JPH04370730A - Semicondcutor pressure sensor - Google Patents

Abstract

PURPOSE:To obtain the sensor whose breakdown strength is high and measurement region is wide. CONSTITUTION:A silicon chip 6 is joined on a base 2 and the pressure from a measurement medium is applied to a diaphragm 7 through a pressure introduction hole 3. In this case, the area of the pressure introduction hole 3 of the base 2 is largely set, compared with the opening area of a recess part 7a of the silicon chip 6. In the case where the pressure is applied, stress is concentrated on the end of the recess part 7a. The damage of the base 2 can be controlled because the part of the stress concentration is isolated from the joint part between the silicon chip 6 and the base 2.

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 used in fields such as automobiles and industrial measurement.

0002

2. Description of the Related Art FIG. 3 is a sectional view showing an example of a conventional semiconductor pressure sensor.

[0003] A recess is provided on the upper surface of the metal container 21, and the silicon sensor 22 is fixed in the center of this recess via a die-bonding resin 24. Further, a connecting pin 26 is provided near the silicon sensor 22. The connecting pin 26 extends below the metal container 21, and the connecting pin 26 and the metal container 21 are electrically insulated by an insulating member 27 interposed between them.

The silicon sensor 22 is equipped with a silicon diaphragm 23 on its upper surface.
3 is formed with a piezo element (not shown). The electrodes of this piezo element are electrically connected to connection pins 26 via thin metal wires 29.

[0005] Furthermore, silicone oil 28 is charged into the recessed portion of the metal container 21, and a metal diaphragm 25 made of stainless steel is disposed in the upper part of the metal container 21. This metal diaphragm 25 is welded to the metal container 21 in a liquid-tight manner.

In the pressure sensor configured as described above, when pressure is applied to the metal diaphragm 25 from the measurement medium, this pressure is transmitted to the silicon diaphragm 23 via the silicone oil 28. This causes the diaphragm 23 to curve, and the piezo element outputs an electrical signal according to the pressure. This signal is transmitted to the outside via the connection pin 26.

This semiconductor pressure sensor has the advantage that since the measurement medium does not come into direct contact with the piezo element, problems such as contamination and corrosion of the sensor by the measurement medium can be avoided, and it can be applied to a variety of measurement media. There are advantages.

However, the semiconductor pressure sensor described above requires a step of manufacturing a thin stainless steel plate with a thickness of approximately 30 μm as the metal diaphragm 25, a step of welding the thin stainless steel plate to the metal container 21 in a liquid-tight manner, and a step of welding the thin stainless steel plate to the metal container 21, and a step of welding the thin stainless steel plate to the metal container 21, and a step of welding the thin stainless steel plate to the metal container 21. This method requires a filling process, etc., and has the disadvantage that manufacturing is complicated and manufacturing costs are high. Furthermore, when the temperature rises, the volume of the silicone oil 28 expands and stress is applied to the silicone diaphragm 23, resulting in a problem in that the output of the sensor fluctuates.

FIG. 4 is a sectional view showing a conventional semiconductor pressure sensor in which such problems have been solved.

A glass pedestal 32 is bonded onto the stem 31, and pressure introduction holes 33 and 34 are provided in the stem 31 and the pedestal 32, respectively. In addition, stem 31
A measuring medium introducing pipe 35 is arranged on the lower surface side of the measuring medium in alignment with the pressure introducing hole 34 .

A silicon chip 36 is placed on the pedestal 32. This silicon chip 36 has a diaphragm 3 formed by providing a recess 37a in the center of the lower surface.
It has 7. Further, this silicon chip 36 is anodically bonded to the pedestal 32 at the periphery of the diaphragm 37.

A piezo element (not shown) is provided on the upper surface side of the silicon diaphragm 37. The electrode of this piezo element is connected to the connecting pin 3 via the thin metal wire 38.
It is electrically connected to 9. This connecting pin 39 is led out below the stem 31.

A metal cap 40 is provided on the stem 31, and the silicon chip 36, pedestal 32, etc. are housed within this metal cap 40.

Note that in this type of semiconductor pressure sensor, there is one in which the inside of the metal cap 40 is vacuum, and one in which the interior of the metal cap 40 is vacuum.
Some caps are provided with holes so that the inside of the cap 40 is at atmospheric pressure. Further, the base 32 and the stem 31 are joined by solder in consideration of mass productivity. Further, the pedestal 32 that supports the silicon chip 36 is usually made of glass because its coefficient of thermal expansion is close to that of single crystal silicon.

In the semiconductor pressure sensor configured as described above, when pressure is applied to the silicon diaphragm 37 via the measurement medium introduction pipe 35, the diaphragm 37 reacts with the pressure inside the cap 40 via the measurement medium introduction pipe 35. The piezo element deforms based on the pressure difference between the piezo element and the applied pressure, and the piezo element outputs an electric signal corresponding to the pressure.

In this semiconductor pressure sensor, the bottom side of the diaphragm 37 comes into contact with the measurement medium, whereas the piezo element is provided on the top side of the diaphragm 37, thereby avoiding deterioration of the sensor due to contact with the measurement medium. In addition, compared to the sensor having the structure shown in FIG. 3, it has the advantage of being easier to manufacture and having lower manufacturing costs.

[0017]

[Problems to be Solved by the Invention] However, in the conventional semiconductor pressure sensor having the structure shown in FIG.
There is a problem that stress is applied in the direction of peeling it off, so it is easily damaged, and the measurable pressure range is narrow.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a semiconductor pressure sensor that can avoid deterioration of the sensor due to contact with a measuring medium and has a wide measurement range.

[0019]

[Means for Solving the Problems] A semiconductor pressure sensor according to the present invention includes a base provided with a pressure introduction hole, and a diaphragm provided by forming a recessed portion at a position aligned with the pressure introduction hole. and a semiconductor chip joined to the pedestal at a peripheral portion, and the area of the pressure introduction hole is larger than the opening area of the recess.

[0020]

[Operation] The inventors of the present invention have conducted various experimental studies in order to obtain a semiconductor pressure sensor that has a higher pressure resistance and a wider measurement range than conventional pressure sensors. As a result, it was found that the withstand pressure of the semiconductor pressure sensor can be improved by making the area of the pressure introduction hole of the pedestal larger than the opening area of the recess of the semiconductor chip. Generally, it is thought that if the area of the pressure introduction hole is made larger than the opening area of the recess of the semiconductor chip, the bonding area between the pedestal and the semiconductor chip decreases, and the breakdown voltage decreases. However, as a result of manufacturing various semiconductor pressure sensors and conducting pressure tests by the inventors of the present application, the following was found.

When a semiconductor chip that has been peeled off from a glass pedestal due to pressure is observed, glass is adhered to the pedestal side. That is, in a semiconductor pressure sensor, the pedestal is not damaged due to peeling of the bonded portion between the pedestal and the semiconductor chip, but the pedestal is damaged due to stress being concentrated on a specific portion of the pedestal. In this case, the bonding strength between the semiconductor chip and the pedestal is sufficiently high.

That is, in the conventional semiconductor pressure sensor, as shown in FIG. 5, when pressure is applied to the diaphragm 44 through the pressure introduction hole 42 of the pedestal 41, the diaphragm 44 deforms as shown by the broken line. . As a result, stress concentrates on the edge of the recess 44a (the portion indicated by arrow A in the figure). As a result, the glass (pedestal 41) in this portion is damaged, and the semiconductor chip 43 is peeled off from the pedestal 41.

On the other hand, in the semiconductor pressure sensor according to the present invention, for example, as shown in FIG.
Since the area of the opening is large compared to the opening area of a, even if the diaphragm 48 is deformed by pressure, the part where stress is concentrated (the part indicated by arrow B in the figure) is separated from the joint part between the semiconductor chip 47 and the pedestal 45. There is. As a result, damage to the pedestal 45 can be suppressed, and the withstand pressure of the semiconductor pressure sensor is improved compared to the conventional one. Therefore, the semiconductor pressure sensor according to the present invention has a wide pressure measurement range.

[0024]

Embodiments Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a semiconductor pressure sensor according to a first embodiment of the present invention.

A glass pedestal 2 is bonded onto the stem 1. This stem 1 is provided with a pressure introduction hole 4 penetrating from its upper surface to its lower surface. Also, on pedestal 2,
A pressure introduction hole 3 is provided at a position aligned with the pressure introduction hole 4 and penetrates from the upper surface to the lower surface. Furthermore, stem 1
A measuring medium introducing pipe 5 is arranged on the lower surface side of the measuring medium in alignment with the pressure introducing hole 4 .

A silicon chip 6 is bonded onto the pedestal 2. A recess 7a is formed in the center of the lower surface of the silicon chip 6, and a silicon diaphragm 7 is provided thereby. Note that the diameter of the pressure introduction hole 3 is
The diameter is set larger than the diameter of the opening of the recess 7a.

A piezo element (not shown) is provided on the upper surface of the diaphragm 7. The electrodes of this piezo element are electrically connected to connection pins 9 via thin metal wires 8. This connecting pin 9 is inserted through the stem 1 and led out below the stem 1. Further, a cap 10 is disposed on the stem 1, and the silicon chip 6, the pedestal 2, etc. are housed within this cap 10.

In this embodiment, the diameter of the pressure introduction hole 3 is larger than the diameter of the opening of the recess 7a. For this reason,
When the pressure from the measurement medium is applied to the diaphragm 7 through the measurement medium introduction pipe 5, the part where stress is concentrated (i.e., the edge of the recess 7a) is separated from the joint part, so that the pedestal 2 Damage can be avoided. Therefore,
The semiconductor pressure sensor according to this embodiment has a higher withstand pressure and a wider measurement range than conventional ones.

A semiconductor pressure sensor having the above structure was actually manufactured and the peel strength between the silicon chip and the pedestal was measured. As a result, the peel strength was 150 to 200 kg/cm2.
Met. On the other hand, a pressure sensor having the conventional structure shown in FIG. 4 was manufactured, and the peel strength between the silicon chip and the pedestal was measured. As a result, the peel strength was 30 to 40 kg/cm2. Generally, a pressure sensor must guarantee a pressure resistance of 1.5 times the full scale. For this reason, the full scale of conventional semiconductor pressure sensors is approximately 20 to 30 kg/cm.
2, whereas the pressure sensor according to this embodiment can have a full scale of approximately 100 kg/cm2 or more.

FIG. 2 is a sectional view showing a pedestal and a silicon chip of a semiconductor pressure sensor according to a second embodiment of the present invention.

This embodiment differs from the first embodiment in that the shape of the pressure introduction hole 13 provided in the pedestal 12 is different.

That is, in this embodiment, the silicon chip 1 in the pressure introduction hole 13 provided in the glass pedestal 12 is
The end portion on the 6th side is enlarged. On the other hand, the silicon chip 16 has a recess 1 at a position aligned with the pressure introduction hole 13.
A diaphragm 17 is provided by forming 7a. The area of the pressure introduction hole 13 of the pedestal 12 is
It is set larger than the opening area of the recess 17a provided in the silicon chip 16.

In this embodiment as well, the part where stress is concentrated when pressure is applied (the edge of the recess 17a) is separated from the joint part between the silicon chip 16 and the pedestal 12. The same effect as in the example can be obtained.

[0035]

[Effects of the Invention] As explained above, in the present invention,
Since the area of the pressure introduction hole of the pedestal is set larger than the opening area of the recess of the silicon chip, damage to the pedestal due to the application of pressure can be suppressed. Therefore, the semiconductor pressure sensor according to the present invention has a high withstand pressure and a wide pressure measurement range.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a semiconductor pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a pedestal and a silicon chip of a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing an example of a conventional semiconductor pressure sensor.

FIG. 4 is a sectional view showing another example of a conventional semiconductor pressure sensor.

FIG. 5 is a schematic diagram showing the occurrence of damage in a conventional semiconductor pressure sensor.

FIG. 6 is a schematic diagram showing the effects of the semiconductor pressure sensor according to the present invention.

[Explanation of symbols]

1, 31; Stem 2, 12, 32, 41, 45; Pedestal 3, 4, 13, 33, 34, 42, 46; Pressure introduction hole 5
, 35; measurement medium introduction tube 6, 16, 36, 43, 47; silicon chip 7, 17
, 23, 25, 37, 44, 48; diaphragm 7a, 17a, 37a, 44a, 48a; recess 8, 29
, 38; thin metal wires 9, 26, 39; connection pins 10, 40; cap 21; metal container 28; silicone oil

Claims (1)

[Claims] 1. A pedestal provided with a pressure introduction hole, a diaphragm provided by forming a recess at a position aligned with the pressure introduction hole, and a semiconductor chip bonded to the pedestal around the periphery of the diaphragm. a semiconductor pressure sensor, wherein the area of the pressure introduction hole is larger than the opening area of the recess.