JP2007205739A - Dynamic quantity sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic quantity sensor in which the separation etc. of a weight made of a thick plating hardly occurs. <P>SOLUTION: An angular velocity sensor has a three-layer structure in which a structure of a movable part is held between an upper glass substrate and a lower glass substrate from upper and lower directions. The structure of the movable part is provided with a flexible substrate; a frame; and the weight. The frame and the weight are made of a thick plating made of metal electrodeposited through the use of an electroforming electrode provided for the flexible substrate formed along the direction of an x-y plane. The weight does not have uniform area in cut surfaces in x-y planes and is constituted in such a way that its composition surface with the flexible substrate supporting the weight may be as small as possible. It is therefore possible to constitute the weight in such a way as to have heavier weight while securing a sufficient beam length and further improve detection sensitivity. Since it is possible to increase the weight of the weight without having to enlarge the electroformed area of the weight, it is possible to prevent separation etc. of platings and secure appropriate adhesion strength between the beams and the weight. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mechanical quantity sensor that detects a mechanical quantity such as acceleration or angular velocity, and a method of manufacturing the mechanical quantity sensor.

In a wide range of fields such as a camera shake correction device for a video camera, an in-vehicle airbag device, and a posture control device for a robot, a mechanical amount sensor for detecting a mechanical amount acting on an object is used.
One type of mechanical quantity sensor is a semiconductor acceleration sensor. This is due to the inertial force of the weight to which acceleration is applied by producing flexible beams (springs) and weights (mass) by silicon micromachining technology such as MEMS (micro electro mechanical system) technology. It is a sensor that detects the acceleration by detecting the displacement of the beam.
In addition, as a method of electrically detecting the displacement of the beam, for example, a method of detecting a change in capacitance of a capacitive element in which one electrode is set to the beam, or a resistance value of a piezoelectric body fixed to the beam. There is a method to detect the change of.

Conventionally, a technique for improving the sensitivity in such an acceleration sensor and suppressing variations in accuracy and shape between individuals has been proposed in the following patent documents.
Japanese Patent Laid-Open No. 11-2111748

  Patent Document 1 proposes a technique in which a metal layer is formed by plating on a piezoelectric body constituting a beam, and a weight body and a frame (support body) are formed on the metal layer using an electroforming method. .

In the mechanical quantity sensor as described above, when the weight body is formed by thick plating (electroforming), stress acts on the joint portion between the weight body and the beam.
Therefore, in a sensor in which the weight body is formed by thick plating as shown in Patent Document 1, there is a possibility that deformation (warping, bending, etc.) may occur in the beam due to the action of stress. In addition, when excessive stress is applied, the adhesion strength at the joint surface between the weight body and the beam cannot be secured, and the weight body may be peeled off.
Further, when the posture of the weight body is changed by an external force and the beam is bent or distorted, the weight may be further peeled off.
Such deformation of the beam, peeling of the weight, and the like may cause a detection error and may cause a decrease in detection sensitivity (detection accuracy) of the sensor.

  Accordingly, an object of the present invention is to provide a mechanical quantity sensor that hardly causes deformation of a beam, peeling of a weight, and the like, and a method for manufacturing the mechanical quantity sensor.

In the first aspect of the present invention, a frame, a flexible beam at least part of which is fixed to the frame, and an electrodeposited metal joined to the beam and joined to the beam. A weight having a cross-sectional area larger than the area of the joint surface, posture detecting means for detecting the posture change of the weight, and based on the posture change of the weight detected by the posture detecting means The object is achieved by providing output means for outputting a change in the mechanical quantity.
According to a second aspect of the present invention, in the mechanical quantity sensor according to the first aspect, the beam includes an electrode for electroforming, and the weight is joined to the beam via the electrode for electroforming. Features.
According to a third aspect of the present invention, in the mechanical quantity sensor according to the first or second aspect, the weight is formed of a metal electrodeposited in a matrix formed by using a photolithography technique. It is characterized by.
According to a fourth aspect of the present invention, in the mechanical quantity sensor according to the first, second, or third aspect, the mechanical quantity sensor includes a fixed electrode disposed to face the weight, and the posture detection means includes the weight and A change in posture of the weight is detected based on a change in capacitance between the fixed electrodes.
According to a fifth aspect of the present invention, in the mechanical quantity sensor according to any one of the first to fourth aspects of the present invention, the mechanical quantity sensor includes a piezoelectric element disposed on the beam, and the posture detection means includes the piezoelectric sensor. A change in posture of the weight is detected based on a change in circuit constant of the element.
According to a sixth aspect of the present invention, in the mechanical quantity sensor according to any one of the first to fifth aspects, the frame is formed of an electrodeposited metal similar to the weight. It is characterized by.
According to a seventh aspect of the present invention, a weight comprising a first weight portion having a joint surface with a beam and a second weight portion having a cross section parallel to the joint surface with the beam that is larger than the joint surface with the beam. A first step of applying a first photosensitive member to the surface of the beam, and a first step of exposing a region for forming the first weight portion. A second step of superimposing the mask on the first photosensitive member and performing a first exposure process, and a third step of forming a first electrode layer at least in a region serving as a matrix of the weight, A fourth step of applying a second photosensitive member on the upper surface of the first photosensitive member including the first electrode layer, and a region for exposing a region for forming the second weight portion. A second step of superimposing the second mask on the second photosensitive member and performing a second exposure process; and A sixth step of melting the region for forming the weight in the photosensitive member and the second photosensitive member and developing the exposed region, and an electroforming process using the region remaining in the sixth step as a mother die A seventh step; posture detecting means for detecting the posture change of the weight formed by the seventh step; and detecting a change in mechanical quantity from the posture change of the weight detected by the posture detecting means. And the eighth step of forming a mechanical quantity detection means.
According to an eighth aspect of the present invention, in the method of manufacturing a mechanical quantity sensor according to the seventh aspect, the method includes a ninth step of forming a second electrode layer on a surface of the beam, wherein the first step includes the first step. A first photosensitive member is applied to the surface of the second electrode layer.

  According to the present invention, the junction area between the beam and the weight is reduced by forming the weight by thick plating in which the cross-sectional area of any part parallel to the junction surface with the beam is larger than the area of the junction surface. Therefore, the stress acting on the joint between the beam and the weight can be reduced. As a result, it is possible to configure a mechanical quantity sensor that is unlikely to cause beam deformation or weight separation.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS.
(1) Outline of Embodiment In this embodiment, an angular velocity sensor that measures an angular velocity acting on a weight based on a displacement amount of the posture state of the weight supported by the frame by a flexible beam will be described.
The angular velocity sensor has a three-layer structure in which a movable part structure is sandwiched from above and below by an upper glass substrate and a lower glass substrate.
The movable part structure includes a flexible substrate, a frame, and a weight.
The frame and the weight are made of metal thick plating (electroforming) electrodeposited (via) an electroforming electrode provided on a flexible substrate formed along the xy plane direction.
The weight is configured such that the area of the cut surface in the xy plane is not uniform, and the joint surface with the flexible substrate (beam) supporting the weight is as small as possible.
According to the present embodiment, the length of the beam can be secured sufficiently long by reducing the joint surface with the weight, that is, the movable range of the weight can be secured widely, and the weight of the weight can be further increased. Since it can be made large, the detection sensitivity (accuracy) of the angular velocity sensor can be further improved.
Further, since the weight of the weight can be increased without increasing the electroforming area of the weight, that is, the joint area between the weight and the beam (flexible substrate), the stress acting on the joint between the weight and the beam It is possible to reduce (suppress) plating peeling and the like. Thereby, the adhesion strength (bonding strength) between the beam and the weight can be appropriately maintained.

(2) Details of Embodiment An angular velocity sensor according to the present embodiment is a semiconductor sensor element formed by processing a semiconductor substrate. The processing of the semiconductor substrate can be performed using MEMS (micro electro mechanical system) technology.
The same direction as the stacking direction of the layers in the substrate constituting the angular velocity sensor is defined as the vertical direction, that is, the z-axis (direction). The axes orthogonal to the z-axis and orthogonal to each other are defined as an x-axis (direction) and a y-axis (direction). That is, the x axis, the y axis, and the z axis are three axes that are orthogonal to each other.
In addition, the angular velocity sensor according to the present embodiment includes a sensor unit that detects a change in the posture of the weight as an electric signal, and a signal processing unit (control unit) that processes the detected electric signal.

FIG. 1 is a perspective view showing a schematic structure of an angular velocity sensor according to the present embodiment.
In FIG. 1, in order to express the structure of the angular velocity sensor in an easy-to-understand manner, the structure of each layer is shown separately, but in actuality, each layer is configured in a stacked state.
As shown in FIG. 1, the angular velocity sensor has a three-layer structure in which a movable part structure 1 is sandwiched from above and below by an upper glass substrate 2 and a lower glass substrate 3.

The movable part structure 1 includes a flexible substrate 10, a frame 11, and a weight 12.
The flexible substrate 10 is a plate-like member having flexibility, and the flexible substrate 10 is etched to form the beam 13 and the weight forming portion 14.
The flexible substrate 10 is formed by using a member having elasticity (spring property) such as Si (silicon), SUS (stainless steel) material, phosphor bronze, for example.
The weight forming portion 14 is a square portion provided in the central portion of the angular velocity sensor, and the beam 13 is a four band-like member extending from the weight forming portion 14 in the radial direction (in the direction of the frame 11) in the cross direction. is there.
On the lower surface of the flexible substrate 10 (the surface facing the lower glass substrate 3), an electrode 15 for electroforming for electroforming (electrodepositing) the frame 11 and the weight 12 is provided.
The electroforming electrode 15 is formed using, for example, Cr / Au (chromium / gold).
Application of a voltage when forming the weight 12 and the frame 11 described later is performed from the outer edge (periphery) of the electrode 15 for electroforming.
In addition, when the flexible substrate 10 is a conductor such as metal and the joining strength when the electroforming is formed can be sufficiently ensured, the electroforming electrode 15 may not be provided.

The frame 11 is a hollow fixed portion provided at the peripheral edge of the movable part structure 1 so as to surround the weight 12, and constitutes the framework of the movable part structure 1. The frame 11, the upper glass substrate 2, and the lower glass substrate 3 constitute an angular velocity sensor housing (exterior body).
The weight 12 is a member having a convex section (reverse T-shape) in the z-axis direction, in which a weight section 120a and a weight section 120b made of large and small rectangular parallelepipeds are overlapped.
The weight part 120b has an end face larger than the weight part 120a, and the weight part 120a is continuously formed at the center of the end face.
The upper end surface (smaller end surface) of the weight 12 is joined to the weight forming portion 14 via the electrode 15 for electroforming.

FIG. 2A shows a plan view of the frame 11 and the weight 12 in the movable part structure 1 as viewed from the upper glass substrate 2 side.
The area of the bottom end surface of the weight 12, that is, the bottom surface of the weight portion 120 b is configured to be larger than at least the upper end surface of the weight 12, that is, the area of the joint surface with the beam 13 in the weight portion 120 a.
Thus, the weight 12 is a mass body fixed (supported) to the hollow portion of the frame 11 by the four beams 13, and can be vibrated or twisted by the force applied from the outside by the action of the beams 13. It has become. The weight 12 has conductivity, and its bottom surface functions as a movable electrode.

The lower glass substrate 3 is provided with a drive electrode 30 for vibrating the weight 12 at the center.
In addition, fixed electrodes 31 to 34 for detecting the posture of the weight 12 are disposed on the lower glass substrate 3 so as to surround the drive electrode 30.
The fixed electrodes 31 to 34 have a trapezoidal shape, and are arranged so that the shorter one of the parallel sides is directed toward the center of the drive electrode 30.
In these fixed electrodes 31 to 34, opposing fixed electrodes, that is, electrodes located on the opposite side across the center are paired to detect each axial component of the posture state of the weight 12, and based on the detection result Angular velocities acting about the x and y axes are detected.
Specifically, the angular velocity around the first detection axis (x axis) is detected by using the fixed electrode 32 and the fixed electrode 34, and the angular velocity around the second detection axis (y axis) is detected by using the fixed electrode 31 and the fixed electrode 33. Angular velocity is detected.

FIG. 2B is a diagram showing a cross section along the x-axis passing through the center of the angular velocity sensor.
As shown in the figure, a movable gap 16 for moving the weight 12 is formed between the upper surface of the flexible substrate 10 (the surface facing the upper glass substrate 2) and the upper glass substrate 2. The upper glass substrate 2 is bonded so as to seal the movable gap 16.
The upper glass substrate 2 and the movable part structure 1 and the lower glass substrate 3 and the movable part structure 1 are joined by, for example, anchor metal (underlying metal) such as Cr (chrome) and Au (gold) on the joint surface. It is performed using eutectic bonding or the like that is laminated and bonded.
Between the lower surface of the flexible substrate 10 (the surface facing the lower glass substrate 3) and the bottom surface of the weight 12, that is, the lower surface (the surface facing the lower glass substrate 3) and the lower glass substrate 3. A movable gap 17 for making the weight 12 movable is formed. The lower glass substrate 3 is bonded so as to seal the movable gap 17. In addition, the movable clearances 16 and 17 can reduce the air resistance when the weight 12 operates by making a vacuum state.

Although not shown on the lower glass substrate 3, the potential of the drive electrode 30 and the fixed electrodes 31 to 3, that is, the signal detected by the sensor unit (detection unit) of the angular velocity sensor is extracted to the outside of the sensor unit. Electrode pads are provided.
The electrode pad is connected to each electrode via a lead wire provided on the inner peripheral wall of the through hole that penetrates in the thickness direction of the lower glass substrate 3.
Further, an electrode pad for drawing out the potential (detection signal) of the weight 12 functioning as a movable electrode to the outside of the sensor is provided on the outer edge portion of the flexible substrate 10.
These electrode pads are connected to a C / V conversion circuit in a signal processing unit (control unit) (not shown).

Next, the operation of the sensor unit of the angular velocity sensor configured as described above will be described.
As shown in FIG. 1, the angular velocity sensor according to the present embodiment primarily vibrates the weight 12 in the vertical direction (z-axis direction), and generates a Coriolis force on the weight 12 that performs this vibration motion. A method of detecting an angular velocity applied around the first detection axis (x axis) and the second detection axis (y axis) is used.
Specifically, an AC voltage is applied between the drive electrode 30 and the movable electrode (weight 12), and the weight 12 is vibrated in the vertical direction (z-axis direction) using the action of electrostatic force acting between these electrodes.

The frequency of the alternating voltage applied to cause the weight 12 to vibrate up and down, that is, the vibration frequency of the weight 12 is set to a resonance frequency f of about 3 kHz at which the weight 12 resonates and vibrates, for example. Thus, a large displacement amount of the weight 12 can be obtained by vibrating the weight 12 at the resonance frequency f.
When an angular velocity Ω is applied around the mass 12 oscillating at this velocity v, a Coriolis force of “F = 2 mvΩ” is generated at the center of the mass 12 in a direction perpendicular to the movement direction of the mass 12. To do.
When this Coriolis force F is generated, the weight 12 is twisted and the posture of the weight 12 changes. That is, the weight 12 is inclined with respect to a plane perpendicular to the vibration direction of the weight 12. By detecting the change in the posture of the weight 12 (inclination and torsion amount), the direction and magnitude of the acting angular velocity are detected.

FIG. 2C is a diagram showing a state in which the posture of the weight 12 has changed.
For example, when the angular velocity acts around the second detection axis (y-axis) of the weight 12 to generate Coriolis force, and the posture of the weight 12 is tilted with respect to the x-axis as shown in FIG. The distance between the electrodes 31 and 33 and the movable electrode (weight 12) changes.
Specifically, the distance between the fixed electrode 33 and the movable electrode is reduced, while the distance between the fixed electrode 31 and the movable electrode is increased.
Since such a change in the distance between the electrodes appears as a change in the capacitance between the electrodes, the posture change of the weight 12 is based on the change in the capacitance between the fixed electrodes 31 and 33 and the movable electrode. Can be detected electrically.

A change in the distance between the electrodes, that is, a change in the capacitance between the electrodes can be electrically detected using a C / V conversion circuit in a signal processing unit (control unit) (not shown).
The signal processing unit detects the generated Coriolis force F based on the detected change in the posture of the weight 12 (inclination direction, degree of inclination, etc.). Then, the angular velocity Ω is calculated (derived) based on the detected Coriolis force F. That is, in this signal processing unit, the amount of change in the posture of the weight 12 is converted into an angular velocity.
Here, the case where the angular velocity acts around the second detection axis (y axis) of the weight 12 has been described, but the case where the angular velocity acts around the first detection axis (x axis) of the weight 12 is similarly fixed. By detecting the posture change of the weight 12 based on the change in the distance between the electrodes 32 and 34 and the movable electrode, the acting angular velocity can be measured.

Next, a method for manufacturing the movable part structure 1 in the angular velocity sensor according to the present embodiment will be described.
3-5 is the figure which showed the manufacturing process of the movable part structure 1 in the angular velocity sensor which concerns on this Embodiment. In addition, in FIGS. 3-5, the front view in each process and sectional drawing in the AA part of a front view are shown.
First, as shown in FIG. 3A, the reinforcing substrate 20 is fixed to the flexible substrate 10 to ensure the strength of the flexible substrate 10 when the movable part structure 1 is manufactured.

The reinforcing substrate 20 is configured by a member having a smooth surface and high rigidity, such as a silicon substrate, a glass substrate, or a SUS substrate, which has the same or larger size as the movable part structure 1 to be formed.
Here, the flexible substrate 10 is made strong by bonding the reinforcing substrate 20, but the flexible substrate 10 and the reinforcing substrate 20 are configured using an SOI (silicon-on-insulator) substrate. It may be. Specifically, the active layer in the SOI substrate is used as the flexible substrate 10 and the support layer is used as the reinforcing substrate 20.
When the SOI substrate is used in this way, an adhesive layer (BOX oxide film layer) is disposed between the flexible substrate 1 and the reinforcing substrate 20 (boundary).

Next, as shown in FIG. 3B, the beam 13 and the weight forming portion 14 are formed by punching the flexible substrate 10 by etching or the like.
The reinforcing substrate 20 to be joined to the flexible substrate 10 may be joined after the beam 13 and the weight forming portion 14 are formed on the flexible substrate 10.
Subsequently, as shown in FIG. 3C, a first electrode, that is, an electroforming electrode 15 is formed on one surface of the flexible substrate 10.
The electrode 15 for electroforming is a part that functions as a conductive layer when the frame 11 and the weight 12 in the movable part structure 1 are formed by electroforming. For example, an electroless plating film is formed after surface activation. Alternatively, Cr and Au can be formed by using a technique such as vacuum deposition (lamination) or sputtering. Note that Cr formed before the deposition of Au functions as a base for improving adhesion.

Next, as shown in FIG. 3D, a photoresist (photosensitive resin) is applied to the surface of the electrode 15 for electroforming with a uniform thickness to form a first layer resist 22.
Here, as a photoresist material (resist material), here, an example using a negative resist is shown. In practice, a heat treatment (bake treatment) or the like for effecting the resist is performed after the resist coating, but the description thereof is omitted here.
When the first-layer resist 22 is formed using a liquid resist material, a step may be generated on the resist surface in a portion where the flexible substrate 10 is removed. Thus, when a level | step difference arises on a resist surface, you may make it form the 1st layer resist 22 by affixing a dry film type resist material.

After the first-layer resist 22 is formed, as shown in FIG. 3E, the first-layer mask 23 is irradiated with ultraviolet rays in a state where the first-layer mask 23 is put together, and the first-layer mask 23 is exposed. Transfer the pattern.
The pattern of the first layer mask 23 includes a pattern disposed in the formation region of the frame 11 and a pattern disposed in the formation region of the weight portion 120a.
After the transfer of the pattern of the first layer mask 23 is completed, as shown in FIG. 4A, the second layer electrode 24 is formed in the region (exposure region) exposed to ultraviolet rays in the previous step.
Similarly to the electrode 15 for electroforming, the second-layer electrode 24 is formed by, for example, forming an electroless plating film after surface activation, or using a technique such as vacuum deposition (lamination) or sputtering of Cr and Au. can do.

Next, as shown in FIG. 4B, a photoresist is applied to the surfaces of the second layer electrode 24 and the first layer resist 22 to form a second layer resist 25.
The second-layer resist 25 is formed so that the surface height after the photoresist application is uniform (flat).
After the second-layer resist 25 is formed, as shown in FIG. 4C, the second-layer mask 26 is irradiated with ultraviolet rays in a state where the second-layer mask 26 is put together, and the second-layer mask 26 is exposed. Transfer the pattern.
The pattern of the second layer mask 26 includes a pattern disposed in the formation region of the frame 11 and a pattern disposed in the formation region of the weight portion 120b.

After the transfer of the pattern of the second layer mask 26 is completed, as shown in FIG. 4 (d), the resist of the portion (unexposed portion) not exposed to light by the first layer mask 23 and the second layer mask 26 is removed as a solvent. Dissolve in and apply development.
After the development process is completed, as shown in FIG. 5A, an electroforming process is performed using the remaining resist area of the exposed portion as a matrix.
Here, a thick metal is electrodeposited using the electroforming electrode 15 and the second layer electrode 24 as a cathode inside the matrix. That is, the thick plating 27 is formed inside the mother die.

Specifically, at the start of electrodeposition, metal is electrodeposited from the surface of the electroforming electrode 15 into the mother die. At this time, since the second layer electrode 24 is not energized, it is not electrodeposited on the surface.
Thereafter, electrodeposition proceeds only in the region of the electrode 15 for electroforming, and when it reaches the height of the second layer electrode 24, the electrode 15 for electroforming and the second layer electrode 24 are electrically connected through the electrodeposited metal. . Then, electrodeposition is also performed from the surface of the second layer electrode 24.
As a result, electrodeposition is performed in a state where the thickness (height) of the metal at the electroforming electrode 15 and the second layer electrode 24 is substantially uniform.
For example, Ni (nickel), Cu (copper), Fe (iron), Au (gold), and alloys thereof are used as the electrodeposited metal (electroformed material).

Next, as shown in FIG. 5B, a portion of the thick plating 27 that protrudes from the base die is shaved, and a polishing process is performed to flatten the surface unevenness. The polishing treatment of the thick plating 27 is performed using, for example, a CMP (Chemical Mechanical Polishing) method.
The CMP method is a polishing method in which the surface of a substrate attached to a spindle is polished by contacting a polishing pad on the surface with a rotary table while flowing a liquid slurry (polishing liquid) containing silica particles.
Then, after the polishing process of the thick plating 27 is completed, as shown in FIG. 5 (c), the matrix, that is, the remaining resist region of the exposed portion is dissolved and removed with a solvent.

Finally, the reinforcing substrate 20 is removed from the flexible substrate 10 as shown in FIG.
When the reinforcing substrate 20 is fixed (bonded) to the flexible substrate 10 with WAX or the like, it is removed using heat treatment, an organic solvent, or the like.
Further, when the reinforcing substrate 20 is formed of a support layer of an SOI substrate, the support layer is removed by an etching process.
When removing the reinforcing substrate 20, if there is a concern about damage to the thick plating 27 (structure) due to stress or the like, the removing process of the reinforcing substrate 20 is performed before the removing process of the mother die. It may be.
In the present embodiment, all the resists are negative, but positive resists may be used. In this case, all the masks have a pattern reverse to that shown in the figure. Whether to use a negative type resist or a positive type resist depends on the film forming conditions of the resist and the accuracy of transfer, but it is possible to select an optimum one.

Further, when an actual angular velocity sensor is manufactured, since a large number of pieces are taken (batch processing) using a single large substrate, a dicing process step for cutting out each sensor is required.
It should be noted that the dicing process for dividing into individual chips may be performed at the time of patterning of the first flexible substrate 10, or after the thick plating 27 is formed inside the mother die or after the mother die (resist region). ) May be removed.
In the angular velocity sensor according to the present embodiment, the beam 13 is first formed on the flexible substrate 10, but the timing (time) for forming the beam 13 is not limited to this.
For example, the formation of the beam 13 (the punching process of the flexible substrate 10) may be performed from the back surface of the formation surface of the electroformed structure, that is, the weight 12 and the frame 11, after the reinforcing substrate 20 is removed. In this case, it is preferable to remove the matrix (resist region) after forming the beam 13.

As described above, according to the present embodiment, the weight of the weight 12 can be configured to be larger while the length of the beam 13 is sufficiently secured, so that the detection sensitivity (accuracy) of the angular velocity sensor is further improved. be able to.
The stress acting on the joint between the weight 12 and the beam 13 tends to increase as the joint area, that is, the electroforming area increases. This is because the deformation amount of the beam 13 in the contact (bonding) region increases as the contact area with the flexible beam 13 increases. As a result, the entire beam 13 is greatly deformed, and the rigidity of the beam 13 and the capacitance value (or piezoelectric resistance value) between the electrodes appear as a difference from the originally required design value, and the angular velocity sensor output Detection error and variation. Moreover, when excessive stress acts, the weight 12 may peel from the beam 13.

However, according to the present embodiment, the weight of the weight 12 can be increased without increasing the electroforming area of the weight 12, that is, the bonding area between the weight 12 and the beam 13 (flexible substrate 10). The possibility of deformation of the beam 13 caused by the stress acting on the joint between the weight 12 and the beam 13 and the separation of the weight 12 (plating) can be reduced (suppressed).
That is, since the joint portion between the weight 12 and the beam 13 (flexible substrate 10) is made small, the influence of the stress acting on the joint portion between the weight 12 and the beam 13 can be suppressed as compared with the conventional sensor. The deformation of the beam 13 and the peeling of the weight 12 (plating) can be reduced (suppressed).
Furthermore, since the area of the bottom surface of the weight 12 (the bottom portion of the weight portion 120b) that functions as a movable electrode for detection can be increased, the detection sensitivity (accuracy) of the angular velocity sensor can be further improved.

(Modification)
In the modification, an angular velocity sensor that uses a piezoresistive element to detect a change in posture of the weight 12 will be described.
FIG. 6 is a cross-sectional view illustrating a schematic configuration of an angular velocity sensor according to a modification.
Here, parts having the same configuration as the angular velocity sensor shown in the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and only different configurations will be described.
FIG. 7 is a plan view of the flexible substrate 10 in the angular velocity sensor according to the modification.
As shown in FIG. 7A, on the surface of the flexible substrate 10 where the beam 13 is formed (the surface facing the lower glass substrate 3), a piezoelectric resistor Rx1 that is a detection element that detects deformation of the beam 13 itself. , Rx2, Ry1, Ry2, Rz1, and Rz2 are formed in a predetermined direction.
When the flexible substrate 10 is formed of a silicon substrate, the piezoelectric resistors Rx1, Rx2, Ry1, Ry2, Rz1, and Rz2 can be directly formed by performing a process such as ion implantation on the flexible substrate 10. it can.

Further, as shown in FIG. 7A, the piezoelectric resistors Rx1 and Rx2, Ry1 and Ry2, and Rz1 and Rz2 are provided on the beam 13 to be opposed to each other.
Similar to the angular velocity sensor described above, when an angular velocity Ω is applied around the mass 12 having a mass m vibrating at a velocity v, a Coriolis force of “F = 2 mvΩ” is applied to the center of the mass 12 in the direction of movement of the mass 12. It occurs in the direction orthogonal to.
When this Coriolis force F is generated, the weight 12 is twisted and the posture of the weight 12 changes. That is, the weight 12 is inclined with respect to a plane perpendicular to the vibration direction of the weight 12.

With the posture of the weight 12, mechanical deformation occurs in the beam 13 that supports the weight 12. When the beam 13 is deformed, the resistance values of the piezoelectric resistors Rx1, Rx2, Ry1, Ry2, Rz1, and Rz2 are changed.
Then, based on the change in the resistance value of the piezoresistor in each axial direction, the change in the posture of the weight 12 (inclination, twist amount) is detected, and the direction and magnitude of the acting angular velocity are determined based on these detection results. Output.
In the modification shown in FIG. 6, unlike the sensor described above, Rz1 and Rz2 are provided for detecting displacement of the weight 12 in the z-axis direction (deflection of the beam 13). This is used when performing control to keep the vibration state (amplitude) of the weight 12 in the z-axis direction constant. In the sensor described above, a similar function can be added by providing an electrode for detecting the displacement of the weight 12 in the z-axis direction.

The x-axis direction component of the external force acting on the weight 12 is calculated based on changes in the resistance values of the piezoelectric resistors Rx1 and Rx2. Similarly, the y-axis direction component of the external force acting on the weight 12 is calculated based on the change in the resistance value of the piezoelectric resistors Ry1 and Ry2, and the z-axis direction component is based on the change in the resistance value of the piezoelectric resistors Rz1 and Rz2. Is calculated.
Further, as shown in FIG. 7A, the signal processing unit (control unit) in which the piezoelectric resistors Rx1, Rx2, Ry1, Ry2, Rz1, and Rz2 are provided outside the sensor at the outer edge portion of the flexible substrate 10. An electrode pad 41 is provided for connection to the sensor, that is, for extracting a detection signal to the outside of the sensor.
The electrode pad 41 is made of a metal such as Al (aluminum).

7B, the surface of the flexible substrate 10 on which the piezoelectric resistors Rx1, Rx2, Ry1, Ry2, Rz1, Rz2, the wiring pattern and the electrode pads 41 are formed (opposite to the lower glass substrate 3). The insulating layer 40 for insulating and protecting the piezoelectric resistors Rx1, Rx2, Ry1, Ry2, Rz1, and Rz2 is formed on the surface).
The insulating layer 40 is formed in a portion where the formation area of the electrode pad 41 is avoided so that the surface is flat.
The insulating layer 40 is made of an insulator such as SiO 2 (silicon oxide).
Further, as shown in FIG. 7 (c), the frame 11 and the weight 12 are formed on the surface of the insulating layer 40 (the surface facing the lower glass substrate 3) for electroforming (electrodeposition formation). An electrode 15 'is provided.
Note that the method for forming the electrode 11 and the weight 12 through the electrode 15 for electroforming (electrodeposition formation) is the same as the above-described angular velocity sensor, and thus the description thereof is omitted.

Moreover, although the angular velocity sensor (including the modification) described above is configured to support the weight 12 via the four beams 13, the method of supporting the weight 12 is not limited to this.
For example, when the flexible substrate 10 is configured by a member having sufficient flexibility to support the weight 12 in a movable state, a diaphragm structure without the beam 13 is used. Also good.
Furthermore, in the present embodiment, a two-axis detection type angular velocity sensor has been described as an example of a mechanical quantity sensor. However, the mechanical quantity sensor is not limited to this. For example, an acceleration sensor that can detect acceleration acting in the x-axis, y-axis, and z-axis directions, a single-axis sensor that detects only acceleration acting in the x-axis direction, and an acceleration that acts in the x-axis and y-axis directions are detected. It may be a biaxial sensor.
In the case of configuring the acceleration sensor, a driving unit for primary vibration of the weight is not necessary.

Further, in the above-described angular velocity sensor (including modifications), the electroforming electrode 15 is also formed in the region of the beam 13 as shown in FIGS.
When the stress acting on the flexible substrate 10 (beam 13) by the electrode 15 for electroforming is sufficiently small, the electrode 15 for electroforming may be formed over the entire surface of the flexible substrate 10 in this way. Good. However, when the stress of the electroforming electrode 15 ′ is large, a patterning process is performed as shown in FIGS. 8A and 8B in order to suppress (prevent) the bending of the flexible substrate 10 (beam 13). It is preferable to perform (masking treatment).
Specifically, as shown in FIGS. 8A and 8B, the electrode 15 ′ for electroforming is formed only in the formation region (electroforming region) of the weight 12 and the formation region (electroforming region) of the frame 11.
The electroforming electrode 15 is formed slightly larger than the electroforming area in consideration of the displacement of the mask (first layer mask 23) when forming the mother die for forming the weight 12 by electroforming. It is preferable to do.

When the flexible substrate 10 is composed of a semiconductor or a nonconductor, as shown in FIGS. 8A and 8B, the formation area of the weight 12 and the frame 11 in the electrode 15 ′ for electroforming The formation region is electrically connected via the wiring pattern 18.
8A and 8B show that the wiring pattern 18 is provided only on a part of the four beams 13, all the beams 13 are considered in consideration of the flexibility balance of the beams 13. Alternatively, the wiring pattern 18 may be provided equally. It is desirable to make the formation area (arrangement area) of the wiring pattern 18 as small as possible.

It is the perspective view which showed schematic structure of the angular velocity sensor which concerns on this Embodiment. (A) shows the top view which looked at the flame | frame and weight in the movable part structure from the upper glass substrate side, (b) shows the cross section along the x-axis which passes along the center in an angular velocity sensor, (c) shows weight of the weight It is the figure which showed the state which the attitude | position changed. It is the figure which showed the manufacturing process of the movable part structure in the angular velocity sensor which concerns on this Embodiment. It is the figure which showed the manufacturing process of the movable part structure in the angular velocity sensor which concerns on this Embodiment. It is the figure which showed the manufacturing process of the movable part structure in the angular velocity sensor which concerns on this Embodiment. It is sectional drawing which showed schematic structure of the angular velocity sensor which concerns on a modification. It is a top view of the flexible substrate in the angular velocity sensor concerning a modification. It is the figure which showed the example of formation of the electrode for electroforming.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Movable part structure 2 Upper glass substrate 3 Lower glass substrate 10 Flexible substrate 11 Frame 12 Weight 13 Beam 14 Weight forming part 15 Electroforming electrode 16 Movable gap 17 Movable gap 18 Wiring pattern 20 Reinforcement substrate 22 First layer resist 23 1st layer mask 24 2nd layer electrode 25 2nd layer resist 26 2nd layer mask 27 Thick plating 30 Drive electrode 31-34 Fixed electrode 40 Insulating layer 41 Electrode pad 120a Weight part 120b Weight part

Claims (8)

Frame,
A flexible beam at least partially secured to the frame;
A weight bonded to the beam, formed of electrodeposited metal, and having a cross-sectional area at any location parallel to the bonding surface with the beam larger than the area of the bonding surface;
Posture detection means for detecting posture change of the weight;
Output means for outputting a change in mechanical quantity based on the posture change of the weight detected by the posture detection means;
A mechanical quantity sensor characterized by comprising: The beam includes an electrode for electroforming,
The mechanical quantity sensor according to claim 1, wherein the weight is joined to the beam via the electroforming electrode.   3. The mechanical quantity sensor according to claim 1, wherein the weight is made of a metal electrodeposited in a mother die formed using a photolithography technique. A fixed electrode disposed opposite to the weight,
4. The mechanical quantity according to claim 1, wherein the posture detection unit detects a change in posture of the weight based on a change in capacitance between the weight and the fixed electrode. 5. Sensor. Comprising a piezoelectric element disposed on the beam;
5. The mechanical quantity sensor according to claim 1, wherein the posture detection unit detects a posture change of the weight based on a change in a circuit constant of the piezoelectric element. .   The mechanical quantity sensor according to any one of claims 1 to 5, wherein the frame is formed of an electrodeposited metal similar to the weight. Manufacture of a mechanical quantity sensor having a weight comprising a first weight portion having a joint surface with a beam and a second weight portion having a cross section parallel to the joint surface with the beam larger than the joint surface with the beam A method,
Applying a first photosensitive member to the surface of the beam;
A second step of overlaying a first mask for exposing a region for forming the first weight portion on the first photosensitive member and performing a first exposure process;
A third step of forming a first electrode layer at least in a region serving as a matrix of the weight;
A fourth step of applying a second photosensitive member to the upper surface of the first photosensitive member including the first electrode layer;
A fifth step of overlaying a second mask for exposing a region for forming the second weight portion on the second photosensitive member and performing a second exposure process;
A sixth step of melting an area for forming the weight in the first photosensitive member and the second photosensitive member, and developing an exposed area;
A seventh step of performing an electroforming process using the region remaining in the sixth step as a matrix;
Forming a posture detecting means for detecting the posture change of the weight formed by the seventh step, and a mechanical quantity detecting means for detecting a change in the mechanical amount from the posture change of the weight detected by the posture detecting means. An eighth step to:
A method of manufacturing a mechanical quantity sensor, comprising: Comprising a ninth step of forming a second electrode layer on the surface of the beam;
8. The method of manufacturing a mechanical quantity sensor according to claim 7, wherein in the first step, a first photosensitive member is applied to a surface of the second electrode layer.

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