Surface plasmon resonance sensor and sensor device

Abstract

To provide a surface plasmon resonance sensor capable of obtaining a clear surface plasmon resonance response. [Solution] The surface plasmon resonance sensor comprises a substrate having a first surface and a second surface opposite to the first surface, a metal film provided on the first surface of the substrate and having a sample placement area on a third surface opposite to the first surface where a sample is placed, and being irradiated with light from the second surface side through the substrate, and a diffraction grating provided on the first surface or the second surface, such that at least a part of it overlaps with at least a part of the sample placement area when viewed in the thickness direction of the substrate, wherein the thickness of the substrate between the first surface and the second surface is t, and the refractive index of the substrate at the wavelength of the light is n, then t / n is 2 μm or less.

Description

Technical Field

[0001] The present invention relates to a surface plasmon resonance sensor and a sensor device.

Background Art

[0002] As a surface plasmon resonance sensor using surface plasmon resonance (SPR: Surface Plasmon Resonance), a sensor is known in which a diffraction grating made of metal is provided on the surface of a silicon substrate and light is irradiated from the back surface of the silicon substrate (for example, Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the surface plasmon resonance sensor according to Non-Patent Document 1, the response of surface plasmon resonance can be detected by using the current flowing between the silicon substrate and the metal film. Further, by irradiating light from the back surface of the silicon substrate, light absorption and scattering by the measurement sample can be reduced. However, the response of surface plasmon resonance is unclear.

[0005] An object of the present disclosure is to provide a surface plasmon resonance sensor capable of obtaining a clear surface plasmon resonance response.

Means for Solving the Problems

[0006] Embodiments of the present invention provide a surface plasmon resonance sensor comprising: a substrate having a first surface and a second surface opposite to the first surface; a metal film provided on the first surface of the substrate and having a sample placement area on a third surface opposite to the first surface where a sample is placed, and which is irradiated with light from the second surface side through the substrate; and a diffraction grating provided on the first surface or the second surface, such that at least a portion of it overlaps with at least a portion of the sample placement area when viewed in the thickness direction of the substrate, wherein when the thickness of the substrate between the first surface and the second surface is t and the refractive index of the substrate at the wavelength of the light is n, t / n is 2 μm or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a surface plasmon resonance sensor capable of obtaining a clear surface plasmon resonance response. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of the SPR sensor according to the first embodiment. [Figure 2] Figure 2 shows the absorption coefficient of the SPR sensor with respect to wavelength λ in comparison configuration 3 in simulation 1. [Figure 3] Figure 3 shows the absorption coefficients for wavelength λ and thickness t in Simulation 1. [Figure 4] Figure 4 shows the absorption coefficients for wavelength λ and thickness t in Simulation 1. [Figure 5] Figure 5 is a schematic diagram of the substrate representing the model in Simulation 2. [Figure 6] Figure 6 is a schematic diagram of the substrate representing the model in Simulation 2. [Figure 7] Figure 7 is an illustrative diagram of the light in Simulation 2 from m=0 to m=2. [Figure 8] Figure 8 shows the thickness t as a function of wavelength λ in Equation 4. [Figure 9] Figure 9 shows the thickness t as a function of wavelength λ in Equation 4. [Figure 10] FIG. 10 is a diagram showing the absorption coefficient with respect to the wavelength λ and the refractive index of the sample in Simulation 3. [Figure 11] FIG. 11 is a cross-sectional view of the SPR sensor according to the second embodiment. [Figure 12A] FIG. 12A is a cross-sectional view showing a method of manufacturing the SPR sensor according to the second embodiment. [Figure 12B] FIG. 12B is a cross-sectional view showing a method of manufacturing the SPR sensor according to the second embodiment. [Figure 12C] FIG. 12C is a cross-sectional view showing a method of manufacturing the SPR sensor according to the second embodiment. [Figure 12D] FIG. 12D is a cross-sectional view showing a method of manufacturing the SPR sensor according to the second embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are examples for embodying the technical idea of the invention, and do not limit the present invention to the described configurations and numerical values. In the drawings, components having the same function may be denoted by the same reference numerals, and redundant descriptions may be omitted. Partial substitution or combination between different embodiments and configuration examples is possible. The sizes, positional relationships, etc. of the respective members shown in each drawing may be exaggerated for easy understanding of the invention.

[0010] (First Embodiment) FIG. 1 is a cross-sectional view of the SPR sensor according to the first embodiment. The thickness direction of the substrate 10 is the Z direction, the periodic direction of the diffraction grating 12 is the X direction, and the grating extension direction of the diffraction grating 12 is the Y direction. As shown in FIG. 1, the sensor device 100 according to the first embodiment includes an SPR sensor 20, a light source 22, and a detector 24. The SPR sensor 20 includes a substrate 10, a metal film 14, and an electrode 16. The SPR sensor 20 is a surface plasmon resonance sensor using surface plasmon resonance.

[0011] The substrate 10 has a first surface 10A and a second surface 10B facing the first surface 10A. The first surface 10A and the second surface 10B are parallel. A diffraction grating 12 is provided on the second surface 10B. The diffraction grating 12 has recesses 12A and protrusions 12B. The recesses 12A are linear grooves formed on the second surface 10B and extending in the Y direction. The protrusions 12B are regions where the recesses 12A are not formed. The protrusions 12B may be linear additional films provided on the second surface 10B of the substrate 10. In this case, the recesses 12A are regions where the additional films are not provided. Although the cross-sectional shapes of the recesses 12A and the protrusions 12B are illustrated as rectangular, the cross-sectional shapes of the recesses 12A and the protrusions 12B may be periodic shapes such as triangular, sawtooth or waveform. The thickness of the diffraction grating 12 is g, and the thickness of the substrate 10 excluding the thickness g is t. The pitch of the diffraction grating 12 is p.

[0012] The metal film 14 and the electrode 16 are provided on the first surface 10A of the substrate 10. The metal film 14 has a third surface 14A. The third surface 14A is a surface on the opposite side of the substrate 10. A sample placement region 15 where the sample 18 is placed is provided on the third surface 14A. When viewed from the Z direction, at least a part of the sample placement region 15 overlaps at least a part of the diffraction grating 12. The thickness of the metal film 14 is h. The electrode 16 is provided separately from the metal film 14 on the first surface 10A.

[0013] The light source 22 is a laser device such as a semiconductor laser device, for example, and irradiates light 22A (for example, laser light) from the side of the second surface 10B. The incident angle of the light 22A on the second surface 10B is θin. The detector 24 detects an electrical response such as a current flowing between the metal film 14 and the electrode 16.

[0014] The substrate 10 is a semiconductor substrate such as a silicon substrate, for example, and transmits the light 22B. The metal film 14 is, for example, gold, silver, aluminum, copper or an alloy having these as main components. The electrode 16 is, for example, gold, silver, aluminum, copper or an alloy having these as main components. The sample 18 is, for example, a liquid, and contains, for example, water, a glucose aqueous solution, and substances to be detected.

[0015] Light 22A is diffracted by the diffraction grating 12 and incident on the substrate 10. If the substrate 10 is a single-crystal silicon substrate, light 22A will pass through the substrate 10 if the wavelength of light 22A is longer than the wavelength corresponding to the silicon bandgap energy. For example, the wavelength of light 22A is between 1 μm and 4 μm. Light 22B that passes through the substrate 10 penetrates into the metal film 14. If the thickness h of the metal film 14 is, for example, 100 nm or less, light 22B undergoes total internal reflection between the third surface 14A of the metal film 14 and the sample 18. The evanescent wave generated at this time couples with the resonant vibration of free electrons in the metal film 14 near the third surface 14A, causing surface plasmon resonance.

[0016] The wavenumber of the SPR is determined by the dielectric constant of the metal film 14 and the dielectric constant of the sample 18. When the wavenumber of the light 22B diffracted by the diffraction grating 12 matches the wavenumber of the SPR, an SPR is generated. When an SPR is generated, the light 22B is absorbed by the metal film 14. As a result, an electric current flows between the metal film 14 and 16. For example, if the substrate 10 is an n-type semiconductor layer, a Schottky barrier is formed between the metal film 14 and the substrate 10. The SPR excites free electrons in the metal film 14, which are then injected into the substrate 10 across the Schottky barrier. The electrons injected into the substrate 10 can move within the substrate 10. Therefore, an electric current flows between the metal film 14 and the electrode 16.

[0017] In SPR response detection, the wavelength of light 22A is fixed, and the incident angle θin of light 22A is changed. The dielectric constant of sample 18 can be detected by the incident angle θin at which the detector 24 detects the current caused by SPR. If the wavelength of light 22A is changed without changing the incident angle θin of light 22A, the dielectric constant of sample 18 can be detected by the wavelength of light 22A at which the detector 24 detects the current caused by SPR.

[0018] (Comparative form) In the SPR sensor of comparative form 1, a metal film is formed on one surface of the prism. The sample is placed on the surface of the metal film. Light is shone on the back surface of the metal film through the prism, and the SPR is detected using the reflected light from the metal film. In comparative form 1, a polarizer is used to polarize the light shone on the prism and a detector is used to detect the reflected light, so the sensor device becomes larger.

[0019] In the SPR sensor of comparative form 2, a diffraction grating 12 is formed on the first surface 10A, and light 22A is irradiated from the first surface 10A side. In comparative form 2, since light 22A passes through the sample 18, the light 22A is absorbed and scattered by the sample 18, causing a decrease in the SPR response or resulting in errors.

[0020] In the SPR sensor of comparative form 3, the structure is the same as in Figure 1, but the substrate 10 is thicker. In comparative form 3, by irradiating light 22B from the second surface 10B of the substrate 10, the absorption and scattering of light by the sample 18 can be reduced. However, the SPR response may be unclear in some cases.

[0021] (Simulation 1) The absorption coefficient of light 22A was simulated below using exact coupled wave analysis. The substrate 10 was single-crystal silicon, the metal film 14 was gold, and the thickness t of the substrate 10 was 625 μm. The absorption coefficient at the interface between the metal film 14 and the sample 18 was simulated for the wavelength of light 22A. The incident angle θin was set to 0°. While SPR response is often measured by fixing the wavelength λ of light 22A and varying the incident angle θin, the incident angle θin was fixed and the wavelength λ was varied for easier simulation.

[0022] Figure 2 shows the absorption coefficient with respect to wavelength λ for comparison configuration 3 in Simulation 1. For comparison configuration 3, the thickness t of the substrate 10 was set to 625 μm. When the absorption coefficient is 1, all of the light 22B is absorbed, and when the absorption coefficient is 0, the light 22B undergoes total internal reflection. As shown in Figure 2, at t=625 μm, the SPR response is buried in noise and cannot be observed.

[0023] As described above, the SPR response becomes unclear when the thickness t of the substrate 10 is large. Therefore, the absorption coefficient was simulated by reducing the thickness t. Figures 3 and 4 show the absorption coefficients for wavelength λ and thickness t in Simulation 1. In Figure 3, the thickness t is set from 0 μm to 2 μm, and in Figure 4, the thickness t is set from 8 μm to 10 μm. The wavelength is set from 1.1 μm to 2 μm. A lower triangle labeled "SPR" is shown at the wavelength of the SPR response. The absorption coefficient increases as the color changes from black to white.

[0024] As shown in Figures 3 and 4, in addition to absorption of the SPR response, many linear and curved absorptions are observed. In particular, in Figure 4, there are many linear and curved absorptions, obscuring the SPR response. In Figure 3, compared to Figure 4, there are fewer linear and curved absorptions, and the SPR response is visible. Thus, we investigated the cause of the linear and curved absorptions that inhibit the SPR response.

[0025] (Simulation 2) We simulated the light that inhibits the SPR response. Figures 5 and 6 are schematic diagrams of the substrate representing the model in Simulation 2. The metal film 14 is not shown in Figures 5 and 6. Figure 5 shows the conditions under which light incident on the diffraction grating 12 reinforces itself. Figure 6 shows the conditions under which light undergoing total internal reflection at the first surface 10A and the second surface 10B of the substrate 10 reinforces itself.

[0026] As shown in Figure 5, consider the light rays 22B1 and 22B2 that travel from point O into the substrate 10 from the diffraction grating 12. The angle between the direction of propagation of light rays 22B1 and 22B2 and the Z direction is φ. The condition for constructive interference between light rays 22B1 and 22B2 is when the optical path difference between light rays 22B1 and 22B1 is an integer multiple of the wavelength of light 22B. At this time, the phases of light rays 22B1 and 22B2 are aligned. The optical path difference between light rays 22B1 and 22B2 is psinφ, where p is the pitch of the diffraction grating 12. The wavelength of light 22B in the substrate 10 is the wavelength λ in a vacuum (or air) multiplied by the refractive index n of the substrate 10. Si This is the value obtained by dividing by . Therefore, the condition for constructive interference between light 22B1 and 22B2 is equation 1.

[0027]

number

[0028] Here, m is the diffraction order, λ is the wavelength of light 22B in a vacuum (or air), and n Si This is the refractive index of the substrate 10 at wavelength λ.

[0029] As shown in Figure 6, light 22B1 incident on the substrate 10 at point O undergoes total internal reflection at point A on the first surface 10A to become light 22B3. Light 22B3 undergoes total internal reflection at point C on the second surface 10B to become light 22B4. When the phases of light 22B1 and light 22B4 are aligned, light 22B and 22B4 interfere constructively. Let B' and C' be the points through which light 22B1', which is a virtually extended light 22B1, passes. The lengths of line segments OA and OC' are the same. Line segments AC' and CD are parallel. Let B' be the point where a line passing through point C and perpendicular to line segment AC' intersects line segment AC'. Let B' be the point where a line passing through point B' and extending in the Z direction intersects line segment AC.

[0030] The condition for constructive interference between light 22B1 and 22B4 is that the path difference between light 22B1' and 22B4 is an integer multiple of the wavelength of light 22B. The path of light 22B1' to point B' is OAB', and the path of light 22B4 to point C is OABC. Therefore, the path difference between light 22B1' and 22B4 is the length of line segment BC. The lengths of line segment BC and line segment B'C' are equal. The length of line segment CC' is twice the thickness t of the substrate 10. Therefore, if the angle of angle B'CC' is θ, the path difference is 2tsinθ. Thus, the condition for constructive interference between light 22B1 and 22B4 is given by equation 2.

[0031]

number

[0032] Here, q is the diffraction order, λ is the wavelength of light 22B in a vacuum (or air), and n Siθ is the refractive index of substrate 10 at wavelength λ. The angle θ of angle B'CC' is equal to the angle between the X direction and the line segment AC'. Thus, θ = 90° - φ. Substituting θ = 90° - φ into equation 2, the condition for constructive interference between light 22B1 and 22B4 is given by equation 3.

[0033]

number

[0034] Removing φ from numbers 1 and 3 results in number 4.

[0035]

number

[0036] The SPR response is inhibited when the wavelength λ and thickness t satisfy equation 4. Figure 7 is an illustrative diagram of the light for m=0 to m=2 in Simulation 2. As shown in Figure 7, the incident angle θin of light 22A onto the substrate 10 is 0°. Light 22B for m=0 corresponds to a standing wave that travels back and forth in the Z direction between the first surface 10A and the second surface 10B of the substrate 10. Light 22B for m=1 and m=2 is light that propagates in the X direction by repeatedly reflecting off the first surface 10A and the second surface 10B of the substrate 10. The distance in the X direction between point O where light 22A is incident on the second surface 10B and point A where it is first reflected on the first surface 10A increases as m increases.

[0037] Figures 8 and 9 show the thickness t as a function of wavelength λ in Equation 4. The results are shown for m = 0 to 2. Comparing Figures 8 and 9 with Figures 3 and 4, the optical absorption other than the SPR response in Figures 3 and 4 can be explained by Equation 4.

[0038] When measuring the SPR response, the incident angle θin of light 22A is fixed and the wavelength λ of light 22A is changed, or the wavelength λ of light 22A is fixed and the incident angle θin of light 22A is changed. The SPR response is detected by the absorption coefficient of light 22B or the current flowing between the metal film 14 and the electrode 16. The dielectric constant of the sample 18 is detected from the wavelength λ or incident angle θin at which the SPR response is detected. In Figures 8 and 9, the points where the straight line with a constant thickness t intersects the line m=0 to 2 are the wavelengths at which light that inhibits the SPR response is generated in an SPR sensor where the thickness of the substrate 10 is t. A large number of points where the straight line with a constant thickness t intersects m=0 to 2 corresponds to a large amount of noise, and a small number of points corresponds to a small amount of noise.

[0039] In Figure 9, for example, the straight line 58B with a thickness t=9μm intersects with many lines with m=0 to 2 between wavelengths λ of 1.1μm and 2.0μm. Therefore, the SPR sensor with t=9μm has a lot of noise that inhibits the SPR response. On the other hand, in Figure 8, for example, the straight line 58A with a thickness t=1μm intersects with only about 10 lines with m=0 to 2 between wavelengths λ of 1.1μm and 2.0μm. Therefore, the SPR sensor with t=1μm has less noise that inhibits the SPR response. In this way, reducing the thickness t of the substrate 10 reduces the noise that inhibits the SPR response.

[0040] From equation 4, the amount of noise that inhibits the SPR response is given by thickness t / refractive index n of substrate 10. Si This can be generalized. The refractive index of silicon in the near-infrared region is 3.4. Therefore, from the viewpoint of reducing noise in the SPR response, t / n Si The thickness t is preferably 2 μm or less, more preferably 1.5 μm or less, and even more preferably 1 μm or less. From the viewpoint that the mechanical strength of the substrate 10 will decrease if the thickness t is too thin, t / n Si The thickness is preferably 0.1 μm or more, and more preferably 0.2 μm or more. If the substrate 10 is a silicon substrate, the thickness t is preferably 7 μm or less, and more preferably 5 μm or less. The thickness t is preferably 0.25 μm or more.

[0041] (Simulation 3) The absorption coefficient of sample 18 was simulated with respect to the wavelength λ of light 22A and the refractive index of sample 18, using a silicon substrate 10 with a thickness t = 5 μm. Figure 10 shows the absorption coefficient of the sample with respect to wavelength λ and the refractive index of the sample in Simulation 3. In Figure 10, the refractive index of water (1.33) is shown by line 50, the refractive index of a 20% glucose aqueous solution (1.36735) is shown by line 51, and the refractive index of a 40% glucose aqueous solution (1.4389) is shown by line 52. In Figure 10, the line with a large absorption coefficient extending from the bottom left to the top right represents absorption that inhibits the SPR response, which corresponds to noise. The vertical line with a constant wavelength λ is a line caused by the SPR response. As the refractive index of sample 18 decreases, the noise of light absorption that inhibits the SPR response decreases. For example, if sample 18 is a 20% glucose aqueous solution, and the thickness t of substrate 10 is 5 μm, it hardly overlaps with the light absorption that inhibits the SPR response.

[0042] According to the first embodiment, when the thickness of the substrate 10 between the first surface 10A and the second surface 10B is t, and the refractive index of the substrate 10 at the wavelength of light 22A is n, then t / n is 2 μm or less. This reduces noise that inhibits the SPR response, and a clear SPR response can be obtained. In the SPR sensor 20 of the first embodiment, the diffraction grating 12 is provided on the second surface 10B, but the diffraction grating 12 may also be provided on the first surface 10A.

[0043] From the viewpoint of light 22B passing through the metal film 14, the thickness h of the metal film 14 is preferably 0.1 times or less the wavelength of light 22B within the metal film 14. The pitch p of the diffraction grating 12 is preferably 0.8 times or more and 3 times or less the wavelength of light 22B within the substrate 10. The wavelength of light 22A is the wavelength through which light 22B passes through the substrate 10. When the substrate 10 is silicon, the wavelength of light 22A is, for example, 1.1 μm or more and 2.5 μm or less.

[0044] In the first embodiment, at least the first surface 10A of the substrate 10 is a semiconductor layer (first semiconductor layer). As a result, when an SPR response occurs, free electrons in the metal film 14 penetrate into the semiconductor layer, allowing the SPR response to be detected by the conductivity of the semiconductor layer. For example, the second surface 10B of the substrate 10 is made of a substrate that is transparent to visible light, such as a sapphire substrate or a glass substrate. The semiconductor layer on the first surface 10A is made of a semiconductor layer that is transparent to visible light, such as gallium nitride. This allows the SPR response in visible light to be detected.

[0045] The electrode 16 is in contact with the semiconductor layer. Surface plasmon resonance can be detected by an electrical signal such as current or voltage between the metal film 14 and the electrode 16. This allows for a smaller detector compared to comparative embodiment 1, in which the SPR response is measured by a photodetector.

[0046] The sensor device 100 includes an SPR sensor 20 and a light source 22 that irradiates the metal film 14 with light from the second surface 10B side through the substrate 10. This allows the sensor device 100 to detect the SPR response.

[0047] The sensor device 100 includes a light source 22 and a detector 24 that detects SPR by an electrical signal between the metal film 14 and the electrode 16. As a result, the detector 24 can be made smaller compared to comparative form 1, and therefore the sensor device 100 can be made smaller.

[0048] (Second Embodiment) The second embodiment is an example of an SPR sensor with a thin substrate 10 thickness t that is easy to manufacture. Figure 11 is a cross-sectional view of the SPR sensor according to the second embodiment. As shown in Figure 11, in the SPR sensor 102 according to the second embodiment, the substrate 10 is a substrate in which a semiconductor layer 11A (first semiconductor layer), an insulating layer 11B, and a semiconductor layer 11C (second semiconductor layer) are laminated. The substrate 10 is, for example, an SOI (Silicon on Insulator) substrate, the semiconductor layers 11A and 11C are silicon layers, and the insulating layer 11B is a silicon oxide (SiO2) layer.

[0049] The surface of the substrate 10 opposite to the first surface 10A is the fourth surface 10C. In the region 54 that overlaps with the diffraction grating 12 when viewed from the Z direction, the insulating layer 11B and the semiconductor layer 11C are not provided, and a recess 13 is provided on the fourth surface 10C. The bottom surface of the recess 13 is the semiconductor layer 11A. Thus, the first surface 10A and the second surface 10B are surfaces of the semiconductor layer 11A. In the region 56 surrounding region 54, the insulating layer 11B and the semiconductor layer 11C are provided on the first surface 10A side. The metal film 14 is provided on the bottom surface of the recess 13. The electrode 16 is provided on the first surface 10A.

[0050] Figures 12A to 12D are cross-sectional views showing a method for manufacturing an SPR sensor according to the second embodiment. As shown in Figure 12A, a substrate 10 is prepared in which a semiconductor layer 11C, an insulating layer 11B, and a semiconductor layer 11A are laminated. The -Z plane of the semiconductor layer 11A is the second plane 10B, and the +Z plane of the semiconductor layer 11C is the fourth plane 10C. The thickness of the semiconductor layer 11A may be adjusted to a desired thickness by polishing the second plane 10B.

[0051] As shown in Figure 12B, a diffraction grating 12 is formed on the second surface 10B of the semiconductor layer 11A. The diffraction grating 12 is formed using photolithography and etching. At this time, the etched surface becomes the second surface 10B.

[0052] As shown in Figure 12C, a recess 13 is formed on the fourth surface 10C by removing the semiconductor layer 11C and the insulating layer 11B in region 54. For the formation of the recess 13, for example, photolithography and etching methods are used. For etching the semiconductor layer 11C, an etching method is used that has high etching selectivity for the semiconductor layer 11C compared to the insulating layer 11B (i.e., an etching method in which the semiconductor layer 11C is etched and the insulating layer 11B is hardly etched). This stops the etching at the insulating layer 11B. Subsequently, for etching the insulating layer 11B, an etching method is used that has high etching selectivity for the insulating layer 11B compared to the semiconductor layer 11A (i.e., an etching method in which the insulating layer 11B is etched and the semiconductor layer 11A is hardly etched). This improves the accuracy of the thickness of the semiconductor layer 11A (thickness t of the substrate 10) in region 54.

[0053] As shown in Figure 12D, a metal film 14 is formed on the first surface 10A, which is the bottom surface of the recess 13, and an electrode 16 is formed on the second surface 10B. For the formation of the metal film 14 and the electrode 16, for example, a vacuum deposition method and a lift-off method are used. The SPR sensor 102 according to the second embodiment is manufactured as described above.

[0054] In the second embodiment, a substrate 10 is used in which a semiconductor layer 11A (first semiconductor layer), an insulating layer 11B, and a semiconductor layer 11C (second semiconductor layer) are laminated. By performing the steps shown in Figures 12A to 12D, the first surface 10A and the second surface 10B are surfaces of the semiconductor layer 11A, and a structure can be formed in which the insulating layer 11B and the semiconductor layer 11C are not provided in the region 54 (first region) that overlaps with the diffraction grating 12 when viewed from the Z direction. This makes it possible to accurately reproduce the thickness t of the substrate 10 (i.e., the semiconductor layer 11A) between the first surface 10A and the second surface 10B.

[0055] Furthermore, in the region 56 (second region) surrounding region 54 when viewed from the Z direction, an insulating layer 11B and a semiconductor layer 11C are provided on the first surface 10A side. This allows the mechanical strength of the SPR sensor 102 to be increased even if the thickness t of region 54 is reduced. Note that region 56 does not need to completely surround region 54; it is sufficient if it surrounds at least a part of the periphery of region 54.

[0056] The planar shape of the recess 13 can be set as appropriate, such as a circle, ellipse, rectangle, or polygon. The width of the recess 13 in the X and Y directions is, for example, 20 μm or more and 500 μm or less.

[0057] The thickness of the semiconductor layer 11C is, for example, 100 μm to 625 μm. Thus, the semiconductor layer 11C is thicker than the semiconductor layer 11A. This improves the mechanical strength of the SPR sensor 102. The thickness of the semiconductor layer 11C is preferably 10 times or more than the thickness of the semiconductor layer 11A, and more preferably 50 times or more. The insulating layer 11B is, for example, thinner than the semiconductor layer 11A.

[0058] To provide the diffraction grating 12 on the first surface 10A, the diffraction grating 12 would have to be formed on the bottom surface of the recess 13. It is difficult to form the diffraction grating 12 on the bottom surface via the recess 13. Therefore, it is preferable to provide the diffraction grating 12 on the second surface 10B.

[0059] In the first embodiment, the substrate 10 and in the second embodiment, the semiconductor layer 11A are silicon layers. This allows for improved accuracy of the thickness t using silicon semiconductor device manufacturing process technology.

[0060] Furthermore, the substrate 10 in the first embodiment and the semiconductor layer 11A in the second embodiment are n-type semiconductor layers. As a result, when free electrons in the metal film 14 are excited and penetrate the semiconductor layer 11A, the conductivity of the semiconductor layer 11A changes significantly, allowing for accurate detection of the SPR response based on the change in conductivity.

[0061] As in the first embodiment, the electrode 16 may be provided on the first surface 10A. As in the second embodiment, the electrode 16 may be provided on the second surface 10B. It is preferable that the electrode 16 is in contact with the semiconductor layer. This allows the SPR to be detected by the electrical signal between the metal film 14 and the electrode 16. Therefore, the detector used for detection can be miniaturized compared to comparative embodiment 1, which detects the SPR response using light.

[0062] The sensor device of the second embodiment includes an SPR sensor 102, a light source 22 and a detector 24 as described in the first embodiment. This allows the sensor device to detect the SPR response.

[0063] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. [Explanation of Symbols]

[0064] 10 circuit boards 10A 1st side 10B 2nd side 10C 4th page 11A, 11C semiconductor layer 11B Insulating layer 12 Diffraction gratings 12A, 13 recess 12B protrusion 14 Metal film 14A, Page 3 15 Sample placement area 16 electrodes 18 samples 20, 102 SPR sensor 22 Light source 22A, 22B, 22B1, 22B2, 22B3, 22B4 light 24 detectors 54, 56 area

Claims

1. A substrate having a first surface and a second surface opposite to the first surface, A metal film is provided on the first surface of the substrate, and has a sample placement area on the third surface opposite to the first surface where the sample is placed, and is irradiated with light from the second surface side through the substrate, Viewed from the thickness direction of the substrate, at least a portion of which overlaps with at least a portion of the sample placement area and a diffraction grating provided on the first or second surface, Equipped with, A surface plasmon resonance sensor in which, when the thickness of the substrate between the first surface and the second surface is t, and the refractive index of the substrate at the wavelength of light is n, t / n is 2 μm or less.

2. The surface plasmon resonance sensor according to claim 1, wherein at least the first surface side of the substrate is a first semiconductor layer.

3. The substrate has a first semiconductor layer, an insulating layer, and a second semiconductor layer stacked in order. The first and second surfaces are surfaces of the first semiconductor layer, The surface plasmon resonance sensor according to claim 1, wherein, when viewed from the thickness direction of the substrate, the insulating layer and the second semiconductor layer are not provided in the first region that overlaps with the diffraction grating, and the insulating layer and the second semiconductor layer are provided on the first surface side in the second region surrounding the first region.

4. The surface plasmon resonance sensor according to claim 3, wherein the diffraction grating is provided on the second surface.

5. The surface plasmon resonance sensor according to claim 3 or 4, wherein the second semiconductor layer is thicker than the first semiconductor layer.

6. The device comprises an electrode that contacts the first semiconductor layer, A surface plasmon resonance sensor according to any one of claims 2 to 4, wherein surface plasmon resonance is detected by an electrical signal between the metal film and the electrode.

7. The surface plasmon resonance sensor according to any one of claims 2 to 4, wherein the first semiconductor layer is a silicon layer.

8. The surface plasmon resonance sensor according to any one of claims 1 to 3, wherein the diffraction grating is provided on the second surface.

9. A surface plasmon resonance sensor according to any one of claims 1 to 4, A light source that irradiates the metal film with light from the second side through the substrate, A sensor device equipped with the following features.

10. A surface plasmon resonance sensor according to claim 6, A light source that irradiates the metal film with light from the second side through the substrate, A detector that detects surface plasmon resonance by an electrical signal between the metal film and the electrode, A sensor device equipped with the following features.

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