JP2010216846A - Sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor device operable without being supplied with external electric power. <P>SOLUTION: The sensor device includes: a base substrate 10 that is formed using a first glass substrate 10a; an oscillator formation substrate 20 having a frame 21 that is formed using a semiconductor substrate 20a and fixed to one surface side of the base substrate 10 and an oscillator 23 that is disposed inside the frame 21 and swingingly supported via a flexible deflection part 22; a cover substrate 30 that is formed using a second glass substrate 30a and fixed to the oscillator formation substrate 20 so as to form a displacement space 35 between the cover substrate and the oscillator formation substrate 20 in which the oscillator 23 is displaceable; a power generation part 24 that is formed in the deflection part 22 and composed of a piezoelectric transducing part for generating an AC voltage according to the oscillation of the oscillator 23; and a sensor 25 that is composed of a movable electrode 27 also disposed in a diaphragm 26 of the frame 21 and a fixed electrode 37 disposed on the cover substrate 30 and biased by the AC voltage from the power generation part 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sensor device.

  Conventionally, as one type of MEMS (micro electro mechanical systems) devices, power generation devices that convert vibration energy caused by arbitrary vibrations such as car vibrations and vibrations caused by human movements into electrical energy have been researched and developed in various places. (For example, refer nonpatent literature 1).

  Here, as shown in FIG. 10, the power generation device disclosed in Non-Patent Document 1 includes a base substrate 110 and two comb-shaped fixed electrodes supported by the base substrate 110 on one surface side of the base substrate 110. 124, 124 and the vibrator 123, which is disposed between the two fixed electrodes 124, 124 apart from the one surface of the base substrate 110 and supported by an anchor portion (not shown) via a support spring portion 122. A comb-shaped movable electrode 125 is provided, and an electret 130 is formed on a portion of the base substrate 110 facing the movable electrode 125. Note that the above-described power generation device is designed so that the rigidity of the support spring portion 122 is low.

  In the power generation device described above, the variable capacitor 126 having the fixed electrode 124 and the movable electrode 125 as the electrodes is formed. Therefore, the vibrator 123 is formed of the two fixed electrodes 124 and 124 along the one surface of the base substrate 110. By vibrating in the parallel direction (left and right direction in FIG. 10B) (the white arrow in FIG. 10A indicates the vibration direction of the vibrator 123), the fixed electrode 124 and the movable electrode 125 And the opposing area change, and the capacitance of the variable capacitor 126 changes. Therefore, if the load resistor 200 is connected between both ends of the series circuit of the variable capacitor 126 and the electret 130 which is a voltage applying means for applying a voltage to the variable capacitor 126, the capacitance of the variable capacitor 126 Since the electric charge is moved in accordance with the change of the current and the current is generated, the vibration energy of the mover 123 generated by the vibration of the vibrator 123 can be converted into electric energy. Here, in order to increase the energy conversion efficiency of the power generation device described above, the amount of change in the capacitance of the variable capacitor 126 may be increased.

T. Sterken, et al, "AN ELECTRET-BASED ELECTROSTATIC μ-GENERATOR", TRANSDUCERS '03, The 12th International Conference on Solid State Sensors, Actuators and Microsystems, Boston, June8-12,2003, p.1291-1294

  By the way, various conventionally known sensor devices (for example, pressure sensors, temperature sensors, etc.) are designed to supply power from an external power source or battery, and power from the external power source or battery is supplied to the sensor device. It was necessary to connect a thin metal wire for supply. Further, when power is supplied from the battery to the sensor device, it is necessary to replace the battery when the battery capacity is exhausted.

  In addition, it is conceivable to use the power generation device having the configuration shown in FIG. 10 as a power source for a sensor device (for example, a pressure sensor or a temperature sensor). Yes (in short, it is necessary to connect a thin metal wire for supplying electric power to the sensor device from the outside in this case), and the size of the entire sensor system including the power generation device and the sensor device is increased. In addition, a power generation device is required separately from the sensor device, and it is difficult to reduce the cost.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a sensor device that can operate without supplying electric power from the outside.

  According to the first aspect of the present invention, a base substrate, a frame portion that is formed using a semiconductor substrate and is fixed to one surface side of the base substrate, and is arranged inside the frame portion and swings via a flexible bending portion. At least a part is provided in the frame part, a vibrator forming substrate having a freely supported vibrator, a power generation part formed of a piezoelectric conversion part that is formed in a bending part and generates an AC voltage according to the vibration of the vibrator, and And a sensor unit biased by an AC voltage from the power generation unit.

  According to the present invention, the vibrator unit substrate having the frame part and the vibrator disposed inside the frame part and supported to be swingable via the flexible flexure part, and the vibrator formed on the flexure part. And a power generation unit composed of a piezoelectric conversion unit that generates an AC voltage in response to vibration, and at least a part of the sensor unit provided in the frame unit is biased by the AC voltage from the power generation unit, so power is supplied from the outside It becomes possible to operate without doing.

  According to a second aspect of the present invention, in the first aspect of the invention, an antenna that radiates the output of the sensor unit as a radio wave is provided.

  According to the present invention, a thin metal wire for taking out the output of the sensor unit is not required, the cost of the system using the sensor device can be reduced, and a small amount of AC power that can be generated by the power generation unit is rectified, boosted, and stored. The output of the sensor unit can be transmitted without doing so.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the sensor unit changes in capacitance value or resistance value in accordance with a change in a physical quantity to be sensed.

  According to the present invention, it is possible to detect a change in the physical quantity to be sensed from a change in the capacitance value or resistance value of the sensor unit.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the sensor unit is configured such that a physical quantity to be sensed is a pressure, and a movable electrode provided in a diaphragm unit formed on the frame unit and the movable electrode are opposed to the movable electrode. And a variable capacitor whose capacitance value changes in accordance with a change in pressure, and is connected between the output terminals of the power generation unit via a reference resistor formed in the frame unit. It is characterized by.

  According to the present invention, the phase difference between the AC voltage generated in the power generation unit and the AC current flowing from the power generation unit to the RC series circuit composed of the variable capacitor and the reference resistance depends on the sensed pressure. Since it changes based on the capacitance value of the variable capacitor, the pressure can be detected based on the phase difference.

  According to a fifth aspect of the present invention, in the third aspect of the present invention, the sensor unit is a temperature-sensitive resistor whose sensing target physical quantity is a temperature and whose resistance value changes according to a change in temperature. It is connected between the output ends of the power generation unit through a provided reference capacitor.

  According to this invention, the phase difference between the AC voltage generated in the power generation unit and the AC current flowing from the power generation unit to the RC series circuit including the reference capacitor and the temperature sensitive resistor depends on the sensed temperature. Therefore, the temperature can be detected based on the phase difference.

  In the invention of claim 1, there is an effect that it becomes possible to operate without supplying electric power from the outside.

The sensor device of Embodiment 1 is shown, (a) is a schematic perspective view, (b) is a schematic exploded perspective view. It is a schematic plan view of the vibrator formation board in the sensor device same as the above. Fig. 2 shows the sensor device of the above, (a) is a schematic sectional view corresponding to the section AA 'in Fig. 2, (b) is a schematic sectional view corresponding to the section BB' in Fig. 2, and (c) is a diagram. It is a schematic sectional drawing corresponding to 2 DD 'cross section. It is an equivalent circuit diagram of a sensor device same as the above. It is operation | movement explanatory drawing same as the above. The sensor device of Embodiment 2 is shown, (a) is a schematic perspective view, (b) is a schematic exploded perspective view. It is a schematic plan view of the vibrator formation board in the sensor device same as the above. The sensor device is shown, (a) is a schematic cross-sectional view corresponding to the cross section AA ′ of FIG. 6, (b) is a schematic cross-sectional view corresponding to the cross section BB ′ of FIG. FIG. 6 is a schematic cross-sectional view corresponding to a DD ′ cross section of FIG. 6. It is an equivalent circuit diagram of a sensor device same as the above. A prior art example is shown, (a) is a schematic perspective view partly broken, (b) is a schematic sectional view.

(Embodiment 1)
Hereinafter, the sensor device of the present embodiment will be described with reference to FIGS.

  The sensor device of the present embodiment is a pressure sensor device, and is formed using a rectangular plate-like base substrate 10 formed using the first glass substrate 10a and a semiconductor substrate (silicon substrate) 20a. 10. A vibrator forming substrate 20 having a frame portion 21 that is fixed to one surface side and a vibrator 23 that is disposed inside the frame portion 21 and is swingably supported via a flexible bending portion 22; Opposite to the base substrate 10 side of the vibrator forming substrate 20 in the form of a displacement space 35 that is formed using the second glass substrate 30a and that allows the vibrator 23 to be displaced between the vibrator forming substrate 20 and the second glass substrate 30a. And a cover substrate 30 fixed to the side, and a power generation unit comprising a piezoelectric conversion unit (piezoelectric conversion element) that generates an alternating voltage in response to the vibration of the vibrator 23 at the bending portion 22 of the vibrator forming substrate 20. 24 is formed.

  In the vibrator forming substrate 20 described above, the insulating film 20b made of a silicon oxide film is formed on the one surface of the semiconductor substrate 20a, and the piezoelectric conversion portion constituting the power generation unit 24 is formed on the insulating film 20b. A lower electrode 24a made of a metal film (for example, a Pt film), a piezoelectric layer 24b made of a PZT film formed on the opposite side of the lower electrode 24a from the insulating film 20b side, and a lower electrode 24a side of the piezoelectric layer 24b Is composed of an upper electrode 24c made of a metal film (for example, an Al film) formed on the opposite side. Note that the piezoelectric material of the piezoelectric layer 24b is not limited to PZT, and for example, lead-free KNN, AlN, or the like may be employed. If these materials are employed, the environmental load can be reduced.

  Further, the sensor device of the present embodiment is formed on the sensor unit 25 biased by the AC voltage from the power generation unit 24 and the one surface side of the cover substrate 30 opposite to the transducer forming substrate 20 side. And an antenna 39 that radiates the output as radio waves (electromagnetic waves).

  The sensor unit 25 includes a movable electrode 27 provided on a diaphragm unit 26 formed on the frame unit 21 and a fixed electrode 37 provided on the cover substrate 30 and opposed to the movable electrode 27 when the physical quantity to be sensed is pressure. And a variable capacitance capacitor whose capacitance value changes according to a change in pressure received by the diaphragm portion 26, and between the output ends of the power generation portion 24 via a reference resistor 38 formed of a metal film formed on the frame portion 21. It is connected to the. Here, the diaphragm part 26 is formed in the frame part 21 of the vibrator forming substrate 20 by forming the recess 20c on the other surface of the semiconductor substrate 20a by the etching technique. The reference resistor 38 is formed in a meandering shape in the plan view on the insulating film 20b (in the illustrated example, a folded shape). As can be seen from the above description, a part of the sensor unit 25 is provided in the frame unit 21.

  In the sensor unit 25, the movable electrode 27 is connected to the lower electrode 24a, which is one of the pair of electrodes of the power generation unit 24, via the metal wiring 29a formed in the frame unit 21, and the fixed electrode 37 is It is connected to one end of the reference resistor 28 through a metal wiring 37 b formed on the cover substrate 30 and a metal wiring 28 b formed on the frame portion 21. The reference resistor 28 has the other end connected to the upper electrode 24c, which is the other electrode of the power generation unit 24, via the metal wiring 29b. The above-described antenna 39 is connected to the metal wiring 29b. Therefore, the equivalent circuit of the sensor device is such that, if the power generation unit 24 is an AC voltage source Vs, the reference resistor 28 is a resistor R, and the sensor unit 25 is a variable capacitor C, as shown in FIG. An RC series circuit of the resistor R and the variable capacitor C is connected, and the antenna 39 is connected to the metal wiring 29b connecting the AC voltage source Vs and the resistor R.

  In the present embodiment, the silicon substrate 20a is used as the semiconductor substrate 20a serving as the basis of the vibrator forming substrate 20. However, the silicon substrate 20a is not limited to the silicon substrate 20a. For example, the silicon substrate 20a is formed of a silicon oxide film on a support substrate made of a silicon substrate. The insulating layer (buried oxide film) may be formed using an SOI substrate having an n-type silicon layer (active layer), and the insulating layer is formed as an etching stopper when the diaphragm portion 26 and the flexible portion 22 are formed. By using it as a layer, the thickness of the diaphragm portion 26 and the bending portion 22 may be increased in accuracy.

  Further, the above-described base substrate 10 has a through-hole 10c that penetrates the space in the recess 20c of the transducer forming substrate 20 in the thickness direction. In short, the space in the recess 20c of the transducer forming substrate 20 communicates with the external space of the sensor device. A displacement space forming recess 10 b for securing the displacement space 15 of the vibrator 23 is formed on the one surface of the base substrate 10. Note that the displacement space 15 toward the base substrate 10 may be secured by reducing the thickness of the vibrator 23 without forming the displacement space forming recess 10 b in the base substrate 10.

  Further, the above-described cover substrate 30 forms a displacement space 35 of the vibrator 23 on the other surface opposite to the one surface side where the above-described antenna 39 is formed (that is, the vibrator forming substrate 20 side). Displacement space forming recess 30b (see FIGS. 3A and 3C) and a gap forming recess 30c for forming a gap between the movable electrode 27 and the fixed electrode 37 (see FIG. 3C). ) And a reference resistance housing recess 30 d (see FIG. 3B) for housing the reference resistor 28. The cover substrate 30 is provided with a through-wiring 38 that connects the antenna 39 and the metal wiring 29 b formed on the frame portion 21 of the vibrator forming substrate 20 in the thickness direction.

  The base substrate 10 and the cover substrate 30 described above are hermetically fixed to the frame 21 of the vibrator forming substrate 20 in a vacuum with a desired degree of vacuum (for example, about 10 Pa). Since the airtight package is configured with the cover substrate 30, by making the inside of the airtight package evacuated, air damping by the air of the vibrator 23 can be prevented and energy conversion efficiency can be improved and reliability can be improved. Can be increased. In the sensor device of the present embodiment, the pressure and gap in the surrounding space of the vibrator 23 (the space formed by the space around the vibrator 23 in the vibrator forming substrate 20 and the above-described displacement spaces 15 and 35). Each of the pressure in the forming recess 10b and the pressure in the reference resistance housing recess 30d has the desired degree of vacuum.

  In the sensor device of the present embodiment, the power generation unit 24 is configured by a piezoelectric conversion unit including the lower electrode 24a, the piezoelectric layer 24b, and the upper electrode 24c. 24b receives stress, and a bias of electric charge occurs between the upper electrode 24c and the lower electrode 24a, and an AC voltage is generated in the power generation unit 24. Further, in the sensor device of the present embodiment, the sensor unit 25 includes the variable capacitor C having the movable electrode 27 and the fixed electrode 37 as a pair of electrodes, so that the diaphragm unit 26 is connected to the base substrate from the outside of the sensor device. The distance between the movable electrode 27 and the fixed electrode 37 is changed by the pressure of gas or liquid introduced through the internal space of the through-hole 10c and the recess 20c of the vibrator forming substrate 20, and the capacitance value of the variable capacitor C is changed. Changes.

  Here, the equivalent circuit of the sensor device of the present embodiment is such that an RC series circuit of the reference resistor 28 and the sensor unit 25 is added to the AC voltage source Vs constituted by the power generation unit 24 as shown in FIG. Since it becomes the connected structure, the output of the sensor part 25 can be radiated | emitted from the antenna 39 as a radio wave.

  The sensor device described above is formed using a MEMS device manufacturing technique or the like. The vibrator forming substrate 20, the base substrate 10 and the cover substrate 30 may be fixed by, for example, an anodic bonding method, a room temperature bonding method, a resin bonding method using an epoxy resin, or the like.

  According to the sensor device of the present embodiment described above, a vibrator is formed that includes the frame portion 21 and the vibrator 23 that is disposed inside the frame portion 21 and is swingably supported via the flexible bending portion 22. The substrate 20 includes a power generation unit 24 formed of a piezoelectric conversion unit that is formed in the bending unit 22 and generates an AC voltage according to the vibration of the vibrator 23, and the sensor unit 25 is biased by the AC voltage from the power generation unit 24. Therefore, it becomes possible to operate without supplying power from the outside. Here, since the capacitance value of the sensor unit 25 changes according to a change in pressure, which is a physical quantity to be sensed, it is possible to detect a change in pressure from a change in the capacitance value of the sensor unit 25.

  In addition, since the sensor device of the present embodiment includes the antenna 39 that radiates the output of the sensor unit 25 as a radio wave, a metal thin line for taking out the output of the sensor unit 25 is not necessary, and the system using the sensor device is not necessary. The cost can be reduced, and the output of the sensor unit 25 can be transmitted without rectifying, boosting, or accumulating a small amount of AC power that can be generated by the power generation unit 24. Thus, for example, in a receiving apparatus including a receiving antenna that receives a radio wave transmitted from the antenna 39 and a microcomputer that obtains pressure based on the output of the receiving antenna, information on pressure is obtained. Is possible. The sensor device is used by being mounted on a vehicle, for example.

  Further, according to the sensor device of the present embodiment, the sensor unit 25 is opposed to the movable electrode 27 and the movable electrode 27 provided on the diaphragm unit 26 formed on the frame unit 21 when the physical quantity to be sensed is pressure. This is a variable capacitor C that is composed of a fixed electrode 37 that is arranged and whose capacitance value changes in accordance with a change in pressure, and is connected between the output ends of the power generation unit 24 through a reference resistor 28 formed in the frame unit 21. Therefore, as shown in FIG. 5, the AC voltage “A” generated in the power generation unit 24 and the AC current “B” flowing from the power generation unit 24 to the RC series circuit including the sensor unit 25 and the reference resistor 28 are reduced. The phase difference δ changes with the capacitance value of the sensor unit 25 according to the sensed pressure. If the resistance value of the reference resistor 28 is R, the capacitance value of the sensor unit 25 is C, and the angular frequency of the AC voltage “A” is ω, tanδ = 1 / ωRC.

  Therefore, if a reference device in which a capacitor having a constant capacitance is formed instead of the variable capacitor C in the sensor device is arranged adjacent to the sensor device, the pressure can be detected based on the phase difference δ between the two. It becomes possible.

(Embodiment 2)
Although the sensor device of the present embodiment described based on FIGS. 6 to 8 is a temperature sensor device, the basic configuration is substantially the same as that of the first embodiment, and thus the same reference numerals are given to the same components as those of the first embodiment. Therefore, the description is omitted as appropriate.

  In the present embodiment, in the vibrator forming substrate 20, instead of the reference resistor 28 (see FIGS. 1 to 3) described in the first embodiment, a temperature sensitivity made of a metal film (for example, a Pt film) having a meandering shape in plan view. The sensor portion 48 made of a resistor is formed. In the vibrator forming substrate 20, the recess 20c (see FIG. 3B) and the diaphragm portion 26 (see FIG. 3B) described in the first embodiment are used. A fixed electrode 47 is formed instead of the movable electrode 27 (see FIG. 3B) without being formed, and the capacitance value between the fixed electrode 47 of the transducer forming substrate 20 and the fixed electrode 37 of the cover substrate 30 is increased. The difference is that a fixed reference capacitor 45 is formed. Further, the base substrate 10 in this embodiment is different in that the through hole 10c described in the first embodiment is not formed.

  Here, the temperature sensitive resistor constituting the sensor unit 48 is formed of a metal film such as a Pt film.

  In the above-described reference capacitor 45, one fixed electrode 47 is connected to the lower electrode 24 a that is one electrode of the pair of electrodes of the power generation unit 24 via the metal wiring 29 a formed in the frame portion 21, and the fixed electrode 37. Is connected to one end of the temperature sensitive resistor 48 through a metal wiring 37 b formed on the cover substrate 30 and a metal wiring 48 b formed on the frame portion 21. The other end of the temperature-sensitive resistor 48 is connected to the upper electrode 24c, which is the other electrode of the power generation unit 24, through the metal wiring 29b. The above-described antenna 39 is connected to the metal wiring 29b. Therefore, the equivalent circuit of the sensor device can be changed to an AC voltage source Vs as shown in FIG. 9, if the power generation unit 24 is an AC voltage source Vs, the sensor unit 48 is a variable resistor R, and the reference capacitor 45 is a capacitor C. An RC series circuit of a resistor R and a capacitor C is connected, and the antenna 39 is connected to a metal wiring 29b that connects the AC voltage source Vs and the variable resistor R.

  In the sensor device of the present embodiment, as can be seen from the above description, the sensor unit 48 formed of the temperature-sensitive resistor provided in the frame unit 21 is biased by the AC voltage from the power generation unit 24, and thus power is supplied from the outside. It becomes possible to operate without. In addition, since the resistance value of the sensor unit 48 in the sensor device of the present embodiment changes in accordance with a change in temperature, which is a physical quantity to be sensed, a change in the physical quantity to be sensed is detected from a change in the resistance value of the sensor unit 48. It becomes possible to detect.

  Here, the equivalent circuit of the sensor device of the present embodiment is such that an RC series circuit of the sensor unit 48 and the reference capacitor 45 is added to the AC voltage source Vs constituted by the power generation unit 24 as shown in FIG. Since it becomes the connected structure, the output of the sensor part 48 can be radiated | emitted from the antenna 39 as a radio wave. Thus, for example, in a receiving apparatus including a receiving antenna that receives a radio wave transmitted from the antenna 39 and a microcomputer that obtains temperature based on the output of the receiving antenna, temperature information is obtained. Is possible. The sensor device is used by being mounted on a vehicle, for example. However, the sensor device is not limited to an on-vehicle use, and is used for other uses.

  Further, according to the sensor device of the present embodiment, the sensor unit 48 is a temperature-sensitive resistor whose sensing target physical quantity is temperature and whose resistance value changes according to the temperature change formed in the frame unit 21. Since it is connected between the output ends of the power generation unit 24 via the reference capacitor 45 formed in the frame unit 21, the AC voltage “I” generated in the power generation unit 24 and the power generation unit are the same as in FIG. The phase difference δ with respect to the alternating current “B” flowing from 24 to the RC series circuit changes based on the resistance value of the sensor unit 48 according to the sensed temperature. If the resistance value of the sensor unit 48 is R, the capacitance value of the reference capacitor 45 is C, and the angular frequency of the AC voltage “A” is ω, tan δ = 1 / ωRC.

  Therefore, if a reference device in which a reference resistance having a constant resistance value is formed instead of the sensor unit 48 in the sensor device is arranged next to the sensor device, the temperature can be detected based on the phase difference δ between the two. It becomes possible.

DESCRIPTION OF SYMBOLS 10 Base substrate 10a 1st glass substrate 20 Vibrator formation board | substrate 20a Silicon substrate 21 Frame part 22 Deflection part 23 Vibrator 24 Electric power generation part 25 Sensor part 26 Diaphragm part 27 Movable electrode 28 Reference resistance 30 Cover substrate 30a 2nd glass substrate 35 Displacement space 37 Fixed electrode 39 Antenna 45 Reference capacitor 48 Sensor part (temperature-sensitive resistance)

Claims (5)

  A base substrate, a frame portion that is formed using a semiconductor substrate and is fixed to one surface side of the base substrate, and a vibrator that is disposed inside the frame portion and is swingably supported via a flexible bending portion An oscillator forming substrate having a power generation section formed of a piezoelectric conversion section that is formed in a flexure section and generates an AC voltage according to the vibration of the oscillator, and at least part of which is provided in the frame section by an AC voltage from the power generation section A sensor device comprising a sensor unit to be biased.   The sensor device according to claim 1, further comprising an antenna that radiates the output of the sensor unit as a radio wave.   The sensor device according to claim 1, wherein the sensor unit changes in capacitance value or resistance value in accordance with a change in a physical quantity to be sensed.   The sensor unit includes a movable electrode provided on a diaphragm unit formed on the frame unit and a fixed electrode disposed opposite to the movable electrode, and a physical quantity to be sensed is pressure. The sensor device according to claim 3, wherein the sensor device is a variable capacitor whose capacitance value changes, and is connected between output terminals of the power generation unit via a reference resistor formed in the frame unit.   The sensor unit is a temperature-sensitive resistor in which a physical quantity to be sensed is temperature, and a resistance value changes according to a change in temperature, and an output terminal of the power generation unit via a reference capacitor provided in the frame unit The sensor device according to claim 3, wherein the sensor device is connected between them.

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