Manufacturing method for oscillation power generation device

Abstract

To provide a manufacturing method for an oscillation power generation device capable of forming an electret film selectively in one of a movable electrode finger and a fixed electrode finger by a simple method.SOLUTION: A manufacturing method for an oscillation power generation device includes: a first silicon substrate patterning step of patterning a first silicon substrate to form a first support part and a fixed electrode finger; a second silicon substrate patterning step of patterning a second silicon layer of a second silicon substrate, in which a first silicon layer and the second silicon layer are stacked, to form a movable electrode finger and patterning the first silicon layer to form a second support part and a movable part; an electret film forming step of forming an electret film in one of the movable electrode finger and the fixed electrode finger; and a bonding step of bonding the first silicon substrate on the second silicon layer side of the second silicon substrate so that the movable electrode finger and the fixed electrode finger face each other.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a vibration power generation device. [Background technology]

[0002] Patent Document 1 describes a power generating vibration element formed by patterning an SOI (Silicon on Insulator) substrate by a semiconductor process. The SOI substrate is a substrate formed by inserting a silicon oxide layer as a BOX layer between a first silicon layer as a handle layer and a second silicon layer as a device layer. The power generating vibration element has a support part, a spring part connected to the support part, a movable part connected to the support part via the spring part, a movable electrode connected to the movable part, and a fixed electrode connected to the support part. A negatively charged electret film is formed on the movable electrode. In such a vibration power generating element, when an external force is applied, the movable part vibrates while elastically deforming the spring part, and the vibration changes the capacitance between the movable electrode and the fixed electrode, thereby generating power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-091647 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned power generating vibration element, both the movable electrode and the fixed electrode are formed from the second silicon layer. Therefore, after the movable electrode and the fixed electrode are patterned by a semiconductor process, it is necessary to selectively form an electret film only on the movable electrode while they are meshed with each other at a narrow pitch. Therefore, there is a problem that it is difficult to form the electret film. [Means for solving the problem]

[0005] The method for manufacturing a vibration power generation device of the present invention includes the steps of: A movable portion that is displaceable in a first direction relative to the support portion; a movable electrode finger connected to the movable portion; and a fixed electrode finger connected to the support portion. a first silicon substrate patterning step of patterning a first silicon substrate by etching to form the first support portion and the fixed electrode finger; a second silicon substrate patterning step of forming the movable electrode finger by etching the second silicon layer of a second silicon substrate having a first silicon layer and a second silicon layer stacked thereon, and forming the second support portion and the movable portion by etching the first silicon layer; an electret film forming step of forming an electret film on one of the movable electrode fingers and the fixed electrode fingers; and a bonding step of bonding the first silicon substrate to the second silicon layer side of the second silicon substrate such that the movable electrode fingers and the fixed electrode fingers face each other. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a top view showing a vibration power generation device according to a preferred embodiment. [Diagram 2] FIG. 2 is a perspective view of the vibration power generation device of FIG. [Diagram 3] FIG. 2 is an exploded perspective view of the vibration power generation device of FIG. [Figure 4] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 5] 3 is a cross-sectional view of a first alignment mark and a second alignment mark. FIG. [Figure 6] 2 is a flowchart showing a method for manufacturing the vibration power generation device shown in FIG. [Figure 7] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 8] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 9] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 10] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 11] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 12] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 13] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 14] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 15] 13 is a top view showing a first silicon substrate according to a modified example of the method for manufacturing a vibration power generation device. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a vibration power generation device according to the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings.

[0008] FIG. 1 is a top view showing a vibration power generation device according to a preferred embodiment. FIG. 2 is a perspective view of the vibration power generation device of FIG. 1. FIG. 3 is an exploded perspective view of the vibration power generation device of FIG. 1. FIG. 4 is a cross-sectional view taken along line AA in FIG. 1. FIG. 5 is a cross-sectional view of a first alignment mark and a second alignment mark. FIG. 6 is a flowchart showing a method for manufacturing the vibration power generation device shown in FIG. 1. FIGS. 7 to 14 are cross-sectional views for explaining a method for manufacturing a vibration power generation device. FIG. 15 is a top view showing a first silicon substrate according to a modified example of the method for manufacturing a vibration power generation device.

[0009] For ease of explanation, the three mutually perpendicular axes are referred to as the X-axis, Y-axis, and Z-axis below. The direction along the X-axis is also referred to as the X-axis direction, the direction along the Y-axis is also referred to as the Y-axis direction, and the direction along the Z-axis is also referred to as the Z-axis direction. The arrow side of each axis is also referred to as the plus side, and the opposite side is also referred to as the minus side. The plus side of the Z-axis direction is also referred to as the upper side, and the minus side is also referred to as the lower side.

[0010] 1 to 3 is a static induction type vibration power generation element that generates power by being driven by an external force. Such a vibration power generation device 1 is manufactured by bonding a first silicon substrate 2 patterned by a semiconductor process to an SOI (Silicon on Insulator) substrate 3, which is a second silicon substrate patterned by a semiconductor process.

[0011] The first silicon substrate 2 is a double-sided mirror silicon substrate, and the thickness of the first silicon substrate 2 is about 200 μm or more and 300 μm or less.

[0012] As shown in Fig. 4, the SOI substrate 3 is a substrate formed by inserting a silicon oxide layer 3B between a first silicon layer 3A and a second silicon layer 3C. The first silicon layer 3A is also called a handle layer, the second silicon layer 3C is also called a device layer, and the silicon oxide layer 3B is also called a BOX layer. The thickness of the first silicon layer 3A is 200 µm or more and 500 µm or less, the thickness of the silicon oxide layer 3B is about 1 µm, and the thickness of the second silicon layer 3C is equal to the thickness of the first silicon substrate 2, that is, about 200 µm or more and 300 µm or less. However, the thickness of each of these parts is not particularly limited.

[0013] 1 to 3, such a vibration power generation device 1 has a support part 4, a spring part 5 connected to the support part 4, a movable part 6 connected to the support part 4 via the spring part 5, a movable electrode 7 connected to the movable part 6, and a first fixed electrode 8 and a second fixed electrode 9 connected to the support part 4. The movable part 6 is displaceable in the X-axis direction, which is a first direction, relative to the support part 4 while elastically deforming the spring part 5. In the vibration power generation device 1 configured as above, when an external force in the X-axis direction is applied, the movable part 6 vibrates in the X-axis direction while elastically deforming the spring part 5, and this vibration changes the capacitance between the movable electrode 7 and the first and second fixed electrodes 8 and 9, thereby generating power.

[0014] ≪Support part 4≫ As shown in FIG. 4, the support portion 4 is formed of a laminate of a first support portion 41 formed from the first silicon substrate 2 and a second support portion 42 formed from the first silicon layer 3A of the SOI substrate 3.

[0015] The second support portion 42 has a frame shape in plan view from the Z-axis direction. In addition, a second alignment mark A2 is formed at each of the four corners of the second support portion 42. The second alignment mark A2 is used to position the first silicon substrate 2 and the SOI substrate 3. As shown in FIG. 5, each second alignment mark A2 is a recess A20 that opens into the upper surface of the second support portion 42. Each recess A20 is square in plan view from the Z-axis direction.

[0016] However, the number, arrangement, and configuration of the second alignment marks A2 are not particularly limited. For example, the second alignment marks A2 may be protrusions protruding from the upper surface of the second silicon layer 3C of the SOI substrate 3 instead of recesses, or may be printed on the upper surface of the second silicon layer 3C of the SOI substrate 3. Also, the second alignment marks A2 may be omitted.

[0017] 1 to 3, the first support portion 41 is divided into a first fixed electrode support portion 411 located on the positive side in the X-axis direction and connected to the first fixed electrode 8, and a second fixed electrode support portion 412 located on the negative side in the X-axis direction and connected to the second fixed electrode 9, and these are insulated from each other. An electrode pad PAD1 for extracting charge from the first fixed electrode 8 is formed on the first fixed electrode support portion 411, and an electrode pad PAD2 for extracting charge from the second fixed electrode 9 is formed on the second fixed electrode support portion 412.

[0018] Further, first alignment marks A1 overlapping with the second alignment marks A2 are formed at the four corners of the first support portion 41. The first alignment marks A1 are used for positioning the first silicon substrate 2 and the SOI substrate 3 relative to each other.

[0019] As shown in FIG. 5, each of the first alignment marks A1 is a through hole A10 penetrating the first silicon substrate 2 in the thickness direction. Therefore, the second alignment mark A2 located below the through hole A10 can be seen through the through hole A10. The through hole A10 has a first portion A11 that opens on the upper surface of the first silicon substrate 2, and a second portion A12 that penetrates the bottom surface of the first portion A11 and the lower surface of the first silicon substrate 2. In a plan view from the Z-axis direction, the first portion A11 and the second portion A12 are each square and formed coaxially. The second portion A12 is smaller than the first portion A11, and a step is formed between them. That is, the opening of the first alignment mark A1 on the upper surface side of the first silicon substrate 2 is larger than the opening on the lower surface side.

[0020] With this configuration, light can easily enter the first alignment mark A1 from the upper opening, and the first silicon substrate 2 and the SOI substrate 3 can be positioned in a brighter environment, that is, in an environment where a sufficient field of view is ensured. In addition, the second portion A12 is formed slightly larger than the second alignment mark A2, and the second alignment mark A2 is positioned so as to be located at the center of the second portion A12. Therefore, the first silicon substrate 2 and the SOI substrate 3 can be positioned with high accuracy.

[0021] However, the number, arrangement, and configuration of the first alignment marks A1 are not particularly limited, and the first alignment marks A1 may be omitted.

[0022] ≪Movable part 6≫ As shown in FIG. 4, the movable part 6 is formed from the first silicon layer 3A of the SOI substrate 3, and is located at the center of the vibration power generation device 1 when viewed from the Z-axis direction.

[0023] <Spring part 5> As shown in FIG. 4, the spring portion 5 is formed from the first silicon layer 3A of the SOI substrate 3. That is, the spring portion 5 is formed from the same layer as the movable portion 6. Therefore, the spring portion 5 can be disposed near the center of gravity of the movable portion 6, and unnecessary displacement of the movable portion 6, that is, displacement in directions other than the X-axis direction, can be effectively suppressed. Also, as shown in FIG. 1 and FIG. 3, the spring portion 5 has a first spring portion 51 that connects the end portion of the movable portion 6 on the positive side in the X-axis direction to the second support portion 42, and a second spring portion 52 that connects the end portion of the movable portion 6 on the negative side in the X-axis direction to the second support portion 42. The first spring portion 51 and the second spring portion 52 each have a beam shape extending in the Y-axis direction and elastically deform in the X-axis direction. In this way, the movable portion 6 can be stably vibrated in the X-axis direction by supporting the movable portion 6 from both sides in the X-axis direction by the first spring portion 51 and the second spring portion 52.

[0024] However, as long as the movable portion 6 is displaceable in the X-axis direction relative to the support portion 4, the configuration of the spring portion 5 is not particularly limited.

[0025] <Moveable electrode 7> As shown in FIG. 4, the movable electrode 7 is formed from the second silicon layer 3C of the SOI substrate 3. Also, as shown in FIGS. 1 to 3, the movable electrode 7 overlaps with the movable part 6 in plan view from the Z-axis direction. In this way, by arranging the movable electrode 7 and the movable part 6 so as to overlap in the Z-axis direction, the movable part 6 can be made larger and its mass can be increased without increasing the planar dimensions of the vibration power generation device 1. Therefore, the sensitivity of the vibration power generation device 1 is improved, and the movable part 6 can be vibrated efficiently even in a low frequency band. Furthermore, since the movable electrode 7 and the first and second fixed electrodes 8 and 9 can be formed over a wide range regardless of the size of the movable part 6, the capacitance between the movable electrode 7 and the first and second fixed electrodes 8 and 9 can be increased. Therefore, the amount of power generated by the vibration power generation device 1 can be increased.

[0026] The movable electrode 7 has a comb-like shape and includes an electrode finger support portion 71 connected to the movable portion 6 via the silicon oxide layer 3B, and a plurality of movable electrode fingers 72 extending from the electrode finger support portion 71. The electrode finger support portion 71 extends in the Y-axis direction. Meanwhile, the plurality of movable electrode fingers 72 include a plurality of first movable electrode fingers 721 extending from the electrode finger support portion 71 to the positive side in the X-axis direction and arranged at equal intervals in the Y-axis direction, and a plurality of second movable electrode fingers 722 extending from the electrode finger support portion 71 to the negative side in the X-axis direction and arranged at equal intervals in the Y-axis direction.

[0027] An electret film EL is formed on the surfaces of the first and second movable electrode fingers 721 and 722, particularly on the side surfaces facing the first and second fixed electrode fingers 82 and 92 described later. The electret film EL is, for example, a negatively charged silicon oxide layer formed by thermally oxidizing the first and second movable electrode fingers 721 and 722. The electret film EL may be formed on the first and second fixed electrode fingers 82 and 92, instead of the first and second movable electrode fingers 721 and 722. However, as in this embodiment, it is preferable to form the electret film EL on the first and second movable electrode fingers 721 and 722. By forming the electret film EL on the first and second movable electrode fingers 721 and 722, which are displaced relative to the support 4, electric charges during power generation can be taken out from the first and second fixed electrode fingers 82 and 92, which are fixed relative to the support 4. This makes it easier to take out electric charges.

[0028] <<First and second fixed electrodes 8, 9>> 1 to 3, the first fixed electrode 8 and the second fixed electrode 9 are each formed from a first silicon substrate 2. Furthermore, the first fixed electrode 8 and the second fixed electrode 9 are each arranged so as not to overlap with the movable portion 6 and the spring portion 5 in a plan view from the Z-axis direction. This makes it possible to suppress contact between the first and second fixed electrodes 8, 9 and the movable portion 6 and the spring portion 5.

[0029] The first fixed electrode 8 has a comb-like shape and includes an electrode finger support portion 81 connected to the first fixed electrode support portion 411 and a plurality of first fixed electrode fingers 82 as fixed electrode fingers extending from the electrode finger support portion 81. The electrode finger support portion 81 includes a first electrode finger support portion 811 located on the positive side of the Y axis direction from the movable portion 6 in a plan view from the Z axis direction so as not to overlap with the movable portion 6, and a second electrode finger support portion 812 located on the negative side of the Y axis direction from the movable portion 6. The first and second electrode finger support portions 811 and 812 are arranged in a straight line along the Y axis direction, and an end portion of the first electrode finger support portion 811 on the positive side of the Y axis direction and an end portion of the second electrode finger support portion 812 on the negative side of the Y axis direction are each connected to the first fixed electrode support portion 411. The plurality of first fixed electrode fingers 82 extend from the first and second electrode finger support portions 811 and 812 to the negative side of the X axis direction and are arranged at equal intervals in the Y axis direction. The plurality of first fixed electrode fingers 82 and the plurality of first movable electrode fingers 721 face each other in a stationary state with a predetermined meshing length in the X-axis direction and with a gap in the Y-axis direction.

[0030] The second fixed electrode 9 is formed symmetrically to the first fixed electrode 8. The second fixed electrode 9 is comb-shaped and has an electrode finger support portion 91 connected to the second fixed electrode support portion 412, and a plurality of second fixed electrode fingers 92 as fixed electrode fingers extending from the electrode finger support portion 91. The electrode finger support portion 91 has a first electrode finger support portion 911 located on the positive side in the Y axis direction from the movable portion 6 in a plan view from the Z axis direction so as not to overlap with the movable portion 6, and a second electrode finger support portion 912 located on the negative side in the Y axis direction from the movable portion 6. The first and second electrode finger support portions 911 and 912 are arranged in a straight line along the Y axis direction, and an end portion of the first electrode finger support portion 911 on the positive side in the Y axis direction and an end portion of the second electrode finger support portion 912 on the negative side in the Y axis direction are each connected to the second fixed electrode support portion 412. The multiple second fixed electrode fingers 92 extend from the first and second electrode finger support portions 911, 912 to the positive side in the X-axis direction, and are disposed at equal intervals in the Y-axis direction. In a stationary state, the multiple second fixed electrode fingers 92 and the multiple second movable electrode fingers 722 face each other with a predetermined meshing length in the X-axis direction and with a gap in the Y-axis direction.

[0031] The configuration of the vibration power generation device 1 has been briefly described above. In the vibration power generation device 1 configured as above, when a force in the X-axis direction is applied, the movable part 6 vibrates in the X-axis direction while elastically deforming the first and second spring parts 51 and 52. Then, the vibration of the movable part 6 changes the meshing length between the first and second movable electrode fingers 721 and 722 and the first and second fixed electrode fingers 82 and 92 in opposite phases, thereby generating power. Specifically, when the movable part 6 is displaced to the positive side in the X-axis direction, the meshing length between the first fixed electrode finger 82 and the first movable electrode finger 721 increases, and a positive charge is charged, and the meshing length between the second fixed electrode finger 92 and the second movable electrode finger 722 decreases, and the charge is discharged. Conversely, when movable part 6 is displaced to the negative side in the X-axis direction, the meshing length of first fixed electrode finger 82 with first movable electrode finger 721 decreases and the stored charge is discharged, and the meshing length of second fixed electrode finger 92 with second movable electrode finger 722 increases and a positive charge is stored in second fixed electrode finger 92. In this way, charging and discharging of charges are repeated in opposite phases between first and second fixed electrode fingers 82, 92.

[0032] As the first and second fixed electrode fingers 82, 92 are repeatedly charged and discharged, a current flows from the vibration power generation device 1 to a rectifier circuit (not shown). This current is rectified by the rectifier circuit and input to the secondary battery. As a result, the power generated by the vibration power generation device 1 is stored in the secondary battery. The power stored in the secondary battery is supplied to a load as needed. The secondary battery is a rechargeable battery such as a lithium secondary battery. The load is, for example, a circuit for realizing the functions of a portable electrical device, and operates by consuming power supplied from the secondary battery. For example, if the portable electrical device is a wristwatch, the load includes a timing circuit and performs various controls such as keeping track of the current time.

[0033] Next, a description will be given of a manufacturing method of the vibration power generation device 1. As shown in Fig. 6, the manufacturing method of the vibration power generation device 1 includes a first silicon substrate patterning step S1 in which the first silicon substrate 2 is patterned by etching to form the first support portion 41 and the first and second fixed electrodes 8 and 9, a second silicon substrate patterning step S2 in which the second silicon layer 3C of the SOI substrate 3 is patterned by etching to form the movable electrode 7 and the first silicon layer 3A is patterned by etching to form the second support portion 42 and the movable portion 6, an electret film formation step S3 in which an electret film EL is formed on the movable electrode 7, and a bonding step S4 in which the first silicon substrate 2 and the SOI substrate 3 are bonded to each other.

[0034] <First silicon substrate patterning process S1> In the first silicon substrate patterning step S1, first, as shown in FIG. 7, a first silicon substrate 2 is prepared. The first silicon substrate 2 is a double-sided mirror silicon substrate and has a thickness of about 200 μm or more and 300 μm or less. Next, as shown in FIG. 8, the first silicon substrate 2 is patterned by etching to form a first alignment mark A1. Next, as shown in FIG. 9, the first silicon substrate 2 is patterned by etching to form a first support 41 and first and second fixed electrodes 8 and 9. Specifically, a portion where the first fixed electrode support 411 and the first fixed electrode 8 are integrally formed, and a portion where the second fixed electrode support 412 and the second fixed electrode 9 are integrally formed are formed.

[0035] The etching method is not particularly limited, but it is preferable to use dry etching, particularly RIE (reactive ion etching). By using dry etching, through holes with a high aspect ratio can be formed with high precision, enabling finer processing.

[0036] <<Second silicon substrate patterning process S2>> In the second silicon substrate patterning step S2, first, as shown in FIG. 10, an SOI substrate 3 is prepared as a second silicon substrate. The SOI substrate 3 is a substrate formed by inserting a silicon oxide layer 3B between a first silicon layer 3A and a second silicon layer 3C, where the first silicon layer 3A has a thickness of 200 μm or more and 500 μm or less, the silicon oxide layer 3B has a thickness of about 1 μm, and the second silicon layer 3C has a thickness equivalent to that of the first silicon substrate 2. In this way, by using the SOI substrate 3 as the second silicon substrate, the silicon oxide layer 3B functions as an etching stop layer. Therefore, the first silicon layer 3A and the second silicon layer 3C can be etched independently, and this step S2 can be performed with high accuracy.

[0037] Next, as shown in FIG. 11, the second silicon layer 3C is patterned by etching from the upper surface side to form the movable electrode 7. At this time, the silicon oxide layer 3B functions as an etching stop layer. Next, as shown in FIG. 12, the first silicon layer 3A is patterned by etching from the lower surface side to form the second support portion 42, the spring portion 5, and the movable portion 6. Next, the silicon oxide layer 3B exposed from the second silicon layer 3C is removed by etching, and then, as shown in FIG. 13, the first silicon layer 3A is patterned by etching to form the second alignment mark A2.

[0038] The etching method is not particularly limited, but it is preferable to use dry etching, particularly RIE (reactive ion etching). By using dry etching, through holes with a high aspect ratio can be formed with high precision, enabling finer processing.

[0039] Moreover, the second silicon substrate patterning step S2 may be performed prior to or in parallel with the first silicon substrate patterning step S1.

[0040] <Electret film formation process S3> In the electret film formation process S3, an electret film EL is formed on the first and second movable electrode fingers 721, 722. In this embodiment, first, the SOI substrate 3 is thermally oxidized to form a silicon oxide film on the surfaces of the first and second movable electrode fingers 721, 722. Then, this silicon oxide film is doped with alkali ions such as potassium ions, and then an electric field is applied to remove the alkali ions from the silicon oxide film, thereby charging it.

[0041] However, the method for forming the electret film EL is not particularly limited. For example, the electret film EL may be charged by a method in which alkali ions are fixed on the surfaces of the first and second movable electrode fingers 721 and 722 by spray coating or the like, the first and second movable electrode fingers 721 and 722 are thermally oxidized to form a silicon oxide film containing alkali ions on the surfaces of the first and second movable electrode fingers 721 and 722, and then an electric field is applied to remove the alkali ions from the silicon oxide film.

[0042] In this embodiment, the electret film EL is formed on the first and second movable electrode fingers 721, 722, but the present invention is not limited to this, and the electret film EL may be formed on the first and second fixed electrode fingers 82, 92. When forming the electret film EL on the first and second fixed electrode fingers 82, 92, the electret film forming step S3 may be performed prior to the second silicon substrate patterning step S2.

[0043] ≪Joining process S4≫ In the bonding step S4, as shown in FIG. 14, the first silicon substrate and the SOI substrate 3 are bonded so that the first and second movable electrode fingers 721, 722 and the first and second fixed electrode fingers 82, 92 mesh with each other. Specifically, the lower surfaces of the first fixed electrode support 411 and the second fixed electrode support 412 are bonded to the upper surface of the second support 42, respectively. This results in a support 4 that is a laminate of the first support 41 and the second support 42. This results in the manufacture of the vibration power generation device 1. Although not shown, a thermal oxide film is also formed on the upper surface of the second support 42 by thermal oxidation in the electret film formation step S3. Therefore, this thermal oxide film is interposed between the first support 41 and the second support 42, and the first support 41 and the second support 42 are insulated from each other.

[0044] In this step, the first silicon substrate 2 and the SOI substrate 3 are positioned based on the first alignment mark A1 formed on the first support portion 41 and the second alignment mark A2 formed on the second support portion 42. This facilitates positioning of the first silicon substrate 2 and the SOI substrate 3. Specifically, the first fixed electrode support portion 411 and the second fixed electrode support portion 412 are positioned relative to the SOI substrate 3 so that each second alignment mark A2 overlaps with the corresponding first alignment mark A1 in a plan view from the Z-axis direction, and the second alignment mark A2 is located at the center of the second portion A12 of the first alignment mark A1. This allows the first silicon substrate 2 and the SOI substrate 3 to be positioned with high accuracy.

[0045] The method for bonding the first fixed electrode support 411 and the second fixed electrode support 412 to the SOI substrate 3 is not particularly limited, and may be, for example, bonded using an adhesive or directly bonded. As the direct bonding, for example, room temperature bonding such as surface activated bonding may be used.

[0046] As described above, in the manufacturing method of the vibration power generation device 1 of this embodiment, the process is divided into a first silicon substrate patterning step S1 and a second silicon substrate patterning step S2, and the movable electrode 7 and the first and second fixed electrodes 8 and 9 are formed from different substrates. Therefore, the electret film EL can be easily formed only on the movable electrode 7. Furthermore, by forming the movable electrode 7 and the first and second fixed electrodes 8 and 9 from different substrates, the distance between the first movable electrode finger 721 and the first fixed electrode finger 82 and the distance between the second movable electrode finger 722 and the second fixed electrode finger 92 can be made smaller than when they are formed from a single substrate. Therefore, the capacitance between the movable electrode 7 and the first and second fixed electrodes 8 and 9 can be increased, and the amount of power generation can be increased.

[0047] The above describes the method for manufacturing the vibration power generation device 1. As described above, the method for manufacturing such a vibration power generation device 1 is a method for manufacturing a vibration power generation device 1 having a support part 4 having a first support part 41 and a second support part 42, a movable part 6 displaceable in the X-axis direction, which is a first direction, relative to the support part 4, a movable electrode finger 72 connected to the movable part 6, and first and second fixed electrode fingers 82, 92, which are fixed electrode fingers connected to the support part 4, and includes a first silicon substrate patterning step S1 in which the first silicon substrate 2 is patterned by etching to form the first support part 41 and the first and second fixed electrode fingers 82, 92, a first silicon layer 3A, a second silicon layer 3C, and a first silicon substrate patterning step S2 in which the first silicon substrate 2 is patterned by etching to form the first support part 41 and the first and second fixed electrode fingers 82, 92, and a second silicon layer 3C. The manufacturing method includes a second silicon substrate patterning step S2 of etching and patterning the second silicon layer 3C of the SOI substrate 3, which is a second silicon substrate on which the first and second fixed electrode fingers 82 and 92 are stacked, to form the movable electrode fingers 72 and the second support portion 42 and the movable portion 6, an electret film forming step S3 of forming an electret film EL on one of the movable electrode fingers 72 and the first and second fixed electrode fingers 82 and 92, and a bonding step S4 of bonding the first silicon substrate 2 to the second silicon layer 3C side of the SOI substrate 3 such that the movable electrode fingers 72 and the first and second fixed electrode fingers 82 and 92 face each other. In this manufacturing method, the process is divided into a first silicon substrate patterning step S1 and a second silicon substrate patterning step S2, and the movable electrode fingers 72 and the first and second fixed electrode fingers 82 and 92 are formed from different substrates. Therefore, the electret film EL can be easily and selectively formed on only one of the movable electrode finger 72 and the first and second fixed electrode fingers 82, 92.

[0048] As described above, the second silicon substrate is an SOI substrate 3 having a silicon oxide layer 3B interposed between a first silicon layer 3A and a second silicon layer 3C. By using the SOI substrate 3 as the second silicon substrate in this manner, the silicon oxide layer 3B functions as an etching stop layer. Therefore, the first silicon layer 3A and the second silicon layer 3C can be etched independently, and the second silicon substrate patterning step S2 can be performed with high accuracy.

[0049] As described above, in the second silicon substrate patterning process S2, the first silicon layer 3A is patterned by etching to form the spring portion 5 that connects the second support portion 42 and the movable portion 6. This allows the movable portion 6 to be supported so as to be displaceable relative to the support portion 4. In particular, by forming the spring portion 5 from the same layer as the movable portion 6, the spring portion 5 can be disposed near the center of gravity of the movable portion 6. Therefore, unnecessary displacement of the movable portion 6, that is, displacement in directions other than the X-axis direction, can be effectively suppressed.

[0050] As described above, the first alignment mark A1 is formed on the first support portion 41, and the second alignment mark A2 is formed on the second support portion 42. Then, in the bonding process S4, the first silicon substrate 2 and the SOI substrate 3 are positioned based on the first alignment mark A1 and the second alignment mark A2. This makes it easy to position the first silicon substrate 2 and the SOI substrate 3.

[0051] As described above, the first alignment mark A1 is a through hole A10 that penetrates the first support portion 41. Then, in the bonding process S4, the first silicon substrate 2 and the SOI substrate 3 are positioned so that the through hole A10 and the second alignment mark A2 overlap with each other. This allows the first silicon substrate 2 and the SOI substrate 3 to be positioned with high accuracy.

[0052] As described above, in the electret film formation step S3, the electret film EL is formed on the movable electrode fingers 72. By forming the electret film EL on the movable electrode fingers 72, which are displaceable relative to the support 4, electric charges generated during power generation can be extracted from the first and second fixed electrode fingers 82, 92, which are fixed relative to the support 4. This makes it easy to extract the electric charges.

[0053] Although the manufacturing method of the vibration power generation device of the present invention has been described above based on the illustrated embodiment, the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration or any process having a similar function. In addition, any other configuration or any process may be added to the present invention.

[0054] In the above-described embodiment, in the first silicon substrate patterning step S1, a portion where the first fixed electrode support 411 and the first fixed electrode 8 are integrally formed and a portion where the second fixed electrode support 412 and the second fixed electrode 9 are integrally formed are formed separately. Therefore, in the bonding step S4, it is necessary to position these two members separately with respect to the SOI substrate 3. Therefore, the positioning may take a long time.

[0055] Therefore, for example, as shown in FIG. 15, in the first silicon substrate patterning step S1, a connecting beam 419 may be formed to connect a portion where the first fixed electrode support 411 and the first fixed electrode 8 are integrally formed and a portion where the second fixed electrode support 412 and the second fixed electrode 9 are integrally formed. According to such a method, in the bonding step S4, these can be positioned with respect to the SOI substrate 3 at once. Therefore, the time required for positioning can be shortened. In this case, after the bonding step S4 is completed, the connecting beam 419 is cut by, for example, etching, laser irradiation, or the like, and the portion where the first fixed electrode support 411 and the first fixed electrode 8 are integrally formed and the portion where the second fixed electrode support 412 and the second fixed electrode 9 are integrally formed are separated and insulated, thereby obtaining the vibration power generation device 1. [Explanation of symbols]

[0056] 1... vibration power generation device, 2... first silicon substrate, 3... SOI substrate, 3A... first silicon layer, 3B... silicon oxide layer, 3C... second silicon layer, 4... support portion, 41... first support portion, 411... support portion for first fixed electrode, 412... support portion for second fixed electrode, 419... connecting beam, 42... second support portion, 5... spring portion, 51... first spring portion, 52... second spring portion, 6... movable portion, 7... movable electrode, 71... electrode finger support portion, 72... movable electrode finger, 721... first movable electrode finger, 722... second movable electrode finger, 8... first fixed electrode, 81... electrode finger support portion, 811... first electrode finger support portion, 8 12...second electrode finger support portion, 82...first fixed electrode finger, 9...second fixed electrode, 91...electrode finger support portion, 911...first electrode finger support portion, 912...second electrode finger support portion, 92...second fixed electrode finger, A1...first alignment mark, A10...through hole, A11...first portion, A12...second portion, A2...second alignment mark, A20...recess, EL...electret film, PAD1...electrode pad, PAD2...electrode pad, S1...first silicon substrate patterning step, S2...second silicon substrate patterning step, S3...electret film forming step, S4...bonding step

Claims

1. a support portion having a first support portion and a second support portion; A movable portion displaceable in a first direction relative to the support portion; a movable electrode finger connected to the movable portion; and a fixed electrode finger connected to the support portion. a first silicon substrate patterning step of patterning a first silicon substrate by etching to form the first support portion and the fixed electrode finger; a second silicon substrate patterning step of forming the movable electrode finger by etching the second silicon layer of a second silicon substrate having a first silicon layer and a second silicon layer stacked thereon, and forming the second support portion and the movable portion by etching the first silicon layer; an electret film forming step of forming an electret film on one of the movable electrode fingers and the fixed electrode fingers; a bonding step of bonding the first silicon substrate to the second silicon layer side of the second silicon substrate so that the movable electrode fingers and the fixed electrode fingers face each other.

2. 2. The method for manufacturing a vibration power generation device according to claim 1, wherein the second silicon substrate is an SOI substrate having a silicon oxide layer interposed between the first silicon layer and the second silicon layer.

3. 2. The method for manufacturing a vibration power generation device according to claim 1, wherein in the second silicon substrate patterning step, the first silicon layer is patterned by etching to form a spring portion that connects the second support portion and the movable portion.

4. a first alignment mark is formed on the first support; a second alignment mark is formed on the second support; 2 . The method for manufacturing a vibration power generation device according to claim 1 , wherein in the bonding step, the first silicon substrate and the second silicon substrate are positioned based on the first alignment mark and the second alignment mark.

5. the first alignment mark is a through hole penetrating the first support portion, The method for manufacturing a vibration power generation device according to claim 4 , wherein in the bonding step, the first silicon substrate and the second silicon substrate are positioned such that the through hole and the second alignment mark overlap each other.

6. The method for manufacturing a vibration power generation device according to claim 1 , wherein in the electret film forming step, the electret film is formed on the movable electrode fingers.

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