JPH1164141A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out precise positioning of a diaphragm part and a warp detecting element, detect pressure at high precision, and make a pressure sensor fine. SOLUTION: While sandwiching a projected wall 4 between them, a pressure receiving groove 2 and a recessed groove 3 are formed in the front side of a silicon substrate 1. An upper plate 12 is fixed on the pressure receiving groove 2 and the recessed groove 3 to form a pressure receiving chamber A and a standard pressure chamber B which are mutually isolated by the diaphragm part C made of the projected wall 4. A piezoelectric resistance element 5 is formed in the diaphragm part C. When pressure is applied to the pressure receiving chamber A, the diaphragm part C is warped and deformed and the piezo electric resistance element 5 sends out a signal corresponding to the pressure reflecting the warping deformation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor suitable for detecting pressure, and more particularly to a semiconductor type pressure sensor formed on a silicon substrate or the like by using a semiconductor manufacturing technique such as an etching process.

[0002]

2. Description of the Related Art Generally, as a semiconductor type pressure sensor,
A device formed on a substrate made of a semiconductor material such as silicon by using a semiconductor manufacturing technique such as etching is known, for example, from Japanese Patent Application Laid-Open No. 2-132337.

A case in which a diaphragm-type pressure sensor according to the prior art is formed on a silicon substrate will be described with reference to FIGS.

[0004] Reference numeral 101 denotes a silicon substrate as a substrate constituting a pressure sensor, and the upper and lower surfaces 101A and 101B of the silicon substrate 101 are substantially coincident with the (100) plane of the silicon crystal. Is formed.

Reference numeral 102 denotes a back surface 101 of the silicon substrate 101
The thin groove portion 103 is formed on the surface side of the silicon substrate 101 by the concave groove formed on the B side. Further, a piezoresistive element for detecting the bending of the diaphragm 103 is provided on the diaphragm 103, and lead terminals 105, 105 are connected to the piezoresistive element 104.

Here, the concave groove 102 is formed in the silicon substrate 10
1 is anisotropically etched to form a square cross section, and the silicon crystal (111)
Four side walls 102A, 102A,
…have.

During operation of the pressure sensor, when a fluid pressure or the like acts on the diaphragm portion 103, the diaphragm portion 103 bends and deforms in its entirety according to the pressure. At this time, since the piezoresistive element 104 is provided in the diaphragm section 103, distortion occurs in the piezoresistive element 104. Since the resistance value of the piezoresistive element 104 changes in accordance with the amount of distortion, the pressure sensor detects the resistance value of the piezoresistive element 104 based on the voltage, current, and the like between the lead terminals 105, so that the diaphragm unit The pressure applied to 103 is detected.

[0008]

In the above-mentioned prior art, the amount of distortion generated in the piezoresistive element 104 is as follows.
It changes depending on the magnitude of the bending deformation of the diaphragm portion 103. Therefore, in order to accurately detect the pressure acting on the diaphragm 103, it is necessary to accurately position the diaphragm 103 and the piezoresistive element 104. Then, the piezoresistive element 104 and the diaphragm 1
In order to align 03 (concave groove 102) on both sides of the silicon substrate 101, an exposure mask for the piezoresistive element 104 is arranged on the surface 101A side of the silicon substrate 101 using, for example, a double-sided exposure equipment. At the same time, an exposure mask for the groove 102 is arranged on the back surface 101B side of the silicon substrate 101, and the two exposure masks are attached to the front surface 101A side and the back surface 1A.
The position is accurately aligned with the 01B side.

However, generally, when two exposure masks are aligned on the front surface 101A side and the back surface 101B side, the accuracy of alignment is lower than when, for example, the exposure masks are aligned only on the front surface 101A side. It is known to That is, in an infrared aligner or a reflective double-sided aligner that aligns two exposure masks, a positional shift may occur between the two exposure masks due to an axis shift of an optical system or the like. Therefore, the piezoresistive element 104 '
For example, as shown by a one-dot chain line in FIG. 21, the position may be shifted from the diaphragm 103 by a dimension d0 of about several μm.

Further, even when the two exposure masks can be accurately aligned, the diaphragm 103 may be displaced from the piezoresistive element 104. That is, the surface 101A serving as the cut surface of the silicon substrate 101 may have a variation of, for example, about 1 to 3 degrees with respect to the (100) plane due to an error in slicing or polishing during cutting. At this time, when the concave groove 102 is formed by anisotropic etching, each side wall 102A 'is replaced with the original side wall 102A as shown by a two-dot chain line in FIG.
Is inclined with respect to. For this reason, the diaphragm 103 is displaced from the piezoresistive element 104 by a dimension d1 of about 10 μm.

As described above, when the displacement between the diaphragm portion 103 and the piezoresistive element 104 occurs, the amount of distortion generated in the piezoresistive element 104 is reduced.
4 differs from the relative position of the diaphragm unit 103, and therefore the diaphragm unit 1 is
There is a problem that it is difficult to detect the pressure acting on the pressure sensor 03 with high accuracy.

On the other hand, by increasing the size of the diaphragm section 103 and the piezoresistive element 104, the difference in the amount of distortion of the piezoresistive element 104 caused by the displacement between the diaphragm section 103 and the piezoresistive element 104 is reduced. The accuracy of detection by the piezoresistive element 104 can be improved. However, in this case, the dimension d2 of one side of the diaphragm 103 is, for example, several hundred μm to several m.
m, which makes it impossible to miniaturize the pressure sensor.

The present invention has been made in view of the above-mentioned problems of the prior art, and the present invention can detect pressure with high accuracy, and can position the diaphragm and the deflection detecting element with high accuracy, thereby achieving a fine structure. It is to provide a pressure sensor which can be used.

[0014]

According to a first aspect of the present invention, there is provided a pressure sensor comprising: a substrate made of a silicon material; and a pressure sensor formed on a front surface of the substrate.
A pressure receiving groove opened on a side surface of the substrate, a concave groove formed on a front surface side of the substrate, and separated from the pressure receiving groove via a protruding wall; and the substrate covering the pressure receiving groove and the concave groove. A pressure receiving chamber is provided on the front side of the pressure receiving groove and receives a pressure from the outside between the pressure receiving groove and the upper plate defining a reference pressure chamber between the pressure receiving chamber and the concave groove. A diaphragm formed between the recessed groove and the projecting wall and displaced by a pressure difference between the pressure receiving chamber and the reference pressure chamber; and a diaphragm provided at least in the diaphragm, wherein the diaphragm is displaced. And a deflection detecting element for detecting the deflection generated when the deflection is performed.

According to the above configuration, when pressure is applied to the pressure receiving chamber, the diaphragm is bent and deformed due to a differential pressure between the pressure receiving chamber and the reference pressure chamber. At this time, the pressure sensor can detect the bending deformation of the diaphragm by the deflection detecting element and detect the pressure acting on the diaphragm.

Further, since the diaphragm and the deflection detecting element are formed on the front surface of the substrate, the diaphragm and the deflection detecting element can be formed by processing only the surface of the substrate, and the diaphragm and the deflection detecting element can be formed. The detection element can be positioned with high accuracy.

Further, according to the invention of claim 2, the protruding wall constituting the diaphragm portion is formed with a thickness capable of being displaced between the pressure receiving groove and the concave groove.

In this case, when a pressure is applied from between the pressure receiving groove and the upper plate, the diaphragm portion is largely displaced at the intermediate portion in the height direction between the substrate and the upper plate, and is flexibly deformed as a whole. . For this reason, pressure can be received by the entire diaphragm portion.

According to a third aspect of the present invention, a plurality of concave grooves are formed on the front surface side of the substrate, and a plurality of diaphragm portions are formed between the concave grooves and the pressure receiving grooves.

According to the above configuration, when pressure is applied to the pressure receiving chamber, the pressure can be detected for each diaphragm. Further, by forming each of the diaphragm portions to have different thickness dimensions, the range of the pressure that can be detected for each of the diaphragm portions can be changed.

According to a fourth aspect of the present invention, the deflection detecting element is constituted by a piezoresistive element provided in the diaphragm.

As a result, when pressure is applied between the pressure receiving groove and the upper plate, and the diaphragm is bent and deformed, distortion occurs in the piezoresistive element. At this time, since the resistance value of the piezoresistive element changes according to the amount of distortion, the pressure applied to the diaphragm can be detected according to the resistance value of the piezoresistive element.

According to a fifth aspect of the present invention, the deflection detecting element comprises: a first electrode provided on the diaphragm;
And a second electrode provided in the recessed groove opposite to the above-mentioned electrode to constitute a capacitance-type element.

Accordingly, when a pressure is applied between the pressure receiving groove and the upper plate, and the diaphragm portion is bent and deformed, the gap between the first electrode on the diaphragm portion side and the second electrode in the concave groove is formed. Is reduced or increased, the capacitance between the first electrode and the second electrode changes according to this distance. For this reason, it is possible to detect the pressure applied to the diaphragm in accordance with the capacitance between the first electrode and the second electrode.

According to a sixth aspect of the present invention, the substrate is formed of a semiconductor material to which impurities are added.

Therefore, the substrate can be formed as an n-type semiconductor or a p-type semiconductor, and the flexural deformation element can be easily formed on the diaphragm by using an ion implantation method or the like.

According to a seventh aspect of the present invention, the substrate is an SOI substrate having an oxide film interposed between two silicon substrates.

By using the SOI substrate, it is possible to easily form the pressure receiving groove and the diaphragm.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pressure sensor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, a first embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

Reference numeral 1 denotes a silicon substrate as a substrate made of a single-crystal silicon material. The silicon substrate 1 is formed in, for example, a substantially rectangular shape having long sides and short sides. Here, in this embodiment, the long side direction of the silicon substrate 1 is the front-back direction, and the short side direction is the left-right direction. The silicon substrate 1 becomes an n-type semiconductor as a semiconductor material by adding an impurity such as phosphorus.

Reference numeral 2 denotes a pressure receiving groove located on the front side of the silicon substrate 1 and recessed on the surface side. The pressure receiving groove 2 is formed by performing a dry etching process or the like on the surface side of the silicon substrate 1. For example, it has a depth dimension of about 20 to 100 μm. The pressure receiving groove 2 is opened in a side surface serving as a front end of the silicon substrate 1, is formed in a substantially square shape from the front end to the rear side of the silicon substrate 1, and has a length L0 in the left-right direction. Have. And the pressure receiving groove 2
The upper plate 12 is covered by the upper plate 12 described later.
And a pressure receiving chamber A for receiving a pressure from the outside.

Reference numeral 3 denotes a concave groove formed in the front surface of the silicon substrate 1, and the concave groove 3 is formed by performing a dry etching process or the like on the front surface of the silicon substrate 1.
The pressure receiving groove 2 is separated from the pressure receiving groove 2 via a projecting wall 4 described later. The concave groove 3 is formed in a substantially square shape as shown in FIG. 2, and is arranged so as to be spaced apart from the pressure receiving groove 2 in the front-rear direction and substantially parallel in the left-right direction.

The concave groove 3 is, for example, 20 to 100.
It has a depth of about .mu.m and a length L0 substantially the same as the pressure receiving groove 2 in the left-right direction. The concave groove 3 is closed by the upper plate 12 to define a sealed reference pressure chamber B between the upper groove 12 and the upper groove 12.

Reference numeral 4 denotes a projecting wall formed between the pressure receiving groove 2 and the concave groove 3. The projecting wall 4 is formed as a thin wall between the concave groove 3 and the pressure receiving groove 2, and is uniform. It extends long in the left-right direction of the substrate 1 with a thickness L1. The projecting wall portion 4 has substantially the same length dimension as the pressure receiving groove 2 and the concave groove 3 in the left-right direction.

The projecting wall 4 forms a diaphragm portion C for isolating the pressure receiving chamber A from the reference pressure chamber B by fixing the upper plate 12. The diaphragm portion C is bent and deformed due to a pressure difference between the pressure receiving chamber A and the reference pressure chamber B. For example, the base portion in the height direction is largely displaced.

Reference numerals 5 and 5 denote, for example, two piezoresistive elements provided as deflection detecting elements on the side of the pressure receiving groove 2 of the diaphragm section 4, and the piezoresistive elements 5 are separated from each other in the left-right direction of the diaphragm section C. It is formed in a buried state at an intermediate portion in the height direction. Further, the piezoresistive element 5 is formed by injecting impurities such as boron from the surface side of the silicon substrate 1 by using, for example, an ion implantation method and diffusing it, and making a part of the piezoresistive into a substantially rectangular shape. Have been. Each piezoresistive element 5 is distorted as the diaphragm C is flexed and deformed, and detects the amount of distortion as a pressure applied to the diaphragm C.

Reference numeral 6 denotes a diffusion layer wiring for connecting the respective piezoresistive elements 5, and the diffusion layer wiring 6 is
Similarly to the case described above, for example, it is formed in a state buried in the diaphragm portion C by using a means such as an ion implantation method. The two ends of the diffusion layer wiring 6 are connected to the respective piezoresistive elements 5. The conductivity of the diffusion layer wiring 6 is the same as or higher than the conductivity of the piezoresistive element 5.

Reference numerals 7 and 7 denote diffusion layer wirings for electrically connecting the respective piezoresistive elements 5 to metal wirings 10 to be described later. Is formed in the silicon substrate 1 in a buried state. Here, each diffusion layer wiring 7 is shown in FIG.
As shown in the figure, one end side reaches the inside of the diaphragm part C,
The other end extends in the front-rear direction along the side surface of the concave groove 3. One end of each diffusion layer wiring 7 is connected to each piezoresistive element 5, and the other end is connected to each connection section 8 described later.

Numerals 8 are provided at the other end of each of the diffusion layer wirings 7 to electrically connect each of the diffusion layer wirings 7 to the metal wiring 10. Each of the connection parts 8 is a diffusion layer wiring. 7 is formed on the surface side of the silicon substrate 1 by using a method such as an ion implantation method. The connection portion 8 extends from the surface of the silicon substrate 1 in the height direction and is connected to the other end of each diffusion layer wiring 7.

Reference numeral 9 denotes an insulating film formed on the front surface side of the silicon substrate 1 and covering the entire silicon substrate 1.
Is formed of, for example, silicon oxide, etc.
The thickness is about 0.9 μm. Also, as shown in FIG. 1, each contact hole 9A is formed in the insulating film 9 at a portion corresponding to each connection portion 8.

Reference numerals 10 and 10 denote insulating films 9 on the silicon substrate 1.
Each metal wiring 10 is a metal wiring provided through
As shown in FIG. 1, it is formed of a metal film such as aluminum.

Each of the metal wirings 10 has one end connected to each connection portion 8 through each contact hole 9 A of the insulating film 9, and the other end extending toward the rear side of the silicon substrate 1. Electrodes 10A, 10A are formed on the other end of each metal wiring 10, and each electrode 10A is connected to an external detection circuit (not shown) or the like. Thus, each metal wiring 10 derives a pressure detection signal output from each piezoresistive element 5 to this detection circuit or the like.

Reference numeral 11 denotes an insulating protective film for protecting the metal wiring 10. The protective film 11 is provided on the surface of the silicon substrate 1 so as to cover the metal wiring 10. Each contact hole 11A is formed in the protective film 11 at a position corresponding to each electrode portion 10A.

Reference numeral 12 denotes an upper plate that covers the pressure receiving groove 2 and closes the concave groove 3. The upper plate 12 is made of, for example, Pyrex glass, and is made of silicon through the insulating film 9 by using an anodic bonding method or the like. It is fixed to the surface side of the substrate 1.

The upper plate 12 has a pressure receiving groove 2 at its front side.
To form a pressure receiving chamber A between the upper plate 12 and the pressure receiving groove 2. The position of the front end of the upper plate 12 is substantially equal to the position of the front end of the silicon substrate 1, and the front end surface of the upper plate 12 and the front end surface of the silicon substrate 1 are flush with each other.
Therefore, the pressure of the detection target can be guided to the pressure receiving chamber A by attaching the front portions of the silicon substrate 1 and the upper plate 12 to the detection target. On the other hand, the upper plate 12 is
To form a reference pressure chamber B between the upper plate 12 and the recessed groove 3 which is maintained at a reference pressure state.

Further, on the rear side of the upper plate 12, a notch step 12A is provided, and the notch step 12A and the silicon substrate 1 are formed.
A gap for accommodating the metal wiring 10 is formed between them.

The pressure sensor according to the present invention has the above-described configuration. Next, the manufacturing process thereof will be described with reference to FIGS.

First, the silicon substrate 1 shown in FIG. 3 is provided in a pressure sensor manufacturing apparatus (not shown). Then, an oxide film 13 is formed on the front surface side of the silicon substrate 1, and the state shown in FIG. 4 is obtained.

Next, as shown in FIG. 5, by performing an exposure step and an etching step, the oxide film 13 where the pressure receiving groove 2 and the concave groove 3 are formed is removed. And FIG.
In the state shown in FIG. 6, the oxide film 13 plays a role as a mask. Therefore, by using the dry etching method, the pressure receiving groove 2 and the concave groove 3 are formed in the silicon substrate 1 as shown in FIG. A protruding wall 4 is formed between the protruding wall 3 and the concave groove 3.

Next, while removing the oxide film 13, impurities such as boron are implanted into the silicon substrate 1 from the surface side by ion implantation or the like and diffused, as shown in FIG.
Each piezoresistive element 5 is formed on the protruding wall 4. In addition, gusset 4
, A diffusion layer wiring 6 is formed, and each diffusion layer wiring 7 is formed on the silicon substrate 1.

After forming the piezoresistive elements 5 and the like, an insulating film 9 such as an oxide film is formed on the surface of the silicon substrate 1. Further, as shown in FIG. 8, a contact hole 9A for connecting the diffusion layer wiring 7 and the metal wiring 10 is formed.

Next, as shown in FIG. 9, an impurity such as boron is implanted into the silicon substrate 1 from the front side through the contact hole 9A and diffused to form the connection portion 8. Then, as shown in FIG. 10, a metal wiring 10 is formed on the surface side of the insulating film 9 by vacuum deposition or the like, and a protective film 11 that covers the metal wiring 10 is formed on the surface side of the silicon substrate 1. Then, a contact hole 11A as a bonding pad region is provided in the protective film 11 at a position corresponding to the electrode portion 10A.

Lastly, the upper plate 12 is placed on the front surface of the silicon substrate 1 via the insulating film 9, and the upper plate 12 is bonded to the silicon substrate 1 by an anodic bonding method or the like.

Thus, in this embodiment, the silicon substrate 1
The upper plate 12 is fixed on the upper surface, and the protruding wall 4 serving as the diaphragm portion C is formed between the pressure receiving groove 2 and the concave groove 3, so that the diaphragm portion C is manufactured by processing from the surface side of the silicon substrate 1. Can be. For this reason, the diaphragm portion C and the piezoresistive element 5 can be positioned with high accuracy, and the diaphragm portion C and the piezoresistive element 5 can be made smaller than those of the prior art. The sensor can be miniaturized and formed compact. Further, the diaphragm portion C is formed by the piezoresistive element 5.
Can be accurately detected.

Since the piezoresistive element 5 is provided in the diaphragm C, pressure acts on the diaphragm C,
When bending deformation occurs, distortion occurs in the piezoresistive element 5. At this time, the piezoresistive element 5
Of the piezoresistive element 5, the pressure applied to the diaphragm C can be detected.

Further, since the piezoresistive elements 5 are formed in the middle of the diaphragm C in the left-right direction and in the height direction, the piezoresistive elements 5 can be more greatly deformed and deformed. That is, when a pressure difference occurs between the pressure receiving chamber A and the reference pressure chamber B, the middle part in the height direction of the diaphragm C is further displaced, and the middle part in the left-right direction is also displaced. For this reason, since each piezoresistive element 5 undergoes a larger distortion deformation, the pressure acting on the diaphragm C by the piezoresistive element 5 can be accurately detected.

Further, a silicon substrate 1 made of an n-type semiconductor
Is used, the piezoresistive element 5 and the like can be easily formed by adding and diffusing impurities such as boron.

Next, a pressure sensor according to a second embodiment of the present invention will be described with reference to FIG. 11. The feature of this embodiment is that an oxide film is interposed between two silicon substrates as a substrate of the pressure sensor. SOI (Silicon on I
nsulator) substrate.

In the figure, reference numeral 21 denotes a square SOI substrate which forms the substrate of the pressure sensor. The SOI substrate 21 has a base portion 2 as one silicon substrate made of silicon single crystal.
1A, a surface layer 21B as another silicon substrate formed on the surface side of the base 21A, and an insulating layer 21C as an oxide film interposed between the surface 21B and the base 21A. It is configured. And the surface layer 21B
Has an thickness of, for example, about 5 to 20 μm, and becomes an n-type semiconductor by adding impurities such as phosphorus.

Reference numeral 22 denotes a pressure receiving groove formed in the front surface of the SOI substrate 21. The pressure receiving groove 22 is formed in a substantially square shape by performing a dry etching process, a wet etching process, or the like on the surface side of the SOI substrate 21. The insulating layer portion 21C is formed and extends from the surface side of the SOI substrate 21 in the height direction.
Has been reached.

Reference numeral 23 denotes a concave groove which is separated from the pressure receiving groove 22 via a projecting wall 24 described later and is formed in the surface layer portion 21B of the SOI substrate 21. The concave groove 23 has the same SOI as the pressure receiving groove 22. It is formed by performing an etching process or the like on the surface side of the substrate 21. Further, the concave groove 23 is formed in a substantially square shape, extends from the surface side of the SOI substrate 21 in the height direction, and reaches the insulating layer portion 21C.

Reference numeral 24 denotes a projecting wall formed as an elongated partition between the concave groove 23 and the pressure receiving groove 22. The projecting wall 24 is formed of SOI.
It extends in the left-right direction of the substrate 21.

Reference numeral 25 denotes a piezoresistive element provided on the protruding wall 24, reference numeral 26 denotes a diffusion layer wiring for connecting the piezoresistive elements 25, and reference numeral 27 denotes an electrical connection between the piezoresistive elements 25 to a metal wiring 30 to be described later. Diffusion layer wirings for connection are shown, each piezoresistive element 25, each diffusion layer wiring 26, 27
Are buried in the silicon substrate 1 in substantially the same manner as the piezoresistive elements 5 and the diffusion layer wirings 6 and 7 according to the first embodiment.

Reference numerals 28, 28 are provided on the other end side of the respective diffusion layer wirings 27, and are connecting portions for electrically connecting the respective diffusion layer wirings 27 and the metal wirings 30. Extends in the height direction toward the back side of the silicon substrate 21 and is connected to the other end of each diffusion layer wiring 27.

Reference numeral 29 denotes an insulating film formed on the front surface side of the SOI substrate 21 and covering the entire SOI substrate 21. The insulating film 29 has contact holes 29A, 29A at portions corresponding to the connection portions 28, respectively. Is formed.

Reference numerals 30 and 30 denote insulating films 2 on the SOI substrate 21.
9, each metal wiring 30
Has one end connected to each connection portion 28 via each contact hole 29A of the insulating film 29, and the other end portion having an electrode portion 30
A, 30A are formed.

Reference numeral 31 denotes the SOI substrate 2 covering the metal wiring 30.
The contact holes 31A, 31A are formed in the protective film 31 at portions corresponding to the respective electrode portions 30A.

Reference numeral 32 denotes an upper plate which covers the pressure receiving groove 22 and closes the concave groove 23. The upper plate 32 has a front side covering the pressure receiving groove 22 similarly to the upper plate 12 according to the first embodiment. Thereby, the pressure receiving chamber A is formed between the upper plate 32 and the pressure receiving groove 22. The upper plate 32 forms a reference pressure chamber B having a reference pressure between the upper plate 32 and the concave groove 23 by closing the concave groove 23. And the upper plate 3
2 is fixed on the protruding wall 24 so that the pressure receiving chamber A
And a reference pressure chamber B to form a diaphragm portion C which is displaced by a differential pressure acting on the reference pressure chamber B.

Further, on the rear side of the upper plate 32, a notch step 32A is provided, and the notch step 32A and the SOI substrate 21 are formed.
A gap for accommodating the metal wiring 30 is formed between the two.

Thus, in the present embodiment having the above-described structure, substantially the same operation and effect as those of the first embodiment can be obtained. In particular, in the present embodiment, the connection between the surface layer portion 21B and the base portion 21A is achieved. Since the SOI substrate 21 having the insulating layer 21C interposed therebetween was used, the etching of the SOI substrate 21 was performed when the pressure receiving groove 22 and the concave groove 23 were formed.
C, for example, when a large number of pressure sensors are manufactured from one SOI substrate 21, the depth dimensions of the pressure receiving grooves 22 and the concave grooves 23 of each pressure sensor are made uniform, and the same pressure is applied. Thus, a pressure detection signal having substantially the same value can be output.

Further, by forming insulating portions 33 made of silicon oxide or the like extending in the height direction on the surface layer portion 21B of the SOI substrate 21 as shown by phantom lines in FIG. The enclosed region and other regions can be electrically insulated. For this reason, an active element such as a MOS transistor which needs to be insulated from other elements can be easily formed on the SOI substrate 21, and a processing circuit for amplifying a detection signal from the piezoresistive element 25 and shaping a waveform, etc. Can be formed integrally with the pressure sensor.

In the second embodiment, the diaphragm C is provided by forming the pressure receiving groove 22 and the concave groove 23 in the surface layer 21B of the SOI substrate 21. However, the height dimension of the diaphragm C is set. To increase
The surface portion 21B may be epitaxially grown. In this case, a piezoresistive element 25 and diffusion layer wirings 26 and 27 are formed on the surface side of the surface layer portion 21B, and then the surface layer portion 21B is epitaxially grown.
Is preferably formed.

Next, a pressure sensor according to a third embodiment of the present invention will be described with reference to FIGS. 12 and 13. The feature of this embodiment is that a plurality of concave grooves are formed on the surface side of the substrate. In addition, a plurality of diaphragm portions are formed between each concave groove and the pressure receiving groove.

Reference numeral 41 denotes a substantially rectangular silicon substrate serving as a substrate of the pressure sensor. The silicon substrate 41 becomes an n-type semiconductor by adding impurities.

Reference numeral 42 denotes a pressure receiving groove which is recessed on the surface of the silicon substrate 41. The pressure receiving groove 42 is formed in a substantially square shape by performing a dry etching process or the like on the surface of the silicon substrate 41. I have. The pressure receiving groove 42 has a dimension longer than the total dimension (L 2 + L 3) of the concave grooves 43 and 44 described later, and the concave grooves 43 and 44 are arranged along the length direction (left and right direction) of the pressure receiving groove 42. It is arranged in.

Reference numeral 43 denotes a first recessed groove located on the rear side of the pressure receiving groove 42 and recessed on the surface side of the silicon substrate 41. The recessed groove 43 has a height of, for example, about 20 to 100 μm. Have. The concave groove 43 is formed in a substantially rectangular shape having a long side and a short side as shown in FIG.

Reference numeral 44 denotes a second concave groove located on the rear side of the pressure receiving groove 42 and recessed on the surface side of the silicon substrate 41. The concave groove 44 has substantially the same depth as the first concave groove 43. It has dimensions, and is disposed apart from the first concave groove 43 in the left-right direction.

The concave groove 44 is formed in a substantially rectangular shape having a long side and a short side, and the length dimension L 3 of the long side of the concave groove 44 is set to the long side of the first concave groove 43. Is approximately equal to the length dimension L2.

45 and 46 are concave grooves 43 and 44 and pressure receiving grooves 4
The first and second protruding walls formed as elongated partitions between the protruding walls 45 and 46 extend in the left-right direction of the silicon substrate 41. The thickness L4 of the protruding wall 45 is greater than the thickness L5 of the protruding wall 46.

Reference numerals 47 and 48 denote piezoresistive elements provided on the protruding walls 45 and 46, respectively.
Similarly to the protruding wall 4 according to the first embodiment, the protruding walls 45 and 46 are separated from each other in the left-right direction, and are buried at an intermediate portion in the height direction.

Reference numeral 49 denotes a diffusion layer wiring for connecting the piezoresistive elements 47, and reference numeral 50 denotes a diffusion layer wiring for electrically connecting the piezoresistive elements 47 to a metal wiring 56 described later. The layer wirings 49 and 50 are buried in the silicon substrate 41 in the same manner as the diffusion layer wirings 6 and 7 according to the first embodiment.

Reference numeral 51 denotes a diffusion layer wiring for connecting the respective piezoresistive elements 48, and reference numeral 52 denotes a diffusion layer wiring for electrically connecting the respective piezoresistive elements 48 to a metal wiring 57 described later. The layer wirings 51 and 52 are buried in the silicon substrate 41 similarly to the diffusion layer wirings 6 and 7 according to the first embodiment.

Numerals 53, 53 are provided on the other end side of the respective diffusion layer wirings 50, and are connection parts for electrically connecting the respective diffusion layer wirings 50 and the metal wirings 56.
And extends in the height direction from the surface of each diffusion layer wiring 50 and is connected to the other end of each diffusion layer wiring 50.

Numerals 54 and 54 are provided on the other end side of each diffusion layer wiring 52 to electrically connect each diffusion layer wiring 52 to the metal wiring 57. The connection part 54 is a silicon substrate 41.
Extend from the front surface to the rear surface in the height direction and are connected to the other end of each diffusion layer wiring 52.

Reference numeral 55 denotes an insulating film formed on the front surface side of the silicon substrate 41 and covering the entire silicon substrate 41. The insulating film 55 has connection portions 53 and 54 as shown in FIG.
Contact holes 55A, 55A
5B are formed.

Reference numerals 56 and 57 denote metal wirings provided on the silicon substrate 41 with an insulating film 55 interposed therebetween.
One end of each of the electrodes 6 and 57 is connected to each of the connection portions 53 and 54 via each of the contact holes 55A and 55B of the insulating film 55, and each of the electrode portions 56A and 57A is formed at the other end.

Reference numerals 58 and 59 denote protection films provided on the surface side of the silicon substrate 41 so as to cover the metal wirings 56 and 57. The protection films 58 and 59 have portions corresponding to the electrode portions 56A and 57A, respectively. Contact holes 58A and 59A are formed.

Reference numeral 60 denotes a pressure receiving groove 42 and a concave groove 43,
44 shows an upper plate for closing the pressure receiving groove 42. The upper plate 60 covers the pressure receiving groove 42 so that the upper plate 60 and the pressure receiving groove 42 are closed.
To form a pressure receiving chamber A. In addition, the upper plate 60
By closing the concave grooves 43, 44, reference pressure chambers B1, B2 having a standard pressure are formed between the upper plate 60 and the concave grooves 43, 44. The upper plate 60 is fixed on the protruding walls 45, 46 to form the diaphragm portions C1, C2.

Further, on the rear side of the upper plate 60, a thin notch step 60A is provided, and between the notch step 60A and the silicon substrate 41, metal wires 56 and 57 are accommodated. Are formed.

Thus, in the present embodiment having the above-described structure, substantially the same operation and effect as those of the first embodiment can be obtained.
Since the two concave grooves 43 and 44 are provided through the interpositions 5 and 46, two diaphragm portions C1 and C2 can be formed. Therefore, when pressure is applied to the pressure receiving chamber A,
The two diaphragm portions C1 and C2 can be bent and deformed, respectively, and the pressure can be detected by the piezoresistive elements 47 and 48 provided in the diaphragm portions C1 and C2. Further, by using a plurality of piezoresistive elements 47 and 48, a plurality of detected values of pressure can be obtained, so that pressure can be detected more accurately.

Further, by making the thicknesses L4 and L5 of the diaphragm portions C1 and C2 different from each other,
The range of detectable pressure can be changed for each of the diaphragm portions C1 and C2. That is, a higher pressure can be detected in the thick diaphragm portion C1 having the thickness L4, and a lower pressure can be detected in the thin diaphragm portion C2 having the thickness L5. For this reason,
By constructing a pressure sensor using the two diaphragm portions C1 and C2, a wider range of pressure can be detected.

Next, a pressure sensor according to a fourth embodiment of the present invention will be described with reference to FIG. 14. The feature of this embodiment is that a plurality of recessed grooves are formed on the surface side of the substrate, and each recess is formed. This is because a plurality of diaphragm portions having different lengths are formed between the groove and the pressure receiving groove. In this embodiment, the third
The same reference numerals are given to the same components as those of the embodiment, and the description thereof will be omitted.

Reference numeral 61 denotes a first concave groove located on the rear side of the pressure receiving groove 42 and recessed on the surface side of the silicon substrate 41. The first concave groove 61 is different from the concave groove 43 according to the third embodiment. Similarly, it is formed on the silicon substrate 41 in a substantially rectangular shape having a long side and a short side.

Reference numeral 62 denotes a second recessed groove located on the rear side of the pressure receiving groove 42 and recessed on the surface side of the silicon substrate 41. The recessed groove 62 has substantially the same depth as the first recessed groove 61. It has dimensions, and is disposed apart from the first concave groove 61 in the left-right direction.

The concave groove 62 is formed in a substantially rectangular shape having a long side and a short side, and the length dimension L7 of the long side of the concave groove 62 is equal to the long side of the first concave groove 61. Is shorter than the length L6.

Reference numerals 63 and 64 denote concave grooves 61 and 62 and pressure receiving grooves 4.
The first and second protruding walls formed as elongated partitions between the protruding walls 2 and 2 extend in the left-right direction of the silicon substrate 41. The thickness L8 of the projecting wall 63 is substantially equal to the thickness L9 of the projecting wall 64.

Thus, in the present embodiment having the above-described structure, substantially the same operation and effect as those of the third embodiment can be obtained.

Next, a pressure sensor according to a fifth embodiment of the present invention will be described with reference to FIGS. 15 and 16. The feature of this embodiment is that the deflection detecting element of the pressure sensor is replaced with a capacitance type element. I did it.

In the figure, reference numeral 71 denotes a square SOI substrate which forms the substrate of the pressure sensor.
Similarly to the SOI substrate 21 according to the embodiment, the base 71A,
It is composed of a surface layer 71B and an insulating layer 71C.

A pressure receiving groove 72 is formed in the surface of the SOI substrate 71 so as to be recessed. The pressure receiving groove 72 is formed in a substantially square shape as shown in FIG. Has been reached.

Reference numeral 73 denotes an SOI located around the pressure receiving groove 72.
A concave groove formed in the surface layer portion 71B of the substrate 71 is shown. The concave groove 73 is formed in an elongated groove shape and extends in the left-right direction of the SOI substrate 71. Further, the concave groove 73 is made of SO
It extends in the height direction from the surface side of the I substrate 71 and reaches the insulating layer portion 71C.

Reference numeral 74 denotes a projecting wall formed as an elongated partition wall between the pressure receiving groove 72 and the concave groove 73. The thickness of the projecting wall 74 between the pressure receiving groove 72 and the concave groove 73 is substantially constant. It is formed as follows.

Numeral 75 denotes a capacitance type element provided between the protruding wall 74 and the concave groove 73.
Is constituted by first and second electrodes 76 and 77 described later.

Reference numeral 76 denotes a first electrode provided on the projecting wall 74. The electrode 76 implants an impurity such as boron into the surface layer portion 71B of the SOI substrate 71 by using, for example, an ion implantation method.
It is formed in a substantially L-shape by diffusion, and a part thereof is exposed in the concave groove 73. And the electrode 76 is
One end of the SOI substrate 71 extends in the left-right direction, and the other end extends toward the rear of the SOI substrate 71. The other end of the electrode 76 has a metal wiring 8 to be described later.
0 is connected.

Reference numeral 77 denotes an SOI which is separated from the first electrode 76.
A second electrode formed on the surface layer portion 71B of the substrate 71, and the electrode 77 faces the first electrode 76 via the concave groove 73. The electrode 77 is formed using an ion implantation method or the like in the same manner as the first electrode 76, and has a substantially square shape. The electrode 77 is connected to a metal wiring 81 described later.

Reference numeral 78 denotes an insulating wall portion for electrically insulating the first and second electrodes 76 and 77. The insulating wall portion 78 is located between the electrode 77 and the surface layer portion 71B of the SOI substrate 71. It is formed in a substantially U-shape. And the insulating wall portion 78
While electrically insulating the electrode 77 and the surface layer portion 71B,
It surrounds the electrode 77 together with the concave groove 73.

Reference numeral 79 denotes an insulating film made of an oxide film or the like formed on the surface layer portion 71B of the SOI substrate 71.
Is located on the rear side of the insulating wall portion 78 and covers the surface layer portion 71B as shown in FIG.
Is insulated between

Reference numerals 80 and 81 denote metal wirings provided on the SOI substrate 71. One end of each of the metal wirings 80 and 81 reaches the first and second electrodes 76 and 77, and the other end thereof includes an insulating film 79. Extends upward. The metal wirings 80 and 81 connect the first and second electrodes 76 and 77 to an external detection circuit (not shown) and the like.

Reference numeral 82 denotes an upper plate that covers the pressure receiving groove 72 and closes the concave groove 73. The upper plate 82 has a front portion that covers the pressure receiving groove 72, so that the upper plate 82 is located between the upper plate 82 and the pressure receiving groove 72. A pressure receiving chamber A is formed at the bottom of the cylinder. The upper plate 82 is provided with the concave groove 7.
By closing 3, a reference pressure chamber B having a reference pressure is formed between the upper plate 82 and the concave groove 73. The upper plate 82 is fixed on the protruding wall 74 to form a diaphragm C.

Further, on the rear side of the upper plate 82, a thin notch step 82A is provided, and the notch step 82A and S
A gap for accommodating the metal wirings 80 and 81 is formed between the OI substrate 71 and the OI substrate 71.

Next, the operation of the pressure sensor according to the present embodiment will be described. First, when pressure is applied to the pressure receiving chamber A and the diaphragm portion C is bent and deformed, the first electrode 76 and the second electrode 77 are moved. The distance between decreases and increases. For this reason, the capacitance between the first and second electrodes 76 and 77 changes according to the separation distance between the first and second electrodes 76 and 77, so that the first and second electrodes 76 and 77 change. The pressure applied to the diaphragm C is detected in accordance with the capacitance between the two.

Thus, also in the present embodiment having the above-described configuration, it is possible to obtain substantially the same operation and effect as those of the first and second embodiments.

Next, a pressure sensor according to a sixth embodiment of the present invention will be described with reference to FIGS. 17 to 19. The feature of this embodiment is that the pressure sensor comprises a static sensor comprising first and second electrodes. In addition to providing a capacitance element, a U-shaped concave groove is provided outside the second electrode. In this embodiment, the same components as those in the fifth embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

Reference numeral 91 denotes a concave groove located in the inner part of the SOI substrate 71 and formed in the surface layer portion 71B.
1 is formed in a substantially U-shape as shown in FIG. 18 and reaches the insulating layer 71C from the front side of the SOI substrate 71.

Reference numeral 92 denotes an insulating wall portion for electrically insulating the first and second electrodes 76 and 77. The insulating wall portion 92 is located on the rear side of the electrode 77 and has an elongated wall shape extending in the left-right direction. Is formed. The insulating wall portion 92 electrically insulates the electrode 77 from the surface layer portion 71B, and surrounds the electrode 77 together with the concave groove 91.

Reference numeral 93 denotes an upper plate which covers the pressure receiving groove 72 and closes the concave groove 91.
As shown in FIG. 9, a pressure receiving chamber A is formed between the upper plate 93 and the pressure receiving groove 72 by covering the pressure receiving groove 72 on the front side. The upper plate 93 closes the concave groove 91 to form a reference pressure chamber B having a reference pressure between the upper plate 93 and the concave groove 91. And the upper plate 93
The diaphragm portion C is formed by being fixed on the protruding wall 74.

Further, on the rear side of the upper plate 93, two notched grooves 93A and 93B are provided, and the notched grooves 93A and 93B are provided.
Between the 93B and the SOI substrate 71, metal wirings 80 and 8 are provided.
1 is formed.

Thus, in the present embodiment having the above-described configuration, substantially the same operation and effect as those of the fourth embodiment can be obtained.

In each of the above embodiments, the silicon substrate, S
Although the surface layer portion of the OI substrate is formed as an n-type semiconductor, the present invention is not limited to this, and may be formed as a p-type semiconductor.

In the first, second and third embodiments, each piezoresistive element is constituted by a p-type semiconductor formed on a silicon substrate or an SOI substrate by ion implantation. However, the present invention is not limited to this. For example, a piezoresistive element may be formed of polycrystalline silicon, a metal film, or the like.

In each of the above embodiments, each piezoresistive element or capacitance type element is used as the deflection detecting element. However, the present invention is not limited to this. For example, pressure is detected using a piezoelectric element or the like. The configuration may be such that

In each of the above embodiments, the silicon substrate,
The upper plate is fixed to the front side of the SOI substrate via an insulating film or the like. An amorphous or polycrystalline silicon film is formed on the insulating film, and the upper plate is anodically bonded to the silicon film. It may be configured.

In each of the above embodiments, the reference pressure chamber is formed as a closed space by closing the concave groove.
When used as a sensor for measuring relative pressure, it is not necessary to close the concave groove and seal the reference pressure chamber,
For example, of the two pressure chambers having different pressures, one of the pressure chambers may communicate with the reference pressure chamber, and the other pressure chamber may communicate with the pressure receiving chamber.

[0125]

As described in detail above, according to the first aspect of the present invention, the pressure receiving groove and the concave groove are provided on the surface side of the substrate via the protruding wall, and the upper plate is placed on the pressure receiving groove and the concave groove. By fixing, the pressure receiving chamber and the reference pressure chamber which are separated from each other by the diaphragm part formed of the protruding wall are formed,
When an external pressure acts on the pressure receiving chamber and the diaphragm is flexed and deformed, the pressure acting on the diaphragm can be detected by the flexure detecting element provided on the diaphragm. And since a diaphragm part and a bending detection element can be formed from the surface side of a board | substrate, a diaphragm part and a bending detection element can be positioned with high precision. Thus, the pressure acting on the diaphragm can be accurately detected, the size of the deflection detecting element and the diaphragm can be reduced, and the pressure sensor can be miniaturized and formed compact.

According to the second aspect of the present invention, since the protruding wall constituting the diaphragm is formed with a displaceable thickness, the diaphragm is bent and deformed as a whole when pressure is applied to the diaphragm. Can be
The pressure can be accurately detected by the deflection detecting element. Further, it is possible to prevent partial pressure from acting on the diaphragm, prevent damage to the diaphragm, and improve durability.

According to the third aspect of the present invention, a plurality of concave grooves are formed around the pressure receiving groove on the front surface side of the substrate, and a plurality of diaphragm portions are formed between the pressure receiving groove and the pressure receiving groove. When pressure is applied, the pressure can be detected for each diaphragm. Further, by forming each of the diaphragm portions with a different thickness dimension, the range of detectable pressure can be changed for each diaphragm portion, and a wider range of pressure can be detected.

According to the fourth aspect of the present invention, since the piezoresistive element is used as the deflection detecting element, when a pressure acts on the diaphragm, the pressure applied to the diaphragm corresponding to the resistance value of the piezoresistive element. Can be detected.

According to the fifth aspect of the present invention, since the capacitance type element is used as the deflection detecting element, the capacitance between the first and second electrodes is reduced when pressure is applied to the diaphragm. Correspondingly, the pressure applied to the diaphragm can be detected.

According to the invention of claim 6, since the substrate is formed of a semiconductor material to which impurities are added, the substrate can be formed as an n-type semiconductor or a p-type semiconductor. The bending deformation element can be easily formed on this substrate.

According to the seventh aspect of the present invention, an SOI substrate including two silicon substrates and an oxide film is used as a substrate.
The etching of the substrate is automatically stopped by the oxide film,
The diaphragm portion can be easily formed. Further, an electrically insulated region can be easily formed on the silicon substrate on the front surface side of the SOI substrate, and an active element for amplifying a signal from the deflection detecting element can be easily formed on the SOI substrate together with the pressure sensor. can do.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a pressure sensor according to a first embodiment.

FIG. 2 is a cross-sectional view as seen from the direction of arrows II-II in FIG.

FIG. 3 is a sectional view showing a silicon substrate used in the first embodiment.

FIG. 4 is a sectional view showing a state where an oxide film is formed on the silicon substrate shown in FIG. 3;

FIG. 5 shows a pressure receiving groove formed from an oxide film from the silicon substrate shown in FIG. 4;
It is sectional drawing which shows the state which removed the part corresponding to the recessed groove.

6 is a cross-sectional view showing a state in which a pressure receiving groove and a concave groove are formed in the silicon substrate shown in FIG.

FIG. 7 is a cross-sectional view showing a state in which a piezoresistive element and a diffusion layer wiring are formed on the silicon substrate shown in FIG. 6 and an insulating film is formed.

8 is a cross-sectional view showing a state where a contact hole is formed in an insulating layer formed on the silicon substrate shown in FIG.

FIG. 9 is a cross-sectional view showing a state where a connection portion is formed on the silicon substrate shown in FIG.

FIG. 10 is a cross-sectional view showing a state where a metal wiring and a protective film are formed on the silicon substrate shown in FIG. 9;

FIG. 11 is a sectional view showing a pressure sensor according to a second embodiment.

FIG. 12 is a sectional view showing a pressure sensor according to a third embodiment.

FIG. 13 is a cross-sectional view as viewed from the direction indicated by arrows XIII-XIII in FIG.

FIG. 14 shows a pressure sensor according to a fourth embodiment.
It is sectional drawing seen from the same direction as (3).

FIG. 15 is a sectional view showing a pressure sensor according to a fifth embodiment.

16 is a cross-sectional view as viewed from the direction indicated by arrows XVI-XVI in FIG.

FIG. 17 is a sectional view showing a pressure sensor according to a sixth embodiment.

18 is a cross-sectional view as viewed from the direction of arrows XVIII-XVIII in FIG. 17;

19 is a cross-sectional view as viewed from the direction indicated by arrows XIX-XIX in FIG. 17;

FIG. 20 is a perspective view showing a conventional pressure sensor.

FIG. 21 is a cross-sectional view showing a conventional pressure sensor.

[Explanation of symbols]

1,41 Silicon substrate (substrate) 2,22,42,72 Pressure receiving groove 3,23,43,44,61,62,73,91 Depressed groove 4,24,45,46,63,64,74 Protrusion wall 5 , 25, 47, 48 Piezoresistive element (bending detection element) 12, 32, 60, 82, 93 Upper plate 21, 71 SOI substrate 75 Capacitance type element (bending detection element) 76 First electrode 77 Second Electrode A Pressure receiving chamber B, B1, B2 Reference pressure chamber C, C1, C2 Diaphragm

Claims (7)

[Claims] 1. A substrate made of a silicon material, a pressure receiving groove formed on a surface side of the substrate and opened on a side surface of the substrate,
A concave groove formed on the front surface side of the substrate and separated from the pressure receiving groove via a protruding wall, provided on the front surface side of the substrate to cover the pressure receiving groove and the concave groove, the pressure receiving groove A pressure receiving chamber for receiving pressure from outside is formed between the upper and lower plates defining a reference pressure chamber with the concave groove, and the upper plate is located between the pressure receiving groove and the concave groove. A diaphragm formed by a projecting wall and displaced by a pressure difference between the pressure receiving chamber and the reference pressure chamber; and a flexure detecting element provided at least in the diaphragm and detecting a flexure generated when the diaphragm is displaced. And a pressure sensor. 2. A projecting wall constituting the diaphragm portion,
2. The pressure sensor according to claim 1, wherein the pressure sensor is formed with a thickness that enables displacement between the pressure receiving groove and the concave groove. 3. 3. The pressure sensor according to claim 1, wherein a plurality of the concave grooves are formed on a front surface side of the substrate, and a plurality of diaphragm portions are formed between the concave grooves and the pressure receiving grooves. 4. The deflection detecting element is a piezoresistive element provided in the diaphragm.
Pressure sensor. 5. The deflection detecting element includes a first electrode provided on the diaphragm portion and a second electrode provided in the concave groove facing the first electrode. 4. The pressure sensor according to claim 1, wherein the pressure sensor is configured as a mold element. 6. The pressure sensor according to claim 1, wherein said substrate is formed of a semiconductor material to which impurities are added. 7. The substrate according to claim 1, wherein said substrate is an SOI substrate having an oxide film interposed between two silicon substrates.
Or the pressure sensor according to 5.