JP4069770B2 - Pressure detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure detection device having a semiconductor substrate having a piezo effect as a pressure detection element, and housing a semiconductor substrate and a pressure transmission member for transmitting pressure to the semiconductor substrate, for example, in a combustion chamber of an engine. The present invention can be applied to a pressure detection device that detects the combustion pressure.
[0002]
[Prior art]
A semiconductor substrate having a piezo effect outputs an electrical signal in accordance with the pressure applied in the direction separating the front and back surfaces, that is, in the thickness direction, and utilizes a change in resistance value according to the strain caused by the pressure application. .
[0003]
As a pressure detection device having such a semiconductor substrate as a pressure detection element, a device in which the semiconductor substrate and a pressure transmission member for transmitting pressure to the semiconductor substrate are housed in a metal housing has been proposed (for example, Patent Documents 1 to 3).
[0004]
In such a pressure detection device, an electrode for detection is provided on the surface side of the semiconductor substrate, a lead member is provided on the outer periphery of the semiconductor substrate, and a signal is extracted by wire bonding the electrode and the lead member. Is going.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-253364 [0006]
[Patent Document 2]
JP-A-7-19981 [0007]
[Patent Document 3]
Japanese Patent No. 3166015 [0008]
[Problems to be solved by the invention]
By the way, for example, when such a pressure detection device is applied to an engine combustion pressure sensor, a housing portion of the pressure transmission member in the housing is inserted into a hole of the engine block, and the pressure in the combustion chamber is received by the pressure transmission member. The pressure is detected by transmitting to the semiconductor substrate.
[0009]
Here, there is a demand for miniaturization and weight reduction for the engine, and it is necessary to reduce the mounting space of the pressure detection device. Therefore, it is desired to reduce the diameter of the pressure detection device, that is, to reduce the diameter of the housing.
[0010]
However, as described above, in the conventional pressure detection device, the lead member is positioned on the outer periphery of the semiconductor substrate in order to perform wire bonding between the semiconductor substrate and the lead member.
[0011]
Therefore, the size of the wire bonding part including the lead member is larger than the size of the semiconductor substrate, and the diameter of the housing is determined by the size of the largest wire bonding part among the housing housing components. In other words, the diameter of the housing is defined by the size of the wire bonding part larger than that of the semiconductor substrate, and there is a restriction on the reduction of the diameter of the pressure detection device.
[0012]
With respect to such a problem, the present inventor can provide electrodes on both the front and back sides of the semiconductor substrate, and sandwich the semiconductor substrate between a part of the metal housing and the lead member. It was considered that wire bonding is not necessary in the take-out, and as a result, the diameter of the housing can be reduced.
[0013]
In this case, in order to obtain electrical continuity, the housing on the surface side of the semiconductor substrate, that is, the side to which pressure is applied, needs to be made of metal. That is, as in the conventional case, if the entire housing is made of metal, an electrode extraction configuration in which the semiconductor substrate is sandwiched is possible.
[0014]
However, if the entire housing is made of metal, in the case of the combustion pressure sensor described above, one end of the housing is exposed to a high-temperature measurement environment such as a combustion chamber, and the high heat is connected to a part of the housing via the housing. Is transmitted to the semiconductor substrate. For this reason, the semiconductor substrate becomes high temperature, which may make it difficult to use the semiconductor substrate.
[0015]
In view of the above problems, an object of the present invention is to provide a pressure detection device capable of suppressing a temperature rise of a semiconductor substrate while reducing the diameter of a housing.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided a semiconductor substrate (30) for outputting an electric signal in accordance with a pressure applied in a direction separating both the front and back surfaces, and a semiconductor provided on the surface side of the semiconductor substrate. A pressure detection device including a pressure transmission member (20) that transmits pressure to a substrate and a housing (10) that houses the semiconductor substrate and the pressure transmission member has the following characteristics.
[0017]
First, the housing includes a first partition (11), a second partition (12) having a lower thermal conductivity than the first partition, and a conductive partition (13) that partitions the first and second sections. ).
[0018]
The semiconductor substrate is accommodated in the first portion of the housing, and the pressure transmission member is accommodated in the second portion of the housing and transmits pressure to the surface of the semiconductor substrate via the partition. .
[0019]
The semiconductor substrate has a first electrode (36a) on the front surface and a second electrode (36b) on the back surface, and an electrical signal is output by the first electrode and the second electrode when pressure is applied. It must be a thing.
[0020]
The first electrode of the semiconductor substrate is electrically connected to the partition portion of the housing, and a lead member (40) electrically independent from the housing is accommodated in the housing on the back side of the semiconductor substrate, The lead member and the second electrode of the semiconductor substrate are electrically connected.
[0021]
According to the present invention having the above characteristics, the electrodes on the front and back surfaces of the semiconductor substrate are provided by providing electrodes on both the front and back surfaces of the semiconductor substrate, and providing the partition portion and the lead member so as to sandwich the front and back surfaces. No wire bonding is required for the removal. Therefore, the housing can be reduced in diameter.
[0022]
Even when the measurement environment becomes high temperature, the second part of the housing located on the measurement environment side has a lower thermal conductivity than the first part, so that heat from the measurement environment is transferred to the semiconductor substrate. Conduction can be suppressed.
[0023]
Therefore, according to the present invention, it is possible to provide a pressure detection device capable of suppressing the temperature rise of the semiconductor substrate while reducing the diameter of the housing.
[0024]
Here, as in the invention described in claim 2, the first portion (11) of the housing (10) can be made of metal, and the second portion (12) can be made of ceramic.
[0025]
Further, as in the invention described in claim 3, it is preferable that the pressure transmission member (20) also has a smaller thermal conductivity than the first portion (11) of the housing (10). The effect of suppressing the heat from the measurement environment from being conducted to the semiconductor substrate can be made more remarkable.
[0026]
In this case, the pressure transmission member (20) can be made of the same material as that of the second portion (12) of the housing (10).
[0027]
In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. FIG. 1 is a schematic cross-sectional view showing the entire pressure detection device S1 according to an embodiment of the present invention. This pressure detection device S1 can be applied as, for example, a combustion pressure sensor that detects the combustion pressure in the combustion chamber of the engine.
[0029]
The housing 10 has a substantially cylindrical shape as a whole, and includes a first portion 11 located on one end (lower end in FIG. 1) and a first portion 11 located on the other end (upper end in FIG. 1). The second portion 12 has a lower thermal conductivity than the portion 11 and a conductive partition 13 that partitions the first portion 11 and the second portion 12.
[0030]
For example, the 1st part 11 and the partition part 13 consist of metals, such as stainless steel, and the 2nd part 12 consists of ceramics, such as an alumina. In this case, the 1st part 11 and the partition part 13 are joined and fixed by adhesion | attachment, welding, etc., and the 2nd part 12 and the partition part 13 are joined and fixed by adhesion | attachment etc.
[0031]
A diaphragm 14 is provided at one end of the housing 10 in the second portion 12 to generate a strain displacement when a pressure P is applied. The diaphragm 14 is made of a ceramic such as alumina, and is joined to the second portion 12 by bonding or the like.
[0032]
In addition, a pressure transmission member 20 for transmitting the pressure P to the semiconductor substrate 30 is provided inside the second portion 12. In the present embodiment, the pressure transmission member 20 also has a lower thermal conductivity than the first portion 11 of the housing 10, and specifically, the same material as the second portion 12 of the housing 10, for example, It can be made of ceramic.
[0033]
In this example, the pressure transmission member 20 has a cylindrical shape, and is housed inside the second portion 12 of the housing 10 such that one end thereof is in contact with the diaphragm 14 and the other end is in contact with the partition portion 13. Yes. This partition part 13 is a disk-shaped thing which has a processus | protrusion on the upper and lower surfaces of the center part, and the said processus | protrusion and the pressure transmission member 20 are contacting.
[0034]
In addition, the semiconductor substrate 30 is accommodated inside one end (end portion on the partitioning portion 13 side) of the first portion of the housing 10. Here, the surface (upper surface in FIG. 1) on the side of the partition portion 13 in the semiconductor substrate 30 is the front surface, and the surface opposite to the front surface (the lower surface in FIG. 1) is the back surface. The semiconductor substrate 30 outputs an electrical signal according to the pressure applied in the direction separating the front and back surfaces, that is, in the thickness direction.
[0035]
The surface of the semiconductor substrate 30 is in contact with the projection of the partition part 13. In addition, in the first portion 11 of the housing 10, a lead member 40 that is electrically independent from the housing 10 is accommodated on the back side of the semiconductor substrate 30.
[0036]
The lead member 40 is in the form of a metal rod such as copper, and the lead member 40 is inserted and held in a columnar lead holding member 41 made of ceramic such as electrically insulating alumina. The space between the lead holding member 41 and the lead member 40 is sealed with hermetic glass or the like.
[0037]
The end portion of the lead member 40 on the semiconductor substrate 30 side protrudes from the lead holding member 41 and is in contact with the back surface of the semiconductor substrate 30. In addition, an electrically insulating ring 42 made of ceramic or the like is inserted into the end of the lead member 40 in contact with the back surface of the semiconductor substrate 30, and the semiconductor substrate 30 is also supported by the ring 42. .
[0038]
On the other hand, the end of the lead member 40 opposite to the semiconductor substrate 30 protrudes from the lead holding member 41 and can be electrically connected to an external wiring member (not shown).
[0039]
Here, the lead holding member 41 is supported by projections 15 and 16 provided on the inner surface of the first portion 11 of the housing 10 so as not to be displaced in the longitudinal direction and the short direction of the housing 10.
[0040]
In such a pressure detection device S1, the pressure P received by the diaphragm 14 is transmitted from the pressure transmission member 20 located on the surface (upper surface in FIG. 1) side of the semiconductor substrate 30 via the partitioning portion 13 to the semiconductor substrate. Transmitted to 30 surfaces.
[0041]
Here, a pressure is applied to the semiconductor substrate 30 in a direction separating both the front and back surfaces, and an electric signal output from the semiconductor substrate 30 is changed by the change in the pressure P. A detailed configuration of the semiconductor substrate 30 in the present embodiment will be described with reference to FIG.
[0042]
FIG. 2 is an enlarged view showing the vicinity of the semiconductor substrate 30 in FIG. The semiconductor substrate 30 is made of, for example, an N-type silicon substrate 31 and has <110> crystal axes in both the front and back surfaces of the silicon substrate 31. Note that the front and back surfaces of the silicon substrate 31 and the front and back surfaces of the semiconductor substrate 30 coincide.
[0043]
On the surface of the silicon substrate 31, a first N + layer 32 formed by impurity implantation or diffusion of phosphorus or the like is formed, and a P + layer 33 formed by impurity implantation or diffusion of boron or the like is formed. , Adjacent to the first N + layer 32 and extending along the <110> crystal axis direction. A second N + layer 34 formed by impurity implantation such as boron or diffusion is formed on the back surface of the silicon substrate 31.
[0044]
Then, silicon oxide films 35a and 35b formed by thermal oxidation or the like are formed so as to cover the front and back surfaces of the silicon substrate 31, and further, sputtering, vapor deposition or the like is performed so as to cover these silicon oxide films 35a and 35b. Conductive films 36a, 36b and 36c made of aluminum or the like are formed.
[0045]
Here, a contact hole is formed in the silicon oxide film 35a on the surface side of the silicon substrate 31 at a position corresponding to the bonding interface between the first N + layer 32 and the P + layer 33. The film 36c is electrically connected. The conductive film 36c is configured as a relay electrode 36c.
[0046]
Further, a contact hole is formed in the silicon oxide film 35a on the surface side of the silicon substrate 31 at a position corresponding to the end portion of the P + layer 33 opposite to the bonding interface between the first N + layer 32 and the P + layer 33. The end of the P + layer 33 and the conductive film 36a are electrically connected. The conductive film 36a is configured as a first electrode 36a.
[0047]
Further, a contact hole is formed in the silicon oxide film 35b on the back surface side of the silicon substrate 31 at a position corresponding to the second N + layer 34, and the second N + layer 34 and the conductive film 36b are electrically connected. Connected. The conductive film 36b is configured as a second electrode 36b.
[0048]
As described above, the semiconductor substrate 30 has the first electrode 36a on the front surface and the second electrode 36b on the back surface, and such a semiconductor substrate 30 is manufactured using a known semiconductor manufacturing technique. Can do.
[0049]
As shown in FIG. 2, the first electrode 36 a is electrically connected to the surface side of the semiconductor substrate 30 in contact with the protrusions of the partition portion 13 of the housing 10, while The second electrode 36 b on the back surface side is in contact with and electrically connected to the lead member 40.
[0050]
Here, each of the first and second electrodes 36a and 36b, the partition portion 13 and the lead member 40 may be in direct contact with each other, and may be electrically connected. However, a conductive adhesive or silver paste (not shown) may be used. It is good also as the form which touched through. In particular, since the first electrode 36a is on the pressure receiving side, the partition portion 13 and the first electrode 36a are preferably fixed via a hard conductive adhesive so that there is no escape of pressure. .
[0051]
In such a semiconductor substrate 30, a voltage is applied via the partition portion 13 and the lead member 40 so that the first electrode 36 a has a GND potential and the second electrode 36 b has a positive potential. This voltage application state is shown in FIG.
[0052]
This voltage application state is such that the lead member 40 is electrically connected to the partition portion 13 by connecting an external wiring member such as a connector to one end (the lower end in FIG. 1) of the housing 10 in FIG. This is realized by setting the first portion 11 of the housing 10 to the GND potential.
[0053]
In this voltage application state, a current flows as shown by an arrow in FIG. That is, current flows from the second electrode 36a and the second N + layer 34 on the back surface side through the inside of the silicon substrate 31 to the first N + layer 32, the relay electrode 36c, and the P + layer 33 on the front surface side. In the P + layer 33, a current flows to the first electrode 36a along the <110> crystal axis direction.
[0054]
Here, as described above, when the pressure P received by the diaphragm 14 is transmitted to the surface of the semiconductor substrate 30 via the pressure transmission member 20 and the partitioning portion 13, both the front and back surfaces of the semiconductor substrate 30 are transferred to the semiconductor substrate 30. Pressure is applied in the direction separating the two, and distortion occurs.
[0055]
Then, the resistance value of the P + layer 33 in the semiconductor substrate 30 changes based on this strain, and the current flowing through the semiconductor substrate 30 also changes due to the change in resistance value. By detecting this change in current as an electrical signal from between the first and second electrodes 36a, 36b, the applied pressure can be obtained.
[0056]
As described above, in the present embodiment, the surface of the semiconductor substrate 30 that outputs an electric signal according to the pressure applied in the direction separating the front and back surfaces described in Patent Document 3 is further provided on the surface. A second electrode 36b is formed on the back surface of the electrode 36a, and an electric signal is output by the first electrode 36a and the second electrode 36b.
[0057]
In the pressure detection device S1 of the present embodiment, the electrodes 36a and 36b are provided on the front and back surfaces of the semiconductor substrate 30, and the partition portion 13 and the lead member 40 of the housing 10 are provided so as to sandwich the front and back surfaces. Thus, wire bonding is not necessary for taking out the electrodes 36a and 36b on the front and back surfaces of the semiconductor substrate 30.
[0058]
Therefore, unlike the prior art, it is not necessary to arrange lead members for wire bonding on the outer periphery of the semiconductor substrate 30, and the housing 10 can be reduced in size to a size closer to the size of the semiconductor substrate 30.
[0059]
Moreover, when applying this pressure detection apparatus S1 as a combustion pressure sensor, the 2nd part 12 which is the accommodating part of the pressure transmission member 20 in the housing 10 will be inserted in the hole of an engine block. The second portion 12 of the housing 10 is exposed to a high temperature measurement environment.
[0060]
Here, in this embodiment, since the second portion 12 of the housing 10 located on the high temperature measurement environment side has a lower thermal conductivity than the first portion 11, heat from the measurement environment is a semiconductor. Conduction to the substrate 30 can be suppressed.
[0061]
Thus, according to the present embodiment, it is possible to provide the pressure detection device S1 that can suppress the temperature rise of the semiconductor substrate 30 while reducing the diameter of the housing 10 as compared with the conventional case.
[0062]
Further, although the pressure transmission member 20 may be made of metal such as stainless steel, the pressure transmission member 20 is also assumed to have a lower thermal conductivity than the first portion 11 of the housing 10 as in the present embodiment. For example, it is clear that the effect of suppressing the heat from the measurement environment from being conducted to the semiconductor substrate 30 becomes more remarkable.
[0063]
Furthermore, in this embodiment, the diaphragm 14 exposed to the measurement environment is also made of ceramic, so that the effect of suppressing heat conduction to the semiconductor substrate 30 is enhanced. The diaphragm 14 may be made of metal such as stainless steel, and in this case, the superiority of the present embodiment does not change compared to the conventional case.
[Brief description of the drawings]
FIG. 1 is an overall schematic cross-sectional view of a pressure detection device according to an embodiment of the present invention.
FIG. 2 is an enlarged view showing a vicinity of a semiconductor substrate in FIG.
[Explanation of symbols]
10 ... housing, 11 ... first part of housing,
12 ... 2nd part of housing, 13 ... Partition part of housing,
20 ... Pressure transmission member, 30 ... Semiconductor substrate, 36a ... First electrode,
36b ... second electrode, 40 ... lead member.

Claims (4)

A semiconductor substrate (30) for outputting an electrical signal in accordance with a pressure applied in a direction separating the front and back surfaces;
A pressure transmission member (20) provided on the surface side of the semiconductor substrate for transmitting pressure to the semiconductor substrate;
In a pressure detection device comprising the semiconductor substrate and a housing (10) for housing the pressure transmission member,
The housing comprises a first part (11), a second part (12) having a lower thermal conductivity than the first part, and a conductive partition part that partitions the first part and the second part. (13)
The semiconductor substrate is housed in the first portion of the housing;
The pressure transmission member is housed in the second portion of the housing and transmits pressure to the surface of the semiconductor substrate through the partition portion.
The semiconductor substrate has a first electrode (36a) on the front surface and a second electrode (36b) on the back surface, and when the pressure is applied, the electrical signal is transmitted to the first electrode and the second electrode. Is output by
The first electrode of the semiconductor substrate is electrically connected to the partition portion of the housing;
A lead member (40) electrically independent of the housing is housed in the housing on the back side of the semiconductor substrate, and the lead member and the second electrode of the semiconductor substrate are electrically connected. A pressure detection device characterized by being provided. The pressure detection device according to claim 1, wherein the first portion (11) of the housing (10) is made of metal, and the second portion (12) is made of ceramic. The pressure detection device according to claim 1 or 2, wherein the pressure transmission member (20) also has a lower thermal conductivity than the first portion (11) of the housing (10). The pressure detection device according to claim 3, wherein the pressure transmission member (20) is made of the same material as the second portion (12) of the housing (10).

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