Resonant pressure sensor with improved linearity

A resonant pressure sensor has high linearity and includes: a housing; and a pressure sensing unit that detects a static pressure based on a change value of a resonance frequency and includes: a housing-fixed portion; a substrate that includes a substrate-fixed portion and a substrate-separated portion; the pressure-receiving fluid that is interposed in a gap between the housing-fixed portion and the substrate and envelops the substrate; and a first resonator that is disposed in the substrate-separated portion and detects the change value of the resonance frequency based on a strain in the substrate caused by the static pressure applied by the pressure-receiving fluid, wherein the first resonator is made of a semiconductor material including an impurity, a concentration of the impurity is 1×1020 (cm−3) or higher, and an atomic radius of the impurity is smaller than an atomic radius of the semiconductor material.

BACKGROUND

Technical Field

The present invention relates to a resonant pressure sensor.

Related Art

For example, resonant pressure sensors conventionally adopt a configuration of measuring pressure by receiving a pressure of a fluid or the like that is a measurement target by a diaphragm and detecting a change in a resonance frequency of a resonator, disposed on a surface of the sensor, caused by a strain arising in the resonator (for example, see patent literature 1 and non-patent literature 1).

Furthermore, when measuring an absolute pressure of the fluid or the like, a pressure reference chamber regulated to a predetermined pressure value needs to be disposed on one side of the diaphragm, and the pressure of the fluid or the like that is the measurement target needs to be applied on another side of the diaphragm.

PATENT LITERATURE

Non-Patent Literature 1 Sensors and Actuators, “Three-dimensional Micromachining of Silicon Pressure Sensor Integrates Resonant Strain Gauge on Diaphragm”, Physical Volume 21, Issues 1-3, p 146-150 (February 1990)

In the prior art taught in non-patent literature 1, when a high static pressure is applied to a diaphragm, a peripheral portion thereof deforms. This mitigates stress arising in the diaphragm itself. That is, a resonant pressure sensor generates a so-called balloon effect, wherein a sensitivity when a static pressure is high appears to be lower than a sensitivity when a static pressure is low, and therefore has an issue wherein a linearity of input and output characteristics as a pressure sensor is remarkably degraded. Therefore, it has an issue wherein high measurement precision is difficult to obtain in, for example, uses wherein a high static pressure is applied.

SUMMARY

One or more embodiments provide a resonant pressure sensor that provides high linearity, regardless of a magnitude of a static pressure applied by a fluid or the like that is a measurement target, and includes excellent measurement precision.

A resonant pressure sensor according to one or more embodiments is a resonant pressure sensor, provided with: a pressure sensing unit that can detect a static pressure based on a change value of a resonance frequency; wherein the pressure sensing unit includes a housing-fixed portion that is fixed to a housing; a substrate portion (i.e., substrate) that has a substrate-fixed portion, in at least one location or more, which is fixed to the housing-fixed portion, and a substrate-separated portion, which is separated from the housing-fixed portion and extends from the substrate-fixed portion; a pressure-receiving fluid that is interposed in a gap between the housing-fixed portion and the substrate portion and envelops the substrate portion; and a first resonator that is disposed in the substrate-separated portion and detects as a change value of a resonance frequency based on a strain arising in the substrate portion according to a static pressure applied by the pressure-receiving fluid.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, the substrate portion has a cantilever structure whose support point is the substrate-fixed portion.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, the substrate portion has a strain-mitigating hole provided so as to penetrate the substrate portion.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, the first resonator is made of a semiconductor material including an impurity, a concentration of the impurity is 1×1020(cm−3) or higher, and an atomic radius of the impurity is smaller than an atomic radius of the semiconductor material, which is a base material.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, the pressure sensing unit includes a second resonator that is disposed in the substrate-separated portion of the substrate portion and detects as a change value of a resonance frequency based on the strain arising in the substrate portion according to the static pressure applied by the pressure-receiving fluid, and the second resonator has a pressure sensitivity of the resonance frequency that differs from a pressure sensitivity of the resonance frequency of the first resonator.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, the pressure sensing unit has at least two or more substrate-separated portions provided to one substrate portion or a plurality of substrate portions, and the first resonator and the second resonator are respectively disposed in different substrate-separated portions.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, both the first resonator and the second resonator are made of a single-crystal silicon material including an impurity, respective concentrations of the impurity in the first resonator and the second resonator being values that differ by at least one order of magnitude or more when a unit is made to be (cm−3), and a temperature coefficient of the resonance frequency of the second resonator is greater than a temperature coefficient of the resonance frequency of the first resonator.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, a thickness dimension of the second resonator along a thickness direction of the substrate portion is greater than a thickness dimension of the first resonator.

Furthermore, a characteristic feature of the resonant pressure sensor according to one or more embodiments is that in the above configuration, the substrate portion has a base substrate, which has the substrate-fixed portion and is fixed to the housing-fixed portion, and a support substrate, which is connected to the base substrate; the support substrate has a fixed portion, which is fixed to the base substrate, and a separated portion, which is separated from the base substrate and extends from the fixed portion; and the pressure-receiving fluid is interposed in a gap between the base substrate and the support substrate and envelops the separated portion.

According to the resonant pressure sensor according to one or more embodiments of the present invention, a configuration is adopted wherein the substrate portion and the first resonator are provided. The substrate portion has the substrate-fixed portion, in at least one location or more, that is fixed to the housing-fixed portion. It also has the substrate-separated portion. The first resonator is disposed in the substrate-separated portion of the substrate portion. Moreover, it detects as the change value of the resonance frequency based on the strain arising according to the static pressure applied to the substrate portion by the pressure-receiving fluid. By this, high linearity is obtained regardless of a magnitude of a static pressure applied by a fluid or the like that is a measurement target, and excellent measurement precision can be realized.

DETAILED DESCRIPTION

Embodiments of the present invention will be described herein with reference to the drawings. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teaching of the present invention and that the present invention is not limited to the embodiments illustrated herein for explanatory purposes.

Resonant pressure sensors according to one or more embodiments are described below while referring toFIGS. 1A-1BtoFIG. 12as appropriate.

The following description first describes a summary of a resonant pressure sensor according to one or more embodiments of the present invention and then details the resonant pressure sensors that are embodiments of first to fifth embodiments. Here, the resonant pressure sensors of the one or more embodiments of the present invention are, for example, ones whereby high measurement precision is obtained in a use wherein a particularly high static pressure is applied.

In the following description, as necessary, positional relationships between members are described while referring to the XYZ orthogonal coordinate system illustrated in the diagrams (the position of the origin being changed as appropriate).

The resonant pressure sensor according to one or more embodiments includes a substrate portion and a first resonator. The substrate portion has a substrate-fixed portion, in at least one location or more, that is fixed to a housing-fixed portion. The substrate portion also has a substrate-separated portion. The first resonator is disposed in the substrate-separated portion of the substrate portion. Moreover, a resonance frequency of the first resonator changes based on a strain that arises according to a static pressure applied to the substrate portion by a pressure-receiving fluid.

In the above basic configuration of one or more embodiments, a pressure (static pressure) of a surrounding environment (fluid) of the resonant pressure sensor, which is a measurement target, is propagated to the pressure-receiving fluid by a pressure-propagating partition-wall member, and the pressure of this pressure-receiving fluid being applied to the substrate portion isotropically compresses the substrate portion. This applies an isotropically compressive stress to the substrate-separated portion but applies a longitudinally compressive stress to the first resonator. As a result, the resonance frequency of the first resonator changes. The resonant pressure sensor according to one or more embodiments measures the static pressure applied to the resonant pressure sensor by measuring this resonance frequency.

In a case of measuring the atmosphere, there may be a situation wherein the above pressure-propagating partition-wall member is not used. In this situation, the pressure-receiving fluid is the “atmosphere” itself.

When using the pressure-propagating partition-wall member as a diaphragm between the pressure-receiving fluid and the atmosphere, for example, a material that is not easily affected by humidity or a material that is not easily affected by wind is used.

Meanwhile, in a resonant pressure sensor of a conventional configuration, as above, a linearity of input and output characteristics as a pressure sensor when a high static pressure is applied is degraded due to the balloon effect compared to input and output characteristics as a pressure sensor when a low static pressure is applied. As such, there are issues such as high measurement precision not being obtained.

In contrast, in the resonant pressure sensor according to one or more embodiments, even when measuring a high static pressure, as above, a support substrate is compressed by an isotropic pressure via the pressure-receiving fluid. As such, the balloon effect that remarkably degrades a linearity of input and output characteristics is avoided in principle. This enables high linearity to be obtained for input and output characteristics as a pressure sensor under a wide range of static pressures regardless of a magnitude of the static pressure applied by the fluid or the like that is the measurement target, and excellent measurement precision can be realized.

First Embodiment

The resonant pressure sensor of the first embodiment is detailed below while referring toFIGS. 1A-1BtoFIG. 5.

FIGS. 1A-1Bare sectional views illustrating resonant pressure sensors1A,1B of one or more embodiments.FIG. 1Ais a diagram illustrating a situation wherein a pressure-receiving fluid F (for example, a liquid or a gas) that is different from a measurement target is used, andFIG. 1Bis a diagram illustrating a situation wherein the measurement target (for example, a liquid or a gas) is used as a pressure-receiving fluid K. Moreover,FIG. 2is a plan view illustrating the pressure sensing unit in the resonant pressure sensors1A,1B illustrated inFIGS. 1A-1B,FIG. 3is a sectional view at line A-A inFIG. 2, andFIG. 4is a sectional view at line B-B inFIG. 2. Moreover,FIG. 5is a block diagram illustrating signal processing operations in the resonant pressure sensors1A,1B.

[Configuration of Resonant Pressure Sensor]

The resonant pressure sensor1A of one or more embodiments of includes a pressure sensing unit1that can detect a static pressure based on a change value of a resonance frequency. It also has a base substrate (housing-fixed portion)2, a support substrate (substrate portion)3, and the pressure-receiving fluid F, which is interposed in a gap S between the base substrate2and the support substrate3and envelops the support substrate3. The support substrate3has a fixed portion (substrate-fixed portion)31, in at least one location or more, that is fixed to the base substrate2. It also has a separated portion (substrate-separated portion)32that is separated from the base substrate2and extends from the fixed portion31in a direction intersecting a Z direction (for example, an X direction). The substrate portion may be referred to as a substrate.

Moreover, the resonant pressure sensor1A of one or more embodiments of has a first resonator4that is disposed in the separated portion32of the support substrate3. A resonance frequency of the first resonator4changes based on a strain that arises according to a static pressure applied to the support substrate3(separated portion32) by the pressure-receiving fluid F. That is, a strain arises in the first resonator4due to the static pressure applied to the support substrate3(separated portion32) by the pressure-receiving fluid F (via the separated portion32), and the resonance frequency of the first resonator4changes based on this strain.

Moreover, the resonant pressure sensor1A of one or more embodiments includes a second resonator5that is disposed in the separated portion32of the support substrate3. A change amount (pressure sensitivity) of a resonance frequency thereof that changes based on a strain that arises according to the static pressure applied to the support substrate3by the pressure-receiving fluid F is less than a change amount (pressure sensitivity) of the resonance frequency of the first resonator4.

In one or more embodiments, the first resonator4above has a function of detecting pressure, and the second resonator5above has a function of detecting temperature.

To give a more detailed description, the first resonator4is excited by an electrostatic force due to, for example, an AC voltage (excitation signal) being input from one electrode. Moreover, by applying a DC voltage between another electrode and the first resonator4, as a capacitance between the other electrode and the first resonator4when the first resonator4is excited changes over time, a current is output to the other electrode. An output voltage of the resonant pressure sensor1A is obtained by the current output to the other electrode at this time being subjected to current-voltage conversion. By applying appropriate feedback to the excitation signal input from the one electrode based on this output voltage, a stable self-exciting state is obtained at the resonance frequency of the first resonator4. This operation is realized inside the analog circuit81illustrated in the block diagram inFIG. 5. The analog circuit81then outputs an output voltage thereof to a frequency counter82.

Like the first resonator4, the second resonator5is excited by an electrostatic force due to an AC voltage (excitation signal) being input from one electrode. Moreover, by applying a DC voltage between another electrode and the second resonator5, as a capacitance between the other electrode and the second resonator5when the second resonator5is excited changes over time, a current is output to the other electrode. An output voltage of the resonant pressure sensor1A is obtained by subjecting this current output to the other electrode to current-voltage conversion, and by applying appropriate feedback to the excitation signal input from the one electrode based on this output voltage, a stable self-exciting state is obtained at the resonance frequency of the second resonator5. This operation is realized inside the analog circuit84illustrated in the block diagram inFIG. 5, and this analog circuit84outputs an output voltage thereof to a frequency counter85.

Next, in the frequency counter82illustrated inFIG. 5, frequency measurement is implemented for the output voltage input from the analog circuit81. The frequency counter82then outputs, to a computation unit83(processor), a digital signal that is a count value of a frequency based on a detection signal of the first resonator4.

In conjunction therewith, in the frequency counter85illustrated inFIG. 5, frequency measurement is implemented for the output voltage input from the analog circuit84, and like the above frequency counter82, the frequency counter85outputs, to the computation unit83, a digital signal that is a count value of a frequency based on a detection signal of the second resonator5.

Afterward, in the computation unit83, a pressure value corresponding to the digital signal input from the frequency counter82is calculated, and a pressure value corresponding to the digital signal input from the frequency counter85is calculated. These pressure values are output to the outside. At this time, the computation unit83uses the digital signal input from the frequency counter85—that is, a digital signal having a frequency according to an internal temperature of the pressure sensing unit1from the second resonator5—as a temperature correction signal and performs temperature correction for a detection result of the pressure sensing unit1according to the internal temperature of the pressure sensing unit1determined based on this signal.

By the operations above, pressure values reflecting a correction according to the internal temperature of the pressure sensing unit1are obtained based on the changes in the resonance frequencies arising in the first resonator4and the second resonator5in the resonant pressure sensor1A.

The above description describes one or more embodiments of measuring pressure using the first resonator4and the second resonator5, but in one or more embodiments, it is also possible to measure pressure using only the first resonator4.

In the illustrated example, the support substrate3is configured so the fixed portion31is a fixed end and the separated portion32is a free end, and the pressure sensing unit1is roughly of a cantilever structure supported at one point.

In the illustrated example, on a surface30of a stacked structure formed on the support substrate3, a shell6is further provided so as to cover this surface30.

The base substrate2is a base of the pressure sensing unit1and is made of a semiconductor substrate such as a single-crystal silicon wafer. The fixed portion31of the support substrate3is fixed to a surface20side of this base substrate2. Moreover, a concave portion20ais disposed in a surface20of the base substrate2, in a region other than a peripheral portion (region opposing the separated portion32) in a plan view of the base substrate2. As detailed below, in one or more embodiments, this ensures the gap S, into which the pressure-receiving fluid F (K) enters, between the base substrate2and the separated portion32of the support substrate3. The resonant pressure sensor according to one or more embodiments of the present invention is not limited to a configuration that ensures a gap, into which the pressure-receiving fluid enters, between the base substrate and the separated portion by providing a concave portion in the base substrate. For example, it may have a configuration that ensures a gap, into which the pressure-receiving fluid enters, between the base substrate and the separated portion by forming the separated portion at a smaller thickness than a thickness of the fixed portion.

The base substrate2may be made of a material that, for example, has a thermal expansion coefficient, elastic constant, and the like that are close to those of the support substrate3, which is detailed below. It may be made of a material wherein these characteristics are identical (the same material). As above, because the support substrate3is directly bonded to the base substrate2, by using materials having similar characteristics for each of these substrates, deformation amounts of when the materials deform due to applied pressure, environmental temperature, or the like become roughly equal. This reduces stress and the like that arise at a bonding interface due to a difference in deformation amounts between the base substrate2and the support substrate3. Therefore, an effect is obtained of improved temperature characteristics, hysteresis, long-term stability, and the like for the resonant pressure sensor1.

The support substrate3is a substrate that supports the first resonator4and the second resonator5, which are detailed below. It has the fixed portion31, which is fixed to the base substrate2, and the separated portion32, which is separated from the concave portion20aprovided in the surface20of the base substrate2by the gap S in the Z direction and extends from the fixed portion31in a direction intersecting the Z direction (for example, the X direction). As above, the support substrate3configures a cantilever structure by the fixed portion31bonded to the base substrate2and the separated portion32separated from the base substrate2.

The support substrate3has the fixed portion31bonded to the surface20of the base substrate2. Moreover, the support substrate3includes a sidewall portion33that, in a plan view of this support substrate3, is formed so as to extend from the fixed portion31roughly in a U shape and is disposed so as to surround the separated portion32. This sidewall portion33is also a sidewall of the pressure sensing unit1and, like the fixed portion31, is bonded to the surface20of the base substrate2. Moreover, in the support substrate3, the separated portion32is formed roughly in a tongue shape that is separated from the sidewall portion33while being surrounded by this sidewall portion33and has a function of a cantilever (see the X direction and the Y direction in the diagrams). Moreover, the separated portion32is formed roughly in a rectangular shape in a plan view and extends from the fixed portion31in the X direction in the diagrams in substantially the same sectional shape (substantially uniformly).

Moreover, a thickness of the separated portion32in the Z direction in the diagrams—that is, a thickness of the support substrate3in a stacking direction—is constant throughout the X direction and the Y direction in the diagrams.

The first resonator4and the second resonator5detailed below are disposed in parallel along the extending direction of the separated portion32in a position near a tip of the separated portion32of the support substrate3(end portion on an opposite side of the fixed portion31). In the illustrated example, the first resonator4and the second resonator5are each disposed in a position of an active layer3cprovided on a support layer3aforming the support substrate3and are each disposed in a state wherein a predetermined clearance C is maintained around the first resonator4and the second resonator5.

Furthermore, pads35a,35b,35c,35d,35e,35fthat are electrically connected to the first resonator4and the second resonator5and are for sending the detection signals of each of these resonators to an external control device are disposed on the surface30, in a position on a fixed-portion31side of the support substrate3. Although a material of these pads35ato35fis not limited in particular, for example, a conventionally known aluminum pad or the like can be adopted without any restrictions whatsoever.

Furthermore, as illustrated inFIG. 2, in one or more embodiments, the pads35a,35care respectively connected to an electrode36aand an electrode36c, and the pad35bis connected to the first resonator4via an electrode36b. Moreover, the pads35d,35fare respectively connected to an electrode36dand an electrode36f, and the pad35eis connected to the second resonator5via an electrode36e. Here, in one or more embodiments, as illustrated in the connection structure between the pad35band the electrode36binFIG. 4, each pad and each electrode are electrically connected by disposing each pad in a hole portion that penetrates the shell6and a TEOS oxide film3ethat is described below.

A conductive material that is conventionally used in this field can also be adopted without any restrictions whatsoever as a material for each of the above electrodes36ato36f.

In one or more embodiments, the excitation signal for exciting the first resonator4is supplied from the outside using the pads35a,35b,35cand the electrodes36a,36b,36c, and a first detection signal generated by the first resonator4(signal having a frequency according to pressure and temperature) is output to the outside. Moreover, the excitation signal for exciting the second resonator5is supplied from the outside using the pads35d,35e,35fand the electrodes36d,36e,36f, and a second detection signal generated by the second resonator5(signal having a frequency according to temperature alone or according to pressure and temperature) is output to the outside.

Although the material of the support substrate3is not limited in particular, as above, it may be made of a material having characteristics similar to those of the base substrate2whereto the fixed portion31of this support substrate3is directly bonded or it may be made of the same material. Details are given below, but as the support substrate3, one made of a semiconductor substrate such as a single-crystal silicon wafer can be adopted.

Furthermore, as in the layered structure illustrated in the sectional view inFIG. 3, an embedded oxide film3b, the active layer3c, an impurity diffusion layer3d, and the TEOS (tetraethoxysilane) oxide film3eare sequentially stacked on the support layer3aforming the support substrate3of one or more embodiments, forming a so-called SOI (silicon on insulator) structure. Moreover, in the example illustrated inFIG. 3and the like, the first resonator4and the second resonator5are formed in a position of the active layer3cin the above layered structure formed on the support layer3a.

The support layer3athat forms the support substrate3is single-crystal silicon doped with an impurity and is a layer having a uniform boron concentration of about 1×1018to 1×1019(cm−3). Moreover, the support layer3afunctions as a base in the above SOI structure.

The embedded oxide film3bis an insulating film that is formed on the support layer3aof the support substrate3and is the single-crystal silicon constituting the support layer3asubjected to an oxidation process. It has a function of electrically insulating the above electrodes from each other (insulating the electrode36aand the electrode36cfrom each other and insulating the electrode36dand the electrode36ffrom each other).

The active layer3cis doped single-crystal silicon and is a layer having a uniform boron concentration of, for example, about 1×1017to 1×1018(cm−3).

The impurity diffusion layer3dis a layer wherein boron (B) is diffused at a high concentration as an impurity in the active layer3c.

Moreover, the TEOS oxide film3eis a silicon oxide film formed using tetraethoxysilane (TEOS gas) as a material from the active layer3cwherefrom the impurity diffusion layer3dis formed. Like the embedded oxide film3b, it functions as an insulating film that electrically insulates the above electrodes from each other (insulates the electrode36aand the electrode36cfrom each other and insulates the electrode36dand the electrode36ffrom each other).

The first resonator4is a pressure-detecting resonator in the resonant pressure sensor1of one or more embodiments and is disposed in the separated portion32of the support substrate3.

As illustrated inFIG. 2toFIG. 5, the first resonator4is formed in a linear shape by machining the single-crystal silicon forming the active layer3cprovided on the support layer3aforming the support substrate3and is formed in a position of the active layer3cin the Z direction.

The first resonator4is disposed so as to be interposed in the Y direction between the electrode36aand the electrode36c.

Moreover, the predetermined clearance C is ensured around the first resonator4in the Y direction and the Z direction, and the first resonator4is formed as a double-supported beam structure wherein both end portions in the X direction are supported.

Moreover, the first resonator4is vacuum sealed between the support substrate3and the shell6by the surrounding clearance C being held in a vacuum state by the shell6, which is detailed below.

Furthermore, the first resonator4is excited by an excitation signal input from the electrode36aand outputs a signal having a frequency according to the applied pressure from the electrode36c.

That is, a strain according to the static pressure applied to the support substrate3by the pressure-receiving fluid F (K) arises in the first resonator4, and as above, a change value of the resonance frequency of the first resonator4that changed based on this strain is output as a frequency signal to the frequency counter82via the analog circuit81illustrated in the block diagram inFIG. 5. In the frequency counter82, frequency measurement is implemented for the output voltage input from the analog circuit81, and a digital signal that is a count value of the frequency is output to the computation unit83. Then, in the computation unit83, a pressure value corresponding to the digital signal input from the frequency counter82is computed.

In the pressure sensing unit1, the first resonator4is disposed so a static pressure (isotropic pressure) that acts on this pressure sensing unit1can be detected by the above configuration.

In one or more embodiments, the first resonator4is made of a semiconductor material including an impurity, a concentration of the impurity is 1×102° (cm−3) or higher, and an atomic radius of the impurity is smaller than an atomic radius of silicon, which is the base material.

To give a more detailed description, as the impurity included in the first resonator4, for example, boron (B) and phosphorous (P) can be mentioned. In this situation, because the impurity whose atomic radius is smaller than the silicon constituting the first resonator4replaces this silicon, the first resonator4deforms to relax this lattice strain. However, because fixed ends4a,4bof the first resonator4are fixed, a tensile stress acts on/is imparted to the first resonator4in advance. As a result, normally, under a high-pressure static pressure, when no tensile stress is being imparted, the first resonator4may buckle under a compressive stress arising in the fixed ends4a,4bof the first resonator4and its pressure measurement function may be lost. In contrast, in the pressure sensing unit1of one or more embodiments, a tensile stress is imparted in advance, and a compressive stress acting on this pressure sensing unit1can be offset by this tensile stress. This can prevent the first resonator4from buckling and enables the pressure measurement function to be maintained.

Here, a situation is described wherein, for example, a semiconductor material wherein the impurity boron is included at a concentration of 1×1020(cm−3) or higher and an atomic radius of the impurity is smaller than an atomic radius of the base material silicon is applied for the resonator having an H shape in a plan view taught in non-patent literature 1 above (H-shaped resonator; seeFIGS. 1A-1Bin non-patent literature 1).

Even in, for example, a resonant pressure sensor provided with the H-shaped resonator of non-patent literature 1, by introducing boron at a concentration of 1×1020(cm−3) or higher at a selective epitaxial step of forming the resonator, a pressure sensor that can measure high static pressure can be realized while preventing buckling of the resonator.

In the pressure sensing unit1provided in the resonant pressure sensor1A of one or more embodiments, from a viewpoint of being able to increase sensitivity and measurement precision as a pressure sensor, it may be for the disposition position of the first resonator4in the separated portion32to be a position that is one-half or more and two-thirds or less of a length of the separated portion32in the X direction illustrated inFIG. 2, the starting point being a connection location between the fixed portion31and the separated portion32.

The second resonator5is a temperature-detecting resonator in the resonant pressure sensor1A of one or more embodiments. Like the first resonator4for pressure detection, it is disposed in the separated portion32of the support substrate3. In the example illustrated inFIG. 2and the like, the second resonator5is disposed parallel to the first resonator4(extending in the X direction) while being separated from the first resonator4in the Y direction. Moreover, it is disposed in a position in the separated portion32wherein it is symmetrical to the first resonator4in the Y direction.

That is, as illustrated inFIG. 2toFIG. 5, the second resonator5is formed in a linear shape extending in the X direction by machining the single-crystal silicon forming the active layer3cprovided on the support layer3aforming the support substrate3and is formed in a position of the active layer3cin the Z direction.

The second resonator5is disposed so as to be interposed in the Y direction between the electrode36dand the electrode36f.

Moreover, like the first resonator4, the predetermined clearance C is ensured around the second resonator5in the Y direction and the Z direction, and the second resonator5is formed as a double-supported beam structure wherein both end portions in the X direction are supported.

Moreover, like the first resonator4, the second resonator5is vacuum sealed between the support substrate3and the shell6by the surrounding clearance C being held in a vacuum state by the shell6, which is detailed below.

Furthermore, the second resonator5is excited by an excitation signal input from the electrode36dand outputs, from the electrode36f, a signal having a frequency according to the pressure—at a different pressure sensitivity than the first resonator4—as a temperature correction signal at a time of pressure measurement.

The resonance frequencies of the first resonator4and the second resonator5change according to the pressure and according to a change in Young's modulus or a difference in linear expansion coefficients between materials according to the internal temperature of the pressure sensing unit1(temperature substantially equal to a temperature of the first resonator4and a temperature of the second resonator5). Additionally, in one or more embodiments, because the pressure sensitivity of the resonance frequency of the second resonator5is less than the pressure sensitivity of the resonance frequency of the first resonator4, the internal temperature of the pressure sensing unit1(temperature detection signal) can be determined based on a difference between a change value of the resonance frequency of the second resonator5and the change value of the resonance frequency of the first resonator4. Then, a more accurate pressure value applied to the pressure sensing unit1can be determined based on the determined internal temperature and the change value of the resonance frequency of the first resonator4(pressure detection signal).

Here, the “pressure sensitivity of the resonance frequency” above is a change amount of the resonance frequency per unit pressure, and the unit thereof is, for example, “Hz/Pa”. Moreover, when representing the pressure sensitivity of the resonance frequency as a rate of change, the unit thereof is, for example, “ppm/Pa”.

Furthermore, in the pressure sensing unit1provided in the resonant pressure sensor1A of one or more embodiments, from a viewpoint of increasing temperature detection precision and also contributing to improved sensitivity and measurement precision as a pressure sensor, like the first resonator4, it may be for the disposition position of the second resonator5in the separated portion32to be a position that is one-half or more and two-thirds or less of the length of the separated portion32in the X direction illustrated inFIG. 2, the starting point being the connection location between the fixed portion31and the separated portion32.

The shell6is disposed on the support substrate3and, in the example illustrated inFIG. 3and the like, is disposed so as to cover the surface30of the TEOS oxide film3edisposed in the uppermost layer in the stacked structure on the support layer3a. Moreover, as above, the shell6vacuum seals the first resonator4and the second resonator5. That is, the shell6is bonded to the above surface30while sealing the clearance C provided around the first resonator4and the second resonator5.

A material of the shell6is not limited in particular, but, for example, polysilicon can be used.

The encased resonant pressure sensor1A or resonant pressure sensor1B illustrated inFIGS. 1A-1Bis configured by housing the pressure sensing unit1and the pressure-receiving fluid F or pressure-receiving fluid K inside a housing50.

By each member constituting the pressure sensing unit1such as the base substrate2and the support substrate3being protected inside the housing50and the pressure-receiving fluids F, K being housed therein, the pressure applied from the outside, which is the measurement target, is transmitted to the support substrate3.

Moreover, the housing50functions as a base in the resonant pressure sensors1A,1B; in the illustrated example, a pedestal53is disposed on an inner bottom portion, and the pressure sensing unit1is disposed thereon.

As the housing50, a box-shaped member formed by, for example, a ceramic such as aluminum oxide or a metal such as Kovar, SUS316L, or Inconel is used.

Moreover, while illustration is omitted inFIGS. 1A-1B, a plurality of terminal portions is disposed in the housing50. The plurality of terminal portions is electrically connected, by a metal wire that is not illustrated, to the pads35ato35fprovided in the pressure sensing unit1housed in the housing50. Moreover, the plurality of terminal portions is used in connecting to an external device.

The resonant pressure sensor1A in the example illustrated inFIG. 1Ahouses the pressure-receiving fluid F, which is isolated from the measurement target by a pressure-propagating partition-wall member52, inside the housing50. It is used, for example, in a use of measuring a static pressure (pressure) in a state wherein a high static pressure from a fluid is applied. The resonant pressure sensor1A in the illustrated example provides the pressure-propagating partition-wall member52in a through hole51provided in a top-plate portion of the housing50. As this pressure-propagating partition-wall member, a metal material, a resin material, or the like that is conventionally used in this field can be adopted without any restrictions whatsoever.

Meanwhile, the resonant pressure sensor1B in the example illustrated inFIG. 1Bhouses the pressure-receiving fluid K as the measurement-target fluid inside the housing50. It is used, for example, in a general use of measuring the atmosphere or the like. In this manner, the resonant pressure sensor1B illustrated inFIG. 1Bis not provided with a pressure-propagating partition-wall member or the like, and the through hole51is in a state of being open to the outside atmosphere.

[Operations of Resonant Pressure Sensor]

Next, operations of the above resonant pressure sensor1A are briefly described.

First, when a static pressure acts on the pressure sensing unit1via the pressure-receiving fluid F, this pressure is applied to the support substrate3, and at least a portion of this support substrate3(portion other than the fixed portion31; in one or more embodiments, the separated portion32) is compressed in a substantially isotropic manner. At this time, a strain according to the compression of the separated portion32(pressure applied to the support substrate3) arises in the first resonator4, and the resonance frequency of the first resonator4changes based on this strain. In conjunction therewith, a strain according to the compression of the separated portion32(pressure applied to the support substrate3) also arises in the second resonator5, and the resonance frequency of the second resonator5changes based on this strain.

The first resonator4is resonant due to the excitation signal input from the electrode36a, and as above, the change value of the resonance frequency arising based on the above strain is as a frequency signal to the frequency counter82via the analog circuit81illustrated inFIG. 5. In the frequency counter82, frequency measurement is implemented for the output voltage input from the analog circuit81, and a digital signal that is a count value of the frequency is output to the computation unit83.

Furthermore, at the same time as the above pressure measurement by the first resonator4, the pressure sensing unit1can, by using a signal having a frequency according to the internal temperature from the second resonator5as a temperature correction signal, perform temperature correction of a detection result of the pressure sensing unit1according to the internal temperature of the pressure sensing unit1determined based on this signal. That is, the second resonator5is resonant due to the excitation signal input from the electrode36d, and as above, the change value of the resonance frequency arising based on the strain according to the compression of the separated portion32is as a frequency signal to the frequency counter85via the analog circuit84. In the frequency counter85, frequency measurement is implemented for the output voltage input from the analog circuit84, and a digital signal that is a count value of the frequency is output to the computation unit83.

Then, in the computation unit83, a pressure value corresponding to the digital signal input from the frequency counter82is computed, and a pressure value corresponding to the digital signal input from the frequency counter85is computed. At this time, the computation unit83uses the digital signal input from the frequency counter85, which has a frequency according to the internal temperature from the second resonator5, as the temperature correction signal and performs temperature correction of the detection result of the pressure sensing unit1according to the internal temperature of the pressure sensing unit1determined based on this signal.

By the above operations, pressure values reflecting a temperature correction according to the internal temperature of the pressure sensing unit1are obtained based on the changes in the resonance frequencies arising in the first resonator4and the second resonator5.

As above, in one or more embodiments, it is also possible to measure pressure using only the first resonator4, without performing temperature correction using the second resonator5.

As described above, according to the resonant pressure sensor1A according to one or more embodiments, provided are at least the support substrate3, which has the fixed portion31, which is fixed to the base substrate2, and the separated portion32, and the first resonator4that is disposed in the separated portion32of the support substrate3and has a resonance frequency that changes based on a strain that arises according to a static pressure applied to the support substrate3by the pressure-receiving fluid F. This enables high linearity and excellent measurement precision to be obtained regardless of a magnitude of a static pressure applied by a liquid, gas, or the like that is a measurement target.

Second Embodiment

The resonant pressure sensor of the second embodiment is detailed below while mainly referring toFIG. 6as appropriate.

In the description of the resonant pressure sensor of the second embodiment, configurations shared with the resonant pressure sensor1A of the first embodiment above are imparted the same reference signs in the diagrams, and detailed description thereof may be omitted.

Moreover, inFIG. 6, only a pressure sensing unit10provided in the resonant pressure sensor of the second embodiment is illustrated, and illustration of, for example, the housing and the pressure-receiving fluid is omitted.

FIG. 6is a plan view for describing the pressure sensing unit10provided in the resonant pressure sensor of the second embodiment. As illustrated inFIG. 6, the resonant pressure sensor of one or more embodiments differs from the resonant pressure sensor1A of the first embodiment above in that a support substrate (substrate portion)3A provided in the pressure sensing unit10has a strain-mitigating hole37provided so as to penetrate this support substrate3A.

The strain-mitigating hole37is disposed so as to penetrate a separated portion (substrate-separated portion)32A in the support substrate3A and the shell6in the Z direction. Moreover, in a plan view of the support substrate3A, the strain-mitigating hole37in the illustrated example is disposed between the first resonator4and the second resonator5.

According to the resonant pressure sensor of one or more embodiments, because the strain-mitigating hole37is disposed in the support substrate3A, a strain that can be propagated from the base substrate2to the separated portion32A via the fixed portion31and a strain that can be propagated in the separated portion32A are absorbed by the strain-mitigating hole37. This suppresses (reduces) both the strain that can be propagated from the base substrate2to the separated portion32A via the fixed portion31and the strain that can be propagated in the separated portion32A such that an influence of these strain propagations that can become a factor in measurement error can be decreased and the resonance frequencies of the first resonator4and the second resonator5indicate changes more reflective of the static pressure.

Therefore, the above effect of obtaining high linearity and excellent measurement precision is more remarkably obtained.

Third Embodiment

The resonant pressure sensor of the third embodiment is detailed below while mainly referring toFIG. 7.

In the description of the resonant pressure sensor of the third embodiment as well, configurations shared with the resonant pressure sensors of the first and second embodiments above are imparted the same reference signs in the diagrams, and detailed description thereof may be omitted.

Moreover, inFIG. 7as well, like the resonant pressure sensor of the second embodiment illustrated inFIG. 6, only a pressure sensing unit10A provided in the resonant pressure sensor of the third embodiment is illustrated, and illustration of the housing, the pressure-receiving fluid, and the like is omitted.

FIG. 7is a plan view for describing the pressure sensing unit10A provided in the resonant pressure sensor of the third embodiment. As illustrated inFIG. 7, the resonant pressure sensor of one or more embodiments differs from the resonant pressure sensor1A and the like of the first and second embodiments above in that in a support substrate (substrate portion)3B provided in the pressure sensing unit10A, the first resonator4and the second resonator5are each disposed in a separated portion (substrate-separated portion)32B or a separated portion (substrate-separated portion)32C that differ.

That is, in the pressure sensing unit10A provided in the resonant pressure sensor of one or more embodiments, the support substrate3B includes two separated portions32B,32C, and the first resonator4or the second resonator5is disposed in each. The support substrate3B may further include another substrate-separated portion (32B or32C).

Specifically, the pressure sensing unit10A provided in the resonant pressure sensor of one or more embodiments has the separated portion32B and the separated portion32C as the substrate-separated portion. The first resonator4for pressure detection is disposed in the separated portion32B, and the second resonator5for temperature detection is disposed in the separated portion32C.

The separated portion32B and the separated portion32C are arranged parallel to each other while being separated in the Y direction. Moreover, the separated portion32B and the separated portion32C are aligned so as to be roughly in the same position and have roughly the same size in an extending direction thereof (X direction).

According to the resonant pressure sensor of one or more embodiments, because, as above, the first resonator4and the second resonator5are each disposed in the separated portion32B or the separated portion32C that are independently provided, oscillation-energy transfer and the like are less likely to arise.

Therefore, it becomes possible to further suppress errors in pressure measurement.

In the example illustrated inFIG. 7, a configuration that provides two separated portions32B,32C in one support substrate3B is illustrated, but the present invention is not limited thereto. For example, three or more separated portions (substrate-separated portion) may be provided in one support substrate (substrate portion). Moreover, for example, a configuration wherein, upon providing a plurality of support substrates (substrate portion), separated portions are individually (independently) provided to each support substrate—that is, a configuration having at least two or more separated portions provided to a plurality of support substrates—may be adopted.

Fourth Embodiment

The resonant pressure sensor of the fourth embodiment is detailed below while mainly referring toFIG. 8toFIG. 10.

In the description of the resonant pressure sensor of the fourth embodiment as well, configurations shared with the resonant pressure sensors of the first, second, and third embodiments above are imparted the same reference signs in the diagrams, and detailed description thereof may be omitted.

Moreover, inFIG. 8toFIG. 10as well, like the resonant pressure sensors of the second and third embodiments illustrated inFIG. 6andFIG. 7, only a pressure sensing unit10B provided in the resonant pressure sensor of the fourth embodiment is illustrated, and illustration of the housing, the pressure-receiving fluid, and the like is omitted.

FIG. 8is a plan view for describing the pressure sensing unit10B provided in the resonant pressure sensor of the fourth embodiment,FIG. 9is a sectional view at line C-C inFIG. 8, andFIG. 10is a sectional view at line D-D inFIG. 8.

In the pressure sensing unit10B provided in the resonant pressure sensor of one or more embodiments illustrated inFIGS. 8 to 10, the first resonator4and the second resonator5are made of a single-crystal silicon material. Moreover, in the first resonator4and the second resonator5in the pressure sensing unit10B, the impurity concentrations in each are values that differ by at least one order of magnitude or more when the unit is made to be (cm−3). Moreover, the pressure sensing unit10B is configured so a temperature coefficient of the resonance frequency of the second resonator5is greater than a temperature coefficient of the resonance frequency of the first resonator4. Here, the above temperature coefficient of the resonance frequency is a rate of change of the resonance frequency per unit temperature, and the unit thereof is, for example, (ppm/° C.).

Described more specifically, in the resonant pressure sensor of one or more embodiments, for example, when the impurity concentration of one among the first resonator4and second resonator5made of the single-crystal silicon material is [a×10n(cm−3)], the impurity concentration of the other among these is [a×10n−1(cm−3)] or less or [a×10n+1(cm3)] or more.

The resonant pressure sensor of one or more embodiments is configured to make the temperature coefficients of the resonance frequencies different by a processing flow, whose illustration is omitted, wherein an impurity of a high concentration is diffused in the first resonator4and no impurity diffusion is performed in the second resonator5. That is, in one or more embodiments, no impurity diffusion is performed in a non-diffusion region R—that is, a region near the second resonator5—of the support substrate3illustrated inFIG. 8.

More specifically, as illustrated inFIG. 9, in the pressure sensing unit10B provided in the resonant pressure sensor of one or more embodiments, the impurity diffusion layer3dis formed in a periphery of the first resonator4in the support substrate3, but the impurity diffusion layer3dis not formed in a periphery of the second resonator5. This enables the pressure sensing unit10B to have a configuration wherein the impurity concentrations greatly differ between the first resonator4and the second resonator5.

It is generally known that a temperature coefficient of a resonance frequency of a resonator changes according to a concentration and type of an impurity included in the resonator, a crystal orientation of a material constituting the resonator, and a resonance mode of the resonator used in pressure measurement. In one or more embodiments, as above, the temperature coefficient of the resonance frequency of the second resonator5is made greater than the temperature coefficient of the resonance frequency of the first resonator4by setting the impurity concentrations [cm−3] at values that differ by at least one order of magnitude or more between the first resonator4and the second resonator5. That is, in one or more embodiments, when the resonant pressure sensor undergoes a temperature change, this signifies that the change amount of the resonance frequency of the second resonator5becomes greater than the change amount of the resonance frequency of the first resonator4. That is, because a temperature sensitivity of the second resonator5becomes higher than a temperature sensitivity of the first resonator4, in pressure measurement using the first resonator4, temperature correction according to temperature measurement using the second resonator5(temperature correction using the internal temperature calculated from the resonance frequencies in the two resonators (the first resonator4and the second resonator5)) can be performed with high precision. Therefore, temperature-correction precision in pressure measurement using the first resonator4is improved.

As one example, a situation is described wherein boron (B) is used as the impurity; in the support substrate3made of the single-crystal silicon material, a crystal orientation of a region wherein the first resonator4is disposed (material constituting the first resonator4) is the <110>direction and a normal direction of a wafer surface is the <100>direction; and fundamental oscillation at the fixed ends4a,4bis in a mode of in-plane oscillation in the wafer. In the above conditions, when the impurity concentration of the first resonator4is made to be about 1020(cm3) and the impurity concentration of the second resonator5is made to be about 1018(cm−3), the temperature coefficients of the resonance frequencies become about −10 (ppm/° C.) in the first resonator4and about −30 (ppm/° C.) in the second resonator5. That is, because the temperature sensitivity of the second resonator5becomes higher than the temperature sensitivity of the first resonator4, in pressure measurement using the first resonator4, temperature correction according to temperature measurement using the second resonator5can be performed with high precision. Therefore, temperature-correction precision in pressure measurement using the first resonator4is improved.

Furthermore, in one or more embodiments, although detailed illustration is omitted, a thickness dimension of the second resonator5along a thickness direction of the support substrate3is greater than a thickness dimension of the first resonator4. That is, a thickness dimension of the second resonator5in the stacking direction of the support substrate3—that is, the Z direction—is greater than the thickness dimension of the first resonator4. Adopting this configuration further increases measurement precision of the internal temperature by the second resonator5and also improves temperature-correction precision. As a result, measurement precision of pressure by the pressure sensing unit1is also increased.

The above configuration wherein the thickness dimension of the second resonator5is greater than the thickness dimension of the first resonator4is dependent on conditions of the manufacturing process described below.

For example, when introducing the impurity to the first resonator4at a high concentration as above, first, to prevent the impurity from being introduced in a region forming the second resonator5, a mask made of a thermal oxide film is formed on this region.

Next, an impurity diffusion source is formed on the first resonator4using a gas material or a coating glass material, and afterward, the impurity is introduced and diffused in the first resonator4under a high temperature of 1,000° C. or higher. Because this process of introducing and diffusing the impurity in the first resonator4under a high temperature is generally implemented while supplying oxygen, on a face whereon a silicon surface is exposed, the silicon is oxidized, forming a silicon oxide film.

As a result of the above process, the above thickness dimension of the first resonator4becomes smaller than an original thickness of the active layer. Meanwhile, the thickness dimension of the second resonator5becomes equal to the original thickness of the active layer. This causes the thickness dimension of the second resonator5to become greater than the thickness dimension of the first resonator4.

The “thickness dimension along a thickness direction of the support substrate (substrate portion)3” described in one or more embodiments is the stacking direction of the support substrate3and refers to a thickness direction in the Z direction in the diagrams.

Fifth Embodiment

The resonant pressure sensor of the fifth embodiment is detailed below while mainly referring toFIG. 11andFIG. 12.

In the description of the resonant pressure sensor of the fifth embodiment as well, configurations shared with the resonant pressure sensors of the first to fourth embodiments above are imparted the same reference signs in the diagrams, and detailed description thereof may be omitted.

Moreover, inFIG. 11andFIG. 12as well, like the resonant pressure sensors of the second to fourth embodiments illustrated inFIG. 6toFIG. 10, only a pressure sensing unit10C provided in the resonant pressure sensor of the fifth embodiment is illustrated, and illustration of the housing, the pressure-receiving fluid, and the like is omitted.

FIG. 11is a sectional view for briefly describing the pressure sensing unit10C provided in the resonant pressure sensor of the fifth embodiment, andFIG. 12is a plan view thereof.FIG. 11is a sectional view at line E-E inFIG. 12.

As illustrated inFIG. 11, in the resonant pressure sensor according to one or more embodiments, the pressure sensing unit10C, which has a base substrate (substrate portion)2A and a support substrate (support portion)3C, is further provided with the pedestal (fixed substrate (housing-fixed portion))53, whereto the base substrate2A is fixed.

Moreover, in the pressure sensing unit10C provided in the resonant pressure sensor according to one or more embodiments, the base substrate2A has a fixed portion (substrate-fixed portion)21, in at least one location or more, that is fixed to a surface53aof the pedestal53. It also has separated portions (substrate-separated portion)22,23that are separated from the pedestal53by a distance S in the Z direction and extend from the fixed portion21along the surface53a(direction intersecting the Z direction; for example, the X direction). In the illustrated example, the base substrate2A is configured as a cantilever structure wherein the fixed portion21is a support point and the separated portion22and the separated portion23are free ends.

Moreover, the resonant pressure sensor according to one or more embodiments is configured so the pressure-receiving fluid, whose illustration is omitted inFIG. 11, envelops the base substrate2A (separated portion22and separated portion23) while being interposed in the gap S between the pedestal53and the base substrate2A.

In the resonant pressure sensor according to one or more embodiments illustrated inFIG. 11andFIG. 12as well, like the resonant pressure sensor of the fourth embodiment illustrated inFIGS. 8 to 10, the impurity diffusion layer3dis formed in the periphery of the first resonator4in the support substrate3C. Meanwhile, the impurity diffusion layer3dis not formed in the periphery of the second resonator5.

According to the resonant pressure sensor of one or more embodiments, by adopting the above configuration wherein the base substrate2A includes the fixed portion21and the separated portions22,23, like the resonant pressure sensors described in the first to fourth embodiments, the resonance frequency of the first resonator4changes based on a strain arising according to a static pressure applied to the support substrate3C by the pressure-receiving fluid. This enables high linearity and excellent measurement precision to be obtained regardless of a magnitude of a static pressure applied by a liquid, gas, or the like that is a measurement target.

Meanwhile, as above, the resonant pressure sensor of one or more embodiments is configured so the base substrate2A has the separated portions22,23relative to the pedestal53. As such, the support substrate3C may be provided with a separated portion described in the first to fourth embodiments but does not need to be provided with such.FIG. 11illustrates a separated portion is also provided between the support substrate3C and the concave portion20aof the base substrate2A.

Like the base substrate and the support substrate, a material such as a single-crystal silicon wafer can be used as the pedestal53without any restrictions whatsoever.

In the resonant pressure sensor according to one or more embodiments, as in the illustrated example, it may be for at least one among a concave strain-isolating groove24and a strain-isolating hole25that penetrates the base substrate2A to be provided in at least a portion of the separated portions22,23in the base substrate2A. In the illustrated example, the concave strain-isolating groove24is disposed in one location of the separated portion22so as to be opened toward a pedestal53side, and the strain-isolating hole25is disposed in one location of the separated portion23.

In one or more embodiments, because the above strain-isolating groove24and strain-isolating hole25are provided in the base substrate2A, a strain that can be propagated from the pedestal53to the support substrate3C via the base substrate2A (separated portion22and separated portion23) and a strain that can be propagated in the base substrate2A are absorbed by the strain-isolating groove24or the strain-isolating hole25. This suppresses (reduces) a strain propagated from the pedestal53to the support substrate3C via the base substrate2A (separated portion22and separated portion23) and the strain that can be propagated in the base substrate2A. As such, an influence of these strain propagations that can become a factor in measurement error can be reduced, and the resonance frequencies of the first resonator4and the second resonator5indicate changes more reflective of the static pressure. Therefore, the above effect of obtaining high linearity and excellent measurement precision is more remarkably obtained.

Embodiments of the present invention are described above. However, these embodiments are illustrated as one example and do not limit the scope of the present invention. These embodiments can be implemented in other various forms and can be applied with various omissions, substitutions, and modifications within a scope that does not depart from the spirit of the invention. These embodiments and variations thereof are included in the scope and spirit of the invention and are likewise included in the invention stated in the scope of patent claims and scopes equivalent thereto.

For example, in the above embodiments, the separated portion in the support substrate or the base substrate has a so-called cantilever structure supported by the base substrate or the pedestal (fixed substrate) at one fixed portion, but the present invention is not limited thereto. For example, a configuration wherein the separated portion is supported at two or more fixed portions can also be adopted.

Furthermore, the configuration adopted in the resonant pressure sensor according to one or more embodiments—wherein the support substrate includes the separated portion having the gap between itself and the base substrate and a resonator is disposed in this separated portion—can also be applied in, for example, a resonant pressure sensor provided with a resonator having an H shape in a plan view (H-shaped resonator; for example, seeFIGS. 1A-1Bin non-patent literature 1 above). For example, actions and effects similar to those of the above embodiments can be obtained by providing, instead of a resonator described in the above embodiments, the above H-shaped resonator in spaces that are the separated portions32,32A,32B,32C in the support substrates3,3A,3B,3C and are vacuum-sealed by the shell6.

The resonant pressure sensor according to one or more embodiments has high linearity and excellent measurement precision regardless of a magnitude of a static pressure applied by a fluid or the like that is a measurement target. Therefore, the resonant pressure sensor according to one or more embodiments is particularly useful in a use wherein a high static pressure is applied. Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.