MEMS device and method for manufacturing MEMS device
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-18
AI Technical Summary
The miniaturization of MEMS devices is hindered by the need for space to install via electrodes and the side-etching of silicon oxide layers, which complicates the movement of movable electrodes and reduces capacitance detection accuracy.
The use of single crystal silicon substrates bonded directly together without intermediate silicon oxide layers, allowing for a compact design with movable portions and capacitance changes detected between the substrates, eliminating the need for via electrodes and side-etching.
This approach enables the miniaturization of MEMS devices while improving detection accuracy by ensuring sufficient movement and reducing the complexity of the device structure, allowing for precise capacitance measurement.
Abstract
Description
MEMS device and method for manufacturing the same
[0001] The present invention relates to a MEMS device and a method for manufacturing a MEMS device.
[0002] 2. Description of the Related Art Devices manufactured using Micro Electro Mechanical Systems (MEMS) technology have become widespread. These devices are formed by bonding an upper substrate to a lower substrate having elements thereon, for example.
[0003] For example, in Patent Document 1, by isolating the first movable electrode and the second movable electrode from the holding portion by a spring portion, even if the top cover is deformed due to external pressure or force caused by thermal expansion differences, the change in the inter-electrode distance between the first movable electrode and the second movable electrode caused by deformation of the top cover is reduced, and a decrease in the detection accuracy of the capacitance value in the capacitance portion is suppressed.
[0004] International Publication No. 2023 / 032304
[0005] However, in the invention described in Patent Document 1, because a silicon oxide layer is laminated on the Si substrate in the capacitance section, it is necessary to provide via electrodes to electrically connect the Si substrate in the capacitance section and the Si film, and it is difficult to miniaturize the MEMS device in order to secure the installation space for the via electrodes. Furthermore, in order to secure the movable range of the first movable electrode and the second movable electrode, it is necessary to side-etch the silicon oxide layer laminated on the Si substrate, and it is necessary to secure a sufficient area of the silicon oxide layer in advance in consideration of the amount to be removed by the side etching, which also makes it difficult to miniaturize the MEMS device.
[0006] The present invention has been made in view of the above circumstances, and has an object to provide a MEMS device that can be miniaturized and a method for manufacturing the MEMS device.
[0007] A MEMS device according to one aspect of the present invention comprises a lower lid, an upper lid that forms a space between itself and the lower lid, a first substrate made of single crystal silicon and positioned opposite the lower lid in the space formed between the upper lid and the lower lid, a second substrate made of single crystal silicon and positioned opposite the upper lid in the space formed between the upper lid and the lower lid, including a movable portion and having single crystal silicon bonded to the first substrate, and a capacitance portion provided at least either between the upper lid and the second substrate or between the first substrate and the second substrate, and configured so that the capacitance changes depending on the distance between the movable portion and the upper lid or the first substrate.
[0008] A method for manufacturing a MEMS device according to one aspect of the present invention includes the steps of: placing a first substrate made of single crystal silicon opposite a lower cover; placing a second substrate made of single crystal silicon and including a movable part opposite an upper cover and bonding the single crystal silicon to the first substrate; placing the first substrate and the second substrate in a space surrounded by the upper cover and the lower cover; and providing a capacitance section between the upper cover and the second substrate and / or between the first substrate and the second substrate, the capacitance of which changes depending on the distance between the movable part and the upper cover or the first substrate.
[0009] According to the present invention, miniaturization can be achieved.
[0010] 1 is a perspective view schematically illustrating an appearance of a MEMS device; FIG. 2 is a cross-sectional view of the MEMS device; FIG. 3 is an enlarged cross-sectional view of a main portion of the MEMS device; FIG. 4 is a schematic view for explaining an example of a manufacturing method of a MEMS device; FIG. 5 is a schematic view for explaining an example of a manufacturing method of a MEMS device; FIG. 6 is a schematic view for explaining an example of a manufacturing method of a MEMS device; FIG. 7 is a schematic view for explaining an example of a manufacturing method of a MEMS device; FIG. 8 is a schematic view for explaining an example of a manufacturing method of a MEMS device; FIG. 9 is a schematic view for explaining another example of a manufacturing method of a MEMS device; FIG. 10 is a schematic view for explaining another example of a manufacturing method of a MEMS device; FIG. 11 is a schematic view for explaining another example of a manufacturing method of a MEMS device; FIG. 12 is a schematic view for explaining another example of a manufacturing method of a MEMS device; Fig. 10 is a schematic diagram for explaining another example of a method for manufacturing a MEMS device;Fig. 11 is a schematic diagram for explaining another example of a method for manufacturing a MEMS device;Fig. 12 is a schematic diagram for explaining another example of a method for manufacturing a MEMS device;Fig. 13 is a schematic diagram for explaining another example of a method for manufacturing a MEMS device;Fig. 14 is a schematic diagram for explaining another example of a method for manufacturing a MEMS device.
[0011] Hereinafter, embodiments of the present invention will be described. In the following description of the drawings, the same or similar components are denoted by the same or similar reference numerals. The drawings are illustrative, and the dimensions and shapes of each part are schematic. The technical scope of the present invention should not be interpreted as being limited to the embodiments.
[0012] A MEMS device 1 according to this embodiment will be described with reference to the drawings.
[0013] In the following description, each drawing may be accompanied by a Cartesian coordinate system consisting of X, Y, and Z axes for the sake of convenience, in order to clarify the relationships between the drawings and to aid in understanding the positional relationships of each component. The directions parallel to the X, Y, and Z axes are referred to as the X-axis, Y-axis, and Z-axis directions, respectively. The plane defined by the X and Y axes is referred to as the XY plane. For convenience, the positive Z-axis direction (the direction of the arrow) will be referred to as the top or upper side, and the negative Z-axis direction (the direction opposite to the arrow) will be referred to as the bottom or lower side, but the orientation of the MEMS device 1 is not limited to this.
[0014] As shown in FIG. 1 , the MEMS device 1 is a device manufactured using MEMS technology and is a device for detecting acceleration in, for example, the X-axis, Y-axis, and Z-axis directions. The MEMS device 1 includes a bottom lid 10, a device layer 20, and an top lid 30. The bottom lid 10, the device layer 20, and the top lid 30 are stacked in this order in the Z-axis direction. Hereinafter, the stacking direction of the bottom lid 10, the device layer 20, and the top lid 30 will be referred to as the "thickness direction." The device layer 20 and the bottom lid 10 are bonded together to form a MEMS substrate 50. The top lid 30 is bonded to the device layer 20 of the MEMS substrate 50. In other words, the top lid 30 is bonded to the bottom lid 10 via the device layer 20. The bottom lid 10 and the top lid 30 face each other in the thickness direction, with the device layer 20 sandwiched between them. The bottom lid 10 and the top lid 30 form a package structure that forms a vibration space inside in which the device layer 20 vibrates.
[0015] The lower lid 10 has a bottom plate 11, sidewalls 12, and a fixing portion 13. The bottom plate 11 is plate-shaped and extends in a plane along the X-axis direction and the Y-axis direction. The sidewalls 12 extend from the peripheral edge of the bottom plate 11 toward the upper lid 30. A silicon oxide film P10 is provided at the tip of the sidewall 12. The sidewall 12 is bonded to the device layer 20 via the silicon oxide film P10. The fixing portion 13 extends from the bottom plate 11 toward the device layer 20. A silicon oxide film P10 is provided at the tip of the fixing portion 13. The fixing portion 13 is bonded to the device layer 20 via the silicon oxide film P10.
[0016] The device layer 20 includes a first substrate 20A and a second substrate 20B.
[0017] The first substrate 20A is made of single-crystal silicon. The first substrate 20A is formed, for example, of a p-type silicon (Si) semiconductor. The first substrate 20A may contain boron (B) or the like as a p-type dopant. The first substrate 20A is bonded to the sidewall 12 and the fixing portion 13 of the lower lid 10 via a silicon oxide film P10. The first substrate 20A closes the opening of the space S1 surrounded by the bottom plate 11 and the sidewall 12 of the lower lid 10. The first substrate 20A includes a plurality of slits that penetrate the first substrate 20A in the thickness direction.
[0018] The second substrate 20B is made of single crystal silicon. The second substrate 20B is formed of, for example, a p-type silicon (Si) semiconductor. The second substrate 20B may contain boron (B) or the like as a p-type dopant. The second substrate 20B is bonded to the first substrate 20A via single crystal silicon. In other words, the second substrate 20B is directly bonded to the first substrate 20A. The thickness of the second substrate 20B is greater than the thickness of the first substrate 20A.
[0019] The second substrate 20B includes a support portion 21B, spring portions 22B and 23B, movable portions 24B and 25B, and a peripheral portion 26B. The support portion 21B, the spring portions 22B and 23B, the movable portions 24B and 25B, and the peripheral portion 26B are formed by patterning the second substrate 20B through a removal process. The removal process is performed by dry etching known as DRIE (Deep Reactive Ion Etch), for example. The removal process may also be performed by other techniques such as wet etching and laser etching.
[0020] The support portion 21B is joined to the fixed portion 13 of the lower cover 10 via the first substrate 20A. The support portion 21B supports the movable portions 24B and 25B via the spring portions 22B and 23B so that they can move in the Z-axis direction.
[0021] The spring portions 22B and 23B include a plurality of slits that penetrate the second substrate 20B in the thickness direction, and are configured to be elastically deformable in the Z-axis direction.
[0022] The movable portion 24B is configured to be movable in the Z-axis direction. The movable portion 24B corresponds to an electrode. Capacitance portions are provided between the movable portion 24B and the top cover 30, and between the movable portion 24B and the first substrate 20A.
[0023] A convex portion 27 is provided on the surface of the movable portion 24B facing the first substrate 20A. The convex portion 27 is located at the center of the movable portion 24B in the Y-axis direction. The amount of protrusion of the convex portion 27 is smaller than the distance between the movable portion 24B and the first substrate 20A. The convex portion 27 is formed by the LOCOS (Local Oxidation of Silicon) method. The LOCOS method is a method in which a silicon substrate is oxidized except for a portion masked with a nitride film, and a region (active region) electrically insulated from the surroundings by this oxide film layer is formed.
[0024] A recess 28 is provided on the surface of the movable portion 24B facing the first substrate 20A. The recess 28 has an outwardly widening, inverted tapered shape and is formed by the local oxidation of silicon (LOCOS) method. A plurality of slits 29 are formed in the bottom surface of the recess 28, linearly penetrating the movable portion 24B in the thickness direction. Furthermore, a plurality of slits 32 are provided in the first substrate 20A at positions facing the recess 28 of the movable portion 24B, linearly penetrating the first substrate 20A in the thickness direction. The plurality of slits 32 open into a space surrounded by the recess 28 of the movable portion 24B and the first substrate 20A.
[0025] When the MEMS device 1 is subjected to an inertial force (e.g., acceleration or angular velocity) or pressure in the Z-axis direction, the movable part 24B moves in the Z-axis direction, and the capacitance formed between the recess 28 of the movable part 24B and the first substrate 20A changes based on the distance between the recess 28 of the movable part 24B and the first substrate 20A.
[0026] The movable portion 25B includes a plurality of slits 29 that penetrate the second substrate 20B in the thickness direction, and is configured to be movable in the X-axis direction and the Y-axis direction. The movable portion 25B corresponds to an electrode. A capacitance portion is provided between portions that face each other in the X-axis direction and the Y-axis direction via the slits 29.
[0027] When the MEMS device 1 is subjected to an inertial force (e.g., acceleration or angular velocity) or pressure in the X-axis or Y-axis direction, the movable part 25B moves in the X-axis or Y-axis direction, and the capacitance formed in these parts changes based on the distance between the parts facing each other in the X-axis and Y-axis directions.
[0028] A convex portion 37 is provided on the surface of the movable portion 25B facing the first substrate 20A. The convex portion 37 is disposed in the center of the movable portion 25B in the Y-axis direction. The protrusion amount of the convex portion 37 is smaller than the distance between the movable portion 25B and the first substrate 20A. The convex portion 37 is formed by the LOCOS (Local Oxidation of Silicon) method.
[0029] A recess 33 is provided on the surface of the movable portion 25B facing the first substrate 20A. The recesses 33 are provided in pairs on both sides of the protrusion 27 in the Y-axis direction. Each of the pair of recesses 31 has an inverse tapered shape that widens outward and is formed by the local oxidation of silicon (LOCOS) method. A plurality of slits 34 are formed in the bottom surface of the recess 33, linearly penetrating the movable portion 25B in the thickness direction. Furthermore, a plurality of slits 35 are provided in the first substrate 20A at positions facing the recess 33 of the movable portion 25B, linearly penetrating the first substrate 20A in the thickness direction. The plurality of slits 35 open into a space surrounded by the recess 33 of the movable portion 25B and the first substrate 20A.
[0030] The peripheral portion 26B is joined to the side wall 12 of the lower cover 10 via the first substrate 20A. The peripheral portion 26B is frame-shaped and configured to surround the movable portions 24B and 25B in a plan view. The peripheral portion 26B is provided at a distance from the movable portions 24B and 25B in the X-axis direction and the Y-axis direction.
[0031] The top cover 30 is provided in a flat plate shape. The top cover 30 is formed of, for example, a p-type silicon (Si) semiconductor. Electrodes 40 and 41 are provided on the underside of the top cover 30. The electrode 40 is provided facing the movable portion 24B in the Z-axis direction, and the electrode 41 is provided facing the movable portion 25B in the Z-axis direction. The electrodes 40 and 41 are formed of, for example, aluminum (Al), an aluminum-copper alloy (AlCu), titanium (Ti), or a titanium-tungsten alloy (TiW). The electrode 40 is used to detect the capacitance formed between the electrode 40 and the movable portion 24B. The electrode 41 is used to detect the capacitance formed between the electrode 40 and the movable portion 25B.
[0032] Next, an example of a method for manufacturing the MEMS device 1, in particular an example of a method for forming a capacitance between the movable portion 24B and the first substrate 20A, will be described below.
[0033] First, as shown in FIG. 4A, a recess 28 is formed by the LOCOS method on the surface of the movable portion 24B facing the first substrate 20A.
[0034] Next, as shown in FIG. 4B, an etching stopper layer S made of a silicon oxide film is formed on the bottom surface of the recess 28 by sputtering, CVD (Chemical Vapor Deposition), thermal oxidation, or the like.
[0035] Next, as shown in FIG. 4C, the movable portion 24B on which the etching stopper layer S is formed is directly bonded to the first substrate 20A.
[0036] Next, as shown in FIG. 4D, the movable portion 24B and the first substrate 20A are etched by reactive ion etching (RIE) up to the position where the etching stopper layer S is formed, to form a slit 29 that penetrates the movable portion 24B in the thickness direction and a slit 32 that penetrates the first substrate 20A in the thickness direction.
[0037] Next, as shown in FIG. 4E, gaseous hydrofluoric acid gas is supplied to the space formed between the recess 28 of the movable portion 24B and the first substrate 20A through the previously formed slits 29 and 32, and the etching stopper layer S is removed.
[0038] As a result, as shown in FIG. 4F, a capacitance section whose capacitance changes depending on the distance between the movable section 24B and the first substrate 20A is formed in the space between the movable section 24B and the first substrate 20A.
[0039] Next, another example of a method for manufacturing the MEMS device 1, in particular another example of a method for forming a capacitance between the movable portion 24B and the first substrate 20A, will be described below.
[0040] 5A, a recess 28 is formed by the LOCOS method on the surface of the movable portion 24B facing the first substrate 20A. Also, an etching stopper layer S made of a silicon oxide film is formed on the surface of the first substrate 20A facing the movable portion 24B by sputtering, CVD (Chemical Vapor Deposition), thermal oxidation, or the like.
[0041] Next, as shown in FIG. 5B, the etching stopper layer S formed on the first substrate 20A is aligned with the recess 28 formed in the movable portion 24B, and the first substrate 20A and the movable portion 24B are bonded by direct bonding.
[0042] Next, as shown in FIG. 5C, the movable portion 24B and the first substrate 20A are etched by reactive ion etching (RIE) up to the position where the etching stopper layer S is formed, to form a slit 29 that penetrates the movable portion 24B in the thickness direction and a slit 32 that penetrates the first substrate 20A in the thickness direction.
[0043] Next, as shown in FIG. 5D, gaseous hydrofluoric acid gas is supplied to the space formed between the recess 28 of the movable portion 24B and the first substrate 20A through the previously formed slits 29 and 32, and the etching stopper layer S is removed.
[0044] As a result, as shown in FIG. 5E, a capacitance section whose capacitance changes depending on the distance between the movable section 24B and the first substrate 20A is formed in the space between the movable section 24B and the first substrate 20A.
[0045] Next, another example of a method for manufacturing the MEMS device 1, in particular another example of a method for forming a capacitance between the movable portion 24B and the first substrate 20A, will be described below.
[0046] First, as shown in FIG. 6A, a recess 28 is formed by the LOCOS method on the surface of the movable portion 24B facing the first substrate 20A.
[0047] Next, as shown in FIG. 6B, an etching stopper layer S made of a silicon oxide film is coated on the surface of the movable portion 24B facing the first substrate 20A.
[0048] Next, as shown in FIG. 6C, the etching stopper layer S is planarized.
[0049] Next, as shown in FIG. 6D, the planarized etching stopper layer S is etched to form an etching stopper layer S on the bottom surface of the recess 28 of the movable portion 24B.
[0050] Next, as shown in FIG. 6E, the movable portion 24B on which the etching stopper layer S is formed is directly bonded to the first substrate 20A.
[0051] Next, as shown in FIG. 6F, the movable portion 24B and the first substrate 20A are etched by reactive ion etching (RIE) up to the position where the etching stopper layer S is formed, to form a slit 29 that penetrates the movable portion 24B in the thickness direction and a slit 32 that penetrates the first substrate 20A in the thickness direction.
[0052] Next, as shown in FIG. 6G, gaseous hydrofluoric acid gas is supplied to the space formed between the recess 31 of the movable portion 24B and the first substrate 20A through the previously formed slits 29 and 32, and the etching stopper layer S is removed.
[0053] As a result, as shown in FIG. 6H, a capacitance section whose capacitance changes depending on the distance between the movable section 24B and the first substrate 20A is formed in the space between the movable section 24B and the first substrate 20A.
[0054] As described above, according to the MEMS device 1 of this embodiment, when the movable portion 24B is displaced starting from the bonding portion of the first substrate 20A to the second substrate 20B, the capacitance changes depending on the distance between the movable portion 24B and the first substrate 20A, and the capacitance also changes depending on the distance between the movable portion 24B and the top cover 30. These changes in capacitance are then detected to determine the inertial force and pressure acting on the MEMS device 1. In this case, in the MEMS device 1 of this embodiment, the first substrate 20A and the second substrate 20B are bonded by direct bonding. Therefore, unlike when a silicon oxide film is interposed between the first substrate 20A and the second substrate 20B, it is not necessary to provide a via electrode or perform side etching, which can contribute to miniaturization of the MEMS device 1.
[0055] Furthermore, according to the MEMS device 1 of this embodiment, the surface of the movable part 24B facing the first substrate 20A is provided with the convex part 27, the protrusion amount of which is smaller than the distance between the movable part 24B and the first substrate 20A. Therefore, when the movable part 24B approaches the first substrate 20A to a position where it comes into contact with the first substrate 20A, the movable part 24B is prevented from adhering to the first substrate 20A and hindering the displacement of the movable part 24B.
[0056] Furthermore, according to the MEMS device 1 of this embodiment, the thickness of the second substrate 20B is greater than the thickness of the first substrate 20A. Therefore, when the MEMS device 1 is subjected to an inertial force (e.g., acceleration or angular velocity) or pressure in the Z-axis direction, the amount of movement of the MEMS device 1 in the Z-axis direction is more easily ensured, which can contribute to improving the detection accuracy of the MEMS device 1.
[0057] Furthermore, according to the manufacturing method of the MEMS device 1 of this embodiment, after forming the recess 28 in the movable portion 24B and forming the etching stopper layer S in the recess 28, the first substrate 20A and the second substrate 20B are etched up to the position where the etching stopper layer S is formed, and then the etching stopper layer S is removed using gaseous hydrofluoric acid gas or hydrofluoric acid. Therefore, unlike the case where the recess 28 is not formed in the movable portion 24B, it is not necessary to provide countless slits in the movable portion 24B for the purpose of removing the etching stopper layer S, which can contribute to miniaturization of the MEMS device 1.
[0058] Furthermore, according to the manufacturing method of the MEMS device 1 of this embodiment, the recess 28 is formed in the movable portion 24B by the LOCOS method, which makes it possible to control the depth of the recess 28 with high precision, and to set the electrostatic capacitance formed between the movable portion 24B and the first substrate 20A to an appropriate value.
[0059] Furthermore, according to the manufacturing method of the MEMS device 1 of this embodiment, the etching stopper layer S is formed in the recess 28 of the movable part 24B, and then the movable part 24B on which the etching stopper layer has been formed is directly bonded to the first substrate 20A. This eliminates the need to align the etching stopper layer S with the recess 28 of the movable part 24B, which can contribute to further miniaturization of the MEMS device 1.
[0060] The above embodiment can also be implemented in the following manner.
[0061] In the above embodiment, the thickness of the second substrate 20B may be approximately the same as the thickness of the first substrate 20A, or may be thinner than the thickness of the first substrate 20A.
[0062] In the above embodiment, an example was given of a configuration in which a convex portion 27 having a smaller protrusion amount than the distance between the first substrate 20A and the second substrate 20B is provided on the surface of the second substrate 20B facing the first substrate 20A, but instead of or in addition to this, a convex portion having a smaller protrusion amount than the distance between the first substrate 20A and the second substrate 20B may be provided on the surface of the first substrate 20A facing the second substrate 20B.
[0063] In the above embodiment, a convex portion whose protrusion amount is smaller than the distance between the top cover 30 and the second substrate 20B may be provided on the surface of the second substrate 20B facing the top cover 30.
[0064] In the above embodiment, a configuration has been described in which the second substrate 20B has a recess 28 on the surface facing the first substrate 20A, and a capacitance portion is provided in the recess 28. Alternatively, or in addition to this, the first substrate 20A may have a recess on the surface facing the second substrate 20B, and a capacitance portion may be provided in the recess.
[0065] In the above embodiment, a recess may be formed on at least one of the surface of the top cover 30 facing the second substrate 20B and the surface of the second substrate 20B facing the top cover 30, and a capacitance portion may be provided in the recess.
[0066] Some or all of the embodiments of the present invention will be described below, but the present invention is not limited to the following descriptions.
[0067] <1> A MEMS device comprising: a lower lid; an upper lid forming a space between itself and the lower lid; a first substrate made of single crystal silicon and arranged opposite the lower lid in the space formed between the upper lid and the lower lid; a second substrate made of single crystal silicon and arranged opposite the upper lid in the space formed between the upper lid and the lower lid, including a movable part, the single crystal silicon being bonded to the first substrate; and a capacitance part provided at least one between the upper lid and the second substrate and between the first substrate and the second substrate, the capacitance of which changes depending on the distance between the movable part and the upper lid or the first substrate.
[0068] <2> The MEMS device according to <1>, wherein at least one of a surface of the top cover facing the second substrate and a surface of the second substrate facing the top cover has a first recess, and the capacitance portion is provided in the first recess.
[0069] <3> The MEMS device according to <1> or <2>, wherein at least one of a surface of the first substrate facing the second substrate and a surface of the second substrate facing the first substrate has a second recess, and the capacitance portion is provided in the second recess.
[0070] <4> The MEMS device according to any one of <1> to <3>, wherein a surface of the second substrate facing the top cover has a convex portion having a protrusion amount smaller than a gap between the top cover and the second substrate.
[0071] <5> The MEMS device according to any one of <1> to <4>, wherein at least one of a surface of the second substrate facing the first substrate and a surface of the first substrate facing the second substrate has a convex portion whose protrusion amount is smaller than a distance between the first substrate and the second substrate.
[0072] <6> The MEMS device according to any one of <1> to <5>, wherein the second substrate is thicker than the first substrate.
[0073] <7> A method for manufacturing a MEMS device, comprising: a step of disposing a first substrate made of single crystal silicon opposite a lower lid; a step of disposing a second substrate made of single crystal silicon and including a movable part opposite an upper lid and bonding the single crystal silicon to the first substrate; a step of disposing the first substrate and the second substrate in a space surrounded by the upper lid and the lower lid; and a step of providing a capacitance part between the upper lid and the second substrate and / or between the first substrate and the second substrate, the capacitance part being configured to change depending on the distance between the movable part and the upper lid or the first substrate.
[0074] <8> The method for manufacturing a MEMS device according to <7>, further comprising a step of forming a convex portion, the convex portion having a protrusion amount smaller than a distance between the upper cover and the second substrate, by thermal oxidation treatment on a surface of the second substrate facing the upper cover.
[0075] <9> The method for manufacturing a MEMS device according to <7> or <8>, further comprising a step of forming a convex portion, the protrusion amount of which is smaller than the distance between the first substrate and the second substrate, by thermal oxidation treatment on at least one of a surface of the second substrate facing the first substrate and a surface of the first substrate facing the second substrate.
[0076] <10> The method for manufacturing a MEMS device according to any one of <7> to <9>, further comprising the steps of: forming a recess by thermal oxidation treatment on at least one of a surface of the first substrate facing the second substrate and a surface of the second substrate facing the first substrate; forming an etching stopper layer in the recess; and etching the first substrate and the second substrate up to a position where the etching stopper layer is formed.
[0077] <11> The method for manufacturing a MEMS device according to <10>, further comprising the step of removing the etching stopper layer using gaseous hydrofluoric acid gas or hydrofluoric acid after the first substrate and the second substrate are etched.
[0078] <12> The method for manufacturing a MEMS device according to <10> or <11>, wherein the step of forming the etching stopper layer includes the steps of: coating a silicon oxide film on a surface of the first substrate or the second substrate on which the recess is formed; planarizing the silicon oxide film; and etching the planarized silicon oxide film.
[0079] As described above, according to one aspect of the present invention, it is possible to provide a MEMS device that can be miniaturized and a method for manufacturing a MEMS device.
[0080] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. The present invention may be modified or improved without departing from its spirit, and equivalents are also included within the scope of the present invention. In other words, designs modified by those skilled in the art as appropriate are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. For example, the elements and their arrangements, materials, conditions, shapes, sizes, etc. of the embodiments are not limited to those illustrated and can be modified as appropriate. Furthermore, the embodiments are merely examples, and partial substitutions or combinations of the configurations shown in different embodiments are naturally possible. These are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention.
[0081] 1...MEMS device, 10...lower cover, 20...device layer, 20A...first substrate, 20B...second substrate, 24B...movable portion, 27...convex portion, 28...concave portion, 30...upper cover, S...etching stopper layer.
Claims
1. The bottom lid and An upper lid that forms a space between itself and the lower lid, A first substrate made of single-crystal silicon is positioned opposite the lower lid in the space formed between the upper lid and the lower lid, A second substrate is positioned opposite the upper lid in the space formed between the upper lid and the lower lid, is made of single-crystal silicon, includes a movable part, and is bonded to the first substrate with other single-crystal silicon; A capacitance portion is provided between the upper cover and the second substrate, and between the first substrate and the second substrate, and is configured such that its capacitance changes according to the distance between the movable portion and the upper cover or the first substrate. Equipped with, MEMS device.
2. The surface of the upper cover facing the second substrate, and at least one of the surfaces of the second substrate facing the upper cover, have a first recess. The capacitance portion is provided in the first recess, The MEMS device according to claim 1.
3. At least one of the surfaces of the first substrate facing the second substrate and the surfaces of the second substrate facing the first substrate has a second recess. The capacitance portion is provided in the second recess, The MEMS device according to claim 1.
4. The surface of the second substrate facing the top cover has a protrusion that is smaller in protrusion than the distance between the top cover and the second substrate. The MEMS device according to claim 1.
5. At least one of the surfaces of the second substrate facing the first substrate and the surfaces of the first substrate facing the second substrate has a protrusion that protrudes less than the distance between the first substrate and the second substrate. The MEMS device according to claim 1.
6. The thickness of the second substrate is greater than the thickness of the first substrate. A MEMS device according to any one of claims 1 to 5.
7. A step of placing a first substrate made of single-crystal silicon opposite the lower cover, The process involves placing a second substrate, which is made of single-crystal silicon and includes a movable part, opposite the top cover, and bonding the single-crystal silicon to the first substrate, A step of placing the first substrate and the second substrate in a space enclosed by the upper cover and the lower cover, A step of providing a capacitance portion in at least one of the spaces between the upper cover and the second substrate, and between the first substrate and the second substrate, configured such that the capacitance changes according to the distance between the movable portion and the upper cover or the first substrate, including, A method for manufacturing MEMS devices.
8. The process further includes a step of forming a protrusion on the surface of the second substrate facing the upper cover by thermal oxidation treatment, wherein the amount of protrusion is less than the distance between the upper cover and the second substrate. A method for manufacturing a MEMS device according to claim 7.
9. The process further includes a step of forming a protrusion on at least one of the surfaces of the second substrate facing the first substrate and the surfaces of the first substrate facing the second substrate by thermal oxidation treatment, wherein the amount of protrusion is less than the distance between the first substrate and the second substrate. A method for manufacturing a MEMS device according to claim 7.
10. A step of forming a recess by thermal oxidation treatment on at least one of the surfaces of the first substrate facing the second substrate and the surfaces of the second substrate facing the first substrate, The process of forming an etching stopper layer in the recess, A step of etching the first substrate and the second substrate to the position where the etching stopper layer is formed, Further including, A method for manufacturing a MEMS device according to claim 7.
11. The process further includes removing the etching stopper layer using gaseous hydrofluoric acid gas or hydrofluoric acid after the first and second substrates have been etched. A method for manufacturing a MEMS device according to claim 10.
12. The step of forming the etching stopper layer is: A step of coating the surface on the first substrate or the second substrate where the recess is formed with a silicon oxide film, The process of planarizing the silicon oxide film, The process of etching the planarized silicon oxide film, including, A method for manufacturing a MEMS device according to claim 10 or 11.