JP2000241273A - Pressure detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve temperature characteristics of the detection sensitivity of the pressure detecting device constituted by joining a single-crystal semiconductor chip where a piezoresistance element is formed to one surface side of a metallic diaphragm for pressure detection. SOLUTION: The pressure detecting device 100 is equipped with a metallic stem 20 having a circular diaphragm surface 10, and the single-crystal semiconductor chip 30 which has the side one surface 31 adhered to the side of one surface 11 of the diaphragm surface 10. A pressure medium is introduced into the side of the other surface 12 of the diaphragm surface 10 to detect pressure according to the deformation of the diaphragm surface 10 and single-crystal semiconductor chip 30. The surface azimuth of the single-crystal semiconductor chip 30 is a (100) surface, two piezoresistance elements 51 to 54 each are arranged on the side of the other surface 32 of the single-crystal semiconductor chip 30 along mutually orthogonal <110> crystal axes, and the four piezoresistance elements 51 to 54 are arranged on the circumference around the center K of the diaphragm surface 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detector having a pressure-receiving metal diaphragm and suitable for detecting the pressure of a high-pressure medium having a pressure of, for example, 1 MPa or more, and more particularly to improving the temperature characteristics of sensitivity.

[0002]

2. Description of the Related Art As a pressure detecting device of this type, a pressure detecting device described in Japanese Patent Publication No. Hei 7-11461 has been proposed.
This is a single crystal semiconductor chip having a (110) plane orientation in which a piezoresistive element (semiconductor strain gauge) is formed and having a stem having a metal diaphragm for pressure reception, and joined to one surface side of the diaphragm. is there.

When a pressure medium is introduced into the other surface of the diaphragm, pressure is detected by detecting a change in the resistance of the piezoresistive element based on the deformation of the diaphragm and the chip. According to this one
Since a metal diaphragm is used, the diaphragm strength is large, and pressure detection is possible even for a high-pressure medium of, for example, 1 MPa or more.

[0004]

However, according to the study by the present inventors, it has been found that the pressure detecting device described in the above-mentioned conventional publication is not suitable for use in controlling the fuel injection pressure or the brake pressure of an engine in a vehicle. Wide temperature range (eg-
(40 ° C. to 140 ° C.), a large error occurs in the temperature characteristics of the sensitivity (detection sensitivity), and it has been found that this causes a practical problem.

FIG. 7 is an example showing the relationship between the detection temperature and the sensitivity. For example, as shown in this figure, the sensitivity is lower at low and high temperatures than at room temperature, and the behavior of the temperature characteristics is two. Shows the next change. With such a temperature characteristic, it is difficult to perform temperature correction of sensitivity from the viewpoint of a circuit.
The temperature characteristic is required to show a temporary change. That is, as shown in FIG. 7, it is preferable that the difference (referred to as TNS) from the temperature characteristic when the actual temperature characteristic shows a temporary change (shown by a two-dot chain line) approaches zero.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to improve the temperature characteristics of detection sensitivity in a pressure detecting device in which a single crystal semiconductor chip having a piezoresistive element formed on one surface of a pressure receiving metal diaphragm is joined. And

[0007]

Means for Solving the Problems The present inventors have intensively studied the temperature characteristics of the detection sensitivity from the viewpoint of the crystal structure of the single crystal semiconductor chip and the arrangement of the piezoresistive elements, as described below. . As a result, it has been found that, in the above-described conventional device, since a single crystal semiconductor chip having a (110) plane orientation is used, a large error occurs in the temperature characteristic of sensitivity, and the TNS increases.

FIG. 4 shows a semiconductor chip J1 having a (110) plane orientation. The (110) plane has two crystal axes <110> and <100> orthogonal to each other due to its structure.
And exists. Here, the sensitivity of the stress generated in the <110> crystal axis direction is very large (for example, about 50 times) as compared with the sensitivity of the stress generated in the <100> crystal axis direction. The stress generated in the <110> crystal axis direction is used in the stress detection on the ()) plane.

By the way, as shown in FIG. 4, the distribution of stress generated in the <110> crystal axis direction decreases from the center K to the outer periphery of the chip J1. And (110)
Since <110> exists only in one direction on the surface,
In order to obtain a higher output with respect to a crystal axis having higher sensitivity, the arrangement of the piezoresistive elements (gauges C1, C2, S1, S2) inevitably results as shown in FIG.

That is, the center gauges C1, C arranged near the center of the chip J1 along the <110> crystal axis direction.
2 and side gauges S1 and S2 disposed outside the center gauge, and a bridge circuit is formed by these four gauges to detect a stress generated in the <110> crystal axis direction. Assuming that the stress at the center gauges C1 and C2 is σ _C and the stress at the side gauges S1 and S2 is σ _S , the output e is proportional to the sum of the two stresses σ _C and σ _S (e∝
(Σ _C + σ _S )).

Here, it is considered that the error in the temperature characteristic of the sensitivity in the conventional structure using the semiconductor chip having the (110) plane orientation is mainly caused by the uneven arrangement of the gauges. That is, as shown in FIG. 4, since the center gauges C1 and C2 and the side gauges S1 and S2 have to be provided at positions where the generated stresses are different from each other, the deformation of the chip due to the temperature change (depending on the location of the gauge). It is considered that there is a large thermal error for each gauge, such as a different degree of expansion or contraction or a change in the generated stress, and therefore a large error occurs in the temperature characteristics of sensitivity.

It is also conceivable that the outer peripheral shape of the chip is not simply circular or rectangular, but is devised so as to reduce thermal errors for each gauge. In such a case, manufacturing difficulties such as difficulties in cutting out chips are expected. Therefore, it is difficult to improve the temperature characteristics of the detection sensitivity in the conventional structure in which the piezoresistive elements are necessarily arranged as described above.

Therefore, the present inventors have studied a structure using a single crystal semiconductor chip having a (100) plane orientation. FIG. 3 shows a semiconductor chip 3 having a (100) plane orientation.
Although it indicates 0, the (100) plane has <110> crystal axes that are orthogonal to each other due to its structure. here,
As shown in FIG. 3, one <110> crystal axis direction is defined as an X direction, and the other <110> crystal axis direction is defined as a Y direction.

In the semiconductor chip 30,
As shown in FIG. 3, a pair of piezoresistive elements (gauges 51 to 54) are arranged along each <110> crystal axis direction. That is, a pair of gauges 51 and 52 located along the X direction and a pair of gauges 53 and 54 located along the Y direction are arranged on the (100) plane of the chip 30, and a bridge is formed by these four gauges. Configure the circuit.

The principle of detection is as follows. Assuming that the generated stress in the X direction is σ _XX and the generated stress in the Y direction is σ _YY , each gauge 5
The output e at 1 to 54 is proportional to the absolute value of the difference D between σ _XX and σ _YY (e∝ | σ _XX −σ _YY |), and detection is performed. In a chip having a (100) plane orientation having such a detection principle, like a conventional (110) plane chip,
It is not necessary to place each gauge at a different point in the stress distribution.

Based on the above findings, the present inventors have found that if all the four gauges forming the bridge are equally arranged at the same stress distribution on the (100) plane of the chip, the temperature change of each gauge is caused. It was considered that thermal errors such as different degrees of chip deformation and changes in generated stress could be reduced. As a result of intensive studies based on this point of view, as shown in FIG. 5, it was experimentally confirmed that the TNS can be reduced by the uniform arrangement as compared with the conventional structure.

The invention according to claim 1 is based on the above study, and comprises a metal stem having a circular diaphragm surface, and a single-crystal semiconductor chip having one surface adhered to one surface of the diaphragm surface. Wherein the single crystal semiconductor chip has a (100) plane orientation and two single crystal semiconductor chips along the two <110> crystal axis directions on the other surface side of the single crystal semiconductor chip. Are arranged, and these four piezoresistive elements are arranged on the circumference with respect to the center of the diaphragm surface.

As in the present invention, in a region corresponding to a circular diaphragm surface in a single crystal semiconductor chip, a stress distribution as shown in FIG. 3 is obtained. Therefore, four piezoresistive elements forming a bridge are connected to the diaphragm surface. By arranging them on the circumference with respect to the center, detection can be performed, and all four piezoresistive elements can be evenly arranged at positions where stress distributions are equal on the (100) plane.

Therefore, according to the present invention, for each piezoresistive element, the degree of deformation of the chip due to a temperature change, the degree of change in generated stress, and the like can be made substantially the same, and thermal errors can be reduced. The temperature characteristics of sensitivity can be improved.
Here, the single crystal semiconductor chip can have a planar shape with a uniform thickness as a whole as in the second aspect of the present invention.

Further, in the pressure detecting device according to any one of claims 1 and 2 having a metal diaphragm having a large diaphragm strength, the pressure of the pressure medium is not less than 1 MPa and not more than 200 MPa.
It has been experimentally confirmed that the method can be applied to a high pressure of a or less (see FIG. 5). In addition, the code | symbol in a parenthesis mentioned above is an example which shows the correspondence with the concrete means of embodiment described later.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows a pressure detecting device 100 according to an embodiment of the present invention. The pressure detecting device 100 is used for controlling a fuel injection pressure of an engine and a brake pressure of a vehicle. In FIG. 1, (a) is a pressure detecting device 1
Single crystal semiconductor chip (sensor chip) 30 at 00
(B) is a cross-sectional view taken along line AA of (a).

The pressure detecting device 100 includes a metal stem 20 having a circular diaphragm surface 10 and a single crystal semiconductor chip (hereinafter, referred to as a semiconductor chip) 30 having one surface 31 bonded to one surface 11 of the diaphragm surface 10. A pressure medium (gas, liquid, or the like) corresponding to the fuel injection pressure of the engine or the like is introduced to the other surface 12 of the diaphragm surface 10, and the pressure is detected based on the deformation of the diaphragm surface 10 and the semiconductor chip 30. It is.

The metal stem 20 has a hollow cylindrical shape formed by cutting or the like, and is made of Kovar or the like, which is a Fi-Ni-Co alloy having the same thermal expansion coefficient as glass. In the metal stem 20, a diaphragm surface 10 is formed on one end side.
As shown by a white arrow in (b), a pressure medium is introduced, and pressure is applied to the other surface 12 of the diaphragm surface 10.

Here, as an example of the dimensions of the metal stem 20, the outer diameter of the cylinder is 6.5 mm, and the inner diameter of the cylinder is 2.5 m.
m, the thickness of the diaphragm surface 10 is, for example, 0.65 mm when measuring at 20 MPa, and 1.40 mm when measuring at 200 MPa. The semiconductor chip 30 bonded to one surface 11 of the diaphragm surface 10 has a plane orientation of (10
0) plane, the entire surface of which is formed of a single-crystal silicon substrate having a planar shape having a uniform thickness, and one surface 31 of which is formed of a glass layer 40 made of low melting point glass or the like.
Is fixed to the one surface 11 of the main body.

Here, an example of the dimensions of the semiconductor chip 30 is a square of 3.56 mm × 3.56 mm, and the thickness is 0.2 mm. The thickness of the glass layer 40 is 0.06 mm. The other surface 3 of the semiconductor chip 30
On the two sides, rectangular gauges 51 to 54, which are four piezoresistive elements, are provided. As described above, (10
0) Due to the structure of the semiconductor chip 30 having the plane orientation, the <110> crystal axes are orthogonal to each other. here,
As shown in FIG. 1A, the direction of the <110> crystal axis on one side (the one coinciding with the section line AA) is set in the X direction, and
> The crystal axis direction is defined as the Y direction.

As shown in FIG. 1A, two of the four gauges 51 to 54 are arranged along the <110> crystal axis directions X and Y, respectively. Here, a pair of gauges 51, 5
No. 2 has its long side direction located along the X direction, and a pair of gauges 53 and 54 has its short side direction located along the Y direction. Further, these four gauges 51 to 54 are arranged on the circumference with respect to the center K of the diaphragm surface 10.

Although not shown in FIG. 1, the following FIG.
As described in the manufacturing process shown in FIG. 5, the semiconductor chip 30 is formed with wirings / patts for connecting four gauges 51 to 54 to form a bridge circuit and connecting to an external circuit, and further, a protective film. FIG. 2 shows main manufacturing steps of the semiconductor chip 30. FIG. 2 shows a cross section corresponding to FIG. The n-type sub-wafer 60 shown in FIG.
After forming a desired pattern by photolithography, boron or the like is diffused to form a P + region 61 (FIG. 2).
(B)). This is the gauge 51 to piezoresistive element
54.

As shown in FIG. 2C, a wiring / pat 62 and an oxide film 63 for ensuring insulation of the wiring / pat 62 are formed thereon, and a protection film 64 is further formed thereon. By etching 64, the semiconductor chip 30 is completed. Then, the completed chip 30 is bonded to the diaphragm surface 10 of the metal stem 20 using low-melting glass, whereby the pressure detecting device 100 shown in FIG. 1 is completed.

The detection principle of the pressure detection device 100 is as follows.
It is as follows. When pressure is applied in the direction of the outlined arrow shown in FIG. 1B, the diaphragm surface 10 and the semiconductor chip 30 are deformed and deformed, and stress is generated in the semiconductor chip 30. Accordingly, each gauge 51 to 54 has <11
0> Stress is generated in the arrow X direction and the arrow Y direction shown in FIG. Here, the generated stress in the X direction is σ _XX , and the generated stress in the Y direction is σ _YY .

FIG. 3 shows a distribution of generated stress in a region of the semiconductor chip 30 located on the diaphragm surface 10. FIG. 3 shows the magnitude of the generated stress σ _XX (shown by a solid line) and σ _YY (shown by a broken line) according to the distance from the center K of the diaphragm surface 10 in the region of the semiconductor chip 30. As shown in FIG. 3, the generated stresses σ _XX and σ
Both _YY become smaller as the distance from the center K increases, but the generated stress σ _YY has a greater decrease degree.

Therefore, each of the <110> crystal axis directions X and Y
E in each of the gauges 51 to 54 arranged along
Can detect and output the difference D between the generated stresses σ _XX and σ _YY . That is, the output e is proportional to the absolute value of the difference between σ _XX and σ _YY (e∝ | σ _XX −σ _YY |), and pressure detection is performed by the bridge circuit. In other words, in the semiconductor chip 30 having the (100) plane orientation, due to its structure, mutually orthogonal crystal axes <110> having high stress sensitivity exist, and two types of stresses σ _XX and σ _{Since YY} occurs, pressure can be detected by the above detection principle.

In the present embodiment, in the semiconductor chip 30 having such a stress distribution, the four gauges 51 to 54 arranged on the circumference with respect to the center K have an equal distance from the center K, that is, The generated stresses σ _XX and σ _YY are arranged at equal positions, the stress values of the gauges 51 to 54 are substantially equal, and the difference D between the two stresses is output. Therefore,
According to the present embodiment, the degree of deformation of the chip due to the temperature change, the degree of change in the generated stress, and the like can be made the same for each of the gauges 51 to 54, so that the conventional semiconductor chip having the (110) plane orientation can be used. In comparison, it is possible to reduce a thermal error such as a difference in the degree of deformation of the chip or a change in the generated stress due to the temperature change, and it is possible to improve the temperature characteristics of the detection sensitivity.

On the other hand, as described above, in the conventional semiconductor chip J1 having the (110) plane orientation as shown in FIG. 4, only one <110> crystal axis exists, and the four gauges C1, C2 , S1, and S2 must be provided at different positions (ie, different stresses) at the center of the chip and at the outside of the chip, resulting in a large thermal error for each gauge due to a temperature change. It is considered that a large error occurs in the temperature characteristic of the sensitivity.

FIG. 5 shows an example of the effect of improving the temperature characteristics of the detection sensitivity according to the present embodiment. FIG. 5 shows the result of measuring the TNS (unit: ppm / ° C.) shown in FIG. 7 described above for the pressure detecting device 100 of the present embodiment shown in FIG. 1, and shows a use temperature range of −40 ° C. to 140 ° C. Shows the value of TNS in FIG. As a comparative example, a result of a conventional structure in which the semiconductor chip has a (110) plane orientation in the pressure detecting device 100 is also shown.

In the TNS, the present embodiment (the number of measurement samples n: 8) and the comparative example (n = 10) in the case where the measurement pressure is set to 20 MPa, and the TNS in the case where the measurement pressure is set to 200 MPa (n = 5) and the above comparative example (n = 10)
Are shown. Here, in the measurement, the dimensions of each part are the dimensions of the above-described example. The material of the metal stem 20 was Kovar when the measurement pressure was 20 MPa, and a metal whose composition was slightly different from that of Kovar when the measurement pressure was 200 MPa.

As shown in FIG. 5, in the present embodiment, it can be seen that the TNS can be reduced as compared with the conventional structure as a comparative example, and can be made close to zero. That is, each of the gauges 51 to 5
4, the variation component is reduced even when pressure is applied, and the error is reduced. And in this embodiment,
Since TNS is close to 0 and the temperature characteristic of the detection sensitivity can be improved so as to change linearly, there is no need to perform temperature correction from the viewpoint of the circuit, and other elements and resistors for correcting other sensitivity temperature characteristics are required. , Sensor characteristics can be satisfied.

In the characteristics of the metal stem 20, the linear expansion coefficient and the Young's modulus are important. The linear expansion coefficient is set to a low linear expansion coefficient (2) of the above Kovar system in order to approach the single crystal silicon (Si) which is the material of the chip 30.
(About 8 ppm / ° C.). Also, those having a large temperature change are also unsuitable in Young's modulus. For example, those having a variation difference of about 8 GPa within a range of 120 GPa to 165 GPa in an operating temperature range (−40 ° C. to 140 ° C.) , Even outside the operating temperature, 11
Those within the range of 0 GPa to 180 GPa are preferred. FIG.
The temperature characteristics of Kovar's Young's modulus used for the metal stem 20 of the present embodiment are shown below.

As described above, the present invention provides, in particular,
It is suitable for use in a pressure detecting device having a metal diaphragm with high strength and suitable for detecting the pressure of a high-pressure medium of, for example, 1 MPa or more, and the temperature characteristic of the detection sensitivity at the time of applying pressure is caused by the crystal structure of the semiconductor chip. Based on this unique point of view, the temperature characteristics of the detection sensitivity can be improved by a novel configuration in which the single crystal semiconductor chip bonded to the metal diaphragm has a (100) plane orientation and the arrangement of the piezoresistive element is devised. It is to improve.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pressure detecting device according to an embodiment of the present invention, wherein (a) is a plan view and (b) is a cross-sectional view taken along line AA of (a).

FIG. 2 is a process chart showing a method for manufacturing the pressure detecting device shown in FIG.

FIG. 3 is a diagram showing a generated stress distribution of a semiconductor chip of the pressure detecting device shown in FIG.

FIG. 4 is a diagram showing a generated stress distribution of a semiconductor chip having a (110) plane orientation.

FIG. 5 is a diagram illustrating an example of an effect of improving temperature characteristics of detection sensitivity in the embodiment.

FIG. 6 is a temperature characteristic diagram of the Young's modulus of the metal stem in the embodiment.

FIG. 7 is a diagram illustrating an example of a relationship between a detected temperature and sensitivity in a pressure detection device.

[Explanation of symbols]

10: Diaphragm surface, 11: One surface of the diaphragm surface,
12 ... other side of diaphragm surface, 20 ... metal stem, 30
... single crystal semiconductor chip, 31 ... one surface of single crystal semiconductor chip, 32 ... other surface of single crystal semiconductor chip, 40 ... glass layer, 51 to 54 ... gauge.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F055 AA11 AA21 BB12 CC02 DD01 EE14 EE15 FF01 GG12 GG16 4M112 AA01 BA01 CA03 CA05 CA09 CA15 DA12 DA18 EA03 EA13 FA05

Claims (3)

[Claims] A metal stem having a circular diaphragm surface, a single crystal semiconductor chip having one surface adhered to one surface of the diaphragm surface, and introducing a pressure medium to the other surface of the diaphragm surface; A pressure detecting device for detecting pressure based on a diaphragm surface and deformation of the single crystal semiconductor chip, wherein the single crystal semiconductor chip has a (100) plane orientation, Orthogonal on the other side <
110> Two piezoresistive elements are arranged along the crystal axis direction, and these four piezoresistive elements are arranged on a circumference with respect to the center of the diaphragm surface. apparatus. 2. The pressure detecting device according to claim 1, wherein the single crystal semiconductor chip has a planar shape with a uniform thickness as a whole. 3. The pressure of the pressure medium is 1 MPa or more and 20 or more.
3. The pressure is 0 MPa or less.
3. The pressure detecting device according to 1.