JP4569242B2 - Physical quantity sensor - Google Patents

Description

  The present invention relates to a physical quantity sensor that detects a physical quantity to be detected as a change in resistance value due to strain of a gauge resistance.

  Conventionally, as this kind of physical quantity sensor, a semiconductor pressure sensor, a semiconductor acceleration sensor, and the like using a piezoresistor whose resistance value changes when an external force is applied to a semiconductor crystal as a gauge resistance have been provided.

  On the other hand, in recent years, physical quantity sensors using carbon nanotubes that have attracted attention in the field of nanotechnology as gauge resistance have been proposed (see, for example, Patent Documents 1 and 2).

  Here, the pressure sensor using carbon nanotubes as the gauge resistance has, for example, the configuration shown in FIG.

  The pressure sensor having the configuration shown in FIG. 12 is formed by processing a silicon substrate by a micromachining technique and has a sensor structure 1 having an insulating film 2 made of a silicon oxide film on one surface side, and insulation of the sensor structure 1. Two gauge resistors R1 and R3 and two reference resistors R2 and R4, each of which is arranged on the film 2 and made of one carbon nanotube, and a glass pedestal 9 fixed to the other surface of the sensor structure 1 And.

  The sensor structure 1 includes a frame 1a having a rectangular frame shape and a thin diaphragm 1b continuously and integrally connected to the frame 1a inside the frame 1a. That is, the sensor structure 1 is formed with a diaphragm 1b that is positioned inside the frame 1a and supported by the frame 1a over the entire circumference. When pressure is applied from the thickness direction of the diaphragm 1a, the diaphragm is bent and deformed. It is like that. Here, the gauge resistors R1 and R3 are arranged so as to straddle the diaphragm 1a and the frame 1a, and the reference resistors R2 and R4 are arranged on the frame 1a. The sensor structure 1 is formed by providing a recess 1c on the other surface by anisotropic etching using an alkaline solution. On the other hand, the base 9 is provided with an introduction hole 9a for introducing a fluid into the recess 1c of the sensor structure 1 in the thickness direction.

  The two gauge resistors R1 and R3 and the two reference resistors R2 and R4 described above are illustrated by a plurality of metal wirings 4 formed on the insulating film 2 on the one surface side of the sensor structure 1. 13 is connected to form a bridge circuit shown in FIG.

  Between each resistance R1-R4 and each metal wiring 4 electrically connected to each resistance R1-R4, it consists of a catalyst metal material (for example, iron, nickel, cobalt etc.) for growing a carbon nanotube. An electrode 5 is interposed between the pair of electrodes 5 and 5 by applying a voltage between the pair of electrodes 5 and 5 and supplying a source gas containing carbon to the one surface side of the sensor structure 1. Carbon nanotubes are grown on the surface. That is, each carbon nanotube constituting each of the resistors R1 to R4 is bridged between the pair of electrodes 5 and 5.

  Therefore, if a suitable power supply E for detection is connected between one terminal at the diagonal position of the bridge circuit, the voltage between the other terminals Vo1 and Vo2 at the other diagonal position is detected, and appropriate correction is applied, the diaphragm 1b A voltage proportional to the pressure acting on the can be obtained. In the pressure sensor described above, a part of each of the four metal wirings 4 constitutes a pad as a terminal.

  Next, an example of an acceleration sensor using carbon nanotubes as gauge resistance will be described with reference to FIG.

  The acceleration sensor configured as shown in FIG. 14 includes a sensor structure 11 formed by micromachining a silicon substrate and having an insulating film 12 made of a silicon oxide film on one surface side, and an insulating film 12 of the sensor structure 11. Two gauge resistors R11, R12 and two reference resistors R13, R14 each formed of one carbon nanotube, and a glass cover 19 fixed to the other surface of the sensor structure 11, A glass cover (not shown) fixed to one surface side of the sensor structure 11 is provided.

  The sensor structure 11 includes a frame 11a having a rectangular frame shape, and two flexures in which one side around a weight part 11b disposed inside the frame 11a and spaced apart from the frame 11a is thinner than the frame 11a. It has a structure connected continuously and integrally to the frame 11a via 11c. That is, in the sensor structure 11, a weight portion 11b that is located inside the frame 11a and is sensitive to acceleration is supported by the frame 11a via two flexure portions 11c, and the flexure portion 11c is provided around the weight portion 11b. A slit 11d is formed between the frame 11a and the frame 11a. Moreover, the bending part 11c is spaced apart in the direction along one side of the weight part 11b, and is formed in two places.

  For example, the weight portion 11b is formed by performing anisotropic etching on a portion corresponding to the slit 11d on the silicon substrate from the back surface side (the other surface side) using an alkaline solution, and then forming a portion corresponding to the slit 11d. It is formed by etching from one surface side of the silicon substrate. Further, a recess 19b for securing a swinging space of the weight portion 11b is formed on the surface of the cover 19 on the other surface side of the sensor structure 11 facing the sensor structure 11. Similarly, a recess for securing a swinging space of the weight portion 11b is also formed on the surface of the cover on the one surface side of the sensor structure 11 that faces the sensor structure 11.

  The two gauge resistors R11 and R12 and the two reference resistors R13 and R14 described above form a bridge circuit by the metal wiring 14 formed on the insulating film 12 on the one surface side of the sensor structure 11. They are connected so as to be configured (note that an interlayer insulating film (not shown) is interposed between the metal wirings 14 and 14 that overlap in the thickness direction of the sensor structure 11).

  In the above-described acceleration sensor, when an external force (acceleration) including a component in the thickness direction of the sensor structure 11 acts on the weight portion 11b, the frame 11a and the weight portion 11b are separated from the sensor structure 11 by the inertia of the weight portion 11b. As a result, the bending portion 11c is bent and the gauge resistances R11 and R12 are deformed, and the resistance values of the gauge resistances R11 and R12 change. In contrast, the resistance values of the reference resistors R13 and R14 arranged so as to overlap the frame 11a do not change even when the weight portion 11b is displaced.

Therefore, it is possible to detect the acceleration acting on the sensor structure 11 by detecting a change in the resistance values of the gauge resistors R11 and R12. In other words, if an appropriate power source for detection is connected between one terminal at the diagonal position of the bridge circuit, a voltage between the other terminal at the diagonal position is detected, and appropriate correction is applied, the weight 11b is acted on. A voltage proportional to the acceleration to be obtained can be obtained. The gauge resistors R11 and R12 are arranged with the extending direction of the bent portion 11c as the longitudinal direction, and are deformed in the same manner as the bent portion 11c.
JP 2004-53424 A JP 2004-163373 A

  By the way, in the physical quantity sensor using the carbon nanotube as the gauge resistance as described above, high sensitivity is expected by improving the gauge ratio of the gauge resistance.

  However, regarding the relationship between the bending angle β and the gauge factor when the inventors bent the carbon nanotube CNT having a length L of 5 μm at the bending angle β as shown by the solid line as shown by the one-dot chain line in FIG. As a result, as shown in FIG. 16, when the bending angle β is in the range of 172 ° to 179 °, the gauge factor is about 120, and when the same relationship is investigated with respect to the piezoresistance of silicon, it is not dependent on the bending angle β. The finding that the gauge factor was approximately 120 was obtained.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a physical quantity sensor capable of increasing the sensitivity as compared with the prior art.

  The invention of claim 1 is a physical quantity sensor that detects a physical quantity to be detected as a change in resistance value due to strain of a gauge resistance, and the gauge resistance is a pair of electrodes formed on one surface of the sensor structure. It is made up of carbon nanotubes that are sandwiched between them, and comes into contact with one side of the sensor structure on the middle of the carbon nanotubes that make up the gauge resistance. In addition to the deformation of the carbon nanotube, a bias portion that bends an intermediate portion of the carbon nanotube is provided.

  According to the present invention, since the bias portion that bends the intermediate portion of the carbon nanotube apart from the deformation of the carbon nanotube caused by the force when at least a force is applied to the sensor structure, the gauge resistance is provided. Compared with a conventional physical quantity sensor using carbon nanotubes, it is possible to increase the gauge factor of carbon nanotubes constituting the gauge resistance, and it is possible to achieve higher sensitivity than in the past.

  According to a second aspect of the present invention, in the first aspect of the present invention, a plurality of bias portions arranged in parallel with the pair of electrodes are in contact with an intermediate portion of the carbon nanotube constituting the gauge resistance. And

  According to the present invention, it is possible to reduce the bending angle of the intermediate portion of the carbon nanotube by the bias portion while making the gauge ratio of the carbon nanotube constituting the gauge resistance the same value as the case where there is one bias portion. In addition, breakage of the carbon nanotubes and breakage of the paired electrodes are less likely to occur, and reliability is improved.

  According to a third aspect of the present invention, in the first aspect of the present invention, the bias portion presses an intermediate portion of the carbon nanotubes constituting the gauge resistance in a state where the force is not applied to the sensor structure, thereby adjusting the bending angle of the carbon nanotubes. The relative positional relationship with the one surface of the sensor structure is set so as to be 172 °.

  According to this invention, when the force is applied to the sensor structure, even if the force is small, the bending angle of the carbon nanotubes constituting the gauge resistance is smaller than 172 ° and the gauge factor is increased. High sensitivity can be achieved.

  According to a fourth aspect of the present invention, in the first to third aspects of the invention, the sensor structure is characterized in that a recess is formed between the pair of electrode forming portions on the one surface.

  According to this invention, it becomes easy to bend the intermediate part of the carbon nanotube which comprises gauge resistance with a bias part, and can achieve high sensitivity compared with the case where the recessed part is not formed.

A fifth aspect of the present invention is the pressure sensor for the pressure sensor according to any one of the first to fourth aspects, wherein the sensor structure has a diaphragm formed by providing a recess on the other surface opposite to the one surface. The structure is characterized in that the gauge resistance is arranged at the center of the diaphragm.

  According to the present invention, since the gauge resistance is arranged at the central portion where the displacement of the diaphragm due to the pressure as the force is large, the gauge resistance is arranged at the peripheral portion where the displacement of the diaphragm due to the pressure as the force is small. If the sensitivity is the same as that provided, the thickness of the diaphragm can be increased, and the mechanical strength of the sensor structure can be increased.

A sixth aspect of the present invention is the pressure sensor for the pressure sensor according to any one of the first to fifth aspects, wherein the sensor structure has a diaphragm formed by providing a recess on the other surface opposite to the one surface. The thickness of the peripheral portion of the diaphragm is set to be thicker than the thickness of the central portion, and the gauge resistance is a step formed on the opposite side of the diaphragm from the one surface side and the thickness direction of the diaphragm It is arrange | positioned in the site | part which overlaps in.

  According to this invention, compared to the case where the thickness of the diaphragm is constant and the gauge resistance is disposed around the diaphragm, the carbon nanotube constituting the gauge resistance is formed by the deformation of the diaphragm due to the pressure as the force. Greater strain can be applied and higher sensitivity can be achieved.

According to a seventh aspect of the invention, there is provided the cover according to any one of the first to sixth aspects, further comprising a cover fixed to the one surface side of the sensor structure, and the bias portion from the surface of the cover facing the sensor structure. It is characterized by being projected.

  According to the present invention, the bias portion can be brought into contact with the carbon nanotube constituting the gauge resistance by fixing the cover to the one surface side of the sensor structure.

The invention according to claim 8 is the insulator film according to any one of claims 1 to 6 , wherein the bias portion is patterned so as to intersect with the carbon nanotube constituting the gauge resistance on the one surface side of the sensor structure. It is characterized by comprising.

  According to the present invention, since the bias portion can be brought into contact with the carbon nanotube constituting the gauge resistance with high positional accuracy without fixing a cover which is another member on the one surface side of the sensor structure, Compared with the invention of claim 8, the cost and thickness can be reduced.

  According to the first aspect of the present invention, compared with a conventional physical quantity sensor using carbon nanotubes as a gauge resistance, it becomes possible to increase the gauge ratio of the carbon nanotubes constituting the gauge resistance, and to achieve higher sensitivity than in the past. There is an effect that it becomes possible.

  In the present embodiment, a pressure sensor that is an example of a physical quantity sensor that detects a physical quantity to be detected as a change in resistance value due to strain of a gauge resistance will be described with reference to FIGS.

  The pressure sensor of the present embodiment is a sensor having an insulating film 2 made of a silicon oxide film on one surface side, which is formed by processing a silicon substrate (hereinafter referred to as a first silicon substrate), which is a semiconductor substrate, by micromachining technology. Structure 1, two gauge resistors R 1 and R 3 and two reference resistors R 2 and R 4 that are arranged on the one surface side of sensor structure 1 and are each made of carbon nanotube CNT, and sensor structure 1 Includes a cover 7 formed by processing another silicon substrate (hereinafter referred to as a second silicon substrate) by a micromachining technique and fixed to the one surface side of the sensor structure 1. Note that the number of carbon nanotubes CNT constituting each of the resistors R1 to R4 is not particularly limited, and may be one or plural. The cover 7 is not limited to the second silicon substrate, and may be formed of a glass substrate.

  The sensor structure 1 includes a rectangular frame 1a and a thin diaphragm 1b continuously and integrally connected to the frame 1a inside the frame 1a. That is, the sensor structure 1 is formed with a diaphragm 1b that is located inside the frame 1a and supported by the frame 1a over the entire circumference. When pressure is applied from the thickness direction of the diaphragm 1a, the diaphragm is bent and curved. It is designed to deform. Here, the gauge resistors R1 and R3 are arranged on the one surface side of the sensor structure 1 corresponding to the peripheral portion of the diaphragm 1a with the direction perpendicular to the boundary between the diaphragm 1a and the frame 1a as the longitudinal direction. The reference resistances R2 and R4 are arranged with the direction perpendicular to the boundary between the diaphragm 1a and the frame 1a at the portion corresponding to the frame 1a on the one surface side of the sensor structure 1 as the longitudinal direction. That is, the gauge resistances R1 and R3 are two sides of the four sides constituting the outer periphery of the diaphragm 1b (the boundary between the diaphragm 1b and the frame 1a) so that the amount of change in the resistance value accompanying the bending deformation of the diaphragm 1b is increased. The reference resistors R2 and R4 are disposed in portions corresponding to the frame 1a so that the resistance value does not change even when the diaphragm 1b is bent and deformed.

  Note that the sensor structure 1 is formed by, for example, performing the anisotropic etching using an alkaline solution such as KOH (potassium hydroxide) or TMAH (tetramethylammonium hydroxide) on the back surface of the first silicon substrate (sensor structure). It is formed by providing a recess 1c on the other surface of the body 1.

  Here, in place of the first silicon substrate as the semiconductor substrate, a so-called SOI substrate (front surface side silicon layer and back surface side) in which an insulating layer made of a buried oxide film (silicon oxide film) is formed in the middle in the thickness direction. If the substrate having the insulating layer interposed between the silicon substrate and the silicon substrate is used, the thickness of the diaphragm 1b can be managed with high accuracy by using the insulating layer as an etching stopper layer when etching from the back side. Thus, the yield can be improved, and as a result, the cost can be reduced.

The two gauge resistors R1 and R3 and the two reference resistors R2 and R4 are a plurality of metal wires (not shown) formed on the insulating film 2 on the one surface side of the sensor structure 1. ) Or the like so as to constitute the bridge circuit shown in FIG. In addition, between each resistance R1-R4 and each metal wiring electrically connected to each resistance R1-R4, it is from a catalyst metal material (for example, iron, nickel, cobalt etc.) for growing a carbon nanotube. An electrode (not shown) is interposed, a voltage is applied between the pair of electrodes via metal wiring, and a raw material gas containing carbon on the one surface side of the sensor structure 1 (for example, hydrocarbon) C ₂ H ₂ gas, C ₂ H ₄ gas, CH ₄ gas, etc.) are supplied and carbon nanotubes are grown between the pair of electrodes 5 and 5 by the CVD method. That is, each carbon nanotube constituting each of the resistors R1 to R4 is bridged between the pair of electrodes 5 and 5.

  Therefore, if a suitable power supply E for detection is connected between one terminal at the diagonal position of the bridge circuit, the voltage between the other terminals Vo1 and Vo2 at the other diagonal position is detected, and appropriate correction is applied, the diaphragm 1b A voltage proportional to the pressure acting on the can be obtained. In the pressure sensor of this embodiment, a part of each of the four metal wirings constitutes a pad as a terminal.

  By the way, as for the sensor structure 1, the recessed part 6 is formed between the formation parts between the paired electrodes on the one surface. In the present embodiment, since the pair of electrodes is provided for each of the resistors R1 to R4, the sensor structure 1 has four recesses 6 formed therein. Here, the opening shape of the recess 6 is an elongated rectangular shape whose longitudinal direction is a direction intersecting the parallel arrangement direction of the paired electrodes on the one surface of the sensor structure 1, and the cross-sectional shape of the recess 6. Has a shape in which the opening width is substantially constant in the depth direction. Therefore, the concave portion 6 may be formed by dry etching a predetermined portion of the concave portion 6 on the one surface side of the sensor structure 1 to a predetermined depth. Here, the shape of the recess 6 is such that the opening width is substantially constant in the depth direction as described above, and the carbon nanotube CNT grown between the pair of electrodes positioned on both sides of the recess 6 is provided. Grows linearly. In the illustrated example, the predetermined depth is set to coincide with the thickness dimension of the insulating film 2, but may be set smaller than the thickness dimension of the insulating film 2.

  On the other hand, the cover 7 has a rectangular plate shape, and a recess 7 a for securing a displacement space of the diaphragm 1 a of the sensor structure 1 is formed on the surface facing the sensor structure 1. Note that the cover 7 is set to have a shorter dimension in the left-right direction in FIG. 1A than the sensor structure 1 so that the pads on the one surface side of the sensor structure 1 can be exposed. It is.

  Here, when a force (here, pressure) is applied to the sensor structure 1 on the inner bottom surface of the recess 7a in the cover 7 in contact with an intermediate portion of the carbon nanotubes CNT constituting the gauge resistors R1 and R3. Apart from the deformation (curvature deformation) of the carbon nanotube CNT caused by the force, two protruding bias portions 7b for bending the intermediate portion of the carbon nanotube CNT are provided. The bias portion 7b has an elongated rectangular shape in cross section, and is formed in a shape in which the cross-sectional area gradually increases as the distance from the inner bottom surface of the recess 7a increases. As shown in FIG. 2, the tip surface of the bias portion 7b A gap is formed between the outer peripheral edge of the sensor structure 1 and the peripheral edge of the recess 6 in the sensor structure 1.

  Here, when no pressure is applied to the diaphragm 1b of the sensor structure 1, the carbon nanotube CNT is folded although the tip surface of the bias portion 7b is in contact with the carbon nanotube CNT as shown in FIG. Although not bent, when pressure is applied to the diaphragm 1b of the sensor structure 1 from below in FIG. 6 (a), the diaphragm 1b is curved and deformed as indicated by a two-dot chain line in FIG. 6 (b). Thus, the intermediate portion of the carbon nanotube CNT is bent into a V-shape that protrudes in the opposite direction to the displacement direction of the diaphragm 1b by the bias portion 7b and enters the inside of the recess 6. In short, the bias part 7b abuts against the intermediate part of the carbon nanotubes CNT constituting the gauge resistors R1 and R3 and applies a stress different from the stress caused by the pressure when the pressure is applied to the sensor structure 1. It has the function added to the middle part.

  Thus, the pressure sensor according to the present embodiment includes the bias portion 7b that bends the intermediate portion of the carbon nanotube CNT separately from the deformation of the carbon nanotube CNT caused by the pressure when the sensor structure 1 is subjected to pressure. Therefore, when a pressure is applied to the sensor structure 1, the intermediate portion of the carbon nanotubes CNT constituting the gauge resistors R1 and R3 is bent as shown in FIG. Since the ratio becomes higher, the gauge ratio of the carbon nanotubes CNT constituting the gauge resistors R1 and R3 can be increased as compared with the conventional pressure sensor, and the sensitivity can be increased as compared with the conventional pressure sensor. . In addition, since the recess 6 is formed between the pair of electrode forming portions on the one surface of the sensor structure 1, the intermediate portion of the carbon nanotubes CNT constituting the gauge resistors R1 and R3 is formed by the bias portion 7b. It becomes easy to bend, and high sensitivity can be achieved compared with the case where the recessed part 6 is not formed.

Incidentally, the bias portion 7b is thereby bending the intermediate portion is pressed as shown in FIG. 8 and an intermediate portion of the carbon nanotubes CNT constituting the gauge resistors R1, R3 in a state where pressure in the sensor structure 1 is not have work You may do it. In this case, if the relative positional relationship between the bias portion 7b and the one surface of the sensor structure 1 is set so that the bending angle β of the carbon nanotube CNT is 172 °, the sensor structure Even when the pressure is applied to the body 1, even if the pressure is small, the bending angle of the carbon nanotubes CNT constituting the gauge resistances R1 and R3 is smaller than 172 ° and the gauge rate is increased, so that higher sensitivity is achieved. Can do.

  In the above example, one bias portion 7b is in contact with the intermediate portion of the carbon nanotubes CNT constituting the gauge resistors R1 and R3. However, as shown in FIG. If the cover 7 is formed so that a plurality of bias portions 7b, 7b arranged in the direction in which the electrodes are arranged in contact with each other, the bias portion 7b has one gauge ratio of the carbon nanotubes CNT constituting the gauge resistors R1, R3. The bending angle of the intermediate portion of the carbon nanotube CNT by the bias portion 7b (the bending angle of the carbon nanotube CNT by the individual bias portion 7b) by the bias portion 7b can be reduced, and the value of the carbon nanotube CNT can be reduced. Breakage and breakage of the paired electrodes are less likely to occur, improving reliability.

Note that the recess 6 formed on the one surface of the sensor structure 1 has a V-shaped cross section as shown in FIG. 9 (a), and an opening angle (an angle formed by two surfaces which are the inner surfaces of the recess 6 and are inclined to each other). ) If α is set to 172 °, the carbon nanotubes CNT bridged by the growth by the above-described CVD method between the pair of electrodes (between the electrodes facing each other with the recess 6 in between) are as shown in FIG. Are bent along the two inner surfaces of the recess 6 that are inclined with respect to each other. The bending angle β of the carbon nanotube CNT at this time is approximately 172 °. As a result, the carbon nanotubes CNT constituting the gauge resistors R1 and R3 can be bent at an angle of 172 ° in a state where no pressure is applied to the sensor structure, thereby further increasing the sensitivity. Can be achieved. Here, from the relationship between the bending angle and the gauge factor in FIG. 16 described above, the gauge factor of the carbon nanotube CNT grown along the inner surface of the recess 6 is increased by making the opening angle α of the recess 6 smaller than 172 °. can do. However, if the opening angle α is too small, the carbon nanotubes CNT will not grow along the inner surface of the recess 6.

  By the way, in this embodiment, the sensor structure 1 constitutes a pressure sensor structure, and the gauge resistors R1 and R3 are arranged on the peripheral portion of the diaphragm 1b of the sensor structure 1. If the gauge resistors R1 and R3 are arranged in the central portion where the displacement amount of the diaphragm 1b due to pressure is large, the same sensitivity as the case where the gauge resistors R1 and R3 are arranged in the peripheral portion where the displacement amount of the diaphragm 1b due to pressure is small. If so, the thickness of the diaphragm 1b can be increased, and the mechanical strength of the sensor structure 1 can be increased.

  Further, as shown in FIG. 10, the thickness of the peripheral portion of the diaphragm 1b is set to be thicker than the thickness of the central portion, and a step portion 1d is formed on the opposite side of the diaphragm 1b from the one surface side. If the carbon nanotubes CNT constituting the gauge resistances R1 and R3 are arranged in a portion overlapping in the thickness direction (vertical direction in FIG. 10) of the stepped portion 1d and the diaphragm 1b in the diaphragm 1b, as shown in FIG. Compared with the case where the thickness of the diaphragm 1b is constant and the gauge resistors R1 and R3 are disposed around the diaphragm 1b, the carbon nanotubes CNT constituting the gauge resistors R1 and R3 are formed by the deformation of the diaphragm 1b due to pressure. Greater strain can be applied and higher sensitivity can be achieved.

  Further, in the example shown in FIG. 1, a bias portion 7 b is projected from a surface of the cover 7 fixed to the one surface side of the sensor structure 1 facing the sensor structure 1. A cover 7 made of a second silicon substrate or a glass substrate is fixed to the one surface side of the sensor structure 1 made of a silicon substrate by a well-known joining method, whereby the carbon nanotubes CNT constituting the gauge resistors R1 and R3 are obtained. The bias portion 7b can be brought into contact.

Instead of fixing the cover 7 having the bias portion 7b to the one surface side of the sensor structure 1 as described above, as shown in FIG. It consists of an insulator film (for example, SiO ₂ film, Si ₃ N ₄ film, polyimide film, etc.) patterned so as to cross (orthogonal) the carbon nanotube CNT constituting R3, and has the same function as the bias part 7b. The bias unit 8 may be provided. The bias portion 8 made of the insulating film patterned in this way, for example, after generating the carbon nanotubes CNT constituting the resistors R1 to R4 on the one surface side of the sensor structure 1, the sensor structure 1 An insulator film may be formed on the entire surface on the one surface side, and the insulator film may be patterned using a lithography technique and an etching technique. Therefore, if such a bias portion 8 is adopted, the bias portion is connected to the carbon nanotube CNT constituting the gauge resistors R1 and R3 without fixing the cover 7 as another member to the one surface side of the sensor structure 1. 8 can be brought into contact with high positional accuracy, so that the cost and thickness can be reduced as compared with the configuration of FIG.

  In the above-described embodiment, the pressure sensor has been described as an example of the physical quantity sensor. However, the technical idea of the present invention is not limited to the pressure sensor, for example, other physical quantity sensors using a gauge resistance (for example, an acceleration sensor, It can also be applied to a gyro sensor or the like.

Embodiments are shown, (a) is a schematic plan view, (b) is an AA ′ sectional view of (a), (c) is a BB ′ sectional view of (a), and (d) is (b). It is an enlarged view of the principal part C of FIG. It is principal part explanatory drawing in the same as the above. The structure for sensors in the same as above is shown, in which (a) is a plan view, (b) is a sectional view taken along the line A-A 'in (a), and (c) is a sectional view taken along the line B-B' in (a). The principal part of the structure for sensors in the same as above is shown, (a) is a plan view and (b) is a sectional view. The cover in the same as above is shown, (a) is a plan view, (b) is a sectional view taken along line AA ′ in (a), (c) is a sectional view taken along line BB ′ in (a), and (d) is a bottom view. is there. It is operation | movement explanatory drawing same as the above. It is principal part sectional drawing of the other structural example same as the above. It is principal part sectional drawing of the other structural example same as the above. It is principal part explanatory drawing of the other structural example same as the above. It is principal part sectional drawing of the other structural example same as the above. It is a principal part perspective view of the other structural example same as the above. A prior art example is shown, (a) is a schematic plan view, (b) is a schematic cross-sectional view, and (c) is an enlarged view of the main part of (b). It is operation | movement explanatory drawing same as the above. Another prior art example is shown, (a) is a schematic plan view, (b) is a schematic cross-sectional view, and (c) is an enlarged view of a main part of (b). It is explanatory drawing of the bending angle of a carbon nanotube. FIG. 4 is a relationship diagram between a bending angle of a carbon nanotube and a gauge factor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor structure 1a Frame 1b Diaphragm 1c Recess 2 Insulating film 6 Recess 7 Cover 7a Recess 7b Bias CNT Carbon nanotube R1, R3 Gauge resistance R2, R4 Reference resistance

Claims (8)

  A physical quantity sensor that detects a physical quantity to be detected as a change in resistance value due to strain of a gauge resistance, in which the gauge resistance is stretched between a pair of electrodes formed on one surface of the sensor structure. A deformation of the carbon nanotube caused by the force when a force is applied to at least the sensor structure by contacting an intermediate portion of the carbon nanotube constituting the gauge resistance on one surface side of the sensor structure. Separately, a physical quantity sensor comprising a bias part that bends an intermediate part of the carbon nanotube.   The physical quantity sensor according to claim 1, wherein a plurality of bias portions arranged in parallel with the pair of electrodes are in contact with an intermediate portion of the carbon nanotube constituting the gauge resistance.   The bias portion presses the intermediate portion of the carbon nanotubes constituting the gauge resistance in a state where the force is not applied to the sensor structure so that the bending angle of the carbon nanotube is 172 °. 2. The physical quantity sensor according to claim 1, wherein a relative positional relationship with the surface is set.   4. The physical quantity sensor according to claim 1, wherein the sensor structure is formed with a recess between a pair of electrode forming portions on the one surface. The sensor structure is a structure for a pressure sensor having a diaphragm formed by providing a recess on the other surface opposite to the one surface, and the gauge resistance is disposed at the center of the diaphragm. physical quantity sensor of the mounting serial to any one of claims 1 to 4, characterized by comprising. The sensor structure is a structure for a pressure sensor having a diaphragm formed by providing a recess on the other surface opposite to the one surface, and the thickness of the peripheral portion of the diaphragm is the thickness of the central portion. The gauge resistance is disposed at a portion overlapping with a stepped portion formed on the opposite side of the diaphragm from the one surface side in the thickness direction of the diaphragm. The physical quantity sensor according to claim 5. 7. The sensor structure according to claim 1, further comprising a cover fixed to the one surface side of the sensor structure , wherein the bias portion projects from a surface of the cover facing the sensor structure . The physical quantity sensor according to any one of the above. Bias unit, to one of the claims 1 to 6, characterized in that it consists of patterned insulating film so as to intersect the carbon nanotubes constituting the gauge resistors on the one surface side of the sensor structure The physical quantity sensor described .

Images