JPH0442580A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To make the title sensor usable in a high-temperature environment by using perfluoropolyether as a working fluid. CONSTITUTION:Chambers A and B separated from each other by an intermediate wall 7 and communicated with each other through communicating holes provided through the intermediate wall 7 are filled with perfluoropolyether 9 which is used as a working fluid. The perfluoropolyether 9 is completely fluorinated oil composed of carbon atoms, fluorine atoms, and oxygen atoms. The perfluoropolyether 9 moves between the chamber A where a sensor element 1 is placed and chamber B where a diaphragm exists through the holes 25 in accordance with the outside force applied to the diaphragm 3 and deforms a sensor chip 11 with a force corresponding to the outside force. As a result, the resistance value of a strain resistance 19 increases and a voltage signal corresponding to the outside pressure is detected from a lead 23. Since the perfluoropolyether 9 has a high thermal decomposition temperature and extremely small coefficient of cubic expansion, excellent detection accuracy is obtained even when this semiconductor pressure sensor is used in a high-temperature environment.

Description

Detailed Description of the Invention ■ Quantitative measurement of skin [Field of industrial application] The present invention relates to a semiconductor pressure sensor, and more specifically, the present invention relates to a semiconductor pressure sensor that transmits the force received by a diaphragm to a sensor element via a working fluid, thereby detecting contaminants and The present invention relates to a semiconductor pressure sensor that protects a sensor element from heat.

[Prior Art] A conventional semiconductor pressure sensor of this type is filled with silicone oil as a working fluid. Since silicone oil has low heat resistance and a high coefficient of volumetric expansion, the operating temperature range is limited to about -30°C to +120°C.

Therefore, as a semiconductor pressure sensor that can be used in higher temperature environments, H
It has been considered that a liquid metal such as G, Na, or the like is sealed as a working fluid.

[Problems to be Solved by the Invention] However, the semiconductor pressure sensor f;&Hg that can be used in the above-mentioned high temperature environment is toxic and contains Na.

Since K has the risk of explosion due to contact with moisture,
There are problems in that they require special consideration in handling and are difficult to manufacture.

In addition, since liquid metals such as Hg, Na, etc. are conductive materials, special configurations are required, such as insulating the input/output terminals of the sensor element from the liquid metal to prevent short circuits.
There are mounting constraints, which make manufacturing even more difficult.

The semiconductor pressure sensor of the present invention solves the above problems and aims to facilitate the manufacture of a semiconductor pressure sensor that can be used in high-temperature environments.

Composition of the skin [Means for solving the problem] The semiconductor pressure sensor of the present invention (constructed between a sensor element that changes a pressure signal depending on the magnitude of an acting force and a diaphragm that receives an external force) A semiconductor pressure sensor in which a gap is filled with a working fluid and a force received by the diaphragm is transmitted to the sensor element via the working fluid, characterized in that the working fluid is filled with perfluoropolyether. shall be.

[Function] In the semiconductor pressure sensor of the present invention having the above configuration (
1. The force exerted by the diaphragm is transmitted to the sensor element via perfluoropolyether as the working fluid. The sensor element changes its output signal depending on the magnitude of the transmitted force. The thermal decomposition temperature of the above-mentioned perfluoropolyether is high, and the coefficient of volumetric expansion is extremely small.

Therefore, perfluoropolyether does not deteriorate even in a high temperature environment. Further, the volume change of perfluoropolyether due to temperature change is minute. As a result, the semiconductor pressure sensor having the above configuration exhibits good detection accuracy even when used in a high temperature environment.

The perfluoropolyethers mentioned above are also chemically stable and have no toxicity or risk of explosion.
Normal handling of the mountain is sufficient.

In addition, perfluoropolyether has high insulating properties, so
There is no need for a structure that insulates the input/output terminals of the sensor element from the working fluid, and there are fewer restrictions on mounting. [Examples] Examples of the semiconductor pressure sensor of the present invention will be described below. FIG. 1 is a longitudinal sectional view of a semiconductor pressure sensor according to a first embodiment.

The semiconductor pressure sensor of the first embodiment (absolute pressure type sensor) includes a sensor element 1, a diaphragm 3,
It includes a housing 5, an intermediate wall 7, and a working fluid 9.

The sensor element] includes a sensor chip] and a pedestal 13, and is attached to the inner bottom of the housing 5 with an adhesive 15.

The sensor chip 11 is a pressure sensitive element made of silicon, and has a diaphragm structure in which a recess is formed in the center of the lower part. A pressure reference chamber 1 is provided between the recess and the pedestal 13.
7 is composed. As shown in the cross-sectional view of FIG. 2 from 1 to the sensor chip 11, strain resistors 19 are formed at four locations by a diffusion process or an ion implantation process. In addition,
In FIG. 2, the illustration of the working fluid in Table 1 is omitted, and the internal structure of the housing 5 is shown.

Four corners of sensor chip 11] Table Bonding wire 21
The lead 23 is connected to the lead 23 for signal retrieval. The lead 23 (as shown in FIG. 1) penetrates the housing 5 and projects to the outside.

The pedestal 13 is made of heat-resistant glass (product name: Pyrex #774
0, etc.), crystallized glass, silicon, etc.

The diaphragm 3 is made of a material with excellent heat resistance and corrosion resistance, such as precipitation hardening stainless steel or Inconel (trademark). Its outer peripheral portion is seam-welded to the housing 5 to maintain airtightness inside the housing 5.

The housing 5 is made of iron, Kovar, various stainless steel materials, or the like. This housing 5 has a thread formed on its outer periphery, and is connected to a pipe for introducing a part of the object to be measured, such as gas or liquid, or a pressure measuring part of a machine.

The intermediate wall 7 is a partially stabilized zirconia molded piece formed to cover the sensor element 1 . Partially stabilized zirconia is a material with excellent heat resistance and thermal insulation properties. The thermal conductivity is 2.5 W/mK, which is extremely low. The side wall of this intermediate wall 7 has a plurality of communication holes 25 in a chamber A where the sensor element 1 is located and a chamber B where the diaphragm is located.
The two rooms are connected. In the embodiment, the intermediate wall 7 is designed so that the filling amount of the working fluid described below is 0.05 cc or less.

Perfluoropolyether 9 as a working fluid is filled in two chambers A and B with which the intermediate wall 7 communicates.

Perfluoropolyether 9 (carbon, fluorine.

It is a fully fluorinated oil consisting of three oxygen atoms. For example, Huonpurin (product name: manufactured by Montefluos).

Italy).

Perfluoropolyether has a thermal decomposition temperature that is higher than that of air (
It is chemically stable even in high temperature environments, with a temperature of 350°C or higher when used in a state where it is shut off from 02, N2). Further, the volume expansion coefficient of perfluoropolyether is lXl0-3, which is extremely small, and the saturated vapor pressure is 0. ITorr, which is low. Furthermore, it has high electrical insulation properties. Its resistivity is I
It is Q+4 [Ωm] or more.

This perfluoropolyether is chemically stable and
There is no need for special care when handling it, as it has no oxidative or explosive properties.

In the semiconductor pressure sensor having the above configuration (, t.

Depending on the amount of external force pushing the diaphragm 3,
Perfluoropolyether 9 as a working fluid moves between the chamber A where the sensor element 1 is located and the chamber B where the diaphragm is located through the communication hole 25 in the intermediate wall 7, and a force corresponding to an external force is generated. to deform the sensor chip 11. As a result of the sensor chip 11 being deformed in this way, the strain resistance 19
The resistance value increases and decreases, and a voltage signal is detected from the lead 23 in response to external force and, ultimately, external pressure.

As mentioned above, the thermal decomposition temperature of perfluoropolyether 9 is high, so perfluoropolyether 9 does not deteriorate even in a high-temperature environment. Therefore, the volume change due to temperature change is very small. Therefore, even if this semiconductor pressure sensor is used in a high temperature environment, good detection accuracy can be obtained.

As explained above, 1: Due to the semiconductor pressure sensor that can be used in a high temperature environment shown in the first embodiment (L), since perfluoropolyether 9 is used as the working fluid, the filling operation can be performed with normal handling. , wire bonding 2] and a configuration for insulating the leads 23,
This has the effect of reducing mounting constraints and significantly reducing manufacturing effort.

Further, an intermediate wall 7 is provided, and the perfluoropolyether 9
Since the amount of filling is small (0.05 CC or less), the volume change of perfluoropolyether 9 due to temperature change is extremely small. Therefore, changes in internal pressure due to changes in volume are reduced, and the load on the diaphragm and sensor chip due to changes in internal pressure is reduced, resulting in excellent measurement accuracy and durability.

Furthermore, since the intermediate wall 7 blocks heat from the outside and prevents the temperature of the sensor chip 1 from rising, measurement errors due to temperature rise of the sensor chip 11 itself are reduced, and the -layer side determination accuracy is improved. There are advantages.

For these reasons, the semiconductor pressure sensor of the first embodiment is suitable for measuring high pressure in a high temperature environment.

It works well even under harsh measurement conditions, such as detecting combustion pressure in gasoline engines. Note that contaminants under these measurement conditions (e.g., C particles, CO
2,820, etc., but of course these do not act on the sensor element 1 due to the sealed structure between the diaphragm 3 and the housing 5.

Next, a second embodiment will be explained. FIG. 3 shows a thin sectional view of the semiconductor pressure sensor.

A semiconductor pressure sensor of the second embodiment (which is an absolute pressure sensor like the first embodiment, sensor element 3),
It includes a diaphragm 33, a housing 35, an intermediate layer 37, and a working fluid 39.

Like the sensor element 1 of the first embodiment, the sensor element 31 includes a sensor chip 41 and a pedestal 43, and is attached to the inner bottom of the housing 35 with an adhesive 45. A recess is formed in the center of the lower part of the sensor chip 41, and a pressure reference chamber 47 is formed between the sensor chip 41 and the pedestal. Sensor chip 41 (connected to lead 51 for signal extraction by bonding wire 49. Lead 5)
It penetrates the upper housing 35 and projects to the outside.

In the second embodiment, the diaphragm 33 is made of a molded product made of stabilized zirconia. The metallizing layer 53 (t, made of tungsten, etc.) is intended to maintain the metallization.

The metal ring 55 is made of a material having a coefficient of linear expansion between that of the partially stabilized zirconia used for the diaphragm 33 and the intermediate wall 371 and that of the material of the housing 35. .This metal ring 5
5, the diaphragm 33, the intermediate wall 37. Strain due to temperature changes in the housing 35 is absorbed or alleviated.

The housing 35 (similar to the first embodiment, is made of iron, Kovar, various stainless steel materials, etc.).

Intermediate wall 37 (similar to the first embodiment above, it is a molded product of partially stabilized zirconia formed to cover the sensor element 1. In the second embodiment, a communication hole 57 is formed in the upper surface part.
is a multi-tiered card with a chamber C in which the sensor element 31 is located,
The two chambers are communicated with the chamber in which the diaphragm 33 is located. This intermediate wall 37 method is designed so that the filling amount of perfluoropolyether is 0.05 CC or less.

Perfluoropolyether 391 as a working fluid
Similar to the first embodiment, the two chambers C and D are communicated with each other by the intermediate wall 37.
is filled with.

In the semiconductor pressure sensor configured as described above, perfluoropolyether 39 as a working fluid moves through the communication hole 57 of the intermediate wall 37 depending on the magnitude of the external force that pushes the diaphragm 33, and the perfluoropolyether 39 moves through the communication hole 57 of the intermediate wall 37. As a result of pressing the sensor chip 41 with a force corresponding to the force, a voltage signal corresponding to the external pressure is detected from the lead 5].

According to the semiconductor pressure sensor of the second embodiment explained above (,
f. In addition to the effects of the first embodiment, the diaphragm 33 is
Since it is made of partially stabilized zirconia that has heat resistance and thermal insulation properties, it has the effect of further improving measurement accuracy and durability in high-temperature environments.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way. For example, the present invention may be applied to a structure that does not use the intermediate walls 7, 37, or a structure that is applied to a differential pressure sensor. It goes without saying that the invention can be implemented in various ways without departing from the scope of the invention.

As detailed above, since the semiconductor pressure sensor of the present invention uses perfluoropolyether as the working fluid, the filling operation can be performed with normal handling. This eliminates the need for a structure that insulates the Ohata force terminals of the element, reducing mounting constraints and significantly reducing the effort required to manufacture semiconductor pressure sensors that can be used in high-temperature environments.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a first embodiment of a semiconductor pressure sensor of the present invention, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a longitudinal cross-sectional view showing a second embodiment. 1...Sensor element 3...Diaphragm 5...Housing 7...Intermediate wall 9...Perfluoropolyether

Claims (1)

[Claims] 1. A working fluid is filled in a gap formed between a sensor element that changes an output signal according to the magnitude of an applied force and a diaphragm that receives an external force, and the diaphragm receives an external force. A semiconductor pressure sensor for transmitting force to the sensor element via the working fluid, characterized in that the working fluid is filled with perfluoropolyether.