Patent ID: 12203824

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A sensor according to a preferred embodiment of the present invention includes a detector including an element substrate, a membrane including an outer surface, an inner surface on an opposite side of the outer surface, and a diaphragm, a side wall provided on the element substrate, the side wall supporting a portion of the inner surface of the membrane outside the diaphragm, and a fixed electrode provided on the element substrate while being surrounded by the side wall, the fixed electrode facing the inner surface of the membrane with a space therebetween, an electrostatic capacitance being generated between the fixed electrode and the diaphragm, in which a first recess portion is provided in the outer surface of the membrane between a center of the diaphragm and the side wall in the thickness direction of the membrane.

With such a configuration, it is possible to reduce or prevent changes in the detection sensitivity that are caused when the membrane of the sensor for detecting a force, such as pressure, is in a planar stress state.

For example, the first recess portion may be provided in the diaphragm along the side wall in the thickness direction.

For example, the first recess portion may have a linear shape extending continuously along the side wall in the thickness direction.

For example, the first recess portion may extend into a portion of the membrane supported by the side wall.

For example, a plurality of first recess portions may be provided to surround a center of the membrane in the thickness direction, the first recess portion being one of the plurality of first recess portions.

For example, a plurality of first recess portions may be provided symmetrically or substantially symmetrically with respect to the center of the membrane as a point of symmetry in the thickness direction, the first recess portion being one of the plurality of first recess portions.

For example, two first recess portions may be provided parallel or substantially parallel to each other to sandwich the center of the membrane in the thickness direction, the first recess portion being one of the two first recess portions.

For example, a first groove may be provided in a portion of a surface of the element substrate, the portion being in contact with the side wall.

For example, a second recess portion may be provided in a portion of the outer surface of the membrane, the portion overlapping the side wall in the thickness direction, and the second recess portion overlaps at least a portion of the first groove in the thickness direction.

For example, a second groove may be provided in the side wall and the second groove overlaps at least a portion of the first groove and overlaps at least a portion of the second recess portion in the thickness direction.

For example, the sensor may further include a package substrate on which the detector is mounted and a resin package provided on the package substrate, the resin package covering the detector, and the resin package may include an exposure hole through which a portion of the detector may be exposed to the outside.

Preferred embodiments of the present invention will be described below with reference to the drawings.

First Preferred Embodiment

FIG.1is a perspective view of a sensor according to a first preferred embodiment of the present invention.FIG.2is a sectional view of the sensor according to the first preferred embodiment of the present invention taken along line A-A inFIG.1.FIG.3is a sectional view of the sensor according to the first preferred embodiment of the present invention taken along line B-B inFIG.1.FIG.4is a top view of the sensor according to the first preferred embodiment of the present invention. The XYZ Cartesian coordinate system illustrated in the drawings is used to facilitate understanding of the present invention and does not limit the present invention.

As illustrated inFIGS.1to4, a sensor10includes a detector12, a package substrate14, and a resin package16. The sensor10is an electrostatic capacitance pressure sensor and can detect pressure by using the detector12. The detector12is mounted on the package substrate14. The resin package16is provided on the package substrate14and includes an exposure hole16a. The detector12is covered with the resin package16with a portion of the detector12exposed to the outside through the exposure hole16a.

FIG.5is an exploded perspective view of the detector of the sensor according to the first preferred embodiment of the present invention.

As illustrated inFIG.5, the detector12includes an element substrate20, a membrane22, a side wall24, and a fixed electrode26.

The element substrate20is, for example, a silicon substrate and includes terminals (not illustrated) electrically connected to the package substrate14.

The membrane22is a flexible thin plate member with a thickness of, for example, about 3.9 μm. The membrane22is conductive. In addition, the membrane22includes an outer surface22aand an inner surface22b. The pressure of a detection target acts on the outer surface22a. The inner surface22bis disposed on the opposite side of the outer surface22a. The membrane22includes a diaphragm22c. The diaphragm22cdeforms in a flexural manner when receiving pressure at the central portion thereof.

The side wall24is a frame provided on the element substrate20. The side wall24is rectangular or substantially rectangular in the thickness direction of the membrane22. The thickness direction of the membrane22is the Z-axis direction of the XYZ Cartesian coordinate system illustrated in the drawings. Accordingly, the thickness direction of the membrane22is the Z-axis direction. The side wall24is insulative. In addition, the side wall24supports the membrane22.

Specifically, the side wall24supports the portion of the inner surface22bof the membrane22outside the diaphragm22c. This enables the diaphragm22cto deform in a flexural manner in the thickness direction of the membrane22. In other words, the portion of the membrane22that is not supported by the side wall24is the diaphragm22c.

The fixed electrode26is provided on the element substrate20and is surrounded by the side wall24. The fixed electrode26is made of, for example, conductive polysilicon. In addition, the fixed electrode26faces the inner surface22bof the membrane22with a space therebetween. An electrostatic capacitance is generated between the fixed electrode26and the diaphragm22c.

As illustrated inFIGS.1to3, a portion of the outer surface22aof the membrane22, that is, the diaphragm22c, is exposed to the outside through the exposure hole16aof the resin package16. This causes pressure to act on the diaphragm22c.

When pressure acts on the portion of the outer surface22aof the membrane22exposed to the outside, the diaphragm22cdeforms in a flexural manner toward the fixed electrode26according to the pressure. This changes the distance between the diaphragm22cand the fixed electrode26and changes the absolute value of the electrostatic capacitance between the diaphragm22cand the fixed electrode26. The pressure acting on the outer surface22aof the membrane22can be detected in accordance with the change in the absolute value of the electrostatic capacitance.

In addition, in the first preferred embodiment, a plurality of recess portions22dare provided in the outer surface22aof the membrane22as illustrated inFIG.5. The recess portions22dare first recess portions. Specifically, as illustrated inFIG.4, the recess portions22dare provided between the center C of the diaphragm22cand the side wall24in the thickness direction of the membrane22. In the first preferred embodiment, the recess portion22dis a linear groove having a width of about 12 μm and a depth of about 0.8 μm, for example. The depth of the recess portion22dis preferably about half or less the thickness of the membrane22, more preferably about 25% or less thereof, to reduce or prevent rigidity of the membrane22from decreasing. In addition, the recess portion22dis provided in the diaphragm22cso as to extend continuously along the side wall24in the thickness direction of the membrane22. Furthermore, the recess portion22dextends to the longitudinal direction of the diaphragm22cin the thickness direction of the membrane22. The longitudinal direction of the diaphragm22cis the X-axis direction of the XYZ Cartesian coordinate system illustrated in the drawings. In the first preferred embodiment, the recess portions22dsurround the center C of the membrane22symmetrically with respect to the center C as the point of symmetry. That is, in the first preferred embodiment, the two recess portions22dare parallel or substantially parallel to each other at an equal or substantially equal distance from the center C to sandwich the center C.

It should be noted that the recess portions22dextend to the outside of the diaphragm22c, that is, the portion of the membrane22supported by the side wall24in the first preferred embodiment. Accordingly, even when the membrane22is provided at a position shifted from a desired position with respect to the side wall24, the recess portions22dare located within the region of the membrane22surrounded by the side wall24, that is, within the diaphragm22cin the thickness direction of the membrane22.

The recess portions22dreduce or prevent changes in the detection sensitivity that are caused when the membrane22is in the planar stress state. Specifically, as illustrated inFIGS.1to3, a compressive stress or a tensile stress in the planar direction of the membrane22is applied to the detector12due to the thermal expansion or thermal contraction of the resin package16, an external force acting on the resin package16, or the like. The planar direction of the membrane22is the X-axis direction and the Y-axis direction of the XYZ Cartesian coordinate system illustrated in the drawings. This puts the membrane22in the planar stress state. The planar stress state of the membrane22will be described with reference to the drawings.

FIG.6Ais a sectional view of a detector of a sensor according to a comparative example when the detector is in a natural state.FIG.6Bis a sectional view of the detector of the sensor according to the comparative example when a tensile stress is applied to the detector.FIG.6Cis a sectional view of the detector of the sensor according to the comparative example when a compressive stress is applied to the detector.FIG.7Ais a sectional view of a detector of a sensor according to an example of a preferred embodiment of the present invention when the detector is in the natural state.FIG.7Bis a sectional view of the detector of the sensor according to the example of a preferred embodiment of the present invention when a tensile stress is applied to the detector.FIG.7Cis a sectional view of the detector of the sensor according to the example of a preferred embodiment of the present invention when a compressive stress is applied to the detector. Here, the natural state is a state in which a compressive stress or a tensile stress in the planar direction of the membrane is not applied to the detector, that is, a state in which the membrane is not in the planar stress state.

As illustrated inFIGS.6A to6C, in the detector112of the sensor according to the comparative example, no recess portions are provided in the outer surface122aof the membrane122.

InFIG.6A, the dot-dash lines indicate the diaphragm122cwhen the pressure P does not act on the outer surface122aof the membrane122in the natural state, and the solid lines indicate the diaphragm122cwhen the pressure P acts on the outer surface122aof the membrane122in the natural state. As illustrated inFIG.6A, the diaphragm122cwhen the pressure P does not act on the outer surface122aof the membrane122in the natural state is flat or substantially flat. Alternatively, as illustrated inFIG.6A, the diaphragm122cwhen the pressure P acts on the outer surface122aof the membrane122in the natural state deforms in a flexural manner toward the fixed electrode126. As a result, the distance Δdn between the diaphragm122cand the fixed electrode126corresponds to the pressure P.

InFIG.6B, the dot-dot-dash lines indicate the diaphragm122cwhen the pressure P does not act on the outer surface122aof the membrane122with a tensile stress Ft in the planar direction of the membrane122applied to the detector112, that is, with the membrane122in the planar stress state due to the tensile stress Ft, and the solid lines indicate the diaphragm122cwhen the pressure P acts on the outer surface122aof the membrane122. As illustrated inFIG.6B, the diaphragm122cwhen the pressure P does not act on the outer surface122aof the membrane122with the membrane122in the planar stress state due to the tensile stress Ft is flat or substantially flat.

As illustrated inFIG.6B, the diaphragm122cwhen pressure P acts on the outer surface122aof the membrane122with the membrane122in the planar stress state due to the tensile stress Ft deforms in a flexural manner toward the fixed electrode126. However, the amount of deformation of the diaphragm122cis smaller than in the natural state illustrated inFIG.6A. As a result, the distance Δdt between the diaphragm122cand the fixed electrode126is larger than the distance Δdn in the natural state illustrated inFIG.6Aeven though the same or substantially the same pressure P acts on the membrane122.

That is, when the tensile stress Ft in the planar direction of the membrane122is applied to the detector112, the deformation rigidity in the thickness direction of the membrane122is larger than in the natural state, and the membrane122is not easily deformed in the thickness direction.

InFIG.6C, the dot-dot-dash lines indicate the diaphragm122cwhen the pressure P does not act on the outer surface122aof the membrane122with the compressive stress Fc in the planar direction of the membrane122applied to the detector112, that is, with the membrane122in the planar stress state due to the compressive stress Fc, and the solid lines indicate the diaphragm122cwhen the pressure P acts on the outer surface122aof the membrane122. As illustrated inFIG.6C, the diaphragm122cwhen the pressure P does not act on the outer surface122aof the membrane122with the membrane122in the planar stress state due to the compressive stress Fc is flat or substantially flat.

As illustrated inFIG.6C, the diaphragm122cwhen the pressure P acts on the outer surface122aof the membrane122with the membrane122in the planar stress state due to the compressive stress Fc deforms in a flexural manner toward the fixed electrode126. However, the amount of deformation of the diaphragm122cis larger than in the natural state illustrated inFIG.6A. As a result, even though the same or substantially the same pressure P acts on the membrane122, the distance Δdc between the diaphragm122cand the fixed electrode126is smaller than the distance Δdn in the natural state illustrated inFIG.6A.

That is, when the compressive stress Fc in the planar direction of the membrane122is applied to the detector112, the deformation rigidity in the thickness direction of the membrane122is smaller than in the natural state, and the membrane122is easily deformed in the thickness direction.

An increase or decrease in the deformation rigidity in the thickness direction of the membrane122as described above when the tensile stress or the compressive stress is applied to the membrane122in the planar direction of the membrane122, that is, when the membrane122is put in the planar stress state, is referred to as the stress-stiffening effect.

As illustrated inFIGS.6A to6C, in the detector112of the sensor according to the comparative example, the distance between the diaphragm122cand the fixed electrode126differs depending on whether the detector112is the natural state or the membrane122is in the planar stress state even though the same or substantially the same pressure P acts on the membrane122. In addition, even when the membrane122is in the planar stress state, the distance between the diaphragm122cand the fixed electrode126differs depending on whether the stress to be applied is a tensile stress or a compressive stress, that is, depending on the direction of the stress generated in the membrane122. As described above, in the detector112of the sensor according to the comparative example, the detection sensitivity when the membrane122is in the planar stress state changes from the detection sensitivity when the membrane122is in the natural state.

Since the plurality of recess portions22dare provided in the diaphragm22cin the first preferred embodiment, changes in the detection sensitivity are reduced or prevented even when the membrane22is in the planar stress state. This will be described with reference toFIGS.7A to7C.

InFIG.7A, the dot-dash lines indicate the diaphragm22cwhen the pressure P does not act on the outer surface22aof the membrane22in the natural state, and the solid lines indicate the diaphragm22cwhen the pressure P acts on the outer surface22aof the membrane22in the natural state. As illustrated inFIG.7A, the diaphragm22cwhen the pressure P does not act on the outer surface22aof the membrane22in the natural state is flat or substantially flat. In addition, as illustrated inFIG.7A, the diaphragm22cwhen the pressure P acts on the outer surface22aof the membrane22in the natural state deforms in a flexural manner toward the fixed electrode26. As a result, the distance Δdn between the diaphragm22cand the fixed electrode26corresponds to the pressure P.

InFIG.7B, the dot-dot-dash lines indicate the diaphragm122cwhen the pressure P does not act on the outer surface122aof the membrane122with the tensile stress Ft in the planar direction of the membrane22applied to the detector112, that is, with the membrane22in the planar stress state due to the tensile stress Ft, and the solid lines indicate the diaphragm122cwhen the pressure P acts on the outer surface122aof the membrane122. As illustrated inFIG.7B, the diaphragm22cwhen the pressure P does not act on the outer surface22aof the membrane22with the membrane22in the planar stress state due to the tensile stress Ft deforms slightly in a flexural manner toward the fixed electrode26. This flexural deformation is caused by the difference between the distribution of the tensile stress on the outer surface22aof the membrane22and the distribution of the tensile stress on the inner surface22b.

Specifically, the tensile stress generated in the region of the outer surface22asandwiched between the plurality of recess portions22dis smaller than the tensile stress generated in the region of the inner surface22bon the opposite side of the region of the outer surface22a.

Accordingly, the membrane22is distorted such that the region of the inner surface22bis distorted more than the region of the inner surface22b. As a result, the diaphragm22cdeforms slightly in a flexural manner such that the inner surface22bprojects.

The diaphragm22cdeforms slightly in a flexural manner such that the inner surface22bprojects as described above, thus increasing the absolute value of the electrostatic capacitance between the diaphragm22cand the fixed electrode26. In addition, the diaphragm22cdeforms easily in a flexural manner toward the fixed electrode26.

The diaphragm22cwhen the pressure P acts on the outer surface22aof the membrane22with the membrane22in the planar stress state due to the tensile stress Ft as illustrated inFIG.7Bdeforms in a flexural manner toward the fixed electrode26as in the natural state illustrated inFIG.7A. The amount of deformation of the diaphragm22cis the same or almost the same as in the natural state illustrated inFIG.7A. When the sectional shape, the width, the depth, and the like of the recess portion22dare appropriate as described above, the distance Δdt between the diaphragm22cand the fixed electrode26when the same or substantially the same pressure P acts on the membrane22is the same or substantially the same as the distance Δdn in the natural state illustrated inFIG.7A.

InFIG.7C, the dot-dot-dash lines indicate the diaphragm22cwhen the pressure P does not act on the outer surface22aof the membrane22with the compressive stress Fc in the planar direction of the membrane22applied to the detector112, that is, with the membrane22in the planar stress state due to the compressive stress Fc, and the solid lines indicate the diaphragm22cwhen the pressure P acts on the outer surface22aof the membrane22. As illustrated inFIG.6C, the diaphragm22cwhen the pressure P does not act on the outer surface22aof the membrane22with the membrane22in the planar stress state due to the compressive stress Fc deforms slightly in a flexural manner to the opposite side of the fixed electrode26, that is, the outer side. This flexural deformation is caused by the difference between the distribution of the compressive stress on the outer surface22aof the membrane22and the distribution of the compressive stress on the inner surface22bof the membrane22.

Specifically, the compressive stress generated in the region of the outer surface22asandwiched between the plurality of recess portions22dis smaller than the compressive stress generated in the region of the inner surface22bon the opposite side of the region of the outer surface22a. Accordingly, the region of the inner surface22bis distorted in the direction in which the region of the inner surface22bshrinks more than the region of the outer surface22a. As a result, the diaphragm22cdeforms slightly in a flexural manner such that the inner surface22bbecomes recessed.

The diaphragm22cdeforms slightly in a flexural manner such that the inner surface22bbecomes recessed as described above, thus reducing the absolute value of the electrostatic capacitance between the diaphragm22cand the fixed electrode26. In addition, the diaphragm22cdoes not easily deform in a flexural manner toward the fixed electrode26.

As illustrated inFIG.7C, the diaphragm22cwhen the pressure P acts on the outer surface22aof the membrane22with the membrane22in the planar stress state due to the compressive stress Fc deforms in a flexural manner toward the fixed electrode26as in the natural state illustrated inFIG.7A. The amount of deformation of the diaphragm22cis the same or substantially the same as in the natural state illustrated inFIG.7A. When the sectional shape, the width, the depth, and the like of the recess portion22dare appropriate as described above, the distance Δdc between the diaphragm22cand the fixed electrode26when the same or substantially the same pressure P acts on the membrane22is the same or substantially the same as the distance Δdn in the natural state illustrated inFIG.7A.

Since the recess portions22dare provided in the outer surface22aof the membrane22as illustrated inFIGS.7A to7C, the distance between the diaphragm22cand the fixed electrode26is the same or substantially the same when the same pressure P acts on the membrane22regardless of whether the detector is in the natural state or the membrane22is in the planar stress state and regardless of whether the tensile stress or the compressive stress is applied, that is, regardless of the direction of the stress generated in the membrane22even if the membrane22is in the planar stress state. That is, in the detector12of the sensor10according to the first preferred embodiment, even when the membrane22is in the planar stress state, the detection sensitivity in the natural state hardly changes, and changes in the detection sensitivity can be reduced or prevented.

The secondary advantageous effect is that the diaphragm22cis locally thinned and deforms easily because the recess portions22dare provided in the outer surface22aof the membrane22. As a result, the detection sensitivity increases, and noise in the signal output from the sensor10is reduced.

According to the first preferred embodiment as described above, it is possible to reduce or prevent changes in the detection sensitivity that are caused when the membrane22of the sensor10for detecting pressure is in the planar stress state.

Second Preferred Embodiment

A second preferred embodiment of the present invention is a modification of the first preferred embodiment described above. Accordingly, a sensor according to the second preferred embodiment will be described focusing on the differences from the first preferred embodiment described above.

FIG.8is a top view of a detector of the sensor according to the second preferred embodiment of the present invention.FIG.9is a sectional view of the detector of the sensor according to the second preferred embodiment of the present invention taken along line C-C inFIG.8.

As illustrated inFIGS.8and9, in a detector212of the sensor according to the second preferred embodiment, a plurality of grooves220aare provided in an element substrate220. The grooves220aare provided in portions of the surface of the element substrate220that are in contact with a side wall224to surround a fixed electrode226. The grooves220aare first grooves.

In addition, in the second preferred embodiment, a plurality of recess portions222ein addition to a plurality of recess portions222dare provided in an outer surface222aof a membrane222. The recess portions222dare the first recess portions and the recess portions222eare second recess portions.

Specifically, as illustrated inFIG.8, the recess portions222eare provided in the portions of the membrane222around the diaphragm222c, that is, the portions of the membrane222that overlap the side wall224in the thickness direction of the membrane222. The thickness direction of the membrane222is the Z-axis direction of the XYZ Cartesian coordinate system illustrated in the drawings. Accordingly, the thickness direction view of the membrane222is the Z-axis direction view. Furthermore, the recess portions222eoverlap at least portions of the grooves220ain the thickness direction of the membrane222.

Furthermore, as illustrated inFIG.9, a plurality of grooves224aare provided in the side wall224in the second preferred embodiment. The grooves224apenetrate through the side wall224in the thickness direction of the membrane222. The grooves224aoverlap at least portions of the grooves220aand overlap at least portions of the recess portions222ein the thickness direction of the membrane222. The grooves224aare the second grooves.

As illustrated inFIG.8, the grooves220a, the recess portions222e, and the grooves224asurround the diaphragm222cin the thickness direction of the membrane222. Accordingly, the grooves220a, the recess portions222e, and the grooves224adefine and function as dampers that reduce a force transmitted to the diaphragm222cby absorbing a compressive stress or a tensile stress in the planar direction of the membrane222when the compressive stress or the tensile stress is applied to the detector12. As a result, the stress generated in the diaphragm222cis reduced, and changes in the detection sensitivity are further reduced or prevented even when the membrane222is in the planar stress state. The planar direction of the membrane222is the X-axis direction and the Y-axis direction of the XYZ Cartesian coordinate system illustrated in the drawings.

The element substrate220may be thickened to further reduce the stress generated in the diaphragm222c. Accordingly, the element substrate220can have rigidity against a compressive stress or a tensile stress in the planar direction. As a result, the stress generated in the diaphragm222cis further reduced.

In addition, the grooves220a, the recess portions222e, and the grooves224amay be, for example, annular in the thickness direction of the membrane222. That is, the numbers and the shapes of the grooves220a, the recess portions222e, and the grooves224aare not limited as long as the grooves220a, the recess portions222e, and grooves224aare provided at positions on the outer side of the diaphragm222cin the thickness direction of the membrane222.

According to the second preferred embodiment described above, it is possible to reduce or prevent changes in the detection sensitivity that are caused when the membrane222of the sensor for detecting pressure is in the planar stress state as in the first preferred embodiment described above.

Preferred embodiments of the present invention have been described above, but preferred embodiments of the present invention are not limited to these preferred embodiments.

For example, in the first preferred embodiment described above, the two recess portions22dare parallel or substantially parallel to each other at an equal or substantially equal distance from the center C of the membrane22as illustrated inFIG.4. However, the preferred embodiments of the present invention are not limited to this example. Recess portions provided in the membrane can be arranged in various configurations.

FIG.10is a top view of a detector of a sensor according to a third preferred embodiment of the present invention.FIG.11is a top view of a detector of a sensor according to a fourth preferred embodiment of the present invention.FIG.12is a top view of a detector of a sensor according to a fifth preferred embodiment of the present invention.FIG.13is a top view of a detector of a sensor according to a sixth preferred embodiment of the present invention.FIG.14is a top view of a detector of a sensor according to a seventh preferred embodiment of the present invention.

As illustrated inFIG.10, in a detector312of the sensor according to the third preferred embodiment of the present invention, two recess portions322dand two recess portions322fare provided in an outer surface322aof a membrane322. Specifically, as illustrated inFIG.10, the recess portions322dand322fare provided between the center C of the diaphragm322cand the side wall324in the thickness direction of the membrane322. The recess portions322dand322fare provided in the diaphragm322calong the side wall324in the thickness direction of the membrane322. The recess portions322dand322fsurround the center C of the membrane322. The recess portions322dand322fare first recess portions.

The recess portions322dextend in the longitudinal direction of the diaphragm322cin the thickness direction of the membrane322. The longitudinal direction of the diaphragm322cis the X-axis direction of the XYZ Cartesian coordinate system illustrated in the drawing. The recess portions322dextend to the outer side portion of the diaphragm322c, that is, the portion of the membrane322supported by the side wall324. The recess portions322dare provided symmetrically or substantially symmetrically with respect to the center C as the point of symmetry. That is, the two recess portions322dare parallel or substantially parallel to each other at an equal or substantially equal distance from the center C.

The recess portions322fextend in the transverse direction of the diaphragm322cin the thickness direction of the membrane322. The transverse direction of the diaphragm322cis the Y-axis direction of the XYZ Cartesian coordinate system illustrated in the drawing. The recess portions322fare provided symmetrically or substantially symmetrically with respect to the center C as the point of symmetry. That is, the two recess portions322fare parallel or substantially parallel to each other at an equal or substantially equal distance from the center C.

As illustrated inFIG.11, in a detector412of the sensor according to the fourth preferred embodiment of the present invention, two recess portions422dare provided in an outer surface422aof a membrane422. The entire or substantially the entire recess portions422dare located within the diaphragm422c.

As illustrated inFIG.12, in a detector512of the sensor according to the fifth preferred embodiment of the present invention, two recess portions522dand two recess portions522fare provided in an outer surface522aof a membrane522. Specifically, as illustrated inFIG.12, the recess portions522dand522fare provided between the center C of the diaphragm522cand the side wall524in the thickness direction of the membrane522. The recess portions522dand522fare provided in the diaphragm522calong the side wall524in the thickness direction of the membrane522. The recess portions522dand522fsurround the center C of the membrane522. The recess portions522dand522fare first recess portions. The entire or substantially the entire recess portions522dand522fare located within the diaphragm522c.

The recess portions522dextend in the longitudinal direction of the diaphragm522cin the thickness direction of the membrane522. The longitudinal direction of the diaphragm522cis the X-axis direction of the XYZ Cartesian coordinate system illustrated in the drawing. The recess portions522dare provided symmetrically or substantially symmetrically with respect to the center C as the point of symmetry. That is, the two recess portions322dare parallel or substantially parallel to each other at an equal distance from the center C.

The recess portions522fextend in the transverse direction of the diaphragm522cin the thickness direction of the membrane522. The transverse direction of the diaphragm522cis the Y-axis direction of the XYZ Cartesian coordinate system illustrated in the drawing. The recess portions522fare provided symmetrically or substantially symmetrically with respect to the center C as the point of symmetry. That is, the two recess portions522fare parallel or substantially parallel to each other at an equal or substantially equal distance from the center C.

As illustrated inFIG.13, in a detector612of the sensor according to the sixth preferred embodiment of the present invention, four recess portions622dand two recess portions622fare provided in an outer surface622aof a membrane622. Specifically, as illustrated inFIG.13, the recess portions622dand622fare provided between the center C of the diaphragm622cand the side wall624in the thickness direction of the membrane622. The recess portions622dand622fare provided in the diaphragm622calong the side wall624in the thickness direction of the membrane622. The recess portions622dand622fsurround the center C of the membrane622. The recess portions622dand622fare first recess portions. The entire or substantially the entire recess portions622dand622fare located within the diaphragm622c.

The recess portions622dextend in the longitudinal direction of the diaphragm622cin the thickness direction of the membrane622. The longitudinal direction of the diaphragm622cis the X-axis direction of the XYZ Cartesian coordinate system illustrated in the drawing. The recess portions622dare provided symmetrically or substantially symmetrically with respect to the center C as the point of symmetry. That is, the four recess portions622dare parallel or substantially parallel to each other at an equal or substantially equal distance from the center C.

The recess portions622fextend in the transverse direction of the diaphragm622cin the thickness direction of the membrane622. The transverse direction of the diaphragm622cis the Y-axis direction of the XYZ Cartesian coordinate system illustrated in the drawing. The recess portions622fare provided symmetrically or substantially symmetrically with respect to the center C as the point of symmetry. That is, the two recess portions622fare parallel or substantially parallel to each other at an equal or substantially equal distance from the center C.

As illustrated inFIG.14, in a detector712of the sensor according to the seventh preferred embodiment of the present invention, a recess portion722dis provided in an outer surface722aof a membrane722. Specifically, as illustrated inFIG.14, the recess portion722dis provided between the center C of a diaphragm722cand a side wall724in the thickness direction of the membrane722. The recess portion722dis provided in the diaphragm722calong the side wall724in the thickness direction of the membrane722. The recess portion722dis annular in the thickness direction of the membrane722and surrounds the center C of the membrane722. The recess portion722dis a first recess portion. The entire or substantially the entire recess portion722dis located within the diaphragm722c.

That is, in the present preferred embodiment of the present invention, the first recess portion is provided in a portion of the outer surface between the center of the diaphragm and the side wall in the thickness direction of the membrane.

In addition, preferably, the first recess portion is provided in a portion close to the side wall, that is, provided along the side wall in the thickness direction of the membrane, instead of a portion close to the center of the diaphragm. This can efficiently reduce or prevent changes in the detection sensitivity that are caused when the membrane is in the planar stress state. In contrast, when the first recess portion is disposed in a portion close to the center, the difference between the stress distribution on the outer surface of the diaphragm and the stress distribution on the inner surface of the diaphragm of the membrane in the planar stress state decreases and the effect of the first recess portion is reduced.

More preferably, a plurality of first recess portions are provided to surround the center of the membrane in the thickness direction of the membrane. This enables the diaphragm to deform in a flexural manner into a shape symmetrical or substantially symmetrical with respect to the center thereof.

Still more preferably, a plurality of first recess portions are provided symmetrically or substantially symmetrically with respect to the center of the membrane as the point of symmetry in the thickness direction of the membrane. This enables the diaphragm to deform in a flexural manner into a shape more symmetrical with respect to the center thereof.

In addition, for example, in the first preferred embodiment described above, the sensor10is an electrostatic capacitance pressure sensor. However, the preferred embodiments of the present invention are not limited to this example. For example, the sensor may be a piezo resistance pressure sensor with an electrical resistance that changes when the membrane deforms when receiving pressure. In addition, the sensor is not limited to a sensor that detect pressure, but may be a sensor that detects the vibration and force applied to the membrane based on the amount of deformation of the membrane, such as, for example, a differential pressure sensor or a force sensor.

In addition, in the first preferred embodiment described above, the detector12is covered with the resin package16as illustrated inFIG.1. However, preferred embodiments of the present invention are not limited to this example. The sensor according to the present invention only needs to have a structure in which a tensile stress or a compressive stress in the planar direction of the membrane can act on the detector.

That is, in a broad sense, a sensor according to a preferred embodiment of the present invention includes the detector including the element substrate, the membrane including the outer surface, the inner surface on the opposite side of the outer surface, and the diaphragm, and the side wall, provided on the element substrate, that supports a portion of the inner surface of the membrane outside the diaphragm, in which the first recess portion is provided in the outer surface of the membrane between the center of the diaphragm and the side wall in the thickness direction of the membrane.

Preferred embodiments of the present invention have been described above, but it is apparent for those skilled in the art that other preferred embodiments of the present invention can be obtained by entirely or partially combining preferred embodiments with at least one other preferred embodiment.

Preferred embodiments of the present invention are applicable to sensors that each detect pressure or the like.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.