Interferometric filters and their manufacturing methods

Abstract

This application provides an interference filter and a method for manufacturing the interference filter. The interference filter comprises: a first transparent substrate having a first inner surface and a first outer surface, wherein a first reflective film is disposed on the first inner surface; a second transparent substrate having a second inner surface and a second outer surface, wherein a second reflective film is disposed on the second inner surface; a first bonding portion bonding the first inner surface and the second inner surface to seal a first internal space between the first substrate and the second substrate; a third transparent substrate facing the first outer surface; a second bonding portion bonding the first outer surface and the third substrate to seal a second internal space between the first substrate and the third substrate; a fourth transparent substrate facing the second outer surface; and a third bonding portion bonding the second outer surface and the fourth substrate to seal a third internal space between the second substrate and the fourth substrate, wherein the first internal space, the second internal space, and the third internal space are depressurized to below atmospheric pressure.

Description

Technical Field

[0001] This invention relates to interferometric filters and methods for manufacturing interferometric filters. Background Technology

[0002] An interference filter is known in the prior art as follows: the interference filter includes a first substrate having a first reflective film and a second substrate having a second reflective film, the first and second substrates being arranged and joined facing each other with the first and second reflective films separated by a gap. Such an interference filter can emit light of a desired wavelength from incident light depending on the size of the gap between the first and second reflective films. Furthermore, for example, it can be configured such that a movable part held by a diaphragm or the like is provided on the second substrate, and the second reflective film is provided on the movable part; and the movable part is displaced towards the first substrate by a driving unit such as an electrostatic actuator, thereby changing the wavelength of the light emitted from the interference filter.

[0003] In such an interference filter, in order to drive the movable part, a third substrate is provided on the side of the second substrate opposite to the first substrate, so that the spaces between the first and second substrates and between the second and third substrates are respectively kept in a depressurized state. As a result, the driving responsiveness can be improved when driving the movable part (see, for example, Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2014-178409

[0005] However, in the interference filter described in Patent Document 1, the side of the first substrate opposite to the second substrate is at atmospheric pressure. Due to the pressure difference between the first and second substrates and the pressure difference on the side of the first substrate opposite to the second substrate, there is a possibility that the first substrate may deflect. Since the first reflective film is disposed on the first substrate, when such deflection occurs, the size of the gap between the first and second reflective films changes depending on their positions, increasing noise in the wavelength of the light emitted from the interference filter. In other words, the beam splitting accuracy of the interference filter decreases because the emitted light contains not only the desired target wavelength but also multiple wavelength components. In particular, in interference filters that split near-infrared light, narrow light with a wavelength half-width may sometimes be emitted; in such interference filters, the effect of the aforementioned first substrate deflection becomes greater. Summary of the Invention

[0006] In view of the aforementioned problems, the object of the present invention is to provide an interferometric filter with high drive responsiveness and capable of splitting light of a desired target wavelength with excellent accuracy, as well as a method for manufacturing the interferometric filter.

[0007] The interference filter according to the first aspect of this disclosure comprises: a light-transmitting first substrate having a first inner surface and a first outer surface facing each other, and a first reflective film disposed on the first inner surface; a light-transmitting second substrate having a second inner surface and a second outer surface facing each other, and a second reflective film disposed on the second inner surface facing the first reflective film; a first joint portion joining the first inner surface and the second inner surface together, the first joint portion sealing a first internal space between the first substrate and the second substrate; a light-transmitting third substrate facing the first outer surface; a second joint portion joining the first outer surface and the third substrate together, the second joint portion sealing a second internal space between the first substrate and the third substrate; a light-transmitting fourth substrate facing the second outer surface; and a third joint portion joining the second outer surface and the fourth substrate together, the third joint portion sealing a third internal space between the second substrate and the fourth substrate, wherein the first internal space, the second internal space, and the third internal space are depressurized to below atmospheric pressure.

[0008] In the interference filter involved in this method, the second bonding portion bonds the first substrate to the third substrate by metal bonding the first metal layer disposed on the first outer surface to the third metal layer disposed on the third opposing surface of the third substrate opposite to the first substrate, and the third bonding portion bonds the second substrate to the fourth substrate by metal bonding the second metal layer disposed on the second outer surface to the fourth metal layer disposed on the fourth opposing surface of the fourth substrate opposite to the second substrate.

[0009] In the interference filter of this method, the first joint portion connects the first substrate and the second substrate through an elastic layer with an elastic modulus smaller than that of the metal film.

[0010] In the interference filter involved in this method, the elastic layer is a plasma polymer film with siloxane as the main component.

[0011] The second aspect of the present disclosure relates to a method for manufacturing an interference filter, comprising: a first substrate forming step, wherein a first reflective film is formed on the first inner surface of a first substrate having a first inner surface and a first outer surface that are mutually opposed; a second substrate forming step, wherein a second reflective film is formed on the second inner surface of a second substrate having a second inner surface and a second outer surface that are mutually opposed; a first bonding step, wherein, under a depressurization environment below atmospheric pressure, the first inner surface and the second inner surface are bonded together through a first bonding portion to seal a first internal space between the first substrate and the second substrate; a second bonding step, wherein, under a depressurization environment below atmospheric pressure, the first outer surface is bonded together with a transparent third substrate through a second bonding portion to seal a second internal space between the first substrate and the third substrate; and a third bonding step, wherein, under a depressurization environment below atmospheric pressure, the second outer surface is bonded together with a transparent fourth substrate through a third bonding portion to seal a third internal space between the second substrate and the fourth substrate.

[0012] The manufacturing method of the interference filter in this manner includes: a first masking step, in which the first reflective film is covered with a first mask; a first elastic layer forming step, in which a first elastic layer is formed on the first inner surface and the first mask is removed, wherein the first elastic layer is a plasma polymerized film with siloxane as the main component; a second masking step, in which the second reflective film is covered with a second mask; and a second elastic layer forming step, in which a second elastic layer is formed on the second inner surface and the second mask is removed, wherein the second elastic layer is a plasma polymerized film with siloxane as the main component; and in the first bonding step, in a depressurization environment where the pressure is reduced to below atmospheric pressure, a first bonding portion is formed by bonding the first elastic layer on the first inner surface and the second elastic layer on the second inner surface to each other, thereby bonding the first substrate and the second substrate to each other.

[0013] The manufacturing method of the interference filter in this manner includes: a first metal forming step, forming a first metal layer on a first outer surface; a third metal forming step, forming a third metal layer on a third opposing surface of a third substrate opposite to the first substrate; a second metal forming step, forming a second metal layer on a second outer surface; and a fourth metal forming step, forming a fourth metal layer on a fourth opposing surface of a fourth substrate opposite to the second substrate. In the second bonding step, a second bonding portion is formed by applying a load in a direction that brings the first substrate and the third substrate closer together to each other, thereby metal bonding the first metal layer and the third metal layer, and the first substrate and the third substrate are bonded. In the third bonding step, the third bonding portion is formed by applying a load in a direction that brings the second substrate and the fourth substrate closer together to each other, thereby metal bonding the second metal layer and the fourth metal layer, and the second substrate and the fourth substrate are bonded.

[0014] In the manufacturing method of the interference filter of this type, the second substrate forming process includes: a second substrate etching process, which etches the second outer surface to form a movable part of a predetermined thickness and a diaphragm part with a thickness thinner than the movable part; and a second reflective film forming process, which forms the second reflective film on the second inner surface of the movable part, and the third bonding process is performed before the second bonding process. Attached Figure Description

[0015] Figure 1 This is a diagram illustrating a simplified configuration of a spectrophotometer according to an embodiment of the present invention.

[0016] Figure 2 This is a top view showing a simplified configuration of the interference filter according to this embodiment.

[0017] Figure 3 It is along Figure 2 The sectional view when cut along line III-III.

[0018] Figure 4 This is a top view of the first substrate of this embodiment as seen from the second substrate side.

[0019] Figure 5 This is a top view of the second substrate of the interference filter in this embodiment, viewed from the first substrate side.

[0020] Figure 6 This is a cross-sectional view showing the cross-sectional structure near the lead-out section.

[0021] Figure 7 This is a flowchart illustrating the manufacturing method of the interference filter according to this embodiment.

[0022] Figure 8 This is a diagram showing the state of the first glass substrate during the first substrate formation process.

[0023] Figure 9 This is a diagram showing the state of the second glass substrate during the second substrate formation process.

[0024] Figure 10 This is a diagram used to illustrate the first joining process.

[0025] Figure 11 This is a diagram used to illustrate the third joining process.

[0026] Figure 12 This is a diagram used to illustrate the second joining process.

[0027] Explanation of reference numerals in the attached figures

[0028] 1…Spectrophotometer, 5…Interference filter, 51…First substrate, 51A…First inner surface, 51B…First outer surface, 52…Second substrate, 52A…Second inner surface, 52B…Second outer surface, 53…Third substrate, 53A…Third inner surface, 53B…Third outer surface, 54…Fourth substrate, 54A…Fourth inner surface, 54B…Fourth outer surface, 55…First joint, 56…Second joint, 57…Third joint, 59…Electrostatic actuator, 5 11…Electrode placement groove, 511A…Annular portion, 511B…Lead-out portion, 512…Reflective film setting portion, 513…Terminal portion, 514…First bonding object portion, 521…Modular portion, 522…Dipple portion, 523…Substrate outer periphery portion, 531…Third substrate recess, 532…Third bonding object portion, 541…Fourth substrate recess, 542…Fourth bonding object portion, 551…First elastic layer, 552…Second elastic layer, 553…Sealing portion, 561…First metal layer 562…Third metal layer, 571…Second metal layer, 572…Fourth metal layer, 581…First reflective film, 582…Second reflective film, 591…First electrode, 591A…First lead electrode, 592…Second electrode, 592A…Second lead electrode, 593…Bump electrode, 593A…Core, 594…Insulating part, G1…Gap, M1…First glass substrate (first substrate), M11…First mask, M2…Second glass substrate (second substrate), M2 1…Second mask, M3…Third glass substrate (third substrate), M4…Fourth glass substrate (fourth substrate), O…Filter center point, S1…First substrate forming process, S2…Second substrate forming process, S3…Third substrate forming process, S4…Fourth substrate forming process, S5…First bonding process, S6…Third bonding process, S7…Second bonding process, S8…Cutting process, Sp1…First internal space, Sp2…Second internal space, Sp3…Third internal space. Detailed Implementation

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0030] Composition of a spectrophotometer

[0031] Figure 1 This is a diagram showing a simplified configuration of the spectrophotometer according to this embodiment.

[0032] The spectrophotometer 1 is an example of an electronic device equipped with the interference filter of the present invention. It is a device for analyzing and measuring the intensity of light at each wavelength in the target light reflected by the target object X and measuring the spectrophotometer spectrum. It should be noted that in this embodiment, an example of measuring the target light reflected by the target object X is shown. However, when using a light-emitting element such as a liquid crystal panel as the target object X, light emitted from that light-emitting element can also be used as the target light. Furthermore, while the spectrophotometer 1 is shown as an example of an electronic device, it is not limited to this; the interference filter of the present invention can also be applied to spectrophotometers, light source devices, etc.

[0033] like Figure 1 As shown, the spectrophotometer 1 of this embodiment includes an optical module 10 and a control unit 20 that processes the signals output from the optical module 10.

[0034] Composition of optical modules

[0035] The optical module 10 includes an interference filter 5, a detector 11, an IV converter 12, an amplifier 13, an A / D converter 14, and a voltage control unit 15.

[0036] The optical module 10 guides the object light reflected by the object X through the incident optical system (not shown) into the interference filter 5, and the detector 11 receives the light output from the interference filter 5. Then, the detection signal output from the detector 11 is output to the control unit 20 via the IV converter 12, the amplifier 13, and the A / D converter 14.

[0037] Construction of an interference filter

[0038] The interference filter 5 assembled in the optical module 10 will now be described.

[0039] Figure 2 This is a top view showing a simplified configuration of the interference filter 5. Figure 3 It is along Figure 2 The sectional view when cut along line III-III.

[0040] like Figure 2 and Figure 3As shown, the interference filter 5 is constructed by stacking and bonding four substrates: a first substrate 51, a second substrate 52, a third substrate 53, and a fourth substrate 54. These substrates 51, 52, 53, and 54 are all light-transmitting substrates. For example, when the wavelength of the light split by the interference filter is in the visible light region, soda ash glass, crystal glass, quartz glass, etc., can be used; in the near-infrared or infrared regions, silicon, etc., can also be used. That is, substrates 51, 52, 53, and 54 are formed from substrates capable of transmitting light split by the interference filter 5.

[0041] More specifically, the first substrate 51 has a first inner surface 51A and a first outer surface 51B that are opposite to each other. That is, in the first substrate 51, the first inner surface 51A and the first outer surface 51B constitute a surface and a back surface, respectively. The second substrate 52 has a first inner surface 51A and a first outer surface 51B that are opposite to each other. That is, in the second substrate 52, the second inner surface 52A and the second outer surface 52B constitute a surface and a back surface, respectively. In the first substrate 51 and the second substrate 52, the first inner surface 51A and the second inner surface 52A are arranged opposite to each other, and the first substrate 51 and the second substrate 52 are joined by a first joining portion 55.

[0042] The third substrate 53 has a third inner surface 53A and a third outer surface 53B that form the surface and back sides of each other, and the fourth substrate 54 has a fourth inner surface 54A and a fourth outer surface 54B that form the surface and back sides of each other.

[0043] The third inner surface 53A of the third substrate 53 corresponds to the third opposing surface in the present invention, and is opposite to the first outer surface 51B of the first substrate 51, and is joined to the first outer surface 51B through the second joining portion 56.

[0044] The fourth inner surface 54A of the fourth substrate 54 corresponds to the fourth opposing surface in the present invention, and is opposite to the second outer surface 52B of the second substrate 52, and is joined to the second outer surface 52B through the third joining portion 57.

[0045] A detailed description of the structure of these joints 55, 56, and 57 will be provided later.

[0046] Furthermore, a first reflective film 581 is provided on the first inner surface 51A of the first substrate 51, and a second reflective film 582 is provided on the second inner surface 52A of the second substrate 52. These first reflective films 581 and second reflective films 582 are arranged opposite each other with a gap G1 between them. In addition, in a top view when observing the first substrate 51 and the second substrate 52 from the thickness direction, the overlapping area of ​​these first reflective films 581 and second reflective films 582 constitutes a light interference region.

[0047] The interference filter 5 includes a gap adjustment section for adjusting the size of the gap G1. The configuration of the gap adjustment section is not particularly limited; however, in this embodiment, an electrostatic actuator 59 is shown as an example of the gap adjustment section.

[0048] This electrostatic actuator 59, by applying a predetermined voltage between opposing electrodes, can easily change the size of the gap G1 through electrostatic attraction, thus simplifying its configuration. The electrostatic actuator 59 can be driven by the voltage control unit 15.

[0049] It should be noted that, in the following description, the top-view observation from the substrate thickness direction of each substrate 51, 52, 53, 54, that is, the top-view observation from the stacking direction of the third substrate 53, the first substrate 51, the second substrate 52, and the fourth substrate 54 when viewing the interference filter 5, is referred to as the filter top-view observation. Furthermore, in this embodiment, it is assumed that the center point of the first reflective film 581 and the center point of the second reflective film 582 coincide when the filter is viewed from above; these center points of the reflective films when viewed from above are referred to as filter center points O, and the straight line passing through these center points of the reflective films is referred to as the central axis.

[0050] The following is a more detailed explanation of the structure of each substrate 51, 52, 53, and 54.

[0051] Structure of the first substrate 51

[0052] Figure 4 This is a top view of the first substrate 51 of this embodiment as viewed from the side of the second substrate 52.

[0053] The first substrate 51 is formed with a thickness greater than that of the second substrate 52, so that the first substrate 51 will not bend due to the electrostatic attraction of the electrostatic actuator 59 or the internal stress of the film component (such as the first reflective film 581) formed on the first substrate 51.

[0054] like Figure 3 and Figure 4 As shown, the first substrate 51 includes an electrode placement groove 511 and a reflective film placement portion 512 formed, for example, by etching. Furthermore, when viewed from above the filter, one end (edge ​​C3-C4) of the first substrate 51 protrudes outward from the outer periphery (edge ​​C5-C6) of the second substrate 52 and the fourth substrate 54, and this protruding portion forms a terminal portion 513.

[0055] The electrode placement groove 511 includes, for example, an annular portion 511A formed in a ring shape centered on the filter center point O of the first substrate 51 when viewed from above, and an extension portion 511B extending from the annular portion 511A toward the outer edge of the substrate.

[0056] exist Figure 4 In the example shown, the shape of the annular portion 511A when viewed from above is approximately circular, but it can also be rectangular or polygonal.

[0057] The lead-out portion 511B extends from the annular portion 511A to the terminal portion 513 of the edge C3-C4 of the first substrate 51.

[0058] Furthermore, the terminal portion 513 and the bottom surface of the electrode placement groove 511 are formed on the same plane.

[0059] A first electrode 591 constituting an electrostatic actuator 59 is disposed on the bottom surface of the electrode placement groove 511. The first electrode 591 can be directly disposed on the bottom surface of the electrode placement groove 511, or other thin film layers can be disposed on the bottom surface of the groove and the first electrode 591 can be disposed on the thin film layer.

[0060] The first electrode 591 is formed in a generally annular shape, preferably in a circular annular shape. It should be noted that the generally annular shape described herein also includes shapes with partial gaps, such as a C-shape. Furthermore, in this embodiment, an example of providing one first electrode 591 is shown; however, it may also be configured such that multiple circular electrodes are arranged in concentric circles and that these multiple electrodes are each independent (insulated).

[0061] In addition, the first electrode 591 is connected to the first lead-out electrode 591A, which is led out from the annular portion 511A through the lead-out portion 511B to the terminal portion 513. At the terminal portion 513, it is electrically connected to the voltage control unit 15, for example, through wire bonding, FPC, etc.

[0062] Materials used to form the first electrode 591 and the first lead-out electrode 591A include, for example, Au / Cr film and ITO (Indium Tin Oxide). Alternatively, an insulating film may be formed on the surface of the first electrode 591.

[0063] Furthermore, a bump electrode 593 is formed in the lead-out portion 511B, which is made of a resin such as polyimide as the core 593A and coated with Au or the like around the core. This bump electrode 593 is led out along the lead-out portion 511B to the terminal portion 513 and is electrically connected to the voltage control portion 15, for example, through wire bonding, FPC, or the like. It should be noted that the bump electrode 593 and the first lead-out electrode 591A are not in contact but are in a mutually insulated relationship.

[0064] When viewed from above, the reflective film placement portion 512 is disposed at the center side of the electrode placement groove 511, for example, it is formed to protrude towards the second substrate 52. The first reflective film 581 is disposed on the protruding front end surface of the reflective film placement portion 512. It should be noted that, in this embodiment, an example is shown where the reflective film placement portion 512 protrudes further towards the second substrate 52 than the bottom surface of the electrode placement groove 511, but it is not limited to this. For example, the reflective film placement portion 512 may also be formed concave, with the bottom surface of the reflective film placement portion 512 located further away from the second substrate 52 than the bottom surface of the electrode placement groove 511, and the first reflective film 581 is disposed on this bottom surface. Alternatively, the reflective film placement portion 512 may also be on the same plane as the bottom surface of the electrode placement groove 511.

[0065] The first reflective film 581 disposed on the reflective film placement portion 512 can be directly disposed on the reflective film placement portion 512, or other thin films (layers) can be disposed on the reflective film placement portion 512, and the first reflective film 581 can be disposed on those layers. For example, a metal film such as Ag or a conductive alloy film such as Ag alloy can be used as the first reflective film 581. When using a metal film such as Ag, it is preferable to form a protective film to suppress the deterioration of Ag.

[0066] In addition, dielectric multilayer films formed by alternating layers of high-refractive-index layers (TiO2) and low-refractive-index layers (SiO2) can also be used. Reflective films formed by stacking dielectric multilayer films and metal films, and reflective films formed by stacking dielectric single-layer films and alloy films can also be used.

[0067] The first reflective film 581 faces the second reflective film 582 of the second substrate 52 across a gap G1. Here, in this embodiment, an example is shown where the gap G1 between the reflective films 581 and 582 is smaller than the gap between the first electrode 591 and the second electrode 592 constituting the electrostatic actuator 59; however, this is not a limitation. For example, when infrared or far-infrared light is used as the target light, a configuration where the gap G1 is larger than the gap between the electrodes 591 and 592 can be adopted according to the wavelength range of the target light. In this case, as described above, the reflective film placement portion 512 of the first substrate 51 is formed in a concave shape.

[0068] When viewed from above, the area outside the electrode placement groove 511, the reflective film placement part 512, and the terminal part 513 is the first bonding object part 514.

[0069] The first inner surface 51A of the first bonding portion 514, that is, the surface facing the second substrate 52, is bonded to the second substrate 52 through the first bonding portion 55. The first outer surface 51B of the first bonding portion 514, that is, the surface facing the third substrate 53, is bonded to the third substrate 53 through the second bonding portion 56.

[0070] like Figure 3 As shown, the first outer surface 51B of the first substrate 51 is formed as a plane and is parallel to the first reflective film 581. It should be noted that an anti-reflective film (not shown) may also be provided on this first outer surface 51B in the area overlapping with the first reflective film 581 when the filter is viewed from above. With such an anti-reflective film, the light reflectivity on the surface of the first outer surface 51B can be reduced, increasing the transmittance.

[0071] Composition of the second substrate

[0072] Figure 5 This is a top view of the second substrate 52 in the interference filter 5 of this embodiment, viewed from the side of the first substrate 51.

[0073] like Figure 2 , Figure 3 as well as Figure 5 As shown, the second substrate 52 includes a circular movable portion 521 centered at the filter center point O when viewed from above, a diaphragm portion 522 coaxial with and holding the movable portion 521, and a substrate outer periphery portion 523 disposed on the outside of the diaphragm portion 522.

[0074] The movable portion 521 is formed with a thickness greater than that of the diaphragm portion 522. For example, in this embodiment, it is formed to have the same thickness as the second substrate 52 (substrate outer periphery 523). When viewed from above the filter, the movable portion 521 has a diameter at least larger than the diameter of the outer periphery of the reflective film placement portion 512. In addition, a second reflective film 582 and a second electrode 592 constituting the electrostatic actuator 59 are provided on the second inner surface 52A side of the movable portion 521 opposite to the first substrate 51. The second reflective film 582 and the second electrode 592 can be directly provided on the second inner surface 52A, or other thin films (layers) can be provided on the second inner surface 52A, and the second reflective film 582 and the second electrode 592 can be provided thereon.

[0075] The second electrode 592, like the first electrode 591, is generally ring-shaped, preferably forming a ring with the filter center point O as the center. Alternatively, the second electrode 592 can also be configured similarly to the first electrode 591, with a portion of the ring cut off, for example, in a C-shape, and can be composed of multiple ring-shaped electrodes. It should be noted that in this embodiment, an example is shown where the second electrode 592 is disposed on the second inner surface 52A of the movable portion 521; however, this is not a limitation. For example, at the second inner surface 52A of the second substrate 52, the second electrode 592 can also be disposed directly from the movable portion 521 to the diaphragm portion 522, or it can be disposed on the diaphragm portion 522.

[0076] The second electrode 592 is connected to the second lead-out electrode 592A, which is led out to the outer periphery of the second substrate 52 along the region opposite to the lead-out portion 511B. More specifically, the second lead-out electrode 592A is configured to face the bump electrode 593 and contact the bump electrode 593 on the core 593A. Thus, the second electrode 592 is connected to the voltage control unit 15 via the bump electrode 593.

[0077] As for the materials used to form the second electrode 592 and the second lead-out electrode 592A, similar to the first electrode 591, for example, Au / Cr film, ITO (Indium Tin Oxide) or the like can be used.

[0078] At the center of the movable part 521, a second reflective film 582 is positioned opposite the first reflective film 581 across a gap G1. This second reflective film 582 uses a reflective film with the same configuration as the first reflective film 581 described above.

[0079] The diaphragm portion 522 is a diaphragm surrounding the movable portion 521, and its thickness is less than that of the movable portion 521. This diaphragm portion 522 is more flexible than the movable portion 521, allowing the movable portion 521 to be displaced towards the first substrate 51 by a small electrostatic attraction. At this time, the movable portion 521 has a larger thickness and greater rigidity compared to the diaphragm portion 522; therefore, even if the movable portion 521 is pulled towards the first substrate 51 due to electrostatic attraction, shape changes of the movable portion 521 can be suppressed.

[0080] It should be noted that in this embodiment, a diaphragm-shaped diaphragm portion 522 is shown as an example, but it is not limited to this. For example, it may also be configured with beam-shaped holding portions arranged at equal angular intervals around the filter center point O of the movable portion 521.

[0081] The outer peripheral portion 523 of the substrate is the portion located outside the diaphragm portion 522 when viewed from above. The second inner surface 52A of the outer peripheral portion 523 is joined to the first joining portion 514 of the first substrate 51 via the first joining portion 55. The second outer surface 52B of the outer peripheral portion 523 is joined to the fourth substrate 54 via the third joining portion 57.

[0082] Composition of the third substrate

[0083] The third substrate 53 is formed by etching a light-transmitting parallel flat substrate. Specifically, the third substrate 53 has a recessed portion 531 formed by etching at the position where it overlaps with the electrode placement groove 511 and the reflective film placement portion 512 when viewed from above. The bottom surface of the recessed portion 531 is flat and parallel to the first outer surface 51B and the reflective films 581 and 582.

[0084] Furthermore, the portion of the third substrate 53 that does not have the third substrate recess 531 is the third bonding target portion 532. The third inner surface 53A of the third bonding target portion 532, that is, the surface opposite to the first substrate 51, is bonded to the first bonding target portion 514 of the first substrate 51 through the second bonding portion 56.

[0085] Composition of the fourth substrate

[0086] The fourth substrate 54 has a shape substantially the same as the third substrate 53 and is formed by etching a light-transmitting parallel flat substrate. Specifically, the fourth substrate 54 has a recessed portion 541 formed by etching at the position where it overlaps with the movable part 521 and the diaphragm part 522 when viewed from above. The bottom surface of the recessed portion 541 is flat and parallel to the second outer surface 52B and the reflective films 581 and 582.

[0087] Furthermore, the portion of the fourth substrate 54 that does not have the fourth substrate recess 541 is the fourth bonding target portion 542. The fourth inner surface 54A of the fourth bonding target portion 542, that is, the surface opposite to the second substrate 52, is bonded to the outer peripheral portion 523 of the second substrate 52 through the third bonding portion 57.

[0088] It should be noted that although the illustrations are omitted, optical films such as anti-reflective films and bandpass filters can also be formed on the third substrate 53 and the fourth substrate 54 as described above. When an anti-reflective film is provided, light reflection from the surfaces of the third substrate 53 and the fourth substrate 54 can be suppressed. Furthermore, by providing a bandpass filter that reflects or absorbs light of wavelengths outside a specific range, light outside the measurement target in the spectrophotometer 1 can be blocked. For example, in a spectrophotometer 1 performing spectrophotometry in the visible light region, a bandpass filter is provided to block light in the infrared and ultraviolet regions. Such a bandpass filter and anti-reflective film can be provided at any one of the third inner surface 53A, the third outer surface 53B, the fourth inner surface 54A, and the fourth outer surface 54B, or multiple locations.

[0089] Composition of the first joint

[0090] The first joint portion 55, which joins the first substrate 51 and the second substrate 52, will now be described.

[0091] like Figure 3 As shown, the first bonding portion 55 includes a first elastic layer 551 disposed on the first inner surface 51A of the first substrate 51 and a second elastic layer 552 disposed on the second inner surface 52A of the second substrate 52. Specifically, these first elastic layers 551 and second elastic layers 552 are plasma-polymerized films with siloxane as the main component, and the first elastic layer 551 and the second elastic layer 552 are bonded by siloxane bonds.

[0092] By using this bonding of substrates utilizing plasma-polymerized films, the parallelism between the substrates can be maintained to a high degree. In other words, the plasma-polymerized film is more elastic than, for example, the metal layer used for metal bonding; therefore, even if foreign matter adheres to the surface of the plasma-polymerized film, the deterioration of parallelism caused by the foreign matter can be suppressed through elastic deformation. Through this bonding using plasma-polymerized films, the parallelism between the first reflective film 581 and the second reflective film 582 is maintained to a high degree, enabling high precision in the wavelength splitting characteristics of the interference filter 5. That is, it suppresses the undesirable situation where the size of the gap G1 changes depending on its position within the interference region, allows light of the target wavelength corresponding to the gap G1 to pass through from each position, and suppresses the undesirable situation where the wavelength half-width of the emitted light is broadened due to the output of light outside the target wavelength.

[0093] Figure 6 This is a cross-sectional view showing the cross-sectional structure near the lead-out portion 511B of the interference filter 5. It should be noted that... Figure 6 The third substrate 53, the fourth substrate 54, the second joint portion 56, and the third joint portion 57 are omitted in the text.

[0094] However, in the portion of the first substrate 51 where the lead-out portion 511B is formed, the dimension between the first substrate 51 and the second substrate 52 is larger than the dimension between the first bonding portion 514 and the outer periphery portion 523 of the substrate. Therefore, the first elastic layer 551 and the second elastic layer 552 do not contact each other. Thus, in this embodiment, in this region... Figure 6 The configuration shown ensures airtightness.

[0095] That is, in the lead-out portion 511B, an insulating portion 594 is provided to cover the first lead-out electrode 591A and the bump electrode 593. It should be noted that the portion of the bump electrode 593 where the core 593A is located needs to be connected to the second lead-out electrode 592A, therefore, the insulating portion 594 is not provided.

[0096] In addition, such as Figure 3 and Figure 6As shown, the first elastic layer 551 and the second elastic layer 552 constituting the first joint portion 55 are disposed at a position closer to the terminal portion 513 than the position where the core 593A is disposed in the lead-out portion 511B. Figure 3 and Figure 6 As shown, the first elastic layer 551 is disposed on the insulating portion 594.

[0097] Furthermore, the first joint portion 55 also has a sealing portion 553 at the lead-out portion 511B, which seals the space between the first elastic layer 551 and the second elastic layer 552. Such a sealing portion 553 can be made of, for example, an adhesive, low-melting-point glass, or a low-melting-point metal; a low-melting-point metal with low venting and high airtightness is particularly preferred. It should be noted that the example shown is of filling the space between the first elastic layer 551 and the second elastic layer 552 at the lead-out portion 511B with the sealing portion 553; however, it is not limited to this configuration. For example, the first elastic layer 551 at the lead-out portion 511B could be formed to the same height as the first elastic layer 551 of the first joint object portion 514. In this case, the sealing portion 511B can be sealed by the first elastic layer 551 and the second elastic layer 552 without providing the sealing portion 553.

[0098] With the configuration described above, the first internal space Sp1, surrounded by the first substrate 51, the second substrate 52, and the first bonding portion 55, is maintained as airtight. It should be noted that the bonding of the first substrate 51 and the second substrate 52 via the first bonding portion 55 is performed within a vacuum chamber. Therefore, the internal pressure of the first internal space Sp1 is maintained in a depressurized environment below atmospheric pressure, preferably a vacuum.

[0099] Composition of the second and third joints

[0100] The second joint 56 and the third joint 57 will now be described.

[0101] like Figure 3 As shown, the second bonding portion 56 includes a first metal layer 561 disposed on the first outer surface 51B of the first substrate 51 and a third metal layer 562 disposed on the third inner surface 53A of the third substrate 53. The first metal layer 561 and the third metal layer 562 are bonded together by metal bonding. As these first metal layers 561 and third metal layers 562, various metal films and alloy films such as Au and Ti can be used, and Au is preferred among metals because it has high flexibility (high plasticity) and can achieve high bonding strength and high airtightness through metal bonding.

[0102] Thus, the second internal space Sp2, surrounded by the first substrate 51, the third substrate 53, and the second joint 56, is maintained as airtight. It should be noted that the bonding of the first substrate 51 and the third substrate 53 via the second joint 56 is performed within a vacuum chamber. Therefore, the internal pressure of the second internal space Sp2 is maintained in a depressurized environment below atmospheric pressure, preferably a vacuum.

[0103] The third joint 57 has the same structure as the second joint 56, and the second substrate 52 and the fourth substrate 54 are joined by metal bonding.

[0104] That is, the third bonding portion 57 includes a second metal layer 571 disposed on the second outer surface 52B of the second substrate 52 and a fourth metal layer 572 disposed on the fourth inner surface 54A of the fourth substrate 54, and the second metal layer 571 and the fourth metal layer 572 are bonded together by metal bonding. As for these second metal layers 571 and the fourth metal layer 572, similarly to the second bonding portion 56, various metal films or alloy films such as Au and Ti can be used, for example. Among the metals, Au, which has high flexibility (high plasticity) and can achieve high bonding strength and high airtightness through metal bonding, is preferred.

[0105] Therefore, the third internal space Sp3, surrounded by the second substrate 52, the fourth substrate 54, and the third joint 57, is maintained as airtight. It should be noted that the bonding of the second substrate 52 and the fourth substrate 54 via the third joint 57 is performed within a vacuum chamber. Thus, the internal pressure of the third internal space Sp3 is maintained in a depressurized environment below atmospheric pressure, preferably a vacuum.

[0106] It should be noted that the first metal layer 561, the third metal layer 562, the second metal layer 571 and the fourth metal layer 572 can be formed directly on the substrate, or a base layer formed by, for example, resin can be provided on the substrate, and the first metal layer 561, the third metal layer 562, the second metal layer 571 and the fourth metal layer 572 can be formed on the base layer.

[0107] Other components of the optical module

[0108] Now, let's go back to... Figure 1 The other components of the optical module 10 will be described.

[0109] Detector 11 receives (detects) the light passing through interference filter 5 and outputs a detection signal based on the amount of light received to IV converter 12.

[0110] IV converter 12 converts the detection signal input from detector 11 into a voltage value and outputs it to amplifier 13.

[0111] Amplifier 13 amplifies the voltage (detection voltage) corresponding to the detection signal input from IV converter 12.

[0112] The A / D converter 14 converts the detection voltage (analog signal) input from the amplifier 13 into a digital signal and outputs it to the control unit 20.

[0113] Based on the control of the control unit 20, the voltage control unit 15 applies a driving voltage to the electrostatic actuator 59 of the interference filter 5. As a result, an electrostatic attraction is generated between the first electrode 591 and the second electrode 592 of the electrostatic actuator 59, and the movable part 521 is displaced toward the first substrate 51.

[0114] Composition of the control unit

[0115] The control unit 20 of the spectrophotometer 1 will now be described.

[0116] The control unit 20, for example, is configured by combining a CPU, memory, etc., and controls the overall operation of the spectrophotometer 1. Figure 1 As shown, the control unit 20 includes a filter drive unit 21, a light acquisition unit 22, and a spectrophotometer 23. Furthermore, the control unit 20 stores V-λ data in its memory, which indicates the relationship between the wavelength of light passing through the interference filter 5 and the driving voltage applied to the electrostatic actuator 59 corresponding to that wavelength.

[0117] The filter drive unit 21 sets the target wavelength of the light extracted by the interference filter 5, and outputs a command signal to the voltage control unit 15, which means to apply a drive voltage corresponding to the set target wavelength to the electrostatic actuator 59, based on the V-λ data.

[0118] The light acquisition unit 22 acquires the amount of light transmitted through the target wavelength of the interference filter 5 based on the amount of light acquired by the detector 11.

[0119] The spectrophotometer 23 measures the spectral characteristics of the light of the object to be measured based on the amount of light acquired by the light acquisition unit 22.

[0120] Manufacturing method of interferometric filters

[0121] The manufacturing method of the above-mentioned interference filter 5 will now be described based on the accompanying drawings.

[0122] Figure 7 This is a flowchart illustrating the manufacturing method of the interference filter 5.

[0123] In the manufacture of the interference filter 5, firstly, a first glass substrate M1 for forming a first substrate 51, a second glass substrate M2 for forming a second substrate 52, a third glass substrate M3 for forming a third substrate 53, and a fourth glass substrate M4 for forming a fourth substrate 54 are prepared, and the first substrate forming process S1, the second substrate forming process S2, the third substrate forming process S3, and the fourth substrate forming process S4 are performed. It should be noted that the process order of the first substrate forming process S1, the second substrate forming process S2, the third substrate forming process S3, and the fourth substrate forming process S4 can also be replaced.

[0124] Then, a first bonding process S5 is performed to join the first glass substrate M1 and the second glass substrate M2 using the first bonding portion 55.

[0125] After the first bonding process S5, a third bonding process S6 is performed to bond the fourth glass substrate M4 to the second glass substrate M2.

[0126] Then, after the third bonding process S6, a second bonding process S7 is performed to bond the third glass substrate M3 to the first glass substrate M1.

[0127] Next, a cutting process S8 is performed to cut the bonded glass substrate into chips.

[0128] The following is a detailed explanation of each process.

[0129] First substrate formation process

[0130] Figure 8 This is a diagram showing the state of the first glass substrate M1 in the first substrate formation process S1.

[0131] In the first substrate formation process S1, firstly, the two sides of the first glass substrate M1 (for example, with a thickness of 1 mm), which is the raw material for manufacturing the first substrate 51, are precision ground until the surface roughness Ra reaches less than 1 nm.

[0132] Next, as Figure 8 As shown in (A), the substrate surface of the first glass substrate M1 is processed by etching.

[0133] Specifically, a resist pattern patterned by photolithography is used as a mask to repeatedly perform wet etching on the first glass substrate M1 using a solvent such as hydrofluoric acid (BHF). First, the electrode placement groove 511, the lead-out portion 511B, the reflective film placement portion 512, and the terminal portion 513 are etched to the height of the reflective film placement portion 512. Then, the electrode placement groove 511, the lead-out portion 511B, and the terminal portion 513 are formed by etching.

[0134] It should be noted that the unetched surface of the first glass substrate M1 is the first bonding object portion 514. Thus, a first glass substrate M1 with a substrate shape that defines the first substrate 51 is formed.

[0135] In this embodiment, a plurality of first substrates 51 are formed from a first glass substrate M1. Therefore, in this process, the first glass substrate M1 is etched in a manner in which the plurality of first substrates 51 are arranged side by side in an array.

[0136] Next, a resin layer such as polyimide is formed on the first glass substrate M1, and then etched to form the core 593A. Additionally, the first electrode 591 and the first lead-out electrode 591A are formed on the first inner surface 51A of the first glass substrate M1 using methods such as vapor deposition and sputtering. Figure 8 And then Figures 10-12 (omitted), electrode material (e.g., Cr / Au layer) for bump electrode 593 is deposited. Additionally, a photoresist is coated onto the first glass substrate M1, and the photoresist is patterned using photolithography corresponding to the shapes of the first electrode 591, the first lead electrode 591A, and the bump electrode 593. After etching the electrode material using an etching solution, the photoresist is removed. Thus, as... Figure 8 As shown in (B), a first electrode 591, a first lead-out electrode 591A, and a bump electrode 593 are formed.

[0137] Subsequently, an insulating film, such as SiO2, is formed on the first inner surface 51A by means of, for example, plasma CVD. In addition, the SiO2 formed on the first lead electrode 591A of the terminal portion 513, the bump electrode 593 of the terminal portion 513, and the bump electrode 593 on the core 593A is removed by means of, for example, dry etching, to form an insulating portion 594.

[0138] Next, a first reflective film 581 is formed on the reflective film setting part 512. When using a metal film such as Ag film or an alloy film such as Ag alloy as the first reflective film 581, after forming a metal reflective film (metal film or alloy film) on the surface (first inner surface 51A) of the first glass substrate M1, it is patterned using photolithography or the like.

[0139] Furthermore, when forming a dielectric multilayer film as the first reflective film 581, patterning is performed, for example, by a lift-off process. In this case, a resist is formed outside the reflective film formation portion on the first glass substrate M1 using a photolithography method or the like (lift-off pattern). Additionally, a film is formed using a material (e.g., a dielectric multilayer film with a high refractive index layer of TiO2 and a low refractive index layer of SiO2) used to form the first reflective film 581, such as by sputtering or evaporation. After forming the first reflective film 581, unwanted portions of the film are removed by lift-off.

[0140] As mentioned above, such as Figure 8 As shown in (C), a plurality of first substrates 51 are formed and arranged in an array of first glass substrates M1.

[0141] Second substrate formation process

[0142] Next, the second substrate formation process S2 will be described. Figure 9 This is a diagram showing the state of the second glass substrate M2 in the second substrate formation process S2.

[0143] In the second substrate formation process S2, firstly, both sides of the second glass substrate M2 are precision ground until the surface roughness Ra of the second glass substrate M2 reaches, for example, less than 1 nm.

[0144] Additionally, an etching mask, such as a Cr / Au layer, is formed on the surface of the second glass substrate M2. For example, hydrofluoric acid (BHF, etc.) is used to etch the area corresponding to the diaphragm portion 522 (second substrate etching process). Afterwards, by removing the Cr / Au layer used as the etching mask, the diaphragm portion 522 is obtained. Figure 9 The second glass substrate M2, whose substrate shape is defined by the second substrate 52, is manufactured as shown in (A). It should be noted that, similar to the first glass substrate M1, in this embodiment, a plurality of second substrates 52 are formed from one second glass substrate M2. Therefore, in this process, the second glass substrate M2 is etched in a manner in which the plurality of second substrates 52 are arranged side-by-side in an array.

[0145] Next, as Figure 9 As shown in (B), a second electrode 592 and a second lead-out electrode 592A are formed. The same method as that used to form the first electrode 591 in the first substrate 51 can be used in the formation of the second electrode 592 and the second lead-out electrode 592A.

[0146] After that, as Figure 9 As shown in (C), a second reflective film 582 is formed at the center of the movable portion 521 in the second inner surface 52A (second reflective film forming process). The second reflective film 582 can also be formed by the same method as the first reflective film 581.

[0147] As described above, a plurality of second substrates 52 are manufactured in an array of second glass substrates M2.

[0148] Third substrate formation process

[0149] In the third substrate formation process S3, both sides of the third glass substrate are precision ground until the surface roughness Ra of the third glass substrate reaches, for example, less than 1 nm.

[0150] In addition, by modifying the third glass substrate M3 ( Figure 12 The third substrate recess 531 is formed by etching at the predetermined position (refer to). It should be noted that optical films such as anti-reflective films and bandpass filters can also be formed on the third inner surface 53A and the third outer surface 53B of the third glass substrate M3.

[0151] Fourth substrate formation process

[0152] In the fourth substrate formation process S4, the fourth glass substrate M4 is formed according to the same process as the third substrate formation process S3.

[0153] That is, in the fourth substrate formation process S4, firstly, both sides are precision ground until the surface roughness Ra reaches, for example, below 1 nm. Additionally, by grinding the fourth glass substrate M4 (refer to...) Figure 11 The fourth substrate recess 541 is formed by etching at a predetermined position. It should be noted that optical films such as anti-reflective films and bandpass filters can also be formed on the fourth inner surface 54A and the fourth outer surface 54B of the fourth glass substrate M4.

[0154] First joining process

[0155] Next, the first joining process S5 will be described.

[0156] In the first bonding process S5, a first elastic layer 551 is first formed on the first bonding target portion 514 of the first glass substrate M1, and a second elastic layer 552 is formed on the outer periphery portion 523 of the second glass substrate M2.

[0157] Specifically, the process includes a first masking process, a second masking process, a first elastic layer forming process, and a second elastic layer forming process.

[0158] Figure 10 This is a diagram used to illustrate the first joining process S5.

[0159] In the first concealment process, such as Figure 10 As shown in (A), a first mask M11 is formed at the first inner surface 51A of the first glass substrate M1, covering the area outside the first bonding target portion 514. In this embodiment, the first mask M11 is a layer used to pattern the first elastic layer 551, which is a plasma polymer film, through a peeling process; for example, a metal film can be used. In other embodiments, a metal mask having a partial opening exposing the first bonding target portion 514 can be attached to the substrate, and the plasma polymer film can be formed by CVD (Chemical Vapor Deposition).

[0160] The second concealment process is roughly the same as the first concealment process, such as... Figure 10 As shown in (A), a second mask M21 is formed at the second inner surface 52A of the second glass substrate M2, covering the outer periphery 523 of the substrate.

[0161] Next, the first elastic layer forming process and the second elastic layer forming process are carried out.

[0162] Specifically, in the first elastic layer formation process, the first glass substrate M1 is placed in the vacuum chamber of a plasma apparatus for forming a plasma polymer film, and vaporized monomers are introduced at a predetermined flow rate for plasma discharge. In this embodiment, for example, hexamethyldisiloxane monomer is used, thereby enabling the formation of a plasma polymer film with siloxane as the main component. At this time, since the first reflective film 581 is covered by the first mask M11, it is not exposed to plasma discharge, thus preventing deterioration of the first reflective film 581. Afterwards, a peeling process is performed to remove the first mask M11. Thus, as... Figure 10 As shown in (B), the first elastic layer 551 of the plasma polymer film can be patterned.

[0163] The second elastic layer formation process is largely the same as the first elastic layer formation process. The second glass substrate M2 is placed in the vacuum chamber of the plasma apparatus, and vaporized monomers are introduced at a predetermined flow rate for plasma discharge. This forms a second elastic layer 552 composed of a plasma-polymerized film with siloxane as the main component. Since the second reflective film 582 is covered by the second mask M21, it is not exposed to plasma discharge, preventing deterioration of the second reflective film 582. Afterwards, a stripping process is performed to pattern the second elastic layer 552 of the plasma-polymerized film. Thus, as... Figure 10 As shown in (B), the second elastic layer 552 of the plasma polymer film can be patterned.

[0164] It should be noted that, in this embodiment, the peeling process performed in the first elastic layer forming process and the second elastic layer forming process can remove the first glass substrate M1 and the second glass substrate M2 from the vacuum chamber and perform the process at room temperature and pressure.

[0165] That is, assuming that the first substrate 51 and the second substrate 52 are bonded by metal bonding, the metal bonding layers formed on the first substrate 51 and the second substrate 52 are activated by plasma treatment or the like, causing the metal bonding layers to adhere tightly to each other and thus achieve metal bonding. However, in this case, a series of processes need to be performed in a vacuum chamber. Therefore, when performing plasma activation treatment to activate the metal bonding layers, it is not possible to cover the first reflective film 581 and the second reflective film 582 with a mask, and there is a possibility that the first reflective film 581 and the second reflective film 582 may deteriorate. Alternatively, it is necessary to select a reflective film material that is resistant to surface treatments such as plasma activation treatment, thus limiting the film materials that can be used for the first reflective film 581 and the second reflective film 582.

[0166] In this embodiment, the first elastic layer 551 and the second elastic layer 552 constituting the first bonding portion 55 are plasma-polymerized films. After these first elastic layers 551 and the second elastic layer 552 are formed, the first glass substrate M1 and the second glass substrate M2 can be removed from the vacuum chamber. That is, the masks M11 and M21 can be removed afterward by a peeling process. Therefore, when the plasma-polymerized film is formed, the first reflective film 581 and the second reflective film 582 can be covered and protected by the masks M11 and M21.

[0167] After the above steps, the first glass substrate M1 and the second glass substrate M2 are placed in a vacuum chamber where the internal pressure is reduced to below atmospheric pressure. Furthermore, a load is applied in the direction that brings the first glass substrate M1 and the second glass substrate M2 closer together, bonding the first elastic layer 551 and the second elastic layer 552 together via siloxane bonds. Here, the first elastic layer 551 and the second elastic layer 552 are composed of plasma-polymerized films, which have a lower elastic modulus compared to metal films. Therefore, even when foreign matter adheres to the surfaces of the first elastic layer 551 and the second elastic layer 552, the first elastic layer 551 and the second elastic layer 552 can be elastically deformed, maintaining a high degree of parallelism between the first reflective film 581 and the second reflective film 582.

[0168] Therefore, as Figure 10 As shown in (C), a first joint body M10 can be formed in which the first glass substrate M1 and the second glass substrate M2 are joined together by the first joint portion 55.

[0169] Third joining process

[0170] Next, the third joining process S6 will be described.

[0171] Figure 11 This is a diagram used to illustrate the third joining process S6.

[0172] In the third joining process S6, firstly, as... Figure 11 As shown in (A), a second metal layer 571 is formed on the second outer surface 52B of the outer peripheral portion 523 of the second glass substrate M2 (second metal formation process), and a fourth metal layer 572 is formed on the fourth inner surface 54A of the fourth glass substrate M4 at a position opposite to the outer peripheral portion 523 (fourth metal formation process). As described above, Au is preferably used as these second metal layers 571 and fourth metal layers 572.

[0173] Furthermore, in order to maintain the pressure between the first substrate 51 and the second substrate 52 in a depressurized state, it is preferable to form the second metal layer 571 while keeping the first glass substrate M1 and the second glass substrate M2, which are joined by the first bonding process S5, i.e., the first bonding body M10, in a vacuum chamber under a depressurized environment with pressure reduced to below atmospheric pressure.

[0174] Next, a fourth glass substrate M4 is placed in a vacuum chamber containing the first bonding body M10, and plasma activation treatment is performed on the surfaces of the second metal layer 571 and the fourth metal layer 572. Then, a load is applied in a direction that brings the first bonding body M10 and the fourth glass substrate M4 closer together, and the second metal layer 571 and the fourth metal layer 572 are bonded together by metal bonding to form a third bonding portion 57. For example, the first bonding body M10 and the fourth glass substrate M4 are clamped and pressed using a clamping device having a pair of flat plate members. At this time, the pressing force of the clamping device does not directly act on the movable portion 521 formed on the second glass substrate M2, thus preventing damage or skewing of the movable portion 521.

[0175] Alternatively, it can be configured as a flat plate component with a heater disposed on the fourth glass substrate M4 side of the clamping device to heat the second metal layer 571 and the fourth metal layer 572.

[0176] As mentioned above, such as Figure 11 As in (B), the first bonding body M10 and the fourth glass substrate M4 are bonded together by the third bonding portion 57. As a result, the third internal space Sp3, which is surrounded by the second substrates 52 provided on the second glass substrate M2, the fourth substrates 54 provided on the fourth glass substrate M4, and the third bonding portion 57, is maintained as a depressurized environment that is reduced to below atmospheric pressure and is airtightly sealed.

[0177] Second joining process

[0178] After the third joining process S6, the second joining process S7 is performed.

[0179] Figure 12 This is a diagram used to illustrate the second joining process S7.

[0180] The second joining process S7 can be implemented in roughly the same way as the third joining process S6.

[0181] That is, in the second joining process S7, firstly, as Figure 12 As shown in (A), a first metal layer 561 is formed on the first outer surface 51B of the first bonding portion 514 of the first glass substrate M1 (first metal forming process), and a third metal layer 562 is formed on the third inner surface 53A of the third glass substrate M3 at a position opposite to the first bonding portion 514 (third metal forming process). As described above, Au is preferably used as these first metal layers 561 and third metal layers 562.

[0182] It should be noted that in order to maintain the pressure between the first substrate 51 and the second substrate 52 in a depressurized state, it is preferable to form the first metal layer 561 while keeping the first bonding body M10 and the bonding body of the fourth glass substrate M4, which are bonded through the third bonding process S6, i.e., the second bonding body M20, in a vacuum chamber under a depressurized environment with pressure reduced to below atmospheric pressure.

[0183] Furthermore, the third glass substrate M3 is placed in the aforementioned vacuum chamber, and a load is applied in a direction that brings the second bonding body M20 and the third glass substrate M3 closer together. The first metal layer 561 and the third metal layer 562 are bonded together by metal bonding to form the second bonding portion 56. For example, the second bonding body M20 and the third glass substrate M3 are clamped and pressed by a clamping device having a pair of flat plate members. At this time, the fourth glass substrate M4 is bonded to the second glass substrate M2 through the third bonding process S6. Therefore, the pressing force of the clamping device does not directly act on the movable part 521 of the second glass substrate M2, and damage or skewing of the movable part 521 can be suppressed.

[0184] Alternatively, it can be configured as a flat plate component with a heater disposed on the third glass substrate M3 side of the clamping device to heat the first metal layer 561 and the third metal layer 562.

[0185] As mentioned above, such as Figure 12 As in (B), the second bonding body M20 and the third glass substrate M3 are bonded together by the second bonding portion 56. As a result, the second internal space Sp2, which is surrounded by the first substrates 51 provided on the first glass substrate M1, the third substrates 53 provided on the third glass substrate M3, and the second bonding portion 56, is maintained as a depressurized environment that is reduced to below atmospheric pressure and is airtightly sealed.

[0186] Cutting process

[0187] After the second joining process S7, the cutting process S8 is performed.

[0188] In order to maintain the pressure between the first substrate 51 and the second substrate 52 in a depressurized state, the cutting process S8 is performed while the third bonding body M30, which is joined by the second bonding process S7, is placed in a vacuum chamber under a depressurized environment with pressure reduced to below atmospheric pressure. In this cutting process S8, the third bonding body M30 is cut using, for example, laser cutting, to cut out interference filters 5 on a chip-by-chip basis.

[0189] Subsequently, the lead-out portions 511B of each interference filter 5 cut out on a chip-by-chip basis are sealed by the sealing portion 553. As a result, the first internal space Sp1 is maintained in a depressurized environment below atmospheric pressure and is airtightly sealed.

[0190] This is used to manufacture the interference filter 5.

[0191] Effects of the first embodiment

[0192] The interference filter 5 of this embodiment includes a first substrate 51, a second substrate 52, a third substrate 53, a fourth substrate 54, a first bonding portion 55, a second bonding portion 56, and a third bonding portion 57. The first substrate 51 is a light-transmitting substrate having a first inner surface 51A and a first outer surface 51B that form a surface and a back surface, respectively, and a first reflective film 581 is provided on the first inner surface 51A. The second substrate 52 is a light-transmitting substrate having a second inner surface 52A and a second outer surface 52B that form a surface and a back surface, respectively, and a second reflective film 582 opposite to the first reflective film 581 is provided on the second inner surface 52A. The third substrate 53 is a light-transmitting substrate disposed opposite to the first outer surface 51B of the first substrate 51. The fourth substrate 54 is a light-transmitting substrate disposed opposite to the second outer surface 52B of the second substrate 52. The first bonding portion 55 joins the first inner surface 51A and the second inner surface 52A, and seals the first internal space Sp1 between the first substrate 51 and the second substrate 52. The second joint 56 joins the first outer surface 51B and the third substrate 53, and seals the second internal space Sp2 between the first substrate 51 and the third substrate 53. The third joint 57 joins the second outer surface 52B and the fourth substrate 54, and seals the third internal space Sp3 between the second substrate 52 and the fourth substrate 54. Furthermore, these first internal spaces Sp1, second internal spaces Sp2, and third internal spaces Sp3 are maintained in a depressurized environment below atmospheric pressure.

[0193] In this configuration of the interference filter 5, a first substrate 51, on which a first reflective film 581 is provided, is sandwiched between a first internal space Sp1 and a second internal space Sp2, which are maintained in a reduced-pressure environment. Furthermore, a second substrate 52, on which a second reflective film 582 is provided, is sandwiched between the first internal space Sp1 and a third internal space Sp3, which are also maintained in a reduced-pressure environment. Therefore, the first substrate 51 and the second substrate 52 will not bend due to the pressure difference between the two spaces sandwiching them, suppressing the effects of bending of the first reflective film 581 and the second reflective film 582, resulting in an interference filter 5 capable of highly accurate beam splitting of light of the desired wavelength. In other words, when light of the target wavelength corresponding to the gap G1 is emitted from the interference filter 5, the mixing of light of different wavelengths into the emitted light can be suppressed, resulting in a high-precision beam splitting characteristic with a narrow half-width.

[0194] Furthermore, the first internal space Sp1 and the third internal space Sp3 that sandwich the movable part 521 are a pressure-reducing environment, which reduces the resistance when driving the movable part 521 and improves the responsiveness when a voltage is applied to the electrostatic actuator 59.

[0195] Furthermore, in the interference filter 5 of this embodiment, a package housing for maintaining a reduced pressure between the first substrate 51 and the second substrate 52 is not required. That is, in the prior art, an interference filter is known that consists only of a first substrate 51 provided with a first reflective film 581 and a second substrate 52 provided with a second reflective film 582. However, in the case of such conventional interference filters, they are housed in a package housing whose internal space is maintained in a reduced pressure environment. However, in order to maintain a reduced pressure environment, such a package housing is generally made of ceramic or the like, making it difficult to miniaturize the package housing containing the interference filter and the electronic device such as the spectrometer 1 assembled with the package housing. In this regard, the interference filter 5 of this embodiment can maintain the first internal space Sp1, the second internal space Sp2, and the third internal space Sp3 in a reduced pressure environment on a wafer basis, without the need for a package housing like conventional interference filters. Therefore, miniaturization is possible, as is miniaturization of the electronic device such as the spectrometer 1 assembled with the interference filter 5.

[0196] In the interference filter 5 of this embodiment, the second bonding portion 56 bonds the first substrate 51 and the third substrate 53 by metal bonding a first metal layer 561 disposed on the first outer surface 51B and a third metal layer 562 disposed on the third inner surface 53A of the third substrate 53 opposite to the first substrate 51. Similarly, the third bonding portion 57 bonds the second substrate 52 and the fourth substrate 54 by metal bonding a second metal layer 571 disposed on the second outer surface 52B and a fourth metal layer 572 disposed on the fourth inner surface 54A of the fourth substrate 54 opposite to the second substrate 52.

[0197] Regarding the bonding of the substrates via such metal bonding, the bonding strength is high and the metal layer surfaces are completely adhered, thereby enabling bonding that maintains high hermeticity. Therefore, it is possible to maintain high hermeticity in both the second internal space Sp2 and the third internal space Sp3.

[0198] In this embodiment, the first bonding portion 55 bonds the first substrate and the second substrate through an elastic layer with an elastic modulus less than that of the metal film. Specifically, the first elastic layer 551 and the second elastic layer 552 constituting the first bonding portion 55 are respectively composed of plasma polymerized films with siloxane as the main component.

[0199] Regarding this type of bonding using the first elastic layer 551 and the second elastic layer 552, even if foreign objects or the like are attached to the surface of the first elastic layer 551 or the second elastic layer 552, the influence of foreign objects or the like can be suppressed through elastic deformation, and the tilting of the first substrate 51 and the second substrate 52 during bonding can be suppressed. Therefore, a high degree of parallelism can be maintained between the first reflective film 581 provided on the first substrate 51 and the second reflective film 582 provided on the second substrate 52.

[0200] Furthermore, in this embodiment, as a manufacturing method for the interference filter 5, a first substrate formation step S1, a second substrate formation step S2, a first bonding step S5, a third bonding step S6, and a second bonding step S7 are performed. In the first substrate formation step S1, a first reflective film 581 is formed on the first inner surface 51A of a first glass substrate M1 arranged in an array on the first substrate 51, forming the first substrate 51. In the second substrate formation step S2, a second reflective film 582 is formed on the second inner surface 52A of a second glass substrate M2 arranged in an array on the second substrate 52, forming the second substrate 52. In the first bonding step S5, under a depressurization environment below atmospheric pressure, the first inner surface 51A and the second inner surface 52A are bonded via a first bonding portion 55. In the second bonding step S7, under a depressurization environment below atmospheric pressure, the first outer surface 51B and the third substrate 53 are bonded via a second bonding portion 56. In the third bonding process S6, the second outer surface 52B and the fourth substrate 54 are bonded through the third bonding part 57 under a depressurization environment where the pressure is reduced to below atmospheric pressure.

[0201] Thus, it is possible to manufacture a small interference filter 5, as shown above, which can split light of the desired wavelength with high precision and has high driving response.

[0202] In this embodiment, the manufacturing method of the interference filter 5 includes a first masking process, a first elastic layer forming process, a second masking process, and a second elastic layer forming process. In the first masking process, a first mask M11 covering the first reflective film 581 is formed on the first glass substrate M1. In the first elastic layer forming process, after forming a plasma-polymerized film, i.e., a first elastic layer 551, with siloxane as the main component, on the first inner surface 51A, the first mask M11 is removed by a peeling process. In the second masking process, a second mask M21 covering the second reflective film 582 is formed on the second glass substrate M2. In the second elastic layer forming process, after forming a plasma-polymerized film, i.e., a second elastic layer 552, with siloxane as the main component, on the second inner surface 52A, the second mask M21 is removed. Furthermore, in the first bonding process S5, under a depressurization environment below atmospheric pressure, a first bonding portion 55 is formed to bond the first elastic layer 551 and the second elastic layer 552, thus bonding the first substrate 51 and the second substrate 52.

[0203] In this embodiment, a first elastic layer 551 and a second elastic layer 552, serving as a plasma-polymerized film, are formed during the bonding of the first substrate 51 and the second substrate 52. When the plasma-polymerized film is formed, if the first reflective film 581 and the second reflective film 582 are exposed to plasma, the deterioration of the reflective films will lead to a decrease in the beam splitting characteristics of the interference filter 5. To address this, in this embodiment, the first reflective film 581 and the second reflective film 582 can be protected by forming a first mask M11 and a second mask M21.

[0204] It should be noted that when using metal bonding with a metal film as the first bonding portion 55, these metal layers need to be activated by plasma activation treatment or the like during bonding. However, after activation treatment, the mask cannot be removed by stripping treatment or the like. Therefore, when activating the metal film, the first reflective film 581 and the second reflective film 582 are exposed to plasma, etc., and the characteristics of the interference filter 5 are reduced due to the deterioration of the reflective films. In this embodiment, such adverse conditions can be avoided, and an interference filter 5 with excellent spectral dispersive characteristics can be manufactured.

[0205] In this embodiment, during the manufacturing of the interference filter 5, a first metal forming process and a third metal forming process are performed in the second bonding process S7. In the first metal forming process, a first metal layer 561 is formed on the first outer surface 51B, and in the third metal forming process, a third metal layer 562 is formed on the third inner surface 53A. Furthermore, in the second bonding process S7, a second bonding portion 56 is formed, which is obtained by applying a load in a direction that brings the first substrate 51 and the third substrate 53 closer together, thereby metal bonding the first metal layer 561 and the third metal layer 562, and bonding the first substrate 51 and the third substrate 53 together.

[0206] Furthermore, a second metal forming process and a fourth metal forming process are performed in the third bonding process S6. In the second metal forming process, a second metal layer 571 is formed on the second outer surface 52B, and in the fourth metal forming process, a fourth metal layer 572 is formed on the fourth inner surface 54A. In the third bonding process S6, a third bonding portion 57 is formed to metal bond the second metal layer 571 and the fourth metal layer 572 by applying a load in a direction that brings the second substrate 52 and the fourth substrate 54 closer together, thereby bonding the second substrate 52 and the fourth substrate 54.

[0207] Therefore, as described above, the first substrate 51 and the third substrate 53, and the second substrate 52 and the fourth substrate 54 can be bonded respectively by metal bonding with high bonding strength and high hermeticity. Thus, the high hermeticity of the second internal space Sp2 and the third internal space Sp3 can be maintained.

[0208] In the manufacturing of the interference filter 5 in this embodiment, the second substrate formation process S2 includes: a second substrate etching process, which etches the second outer surface 52B to form a movable portion 521 of a predetermined thickness and a diaphragm portion 522 with a thickness thinner than the movable portion 521; and a second reflective film formation process, which forms a second reflective film 582 on the second inner surface 52A of the movable portion 521. Furthermore, in this embodiment, a third bonding process S6 is performed before the second bonding process S7.

[0209] That is, in this embodiment, in the second substrate forming process S2, a second substrate 52 is formed having a movable portion 521 and a diaphragm portion 522 that holds the movable portion 521 so that it can move. With such a second substrate 52, if stress is directly applied to the movable portion 521, there is a possibility that the diaphragm portion 522 will break or that the movable portion 521 will tilt due to excessive stress. For example, for the first bonding body M10, if the second bonding process S7 is performed before the third bonding process S6, the flat plate member of the clamping device abuts against the second glass substrate M2 of the first bonding body M10, thereby directly applying stress to the movable portion 521 from the flat plate member, which is not preferable.

[0210] In this embodiment, the fourth substrate 54 is bonded to the second substrate 52 by performing a third bonding process S6 before the second bonding process S7. This allows the movable portion 521 of the second substrate 52 to be protected by the fourth substrate 54. In other words, when the second bonding process S7 is performed, the fourth substrate 54 covering the second substrate 52 abuts against the flat plate member of the clamping device, thus preventing direct stress on the second substrate 52 and suppressing tilting of the movable portion 521 and damage to the diaphragm portion 522.

[0211] Other implementation methods

[0212] It should be noted that the present invention is not limited to the aforementioned embodiments, and all modifications and improvements that can achieve the purpose of the present invention are included in the present invention.

[0213] Variation Example 1

[0214] For example, in the above embodiment, the first internal space Sp1 and the third internal space Sp3 are each an independent airtight space; however, the first internal space Sp1 and the third internal space Sp3 may also be connected. More specifically, a through hole may be provided in the diaphragm portion 522 to connect the first internal space Sp1 and the third internal space Sp3. In this case, the internal pressure difference between the first internal space Sp1 and the third internal space Sp3 when the movable part 521 changes can be eliminated, and the driving responsiveness of the movable part 521 can be further improved.

[0215] Variation Example 2

[0216] In the above embodiment, the first joint 55 is exemplified by sealing the gap between the first elastic layer 551 and the second elastic layer 552 at the lead-out portion 511B with the sealing portion 553; however, it is not limited to this. For example, by forming the height position of the first elastic layer 551 at the lead-out portion 511B to the height position of the first elastic layer 551 at the first joint target portion 514, the first elastic layer 551 and the second elastic layer 552 can be joined even at the lead-out portion 511B. Alternatively, at the lead-out portion 511B, the insulating portion 594 can be formed to the height position of the first joint target portion 514, in which case the sealing portion 553 is not required.

[0217] Variation Example 3

[0218] In the above embodiment, in the first bonding process S5, after the first glass substrate M1 and the second glass substrate M2 are bonded in the vacuum chamber, the third bonding process S6, the second bonding process S7, and the cutting process S8 are performed while the first bonded body M10 obtained by bonding is kept in the vacuum chamber, and the sealing part 553 is used for sealing.

[0219] To address this, the bonding of the first elastic layer 551 and the second elastic layer 552 in the first bonding step S5 can also be performed without depressurization. In this case, in the cutting step S8, after cutting out the interference filters 5 on a chip-by-chip basis, each interference filter is placed in a vacuum chamber, and the first internal space Sp1 is depressurized. The gap at the lead-out portion 511B is sealed by the sealing portion 553 constituting the first bonding portion 55.

[0220] Furthermore, as described in Modification 2 above, when the first elastic layer 551 of the lead-out portion 511B is formed at the same height as the first elastic layer 551 on the first bonding target portion 514, and when the insulating portion 594 formed on the lead-out portion 511B is formed at the same height as the first bonding target portion 514 in the first substrate forming process S1, the first internal space Sp1 is sealed by performing the first bonding process S5. Therefore, it is also possible to form the first metal layer 561 and the second metal layer 571 after the first bonding body M10 and the second bonding body M20 are removed from the vacuum chamber.

[0221] Variation Example 4

[0222] In this embodiment, an example is shown where the second joint 56 and the third joint 57 are joined by metal bonding; however, this is not a limitation. Either or both of the second joint 56 and the third joint 57 may also be plasma-polymerized joined, similar to the first joint 55, to join plasma-polymerized films together.

[0223] Variation Example 5

[0224] As the first bonding portion 55, an example is shown where a first elastic layer 551 and a second elastic layer 552, which are plasma polymer films with siloxane as the main component, are formed and these first elastic layers 551 and second elastic layers 552 are bonded by siloxane bonds, but it is not limited to this. The first elastic layer 551 and the second elastic layer 552 may also be formed from raw materials such as resins with an elastic modulus lower than that of metals.

[0225] Furthermore, the first bonding portion 55 can also be metal-bonded using a metal film, similar to the second bonding portion 56 and the third bonding portion 57. In this case, during bonding, if foreign matter or the like adheres to the metal film, there is a possibility that the parallelism between the first reflective film 581 and the second reflective film 582 may deteriorate. To address this, by forming a base layer made of resin or the like between the first substrate 51 and the metal layer, and between the second substrate 52 and the metal layer, the influence of foreign matter can be suppressed.

[0226] Variation Example 6

[0227] In the above embodiments, an electrostatic actuator 59 is shown as an example of a gap changing unit that drives the movable part 521; however, it is not limited to this.

[0228] For example, the gap changing part can be configured as an induction actuator consisting of a first induction coil provided on the first substrate 51 and a second induction coil or permanent magnet provided on the second substrate 52.

[0229] Alternatively, a piezoelectric actuator can be used instead of the electrostatic actuator 59. In this case, for example, a lower electrode layer, a piezoelectric film, and an upper electrode layer are stacked in the diaphragm portion 522. By using the voltage applied between the lower electrode layer and the upper electrode layer as an input value and making it variable, the piezoelectric film can be stretched and contracted, causing the diaphragm portion 522 to flex.

[0230] Variation Example 7

[0231] Furthermore, the present invention can also be applied to wavelength-fixed Fabry-Perot etalons without a gap changing section.

[0232] In the wavelength-fixed interference filter, the movable part 521 and the diaphragm part 522 as described in the above embodiment are not provided, and the gap G1 between the first substrate 51 and the second substrate 52 is maintained at a constant value.

[0233] At this time, the first substrate 51 and the second substrate 52 are joined with high airtightness through the first joint 55, thus effectively preventing foreign matter from entering between the first substrate 51 and the second substrate 52 and suppressing the deterioration of the reflective films 581 and 582. Furthermore, the third substrate 53 is joined to the first substrate 51 through the second joint 56, and the fourth substrate 54 is joined to the second substrate 52 through the third joint 57. Therefore, regardless of the installation environment of the interference filter 5, the pressure difference between the first internal space Sp1, the second internal space Sp2, and the third internal space Sp3 remains constant. That is, even if the third substrate 53 and the fourth substrate 54 are subjected to pressure due to the installation environment of the interference filter, the second internal space Sp2 and the third internal space Sp3 will function as buffers, and the internal pressure change of the first internal space Sp1 will be suppressed. Thus, the parallelism of the first reflective film 581 and the second reflective film 582 can be maintained to a high degree.

[0234] Variation Example 8

[0235] In the above embodiments, as an example of an electronic device equipped with the interference filter 5, the spectrophotometer 1 is shown; however, it is not limited to this. In addition to the electronic device equipped with the interference filter 5, it can also be appropriately assembled into electronic devices such as spectrophotometers and light source devices that select a predetermined wavelength from the incident light and emit it.

Claims

1. An interference filter, characterized by Possessing: a first substrate having a first inner surface and a first outer surface facing each other, a first reflecting film being provided on the first inner surface; a second substrate having a second inner surface and a second outer surface facing each other, a second reflecting film being provided on the second inner surface so as to face the first reflecting film; a first bonding portion bonding the first inner surface and the second inner surface to each other, the first bonding portion sealing a first internal space between the first substrate and the second substrate; a third substrate having a light-transmitting property, the third substrate facing the first outer surface; a second bonding portion bonding the first outer surface and the third substrate to each other, the second bonding portion sealing a second internal space between the first substrate and the third substrate; a fourth substrate having a light-transmitting property, the fourth substrate facing the second outer surface; and a third bonding portion bonding the second outer surface and the fourth substrate to each other, the third bonding portion sealing a third internal space between the second substrate and the fourth substrate, the first internal space, the second internal space, and the third internal space are depressurized to be lower than an atmospheric pressure, a substrate thickness of the first substrate is greater than the second substrate, the second substrate includes a movable portion provided with the second reflecting film, a diaphragm portion surrounding an outer periphery of the movable portion, the diaphragm portion having a thickness smaller than the movable portion, and a substrate outer periphery portion provided outside the diaphragm portion, the substrate outer periphery portion having a thickness greater than the diaphragm portion, the interference filter is provided with an electrostatic actuator that displaces the movable portion toward the first substrate side.

2. The interference filter according to claim 1, wherein the second bonding portion bonds the first substrate and the third substrate by metal bonding of a first metal layer provided on the first outer surface and a third metal layer provided on a third opposing surface of the third substrate facing the first substrate, the third bonding portion bonds the second substrate and the fourth substrate by metal bonding of a second metal layer provided on the second outer surface and a fourth metal layer provided on a fourth opposing surface of the fourth substrate facing the second substrate.

3. The interference filter according to claim 1 or 2, wherein the first bonding portion bonds the first substrate and the second substrate by an elastic layer having an elastic modulus smaller than an elastic modulus of a metal film.

4. The interference filter according to claim 3, wherein the elastic layer is a plasma polymerized film having siloxane as a main component. Implementation:

5. A method of manufacturing an interference filter, characterized by, a first substrate forming process in which a first reflecting film is formed on a first inner surface of a first substrate having a first inner surface and a first outer surface facing each other; a second substrate forming process in which a second reflecting film is formed on a second inner surface of a second substrate having a second inner surface and a second outer surface facing each other; a third substrate forming process in which a third substrate having a light-transmitting property is formed, the third substrate facing the first outer surface; a first bonding process of bonding the first inner surface and the second inner surface to each other by a first bonding portion in a reduced-pressure environment reduced to a pressure lower than an atmospheric pressure, and sealing a first internal space between the first substrate and the second substrate; a second bonding process of bonding the first outer surface and a third substrate that is transparent to light to each other by a second bonding portion in a reduced-pressure environment reduced to a pressure lower than an atmospheric pressure, and sealing a second internal space between the first substrate and the third substrate; a third bonding process of bonding the second outer surface and a fourth substrate that is transparent to light to each other by a third bonding portion in a reduced-pressure environment reduced to a pressure lower than an atmospheric pressure, and sealing a third internal space between the second substrate and the fourth substrate, in the first substrate forming process, the first substrate is formed, the first substrate has a substrate thickness greater than the second substrate, in the second substrate forming process, the second substrate is formed, the second substrate includes a movable portion, a diaphragm portion, and a substrate peripheral portion, the movable portion is provided with a second reflective film, the diaphragm portion surrounds a periphery of the movable portion, and the diaphragm portion has a thickness smaller than the movable portion, the substrate peripheral portion is provided outside the diaphragm portion, and the substrate peripheral portion has a thickness greater than the diaphragm portion, and the movable portion is capable of being displaced to the first substrate side by an electrostatic actuator. The manufacturing method includes:

6. The method of manufacturing an interference filter according to claim 5, wherein, a first masking process of covering the first reflective film with a first mask; a first elastic layer forming process of forming a first elastic layer on the first inner surface, and removing the first mask, the first elastic layer being a plasma polymerization film in which siloxane is a main component; a second masking process of covering the second reflective film with a second mask; and a second elastic layer forming process of forming a second elastic layer on the second inner surface, and removing the second mask, the second elastic layer being a plasma polymerization film in which siloxane is a main component, in the first bonding process, the first bonding portion obtained by bonding the first elastic layer of the first inner surface and the second elastic layer of the second inner surface to each other is formed in a reduced-pressure environment reduced to a pressure lower than an atmospheric pressure, and the first substrate and the second substrate are bonded to each other. The manufacturing method includes:

7. The method of manufacturing an interference filter according to claim 5 or 6, characterized in that, a first metal forming process of forming a first metal layer on the first outer surface; a third metal forming process of forming a third metal layer on a third opposing surface of the third substrate that opposes the first substrate; a second metal forming process of forming a second metal layer on the second outer surface; and a fourth metal forming process of forming a fourth metal layer on a fourth opposing surface of the fourth substrate that opposes the second substrate, in the second bonding process, the second bonding portion obtained by causing the first metal layer and the third metal layer to be metal-bonded by applying a load in a direction in which the first substrate and the third substrate are caused to approach each other is formed, and the first substrate and the third substrate are bonded to each other, ​ In the third joining process, the third joining portion obtained by metal bonding the second metal layer and the fourth metal layer by applying a load in a direction in which the second substrate and the fourth substrate are brought close to each other is formed, and the second substrate and the fourth substrate are joined.

8. The method of manufacturing an interference filter according to claim 7, wherein the second substrate forming process includes: a second substrate etching process of performing an etching process on the second outer surface to form the movable portion having a predetermined thickness and the diaphragm portion having a thickness thinner than that of the movable portion; and a second reflective film forming process of forming the second reflective film on the second inner surface of the movable portion, the third joining process is performed before the second joining process.

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