JPH0688761A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To contrive high accuracy of pressure measurement and prevent a sensor from breakage due to excessive pressure. CONSTITUTION:The title is provided with a semiconductor board 12 which has first and second faces 13 and 14 with a specified opening section 15 thereon and a pressure-transmitting passage 19 of which one end face is bonded to the first face 13 of the board 12 in a manner to cover the opening 15 and passes through the opening 15. A whole body consists of a base tube 11 made of a material different from that of the board 12 and a plurality of strain sensors 17 and 18 which are formed around peripheral section 16 of the opening 15 on the second face of the board 12.

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 for detecting pressure, and more particularly to a semiconductor pressure sensor used for pressure measurement under high pressure.

[0002]

2. Description of the Related Art Various types of sensors for detecting pressure are known, but semiconductor pressure sensors are often used in differential pressure transmitters and the like. A semiconductor pressure sensor forms a thin film diaphragm on a single crystal semiconductor (for example, silicon), and uses the excellent elasticity of the thin film diaphragm to detect the stress according to the pressure difference applied to both sides of the diaphragm. is there. FIG. 2 shows a configuration example of a semiconductor pressure sensor conventionally used in a differential pressure transmitter.
It is shown in (a) and (b).

In the semiconductor pressure sensor shown in the figure, a circular cavity 2 is formed on one surface of a single crystal semiconductor sensor chip 1, and a pedestal tube 3 is bonded to the single crystal semiconductor sensor chip 1 so as to cover the circular cavity 2. Has been done. The pedestal tube 3 is formed with a pressure guiding path 4 for introducing pressure into the circular cavity 2.

In the single crystal semiconductor sensor chip 1, the thinned area by the circular cavity 2 is the thin film diaphragm 5.
Are configured. The thin film diaphragm 5 has a pair of radial strain sensors 6a and 6b and a pair of tangential strain sensors 7a and 7a on the surface opposite to the circular cavity forming surface.
7b is built in. These sensors 6a, 6b,
Reference numerals 7a and 7b are differential pressure sensors for detecting a differential pressure applied to both surfaces of the thin film diaphragm 5. The differential pressure sensor and the static pressure sensor are stress sensors having piezoresistive characteristics, and the resistance of the sensor changes according to the stress applied to the sensor when the stress inside the chip changes. These differential pressure sensors are connected to each other so as to form a bridge circuit, and output a signal indicating the differential pressure applied to the thin film diaphragm 5.

Further, a plurality of pairs of static pressure sensors 8a, 8b, 9a, 9b for detecting strain generated under static pressure are provided on the same substrate as the differential pressure sensor in the same arrangement. The term “under static pressure” means a state in which the same pressure is applied to both surfaces of the diaphragm and the differential pressure is zero. Like the differential pressure sensor, this static pressure sensor is also a stress sensor and is bridge-connected to each other.

In the semiconductor pressure sensor configured as described above, the differential pressure sensor outputs a differential pressure detection signal in response to the strain induced in the thin film diaphragm 5. However, this differential pressure sensor is also sensitive to the strain generated in the thin film diaphragm 5 during static pressure. Therefore, the differential pressure detection signal is corrected by the signal of the static pressure sensor which is sensitive only to the strain generated in the thin film diaphragm 5 during static pressure.

By the way, the semiconductor pressure sensor described above can be used not only for differential pressure measurement but also for general pressure measurement. By placing the semiconductor pressure sensor in the pressure measuring atmosphere, the same conditions as under the above static pressure will be obtained.
The pressure can be measured from the output signals of a, 8b, 9a and 9b.

However, in such a pressure sensor using a diaphragm, the stress field appearing in the diaphragm due to the applied pressure may not generally generate a unique signal. In addition, if excessive pressure outside the rating is applied,
The thin film diaphragm may be damaged.

[0009]

As described above, in the conventional semiconductor pressure sensor, it is difficult to obtain a reproducible linear signal, and there is a risk that the sensor may be damaged by excessive pressure. was there.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor pressure sensor capable of preventing damage to the sensor due to excessive pressure and capable of realizing highly accurate pressure measurement. .

[0011]

In order to achieve the above object, a semiconductor pressure sensor of the present invention has first and second surfaces, and a predetermined penetrating from the first surface to the second surface. A semiconductor substrate in which a shaped opening is formed, one end surface of which is joined to the first surface of the semiconductor substrate so as to cover the opening, and which has a pressure guiding path leading to the opening, Includes a pedestal tube made of a different material, and a plurality of strain sensors formed on the second surface of the semiconductor substrate in the vicinity of the peripheral edge of the opening.

[0012]

In the semiconductor pressure sensor of the present invention, when the pressure to be measured is applied to the pedestal tube and the semiconductor substrate, the pedestal tube and the semiconductor substrate are dissimilar to each other due to the difference in compressibility due to different materials. Occurs. The strain generated at the joint surface is transmitted to the strain sensor formed on the sensor formation surface side of the semiconductor substrate, and the strain sensor outputs a pressure signal according to the strain stress to perform pressure measurement.

[0013]

EXAMPLES Examples of the present invention will be described below.

1A and 1B show the structure of a semiconductor pressure sensor according to an embodiment of the present invention. FIG. 1A is a plan view and FIG. 1B is a plan view. A sectional view taken along line A-A is shown. The semiconductor pressure sensor according to the present embodiment includes a sensor chip 10 serving as a pressure detecting portion and a square pedestal tube 11 to which the sensor chip 10 is attached.

The sensor chip 10 is composed of a semiconductor substrate 12 made of a single crystal semiconductor material such as silicon and having a rectangular shape as a whole. The semiconductor substrate 12 has a first surface 1
3 and the second surface 14, and a square opening 15 penetrating from the first surface 13 to the second surface 14 is formed in the central portion by anisotropic etching.

The opening 15 has a trapezoidal vertical cross-section with the opening on the first surface side being the lower bottom and the opening on the second surface side being the upper bottom. That is, the opening 15 has the first surface 1
It has a truncated cone shape whose diameter continuously decreases from 3 to the second surface 14.

Since the opening 15 of the semiconductor substrate 12 has the above-mentioned truncated cone shape, the peripheral portion 16 of the opening 15 on the second surface 14 is larger than the peripheral portion 16 of the opening on the first surface 13. It has a shape that protrudes inward.

First peripheral strain sensors 17a and 17b for detecting strains in the peripheral portion 16 in a direction parallel to the chip surface of the sensor chip 10 and second strain sensors for detecting vertical strains in the sensor chip 10. Sensors 18a and 18b are built in.

The first strain sensors 17a and 17b are respectively located on the vertical bisectors of the two opposite sides of the sensor chip 10. In addition, the second strain sensors 18a and 18b
Are located on the other perpendicular two bisectors of the sensor chip 10.

The strain sensors are integrally formed on the surface of the sensor chip by implanting impurities (for example, boron) into the sensor formation region on the second surface of the semiconductor substrate 12 by diffusion or the like. The strain sensor thus formed has a piezoresistive characteristic, and its resistance value changes according to the magnitude of strain received by the strain sensor. The shape of the strain sensor is determined according to the shape of the sensor chip 10.

The square pedestal tube 11 is made of, for example, Pyrex glass and has an overall shape of a quadrangular prism. A pressure guiding path 19 having a circular cross section and having a diameter smaller than one side of the opening 15 is formed in the central portion of the rectangular pedestal tube 11. The center of the pressure guiding path 19 and the opening 1 of the semiconductor substrate 12
The one end surface 21 of the rectangular pedestal tube 11 is joined to the first surface 13 of the semiconductor substrate 12 so as to coincide with No. 5. Since the diameter of the pressure guiding path 19 is smaller than the length of one side of the opening 15, the central portion of the one end surface 21 of the rectangular pedestal tube 11 is exposed.

In the semiconductor pressure sensor of the present embodiment constructed as described above, when pressure is applied to the sensor chip 10 and the rectangular pedestal tube 11, the largest pressure is generated near the midpoint of each side of the rectangular pedestal tube 11. A compressive force is applied, causing the largest distortion near each of the midpoints and causing deformation. Due to the deformation of the rectangular pedestal tube 11, distortion occurs in the joint surface between the rectangular pedestal tube 11 and the sensor chip 10, and the rectangular sensor chip 10 causes particularly large distortion in the vicinity of the perpendicular bisector of each side. Become.

That is, since the pedestal tube 11 has a rectangular shape and the pressure guiding path 19 having a circular cross section is formed in the center thereof, a large compressive strain due to pressure is generated in the vicinity of the vertical bisector of each side. Moreover, the pedestal tube 11 has a sensor chip 1 of a different material.
Sensor chip 1 with a low compression ratio because 0 is bonded
A large strain due to the pedestal tube 11 is easily transmitted to 0. Therefore, the deformation generated near the midpoint of each side of the rectangular pedestal tube 11 according to the applied pressure is efficiently transmitted as a large strain near the vertical bisector of each side of the sensor chip 10.

Near the vertical bisector of each side of the sensor chip, the first and second strain sensors 17a, 17b, 18a,
Since 18b is arranged, the strain generated corresponding to the pressure to be detected can be detected with the highest sensitivity.

Further, since the central portion of the semiconductor substrate 12 has a large opening, even if an excessive pressure is applied, since there is no diaphragm that receives the pressure, the possibility that the sensor chip 10 will be damaged is extremely low. .

As described above, according to the present embodiment, the opening 15 is provided in the center of the semiconductor substrate 12, and the first surface 13 of the semiconductor substrate 12 is covered with the opening 15 so as to have a circular cross section. Since the square pedestal tube 11 having the passage 19 is joined and the first and second strain sensors 17a, 17b, 18a, 18b are provided near the vertical bisector of each side of the semiconductor substrate 12,
The pressure can be detected extremely accurately, and the sensor can be prevented from being damaged by excessive pressure.

The shapes of the semiconductor substrate and the pedestal tube are not limited to those in the above-mentioned embodiments. For example, it is possible to replace the shape of the semiconductor substrate with a quadrangular shape, form a circular opening in the central part thereof, and make the pedestal tube joined to this a cylindrical shape. Alternatively, the shape of the semiconductor substrate may be circular, a circular hole may be formed in the center thereof, and the pedestal tube joined to this may be replaced with a cylindrical shape.

Further, in the above-described embodiment, the shape of the opening 15 is a truncated cone, but it may be a cylindrical shape whose diameter does not change or a shape whose diameter changes stepwise. it can. Furthermore, the size relation between the diameter of the opening of the sensor chip and the diameter of the pressure guiding path of the pedestal tube is not limited to the above embodiment.

Further, even when the compressibility of the pedestal tube is smaller than that of the sensor chip, it is possible to generate a strain corresponding to the pressure on the joint surface between the two. Therefore, it is possible to replace it with one set in such a relationship of the compression ratio. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0030]

As described above in detail, according to the present invention, a highly reliable semiconductor pressure sensor capable of detecting pressure with extremely high accuracy and preventing destruction of the sensor due to excessive pressure is provided. it can.

[Brief description of drawings]

FIG. 1 is a view showing a plane and a cross section of a semiconductor pressure sensor according to an embodiment of the present invention, respectively.

FIG. 2 is a diagram showing a plane and a cross section of a conventional semiconductor pressure sensor, respectively.

[Explanation of symbols]

10 ... Sensor chip, 11 ... Pedestal tube, 12 ... Semiconductor substrate, 13 ... 1st surface, 14 ... 2nd surface, 15 ... Opening part,
17a, 17b ... 1st distortion sensor, 18a, 18b ...
Second strain sensor, 19 ... Pressure guiding path.

Claims (1)

[Claims] 1. A semiconductor substrate having first and second surfaces, wherein an opening having a predetermined shape is formed so as to penetrate from the first surface to the second surface, and the first of the semiconductor substrates. A pedestal tube having one end surface joined to the surface so as to cover the opening and having a pressure guiding path leading to the opening, and a pedestal tube made of a material different from that of the semiconductor substrate; and a second surface of the semiconductor substrate. A semiconductor pressure sensor, comprising: a plurality of strain sensors formed in the vicinity of the periphery of the opening.