JP2018169177A - Pressure sensor element and pressure sensor using the same - Google Patents

Abstract

To provide a pressure sensor element with improved detection accuracy.SOLUTION: In order to achieve this purpose, the pressure sensor element of this disclosure has: a substrate 12 with a diaphragm part 11 having a first principal surface 9 and a second principal surface 10; first, second, third and fourth piezoresistive elements 13, 14, 15 and 16 formed on the first principal surface 9 to detect a pressure applied to the diaphragm part 11; and metal wiring 18 disposed on the substrate 12 to surround the diaphragm part 11, and is configured so that the first piezoresistive element 13 and the fourth piezoresistive element 16 are provided in one end side of the diaphragm part 11 in a first direction 32 and the second piezoresistive element 14 and the third piezoresistive element 15 are provided in the other end side of the diaphragm part 11 in the first direction 32.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a pressure sensor element that detects the pressure of a fluid such as a gas.

  Conventionally, there has been known a pressure sensor in which a circuit is provided on a surface of a substrate having a diaphragm portion provided with a plurality of piezoresistive elements so as to surround the diaphragm portion. (Patent Documents 1 and 2)

JP 2014-77744 A JP 2014-77745 A

  However, in the pressure sensor element used in the conventional pressure sensor, when the metal wiring constituting the circuit is provided around the diaphragm portion, the detection accuracy of the pressure sensor is reduced as the stress of the metal wiring is released. There was a problem.

  The present disclosure solves the above problems and provides a pressure sensor that stabilizes the output by limiting the influence of the stress received from the metal wiring on the piezoresistive element even if the metal wiring constituting the circuit is provided around the diaphragm portion. The purpose is to do.

  In order to solve the above-described problem, the present disclosure provides a substrate including a diaphragm portion having a first main surface and a second main surface, and a pressure formed on the first main surface and applied to the diaphragm portion. 1st, 2nd, 3rd, 4th piezoresistive element for detecting, and metal wiring arranged on the substrate so as to surround the diaphragm portion, and the first piezoresistive element, The second piezoresistive element is provided on one end side of the diaphragm portion in the first direction, and the third piezoresistive element and the fourth piezoresistive element are arranged in the first direction of the diaphragm portion. The structure is provided on the other end side.

  With this configuration, the present disclosure stabilizes the influence of stress on the first to fourth piezoresistive elements by forming the first to fourth piezoresistive elements at the end portions in the first direction of the diaphragm portion. be able to.

Top view of pressure sensor element according to Embodiment 1 The figure which shows the bridge circuit of the same pressure sensor element Side view of a pressure sensor using the same pressure sensor element AA line cross section of the same pressure sensor Partial enlarged sectional view of the pressure sensor element of the same pressure sensor Explanatory drawing of the manufacturing method of the pressure sensor element

(Embodiment 1)
Hereinafter, the pressure sensor element of Embodiment 1 and the pressure sensor using the pressure sensor element will be described with reference to the drawings.

  1 is a top view of the pressure sensor element of the first embodiment, FIG. 2 is a diagram showing a bridge circuit of the pressure sensor element, FIG. 3 is a side view of a pressure sensor using the pressure sensor element, and FIG. FIG. 5 is a partially enlarged cross-sectional view of the pressure sensor element of the pressure sensor.

  The pressure sensor 1 includes a pressure sensor element 2, a case 3 containing the pressure sensor element 2 and having a bottom surface, a processing circuit (not shown) provided in the case 3, and a terminal 4 inserted into the case 3 have.

  The case 3 is made of resin and has a main body portion 5 and a tube portion 6, and the tube portion 6 is provided with a pressure introduction hole 7 communicating with the outside. A fluid to be measured is introduced from the pressure introduction hole 7. The pressure sensor element 2 is disposed so as to close the pressure introducing hole 7. The diameter of the pressure introduction hole 7 changes midway, and the position of the center of the pressure introduction hole 7 in the radial direction is different between the inner end and the outer end of the pipe part 6. The main body 5 is provided with an air introduction hole 8 for introducing air.

  The pressure sensor element 2 includes a substrate 12 on which a diaphragm portion 11 having a first main surface 9 and a second main surface 10 is formed, and a first piezo provided on the first main surface 9 of the diaphragm portion 11. Resistive element 13, second piezoresistive element 14, third piezoresistive element 15, fourth piezoresistive element 16, and power supply wiring 17 provided on the surface of substrate 12 so as to surround diaphragm 11. Metal wiring 18 is included. In the pressure sensor 1, the power supply wiring 17 is provided so as to surround the diaphragm portion 11. However, the power supply wiring 17 is not limited to this, and the wiring method can be appropriately changed according to the use of the pressure sensor 1.

  The substrate 12 is made of a semiconductor material such as silicon. The diaphragm portion 11 is formed in a square shape at the center of the substrate 12, but the shape of the diaphragm portion 11 may be changed according to the intended use. The pressure sensor element 2 includes an N well 19 formed in the substrate 12, a first P well 20 and a second P well 21 formed in the N well 19, and a thermal oxide film 22 formed thereon. The first to third interlayer insulating films 23, 24 and 25 formed on the thermal oxide film 22, the first to third wirings 26, 27 and 28, and the third interlayer insulating film 25 are formed. The passivation film 29 is formed.

The first to fourth piezoresistive elements 13, 14, 15 and 16 are connected to a ground terminal GND, a voltage output terminal _Vout +, a voltage output terminal _Vout− , and a bias voltage application terminal _Vdd which are not shown. One end of the fourth piezoresistive element 16 is connected to the ground terminal GND via the diffusion wiring 30 and the power supply wiring 17, and the other end is connected to the voltage output terminal V _out + via the diffusion wiring 30 and the power supply wiring 17. Has been. One end of the second piezoresistive element 14 is connected to the voltage output terminal V _out − via the diffusion wiring 30 and the power supply wiring 17, and the other end is connected to the bias voltage application terminal via the diffusion wiring 30 and the power supply wiring 17. Connected to V _dd . One end of the third piezoresistive element 15 is connected to the voltage output terminal V _out + via the diffusion wiring 30 and the power supply wiring 17, and the other end is connected to the bias voltage application terminal via the diffusion wiring 30 and the power supply wiring 17. Connected to V _dd . One end of the first piezoresistive element 13 is connected to the ground terminal GND via the diffusion wiring 30 and the power supply wiring 17, and the other end is connected to the voltage output terminal V _out − via the diffusion wiring 30 and the power supply wiring 17. Has been.

The first piezoresistive element 13 and the third piezoresistive element 15 are paired, and the second piezoresistive element 14 and the fourth piezoresistive element 16 are paired to form a bridge circuit 31. Opposed on top. When pressure sensor 1 having such a configuration receives pressure from first main surface 9 or second main surface 10 of diaphragm portion 11, diaphragm portion 11.
When the differential pressure is generated between the first main surface 9 side and the second main surface 10, the diaphragm portion 11 is bent. Due to this bending, the crystals constituting the first to fourth piezoresistive elements 13, 14, 15 and 16 are distorted and the resistance value changes. The change in resistance value of the first to fourth piezoresistive elements 13, 14, 15, 16 is output as a voltage change with respect to the bias voltage applied to the bias voltage application terminal V _dd using the bridge circuit 31. Detect from terminals V _out + and V _out −.

A circuit for processing a voltage change obtained by the first to fourth piezoresistive elements 13, 14, 15 and 16 is formed by the metal wiring 18 provided on the substrate 12. As a circuit formed by the metal wiring 18, for example, detection of voltages from the voltage output terminals V _out + and V _out − in the first to fourth piezoresistive elements 13, 14, 15 and 16 is controlled, and an output amplifier A control circuit for controlling (not shown), a front processing circuit for extracting a voltage value, a sensitivity / temperature characteristic adjusting circuit for performing predetermined processing on a signal corresponding to the voltage value extracted by the front processing circuit, and the like are formed. The Accordingly, the sensitivity / temperature special adjustment circuit performs sensitivity adjustment and temperature characteristic adjustment of the pressure sensor 1. The circuit formed by the metal wiring 18 is not limited to this, and can be changed as appropriate according to the application of the pressure sensor 1.

  The first piezoresistive element 13 and the fourth piezoresistive element 16 are provided on one end side in the first direction 32 of the diaphragm portion 11, and the second piezoresistive element 14 and the fourth piezoresistive element 15 are provided in the diaphragm portion. 11 on the other end side in the first direction 32. Thereby, since the influence of the stress on the first to fourth piezoresistive elements 13, 14, 15, 16 by the metal wiring 18 can be reduced, the first to fourth piezoresistive elements 13, 14, 15 can be reduced. , 16 can stably detect the distortion generated in the diaphragm section 11. Thereby, the output of the pressure sensor 1 is stabilized. Further, the first to fourth piezoresistive elements 13, 14, 15, 16 are arranged side by side in the central portion of the diaphragm portion 11 in the second direction 33. As a result, the distance in the second direction 33 from the metal wiring 18 to the first to fourth piezoresistive elements 13, 14, 15, and 16 is increased, and the stress is released by the stress in the metal wiring 18 in the second direction 33. The influence on the first to fourth piezoresistive elements 13, 14, 15, 16 is further reduced. The distance between the first piezoresistive element 13 and the fourth piezoresistive element 16 and the distance between the second piezoresistive element 14 and the third piezoresistive element 15 are closer to each other in the second direction 33. The influence of stress release of the metal wiring 18 is reduced. For this reason, it is better to arrange the first piezoresistive element 13 and the fourth piezoresistive element 16, the second piezoresistive element 14 and the third piezoresistive element 15 as close as possible, and each can be manufactured. If it is arranged at a position close within a certain range, it is possible to effectively reduce the influence of stress release of the metal wiring 18 in the second direction 33. When the plane orientation of the surface on which the first to fourth piezoresistive elements 13, 14, 15, and 16 are provided is the (100) plane, the distortion of the diaphragm portion 11 increases as the outer periphery of the diaphragm portion 11 is closer. . For this reason, if the first to fourth piezoresistive elements 13, 14, 15, 16 are provided in the vicinity of the outer periphery of the diaphragm portion 11, the sensitivity of the pressure sensor 1 can be improved.

The metal wiring 18 is formed so that the inner circumference has a rectangular shape in which the length in the first direction 32 is longer than the length in the second direction 33. In addition, although the shape of the inner periphery of the metal wiring 18 can be easily formed by making it a rectangular shape, it may be a shape other than the rectangular shape. Since the inner periphery of the metal wiring 18 has a rectangular shape surrounding the diaphragm portion 11, the first distance L1 between the inner periphery of the metal wiring 18 and the outer periphery of the diaphragm portion 11 in the first direction 32 is the second distance L1. It is longer than the second distance L2 between the inner periphery of the metal wiring 18 in the direction 33 and the outer periphery of the diaphragm portion 11. Here, the first distance L1 indicates the distance in the direction parallel to the first direction 32 at the center position in the second direction 33, and the second distance L2 indicates the position in the center in the first direction 32. The distance in a direction parallel to the second direction 33 is shown. Since the influence of the stress release of the metal wiring 18 on the first diaphragm portion 11 decreases as the distance between the outer periphery of the diaphragm portion 11 and the inner periphery of the metal wiring 18 becomes longer, the influence on the diaphragm portion 11 in the first direction 32 is reduced. The influence of stress release of the metal wiring 18 is reduced. Further, the metal wiring 18 is disposed at a position surrounding the diffusion wiring 30. The pressure sensor element 2 formed in this way can improve the detection accuracy of the pressure sensor element 2 by reducing the influence of stress release of the metal wiring 18 without increasing the size of the pressure sensor element 2. Yes.

  Next, a manufacturing process of the pressure sensor element 2 will be described. FIG. 6 is a diagram showing a method for manufacturing the pressure sensor element of the first embodiment.

  First, a silicon substrate is prepared, and the surface is thermally oxidized to form a thermal oxide film 22. Next, a first wiring 26 made of a metal is formed on the thermal oxide film 22, and a silicon oxide film is formed on the first wiring 26 and the thermal oxide film 22 by a CVD method, whereby a first interlayer insulating film is formed. 23 is formed. A second wiring 27 is formed on the first interlayer insulating film 23, and a second interlayer insulating film 24 made of a silicon oxide film is further formed on the second wiring 27. A third wiring 28 is formed outside the first wiring 26 and the second wiring 27 below the second interlayer insulating film 24, and a third interlayer insulating film made of a silicon oxide film is further formed thereon. A film 25 is formed. A passivation film 29 is formed on the third interlayer insulating film 25, and the third interlayer insulating film 25 and the passivation film 29 are etched to expose the third wiring 28. Finally, a photoresist pattern is formed on the entire front surface and the back surface, and anisotropic etching is performed to thin the substrate 12 from the back surface, thereby forming the diaphragm portion 11.

  By using the pressure sensor element 2 formed in this way, the detection accuracy of the pressure sensor 1 can be improved without increasing the size of the pressure sensor 1.

  The pressure sensor of the present disclosure is useful as a sensor for detecting fluids such as various types of gases because the detection accuracy of the pressure sensor is improved without increasing the size.

DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Pressure sensor element 3 Case 4 Terminal 5 Body part 6 Pipe part 7 Pressure introduction hole 8 Atmospheric introduction hole 9 1st main surface 10 2nd main surface 11 Diaphragm part 12 Board | substrate 13 1st piezoresistive element 14 Second piezoresistive element 15 Third piezoresistive element 16 Fourth piezoresistive element 17 Power supply wiring 18 Metal wiring 19 N well 20 First P well 21 Second P well 22 Thermal oxide film 23 First interlayer Insulating film 24 Second interlayer insulating film 25 Third interlayer insulating film 26 First wiring 27 Second wiring 28 Third wiring 29 Passivation film 30 Diffusion wiring 31 Bridge circuit 32 First direction 33 Second direction

Claims (7)

A substrate comprising a diaphragm portion having a first main surface and a second main surface;
First, second, third, and fourth piezoresistive elements that are formed on the first main surface and detect pressure applied to the diaphragm portion;
Metal wiring disposed on the substrate so as to surround the diaphragm portion, and
The first piezoresistive element and the fourth piezoresistive element are provided on one end side in the first direction of the diaphragm portion,
The second piezoresistive element and the third piezoresistive element are pressure sensor elements provided on the other end side in the first direction of the diaphragm portion. The inner periphery of the metal wiring is formed in a rectangular shape in which the first direction is longer than the second direction,
The first distance between the inner circumference of the metal wiring in the first direction and the outer circumference of the diaphragm portion is a second distance between the inner circumference of the metal wiring and the outer circumference of the diaphragm portion in the second direction. The pressure sensor element according to claim 1 longer. The first piezoresistive element and the second piezoresistive element are arranged side by side in a central portion of the diaphragm portion in the second direction;
3. The pressure sensor element according to claim 1, wherein the third piezoresistive element and the fourth piezoresistive element are arranged side by side at a central portion in the second direction of the diaphragm portion. Between the diaphragm portion of the substrate, the metal wiring, and the first direction, there is provided a diffusion wiring that forms a bridge circuit by connecting the first, second, third, and fourth piezoresistive elements. The pressure sensor element according to claim 1. The pressure sensor element according to claim 1, wherein a plane orientation of the substrate is a (100) plane. A pressure sensor element according to any one of claims 1 to 5;
A case housing the pressure sensor element;
A pressure sensor having a terminal inserted into the case. The case has a main body that houses the pressure sensor element and a pipe connected to the center of the main body.
The pipe part has a pressure introduction hole that communicates the outside and the inside of the pipe part,
The pressure sensor according to claim 6, wherein the pressure sensor element is disposed so as to close the pressure introducing hole.

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