JP2010203932A - Physical quantity sensor and physical quantity measurement device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a physical quantity sensor which has high measurement sensitivity and in which an electrode is easily formed. <P>SOLUTION: The physical quantity sensor 100 includes: a base body 10; a beam 20 including both ends supported by the base body 10 and generating thickness-shear strain when an electric field is applied in a thickness direction; and upper and lower electrodes 32 and 34 holding the beam 20 in between in the thickness direction and formed on upper and lower surfaces of the beam 20 except the central area of the beam 20. The base body 10 is flexible so as to be bent in the thickness direction by external force applied to the base body 10. The beam 20 gets bending vibration generated by the thickness-shear vibration generated when a drive signal is applied to the upper and lower electrodes 32 and 34. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a physical quantity sensor and a physical quantity measuring device.

  Various physical quantity sensors that detect physical quantities such as acceleration, pressure, temperature, and the like with a crystal vibrating piece are known. For example, acceleration sensors are used in a wide range of fields such as automobiles, aircraft, rockets, and abnormal vibration monitoring devices for various plants.

  For example, Patent Document 1 discloses an acceleration sensor element having a vibration part in which two beams are suspended on a frame. The acceleration sensor element described in the publication has a double tuning fork structure, that is, a structure in which the free ends of two tuning fork type vibrating pieces are connected to each other. The two beams have a shape in which both ends are supported by a frame and have a vibration mass in a central region. The acceleration sensor element disclosed in this publication is formed by etching a Z-cut quartz substrate on a frame and a beam, and thus the beam has piezoelectricity. This beam can vibrate when a voltage is applied by an electrode formed on the surface. At the same time, the vibration of the beam can be detected by the voltage generated at the electrode.

  The acceleration sensor element of the publication discloses a tensile force or a compressive force at both ends of the beam when the frame is deformed by applying an external force or the like while the beam is excited. Since the acceleration sensor element changes the vibration frequency of the beam in proportion to the applied acceleration (force), the magnitude of the force can be measured by detecting the amount of change in the vibration frequency.

  Such a physical quantity sensor using the vibration of the beam is easy to process data and has excellent measurement accuracy, measurement sensitivity, reproducibility, temperature characteristics, and the like.

JP 2007-163244 A

  However, the physical quantity sensor is required to be further downsized and highly sensitive. Therefore, thinner and thinner beams have been formed in the vibration part of the physical quantity sensor. As a result, the electrodes formed on the beam have become very small. Therefore, in particular, it has become difficult to form electrodes on the side surfaces (surfaces parallel to the thickness direction) of the beam.

  An object of some embodiments of the present invention is to provide a physical quantity sensor having high measurement sensitivity and easy electrode formation.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
A substrate;
Beams that are supported at both ends by the substrate and cause thickness-slip distortion when an electric field is applied in the thickness direction;
Sandwiching the beam in the thickness direction, avoiding the central region of the beam, upper and lower electrodes formed on the upper and lower surfaces of the beam; and
Including
The base body has flexibility such that it is bent in the thickness direction by an external force applied to the base body,
The physical quantity sensor in which the beam generates bending vibration by thickness shear vibration generated when a driving signal is applied to the upper electrode and the lower electrode.

  Such a physical quantity sensor has high measurement sensitivity and has electrodes on the upper and lower surfaces of the beam, so that the electrodes can be easily formed.

[Application Example 2]
In application example 1,
The base body has a frame-like shape having an opening part surrounded by a frame part,
The beam is a physical quantity sensor in which both ends are supported by the frame portion of the base and are bridged inside the opening.

  Such a physical quantity sensor has the characteristics of Application Example 1, and further has high robustness and excellent mountability.

[Application Example 3]
In application example 2,
The physical body sensor is a physical quantity sensor having a constricted portion formed by cutting out in the thickness direction at a portion parallel to the beam of the frame portion.

  Such a physical quantity sensor has the characteristics of Application Example 2 and has higher measurement sensitivity.

[Application Example 4]
In application example 1,
The base body has a flat plate shape having at least two protrusions on the upper surface,
Both ends of the beam are supported by the two protrusions, and the beam is bridged between the two protrusions.

  Such a physical quantity sensor has the characteristics of Application Example 1, and further has high robustness and excellent mountability.

[Application Example 5]
In application example 4,
The said base | substrate has a constriction part of the shape extended in the direction which cross | intersects the said beam between the two said protrusions which support the both ends of the said beam.

  Such a physical quantity sensor has the characteristics of Application Example 4 and has higher measurement sensitivity.

[Application Example 6]
In any one of the application examples 1 to 5,
And a counter beam that protrudes from the base of the beam and extends in parallel to the beam toward the central region of the beam,
The physical quantity sensor, wherein the counter beam is displaced so as to cancel the mass displacement in the bending vibration of the beam.

  Such a physical quantity sensor has the above-described characteristics and a smaller vibration leakage.

[Application Example 7]
In any one of the application examples 1 to 6,
A physical quantity sensor, wherein the thickness shear vibration frequency of the beam is a signal for detecting a physical quantity.

  Such a physical quantity sensor has the above-described characteristics and has higher measurement sensitivity.

[Application Example 8]
The physical quantity sensor according to any one of Application Examples 1 to 8, and
A detection unit for detecting a change in frequency of the bending vibration or the thickness shear vibration of the beam;
A physical quantity measuring device.

  Such a physical quantity measuring device includes at least a physical quantity sensor having high measurement sensitivity and easy electrode formation, and can measure a physical quantity with high sensitivity.

FIG. 3 is a top view schematically showing the physical quantity sensor 100 according to the embodiment. The bottom view which shows typically the physical quantity sensor 100 concerning embodiment. Sectional drawing which shows typically the physical quantity sensor 100 concerning embodiment. Sectional drawing which shows typically the behavior of the beam 20 of the physical quantity sensor concerning embodiment. Sectional drawing which shows typically operation | movement of the physical quantity sensor concerning embodiment. Sectional drawing which shows typically operation | movement of the physical quantity sensor concerning embodiment. The schematic diagram of the impedance curve of a physical quantity sensor. The schematic diagram of the equivalent circuit of the physical quantity sensor concerning embodiment. The top view which shows typically the physical quantity sensor 200 concerning embodiment. Sectional drawing which shows typically the physical quantity sensor 200 concerning embodiment. FIG. 3 is a top view schematically showing a physical quantity sensor 300 according to the embodiment. Sectional drawing which shows typically the physical quantity sensor 300 concerning embodiment. FIG. 3 is a top view schematically showing a physical quantity sensor 400 according to the embodiment. Sectional drawing which shows typically the physical quantity sensor 400 concerning embodiment. Sectional drawing which shows typically the physical quantity measuring apparatus 1000 concerning embodiment.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, the following embodiment demonstrates the example of this invention.

1. 1. First embodiment 1.1. Physical Quantity Sensor FIGS. 1 and 2 are a top view and a bottom view schematically showing a physical quantity sensor 100 according to the present embodiment. FIG. 3 is a cross-sectional view schematically showing the physical quantity sensor 100 according to the present embodiment. A cross section taken along line AA in FIGS. 1 and 2 corresponds to FIG. In addition, the arrow which shows a direction is drawn on each right side of FIGS. 1-3 for convenience of explanation. FIG. 4 is a cross-sectional view schematically showing the behavior of the beam 20.

  The physical quantity sensor 100 of this embodiment includes a base body 10, a beam 20, an upper electrode 32, and a lower electrode 34.

  The substrate 10 functions as a support that supports the physical quantity sensor 100. The base 10 has such flexibility that it bends in the thickness direction (± Y direction) by an external force applied in the ± Y direction. In the present embodiment, the base body 10 has a frame shape (frame shape) having an opening 12 and a frame portion 14. The planar outer shape of the base body 10 (frame portion 14) is rectangular in the illustrated example, but is not limited thereto. As shown in FIG. 3, the frame portion 14 may have portions having different thicknesses. In the example of FIG. 3, the frame portion 14 includes an outer peripheral portion 14a having a thickness t1, a thin portion 14b having a thickness t2 smaller than the thickness t1, and an inclined portion 14c formed between the outer peripheral portion 14a and the thin portion 14b. have. The frame part 14 does not need to have the thin part 14b and the inclined part 14c. In this case, the inner periphery of the outer peripheral part 14a and the outer periphery of the opening part 12 coincide. In the illustrated example, the frame portion 14 has a thin portion 14 b, and the inner periphery of the thin portion 14 b coincides with the outer periphery of the opening portion 12. Further, a weight (not shown) may be formed on the frame portion 14. When a weight is formed on the frame portion 14, the amount of bending of the base body 10 can be adjusted, and for example, the measurement sensitivity of the physical quantity sensor 100 can be increased.

  The position where the opening 12 is formed in the base 10 is arbitrary as long as the deformation of the frame 14 can be transmitted to a beam 30 described later. If the position where the opening 12 is formed is appropriately selected, for example, the arrangement of the mass of the frame 14 can be adjusted, and the measurement sensitivity of the physical quantity sensor 100 can be increased. In the illustrated example, the opening 12 is formed at a position slightly deviated in the + Z direction from the center of the base 10. Further, the position of the opening 12 may be selected, and for example, an electrode pad forming region may be provided in the frame portion 14 or a region for supporting the physical quantity sensor 100 may be provided. The planar shape of the opening 12 is arbitrary. In the illustrated example, the opening 12 is rectangular.

  The material of the substrate 10 can be, for example, an inorganic material such as quartz, silicon, various metals, or an organic material such as polyimide. In the present embodiment, the base body 10 is formed integrally with the beam 20. Therefore, a material that causes a thickness slip when an electric field is applied in the thickness direction is used. Examples of the material that can have such properties include piezoelectric materials such as quartz, lithium tantalate, and lithium niobate.

  For example, when a quartz substrate is selected as the material of the base 10 and the beam 20, the thickness direction includes the X-axis or Y-axis component of the crystal axis of the quartz. Accordingly, as a substrate for forming the base 10, an AT-cut quartz substrate (hereinafter sometimes referred to as an AT plate), a BT-cut quartz substrate (hereinafter sometimes referred to as a BT plate), Examples thereof include a quartz substrate (hereinafter sometimes referred to as a Y plate) whose normal direction is the Y axis of the crystal axis of quartz. If an AT plate, a BT plate, or a Y plate is selected as the substrate 10, a thickness shear vibration can be generated more easily by applying a voltage signal in the thickness direction. In the present embodiment, a case where a crystal Y plate is selected as the material of the base 10 will be described below. Accordingly, in each drawing, an arrow is drawn so that the upward direction in the normal direction of the substrate 10 is the + Y direction.

  In the present embodiment, the beam 20 is supported at both ends by the base body 10 and is formed so as to be bridged in the opening 12 of the base body 10. In this specification, the extending direction of the beam 20 is defined as ± Z direction. The beam 20 has a component in the ± Y direction (thickness direction of the base body 10) orthogonal to the ± Z direction and can flexurally vibrate. In the present specification, directions perpendicular to the ± Y direction and the ± Z direction are referred to as ± X directions. In the present specification, the vicinity of the two support ends of the beam 20 may be referred to as a root region.

  The beam 20 functions as a vibration unit of the physical quantity sensor 100. The beam 20 can have a columnar shape. For example, the cross-sectional shape of the beam 20 taken along the XY plane can be a polygon, a quadrangle, or the like. In the present embodiment, the beam 20 is formed integrally with the base body 10. Therefore, the material of the base 10 is the same as the material of the base 10. Therefore, the beam 20 can cause a thickness slip distortion when an electric field is applied in the thickness direction. The planar position where the beam 20 is formed is arbitrary as long as it is within the opening 12. For example, when the frame portion 14 is bent under a force, a tensile or compressive stress in the longitudinal direction of the beam 20 is used. Can be arranged to occur. In the illustrated example, the planar arrangement of the beams 20 passes through the center of the opening 12, and the frame portion 14 is axisymmetric with respect to the direction in which the beams 20 extend (± Z direction). In this way, the ± X direction component of the stress applied to the beam 20 can be reduced.

  In the present embodiment, the thickness of the beam 20 is smaller than the thickness of the outer peripheral portion 14 a of the frame portion 14 of the base body 10. When the thickness of the beam 20 is the same as the thickness of the outer peripheral portion 14a, there is a case where tensile or compressive stress is hardly generated in the longitudinal direction of the beam 20 when the frame portion 14 is bent. In the example of FIG. 3, the beam 20 has the same thickness as the thickness t <b> 2 of the thin portion 14 b of the frame portion 14 of the base body 10. In the thickness direction (± Y direction) of the base body 10, the position where the beam 20 is connected is biased toward the upper surface or the lower surface side of the base body 10 when viewed from the center in the thickness direction of the base body 10. When the beam 20 is provided symmetrically in the thickness direction with respect to the center in the thickness direction of the base body 10, when the frame portion 14 is bent, tensile or compressive stress may not easily occur in the longitudinal direction of the beam 20. In the example of FIG. 3, the beam 20 is provided so as to be biased toward the upper surface side in the thickness direction of the substrate 10, and the upper surface of the frame portion 14 (substrate 10) and the upper surface of the beam 20 coincide. In this way, when manufacturing the physical quantity sensor 100, the substrate 10 can be etched only from the lower surface side.

  The beam 20 may have a groove and a through hole. The groove and the through hole can be provided, for example, to adjust the distribution of mass in the beam 20 and to adjust the direction of the electric field applied to the beam 20. Further, the beam 20 may be provided with a member having an additional mass in the central region, for example. The frequency of vibration of the beam 20 can be adjusted by providing such a member and adjusting the mass of the member.

  The upper electrode 32 and the lower electrode 34 are formed on the upper surface and the lower surface of the beam 20, avoiding the central region of the beam 20. The upper electrode 32 and the lower electrode 34 are formed as a pair with the beam 20 sandwiched in the thickness direction (± Y direction). The upper electrode 32 and the lower electrode 34 extend from the root region of the beam 20 toward the central region. The upper electrode 32 and the lower electrode 34 are formed so that the one that extends from one end of the beam 20 does not come into contact with the one that extends from the other end.

  Examples of the functions of the upper electrode 32 and the lower electrode 34 include a function of exciting the beam 20 and a function of detecting the vibration of the beam 20. The upper electrode 32 and the lower electrode 34 can be electrically connected to an external circuit (not shown). Examples of the material of the upper electrode 32 and the lower electrode 34 include conductive metals such as Cr and Au. A laminated structure of these Cr layer and Au layer can also be used.

  The upper electrode 32 is formed on the upper surface of the beam 20. The lower electrode 34 is formed on the lower surface of the beam 20. The upper electrode 32 and the lower electrode 34 are electrically connected to the wiring 40, respectively. In the present specification, the electrodes (32, 34) and the wirings 40 having the same potential are denoted by the same auxiliary symbols (a, b).

  In the example shown in FIGS. 1 to 3, a pair of two pairs of the upper electrode 32 and the lower electrode 34 is provided so as to face each other through the beam 20. As shown in FIG. 3, the pair of the upper electrode 32 and the lower electrode 34 facing each other can have different potentials. Thereby, a voltage signal (electric field) in the thickness direction (± Y direction) can be applied to the beam 20. In the illustrated example, the upper electrode 32a and the lower electrode 34b, and the upper electrode 32b and the lower electrode 34a are arranged to face each other in two root regions of the beam 20.

  Next, an example of the wiring 40 connected to each electrode will be described with reference to FIGS. The upper electrode 32 a is connected to the wiring 40 a in one root region of the beam 20. The wiring 40 a is routed on the upper surface of the base body 10 (frame portion 14) and extends to the lower surface side of the base body 10. The wiring 40 a extended to the lower surface side of the base body 10 is routed on the lower surface of the base body 10 and connected to the lower electrode 34 a in the other root region of the beam 20. Similarly, the upper electrode 32 b is connected to the wiring 40 b in the other root region of the beam 20. The wiring 40 b is routed on the upper surface of the base body 10 and extends to the lower surface side of the base body 10. The wiring 40b extended to the lower surface side of the base body 10 is routed on the lower surface of the base body 10 and connected to the lower electrode 34b in one root region of the beam 20. The wiring 40a and the wiring 40b are electrically separated from each other and can have different potentials. The above is an example, and the routing route of the wiring 40a and the wiring 40b is arbitrary. Further, an external connection pad 42 connected to the wiring 40a and the wiring 40b at an arbitrary position may be formed. In the illustrated example, a pad 42 a and a pad 42 b are formed on the upper surface side of the substrate 10.

  When the electrode and wiring configurations as exemplified above are employed, the electric field applied to the beam 20 can be easily reversed in one root region and the other root region of the beam 20. For example, if an AC electric field is applied to each electrode via a pad and a wiring, a thickness-shear vibration whose phase is reversed in the vicinity of both ends of the beam 20 can be generated.

  Next, the relationship between the bending and the thickness slip of the beam 20 will be described with reference to FIG. FIG. 4 shows a state in which thickness slips having opposite phases occur near both ends of the beam 20. A solid line in the drawing depicts a state in which the beam 20 is bent by the thickness slip. The state where the thickness slip has occurred, as schematically shown by the broken line in the figure, the displacement amount of the substance constituting the beam 20 in the ± Z direction is distributed with respect to the position in the ± Y direction (thickness direction). Points to the state. By such a thickness slip, displacements having different sizes or directions can be generated on the upper surface side and the lower surface side of the beam 20, and the beam 20 can be bent in the ± Y direction.

  The direction of the thickness slip and the direction of bending of the beam 20 can be easily reversed by reversing the electric field applied to each electrode. Therefore, if an AC electric field is applied to each electrode, the beam 20 Further, bending vibration based on thickness shear vibration can be generated.

1.2. Operation of Physical Quantity Sensor FIGS. 5 and 6 are cross-sectional views schematically showing the behavior of the physical quantity sensor 100 according to the present embodiment. 5 and 6 show a state in which a part of the frame portion 14 of the base body 10 of the physical quantity sensor 100 is fixed to the base 50 with the adhesive 52. In the figure, the physical quantity sensor 100 is in a state where the left-side (−Z direction side) frame portion 14 is fixed and held in a cantilever shape toward the right side (+ Z direction). Further, in FIG. 5 and FIG. 6, each electrode is not shown.

  FIG. 5 shows a state when acceleration in the + Y direction or force in the −Y direction is applied to the physical quantity sensor 100. FIG. 6 shows a state when acceleration in the −Y direction or force in the + Y direction is applied to the physical quantity sensor 100.

  As indicated by the chain line in FIG. 5, the physical quantity sensor 100 to which acceleration in the + Y direction or force in the −Y direction is applied is flexed in the −Y direction on the free end side of the cantilever beam with the fixed end of the cantilever beam as a reference. Mu Then, as described above, since the beam 20 is formed at a position biased toward the upper surface side of the physical quantity sensor 100, the beam 20 is expanded in the arrow direction. When the beam 20 is stretched, the resonance frequency of the bending vibration increases. By comparing the change in the resonance frequency of the beam 20 at this time with, for example, a reference frequency, the magnitude of the acceleration in the + Y direction or the force in the −Y direction can be known.

  On the other hand, as shown by the chain line in FIG. 6, in the physical quantity sensor 100 to which acceleration in the -Y direction or force in the + Y direction is applied, the free end side of the cantilever is in the + Y direction with the fixed end of the cantilever as a reference. Bend. Then, the beam 20 is contracted in the arrow direction. When the beam 20 is contracted, the resonance frequency of bending vibration is lowered. By comparing the change in the resonance frequency of the beam 20 at this time with, for example, a reference frequency, the magnitude of the acceleration in the −Y direction or the force in the + Y direction can be known.

  In either case of FIG. 5 and FIG. 6, it is easier to calculate the correlation between the difference between the resonance frequency and the reference frequency and the magnitude of acceleration or force in advance and tabulate the obtained data. The magnitude of acceleration or force can be measured. 5 and 6, the physical quantity sensor 100 is fixed on the lower surface side with respect to the base 50, but the same applies to the case where the upper surface side is fixed.

  As described above, when a physical quantity such as acceleration or force is applied to the physical quantity sensor 100, the physical quantity sensor 100 bends in the ± Y direction, and the resonance frequency of the beam 20 changes. Therefore, the physical quantity applied to the physical quantity sensor 100 can be immediately grasped from the change in the resonance frequency.

  Next, a method for detecting a change in the resonance frequency of the physical quantity sensor 100 will be described. FIG. 7 is a graph schematically showing an impedance curve of the physical quantity sensor 100. In the graph, the vertical axis represents C.I. I. Value (Crystal Impedance) with frequency on the horizontal axis. FIG. 8 is a diagram illustrating an example of a simplified equivalent circuit of the physical quantity sensor 100 and a configuration for detecting a change in the resonance frequency.

  The beam 20 of the physical quantity sensor 100 has a plurality of resonance frequencies for each vibration mode. For example, as shown in FIG. 7, the resonant frequency (f1, f2) of the bending mode is present in the frequency range of kHz, and the resonant frequency (f3, f4) of the thickness shear mode is present in the frequency region of MHz. Have In addition, the resonance frequency of both modes is not limited to one, and as shown in FIG. I. A small (highly efficient) resonance frequency (f1, f4); I. There are resonance frequencies (f2, f3) with large values (low efficiency). In the illustrated example, the resonance frequencies f1 to f4 are illustrated, but the number and order of the resonance frequencies are generally generated randomly depending on the fine shape of the beam 20 and the like. Each resonance frequency has a constant value as long as there is no change in the environment such as temperature, and has a character as a characteristic value possessed by each beam 20 (physical quantity sensor 100).

When the physical quantity sensor 100 has an impedance curve as shown in FIG. 7, an equivalent circuit as shown in FIG. 8 can be considered. In FIG. 8, C ₀ indicates a capacitance between the upper electrode 32 and the lower electrode 34. In FIG. 8, equivalent circuits corresponding to the resonance frequencies (f1, f2, f3, f4) shown in FIG. 7 are drawn in parallel, and the magnitudes of the resistors r1 to r4 of each equivalent circuit are shown at each resonance frequency. C. I. Can be considered a value. Therefore, it is assumed here that the resistors r1 and r4 have a smaller value than the resistors r2 and r3.

  As an example, detection of acceleration, force, and the like by the physical quantity sensor 100 can be performed using a low-frequency OSC circuit and a frequency counter as shown in FIG. The low frequency OSC circuit drives the physical quantity sensor 100 at an efficient resonance frequency f1. In the state driven at the resonance frequency f1, the beam 20 is bending-vibrated. When the physical quantity sensor 100 receives acceleration or force, the resonance frequency f1 of the bending vibration changes. By detecting this change with a frequency counter, the acceleration or force received by the physical quantity sensor 100 can be known.

  On the other hand, detection of the temperature or the like by the physical quantity sensor 100 can be performed by using a high frequency OSC circuit and a frequency counter as shown in FIG. The high frequency OSC circuit drives the physical quantity sensor 100 at an efficient resonance frequency f4. In the state driven at the resonance frequency f4, the beam 20 vibrates in thickness. When the temperature of the physical quantity sensor 100 changes, the resonance frequency f4 of the thickness shear vibration changes. By detecting this change with a frequency counter, the temperature (physical quantity) of the physical quantity sensor 100 can be known.

  In the example of FIG. 8, the low-frequency OSC circuit and the high-frequency OSC circuit connected to the physical quantity sensor 100 are switched by switches, but any circuit configuration is possible as long as it has the above-described functions.

  When the circuit configuration as shown in FIG. 8 is adopted, a physical quantity to be measured, that is, a mechanical quantity (acceleration or force) and temperature can be easily switched. Therefore, for example, a single physical quantity sensor 100 can detect a plurality of types of physical quantities.

  The temperature measured by the physical quantity sensor 100 is the temperature of the physical quantity sensor 100 itself, and the physical quantity sensor 100 itself can be calibrated using the measured temperature. In other words, the temperature of the physical quantity sensor 100 itself can be measured, and values such as acceleration and force measured by the physical quantity sensor 100 can be corrected using the temperature. Thereby, the measurement accuracy of the physical quantity sensor 100 can be further increased.

  The physical quantity sensor 100 of the present embodiment described above has a high measurement sensitivity because it has one beam 20 supported at both ends. In addition, the physical quantity sensor 100 according to the present embodiment has the upper electrode 32 and the lower electrode 34 on the upper surface and the lower surface of the beam 20, respectively, and it is not necessary to form electrodes on the side surfaces of the beam 20. .

1.3. Modification FIG. 9 is a top view of a physical quantity sensor 200 according to a modification of the present embodiment. FIG. 10 is a cross-sectional view schematically showing a physical quantity sensor 200 according to a modification of the present embodiment. A cross section taken along line BB in FIG. 9 corresponds to FIG. FIG. 11 is a top view of a physical quantity sensor 300 according to another modification of the present embodiment. FIG. 12 is a cross-sectional view schematically showing a physical quantity sensor 300 according to another modification of the present embodiment. A cross section taken along line CC in FIG. 11 corresponds to FIG.

  A physical quantity sensor 200 according to the modification includes a base body 10, a beam 20, an upper electrode 32, and a lower electrode 34. Since the physical quantity sensor 200 is the same as the physical quantity sensor 100 described above except that the shape of the base 10 is different, members other than the base 10 are denoted by the same reference numerals as those of the physical quantity sensor 100, and detailed description thereof is omitted.

  The material of the base 10 of the physical quantity sensor 200, the planar outer shape, the opening 12 and the like are the same as those of the physical quantity sensor 100. As shown in FIGS. 9 and 10, in the physical quantity sensor 200, a constricted portion 16 that is cut out in the thickness direction is formed in a portion of the frame portion 14 of the base body 10 that extends in parallel with the beam 20. Has been. In the constricted portion 16, the thickness of the base 10 is smaller than that of other portions. Therefore, by having the constricted portion 16, the base 10 can be more easily bent in the ± Y direction. Thereby, the measurement sensitivity with respect to the acceleration or force of the physical quantity sensor 200 can be increased.

  The position at which the constricted portion 16 is provided is preferably provided at a symmetrical position with respect to the beam 20 so that the bending of the base 10 does not include a component in the ± X direction. Further, the constricted portion 16 is preferably provided closer to the fixed end side of the physical quantity sensor 200 in order to increase the bending of the base body 10.

  In the illustrated example, the shape of the constricted portion 16 is notched in the thickness direction from the upper surface and the lower surface of the base body 10, but is not limited thereto. For example, the constricted portion 16 may be provided by being cut out from one side of the upper surface or the lower surface of the base body 10. When the beam 20 is provided so as to be biased toward the upper surface side in the thickness direction of the base body 10, the constricted portion 16 is more preferably cut out from the upper surface side of the base body 10. In this way, the action of compression or expansion of the beam 20 due to the bending of the base body 10 can be further enhanced. The wiring 40 can be provided so as to cross the constricted portion 16.

  11 and 12 are diagrams schematically illustrating a physical quantity sensor 300 according to another modification. A physical quantity sensor 300 according to another modification includes a base body 10, a beam 20, an upper electrode 32, and a lower electrode 34. Since the physical quantity sensor 300 is the same as the above-described physical quantity sensor 100 except that it includes the counter beam 22, members other than the counter beam 22 are denoted by the same reference numerals as those of the physical quantity sensor 100, and detailed description thereof is omitted.

  The counter beam 22 is provided so as to protrude from the root of the beam 20 and extend toward the central region of the beam 20 in parallel with the beam 20. In the illustrated example, the counter beam 22 protrudes from the base of the beam 20 in a shape that is continuous with the base body 10, but may protrude from the side surface of the beam 20 without being continuous with the base body 10 (not shown). . The counter beam 22 preferably has a cantilever shape. When the counter beam 22 is provided in the form of a doubly supported beam similar to the beam 20, when acceleration or force is applied to the physical quantity sensor 300, compression or expansion stress generated in the beam 20 may be reduced. It is preferable that an even number of counter beams 22 be provided. In this way, the moment of rotation generated around the Z direction of the physical quantity sensor 300 can be suppressed. The counter beam 22 is preferably provided symmetrically with respect to the beam 20. In the example shown in FIG. 11, four cantilevered counter beams 22 are provided along the beam 20 and symmetrically with respect to the beam 20. The counter beam 22 preferably has a mass that can offset the mass displacement of the beam 20. The counter beam 22 may be provided with a weight or wiring not shown.

  One of the functions of the counter beam 22 is to cancel the mass displacement when the beam 20 bends and vibrates in the ± Y direction. Each of the counter beams 22 can vibrate with a displacement component in the ± Y direction. As indicated by arrows in FIG. 12, the counter beam 22 is displaced in a direction opposite to the beam 20 and vibrates. Therefore, when the beam 20 bends and vibrates, the mass displacement in the ± Y direction cancels each other, and the displacement component in the ± Y direction of the mass of the entire physical quantity sensor 300 can be reduced. That is, when the counter beam 22 is provided, vibration leakage of the physical quantity sensor 300 can be reduced.

  The modifications exemplified above can be combined, and can be freely applied not only to this embodiment but also to other embodiments.

2. Second Embodiment 2.1. Physical Quantity Sensor FIG. 13 is a top view schematically showing a physical quantity sensor 400 according to the present embodiment. FIG. 4 is a cross-sectional view schematically showing the physical quantity sensor 400 according to the present embodiment. A cross section taken along line DD in FIG. 13 corresponds to FIG.

  The physical quantity sensor 400 of this embodiment includes a base body 60, a beam 20, an upper electrode 32, and a lower electrode 34. The physical quantity sensor 400 is the same as the physical quantity sensor 100 of the first embodiment except that the shape of the base body 60 and the manner in which the beam 20 is provided are different. Therefore, members other than the base body 60 and the beam 20 are the same as the physical quantity sensor 100. The same reference numerals are given and detailed description is omitted.

  The base body 60 of the physical quantity sensor 400 of the present embodiment has a flat plate shape developed on the XZ plane. The base body 60 has such flexibility that it bends in the thickness direction (± Y direction) by the applied external force. Examples of the material of the base 60 include inorganic materials such as crystal, silicon, and various metals, and organic materials such as polyimide. In the present embodiment, the beam 20 can be formed separately from the base body 60 and then joined to the base body 60. Therefore, the material of the base body 60 and the material of the beam 20 may be different.

  The planar outer shape of the base body 60 is rectangular in the illustrated example, but is not limited thereto. The base body 60 may be formed with a weight (not shown). When a weight is formed on the base body 60, the amount of bending of the base body 60 can be adjusted. For example, the measurement sensitivity of the physical quantity sensor 300 can be increased.

  The base body 60 has at least two protrusions 62 on the upper surface. One of the functions of the protrusion 62 is to support both ends of the beam 20 with the two protrusions 62 and bridge the beam 20 between the two protrusions 62. The shape of the protrusion 62 is arbitrary as long as the beam 20 can be supported so as not to contact the upper surface of the base 10. The shape of the protrusion 62 can be a rectangular parallelepiped, for example. In the example of FIGS. 13 and 14, the base body 60 has two protrusions 62 formed in a stepped shape on the upper surface.

  In the present embodiment, both ends of the beam 20 are supported by the protrusions 62 of the base body 60 and are separated from the upper surface of the base body 60 to be bridged. Further, the planar position where the beam 20 is formed on the base body 60 is arbitrary as in the first embodiment. For example, when the base body 60 is bent by receiving a force, the longitudinal direction of the beam 20 is determined. Can be arranged to produce a tensile or compressive stress. In the illustrated example, the planar arrangement of the beams 20 passes through the center of the base body 60 in the ± X direction and is provided so that the longitudinal direction of the beams 20 extends along the ± Z direction. The beam 20 can be fixed to the base body 60 with an adhesive or the like. Moreover, the base 24 for fixing to the base | substrate 60 like illustration may be formed in the both ends of the beam 20. As shown in FIG. Furthermore, the thickness of the base portion 24 may be larger than the thickness of the beam 20.

  In the example of FIGS. 13 and 14, the base body 60 has a constricted portion 64 having a shape extending in a direction (± X direction) intersecting the beam 20 between two protrusions 62 that support both ends of the beam 20. Have. The constricted portion 64 is substantially the same as the constricted portion 16 described in the modification of the first embodiment, and can have the same effect.

  The beam 20 can function as a vibration unit of the physical quantity sensor 400. The details of the shape and material of the beam 20 are the same as those in the first embodiment.

2.2. Operation of Physical Quantity Sensor The operation of the physical quantity sensor 400 is substantially the same as described in the first embodiment. That is, when acceleration or force is applied to the physical quantity sensor 400 fixed in a cantilever shape, the free end side of the cantilever beam bends with respect to the fixed end. Then, since the beam 20 is formed above the upper surface of the physical quantity sensor 400, an elongation or compression stress is generated in the beam 20. As a result, the magnitude of acceleration can be measured from the difference between the resonance frequency generated when acceleration or force is applied and the reference frequency.

  In the physical quantity sensor 400, when a physical quantity such as acceleration or force is applied, the physical quantity sensor 400 bends in the ± Y direction, and the resonance frequency of the beam 20 changes. Therefore, the physical quantity applied to the physical quantity sensor 400 can be immediately grasped from the change in the resonance frequency.

  The physical quantity sensor 400 of the present embodiment described above has a high measurement sensitivity because it has one beam 20 supported at both ends. In addition, the physical quantity sensor 100 according to the present embodiment has the upper electrode 32 and the lower electrode 34 on the upper surface and the lower surface of the beam 20, respectively, and it is not necessary to form electrodes on the side surfaces of the beam 20. .

3. Physical Quantity Measuring Device The physical quantity measuring device according to the present invention includes any one of a detection unit and the physical quantity sensor of the above-described embodiment. FIG. 15 is a cross-sectional view schematically showing a physical quantity measuring apparatus 1000 that is an example of a physical quantity measuring apparatus.

  As shown in FIG. 15, the physical quantity measuring device 1000 may be configured such that, for example, the physical quantity sensor 100 and the detection unit 600 are sealed in a package 500 including a package base 510 and a lid 520.

  The package base 510 has a container shape that can accommodate the physical quantity sensor 100. The planar shape of the package base 510 and the depth as a container are arbitrary. The upper portion of the package base 510 has an opening that allows the physical quantity sensor 100 to be placed inside the package base 510. The opening of the package base 510 can be hermetically sealed by the lid 520. The material of the package base 510 can be an inorganic material such as ceramic or glass.

  The lid 520 has a flat plate shape that seals the upper opening of the package base 510. The planar shape of the lid 520 is arbitrary as long as the opening of the package base 510 can be sealed. Examples of the material of the lid 520 include ceramic, glass, metal, and the like. The bonding between the package base 510 and the lid 520 can be performed using, for example, plasma welding, seam welding, ultrasonic bonding, or an adhesive. A cavity (space) in the package 500 formed by the package base 510 and the lid 520 is a space for holding the physical quantity sensor 100 in a cantilever shape. Further, since the cavity can be sealed, the physical quantity sensor 100 can be installed in a reduced pressure space or an inert gas atmosphere.

  As illustrated, the physical quantity sensor 100 can be fixed in a cantilever shape to the bottom surface of the package base 520 using, for example, an adhesive 530. Further, the physical quantity sensor 100 can be freely arranged in the package 500 so as to correspond to the direction of acceleration or force that is a measurement target of the physical quantity measuring apparatus 1000 in addition to the exemplified arrangement.

  The detection unit 600 can drive the physical quantity sensor 100 and detect a change in the resonance frequency of the bending vibration or thickness shear vibration of the beam 20. The detection unit 600 can be configured by an IC chip having the circuit configuration described in the first embodiment, for example. The detection unit 600 can be electrically connected to the wiring 40 of the physical quantity sensor 100 via the bonding wire 700 or the like in the package 500. In addition, a through hole can be provided in the package base 520 to connect the wiring in the package 500 and the external electrode 710 on the lower surface of the package base 520. The external electrode 710 can function as an external terminal of the physical quantity measuring apparatus 1000.

  Since the physical quantity measuring apparatus 1000 as exemplified above includes the physical quantity sensor 100, physical quantities such as acceleration, force, temperature, etc. can be measured with high sensitivity.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and effects). In addition, the present invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 10,60 ... Base | substrate, 12 ... Opening part, 14 ... Frame part, 14a ... Outer peripheral part, 14b ... Thin-walled part,
14c ... inclined part, 16, 64 ... constricted part, 20 ... beam, 22 ... counter beam,
24 ... base, 32, 32a, 32b ... upper electrode, 34, 34a, 34b ... lower electrode,
40a, 40b ... wiring, 42, 42a, 42b ... pad, 50 ... base,
52,530 ... adhesive, 62 ... projection,
100, 200, 300, 400 ... physical quantity sensor, 500 ... package,
510 ... Package base, 520 ... Lid, 600 ... Detection part,
700 ... Bonding wire, 710 ... External electrode, 1000 ... Physical quantity measuring device

Claims (8)

A substrate;
Beams that are supported at both ends by the substrate and cause thickness-slip distortion when an electric field is applied in the thickness direction;
Sandwiching the beam in the thickness direction, avoiding the central region of the beam, upper and lower electrodes formed on the upper and lower surfaces of the beam; and
Including
The base body has flexibility such that it is bent in the thickness direction by an external force applied to the base body,
The physical quantity sensor in which the beam generates bending vibration by thickness shear vibration generated when a driving signal is applied to the upper electrode and the lower electrode. In claim 1,
The base body has a frame-like shape having an opening part surrounded by a frame part,
The beam is a physical quantity sensor in which both ends are supported by the frame portion of the base and are bridged inside the opening. In claim 2,
The physical body sensor is a physical quantity sensor having a constricted portion formed by cutting out in the thickness direction at a portion parallel to the beam of the frame portion. In claim 1,
The base body has a flat plate shape having at least two protrusions on the upper surface,
Both ends of the beam are supported by the two protrusions, and the beam is bridged between the two protrusions. In claim 4,
The said base | substrate has a constriction part of the shape extended in the direction which cross | intersects the said beam between the two said protrusions which support the both ends of the said beam. In any one of Claims 1 thru | or 5,
And a counter beam that protrudes from the base of the beam and extends in parallel to the beam toward the central region of the beam,
The physical quantity sensor, wherein the counter beam is displaced so as to cancel the mass displacement in the bending vibration of the beam. In any one of Claims 1 thru | or 6,
A physical quantity sensor, wherein the thickness shear vibration frequency of the beam is a signal for detecting a physical quantity. A physical quantity sensor according to any one of claims 1 to 8,
A detection unit for detecting a change in frequency of the bending vibration or the thickness shear vibration of the beam;
A physical quantity measuring device.

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