JP2018049037A - Pressure sensor, microphone, ultrasonic sensor, blood pressure sensor, and touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-sensitive pressure sensor.SOLUTION: A pressure sensor in one embodiment includes: a support part; a film part; and a magnetic resistance element. The film part is supported by the support part, is flexible, and includes a first area and a second area having rigidity lower than that of the first area. The magnetic resistance element is provided on the film part, and includes: a first magnetic layer; a second magnetic layer; and a spacer layer disposed between the first magnetic layer and the second magnetic layer.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a pressure sensor, a microphone, an ultrasonic sensor, a blood pressure sensor, and a touch panel.

  Examples of pressure sensors using MEMS (Micro Electro Mechanical Systems) technology include a piezoelectric type, a piezoresistive type, and a capacitance type. On the other hand, pressure sensors using a spin technique have been proposed that have different detection principles from these types of pressure sensors. In a pressure sensor using a spin technique, a resistance change corresponding to an anisotropic strain caused by an external pressure is detected by a spin valve strain element (also referred to as a magnetoresistive element or an MR element). In a pressure sensor using a spin technique, an improvement in sensitivity is desired.

Patrick R. Scheeper et al., “The Design, Fabrication, and Testing of Corrugated Silicon Nitride Diaphragms”, Journal of Microelectromechanical Systems, Vol.3, No.1, March 1994, p.36-42

  The problem to be solved by the present invention is to provide a highly sensitive pressure sensor, microphone, ultrasonic sensor, blood pressure sensor, and touch panel.

  A pressure sensor according to an embodiment includes a support part, a film part, and a magnetoresistive element. The film part is supported by the support part and has flexibility, and includes a first region and a second region having rigidity lower than that of the first region. The magnetoresistive element includes a first magnetic layer, a second magnetic layer, and a spacer layer disposed between the first magnetic layer and the second magnetic layer.

The perspective view which shows the pressure sensor which concerns on 1st Embodiment. The top view which shows the pressure sensor which concerns on 1st Embodiment. Sectional drawing of the pressure sensor which concerns on 1st Embodiment. FIG. 3 is a partial cross-sectional view showing a first structural example of the diaphragm shown in FIG. 2. The fragmentary sectional view which shows the 2nd structural example of the diaphragm shown in FIG. The fragmentary sectional view which shows the 3rd structural example of the diaphragm shown in FIG. The perspective view which shows the magnetoresistive element shown in FIG. The top view which shows the pressure sensor which concerns on the 1st example of 2nd Embodiment. The top view which shows the pressure sensor which concerns on the 2nd example of 2nd Embodiment. The top view which shows the pressure sensor which concerns on 3rd Embodiment. FIG. 4 is a partial cross-sectional view showing a first structural example of the diaphragm shown in FIG. 3. FIG. 4 is a partial cross-sectional view showing a second structure example of the diaphragm shown in FIG. 3. FIG. 4 is a partial cross-sectional view showing a third structure example of the diaphragm shown in FIG. 3. The top view which shows the pressure sensor which concerns on 4th Embodiment. The top view which shows the pressure sensor which concerns on 5th Embodiment. The top view which shows the pressure sensor which concerns on 6th Embodiment. The top view which shows the pressure sensor which concerns on 7th Embodiment. Sectional drawing which shows the microphone which concerns on 8th Embodiment. The front view which shows the portable information terminal with which the microphone shown in FIG. 14 was integrated. Sectional drawing which shows the blood pressure sensor which concerns on 9th Embodiment. The block diagram which shows the touchscreen which concerns on 10th Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. Embodiments relate to a pressure sensor using MEMS (Micro Electro Mechanical Systems) technology, and a microphone, an ultrasonic sensor, a blood pressure sensor, and a touch panel using the pressure sensor. Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings. In the following embodiments, the same components are denoted by the same reference numerals, and repeated description is omitted as appropriate.

(First embodiment)
1 and 2 are a perspective view and a top view schematically showing a pressure sensor according to the first embodiment. FIG. 3 schematically shows a cross section of the pressure sensor obtained along the line III-III ′ shown in FIG. In FIGS. 1, 2 and 3, the insulating portion and the conductive portion are omitted for easy understanding of the drawings. The pressure sensor shown in FIG. 1 includes a resin substrate 11 and a MEMS chip 20 attached on the resin substrate 11. The MEMS chip 20 is bonded and fixed to the resin substrate 11 using an adhesive (die bond material) such as a thermosetting resin.

  The MEMS chip 20 includes a support portion 21 provided on the resin substrate 11, a diaphragm 22 as a flexible film portion supported by the support portion 21, and a magnetoresistive element 23 provided on the diaphragm 22. And including. The diaphragm 22 bends when an external pressure is applied, and causes the magnetoresistive element 23 provided thereon to be distorted. The external pressure can be, for example, pressure due to pressing, sound waves, ultrasonic waves, or the like. The electric resistance of the magnetoresistive element 23 changes according to the magnitude of the distortion generated in the magnetoresistive element 23. The pressure sensor according to the present embodiment can sense an external pressure by detecting a change in electrical resistance.

  Although FIG. 1 shows an example in which six magnetoresistive elements 23 are provided, the number of magnetoresistive elements 23 is not limited to six and may be one, or 2 to 5 or 7 It may be the above.

  The support unit 21 is, for example, a silicon (Si) substrate. The support portion 21 is formed in, for example, a rectangular tube shape having the cavity portion 26 shown in FIG. The cavity 26 is opened in two surfaces facing each other. One of these two surfaces is an adhesive surface with the resin substrate 11, and the diaphragm 22 is fixed to the end portion on the other surface side. The cavity 26 is sealed by the resin substrate 11 and the diaphragm 22. The cavity 26 may be filled with a gas such as air or an inert gas, or may be vacuumed by being decompressed, or may be filled with a liquid. The shape of the support portion 21 is not limited to the shape described above, and may be any other shape as long as the diaphragm 22 can be supported so that the diaphragm 22 can be bent by an external pressure.

  The diaphragm 22 is formed of a thin film such as an amorphous silicon (a-Si) film, a silicon oxide (SiOx) film, an aluminum oxide (AlOx) film, or a silicon nitride (SiN) film. The thin film forming the diaphragm 22 may be continuously formed outside the portion bent by the external pressure. Here, a portion of the thin film that is bent by an external pressure is called a diaphragm (film portion). The film part is a thin film region processed thinly.

  The change in the electrical resistance of the magnetoresistive element 23 increases as the strain generated in the magnetoresistive element 23 (more specifically, the anisotropic strain that is the difference between the maximum main strain and the minimum main strain) increases. For this reason, in order to increase the sensitivity of the pressure sensor, the diaphragm 22 may be formed so that a larger strain is generated with respect to the external pressure. That is, from the viewpoint of increasing the sensitivity of the pressure sensor, the bending rigidity of the diaphragm 22 is preferably low. For example, the spring constant k of the circular diaphragm is expressed by the following formula (1).

  Where E is the Young's modulus of the diaphragm, h is the thickness of the diaphragm, a is the diameter of the diaphragm, and ν is the Poisson's ratio. Further, σ represents a film stress, and takes a positive value when the film stress is a tensile stress and takes a negative value when the film stress is a compressive stress. According to equation (1), the bending stiffness of the diaphragm increases when the diaphragm membrane stress is tensile, and decreases when it is compressed. Therefore, in order to increase the sensitivity of the pressure sensor, it is necessary to reduce the film stress. However, when excessive compressive stress is generated as the membrane stress of the diaphragm, wrinkles due to buckling are formed in the diaphragm. In this case, an appropriate strain cannot be applied to the magnetoresistive element provided on the diaphragm.

  In the pressure sensor according to this embodiment and other embodiments described later, a low rigidity region is provided in a part of the diaphragm 22. Specifically, as shown in FIG. 2, the diaphragm 22 includes a first region 22A and a second region 22B having rigidity lower than that of the first region 22A. The second area 22B corresponds to the low rigidity area. In this embodiment and other embodiments to be described later, by providing the low rigidity region in a part of the diaphragm 22, the compressive stress generated in the diaphragm 22 is partially relieved. Thereby, generation | occurrence | production of wrinkles in the diaphragm 22 can be suppressed. As a result, the membrane stress of the diaphragm 22 can be further reduced in order to increase the sensitivity of the pressure sensor.

  In the present embodiment, the diaphragm 22 is formed in a rectangular shape, the second region 22B is located at both ends on the short side, and the first region 22A is a region sandwiched between the second regions 22B. The first region 22 </ b> A includes both end portions and a center portion on the long side of the diaphragm 22. The magnetoresistive element 23 is disposed on a part of the first region 22A. That is, the position of the magnetoresistive element 23 is different from the position of the second region 22B, which is the low rigidity region. In the example shown in FIG. 2, three magnetoresistive elements 23 are arranged at both ends on the long side. The diaphragm 22 is fixed to the support portion 21 at the periphery (two long sides and two short sides). In the rectangular diaphragm 22, an anisotropic strain is generated at the end portion on the long side, which is larger than the end portion or the center portion on the short side. Therefore, it is preferable to dispose the magnetoresistive element 23 at the end portion on the long side of the diaphragm 22.

With reference to FIG. 4A, FIG. 4B, and FIG. 4C, the structural example of the diaphragm 22 which concerns on this embodiment is demonstrated.
FIG. 4A is a partial cross-sectional view of the pressure sensor along the line IV-IV ′ shown in FIG. 2, and schematically shows a first structural example of the diaphragm 22. In the first structure example shown in FIG. 4A, the thickness of the second region 22B is smaller than the thickness of the first region 22A. That is, the diaphragm 22 is formed to be thinner in the second region 22B than in the first region 22A. FIG. 4B is a partial cross-sectional view of the pressure sensor along the line IV-IV ′ shown in FIG. 2, and schematically shows a second structure example of the diaphragm 22. In the second structure example shown in FIG. 4B, the diaphragm 22 in the first region 22A is formed flat, and the diaphragm 22 in the second region 22B is formed in a corrugated shape. FIG. 4C is a partial cross-sectional view of the pressure sensor along the line IV-IV ′ shown in FIG. 2 and schematically shows a third structure example of the diaphragm 22. In the third structure example shown in FIG. 4C, the Young's modulus of the second region 22B is lower than the Young's modulus of the first region 22A. Specifically, the second region 22B is formed of a material having a lower Young's modulus than the material of the first region 22A.

  In addition, the method of providing the low rigidity region in the diaphragm 22 is not limited to the three structural examples described above, and two or more of these three structural examples may be used in combination, or other structures may be used. Good.

  FIG. 5 schematically shows one of the six magnetoresistive elements 23 shown in FIG. The remaining five of the magnetoresistive elements 23 shown in FIG. 1 may have the same structure as the magnetoresistive element 23 shown in FIG. In FIG. 5, a part of the magnetoresistive element 23 is shown. As shown in FIG. 5, the magnetoresistive element 23 includes a first magnetic layer 51, a second magnetic layer 53, and an intermediate layer (spacer layer) disposed between the first magnetic layer 51 and the second magnetic layer 53. 52). At least one of the first magnetic layer 51 and the second magnetic layer 53 is a magnetization free layer whose magnetization direction is variable. In the present embodiment, the first magnetic layer 51 is a magnetization free layer, and the second magnetic layer 53 is a magnetization fixed layer whose magnetization direction is fixed. The intermediate layer 52 is a nonmagnetic layer.

  The operation in which the magnetoresistive element 23 functions as a strain sensor is based on the application of the “inverse magnetostriction effect” and the “magnetoresistance (MR) effect”. The inverse magnetostrictive effect is obtained in the ferromagnetic layer used for the magnetization free layer. The MR effect is manifested in a laminated film in which a magnetization free layer, an intermediate layer, and a reference layer (for example, a magnetization fixed layer) are laminated.

  The inverse magnetostriction effect is a phenomenon in which the magnetization direction of a ferromagnetic material changes due to strain generated in the ferromagnetic material. That is, when an external strain is applied to the laminated film of the magnetoresistive element 23, the magnetization direction of the magnetization free layer changes. As a result, the relative angle between the magnetization direction of the magnetization free layer and the magnetization direction of the reference layer changes. At this time, a change in electrical resistance is caused by the MR effect. The MR effect includes, for example, a GMR (Giant magnetoresistance) effect or a TMR (Tunneling magnetoresistance) effect. The MR effect is manifested by passing a current through the laminated film. By passing a current through the laminated film, a change in the relative angle of the magnetization direction can be read as a change in electrical resistance. For example, distortion occurs in the laminated film (the magnetoresistive element 23), and the magnetization direction of the magnetization free layer changes due to this distortion, and the relative angle between the magnetization direction of the magnetization free layer and the magnetization direction of the reference layer changes. That is, the MR effect is manifested by the inverse magnetostrictive effect.

The magnetic layer used for the magnetization fixed layer directly contributes to the MR effect. For the second magnetic layer 53 which is a magnetization fixed layer, for example, a Co—Fe—B alloy is used. Specifically, the second magnetic layer _{53, (Co x Fe 100-} x) 100-y B y alloys (x is a 0 atomic.% Or more 100 atomic.% Or less, y is 0 atomic.% Or more 30 at. % Or less.) Can be used. For the second magnetic layer 53, for example, other materials such as an Fe—Co alloy may be used.

For example, the intermediate layer 52 breaks the magnetic coupling between the first magnetic layer 51 and the second magnetic layer 53. For the intermediate layer 52, for example, a metal, an insulator, or a semiconductor is used. For example, Cu, Au, or Ag can be used as the metal. Examples of the insulator or semiconductor include magnesium oxide (such as MgO), aluminum oxide (such as Al ₂ O ₃ ), titanium oxide (such as TiO), zinc oxide (such as ZnO), or gallium oxide (Ga). -O) and the like can be used. As the intermediate layer 52, for example, a CCP (Current-Confined-Path) spacer layer may be used. When a CCP spacer layer is used as the intermediate layer 52, for example, a structure in which a copper (Cu) metal path is formed in an insulating layer of aluminum oxide (Al ₂ O ₃ ) is used.

  A ferromagnetic material is used for the first magnetic layer 51 which is a magnetization free layer. Specifically, as the material of the first magnetic layer 51, for example, an alloy containing at least one of Fe and Co, such as an FeCo alloy and a NiFe alloy, can be used. Alternatively, the first magnetic layer 51 includes a Co—Fe—B alloy, an Fe—Co—Si—B alloy, an Fe—Ga alloy having a large magnetostriction constant λs, an Fe—Co—Ga alloy, a Tb—M—Fe alloy, You may use Tb-M1-Fe-M2 alloy, Fe-M3-MB alloy, Ni, Fe-Al, or a ferrite.

  In the pressure sensor according to the present embodiment, when an external pressure is applied to the diaphragm 22, the diaphragm 22 is deformed. Along with this, distortion occurs in the magnetoresistive element 23. In particular, at the end of the long side of the rectangular diaphragm 22 provided with the magnetoresistive element 23, a large anisotropic strain, that is, the difference between the strain in the longitudinal direction and the strain in the short direction (maximum main strain and minimum strain). Distortion with a large difference) is generated. Furthermore, by arranging the magnetoresistive element 23 in the first region 22A different from the low rigidity region, it is possible to cause a larger anisotropic strain in the magnetoresistive element 23. As a result, the sensitivity of sensing external pressure can be improved.

  As described above, in the pressure sensor according to the first embodiment, the low rigidity region is provided at both ends on the short side of the diaphragm. Thereby, the film | membrane stress of a diaphragm can be reduced, without generating a wrinkle in a diaphragm. As a result, the sensitivity for sensing pressure can be improved.

(Second Embodiment)
The second embodiment is different from the first embodiment in the arrangement of the low rigidity region on the diaphragm. Specifically, in the second embodiment, the low rigidity region is provided at the end portions along the three sides of the diaphragm formed in a rectangular shape. In the second embodiment, parts different from the first embodiment will be described, and description of parts similar to the first embodiment will be omitted as appropriate.

  FIG. 6 schematically shows a pressure sensor according to a first example of the second embodiment. In FIG. 6, in order to make the drawing easy to see, an insulating portion, a conductive portion, and the like are omitted. The pressure sensor illustrated in FIG. 6 includes a resin substrate 11, a support portion 21 provided on the resin substrate 11, a flexible diaphragm 22 supported by the support portion 21, and at least one provided on the diaphragm 22. Two (three in this example) magnetoresistive elements 23 are provided.

  The diaphragm 22 includes a first region 22A and a second region 22B having rigidity lower than that of the first region 22A. In the pressure sensor shown in FIG. 6, the diaphragm 22 is formed in a rectangular shape, and the second region 22 </ b> B is located over both ends on the short side and one end on the long side of the diaphragm 22. The magnetoresistive element 23 is disposed at the other end portion on the long side which is the first region 22A.

  FIG. 7 schematically shows a pressure sensor according to a second example of the second embodiment. In FIG. 7, in order to make the drawing easier to see, an insulating portion and a conductive portion are omitted. In the pressure sensor shown in FIG. 7, the second region 22 </ b> B is located over both ends on the long side and one end on the short side of the diaphragm 22. The magnetoresistive element 23 is disposed at the other end on the short side which is the first region 22A.

  According to the second embodiment, the sensitivity of the pressure sensor can be improved as in the first embodiment.

(Third embodiment)
The third embodiment is different from the first embodiment in the arrangement of the low rigidity region on the diaphragm. Specifically, in the third embodiment, a low rigidity region is provided at the center of a rectangular diaphragm. In the third embodiment, parts different from the first embodiment will be described, and description of parts similar to those of the first embodiment will be omitted as appropriate.

  FIG. 8 schematically shows a pressure sensor according to the third embodiment. In FIG. 8, in order to make the drawing easy to see, an insulating portion and a conductive portion are omitted. The pressure sensor shown in FIG. 8 includes a resin substrate 11, a support portion 21 provided on the resin substrate 11, a flexible diaphragm 22 supported by the support portion 21, and at least one provided on the diaphragm 22. Two (six in this example) magnetoresistive elements 23 are provided.

  The diaphragm 22 includes a first region 22A and a second region 22B having rigidity lower than that of the first region 22A. In the present embodiment, the second region 22B is located at the center of the diaphragm 22 and has a circular shape. Three magnetoresistive elements 23 are arranged at both ends on the long side, which is the first region 22A.

  FIG. 9A is a partial cross-sectional view of the pressure sensor along the line IX-IX ′ shown in FIG. 8, and schematically shows a first structural example of the diaphragm 22. In the first structure example shown in FIG. 9A, the thickness of the second region 22B is smaller than the thickness of the first region 22A. FIG. 9B is a partial cross-sectional view of the pressure sensor along the line IX-IX ′ shown in FIG. 8, and schematically shows a second structure example of the diaphragm 22. In the second structural example shown in FIG. 9B, the diaphragm 22 in the second region 22B is formed in a corrugated shape. FIG. 9C is a partial cross-sectional view of the pressure sensor along the line IX-IX ′ shown in FIG. 8 and schematically shows a third structure example of the diaphragm 22. In the third structure example shown in FIG. 9C, the Young's modulus of the second region 22B is lower than the Young's modulus of the first region 22A.

  According to the third embodiment, the sensitivity of the pressure sensor can be improved as in the first embodiment.

(Fourth embodiment)
The fourth embodiment is different from the first embodiment in the arrangement of the low rigidity region on the diaphragm. Specifically, the fourth embodiment corresponds to the combination of the first embodiment and the third embodiment, that is, low in both ends and the center of the short side of the rectangular diaphragm. A stiffening region is provided. In the fourth embodiment, parts different from the first embodiment will be described, and description of parts similar to those of the first embodiment will be omitted as appropriate.

  FIG. 10 schematically shows a pressure sensor according to the fourth embodiment. In FIG. 10, in order to make the drawing easy to see, an insulating portion and a conductive portion are omitted. The pressure sensor shown in FIG. 10 includes a resin substrate 11, a support portion 21 provided on the resin substrate 11, a flexible diaphragm 22 supported by the support portion 21, and at least one provided on the diaphragm 22. Two (six in this example) magnetoresistive elements 23 are provided.

  The diaphragm 22 includes a first region 22A and a second region 22B having rigidity lower than that of the first region 22A. In the present embodiment, the second region 22 </ b> B is located at both ends and the center of the short side of the diaphragm 22. Three magnetoresistive elements 23 are arranged at both ends on the long side, which is the first region 22A.

  According to the fourth embodiment, the sensitivity of the pressure sensor can be improved as in the first embodiment.

(Fifth embodiment)
The fifth embodiment is different from the first embodiment in the shape of the diaphragm and the arrangement of the magnetoresistive elements. Specifically, in the fifth embodiment, the diaphragm is formed in a circular shape. In the fifth embodiment, parts different from the first embodiment will be described, and description of parts similar to those of the first embodiment will be omitted as appropriate.

  FIG. 11 schematically shows a pressure sensor according to the fifth embodiment. In FIG. 11, in order to make the drawing easy to see, an insulating portion and a conductive portion are omitted. The pressure sensor shown in FIG. 11 includes a resin substrate 11, a support portion 21 provided on the resin substrate 11, a flexible diaphragm 22 supported by the support portion 21, and at least one provided on the diaphragm 22. Two (six in this example) magnetoresistive elements 23 are provided.

  The diaphragm 22 includes a first region 22A and a second region 22B having rigidity lower than that of the first region 22A. In the present embodiment, the second region 22 </ b> B is a circular region and is located at the center of the diaphragm 22. The magnetoresistive element 23 is disposed along the periphery of the diaphragm 22. Specifically, three are arranged at two end portions facing each other through the second region 22B.

  According to the fourth embodiment, the sensitivity of the pressure sensor can be improved as in the first embodiment.

(Sixth embodiment)
The sixth embodiment is different from the first embodiment in the shape of the diaphragm. In the sixth embodiment, the diaphragm is formed in a circular shape as in the fifth embodiment, but the arrangement of the low rigidity region on the diaphragm is different from that in the fifth embodiment. Specifically, in the sixth embodiment, a low rigidity region is provided in at least a part of the peripheral edge portion of the diaphragm formed in a circular shape. In the fifth embodiment, parts different from the first embodiment will be described, and description of parts similar to those of the first embodiment will be omitted as appropriate.

  FIG. 12 schematically shows a pressure sensor according to the sixth embodiment. In FIG. 12, in order to make the drawing easy to see, an insulating portion and a conductive portion are omitted. The pressure sensor shown in FIG. 12 includes a resin substrate 11, a support portion 21 provided on the resin substrate 11, a flexible diaphragm 22 supported by the support portion 21, and at least one provided on the diaphragm 22. Two (six in this example) magnetoresistive elements 23 are provided.

  The diaphragm 22 includes a first region 22A and a second region 22B having rigidity lower than that of the first region 22A. In the present embodiment, the second region 22 </ b> B is located at two portions in the peripheral edge portion of the diaphragm 22. These two parts are opposed to each other via the center of the diaphragm 22. The magnetoresistive element 23 is disposed along the periphery of the diaphragm 22 on the first region 22A. Specifically, three magnetoresistive elements 23 are arranged in two portions different from the second region 22 </ b> B in the peripheral portion of the diaphragm 22. The peripheral portion of the diaphragm 22 includes two parts of the second region 22B and two parts of the first region 22A located between the two parts.

  According to the sixth embodiment, the sensitivity of the pressure sensor can be improved as in the first embodiment.

(Seventh embodiment)
The seventh embodiment is different from the first embodiment in the shape of the diaphragm. The seventh embodiment corresponds to the combination of the fifth embodiment and the sixth embodiment, and a low rigidity region is provided at the center portion and at least a part of the peripheral portion of the diaphragm formed in a circular shape. ing. In the seventh embodiment, parts different from the first embodiment will be described, and description of parts similar to those of the first embodiment will be omitted as appropriate.

  FIG. 13 schematically shows a pressure sensor according to the seventh embodiment. In FIG. 13, in order to make the drawing easier to see, an insulating portion, a conductive portion, and the like are omitted. The pressure sensor shown in FIG. 13 includes a resin substrate 11, a support portion 21 provided on the resin substrate 11, a flexible diaphragm 22 supported by the support portion 21, and at least one provided on the diaphragm 22. Two (six in this example) magnetoresistive elements 23 are provided.

  The diaphragm 22 includes a first region 22A and a second region 22B having rigidity lower than that of the first region 22A. In the present embodiment, the second region 22B is located at the center portion of the diaphragm 22 and the two portions at the peripheral portion. These two portions are opposed to each other via the center portion of the diaphragm 22. Three magnetoresistive elements 23 are arranged in two portions of the peripheral portion of the diaphragm 22 different from the second region 22B.

  According to the seventh embodiment, similarly to the first embodiment, the sensitivity of the pressure sensor can be improved.

  The planar shape of the diaphragm 22 is not limited to the shapes (rectangles and circles) illustrated in the first to seventh embodiments, but may be other shapes such as an ellipse. Further, the position of the second region (low rigidity region) 22B on the diaphragm 22 and the arrangement of the magnetoresistive elements 23 are not limited to the examples described in the first to seventh embodiments, and can be changed as appropriate. The shape of the second region (low rigidity region) 22B on the diaphragm 22 is not limited to the illustrated circle, and may be other shapes such as a square, a rectangle, and an ellipse. The substrate on which the MEMS chip 20 is mounted is not limited to a resin substrate, and may be a ceramic substrate.

(Eighth embodiment)
FIG. 14 schematically shows a microphone 140 according to the eighth embodiment. The microphone 140 includes a pressure sensor 141. The pressure sensor 141 can be any of the pressure sensors described in the first to seventh embodiments or a modification thereof. The pressure sensor 141 of this embodiment is a pressure sensor according to the first embodiment.

  The pressure sensor 141 includes a resin substrate 11 and a MEMS chip 20 mounted on the resin substrate 11. The resin substrate 11 includes, for example, a circuit such as an amplifier. A cover 143 is provided on the resin substrate 11 so as to cover the MEMS chip 20. An opening 142 is formed in the cover 143. The sound wave 144 enters the inside of the cover 143 through the opening 142.

  The microphone 140 is sensitive to the sound pressure of the sound wave 144. By using a pressure sensor with high sensitivity, the microphone 140 having high sensitivity with respect to a wide frequency range can be obtained. As a method of relieving the compressive stress generated in the diaphragm, a method of providing a slit or a through hole in the diaphragm can be considered. However, when a pressure sensor is used for a microphone, the slit or the through-hole causes a reduction in sensitivity (Roll-off) due to the wraparound of sound waves in a low frequency region. In the pressure sensor 141 of the present embodiment, the sensitivity is not lowered (Roll-off) due to the wraparound of the sound wave, and the sensitivity is high even in the low frequency region.

  The sound wave 144 is not limited to an audible signal, and may be an ultrasonic wave. The microphone 140 can function as an ultrasonic sensor by designing the diaphragm 22 so that the resonance frequency of the diaphragm 22 is in the ultrasonic frequency band. More preferably, since the rectilinearity of the sound wave 144 is increased in the ultrasonic wave, the position of the opening 142 is disposed immediately above the diaphragm (not shown in FIG. 14) of the pressure sensor 141 or on the resin substrate 11 immediately below the diaphragm. An opening 142 is provided. Further, it is desirable to provide a dustproof mesh in the opening 142.

  FIG. 15 schematically shows an example in which the microphone 140 is applied to the portable information terminal 150. As shown in FIG. 15, the microphone 140 is incorporated at the end of the portable information terminal 150. For example, the microphone 140 is disposed such that the diaphragm 22 included in the pressure sensor 141 is substantially parallel to the surface on which the display unit 151 of the portable information terminal 150 is provided. The arrangement of the diaphragm 22 is not limited to the arrangement example shown in FIG. 14 and can be changed as appropriate.

  The microphone 140 is not limited to the example applied to the portable information terminal 150 as shown in FIG. 15, but may be applied to an IC recorder, a pin microphone, or the like.

(Ninth embodiment)
FIG. 16 schematically shows a blood pressure sensor 160 according to the ninth embodiment. A blood pressure sensor 160 shown in FIG. 16 measures human blood pressure, and includes a pressure sensor 161. The pressure sensor 161 may be any of the pressure sensors described in the first to seventh embodiments or a modification thereof. The pressure sensor 161 of the present embodiment is a pressure sensor according to the first embodiment, and is small and highly sensitive pressure sensing is possible.
The blood pressure sensor 160 can continuously measure blood pressure by pressing the pressure sensor 161 against the skin 163 above the arterial blood vessel 162. According to this embodiment, a highly sensitive blood pressure sensor 160 is provided.

(Tenth embodiment)
FIG. 17 schematically shows a touch panel 170 according to the tenth embodiment. As shown in FIG. 17, the touch panel 170 includes a plurality of first wires 174, a plurality of second wires 175, a plurality of pressure sensors 171, and a control unit 176. Each of the pressure sensors 171 may be any of the pressure sensors according to the first to seventh embodiments or a modification thereof. The pressure sensor 171 is mounted on at least one of the inside of the display and the outside of the display.

  The plurality of first wirings 174 are arranged along the first direction. Each of the plurality of first wirings 174 extends along a second direction that intersects the first direction. The plurality of second wirings 175 are arranged along the second direction. Each of the plurality of second wirings 175 extends along the first direction.

  Each of the plurality of pressure sensors 171 is provided at each intersection of the plurality of first wires 174 and the plurality of second wires 175. Each of the pressure sensors 171 becomes one of detection elements 171e for detection. Here, the intersection includes a position where the first wiring 174 and the second wiring 175 intersect and a region around the position.

  One end 172 of each of the plurality of pressure sensors 171 is connected to each of the plurality of first wirings 174. The other ends 173 of the plurality of pressure sensors 171 are connected to the plurality of second wirings 175, respectively.

  The control unit 176 is connected to the plurality of first wirings 174 and the plurality of second wirings 175. The control unit 176 includes a first wiring circuit 176a connected to the plurality of first wirings 174, a second wiring circuit 176b connected to the plurality of second wirings 175, the first wiring circuit 176a, and the second wiring circuit 176a. And a control circuit 177 connected to the wiring circuit 176b.

  The pressure sensor 171 is small and can perform highly sensitive pressure sensing. Therefore, a high-definition touch panel can be realized.

  The pressure sensor according to the first to seventh embodiments can be used for various pressure sensor devices such as a pressure sensor and a tire pressure sensor in addition to the above application.

  According to the embodiment, a highly sensitive pressure sensor, microphone, ultrasonic sensor, blood pressure sensor, and touch panel can be provided.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 ... Resin board | substrate, 20 ... MEMS chip, 21 ... Support part, 22 ... Diaphragm, 22A ... Area | region, 22B ... Area | region (low rigidity area | region), 23 ... Magnetoresistance element, 26 ... Cavity part, 51 ... 1st magnetic layer 52 ... Intermediate layer, 53 ... Second magnetic layer, 140 ... Microphone, 141 ... Pressure sensor, 142 ... Opening, 143 ... Cover, 144 ... Sound wave, 150 ... Portable information terminal, 151 ... Display unit, 160 ... Blood pressure sensor, 161 ... Pressure sensor, 170 ... Touch panel, 171 ... Pressure sensor, 171e ... Detection element, 174, 175 ... Wiring, 176 ... Control unit, 176a ... Wiring circuit, 176b ... Wiring circuit, 177 ... Control circuit.

Claims (1)

A support part;
A flexible membrane portion supported by the support portion, the membrane portion including a first region and a second region having rigidity lower than that of the first region;
A magnetoresistive element provided in the film portion and including a first magnetic layer, a second magnetic layer, and a spacer layer disposed between the first magnetic layer and the second magnetic layer;
A pressure sensor comprising: