JPH11304613A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor pressure sensor having good temperature characteristics and detecting an accurate pressure. SOLUTION: Bottom face of a supporting substrate 4 being bonded with a die 15 is inclined from one end of the outer circumferential face and the inner side face of the substrate 4 toward the central part of the bottom face and the central part of the lower surface of the substrate 4 is recessed. A thin metal film 6 is not formed in the central part of the substrate 4 and since a solder 5 does not adhere to the substrate 4 at that part, a cavity 7 is formed thereat. Consequently, deformation of the solder 5 due to thermal contraction can be absorbed by the cavity 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor using a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, various semiconductor pressure sensors have been provided. FIG. 4 is a sectional view showing an example of a conventional semiconductor pressure sensor. In this pressure sensor, a silicon single crystal substrate 1 as a sensor unit for converting the pressure of a fluid to be detected into an electric signal is housed in a package 10, and is provided with a pressure introducing hole 12 for introducing the fluid. A pressure introducing pipe 8 is provided in a package 10. On a silicon single crystal substrate 1, a diaphragm 2 and a resistance element 3 (piezoresistor or the like) for detecting distortion of the diaphragm 2 due to pressure are formed by anisotropic etching. The resistance element 3 changes its resistance value by a piezoresistance effect, and is formed in a plurality on the silicon single crystal substrate 1, and by connecting them, a Wheatstone bridge circuit is formed. In this type of semiconductor pressure sensor, a silicon single crystal substrate 1 having a diaphragm 2 and a support substrate 4 having a metal thin film 6 are bonded by anodic bonding or the like. The support substrate 4 functions to alleviate the stress exerted on the silicon single crystal substrate 1 from the package 10 or the like. As the material of the support substrate 4, glass or a silicon substrate having a thermal expansion coefficient close to that of the silicon single crystal substrate 1 is used. On the other hand, a plating layer made of a material which is easily eutectic-bonded to the solder 5 is provided on the surface of the supporting portion 15 (hereinafter, referred to as a package die) of the package. It is common to form a six-layer metal thin film made of a material to be eutectic-bonded to be solder-bonded to the die 15 of the package. Also, a plurality of terminals 9 for extracting an electric signal from the silicon single crystal substrate 1 as a sensor to the outside are implanted in the package 10 by insert molding.
Is connected to the silicon single crystal substrate 1 by a wire 11 made of gold, aluminum or the like. In the semiconductor pressure sensor configured as described above, when a detection target fluid such as a liquid or a gas is introduced from the outside into the pressure introduction hole 12 of the pressure introduction pipe 8, the diaphragm 2 is pressurized, and the surface of the diaphragm 2 is further pressurized. Changes the resistance value of the resistance element 3. At this time,
When a current or the like is supplied to the Wheatstone bridge circuit from the outside, a change in resistance value is detected as a change in voltage. Thus, a change in pressure transmitted from the pressure introduction hole 12 is detected as a change in an electric signal.

[0003]

However, in the semiconductor pressure sensor constructed as described above, in order to solder the package die 15 and the support substrate 4 in manufacturing,
It is necessary to join at a temperature higher than the melting point of the solder, which is generally higher than 200 ° C. For this reason, as the solder 5 is cooled to a temperature at which the semiconductor pressure sensor is used, the physical properties of the solder 5 and the supporting substrate 4 joined to the silicon single crystal substrate 1 are different, so that the solder 5 and the supporting substrate 4 exert forces on each other. Becomes Generally, a silicon single crystal substrate 1
The solder 5 has a larger coefficient of thermal expansion than the support substrate 4 bonded to the silicon single crystal substrate 1 and the solder 5, and at room temperature, the solder 5 contracts more than the silicon single crystal substrate 1 and the support substrate 4. As a result, the solder 5 exerts a force that swells and pushes up the support substrate 4 from below, and a part of the force acts on the silicon single crystal substrate 1 and the diagram 2
However, there is a problem that the resistance element 3 itself formed is distorted. For this reason, the sensor is used in a state in which stress is applied from a fluid other than the pressure detection fluid to be detected, and accurate pressure cannot be detected. In addition, if the operating temperature of the sensor is increased, there is a problem that the sensor characteristics may be distorted (reduced linearity).

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a means for releasing stress due to heat at a solder joint between a package die and a supporting substrate, thereby absorbing the stress and providing an accurate stress. An object of the present invention is to provide a semiconductor pressure sensor that detects pressure and has good temperature characteristics.

[0005]

In order to achieve the above object, a first aspect of the present invention is a silicon monolithic device having a resistance element formed on one surface by diffusion of impurities and a diaphragm formed on the other surface by anisotropic etching. A crystal substrate, a support substrate having a through hole communicating with the diaphragm, and the silicon single crystal substrate joined to one surface side, and a package in which the support substrate and the silicon single crystal substrate are housed. In a semiconductor pressure sensor in which the other surface of the support substrate is solder-bonded to a die in a package, a means for releasing stress caused by heat at a solder joint between the die and the support substrate is provided, so that the heat of the solder is reduced. Even if the shape changes due to shrinkage, the stress of the solder can be released by the stress release means, and accurate pressure can be detected without transmitting the stress to the supporting substrate. Widely in degrees can be made to the strain (decrease in linearity) does not occur even sensor characteristics.

According to a second aspect of the present invention, in the first aspect of the present invention, the means for relieving the stress is provided substantially at the center of the surface of the supporting substrate on the side of the solder joint, and has a concave surface on which a metal thin film is not formed. In this way, even if the shape changes due to the thermal shrinkage of the solder, it can be absorbed in these recesses, and the stress can be prevented from being transmitted to the supporting substrate, and the accurate pressure can be detected. Further, even if the operating temperature of the semiconductor pressure sensor is widened, it is possible to prevent the sensor characteristics from being distorted (reduced linearity).

According to a third aspect of the present invention, in the first aspect of the present invention, the means for relieving the stress is provided on a surface of the support substrate on the solder joint side, and comprises a plurality of recesses on which a metal thin film is not formed. Therefore, even if the shape changes due to the thermal shrinkage of the solder, the stress of the solder can be prevented from being transmitted to the supporting substrate in the concave portion, so that accurate pressure can be detected and the operating temperature of the semiconductor pressure sensor can be broadened. Even in this case, it is possible to prevent distortion (reduction in linearity) from occurring in the sensor characteristics.

[0008]

(Embodiment 1) FIG. 1 is a sectional view showing Embodiment 1 of the present invention. The basic configuration of the present embodiment is almost the same as that of the conventional example. Therefore, the same reference numerals are given to the common portions, and the description thereof will be omitted.

That is, the present embodiment is characterized in that means for absorbing the stress generated at the solder joint between the support substrate 4 and the die 15 of the package is provided on the support substrate 4 in the package 10.

In FIG. 1, the stress absorbing means is inclined from the one end of the outer peripheral surface and one end of the inner surface of the support substrate 4 to the vicinity of substantially the center of the bottom surface. The metal thin film 6 is formed except for the vicinity of the center of the recess. That is, the metal thin film 6 is formed at the center of the recess.
Is not formed, the cavity 7 is formed without the support substrate 4 and the solder 5 being bonded. Accordingly, even when the shape of the solder 5 changes due to thermal contraction, the cavity 7 can absorb the shape-changed portion of the solder 5.

On the other hand, a package die 15 is joined to the lower surface of the metal thin film 6 by solder 5. In this solder joint, as a structure that is easy to solder joint,
For example, when using Au—Si solder as the solder 5, Au is used as the material of the metal thin film 6. In addition, package 1
Au plating is also applied to the package die 15 connected to the pressure introduction pipe 8 of zero. In addition, there is a problem of adhesion between the silicon single crystal substrate 1 and the supporting substrate 4 serving as a pedestal. Generally, a plurality of metal films are formed and the supporting substrate 4 and the solder 5
In some cases, the device is devised so as not to peel off.

Here, in order to solder-bond the support substrate 4 bonded to the silicon single crystal substrate 1 to the package die 15, the solder 5 is melted at a temperature higher than the melting point of the solder 5, and the support substrate 4 and the package are bonded together. -Join the die 15 of the die. At this time, since the melting point of the solder 5 is a high temperature exceeding 200 ° C.,
, The package 10 and the support substrate 4 do not exert any stress on each other, so that no distortion occurs in the silicon single crystal substrate 1. Eventually,
The solder 5 is cooled down to the room temperature level and joins the support substrate 4 and the package die 15. Since the thermal expansion coefficient of the solder 5 is larger than that of the support substrate 4 connected to the silicon single crystal substrate 1, the solder 5 is at room temperature level. In the above, the solder 5 thermally shrinks, so that the surface of the solder 5 on the support substrate 4 side rises. At this time, as shown in FIG. 2, the support substrate 4 joined to the silicon single crystal substrate 1 is provided with the cavity 7 as a means for releasing the stress as described above. Is absorbed in the cavity 7.

As a result, the operation in which the solder 5 lifts the support substrate 4 is prevented, and the resistance element 3 formed on the surface of the silicon support substrate 1 joined to the support substrate 4 is not subjected to stress. Therefore, the resistance element 3 is not distorted, and the sensor is used in a state where it is not subjected to a stress other than the pressure medium to be detected, so that accurate pressure can be detected and the operating temperature of the pressure semiconductor sensor can be detected. Can be prevented from causing a distortion (decrease in linearity) in the sensor characteristics even if the distance is increased. Further, since only a recess is provided in the support substrate 4 as a means for releasing the stress of the solder 5, the manufacturing is easy. (Embodiment 2) FIG. 3 is a sectional view of Embodiment 2 of the present invention. In the present embodiment, a plurality of recesses 14 are provided on the bottom surface of the support substrate 4 that is bonded to the die 15. Furthermore, the metal thin film 6 is not formed in this portion, and a space is provided between the concave portion 14 of the support substrate 4 and the solder 5.

Here, when the support substrate 4 and the die 15 of the package 10 are joined by soldering, the solder 5 thermally contracts at the room temperature level as described above. Is filled in the recessed portion 14 provided in the recess. For this purpose, the silicon single crystal substrate 1
No stress is applied to the supporting substrate 4 bonded to the substrate 1, and the resistance element 3 formed by diffusion on the surface of the silicon single crystal substrate 1 is not distorted.

As a result, as in the first embodiment, the sensor can be used in a state where it is not subjected to stress from a pressure medium other than the pressure medium to be detected, so that accurate pressure can be detected and the pressure semiconductor sensor can be used. Even if the temperature is widened, it is possible to prevent the sensor characteristics from being distorted (reduced linearity).

[0016]

According to a first aspect of the present invention, there is provided a silicon single crystal substrate having a resistance element formed on one surface by diffusion of impurities and a diaphragm formed on the other surface by anisotropic etching, and a through hole communicating with the diaphragm. A support substrate having the silicon single crystal substrate bonded to one surface thereof; and a package in which the support substrate and the silicon single crystal substrate are housed. In a semiconductor pressure sensor having a surface side joined by solder, by providing a means for releasing stress caused by heat at a solder joint portion between the die and the support substrate, the stress is released even if a shape change occurs due to thermal contraction of solder. Means to release the stress of the solder and accurately detect the pressure without transmitting the stress to the supporting substrate. Also, even if the operating temperature of the semiconductor pressure sensor is widened, the sensor characteristics will be distorted (linearity). There is an effect that it is possible to make reduced) does not occur.

According to a second aspect of the present invention, the means for releasing the stress is provided substantially at the center of the surface of the support substrate on the solder joint side,
Due to the concave portion where the metal thin film is not formed on the surface, even if the shape changes due to the thermal shrinkage of the solder, it can be absorbed by this concave portion and the stress can not be transmitted to the supporting substrate, It is possible to detect the pressure accurately and to prevent the sensor characteristics from being distorted (reduced linearity) even when the operating temperature of the semiconductor pressure sensor is increased.

According to a third aspect of the present invention, the means for releasing the stress comprises a plurality of recesses provided on the surface of the support substrate on the side of the solder joints and on which no metal thin film is formed.
Even if the shape changes due to the thermal shrinkage of the solder, it is possible to prevent the stress of the solder from being transmitted to the supporting substrate in this concave portion, and it is possible to accurately detect the pressure and widen the operating temperature of the semiconductor pressure sensor. This also has the effect that distortion (reduction in linearity) does not occur in the sensor characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of Embodiment 1 of the present invention.

FIG. 2 is a sectional view when the solder is thermally contracted.

FIG. 3 is a cross-sectional view of Embodiment 2 of the present invention.

FIG. 4 is a sectional view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon single crystal substrate 2 Diaphragm 3 Resistance element 4 Support substrate 5 Solder 6 Metal thin film 7 Cavity 10 Package

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[Procedure amendment]

[Submission date] July 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art Conventionally, various semiconductor pressure sensors have been provided. FIG. 4 is a sectional view showing an example of a conventional semiconductor pressure sensor. In this pressure sensor, a silicon single crystal substrate 1 as a sensor unit for converting the pressure of a fluid to be detected into an electric signal is housed in a package 10, and is provided with a pressure introducing hole 12 for introducing the fluid. A pressure introducing pipe 8 is provided in a package 10. On a silicon single crystal substrate 1, a diaphragm 2 and a resistance element 3 (piezoresistor or the like) for detecting distortion of the diaphragm 2 due to pressure are formed by anisotropic etching. The resistance element 3 changes its resistance value by a piezoresistance effect, and is formed in a plurality on the silicon single crystal substrate 1, and by connecting them, a Wheatstone bridge circuit is formed. In this type of semiconductor pressure sensor, a silicon single crystal substrate 1 having a diaphragm 2 and a support substrate 4 having a metal thin film 6 are bonded by anodic bonding or the like. The supporting substrate 4 is to serve to relax the stress exerted from the package 10 or the like to the silicon single crystal base plate 1. As the material of the support substrate 4, glass or a silicon substrate having a thermal expansion coefficient close to that of the silicon single crystal substrate 1 is used. On the other hand, a plating layer made of a material which is easily eutectic-bonded to the solder 5 is provided on the surface of the supporting portion 15 (hereinafter, referred to as a package die) of the package. It is common to form a six-layer metal thin film made of a material to be eutectic-bonded to be solder-bonded to the die 15 of the package. Also, a plurality of terminals 9 for extracting an electric signal from the silicon single crystal substrate 1 as a sensor to the outside are implanted in the package 10 by insert molding.
Is connected to the silicon single crystal substrate 1 by a wire 11 made of gold, aluminum, or the like. In the semiconductor pressure sensor thus configured, a liquid or gas is externally supplied to the pressure introduction hole 12 of the pressure introduction pipe 8. When the fluid to be detected is introduced, the diaphragm 2 is pressurized,
Further, the resistance value of the resistance element 3 changes on the surface of the diaphragm 2. At this time, when a current or the like is externally supplied to the Wheatstone bridge circuit, a change in the resistance value is detected as a change in the voltage. Thus, a change in pressure transmitted from the pressure introduction hole 12 is detected as a change in an electric signal.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a means for releasing a stress generated by thermal shrinkage of solder at a solder joint between a die of a package and a supporting substrate. An object of the present invention is to provide a semiconductor pressure sensor that absorbs, detects an accurate pressure, and has good temperature characteristics.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

In order to achieve the above object, a first aspect of the present invention is a silicon monolithic device having a resistance element formed on one surface by diffusion of impurities and a diaphragm formed on the other surface by anisotropic etching. A crystal substrate, a support substrate having a through hole communicating with the diaphragm, and the silicon single crystal substrate joined to one surface side, and a package in which the support substrate and the silicon single crystal substrate are housed. In a semiconductor pressure sensor in which the other surface of the support substrate is soldered to a die in a package, the die and the support substrate are connected.
Equipped with a means to release the stress generated by the thermal shrinkage of the combined solder.Even if the shape changes due to the thermal shrinkage of the solder, the stress is released by the means to release the stress. Pressure can be detected, and even if the operating temperature of the semiconductor pressure sensor is increased, distortion (decrease in linearity) does not occur in the sensor characteristics.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

That is, in this embodiment , the heat is generated by the thermal contraction of the solder at the solder joint between the support substrate 4 and the die 15 of the package.
It is characterized in that provided on the support substrate 4 of the di 10 - means for absorbing raw stress package.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

[0016]

According to a first aspect of the present invention, there is provided a silicon single crystal substrate having a resistance element formed on one surface by diffusion of impurities and a diaphragm formed on the other surface by anisotropic etching, and a through hole communicating with the diaphragm. A support substrate having the silicon single crystal substrate bonded to one surface thereof; and a package in which the support substrate and the silicon single crystal substrate are housed. In a semiconductor pressure sensor in which the surface side is solder-joined, by providing a means for releasing a stress generated by thermal shrinkage of the solder joining the die and the support substrate , even if a shape change due to the heat shrinkage of the solder occurs, Relieve the stress of solder by means of releasing stress,
Accurate pressure can be detected without transmitting stress to the supporting substrate, and even if the operating temperature of the semiconductor pressure sensor is increased, distortion (decrease in linearity) does not occur in the sensor characteristics. This has the effect.

Claims (3)

[Claims] 1. A silicon single crystal substrate having a resistance element formed by diffusion of impurities on one surface and a diaphragm formed on the other surface by anisotropic etching, and a silicon single crystal substrate having a through hole communicating with the diaphragm. And a package accommodating the support substrate and the silicon single crystal substrate, the other surface having a metal thin film of the support substrate formed on a die in the package. A semiconductor pressure sensor having a solder-joined side and a means for releasing stress caused by heat at a solder joint between the die and the support substrate. 2. The device according to claim 1, wherein the means for releasing the stress is provided substantially at the center of the surface of the supporting substrate on the side of the solder joint, and comprises a recess having no metal thin film formed on the surface.
A semiconductor pressure sensor according to claim 1. 3. The device according to claim 1, wherein the means for relieving the stress is provided on a surface of the support substrate on the side of the solder joint, and includes one or a plurality of recesses on which a metal thin film is not formed.
A semiconductor pressure sensor according to claim 1.