Manufacturing method for oscillation power generation device
Patent Information
- Application Number
- JP2023145329
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-09-07
- Publication Date
- 2025-03-19
Smart Images
Figure 2025038608000001_ABST
Abstract
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 vibration power generation 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 vibration power generation 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 generation 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 vibration power generation 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 a first silicon layer patterning step of forming a first comb-teeth electrode that moves relatively and a second comb-teeth electrode aligned with the first comb-teeth electrode by patterning a first silicon layer; an alkaline ion solution supplying step of supplying an alkaline ion solution to a surface of the first comb tooth electrode and a surface of the second comb tooth electrode in a state where a voltage is applied between the first comb tooth electrode and the second comb tooth electrode such that the first comb tooth electrode has a higher potential than the second comb tooth electrode; a drying step of drying the alkali ion solution; an oxide film forming step of forming a first oxide film on a surface of the first comb-teeth electrode and a second oxide film on a surface of the second comb-teeth electrode by heat-treating the first silicon layer; and a charging step of applying a voltage to the second comb electrode to charge the second oxide film, thereby forming an electret film. [Brief description of the drawings]
[0006] [Figure 1] FIG. 1 is a plan view of a vibration power generation device according to a preferred embodiment. [Diagram 2] 2 is a plan view of the vibration power generation device of FIG. 1 with a first silicon layer removed. FIG. [Diagram 3] 2 is a cross-sectional view taken along line AA in FIG. 1. [Figure 4] 1 is a flowchart showing a manufacturing process for a vibration power generation device. [Diagram 5] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 6] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [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] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 16] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 17] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 18] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 19] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. [Figure 20] 1A to 1C are cross-sectional views illustrating a method for manufacturing a vibration power generation device. 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 plan view of a vibration power generation device according to a preferred embodiment. Fig. 2 is a plan view of the vibration power generation device of Fig. 1 after removing a first silicon layer. Fig. 3 is a cross-sectional view taken along line AA in Fig. 1. Fig. 4 is a flowchart showing the manufacturing process of the vibration power generation device. Figs. 5 to 20 are cross-sectional views for explaining a manufacturing method of the vibration power generation device.
[0009] In each figure except for Figure 4, the X-axis, Y-axis, and Z-axis are shown as three mutually perpendicular axes. The direction along the X-axis, i.e., the direction parallel to the X-axis, is also called the "X-axis direction," the direction along the Y-axis, the "Y-axis direction," and the direction along the Z-axis, the "Z-axis direction." The side of the arrow tip of each axis is also called the "plus side," and the opposite side is also called the "negative side." The plus side of the Z-axis direction is also called the "upper," and the negative side of the Z-axis direction is also called the "lower."
[0010] 1 and 2 is a static induction type vibration power generation device that generates power by being driven by an external force. Such a vibration power generation device 1 is manufactured by patterning an SOI (Silicon on Insulator) substrate 2 by a semiconductor process.
[0011] As shown in Fig. 3, the SOI substrate 2 is a substrate in which a silicon oxide layer 2B is interposed between a first silicon layer 2A and a second silicon layer 2C. The first silicon layer 2A is also called a device layer, the second silicon layer 2C is also called a handle layer, and the silicon oxide layer 2B is also called a BOX layer. The thickness of the first silicon layer 2A is about 200 µm or more and 300 µm or less, the thickness of the silicon oxide layer 2B is about 20 µm, and the thickness of the second silicon layer 2C is about 200 µm or more and 500 µm or less. However, the thickness of each of these parts is not particularly limited.
[0012] 1 and 2, the vibration power generation device 1 has a support section 3, a movable section 5 movable relative to the support section 3, a spring section 4 connecting the support section 3 and the movable section 5, a movable electrode 6 which is a second comb-tooth electrode connected to the movable section 5, and first and second fixed electrodes 7 and 8 which are first comb-tooth electrodes connected to the support section 3. The movable section 5 is displaceable in the X-axis direction which is a first direction relative to the support section 3 while elastically deforming the spring section 4. In the vibration power generation device 1 configured as above, when an external force in the X-axis direction is applied, the movable section 5 vibrates in the X-axis direction while elastically deforming the spring section 4, and this vibration changes the capacitance between the movable electrode 6 and the first and second fixed electrodes 7 and 8, thereby generating power.
[0013] ≪Support part 3≫ 3, the support 3 is formed of a laminate of a first silicon layer 2A, a silicon oxide layer 2B, and a second silicon layer 2C, and has a frame shape when viewed from the Z-axis direction. The other components are disposed inside the support 3.
[0014] As shown in FIG. 3, the support 3 has a first support 3A formed from a first silicon layer 2A and a second support 3B formed from a second silicon layer 2C, and is configured such that the first support 3A and the second support 3B are laminated via a silicon oxide layer 2B. As shown in FIG. 2, the second support 3B located in the lowermost layer has a frame shape in a plan view from the Z-axis direction. On the other hand, as shown in FIG. 1, the first support 3A located in the uppermost layer is divided into a first fixed electrode support 31 to which the first fixed electrode 7 is connected and a second fixed electrode support 32 to which the second fixed electrode 8 is connected. That is, the first fixed electrode support 31 and the second fixed electrode support 32 are supported separately by the second support 3B, and these are integrated to form the support 3. The first fixed electrode support 31 and the second fixed electrode support 32 are insulated from each other by the silicon oxide layer 2B. The insulation between the first fixed electrode support part 31 and the second fixed electrode support part 32 may be achieved by designing the patterns of the first fixed electrode support part 31 and the second fixed electrode support part 32 in a planar view so that the first fixed electrode support part 31 and the second fixed electrode support part 32 are spaced apart, thereby providing insulation between them.
[0015] As shown in FIG. 1, an electrode pad T1 electrically connected to the first fixed electrode 7 is arranged on the first fixed electrode support portion 31, and an electrode pad T2 electrically connected to the second fixed electrode 8 is arranged on the second fixed electrode support portion 32.
[0016] ≪Movable part 5≫ As shown in FIG. 2, the movable part 5 is formed from the second silicon layer 2C, and is located at the center of the vibration power generation device 1 when viewed from a plane in the Z-axis direction.
[0017] <Spring part 4> As shown in FIG. 2, the spring portion 4 is formed from the second silicon layer 2C. That is, the spring portion 4 is formed from the same layer as the movable portion 5. Therefore, the spring portion 4 can be disposed near the center of gravity of the movable portion 5, and unnecessary displacement of the movable portion 5, that is, displacement in directions other than the X-axis direction which is the vibration direction, can be suppressed. Therefore, efficient power generation can be performed. In addition, the spring portion 4 has a first spring portion 41 and a second spring portion 42 which elastically deform in the X-axis direction. The first spring portion 41 is located on the positive side of the X-axis direction of the movable portion 5, and connects the end of the movable portion 5 on the positive side in the X-axis direction to the support portion 3. On the other hand, the second spring portion 42 is located on the negative side of the X-axis direction of the movable portion 5, and connects the end of the movable portion 5 on the negative side in the X-axis direction to the support portion 3. In this way, by supporting the movable portion 5 from both sides in the X-axis direction with the first and second spring portions 41 and 42, the movable portion 5 can be stably vibrated in the X-axis direction.
[0018] In this embodiment, the first and second spring portions 41, 42 are connected to the first support portion 3A, but this is not limited to this, and the first and second spring portions 41, 42 may also be connected to the second support portion 3B.
[0019] <Moveable electrode 6> As shown in FIG. 1, the movable electrode 6 is formed from the first silicon layer 2A. Moreover, the movable electrode 6 overlaps with the movable part 5 in a plan view from the Z-axis direction. Moreover, as shown in FIG. 3, the movable electrode 6 is connected to the movable part 5 and protrudes from the upper surface of the movable part 5 to the positive side in the Z-axis direction. In this way, by arranging the movable electrode 6 and the movable part 5 so as to overlap in the Z-axis direction, the movable part 5 can be enlarged 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 5 can be vibrated efficiently even in a low frequency band. Furthermore, since the movable electrode 6 and the first and second fixed electrodes 7 and 8 can be formed over a wide range regardless of the size of the movable part 5, the capacitance between the movable electrode 6 and the first and second fixed electrodes 7 and 8 can be increased. Therefore, the amount of power generated by the vibration power generation device 1 can be increased.
[0020] 3, the silicon oxide layer 2B is not formed between the movable electrode 6 and the movable portion 5, and the first silicon layer 2A and the second silicon layer 2C are in contact with each other. Therefore, the movable electrode 6 is electrically connected to the movable portion 5. With this configuration, the charging step S54, which will be described later, can be easily performed.
[0021] As shown in FIG. 1, the movable electrode 6 has a plurality of movable electrode fingers 61 extending in the X-axis direction. The plurality of movable electrode fingers 61 are arranged in a matrix along the X-axis direction and the Y-axis direction. In the illustrated configuration, three rows in which the plurality of movable electrode fingers 61 are aligned in a comb-like shape in the Y-axis direction are arranged in the X-axis direction. In the following, for convenience of explanation, the row on the positive side in the X-axis direction among these three rows is also referred to as movable electrode finger group 61A, the row on the negative side in the X-axis direction is also referred to as movable electrode finger group 61C, and the central row is also referred to as movable electrode finger group 61B. However, the number and arrangement of the movable electrode fingers 61 are not particularly limited.
[0022] Moreover, an electret film EL is formed on the surface of each movable electrode finger 61, particularly on the side facing the first and second fixed electrode fingers 71 and 81 described later. The electret film EL is a negatively charged film. The electret film EL may be formed on the first and second fixed electrode fingers 71 and 81. In this case, the movable electrode 6 becomes the first comb-tooth electrode, and the first and second fixed electrodes 7 and 8 become the second comb-tooth electrodes, in contrast to the present embodiment. However, it is preferable to form the electret film EL on the movable electrode finger 61 as in the present embodiment. By forming the electret film EL on the movable electrode finger 61, which is the side that is displaced relative to the support 3, electric charges during power generation can be taken out from the first and second fixed electrode fingers 71 and 81, which are the sides that are fixed relative to the support 3. This makes it easier to take out electric charges.
[0023] ≪First and second fixed electrodes 7, 8≫ As shown in FIG. 1, the first fixed electrode 7 and the second fixed electrode 8 are each formed from the first silicon layer 2A. In addition, the first fixed electrode 7 and the second fixed electrode 8 each overlap the movable part 5 in a plan view from the Z-axis direction. In addition, as shown in FIG. 3, the silicon oxide layer 2B between the first and second fixed electrodes 7, 8 and the movable part 5 is removed, and a gap of about the thickness of the silicon oxide layer 2B is formed between them. This suppresses contact between the movable part 5 and the first and second fixed electrodes 7, 8, that is, a short circuit between the movable electrode 6 and the first and second fixed electrodes 7, 8 via the movable part 5.
[0024] As shown in FIG. 1, the first fixed electrode 7 extends in the X-axis direction and has a plurality of first fixed electrode fingers 71 arranged in parallel with the movable electrode fingers 61 in the Y-axis direction. In other words, the first fixed electrode 7 extends in the X-axis direction and has a plurality of first fixed electrode fingers 71 arranged at positions facing the movable electrode fingers 61. Specifically, the first fixed electrode 7 has a comb-teeth-shaped first fixed electrode finger group 71A having a plurality of first fixed electrode fingers 71 that mesh with the movable electrode finger group 61A from the positive side in the X-axis direction, a comb-teeth-shaped first fixed electrode finger group 71B having a plurality of first fixed electrode fingers 71 that mesh with the movable electrode finger group 61B from the positive side in the X-axis direction, and a comb-teeth-shaped first fixed electrode finger group 71C having a plurality of first fixed electrode fingers 71 that mesh with the movable electrode finger group 61C from the positive side in the X-axis direction. The movable electrode fingers 61 and the first fixed electrode fingers 71 face each other in a stationary state with a predetermined meshing length in the X-axis direction and with a gap G in the Y-axis direction.
[0025] 1, the second fixed electrode 8 extends in the X-axis direction and has a plurality of second fixed electrode fingers 81 arranged in parallel with the movable electrode fingers 61 in the Y-axis direction. Specifically, the second fixed electrode 8 has a comb-teeth-shaped second fixed electrode finger group 81A having a plurality of second fixed electrode fingers 81 that mesh with the movable electrode finger group 61A from the negative side in the X-axis direction, a comb-teeth-shaped second fixed electrode finger group 81B having a plurality of second fixed electrode fingers 81 that mesh with the movable electrode finger group 61B from the negative side in the X-axis direction, and a comb-teeth-shaped second fixed electrode finger group 81C having a plurality of second fixed electrode fingers 81 that mesh with the movable electrode finger group 61C from the negative side in the X-axis direction. The movable electrode fingers 61 and the second fixed electrode fingers 81 face each other in a stationary state with a predetermined meshing length in the X-axis direction and across a gap G in the Y-axis direction.
[0026] 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 5 vibrates in the X-axis direction while elastically deforming the first and second spring parts 41 and 42. Then, the vibration of the movable part 5 changes the meshing length between the movable electrode finger 61 and the first and second fixed electrode fingers 71 and 81 in opposite phases, and power is generated. Specifically, when the movable part 5 is displaced to the positive side in the X-axis direction, the meshing length between the first fixed electrode finger 71 and the movable electrode finger 61 increases, and a positive charge is charged, and the meshing length between the second fixed electrode finger 81 and the movable electrode finger 61 decreases, and the charge is discharged. Conversely, when the movable part 5 is displaced to the negative side in the X-axis direction, the meshing length between the first fixed electrode finger 71 and the movable electrode finger 61 decreases, and the charged charge is discharged, and the meshing length between the second fixed electrode finger 81 and the movable electrode finger 61 increases, and a positive charge is charged. In this manner, charging of electric charges is repeated in opposite phases between the first and second fixed electrode fingers 71 and 81 .
[0027] As the first and second fixed electrode fingers 71, 81 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.
[0028] Next, a description will be given of a manufacturing method of the vibration power generation device 1. As shown in Fig. 4, the manufacturing method of the vibration power generation device 1 includes a preparation step S1 of preparing an SOI substrate 2, a first silicon layer patterning step S2 of patterning the first silicon layer 2A to form a first support portion 3A, a movable electrode 6, and first and second fixed electrodes 7 and 8 on the first silicon layer 2A, a second silicon layer patterning step S3 of patterning the second silicon layer 2C to form a second support portion 3B, a spring portion 4, and a movable portion 5 on the second silicon layer 2C, a silicon oxide layer removal step S4 of removing a part of the silicon oxide layer 2B to separate the movable portion, and an electret film formation step S5 of forming an electret film EL on the movable electrode 6.
[0029] ≪Preparation process S1≫ The preparation step S1 is a step of preparing an SOI substrate 2 in which a silicon oxide layer 2B is interposed between a first silicon layer 2A and a second silicon layer 2C. In this step S1, as shown in Fig. 9, an SOI substrate 2 is prepared in which the silicon oxide layer 2B is removed from between a movable electrode forming region Q6 as a second comb-tooth electrode forming region in which the movable electrode 6 of the first silicon layer 2A is formed, and a movable part forming region Q5 in which the movable part 5 of the second silicon layer 2C is formed. As a result, the silicon oxide layer 2B is not interposed between the movable electrode 6 and the movable part 5, and they are structurally electrically connected to each other.
[0030] As shown in FIG. 4, this process S1 includes a second silicon layer preparation process S11 for preparing a second silicon layer 2C, a recess formation process S12 for forming a recess 21 on the upper surface of the second silicon layer 2C, a silicon oxide layer formation process S13 for forming a silicon oxide layer 2B on the upper surface of the second silicon layer 2C, a silicon oxide layer removal process S14 for removing the silicon oxide layer 2B while leaving the portion filled in the recess 21, thereby exposing the upper surface of the second silicon layer 2C, and a first silicon layer bonding process S15 for bonding the first silicon layer 2A to the upper surface of the second silicon layer 2C.
[0031] -Second silicon layer preparation process S11- First, the second silicon layer 2C is prepared as shown in Fig. 5. The second silicon layer 2C is, for example, a silicon substrate having a thickness of about 200 µm or more and 500 µm or less.
[0032] - Recess formation process S12 - 6, a recess 21 is formed on the upper surface of the second silicon layer 2C. The recess 21 is formed in a portion other than the region where the movable electrode forming region Q6 and the movable portion forming region Q5 overlap. The method for forming the recess 21 is not particularly limited, but may be, for example, RIE (reactive ion etching). The thickness of the recess 21 is, for example, about 20 μm.
[0033] -Silicon oxide layer deposition process S13- 7, a silicon oxide layer 2B is formed on the upper surface of the second silicon layer 2C. The film formation method is not particularly limited, and may be, for example, thermal oxidation, plasma CVD (chemical vapor deposition) using TEOS (tetra ethoxy silane), SiH4, or the like as a raw material gas, or the like.
[0034] -Silicon oxide layer removal process S14- 8, the silicon oxide layer 2B is removed leaving the portion filled in the recess 21, thereby exposing the upper surface of the second silicon layer 2C. The method for removing the silicon oxide layer 2B is not particularly limited, but for example, CMP (chemical mechanical polishing) can be used.
[0035] -First silicon layer bonding process S15- Next, the first silicon layer 2A is prepared. The first silicon layer 2A is, for example, a silicon substrate having a thickness of about 200 μm to 300 μm. Next, as shown in FIG. 9, the first silicon layer 2A is bonded to the upper surface of the second silicon layer 2C.
[0036] The above steps provide the SOI substrate 2. This method makes it possible to easily manufacture the SOI substrate 2. However, the method for manufacturing the SOI substrate 2 is not particularly limited.
[0037] <First silicon layer patterning process S2> In the first silicon layer patterning step S2, the first silicon layer 2A is patterned by etching to form the first support portion 3A, the movable electrode 6, and the first and second fixed electrodes 7, 8 on the first silicon layer 2A. Specifically, as shown in Fig. 10, the first silicon layer 2A is etched from the upper surface side to form through-holes penetrating the first silicon layer 2A, thereby forming the first support portion 3A, the movable electrode 6, and the first and second fixed electrodes 7, 8 on the first silicon layer 2A. At this time, the silicon oxide layer 2B functions as an etching stop layer.
[0038] For example, dry etching, particularly RIE (reactive ion etching), can be used for the etching. By using dry etching, through holes with a high aspect ratio can be formed with high precision, and therefore the gap G between the movable electrode finger 61 and the first and second fixed electrode fingers 71, 81 can be designed to be smaller. This makes it possible to manufacture a vibration power generation device 1 with excellent power generation characteristics. However, the etching method is not particularly limited, and may be, for example, wet etching.
[0039] <<Second silicon layer patterning process S3>> In the second silicon layer patterning step S3, the second silicon layer 2C is patterned by etching to form the second support portion 3B, the spring portion 4, and the movable portion 5 in the second silicon layer 2C. Specifically, as shown in Fig. 11, the second silicon layer 2C is etched from the lower surface side to form through-holes penetrating the second silicon layer 2C, thereby forming the second support portion 3B, the spring portion 4, and the movable portion 5 in the second silicon layer 2C. At this time, the silicon oxide layer 2B functions as an etching stop layer.
[0040] For the etching, for example, dry etching, particularly RIE (reactive ion etching), can be used. By using dry etching, through holes with a high aspect ratio can be formed with high precision. Therefore, the distance between the movable electrode 6 and the first and second fixed electrodes 7, 8 can be reduced, and the capacitance therebetween can be increased accordingly. Therefore, the amount of power generated by the vibration power generation device 1 can be increased. However, the etching method is not particularly limited, and may be, for example, wet etching.
[0041] The second silicon layer patterning step S3 may be performed before the first silicon layer patterning step S2, or may be performed simultaneously with the first silicon layer patterning step S2.
[0042] <Silicon oxide layer removal process S4> 12, in the silicon oxide layer removal step S4, the silicon oxide layer 2B is removed from all portions except the support portion 3, and the spring portion 4 and the movable portion 5 are rendered movable relative to the support portion 3. However, as long as the spring portion 4 and the movable portion 5 can be rendered movable relative to the support portion 3, the removed portion of the silicon oxide layer 2B is not particularly limited.
[0043] In this manner, the outer shape of the vibration power generation device 1 is formed. By forming the outer shape of the vibration power generation device 1 by patterning a single SOI substrate 2 in this manner, it is possible to achieve excellent dimensional accuracy and to further reduce the gaps between the movable electrode finger 61 and the first and second fixed electrode fingers 71, 81. As a result, it is possible to further increase the capacitance between the movable electrode 6 and the first and second fixed electrodes 7, 8.
[0044] <Electret film forming process S5> In the electret film forming step S5, an electret film EL is formed on the movable electrode 6. As shown in Fig. 4, the electret film forming step S5 includes an alkali ion solution supplying step S51 for supplying an alkali ion solution L to the movable electrode 6 and the first and second fixed electrodes 7 and 8, a drying step S52 for drying the alkali ion solution L attached to the movable electrode 6 and the first and second fixed electrodes 7 and 8, an oxide film forming step S53 for forming a second oxide film 9B on the movable electrode 6 by heating the first silicon layer 2A and forming a first oxide film 9A on the first and second fixed electrodes 7 and 8, and a charging step S54 for applying a voltage to the movable electrode 6 to charge the second oxide film 9B.
[0045] -Alkaline ion solution supply process S51- 13, in the alkaline ion solution supplying step S51, first, a voltage is applied between the movable electrode 6 and the first and second fixed electrodes 7, 8 so that the first and second fixed electrodes 7, 8 have a higher potential than the movable electrode 6. In other words, a voltage is applied between the first and second fixed electrodes 7, 8 so that they become positive electrodes and the movable electrode 6 becomes negative electrodes.
[0046] Next, while maintaining the state in which a voltage is applied between the movable electrode 6 and the first and second fixed electrodes 7, 8, an alkaline ion solution L is supplied to the surface of the movable electrode 6 and the surfaces of the first and second fixed electrodes 7, 8. The alkaline ion solution L is not particularly limited, and for example, a KOH (potassium hydroxide) aqueous solution, a NaOH (sodium hydroxide) aqueous solution, or the like can be used. In this embodiment, as shown in FIG. 14, the entire SOI substrate 2 is immersed in the alkaline ion solution L to supply the alkaline ion solution L to the surface of the movable electrode 6 and the surfaces of the first and second fixed electrodes 7, 8. However, the method of supplying the alkaline ion solution L to the surface of the movable electrode 6 and the surfaces of the first and second fixed electrodes 7, 8 is not particularly limited, and for example, spin coating, spray coating, or the like can be used.
[0047] In this way, when the movable electrode 6 and the first and second fixed electrodes 7 and 8 are immersed in the alkaline ion solution L while maintaining the state in which a voltage is applied between the movable electrode 6 and the first and second fixed electrodes 7 and 8, negatively charged hydroxide ions (OH - ) is attracted to the movable electrode 6, which is a negative electrode, and conversely, positively charged alkali ions are attracted to the movable electrode 6. Here, for the sake of convenience, the alkali ions are referred to as "K + Therefore, around the first and second fixed electrodes 7 and 8, there are fewer alkali ions and more hydroxide ions, whereas around the movable electrode 6, there are more alkali ions and less hydroxide ions.
[0048] It is also possible to apply a voltage between the movable electrode 6 and the first and second fixed electrodes 7, 8 after immersing the movable electrode 6 and the first and second fixed electrodes 7, 8 in the alkaline ion solution L.
[0049] -Drying process S52- In the drying step S52, the alkaline ion solution L attached to the movable electrode 6 and the first and second fixed electrodes 7, 8 is dried. Specifically, first, as shown in Fig. 16, the movable electrode 6 and the first and second fixed electrodes 7, 8 are taken out from the alkaline ion solution L while maintaining the state in which a voltage is applied between the movable electrode 6 and the first and second fixed electrodes 7, 8.
[0050] As described above, since the movable electrode 6 and the first and second fixed electrodes 7, 8 are removed from the alkali ion solution L while maintaining the applied voltage, many alkali ions are present in the alkali ion solution L attached to the surface of the movable electrode 6, and conversely, no alkali ions are present in the alkali ion solution L attached to the surfaces of the first and second fixed electrodes 7, 8. In this way, by using the method of applying a voltage, a difference in alkali ion concentration can be easily generated between the alkali ion solution L attached to the surface of the movable electrode 6 and the alkali ion solution L attached to the surfaces of the first and second fixed electrodes 7, 8.
[0051] Ideally, no alkali ions are present in the alkali ion solution L attached to the first and second fixed electrodes 7, 8, but depending on the applied voltage, the concentration of the alkali ion solution L, the immersion time, etc., there are cases where a small amount of alkali ions are present in the alkali ion solution L attached to the first and second fixed electrodes 7, 8, in other words, where the alkali ions are present at a concentration significantly lower than that of the movable electrode 6. For ease of explanation, in this specification, the phrase "no alkali ions are present in the alkali ion solution L attached to the first and second fixed electrodes 7, 8" will be used to include cases where a small amount of alkali ions are present in the alkali ion solution L attached to the first and second fixed electrodes 7, 8.
[0052] Next, the alkali ion solution L attached to the movable electrode 6 and the first and second fixed electrodes 7, 8 is dried. The drying method is not particularly limited, and may be natural drying or heating and drying using a heater or the like. As a result, many alkali ions are fixed on the surface of the movable electrode 6, as shown in FIG. 17. On the other hand, alkali ions are not fixed on the surfaces of the first and second fixed electrodes 7, 8.
[0053] Here, the gap G between the movable electrode 6 and the first and second fixed electrodes 7, 8 is narrow. Therefore, as shown in Fig. 18, it is considered that the alkali ion solution L adhering to the surface of the movable electrode 6 and the alkali ion solution L adhering to the surfaces of the first and second fixed electrodes 7, 8 are integrated without being separated due to the surface tension of the alkali ion solution L, and the alkali ions move therethrough.
[0054] Therefore, it is preferable to perform the drying step S52 while maintaining a state in which a voltage is applied between the movable electrode 6 and the first and second fixed electrodes 7, 8. This makes it possible to suppress the movement of alkali ions from when the movable electrode 6 and the first and second fixed electrodes 7, 8 are removed from the alkali ion solution L until the drying is completed. This makes it possible to more reliably create a state in which many alkali ions are fixed on the surface of the movable electrode 6 and no alkali ions are fixed on the surfaces of the first and second fixed electrodes 7, 8.
[0055] -Oxide film formation step S53- In the oxide film forming step S53, the first silicon layer 2A is thermally oxidized. In this embodiment, the SOI substrate 2 is placed in a thermal oxidation furnace and heated in an oxygen atmosphere. As a result, as shown in FIG. 19, a second oxide film 9B, which is a silicon oxide film, is formed on the surface of the movable electrode 6, and a first oxide film 9A, which is a silicon oxide film, is formed on the first and second fixed electrodes 7 and 8. Of these, the second oxide film 9B is an alkali-added oxide film that incorporates the alkali ions that have been attached to the surface of the movable electrode 6 in the drying step S52. The alkali ions in the second oxide film 9B are positively charged, but are paired with the electrons of the silicon atoms. Therefore, the positive charges of the alkali ions and the negative charges of the silicon atoms cancel each other out, making the second oxide film 9B electrically neutral. Therefore, in this state, the second oxide film 9B is electrically neutral and does not have a surface potential.
[0056] -Charging process S54- In the charging step S54, a voltage is applied to the movable electrode 6 to charge the second oxide film 9B, thereby forming an electret film EL. For example, the SOI substrate 2 is placed on a positive electrode plate, and a negative electrode terminal is brought into contact with the surface of the second oxide film 9B, and a voltage is applied between the positive electrode plate and the negative electrode terminal. Then, the positively charged alkali ions are attracted to the negative electrode terminal, which becomes the negative electrode, inside the second oxide film 9B, and combine with electrons to lose the positive charge and become neutral. Then, as shown in FIG. 20, only the electrons that formed pairs with the alkali ions remain inside the second oxide film 9B as a result of losing the alkali ions. Since the electrons have a negative charge, the second oxide film 9B becomes an electret film EL that is negatively charged and has a surface potential.
[0057] As described above, in the vibration power generation device 1, the silicon oxide layer 2B is removed from between the movable electrode 6 and the movable part 5, and they are electrically connected. Therefore, in this step S54, a voltage can be applied to the movable electrode 6 via the movable part 5. Therefore, this step S54 can be easily performed.
[0058] In the charging step S54, it is preferable to apply a voltage only to the movable electrode 6 as in this embodiment, and not to the first and second fixed electrodes 7 and 8. As described above, a small amount of alkali ions may adhere to the surfaces of the first and second fixed electrodes 7 and 8, and in this case, a small amount of alkali ions will also be present in the first oxide film 9A. Therefore, if a voltage is applied to the first and second fixed electrodes 7 and 8, the first oxide film 9A will be slightly charged, and the potential difference between the movable electrode 6 and the first and second fixed electrodes 7 and 8 will be reduced due to the charging, which may reduce the amount of power generation. Therefore, the amount of power generation can be increased by not applying a voltage to the first and second fixed electrodes 7 and 8 and maintaining the first oxide film 9A in an electrically neutral state.
[0059] The vibration power generation device 1 is manufactured by the above steps. This manufacturing method makes it easy to create a difference in alkali ion concentration between the alkali ion solution L attached to the surface of the movable electrode 6 and the alkali ion solution L attached to the surfaces of the first and second fixed electrodes 7, 8. Therefore, even when the movable electrode 6 and the first and second fixed electrodes 7, 8 are engaged with each other, the electret film EL can be selectively formed only on the movable electrode 6 by a simple process.
[0060] The method for manufacturing the vibration power generation device 1 has been described above. As described above, this manufacturing method includes the first silicon layer patterning step S2 of patterning the first silicon layer 2A to form the first and second fixed electrodes 7, 8, which are first comb-tooth electrodes that move relatively, and the movable electrode 6, which is a second comb-tooth electrode aligned with the first and second fixed electrodes 7, 8; the alkali ion solution supplying step S51 of supplying an alkali ion solution L to the surfaces of the first and second fixed electrodes 7, 8 and the surface of the movable electrode 6 while applying a voltage between the first and second fixed electrodes 7, 8 and the movable electrode 6 so that the first and second fixed electrodes 7, 8 have a higher potential than the movable electrode 6; the drying step S52 of drying the alkali ion solution L; the oxide film forming step S53 of heat-treating the first silicon layer 2A to form a first oxide film 9A on the surfaces of the first and second fixed electrodes 7, 8 and to form a second oxide film 9B on the surface of the movable electrode 6; and the charging step S54 of applying a voltage to the movable electrode 6 to charge the second oxide film 9B, thereby forming an electret film EL. According to such a manufacturing method, a difference in alkali ion concentration can be easily generated between the alkali ion solution L adhered to the surface of the movable electrode 6 and the alkali ion solution L adhered to the surfaces of the first and second fixed electrodes 7, 8. Therefore, even when the movable electrode 6 and the first and second fixed electrodes 7, 8 are engaged with each other, the electret film EL can be selectively formed only on the movable electrode 6 in a simple process.
[0061] As described above, in the drying step S52, the alkaline ion solution L is dried in a state where a voltage is applied between the first and second fixed electrodes 7, 8 and the movable electrode 6 so that the first and second fixed electrodes 7, 8 have a higher potential than the movable electrode 6. According to such a method, it is possible to more reliably create a state where a large number of alkaline ions are fixed on the surface of the movable electrode 6 and no alkaline ions are fixed on the surfaces of the first and second fixed electrodes 7, 8.
[0062] As described above, in the charging step S54, no voltage is applied to the first and second fixed electrodes 7 and 8. This makes it possible to maintain the first oxide film 9A in an electrically neutral state, thereby increasing the amount of power generation.
[0063] As described above, in the first silicon layer patterning step S2, the first silicon layer 2A is patterned to form one of the first and second fixed electrodes 7, 8 and the movable electrode 6, which in this embodiment is the first support portion 3A that supports the first and second fixed electrodes 7, 8. This makes it possible to connect the first and second fixed electrodes 7, 8 and the support portion 3 with a simple configuration.
[0064] As described above, the manufacturing method of the vibration power generation device 1 includes a preparation step S1, which is performed before the first silicon layer patterning step S2, to prepare an SOI substrate 2 having a first silicon layer 2A, a second silicon layer 2C, and a silicon oxide layer 2B interposed between the first silicon layer 2A and the second silicon layer 2C, and a second silicon layer patterning step S3 to pattern the second silicon layer 2C to form a second support portion 3B that is integrated with the first support portion 3A to become the support portion 3, and a movable portion 5 that is movable relative to the second support portion 3B and supports the other of the first and second fixed electrodes 7, 8 and the movable electrode 6, the movable electrode 6 in this embodiment. This method has excellent dimensional accuracy and can further reduce the gap G between the movable electrode finger 61 and the first and second fixed electrode fingers 71, 81. Therefore, the capacitance between the movable electrode 6 and the first and second fixed electrodes 7, 8 can be further increased.
[0065] As described above, the first and second fixed electrodes 7, 8 are supported by the first support portion 3A, and the movable electrode 6 is supported by the movable portion 5. In this manner, by forming the electret film EL on the movable electrode finger 61, which is the side that displaces with respect to the support portion 3, electric charges generated can be extracted from the first and second fixed electrode fingers 71, 81, which are the sides that are fixed with respect to the support portion 3. This makes it easy to extract the electric charges.
[0066] As described above, in the preparation step S1, an SOI substrate 2 is prepared in which the silicon oxide layer 2B is removed from between a movable electrode forming region Q6 as a second comb-tooth electrode forming region in which the movable electrode 6 of the first silicon layer 2A is formed, and a movable part forming region Q5 in which the movable part 5 of the second silicon layer 2C is formed. By preparing such an SOI substrate 2, it is possible to easily obtain a movable electrode 6 electrically connected to the second silicon layer 2C. Therefore, in the charging step S54, a voltage can be applied to the movable electrode 6 via the second silicon layer 2C. Therefore, the charging step S54 can be easily performed.
[0067] As described above, in the first silicon layer patterning step S2 and the second silicon layer patterning step S3, patterning is performed by dry etching. This allows the first silicon layer 2A and the second silicon layer 2C to be patterned with high precision. In addition, since a through hole with a high aspect ratio can be formed, the gap G between the movable electrode 6 and the first and second fixed electrodes 7 and 8 can be made smaller. This allows the amount of power generation to be increased.
[0068] 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. [Explanation of symbols]
[0069] REFERENCE SIGNS LIST 1... vibration power generation device, 2... SOI substrate, 2A... first silicon layer, 2B... silicon oxide layer, 2C... second silicon layer, 21... recess, 3... support portion, 3A... first support portion, 3B... second support portion, 31... first fixed electrode support portion, 32... second fixed electrode support portion, 4... spring portion, 41... first spring portion, 42... second spring portion, 5... movable portion, 6... movable electrode, 7... first fixed electrode, 8... second fixed electrode, 9A... first oxide film, 9B... second oxide film, 61... movable electrode finger, 61A... movable electrode finger group, 61B... movable electrode finger group, 61C... movable electrode finger group, 71... first fixed electrode finger, 71A... first fixed electrode finger group, 71B... first fixed electrode finger group, 71C... first fixed electrode finger group, 81... second fixed electrode finger, 81A... second fixed electrode finger group , 81B...second fixed electrode finger group, 81C...second fixed electrode finger group, EL...electret film, G...gap, L...alkaline ion solution, Q5...movable portion forming area, Q6...movable electrode forming area, S1...preparation step, S11...second silicon layer preparation step, S12...recess forming step, S13...silicon oxide layer forming step, S14...silicon oxide layer removing step, S15...first silicon layer bonding step, S2...first silicon layer patterning step, S3...second silicon layer patterning step, S4...silicon oxide layer removing step, S5...electret film forming step, S51...alkaline ion solution supplying step, S52...drying step, S53...oxide film forming step, S54...charging step, T1...electrode pad, T2...electrode pad
Claims
1. a first silicon layer patterning step of forming a first comb-teeth electrode that moves relatively and a second comb-teeth electrode aligned with the first comb-teeth electrode by patterning a first silicon layer; an alkaline ion solution supplying step of supplying an alkaline ion solution to a surface of the first comb tooth electrode and a surface of the second comb tooth electrode in a state where a voltage is applied between the first comb tooth electrode and the second comb tooth electrode such that the first comb tooth electrode has a higher potential than the second comb tooth electrode; a drying step of drying the alkali ion solution; an oxide film forming step of forming a first oxide film on a surface of the first comb-tooth electrode and a second oxide film on a surface of the second comb-tooth electrode by heat-treating the first silicon layer; and a charging step of forming an electret film by applying a voltage to the second comb electrode to charge the second oxide film.
2. 2. The method for manufacturing a vibration power generation device according to claim 1, wherein in the drying step, the alkaline ion solution is dried in a state in which a voltage is applied between the first comb tooth electrode and the second comb tooth electrode such that the first comb tooth electrode has a higher potential than the second comb tooth electrode.
3. The vibration power generating device according to claim 1 , wherein in the charging step, no voltage is applied to the first comb electrode.
4. 2. The method for manufacturing a vibration power generation device according to claim 1, wherein in the first silicon layer patterning step, a first support portion that supports one of the first comb tooth electrode and the second comb tooth electrode is formed by patterning the first silicon layer.
5. a preparation step, which is performed prior to the first silicon layer patterning step, of preparing an SOI substrate having the first silicon layer, a second silicon layer, and a silicon oxide layer interposed between the first silicon layer and the second silicon layer; and a second silicon layer patterning step of patterning the second silicon layer to form a second support portion that is integrated with the first support portion to form a support portion, and a movable portion that is movable relative to the second support portion and supports the other of the first comb-tooth electrode and the second comb-tooth electrode.
6. the first comb-tooth electrode is supported by the first support portion, The method for manufacturing a vibration power generation device according to claim 5 , wherein the second comb electrode is supported by the movable part.
7. 7. The method for manufacturing a vibration power generation device according to claim 6, wherein the preparation step includes preparing an SOI substrate in which the silicon oxide layer is removed from between a second comb-tooth electrode formation region of the first silicon layer in which the second comb-tooth electrode is formed and a movable part formation region of the second silicon layer in which the movable part is formed.
8. 8. The method for manufacturing a vibration power generation device according to claim 5, wherein in the first silicon layer patterning step and the second silicon layer patterning step, patterning is performed by dry etching, respectively.
Citation Information
Patent Citations
Method for manufacturing vibration device and vibration device
JP2023091647A