JP2002357497A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor of high reliability and durability capable of outputting a signal from a deflection detecting element even when metal film wiring is damaged. SOLUTION: A recessed groove 4 is provided in a base plate 1 to form a diaphragm part 4. On the diaphragm part 4, a piezo-resistance element 5 is formed, and metal film wiring 7 connected to the piezo-resistance element 5 is formed. In addition, on the diaphragm part 4, diffusion layer wiring 8 extended along the metal film wiring 7 in contact with it along the whole length of it is formed. Even when metal fatigue or the like is generated in the metal film wiring 7 due to deflection deformation of the diaphragm part 4, a signal from the piezo-resistance element 5 can be transmitted thought the diffusion layer wiring 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor formed by subjecting a semiconductor material to etching or the like, and suitable for detecting a pressure by utilizing a bending deformation of a diaphragm.

[0002]

2. Description of the Related Art Generally, as a pressure sensor, as shown in FIGS. 6 and 7, a substrate 101 made of a semiconductor material having a surface 101A covered with an oxide film 102,
By forming a concave groove 103 in the back surface 101B of the substrate 101, a diaphragm portion 104 provided on the front surface 101A side of the substrate 101 and a deflection when the diaphragm portion 104 is deformed by pressure provided in the diaphragm portion 104 are detected. A piezoresistive element 105 and a metal film wiring 106 connected to the piezoresistive element 105 and extending from the diaphragm 104 over the substrate 101 are known (for example, Japanese Patent Application Laid-Open No. 11-68).
No. 121, etc.).

In such a conventional pressure sensor, when a fluid pressure or the like acts on the diaphragm portion 104, the diaphragm portion 104 bends and deforms in response to the pressure, and the piezoresistive element 105 is distorted by the diaphragm portion 104. Outputs the corresponding signal. This allows the pressure sensor to:
A signal from the piezoresistive element 105 is transmitted to a metal film wiring 106,
Output to the outside through the electrode 107,
4 is to detect the pressure applied to the pressure.

[0004]

However, in the above-mentioned prior art, the metal film wiring 106 is not connected to the piezoresistive element 105.
And the electrodes 107 or the plurality of piezoresistive elements 105 are connected to each other.
5, is formed on the diaphragm portion 104. On the other hand, since the diaphragm portion 104 is flexed and deformed by the pressure, a stress also acts on the metal film wiring 106 in accordance with the flexing deformation, and in particular, as shown in portion A in FIG.
In the vicinity of the outer peripheral edge of No. 04, the stress tends to increase. As a result, metal fatigue occurs gradually in the metal film wiring 106, which may cause damage such as generation of cracks or disconnection, and there is a problem that reliability and durability are likely to be reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and the present invention can output a signal from a flexure detecting element to the outside even when a metal film wiring is damaged, thereby improving reliability and durability. To provide a high pressure sensor.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a substrate made of a semiconductor material and a recess provided on the back surface of the substrate to form a groove on the front surface of the substrate. A diaphragm portion, a flexure detecting element provided in the diaphragm portion for detecting flexure when the diaphragm portion is deformed by pressure, and a metal film wiring connected to the flexure detector and extending from the diaphragm portion on the substrate. This is applied to a pressure sensor consisting of

A feature of the structure adopted in the first aspect of the invention is that a diffusion layer wiring formed by diffusing an impurity and connected in parallel with a metal film wiring is provided in the diaphragm portion.

With this configuration, even when a break occurs in the metal film wiring, a signal from the flexure detecting element is output and transmitted to the outside through the diffusion layer wiring connected in parallel with the metal film wiring. be able to.

According to the second aspect of the present invention, the diffusion layer wiring extends substantially parallel to the metal film wiring, and is in contact with the metal film wiring over its entire length.

Thus, since the metal film wiring and the diffusion layer wiring are brought into contact over the entire length, a signal is transmitted through the diffusion layer wiring having a larger resistance value than the metal film wiring only at the portion where the metal film wiring is damaged. This can prevent signal deterioration.

According to a third aspect of the present invention, an insulating film having a plurality of through holes is provided on the surface of the diffusion layer wiring, and the metal film wiring is located on the surface of the insulating film and extends along the diffusion layer wiring. The structure is such that the through-hole is filled to be in contact with the diffusion layer wiring.

Thus, the diffusion layer wiring can be protected by the insulating film. Further, even when the metal film wiring is damaged, a signal from the deflection detecting element can be transmitted to the outside through the through hole and the diffusion layer wiring.

[0013]

DETAILED 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 FIGS.

First, FIGS. 1 and 2 show a first embodiment. In the figures, reference numeral 1 denotes a square substrate formed of a semiconductor material such as silicon single crystal, for example. Is formed with an insulating film 2 made of a silicon nitride film, a silicon oxide film or the like. The insulating film 2 is formed in a substantially quadrangular frame shape on the outer peripheral side of the substrate 1 excluding a diaphragm portion 4 to be described later, and has a substantially rectangular opening inside which the surface 1A of the substrate 1 is exposed. 2A is formed.

Reference numeral 3 denotes a concave groove for defining a pressure chamber in which the inside becomes a reference pressure with respect to the pressure sensor.
It is located in the center of the substrate 1 and is recessed in a substantially square shape on the back surface 1B side. The concave groove 3 is formed by performing anisotropic etching from the back surface 1B side of the substrate 1 and forms a tapered bottomed hole that is gradually reduced from the back surface 1B of the substrate 1 toward the front surface 1A. It is.

Reference numeral 4 denotes a thin diaphragm portion provided on the surface 1A side of the substrate 1 by the concave groove 3. The diaphragm portion 4 has a substantially square shape corresponding to the concave groove 3.
The diaphragm 4 is deformed in accordance with the pressure difference between the pressure inside the concave groove 3 and the external pressure.

5, 5,... Are, for example, 4
A piezoresistive element as a deflection detection element provided,
Each of the piezoresistive elements 5 has a narrow narrow line shape, and is formed by injecting and diffusing an impurity such as boron into the surface 1A side of the substrate 1 to form a piezoresistance. Further, a metal film wiring 7 and a diffusion layer wiring 8 described later are connected to each piezoresistive element 5, and the piezoresistive element 5 is connected to an electrode 6 described later through the metal film wiring and the diffusion layer wiring. The resistance value of the piezoresistive element 5 changes according to the bending deformation of the diaphragm portion 4.

Are electrodes formed on the insulating film 2 on the surface 1A side of the substrate 1, and a total of five electrodes 6, 6,.
Are formed in a substantially rectangular island shape by a thin film using a conductive metal material such as aluminum, and are connected to the piezoresistive element 5 through a metal film wiring 7 and a diffusion layer wiring 8 described later. The electrode 6 is connected to an external wiring or the like by bonding a metal wire or the like.

7, 7,... Are metal film wirings for connecting between the piezoresistive element 5 and the electrode 6 or for connecting between the two piezoresistive elements 5, and the metal film wiring 7 is, for example, an electrode 6
Similarly to the above, it is formed in a substantially band shape by a thin film using a conductive metal material such as aluminum. The metal film wiring 7 is formed on the diaphragm 4 of the substrate 1 so as to be located in the opening 2A of the insulating film 2.

Are diffusion layer wirings extending from the diaphragm portion 4 to the outer peripheral side of the thickened substrate 1 and connected in parallel with the metal film wiring 7. 8 is formed by injecting and diffusing an impurity such as boron into the surface 1A side of the substrate 1 similarly to the piezoresistive element 5. The diffusion layer wiring 8 has its impurity concentration set to a value higher than that of the piezoresistive element 5, and the diffusion depth of the impurity is set to a value larger than that of the piezoresistive element 5 by lengthening the diffusion time. ing.
As a result, the resistance value of the diffusion layer wiring 8 is set to a value much smaller than that of the piezoresistive element 5.

The diffusion layer wiring 8 is formed on the surface 1A side of the substrate 1 with a width substantially equal to or larger than the metal film wiring 7, extends substantially parallel to the metal film wiring 7, and extends over the entire length thereof. And is in contact with the metal film wiring 7.

The pressure sensor according to the present embodiment has the above-described configuration, and its operation will be described next.

First, the inside of the concave groove 3 of the pressure sensor is sealed, and a fluid pressure or the like is applied to the surface 1A of the substrate 1. As a result, a pressure difference is generated between the inside of the recessed groove 3 and the outside (the surface 1A side). It changes according to the bending (strain) that occurs.
Therefore, by detecting the resistance value of the piezoresistive element 5 through the metal film wiring 7 and the diffusion layer wiring 8, the pressure applied to the diaphragm unit 4 can be detected.

However, the metal film wiring 7 is connected to the diaphragm 4
, Metal fatigue accumulates as the diaphragm portion 4 is flexed and deformed, which may cause breakage, disconnection, and the like. However, even when the metal film wiring 7 is damaged in this way, the diffusion layer wiring 8 is in contact with the metal film wiring 7 over its entire length and is connected in parallel. The increased portion is connected by the diffusion layer wiring 8. That is, although the signal from the piezoresistive element 5 normally passes through the metal film wiring 7 having a low resistance value, if the metal film wiring 7 is damaged, the diffusion layer wiring 8 is formed around the damaged portion. Bypass around. As a result, even if the metal film wiring 7 is damaged or the like, a signal from the piezoresistive element 5 can be reliably transmitted to the electrode 6 or the like.

Thus, in this embodiment, the diffusion layer wiring 8 connected in parallel with the metal film wiring 7 is provided in the diaphragm portion 4.
Is provided, even if the metal film wiring 7 is damaged or the like, a signal can be transmitted through the diffusion layer wiring 8 at the damaged portion, and the reliability and durability of the pressure sensor can be improved.

Further, since the diffusion layer wiring 8 is configured to be in contact with the metal film wiring 7 over the entire length, the distance that the metal film wiring 7 passes through the diffusion layer wiring 8 when the metal film wiring 7 is damaged is reduced. Therefore, it is possible to prevent the signal passing through the metal film wiring 7 or the like from deteriorating.

Next, FIGS. 3 to 5 show a second embodiment. The feature of this embodiment is that an insulating film having a plurality of through holes is provided on the surface of the diffusion layer wiring, And a metal film wiring connected to the diffusion layer wiring by filling the through hole and extending on the surface of the diffusion layer wiring. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Reference numeral 21 denotes an insulating film formed on the surface 1A of the substrate 1. The insulating film 21 is formed of, for example, a silicon nitride film, a silicon oxide film or the like, like the insulating film 2 according to the first embodiment. I have. Although the insulating film 21 covers the substrate 1 over substantially the entire surface, the insulating film 21 has a plurality of through holes 21A along a metal film wiring 22 (diffusion layer wiring 8) described later.
Are provided to penetrate.

Are metal film wirings that connect between the piezoresistive element 5 and the electrode 6 or connect between the two piezoresistive elements 5, and the metal film wiring 22 is a first film wiring. Like the metal film wiring 7 according to the embodiment, it is formed in a substantially band shape by a thin film using a conductive metal material such as aluminum. Further, the metal film wiring 22 extends along the diffusion layer wiring 8 at the diaphragm portion 4. The metal film wiring 22 contacts the diffusion layer wiring 8 at a plurality of locations via the through holes 21A, and is connected to the diffusion layer wiring 8 in parallel.

Thus, in the present embodiment, the same operation and effect as those of the first embodiment can be obtained. However, in the present embodiment, the diffusion layer wiring 8 and the metal film wiring 22
An insulating film 21 having a plurality of through holes 21A is provided between them, and the through hole 21A is filled with the metal film wiring 22 so that the diffusion layer wiring 8 and the metal film wiring 22 are contacted at a plurality of locations. Therefore, even if the metal film wiring 22 is damaged or the like, a signal can be transmitted through the through hole 21A and the diffusion layer wiring 8. Further, the substrate 1 is formed by the insulating film 21.
Can be covered over the entire surface, and the piezoresistive element 5 and the diffusion layer wiring 8 can be protected.

In each of the above embodiments, the substrate 1 is formed of single crystal silicon.
It may be formed by an OI (Silicon on Insulator) substrate.

Further, in each of the above-described embodiments, the recessed groove 3 is closed to define a pressure chamber in which the inside becomes a reference pressure. For example, this is described in Japanese Patent Application Laid-Open No. H11-118642. As described above, a frame-shaped projection is provided on the surface 1A of the substrate 1 so as to project in a frame shape, and a pressure chamber which becomes a reference pressure by closing the frame-shaped projection with a glass plate or the like is defined.
A configuration in which fluid pressure is applied to the inside of the concave groove 3 may be adopted.

[0033]

As described above in detail, according to the first aspect of the present invention, since the diaphragm portion is provided with the diffusion layer wiring connected in parallel to the metal film wiring, even if the metal film wiring is damaged, etc. A signal can be transmitted through the diffusion layer wiring at the damaged portion, and the reliability and durability of the pressure sensor can be improved.

According to the second aspect of the present invention, since the metal film wiring is configured to contact the diffusion layer wiring over the entire length, when the metal film wiring is damaged, the metal film wiring passes through the diffusion layer wiring. The distance can be shortened, and deterioration of a signal passing through a metal film wiring or the like can be prevented.

According to the third aspect of the present invention, an insulating film having a plurality of through holes is provided on the surface of the diffusion layer wiring, and the metal film wiring is located on the surface of the insulating film along the diffusion layer wiring. Since the extended through hole is filled to be in contact with the diffusion layer wiring, a signal can be transmitted through the through hole and the diffusion layer wiring even if the metal film wiring is damaged. Further, the substrate can be covered over the entire surface by the insulating film, and the deflection detecting element and the diffusion layer wiring can be protected.

[Brief description of the drawings]

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

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

FIG. 3 is a plan view showing a pressure sensor according to a second embodiment.

FIG. 4 is a cross-sectional view of the pressure sensor as viewed from a direction indicated by arrows IV-IV in FIG. 3;

5 is an enlarged cross-sectional view showing a through-hole and the like of the pressure sensor in FIG. 4 in an enlarged manner.

FIG. 6 is a plan view showing a conventional pressure sensor.

7 is a cross-sectional view of the pressure sensor as seen from the direction of arrows VII-VII in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 21 Insulating film 3 Depressed groove 4 Diaphragm part 5 Piezoresistive element (bending detection element) 6 Electrode 7, 22 Metal film wiring 8 Diffusion layer wiring 21A Through hole

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F055 AA40 BB20 CC02 DD05 EE14 FF49 GG01 GG15 4M112 AA01 BA01 CA03 CA04 CA05 CA08 CA09 CA11 CA13 DA12 EA03 EA06 EA07 EA11 FA06 FA10

Claims (3)

[Claims] 1. A substrate made of a semiconductor material, a diaphragm provided on a front surface of the substrate by forming a concave groove on a back surface of the substrate, and a diaphragm provided on the diaphragm by pressure. In a pressure sensor comprising a deflection detection element for detecting deflection when deformed and a metal film wiring connected to the deflection detection element and extending on the substrate from the diaphragm portion, impurities are diffused into the diaphragm portion. A pressure sensor having a diffusion layer wiring formed and connected in parallel to the metal film wiring. 2. The pressure sensor according to claim 1, wherein the diffusion layer wiring extends substantially in parallel with the metal film wiring, and is configured to contact the metal film wiring over the entire length. 3. An insulating film having a plurality of through holes is provided on the surface of the diffusion layer wiring, and the metal film wiring is located on the surface of the insulating film and extends along the diffusion layer wiring to form the through hole. The pressure sensor according to claim 1, wherein the pressure sensor is configured to be buried and contact the diffusion layer wiring.