JPH0313832A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To make it possible to use a sensor under high pressure by using one surface of a semiconductor element as a pressure receiving surface on which external pressure is applied, providing a pressure sensitive element on the rear surface of the element, bonding a supporting member having a through hole to the rear surface of the semiconductor element, and taking out the output of the pressure sensitive element by way of the through hole. CONSTITUTION:Two diaphragms 22 are formed on a lower surface 21a of a semiconductor pressure sensitive element 21. Strain gages 23 are formed on a region 21b which is held with the diaphragms 22. Said semiconductor pressure sensitive element 21 is bonded to a stage 25 having a through hole 25a. When external pressure is applied on an upper surface 21c of the semiconductor pressure sensitive element 21, the semiconductor pressure sensitive element 21 receives strain. The strain causes the change in resistance value of each strain gage 23. At this time, the pressure (a) which is applied on the pressure receiving surface 21c of the semiconductor pressure sensitive element 21 acts on the bonding surface of the stage 25 as the stress in the compressing direction. The stress in the direction for peeling the bonding surface does not act on. Therefore, this sensor can be used even under high pressure.

Description

[Detailed description of the invention] [Summary] The present invention has one surface of a semiconductor element as a pressure-receiving surface to which external pressure is applied, a pressure-sensitive element on the back surface, and a penetrating surface on the back surface of the semiconductor element. A support member having a hole is bonded to the support member, and the output of the pressure sensitive element is taken out through the through hole. As a result, the pressure sensitive element is not directly exposed to the detection medium that performs pressure detection, so the structure of the pressure sensor can be simplified and it can be used even under high pressure.

. [Industrial Application Field] The present invention relates to a semiconductor pressure sensor used for, for example, hydraulic control and detection of intake pressure and exhaust pressure of automobiles and the like.

[Conventional technology]

FIG. 5 is a sectional view of a conventional semiconductor pressure sensor. In the figure, a pedestal 2 is fixed on a stem 1 by being bonded or glued. A semiconductor pressure-sensitive element 4 formed by forming a strain gauge 3 on a silicon substrate is bonded onto the pedestal 2, and a reference pressure maintained in a vacuum is maintained between the back surface of the semiconductor pressure-sensitive element 4 and the pedestal 2. A chamber 5 is provided. The pedestal 2 and the semiconductor pressure sensitive element 4 constitute a pressure element 6. Further, an electrode 7 connected to the strain gauge 3 is formed on the semiconductor pressure sensitive element 4, and this electrode 7 is connected to a lead terminal 8 provided through the stem 1 with a bonding wire 9.
connected via.

Further, a metal diaphragm 10 is joined to the stem 1 by welding or the like, and an inert liquid such as silicone oil 11 is sealed inside the metal diaphragm 10.

In the semiconductor sensor having the above configuration, when pressure is applied to the metal diaphragm IO, the pressure is applied to the semiconductor pressure sensitive element 4 using the silicone oil 11 as a pressure medium, and the semiconductor pressure sensitive element 4 is distorted. Then, depending on the strain, strain gauge 3
The resistance value changes, and the change in resistance value is detected by an external circuit via the lead terminal 8, and the pressure applied from the outside is detected.

FIG. 6 is a sectional view of another conventional semiconductor pressure sensor.

In this figure, the same members as those shown in FIG. 5 are given the same reference numerals, and their explanations will be omitted.

In this semiconductor sensor, a recess 12 is provided on the surface of the semiconductor pressure-sensitive element 4 that is connected to the pedestal 2 . Further, a through hole 13 is provided along the central axis of the pedestal 2 and the stem 1, and the through hole 13 is connected to the recess 12 of the semiconductor pressure sensitive element 4.
It is familiar to

In the semiconductor pressure sensor configured as described above, external pressure is applied to the recess 12 of the semiconductor pressure sensitive element 4 through the through hole 13 of the stem 1 and the pedestal 2, thereby distorting the semiconductor pressure sensitive element 4. The resistance value of the strain gauge 3 changes due to the strain, and the change in resistance value is detected by an external circuit via the lead terminal 8 to perform pressure detection.

[Problem to be solved by the invention]

In the above-mentioned semiconductor pressure sensor, the pressure-sensitive element is directly exposed to the pressure medium (gas or liquid) to prevent the pressure-sensitive element (for example, strain gauge) and electrodes formed on the semiconductor surface from being attacked by the pressure medium (gas or liquid) that performs pressure detection. The structure is such that it cannot be touched.

For example, in the semiconductor pressure sensor shown in FIG. 5, silicone oil 11 is sealed with a metal diaphragm 10 to prevent the semiconductor pressure-sensitive element 4 from coming into direct contact with the pressure medium.

In addition, in the semiconductor pressure sensor shown in Fig. 6, by using the back side of the surface on which the pressure-sensitive element and electrodes are formed as the pressure-receiving surface, the surface on which the pressure-sensitive element and electrodes are formed is exposed to an external pressure medium. I try not to touch it directly.

However, in the case of the structure shown in FIG. 5, it is necessary to weld the metal diaphragm 10 to the stem 1 and further seal silicone oil in the metal diaphragm 10, which complicates the structure of the semiconductor pressure sensor. There was a drawback. Another drawback is that the zero point of the detected pressure fluctuates depending on the temperature characteristics of the sealed silicone oil or the like.

Furthermore, in the case of the structure shown in FIG. 6, the pressure applied to the recess 12 of the semiconductor pressure-sensitive element 4 acts as a tensile stress on the joint surface between the semiconductor pressure-sensitive element 4 and the pedestal 2.
This method has the drawback that it cannot be used to detect high pressures because it tends to cause damage to the bonding surfaces.

Furthermore, in any of the above semiconductor pressure sensors, after the pressure reference chamber 5 and the recess 12 for applying external pressure are formed by etching or the like, a pressure sensitive part such as the strain gauge 3 is formed on the back surface thereof. In this case, it is necessary to align the strain gauge 3 so as not to deviate from the position of the etched portion, which causes the problem that the process of manufacturing the device becomes complicated.

An object of the present invention is to provide a semiconductor pressure sensor that has a simple structure, does not require alignment with an etched portion, and can be used over a wide pressure range.

[Means to solve the problem]

The present invention provides a semiconductor pressure sensor that detects pressure applied from the outside with a pressure-sensitive element provided on a semiconductor element, in which one surface of the semiconductor element is used as a pressure-receiving surface for the pressure applied from the outside, and the pressure-sensitive element is placed on the back surface of the semiconductor element. A support member having a through hole is bonded to the back surface of the semiconductor element, and the output of the pressure sensitive element is taken out through the through hole of the support member.

[For production]

In the semiconductor pressure sensor having the above configuration, since the pressure sensing element is provided on the back side of the pressure receiving surface, the pressure sensing element is not directly exposed to the pressure atmosphere, and the output of the pressure sensing element is transmitted through the through hole of the support member. By taking out the pressure, the surface on which pressure applied from the outside acts as compressive stress on the bonding surface between the semiconductor element and the support member can be used as the pressure receiving surface, and a pressure sensor that can be used up to high pressure can be realized.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

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

In the figure, there are two diaphragms (recesses) on the lower surface 21a of the semiconductor pressure-sensitive element 21 made of, for example, a silicon substrate.
22 is formed by etching or the like. A strain gauge is formed on the region 21b sandwiched between the two diaphragms 22 by diffusion or the like.

FIG. 2 is a transparent perspective view of the main parts of the semiconductor pressure sensor.

On the region 21b sandwiched between the two diaphragms 22,
Four strain gauges 23 are formed.

Each strain gauge is connected by a conductive pattern, forming a full bridge circuit as a whole.

Furthermore, four electrode pads 24 are formed on the lower surface 21a of the semiconductor pressure sensitive element, and these electrode pads 24 are connected to each connection point of the full bridge circuit. This electrode pad 24 may be formed on the region 24b.

In this embodiment, the upper surface 21c of the semiconductor pressure sensitive element 21
Two diaphragms 22 are provided, and the cross-sectional shape of the semiconductor pressure-sensitive element 21 is made into an E-shape so that distortion of the semiconductor pressure-sensitive element 21 due to the pressure applied to the pressure-receiving surface can be well detected when the pressure-receiving surface is However, the shape and number of the diaphragms 22 and the arrangement of the strain gauges 23 may be other configurations.

For example, it is also possible to provide one recess (diaphragm) on the back surface of the semiconductor pressure-sensitive element 21 and arrange the strain gauge 23 on the bottom surface of the recess.

Returning to FIG. 1, the semiconductor pressure sensitive element 21 is joined to a pedestal 25 having a through hole 25a large enough to expose the strain gauge 23 and the electrode pad 24; It is fixed to a stem 26 having a through hole 26a that is the same size as or larger than 25a.

Further, the electrode pad 24 connected to the strain gauge 23 is
It is connected to an electrode 27 provided on the lower surface of the stem 26 via a bonding wire 28.

In the pressure sensor configured as described above, when pressure is applied from the outside to the top surface of the semiconductor pressure-sensitive element 21, the semiconductor pressure-sensitive element 21 is distorted, and the distortion is formed on the region 21b sandwiched between the two diaphragms 22. This appears as a change in the resistance value of the strain gauge 23. At this time, the semiconductor pressure sensitive element 2
The pressure applied to the pressure-receiving surface of 1 acts as a stress in the compressive direction on the joint surface with the pedestal 25, and the stress in the direction of peeling off the joint surface does not work, so the zero-pressure sensor can be used even under high pressure. can.

Changes in the resistance value of the strain gauge 23 are detected by an external circuit (not shown) via the electrodes 27, and the pressure applied to the pressure sensor is detected.

As described above, since the pressure sensing element such as the strain gauge 23 is formed on the back side of the pressure receiving surface of the semiconductor pressure sensing element 21, the pressure sensing element does not come into direct contact with the gas or liquid for which pressure is to be detected.
The pressure sensitive element will not be corroded even by corrosive gas or liquid. Therefore, there is no need to seal the pressure sensor using a metal diaphragm or the like as in the past, so pressure errors due to thermal expansion of sealed silicone oil, etc. do not occur, and the structure of the pressure sensor can be simplified. Therefore, the manufacturing cost of the pressure sensor can be reduced.

Furthermore, since the strain gauge 23 and the electrode pad 24 are provided on the same surface as the diaphragm 22 formed by etching, a concave portion such as a reference pressure chamber is provided on one surface of the semiconductor pressure-sensitive element, and the other surface is This eliminates the need for alignment between the two, which is required when forming a strain gauge or the like, and the manufacturing process of the element can be simplified.

Next, FIG. 3 is a sectional view of a pressure sensor according to a second embodiment of the present invention.

In this embodiment, the stem 29 is made of glass, ceramic, or the like having approximately the same coefficient of linear expansion as the semiconductor pressure-sensitive element 21 made of a silicon substrate, etc., and the semiconductor pressure-sensitive element 21 is bonded onto the stem 29 by bonding, gluing, or the like. It is fixed. According to this embodiment, the structure of the pressure sensor can be further simplified, and the bonding wire 28 can be drawn out more easily through the through hole of the stem 29.

Furthermore, FIG. 4 is a sectional view of a pressure sensor according to a third embodiment of the present invention.

In this embodiment, the semiconductor pressure-sensitive element 21 is bonded to the stem 30, and the pedestal 31 is bonded to the semiconductor pressure-sensitive element 21. The bonding wire 28 can be easily drawn out, and the semiconductor pressure-sensitive element 21 is reinforced with the pedestal 31 to prevent distortion of the semiconductor pressure-sensitive element 21 due to thermal stress generated between the stem 30 and the semiconductor pressure-sensitive element 21. can be reduced.

Note that the semiconductor pressure-sensitive element is not limited to the above-described one in which a strain gauge is provided on a silicon substrate, but any element that can detect pressure may be used.

In addition, a recess formed on the back side of the pressure receiving surface (diaphragm 22
) is not limited to the above-described shape, but may be any shape suitable for pressure detection depending on the material, shape, etc. of the semiconductor pressure-sensitive element used.

〔Effect of the invention〕

According to the present invention, since a pressure sensing element such as a strain gauge can be formed on the back side of the pressure receiving surface, the pressure medium to be detected and the pressure sensing element do not come into direct contact with each other, and the structure of the pressure sensor can be simplified. can be made smaller and lower in cost. Moreover, since the pressure on the pressure-receiving surface acts as compressive stress on the joint surface between the semiconductor pressure-sensitive element and the pedestal, it can be used even under high pressure.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the first embodiment of the present invention, and FIG. 2 is a sectional view of the first embodiment of the present invention.
3 is a sectional view of the second embodiment of the present invention, FIG. 4 is a sectional view of the third embodiment of the present invention, and FIG. 5 is a perspective view of the main parts of the first embodiment. and FIG. 6 are cross-sectional views of a conventional semiconductor pressure sensor. 21... Semiconductor pressure sensitive element, 22... Diaphragm, 25... Pedestal, 25a... Through hole, 26... Stem, 27... Electrode, 28... Bonding wire. Figure 1

Claims (1)

[Claims] 1) In a semiconductor pressure sensor that detects pressure applied from the outside with a pressure sensing element provided on a semiconductor element, one surface of the semiconductor element is used as a pressure receiving surface for the pressure applied from the outside, and the back surface is used as a pressure sensing surface. A pressure element is provided, a support member having a through hole is bonded to the back surface of the semiconductor element, and an output of the pressure sensitive element provided on the back surface of the semiconductor element is taken out through the through hole of the support member. Features of semiconductor pressure sensor. 2) At least two recesses are provided on the back side of the pressure-receiving surface of the semiconductor element, a pressure-sensitive element is provided on the area sandwiched between the two recesses, and the output of the pressure-sensitive element and the output terminal provided on the support member are connected. 2. The semiconductor pressure sensor according to claim 1, wherein the semiconductor pressure sensor is connected by a bonding wire through a through hole of the support member.