JP3071932B2 - Semiconductor pressure sensor - Google Patents

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 capable of detecting signals generated under a static pressure and a differential pressure to detect the static pressure and the differential pressure with extremely high accuracy. Related to sensors.

[0002]

2. Description of the Related Art A semiconductor pressure sensor is known as one of sensors for detecting pressure.

This semiconductor pressure sensor utilizes the excellent elasticity of a single crystal semiconductor (for example, silicon or the like) to detect a stress responsive to a pressure difference between both ends of a thin film silicon diaphragm.

FIG. 6 is a sectional view showing an example of such a semiconductor pressure sensor.

The semiconductor pressure sensor 100 shown in FIG.
A concave portion 1 on one surface of a silicon single crystal substrate
02 is formed into a thin-walled diaphragm 103, and p-type impurities are diffused on the surface opposite to the surface on the side of the recess 102 to form differential pressure sensors (strain gauge resistors) 104 to 106 as shown in FIG. After that, these differential pressure sensors 1
An oxide film 107 is formed on the surface of the single crystal substrate 101 on which the layers 04 to 106 have been formed to cover the respective differential pressure sensors 104 to 106, and further, through a hole 108 provided through the oxide film 107, An electrode layer 109 is connected to both ends of each of the differential pressure sensors 104 to 106, and is formed.
The electrode layer 109 is fixed to a pedestal tube 112 formed in a cylindrical shape, and the electrode layer 109 is connected to an external terminal (not shown) by a wire 110 made of a gold wire or the like.

In FIG. 7, the electrode layer 109 is provided only on the right differential pressure sensors 104 to 106. However, in practice, the electrode layer 109 is provided for each of the differential pressure sensors 104 to 106. ing.

In the semiconductor pressure sensor 100 configured as described above, when the diaphragm 103 is subjected to stress by pressure, a predetermined one of the differential pressure sensors 104 to 106 formed on the surface of the diaphragm 103 is determined. The resistance value of one of the differential pressure sensors 104 to 1 is increased while the resistance value of another of the differential pressure sensors 104 to 1 is decreased while the resistance value of the other one is decreased.
The output voltage of a Wheatstone bridge circuit (not shown) constituted by the reference numeral 06 changes, and a detection signal corresponding to the change is output.

[0008]

However, in such a semiconductor pressure sensor 100, an erroneous signal called zero shift is generated even under a static pressure (a common pressure applied to both surfaces of the diaphragm).

Therefore, as a method of solving such a problem, there is a method of detecting a static pressure using a pressure sensor separate from the semiconductor pressure sensor 100 and correcting the output of the semiconductor pressure sensor 100 based on the detection result. Attempted.

However, in such a method, since two elements must be used, it is preferable to use a single type element to generate two signals from two signals by simple correction. It is desirable to do.

Therefore, as a method for satisfying such requirements, a surface of a silicon single crystal substrate 115 formed in a square plate shape as shown in FIG. 8 (a surface opposite to a surface to be joined to a cylindrical pedestal tube 116). Pressure sensors 117 to 120 provided in
Sensors (static pressure sensors) 121 to 124 for detecting distortion caused by static pressure in the same arrangement as those described above, and based on the outputs of the static pressure sensors 121 to 124, the differential pressure sensor 11
Correction of outputs of 7 to 120 is also performed.

In this case, the pedestal tube 116 has a cylindrical shape, and the silicon single crystal substrate 115 has a square plate shape to be asymmetric with respect to compressive strain. The output is increased.

However, the static pressure sensors 121 to 124 used in such a semiconductor pressure sensor need to have a differential pressure sensor 117 to
Since the static pressure sensors 121 to 124 are arranged on the same substrate as that of the static pressure sensors 4 so as to have the same arrangement positional relationship, the static pressure sensors 121 to 124 are also affected by the differential pressure distortion, and their response characteristics Is often not a unique signal, and it is necessary to perform correction on such static pressure sensors 121 to 124 based on the outputs of the differential pressure sensors 117 to 120. A relationship was needed.

In the method of correcting the signals of the differential pressure sensors 117 to 120 by the static pressure sensors 121 to 124, there is a danger of giving an extremely large error.

In view of the above circumstances, the present invention can compensate for signals generated under static pressure and differential pressure, and can perform static pressure and differential pressure on the same semiconductor substrate with extremely high accuracy and high reliability. It is an object of the present invention to provide a semiconductor pressure sensor capable of detecting the pressure.

[0016]

In order to achieve the above object, a semiconductor pressure sensor according to the present invention has a first surface and a second surface, and a single crystal in which a rectangular cavity is formed in the first surface. A square plate-shaped semiconductor substrate made of a semiconductor material, and one end thereof is joined to the first surface of the semiconductor substrate so as to surround the cavity formed in the first surface of the semiconductor substrate, and the pressure to be detected is A prismatic pedestal tube having a pressure guiding passage for introducing into the cavity, at least one vertical differential pressure sensor formed on the second surface of the semiconductor substrate opposite to the cavity, and at least one A differential pressure sensor in the parallel direction, and at least one formed at a position shifted from the diagonal line of the semiconductor substrate by a predetermined angle on the opposite side of one end of the semiconductor substrate joined to the pedestal tube on the second surface. 2
And at least two static pressure sensors.

[0017]

In the above structure, a concave portion is formed on the lower surface of the semiconductor substrate, a differential pressure sensor is disposed on the front surface side in this portion, and a square cylindrical pedestal tube is connected to the lower surface side of the semiconductor substrate. By disposing each static pressure sensor at a position inclined by a predetermined angle from each diagonal line of the semiconductor substrate in a portion of the semiconductor substrate above the pedestal tube, the static pressure and the differential pressure are accurately detected.

[0018]

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

The semiconductor pressure sensor 1 shown in FIG. 1 comprises a thin rectangular semiconductor substrate 2 and a pedestal tube 3 joined to one surface of the semiconductor substrate 2.

The semiconductor substrate 2 is formed of a rectangular substrate made of a single crystal material such as silicon, and a rectangular recess 4 is formed below the central portion of the semiconductor substrate 2 (the lower side in FIG. 1). Is formed, and an impurity such as boron is implanted by diffusion into the upper side (the upper side in FIG. 1) of the diaphragm portion 5 as shown in FIG. The differential pressure sensors 6 to 9 having a desired shape and integrally formed with piezo characteristics and the static pressure sensors 10 to 17 having a desired shape are formed.

In this case, the differential pressure sensors 6 to 9 are arranged such that the differential pressure sensors 6 and 8 are arranged in one crystal axis direction and the other differential pressure sensors 7 and 9 are arranged in a direction orthogonal to the crystal axis direction. They are arranged and bridge-connected as shown in FIG.

When the diaphragm 5 is distorted due to the pressure difference between the upper surface and the lower surface of the diaphragm 5, the resistance of each of the differential pressure sensors 6 to 9 changes according to the distortion. This is output to the outside as a differential pressure detection signal.

Each of the static pressure sensors 10 to 17 above the semiconductor substrate 2 (the upper side in FIG. 1) connects each line connecting the center of the semiconductor substrate 2 to each of the differential pressure sensors 6 to 9, It is arranged at a position inclined by, for example, 22.5 degrees from the diagonal line of the semiconductor substrate 2 with respect to the diagonal line. As shown in FIG. 3, each of the two static pressure sensors 10 to 17 is combined and bridge-connected.

When the semiconductor substrate 2 is distorted by the static pressure of the portion where the semiconductor substrate 2 is stored,
The resistance value of each of the static pressure sensors 10 to 17 changes according to this distortion, and this is output as a static pressure detection signal.

The pedestal tube 3 is formed to have the same outer diameter as the length in contact with the outer edge of the semiconductor substrate 2, and has an inner diameter considerably shorter than the diameter of the concave portion 4. The upper end (the upper end in FIG. 1) of the semiconductor substrate 2 is made of Pyrek glass or the like.
The pressure medium to be detected is guided to the concave portion 4 of the semiconductor substrate 2 by a pressure guiding passage 18 having a circular cross section formed therein.

Next, the relationship between the structure and the effect of this embodiment will be described with reference to FIGS.

First, since the pedestal tube 3 made of a different material, such as Pyrex glass, is joined to the semiconductor substrate 2 on which the diaphragm portion 4 is formed, the differential pressure applied to the diaphragm portion 5 becomes zero, When only pressure is applied,
Large distortion is transmitted from the pedestal tube 3 having a high compression ratio to the semiconductor substrate 2 having a low compression ratio. When a differential pressure is applied, the position of each of the static pressure sensors 10 to 17 is tilted by 22.5 degrees from the diagonal line from the position where the strain generated in the diaphragm acts on the piezoresistance. 10 to 17 are hardly affected by the differential pressure.

In the application of static pressure, the strain induced on the upper surface (the upper surface in FIG. 1) of the semiconductor substrate 2 immediately above the joint surface between the semiconductor substrate 2 and the pedestal tube 3 is longer than the strain induced on the diaphragm 5 by the transmission distance , Each of the static pressure sensors 10-1
7 outputs a large static pressure signal.

Thus, the static pressure sensors 10 to 17, which mainly detect static pressure, have a small error due to the differential pressure, and exhibit a unique error characteristic within the differential pressure measurement range.

On the other hand, since the rectangular concave portion 4 is formed on the lower surface of the semiconductor substrate 2 on which the differential pressure sensors 6 to 9 are formed, even if a static pressure is applied to the semiconductor substrate 2, distortion occurs. The output is almost zero with respect to the static pressure.

Then, only when a differential pressure is applied to both surfaces of the diaphragm section 5, a strain is induced on the diaphragm surface by this differential pressure, and a large differential pressure signal is output from each of the differential pressure sensors 6-9.

As a result, one set of four differential pressure sensors 6 to 9 mainly detects the differential pressure applied to the diaphragm portion 5, and another set of eight static pressure sensors 10 to 17 A signal generated only by a static pressure change applied to the semiconductor substrate 2 and the pedestal tube 3 is output.

As described above, in this embodiment, the concave portion 4 is formed on the lower surface of the semiconductor substrate 2 and the differential pressure sensors 6 to 9 are arranged on the front surface side in this portion.
A pedestal tube 3 having a rectangular cylindrical shape is connected to the lower surface side of the semiconductor substrate 2, and each of the pedestal tubes 3 is located at a position inclined by 22.5 degrees from each diagonal line of the semiconductor substrate 2 in a portion of the semiconductor substrate 2 above the pedestal tube 3. Since the pressure sensors 10 to 17 are arranged, the static pressure and the differential pressure can be detected on the same semiconductor substrate 2 with extremely high accuracy and high reliability.

In the above-described embodiment, each of the static pressure sensors 10 to 17 is arranged at a position inclined by 22.5 degrees from the diagonal line of the semiconductor substrate 2. However, as shown in FIG. The static pressure sensors 20 to 23 are provided at positions inclined by 22.5 degrees from one of the two diagonal lines, and the static pressure sensors 20 to 23 are bridge-connected as shown in FIG. The same effect as the example can be obtained.

[0035]

As described above, according to the present invention, signals generated under static pressure and differential pressure can be compensated, and the static pressure and differential pressure can be controlled on the same semiconductor substrate with very high accuracy. It can be detected with high reliability.

[Brief description of the drawings]

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

FIG. 2 is a plan view of the semiconductor pressure sensor shown in FIG.

FIG. 3 is a circuit diagram showing a connection example of each differential pressure sensor and each static pressure sensor constituting the semiconductor pressure sensor shown in FIG. 1;

FIG. 4 is a plan view showing another embodiment of the semiconductor pressure sensor according to the present invention.

5 is a circuit diagram showing a connection example of each differential pressure sensor and each static pressure sensor constituting the semiconductor pressure sensor shown in FIG. 4;

FIG. 6 is a sectional view showing an example of a conventionally known semiconductor pressure sensor.

FIG. 7 is a plan view of the semiconductor pressure sensor shown in FIG. 6;

FIG. 8 is a plan view showing an example of a semiconductor pressure sensor made to solve the problem of the semiconductor pressure sensor shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor pressure sensor 2 Semiconductor substrate 3 Pedestal pipe 4 Cavity 6-9 Differential pressure sensor 10-17 Static pressure sensor

Claims (1)

(57) [Claims] 1. A plate-shaped single-crystal semiconductor substrate having a first surface and a second surface and having a square concave portion on the first surface, and joined to the first surface so as to surround the concave portion. A square tube-shaped pedestal tube having one end to be detected, and a pressure guide path for introducing a pressure to be detected into the concave portion; and a first side of the square provided on the second surface opposite to the concave portion. A first differential pressure sensor provided in the vicinity of the central portion of the first side, and provided on the second surface on the opposite side of the concave portion, and provided in the vicinity of the central portion of a second side adjacent to the first side. Second
An angle between a straight line that is provided on the second surface on the opposite side of the one end and that connects the intersection of the two diagonal lines of the square with the diagonal line is about 22.5 degrees. A semiconductor pressure sensor comprising a certain two static pressure sensors.