JP6594527B2 - Compound sensor - Google Patents

Description

  The present invention relates to a composite sensor that detects angular velocity and acceleration.

  Angular velocity sensors and acceleration sensors are used for attitude control, navigation, and the like of electronic devices such as game machines, portable information terminals, digital cameras, automobiles, airplanes, and ships. Sensors that detect physical quantities such as angular velocity and acceleration are based on electrostatic systems that detect changes in physical quantities based on the displacement of the capacitance between the fixed electrode and the movable electrode, and on the basis of changes in strain caused by piezoelectric elements. For example, a piezoelectric method for detecting a change in physical quantity is known.

  Patent Documents 1, 2, and 8 disclose angular velocity sensors using piezoelectric elements. Patent Document 1 and Non-Patent Document 1 disclose that six axes (acceleration three axes, angular velocity three axes) can be measured using a piezoelectric element. However, a piezoelectric sensor cannot detect a static acceleration such as a gravitational acceleration because of the principle of detecting a charge generated by a change in stress. Even if the acceleration is dynamic, it may not be detected if the movement (change) is very slow (for example, 1 Hz or less).

  On the other hand, static acceleration can be detected with a sensor using an electrostatic method (Patent Documents 3, 4, etc.). Also, combined with piezoelectric type angular velocity detection and piezoresistive type acceleration detection to detect angular velocity, dynamic acceleration and static acceleration (Patent Documents 5 and 6), and piezoelectric type angular velocity detection. A composite sensor (for example, Patent Document 7) combining acceleration detection by an electrostatic method has been proposed.

JP 2006-23320 A JP 2014-66708 A Japanese Patent Laid-Open No. 11-230760 JP 2010-181240 A JP 2008-190931 A JP2015-92145A JP 2014-157063 A JP2013-217872A

Kazuaki Okada et.al. "Development of 6-axis Motion Sensors Using Piezoelectric Elements", PROCEEDINGS OF THE 21ST SENSOR SYMPOSIUM, 2004.pp.385-390

  The composite sensors described in Patent Documents 5 and 6 are a combination of a piezoelectric sensor for measuring angular velocity and a piezoresistive acceleration sensor, which can be realized in a small size without increasing the size, and can also measure static acceleration. is there. However, in order to form the piezoresistor, processes such as ion implantation into the substrate and impurity diffusion are necessary, and the manufacturing process becomes complicated.

  In addition, the composite sensor described in Patent Document 7 is an integrated angular velocity sensor using a piezoelectric method and an acceleration sensor using an electrostatic method. It cannot be realized, and the size may increase.

  In view of the above circumstances, an object of the present invention is to provide a composite sensor capable of detecting static acceleration in addition to angular velocity, which can be easily manufactured and can be downsized.

The composite sensor of the present invention calculates the angular velocity by detecting the weight portion, the vibration excitation portion that induces vibration in the direction of the predetermined vibration axis with respect to the weight portion, and the displacement of the weight portion caused by the Coriolis force. An angular velocity sensor comprising: a vibration excitation portion and an angular velocity detection portion each comprising a piezoelectric element comprising a laminate of a lower electrode, a piezoelectric film and an upper electrode provided on the surface of a plate-like substrate. An angular velocity sensor comprising a weight part and a support part provided with a space between the weight parts as a part of the plate-like base material,
A movable electrode provided in a part of the weight part, a fixed electrode provided on the surface of the sub-plate-like base material which is a separate member from the plate-like base material and connected to the support part , and the movable electrode and the fixed electrode An acceleration sensor including an acceleration detection unit that detects the change in capacitance between the two and calculates the acceleration,
The electrode film constituting the movable electrode covers the surface of the support portion, and the portion of the electrode film that covers the support portion is connected to the sub-plate-like substrate directly or via a conductive spacer.

  Note that the number of weight portions is not limited to one, and two or more weight portions may be provided.

  The composite sensor of the present invention preferably includes a housing that includes an angular velocity sensor and an acceleration sensor, and the atmospheric pressure in the housing is preferably less than atmospheric pressure.

  In the composite sensor of the present invention, the fixed electrode is preferably composed of two or more fixed electrode pieces with respect to one weight portion.

  In the composite sensor of the present invention, the distance between the movable electrode and the fixed electrode is preferably less than the distance at which the stress applied to the piezoelectric film due to the displacement of the weight portion in the direction in which the two are close to each other becomes the breaking stress.

Composite sensor of the present invention, the plate Jomotozai is, and the movable electrode and the fixed electrode, it is preferably joined with the auxiliary plate-shaped substrates at a position which is opposed at a predetermined interval during non-driving.

In addition, it is preferable that the said plate-shaped base material and a sub-plate-shaped base material are joined through the spacer.
When the spacer is provided, it is preferable that the spacer has conductivity and has an electrode wiring function.

  In the composite sensor of the present invention, it is preferable that the sub-plate-like substrate has an angular velocity detection control circuit using an angular velocity sensor.

  In the composite sensor of the present invention, it is preferable that the piezoelectric element that constitutes a part of the angular velocity sensor functions as a part of the dynamic acceleration sensor that detects the dynamic acceleration.

  The composite sensor of the present invention includes a piezoelectric angular velocity sensor, a movable electrode provided in a part of a weight portion which is one of the components of the angular velocity sensor, and a fixed position facing the movable electrode. A fixed electrode, and an acceleration sensor having an acceleration detection unit that calculates an acceleration by detecting a change in capacitance between the movable electrode and the fixed electrode. The acceleration detection unit generates static acceleration. It is possible to detect. The composite sensor having such a configuration includes a movable electrode for detecting capacitance at a part of the weight portion of the angular velocity sensor, and thus can be miniaturized and easily manufactured.

Cut end view of the composite sensor according to the first embodiment of the present invention The figure which shows the upper electrode pattern of the angular velocity sensor of the composite sensor which concerns on embodiment The figure which shows an example of a fixed electrode The figure which shows the manufacturing process of the composite sensor which concerns on 1st Embodiment (the 1) The figure which shows the manufacturing process of the composite sensor which concerns on 1st Embodiment (the 2) Cut end view of compound sensor of design change example 1 Cut end view of compound sensor of design change example 2 Cut end view of the composite sensor according to the second embodiment of the present invention The figure which shows the upper electrode pattern of the angular velocity sensor of the composite sensor which concerns on 2nd Embodiment.

  A sensor according to an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings shown below, the scales of the constituent elements are appropriately different from the actual ones for easy visual recognition.

FIG. 1 is a schematic cut end view of a composite sensor 1 according to an embodiment of the present invention.
The composite sensor 1 of the present embodiment includes a plate-like base material 10 in which a weight portion 15 and piezoelectric elements 25 and 26 are formed, and a fixed electrode 45 facing a movable electrode 35 provided in a part of the weight portion 15. The sub-plate-like base material 40 provided, and the casing 50 in which the plate-like base material 10 and the sub-plate-like base material 40 are contained are provided.

  The plate-like base material 10 includes a weight portion 15 formed by deeply digging the periphery on one surface side. A region (deep digging region) in which a part of the plate-like base material 10 is deeply dug to reduce the thickness (deep digging region) uses a part having the original thickness of the plate-like base material 10 around the deep digging region as a support portion. It constitutes a diaphragm. That is, the plate-like base material 10 is provided with a diaphragm, and the weight portion 15 is provided in the approximate center of the diaphragm. On the other surface side of the plate-like substrate 10, a plurality of piezoelectric elements 25 and 26 are provided in which a lower electrode 21, a piezoelectric film 22, and upper electrodes 24 </ b> A and 24 </ b> B are sequentially stacked. The lower electrode 21 and the piezoelectric film 22 are formed in a continuous film shape over almost the entire area on the other surface side, and the upper electrodes 24A and 24B provided on the piezoelectric film 22 are patterned to form individual piezoelectric elements. Elements 25 and 26 are defined. Here, “lower” and “upper” do not mean top and bottom. Regarding a pair of electrodes provided with a piezoelectric film interposed therebetween, one electrode disposed on the plate-like substrate 10 side is simply referred to as a lower electrode, and the other electrode is referred to as an upper electrode.

  FIG. 2 is a schematic plan view showing a pattern example of the upper electrodes 24A and 24B. In this example, four upper electrodes 24A that define the piezoelectric element 25 for vibration excitation and four upper electrodes 24B that define the piezoelectric element 26 for angular velocity detection are provided. The upper electrode 24A is formed across the boundary between the outer peripheral edge of the diaphragm and the support portion, and the upper electrode 24B is formed across the boundary between the outer peripheral edge of the weight portion 15 and the deep digging region. That is, the piezoelectric element 25 constitutes a part of the vibration excitation unit, and the piezoelectric element 26 constitutes a part of the angular velocity detection unit that detects the displacement of the weight 15 caused by the Coriolis force and calculates the angular velocity.

  By driving the four piezoelectric elements 25 and applying desired vibration to the diaphragm, the weight portion 15 is induced to vibrate in the direction of a predetermined vibration axis. The piezoelectric film 22 is distorted in accordance with the displacement of the weight portion caused by the Coriolis force received by the vibrating weight portion 15, and the electric speed generated by the strain is detected by the piezoelectric element 26 to obtain the angular velocity.

  That is, the piezoelectric element 25 formed of a laminate of the lower electrode 21, the piezoelectric film 22, and the upper electrode 24A provided on the diaphragm including the weight portion 15 and the weight portion 15 formed on the plate-like substrate 10 functions as a piezoelectric actuator. The piezoelectric element 26 composed of a laminate of the lower electrode 21, the piezoelectric film 22 and the upper electrode 24B functions as a piezoelectric sensor, and the piezoelectric element 25 and the piezoelectric element 26 constitute a part of the angular velocity sensor. A driving control for driving the piezoelectric element 25 and a calculation unit for obtaining acceleration based on the current value detected by the piezoelectric element 26 are provided in an angular velocity detection control circuit described later.

  The angular velocity sensor of this configuration defines an XYZ three-dimensional orthogonal coordinate system having an origin O at the center position of the diaphragm, an XY plane including the surface of the diaphragm, and Z as a direction perpendicular thereto. One of the X axis and the Z axis is set as a vibration axis, and the other is set as a displacement axis, and an angular velocity around the Y axis is detected based on a detection value from an angular velocity detection electrode constituting the displacement detector. In order to detect the angular velocities around the X-axis and the Y-axis, the weight portion may be vibrated in the Z-axis direction and the displacement in the Y-axis direction and the X-axis direction may be detected. Further, in order to detect the angular velocity around the Z axis, the weight portion may be vibrated in the X axis direction or the Y axis direction, and the displacement in the Y axis direction or the X axis direction may be detected.

  The configuration of the diaphragm and the electrode of the angular velocity sensor is an example, and for example, the one described in Patent Document 2 (Japanese Patent Laid-Open No. 2014-66708) is applied in order to improve the accuracy as the angular velocity sensor. Also good. Furthermore, a structure such as that disclosed in Patent Document 8 (Japanese Patent Laid-Open No. 2013-217872) may be used.

  An electrode film 32 is uniformly formed on the surface side of the plate-like substrate 10 on which the weight portion 15 is provided via the adhesion layer 31. A portion of the electrode film 32 provided on the lower end surface in the drawing of the weight portion 15 functions as the movable electrode 35. Here, the electrode film 32 is provided on the entire surface of the plate-like substrate 10 on the weight portion 15 side, but it is sufficient that it is provided at least on the lower end surface of the weight portion 15. In this configuration, the movable electrode 35 is set to the ground potential.

  A fixed electrode 45 is provided on one surface of the sub-plate-like base material 40 prepared as a separate member from the plate-like base material 10, and the plate-like base material 10 includes the movable electrode 35 and the fixed electrode 45 of the weight portion 15. Are bonded (adhered) to the sub-plate-like base material 40 in a state of being opposed to each other. Further, the plate-like substrate 10 and the sub-plate-like substrate 40 are set so that the distance d between the movable electrode 35 and the fixed electrode 45 is a predetermined distance when the sensor 1 is not driven (when not driven). A spacer 48 is provided as an interval maintaining mechanism defined in FIG. The spacer 48 preferably has an adhesion function and a spacing maintaining function. For example, a mixture of Au-Sn metal material for eutectic bonding with glass beads whose shape does not change to maintain the spacing d is used. Can do.

  When the distance d between the movable electrode 35 and the fixed electrode 45 changes, the capacitance between the electrodes changes. A change in the relative position of the movable electrode 35 with respect to the fixed electrode 45 is detected by detecting a change in capacitance, thereby obtaining an acceleration. That is, the movable electrode 35 provided on the weight portion 15 and the fixed electrode 45 provided on the sub-plate base material 40 constitute a part of the acceleration sensor. A calculation unit for obtaining acceleration from a change in capacitance between the movable electrode 35 and the fixed electrode 45 is provided in an acceleration detection control circuit described later. According to the acceleration sensor of this configuration, static acceleration can be detected.

FIG. 3 is a schematic diagram showing an example of the configuration of the fixed electrode 45.
As shown in FIG. 3, in this embodiment, the fixed electrode 45 provided for one weight part 15 which is movable electrode 35 is obtained with the four fixed electrode pieces _{45x 1,} 45x 2, 45y ₁ , 45y ₂ . Although the fixed electrode 45 should just be comprised from two or more fixed electrode pieces, it is more preferable that it is four or more. Here, each of the electrostatic capacitance between the detecting a change in capacitance, the _45x movable electrode 35 and the individual fixed electrode pieces _{1, 45x 2, 45y 1,} 45y 2 between the fixed electrode 45 and movable electrode 35 It means detecting a change in Cx ₁ , Cx ₂ , Cy ₁ , Cy ₂ , or a change in their capacitance ratio.

Four fixed electrode pieces _{45x 1, 45x 2, 45y 1} , 45y 2 are their centers are arranged to coincide with the center of the movable electrode 35, the direction of the gravitational acceleration coincides with the z-axis direction It is preferable that the capacitance ratio Cx ₁ : Cx ₂ : Cy ₁ : Cy ₂ is 1: 1: 1: 1. In the sensor 1 of this configuration shown in FIG. 1, the change in the ratio of the capacitance between the fixed electrode pieces 45 x ₁ , 45 x ₂ , 45 y ₁ , 45 y ₂ and the movable electrode 35 depends on the direction of gravitational acceleration applied to the weight portion 15. By detecting, static gravity acceleration can be observed in the Z-axis direction.

The sensor 1, the inclination of the X direction or Y direction, the output _{Y 1} and Y from the output _{X 1} and _{X 2} or the fixed electrode pieces _45y 1, 45y _2, from the fixed electrode pieces _45x 1, 45x ₂ in FIG. 3 ₂ can be detected. Each absolute value can be measured in advance by reference measurement. For example, as a reference measurement, absolute acceleration is obtained by applying a known acceleration to the sensor in advance, measuring the capacitance at that time, graphing the relationship between acceleration and capacitance, and correcting based on the data. The value can be determined.

  As described above, a change in capacitance between the movable electrode 35 and the fixed electrode 45 is detected. As the distance d between the movable electrode 35 and the fixed electrode 45 provided on the sub-plate-like substrate 40 increases, Since the capacitance becomes smaller and the change in capacitance becomes minute, the distance d between the movable electrode 35 and the fixed electrode 45 should be as narrow as possible. On the other hand, the distance d needs to be made larger than the amplitude necessary for angular velocity sensing because it is necessary to vibrate the weight portion 15 in the Z direction for sensing angular velocity. If air exists around the weight 15, the movement may be suppressed due to the air damping effect. Therefore, it is preferable to reduce the air pressure by removing the air around the weight 15. Therefore, the atmospheric pressure inside the housing 50 is preferably at least less than atmospheric pressure (1 atm), and the smaller the degree of vacuum, the better.

  Although sensing is possible even when the circumference of the weight portion 15 is atmospheric pressure, the movement of the weight portion 15 is obstructed by air, so that the position change becomes small and the change in capacitance becomes small. Higher sensitivity is required. The measurement sensitivity can be increased to some extent by a device on the circuit side. As a circuit device, a bridge circuit, a comparison and ratio of capacitance between electrodes, and the like can be considered.

  In addition, when a large impact is applied to the composite sensor 1 (during a drop test or the like), if the weight portion 15 is greatly displaced, a stress greater than the destructive stress is applied to the piezoelectric film 22 and the piezoelectric film 22 is destroyed. It is preferable that the piezoelectric film 22 is configured not to be applied with a stress greater than the fracture stress. That is, the distance d between the movable electrode 35 and the fixed electrode 45 is such that the stress applied to the piezoelectric film 22 by the displacement of the weight portion 15 in the direction in which they are close to each other (that is, the Z-axis direction in this example) is the fracture stress. Preferably, the fixed electrode 45 side is made to function as a stopper that limits the amount of movement of the weight portion 15.

  In a stationary state where the composite sensor 1 is not driven, the distance d between the movable electrode 35 and the fixed electrode 45 is preferably about 15 μm or less and about 0.5 μm or more, for example, 1 μm. However, the preferable distance d needs to be appropriately determined according to the size of the weight portion 15, the size of the diaphragm, the thickness of the piezoelectric film, and the like. For example, in the case of a 2 μm-thick piezoelectric film made of PZT (lead zirconate titanate), it is destroyed when a stress of about 200 MPa or more is applied. Therefore, the interval d is set so that a stress of 200 MPa or more is not applied to the piezoelectric film.

  The fracture stress varies depending on the material and thickness of the piezoelectric film, and can be measured, for example, by forming a top electrode on a piezoelectric film formed on an Si substrate via an electrode with a cantilever structure. That is, an alternating voltage is applied between the upper and lower electrodes of the piezoelectric film having a cantilever structure to drive resonance, and the cantilever is displaced greatly by applying a drive voltage. Increasing the driving voltage increases the displacement and structurally breaks the piezoelectric film. The displacement stress at that time can be calculated by FEM (Finite Element Method) or the like.

  The acceleration sensor configured as described above can detect not only static acceleration but also dynamic acceleration. Since the amount of displacement differs greatly between detection of dynamic acceleration and detection of static acceleration, two dynamic ranges are prepared on the detection circuit side, and the dynamic range is switched and detected at a predetermined threshold. It is preferable.

  Alternatively, the acceleration sensor has only one dynamic range on the detection side, the acceleration sensor is used to detect static acceleration or very slow dynamic acceleration, and the angular velocity sensor also serves as the dynamic acceleration sensor. (See the above-mentioned Patent Document 1: Japanese Patent Laid-Open No. 2006-23320).

  The sub-plate-like base material 40 is preferably provided with an ASIC (Application specific integrated circuit). The ASIC includes an angular velocity detection control circuit for the angular velocity sensor and an acceleration detection control circuit for the acceleration sensor.

  The spacer 48 in contact with the electrode film 32 having the same electric potential as that of the movable electrode 35 is used to electrically connect the movable electrode 35 to the circuit of the sub-plate-like substrate 40 or to the outside. Therefore, it is preferable to have conductivity and have an electrode wiring function.

  As the plate-like substrate 10 and the sub-plate-like substrate 40, it is preferable to use a Si wafer, an SOI (silicon on insulator) wafer, or the like because it is easy to process.

  The material of the lower electrode 21 is not particularly limited, and may be a metal or an oxide conductor material. Specifically, Pt (platinum), Al (aluminum), Mo (molybdenum), TiN (titanium nitride), Ru (ruthenium), Au (gold), silver (Ag), Ir (iridium), ITO (indium tin) A material such as an oxide) can be used. Further, Ti, TiW, or the like may be provided between the Si active layer 13 and the lower electrode 21 as an adhesion layer for improving the adhesion with the Si active layer 13.

  The thickness of the lower electrode 21 can be designed to an appropriate thickness, but is preferably 50 to 500 nm. If the lower electrode 21 is too thick, the rigidity is increased and the displacement of the piezoelectric film 22 may be restricted. Therefore, the thickness is more preferably 50 to 300 nm.

There is no restriction | limiting in the material and thickness of the piezoelectric film 22, A thing suitable as an angular velocity sensor can be used. Preferably, a material that does not require polarization after film formation is preferable.
As the piezoelectric film 22, for example, one or more perovskite oxides represented by the following general formula (P) can be used, and the substrate temperature is raised by a vapor deposition method typified by sputtering. It can be formed by a method of crystallizing during film formation (preferably at 400 ° C. or higher).

General formula ABO ₃ (P)
(In the formula, A is an A site element and at least one element including Pb, B is an element of a B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, At least one element selected from the group consisting of Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, and a lanthanide element, O: oxygen atom, and a molar ratio of A: B: O is 1: 1: 3 is the standard, but this molar ratio may deviate within a range where a perovskite structure can be taken.)

_{Particularly, Pb (Zr y, Ti z} , Nb 1-y-z) O 3, 0 <y <1,0 <z < represented by 1, so-called PZT (lead zirconate titanate), or Nb-PZT ( A perovskite oxide called Nb doped lead zirconate titanate is preferable, and Nb-PZT having an Nb / (Zr + Ti + Nb) molar ratio of 0.06 to 0.20 is particularly preferable. The Nb-PZT film exhibits spontaneous polarization immediately after the film formation (as-depo state, as-deposited), and does not require polarization treatment.

  The thickness of the piezoelectric film 22 is preferably 0.3 μm or more and 10 μm or less, more preferably 0.5 μm or more and 8 μm or less, and further preferably 1 μm or more and 7 μm or less. If the thickness is 0.3 μm or more, a sufficient driving force as an actuator can be generated, and a sufficient voltage signal as a sensor or a power generation device can be extracted.

With reference to FIG. 4 and FIG. 5, the manufacturing process of the composite sensor of the said embodiment is demonstrated.
First, the plate-like base material 10 is prepared. As the plate-like substrate 10, an SOI wafer (hereinafter referred to as an Si wafer 11) composed of a Si substrate 11, a BOX (Buried Oxide) layer 12 made of SiO ₂ , and a Si active layer 13 facing the Si substrate 11 with the BOX layer 12 interposed therebetween. “SOI wafer 10”) is preferable. A lower electrode 21 is formed on the surface of the Si active layer 13 of the SOI wafer 10, and a piezoelectric film 22 is formed on the lower electrode 21 (step S1 in FIG. 4).

  The specification of the SOI wafer 10 is preferably a specification suitable for an angular velocity sensor. For example, the thickness of the BOX layer 12 is preferably 0.3 to 1.0 μm, and the thickness of the Si active layer 13 is preferably 3 to 50 μm. However, these specifications can be appropriately selected depending on the structure of the sensor.

  The lower electrode and the piezoelectric film can be formed by a known thin film forming method. Thin film formation methods include physical vapor deposition (PVD), chemical vapor deposition (CVD), and liquid deposition (plating, coating, sol-gel, spin Coating method) and thermal oxidation method. Although an appropriate film formation method can be selected for each layer, a structure in which all layers are formed by vapor deposition is most preferable. The vapor phase growth method can control the thickness dimension with high accuracy. In addition, since the material is inexpensive, the film formation rate is high, and it is suitable for mass production, the cost of the device can be reduced. In particular, it is preferable to form a film by sputtering.

  The method for forming the piezoelectric film is not limited to the sputtering method, and various methods such as an ion plating method, an MOCVD method (metal organic chemical vapor deposition method), and a PLD method (pulse laser deposition method) can be applied. It is also conceivable to use a method other than vapor phase growth (for example, a sol-gel method).

  However, the manufacturing process can be simplified by forming the piezoelectric film directly on the substrate by sputtering and reducing the thickness of the piezoelectric film.

  Next, an upper electrode layer is formed on the piezoelectric film 22, and then the upper electrode layer is formed into individual upper electrodes 24A and 24B and wirings in order to form a piezoelectric element that functions as a piezoelectric actuator and a piezoelectric sensor at a desired position. Is patterned (step S2 in FIG. 4). Further, by etching a part of the piezoelectric film 22, the lower electrode 21 is exposed and can be connected to the control circuit.

  Thereafter, the Si base material 11 is etched from the surface of the SOI wafer 10 on the Si base material 11 side to the BOX layer 12 in a deep digging process to produce the weight portion 15 (Step S3 in FIG. 4).

  Further, a Ti adhesion layer is formed on the entire surface of the SOI wafer on the Si substrate 11 side by sputtering, and an Au electrode is formed thereon (step S4 in FIG. 4). The Au electrode portion on the lower surface of the weight portion 15 in the drawing is a portion that functions as the movable electrode 35 for detecting capacitance, and is set to the ground potential. Since the surface on the weight portion 15 side has large irregularities formed in the deep digging process, in order to form an electrode film uniformly on this surface, for example, sputtering rather than vapor deposition is used, and CVD using sputtering is used. The method is preferable because of its good coverage.

  A sub-plate-like base material 40, which is prepared separately and on which a fixed electrode 45 for acceleration sensor is patterned, is prepared (step S5 in FIG. 5). As the sub-plate base material 40, for example, a Si wafer is suitable. The sub-plate-like substrate 40 preferably has an ASIC function for driving and processing the sensor.

  Thereafter, the weight 15, the piezoelectric element, and the SOI wafer 10 in which the movable electrode is incorporated and the sub-plate-like base material 40 are opposed to the movable electrode 35 of the weight portion 15 facing the fixed electrode 45 on the sub-plate-like base material 40. Then, they are positioned and bonded together (step S6 in FIG. 5). For bonding, eutectic bonding, bonding with Au particles, bonding with an epoxy resin, or the like can be used. For example, Au—Sn metal can be formed on a 1 μm edge portion and bonded by heating and pressing. Since it is important to control the gap between the movable electrode 35 and the fixed electrode 45 at the time of bonding, glass beads that function as the spacers 48 may be mixed in the bonding material.

The portion of the electrode film 32 formed on the weight 15 side of the SOI wafer 10 that can be in contact with the sub-plate-like base material 40 so that the weight portion 15 and the sub-plate-like base material 40 can be insulated. It is previously covered with an insulating film (not shown) such as a SiO ₂ film.

  Finally, after connecting various wirings, the composite sensor 1 shown in FIG. 1 can be manufactured by sealing in a housing 50 under a reduced pressure atmosphere.

  The composite sensor 1 according to the first embodiment described above includes the movable electrode 35 on a part of the weight portion 15 which is one of the components of the angular velocity sensor, and the movable electrode 35 is provided to face the movable electrode 35. By providing an acceleration sensor that includes an acceleration detection unit that detects the change in capacitance with the fixed electrode 45 and calculates the acceleration, static acceleration can be detected with a small configuration. It has become. Moreover, since the composite sensor 1 has a simple configuration, it can be easily manufactured.

  In the composite sensor 1 of the first embodiment, the spacer 48 is provided as a gap maintaining mechanism for controlling the gap between the movable electrode 35 and the fixed electrode 45. However, the mechanism for maintaining the gap is provided here. Not exclusively. 6 and 7 show cut end views of the composite sensor 1A of the design change example 1 and the composite sensor 1B of the design change example 2, respectively.

  As shown in FIG. 6, the distance d can be adjusted by shortening the length of the weight portion 15A in comparison with the thickness of the support portion around the diaphragm. Alternatively, as shown in FIG. 7, it is also possible to provide a recess 43 in a portion where the fixed electrode 45 of the sub-plate-like substrate 40 is formed, and to adjust the distance d depending on the depth of this recess.

  In the case of FIG. 6 and FIG. 7, the adhesion layer 31 and the electrode film 32 to be connected to the sub-plate-like substrate 40 on the plate-like substrate 10 side are removed, and the plate-like substrate is obtained using the Si wafer direct bonding technique. The material 10 and the sub-plate-like substrate 40 can be directly joined. According to such a configuration, it is possible to improve the interval adjustment accuracy as compared with the case where an adhesive is used, and it is possible to increase the bonding strength.

Next, a composite sensor according to a second embodiment of the present invention will be described.
FIG. 8 is a cut end view of the composite sensor 2 according to the second embodiment. In this configuration, the plate-like base material 10 in the composite sensor 2 of the first embodiment is arranged opposite to the top and bottom. The same components as those of the composite sensor 2 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 8, in the composite sensor 2, the movable electrode 24 </ b> C (35) is provided on a part of the weight portion 15 on the diaphragm side. FIG. 9 shows an upper electrode pattern on one surface of the plate-like substrate 10. In addition to the upper electrodes 24A and 24B of the piezoelectric elements 25 and 26, a movable electrode 24C is provided at the center of the upper electrodes 24A and 24B. The movable electrode 24C can be patterned simultaneously with the upper electrodes 24A and 24B.

  According to this configuration, the manufacturing process can be simplified as compared with the case where the movable electrode 35 is provided on the lower end side of the weight portion 15. Further, in this configuration, either the movable electrode 24C or the fixed electrode 45 may be a ground potential.

  The detection method of angular velocity and acceleration in the composite sensor 2 of this embodiment is the same as that of the composite sensor 1 of the first embodiment. According to the composite sensor 2, the same effect of downsizing as the composite sensor 1 can be achieved, and the manufacture can be further facilitated.

  In each of the above embodiments, an angular velocity sensor capable of detecting a three-axis angular velocity with a single weight portion (movable portion) having a weight portion provided at the center of the diaphragm is provided. The movable part of the angular velocity sensor provided may be of other shapes such as a tuning fork type and a butterfly type used in known angular velocity sensors. In other words, the number of movable parts is not limited to one, and a plurality of movable parts may be provided. If a movable electrode is provided on a part of the movable part and a fixed electrode is arranged opposite to the movable electrode, It is possible to configure an acceleration sensor that can detect a simple acceleration.

1, 1A, 1B, 2 Composite sensor 10 Plate base material (SOI wafer)
DESCRIPTION OF SYMBOLS 11 Si base material 12 BOX layer 13 Si active layer 15, 15A Weight part 21 Lower electrode 22 Piezoelectric film 24A, 24B Upper electrode 24C, 35 Movable electrode 25, 26 Piezoelectric element 31 Adhesion layer 32 Electrode film 40 Sub-plate-like base material 43 recess 45 fixed electrode _{45x 1, 45x 2, 45y 1} , 45y 2 fixed electrode piece 48 spacer 50 housing

Claims (7)

A weight portion, a vibration excitation portion that induces vibration in the direction of a predetermined vibration axis with respect to the weight portion, and an angular velocity detection portion that detects a displacement of the weight portion caused by Coriolis force and calculates an angular velocity. An angular velocity sensor provided, wherein the vibration excitation unit and the angular velocity detection unit each include a piezoelectric element composed of a laminate of a lower electrode, a piezoelectric film, and an upper electrode provided on the surface of a plate-like substrate, An angular velocity sensor in which the weight part and a support part provided with a space between the weight part are configured as a part of the plate-like substrate;
A movable electrode provided in a part of the weight part, a fixed electrode provided on a surface of a sub-plate-like base material that is a separate member from the plate-like base material and connected to the support part , and the movable electrode And an acceleration sensor including an acceleration detection unit that calculates an acceleration by detecting a change in capacitance between the fixed electrode and the fixed electrode,
The electrode film constituting the movable electrode covers the surface of the support part, and the part of the electrode film covering the support part is connected to the sub-plate base material directly or via a conductive spacer. Compound sensor. The composite sensor according to claim 1, further comprising a housing that includes the angular velocity sensor and the acceleration sensor, wherein an atmospheric pressure in the housing is less than an atmospheric pressure. The composite sensor according to claim 1, wherein the fixed electrode is composed of two or more fixed electrode pieces with respect to one weight portion. 4. The distance between the movable electrode and the fixed electrode is less than a distance at which stress applied to the piezoelectric film due to displacement of the weight portion in a direction in which the movable electrode and the fixed electrode are close to each other becomes a fracture stress. The composite sensor according to item. Prior Symbol plate-shaped substrates, wherein the movable electrode and the fixed electrode, any of the sub-plate according to claim 1, substrate and are joined at the position at the time of non-driving are opposed at a predetermined interval 4 The composite sensor according to item 1. The sub-plate base has a circuit for angular velocity detection control by the angular velocity sensor.
The composite sensor according to claim 1 . Said piezoelectric element, a composite sensor according to claim 1 to 6 any one of claims to act as part of the dynamic acceleration sensor for detecting a dynamic acceleration constituting a part of the angular velocity sensor.

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