MEMS sensor

Abstract

To provide a MEMS sensor with improved sensitivity.SOLUTION: Provided is a MEMS sensor 1 comprising at least one strain sensing element 31, and a pair of strain gauges 317L, 317R provided on each strain sensing element, where the pair of strain gauges 317L, 317R is juxtaposed only on a stress concentration portion 312 of each strain sensing element.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This disclosure relates to MEMS sensors.

Background Art

[0002] In recent years, in industrial fields and medical fields, etc., the spread of industrial robots, virtual reality, and the development of telemedicine have advanced, and tactile sensing technology using MEMS sensors has attracted attention. Although various technologies have been proposed for such MEMS sensors (for example, Patent Documents 1 to 3, Non-Patent Document 1), standard technologies have not been established.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Strain gauges are used to detect deformation of strain sensing elements, such as microcantilever structures, in MEMS sensors due to the application of external forces. Strain gauges detect deformation of the strain sensing element based on the change in electrical resistance associated with this deformation. However, since the deformation of the strain sensing element is minute, ingenuity is required to improve sensitivity. In particular, because the deformation of the strain sensing element is minute, output amplification is necessary, and there is a risk of noise being introduced into the output signal during the output amplification process. Thus, conventional MEMS sensors have had problems in terms of sensitivity.

[0005] In light of these circumstances, the purpose of this disclosure is to improve the sensitivity of MEMS sensors. [Means for solving the problem]

[0006] A MEMS sensor according to one embodiment of this disclosure is At least one strain sensing element, A pair of strain gauges are provided on each strain sensing element, A MEMS sensor comprising, The pair of strain gauges are characterized in that they are arranged side by side only at the stress concentration points of each strain sensing element.

[0007] Furthermore, a MEMS sensor according to one embodiment of this disclosure is Each strain sensing element is characterized by having a cantilever structure.

[0008] Furthermore, a MEMS sensor according to one embodiment of this disclosure is The stress concentration point is characterized in that it is near the fixed end of the cantilever structure.

[0009] Furthermore, a MEMS sensor according to one embodiment of this disclosure is The pair of strain gauges are characterized in that they are arranged side by side in the short direction of the cantilever structure near the fixed end.

[0010] Furthermore, a MEMS sensor according to one embodiment of this disclosure is It is provided with a Wheatstone bridge circuit connected to the pair of strain gauges and having a plurality of reference resistors. It is characterized in that the plurality of reference resistors are provided in the vicinity of the strain gauges.

[0011] Also, the MEMS sensor according to an embodiment of the present disclosure is characterized in that the strain gauge and the reference resistor are made of the same material.

[0012] Also, the MEMS sensor according to an embodiment of the present disclosure is characterized in that the material is NiCr.

[0013] Also, the MEMS sensor according to an embodiment of the present disclosure is characterized in that the number of the strain detection elements is 2.

Advantages of the Invention

[0014] According to an embodiment of the present disclosure, it becomes possible to improve the sensitivity of the MEMS sensor.

Brief Description of the Drawings

[0015] [Figure 1] It is a diagram showing a schematic configuration of a MEMS sensor according to an embodiment of the present disclosure. [Figure 2] It is a diagram showing a schematic configuration of a MEMS sensor according to a comparative example. [Figure 3] It is a diagram showing a schematic configuration of a microcantilever according to an embodiment of the present disclosure. <000089> [Figure 4] It is a diagram showing a manufacturing procedure of a microcantilever according to an embodiment of the present disclosure. [Figure 5] It is a diagram showing a detection principle of an external force by a MEMS sensor according to an embodiment of the present disclosure. [Figure 6] It is a schematic diagram of a circuit configuration of a MEMS sensor according to a comparative example. [Figure 7] It is a schematic diagram of a circuit configuration of a MEMS sensor according to an embodiment of the present disclosure. [Figure 8] It is a diagram showing the arrangement of the reference resistor according to an embodiment of the present disclosure. [Figure 9] It is a diagram showing an overview of the vertical and horizontal load application tests. [Figure 10] It is a diagram showing the resistance change rate of the strain gauge when a vertical load is applied to a MEMS sensor according to an embodiment of the present disclosure and a MEMS sensor according to a comparative example. [Figure 11] It is a diagram showing the resistance change rate of the strain gauge when a longitudinal load of the microcantilever is applied to a MEMS sensor according to an embodiment of the present disclosure and a MEMS sensor according to a comparative example. [Figure 12] It is a diagram showing the resistance change rate of the strain gauge when a lateral load of the microcantilever is applied to a MEMS sensor according to an embodiment of the present disclosure and a MEMS sensor according to a comparative example. [Figure 13] It is a diagram showing the resistance change rate of the strain gauge when a horizontal load is applied to a MEMS sensor according to an embodiment of the present disclosure while changing it 360°.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each figure, the same reference numerals indicate the same or equivalent components. The MEMS sensor of this embodiment will be described as an example of a sensor for tactile measurement (tactile sensor). In each figure, the same or corresponding parts are denoted by the same reference numerals. In the description of this embodiment, the description of the same or corresponding parts will be omitted or simplified as appropriate.

[0017] Referring to Figure 1, the configuration of the MEMS sensor 1 according to this embodiment will be described. The MEMS sensor 1 has a microstructure strain sensing element on a Si substrate. The MEMS sensor 1 also has a protruding structure whose entire body is covered with an elastomer (for example, poly-dimethyl-siloxane (PDMS)). When an external force is applied to the top of the elastomer, the entire elastomer deforms, and the strain sensing element is simultaneously deformed by being pulled by this deformation. The change in resistance accompanying this deformation of the strain sensing element is measured, and the external force is calculated inside the computer. Figure 1(a) is a perspective view of the MEMS sensor 1 according to this embodiment. Figure 1(b) is a photograph of the MEMS sensor 1 according to this embodiment. The MEMS sensor 1 according to this embodiment comprises a sensor chip 3 sealed with an elastic resin 2 and a contact portion 4.

[0018] As shown in Figure 1, the sensor chip 3 is protected by being sealed with an elastic resin 2. The elastic resin 2 is, for example, an elastomer (e.g., poly-dimethyl-siloxane (PDMS)). In this embodiment, the elastic resin 2 will be described as PDMS.

[0019] The sensor chip 3 is mounted on a printed circuit board 5. The sensor chip 3 includes strain sensing elements 31 to 33. In this embodiment, the strain sensing elements 31 to 33 have a cantilever structure with a strain gauge mounted on it. In other words, in this embodiment, the strain sensing elements 31 to 33 are three microcantilevers (tiny cantilevers) 31 to 33 with strain gauges mounted on them. Hereinafter, the strain sensing elements 31 to 33 will also be referred to as microcantilevers 31 to 33. The microcantilevers 31 to 33 have an inclined structure to detect the magnitude and direction of force. The sensor chip 3 is a 5 mm square. The microcantilevers 31 to 33 are arranged within a circle with a diameter of 1 mm from the center of the sensor chip 3, with their tips facing in a direction rotated 120 degrees. In this embodiment, an example is described in which the MEMS sensor 1 has three microcantilevers, but it is not limited to this. The number of microcantilevers that the MEMS sensor 1 has may be two. In other words, the microcantilevers of the MEMS sensor 1 may consist only of microcantilevers 31 and 32. In this case, microcantilevers 31 and 32 are positioned within a circle with a diameter of 1 mm from the center of the sensor chip 3, with their tips facing in directions rotated 120 to 180 degrees.

[0020] The contact portion 4 is the part that comes into contact with the object. The shape and material of the contact portion 4 are determined appropriately according to the properties and application of the object. The properties of the object include hardness, flexibility, brittleness, durability, wear resistance, etc. For example, the hardness of the contact portion 4 and the contact area with the object can be adjusted appropriately depending on whether the object is flexible or fragile. For example, the shape of the contact portion 4 may be hemispherical, cylindrical, elliptical, prismatic, or triangular pyramidal. The shape of the contact portion 4 is not limited to these, and any shape can be adopted as long as it is a protruding shape. The material of the contact portion 4 may be PDMS, acrylic, etc. The material of the contact portion 4 is not limited to these, and any material can be adopted. The contact portion 4 serves to limit the contact area with the object and to concentrate the load on the sensor chip 3 towards the center.

[0021] The contact portion 4 may be detachably fixed to the sensor chip 3. In this disclosure, "detachable" includes being peelable, removable, etc. For example, the contact portion 4 is detachably (peelable) fixed to the sensor chip 3 with a re-peelable adhesive. As the adhesive, for example, the liquid adhesive BBX from Cemedyne Co., Ltd. can be used. Since the contact portion 4 is detachable from the sensor chip 3 in this way, the MEMS sensor 1 according to this embodiment can be used by appropriately replacing the contact portion 4 with a shape or material suited to various applications and objects.

[0022] Next, the schematic configuration of the microcantilever is shown. First, for comparison, the schematic configuration of the MEMS sensor 101 and microcantilever 41 according to the comparative example is shown in Figure 2. As shown in Figure 2(a), the MEMS sensor 101 according to the comparative example, like the MEMS sensor 1, comprises a sensor chip 103 sealed with elastic resin 102 and a contact portion 104. The sensor chip 103 includes strain sensing elements 41 to 43. In the comparative example, the strain sensing elements 41 to 43 included in the sensor chip 103 are three microcantilevers 41 to 43 on which strain gauges are mounted. As shown in Figure 2(b), the microcantilever 41 according to the comparative example includes a free end 411, a fixed end 412, and a strain gauge 417. Here, as shown in Figure 2, the strain gauge 417 is arranged across the entire surface of the microcantilever 41. Specifically, the strain gauge 417 is arranged meanderingly across the entire surface of the microcantilever 41. In other words, the strain gauge 417 is provided extending from the free end 311 to the fixed end 312 of the microcantilever 41.

[0023] Next, with reference to Figure 3, the schematic configuration of the microcantilever 31 according to this embodiment is shown. The microcantilever 31 includes a free end 311, a fixed end 312, and a pair of strain gauges 317L and 317R. As shown in Figure 2, the pair of strain gauges 317L and 317R are provided at the fixed end 312 of the strain sensing element (microcantilever 31) aligned along the short-side direction of the strain sensing element. In other words, the pair of strain gauges 317L and 317R are provided only at the stress concentration points of the strain sensing element. The configuration of microcantilevers 32 and 33 is the same as that of microcantilever 31. That is, the pair of strain gauges 327L and 327R are provided at the fixed end of the strain sensing element (microcantilever 32) aligned along the short-side direction of the strain sensing element. Furthermore, the pair of strain gauges 337L and 337R are provided at the fixed end of the strain sensing element (microcantilever 33), aligned along the short-side direction of the strain sensing element.

[0024] Referring to Figure 4, the procedure for fabricating the microcantilever 31 according to this embodiment is shown. The fabrication procedures for microcantilevers 32 and 33 are the same as those for microcantilever 31, so their explanation is omitted. For the fabrication of microcantilever 31, a silicon on insulator (SOI) wafer consisting of a three-layer structure of a support substrate 313, a BOX layer 314, and an active layer 315 is used. Here, the support substrate 313 is made of Si. The BOX layer 314 is made of SiO2. The active layer 315 is made of Si. As preparation before fabrication, the SOI wafer is subjected to pre-treatment of film deposition by ultrasonic cleaning with acetone and removal of the native oxide film with dilute hydrofluoric acid.

[0025] First, Si3N4 is deposited on the SOI wafer as an insulating layer 316 by LPCVD, NiCr as strain gauges 317R and 317L, and Au as wiring portion 318 by sputtering, and these are patterned by photolithography and etching. Next, Cr is deposited as a film 319 for tilting the cantilever structure by electron beam evaporation and patterned by lift-off method. After that, a cantilever structure is formed using a method to create a hollow structure by selective etching (hereinafter also called sacrificial layer etching), with the BOX layer 314 as the sacrificial layer.

[0026] After patterning by photolithography, the active layer 315 is etched, leaving the cantilever structure. To ensure uniform and efficient sacrificial layer etching, multiple holes exposing the BOX layer 314 are arranged in the microcantilever 31. Next, to separate the active layer 315, which will become the microcantilever 31, from the support substrate 313, the BOX layer 314 is selectively etched using buffered hydrofluoric acid (BHF). For example, Stella Chemifa Co., Ltd.'s NH4F product with a concentration of 20% can be used as the buffered hydrofluoric acid. At this point, as the active layer 315 separates from the substrate and becomes a hollow structure, the microcantilever 31 autonomously forms a gradient structure due to the tensile stress caused by the difference in the coefficients of linear expansion between the film 319 (Cr) and the active layer 315 (Si). After sacrificial layer etching, the sensor chip 3 is washed with pure water, and ethanol replacement is performed to prevent the microcantilever from sticking to the support substrate 313 due to the surface pressure of the pure water. Afterward, vacuum drying is performed to complete sensor chip 3.

[0027] The fabricated sensor chip 3 is bonded to the printed circuit board 5 using epoxy adhesive. For example, ESCO Corporation's ultra-fast epoxy adhesive can be used as the epoxy adhesive. The sensor chip 3 is also electrically connected to the printed circuit board 5 via a wiring connection. For example, a gold wire (Φ25) can be used for the wiring connection. μThe sensor chip 3 and the printed circuit board 5 are connected by wire bonding.

[0028] Figure 5 is a schematic diagram illustrating the principle of external force detection by the MEMS sensor 1. As shown in Figure 4, when an external force is applied to the contact portion 4, the microcantilevers 31-33 deform. When the external force is applied to the contact portion 4, the amount of deflection of the microcantilevers 31-33 changes in accordance with the deformation of the contact portion 4. Here, the magnitude of the applied force can be estimated by measuring the change in electrical resistance of the strain gauges 317L and 317R on the microcantilevers 31-33. The microcantilevers 31-33 have an inclined structure and are arranged at different angles. For example, as shown in Figure 5(a), when a vertical force (vertical load) is applied to the contact portion 4, the PDMS moves horizontally to escape due to its incompressibility and expands horizontally. In other words, in this case, the amount of deflection of all microcantilevers 31-33 increases, and the electrical resistance of the strain gauges 317L and 317R decreases uniformly. On the other hand, as shown in Figure 4(b), when a shear force (shear load) is applied, the microcantilevers 31 to 33 exhibit different movements depending on the direction of the shear load. Similarly, the electrical resistances of the strain gauges 317L and 317R also show different responses. Therefore, by measuring the sensitivity characteristics of each microcantilever 31 to 33 to the load in advance, the magnitude and direction of the applied force can be estimated.

[0029] Next, the circuit configuration of MEMS sensor 1 will be described. First, Figure 6 shows the circuit configuration of the microcantilever 41 of the MEMS sensor 101 in the comparative example. The circuit configurations of cantilevers 42 and 43 are the same as those of the microcantilever 41, so their explanation will be omitted. The circuit configuration of the microcantilever 41 is a Wheatstone bridge circuit, and a strain gauge 417 is provided on one side of the Wheatstone bridge circuit. Reference resistors 418 to 420 are provided on the remaining three sides of the Wheatstone bridge circuit. The strain output (V) with respect to the resistance change rate (dR / R) of the strain gauge is expressed by the following approximate formula (1) when R >> dR.

number

[0030] Figure 7 is a schematic diagram of the circuit configuration related to the microcantilever 31 of the MEMS sensor 1 according to this embodiment. The circuit configuration related to the microcantilever 32 and 32 is the same as the circuit configuration related to the microcantilever 31, so its explanation is omitted. As shown in Figure 7, the circuit configuration related to the microcantilever 31 of the MEMS sensor 1 uses the two-gauge method of opposite sides of a Wheatstone bridge circuit. That is, this circuit configuration has strain gauges 317L and 317R provided on two sides of the Wheatstone bridge circuit, and reference resistors 511 and 512 provided on the other two sides of the Wheatstone bridge circuit. In this circuit configuration, the strain output (V) with respect to the resistance change rate (dR / R) of the strain gauge is expressed by the following approximate formula (2) when R >> dR.

number

[0031] In other words, the circuit configuration of the MEMS sensor 1 according to this embodiment doubles the strain output compared to the circuit configuration of the MEMS sensor 101 according to the comparative example. To put it another way, the MEMS sensor 1 according to this embodiment can obtain twice the output based on its circuit configuration compared to the MEMS sensor 101 according to the comparative example, thereby improving the sensor sensitivity of the MEMS sensor 1 according to this embodiment.

[0032] Generally, electrical resistance is temperature-dependent, so changes in ambient temperature and temperature differences with the contacting object cause drift in the output. To reduce this, self-temperature compensation using a Wheatstone bridge circuit is commonly used in circuits with strain gauges, but temperature compensation cannot be fully achieved due to differences in the temperature and temperature coefficient of each resistor that makes up the circuit.

[0033] To solve the problems related to temperature compensation, the reference resistors 511 and 512 according to one embodiment of the present disclosure are provided in the vicinity of the strain gauges 317L and 317R. Figure 8 shows the arrangement of the reference resistors 511 and 512 on the chip 3 according to one embodiment of the present disclosure. As shown in Figure 8, the reference resistors 511 and 512 are provided in the vicinity of the strain gauges 317L and 317R. Specifically, for example, the reference resistors 511 and 512 are provided on the sensor chip 3 within a predetermined range from the strain gauges 317L and 317R. More specifically, in Figure 8, the reference resistors 511 and 512 are provided on both sides of the strain gauges 317L and 317R. By placing the reference resistors 511 and 512 near the strain gauges 317L and 317R in this manner, the temperature difference between the strain gauges 317L and 317R and the reference resistors 511 and 512 can be reduced, thereby reducing the effect of resistance changes due to temperature. As shown in Figure 8, the reference resistors 513 and 514 in the circuit related to the microcantilever 32 are also placed near the strain gauges 327L and 327R on the microcantilever 32. Similarly, the reference resistors 515 and 516 in the circuit related to the microcantilever 33 are also placed near the strain gauges 337L and 337R on the microcantilever 33.

[0034] Furthermore, the reference resistors 511 and 512 according to one embodiment of this disclosure are made of the same material as the strain gauges 317L and 317R. Such material is, for example, NiCr. When the reference resistors 511 and 512 are made of the same material as the strain gauges 317L and 317R, the influence of differences in temperature characteristics can be reduced. By making the material of the reference resistors 511 and 512 the same as that of the strain gauges 317L and 317R in this way, the temperature dependence of the strain output V can be reduced, and the sensor sensitivity can be improved.

[0035] Referring to Figures 9 to 13, an overview of the load application test on the MEMS sensor 1 according to this embodiment will be described. In this test, in order to evaluate the response of the strain gauges to forces in each direction for the MEMS sensor 1 according to this embodiment and the MEMS sensor 101 according to the comparative example, vertical loads and horizontal loads (shear loads) were applied to the MEMS sensor 1 and the MEMS sensor 101, and the rate of change of resistance of each strain gauge was measured.

[0036] Figure 9 shows an overview of the vertical and horizontal load application tests of the MEMS sensor 1 according to this embodiment. As shown in Figures 9(a) and 9(b), the MEMS sensor 1 according to this embodiment is placed on a three-axis stage, and a vertical load or a horizontal load is applied by a jig 6, respectively. The resistance change rate of each strain gauge is measured by a digital multimeter 8. The method for the vertical and horizontal load application tests of the MEMS sensor 101 according to the comparative example is the same.

[0037] Figure 10 shows the resistance change rate of the strain gauges when a vertical load is applied to the MEMS sensor 1 according to this embodiment and the MEMS sensor 101 according to a comparative example. In Figures 10 to 13, the resistance change rates for strain gauges 317L and 317R of the MEMS sensor 1 according to this embodiment are shown as "strain gauge L" and "strain gauge R," respectively. On the other hand, the resistance change rate for strain gauge 417 of the MEMS sensor 101 is shown as "comparative example." As shown in Figure 10, the slope of the resistance change rate for strain gauges 317L and 317R is about 5 to 6 times greater than the slope of the resistance change rate for strain gauge 417. In other words, strain gauges 317L and 317R are about 5 to 6 times more sensitive than strain gauge 417. This is because the strain gauges 317L and 317R are positioned near the stress-concentrated fixed end 312, compared to the strain gauge 417 of the comparative example. In other words, in the MEMS sensor 1 according to this embodiment, the pair of strain gauges 317L and 317R are provided side by side only at the stress-concentrated portion of the microcantilever 31, thereby increasing the sensitivity of the sensor.

[0038] Figure 11 shows the resistance change rate of the strain gauges when a horizontal load is applied to the MEMS sensor 1 according to this embodiment and the MEMS sensor 101 according to the comparative example. The horizontal load in Figure 11 is the load in the longitudinal direction (direction from the fixed end to the free end of each microcantilever) of the microcantilever 31 and microcantilever 41. As shown in Figure 11, the slope of the resistance change rate for strain gauge 317L and strain gauge 317R is greater than the slope of the resistance change rate for strain gauge 417. In other words, strain gauge 317L and strain gauge 317R are more sensitive than strain gauge 417. This is because strain gauge 317L and strain gauge 317R are positioned near the fixed end 312 where stress is concentrated, compared to strain gauge 417 of the comparative example. In other words, in the MEMS sensor 1 according to this embodiment, the pair of strain gauges 317L and 317R are arranged side by side only at the stress concentration point of the microcantilever 31, thereby increasing the sensitivity of the sensor.

[0039] Figure 12 shows the rate of change in resistance of the strain gauges when a horizontal load is applied to the MEMS sensor 1 according to this embodiment and the MEMS sensor 101 according to the comparative example. The horizontal load in Figure 12 is a load applied to the MEMS sensor 1 according to this embodiment and the MEMS sensor 101 according to the comparative example in the short-side direction (perpendicular to the longitudinal direction) of the microcantilever. Since the direction of this load is the torsional direction of the microcantilever, as shown in Figure 12, the rate of change in resistance for strain gauges 317L and 317R is reversed. Therefore, by summing the outputs of strain gauges 317L and 317R of the MEMS sensor 1, the effect of deformation in the torsional direction of the microcantilever 31 can be canceled out. In other words, in the MEMS sensor 1 according to this embodiment, a pair of strain gauges 317L and 317R are provided side by side in the short direction near the fixed end of the microcantilever 31, so that the effects of deformation in the torsional direction can be canceled out, and the sensitivity of the sensor can be increased.

[0040] Figure 13 shows the angular dependence of the resistance change rate of the MEMS sensor 1 according to this embodiment. Specifically, Figure 13 shows the resistance change rates of strain gauges 317L and 317R when a horizontal load is applied with a 360-degree change. Here, θ in Figure 13 represents the angle of the horizontal load, and when θ = 0°, the direction of the load is the same as in Figure 12 (the short side of the microcantilever 31), with clockwise being positive. That is, for example, when θ = 90°, θ is set so that the direction of the load is the same as in Figure 11 (the long side of the microcantilever 31). As shown in Figure 13, the strain gauges 317L and 317R show different angular dependencies depending on the angle of the horizontal load. By utilizing this angular dependence, the MEMS sensor 1 according to this embodiment can detect the applied horizontal load with high sensitivity. In other words, even if the MEMS sensor 1 has only two microcantilevers, it can detect the horizontal load with high accuracy.

[0041] As described above, the MEMS sensor 1 according to this embodiment has higher sensitivity than the MEMS sensor 101 of the comparative example because the strain gauges 317L and 317R are arranged only at the stress concentration points of the microcantilever 31. Furthermore, the MEMS sensor 1 according to this embodiment can reduce the effect of torsion, thereby reducing the error in the calibration matrix when converting the output of each sensing element into force in the x, y, and z axes, enabling more accurate measurement of vector forces.

[0042] Furthermore, since the MEMS sensor 1 according to this embodiment uses the two-gauge method for opposite sides of a Wheatstone bridge circuit, the strain output can be doubled compared to the comparative example, thereby increasing the sensitivity of the sensor. Also, because the strain output is increased, the amount of amplification of the sensor output can be suppressed in the MEMS sensor 1 according to this embodiment, and the influence of mechanical and electrical noise in output amplification can also be suppressed.

[0043] Furthermore, according to this embodiment, the reference resistors 511 and 512 of the Wheatstone bridge circuit are provided near the strain gauges 317L and 317R. This suppresses drift due to external temperature and self-heating of the reference resistors 511 and 512, and maintains high sensitivity even when measuring in high or low temperature environments or when measuring when in contact with objects with large temperature differences. For example, when measuring the gripping condition of an object by placing it on a person's hand, it was previously necessary to wait until the temperature stabilized in order to reduce the influence of body temperature. However, with the MEMS sensor 1 according to this embodiment, there is no need to wait until the temperature stabilizes, and measurement can be started immediately.

[0044] In this embodiment, the reference resistors 511 to 516 of the Wheatstone bridge circuit are shown to be located near their respective pairs of strain gauges (317L, 317R, 327L, 327R, 337L, 337R). However, the reference resistors 511 to 516 may also be located on a sensing element on which the corresponding pairs of strain gauges are located. For example, the reference resistors 511 and 512 may be located on the microcantilever 31. Specifically, for example, the reference resistors 511 and 512 may be located on the back surface of the microcantilever 31 where the strain gauges 317L and 317R are located. Alternatively, the reference resistors 511 and 512 may be located at the fixed end of the back surface of the microcantilever 31 where the strain gauges 317L and 317R are located.

[0045] In this embodiment, the case where the MEMS sensor 1 is a tactile sensor has been described, but it is not limited to this. The MEMS sensor 1 may be something other than a tactile sensor, such as a pressure sensor or a flow sensor. Alternatively, the MEMS sensor 1 may be a proximity sensor.

[0046] In this embodiment, an example has been described in which the sensor chip 3 includes microcantilevers 31-33, but it is not limited to this. In addition to the microcantilevers, or instead of the microcantilevers, the sensor chip 3 may include any strain sensing element. Such a strain sensing element may be, for example, a beam fixed at both ends. Also, if the strain sensing element is rectangular, it may be a beam fixed on all four sides, or a beam fixed on part of all four sides. In any case, the strain gauge is provided only at the stress concentration point of the strain sensing element.

[0047] While this disclosure has been described based on the drawings and embodiments, it should be noted that those skilled in the art will find it easy to make various modifications and alterations based on this disclosure. Therefore, it should be noted that these modifications and alterations are within the scope of this disclosure. For example, the functions included in each means and component can be rearranged in a logically consistent manner. [Explanation of Symbols]

[0048] 1. 101 MEMS Sensor 2, 102 Elastic resin 3. 103 Sensor Chips 31, 32, 33, 41, 42, 43 Microcantilever 311 313 Support substrate 314 BOX layer 315 Active layer 316 Insulating layer 317R, 317L, 327R, 327L, 337R, 337L, 417 strain gauges 318 Wiring section 319 Membrane 418, 419, 420, 511, 512, 513, 514, 515, 516 reference resistor 4, 104 Contact area 5 Printed circuit boards 6. Jig 7. 3-axis stage 8 Digital Multimeter

Claims

1. At least one strain sensing element having a cantilever structure, A pair of strain gauges are provided on each strain sensing element, A Wheatstone bridge circuit with multiple reference resistors, A MEMS sensor comprising, A MEMS sensor characterized in that the pair of strain gauges are provided side by side only at the stress concentration points of each strain sensing element, and the plurality of reference resistors are provided on both sides of the pair of strain gauges.

2. At least one strain sensing element, A pair of strain gauges are provided on each strain sensing element, A Wheatstone bridge circuit with multiple reference resistors, A MEMS sensor comprising, The MEMS sensor is characterized in that the pair of strain gauges are provided side by side only at the stress concentration points of each strain sensing element, and the plurality of reference resistors are provided on each strain sensing element.

3. A MEMS sensor according to claim 2, A MEMS sensor characterized by each strain sensing element having a cantilever structure.

4. A MEMS sensor according to claim 1 or 3, A MEMS sensor characterized in that the stress concentration area is near the fixed end of the cantilever structure.

5. A MEMS sensor according to claim 4, A MEMS sensor characterized in that the pair of strain gauges are arranged side by side in the short direction of the cantilever structure near the fixed end.

6. A MEMS sensor according to claim 1 or 2, A MEMS sensor characterized in that the strain gauge and the reference resistor are made of the same material.

7. A MEMS sensor according to claim 6, The aforementioned material is NiCr, and the MEMS sensor is characterized by this.

8. A MEMS sensor according to any one of claims 1 to 7, A MEMS sensor characterized in that the number of strain sensing elements is two.

Images