Interference filter and method for manufacturing the interference filter

Abstract

To provide an interference filter that has high drive responsiveness and can accurately disperse light with a desired target wavelength, and a method for manufacturing an interference filter.SOLUTION: An interference filter comprises: a light-transmissive first substrate that has a first inner surface and a first outer surface opposite to each other and is provided with a first reflection coating on the first inner surface; a light-transmissive second substrate that has a second inner surface and a second outer surface opposite to each other and is provided with a second reflection coating on the second inner surface; a first junction that joins the first inner surface and the second inner surface to each other to seal a first internal space between the first substrate and the second substrate; a light-transmissive third substrate that is opposite to the first outer surface; a second junction that joins the first outer surface and the third substrate to each other to seal a second internal space between the first substrate and the third substrate; a light-transmissive fourth substrate that is opposite to the second outer surface; and a third junction that joins the second outer surface and the fourth substrate to each other to seal a third internal space between the second substrate and the fourth substrate. The first internal space, second internal space, and third internal space have a reduced pressure below the atmospheric pressure.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an interference filter and a method for manufacturing the interference filter.

Background Art

[0002] Conventionally, there is known an interference filter including a first substrate provided with a first reflection film and a second substrate provided with a second reflection film, wherein the first substrate and the second substrate are disposed opposite to each other and joined such that the first reflection film and the second reflection film face each other with a gap therebetween. Such an interference filter can emit light of a desired wavelength from incident light according to the dimension of the gap between the first reflection film and the second reflection film. Further, for example, a movable part held by a diaphragm or the like is provided on the second substrate, and the second reflection film is provided on the movable part, and the movable part is displaced toward the first substrate side by a driving means such as an electrostatic actuator, whereby the wavelength of the light emitted from the interference filter can be changed. 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, and the spaces between the first substrate and the second substrate and between the second substrate and the third substrate are each maintained in a reduced pressure state. Thereby, it becomes possible to improve the driving responsiveness when driving the movable part (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in an interference filter such as Patent Document 1 above, the pressure on the side of the first substrate opposite to the second substrate is atmospheric pressure, and due to the difference between the pressure between the first substrate and the second substrate and the pressure on the side of the first substrate opposite to the second substrate, the first substrate may bend. Since the first reflection film is provided on the first substrate, when such bending occurs, the dimension of the gap between the first reflection film and the second reflection film changes depending on the position, and noise increases in the wavelength of the light emitted from the interference filter. That is, the spectral accuracy by the interference filter decreases so that not only the light of the desired target wavelength but also the light of a plurality of wavelength components is included in the emitted light. In particular, in an interference filter that spectrally disperses light in the near-infrared region, etc., light with a narrow wavelength half-width may be emitted, and in such an interference filter, the influence of the bending of the first substrate described above becomes large.

[0005] In view of the above problems, an object of the present invention is to provide an interference filter having high driving responsiveness and capable of accurately spectrally dispersing light of a desired target wavelength, and a method for manufacturing the interference filter.

Means for Solving the Problems

[0006] An interference filter according to a first aspect of the present disclosure is a first substrate having a first inner surface and a first outer surface facing each other, the first substrate being a light-transmissive substrate provided with a first reflection film on the first inner surface, and A second substrate having a second inner surface and a second outer surface facing each other, the second substrate being translucent and having a second reflective film provided on the second inner surface facing the first reflective film; a first joint portion joining the first inner surface and the second inner surface to each other, the first joint portion sealing a first internal space between the first substrate and the second substrate; a translucent third substrate facing the first outer surface; a second joint portion joining the first outer surface and the third substrate to each other, the second joint portion sealing a second internal space between the first substrate and the third substrate; a translucent fourth substrate facing the second outer surface; and a third joint portion joining the second outer surface and the fourth substrate to each other, 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 relative to atmospheric pressure.

[0007] In the interference filter according to this aspect, the second joint portion joins the first substrate and the third substrate by metal-bonding a first metal layer provided on the first outer surface and a third metal layer provided on a third facing surface of the third substrate facing the first substrate, and the third joint portion joins the second substrate and the fourth substrate by metal-bonding a second metal layer provided on the second outer surface and a fourth metal layer provided on a fourth facing surface of the fourth substrate facing the second substrate.

[0008] In the interference filter of this aspect, the first joint portion joins the first substrate and the second substrate with an elastic layer having a lower elastic modulus than that of a metal film.

[0009] In the interference filter according to this aspect, the elastic layer is a plasma polymerization film mainly composed of siloxane.

[0010] The method for manufacturing an interference filter according to the second aspect of the present disclosure includes a first substrate forming step of forming a first reflective film on the first inner surface of a light-transmissive first substrate having a first inner surface and a first outer surface facing each other; a second substrate forming step of forming a second reflective film on the second inner surface of a light-transmissive second substrate having a second inner surface and a second outer surface facing each other; a first bonding step of bonding the first inner surface and the second inner surface to each other by a first bonding portion in a reduced-pressure environment that is lower than atmospheric pressure, and sealing a first internal space between the first substrate and the second substrate; a second bonding step of bonding the first outer surface and a light-transmissive third substrate to each other by a second bonding portion in a reduced-pressure environment that is lower than atmospheric pressure, and sealing a second internal space between the first substrate and the third substrate; and a third bonding step of bonding the second outer surface and a light-transmissive fourth substrate to each other by a third bonding portion in a reduced-pressure environment that is lower than atmospheric pressure, and sealing a third internal space between the second substrate and the fourth substrate.

[0011] In the method for manufacturing an interference filter of this aspect, it includes a first masking step of covering the first reflective film with a first mask; a first elastic layer forming step of forming a first elastic layer, which is a plasma polymerization film mainly composed of siloxane, on the first inner surface and removing the first mask; a second masking step of covering the second reflective film with a second mask; a second elastic layer forming step of forming a second elastic layer, which is a plasma polymerization film mainly composed of siloxane, on the second inner surface and removing the second mask. The first bonding step forms the first bonding portion by bonding the first elastic layer on the first inner surface and the second elastic layer on the second inner surface to each other in a reduced-pressure environment that is lower than atmospheric pressure, and bonds the first substrate and the second substrate to each other.

[0012] In the method for manufacturing the interference filter of this aspect, a first metal forming step of forming a first metal layer on the first outer surface, a third metal forming step of forming a third metal layer on a third opposing surface of the third substrate facing the first substrate, a second metal forming step of forming a second metal layer on the second outer surface, and a fourth metal forming step of forming a fourth metal layer on a fourth opposing surface of the fourth substrate facing the second substrate are included. In the second bonding step, a load is applied in a direction in which the first substrate and the third substrate approach each other to form the second joint portion in which the first metal layer and the third metal layer are metallically bonded, thereby bonding the first substrate and the third substrate. In the third bonding step, a load is applied in a direction in which the second substrate and the fourth substrate approach each other to form the third joint portion in which the second metal layer and the fourth metal layer are metallically bonded, thereby bonding the second substrate and the fourth substrate.

[0013] In the method for manufacturing the interference filter of this aspect, the second substrate forming step includes a second substrate etching step of etching the second outer surface to form a movable portion having a predetermined thickness and a diaphragm portion having a thickness thinner than that of the movable portion, and a second reflective film forming step of forming the second reflective film on the second inner surface of the movable portion. The third bonding step is performed before the second bonding step.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Configuration of Spectrophotometer] FIG. 1 is a diagram showing a schematic configuration of the spectrophotometer according to the present embodiment. The spectrophotometer 1 is an example of an electronic device equipped with the interference filter of the present invention, and is a device that analyzes the light intensity of each wavelength in the measurement target light reflected by the measurement target X and measures the spectral spectrum. In the present embodiment, an example of measuring the measurement target light reflected by the measurement target X is shown. However, when a light emitter such as a liquid crystal panel is used as the measurement target X, the light emitted from the light emitter may be used as the measurement target light. Further, as an example of an electronic device, the spectrophotometer 1 is exemplified, but the present invention is not limited thereto, and the interference filter of the present invention can also be applied to, for example, a spectral camera or a light source device. As shown in FIG. 1, the spectrophotometer 1 of the present embodiment includes an optical module 10 and a control unit 20 that processes a signal output from the optical module 10.

[0016] [Configuration of Optical Module] The optical module 10 includes an interference filter 5, a detector 11, an I-V converter 12, an amplifier 13, an A / D converter 14, and a voltage control unit 15. This optical module 10 guides the measurement target light reflected by the measurement target X to the interference filter 5 via an incident optical system (not shown in detail), and the light output from the interference filter 5 is received by the detector 11. Then, the detection signal output from the detector 11 is output to the control unit 20 via the I-V converter 12, the amplifier 13, and the A / D converter 14.

[0017] [Configuration of the interference filter] Next, the interference filter 5 incorporated in the optical module 10 will be described. Figure 2 is a plan view showing the schematic configuration of the interference filter 5. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. As shown in FIGS. 2 and 3, the interference filter 5 is configured by laminating and bonding four sheets of a first substrate 51, a second substrate 52, a third substrate 53, and a fourth substrate 54. These substrates 51, 52, 53, 54 are each a light-transmissive substrate. For example, when the wavelength of the light spectrally separated by the interference filter is in the visible light region, soda glass, crystalline glass, quartz glass, etc. can be used, and when it is in the near-infrared region or the infrared region, silicon or the like may be used. That is, the substrates 51, 52, 53, 54 are formed of a substrate capable of transmitting the light spectrally separated by the interference filter 5.

[0018] More specifically, the first substrate 51 has a first inner surface 51A and a first outer surface 51B facing each other. That is, in the first substrate 51, the first inner surface 51A and the first outer surface 51B are front and back surfaces of each other. The second substrate 52 has a first inner surface 51A and a first outer surface 51B facing each other. That is, in the second substrate 52, the second inner surface 52A and the second outer surface 52B are front and back surfaces of each other. The first substrate 51 and the second substrate 52 are arranged with the first inner surface 51A and the second inner surface 52A facing each other and are joined by the first joint portion 55. The third substrate 53 has a third inner surface 53A and a third outer surface 53B that are front and back surfaces of each other, and the fourth substrate 54 has a fourth inner surface 54A and a fourth outer surface 54B that are front and back surfaces of each other. The third inner surface 53A of the third substrate 53 corresponds to the third opposing surface in the present invention, faces the first outer surface 51B of the first substrate 51, and is joined to the first outer surface 51B by the second joining portion 56. The fourth inner surface 54A of the fourth substrate 54 corresponds to the fourth opposing surface in the present invention, faces the second outer surface 52B of the second substrate 52, and is joined to the second outer surface 52B by the third joining portion 57. Details of the configurations of these joining portions 55, 56, and 57 will be described later.

[0019] Also, a first reflection film 581 is provided on the first inner surface 51A of the first substrate 51, and a second reflection film 582 is provided on the second inner surface 52A of the second substrate 52. These first reflection film 581 and second reflection film 582 are arranged to face each other with a gap G1 therebetween. And in a plan view of the first substrate 51 and the second substrate 52 as seen from the thickness direction, an optical interference region is formed by a region where these first reflection film 581 and second reflection film 582 overlap.

[0020] The interference filter 5 is provided with a gap changing portion used to adjust the dimension of the gap G1. The configuration of the gap changing portion is not particularly limited, but in this embodiment, an electrostatic actuator 59 is exemplified as the gap changing portion. By applying a predetermined voltage between the opposing electrodes of such an electrostatic actuator 59, the dimension of the gap G1 can be easily changed by electrostatic attraction, and simplification of the configuration can be achieved. The electrostatic actuator 59 can be driven under the control of the voltage control unit 15. In the following description, a plan view of the interference filter 5 as seen from the thickness direction of each of the substrates 51, 52, 53, and 54, that is, a plan view of the interference filter 5 as seen from the stacking direction of the third substrate 53, the first substrate 51, the second substrate 52, and the fourth substrate 54, is referred to as a filter plan view. Also, in this embodiment, in the filter plan view, it is assumed that the center point of the first reflection film 581 and the center point of the second reflection film 582 coincide with each other. The center point of these reflection films in the filter plan view is referred to as the filter center point O, and a straight line passing through the center points of these reflection films is referred to as the central axis. Hereinafter, the configurations of the respective substrates 51, 52, 53, and 54 will be described in more detail.

[0021] (Configuration of the first substrate 51) FIG. 4 is a plan view of the first substrate 51 of the present embodiment as viewed from the side of the second substrate 52. The first substrate 51 is formed to have a larger thickness dimension than the second substrate 52, and there is no bending of the first substrate 51 due to the electrostatic attraction by the electrostatic actuator 59 or the internal stress of the film member (for example, the first reflective film 581, etc.) formed on the first substrate 51. As shown in FIGS. 3 and 4, this first substrate 51 includes, for example, an electrode arrangement groove 511 and a reflective film installation portion 512 formed by etching or the like. Also, one end portion (side C3 - C4) of the first substrate 51 protrudes outside the outer peripheral edges (side C5 - C6) of the second substrate 52 and the fourth substrate 54 in a plan view of the filter, and a terminal portion 513 is formed by this protruding portion.

[0022] The electrode arrangement groove 511 includes, for example, an annular portion 511A formed in an annular shape centered on the filter center point O of the first substrate 51 in a plan view of the filter, and a lead - out portion 511B continuous from the annular portion 511A toward the outer edge of the substrate. In the example shown in FIG. 4, the shape of the annular portion 511A in a plan view of the filter is substantially annular, but it may be rectangular - frame - shaped or other polygonal shapes. The lead - out portion 511B extends from the annular portion 511A to the terminal portion 513 of the side C3 - C4 of the first substrate 51. Also, the terminal portion 513 is formed in the same plane as the groove bottom surface of the electrode arrangement groove 511. The groove bottom surface of this electrode arrangement groove 511 is where the first electrode 591 constituting the electrostatic actuator 59 is arranged. The first electrode 591 may be provided directly on the groove bottom surface of the electrode arrangement groove 511, or another thin - film layer may be provided on the groove bottom surface and the first electrode 591 may be installed on the thin - film layer.

[0023] The first electrode 591 is formed in a substantially annular shape, preferably in an annular shape. Here, the substantially annular shape mentioned includes shapes with a notch in part, such as a C-shaped one. In this embodiment, an example where one first electrode 591 is provided is shown. However, for example, a plurality of annular electrodes may be arranged concentrically, and these plurality of electrodes may be configured to be independent (insulated) from each other. And a first lead-out electrode 591A is connected to the first electrode 591. This first lead-out electrode 591A 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 by, for example, wire bonding or an FPC. Examples of materials for forming such a first electrode 591 and a first lead-out electrode 591A include an Au / Cr film, ITO (Indium Tin Oxide), etc. Also, an insulating film may be formed on the surface of the first electrode 591.

[0024] Furthermore, on the lead-out portion 511B, a bump electrode 593 is formed with a resin such as polyimide as a core 593A and plated 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 unit 15 by, for example, wire bonding or an FPC. Note that the bump electrode 593 and the first lead-out electrode 591A do not contact each other and are in an insulating relationship.

[0025] The reflection film installation portion 512 is arranged on the center side of the electrode arrangement groove 511 in a plan view of the filter, and is formed to protrude, for example, toward the second substrate 52 side. A first reflection film 581 is arranged on the protruding front end surface of the reflection film installation portion 512. In this embodiment, a configuration where the reflection film installation portion 512 protrudes toward the second substrate 52 from the groove bottom surface of the electrode arrangement groove 511 is illustrated, but it is not limited to this. For example, the reflection film installation portion 512 may be formed in a concave shape, the bottom surface of the reflection film installation portion 512 may be located away from the groove bottom surface of the electrode arrangement groove 511 from the second substrate 52, and the first reflection film 581 may be provided on the bottom surface. Or the reflection film installation portion 512 may be on the same plane as the groove bottom surface of the electrode arrangement groove 511.

[0026] The first reflective film 581 installed in the reflective film installation part 512 may be directly provided in the reflective film installation part 512, or other thin films (layers) may be provided on the reflective film installation part 512 and the first reflective film 581 may be installed thereon. As the first reflective film 581, for example, a metal film such as Ag or a conductive alloy film such as an Ag alloy can be used. When using a metal film such as Ag, it is preferable to form a protective film to suppress the deterioration of Ag. Also, for example, a high refractive index layer is TiO 2 and a low refractive index layer is SiO 2 and a dielectric multilayer film formed by alternately laminating a high refractive index layer and a low refractive index layer may be used, or a reflective film formed by laminating a dielectric multilayer film and a metal film, a reflective film formed by laminating a dielectric single layer film and an alloy film, etc. may also be used.

[0027] The first reflective film 581 faces the second reflective film 582 of the second substrate 52 with a gap G1 therebetween. Here, in the present 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, but it is not limited thereto. For example, depending on the wavelength range of the measurement target light, such as when using infrared light or far-infrared light as the measurement target light, the gap G1 may be configured to be larger than the gap between the electrodes 591 and 592. In this case, as described above, the reflective film installation part 512 of the first substrate 51 is formed in a concave shape.

[0028] In a plan view of the filter, the regions other than the electrode arrangement groove 511, the reflective film installation part 512, and the terminal part 513 become the first bonding target part 514. The first inner surface 51A of the first bonding target part 514, that is, the surface facing the second substrate 52, is bonded to the second substrate 52 by the first bonding part 55. The first outer surface 51B of the first bonding target part 514, that is, the surface facing the third substrate 53, is bonded to the third substrate 53 by the second bonding part 56.

[0029] The first outer surface 51B of the first substrate 51 is formed in a plane as shown in FIG. 3 and is parallel to the first reflection film 581. Note that, on this first outer surface 51B, an antireflection film (not shown) may be provided in a region overlapping the first reflection film 581 in a plan view of the filter. When such an antireflection film is provided, the light reflectance on the surface of the first outer surface 51B can be reduced and the transmittance can be increased.

[0030] (Configuration of the second substrate) FIG. 5 is a plan view of the second substrate 52 in the interference filter 5 of the present embodiment as viewed from the first substrate 51 side. As shown in FIGS. 2, 3, and 5, the second substrate 52 includes a circular movable portion 521 centered on the filter center point O in a plan view of the filter, a diaphragm portion 522 that is coaxial with the movable portion 521 and holds the movable portion 521, and a substrate outer peripheral portion 523 provided outside the diaphragm portion 522.

[0031] The movable portion 521 is formed to have a greater thickness than the diaphragm portion 522. For example, in the present embodiment, it is formed to have the same dimension as the thickness of the second substrate 52 (substrate outer peripheral portion 523). In a plan view of the filter, the movable portion 521 is formed to have a diameter dimension larger than at least the diameter dimension of the outer peripheral edge of the reflection film installation portion 512. On the side of the second inner surface 52A of the movable portion 521 facing the first substrate 51, a second reflection film 582 and a second electrode 592 constituting an electrostatic actuator 59 are provided. The second reflection film 582 and the second electrode 592 may be provided directly on the second inner surface 52A, or another thin film (layer) may be provided on the second inner surface 52A and they may be provided thereon.

[0032] The second electrode 592 is formed in a substantially annular shape, similar to the first electrode 591, and preferably forms an annular shape around the filter center point O. Also, similar to the first electrode 591, the second electrode 592 may be configured in a shape where a part of the ring is cut out, such as a C-shaped etc., or may be composed of a plurality of annular electrodes. In this embodiment, an example is shown where the second electrode 592 is provided on the second inner surface 52A of the movable part 521, but it is not limited to this. For example, the second electrode 592 may be provided across the diaphragm part 522 from the movable part 521 on the second inner surface 52A of the second substrate 52, or may be provided on the diaphragm part 522.

[0033] A second lead-out electrode 592A is connected to the second electrode 592, and this second lead-out electrode 592A is drawn out to the outer peripheral edge of the second substrate 52 along the region facing the lead-out part 511B. More specifically, the second lead-out electrode 592A is provided to face the bump electrode 593 and contacts the bump electrode 593 on the core 593A. Thereby, the second electrode 592 is connected to the voltage control unit 15 via the bump electrode 593. As materials for forming such a second electrode 592 and a second lead-out electrode 592A, similar to the first electrode 591, for example, an Au / Cr film, ITO (Indium Tin Oxide), etc. can be used.

[0034] The second reflective film 582 is provided facing the first reflective film 581 with a gap G1 at the center of the movable part 521. As this second reflective film 582, a reflective film having the same configuration as the above-described first reflective film 581 is used.

[0035] The diaphragm part 522 is a diaphragm surrounding the periphery of the movable part 521 and is formed to be thinner than the movable part 521. Such a diaphragm part 522 is more flexible than the movable part 521, and it is possible to displace the movable part 521 toward the first substrate 51 side by a slight electrostatic attraction force. At this time, since the movable part 521 has a larger thickness dimension and higher rigidity than the diaphragm part 522, even when the movable part 521 is pulled toward the first substrate 51 side by the electrostatic attraction force, a change in the shape of the movable part 521 can be suppressed. In addition, in the present embodiment, a diaphragm-shaped diaphragm portion 522 is illustrated, but the present invention is not limited thereto. For example, a configuration in which beam-shaped holding portions arranged at equal angular intervals are provided around the filter center point O of the movable portion 521 may be adopted.

[0036] The outer peripheral portion 523 of the substrate is a portion provided outside the diaphragm portion 522 in a plan view of the filter. The second inner surface 52A of the outer peripheral portion 523 of the substrate is joined to the first joining target portion 514 of the first substrate 51 by the first joining portion 55. The second outer surface 52B of the outer peripheral portion 523 of the substrate is joined to the fourth substrate 54 by the third joining portion 57.

[0037] (Configuration of the third substrate) The third substrate 53 is formed by processing a light-transmissive parallel plate substrate by etching. Specifically, the third substrate 53 includes a third substrate recess 531 formed in a concave shape by etching at a position overlapping the electrode arrangement groove 511 and the reflection film installation portion 512 in a plan view of the filter. The groove bottom surface of the third substrate recess 531 is flat and parallel to the first outer surface 51B and the reflection films 581 and 582. In addition, the portion of the third substrate 53 where the third substrate recess 531 is not provided becomes the third joining target portion 532. The third inner surface 53A of the third joining target portion 532, that is, the surface facing the first substrate 51, is joined to the first joining target portion 514 of the first substrate 51 by the second joining portion 56.

[0038] (Configuration of the fourth substrate) The fourth substrate 54 has substantially the same shape as the third substrate 53 and is formed by processing a light-transmissive parallel plate substrate by etching. Specifically, the fourth substrate 54 includes a fourth substrate recess 541 formed in a concave shape by etching at a position overlapping the movable portion 521 and the diaphragm portion 522 in a plan view of the filter. The groove bottom surface of the fourth substrate recess 541 is flat and parallel to the second outer surface 52B and the reflection films 581 and 582. Further, the portion of the fourth substrate 54 where the fourth substrate recess 541 is not provided becomes the fourth bonding target portion 542. The fourth inner surface 54A in the fourth bonding target portion 542, that is, the surface facing the second substrate 52, is bonded to the outer peripheral portion 523 of the substrate of the second substrate 52 by the third bonding portion 57.

[0039] Although not shown, an optical film such as an antireflection film or a band-pass filter may be formed on the third substrate 53 and the fourth substrate 54 as described above. When the antireflection film is provided, the reflection of light on the surfaces of the third substrate 53 and the fourth substrate 54 can be suppressed. Further, by providing a band-pass filter that reflects or absorbs light having a wavelength outside a specific range, light outside the measurement target in the spectroscopic measurement device 1 can be cut off. For example, in the spectroscopic measurement device 1 that performs spectroscopic measurement on the visible light region, a band-pass filter that shields the infrared region and the ultraviolet region is provided. Such a band-pass filter or antireflection film may 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 may be provided at a plurality of locations.

[0040] (Configuration of the first bonding portion) Next, the first bonding portion 55 that bonds the first substrate 51 and the second substrate 52 will be described. As shown in FIG. 3, the first bonding portion 55 includes a first elastic layer 551 provided on the first inner surface 51A of the first substrate 51 and a second elastic layer 552 provided on the second inner surface 52A of the second substrate 52. Specifically, these first elastic layer 551 and second elastic layer 552 are plasma polymerization films mainly composed of siloxane, and the first elastic layer 551 and the second elastic layer 552 are bonded by siloxane bonds. By using the bonding of substrates using such a plasma polymerization film, it becomes possible to highly maintain the parallelism between the substrates. That is, since the plasma polymerization film has elasticity compared to, for example, a metal layer used for metal bonding, even when foreign matter or the like adheres to the surface of the plasma polymerization film, it can be elastically deformed to suppress deterioration of parallelism due to foreign matter. By bonding using such a plasma polymerization film, the parallelism between the first reflection film 581 and the second reflection film 582 is highly maintained, so that the wavelength spectral characteristics in the interference filter 5 can be made highly accurate. That is, the inconvenience that the dimension of the gap G1 changes depending on the position in the interference region is suppressed, and light of the target wavelength corresponding to the gap G1 can be transmitted from each position, and the inconvenience that the wavelength half-value width of the emitted light widens due to the output of light other than the target wavelength is suppressed.

[0041] FIG. 6 is a cross-sectional view showing a cross-sectional structure in the vicinity of the lead-out portion 511B of the interference filter 5. In FIG. 6, the third substrate 53, the fourth substrate 54, the second bonding portion 56, and the third bonding portion 57 are omitted. Incidentally, 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 becomes larger than the dimension between the first bonding target portion 514 and the outer peripheral portion 523 of the substrate. For this reason, the first elastic layer 551 and the second elastic layer 552 do not come into contact with each other. Therefore, in the present embodiment, airtightness is ensured in this region by the configuration shown in FIG. 6. That is, in the lead-out portion 511B, an insulating portion 594 is provided so as to cover the first lead-out electrode 591A and the bump electrode 593. Note that since the portion where the core 593A of the bump electrode 593 is provided needs to be electrically connected to the second lead-out electrode 592A, the insulating portion 594 is not provided. Further, as shown in FIGS. 3 and 6, the first elastic layer 551 and the second elastic layer 552 constituting the first bonding portion 55 are provided on the terminal portion 513 side rather than the position where the core 593A is provided in the lead-out portion 511B, and the first elastic layer 551 is provided on the insulating portion 594 as shown in FIGS. 3 and 6. And the first joint portion 55 further has a sealing portion 553 at the lead-out portion 511B, and the sealing portion 553 seals the space between the first elastic layer 551 and the second elastic layer 552. As such a sealing portion 553, for example, an adhesive, a low melting point glass, a low melting point metal, etc. can be used, and a low melting point metal with particularly little outgassing and high airtightness is preferable. Although the configuration in which the sealing portion 553 fills the space between the first elastic layer 551 and the second elastic layer 552 at the lead-out portion 511B is illustrated, it is not limited thereto. For example, the first elastic layer 551 at the lead-out portion 511B may be formed to the same height as the first elastic layer 551 of the first joint target portion 514. In this case, the lead-out portion 511B can be sealed by the first elastic layer 551 and the second elastic layer 552 without providing the sealing portion 553.

[0042] With the above configuration, the first internal space Sp1 surrounded by the first substrate 51, the second substrate 52, and the first joint portion 55 is maintained airtight. The joining of the first substrate 51 and the second substrate 52 by the first joint portion 55 is performed in a vacuum chamber. Thereby, the internal pressure of the first internal space Sp1 is maintained in a reduced pressure environment that is lower than the atmospheric pressure, and preferably maintained in a vacuum.

[0043] (Configuration of the second joint portion and the third joint portion) Next, the second joint portion 56 and the third joint portion 57 will be described. As shown in FIG. 3, the second joint portion 56 includes a first metal layer 561 provided on the first outer surface 51B of the first substrate 51 and a third metal layer 562 provided on the third inner surface 53A of the third substrate 53, and the first metal layer 561 and the third metal layer 562 are joined by metal bonding. As these first metal layer 561 and third metal layer 562, for example, various metal films and alloy films such as Au and Ti can be used, and it is preferable to use Au which is relatively flexible (has a large plasticity) in metals and enables joining with high joining strength and high airtightness by metal bonding. As a result, the second internal space Sp2 surrounded by the first substrate 51, the third substrate 53, and the second joint 56 is maintained airtight. Note that the joining of the first substrate 51 and the third substrate 53 by the second joint 56 is performed in a vacuum chamber. Thereby, the internal pressure of the second internal space Sp2 is maintained in a reduced-pressure environment that is lower than the atmospheric pressure, and preferably maintained in a vacuum.

[0044] The third joint 57 has the same configuration as the second joint 56 and joins the second substrate 52 and the fourth substrate 54 by metal bonding. That is, the third joint 57 includes a second metal layer 571 provided on the second outer surface 52B of the second substrate 52 and a fourth metal layer 572 provided on the fourth inner surface 54A of the fourth substrate 54, and the second metal layer 571 and the fourth metal layer 572 are joined by metal bonding. As these second metal layer 571 and fourth metal layer 572, similar to the second joint 56, various metal films and alloy films such as Au and Ti can be used, and it is preferable to use Au which is relatively flexible (has a large plasticity) in metals and enables joining with high joint strength and high airtightness by metal bonding. As a result, the third internal space Sp3 surrounded by the second substrate 52, the fourth substrate 54, and the third joint 57 is maintained airtight. Note that the joining of the second substrate 52 and the fourth substrate 54 by the third joint 57 is performed in a vacuum chamber. Thereby, the internal pressure of the third internal space Sp3 is maintained in a reduced-pressure environment that is lower than the atmospheric pressure, and preferably maintained in a vacuum.

[0045] Note that the first metal layer 561, the third metal layer 562, the second metal layer 571, and the fourth metal layer 572 may be formed directly on the substrate, or a base layer formed of, for example, resin or the like may be provided on the substrate, and they may be formed on the base layer.

[0046] [Other configurations of the optical module] Next, returning to FIG. 1, other components of the optical module 10 will be described. The detector 11 receives (detects) the light transmitted through the interference filter 5 and outputs a detection signal based on the received light amount to the I-V converter 12. The I-V converter 12 converts the detection signal input from the detector 11 into a voltage value and outputs it to the amplifier 13. The amplifier 13 amplifies the voltage (detection voltage) corresponding to the detection signal input from the I-V converter 12. 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.

[0047] 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 force 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 side.

[0048] [Configuration of the control unit] Next, the control unit 20 of the spectroscopic measurement device 1 will be described. The control unit 20 is configured by combining, for example, a CPU and a memory, etc., and controls the overall operation of the spectroscopic measurement device 1. As shown in FIG. 1, this control unit 20 includes a filter drive unit 21, a light quantity acquisition unit 22, and a spectroscopic measurement unit 23. In addition, the memory of the control unit 20 stores V-λ data indicating the relationship between the wavelength of the light transmitted through the interference filter 5 and the driving voltage applied to the electrostatic actuator 59 corresponding to the wavelength.

[0049] The filter drive unit 21 sets the target wavelength of the light to be extracted by the interference filter 5, and based on the V-λ data, outputs a command signal to the voltage control unit 15 to apply the driving voltage corresponding to the set target wavelength to the electrostatic actuator 59. The light quantity acquisition unit 22 acquires the light quantity of the light of the target wavelength transmitted through the interference filter 5 based on the light quantity acquired by the detector 11. The spectroscopic measurement unit 23 measures the spectral characteristics of the light to be measured based on the light quantity acquired by the light quantity acquisition unit 22.

[0050] [Manufacturing method of the interference filter] Next, the manufacturing method of the interference filter 5 described above will be described with reference to the drawings. FIG. 7 is a flowchart showing the manufacturing method of the interference filter 5. In the manufacture of the interference filter 5, first, a first glass substrate M1 for forming the first substrate 51, a second glass substrate M2 for forming the second substrate 52, a third glass substrate M3 for forming the third substrate 53, and a fourth glass substrate M4 for forming the fourth substrate 54 are prepared, and a first substrate forming step S1, a second substrate forming step S2, a third substrate forming step S3, and a fourth substrate forming step S4 are carried out. Note that the order of the first substrate forming step S1, the second substrate forming step S2, the third substrate forming step S3, and the fourth substrate forming step S4 may be interchanged. Thereafter, a first bonding step S5 of bonding the first glass substrate M1 and the second glass substrate M2 using the first bonding portion 55 is carried out. After the first bonding step S5, a third bonding step S6 of bonding the fourth glass substrate M4 to the second glass substrate M2 is carried out. Then, after the third bonding step S6, a second bonding step S7 of bonding the third glass substrate M3 to the first glass substrate M1 is carried out. Thereafter, a cutting step S8 of cutting out the bonded glass substrates in chip units is carried out. Hereinafter, each step will be described in detail.

[0051] (First Substrate Forming Step) FIG. 8 is a view showing the state of the first glass substrate M1 in the first substrate forming step S1. In the first substrate forming step S1, first, both surfaces of the first glass substrate M1 (for example, having a thickness of 1 mm), which is the manufacturing material of the first substrate 51, are precisely polished until the surface roughness Ra becomes 1 nm or less on both surfaces.

[0052] Next, as shown in FIG. 8(A), the substrate surface of the first glass substrate M1 is processed by etching. Specifically, using the resist pattern patterned by photolithography as a mask, wet etching using, for example, a hydrofluoric acid-based solution (such as BHF) is repeatedly performed on the first glass substrate M1. First, the electrode arrangement groove 511, the lead-out portion 511B, the reflection film installation portion 512, and the terminal portion 513 are etched up to the height position of the reflection film installation portion 512. After that, the electrode arrangement groove 511, the lead-out portion 511B, and the terminal portion 513 are formed by etching. Note that the unetched surface of the first glass substrate M1 becomes the first bonding target portion 514. Thereby, the first glass substrate M1 with the substrate shape of the first substrate 51 determined is formed. Here, in the present embodiment, a plurality of first substrates 51 are formed from one first glass substrate M1. Therefore, in this step, etching is performed so that a plurality of first substrates 51 are manufactured in a state of being arranged in parallel in an array on the first glass substrate M1.

[0053] Next, a resin layer such as polyimide is formed on the first glass substrate M1 and etched to form the core 593A. Then, an electrode material (for example, a Cr / Au layer) for forming the first electrode 591, the first lead-out electrode 591A (omitted in FIGS. 8 and FIGS. 10 to 12 described later), and the bump electrode 593 on the first inner surface 51A of the first glass substrate M1 is formed by a deposition method such as vapor deposition or a sputtering method. Then, a resist is applied to the first glass substrate M1, and the resist is patterned according to the shapes of the first electrode 591, the first lead-out electrode 591A, and the bump electrode 593 using photolithography. Then, after etching the electrode material with an etching solution, the resist is removed. Thereby, as shown in FIG. 8(B), the first electrode 591, the first lead-out electrode 591A, and the bump electrode 593 are formed. After that, an insulating film such as SiO 2 is formed on the first inner surface 51A by, for example, plasma CVD. Then, the SiO 2 formed on the first lead-out 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, for example, dry etching to form the insulating portion 594.

[0054] Next, a first reflective film 581 is formed on the reflective film installation portion 512. When a metal film such as an Ag film or an alloy film such as an Ag alloy is used 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, patterning is performed using a photolithography method or the like. When a dielectric multilayer film is formed as the first reflective film 581, patterning is performed, for example, by a lift-off process. In this case, a resist (lift-off pattern) is formed on the first glass substrate M1 except for the reflective film formation portion by a photolithography method or the like. Then, a material for forming the first reflective film 581 (for example, a dielectric multilayer film with a high refractive index layer of TiO 2 and a low refractive index layer of SiO 2 ) is formed by a sputtering method, an evaporation method, or the like. After forming the first reflective film 581, the unnecessary film is removed by lift-off. As described above, as shown in FIG. 8(C), a first glass substrate M1 on which a plurality of first substrates 51 are arranged in an array is formed.

[0055] (Second substrate forming step) Next, the second substrate forming step S2 will be described. FIG. 9 is a diagram showing the state of the second glass substrate M2 in the second substrate forming step S2. In the second substrate forming step S2, first, both surfaces of the second glass substrate M2 are precisely polished until the surface roughness Ra becomes, for example, 1 nm or less. Then, an etching mask such as a Cr / Au layer is formed on the surface of the second glass substrate M2, and the region corresponding to the diaphragm portion 522 is etched using, for example, a hydrofluoric acid-based (BHF, etc.) (second substrate etching step). After that, by removing the Cr / Au layer used as the etching mask, as shown in FIG. 9(A), the second glass substrate M2 with the substrate shape of the second substrate 52 determined is manufactured. 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 step, etching is performed so that a plurality of second substrates 52 are manufactured in a state of being arranged in parallel in an array on the second glass substrate M2.

[0056] Next, as shown in FIG. 9(B), the second electrode 592 and the second lead electrode 592A are formed. In the formation of the second electrode 592 and the second lead electrode 592A, the same method as the formation of the first electrode 591 on the first substrate 51 can be used.

[0057] After that, as shown in FIG. 9(C), a second reflective film 582 is formed at the center of the movable portion 521 of the second inner surface 52A (second reflective film forming step). The formation of this second reflective film 582 can also be performed by the same method as the first reflective film 581. As described above, a second glass substrate M2 on which a plurality of second substrates 52 are arranged in an array is manufactured.

[0058] (Third substrate forming step) In the third substrate forming step S3, both surfaces are precisely polished until the surface roughness Ra of the third glass substrate becomes, for example, 1 nm or less. Then, by etching a predetermined position of the third glass substrate M3 (see FIG. 12), a third substrate recess 531 is formed. Note that an optical film such as an antireflection film or a band-pass filter may be formed on the third inner surface 53A or the third outer surface 53B of the third glass substrate M3.

[0059] (Fourth substrate forming step) The fourth substrate forming step S4 forms the fourth glass substrate M4 by the same procedure as the third substrate forming step S3. That is, in the fourth substrate forming step S4, first, both surfaces are precisely polished until the surface roughness Ra becomes, for example, 1 nm or less. Then, by etching a predetermined position of the fourth glass substrate M4 (see FIG. 11), a fourth substrate recess 541 is formed. Note that an optical film such as an antireflection film or a band-pass filter may be formed on the fourth inner surface 54A or the fourth outer surface 54B of the fourth glass substrate M4.

[0060] (First bonding step) Next, the first bonding step S5 will be described. In the first bonding step S5, first, a first elastic layer 551 is formed on a first bonding target portion 514 of the first glass substrate M1, and a second elastic layer 552 is formed on a substrate outer peripheral portion 523 of the second glass substrate M2. Specifically, a first masking step, a second masking step, a first elastic layer forming step, and a second elastic layer forming step are performed. FIG. 10 is a diagram for explaining the first bonding step S5. In the first masking step, as shown in FIG. 10(A), on the first inner surface 51A of the first glass substrate M1, a first mask M11 that covers portions other than the first bonding target portion 514 is formed. The first mask M11 of the present embodiment is a layer for patterning the first elastic layer 551, which is a plasma polymerization film, by a lift-off process, and for example, a metal film or the like can be used. In other embodiments, a metal mask having a partial opening that exposes the first bonding target portion 514 may be attached to the substrate, and a plasma polymerization film may be formed by a CVD (Chemical Vapor Deposition) method. The second masking step is substantially the same as the first masking step. As shown in FIG. 10(A), on the second inner surface 52A of the second glass substrate M2, a second mask M21 that covers portions other than the substrate outer peripheral portion 523 is formed.

[0061] Next, the first elastic layer forming step and the second elastic layer forming step are performed. Specifically, in the first elastic layer forming step, the first glass substrate M1 is placed in the vacuum chamber of a plasma device for forming a plasma polymerized film, and the vaporized monomer is introduced at a predetermined flow rate to perform plasma discharge. In this embodiment, for example, hexamethyldisiloxane monomer is used, and thereby a plasma polymerized film mainly composed of siloxane can be formed. At this time, since the first reflective film 581 is covered with the first mask M11, it is not exposed to plasma discharge, and alteration of the first reflective film 581 can be prevented. Thereafter, a lift-off process is performed to remove the first mask M11. Thereby, as shown in FIG. 10(B), the first elastic layer 551 of the plasma polymerized film can be patterned.

[0062] The second elastic layer forming step is substantially the same as the first elastic layer forming step. The second glass substrate M2 is placed in the vacuum chamber of the plasma device, and the vaporized monomer is introduced at a predetermined flow rate to perform plasma discharge. Thereby, the second elastic layer 552 composed of a plasma polymerized film mainly composed of siloxane is formed. Since the second reflective film 582 is covered with the second mask M21, it is not exposed to plasma discharge, and alteration of the second reflective film 582 can be prevented. Thereafter, a lift-off process is performed to pattern the second elastic layer 552 of the plasma polymerized film. Thereby, as shown in FIG. 10(B), the second elastic layer 552 of the plasma polymerized film can be patterned.

[0063] Note that in this embodiment, as the lift-off process performed in the first elastic layer forming step and the second elastic layer forming step, the first glass substrate M1 and the second glass substrate M2 can be taken out from the vacuum chamber and performed at normal temperature and normal pressure. That is, if the first substrate 51 and the second substrate 52 are joined by metal bonding, the metal bonding layer formed on the first substrate 51 and the metal bonding layer formed on the second substrate 52 are activated by plasma treatment or the like, and the metal bonding layers are brought into close contact with each other to effect metal bonding. However, in this case, it is necessary to perform a series of steps in a vacuum chamber. Therefore, during the plasma activation treatment for activating the metal bonding layer, the first reflective film 581 and the second reflective film 582 cannot be covered with a mask, and there is a risk that the first reflective film 581 and the second reflective film 582 will be deteriorated. Alternatively, it is necessary to select a reflective film material having resistance to surface treatment such as plasma activation treatment, and the film materials of the first reflective film 581 and the second reflective film 582 that can be used are limited. On the other hand, in the present embodiment, the first elastic layer 551 and the second elastic layer 552 constituting the first joint portion 55 are plasma polymer films, and after the formation of these first elastic layer 551 and second elastic layer 552, the first glass substrate M1 and the second glass substrate M2 can be taken out of the vacuum chamber. That is, since the masks M11 and M21 can be removed later by lift-off processing, the first reflective film 581 and the second reflective film 582 can be covered and protected with the masks M11 and M21 when forming the plasma polymer film.

[0064] Thereafter, the first glass substrate M1 and the second glass substrate M2 are placed in a vacuum chamber whose internal pressure is reduced from atmospheric pressure. Then, a load is applied in a direction in which the first glass substrate M1 and the second glass substrate M2 approach each other, and the first elastic layer 551 and the second elastic layer 552 are joined by a siloxane bond. Here, the first elastic layer 551 and the second elastic layer 552 are constituted by plasma polymer films and have a smaller elastic modulus than metal films. Therefore, even if 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, and the parallelism of the first reflective film 581 and the second reflective film 582 can be maintained high. As a result, as shown in FIG. 10(C), a first joined body M10 in which the first glass substrate M1 and the second glass substrate M2 are joined by the first joint portion 55 can be formed.

[0065] (Third bonding step) Next, the third bonding step S6 will be described. FIG. 11 is a diagram for explaining the third bonding step S6. In the third bonding step S6, first, as shown in FIG. 11(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 forming step), and a fourth metal layer 572 is formed at a position on the fourth inner surface 54A of the fourth glass substrate M4 that faces the outer peripheral portion 523 (fourth metal forming step). As described above, it is preferable to use Au for these second metal layer 571 and fourth metal layer 572. In order to maintain the pressure between the first substrate 51 and the second substrate 52 in a reduced-pressure state, while the first bonded body M10, which is a bonded body of the first glass substrate M1 and the second glass substrate M2 bonded in the first bonding step S5, is placed in a vacuum chamber in a reduced-pressure environment that is depressurized from atmospheric pressure, it is preferable to form the second metal layer 571.

[0066] Next, the fourth glass substrate M4 is placed in the vacuum chamber in which the first bonded body M10 is placed, and plasma activation treatment is performed on the surfaces of the second metal layer 571 and the fourth metal layer 572. After that, a load is applied in a direction in which the first bonded body M10 and the fourth glass substrate M4 approach each other, and the second metal layer 571 and the fourth metal layer 572 are bonded by metal bonding to form a third bonding portion 57. For example, the first bonded body M10 and the fourth glass substrate M4 are sandwiched and pressed by a clamp device having a pair of flat plate members. At this time, since the pressing force by the clamp device does not directly act on the movable portion 521 formed on the second glass substrate M2, breakage and distortion of the movable portion 521 can be suppressed. Also, a heater may be provided on the flat plate member on the fourth glass substrate M4 side of the clamp device so that the second metal layer 571 and the fourth metal layer 572 are heated. As described above, as shown in FIG. 11(B), the first joining member M10 and the fourth glass substrate M4 are joined by the third joining portion 57. As a result, the third internal space Sp3 surrounded by each second substrate 52 provided on the second glass substrate M2, each fourth substrate 54 provided on the fourth glass substrate M4, and the third joining portion 57 is maintained in a reduced-pressure environment that is reduced in pressure from atmospheric pressure and hermetically sealed.

[0067] (Second joining step) After the third joining step S6, the second joining step S7 is performed. FIG. 12 is a diagram for explaining the second joining step S7. This second joining step S7 can be performed by substantially the same method as the third joining step S6. That is, in the second joining step S7, first, as shown in FIG. 12(A), a first metal layer 561 is formed on the first outer surface 51B of the first joining target portion 514 of the first glass substrate M1 (first metal forming step), and a third metal layer 562 is formed at a position on the third inner surface 53A of the third glass substrate M3 that faces the first joining target portion 514 (third metal forming step). As these first metal layer 561 and third metal layer 562, as described above, it is preferable to use Au. In order to maintain the pressure between the first substrate 51 and the second substrate 52 in a reduced-pressure state, while the second joining member M20, which is the joined body of the first joining member M10 and the fourth glass substrate M4 joined by the third joining step S6, is placed in a vacuum chamber under a reduced-pressure environment that is reduced in pressure from atmospheric pressure, it is preferable to form the first metal layer 561.

[0068] Then, a third glass substrate M3 is placed in the vacuum chamber, and a load is applied to the second bonded body M20 and the third glass substrate M3 in a direction in which they approach each other, and the first metal layer 561 and the third metal layer 562 are joined by metal bonding to form a second joint portion 56. For example, the second bonded body M20 and the third glass substrate M3 are sandwiched and pressed by a clamping device having a pair of flat plate members. At this time, since the fourth glass substrate M4 is bonded to the second glass substrate M2 in the third bonding step S6, the pressing force by the clamping device does not directly act on the movable portion 521 of the second glass substrate M2, and breakage or distortion of the movable portion 521 can be suppressed. Further, a heater may be provided on the flat plate member on the third glass substrate M3 side of the clamping device, and the first metal layer 561 and the third metal layer 562 may be configured to be heated. As described above, as shown in FIG. 12(B), the second bonded body M20 and the third glass substrate M3 are joined by the second joint portion 56. Thereby, the second internal space Sp2 surrounded by each first substrate 51 provided on the first glass substrate M1, each third substrate 53 provided on the third glass substrate M3, and the second joint portion 56 is maintained in a reduced-pressure environment reduced in pressure from the atmospheric pressure and hermetically sealed.

[0069] (Cutting step) After the second bonding step S7, a cutting step S8 is performed. The cutting step S8 is performed while the third bonded body M30 joined in the second bonding step S7 is placed in a vacuum chamber in a reduced-pressure environment reduced in pressure from the atmospheric pressure in order to maintain the pressure between the first substrate 51 and the second substrate 52 in a reduced-pressure state. In this cutting step S8, the third bonded body M30 is cut using, for example, laser cutting or the like to cut out the interference filter 5 in chip units. Thereafter, a sealing portion 553 is injected and sealed with respect to the lead-out portion 511B of each interference filter 5 cut out in chip units. Thereby, the first internal space Sp1 is maintained in a reduced-pressure environment reduced in pressure from the atmospheric pressure and hermetically sealed. As described above, the interference filter 5 is manufactured.

[0070] [Operation and effect of the first embodiment] The interference filter 5 of the present embodiment includes a first substrate 51, a second substrate 52, a third substrate 53, a fourth substrate 54, a first joint 55, a second joint 56, and a third joint 57. The first substrate 51 has a first inner surface 51A and a first outer surface 51B that face each other, and is a light-transmissive substrate on which a first reflective film 581 is provided on the first inner surface 51A. The second substrate 52 has a second inner surface 52A and a second outer surface 52B that face each other, and is a light-transmissive substrate on which a second reflective film 582 facing the first reflective film 581 is provided on the second inner surface 52A. The third substrate 53 is a light-transmissive substrate disposed opposite to the first outer surface 51B of the first substrate 51. The fourth substrate 54 is a light-transmissive substrate disposed opposite to the second outer surface 52B of the second substrate 52. The first joint 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. And these first internal space Sp1, second internal space Sp2, and third internal space Sp3 are maintained in a reduced-pressure environment that is reduced in pressure from atmospheric pressure.

[0071] In the interference filter 5 having such a configuration, the first substrate 51 provided with the first reflective film 581 is sandwiched between the first internal space Sp1 and the second internal space Sp2 maintained in a reduced-pressure environment. Also, the second substrate 52 provided with the second reflective film 582 is sandwiched between the first internal space Sp1 and the third internal space Sp3 maintained in a reduced-pressure environment. Therefore, these first substrate 51 and second substrate 52 are not bent by the pressure difference between the two spaces sandwiching the substrate, and the influence of the bending of the first reflective film 581 and the second reflective film 582 can be suppressed, and an interference filter 5 capable of spectroscopically analyzing light of a desired wavelength with high precision can be obtained. That is, when emitting light of a target wavelength corresponding to the gap G1 from the interference filter 5, it is possible to suppress the mixing of light of a wavelength different from the target wavelength into the emitted light, and a highly accurate spectroscopic characteristic with a narrow wavelength half-value width can be obtained. In addition, since the first internal space Sp1 and the third internal space Sp3 that sandwich the movable part 521 are in a reduced-pressure environment, the resistance during the driving of the movable part 521 can be reduced, and the responsiveness when a voltage is applied to the electrostatic actuator 59 can be improved. Furthermore, in the interference filter 5 of the present embodiment, a package housing for maintaining a reduced pressure between the first substrate 51 and the second substrate 52 is not required. That is, conventionally, an interference filter composed 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 is known. In such a conventional interference filter, it is housed and used in a package housing in which the internal space is maintained in a reduced-pressure environment. However, such a package housing is generally composed of ceramic or the like to maintain a reduced-pressure environment, making it difficult to miniaturize the package housing containing the interference filter and electronic devices such as the spectroscopic measurement device 1 in which the package housing is incorporated. In contrast, the interference filter 5 of the present embodiment can maintain the first internal space Sp1, the second internal space Sp2, and the third internal space Sp3 in a reduced-pressure environment in wafer units, and thus does not need to use a package housing like a conventional interference filter, enabling miniaturization, and also enabling miniaturization of electronic devices such as the spectroscopic measurement device 1 incorporating the interference filter 5.

[0072] In the interference filter 5 of the present embodiment, the second joint 56 joins the first substrate 51 and the third substrate 53 by metal-bonding a first metal layer 561 provided on the first outer surface 51B and a third metal layer 562 provided on the third inner surface 53A of the third substrate 53 facing the first substrate 51. Similarly, the third joint 57 joins the second substrate 52 and the fourth substrate 54 by metal-bonding a second metal layer 571 provided on the second outer surface 52B and a fourth metal layer 572 provided on the fourth inner surface 54A of the fourth substrate 54 facing the second substrate 52. Such joining of substrates by metal bonding can achieve a high joining strength and, by ensuring that the entire surface of the metal layer is in close contact, can perform a joining with high airtightness. Therefore, the airtightness of the second internal space Sp2 and the third internal space Sp3 can be maintained at a high level.

[0073] In this embodiment, the first bonding portion 55 bonds the first substrate and the second substrate with an elastic layer having a lower elastic modulus than the metal film. Specifically, the first elastic layer 551 and the second elastic layer 552 that constitute the first bonding portion 55 are each constituted by a plasma polymerization film mainly composed of siloxane. In the bonding using such first elastic layer 551 and second elastic layer 552, even if foreign matter or the like adheres to the surface of the first elastic layer 551 or the second elastic layer 552, the influence of foreign matter or the like can be suppressed by elastic deformation, and the inclination of the first substrate 51 and the second substrate 52 during bonding can be suppressed. Therefore, the parallelism between the first reflection film 581 provided on the first substrate 51 and the second reflection film 582 provided on the second substrate 52 can be maintained at a high level.

[0074] Also, in this embodiment, as a manufacturing method for manufacturing the interference filter 5, a first substrate forming step S1, a second substrate forming step S2, a first bonding step S5, a third bonding step S6, and a second bonding step S7 are performed. In the first substrate forming step S1, the first reflection film 581 is formed on the first inner surface 51A of the first glass substrate M1 on which the first substrates 51 are arranged in an array, to form the first substrate 51. In the second substrate forming step S2, the second reflection film 582 is formed on the second inner surface 52A of the second glass substrate M2 on which the second substrates 52 are arranged in an array, to form the second substrate 52. In the first bonding step S5, in a reduced-pressure environment that is reduced in pressure from atmospheric pressure, the first inner surface 51A and the second inner surface 52A are bonded by the first bonding portion 55. In the second bonding step S7, in a reduced-pressure environment that is reduced in pressure from atmospheric pressure, the first outer surface 51B and the third substrate 53 are bonded by the second bonding portion 56. In the third bonding step S6, in a reduced-pressure environment that is reduced in pressure from atmospheric pressure, the second outer surface 52B and the fourth substrate 54 are bonded by the third bonding portion 57. Thereby, it is possible to manufacture the small-sized interference filter 5 that can spectroscopically analyze light of a desired wavelength with high accuracy and has high driving responsiveness as described above.

[0075] In this embodiment, in the manufacturing method of the interference filter 5, a first masking step, a first elastic layer forming step, a second masking step, and a second elastic layer forming step are performed. In the first masking step, a first mask M11 covering the first reflective film 581 is formed on the first glass substrate M1. In the first elastic layer forming step, after forming a first elastic layer 551, which is a plasma polymerization film mainly composed of siloxane, on the first inner surface 51A, the first mask M11 is removed by a lift-off process. In the second masking step, a second mask M21 covering the second reflective film 582 is formed on the second glass substrate M2. In the second elastic layer forming step, after forming a second elastic layer 552, which is a plasma polymerization film mainly composed of siloxane, on the second inner surface 52A, the second mask M21 is removed. Then, in the first bonding step S5, a first bonding portion 55 is formed by bonding the first elastic layer 551 and the second elastic layer 552 in a reduced-pressure environment that is reduced in pressure from atmospheric pressure, and the first substrate 51 and the second substrate 52 are bonded together. In this embodiment, in the bonding of the first substrate 51 and the second substrate 52, the first elastic layer 551 and the second elastic layer 552, which are plasma polymerization films, are formed. When forming a plasma polymerization film, if the first reflective film 581 or the second reflective film 582 is exposed to plasma, the spectral characteristics of the interference filter 5 deteriorate due to the deterioration of the reflective film. In contrast, in this embodiment, by forming the first mask M11 and the second mask M21, the first reflective film 581 and the second reflective film 582 can be protected. In addition, when using a metal bond with a metal film as the first bonding portion 55, it is necessary to activate these metal layers by plasma activation treatment or the like during bonding. However, after the activation treatment, the mask cannot be removed by a lift-off process or the like, so the first reflective film 581 and the second reflective film 582 are exposed to plasma or the like when activating the metal film, and the characteristics of the interference filter 5 deteriorate due to the deterioration of the reflective film. In this embodiment, such inconveniences can be avoided, and an interference filter 5 with good spectral characteristics can be manufactured.

[0076] In this embodiment, in the manufacture of the interference filter 5, in the second bonding step S7, a first metal forming step and a third metal forming step are performed. In the first metal forming step, a first metal layer 561 is formed on the first outer surface 51B, and in the third metal forming step, a third metal layer 562 is formed on the third inner surface 53A. Then, in the second bonding step S7, a load is applied in the direction in which the first substrate 51 and the third substrate 53 approach each other to form a second joint portion 56 in which the first metal layer 561 and the third metal layer 562 are metallically bonded, and the first substrate 51 and the third substrate 53 are bonded together. Also, in the third bonding step S6, a second metal forming step and a fourth metal forming step are performed. In the second metal forming step, a second metal layer 571 is formed on the second outer surface 52B, and in the fourth metal forming step, a fourth metal layer 572 is formed on the fourth inner surface 54A. In the third bonding step S6, a load is applied in the direction in which the second substrate 52 and the fourth substrate 54 approach each other to form a third joint portion 57 in which the second metal layer 571 and the fourth metal layer 572 are metallically bonded, and the second substrate 52 and the fourth substrate 54 are bonded together. Thereby, as described above, the first substrate 51 and the third substrate 53, and the second substrate 52 and the fourth substrate 54 can be respectively bonded by a metallic bond having high bonding strength and high airtightness. Therefore, the airtightness of the second internal space Sp2 and the third internal space Sp3 can be maintained at a high level.

[0077] In the manufacture of the interference filter 5 of this embodiment, in the second substrate forming step S2, a second substrate etching step of etching the second outer surface 52B to form a movable portion 521 having a predetermined thickness and a diaphragm portion 522 having a thickness thinner than that of the movable portion 521, and a second reflective film forming step of forming a second reflective film 582 on the second inner surface 52A of the movable portion 521 are included. And in this embodiment, the third bonding step S6 is performed before the second bonding step S7.

[0078] That is, in the present embodiment, in the second substrate forming step S2, a second substrate 52 having a movable portion 521 and a diaphragm portion 522 that movably holds the movable portion 521 is formed. When direct stress is applied to the movable portion 521 of such a second substrate 52, there is a risk that the diaphragm portion 522 may be damaged or the movable portion 521 may be tilted by excessive stress. For example, if the second bonding step S7 is first performed on the first bonded body M10 before the third bonding step S6, the flat plate member of the clamping device abuts against the second glass substrate M2 of the first bonded body M10, so that direct stress is applied to the movable portion 521 from the flat plate member, which is not preferable. In contrast, in the present embodiment, the fourth substrate 54 is bonded to the second substrate 52 by performing the third bonding step S6 before the second bonding step S7. Thereby, the movable portion 521 of the second substrate 52 can be protected by the fourth substrate 54. That is, when the second bonding step S7 is performed, the fourth substrate 54 covering the second substrate 52 comes into contact with the flat plate member of the clamping device, and direct stress is not applied to the second substrate 52, so that tilting of the movable portion 521 and breakage of the diaphragm portion 522 can be suppressed.

[0079] [Other Embodiments] Note that the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention.

[0080] [Modification Example 1] For example, in the above embodiment, the first internal space Sp1 and the third internal space Sp3 are each an independent airtight space, but the first internal space Sp1 and the third internal space Sp3 may communicate with each other. More specifically, a through hole that communicates the first internal space Sp1 and the third internal space Sp3 may be provided in the diaphragm portion 522. In this case, the internal pressure difference between the first internal space Sp1 and the third internal space Sp3 when the movable portion 521 fluctuates can be eliminated, and the drive responsiveness of the movable portion 521 can be further enhanced.

[0081] [Modification Example 2] In the above-described embodiment, as the first joint portion 55, an example of a configuration in which the gap between the first elastic layer 551 and the second elastic layer 552 in the lead-out portion 511B is sealed by the sealing portion 553 is illustrated, but the present invention is not limited thereto. For example, by forming the height position of the first elastic layer 551 in the lead-out portion 511B up to the height position of the first elastic layer 551 of the first joint target portion 514, the first elastic layer 551 and the second elastic layer 552 can also be joined in the lead-out portion 511B. Alternatively, in the lead-out portion 511B, the insulating portion 594 may be formed up to the height position of the first joint target portion 514. Even in this case, the sealing portion 553 becomes unnecessary.

[0082] (Modification Example 3) In the above-described embodiment, in the first joining step S5, after joining the first glass substrate M1 and the second glass substrate M2 in a vacuum chamber, while holding the first joined body M10 obtained by joining in the vacuum chamber, the subsequent third joining step S6, second joining step S7, and cutting step S8 were performed to perform sealing by the sealing portion 553. On the other hand, the joining of the first elastic layer 551 and the second elastic layer 552 in the first joining step S5 may not be performed under reduced pressure. In this case, in the cutting step S8, after cutting out the interference filter 5 in chip units, each interference filter is placed in the vacuum chamber, the first internal space Sp1 is brought into a reduced pressure state, and the gap in the lead-out portion 511B may be sealed with the sealing portion 553 constituting the first joint portion 55. Also, as described in the above Modification Example 2, when the first elastic layer 551 of the lead-out portion 511B is formed up to the same height position as the first elastic layer 551 on the first joint target portion 514, or when the insulating portion 594 formed in the lead-out portion 511B in the first substrate forming step S1 is formed up to the height position of the first joint target portion 514, the first internal space Sp1 is sealed by performing the first joining step S5. Therefore, after taking out the first joined body M10 and the second joined body M20 from the vacuum chamber, the first metal layer 561 and the second metal layer 571 can also be formed.

[0083] (Modification Example 4) In this embodiment, an example in which the second joint portion 56 and the third joint portion 57 are joined by metal bonding has been shown, but the present invention is not limited thereto. Either one or both of the second joint portion 56 and the third joint portion 57 may be plasma polymerization bonding for joining plasma polymerization films to each other, similar to the first joint portion 55.

[0084] (Modification 5) As the first joint portion 55, an example in which the first elastic layer 551 and the second elastic layer 552, which are plasma polymerization films mainly composed of siloxane, are formed, and the first elastic layer 551 and the second elastic layer 552 are joined by siloxane bonding has been shown, but the present invention is not limited thereto. The first elastic layer 551 and the second elastic layer 552 may be formed of a material such as a resin having a smaller elastic modulus than that of metal. Further, as the first joint portion 55, similar to the second joint portion 56 and the third joint portion 57, metal bonding using a metal film may be used. In this case, when foreign substances or the like adhere to the metal film during bonding, there is a possibility that the parallelism between the first reflection film 581 and the second reflection film 582 deteriorates. On the other hand, by forming an underlayer 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, respectively, the influence of foreign substances can be suppressed.

[0085] (Modification 6) In each of the above-described embodiments, the electrostatic actuator 59 has been exemplified as the gap changing portion for driving the movable portion 521, but the present invention is not limited thereto. For example, as the gap changing portion, a configuration using a dielectric actuator composed of a first dielectric coil provided on the first substrate 51 and a second dielectric coil or a permanent magnet provided on the second substrate 52 may be used. Furthermore, a configuration using a piezoelectric actuator instead of the electrostatic actuator 59 may be used. In this case, for example, a lower electrode layer, a piezoelectric film, and an upper electrode layer are laminated on the diaphragm portion 522, and the piezoelectric film is expanded and contracted by varying the voltage applied between the lower electrode layer and the upper electrode layer as an input value, thereby bending the diaphragm portion 522.

[0086] (Modification 7) Furthermore, the present invention can also be applied to a wavelength-fixed Fabry-Perot etalon that is not provided with a gap-changing section. In a wavelength-fixed interference filter, a movable part 521 and a diaphragm part 522 as in the above-described embodiment are not provided, and the gap G1 between the first substrate 51 and the second substrate 52 is maintained constant. At this time, since the first substrate 51 and the second substrate 52 are joined with high airtightness by the first joining part 55, it is possible to suitably prevent foreign matter from entering between the first substrate 51 and the second substrate 52, and to suppress deterioration of the reflection films 581 and 582. Further, since the third substrate 53 is joined to the first substrate 51 by the second joining part 56 and the fourth substrate 54 is joined to the second substrate 52 by the third joining part 57, 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 becomes constant. That is, even if the third substrate 53 or the fourth substrate 54 receives pressure depending on the installation environment of the interference filter, the second internal space Sp2 and the third internal space Sp3 function as cushions, and a change in the internal pressure of the first internal space Sp1 is suppressed. Thereby, the parallelism between the first reflection film 581 and the second reflection film 582 can be maintained at a high level.

[0087] (Modification Example 8) In the above-described embodiment, the spectroscopic measurement device 1 was exemplified as an example of an electronic device in which the interference filter 5 is incorporated, but the present invention is not limited to this. As an electronic device in which the interference filter 5 is incorporated, it can be appropriately incorporated into other devices such as a spectroscopic camera and a light source device that select and emit a predetermined wavelength from incident light.

Description of Reference Numerals

[0088] 1... Spectrophotometric device, 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, 511... Electrode arrangement groove, 511A... Annular part, 511B... Lead-out part, 512... Reflective film installation part, 513... Terminal part, 514... First joint target part, 521... Movable part, 522... Diaphragm part, 523... Substrate outer peripheral part, 531... Third substrate recess, 532... Third joint target part, 541... Fourth substrate recess, 542... Fourth joint target part, 551... First elastic layer, 552... Second elastic layer, 553... Sealing part, 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-out electrode, 592... Second electrode, 592A... Second lead-out 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), M21... 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 joint process, S6... Third joint process, S7... Second joint process, S8... Cutting process, Sp1... First internal space, Sp2... Second internal space, Sp3... Third internal space.

Claims

1. A first substrate having a first inner surface and a first outer surface facing each other, the first substrate being translucent and having a first reflective film provided on the first inner surface; A second substrate having a second inner surface and a second outer surface facing each other, the second substrate being translucent and having a second reflective film provided on the second inner surface facing the first reflective film; A first joint portion that joins the first inner surface and the second inner surface to each other, the first joint portion sealing a first internal space between the first substrate and the second substrate; A translucent third substrate facing the first outer surface; A second joint portion that joins the first outer surface and the third substrate to each other, the second joint portion sealing a second internal space between the first substrate and the third substrate; A translucent fourth substrate facing the second outer surface; A third joint portion that joins the second outer surface and the fourth substrate to each other, the third joint portion sealing a third internal space between the second substrate and the fourth substrate, comprising: The first internal space, the second internal space, and the third internal space are depressurized relative to atmospheric pressure; The first substrate has a greater substrate thickness than the second substrate; The second substrate includes a movable portion provided with the second reflective film, a diaphragm portion surrounding the outer periphery of the movable portion and having a smaller substrate thickness than the movable portion, and a substrate outer peripheral portion provided outside the diaphragm portion and having a greater substrate thickness than the diaphragm portion; An interference filter comprising an electrostatic actuator that displaces the movable portion toward the first substrate side.

2. The second joint portion joins the first substrate and the third substrate by metal-bonding a first metal layer provided on the first outer surface and a third metal layer provided on a third facing surface of the third substrate facing the first substrate; The third joint portion joins the second substrate and the fourth substrate by metal-bonding a second metal layer provided on the second outer surface and a fourth metal layer provided on a fourth facing surface of the fourth substrate facing the second substrate. The interference filter according to claim 1.

3. The first joint portion joins the first substrate and the second substrate with an elastic layer having a lower elastic modulus than a metal film; The interference filter according to claim 1 or claim 2.

4. The elastic layer is a plasma polymerization film mainly composed of siloxane; The interference filter according to claim 3.

5. A first substrate forming step of forming a first reflective film on the first inner surface of a translucent first substrate having a first inner surface and a first outer surface facing each other; A second substrate forming step of forming a second reflective film on the second inner surface of a translucent second substrate having a second inner surface and a second outer surface facing each other; A first bonding step of bonding the first inner surface and the second inner surface to each other with a first bonding portion in a reduced-pressure environment reduced from atmospheric pressure, and sealing a first internal space between the first substrate and the second substrate; A second bonding step of bonding the first outer surface and a translucent third substrate to each other with a second bonding portion in a reduced-pressure environment reduced from atmospheric pressure, and sealing a second internal space between the first substrate and the third substrate; A third bonding step of bonding the second outer surface and a translucent fourth substrate to each other with a third bonding portion in a reduced-pressure environment reduced from atmospheric pressure, and sealing a third internal space between the second substrate and the fourth substrate, are performed; In the first substrate forming step, the first substrate having a larger substrate thickness than the second substrate is formed; In the second substrate forming step, a movable portion provided with the second reflective film, a diaphragm portion surrounding the outer periphery of the movable portion and having a smaller substrate thickness than the movable portion, and a substrate outer peripheral portion provided outside the diaphragm portion and having a larger substrate thickness than the diaphragm portion are included, and the second substrate in which the movable portion can be displaced toward the first substrate side by an electrostatic actuator is formed. A method for manufacturing an interference filter.

6. A first masking step of covering the first reflective film with a first mask; A first elastic layer forming step of forming a first elastic layer, which is a plasma polymerization film mainly composed of siloxane, on the first inner surface and removing the first mask; A second masking step of covering the second reflective film with a second mask; A second elastic layer forming step of forming a second elastic layer, which is a plasma polymerization film mainly composed of siloxane, on the second inner surface and removing the second mask, are included; The first bonding step forms the first bonding portion by bonding the first elastic layer on the first inner surface and the second elastic layer on the second inner surface to each other in a reduced-pressure environment reduced from atmospheric pressure, and bonds the first substrate and the second substrate to each other; The method for manufacturing an interference filter according to claim 5.

7. A first metal forming step of forming a first metal layer on the first outer surface; A third metal forming step of forming a third metal layer on a third opposing surface of the third substrate facing the first substrate; a second metal forming step of forming a second metal layer on the second outer surface; a fourth metal forming step of forming a fourth metal layer on a fourth facing surface of the fourth substrate facing the second substrate, the method comprising: the second bonding step includes forming the second bonding portion by adding a load in a direction in which the first substrate and the third substrate are close to each other to metal-bond the first metal layer and the third metal layer, and bonding the first substrate and the third substrate; the third bonding step includes forming the third bonding portion by adding a load in a direction in which the second substrate and the fourth substrate are close to each other to metal-bond the second metal layer and the fourth metal layer, and bonding the second substrate and the fourth substrate; The method for manufacturing an interference filter according to claim 5 or claim 6.

8. the second substrate forming step includes a second substrate etching step of etching the second outer surface to form the movable portion and the diaphragm portion having a predetermined thickness, and a second reflective film forming step of forming the second reflective film on the second inner surface of the movable portion; the third bonding step is performed before the second bonding step; The method for manufacturing an interference filter according to claim 7.

Images