MEMS device

Abstract

To solve problems of thermal demagnetization that an MEMS device including a hard magnetic body having a plurality of magnetization regions differing in a magnetization direction has.SOLUTION: An MEMS device 1 according to the present invention comprises: a housing body 10 made at least partially from a material that transmits infrared rays or visible beams; and a hard magnetic body 22 housed in the housing body 10. When an in-plane direction of the hard magnetic body 22 is represented as an x-direction, the hard magnetic body 22 has a plurality of magnetized regions 22A, 22B arranged along the x-direction, and magnetization directions of neighboring magnetized regions 22A, 22B in the x-direction are different from each other. An interior of the housing 10 is hermetically sealed, and a width of each of the magnetized regions 22A, 22B in the x-direction is 1 mm or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a MEMS device and a manufacturing method thereof, and more particularly to a MEMS device including a hard magnetic material having a plurality of magnetized regions with different magnetization directions, and a manufacturing method thereof. [Background technology]

[0002] Patent Documents 1 and 2 disclose a method for multi-pole magnetization of hard magnetic materials using laser light. Localized magnetization using this method makes it possible to improve the magnetic circuits of MEMS devices, including magnetic devices such as actuators and energy harvesters. However, since many MEMS devices are susceptible to the effects of dust and water vapor, hermetic sealing to block these is considered important. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 63-99509 [Patent Document 2] Japanese Patent Application Publication No. 60-218809 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when hermetically sealing a MEMS device, it is often exposed to high temperatures, and there is a problem that thermal demagnetization occurs when the device is hermetically sealed after being multi-pole magnetized using laser light.

[0005] Therefore, an object of the present invention is to solve the problem of thermal demagnetization in an MEMS device having a plurality of magnetized regions with different magnetization directions. [Means for solving the problem]

[0006] The MEMS device according to the present invention comprises a housing, at least a portion of which is made of a material that transmits infrared rays or visible light, and a hard magnetic body housed inside the housing, and the hard magnetic body is characterized by having a plurality of magnetized regions whose magnetization directions are different from each other.

[0007] According to the present invention, at least a part of the housing is made of a material that transmits infrared rays or visible light, so that the housing can be magnetized using light such as a laser after being hermetically sealed, thereby preventing thermal demagnetization of the multiple magnetized regions.

[0008] In the present invention, the hard magnetic body having multiple magnetized regions may be elastically supported by a housing. This makes it possible to configure a magnetic device with a moving part, such as an actuator or an energy harvester. In this case, the hard magnetic body having multiple magnetized regions may include a magnetized region made of a first hard magnetic body elastically supported by the housing, and a magnetized region made of a second hard magnetic body elastically supported by the housing independently of the first hard magnetic body.

[0009] In the present invention, at least a portion of the housing may be made of a material that blocks visible light and transmits infrared light. This prevents visible light from entering the MEMS device during actual use, making it possible to prevent deterioration and malfunctions caused by the incidence of visible light. In this case, at least a portion of the housing may be made of silicon or gallium arsenide. This not only makes it easier to process the housing, but also makes it possible to prevent stress caused by differences in thermal expansion coefficients by making the entire housing out of silicon or gallium arsenide.

[0010] The method for manufacturing a MEMS device according to the present invention is characterized in that a hard magnetic material is placed inside a container, and then the hard magnetic material is locally magnetized by irradiating light onto the hard magnetic material through the container while a magnetic field is applied.

[0011] According to the present invention, the hard magnetic material is placed inside the container and then magnetized using light such as a laser, making it possible to prevent thermal demagnetization of the magnetized hard magnetic material.

[0012] In the present invention, a hard magnetic material may be magnetized in one direction by a uniform strong magnetic field, and then irradiated with light while applying a magnetic field in a direction different from the magnetization direction, thereby forming multiple magnetized regions with different magnetization directions in the hard magnetic material. This makes it possible to reduce the number of times the material is magnetized.

[0013] In the present invention, multiple magnetized regions with different magnetization directions may be formed in a hard magnetic material by irradiating the material with light while applying a magnetic field in a predetermined direction, and then irradiating the material with light while applying a magnetic field in a direction different from the predetermined direction. This makes it possible to omit magnetization using a strong magnetic field. Alternatively, by forming three or more magnetized regions with different magnetization directions in a hard magnetic material, it is possible to realize a more complex magnetization pattern such as a Halbach array.

[0014] In the present invention, the hard magnetic material may be magnetized at multiple locations simultaneously by irradiating the material with light through a mask having regions that partially block the light, which makes it possible to complete magnetization using light such as a laser in a short period of time.

[0015] In the present invention, at least a part of the housing may be made of a material that blocks visible light and transmits infrared light, and light having an infrared wavelength may be irradiated through at least a part of the housing. In this way, visible light does not enter the MEMS device during actual use, making it possible to prevent deterioration and malfunction due to the incidence of visible light. [Effects of the Invention]

[0016] As described above, according to the present invention, it is possible to prevent thermal demagnetization caused by hermetic sealing in an MEMS device including a magnetic device. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating the structure of a MEMS device 1 according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram for explaining a first method for manufacturing the MEMS device 1. As shown in FIG. [Figure 3] FIG. 3 is a schematic diagram for explaining a first method for manufacturing the MEMS device 1. As shown in FIG. [Figure 4] FIG. 4 is a schematic diagram for explaining a first method for manufacturing the MEMS device 1. As shown in FIG. [Figure 5] FIG. 5 is a schematic diagram for explaining a second method for manufacturing the MEMS device 1. As shown in FIG. [Figure 6] FIG. 6 is a schematic diagram for explaining a second method for manufacturing the MEMS device 1. As shown in FIG. [Figure 7] FIG. 7 is a schematic diagram for explaining a second manufacturing method of the MEMS device 1. As shown in FIG. [Figure 8] FIG. 8 is a schematic diagram for explaining a second method for manufacturing the MEMS device 1. As shown in FIG. [Figure 9] FIG. 9 is a schematic diagram for explaining a second method for manufacturing the MEMS device 1. As shown in FIG. [Figure 10] FIG. 10 is a schematic diagram for explaining a second method for manufacturing the MEMS device 1. As shown in FIG. [Figure 11] FIG. 11 is a schematic diagram showing an example in which magnetized regions 22A to 22D are arranged in a Halbach array. [Figure 12] FIG. 12 is a schematic diagram for explaining a method of irradiating laser light 48 through a mask 47. In FIG. [Figure 13] FIG. 13 is a schematic cross-sectional view illustrating the structure of a MEMS device 2 according to the second embodiment of the present invention. [Figure 14] FIG. 14 is a graph showing the evaluation results of the examples. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0019] FIG. 1 is a schematic cross-sectional view illustrating the structure of a MEMS device 1 according to a first embodiment of the present invention.

[0020] The MEMS device 1 shown in FIG. 1 includes a housing 10 and a magnetic device 20 housed within the housing 10. The housing 10 supports and hermetically seals the magnetic device 20 and is composed of a circuit board 11 and a lid 12. The lid 12 is made of a material that transmits infrared rays or visible light. Examples of materials that transmit infrared rays or visible light include silicon, gallium arsenide, glass, and resin. Silicon transmits infrared rays with wavelengths of approximately 1100 nm or more and blocks light with wavelengths shorter than that. Gallium arsenide transmits infrared rays with wavelengths of 900 nm or more and blocks light with wavelengths shorter than that. The optical transparency of glass and resin varies depending on their compositions. The circuit board 11 does not need to be made of a material that transmits infrared rays or visible light, but using the same material as the lid 12 can reduce stress applied to the joint 13 due to temperature changes. The joint 13 may be an indirect joint in which an adhesive or metal is sandwiched between the substrates as an adhesive layer, or may be a direct joint in which the substrates are directly joined together.

[0021] The magnetic device 20 has a configuration in which a hard magnetic material 22 is formed on the surface of a substrate 21, and is elastically supported on the housing 10 by a spring 23. In the schematic diagram shown in FIG. 1 , the spring 23 is supported on the lid portion 12, but it may be supported on the circuit board portion 11, or the spring 23 may be part of a three-dimensionally processed substrate 21. In other words, it may be configured such that the substrate 21 itself is fixed to the housing 10, and a part of the three-dimensionally processed substrate 21 serves as the spring 23, which supports the hard magnetic material 22. In this way, the hard magnetic material 22 may be elastically supported directly on the housing 10, or indirectly on the housing 10. Although not particularly limited, in this embodiment, the substrate 21 is made of the same material as the lid portion 12. As an example, both the lid portion 12 and the substrate 21 are made of silicon.

[0022] The hard magnetic body 22 has multiple magnetized regions 22A and 22B with different magnetization directions. Arrows on the magnetized regions 22A and 22B indicate the direction of the magnetic field, with the tip of the arrow representing the north pole and the base of the arrow representing the south pole. In the example shown in FIG. 1, the magnetized regions 22A and 22B are alternately arranged in the x direction and are all magnetized in the y direction. The thickness of the hard magnetic body 22 is approximately 0.1 μm to 1 mm. It may be a film formed on the substrate 21 using a vacuum deposition method or a thick film formed on the substrate 21 using a plating method. Although not particularly limited, it is preferable to use an R-Fe-B hard magnetic material as the hard magnetic body 22, which has a large decrease in coercivity due to temperature rise. This allows laser magnetization at a relatively low temperature. The size of each magnetized region 22A and 22B is very small, with a width in the x direction of 1 mm or less. As described above, since the magnetized regions 22A and 22B have a minute size, it is not practical to form the hard magnetic body 22 by adhering a pre-magnetized bulk hard magnetic body to the substrate 21.

[0023] As shown in FIG. 1 , a plurality of wiring patterns 31 are formed on the circuit board 11 so as to face the hard magnetic materials 22. The wiring patterns 31 are connected to external terminals 33 through via conductors 32 that penetrate the circuit board 11. When a current flows through the wiring patterns 31 in a predetermined direction, an electromagnetic force acts between the hard magnetic materials 22 and the wiring patterns 31, changing the relative positional relationship between the hard magnetic materials 22 and the wiring patterns 31 in the x direction. In this case, the MEMS device 1 according to this embodiment functions as an actuator. Alternatively, when an external force acts to change the relative position between the hard magnetic materials 22 and the wiring patterns 31 in the x direction, an induced current is generated in the wiring patterns 31. Therefore, the MEMS device 1 according to this embodiment also functions as an energy harvester. Furthermore, by incorporating a system that detects the movement of the hard magnetic materials instead of a similar configuration or wiring patterns, the MEMS device 1 according to this embodiment can also function as an accelerometer, a magnetic field sensor, or a displacement sensor.

[0024] Next, a method for manufacturing the MEMS device 1 according to this embodiment will be described.

[0025] 2 to 4 are schematic views for explaining a first method for manufacturing the MEMS device 1. FIG.

[0026] In the first manufacturing method, first, the magnetic device 20 is hermetically sealed in the housing 10, and then the hard magnetic material 22 is magnetized in one direction by passing a current through the coil 40 of the strong magnetic field generator, as shown in Fig. 2. When hermetically sealing the magnetic device 20, the magnetic device 20 is exposed to high heat, but since the magnetic material 22 is magnetized after the hermetically sealing, the problem of thermal demagnetization does not occur.

[0027] 3, while a magnetic field 42 is applied in a predetermined direction using a magnet 41, laser light 43 is irradiated onto a predetermined position 22H of the hard magnetic material 22 via the lid 12 and the substrate 21. The wavelength of the laser light 43 must be selected so that it can be transmitted through the lid 12 and the substrate 21. For example, if the lid 12 and the substrate 21 are made of silicon, an infrared laser with a wavelength of approximately 1100 nm or more is used.

[0028] As a result, the hard magnetic material 22 is locally heated at position 22H irradiated with laser beam 43, resulting in thermal demagnetization. When the temperature is raised sufficiently, the position irradiated with laser beam 43 is magnetized in the same direction as magnetic field 42, forming magnetized region 22B, as shown in FIG. 4. By appropriately adjusting laser beam 43 and magnetic field 42, the magnetization of magnetized region 22B is maintained even after the temperature drops. By repeatedly irradiating required positions with laser beam 43 in this manner, multiple magnetized regions 22A and 22B with different magnetization directions can be formed, as shown in FIG. 1.

[0029] As described above, in this embodiment, the lid portion 12 and the substrate 21 are made of materials that transmit infrared or visible light. After the magnetic device 20 is hermetically sealed in the housing 10, laser magnetization is performed via the lid portion 12 and the substrate 21. This allows for the formation of multiple magnetized regions 22A, 22B with mutually different magnetization directions. In the example shown in FIGS. 2 to 4 , the laser beam 43 is irradiated from the lid portion 12 side. However, the laser beam 43 may be irradiated from the circuit board portion 11 side as long as the laser beam 43 can be irradiated while avoiding the wiring pattern 31. In this case, the circuit board portion 11 may be made of a material that transmits infrared or visible light. The lid portion 12 and the substrate 21 do not need to be made of a material that transmits infrared or visible light. Furthermore, the entire circuit board portion 11 or the lid portion 12 do not need to be made of a material that transmits infrared or visible light. Only the portions that need to transmit the laser beam 43 may be made of a material that transmits infrared or visible light.

[0030] In particular, if a material that blocks visible light and transmits infrared light, such as silicon or gallium arsenide, is used as the material for circuit board 11 or lid 12, visible light will not be incident on MEMS device 1 during actual use, thereby preventing deterioration or malfunction due to the incidence of visible light. Moreover, silicon or gallium arsenide are materials widely used in semiconductor processes, and are easy to process and have well-developed processing techniques. Therefore, using these materials for circuit board 11 or lid 12 can reduce manufacturing costs.

[0031] Furthermore, in the method shown in FIGS. 2 to 4, the hard magnetic body 22 is entirely magnetized in one direction by a strong magnetic field before laser magnetization, which makes it possible to reduce the number of times the laser light 43 is irradiated.

[0032] The heating method in this manufacturing method is not limited to using a laser, and any light can be used as long as it has a wavelength that can penetrate the container. This method can be applied without additional equipment by using exposure equipment, which is widely used in semiconductor processes.

[0033] Furthermore, in this manufacturing method, the magnetic device 20 is hermetically sealed, but this method can also be applied to cases where laser magnetization after assembly is required, not just hermetically sealed cases.

[0034] 5 to 10 are schematic views for explaining the second manufacturing method of the MEMS device 1. FIG.

[0035] In the second manufacturing method, first, as shown in Fig. 5, the magnetic device 20 is hermetically sealed in the housing 10, and then, as shown in Fig. 6, a laser beam 43 is irradiated onto a predetermined position 22H of the hard magnetic material 22 via the lid 12 and the substrate 21 while a magnetic field 42 is applied in a predetermined direction using a magnet 41. As a result, the position irradiated with the laser beam 43 is locally magnetized, forming a magnetized region 22B, as shown in Fig. 7. By repeatedly irradiating the required positions with the laser beam 43, multiple magnetized regions 22B are formed, as shown in Fig. 8.

[0036] Next, as shown in Fig. 9, a magnetic field 45 is applied in the opposite direction using a magnet 44 having a polarity opposite to that of the magnet 41, and a laser beam 46 is irradiated onto a predetermined position 22H of the hard magnetic material 22 through the lid 12 and the substrate 21. As a result, the position irradiated with the laser beam 46 is locally magnetized, forming a magnetized region 22A, as shown in Fig. 10. By repeatedly irradiating the required positions with the laser beam 46, a plurality of magnetized regions 22A and 22B having different magnetization directions can be formed, as shown in Fig. 1.

[0037] As described above, the methods shown in FIGS. 5 to 10 omit magnetization using a strong magnetic field, eliminating the need for a strong magnetic field generator. Furthermore, by performing laser magnetization while applying a magnetic field in the x direction, it is possible to form magnetized regions 22C and 22D magnetized in the x direction, as shown in FIG. 11. Here, if the magnetized regions 22C and 22D magnetized in the x direction are formed between the magnetized regions 22A and 22B, a Halbach array can also be realized. Furthermore, as shown in FIG. 12, it is possible to simultaneously magnetize multiple locations of the hard magnetic material 22 by irradiating the hard magnetic material 22 with a large-diameter laser beam 48 through a mask 47 having an area that partially blocks the laser beam 46. This allows laser magnetization to be completed in a short time.

[0038] FIG. 13 is a schematic cross-sectional view illustrating the structure of a MEMS device 2 according to the second embodiment of the present invention.

[0039] The MEMS device 2 shown in Fig. 13 includes a housing 50 and a magnetic device 60 housed inside the housing 50. The housing 50 is composed of a circuit board 51, a lid 52, and a spacer 53 that forms a space between the circuit board 51 and the lid 52. Of these, the lid 52 is made of a material that transmits infrared rays or visible light, such as silicon. The circuit board 51 and the lid 52 may also be made of a material that does not transmit infrared rays or visible light, such as an opaque resin.

[0040] The magnetic device 60 has a substrate 61 with two cavities, and movable parts 62 and 63 that are independently and elastically supported within the cavities of the substrate 61 by springs 66. Hard magnetic bodies 64 and 65 are formed on the surfaces of the movable parts 62 and 63, respectively. The hard magnetic bodies 64 and 65 are each a single hard magnetic body that is magnetized in mutually different directions. The substrate 61 of the magnetic device 60 is connected via bonding wires 71 to external terminals 72 provided on the circuit board part 51.

[0041] In the MEMS device 2 having such a configuration, similar to the MEMS device 1 described above, after hermetically sealing, the hard magnetic bodies 64 and 65 can be magnetized in different directions by laser magnetization via the lid 52 or by a combination of unidirectional magnetization using a strong magnetic field and laser magnetization. As illustrated in this embodiment, in the present invention, multiple magnetized regions with different magnetization directions do not necessarily need to be formed within a single hard magnetic body. Multiple hard magnetic bodies with different magnetization directions may be separately provided within different hard magnetic bodies. Such a MEMS device 2 can function as, for example, a multi-degree-of-freedom actuator, a harvester capable of generating electricity by vibration from multiple directions, an inertial sensor, and so on. Furthermore, by independently arranging the movable parts in an array, the device can function as a digital micromirror device or a tactile device. Furthermore, by combining it with a system capable of detecting the movement of the hard magnetic bodies, the device can also function as a magnetic field sensor or a displacement sensor.

[0042] The above describes a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the present invention, and it goes without saying that these modifications are also included within the scope of the present invention. [Example]

[0043] A precursor of the MEMS device 1 shown in Figure 2 was actually fabricated and magnetized by irradiating it with laser light 43 as shown in Figure 3. A 200-μm-thick double-sided polished silicon substrate with a 3-μm-thick oxide film on its surface was used as the substrate 21. A 6-μm-thick Nd-Fe-B hard magnetic material film was deposited on the surface by sputtering to form the hard magnetic material 22. The circuit board portion 11 and the lid portion 12 were both made of silicon and were directly bonded together. After bonding, the hard magnetic material 22 was uniformly magnetized by applying a pulsed magnetic field of up to 7 T to the entire device, and then heated with laser light 43. The laser light 43 had a wavelength of 1100 nm, a spot diameter of 50 μm, an output of 2.7 W, and a scanning speed of 500 mm / s. The magnetic field 42 was a static magnetic field of 0.5 T.

[0044] After the laser magnetization, the substrate 21 and hard magnetic material 22 were removed from the MEMS device 1, and a Hall element was used to scan a position 100 μm from the surface of the hard magnetic material 22, measuring the magnetic field distribution in the out-of-plane direction of the substrate to evaluate the magnetization state. As a result, it was confirmed that an alternating magnetic field was formed in the hard magnetic material 22, as shown in Figure 14, and it was confirmed that laser magnetization had been achieved. [Explanation of symbols]

[0045] 1,2 MEMS devices 10,50 Containment Unit 11,51 Circuit board section 12,52 Lid 13 Joint 20,60 Magnetic Devices 21,61 PCB 22,64,65 Hard magnetic material 22A~22D magnetization area 22H Laser light irradiation position 23,66 spring 31 Wiring Pattern 32 via conductor 33 External terminal 40 coils 41,44 Magnet 42,45 magnetic field 43, 46, 48 Laser light 47 Mask 48 Laser Light 53 Spacer 62,63 Moving parts 71 Bonding Wire 72 External terminal

Claims

1. a container at least a portion of which is made of a material that transmits infrared rays or visible light; a hard magnetic body accommodated inside the housing; When the in-plane direction of the hard magnetic material is represented as the x direction, the hard magnetic body has a plurality of magnetized regions arranged along the x direction, and the magnetization directions of the magnetized regions adjacent to each other in the x direction are different from each other; The interior of the container is hermetically sealed, A MEMS device, characterized in that the width of each magnetized region in the x-direction is 1 mm or less.

2. 2. The MEMS device of claim 1, wherein a single surface of said hard magnetic material has said plurality of magnetized regions.

3. 3. The MEMS device according to claim 1, wherein the hard magnetic body having the plurality of magnetized regions is elastically supported by the container.

4. 4. The MEMS device according to claim 3, wherein the hard magnetic body having the plurality of magnetized regions includes a magnetized region made of a first hard magnetic body elastically supported by the housing, and a magnetized region made of a second hard magnetic body elastically supported by the housing independently of the first hard magnetic body.

5. 5. The MEMS device according to claim 1, wherein the at least part of the container is made of a material that blocks visible light and transmits infrared light.

6. 6. The MEMS device of claim 5, wherein the at least a portion of the enclosure is made of silicon or gallium arsenide.

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