JP2005055790A - Wavelength variable optical filter and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength variable optical filter and a method for manufacturing the same, permitting the driving at a low voltage, other than the adjustment of an electrostatic gap or the like. <P>SOLUTION: The wavelength variable optical filter, which displaces a spacing, by moving a highly reflective film 23 in the direction perpendicular to the surface on which a highly reflective film 32 is formed, so as to transmit the light having a prescribed wavelength based on the spacing, from the light reflected between the highly reflective film 32 and the highly reflective film 23, is at least provided with a movable part 2, wherein a movable body 21a having the highly reflective film 23 formed thereon is integrated with a support body in which a hinge 21b for supporting the movable body 21a is formed so as to have the thickness at least different from that of the movable body 21a and which includes a support part 21c for supporting the movable body 21a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wavelength division multiplexing (WDM) optical communication network or the like in order to extract light having a desired wavelength from a plurality of lights having different wavelengths transmitted through an optical fiber. The present invention relates to a tunable optical filter that selectively transmits light and a method of manufacturing the same.

  A conventional tunable optical filter uses the principle of a Fabry-Perot interferometer. A fixed mirror is formed on the substrate, and a movable mirror is disposed in parallel with the fixed mirror at a predetermined interval (hereinafter referred to as an electrostatic gap). By applying a driving voltage between the movable electrode provided on the movable mirror and the fixed electrode provided on the fixed mirror, the movable mirror changes relative to the fixed mirror within the range of the electrostatic gap. This electrostatic gap is formed by providing a sacrificial layer having a predetermined shape and size between the fixed mirror and the movable mirror using micromachining technology, and then etching all or part of the sacrificial layer by etching. It forms by removing (for example, refer patent document 1).

In addition, some conventional wavelength tunable optical filters use the silicon dioxide (SiO ₂ ) layer of an SOI (Silicon on Insulator) wafer as a sacrificial layer to form the electrostatic gap (for example, Patent Documents). 2).
JP 2002-174721 A ([Claim 9], [0005], [0018], [0037], [0049] to [0056], FIG. 6) US Pat. No. 6341039 (columns 6-7, FIGS. 4A-4I)

As described above, in the wavelength tunable optical filter, the drive voltage is applied to the parallel plate capacitor formed by the movable electrode provided on the movable mirror and the fixed electrode provided on the fixed mirror, so that the gap between the movable mirror and the fixed mirror is obtained. An electrostatic attractive force is generated on the movable mirror, and the movable mirror is changed with respect to the fixed mirror. Here, when a driving voltage V is applied to a parallel plate capacitor in which two electrode plates having an area S and a distance d are opposed to each other with a dielectric having a dielectric constant ε, a static force acting on the two electrode plates is applied. The electric attractive force F is represented by the formula (1) as is well known.
F = (1/2) · ε · (V / d) ² · S (1)

  Considering from the equation (1), the electrostatic gap and the drive voltage are in an inversely proportional relationship. That is, in order to obtain the same electrostatic attraction, the drive voltage can be reduced by narrowing the electrostatic gap. However, since there is a limit to narrowing the electrostatic gap due to manufacturing conditions and other relationships, other means are required to further reduce the drive voltage. In order to reduce the drive voltage, it is conceivable to move the movable mirror and reduce the thickness of the substrate to be supported, but if the movable mirror or the like is composed of a multilayer film, the movable mirror warps, There are problems in quality such as wavelength selectivity and durability, and the strength of the substrate also decreases.

  In order to solve the above-described problems, an object of the present invention is to obtain a wavelength tunable optical filter that can be driven at a low pressure in addition to adjustment of an electrostatic gap and the like, and a manufacturing method thereof.

The wavelength tunable optical filter according to the present invention is based on the interval from the light reflected between the fixed mirror and the movable mirror by moving the movable mirror in the direction perpendicular to the surface on which the fixed mirror is formed. In a wavelength tunable optical filter that transmits light of a predetermined wavelength, a movable body on which a movable mirror is formed, and a suspension body that suspends the movable body is formed with a thickness different from that of the movable body, and supports the movable body And at least a movable part.
According to the present invention, the movable body and the suspension means are formed with different thicknesses, and in particular, by making the suspension means thinner than the movable body, the spring constant is lowered, and the electrostatic force for changing the movable body Can be reduced. Therefore, the drive voltage can also be lowered and power consumption can be reduced. In addition, since the movable body is not thinned, the movable mirror provided on the movable body is not warped, and a wavelength variable optical filter with high quality can be obtained without impairing wavelength selectivity and durability. In particular, when the substrate is processed to integrally form the movable body and the support body, the thickness remains the same unless additional processing is performed. Can be obtained. Even if this is formed with a thickness different from that of the movable body including not only the suspension means but also the support body, the same effect can be obtained.

The wavelength tunable optical filter according to the present invention includes a movable mirror that reflects light of a certain wavelength formed on one surface, a movable body that can be driven in a direction perpendicular to the one surface, and a thickness smaller than that of the movable body. A movable part integrally formed with a support body that supports the movable body via a suspension means formed by the above-mentioned structure, and a movable body and a surface opposite to one surface across a predetermined electrostatic gap. The drive electrode part having the drive electrode and the optical gap part having the fixed mirror facing the movable mirror with a predetermined optical gap are joined to each other.
According to the present invention, each part can be manufactured with high accuracy (particularly in the thickness direction), and by joining the parts, a wavelength-tunable light having a good quality that performs a designed operation without applying a predetermined voltage. A filter can be obtained. In particular, even when, for example, a plurality of filters are manufactured at the same time in units of wafers, the operations of the filters do not vary and can be manufactured to be uniform. In addition, by forming the suspension means after forming it thinly, it is possible to perform processing from one side or both sides of the drive electrode portion side or the optical gap portion side with high accuracy.

In the wavelength tunable optical filter according to the present invention, a space is provided on at least one of the one surface side or the opposite surface, and the thickness of the suspension means is smaller than that of the movable body.
According to the present invention, since there is a space on at least one of the one surface side or the opposite surface surface and the space is formed thinly, the spring constant by the suspending means can be lowered. In particular, when removed from both sides, the suspension means is connected to the center position of the movable body and suspends the movable body, so that the movable body can be changed stably.

In the wavelength tunable optical filter according to the present invention, the space is formed by using at least one of a dry etching method and a wet etching method so that the thickness of the suspending means is smaller than that of the movable body.
According to the present invention, by using dry etching or wet etching, a plurality of suspension means thinner than the movable body can be formed at a time.

In the wavelength tunable optical filter according to the present invention, the movable part is made of silicon, and either one or both of the drive electrode part and the optical gap part are made of glass.
According to the present invention, for example, by using a glass that is transparent at least in visible light, it is possible to easily check the operation of the movable part. If the optical gap portion is made of glass, the wavelength of light to be transmitted can be selected widely including visible light. Furthermore, since each part can be joined by anodic joining or low melting point glass joining during manufacturing, the electrostatic gap and the optical gap can be joined with high accuracy while being kept at a predetermined interval.

In the tunable optical filter according to the present invention, an insulating film is formed on one or both of the drive electrode and the region facing the drive electrode of the movable body.
According to the present invention, when the movable body is electrostatically driven by applying a voltage to the drive electrode and the movable body by forming the insulating film, sticking (sticking) between the drive electrode and the movable body may occur. Can be prevented.

In the method of manufacturing a wavelength tunable optical filter according to the present invention, the movable mirror is moved in a direction perpendicular to the surface on which the fixed mirror is formed, the interval is changed, and the reflected light is reflected between the fixed mirror and the movable mirror. A method of manufacturing a wavelength tunable optical filter that transmits light having a predetermined wavelength based on a distance from light, wherein a movable body provided with a movable mirror and a support body that supports the movable body via a suspension means are integrally formed. Thus, at least the suspension means is formed with a thickness different from that of the movable body.
According to the present invention, the movable body and the support are integrally formed while making the movable body and the suspension means different in thickness, and in particular, the spring constant is lowered by making the suspension means thinner than the movable body, The electrostatic force for making the change can be reduced. Therefore, the drive voltage can also be lowered and power consumption can be reduced. In addition, since the movable body is not thinned, the movable mirror provided on the movable body is not warped, and a wavelength variable optical filter with high quality can be obtained without impairing wavelength selectivity and durability.

Further, in the method for manufacturing a wavelength tunable optical filter according to the present invention, after etching the opening for spatially partitioning the movable body and the support to the thickness of the suspension means, the etching is further performed except for the portion to be the suspension means. It is opened and formed integrally.
According to the present invention, the suspending means thinner than the movable portion is formed by etching in two stages, so that the suspending means having a desired shape can be formed with high accuracy (particularly in the thickness direction). .

In the method of manufacturing a wavelength tunable optical filter according to the present invention, the etching up to the thickness of the suspending means is performed by a dry etching method or a wet etching method, and the etching performed while leaving the portion to be the suspending means is performed by a dry etching method.
According to the present invention, since the etching at the stage of opening is performed by dry etching, the drive electrode is exposed to the etchant even when it is previously joined to a member having the drive electrode, etc. A good quality filter can be obtained.

Further, the method of manufacturing a wavelength tunable optical filter according to the present invention is provided on the fixed mirror and the movable body by moving the movable body in the vertical direction by electrostatic force to the surface on which the fixed mirror is formed, and changing the interval. A method of manufacturing a wavelength tunable optical filter that transmits light having a predetermined wavelength based on a distance from light reflected between the movable mirror and the first recess after the first recess is formed on the first substrate. Forming a drive electrode on the bottom surface of the first substrate to form a drive electrode portion, and forming a second recess on the second substrate, and then forming a fixed mirror on the bottom surface of the second recess to form an optical gap portion The second substrate and the third substrate and the drive electrode unit are joined, and the movable body, the support body, and the suspension means having a thickness different from that of the movable body are integrally formed on the third substrate, and the movable body is formed on the movable body. The third step of forming the movable mirror was manufactured in the third step with the movable mirror and the fixed mirror facing each other. Having at least a fourth step of bonding the polymer and the optical gap. The order of the procedure of the first step and the second step may be arbitrary.
According to the present invention, each part is manufactured with high accuracy (especially in the thickness direction), and then joined to manufacture the wavelength tunable optical filter. Therefore, the operation as designed is performed by applying a predetermined voltage without adjustment. A tunable optical filter with high quality can be manufactured. In particular, the distance between the drive electrode and the movable body can be made narrow, and the suspension means is made thin, so that it can be driven at a lower voltage than the prior art, and the power consumption can be reduced.

Further, the method of manufacturing a wavelength tunable optical filter according to the present invention is provided on the fixed mirror and the movable body by moving the movable body in the vertical direction by electrostatic force to the surface on which the fixed mirror is formed, and changing the interval. A method of manufacturing a wavelength tunable optical filter that transmits light having a predetermined wavelength based on a distance from light reflected between the movable mirror and the first recess after the first recess is formed on the first substrate. A first step of forming a drive electrode on the second substrate to form a drive electrode portion; and a second step of forming a second recess in the second substrate and then forming a fixed mirror in the second recess to form an optical gap portion. And the third substrate on which the movable mirror is formed and the optical gap portion are joined with the movable mirror and the fixed mirror facing each other, and the movable body, the support body, and the movable body have a thickness. A third step of forming the suspension means on the third substrate, and the structure manufactured in the third step; And a dynamic electrode portion, at least a fourth step of bonding to face the movable member and the drive electrode. The order of the procedure of the first step and the second step may be arbitrary.
According to the present invention, the tunable optical filter is manufactured by manufacturing the parts with high accuracy (particularly in the thickness direction) and then joining them. A tunable optical filter with good quality can be manufactured. In particular, the distance between the drive electrode and the movable body can be made narrow, and the suspension means is made thin, so that it can be driven at a lower voltage than the prior art, and the power consumption can be reduced.

Further, in the method of manufacturing a wavelength tunable optical filter according to the present invention, in the third step, after etching the opening that spatially partitions the movable body and the support to the thickness of the suspension means, a portion that becomes the suspension means is formed. The remaining etching is performed and the openings are opened to form a movable body, a support body, and a suspension unit having a thickness different from that of the movable body on the third substrate.
According to the present invention, since the suspension means thinner than the movable portion is formed by etching in two stages, the suspension means having a desired shape (particularly thickness) can be formed with high accuracy.

In the third step, the wavelength tunable optical filter manufacturing method according to the present invention includes etching the opening that spatially partitions the movable body and the support body to the thickness of the suspension means, and then etching the etched side surface. Etching from the surface opposite to the bonded surface, leaving the portion to be the suspension means, and opening the desired portion, and the suspension means having a thickness different from that of the movable body, the support body and the movable body is the third substrate. To form.
According to the present invention, after the etching for thinning the suspending means is performed, the surfaces are joined. Therefore, in order to open a desired portion, the etching is performed on the opposite surface as in the conventional case. The resist pattern can be used. Moreover, since the etching means can be etched from both sides and the suspension means connected at the center of the movable body can be formed, the movable body can be changed stably.

Further, in the third method of manufacturing a wavelength tunable optical filter according to the present invention, in the third step, the active layer of the substrate in which the base layer, the insulating layer, and the conductive active layer are sequentially stacked is used as the third substrate, and the active layer After the substrates stacked from the side are joined, the base layer and the insulating layer are sequentially removed, and a movable body, a support body, and a suspension means having a thickness different from that of the movable body are formed in the active layer.
According to the present invention, since the active layer is stably bonded by the base substrate and then removed, the thin substrate serving as the movable portion can be stably bonded. In addition, since the insulating layer serves as an etching stopper when removing the base layer, the thickness of the active layer serving as the third substrate can be maintained with high accuracy.

Also, in the method of manufacturing a wavelength tunable optical filter according to the present invention, an SOI substrate, an SOS substrate, or a silicon substrate having a silicon oxide film formed on at least one surface and a silicon substrate are bonded to each other on the surface on which the silicon oxide film is formed. The substrate is a laminated substrate.
According to the present invention, since the SOI substrate and the SOS substrate sandwiching the material serving as an etching stopper when etching silicon are used, the third substrate can be formed with high accuracy using the active layer. Can be formed.

The method for manufacturing a wavelength tunable optical filter according to the present invention further includes a step of forming an insulating film on at least the drive electrode in the first step.
According to the present invention, by including the step of forming an insulating film on the drive electrode, sticking that can occur between the drive electrode and the movable body can be prevented.

Further, in the method of manufacturing a wavelength tunable optical filter according to the present invention, in the third step, after forming an insulating film in a region on the third substrate facing the driving electrode as a movable body, the driving electrode and the insulating film are formed. It joins facing the formed surface.
According to the present invention, the step of forming the insulating film in the region to be the movable body can prevent sticking (sticking) that may occur between the drive electrode and the movable body.

Further, in the method for manufacturing a wavelength tunable optical filter according to the present invention, in the first step, an antireflection film is formed on the surface of the first substrate where the first recess is formed and on the opposite surface,
In the second step, an antireflection film is formed on the surface of the second substrate opposite to the side on which the second recess is formed,
The third step further includes a step of forming an antireflection film on a region on the third substrate facing the drive electrode as a movable body, and then bonding the drive electrode to the surface on which the insulating film is formed. .
According to the present invention, in each step, the reflection of light by the substrate is prevented by forming an antireflection film at the interface between the substrate and the space, and light that becomes noise between the fixed mirror and the movable mirror is prevented. The incident can be prevented.

In the wavelength tunable optical filter manufacturing method according to the present invention, the third substrate is made of silicon, and one or both of the first substrate and the second substrate are made of glass, and the third step or the second step is performed. Bonding in any one or both of the four steps is performed by anodic bonding, low melting point glass bonding, or bonding with an adhesive.
According to the present invention, either or both of the first substrate and the second substrate are made of glass, and the third substrate is made of silicon, so that anodic bonding can be performed without using an adhesive. , Low melting point glass bonding can be performed. In this case, it is possible to perform strong bonding with high accuracy (particularly in the thickness direction). If an adhesive is used, joining can be performed easily. In addition, it is possible to easily check the operation of the movable part formed on the third substrate. Furthermore, if the second substrate is made of glass, the wavelength of light to be transmitted can be widely selected including visible light. Furthermore, since each part can be joined by anodic joining or low melting point glass joining during manufacturing, the electrostatic gap and the optical gap can be joined with high accuracy while being kept at a predetermined interval.

Embodiment 1 FIG.
FIG. 1 is a sectional view showing a wavelength tunable optical filter according to the first embodiment of the present invention. FIG. 1 is a cross-sectional view at a substantially central position of the wavelength tunable optical filter (see the AA ′ cross section in FIG. 2). The wavelength tunable optical filter according to the present embodiment includes a drive electrode unit 1, a movable unit 2, and an optical gap unit 3. When not driven, an electrostatic gap EG having a distance of about 4 μm between the drive electrode 12 (electrode insulating film 13) of the drive electrode portion 1 and the movable body 21a of the movable portion 2 is a movable body of the movable portion 2. An optical gap OG having an interval of about 30 μm is formed between 21 a and the highly reflective film 32 of the optical gap portion 3.

  The drive electrode portion 1 is configured by forming a substantially ring-shaped drive electrode 12 on a concave portion 11a formed at a substantially central portion of a glass substrate 11 having a substantially U-shaped cross section and an electrode insulating film 13 on the drive electrode. ing. The glass substrate 11 serving as the first substrate is made of, for example, glass containing an alkali metal such as sodium (Na) or potassium (K). An example of this type of glass is borosilicate glass containing an alkali metal. Here, when the drive electrode portion 1 and the movable portion 2 are joined by anodic bonding as will be described later, since the glass substrate 11 is heated, the glass that becomes the glass substrate 11 is thermally expanded with silicon that becomes the movable portion 2. The coefficients are required to be approximately equal. As a glass that meets this requirement, for example, # 7740 (trade name) manufactured by Corning Corporation is preferable.

The drive electrode 12 is made of, for example, a conductive metal such as gold (Au) or chromium (Cr) or a transparent conductive material. Examples of the transparent conductive material include tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), and tin-doped indium oxide (ITO). The thickness of the drive electrode 12 is 0.1 to 0.2 μm, for example. The drive electrode 12 is electrically connected to a terminal (not shown) provided outside the glass substrate 11 via a wiring. The insulating film 13 is made of, for example, silicon dioxide (SiO ₂ ), silicon nitride (SiN _x ) or the like, and is formed to prevent sticking between the drive electrode 12 and the movable body 21a. The antireflection films 18 and 19 are provided so that incident light from the outside is not reflected at the interface of the glass substrate 11. The antireflection films 18 and 19 are made of, for example, a multilayer film in which thin films of silicon dioxide (SiO ₂ ) and tantalum pentoxide (Ta ₂ O ₅ ) are alternately stacked. Alternatively, a silicon nitride (SiN _x ), silicon oxynitride (SiON) thin film, or the like can be stacked.

  FIG. 2 is a top view of the movable part substrate 21 constituting the wavelength tunable optical filter. The movable part 2 includes a movable part substrate 21, an antireflection film 22, and a high reflection film 23. The movable part substrate 21 serving as the third substrate is made of, for example, silicon (Si) and has a thickness of about 10 μm. As shown in FIG. 2, in the present embodiment, the movable body 21a, the four hinges 21b serving as the suspension means, and the support portion 21c are integrally formed, and the space that becomes the opening portion 21d is used. Divided into parts. The hinge 21b and the support portion 21c constitute a support. Here, the opening 21d includes not only the space shown in FIG. 2 but also a space removed to form the hinge 21b thin. The movable body 21 a has a substantially disc shape and is formed at the approximate center of the movable part substrate 21. The movable body 21a is supported by a support portion 21c via four hinges 21b formed on the peripheral edge thereof, and can move in a direction perpendicular to the surface formed by the movable portion substrate 21.

  The four hinges 21b are located adjacent to each other on the periphery of the movable body 21a at an angle of about 90 degrees. In the present embodiment, as shown in FIG. 1, the thickness of the four hinges 21b is formed to be at least thinner than the thickness of the movable body 21a. As a result, the spring constant determined by the elasticity of the hinge 21b is lowered so that the movable body 21a can obtain the same level of change as the conventional one even if it is smaller than the conventional electrostatic force. Accordingly, the voltage applied to generate the electrostatic force can be lowered, and the power consumption can be reduced. Of course, since it is necessary for the support to effectively support the weight of the movable body 21a when the electrostatic force is not working, the weight and size of the movable body 21a, the number of hinges 21b, and the thickness of the movable portion substrate 21 are required. Since the thickness varies depending on the thickness and the like, the range cannot be defined, but this is the limit of the thickness of the hinge 21b. Therefore, the hinge 21b may not be made too thin. In the present embodiment, the lower portions (the drive electrode portion 1 side) of the movable portion substrate 21a and the support portion 21c are connected to the hinge 21b.

  Here, in the present embodiment, the movable body 21a has a disc shape, but the shape is not limited to the disc shape. For example, it may be a shape such as a regular polygon that allows the movable body 21a to move vertically to the highly reflective film 32 (the surface of the movable portion substrate 21) and maintain a predetermined optical gap OG. As for the shape and number of the hinges 21b, the shape and number shown in this embodiment can be used as long as the weight of the movable body 21a is supported and the desired movable body 21a can be displaced with a predetermined driving voltage. It is not limited and may be arbitrary.

The antireflection film 22 is formed in a substantially disc shape in accordance with the shape of the movable body 21a over almost the entire lower surface (the drive electrode portion 1 side) of the movable body 21a. The antireflection film 22 is formed of, for example, a multilayer film in which thin films of silicon dioxide (SiO ₂ ) and tantalum pentoxide (Ta ₂ O ₅ ) are alternately stacked. Alternatively, the antireflection film 22 can be formed by laminating silicon nitride (SiN _x ) and silicon oxynitride (SiON) thin films. The antireflection film 22 prevents light incident from substantially below the center of the drive electrode portion 1 in FIG. 1 (see the arrow in FIG. 1) from being reflected downward in the figure, and once above the antireflection film 22. Then, the light reflected by the highly reflective film 23 is prevented from being reflected again upward in the figure. The highly reflective film 23 serving as a movable mirror is formed in a substantially disc shape in accordance with the shape of the movable body 21a on almost the entire upper surface (on the optical gap portion 3 side) of the movable body 21a. It consists of a multilayer film (about 2 to 40 layers) in which thin films of silicon (SiO ₂ ) and tantalum pentoxide (Ta ₂ O ₅ ) are alternately stacked. The antireflection film 22 and the high reflection film 23 have different thin film thicknesses. By adjusting the film thickness, the antireflection film 22 and the high reflection film 23 can be a reflection film or an antireflection film for light having a predetermined wavelength. The highly reflective film 23 is incident on the lower part of the drive electrode unit 1 in FIG. 1 (see the arrow in FIG. 1), and once transmitted therethrough, the lower surface of the glass substrate 31 constituting the optical gap unit 3. This is for reflecting a plurality of times with the highly reflective film 32 formed on the (movable part 2 side). Here, the high reflection film refers to, for example, a reflection film having a reflectance of 95% or more. In the multilayer film of the present embodiment, the reflectance is 98% or more.

The optical gap portion 3 includes a glass substrate 31, a high reflection film 32, and an antireflection film 33. The glass substrate 31 serving as the second substrate is made of glass of the same material as that of the glass substrate 11 and has a substantially doubly-supported cross section in which a concave portion 31a is formed in a substantially central portion thereof. The high reflection film 32 is formed, for example, in a substantially disk shape on the lower surface (movable part 2 side) of the concave portion 31a of the optical gap portion 3, for example, in a substantially disc shape, and is formed of a silicon dioxide (SiO ₂ ) thin film and tantalum pentoxide. It consists of a multilayer film in which thin films of (Ta ₂ O ₅ ) are alternately stacked. The high reflection film 32 serving as a fixed mirror is incident on the movable part 2 from the lower part of the center of the movable part 2 in FIG. It is for reflecting over. The antireflection film 33 is formed in a substantially disc shape on the substantially central upper surface of the optical gap portion 3, and is a multilayer film in which thin films of silicon dioxide (SiO ₂ ) and tantalum pentoxide (Ta ₂ O ₅ ) are alternately stacked. Consists of. The antireflection film 33 prevents light transmitted through the glass substrate 31 constituting the optical gap portion 3 in FIG. 1 from being reflected downward in the drawing.

  3 to 8 are diagrams showing manufacturing steps of the wavelength tunable optical filter according to the first embodiment. 3 and 4 show a manufacturing process of the drive electrode portion 1 as a first process. FIG. 5 shows a process of processing the SOI substrate 24 that becomes the movable part 2. 6 and 7 show a manufacturing process of a joined body of the SOI substrate 24 to be the movable part 2 and the drive electrode part 1 including the third process. FIG. 8 shows a manufacturing process of the optical gap portion 3 which is the second process.

  First, the manufacturing process of the drive electrode unit 1 will be described with reference to FIGS. In order to manufacture the drive electrode portion 1, as shown in FIG. 3 (2), gold (Au) is formed on one surface of the glass substrate 14 (see FIG. 3 (1)) made of Corning # 7740 described above. And a metal film 15 of chromium (Cr) or the like is formed. For the formation of the metal film 15, a chemical vapor deposition (CVD) apparatus or a physical vapor deposition (PVD) apparatus is used. Here, examples of the PVD apparatus include a sputtering apparatus, a vacuum deposition apparatus, and an ion plating apparatus. When gold (Au) is used for the metal film 15 as the mask material, chromium (Cr) is deposited to 0.03 μm, for example, and then gold is deposited to 0.07 μm, for example.

  Next, a photoresist (not shown) is applied to the entire surface of the metal film 15. The photoresist applied on the entire surface of the metal film 15 is exposed with a mask aligner by using a photolithography method, and then developed with a developer. Among the glass substrates 14, the recesses 11 a ( A photoresist pattern (not shown) is formed to form a portion to be a reference (see FIG. 1). Next, using wet etching technology, for example, hydrochloric acid or sulfuric acid (in the case of a chromium film), or a solution containing cyanide ions in the presence of aqua regia or oxygen or water (in the case of a gold film) (hereinafter referred to as metal) After the unnecessary portion of the metal film 15 is removed by an etching solution), the above-described photoresist pattern is removed to obtain an etching pattern 16 shown in FIG.

  Next, using a wet etching technique, unnecessary portions of the glass substrate 14 are removed by, for example, hydrofluoric acid (HF) to form the recesses 11a shown in FIG. Thereafter, using the wet etching technique, the etching pattern 16 is removed with the above-described metal etchant, and as shown in FIG. 3 (5), the glass substrate 11 on which the recess 11a having a depth of about 4 μm is formed. Get.

Further, as shown in FIG. 3 (6), a metal film 17 such as gold (Au) or chromium (Cr) is formed on the surface where the recess 11a is formed using a CVD apparatus or a PVD apparatus. The film thickness of the metal film 17 is, for example, 0.1 to 0.2 μm. Next, after applying a photoresist (not shown) on the entire surface of the metal film 17, using a photolithography technique, a photoresist pattern (for leaving a portion that will later become the drive electrode 12) in the metal film 17. (Not shown). Next, using the wet etching technique, unnecessary portions of the metal film 17 are removed with the above-described metal etchant, and then the above-described photoresist pattern is removed, as shown in FIG. The drive electrode 12 is obtained. Next, using a CVD apparatus, an insulating film 13 made of silicon dioxide (SiO ₂ ) or silicon nitride (SiN _x ) is formed on the drive electrode 12 as shown in FIG. Then, a thin film of silicon dioxide (SiO ₂ ) and a thin film of tantalum pentoxide (Ta ₂ O ₅ ) are alternately stacked in a substantially central portion using a CVD apparatus, a PVD apparatus, or the like (here, for example, 10 to 10). The antireflection films 18 and 19 shown in FIG. 4 (3) are formed. The drive electrode unit 1 shown in FIG. 1 is manufactured by the manufacturing process described above.

Next, an SOI substrate processing step will be described with reference to FIG. In the present embodiment, an SOI substrate 24 as shown in FIG. 5A is used to manufacture the movable part 2. The SOI substrate 24 includes a base layer 25, an insulating layer 26, and an active layer 27. The base layer 25 is made of silicon (Si) and has a film thickness of 500 μm, for example. The insulating layer 26 is made of silicon dioxide (SiO ₂ ) and has a thickness of 4 μm, for example. The active layer 27 is made of silicon (Si) and has a thickness of 10 μm, for example. The movable part substrate 21 of the movable part 2 is thinner than other substrates and is difficult to join as it is. Therefore, after the base layer 25 is thick and bonded to another substrate using the stable SOI substrate 24, the base layer 25 and the insulating layer 26 are removed. Therefore, in the wavelength tunable optical filter of this embodiment, the active layer 27 finally becomes the movable part 2. In addition, since the insulating layer 26 of the SOI substrate 24 serves as an etching stopper, the movable portion substrate 21 with high thickness accuracy can be obtained.

A thin film of silicon dioxide (SiO ₂ ) and a thin film of tantalum pentoxide (Ta ₂ O ₅ ) are alternately stacked at a substantially central portion on the active layer 27 using a CVD apparatus, a PVD apparatus, or the like (here, For example, the antireflection film 22 shown in FIG. 5B is formed. Here, a film is laminated only at a desired location using a mask. However, since this film has insulating properties, it can be formed other than the portion that reflects light, and can function as an insulating film.

Next, the drive electrode portion 1 and the SOI substrate 24 on which the antireflection film 22 shown in FIG. 5B is formed are opposed to the ring portion of the drive electrode 12 having a substantially disk shape. To join. As a bonding method, for example, anodic bonding (surface activated bonding) or bonding with an adhesive can be used. Among these, anodic bonding is performed through the following steps. First, in a state where the SOI substrate 24 on which the antireflection film 22 is formed is placed on the upper surface (the surface having the recess 11 a) of the drive electrode portion 1 so that the antireflection film 22 faces the ring portion of the drive electrode 12. A negative terminal of a DC power source (not shown) is connected to the glass substrate 11, and a positive terminal of the DC power source is connected to the active layer 27. Next, a DC voltage of, for example, about several hundred volts is applied between the glass substrate 11 and the active layer 27 while heating the glass substrate 11 to, for example, about several hundred degrees Celsius. By heating the glass substrate 11, alkali metal positive ions contained in the glass substrate 11, for example, sodium ions (Na ⁺ ) are easily moved. When the alkali metal positive ions move in the glass substrate 11, the bonding surface of the glass substrate 11 with the active layer 27 is relatively negatively charged, whereas the bonding surface of the active layer 27 with the glass substrate 11 is relatively charged. Is positively charged. As a result, the glass substrate 11 and the active layer 27 are joined as shown in FIG. 6 by the covalent bond in which silicon (Si) and oxygen (O) share an electron pair. The glass substrate used in the present embodiment is not made of so-called low-melting glass, but when so-called low-melting glass is used for the glass substrate, the glass interface is fused and bonded, Low melting glass bonding can also be used.

  Next, the base layer 25 is removed from the structure shown in FIG. 6 to obtain the structure shown in FIG. The base layer 25 is removed by wet etching, dry etching, or polishing. In the removal method by etching, since the insulating layer 26 serves as an etching stopper for the active layer 27, the active layer 27 facing the drive electrode 12 is not damaged, and a tunable optical filter having a high yield is obtained. Can be manufactured. Hereinafter, the wet etching removal method and the dry etching removal method will be described. As for the polishing removal method, since a well-known polishing removal method used in the semiconductor manufacturing field can be used, the description thereof is omitted.

(1) Wet Etching Removal Method The base layer 25 is immersed in a potassium hydroxide (KOH) aqueous solution having a concentration of 1 to 40% by weight (preferably around 10% by weight), for example, by immersing the structure shown in FIG. The constituent silicon (Si) is etched. In this case, the insulating layer 26 serves as an etching stopper for the active layer 27 made of silicon (Si).

  Etching solutions used in this case include tetramethylammonium hydroxide (TMAH) aqueous solution, ethylenediamine-pyrocatechol-diazine (EPD) aqueous solution, and hydrazine (Hydrazine) aqueous solution. Here, when a plurality of wafers are formed, batch processing (batch processing) can be performed while making the production conditions and the like substantially equal, and productivity can be improved.

(2) Dry Etching Removal Method After the structure shown in FIG. 6 is placed in a chamber of a dry etching apparatus and evacuated, for example, xenon difluoride (XeF ₂ ) at a pressure of 390 Pa is placed in the chamber for 60 seconds. By introducing, the silicon (Si) constituting the base layer 25 is etched. Note that a plasma etching method using carbon tetrafluoride (CF ₄ ) or sulfur hexafluoride (SF ₆ ) can also be used.

  Next, as shown in FIG. 7 (2), the insulating layer 26 is completely removed from the structure shown in FIG. 7 (1) by using wet etching technology, for example, with hydrofluoric acid (HF). .

  Then, after applying a photoresist (not shown) on the entire surface of the active layer 27, a photoresist pattern (not shown) for leaving a portion to become the movable part substrate 21 is formed on the active layer 27 by the photolithography technique described above. To do. Here, in this embodiment, in order to form the hinge 21b thin, two-stage anisotropic dry etching is performed using half etching. For this reason, in the first stage, a photoresist is not formed on the portion to be the opening 21d (including the portion except for thinning the hinge 21b), and this portion has a desired thickness (that is, the thickness of the hinge 21b). Etching is performed until Then, in the second stage, a photoresist is formed on a portion to be the hinge 21b, and etching is performed while leaving this portion. In both the first stage and the second stage, the portion where the photoresist is not formed is penetrated to form an opening 21d.

As an anisotropic dry etching method, for example, after being placed in a chamber (container) of a dry etching apparatus, for example, sulfur hexafluoride (SF ₆ ) is used as an etching gas at a flow rate of 130 cm ³ / min (sccm). Second, cyclobutane octafluoride (C ₄ F ₈ ) as a deposition (deposition) gas is alternately introduced into the chamber at a flow rate of 50 cm ³ / min (sccm) for 7 seconds to remove unnecessary portions. Such anisotropic dry etching is performed for the following reason. First, when the wet etching technique is used, the etching solution enters the drive electrode part 1 from the hole that becomes the opening 21d, and the drive electrode 12 and the insulating film 13 are removed. However, the dry etching technique is used. If you do, there is no such danger. In the isotropic etching, the active layer 27 is isotropically etched and side etching occurs. In particular, when side etching occurs in the hinge 21b, the strength is weakened and the durability is deteriorated. When processing for thinning the hinge 21b is performed as in the present embodiment, in the worst case, a portion that should be left as the hinge 21b may be etched. On the other hand, when anisotropic etching is used, side etching does not occur, the etching dimension is excellent, and the side surface of the hinge 21b is formed substantially vertically, so that the strength is weakened. Absent. Here, anisotropic dry etching is used in both the first stage and the second stage. However, since the opening 21d does not penetrate in the first stage, anisotropic wet etching can also be used.

  After the etching, the photoresist pattern (not shown) is removed using, for example, oxygen plasma to obtain the movable part substrate 21 as shown in FIG. Here, the photoresist pattern (not shown) is removed using oxygen plasma when the stripping solution, sulfuric acid or other acidic solution is used, the liquid enters from the hole formed in the movable part substrate 21. This is because the drive electrode 12 and the insulating film 13 are removed.

Next, a thin film of silicon dioxide (SiO ₂ ) and tantalum pentoxide (Ta ₂ ) are used at a substantially central portion of the upper surface of the movable portion substrate 21 (the surface facing the optical gap portion 3) using a CVD apparatus or a PVD apparatus. The high reflection film 23 shown in FIG. 7 (4) is formed by alternately stacking, for example, about 10 to 20 layers of the O ₅ ) thin film. The movable part 2 is produced by the process described above.

  Next, in order to manufacture the optical gap portion 3, for example, as shown in FIG. 8 (2) on one surface of the glass substrate 34 (see FIG. 8 (1)) made of Corning # 7740 described above. Then, a metal film 35 such as gold (Au) or chromium (Cr) is formed using a CVD apparatus or a PVD apparatus. When gold (Au) is used for the metal film 35 as the mask material, chromium (Cr) is deposited to 0.03 μm, for example, and then gold is deposited to 0.07 μm, for example.

  Next, a photoresist (not shown) is applied to the entire surface of the metal film 35, and the concave portion 31a (see FIG. 1) of the glass substrate 31 is later formed in the glass substrate 34 by using the photolithography technique described above. In order to form the portion, a photoresist pattern (not shown) is formed. Next, an unnecessary portion of the metal film 35 is removed with the above-described metal etching solution using a wet etching technique, and then a photoresist pattern (not shown) is removed to obtain an etching pattern shown in FIG. Get 36.

  Next, using wet etching technology, for example, unnecessary portions of the glass substrate 34 are removed by hydrofluoric acid (HF) to form the recesses 31a shown in FIG. 8 (4), and then wet etching technology is used. Then, the etching pattern 36 is removed with the above-described metal etching solution to obtain the glass substrate 31 with the recesses 31a as shown in FIG. 8 (5). Note that the glass substrate 31 has a substantially cantilever cross section as shown in FIG. 8 (5) because it is isotropically etched with hydrofluoric acid (HF). The same applies to the recess 11a of the drive electrode substrate 1, but it is not noticeable because the etching is not deep. Here, since the isotropic etching is used, the concave portion 31a has such a shape. However, the high reflection film 32 serving as a fixed mirror can secure a predetermined area, the parallelism with the high reflection film 22 and the optical gap OG. If it can ensure, the shape will not be ask | required.

Next, a thin film of silicon dioxide (SiO ₂ ) and pentoxide are formed at the center of the upper surface (outer surface) and the substantially lower surface (movable portion 2 side) of the recess 31a of the glass substrate 31 by using a CVD apparatus or PVD apparatus. By alternately laminating, for example, about 10 to 20 layers of tantalum (Ta ₂ O ₅ ) thin films, the high reflection film 32 and the antireflection film 33 shown in FIG. 8 (6) are formed. The optical gap portion 3 shown in FIG. 1 is manufactured by the manufacturing process described above.

  Then, the structure shown in FIG. 7 (4) and the optical gap portion 3 are bonded so that the highly reflective film 23 and the highly reflective film 32 face each other in parallel. For this bonding, for example, the above-described anodic bonding, surface activated bonding, or bonding with an adhesive is used. At the time of this joining, joining may be performed in a vacuum chamber so that the inside becomes a vacuum (vacuum sealing) or joining under an optimum pressure such as a reduced pressure state.

  In the case where a plurality of joined bodies that are to be the wavelength tunable optical filters are integrally manufactured in wafer units, dicing is performed to separate the tunable optical filters into the respective wavelength tunable optical filters. The wavelength tunable optical filter shown in FIG. 1 is manufactured by the process as described above.

  Next, the operation of the wavelength tunable optical filter having the above configuration will be described with reference to FIG. A drive voltage is applied between the drive electrode 12 and the movable body 21a. This drive voltage is, for example, an AC sine wave voltage of 60 Hz or a pulsed voltage. The drive electrode 12 is applied via a terminal and wiring (not shown) provided outside the glass substrate 11, while the movable body 21a is driven via a support portion 21c and a hinge 21b (see FIG. 2). A potential difference is given between Due to the potential difference due to the drive voltage, an electrostatic force is generated between the drive electrode 12 and the movable body 21a, and the movable body 21a changes toward the drive electrode 12, that is, the electrostatic gap EG and the optical gap OG change. At this time, since the hinge 21b has elasticity, the movable body 21a changes elastically.

  In this tunable optical filter, light having a plurality of (for example, 60 to 100) infrared wavelength bands (signals are included in each wavelength band) in FIG. The light enters from below the center (see the arrow in FIG. 1) and passes through the glass substrate 11. This light is hardly reflected by the antireflection film 22 and passes through the movable body 21a made of silicon, and is a space in which the high reflection film 23 is formed below and the high reflection film 32 is formed above (reflection). Enter (space). The light that has entered the reflection space is repeatedly reflected between the high reflection film 23 and the high reflection film 32, and finally passes through the high reflection film 32 and the glass substrate 31 and is emitted from above the wavelength tunable optical filter. To do. At this time, since the antireflection film 33 is formed on the upper surface of the glass substrate 31, the light is emitted without being substantially reflected at the interface between the glass substrate 31 and the air.

  In the process where light is repeatedly reflected between the high reflection film 32 (fixed mirror) and the high reflection film 23 (movable mirror), the distance between the high reflection film 32 and the high reflection film 23 (optical gap OG). The light having a wavelength that does not satisfy the interference condition corresponding to is rapidly attenuated, and only the light having the wavelength that satisfies the interference condition is finally emitted from the wavelength tunable optical filter. This is the principle of the Fabry-Perot interferometer, and light having a wavelength satisfying this interference condition is transmitted. Therefore, by changing the drive voltage, the movable body 21a changes and the optical gap OG is changed. Then, it becomes possible to select the wavelength of the transmitted light.

  As described above, the wavelength tunable optical filter according to the present embodiment includes the drive electrode portion 1 having the glass substrate 11, the movable portion 2 made of silicon (Si), and the optical gap portion 3 having the glass substrate 31 with high accuracy. Since it is fabricated (particularly in the thickness direction) and joined, the electrostatic gap EG and the optical gap OG are formed with high accuracy. Therefore, an electrostatic attractive force as designed can be generated between the movable body 21a and the drive electrode 12, and the movable body 21a can be displaced. In addition, since the hinge 21b is formed thinner than the thickness of the movable body 21a (movable part substrate 21) and the spring constant by the hinge 21b is reduced, an electrostatic force (in this case) for displacing the movable body 21a is used. (Electrostatic attractive force) can be reduced. Therefore, the drive voltage can also be lowered and power consumption can be reduced. Further, although the hinge 21b is thin, the movable body 21a has the same thickness, so that the warp caused by the stress of the antireflection film 22 or the high reflection film 23 does not occur in the movable body 21a.

  In the wavelength tunable optical filter according to this embodiment, since the movable portion 2 is formed from the SOI substrate 24, stable bonding can be performed using the thick base layer 25 as a base, and insulation serving as an etching stopper can be achieved. Since the layer 26 is provided, the movable part substrate 21 (movable body 21a) having a highly accurate film thickness can be formed.

Embodiment 2. FIG.
FIG. 9 is a sectional view showing a wavelength tunable optical filter according to the second embodiment of the present invention. Those denoted by the same reference numerals as those in FIG. 1 correspond to those described in the first embodiment, and thus description thereof is omitted. The wavelength tunable optical filter of the present embodiment is the same as that of the first embodiment in that the upper portions (on the optical gap 3 side) of the movable part substrate 21a and the support part 21c are connected to the hinge 21e. Different from filter.

  FIG. 10 shows a manufacturing process of a joined body of the movable part 2 and the optical gap part 3. In the first embodiment, a joined body of the drive electrode portion 1 and the movable portion 2 is manufactured and then joined to the optical gap portion 3. In the present embodiment, the movable part 2 and the optical gap part 3 are joined first.

  Next, a manufacturing process will be described with reference to FIG. Here, although the antireflection film 22 is formed on the active layer 27 of the SOI substrate 24 in the first embodiment, the high reflection film 23 is formed in the present embodiment. About the formation method, it forms by the method similar to the method demonstrated in 1st Embodiment. The optical gap 3 is manufactured by the method described in the first embodiment, and the description thereof is omitted.

  Then, as shown in FIG. 10A, the optical gap portion 3 and the SOI substrate 24 on which the high reflection film 23 is formed are bonded so that the high reflection film 23 and the high reflection film 32 face each other in parallel. To do. For this bonding, as in the first embodiment, for example, anodic bonding, bonding with an adhesive, or the like is used.

  By removing the base layer 25 from the joined body, the structure shown in FIG. For removal of the base layer 25, wet etching, dry etching, or polishing is used as in the first embodiment. Further, the wet etching technique is used to remove all of the insulating layer 26 using, for example, hydrofluoric acid (HF) as shown in FIG.

  Then, a photoresist pattern (not shown) is formed on the active layer 27 using a photolithography technique, and two-stage anisotropic dry etching is performed as in the first embodiment. When etching is performed according to this procedure, a wavelength tunable optical filter in which the upper part (on the optical gap 3 side) of the movable part substrate 21a and the support part 21c is connected to the hinge 21e is manufactured.

  After the etching, for example, the photoresist pattern is removed using oxygen plasma to obtain the movable part substrate 21 as shown in FIG. Then, in the same manner as in the first embodiment, an antireflection film 22 is formed as shown in FIG. 10 (5) on the substantially central portion of the lower surface of the movable portion substrate 21 (the surface facing the drive electrode 12). The movable part 2 is produced by the process described above.

  Then, the driving electrode unit 1 and the joined body created by the method described in the first embodiment are joined by a method such as anodic bonding, bonding with an adhesive, surface activation bonding, and the like, and a dicing process or the like is performed. The tunable optical filter shown in FIG. 9 is manufactured.

Embodiment 3 FIG.
FIG. 11 is a sectional view showing a wavelength tunable optical filter according to the third embodiment of the present invention. Those denoted by the same reference numerals as those in FIG. 1 correspond to those described in the first embodiment, and thus description thereof is omitted. The tunable optical filter of the present embodiment is different from the tunable optical filters of the first and second embodiments in that the center positions of the movable part substrate 21a and the support part 21c are connected to the hinge 21f.

  FIG. 12 shows a process of processing the SOI substrate 24 that becomes the movable part 2. In the present embodiment, as described in the first embodiment, the SOI substrate 24 is processed as a process for manufacturing a joined body with the drive electrode unit 1 later. First, a photoresist pattern (not shown) of the opening 21d is formed on the active layer 27 of the SOI substrate 24 by using a photolithography technique. Then, as shown in FIG. 12A, etching is performed to the depth of the portion to be left as the hinge 21e. Then, similarly to the first embodiment, an antireflection film 22 as shown in FIG. 12B is formed using a CVD apparatus, a PVD apparatus, or the like. Here, the antireflection film 22 is formed after etching. However, if the antireflection film 22 can be protected from etching by a photoresist, the antireflection film 22 may be formed first and then etched. . In addition, when joining with the optical gap part 3 like 2nd Embodiment, the highly reflective film | membrane 23 is formed instead of an antireflection film.

  Then, as in the first embodiment, as shown in FIG. 12 (3), the drive electrode unit 1 is joined by anodic bonding or the like, and after removing the base layer 25 and the insulating layer 26, a photo is formed on the active layer 27. A photoresist pattern (not shown) of the opening 21d is formed using a lithography technique. Then, etching is performed from the surface opposite to the joint surface to form the opening 21d and the hinge 21e as shown in FIG. Here, if the hinge portion is registered with a photoresist, the movable body 21a and the support portion 21c are connected at the upper portion (on the optical gap portion 3 side) as shown in FIG. 9 (as in the second embodiment). When it is joined to the optical gap part 3, it is connected at the lower part (the drive electrode part 1 side), and the process until the wavelength tunable optical filter is finally manufactured is the same as in the first embodiment. Since the hinge 21e in this embodiment is connected to the movable body 21a at the center position thereof, the movable body 21a can be changed stably.

Embodiment 4 FIG.
Although the above embodiment has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention.

For example, in the above-described embodiment, an example in which the SOI substrate 24 is used to manufacture the movable portion 2 has been described. However, the present invention is not limited to this, and an SOS (Silicon On Sapphire: Al ₂ O ₃ ) substrate is used. Also good. Alternatively, a silicon substrate in which a silicon dioxide (SiO ₂ ) film is formed on one surface and another silicon substrate laminated with the upper surfaces thereof overlapped may be used. If the thickness of the movable part substrate 21 can be made with high accuracy, the movable part substrate 21 (movable part 2) is obtained by polishing or etching after bonding the silicon substrate to another substrate. May be.

  Moreover, in the above-mentioned embodiment, although the example which comprises both the drive electrode part 1 and the optical gap part 3 with a glass substrate was shown, it is not limited to this, The drive electrode part 1 and the optical gap part 3 are A material that transmits light in a desired transmission wavelength band such as infrared, for example, silicon, sapphire, germanium, or the like may be used as the substrate material.

In the above-described embodiment, the example in which the insulating film 13 is formed on the drive electrode 12 has been described. However, the present invention is not limited to this, and the lower surface of the movable body 21a and at least the region facing the drive electrode 12 An insulating film may be formed. As a method for forming this insulating film, for example, a silicon dioxide (SiO ₂ ) film is formed using thermal oxidation in which silicon is heated in an oxidizing atmosphere or a TEOS (Tetra Ethyl Ortho Silicate) -CVD apparatus. . Further, both the silicon dioxide (SiO ₂ ) film and the tantalum pentoxide (Ta ₂ O ₅ ) film constituting the antireflection film 22 formed on the substantially lower surface of the movable body 21a are insulators. Therefore, the antireflection film 22 may be formed on the entire lower surface of the movable body 21a to be used as the above-described insulating film. In this case, it is not necessary to form the number of layers sufficient to function as the antireflection film 22 in the peripheral portion on the lower surface of the movable body 21a, and it is sufficient to form the number of layers sufficient to function as an insulating film. Further, both the insulating film 13 and the insulating film formed on the lower surface of the movable body 21a may be formed. Thus, if the antireflection film 22 is also used as an insulating film, the same effects as those of the above-described embodiment can be obtained with a small number of manufacturing steps, and a wavelength tunable optical filter can be configured at low cost. In the above-described embodiment, the example in which the highly reflective film 32 is formed on the entire lower surface of the optical gap portion 3 has been described. However, the present invention is not limited to this, and the highly reflective film 32 is formed on the lower surface of the optical gap portion 3. Of these, it may be formed only in a region facing the highly reflective film 23.

Embodiment 5 FIG.
In the above-described embodiment, the wavelength tunable optical filter having the three-layer structure of the drive electrode unit 1, the movable unit 2, and the optical gap unit 3 has been described. However, the present invention is not limited to the filter of this structure, but also in other structures. The present invention can be applied to a wavelength tunable optical filter that supports a movable body provided with a movable mirror via a hinge.

  Further, although the hinges 21b, 21e, and 21f are made thinner than the movable body 21a, for example, the support portion 21c may be made thinner than the movable body 21a. In this case, considering the distance from the electrostatic gap EG, it is better to have the hinge 21b on the drive electrode portion 1 side like the hinge 21b. Moreover, although it is not very practical with a small filter, it is also conceivable to make the hinge thicker than the movable body 21a.

1 is a cross-sectional view of a wavelength tunable optical filter showing a first embodiment. The top view of the movable part board | substrate 21 which comprises a wavelength variable optical filter. The figure showing the preparation process of the drive electrode part 1. FIG. The figure showing the manufacturing process of the drive electrode part 1 following FIG. The process of the SOI substrate 24 is represented. 4A and 4B are diagrams illustrating a manufacturing process of a bonded body of an SOI substrate 24 and a drive electrode unit 1. 4A and 4B are diagrams illustrating a manufacturing process of a bonded body of an SOI substrate 24 and a drive electrode unit 1. The figure showing the preparation process of the optical gap part 3. FIG. Sectional drawing of the wavelength tunable optical filter which shows 2nd Embodiment. The figure showing the manufacturing process of the conjugate | zygote of the movable part 2 and the optical gap part 3. FIG. Sectional drawing of the wavelength tunable optical filter which shows 3rd Embodiment. The figure showing the process of SOI substrate 24.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive electrode part, 2 Movable part, 3 Optical gap part, 11, 14, 31, 34 Glass substrate, 11a, 31a Recessed part, 12 Drive electrode, 13 Insulating film, 15, 17, 35 Metal film, 16, 36 Etching pattern , 21 Movable part substrate, 21a Movable body, 21b, 21e, 21f Hinge, 21c Support part, 21d Opening part, 18, 19, 22, 33 Antireflection film, 23, 32 High reflection film, 24 SOI substrate, 25 Base layer , 26 insulating layer, 27 active layer, EG electrostatic gap, OG optical gap.

Claims (19)

By moving the movable mirror in the direction perpendicular to the surface on which the fixed mirror is formed, the interval is changed, and light having a predetermined wavelength based on the interval is transmitted from the light reflected between the fixed mirror and the movable mirror. In the tunable optical filter,
A movable body on which the movable mirror is formed;
A wavelength tunable optical filter comprising at least a movable part having suspension means for suspending the movable body formed at least in a thickness different from that of the movable body and having a support for supporting the movable body. A movable mirror that reflects light of a certain wavelength is formed on one surface, a movable body that can be driven in a direction perpendicular to the one surface, and a suspension means that is formed with a thickness smaller than the movable body. A movable part integrally formed with a support that supports the movable body;
A drive electrode unit having a drive electrode provided opposite to the one surface across a predetermined electrostatic gap from the movable body;
A wavelength tunable optical filter, wherein the movable mirror and an optical gap portion having a fixed mirror facing each other with a predetermined optical gap are joined to each other. The wavelength tunable optical filter according to claim 2, wherein a space is provided on at least one of the one surface side or the opposite side, and the thickness of the suspension means is formed thinner than that of the movable body. 4. The wavelength tunable optical filter according to claim 3, wherein the space is formed by using at least one of a dry etching method and a wet etching method, and the thickness of the suspension means is made thinner than that of the movable body. 5. The wavelength tunable light according to claim 2, wherein the movable part is made of silicon, and one or both of the drive electrode part and the optical gap part are made of glass. filter. 6. The wavelength tunable light according to claim 2, wherein an insulating film is formed on one or both of the drive electrode and a region of the movable body facing the drive electrode. filter. The distance between the movable mirror is changed by moving the movable mirror in a direction perpendicular to the surface on which the fixed mirror is formed, and light having a predetermined wavelength based on the distance is transmitted from the light reflected between the fixed mirror and the movable mirror. A method of manufacturing a wavelength tunable optical filter, wherein a movable body provided with the movable mirror and a support body that supports the movable body via a suspension means are integrally formed,
A method of manufacturing a wavelength tunable optical filter, wherein at least the suspension means is formed with a thickness different from that of the movable body. An opening for spatially partitioning the movable body and the support body is etched to the thickness of the suspension means, and then etched to leave a portion that becomes the suspension means, and is integrally formed by opening. Item 8. A method for producing a wavelength tunable optical filter according to Item 7. 8. The wavelength tunable optical filter according to claim 7, wherein the etching up to the thickness of the suspension means is performed by a dry etching method or a wet etching method, and the etching performed while leaving the portion to be the suspension means is performed by a dry etching method. Manufacturing method. The distance from the light reflected between the fixed mirror and the movable mirror provided on the movable body is changed by moving the movable body in the vertical direction by electrostatic force with respect to the surface on which the fixed mirror is formed. A method of manufacturing a tunable optical filter that transmits light of a predetermined wavelength based on
A first step of forming a first recess on the first substrate and then forming a drive electrode on the bottom surface of the first recess to form a drive electrode portion;
A second step of forming a second recess on the second substrate and then forming the fixed mirror on the bottom surface of the second recess to form an optical gap portion;
A third substrate and the drive electrode unit are joined, and a movable body, a support body, and a suspension means having a thickness different from that of the movable body are integrally formed on the third substrate, and the movable mirror is mounted on the movable body. A third step of forming;
A wavelength tunable optical filter comprising at least a fourth step of bonding the joined body manufactured in the third step and the optical gap portion with the movable mirror and the fixed mirror facing each other. Manufacturing method. The distance from the light reflected between the fixed mirror and the movable mirror provided on the movable body is changed by moving the movable body in the vertical direction by electrostatic force with respect to the surface on which the fixed mirror is formed. A method of manufacturing a tunable optical filter that transmits light of a predetermined wavelength based on
A first step of forming a first recess in the first substrate and then forming a drive electrode in the first recess to form a drive electrode portion;
A second step of forming a second recess in the second substrate and then forming the fixed mirror in the second recess to form an optical gap portion;
The electrically conductive third substrate on which the movable mirror is formed and the optical gap portion are joined with the movable mirror and the fixed mirror facing each other, and the movable body, the support body, and the movable body have a thickness. A third step of forming different suspension means on the third substrate;
A wavelength tunable optical filter comprising at least a fourth step of joining the structure manufactured in the third step and the drive electrode portion with the movable body and the drive electrode facing each other. Manufacturing method. In the third step, after the opening that spatially partitions the movable body and the support is etched to the thickness of the suspension means, the portion that becomes the suspension means is left to be further etched and opened, The method for manufacturing a wavelength tunable optical filter according to claim 10 or 11, wherein a suspension member having a thickness different from that of the movable body, the support body, and the movable body is formed on the third substrate. In the third step, after the opening for spatially partitioning the movable body and the support is etched to the thickness of the suspension means, the etched side surfaces are joined to leave a portion that becomes the suspension means. Etching from a surface opposite to the bonded surface is performed to open a desired portion, and the movable body, the support body, and the suspension means having a thickness different from that of the movable body are formed on the third substrate. A method for producing a wavelength tunable optical filter according to claim 11 or 12. In the third step, after the active layer of the substrate in which the base layer, the insulating layer, and the active layer having conductivity are sequentially stacked is used as the third substrate, the stacked substrate is bonded from the active layer side. 14. The base layer and the insulating layer are sequentially removed, and a movable body, a support body, and suspension means having a thickness different from that of the movable body are formed in the active layer. Manufacturing method of the wavelength tunable optical filter. An SOI substrate, an SOS substrate, or a substrate obtained by bonding a silicon substrate formed with a silicon oxide film on at least one surface and a silicon substrate on the surface formed with the silicon oxide film is used as the stacked substrate. Item 15. A method for producing a wavelength tunable optical filter according to Item 14. 12. The method of manufacturing a wavelength tunable optical filter according to claim 10, further comprising a step of forming an insulating film on at least the drive electrode in the first step. In the third step, an insulating film is formed in the region on the third substrate facing the driving electrode as the movable body, and then bonded so as to face the surface on which the driving electrode and the insulating film are formed. The method of manufacturing a wavelength tunable optical filter according to claim 10. In the first step, an antireflection film is formed on the surface of the first substrate on which the first recess is formed and on the opposite surface,
In the second step, an antireflection film is formed on the surface of the second substrate opposite to the side on which the second recess is formed,
In the third step, an antireflection film is formed on the region on the third substrate facing the driving electrode as the movable body, and then bonded to the surface on which the driving electrode and the insulating film are formed. The method of manufacturing a wavelength tunable optical filter according to claim 10, further comprising: The third substrate is made of silicon, and either one or both of the first substrate and the second substrate is made of glass, and in either one or both of the third step and the fourth step. The method for producing a wavelength tunable optical filter according to any one of claims 7 to 18, wherein the bonding is performed by anodic bonding, low melting point glass bonding, or bonding with an adhesive.

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