JP2010032389A - Physical quantity sensor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliable physical quantity sensor which can respond to making its power consumption low and suppresses variations in its output characteristic, and to provide a manufacturing method therefor. <P>SOLUTION: The sensor is equipped with: a frame part having an aperture; a spindle part disposed in the aperture of the frame part; at least one beam part for connecting the frame part and the spindle part; and two or more detecting parts for detecting the physical quantity which are formed on the beam part and respectively disposed on an area where one end of the beam part is connected with the frame part, and an area where the other end of the beam part is connected with the spindle part. The detecting part is characterized in such the configuration that a plurality of piezoresistive elements are connected in series by interconnections made of a metallic material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a physical quantity sensor capable of detecting a physical quantity variation and a manufacturing method thereof, and more particularly to a physical quantity sensor of a type that detects acceleration in a plurality of directions using a piezoresistive element as a detection element and a manufacturing method thereof.

  In recent years, a sensor using a piezoresistor as a detection element (so-called piezoresistive acceleration sensor) has been put into practical use as a sensor having a small and simple structure using MEMS (Micro Electro Mechanical Systems) technology (Patent Document 1). . Piezoresistive acceleration sensors are used in a wide range of fields such as HDD (hard disk drive) drop detection devices, in-vehicle airbag devices, and portable terminals such as cellular phones.

  In the acceleration sensor disclosed in Patent Document 1, the weight body portion is displaced according to the applied acceleration, and the flexible portion is bent according to the displacement. The piezoresistive element formed in the flexible part changes the resistance value according to the amount of bending (stress) of the flexible part. Then, a voltage is applied to the piezoresistive element, and the acceleration is detected by referring to the voltage value accompanying the resistance change. The stress generated in the flexible portion is concentrated at the connection portion of the frame portion and the weight portion, and rapidly decreases as the distance from the connection portion increases, and the stress is zero at the center of the flexible portion. The resistance change that occurs in the piezoresistive element is due to the average stress change in the entire length of the piezoresistive element. It is efficient to arrange them selectively. However, if the piezoresistive element is simply shortened, there is a problem that the resistance value is lowered and the power consumption is increased.

Therefore, an acceleration sensor as disclosed in Patent Document 2 has been proposed. According to Patent Document 2, a plurality of pairs of piezoresistive elements for detecting acceleration in each direction are arranged symmetrically with respect to the center line of the flexible part at the stress concentration part on the flexible part, and they are highly doped with impurities. They are connected by high-density diffusion wiring formed by diffusion.
JP 2003-92413 A JP 2006-98321 A

  However, since the acceleration sensors described in Patent Document 1 and Patent Document 2 apply a voltage to the piezoresistive element during driving, Joule heat is generated from the piezoresistive element. In Patent Document 2, since a plurality of piezoresistive elements are connected by a high-concentration diffusion wiring (semiconductor layer), heat is also generated in the high-concentration diffusion wiring and it is difficult to dissipate heat to the outside. Due to the Joule heat, the lead wire formed on the flexible part or the flexible part and the protective film such as a silicon oxide film and a silicon nitride film are thermally expanded, resulting in fluctuations in sensor output characteristics. When piezoresistive elements are connected with high-concentration wiring, not only is the heat generated by the piezoresistive elements difficult to escape to the outside, but because the high-concentration wiring itself is a resistor, heat is generated and output characteristics fluctuate greatly. . When the above acceleration sensor is put into actual use, the influence of output fluctuation due to heat generated in the piezoresistive element and the high-concentration diffusion wiring appears. As described above, in the conventional sensor, the output characteristics change with time, and thus there is a problem that the reliability of the product is lacking.

  In view of the above, an object of the present invention is to provide a highly reliable physical quantity sensor that can cope with low power consumption and that suppresses fluctuations in output characteristics, and a method for manufacturing the same.

  The physical quantity sensor according to the present invention includes a frame part having an opening, a weight part disposed in the opening of the frame part, at least one beam part connecting the frame part and the weight part, and the beam A plurality of portions for detecting a physical quantity variation, each of which is formed in a portion and arranged in a region where one end of the beam portion is connected to the frame portion and a region where the other end of the beam portion is connected to the weight portion. The detection unit is configured by connecting a plurality of piezoresistive elements in series by wires made of a metal material. With the above configuration, low power consumption can be achieved by connecting a plurality of piezoresistive elements in series and obtaining a desired resistance value. Furthermore, by connecting a plurality of piezoresistive elements with wiring made of a metal material having high heat dissipation to improve heat dissipation, fluctuations in output characteristics can be suppressed.

  A method of manufacturing a physical quantity sensor according to the present invention is a method of manufacturing a sensor that detects a physical quantity using a semiconductor substrate, and forms a plurality of piezoresistive elements by diffusing impurities on one surface of the semiconductor substrate. Forming a frame portion having an opening, a weight portion disposed in the opening of the frame portion, and at least one beam portion connecting the frame portion and the weight portion from the semiconductor substrate; A step of connecting a predetermined piezoresistive element in series by a wiring made of a metal material to form a detection unit; and the detection so as to constitute a bridge circuit on the flexible unit and the frame unit Forming a bridge wiring for connecting the sections.

  According to the present invention, it is possible to provide a highly reliable physical quantity sensor that can cope with low power consumption and that suppresses fluctuations in output characteristics, and a method for manufacturing the same.

Hereinafter, a semiconductor triaxial acceleration sensor which is an aspect of the physical quantity sensor according to the present invention will be described with reference to the drawings. FIG. 1 is an overall perspective view of an acceleration sensor according to the present invention.
As shown in FIG. 1, the acceleration sensor 1 is a substantially rectangular parallelepiped, and is composed of a sensor body 2 made of a semiconductor substrate and a support substrate 3 made of glass or the like. For the sake of explanation, in the figure, two axes (X axis and Y axis) perpendicular to the plane of the acceleration sensor are set, and a direction perpendicular to the two axes is defined as the Z axis. The sensor body 2 is composed of an SOI (Silicon On Insulator) substrate 110, and is formed by sequentially laminating a silicon film 120, a silicon oxide film 130, and a silicon substrate 140. A weight body (weight section 142) is arranged in a frame having an opening (frame section 121 and frame section 141), and the weight body is supported by a beam (beam section 123) having flexibility with respect to the frame. Configured. The support substrate 3 has a function as a pedestal for supporting the sensor body 2 and a function as a stopper substrate for restricting excessive displacement of the weight body in the downward direction (Z-axis negative direction). Note that when the sensor body 2 is directly mounted on a package substrate (not shown), the support substrate 3 is not necessarily required.

FIG. 2 is an exploded perspective view of the acceleration sensor. The silicon film 120 includes a fixed frame part 121 (the upper part of the frame), a weight joint part 122 disposed in the frame part 121, and two pairs (four in total) that connect the frame part 121 and the weight joint part 122. The beam part 123 is provided. The frame portion 121, the weight joint portion 122, and the beam portion 123 are defined by the opening 124. The frame part 121 is joined to the frame part 141 (the lower part of the frame) via the silicon oxide film 130. Further, the weight joint portion 122 is joined to the weight portion 142 having a substantially crowbar shape in the vertical view through the silicon oxide film 130. The weight part 142 is disposed in the frame part 141 so as to be separated.
The support substrate 3 is made of, for example, a glass substrate and is bonded to the sensor body 2 by anodic bonding.

FIG. 3 is a plan view and a sectional view of the sensor body. FIG. 3A is a plan view of the sensor main body, and detection units Rx to Rz for detecting acceleration in three axis (XYZ) directions are arranged on the four beam portions 123. The detection unit is disposed in a region where the beam unit 123 is connected to the frame unit 121 and the weight joint unit 122. In the drawing, detectors Rx1 to Rx4 and Rz1 to Rz4 are arranged on a pair of beam portions arranged in a direction along the X axis in order to detect acceleration in the X direction and the Z direction. On the other hand, detection units Ry1 to Ry4 for detecting acceleration in the Y direction are arranged in a pair of beam portions arranged in the direction along the Y axis. In addition, you may arrange | position the detection parts Rz1-Rz4 to a pair of beam part arrange | positioned in the direction along the Y-axis.
FIG. 3B is a cross-sectional view of the sensor main body along AA. The lower surface of the weight portion 142 is higher than the lower end of the frame portion 141, and a Z-negative direction is caused by a gap between the sensor substrate 142 and the glass substrate 3. It is set so that a certain amount of displacement is possible. FIG. 3C is a cross-sectional view of the sensor body along BB, and the beam portion 123 is a self-supporting thin film having flexibility.

4A and 4B are diagrams for explaining the details of the detection unit. FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view (a CC cross section in FIG. 4A). A plurality of piezoresistive elements r are arranged in the beam portion 123, and a piezoresistive group R is formed in the stress concentration portion. In the drawing, a case where six piezoresistive elements r are arranged is illustrated. One end of the piezoresistive element r shows an example in which the beam portion 123 is disposed so as to be in contact with the boundary where the beam portion 123 is connected to the frame portion 121 and the boundary where the beam portion 123 is connected to the weight joint portion 122. A piezoresistive element r may be arranged in
The piezoresistive element r is covered with an insulating layer 150, and has a contact hole 151 at a connection location with a wiring 152 and a bridge wiring L described later. In order to lower the connection resistance, the piezoresistive element exposed through the contact hole 151 may be connected by providing a high-concentration diffusion region (an impurity region having a concentration of about 1 to 3 digits higher than that of the piezoresistive element).

  Note that a total of twelve detection units Rx1 to Rx4, Ry1 to Ry4, and Rz1 to Rz4 are connected for each detection direction to form a bridge circuit as shown in FIG. At least two or more piezoresistive elements r are disposed on each of the four sides. Regarding the relationship between the bridge circuit and the output of the sensor, reference can be made to Japanese Patent Application Laid-Open No. 2007-322297, which is a patent application of the present applicant. An electrode pad (not shown) for connecting to an external circuit is provided on the frame portion 121, and an extension portion of a bridge wiring L described later is connected to the electrode pad so that an electrical signal accompanying acceleration is transmitted to the external circuit. I'm taking it out.

  In this specification, the wiring 152 is a metal wiring for connecting the piezoresistive element r, and the bridge wiring L is a wiring for connecting the detection units or between the detection unit and an electrode pad (not shown). It points to that.

5-8 is a figure which shows the 1st-4th embodiment of this invention. Hereinafter, the first embodiment will be described in order.
(First embodiment)
The first embodiment will be described with reference to FIG. FIG. 5 is a diagram illustrating a first embodiment according to the present invention, FIG. 5A is a diagram illustrating details of the detection unit, and FIG. 5B is a diagram illustrating the arrangement of the detection unit. is there. In FIG. 5A, as an example, the piezoresistive groups R including six piezoresistive elements r are arranged in regions where the beam portion 123 is connected to the frame portion 121 and the weight joint portion 122, respectively. Of the six piezoresistive elements r, three piezoresistive elements r are connected in series by a wiring 152 made of a metal material to constitute a detection unit Rx for detecting acceleration in the X direction. Further, the remaining three piezoresistive elements are similarly connected by a wiring 152 to constitute a detection unit Rz for detecting acceleration in the Z direction. The detection units Rx1 to Rx4 and Rz1 to Rz4 are connected by a bridge line L, respectively. By configuring the wiring 152 and the bridge wiring L from a metal material, the heat generated in the detection unit can be radiated to the outside.

  The piezoresistive element constituting the detection unit Rx (first detection unit) is configured not to sandwich the piezoresistive element constituting the detection unit Rz (second detection unit). That is, the nearest piezoresistive elements are connected. Accordingly, the routing of the wiring 152 can be simplified, the wiring length can be shortened, and the wiring resistance can be reduced.

Further, as shown in FIG. 5B, when the detection unit is disposed symmetrically with respect to the width center line L _C of the beam unit 123 and point-symmetrically with respect to the center G of the weight unit 142, the beam unit 123 generated by acceleration is detected. By twisting (rotation of the weight portion 142), detection of physical quantity fluctuations in the direction that is not desired to be detected (other-axis sensitivity) can be suppressed. Therefore, the accuracy of the detection signal can be improved. The center G of the weight part 142 refers to the position where the center of gravity of the weight part exists.

  By arranging the short piezoresistive element r at the location, the physical quantity variation can be detected effectively. In addition, it is possible to achieve both high sensitivity and low power consumption by connecting a plurality of piezoresistive elements in series to obtain an appropriate resistance value. The detection units Rx3 to Rx4 and Rz3 to Rz4 arranged in the pair of beam portions 123 are similarly configured by three piezoresistive elements, and 4 × 3 = 12 pieces per detection direction. A bridge circuit is constituted by the piezoresistive elements r (4N, in this embodiment, N = 3). According to the present invention, since a bridge circuit is formed by 4N (N is an integer of 2 or more) piezoresistive elements in each direction, low power consumption and high sensitivity can be achieved.

Next, a method for manufacturing the acceleration sensor according to the first embodiment will be described with reference to FIG. FIG. 9 is a drawing showing the manufacturing method of the first embodiment according to the present invention.
Acceleration sensor manufacturing method according to first embodiment (1) Preparation of SOI substrate (see FIG. 9A)
An SOI substrate 110 in which a silicon film 120, a silicon oxide film 130, and a silicon substrate 140 are stacked is prepared. As described above, the silicon film 120 is a layer constituting the frame part 121, the weight joint part 122, and the beam part 123. The silicon oxide film 130 is a layer that joins the silicon film 120 and the silicon substrate 140 and functions as an etching stopper layer. The silicon substrate 140 is a layer constituting the frame part 141 and the weight part 142. The SOI substrate 110 is produced by SIMOX or a bonding method. In the SOI substrate 110, the silicon film 120, the silicon oxide film 130, and the silicon substrate 140 have thicknesses of 5 μm, 2 μm, and 600 μm, respectively. A plurality of acceleration sensors 1 having a square outer circumference of 1 to 2 mm are arranged in a multi-sided manner on a wafer having a diameter of 150 mm to 200 mm.

(2) Formation of a piezoresistive group (see FIG. 9B)
An impurity diffusion mask (not shown) is formed on the SOI film 110 on the silicon film 120 side. As this mask material, for example, a silicon nitride film (Si ₃ N ₄ ) or a silicon oxide film (SiO ₂ ) can be used. After a silicon nitride film is formed on the entire surface of the silicon film 120 by LP-CVD (Low Pressure Chemical Vapor Deposition), a resist pattern (not shown) is formed on the silicon nitride film, and a piezoresistive element r is formed on the silicon nitride film. An opening corresponding to is formed by RIE (Reactive Ion Etching).

After removing the resist pattern, a diffusing agent containing B (boron) or the like is applied on the silicon film 120. Then, heat treatment (about 1000 ° C.) is performed to diffuse (drive in) the silicon film 120 to form a piezoresistive group R including a plurality of piezoresistive elements r. Unnecessary diffusing agent is removed using hydrofluoric acid or the like. Note that the piezoresistive element r may be formed by ion implantation other than the thermal diffusion method. Thereafter, the silicon nitride film (Si ₃ N ₄ ) is removed by etching with hot phosphoric acid.

(3) Formation of insulating layer and contact hole (see FIG. 9C)
An insulating layer 150 is formed on the silicon film 120. For example, by thermally oxidizing the surface of the silicon film 120, a SiO ₂ layer can be formed as an insulating layer. A contact hole 151 is formed on the insulating layer 150 by RIE using a resist as a mask. Note that the contact hole 151 may be formed after the silicon substrate 140 is processed.

(4) Gap formation (see FIG. 9D)
The gap 160 is formed by etching the silicon substrate 140 using a mask having an opening along the inner frame of the frame portion 141. The gap 160 is an interval necessary for the weight portion 142 to be displaced downward (on the glass substrate 3 side), and is, for example, 5 to 10 μm. The value of the gap 160 can be appropriately set according to the dynamic range of the sensor.

(5) Processing of silicon substrate (see FIG. 9E)
Next, a mask for defining the frame part 141 and the weight part 142 is formed on the lower surface of the silicon substrate 140. Using this mask, the silicon substrate 140 is etched until the lower surface of the silicon oxide film 130 is exposed. It is preferable to use DRIE (Deep Reactive Ion Etching) for the etching.

In DRIE, an etching step of digging while eroding the material layer in the thickness direction and a deposition step of forming a polymer wall on the side wall of the carved hole are alternately repeated. Since the side wall of the hole that has been dug is protected by forming a polymer wall in sequence, it is possible to advance erosion almost only in the thickness direction. An ion / radical supply gas such as SF ₆ can be used as an etching gas, and C ₄ F ₈ or the like can be used as a deposition gas.

(6) Creation of wiring (see FIG. 9F)
The wiring 152 and the bridge wiring L are formed. The wiring 152 and the bridge wiring L can be obtained by forming a metal material such as Al, Al—Si alloy, Al—Nd alloy or the like by vapor deposition or sputtering, and patterning the film. Metal materials such as Cu and Au can be used. However, when Cu is used, there is a possibility of metal contamination, and when Au is used, the manufacturing cost increases. An Al-based material is preferable in terms of product reliability and manufacturing cost. Note that heat treatment (380 ° C. to 400 ° C.) is performed in order to form an ohmic contact between the wiring 152 and the bridge wiring L and the piezoresistive element r. Note that a film such as a silicon nitride film (Si ₃ N ₄ ) may be provided over the wiring 152 as a protective film. By configuring the wiring 152 with a metal material having excellent heat dissipation, the influence of heat generated in the piezoresistive element r can be suppressed as compared with the high-concentration diffusion wiring.

  The wiring 152 and the bridge wiring L can be created in the same process. Therefore, it is possible to manufacture an acceleration sensor while suppressing output fluctuations without causing an increase in the number of processes.

(7) Processing of silicon film (see FIG. 9G)
The silicon film 120 is etched by RIE until the upper surface of the silicon oxide film 130 is exposed to form an opening 124, thereby defining the frame portion 121, the weight joint portion 122, and the beam portion 123.

(8) Removal of unnecessary silicon oxide film (see FIG. 9H)
The unnecessary silicon oxide film used as an etching stopper is removed by RIE or wet etching. Thus, the silicon oxide film 130 exists between the frame portion 121 and the frame portion 141, and the weight joint portion 122 and the weight portion 142.

(9) Bonding of glass substrates (see FIG. 9I)
The sensor body 2 and the glass substrate 3 are joined. The glass substrate 3 is so-called Pyrex (registered trademark) glass containing movable ions such as Na ions, and anodic bonding is used for bonding to the SOI substrate 110. In order to prevent the weight portion 142 from sticking to the upper surface of the glass substrate 3 due to electrostatic attraction during anodic bonding, a sticking prevention film (not shown) such as Cr is formed on the upper surface of the glass substrate 3 by sputtering. You may keep it. Thereby, the sensor main body 2 and the glass substrate 3 are joined, and the acceleration sensor 1 is comprised.

(10) Individualization The acceleration sensor 1 is diced with a dicing saw or the like, and is divided into individual acceleration sensors 1. In the present specification, the “acceleration sensor” arranged in a multi-face manner on the wafer and the “acceleration sensor” separated into pieces are referred to as the acceleration sensor 1 without any particular distinction.

(Second Embodiment)
A second embodiment will be described with reference to FIG. Except for the point that the piezoresistive elements constituting the first detection unit Rx and the second detection unit Rz are arranged symmetrically with respect to the width center line L _C (dotted line in the figure) of the beam portion 123, This is substantially the same as the embodiment. With the above-described configuration, when a piezoresistive element that is not detected is generated when the piezoresistive element is arranged symmetrically with respect to the width center line of the beam portion 123, stress in the opposite direction is applied to the piezoresistive element. Therefore, the influence of stress can be offset. As a result, it is possible to suppress the influence of other-axis sensitivity and improve detection accuracy.

Method of Manufacturing Acceleration Sensor According to Second Embodiment The piezoresistive elements r are arranged so as to be symmetric with respect to the width center line L _C of the beam portion 123, and they are symmetrical with respect to the width center line L _C in each direction. The wiring 152 may be connected in series so as to be substantially the same as the method for manufacturing the acceleration sensor according to the first embodiment, and a description thereof will be omitted.

(Third embodiment)
A third embodiment will be described with reference to FIG. The first embodiment except that the position of the detection unit is adjusted in the width direction of the beam unit 123 according to the output difference for each detection direction, not the detection unit is symmetric with respect to the width center line L _C of the beam unit 123. It is almost the same as the form. The arrangement shown in FIG. 7 is an example of a layout for increasing the output in the Z direction. The stress generated in the beam portion 123 has a distribution in a direction perpendicular to the width C of the beam portion 123 (width direction of the beam portion 123). The stress increases as the distance from the width center line L _C of the beam portion 123 increases, and the stress decreases as it approaches the opposite direction. Therefore, the acting stress can be adjusted by shifting the position of the detection unit in the width direction. By setting it as said structure, the output difference between detection directions can be suppressed. When the output due to the physical quantity variation from the first detection unit is larger than the output of the physical quantity variation from the second detection unit, the width of the center line L _{C of the} beam 123 is changed from the first detection unit to the second detection unit. If the output due to the physical quantity variation from the first detection unit is smaller than the output of the physical quantity variation from the second detection unit, the first detection unit is replaced with the second detection unit. Rather than the width center line L _C of the beam 123.

Acceleration Sensor Manufacturing Method According to Third Embodiment Acceleration according to the first embodiment, except that the piezoresistive element r is formed using a mask whose position is adjusted in the width direction of the beam portion 123 according to the output difference. This is substantially the same as the manufacturing method of the sensor, and the description is omitted.

(Fourth embodiment)
A modification of the fourth embodiment will be described with reference to FIG. The first embodiment except that the beam portion 123 has a dummy electrode S and a heat radiation fin F that are electrically independent of the wiring 152 and / or the bridge wiring L or extended from the wiring 152 and / or the bridge wiring L. It is almost the same as the form. By arranging the dummy electrode S, the wiring layout on the beam can be made substantially uniform. The dummy electrode S may be a dot pattern, an isolated or continuous line pattern. It may be configured such that at least a part of the surface of the wiring 152 and / or the bridge wiring L is exposed (a protective film is opened) and is in contact with the atmosphere. In that case, heat dissipation characteristics can be improved.

  In order to further improve heat dissipation, it is preferable to dispose heat radiation fins F made of a metal material that extends from the wiring 152 and is integrally formed. Thereby, the surface area of the wiring 152 can be increased, and heat dissipation can be improved.

  If the area ratio of the dummy electrode S / radiating fin F to the beam portion 123 becomes too large, the output characteristics fluctuate due to the difference in the coefficient of linear expansion between the silicon that is the material of the beam portion 123 and the metal that is the material of the wiring. Therefore, it is preferable to avoid overuse.

When forming the wiring 152 and the bridge wiring L of the acceleration sensor according to the fourth embodiment , the dummy electrode S / heat radiation fin F may be formed. Other points are substantially the same as the method of manufacturing the acceleration sensor according to the first embodiment, and a description thereof will be omitted. By forming the dummy electrode S / radiating fin F in the same material and the same process as the bridge wiring L, it is possible to provide an acceleration sensor with excellent reliability without adding a new process.

(Example)
A 1.5 mm square acceleration sensor was fabricated on a SOI substrate (5 μm / 2 μm / 625 μm) with multiple faces. The detection unit in each direction in the acceleration sensor was configured by connecting two piezoresistive elements in series with a wiring made of an Al material. The output fluctuation in a state where a voltage of 3 V was applied to the bridge circuit was observed for 10 minutes (600 seconds). In the acceleration sensor according to the present invention, the output fluctuation after the initial operation (10 seconds after the start of driving) is in the range of ± 0.03 mV, and it was confirmed that the output fluctuation was small.

(Comparative example)
When the output fluctuation was measured in the same manner as described above for the sensor in which the piezoresistive elements were connected by the high-concentration diffusion wiring, the output fluctuation after the initial operation (10 seconds after the start of driving) varied within a range of ± 2.0 mV. The output fluctuation was large.

  As described above, the embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.

1 is an overall perspective view of an acceleration sensor according to the present invention. It is a disassembled perspective view of an acceleration sensor. It is the top view and sectional drawing of a sensor main body. It is drawing explaining the detail of a detection part. 1 is a diagram illustrating a first embodiment according to the present invention. It is drawing showing 2nd Embodiment which concerns on this invention. It is drawing showing 3rd Embodiment which concerns on this invention. It is drawing which shows 4th Embodiment based on this invention. It is drawing showing the manufacturing method of 1st Embodiment which concerns on this invention. It is drawing which shows the outline | summary of a bridge circuit.

Explanation of symbols

1: Acceleration sensor 2: Sensor body 3: Support substrate 110: SOI substrate 120: Silicon film 121: Frame portion 122: Weight joint portion 123: Beam portion 124: Opening 130: Silicon oxide film 140: Silicon substrate 141: Frame portion 142 : Weight 150: insulating layer 151: contact hole 152: wiring 160: gap

r: Piezoresistive element R: Piezoresistive group Rx: Detection unit Ry: Detection unit Rz: Detection unit F: Radiation fin G: Center G of weight
L: Bridge wiring L _C : Beam width center line S: Dummy electrode

Claims (10)

A frame portion having an opening;
A weight portion disposed in the opening of the frame portion;
At least one beam portion connecting the frame portion and the weight portion;
Formed in the beam portion and one end of the beam portion is connected to the frame portion and the other end of the beam portion is connected to the weight portion, respectively, for detecting a physical quantity variation A plurality of detection units,
The physical quantity sensor, wherein the detection unit is configured by connecting a plurality of piezoresistive elements in series by a wiring made of a metal material.   The physical quantity sensor according to claim 1, wherein the wiring has a radiation fin made of a metal material.   3. The physical quantity sensor according to claim 1, wherein at least a part of the surface of the wiring is exposed to the atmosphere. On the beam part, provided with a bridge wiring for connecting the detection part so as to constitute a bridge circuit,
The dummy electrode which is electrically independent from the wiring and / or the bridge wiring or is extended from the wiring and / or the bridge wiring is arranged. The physical quantity sensor described in the item. The detection unit includes a first detection unit for detecting a physical quantity variation in a first direction, and a second detection unit for detecting a physical quantity variation in a second direction that intersects the first direction. Including
5. The physical quantity sensor according to claim 1, wherein the piezoresistive element configuring the first detection unit is configured not to sandwich the second detection unit therebetween. 6. . The detection unit includes a first detection unit for detecting a physical quantity variation in a first direction, and a second detection unit for detecting a physical quantity variation in a second direction that intersects the first direction. Including
5. The device according to claim 1, wherein the first detection unit and the second detection unit are arranged symmetrically with respect to a width center line of the beam portion and point-symmetrically with respect to the center of the weight portion. Item 1. A physical quantity sensor according to item 1. The detection unit includes a first detection unit for detecting a physical quantity variation in a first direction, and a second detection unit for detecting a physical quantity variation in a second direction orthogonal to the first direction. Including
The plurality of piezoresistive elements constituting the first detection unit and the plurality of piezoresistive elements constituting the second detection unit are respectively arranged symmetrically with respect to the width center line of the beam portion. The physical quantity sensor according to any one of claims 1 to 4. The detection unit includes a first detection unit for detecting a physical quantity variation in a first direction, and a second detection unit for detecting a physical quantity variation in a second direction orthogonal to the first direction. Including
When the output due to the physical quantity fluctuation from the first detection unit is larger than the output due to the physical quantity fluctuation from the second detection part, the first detection part of the beam part is moved from the second detection part. Is also arranged close to the width center line of the beam,
When the output due to the physical quantity variation from the first detection unit is smaller than the output due to the physical quantity variation from the second detection unit, the first detection unit of the beam unit is more than the second detection unit. The physical quantity sensor according to any one of claims 1 to 4, wherein the physical quantity sensor is arranged away from a width center line of the beam. A method of manufacturing a sensor for detecting a physical quantity using a semiconductor substrate,
A step of diffusing impurities on one surface of the semiconductor substrate to form a plurality of piezoresistive elements;
Forming from the semiconductor substrate a frame portion having an opening, a weight portion disposed in the opening of the frame portion, and at least one beam portion connecting the frame portion and the weight portion; ,
Connecting the predetermined piezoresistive element in series by a wire made of a metal material to form a detection unit;
Forming a bridge wiring connecting the detection unit so as to form a bridge circuit on the flexible part and the frame part.   The physical quantity sensor manufacturing method according to claim 9, wherein the wiring and the bridge wiring are formed simultaneously.

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