WO2017073207A1

WO2017073207A1 - Semiconductor pressure sensor

Info

Publication number: WO2017073207A1
Application number: PCT/JP2016/077850
Authority: WO
Inventors: 直樹高山
Original assignee: 株式会社フジクラ
Priority date: 2015-10-28
Filing date: 2016-09-21
Publication date: 2017-05-04

Abstract

Provided is a semiconductor pressure sensor, wherein: the semiconductor pressure sensor is provided with a semiconductor substrate having a diaphragm part, a plurality of piezoresistors formed on the surface of the diaphragm part, a plurality of wirings that connect the plurality of piezoresistors to constitute part of a bridge circuit, an insulation film formed so as to cover the surface of the semiconductor substrate including the surfaces of the plurality of piezoresistors, and an electroconductive film having a plurality of electroconductive regions independently formed on the insulation film correspondingly with respect to the plurality of piezoresistors; at least one of the electroconductive regions being connected to a first end or a second end of one of the piezoresistors.

Description

Semiconductor pressure sensor

The present invention relates to a semiconductor pressure sensor.
This application claims priority based on Japanese Patent Application No. 2015-212005 filed in Japan on October 28, 2015 and Japanese Patent Application No. 2016-122130 filed in Japan on June 20, 2016. , The contents of which are incorporated herein.

In recent years, semiconductor pressure sensors that are manufactured using MEMS (Micro Electro-Mechanical Systems) technology and measure pressure using the piezoresistive effect (a phenomenon in which resistivity changes due to stress applied to the piezoresistor) have been developed. . This semiconductor pressure sensor includes a diaphragm (pressure receiving portion) formed on a silicon substrate and a piezoresistor formed on the diaphragm by diffusion or ion implantation. When the diaphragm is bent under pressure In addition, it is a sensor that measures a pressure by detecting a change in resistivity caused by applying a stress corresponding to the deflection to the piezoresistor. Such a semiconductor pressure sensor has characteristics of being ultra-small and ultra-light, and thus is used in various devices such as wrist watches, mobile phones, and other portable devices.

The following Patent Document 1 discloses a conventional semiconductor pressure sensor using a piezoresistive effect. Specifically, in Patent Document 1 below, a bridge circuit (a circuit configured by a piezoresistor and detecting the change in resistivity described above) is formed so as to cover an upper portion of the piezoresistor via an insulating film. A semiconductor pressure sensor comprising a conductor film connected to the highest potential part is disclosed. In this semiconductor pressure sensor, the above-described conductor film reduces measurement errors caused by changes in the resistance value of the piezoresistance caused by ions on the sensor surface or charging.

Japanese Patent No. 5002468

By the way, in the semiconductor pressure sensor disclosed in Patent Document 1 described above, since all the piezoresistors are covered with the conductor film connected to the highest potential portion of the bridge circuit, the piezoresistor and the conductor film are not connected. The potential difference differs depending on the position of the piezoresistor. As a result, the carrier distribution on the surface of the silicon substrate changes according to the position of the piezoresistor, so that there is a problem that an output offset or a change in sensitivity occurs and a measurement error occurs.

Moreover, in the semiconductor pressure sensor disclosed in Patent Document 1 described above, the rising characteristics of the semiconductor pressure sensor are deteriorated due to the parasitic capacitance formed between the conductor film and the piezoresistor.
When such a rise characteristic is deteriorated, there is a problem that a measurement error is caused when an intermittent operation is performed to suppress the power consumption of the semiconductor pressure sensor. The measurement error becomes smaller as the potential difference between the piezoresistor and the conductor film is smaller. This is because the smaller the potential difference between the piezoresistor and the conductor film, the smaller the charge accumulated in the parasitic capacitance and the smaller the change in resistance value of the piezoresistor.

In the semiconductor pressure sensor disclosed in Patent Document 1 described above, since the conductor film is formed so as to cover all the piezoresistors, the thermal expansion between the conductor film and the diaphragm (or the insulator) is performed. The stress caused by the difference in coefficients increases. When such stress increases, there is a problem in that a measurement error occurs because the degree of bending when the diaphragm is subjected to pressure changes.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor pressure sensor capable of reducing measurement errors as compared with the prior art.

In order to solve the above problems, a semiconductor pressure sensor according to a first aspect of the present invention includes a semiconductor substrate having a diaphragm portion, a plurality of piezoresistors formed on the surface of the diaphragm portion, and the plurality of piezoresistors. A plurality of wires connected to form a bridge circuit; an insulating film formed to cover a surface of the semiconductor substrate including a surface of the plurality of piezoresistors; and the insulating film corresponding to the plurality of piezoresistors A conductive film having a plurality of conductive regions individually formed thereon, and at least one conductive region is connected to a first end or a second end of one piezoresistor.
At least one of the plurality of conductive regions may be formed on the insulating film so as to cover the piezoresistor in plan view.
At least one of the plurality of wirings is a first wiring formed on the insulating film, and at least one of the plurality of wirings is formed on the surface of the diaphragm portion, and is formed on the insulating film. The second wiring may be connected to the first wiring through the formed contact portion.
The first wiring is connected to the first end or the second end of the piezoresistor, and the conductive region is formed on the insulating film from the first end or the second end of the piezoresistor. You may form so that it may extend toward wiring.
The plurality of piezoresistors include a first piezoresistor and a second piezoresistor, one end of which is connected to each other, and at least one of the plurality of conductive regions is formed corresponding to the first piezoresistor. It may be a first conductive region, and at least one of the plurality of conductive regions may be a second conductive region formed corresponding to the second piezoresistor.
The first piezoresistor and the second piezoresistor may be formed side by side so that the longitudinal direction of the first piezoresistor and the longitudinal direction of the second piezoresistor are in the same direction.
The plurality of conductive regions may be formed on the insulating film such that a part of the plurality of conductive regions is located outside the diaphragm portion in plan view.
The planar view shape of the plurality of conductive regions on the diaphragm portion may be a point-symmetric shape with respect to the central portion of the diaphragm portion.

According to the above aspect, the conductor film (conductive region) is individually provided corresponding to each of the plurality of piezoresistors formed on the surface of the diaphragm portion, and each conductor film is provided with the first end of the corresponding piezoresistor or Since the connection is made to the second end, the potential difference between the piezoresistor and the conductor film can be reduced, and the measurement error can be reduced as compared with the conventional case.
In addition, the conductor film is provided corresponding to each of the piezoresistors and is not formed so as to cover all the piezoresistors as in the prior art, so the heat between the conductor film and the diaphragm portion is not provided. It is possible to reduce the stress caused by the difference in the expansion coefficient, and to reduce the measurement error.

1 is a plan perspective view of a semiconductor pressure sensor according to a first embodiment of the present invention. FIG. 2 is an enlarged view of a portion indicated by a symbol X in FIG. 1. FIG. 2 is a sectional view taken along line AA in FIG. 1. It is a figure which shows the bridge circuit comprised by 1st Embodiment of this invention. It is a figure which shows the bridge circuit comprised by 2nd Embodiment of this invention. It is a figure which shows the bridge circuit comprised by 3rd Embodiment of this invention. It is a figure which shows the bridge circuit comprised by 3rd Embodiment of this invention. It is a figure which shows the bridge circuit comprised by 3rd Embodiment of this invention. It is a figure which shows the bridge circuit comprised by 4th Embodiment of this invention. It is a figure which shows the bridge circuit comprised by 5th Embodiment of this invention. It is a top view which shows the principal part structure of the semiconductor pressure sensor which concerns on 5th Embodiment of this invention.

Hereinafter, a semiconductor pressure sensor according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following, for easy understanding, the positional relationship of each member will be described with reference to the XYZ orthogonal coordinate system (the position of the origin is changed as appropriate) set in the drawing as necessary. Further, in the drawings referred to below, the dimensions of each member are appropriately changed as necessary for easy understanding.

[First Embodiment]
FIG. 1 is a plan perspective view of the semiconductor pressure sensor according to the first embodiment of the present invention. FIG. 2 is an enlarged view of a portion indicated by a symbol X in FIG. FIG. 3 is a sectional view taken along the line AA in FIG. As shown in FIGS. 1 to 3, the semiconductor pressure sensor 1 according to this embodiment includes a semiconductor substrate 10, piezoresistors 11 to 14, diffusion wirings 21 to 24 (second wiring), an insulating film 30, a conductor film 41 to 44 and metal wires 51 to 54 (first wires). Hereinafter, at least one of the conductor films 41 to 44 may be referred to as a conductive region. In other words, an individual conductive film among the conductive films 41 to 44 may be indicated as a conductive region.

The semiconductor substrate 10 is, for example, a silicon substrate having a rectangular shape in plan view. A diaphragm portion 10 a having a rectangular shape in plan view is formed in the central portion of the semiconductor substrate 10. The diaphragm part 10a is a part where the pressure of the measurement target (for example, fluid) acts, and is configured to bend according to the received pressure. The diaphragm portion 10a is formed, for example, by etching the back surface of the semiconductor substrate 10 to a predetermined thickness.

The piezoresistors 11 to 14 are elements in which a piezoresistive effect (a phenomenon in which the resistivity changes due to applied stress) occurs, and is provided for measuring the pressure acting on the diaphragm portion 10a. The piezoresistors 11 to 14 are formed on the surface of the diaphragm portion 10a (surface on the + Z side) so as to be close to the four sides SD1 to SD4 of the diaphragm portion 10a in plan view. The piezoresistors 11 to 14 are formed, for example, by diffusing impurities on the surface of the diaphragm portion 10a.

Each of the piezoresistors 11 to 14 includes a pair of piezoresistors that are connected in close proximity to each other. Specifically, the piezoresistor 11 includes a piezoresistor 11a (first piezoresistor) and a piezoresistor 11b (second piezoresistor). The piezoresistor 12 includes a piezoresistor 12a (first piezoresistor) and a piezoresistor 12b (second piezoresistor). The piezoresistor 13 includes a piezoresistor 13a (first piezoresistor) and a piezoresistor 13b (second piezoresistor). The piezoresistor 14 includes a piezoresistor 14a (first piezoresistor) and a piezoresistor 14b (second piezoresistor).

The

piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, and 14b are all formed so as to extend in the Y direction (the longitudinal directions are the same). The

piezoresistors

11a and 11b are formed side by side in the X direction at a position close to the side SD1 of the diaphragm portion 10a in plan view. The

piezo resistors

12a and 12b are formed side by side in the X direction at a position close to the side SD2 of the diaphragm portion 10a in plan view. The

piezoresistors

13a and 13b are formed side by side in the X direction at a position close to the side SD3 of the diaphragm portion 10a in plan view. The

piezoresistors

14a and 14b are formed side by side in the X direction at a position close to the side SD4 of the diaphragm portion 10a in plan view.

The diffusion wirings 21 to 24 are wirings formed on the surface of the diaphragm portion 10a in order to constitute the bridge circuit BR1 (see FIG. 4) of the piezoresistors 11 to 14. The diffusion wirings 21 to 24 are formed, for example, by diffusing impurities on the surface of the diaphragm portion 10a.

The diffusion wiring 21 connects the diffusion wiring 21a connected to the other end (second end) of the piezoresistor 11a, one end (first end) of the piezoresistor 11a, and one end (first end) of the piezoresistor 11b. A diffusion wiring 21b and a diffusion wiring 21c connected to the other end (second end) of the piezoresistor 11b are configured. The diffusion wiring 22 connects the diffusion wiring 22a connected to the other end (second end) of the piezoresistor 12a, one end (first end) of the piezoresistor 12a, and one end (first end) of the piezoresistor 12b. The diffusion wiring 22b and the diffusion wiring 22c connected to the other end (second end) of the piezoresistor 12b are configured.

The diffusion wiring 23 connects the diffusion wiring 23a connected to the other end (second end) of the piezoresistor 13a, one end (first end) of the piezoresistor 13a, and one end (first end) of the piezoresistor 13b. A diffusion wiring 23b and a diffusion wiring 23c connected to the other end (second end) of the piezoresistor 13b are configured. The diffusion wiring 24 connects the diffusion wiring 24a connected to the other end (second end) of the piezoresistor 14a, one end (first end) of the piezoresistor 14a, and one end (first end) of the piezoresistor 14b. A diffusion wiring 24b and a diffusion wiring 24c connected to the other end (second end) of the piezoresistor 14b are configured.

The insulating film 30 is a member that insulates the surface of the semiconductor substrate 10 on which the piezoresistors 11 to 14 and the diffusion wirings 21 to 24 are formed. As shown in FIGS. 1 and 3, the insulating film 30 is formed on the entire surface of the semiconductor substrate 10 including the surfaces of the piezoresistors 11 to 14 and the surfaces of the diffusion wirings 21 to 24 (so as to cover the entire surface). . As a material of the insulating film 30, for example, an oxide film (SiO ₂ ) or silicon nitride (SiN) can be used, and the thickness of the insulating film 30 is set to about 100 [nm], for example.

The conductor films 41 to 44 are individually formed on the insulating film 30 corresponding to each of the piezoresistors 11 to 14, and the resistance values of the piezoresistors 11 to 14 generated by ions on the surface of the semiconductor substrate 10 or charging. It is provided in order to reduce the measurement error due to the change of. The conductor films 41 to 44 are formed so as to cover the corresponding piezoresistors 11 to 14 in plan view. For example, polysilicon can be used as the material of the conductor films 41 to 44, and the thickness of the conductor films 41 to 44 is set to, for example, about 100 to 500 [nm].

The conductor films 41 to 44 include a pair of conductor films formed corresponding to the pair of piezoresistors included in the piezoresistors 11 to 14, respectively. Specifically, the conductor film (conductive region) 41 corresponds to the piezoresistor 11a and is formed so as to cover the piezoresistor 11a in plan view (first conductor film, first conductive region). And a conductor film 41b (second conductor film, second conductive region) corresponding to the piezoresistor 11b and formed to cover the piezoresistor 11b in plan view. The conductor film (conductive region) 42 corresponds to the piezoresistor 12a, and a conductor film 42a (first conductor film, first conductive region) formed so as to cover the piezoresistor 12a in plan view, and a piezoresistor. And a conductor film 42b (second conductor film, second conductive region) formed so as to cover the piezoresistor 12b in plan view.

Further, the conductor film (conductive region) 43 corresponds to the piezoresistor 13a, and a conductor film 43a (first conductor film, first conductive region) formed so as to cover the piezoresistor 13a in plan view; Corresponding to the piezoresistor 13b, a conductor film 43b (second conductor film, second conductive region) formed so as to cover the piezoresistor 13b in plan view is provided. The conductor film (conductive region) 44 corresponds to the piezoresistor 14a, and a conductor film 44a (first conductor film, first conductive region) formed so as to cover the piezoresistor 14a in plan view, and a piezoresistor. 14b, and a conductor film 44b (second conductor film, second conductive region) formed so as to cover the piezoresistor 14b in plan view.

The

conductor films

41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b are all on the other end (second end) of the

corresponding piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b. Each is connected. For example, as shown in FIGS. 1 and 2, the conductor film 41a is connected to the other end (second end) of the corresponding piezoresistor 11a via the metal wiring 51 and the diffusion wiring 21a. The other end (second end) of the corresponding piezoresistor 11b is connected through the metal wiring 52 and the diffusion wiring 21c. This connection is made between the

conductor films

41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b and the

corresponding piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b. This is to reduce the measurement error by reducing the potential difference between them as much as possible.

The conductor films 41 to 44 (

conductor films

41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b) all extend from the inside (inside) to the outside (outside) of the diaphragm portion 10a in plan view. It is formed on the insulating film 30 so as to exist. That is, the conductor films 41 to 44 are formed such that a part of the conductor films 41 to 44 is located outside (outside) the diaphragm portion 10a in plan view. The reason why a part of the conductor films 41 to 44 is formed so as to be located outside the diaphragm portion 10a in plan view is mainly to reduce measurement errors.

If a metal wiring exists above the diaphragm portion 10a (on the insulating film 30 on the + Z side of the diaphragm portion 10a), a large stress change appears in the diaphragm portion 10a due to the deformation of the metal wiring, resulting in an error in measurement pressure. In the present embodiment, as shown in FIG. 1, the metal wirings 51 to 54 are formed outside the diaphragm portion 10a in a plan view, and part of the conductor films 41 to 44 are positioned outside the diaphragm portion 10a in a plan view. The metal wirings 51 to 54 and the conductor films 41 to 44 are connected to each other outside the diaphragm portion 10a (outside in plan view, outside). In this way, the stress due to the deformation of the metal wirings 51 to 54 is prevented from being applied to the diaphragm portion 10a, thereby preventing an error in the measurement pressure.

Instead of the above configuration, the conductive film formed inside the diaphragm portion 10a in plan view and the metal wiring formed outside the diaphragm portion 10a in plan view are connected by wiring. It is also possible. Specifically, a first contact portion that connects the conductor film and the surface of the diaphragm portion 10a and a second contact portion that connects the metal wiring and the surface of the semiconductor substrate 10 are formed. The first contact portion and the second contact portion are connected by a diffusion wiring formed on the surface of the semiconductor substrate 10 (diaphragm portion 10a). However, in such a configuration, it is necessary to form the first contact portion by cutting the insulating film 30 on the diaphragm portion 10a, and the stress is likely to concentrate on the first contact portion, resulting in a decrease in sensor sensitivity. Resulting in.

Further, the conductor films (conductive regions) 41 to 44 (

conductor films

41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b) have at least a plan view shape on the diaphragm portion 10a as shown in FIG. These are arranged in a point-symmetric shape with respect to the central portion Q of the diaphragm portion 10a. The reason why the conductor films 41 to 44 are arranged in a point-symmetrical shape is mainly to prevent an error from occurring in the output of the semiconductor pressure sensor 1.

In the semiconductor pressure sensor 1, when the diaphragm portion 10 a is bent under pressure, the piezoresistors (piezoresistor 11 and piezoresistor 13 or piezoresistor 13 or piezoresistors 13) disposed at positions facing each other with the central portion Q of the diaphragm portion 10 a interposed therebetween. It is desirable that the same stress changes occur in the resistor 12 and the piezoresistor 14). Therefore, as shown in FIG. 1, the piezoresistors 11 to 14 are arranged point-symmetrically with respect to the central portion Q of the diaphragm portion 10a. When the planar view shapes (plan view shapes on the diaphragm portion 10a) of the conductor films 41 to 44 formed corresponding to the piezoresistors 11 to 14 are asymmetric with respect to the central portion Q of the diaphragm portion 10a. In this case, the stress applied to the piezoresistors 11 to 14 becomes asymmetric, and an error occurs in the output of the semiconductor pressure sensor 1.

In the present embodiment, as shown in FIG. 1, the shape of the conductor films 41 to 44 in a plan view (a plan view shape on the diaphragm portion 10a) is made point-symmetric with respect to the central portion Q of the diaphragm portion 10a. Thus, an error in the output of the semiconductor pressure sensor 1 is prevented. Not only the shape of the conductor films 41 to 44 in plan view on the diaphragm portion 10a but also the overall shape of the conductor films 41 to 44 (including the shape of the portion extending outside the diaphragm portion 10a in plan view). The shape may be point-symmetric with respect to the central portion Q of the diaphragm portion 10a.

The metal wires 51 to 54 are wires formed on the insulating film 30 in order to constitute the bridge circuit BR1 (see FIG. 4) of the piezoresistors 11 to 14 together with the diffusion wires 21 to 24. As a material of the metal wirings 51 to 54, for example, aluminum (Al) can be used, and the thickness of the metal wirings 51 to 54 is set to, for example, about 1500 [nm].

The metal wiring 51 includes a pad portion 51a provided at the upper left corner of the insulating film 30, a wiring portion 51b extending from the pad portion 51a in the −Y direction, and a wiring portion 51c extending from the pad portion 51a in the + X direction. The metal wiring 52 includes a pad portion 52a provided at the upper right corner of the insulating film 30 in the drawing, a wiring portion 52b extending from the pad portion 52a in the −X direction, and a wiring portion 52c extending from the pad portion 52a in the −Y direction.

The metal wiring 53 includes a pad portion 53a provided at the lower right corner of the insulating film 30, a wiring portion 53b extending from the pad portion 53a in the + Y direction, and a wiring portion 53c extending from the pad portion 53a in the −X direction. The metal wiring 54 includes a pad part 54a provided at the lower left corner of the insulating film 30, a wiring part 54b extending from the pad part 54a in the + X direction, and a wiring part 54c extending from the pad part 54a in the + Y direction.

The metal wirings 51 to 54 are connected to the diffusion wirings 21 to 24 through contact portions formed on the insulating film 30. Specifically, as shown in FIG. 2, the metal wiring 51 (wiring part 51c) is connected to the diffusion wiring 21 (diffusion wiring 21a) via the contact part CN. The metal wiring 52 (wiring part 52b) is connected to the diffusion wiring 21 (diffusion wiring 21c) via the contact part CN. Similarly, the metal wiring 52 (wiring part 52c) is connected to the diffusion wiring 22 (diffusion wiring 22a) through a contact part (not shown). The metal wiring 53 (wiring part 53b) is connected to the diffusion wiring 22 (diffusion wiring 22c) through a contact part (not shown). The contact portion is formed, for example, by etching the insulating film 30, and the metal wiring and the diffusion wiring are connected by filling the contact portion with the metal wiring.

The metal wiring 53 (wiring portion 53c) is connected to the diffusion wiring 23 (diffusion wiring 23a) through a contact portion (not shown). The metal wiring 54 (wiring portion 54b) is connected to the diffusion wiring 23 (diffusion wiring 23c) through a contact portion (not shown). The metal wiring 54 (wiring part 54c) is connected to the diffusion wiring 24 (diffusion wiring 24a) through a contact part (not shown). The metal wiring 51 (wiring part 51b) is connected to the diffusion wiring 24 (diffusion wiring 24c) through a contact part (not shown).

As shown in FIGS. 1 and 2, the conductor film (conductive region) 41a is formed to extend from the first end of the piezoresistor 11a toward the metal wiring 51 (wiring portion 51c). As shown in FIGS. 1 and 2, the conductor film (conductive region) 41b is formed so as to extend from the first end of the piezoresistor 11b toward the metal wiring 52 (wiring portion 52b). The metal wiring 51 (wiring part 51c) is connected to the second end of the piezoresistor 11a via the contact part CN and the diffusion wiring 21a. The metal wiring 52 (wiring part 52b) is connected to the second end of the piezoresistor 11b via the contact part CN and the diffusion wiring 21c. Therefore, the conductor film 41a is formed on the insulating film 30 so as to extend from the first end of the piezoresistor 11a toward the metal wiring 51 (wiring part 51c) connected to the second end of the piezoresistor 11a. ing. The conductor film 41b is formed on the insulating film 30 so as to extend from the first end of the piezoresistor 11b toward the metal wiring 52 (wiring part 52b) connected to the second end of the piezoresistor 11b. ing.

Similarly, on the insulating film 30, the conductor film (conductive region) 42a is directed from the first end of the piezoresistor 12a to the metal wiring 52 (wiring portion 52c) connected to the second end of the piezoresistor 12a. It is formed to extend. On the insulating film 30, the conductor film (conductive region) 42b extends from the first end of the piezoresistor 12b toward the metal wiring 53 (wiring portion 53b) connected to the second end of the piezoresistor 12b. Is formed. The conductor film (conductive region) 43a extends on the insulating film 30 from the first end of the piezoresistor 13a toward the metal wiring 53 (wiring portion 53c) connected to the second end of the piezoresistor 13a. It is formed as follows. The conductor film (conductive region) 43b extends on the insulating film 30 from the first end of the piezoresistor 13b toward the metal wiring 54 (wiring portion 54b) connected to the second end of the piezoresistor 13b. Is formed. The conductor film (conductive region) 44a extends on the insulating film 30 from the first end of the piezoresistor 14a toward the metal wiring 54 (wiring portion 54c) connected to the second end of the piezoresistor 14a. It is formed as follows. The conductor film (conductive region) 44b extends on the insulating film 30 from the first end of the piezoresistor 14b toward the metal wiring 51 (wiring part 51b) connected to the second end of the piezoresistor 14b. Is formed.

FIG. 4 is a diagram showing a bridge circuit configured in the first embodiment of the present invention. In FIG. 4, the same reference numerals are given to the components corresponding to the members shown in FIGS. As shown in FIG. 4, the bridge circuit BR1 includes a piezoresistor 11 (11a, 11b), a piezoresistor 12 (12a, 12b), a piezoresistor 13 (13a, 13b), and a piezoresistor 14 (14a, 14b). It is a connected circuit. A metal wiring 51 is connected between the piezoresistor 14 and the piezoresistor 11. A metal wiring 52 is connected between the piezoresistor 11 and the piezoresistor 12. A metal wiring 53 is connected between the piezoresistor 12 and the piezoresistor 13. A metal wiring 54 is connected between the piezoresistor 13 and the piezoresistor 14. In the bridge circuit BR1 shown in FIG. 4, for example, the metal wiring 51 is connected to the power source, the metal wiring 53 is grounded, and the

metal wirings

52 and 54 are connected to the voltage output terminal.

Further, the bridge circuit BR1 shown in FIG. 4 corresponds to the piezoresistor 11 (11a, 11b), the piezoresistor 12 (12a, 12b), the piezoresistor 13 (13a, 13b), and the piezoresistor 14 (14a, 14b). The conductor film 41 (41a, 41b), the conductor film 42 (42a, 42b), the conductor film 43 (43a, 43b), and the conductor film 44 (44a, 44b) are provided. The

conductor films

41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b are connected to the second ends of the

corresponding piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b, respectively. Yes.

In the semiconductor pressure sensor 1 having the above configuration, when pressure is applied to the diaphragm portion 10a, the diaphragm portion 10a bends. Then, stress corresponding to the deflection of the diaphragm portion 10a is applied to the piezoresistors 11 (11a, 11b), piezoresistors 12 (12a, 12b), piezoresistors 13 (13a, 13b), and piezoresistors 14 (14a, 14b). Acts and the resistance value changes. When such a change in resistance value occurs, the voltage between the voltage output terminals to which the

metal wirings

52 and 54 are connected changes, and the pressure applied to the diaphragm portion 10a is obtained by detecting the voltage change between the voltage output terminals. be able to.

Here, the potential difference between the piezoresistor and the conductor film is considered. Here, for easy understanding, it is assumed that the power supply voltage is 4 [V] and the resistance values of the

piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, and 14b are all equal. When the conductor film is formed so as to cover all the piezoresistors as in the conventional semiconductor pressure sensor, the potential difference between the conductor film and the piezoresistors is a maximum of the power supply voltage (4 [V]). It becomes the same level. On the other hand, in the present embodiment, the conductor film (conductive region) corresponding to the piezoresistor is individually formed and connected to the second end of the corresponding piezoresistor. The maximum potential difference is approximately the same as the voltage drop of each piezoresistor (1 [V]), and the potential difference can be significantly reduced as compared with the conventional case. Thereby, a measurement error can be reduced as compared with the conventional case.

As described above, in the present embodiment, the

conductor films

41a, 41b, 42a, 42b, 43a corresponding to each of the

piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b constituting the bridge circuit BR1. 43b, 44a, and 44b are individually provided on the insulating film 30. The

conductor films

41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b are connected to the second ends of the

corresponding piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b. ing. Thereby, the potential difference between the piezoresistor and the corresponding conductor film can be made smaller than before, and the measurement error can be reduced more than before.

In the present embodiment, the conductive film is not formed so as to cover all the piezoresistors as in the prior art, but the conductive regions are individually formed so as to cover each of the piezoresistors in plan view. Therefore, the stress generated by the difference in thermal expansion coefficient between the conductor film and the diaphragm portion 10a (or the insulating film 30) can be reduced. This also makes it possible to reduce measurement errors.

[Second Embodiment]
FIG. 5 is a diagram showing a bridge circuit configured in the second embodiment of the present invention. In FIG. 5, the same members as those shown in FIG. 4 are denoted by the same reference numerals. As shown in FIG. 5, the bridge circuit BR2 configured in the present embodiment is similar to the bridge circuit BR1 shown in FIG. 4. The piezoresistor 11 (11a, 11b), the piezoresistor 12 (12a, 12b), and the piezoresistor 13 (13a, 13b) and a piezoresistor 14 (14a, 14b) are connected in a ring shape. A metal wiring 51 is connected between the piezoresistor 14 and the piezoresistor 11. A metal wiring 52 is connected between the piezoresistor 11 and the piezoresistor 12. A metal wiring 53 is connected between the piezoresistor 12 and the piezoresistor 13. A metal wiring 54 is connected between the piezoresistor 13 and the piezoresistor 14.

However, the bridge circuit BR2 configured in this embodiment is different from the bridge circuit BR1 shown in FIG. 4 in that the conductor films (conductive regions) 41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b are supported. The

piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b are respectively connected to the first ends. That is, in the present embodiment, the conductor films 41 to 44 shown in FIG. 1 are not connected to the metal wirings 51 to 52, but are connected to the diffusion wirings 21 to 24, which is different from the first embodiment. Different.

Specifically, the conductor film 41 (41a, 41b) is not connected to the metal wirings 51, 52 (

wiring portions

51c, 52b), but is connected to the diffusion wiring 21 (21b). The conductor film 42 (42a, 42b) is not connected to the metal wirings 52, 53 (

wiring portions

52c, 53b), but is connected to the diffusion wiring 22 (22b). The conductor film 43 (43a, 43b) is not connected to the metal wirings 53, 54 (

wiring portions

53c, 54b), but is connected to the diffusion wiring 23 (23b). The conductor film 44 (44a, 44b) is not connected to the metal wirings 54, 51 (

wiring portions

54c, 51b), but is connected to the diffusion wiring 24 (24b).

As described above, the semiconductor pressure sensor according to the present embodiment has the

conductor films

41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b for the

piezoresistors

11a, 11b, 12a, 12b, 13a, 13b, 14a, 14b. The basic configuration is the same as that of the semiconductor pressure sensor according to the first embodiment, except that the positions of the connection points are different. For this reason, also in this embodiment, it is possible to reduce a measurement error compared with the past.

[Third Embodiment]
6A to 6C are diagrams showing a bridge circuit configured in the third embodiment of the present invention. 6A to 6C, like FIG. 5, the same members as those shown in FIG. 4 are denoted by the same reference numerals. In the semiconductor pressure sensor according to the first embodiment and the second embodiment described above, the piezoresistors 11 to 14 each include a pair of piezoresistors arranged in close proximity with one end connected to each other. (Regions) 41 to 44 have a configuration including a pair of conductor films formed corresponding to the pair of piezoresistors included in the piezoresistors 11 to 14, respectively. In contrast, the semiconductor pressure sensor according to the present embodiment has a configuration in which each of the piezoresistors 11 to 14 is composed of one element, and the conductor films 41 to 44 are provided for the piezoresistors 11 to 14, respectively. Have.

Therefore, in the bridge circuit BR3 configured in the present embodiment, as shown in FIGS. 6A to 6C, four piezoresistors 11 to 14 are connected in a ring shape. A metal wiring 51 is connected between the piezoresistor 14 and the piezoresistor 11. A metal wiring 52 is connected between the piezoresistor 11 and the piezoresistor 12. A metal wiring 53 is connected between the piezoresistor 12 and the piezoresistor 13. A metal wiring 54 is connected between the piezoresistor 13 and the piezoresistor 14.
The conductor films 41 to 44 need only be provided corresponding to the piezoresistors 11 to 14, respectively, and the positions of the connection points of the conductor films 41 to 44 to the piezoresistors 11 to 14 are arbitrary.

For example, as shown in FIG. 6A, the conductor films 41 to 44 may be connected to the first ends of the piezoresistors 11 to 14. As shown in FIG. 6B, the conductor films 41 to 44 may be connected to the second ends of the piezoresistors 11 to 14. In the example shown in FIG. 6A, the conductor film 41 and the conductor film 44 are connected to the metal wiring 51 to have the same potential, and the conductor film 42 and the conductor film 43 are connected to the metal wiring 53 to have the same potential. . In the example shown in FIG. 6B, the conductor film 41 and the conductor film 42 are connected to the metal wiring 52 to have the same potential, and the conductor film 43 and the conductor film 44 are connected to the metal wiring 54 to have the same potential. become.

6C, the conductor film 41 is connected to the first end of the piezoresistor 11, the conductor film 42 is connected to the second end of the piezoresistor 12, and the conductor film 43 is connected to the first end of the piezoresistor 13. The conductor film 44 may be connected to the second end of the piezoresistor 14. In the example shown in FIG. 6C, the conductor films 41 to 44 are connected to different metal wirings 51 to 54, respectively. That is, the conductor film 41 is connected to the metal wiring 51, the conductor film 42 is connected to the metal wiring 52, the conductor film 43 is connected to the metal wiring 53, and the conductor film 44 is connected to the metal wiring 54. .

As described above, the semiconductor pressure sensor according to the present embodiment has a configuration in which the piezoresistors 11 to 14 are composed of one element, and the conductor films 41 to 44 are provided corresponding to the piezoresistors 11 to 14, respectively. . As described above, the semiconductor pressure sensor according to the present embodiment corresponds to each of the piezoresistors although the number of piezoresistors and conductor films is different from the semiconductor pressure sensor according to the first embodiment and the second embodiment. The conductive film is individually formed and is the same as the first and second embodiments in that the conductive film is connected to the first end or the second end of the corresponding piezoresistor. . For this reason, also in this embodiment, it is possible to reduce a measurement error compared with the past.

[Fourth Embodiment]
FIG. 7 is a diagram showing a bridge circuit configured in the fourth embodiment of the present invention. In FIG. 7 as well, like FIG. 5 and FIGS. 6A to 6C, the same members as those shown in FIG. Each of the semiconductor pressure sensors according to the first to third embodiments described above has a configuration in which one conductor film is formed corresponding to one piezoresistor. On the other hand, the semiconductor pressure sensor according to the present embodiment has a configuration in which a plurality of conductor films (conductive regions) are formed corresponding to one piezoresistor.

Specifically, in the semiconductor pressure sensor according to the first and second embodiments, the piezoresistor 11 (11a, 11b), the piezoresistor 12 (12a, 12b), the piezoresistor 13 (13a, 13b), and the piezoresistor. 14 (14a, 14b), conductor film 41 (41a, 41b), conductor film 42 (42a, 42b), conductor film 43 (43a, 43b), and conductor film 44 (44a, 44b). ) Were formed. In the third embodiment, the conductor films 41 to 44 are formed for the piezoresistors 11 to 14, respectively.

On the other hand, in the semiconductor pressure sensor according to the present embodiment, a conductor film 41 composed of two conductor films (conductive regions) 41a and 41b is formed corresponding to one piezoresistor 11 and correspondingly formed. A conductor film 42 composed of two

conductor films

42 a and 42 b is formed corresponding to one piezoresistor 12. Similarly, a conductor film 43 composed of two

conductor films

43 a and 43 b is formed corresponding to one piezoresistor 13, and two conductors corresponding to one piezoresistor 14. A conductor film 44 composed of the

films

44a and 44b is formed correspondingly. That is, in the semiconductor pressure sensor according to the present embodiment, the piezoresistors 11 to 14 (piezoresistors each having a pair of piezoresistors) constituting the bridge circuit BR1 shown in FIG. This is a configuration that replaces the piezoresistors 11 to 14 formed of one element.

As described above, the semiconductor pressure sensor according to the present embodiment has a configuration in which the piezoresistors 11 to 14 are composed of one element, and a plurality of conductor films are provided corresponding to the piezoresistors 11 to 14, respectively. Thus, also in the semiconductor pressure sensor according to the present embodiment, the conductor film is individually formed corresponding to each of the piezoresistors, and the first end or the second end of the piezoresistor corresponding to the conductor film. This is the same as the first to third embodiments in that it is connected to. For this reason, also in this embodiment, it is possible to reduce a measurement error compared with the past.

[Fifth Embodiment]
FIG. 8 is a diagram showing a bridge circuit configured in the fifth embodiment of the present invention. Also in FIG. 8, the same members as those shown in FIG. 4 are denoted by the same reference numerals as in FIGS. In the semiconductor pressure sensor according to the present embodiment, the number of piezoresistors provided in each of the piezoresistors 11 to 14 and the number of conductor films (conductive regions) provided in each of the conductor films 41 to 44 are set as follows. The configuration is increased from that in the embodiment and the second embodiment. Specifically, in the semiconductor pressure sensor according to the present embodiment, each of the piezoresistors 11 to 14 is provided with four piezoresistors, and each of the conductor films 41 to 44 is provided with four conductor films. Yes.

As shown in FIG. 8, the bridge circuit BR5 configured in this embodiment includes a piezoresistor 11 (11a to 11d), a piezoresistor 12 (12a to 12d), a piezoresistor 13 (13a to 13d), and a piezoresistor 14 ( 14a to 14d) are connected in a ring shape. A metal wiring 51 is connected between the piezoresistor 14 and the piezoresistor 11. A metal wiring 52 is connected between the piezoresistor 11 and the piezoresistor 12. A metal wiring 53 is connected between the piezoresistor 12 and the piezoresistor 13. A metal wiring 54 is connected between the piezoresistor 13 and the piezoresistor 14.

Specifically, the first end of the piezoresistor 11a and the first end of the piezoresistor 11b are connected to each other. The first end of the piezoresistor 11c and the first end of the piezoresistor 11d are connected to each other. The second end of the piezoresistor 11b and the second end of the piezoresistor 11c are connected to each other. The first end of the piezoresistor 12a and the first end of the piezoresistor 12b are connected to each other. The first end of the piezoresistor 12c and the first end of the piezoresistor 12d are connected to each other. The second end of the piezoresistor 12b and the second end of the piezoresistor 12c are connected to each other.

Similarly, the first end of the piezoresistor 13a and the first end of the piezoresistor 13b are connected to each other. The first end of the piezoresistor 13c and the first end of the piezoresistor 13d are connected to each other. The second end of the piezoresistor 13b and the second end of the piezoresistor 13c are connected to each other. The first end of the piezoresistor 14a and the first end of the piezoresistor 14b are connected to each other. The first end of the piezoresistor 14c and the first end of the piezoresistor 14d are connected to each other. The second end of the piezoresistor 14b and the second end of the piezoresistor 14c are connected to each other.

8 corresponds to the piezoresistors 11 (11a to 11d), the piezoresistors 12 (12a to 12d), the piezoresistors 13 (13a to 13d), and the piezoresistors 14 (14a to 14d). The conductive film 41 (41a to 41d), the conductive film 42 (42a to 42d), the conductive film 43 (43a to 43d), and the conductive film 44 (44a to 44d) are provided. The conductor films 41a to 41d, 42a to 42d, 43a to 43d, 44a to 44d are connected to the second ends of the corresponding piezoresistors 11a to 11d, 12a to 12d, 13a to 13d, and 14a to 14d, respectively. Yes.

FIG. 9 is a plan view showing the main configuration of a semiconductor pressure sensor according to the fifth embodiment of the present invention, which corresponds to FIG. In FIG. 9, the same members as those shown in FIG. As described above, in the semiconductor pressure sensor according to the present embodiment, the number of piezoresistors provided in each of the piezoresistors 11 to 14 and the number of conductor films provided in each of the conductor films 41 to 44 are set as follows. The configuration is twice that of the embodiment. For this reason, the configuration of the part indicated by the symbol X in FIG. 1 is generally a configuration in which two configurations shown in FIG. 2 are arranged in the X direction as shown in FIG.

Specifically, each of the piezoresistors 11a to 11d provided in the piezoresistor 11 is formed so as to extend in the Y direction (the longitudinal direction is the same direction), and the piezoresistors 11a to 11d are X Arranged side by side. The diffusion line 21 includes a diffusion line 21a connected to the second end of the piezoresistor 11a, a diffusion line 21b connecting the first end of the piezoresistor 11a and the first end of the piezoresistor 11b, and the first of the piezoresistor 11b. A diffusion line 21c connected to two ends, a diffusion line 21d connected to the second end of the piezoresistor 11c, a diffusion line 21e connecting the first end of the piezoresistor 11c and the first end of the piezoresistor 11d, and It comprises a diffusion wiring 21f connected to the second end of the piezoresistor 11d.

The conductor film 41 corresponds to the piezoresistor 11a, and is formed so as to cover the piezoresistor 11a in plan view, and to correspond to the piezoresistor 11b and to cover the piezoresistor 11b in plan view. Corresponding to the conductive film 41b and the piezoresistor 11c, the conductive film 41c formed to cover the piezoresistor 11c in plan view, and to correspond to the piezoresistor 11d and to cover the piezoresistor 11d in plan view And a conductor film 41d formed on the substrate. The conductive film 41b and the conductive film 41c are connected at the end on the -Y side.

The conductor films 41a to 41d are all connected to the second ends of the corresponding piezoresistors 11a to 11d, respectively. Specifically, the conductor film 41a is connected to the second end of the corresponding piezoresistor 11a via the metal wiring 51 and the diffusion wiring 21a, and the

conductor films

41b and 41c are connected to the metal wiring 55 and the

diffusion wirings

21c and 21d. Are connected to the second ends of the

corresponding piezoresistors

11b and 11c, respectively, and the conductor film 41d is connected to the second end of the corresponding piezoresistors 11d via the metal wiring 52 and the diffusion wiring 21f. The metal wiring 55 is a wiring formed on the insulating film 30 in order to connect the diffusion wiring 21c, the diffusion wiring 21d, and the

conductor films

41b and 41c.

As described above, the semiconductor pressure sensor according to the present embodiment differs only in the number of piezoresistors provided in each of the piezoresistors 11 to 14 and the number of conductor films provided in each of the conductor films 41 to 44. The basic configuration is the same as that of the semiconductor pressure sensor according to the first embodiment. For this reason, also in this embodiment, it is possible to reduce a measurement error compared with the past.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, It can change freely within the scope of the present invention. For example, in the above-described embodiment, the semiconductor pressure sensor 1 in which the planar shape of the diaphragm portion 10a is rectangular has been described as an example, but the planar shape of the diaphragm portion 10a is not limited to the rectangular shape. Any shape (for example, a circular shape) may be used.

In the above-described embodiment, an example in which the insulating film 30 is formed on the entire surface of the semiconductor substrate 10 including the surfaces of the piezoresistors 11 to 14 and the surfaces of the diffusion wirings 21 to 24 (so as to cover the entire surface). explained. However, the insulating film 30 above the diaphragm portion 10a (except for the portion where the piezoresistors 11 to 14, the diffusion wirings 21 to 24, and the conductor films 41 to 44 are formed) may be omitted.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor pressure sensor 10 ... Semiconductor substrate 10a ... Diaphragm part 11-14 ... Piezoresistor 11a-11d ... Piezoresistor 12a-12d ... Piezoresistor 13a-13d ... Piezoresistor 14a-14d ... Piezoresistor 21-24 ... Diffusion wiring 30 ... Insulating films 41 to 44 ... Conductor film (conductive region)
41a to 41d ... Conductor film (conductive region)
42a to 42d ... Conductor film (conductive region)
43a to 43d ... Conductor film (conductive region)
44a to 44d ... Conductor film (conductive region)
51 to 54 Metal wiring BR1 to BR5 Bridge circuit CN Contact portion

Claims

A semiconductor pressure sensor,
A semiconductor substrate having a diaphragm portion;
A plurality of piezoresistors formed on the surface of the diaphragm portion;
A plurality of wires connecting the plurality of piezoresistors to form a bridge circuit;
An insulating film formed to cover the surface of the semiconductor substrate including the surfaces of the plurality of piezoresistors;
A conductor film having a plurality of conductive regions individually formed on the insulating film corresponding to the plurality of piezoresistors,
At least one conductive region is connected to a first end or a second end of one piezoresistor;
Semiconductor pressure sensor.
The semiconductor pressure sensor according to claim 1, wherein at least one of the plurality of conductive regions is formed on the insulating film so as to cover the piezoresistor in a plan view.
At least one of the plurality of wirings is a first wiring formed on the insulating film,
At least one of the plurality of wirings is a second wiring formed on the surface of the diaphragm portion and connected to the first wiring via a contact portion formed in the insulating film.
The semiconductor pressure sensor according to claim 1 or 2.
The first wiring is connected to the first end or the second end of the piezoresistor;
The semiconductor pressure sensor according to claim 3, wherein the conductive region is formed on the insulating film so as to extend from the first end or the second end of the piezoresistor toward the first wiring.
The plurality of piezoresistors include a first piezoresistor and a second piezoresistor, one end of which is connected to each other,
At least one of the plurality of conductive regions is a first conductive region formed corresponding to the first piezoresistor,
5. The semiconductor pressure sensor according to claim 1, wherein at least one of the plurality of conductive regions is a second conductive region formed corresponding to the second piezoresistor. 6.
6. The first piezoresistor and the second piezoresistor are formed side by side so that the longitudinal direction of the first piezoresistor and the longitudinal direction of the second piezoresistor are in the same direction. Semiconductor pressure sensor.
The plurality of conductive regions are formed on the insulating film so that a part of the plurality of conductive regions is positioned outside the diaphragm portion in a plan view. The semiconductor pressure sensor according to item.
The semiconductor pressure sensor according to any one of claims 1 to 7, wherein a shape of the plurality of conductive regions in a plan view on the diaphragm portion is a point-symmetric shape with respect to a central portion of the diaphragm portion.