output step E) above outputs the film thickness of each layer stacked on the base substrate. The output can be done by outputting the type and film thickness of each layer as data, or by outputting it on the screen along with a reflection circle diagram. [Effects of the Invention]

[0026] According to the present invention, a non-reflective multilayer substrate can be provided, which is a multilayer substrate in which dielectric layers and light-absorbing layers are laminated on an opaque base substrate, and which has zero reflectivity at a predetermined wavelength. Furthermore, in the fabrication of the non-reflective multilayer substrate, the structure of the multilayer substrate can be visually illustrated on a complex plane, and by referring to this figure, the material, film thickness, and stacking order of each layer of the multilayer film can be considered, enabling visual optical design. As a result, it becomes possible to determine the multilayer structure in relation to the actual film deposition process in order to deposit a stable and flat thin film. Moreover, it becomes possible to design a non-reflective multilayer substrate having any material on its surface. [Brief explanation of the drawing]

[0027] [Figure 1] Schematic diagram of a non-reflective multilayer substrate (Example 1) [Figure 2] Schematic diagram of a non-reflective multilayer substrate (Example 2) [Figure 3] Flowchart for fabrication of anti-reflective multilayer substrates [Figure 4] Diagram illustrating the reflection circle in the fabrication flow of a non-reflective multilayer substrate. [Figure 5] (1) Multilayer substrate model with p layers, (2) Intermediate model of the first layer, (3) Intermediate model of the q layer, (4) Single-layer substrate model on a virtual substrate including a multilayer with p-1 layers [Figure 6] Reflection circle diagrams used for fabricating various reflective multilayer substrates at λ=530nm. [Figure 7] Diagram illustrating the method for fabricating a non-reflective multilayer substrate (Si-based substrate) (Example 3) [Figure 8] Diagram illustrating the method for fabricating a non-reflective multilayer substrate (Example 4): (1) Reflection circle diagram of a non-reflective SiO2 / Cr / Au multilayer substrate using different base substrates (Si, Cu, Ag), (2) Reflection circle diagram of a non-reflective SiO2 / Cr / Au multilayer substrate using the same base substrate (Ag). [Figure 9] Reflection circle diagram showing the trajectories of various materials within the multilayer film of a non-reflective multilayer substrate (Example 5) [Figure 10] Reflection circle diagram showing the trajectories of various materials within the multilayer film of a non-reflective multilayer substrate (Example 6) [Figure 11]Reflection circle diagram showing the trajectories of various materials within the multilayer film of a non-reflective multilayer substrate (Example 7) [Figure 12] Reflection circle diagram showing the trajectories of various materials within the multilayer film of a non-reflective multilayer substrate (Example 8) [Figure 13] Flowchart of the fabrication program for an anti-reflective multilayer substrate (Example 9) [Figure 14] Example screen of the fabrication program for a non-reflective multilayer substrate (Example 9) [Figure 15] Characterization of multilayer hBN flakes on Si / SiNx / SiO2 (Example 10) [Figure 16] (1) Contrast spectra of 1 to 4 layers of hBN film on a substrate, (2) Explanatory diagram of contrast according to the number of layers at λ=450, 470, 530, and 600 nm (Example 10) [Figure 17] Configuration diagram and reflection spectrum of a non-reflective multilayer substrate with Au as the top layer (Example 11) [Figure 18] FE-SEM images of the Au surface before and after annealing (Example 11) [Figure 19] Reflectance spectra before and after annealing (Example 11) [Figure 20] Figure (Example 11) shows the results of evaluating the crystallinity of the Au film using X-ray diffraction. [Figure 21] FE-SEM images of the Au surface in response to changes in annealing temperature (Example 11) [Modes for carrying out the invention]

[0028] First, the method for fabricating the anti-reflective multilayer substrate of the present invention will be explained with specific examples. Figure 3 shows the fabrication flow of the anti-reflective multilayer substrate. As shown in Figure 3, the fabrication of the anti-reflective multilayer substrate of the present invention consists of three steps S01 to S05. First, a wavelength that makes the reflectance zero (for example, wavelength λ = 530 nm) is determined (S01), and the complex reflection coefficient of the base substrate is coordinated on the complex plane (S02). As a concrete example, we will explain the case where, for example, a Si substrate and an Ag substrate are used as the base substrate, referring to Figure 4. In the reflection circle diagram in Figure 4, the coordinates of the complex reflection coefficients of the Si substrate and the Ag substrate are plotted. For the processing in step S02, the complex reflection coefficients can be stored as coordinates on the complex plane, but it is also possible to display a reflection circle diagram like the one shown in Figure 4 on the screen and plot the coordinates of the complex reflection coefficients of the base substrate.

[0029] Next, the coordinates of the complex reflection coefficient of the base substrate are used as the starting point, and the material, stacking order, and film thickness of each layer are adjusted (S03). The change in the complex reflection coefficient as each layer is formed is represented by a trajectory on the complex plane (S04). In the reflection circle diagram of Figure 4, when a 76.3 nm SiO2 film is stacked on a Si substrate, the trajectory shows how the complex reflection coefficient changes clockwise around a point near the origin on the complex plane as the thickness of the stacked film increases. Similarly, the same behavior is observed when a 105.4 nm PMMA (Polymethyl methacrylate) film is stacked on an Ag substrate. Although both SiO2 and PMMA are dielectrics that do not absorb light, in this technology, when a dielectric is deposited on the base substrate or multilayer film, the reflection circle diagram has the characteristic of moving clockwise along a circle centered on a point on the real axis. If the deposition of dielectrics continues further, the trajectory continues to move along the circular orbit, completing one revolution with a film having an optical thickness of half a wavelength (for example, 181.1 nm in the case of SiO2), and returning to the initial coordinate point. In other words, the curve shown in Figure 4 is an arc, which is part of a circle. Furthermore, the size and position of the circle depend on the complex refractive index N and the initial point of the trajectory. The reason why the arc drawn in Figure 4 is larger for the Ag substrate than for the Si substrate is due to the difference in the coordinate points of the substrate before dielectric deposition.

[0030] Subsequently, as the next layer is stacked, the trajectory changes continuously, with the endpoint of the previous trajectory becoming the new starting point. In the reflection circle diagram of Figure 4, a 6.0 nm thick layer of graphite is stacked on a substrate with an SiO2 film on a Si substrate, and the trajectory extends towards the origin, eventually reaching the origin. Similarly, a 27.0 nm thick layer of Au is stacked on a substrate with a PMMA film on an Ag substrate, and the end of the trajectory extends towards the origin on the complex plane, eventually reaching the origin. Since both graphite and Au are thin films that absorb light (light-absorbing layers), their trajectories are not circular arcs. The trajectories of many common light-absorbing materials are curves, and they tend to move toward the second quadrant on the complex plane as the film thickness increases. Here, the circular, square, and triangular markers on the trajectory lines in the reflection circle diagram of Figure 4 represent the changes in the complex reflectance coefficient per unit thickness of 10 nm, 5 nm, and 1 nm for each layer, respectively. Thus, the distance traveled by the trajectory corresponding to each film thickness varies not only depending on the material but also on the stacking order. In this way, the reflection circle diagram is characterized by its ability to visualize the change in the complex reflection coefficient when layers are formed, and because the trajectories of the dielectric layer and the light-absorbing layer can be roughly predicted, the materials of the thin films, the stacking order, and the optimal film thickness can be visually examined based on the trajectories drawn in the reflection circle diagram.

[0031] Next, it is checked whether the final endpoint of the trajectory is at or near the origin (S05). In the reflection circle diagram in Figure 4, it can be confirmed that the final endpoint of both substrates reaches the origin, which corresponds to the theoretically zero reflectivity at the specified 530 nm light. If the final endpoint does not reach the origin, the material, stacking order, and film thickness of each layer are re-examined, and the trajectory is redrawn, and adjustments are continued so that the endpoint is located at the origin (or near the origin) on the complex plane. Note that some of these adjustments can also be made by optimizing the film thickness by solving modeled nonlinear equations.

[0032] Here, we will explain the calculation model for multilayer substrates. Figure 5(1) shows the base substrate N bThe schematic diagram of a multilayer substrate with a p layer is shown above. N and d for each layer represent the complex refractive index and thickness, respectively. N is represented by N = n - ik (i is the imaginary unit). N m and N b are the refractive indices of the incident medium and the base substrate, respectively. When the incident medium is air, N m is set to 1.0. However, in the case of observation in a liquid, etc., it becomes the value of the refractive index of the incident medium itself and is not limited to 1.0.

[0033] In the reflection circle diagram, the change in the complex reflection coefficient (ρ) at the front surface of the multilayer substrate is visualized. Each layer is constructed on top of the previous layer in the final incident medium, and is drawn on the complex plane assuming that the thickness gradually grows from 0 regardless of the actual film formation method. At this time, the complex reflection coefficient (ρ) starts from the value of the base substrate (ρ b ) and continuously changes to the value (ρ sub ) when the final layer is constructed. Actually, the trajectory is drawn by individually calculating the complex reflection coefficient (ρ) at each stage of growth in each layer and plotting it on the complex plane. The reflectivity R of the final multilayer substrate sub is calculated as |ρ sub | 2 . Therefore, to construct a non-reflective multilayer substrate, ρ sub = 0, or the optical design is such that |ρ sub | becomes small.

[0034] ρ in FIG. 5 p corresponds to the case of a p-layer substrate. In this structure, ρ continuously changes from the value of the base substrate (ρ sub ) to the value of the uppermost layer (ρ b ). The changes at the film layer growth stage are calculated sequentially. First, the value of the base substrate (ρ p ) is calculated by the following Equation 1. b ) is calculated by the following Equation 1.

[0035]

Equation

[0036] Next, FIG. 5(2) is a schematic diagram of a single film with thickness d (0 < d < d1), which shows the state during the formation of the layer (intermediate model of the first layer) initially deposited on the base substrate. In this case, ρ is represented by the following Equation 2. Here, δ1 = 2πN1d1 / λ, ρ1 T =(N m -N1) / (N m +N1), ρ1 B =(N1-N b ) / (N1+N b ) are the reflection coefficients at the upper and lower boundaries, respectively. The locus of ρ of the first layer is calculated by changing the thickness d.

[0037]

Number

[0038] Similarly, for the subsequent laminated films, ρ is calculated using the intermediate model. FIG. 5(3) is a schematic diagram during the deposition of the qth layer with thickness d (0 < d < d q ). Here, q is 1 < q < p, and ρ q (d) is calculated from the characteristic matrix of the thin film as a method for calculating the reflectance in a general multilayer film model. By changing d q and performing calculations respectively, the change in the structure of the multilayer film during the deposition of the qth layer is calculated and plotted on the reflection circle diagram. By performing the same procedure up to the pth layer, the locus up to the final ρ p is drawn. Therefore, by appropriately changing the material, lamination order, and film thickness of each layer, it becomes possible to design a non-reflective multilayer substrate. Note that the above explanation is for the case of normal incidence, but ρ for the case of oblique incidence is calculated in the same way.

[0039] Next, the case of designing the top layer with an arbitrary material will be explained. In the locus of the above circle diagram, the R sub of the completed multilayer substrate is p (d p )| 2 given by |ρ p (d p ). Here, ρ subThis is the endpoint of the locus of ρ in the uppermost layer that corresponds to it. In other words, the locus of the uppermost layer is the locus of the p layer, and therefore R sub Since this is determined, ρ in a specific material p Since it is worthwhile to examine the trajectory of (d) in detail, Figure 5(4) shows N including the (p-1) layer. v Let's consider a model that assumes a single layer on a virtual board with ρ. p (d) is similar to the single-film model shown in Figure 5(2) and is calculated by the following equation 3. Here, δ p =2πN p d p / λ, ρ p T =(N m -N p ) / (N m +N p ), ρ p B =(N p -N v ) / (N p +N v ) are the reflection coefficients at the upper and lower boundaries, respectively.

[0040]

number

[0041] Mathematical expression of ρ p (d) When passing through the origin, ρ p The trajectory of (d) is R sub It is important to obtain a non-reflective multilayer substrate with ρ = 0. p-1 (d p-1 If the endpoint of the trajectory of ) lies on that trajectory, then the thickness d p By adjusting, R sub A substrate with =0 is obtained. p (d p The condition for )=0 is given by equation 4 below.

[0042]

number

[0043] Rearranging equation 4 above, N v This can be expressed as shown in equation 5 below. This gives N = 0 v This indicates that it is uniquely determined. In this case, the reflectance of the virtual base substrate (ρ v ) is ρ p (d) corresponds to ρ v (N m -N v ) / (N m +N v It is calculated as ρ. p (d) = ρ v The trajectory is, d p By varying |ρ|≦1, the reflection circle diagram will be drawn.

[0044]

number

[0045] Figure 6(1) shows the ρ passing through the origin in materials Cr, Ti, Cu, Au, and Al. p (d p The figure shows the locus of |ρ|. The dashed circle indicates |ρ|=1. As shown in the figure, the locus passing through the origin is a single curve independent of the layer structure below the p layer. Therefore, the target ρ p (d p By controlling the intermediate layer so that the end of the p-1 substrate aligns with the trajectory of the dielectric material, it becomes possible to design a non-reflective multilayer substrate with the desired material as the top layer. Dielectric materials such as TiO2, Al2O3, PMMA, and SiO2 are also depicted in the figure. As mentioned above, the trajectory of the dielectric material is a circle in the reflection circle diagram, so in Figure 6, a circle passing through the origin is depicted.

[0046] The following section will explain in detail, with reference to the diagrams, how to fabricate a non-reflective multilayer substrate using a reflection circle diagram, which graphically visualizes the continuous change in the complex reflection coefficient (ρ) during the construction of the non-reflective multilayer substrate. Unless otherwise specified, the explanation assumes that the incident light (λ=530nm) is perpendicular to the multilayer substrate. Furthermore, the scope of the present invention is not limited to the following embodiments and illustrated examples, and numerous modifications and variations are possible. [Examples]

[0047] The anti-reflective multilayer substrate of the present invention will be described with reference to the figures. Figure 1 shows examples of schematic diagrams of three types of anti-reflective multilayer substrates. Figure 1(1) shows an example of an anti-reflective multilayer substrate according to the first aspect of the present invention, which has a dielectric portion consisting of three dielectric layers A, B, and C on an opaque base substrate, with dielectric layer C as the uppermost layer. In the multilayer substrate of Figure 1(1), the thickness of each layer is adjusted so that the reflectivity is zero at a wavelength of 530 nm.

[0048] Furthermore, Figure 1(2) shows an example of a non-reflective multilayer substrate according to a second aspect of the present invention, which has a light-absorbing layer as the uppermost layer. This multilayer substrate has a dielectric portion consisting of two dielectric layers A and B on an opaque base substrate, a light-absorbing portion consisting of three light-absorbing layers A, B, and C on dielectric layer B, and a light-absorbing layer C as the uppermost layer. In this multilayer substrate as well, the thickness of each layer is adjusted so that the reflectivity is zero at a wavelength of 530 nm.

[0049] Furthermore, Figure 1(3) shows an example of a non-reflective multilayer substrate according to a third aspect of the present invention, which has an opaque base substrate, a first dielectric portion consisting of two dielectric layers A and B, a light-absorbing portion consisting of three light-absorbing layers A, B, and C on dielectric layer B, a second dielectric portion consisting of two dielectric layers C and D on the light-absorbing portion, and a dielectric layer D as the uppermost layer. In this multilayer substrate as well, the thickness of each layer is adjusted so that the reflectivity is zero at a wavelength of 530 nm. [Examples]

[0050] In this embodiment, the non-reflective multilayer substrate is shown as an example in which the top layer is made dielectric by further stacking one or more dielectric layers having a thickness that is an integer multiple of the optical thickness of half a wavelength on top of the top light-absorbing layer in the non-reflective multilayer substrate of the second aspect described in Figure 1(2) of Embodiment 1. In the non-reflective multilayer substrate shown in Figure 2(1), an opaque base substrate has a dielectric portion consisting of two dielectric layers A and B, an optical absorption portion consisting of three optical absorption layers A, B, and C on dielectric layer B, and one dielectric layer C having a thickness that is an integer multiple of the optical thickness of half a wavelength is laminated on optical absorption layer C.

[0051] For example, a non-reflective multilayer substrate is constructed by laminating an opaque Ni substrate as the base substrate, a dielectric layer of SiO2 (75.5 nm) on top of it, a light-absorbing layer of Cr (3.2 nm) on top of that, and a dielectric layer of PMMA (177.3 nm) on the top layer. The top layer has an optical thickness of half a wavelength (177.3 nm in the case of PMMA). By depositing the target dielectric material onto the top layer to an optical thickness of half a wavelength, a non-reflective multilayer substrate with the dielectric material on the top layer is obtained. For example, a non-reflective multilayer substrate with a dielectric on top can be obtained by stacking a Ni substrate as an opaque base substrate, a dielectric layer of SiO2 (75.5 nm) on top of it, a light-absorbing layer of Cr (3.2 nm) on top of that, and finally stacking a dielectric layer of PMMA (177.3 nm in the case of PMMA) with an optical thickness of half a wavelength.

[0052] Furthermore, in the non-reflective multilayer substrate shown in Figure 2(2), an opaque base substrate has a dielectric portion consisting of two dielectric layers A and B, an optical absorption portion consisting of three optical absorption layers A, B and C on dielectric layer B, and two dielectric layers C and D with thicknesses that are integer multiples of the optical thickness of half a wavelength stacked on optical absorption layer C. For example, this applies to a material where SiO2 (181.1 nm) is deposited on top of the aforementioned Ni / SiO2 (75.5 nm) / Cr (3.2 nm) / PMMA (177.3 nm). [Examples]

[0053] Figure 7 shows three examples of non-reflective multilayer substrates with a Si base substrate, optically designed using a circular diagram. Here, the circular, square, and triangular markers in the figure indicate the movement of ρ per unit thickness of 10 nm, 5 nm, and 1 nm, respectively, for each layer. All trajectories represent the complex reflection coefficient ρ of the base substrate. b It starts from there and ends at the origin (ρ=0) or a neighborhood of the origin. For ρ locus values ​​of abo, the ρ of the Si-based substrate sub It starts from coordinate point a, which corresponds to the first aspect of the present invention. When an SiO2 film is deposited on a Si-based substrate, with the deposition of a 19.4 nm SiO2 film, ρ moves to coordinate point b. The end of the first layer deposited on the base substrate becomes the initial ρ of the next layer to be deposited. The trajectory of ρ of the second hexagonal boron nitride (hBN) film starts continuously from coordinate point b and moves to the final coordinate point o where |ρ|=0, i.e., R=0. This corresponds to the non-reflective multilayer substrate of the first aspect of the present invention.

[0054] Furthermore, in Figure 7, the trajectory of ρ, when adgo, starts from coordinate point a on the Si-based substrate. With the deposition of a 112.2 nm SiO2 film on the Si-based substrate, ρ moves to coordinate point d. Further deposition of a 0.5 nm Cr adhesive film on the SiO2 film, followed by the deposition of an 8.3 nm Au film as the top layer, causes the trajectory to end at point o. This corresponds to the non-reflective multilayer substrate according to the second aspect of the present invention, i.e., the case where the top layer has a light-absorbing layer.

[0055] Furthermore, in Figure 7, the trajectory of ρ, where ah is the coordinate point a of the Si-based substrate, starts from the Si-based substrate and is located on a 62.0 nm SiN layer on the Si-based substrate. x During film deposition, the end of the trajectory of ρ reaches point o. This is because SiN is deposited on a Si-based substrate. x This is a single-layer coating. Theoretically, if a single layer film with an optically matched refractive index is deposited on a light-absorbing substrate such as a Si-based substrate, the reflectivity R will become 0 (zero) at a certain wavelength. SiN x Since the refractive index of the film is close to the ideal value for Si, the coordinate point h at the end of the ρ trajectory corresponds to R=0.28%, making it usable for visualizing ultrathin films. [Examples]

[0056] This embodiment describes a non-reflective multilayer substrate in which the uppermost layer is formed of an Au film. Technically, in order to form a flat and stable Au film using a general vacuum deposition method, it is important to insert a thin adhesive layer beneath the Au film and to form the Au film as thick as possible. By using a reflection circle diagram, it is possible to visually examine what kind of multilayer structure is appropriate from an optical design perspective. Figure 8(1) shows the reflection circle diagrams of SiO2 / Cr / Au multilayer films using different base substrates (Si, Cu, Ag) on ​​a non-reflective multilayer substrate, and Figure 8(2) shows the reflection circle diagram of SiO2 / Cr / Au multilayer films using the same base substrate (Ag). In the reflection circle diagram shown in Figure 8(1), the thickness of the Cr film is fixed at 0.5 nm, and the thickness of the Au film is optimized. The trajectory of ρ represents the ρ of each base substrate. sub It starts from there. For comparison, the ρ of various base substrates other than the base substrate (Si, Cu, Ag) sub The values ​​are plotted as black circles.

[0057] The final endpoints of the trajectories of the three types of base substrates all coincide with the origin, and theoretically, their reflectivity is zero. Now, if we focus on the curve of the trajectory of the topmost Au film, we find that they all share a common curve. That is, the trajectory of the Au film passing through ρ=0 is uniquely determined regardless of the substrate before the Au film was deposited (called the p-1 substrate). In other words, to make the Au film surface non-reflective, the end of the layer before the Au film (in this case, the Cr film) must be at a coordinate on the curve of the trajectory of the Au film passing through ρ=0. In the example shown in the figure, the endpoint of the Si base substrate with SiO2 / Cr coating must lie on the curve of the Au film passing through ρ=0, and this requirement is satisfied by adjusting the thickness of the SiO2 film. This utilizes the characteristic that the SiO2 trajectory traces a circular arc with a point near the origin as the origin, and can be easily understood by looking at a circle diagram. Ultimately, by depositing an Au film of appropriate thickness, a non-reflective multilayer substrate with ρ=0 can be obtained by following the curve of the Au film's trajectory passing through ρ=0. The thickness of the Au film at ρ=0 is 8.3, 14.8, and 23.4 nm for Si, Cu, and Ag base substrates, respectively. This shows that using a highly reflective Ag substrate results in a thicker Au film. The dashed trajectory in Figure 8(1) represents the trajectory when Au deposition continues. As deposition increases, the trajectory moves to the second quadrant, and when it becomes an optically sufficiently thick thin film, it finally coincides with the coordinate point of the Au substrate. This behavior is the same for other materials and can be easily understood by considering the principle of a circle diagram.

[0058] Next, we consider the adhesive layer. Figure 8(2) shows Ag / SiO2 / Cr / Au substrates with different Cr adhesive film thicknesses. These correspond to Cr adhesive film thicknesses of 3.0, 1.5, and 0.5 nm, respectively. By changing the thickness of the SiO2 layer as described above, the optical design is achieved by aligning the curve of the trajectory of the Au film passing through ρ=0. In this case, the Au film thicknesses are 7.6, 16.7, and 23.4 nm, respectively. From the above, it can be seen that, from a technical standpoint, a thin Cr adhesive film is preferable for forming a flat and stable Au film. [Examples]

[0059] In this embodiment, the non-reflective multilayer substrate of the second aspect of the present invention, that is, the case where the uppermost layer is made of an arbitrary metal material, will be described. As shown in FIG. 5, if the metal thin film of the uppermost layer is taken as the p layer, the locus of the metal of the uppermost layer passing through ρ = 0 is uniquely determined regardless of the structure under the p layer. Therefore, if the termination of ρ of the p - 1 substrate can be controlled to the coordinates on the curve of the target metal material, a non-reflective multilayer substrate can be formed by depositing a p layer of appropriate thickness thereon. Regarding the position control of the termination of the p - 1 substrate, a structure in which a dielectric material is deposited in one layer on the base substrate can be effectively utilized. This is because the reflection pattern can be freely controlled over a wide range by adjusting the material of the base substrate and the film thickness of the dielectric.

[0060] FIG. 9 shows a specific example of a non-reflective multilayer substrate with Au and Ti as the base substrates. In the Au / PMMA / Ti non-reflective multilayer substrate, starting from the coordinates of the complex reflection coefficient of the Au base substrate, the trajectories on the complex plane when each layer is laminated in the order of the PMMA film and the Ti film are shown, and the thicknesses of each layer are designed so that the termination of the trajectory of the uppermost Ti film reaches the origin (ρ = 0) of the complex plane. Specifically, when a PMMA film (65.5 nm) and a Ti film (4.2 nm) are laminated on the Au base substrate, an Au / PMMA / Ti non-reflective multilayer substrate is obtained.

[0061] Similarly, in the Ti / TiO x / Cu non-reflective multilayer substrate, starting from the coordinates of the complex reflection coefficient of the Ti base substrate, the trajectories on the complex plane when each layer is laminated in the order of the TiO x film and the Cu film are shown, and the thicknesses of each layer are designed so that the termination of the trajectory of the uppermost Cu film reaches the origin (ρ = 0) of the complex plane. Specifically, when a TiO x film (51.8 nm) and a Cu film (5.7 nm) are laminated on the Ti base substrate, a Ti / TiO x / Cu non-reflective multilayer substrate is obtained. In either case, by simply adjusting the thickness of the dielectric layer, it is possible to make the termination of ρ of the p - 1 substrate coincide with the trajectory passing through ρ = 0 of the target Au or Ti.

Example

[0062] This embodiment describes a case in which the top layer of the anti-reflective multilayer substrate is composed of an arbitrary dielectric material. Similar to Embodiment 5, if the top dielectric thin film is a p-layer, it is important to place the end of ρ of the p-1 substrate on the trajectory of the top dielectric layer passing through ρ=0. The difference from Embodiment 5 is that the trajectory of the dielectric passing through ρ=0 is a circle. If the end of ρ of the p-1 substrate is connected somewhere on the target circle in the reflection circle diagram, an anti-reflective multilayer substrate can be formed by depositing a p-layer of appropriate thickness on top of it. Several variations in the position of this connection are possible, and each will be explained.

[0063] First, we will show an example in which a metal thin film is used as the top layer, as described in the second aspect of the present invention regarding the non-reflective multilayer substrate. Figure 10 shows an example of a reflection circle diagram of a non-reflective multilayer substrate in which a 75.5 nm SiO2 film, a 3.2 nm Cr film, and a 177.3 nm PMMA film are stacked on a Ni-based substrate. The complex plane trajectory is shown when each layer is stacked in the order of SiO2 film, Cr film, and PMMA film, starting from the coordinate of the complex reflection coefficient of the Ni-based substrate. Focusing on the coordinate of ρ at the stage when the Cr film is deposited, it reaches the origin, so it can be said that at this stage it is a non-reflective multilayer substrate with Cr on the top surface. The trajectory of the PMMA that passes through the target ρ=0 also passes through the origin, so the PMMA trajectory continues with the origin as the connection point. The trajectory of the topmost PMMA film traces a perfect circle clockwise from ρ=0, depositing an optical thickness of half a wavelength (177.3 nm in the case of PMMA), and then returning to ρ=0. In this way, by depositing the desired dielectric material to an optical thickness of half a wavelength onto an anti-reflective multilayer substrate having a thin metal film as the top layer, an anti-reflective substrate with a dielectric material as the top layer can be designed. Anti-reflective multilayer substrates with a thin metal film as the top layer are not limited to a specific metal, and various cases can be used. [Examples]

[0064] Next, we will show an example where the trajectory of a dielectric circle passing through ρ=0 is connected at a position other than the origin. Figure 11 shows the reflection circle diagram of a non-reflective multilayer substrate in which a 90.8 nm PMMA film, a 9.2 nm Cr film, and a 70.0 nm Al2O3 film are stacked on a Si-based substrate. The trajectory on the complex plane is shown when each layer is stacked in the order of PMMA film, Cr film, and Al2O3 film, starting from the coordinate of the complex reflection coefficient of the Si-based substrate. Focusing on the trajectory of the Cr film in this trajectory, it can be seen that it passes through the origin between the start and end points of the Cr film. This means that if the deposition of Cr is stopped at the origin, it will be a non-reflective multilayer substrate with Cr as the uppermost layer. In other words, the trajectory in Figure 11 can be considered as having excess Cr stacked on a non-reflective multilayer substrate with Cr as the uppermost layer until it connects with the circle of the target Al2O3 film. As a result, the Si / PMMA / Cr multilayer substrate connects to the target Al2O3 film circle twice. Then, after reaching the intersection point in a region other than the origin, depositing an Al2O3 film of the appropriate thickness creates an arc in the reflection circle diagram, ultimately tracing a trajectory that returns to ρ=0. Thus, by utilizing a non-reflective multilayer substrate having a thin metal film on its surface, and further increasing the thickness of the thin metal film on the outermost surface, it becomes possible to connect to the circle of the target dielectric at a point other than the origin, thereby enabling the design of a non-reflective substrate with the dielectric as the uppermost layer. This example corresponds to a non-reflective multilayer substrate according to the third aspect of the present invention. [Examples]

[0065] Next, we present an example of designing a non-reflective substrate with a dielectric on its surface, without using a non-reflective multilayer substrate with a metal thin film on its surface. Instead, we connect the trajectory of a dielectric circle passing through ρ=0 at a position other than the origin. Figure 12 shows the reflection circle diagram of a non-reflective multilayer substrate on an Al-based substrate, with a 37.0 nm Al2O3 film, a 10.0 nm Ti film, and a 33.0 nm TiO2 film stacked on the substrate. Starting from the coordinates of the complex reflection coefficient of the Al-based substrate, the trajectories on the complex plane are shown for each layer stacked in the order of Al2O3 film, Ti film, and TiO2 film. The thickness of each layer is determined such that the end of the trajectory of the uppermost TiO2 film reaches the origin (ρ=0) of the complex plane. Unlike the example in Figure 11 above, the endpoint of the Al / Al2O3 / Ti multilayer substrate is not located at the origin, but is directly connected to the target TiO2 film circle at a position other than the origin. Subsequently, by depositing a TiO2 film of appropriate thickness, an arc is drawn in the reflection circle diagram, ultimately creating a trajectory where ρ=0. This example corresponds to the non-reflective multilayer substrate according to the third aspect of the present invention.

[0066] Thus, precise position control of the p-1 substrate termination is crucial, and it is important to connect it to the dielectric circle that passes through the target ρ=0. A two-layer substrate structure, in which a dielectric thin film and a metal thin film are laminated on a base substrate, can be effectively used when designing an anti-reflective substrate with the dielectric as the uppermost layer. [Examples]

[0067] This embodiment describes a program for fabricating a non-reflective multilayer substrate. Figure 13 shows a flowchart of the non-reflective multilayer substrate fabrication program, and Figure 14 shows an example of the fabrication program screen. The program for fabricating a non-reflective multilayer substrate instructs the computer to execute steps S11 to S15 shown in Figure 13. Specifically, in the input step, the wavelength of light that will result in non-reflection, information about the base substrate, and information about the multilayer film to be laminated on the base substrate are input (S11). Here, the information about the base substrate is the material of the base substrate. If the material is known, its complex reflection coefficient can be uniquely determined. The information about the multilayer film to be laminated on the base substrate is the material of the multilayer film, the lamination order and type of each film, and the range of the target film thickness. This information is input into the computer.

[0068] Next, in the coordinate conversion step, the complex reflection coefficient of the base substrate before lamination is expressed in coordinates on the complex plane (S12). The complex reflection coefficient of the base substrate is processed as coordinate data on the complex plane. The coordinate data of the base substrate can be used as processing data for the program. Subsequently, in the trajectory generation step, the change in the complex reflection coefficient as each layer is formed, starting from the coordinates of the base substrate and following the stacking order of the multilayer film, is represented by a trajectory on the complex plane (S13). Then, in the film thickness adjustment step, the film thickness of each layer is adjusted based on the material and stacking order of each layer of the multilayer film, so that the end of the trajectory represented in the trajectory generation step is located at or near the origin on the complex plane (S14). In the output step, the film thickness of each layer to be stacked on the base substrate is output (S15).

[0069] The above program may run on a personal computer (PC) or on a mobile device such as a smartphone or tablet. Furthermore, information about the base substrate and the multilayer film to be laminated on the base substrate can be input via the screen. Here, the PC or mobile device handles the screen input, transmits the input information to a server computer via the network, and causes the server computer to execute steps S12 to S14 of the program. The execution results, including the film thickness of each layer laminated on the base substrate and the trajectory on the complex plane, are then transmitted to the mobile device, allowing the PC or mobile device to display and output the film thickness of each layer on the screen.

[0070] Figure 14(1) shows an example of an input screen for a PC or mobile device, and Figure 14(2) shows an example of an output screen for a PC or mobile device. In the input screen of Figure 14(1), the wavelength of light (e.g., 530 nm), the material of the base substrate (e.g., Si), the material of the intermediate layers to be stacked (e.g., the first layer is SiO2, the P-1 layer is Cr), and the material of the top layer (P layer) (e.g., Au) are shown. These materials can be selected using a pull-down menu. Although not shown, the target film thickness range can also be specified.

[0071] In the output screen of Figure 14(2), a complex plane is shown on the left side of the screen, and the trajectories of each layer are displayed on the complex plane. In addition, as information about the process of stacking each layer, the film thickness of each layer based on the length of the trajectory of each layer is displayed on the screen. On the right side of the screen, a schematic diagram of the multilayer substrate is shown, and the film thickness of each layer is displayed on the screen. [Examples]

[0072] In this embodiment, SiN formed on a Si-based substrate x This document describes the specific fabrication process for a two-layer anti-reflective multilayer substrate consisting of SiN and SiO2, and presents examples of observations of ultrathin films. x Using a Si-based substrate, the material was ultrasonically cleaned with acetone and 2-propanol for 5 minutes each. Then, UV / ozone treatment was performed for 10 minutes, and an SiO2 film exceeding 100 nm in thickness was deposited at room temperature using 400 W high-frequency sputtering with an SiO2 target. Next, the deposited SiO2 was chemically etched with hydrofluoric acid at room temperature to adjust the film thickness to 20-60 nm, as designed. By changing the SiO2 film thickness, the wavelength at which reflectivity becomes zero can be controlled. In this example, commercially available SiN was used. x Using a Si-based substrate having the specified properties, SiO2 was deposited by sputtering, but the deposition method for each film is not limited. For example, films may be deposited using various conventional techniques such as spin coating, chemical vapor deposition, sputtering, or sol-gel methods, or films may be deposited using commercially available reagents such as spin-on glass.

[0073] The effect of the fabricated antireflection multilayer substrate was evaluated by observing small crystals of thin hexagonal boron nitride (hBN) obtained by the exfoliation method. hBN is an optically transparent layer material in the visible light region and can be mechanically exfoliated down to a monolayer film with an atomic-scale thickness of 0.33 nm, so it is effective for evaluating antireflection multilayer substrates.

[0074] Figures 15(1), (2), and (3) are images taken with a 50x objective lens after placing single-layer and multi-layer hBN on the fabricated Si / SiO2(25 nm) / SiN x (50 nm) antireflection multilayer substrate. Here, Figures 15(1) and (2) are images observed with monochromatic light of 470 nm using a narrow-band pass filter. Figure 15(1) is an image taken with a monochrome camera, and Figure 15(2) is an image taken with a color camera. The numbers shown in Figure 15(1) indicate the layer numbers determined by AFM, that is, the number of layers of hBN from single-layer (1L) to four-layer (4L). As shown in Figures 15(1) and (2), by using the fabricated antireflection multilayer substrate, a single-layer hBN, which is usually difficult to observe, can be clearly confirmed by a general optical microscope system. Also, Figure 15(3) is a photograph taken with a color camera by observing the same location with white light, indicating that a narrow-band pass filter is not necessarily required. This means that this method can be used in a more general optical microscope system.

[0075] Figures 15(4) and (5) show the phase image and height image obtained in tapping mode by AFM at the locations corresponding to the square regions in Figure 15(1), respectively, indicating the basis for determining that it is a single-layer film. Figure 15(6) shows the average height profile along the thick solid line in Figure 15(5). The height step of 0.4 - 0.5 nm indicates that it is a single-layer film. In the height image shown in Figure 15(5), it is difficult to detect a clear height difference corresponding to the single-layer film, but in the phase image shown in Figure 15(4), a phase difference of about 5° is detected depending on the presence or absence of hBN, clearly confirming the existence of the single-layer film.

[0076] Figure 16(1) shows the contrast spectra of 1L to 4L hBN films on the non-reflective multilayer substrate shown in Figures 15(1), (2), and (3). A positive contrast peak was observed at λ=470nm and a negative contrast peak at λ=530nm for all layers. The dashed line represents the numerical calculation with NA=0.7, which is in close agreement with the experiment and indicates that the experiment and measurement were performed accurately.

[0077] Furthermore, Figure 16(2) shows the contrast against the number of layers when observed with monochromatic light at λ=450, 470, 530, and 600 nm, and corresponds to Figure 16(1). The dots in the figure represent experimental results, and the dashed lines represent numerical calculation results. As the calculation results (dashed lines) show, the contrast increases almost linearly as the number of layers increases from zero. In addition, the experimental contrast roughly matches the numerical calculation results for all layers, and the intercept of each layer is close to zero. This supports the determination of the number of layers by contrast and AFM measurement, showing that the hBN thin film being observed is indeed a monolayer film, and demonstrating that a non-reflective multilayer substrate can be applied to the determination of the number of layers of hBN. Conventionally, the number of layers of hBN has been determined by AFM, electrical tunneling current, or Raman shift measurement, but compared to conventional techniques, this technique allows for rapid and non-destructive determination of the number of layers using a general optical microscope.

[0078] Focusing on the contrast value of the single-layer hBN in Figure 16(2), the absolute value of the contrast is 17% at a maximum of 470 nm. This is linearly approximated to estimate the vertical resolution of this technology. The monochrome camera used in the experiment is capable of detecting luminance values ​​with a contrast of effectively 3%. Since this corresponds to a single-layer thickness of 59 pm, the vertical resolution of this technology can be estimated to be 59 pm. This means that even if there is a 59 pm step on the substrate surface or a virtually 59 pm film on the substrate, observation is possible with the monochrome camera used. Since the size of an atom is several hundred pm, it can be said that atomic-level measurements are possible. [Examples]

[0079] In this embodiment, we will describe an example in which an anti-reflective multilayer substrate, in which a dielectric portion of an SiO2 layer is laminated on a Si-based substrate and an Au film light-absorbing layer is laminated on the top layer is observed and evaluated, in the second aspect of anti-reflective multilayer substrate. In the above-described Example 4, reflection circles of SiO2 / Cr / Au anti-reflective multilayer substrates using different base substrates (Si, Cu, Ag) are shown (see Figure 8(1)). Generally, it is difficult to make Au films thick from an optical design perspective, and an adhesive layer such as Cr is necessary to form a flat and stable Au thin film. However, forming a stable and flat ultrathin Au film on silicon oxide (SiO2) or the like is not easy, and even when using a Cr adhesive layer, which is commonly used as an adhesive layer, there are heat resistance problems such as changes in optical properties when heated to around 150°C. Furthermore, in a non-reflective multilayer substrate with a Si / SiO2 / Cr / Au structure, the reflectivity can theoretically be reduced to zero at a specific wavelength (λ) by adjusting the film thickness of Au, Cr, and SiO2. Here, reducing the Cr film thickness is effective in increasing the thickness of the Au film, but there is a problem that Cr essentially diffuses into the Au film, reducing optical stability.

[0080] Therefore, as shown in Figure 17(1), a stable and flat ultrathin Au film was formed on SiO2 using an organic monolayer as an adhesive layer. The organic monolayer used was MPTMS (3-mercaptopropyltrimethoxysilane) having thiol groups (-SH groups). After forming the organic monolayer on a thermal silicon oxide substrate with a 113 nm SiO2 film using MPTMS as a silane coupling agent, an 18 nm Au film was deposited by vacuum deposition. The Au film bonded with the thiol groups of MPTMS, improving adhesion. Figure 17(2) shows the reflection spectrum of the non-reflective multilayer substrate. Theoretically, non-reflectiveness is achieved at around 10 nm, but even when 18 nm of Au was deposited, the reflectivity was a minimum of 3%, which was sufficient for visualization.

[0081] Figures 18(1) to (3) show FE-SEM (Field Emission Scanning Electron Microscope) images of the Au surface before and after annealing, for no adhesive layer, a Cr adhesive layer (0.5 nm), and an MPTMS adhesive layer (approximately 1 nm), respectively. The image on the left of Figure 18 is the surface image before annealing, and the image on the right is the surface image after annealing. From Figure 18, it was observed that in all cases, the surface structure changed significantly due to annealing. Furthermore, as shown in the reflectance graph in Figure 19, in the case of the MPTMS adhesive layer, there was almost no change in the reflectance of the Au surface before and after annealing, but in the case of no adhesive layer and the Cr adhesive layer, a large change in the reflectance of the Au surface was observed before and after annealing. This is due to a change in the morphology (physical properties such as form and spectrum) of the Au film due to annealing. Annealing was performed at 250°C for 10 minutes after deposition. When an MPTMS adhesive layer was used, the spectral changes due to similar annealing were minimal, indicating that a highly heat-resistant, non-reflective multilayer substrate could be constructed by preheating it as part of the annealing process.

[0082] Figure 20 shows the results of evaluating the crystallinity of the Au film using X-ray diffraction (XRD). Figure 20(1) is the XRD pattern at room temperature, and it can be seen that the 111 diffraction peak of Au is observed at 38°. In the figure, the asterisk (*) indicates a peak originating from the Si-based substrate. Furthermore, Figures 20(2) and (3) show the results of measurements taken by heating from 50°C to 350°C in 50°C increments. From the results around 38° and 82°C in Figures 20(2) and (3), it was found that the intensity of the 111 and 222 diffraction peaks of Au increased with increasing annealing temperature, indicating improved crystallinity. In particular, the change around 200°C was significant, which is thought to correspond to the structural change of the Au surface observed in Figure 18(3). The reflectivity of the fabricated anti-reflective multilayer substrate did not change even when heated up to 350°C, indicating improved heat resistance. Figure 21 shows FE-SEM images of the Au surface as the annealing temperature changes (200°C, 250°C, 350°C). From the observed images of the Au surface, it can be seen that the surface structure changes and increases with increasing annealing temperature. Furthermore, a step terrace structure, which is often seen in high-quality Au films, can be observed in the film at 350°C, confirming an improvement in crystallinity. [Industrial applicability]

[0083] The anti-reflective multilayer substrate of the present invention, as well as the anti-reflective multilayer substrate fabricated by the present invention's fabrication method and fabrication program, are, in principle, useful as a surface analysis technique for easily imaging atomic-level reactions, as they allow observation of not only the surface irregularities of a sample but also the physical and chemical temporal changes occurring on the surface. Since they can also detect fine particles and proteins adsorbed on the substrate, they are expected to be useful in the development of electronic devices and solar cells, as well as in biosensors.

Claims

1. A non-reflective multilayer substrate having a dielectric portion in which two or more dielectric layers are laminated on an opaque base substrate, and having a dielectric layer as the uppermost layer, wherein the thickness of each layer is adjusted so that the reflectivity is zero at a predetermined wavelength.

2. The non-reflective multilayer substrate according to claim 1, characterized in that the uppermost dielectric layer is an oxide or polymer layer.

3. The aforementioned oxide is SiO ２ Al ２ O ３ , ITO, ZnO, SnO ２ NiO ｘ , In-Ga-ZnO ４ The non-reflective multilayer substrate according to claim 2, characterized in that it is selected from the group.

4. SiN on the Si substrate ｘ and SiO ２ having two layers, and having a SiO ２ layer on the outermost layer, the antireflection multilayer substrate according to claim 1, characterized in that.

5. A non-reflective multilayer substrate having a dielectric portion in which one or more dielectric layers are laminated on an opaque base substrate, and a light-absorbing portion in which one or more light-absorbing layers are laminated on the dielectric portion, and having a light-absorbing layer as the uppermost layer, wherein the thickness of each layer is adjusted so that the reflectance becomes zero at a predetermined wavelength.

6. The non-reflective multilayer substrate according to claim 5, characterized in that one or more dielectric layers having a thickness that is an integer multiple of the optical thickness at half a wavelength are further laminated on the uppermost light-absorbing layer.

7. The base substrate is Ag or Al or a metal having a reflectance of 50% or more. The dielectric part is SiO ２ The non-reflective multilayer substrate according to claim 5, characterized in that the light-absorbing portion is composed of an adhesive layer such as Cr or Ti and an uppermost layer of Au.

8. A non-reflective multilayer substrate having a first dielectric portion in which one or more dielectric layers are laminated on an opaque base substrate, a light-absorbing portion in which one or more light-absorbing layers are laminated on the first dielectric portion, a second dielectric portion in which one or more dielectric layers are laminated on the light-absorbing portion, and a dielectric layer on the uppermost layer, wherein the thickness of each layer is adjusted so that the reflectivity becomes zero at a predetermined wavelength.

9. The non-reflective multilayer substrate according to claim 5, characterized in that the light-absorbing portion is composed of an adhesive layer of an organic molecular film having a functional group containing S (sulfur), and the uppermost layer is composed of Au, Ag, or Cu.

10. The non-reflective multilayer substrate according to claim 9, characterized in that the functional group is a thiol group.

11. The non-reflective multilayer substrate according to claim 9, characterized in that the organic molecular film is MPTMS (3-Mercaptopropyltrimethoxysilane).

12. The non-reflective multilayer substrate according to claim 11, characterized in that the adhesive layer of the organic molecular film and the uppermost layer of Au, Ag, Cu, Pt, Pd, Ni, Ir, Rd, or Rh are annealed, thereby improving the crystallinity of the uppermost layer.

13. A method for producing an anti-reflective film by laminating a multilayer film on a base substrate of any of the anti-reflective multilayer substrates according to claims 1 to 12, A coordinateization step in which the complex reflection coefficient of the base substrate before lamination is shown in coordinates on the complex plane, A trajectory representation step in which, starting from the aforementioned coordinates, the change in the complex reflection coefficient as each layer is formed in the stacking order of the multilayer film is represented as a trajectory on the complex plane, A method for manufacturing an anti-reflective multilayer substrate, comprising a film thickness adjustment step, in which the film thickness of each layer is adjusted based on the material and stacking order of each layer of the multilayer film, such that the end of the trajectory represented in the trajectory calculation step is located at or near the origin on the complex plane.

14. A method for fabricating an anti-reflective film by stacking multilayer films on a base substrate, A coordinateization step in which the complex reflection coefficient of the base substrate before lamination is shown in coordinates on the complex plane, A trajectory representation step in which, starting from the aforementioned coordinates, the change in the complex reflection coefficient as each layer is formed in the stacking order of the multilayer film is represented as a trajectory on the complex plane, A method for manufacturing an anti-reflective multilayer substrate, comprising a film thickness adjustment step, in which the film thickness of each layer is adjusted based on the material and stacking order of each layer of the multilayer film, such that the end of the trajectory represented in the trajectory calculation step is located at or near the origin on the complex plane.

15. The method for manufacturing an anti-reflective substrate according to claim 14, characterized in that optical design is performed using the trajectories of various materials in a multilayer film that pass through the origin on the complex plane.

16. The method for manufacturing an anti-reflective substrate according to claim 14, characterized in that optical design is performed by controlling the position of the endpoint of the trajectory when the uppermost layer is excluded.

17. A program for producing an anti-reflective film by laminating a multilayer film onto the base substrate of any anti-reflective multilayer substrate according to claims 1 to 12, On the computer, An input step in which information about the base substrate and information about the multilayer film to be stacked on the base substrate is input. A coordinateization step that shows the complex reflection coefficient of the base substrate before lamination in coordinates on the complex plane, A trajectory representation step in which, starting from the aforementioned coordinates, the change in the complex reflection coefficient as each layer is formed in the stacking order of the multilayer film is represented as a trajectory on the complex plane. A film thickness adjustment step, in which the film thickness of each layer of the multilayer film is adjusted based on the material and stacking order of each layer, such that the end of the trajectory represented in the trajectory calculation step is located at or near the origin on the complex plane. Output step to output the film thickness of each layer, A program for fabricating anti-reflective multilayer substrates to enable this process.

18. On the computer, An input step in which information about the base substrate and information about the multilayer film to be stacked on the base substrate is input. A coordinateization step that shows the complex reflection coefficient of the base substrate before lamination in coordinates on the complex plane, A trajectory representation step in which, starting from the aforementioned coordinates, the change in the complex reflection coefficient as each layer is formed in the stacking order of the multilayer film is represented as a trajectory on the complex plane. A film thickness adjustment step, in which the film thickness of each layer of the multilayer film is adjusted based on the material and stacking order of each layer, such that the end of the trajectory represented in the trajectory calculation step is located at or near the origin on the complex plane. Output step to output the film thickness of each layer, A program for fabricating anti-reflective multilayer substrates to enable this process.

19. The program for manufacturing an anti-reflective multilayer substrate according to claim 18, characterized in that the input step accepts input information on the type of base substrate, the stacking order and type of multilayer films, and the range of the target film thickness.

20. In the aforementioned coordinate conversion step, the aforementioned trajectory conversion step, and the aforementioned film thickness adjustment step, A program for manufacturing a non-reflective multilayer substrate according to claim 18, characterized in that it displays the complex plane, the coordinates on the complex plane, and the trajectories of each layer on a computer screen.

21. The film thickness adjustment step is characterized by optimizing the film thickness of each layer using a nonlinear equation such that the end of the trajectory represented in the trajectory creation step is located at or near the origin on the complex plane, as described in the program for manufacturing a non-reflective multilayer substrate according to claim 18.

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