JP2000221091A - Distortion detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high reliable distortion detection sensor allowing reduction of a defect in conductivity of a shield film in a contact part, and allowing suppression of an aging effect on an output. SOLUTION: In this distortion detection sensor, a shield film 6a is sandwiched between a contact part 5a made of a metal such as aluminum and an insulating film (layer) 20 to prevent thinning, cutting due to a step, a defect in conductivity, or the like of the shield film 6a in the step between the contact part 5a and the insulating film 20. Thereby, high reliability of connection can be secured, and stability of electric potential that is a function of the shield film 6a can be certainly brought out. The distortion detection sensor can have a structure difficult to oxidize in an assembling process and in a surrounding atmosphere by disposing an insert material 61a between the shield film 6a and the insulating film 20 to make the shield film 6a a two-layer structure, and by using a material difficult to oxidize, such as Au, Pt, or the like for the front face side of the shield film 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain detecting sensor used for a differential pressure transmitter, a pressure transmitter, and the like for detecting a flow rate and a pressure in a chemical plant or a power plant.

[0002]

2. Description of the Related Art As an example of a distortion detecting sensor, a conventional technique used for a differential pressure sensor is shown in FIGS. 6 and 7 which is a partial sectional view of FIG. 6 and 7, in order to detect a differential pressure, four strain-sensitive elements (piezoresistive elements) 3a and 3b are provided on a silicon diaphragm 2 of a sensor substrate 1.
3c and 3d are formed, and these strain-sensitive elements 3a to 3d
It is covered with an insulating film such as silicon dioxide (SiO ₂ ).

Further, in order to stabilize the resistance value of each piezoresistive element, each of the strain-sensitive resistive elements 3a to 3d is formed of a conductive shield film 6a, 6b, 6 made of aluminum or the like.
c, protected by 6d.

In order to detect static pressure, four gauge resistance elements 4a, 4b, 4c, 4d are formed on the silicon substrate 1 on the outer peripheral side of the silicon diaphragm 2, and these gauge resistance elements 4a to 4d Similarly, the resistance elements 3a to 3d are covered with an insulating film such as silicon dioxide (SiO ₂ ).

Further, in order to stabilize the resistance value of each of the gauge resistance elements 4a to 4d, each of the resistance elements 4a to 4d is made of a conductive shield film 7a, 7 made of aluminum or the like.
protected by b, 7c, 7d.

In order to detect the temperature, a temperature gauge element 5 is formed on the silicon substrate 1 on the outer peripheral side of the silicon diaphragm 2, and this temperature gauge element 5 is also formed of an insulating film such as silicon dioxide (SiO ₂ ). And is protected by a conductive shield film 8 made of aluminum or the like. 14 is a wiring, 15a to 15d, 16a to 16
d and 17 to 19 are bonding pads.

Reference numerals 5a to 5d denote contact portions between the silicon substrate 1 and the shield film.

Further, there is a type in which each of the above-mentioned shield films is electrically contacted with a substrate via an insulating film.

Originally, the purpose of providing a shield film on the strain detection sensor is to stabilize the potential of the insulating film 20 on the surface of the piezoresistive element and suppress the time drift of the resistance value.

As shown in FIG. 7, the conventional shielding method employs contact portions 51a, 5
a, from which the shield film 6a is placed over the strain-sensitive element 3a. Normally, the thickness of the shield film 6a is several tens nm to suppress temperature hysteresis.
It is about thin.

[0011]

However, in the shield of the conventional strain detecting sensor, since the shield material covers the contact portion 5a from above, the contact portion 5a is as thick as several hundred nm to 1 μm. The shield film 6a must be thinned and cut off due to a step between the contact portion 5a and the insulating film 20, because the metal layer must be over a metal layer made of aluminum or the like.

Further, there is a problem in reliability such that the shield film such as the shield film 6a is oxidized in the subsequent assembling step at the step portion, and the shield film such as the shield film 6a becomes non-conductive. was there.

An object of the present invention is to realize a highly reliable strain detection sensor that reduces conduction failure of a shield film at a contact portion and suppresses a temporal change in output.

[0014]

In order to achieve the above object, the present invention is configured as follows. (1) A plurality of strain-sensitive elements are formed on one semiconductor substrate, an insulating film is formed on these strain-sensitive elements, and a conductive thin film is provided on the insulating film. In a strain detection sensor having a structure in which a contact portion for electrically connecting the conductive thin film and the semiconductor substrate is fixed at the same potential, at least a part of the conductive thin film is formed on the insulating film and the insulating film. Inserted between the contact part.

By inserting a conductive film between the contact portion and the insulating film and sandwiching the conductive film between the contact portion and the insulating film, a contact portion generated when the conductive film is formed so as to cover the contact portion from above the contact portion is formed. It is possible to prevent the conductive film from becoming thinner at the step with the insulating film, disconnection of the conductive film, poor conduction, and the like.

Thus, high reliability of the electrical connection between the conductive film and the semiconductor substrate can be secured, and the stability of the potential, which is a function of the conductive film, can be reliably exhibited.

(2) Preferably, in the above (1),
The conductive thin film has a multilayer structure, and its surface layer is made of a material that is hardly oxidized.

If the conductive thin film has a multilayer structure and its surface layer is made of a material which is hardly oxidized, it is possible to make the structure hardly oxidized in an assembling process or an ambient atmosphere.

(3) Preferably, in the above (1), the region of the conductive thin film is divided so as to cover each of the strain-sensitive elements, and each of the divided regions is provided with the contact portion. Having.

(4) Preferably, in the above (4), the region of the conductive thin film is divided so as to cover each strain-sensitive element, and the divided conductive thin films are electrically connected to each other. And a part of the conductive thin film is electrically connected to the substrate by a contact portion.

(5) In the method for manufacturing a strain detection sensor, a step of forming a plurality of strain-sensitive elements on one semiconductor substrate; a step of forming an insulating film on the strain-sensitive element; Forming a conductive thin film, forming a contact portion that penetrates the conductive thin film and the insulating film and connects to the semiconductor substrate, and that sandwiches a part of the conductive thin film between the conductive thin film and the insulating film. And a step of forming a diaphragm on the semiconductor substrate.

According to the above-described manufacturing method, it is possible to manufacture a highly reliable strain detecting sensor by reducing the conduction failure of the shield film at the contact portion, suppressing the output from changing over time.

[0023]

FIG. 1 is a top view of a distortion detecting sensor according to an embodiment of the present invention, and FIG. 2 is a partial sectional view of FIG. 1 and 2, the same parts as those shown in FIGS. 6 and 7 are denoted by the same reference numerals.

The distortion detection sensor shown in FIGS.
The silicon substrate 1 is etched with an alkali solution or the like to form a diaphragm 2 on which the piezoresistive elements 3a to 3
e, 4a to 4d are pressure sensors.

Here, 5a to 5e and 8a to 8d correspond to the substrate 1
A high-concentration impurity layer 51a as shown in FIG. 2 is provided on the substrate 1 side. In this embodiment, one shield-substrate contact portion is provided for each piezoresistive element. 6a to 6e and 7a to 7d represent shield films. 3e is a piezoresistive element.

Here, the shield film 6a is used for the strain detection sensor.
The purpose of providing 6e or the like is to stabilize the potential of the insulating film 20 on the surface of the piezoresistive elements 3a to 3e or the like and to suppress the temporal drift of the resistance value. On the other hand, as shown in FIG. 2, by sandwiching the shield film 6a between the contact portion 5a made of a metal such as aluminum and the insulating film (layer) 20, a step between the contact portion 5a and the insulating film 20 is formed. It is possible to prevent the shield film 6a from being made thinner, cut off, and have poor conduction.

As a result, high reliability of the electrical connection between the shield film 6a and the substrate 1 can be ensured, and the above-mentioned function of the shield film 6a, that is, the potential stability can be reliably exhibited.

Further, in this example, the shielding film 6
The shield material 6a has a two-layer structure by disposing an insert material 61a between a and the insulating film 20. The surface side of the shield film 6a is made of a material which is hard to be oxidized such as Au, Pt or the like, so that the structure is hardly oxidized in an assembling process or an ambient atmosphere. When Au is used on the front surface side of the shield film 6a, it is necessary to provide the insert material 61a such as Ti, Cr or Ni in order to improve the adhesion to the base.

As described above, according to one embodiment of the present invention, the shield film 6a and the like are contacted with the contact portion 5a and the insulating film 2a.
0, the shield film 6a and the like become thin and cut off due to a step between the contact portion 5a and the like and the insulating film 20, so that the shield film 6a and the like become non-conductive. Can be avoided.

Therefore, it is possible to realize a highly reliable strain detection sensor by reducing the conduction failure of the shield film at the contact portion and suppressing the output from changing with time.

Further, according to one embodiment of the present invention, an insert material 61a is provided between the shield film 6a and the insulating film 20.
And the shield film 6a has a two-layer structure, so that there is also an effect that it is difficult to be oxidized in an assembling process or an ambient atmosphere.

FIG. 3 shows a distortion detecting sensor according to an embodiment of the present invention, in which a shield film 9 covering piezoresistive elements 3a to 3e is connected in a ring shape, and two points (12
This is an example in which the present invention is applied to a case where a contact between a shield and a substrate is taken in a and 12b).

As in the example of FIG. 3, compared with the example of FIG. 1, the hysteresis of residual strain (temperature hysteresis) when a temperature cycle is applied is reduced by reducing the thick metal portion (contact portion). can do.

FIGS. 4 and 5 are views showing a manufacturing process of the strain detection sensor according to the embodiment of the present invention. In FIG. 4, after the silicon substrate 1 is lightly oxidized to form an oxide film 20, a piezoresistive element 3a is formed by ion implantation or the like (step (a)).

Next, a high-concentration impurity layer 51a for making contact between the silicon substrate 1 and the shield film is formed (step (b)). Further, a passivation film 20 such as an oxide film is formed (step (c)).

Then, T is formed on the passivation film 20.
An insert material 61a such as i or Cr is formed (step (d)). Further, A is placed on the insert material 61a.
A shield film 6a, such as u, which is difficult to oxidize is formed (step (e)).

Next, referring to FIG.
The substrate 1 on which the shield film 6a is formed by photolithography, for example, Au or the like is etched and patterned with an iodine-based etchant (step (f)).

Subsequently, the previously formed high-concentration impurity layer 51
A contact hole 50a is formed on a (step (g)). Then, a contact metal 5a made of aluminum or the like is formed by sputtering or the like through the contact hole 50a and is patterned (step (h)).

Finally, the back surface of the silicon substrate 1 is etched with an alkaline aqueous solution or the like to process the diaphragm 2 (step (i)).

Therefore, according to the above manufacturing process,
It is possible to manufacture a highly reliable strain detection sensor by reducing the conduction failure of the shield film at the contact portion and suppressing the change with time of the output.

[0041]

According to the present invention, it is possible to realize a highly reliable strain detection sensor by reducing the conduction failure of the shield film at the contact portion and suppressing the output from changing over time.

If the shield film has a multilayer structure and its surface layer is made of a material which is hardly oxidized, it is possible to make the structure hardly oxidized in an assembling process or an ambient atmosphere.

Further, according to the manufacturing method of the present invention, the above-mentioned distortion detecting sensor can be manufactured.

[Brief description of the drawings]

FIG. 1 is a top view of a distortion detection sensor according to an embodiment of the present invention.

FIG. 2 is a partial sectional view of FIG.

FIG. 3 is a diagram illustrating an application example of an embodiment of the present invention.

FIG. 4 is a diagram illustrating a manufacturing process of the distortion detection sensor according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating a manufacturing process of the distortion detection sensor according to the embodiment of the present invention.

FIG. 6 is a top view of an example of a conventional distortion detection sensor.

FIG. 7 is a partial sectional view of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Diaphragm 3a-3e Strain-sensitive resistance (gauge resistance) 4a-4d Strain-sensitive resistance (gauge resistance) 5a-5e Contact part between substrate and shield 6a-6e Gauge resistance shield 7a-7d Gauge resistance shield 8a -8d Contact portion between substrate and shield 9 Shield network 12a, 12b Shield network contact portion 14 Wiring 15a-15b Bonding pad 16a-16b Bonding pad 17-19 Bonding pad 20 Insulating film 50a Contact hole 51a High density provided on substrate Impurity layer 61a Shield film insert material

Claims (5)

[Claims] 1. A plurality of strain-sensitive elements are formed on one semiconductor substrate, an insulating film is formed on these strain-sensitive elements, and a conductive thin film is provided on the insulating film. In a strain detection sensor having a structure in which a contact portion for electrically connecting a substrate is provided and the conductive thin film and the semiconductor substrate are fixed at the same potential, at least a part of the conductive thin film is formed of the insulating film. A strain detection sensor inserted between the contact portion and the contact portion. 2. The distortion detection sensor according to claim 1, wherein
The conductive thin film has a multilayer structure, and a surface layer of the conductive thin film is made of a hardly oxidizable material. 3. The distortion detecting sensor according to claim 1, wherein
The strain detecting sensor is characterized in that the region of the conductive thin film is divided so as to cover each of the strain-sensitive elements, and each of the divided regions has the contact portion. 4. The distortion detection sensor according to claim 1, wherein
The region of the conductive thin film is divided so as to cover each strain-sensitive element, and the divided conductive thin films are electrically connected to each other, and a part of the conductive thin film is connected to the substrate by a contact portion. A strain detection sensor electrically connected to the sensor. 5. A method of manufacturing a strain detection sensor, comprising: forming a plurality of strain-sensitive elements on one semiconductor substrate; forming an insulating film on the strain-sensitive elements; Forming a thin film, connecting to the semiconductor substrate through the conductive thin film and the insulating film, and forming a contact portion sandwiching a part of the conductive thin film between the insulating film; Forming a diaphragm on the semiconductor substrate. A method for manufacturing a strain detection sensor, comprising: