JPH0744992Y2 - Pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a pressure sensor having improved corrosion resistance.

[Conventional technology]

Conventionally, as a semiconductor pressure sensor, for example, JP-A-60-1
This is disclosed in Japanese Laid-Open Patent Publication No. 00026 and Japanese Utility Model Laid-Open No. 61-87338. Among them, in the case of the former Japanese Laid-Open Patent Publication No. 60-100026, a common semiconductor substrate has a diaphragm portion and four piezoresistors, respectively. Two sets of identical pressure detectors consisting of element groups are provided, and one of the pressure detectors is formed to apply the pressure on the test side, and the output of each bridge circuit formed by each piezoresistive element group. Is formed so as to take a difference between the two, and an error due to residual distortion or the like is removed.

Further, in the latter case of Japanese Utility Model Laid-Open No. 61-87338, an opening is provided at the center of the stem, a pressure introducing pipe is provided below the opening, and the atmosphere is provided at a position away from the opening. An opening is provided, a diaphragm for detecting the differential pressure between the pressure in the pressure introducing pipe and the atmospheric pressure is provided in the center, a semiconductor chip is fixed to the atmospheric opening, and this semiconductor chip is covered with a lid. is there.

[Problems to be solved by the device]

Since the conventional semiconductor pressure sensor is configured as described above, in general, although the both sides of the semiconductor chip come into contact with the pressure medium, Al is often used as the electrode, and the wiring portion is also used. Al is often used.

Therefore, it is easily corroded. To prevent this corrosion, Si
Attempts have also been made to fill the surface of pressure sensors with gel.

However, it is difficult to apply the same amount to the two diaphragms in a pressure sensor whose surface is filled with such Si gel, which causes an imbalance in the amount of Si gel on the two diaphragms. The vibration resistance of the pressure sensor will be deteriorated.

As a result, the application of Si gel is inevitably stopped, and the Al electrodes and Al wirings are left exposed, and as described above, there is a problem that these corrosions cannot be avoided.

The present invention has been made to solve the above problems, and an object thereof is to obtain a pressure sensor capable of improving the corrosion resistance of electrodes and wiring portions.

[Means for Solving the Problems]

A pressure sensor according to the present invention is provided in a semiconductor chip so as to be a partition wall of first and second pressure chambers and a partition wall of third and fourth pressure chambers, respectively, and has a same shape and a same electrical characteristic. Then, the second diaphragm and the first and second bridge circuits formed by bridge-connecting the piezoresistive element on the first and second diaphragms with the wiring portion made of semiconductor are connected to the wiring portion. Therefore, a gold electrode provided on the semiconductor chip and a gold wire connected between the gold electrode and the terminal are provided.

[Action]

In this invention, since the wiring portion for forming the bridge circuit by the piezoresistive element is a semiconductor and is connected to the terminal through the metal electrode and the metal wire,
When the pressure medium touches this, it does not corrode, improving the corrosion resistance.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 2 is a sectional view of one embodiment thereof, FIG. 2 is a sectional view taken in a direction perpendicular to FIG. 1, and FIG. 3 is a plan view of a portion of one semiconductor chip.

In FIGS. 1 to 3, 1 is a pressure sensor, 2,
Reference numeral 3 is a case of the pressure sensor 1, and the cases 2 and 3 form first to fourth pressure chambers 21 to 24.

The first and second pressure chambers 21 are provided on the mating surfaces of the case 2 and the case 3.
The semiconductor chip 4 having the diaphragm 4a is provided so as to form partition walls 22 and 22.

Similarly, the semiconductor chip 5 having the diaphragm 5a is provided so as to serve as the partition walls of the third and fourth pressure chambers 23 and 24.

These semiconductor chips 4 and 5 are provided on the substrate 6.
In this way, the diaphragm 4a is arranged so as to face the first pressure chamber 21 and the second pressure chamber 22, and the diaphragm 5a is arranged so as to face the third and fourth pressure chambers 23 and 24.

The semiconductor chips 4 and 5 have the same structure, and FIG. 3 is a plan view showing the semiconductor chip 4 as a representative. This third
As is clear from the figure, the diaphragm of the semiconductor chip 4
Four piezoresistive elements 40 are provided on 4a. The piezoresistive elements 40 are bridge-connected by a wiring section 41 made of a semiconductor (diffusion layer) so as to form a bridge circuit, and are used for strain detection. A bridge circuit is configured.

These wiring portions 41 are connected to the gold electrodes 42 provided on the semiconductor chip 4. The gold electrode 42 is connected to the terminal 7 via the gold wire 8.

Reference numerals 25 and 26 in FIG. 2 are pressure guiding tube portions. The pressure guiding pipe portion 25 communicates with the first pressure chamber 21 and the fourth pressure chamber 24, and the pressure guiding pipe portion 26 communicates with the second pressure chamber 22 and the third pressure chamber 23.

FIG. 4 is an electric circuit diagram of the control unit of the pressure sensor 1. In FIG. 4, 101 and 102 are diaphragms 4a,
Distortion detecting bridge circuits composed of four piezoresistive elements provided in each of 5a, 103 and 104 are first and second operation circuits which receive outputs of the first bridge circuit 101 and the second bridge circuit 102, respectively. A differential amplifier circuit 105 is a third differential amplifier circuit that operates by receiving the outputs of the first differential amplifier circuit 103 and the second differential amplifier circuit 104, and 106 is a third differential amplifier circuit 105. A waveform shaping circuit that operates by receiving an output is a power supply circuit for the first bridge circuit 101 and the second bridge circuit 102.

Next, the operation will be described. Now the impulse piping 25 and the impulse piping
If a pressure difference is generated between the pressure guiding tube portions 25 and the pressure guiding tube portion 25 has a higher pressure than the pressure guiding tube portion 26, the diaphragm 4a has the second pressure.
Of the diaphragm 5a is curved toward the pressure chamber 22 side of the third pressure chamber.
Bend to side 23.

Here, the signal output of the bridge circuit 101 when the diaphragm 4a bends to the second pressure chamber 22 side is + V _B, and the signal output of the bridge circuit 102 when the diaphragm 5a bends to the third pressure chamber 23 side. the When -V _B, each signal from the first differential amplifier circuit 103 through the second differential amplifier circuit 104 having the same gain output + V _B, the -V _B. However, V _B = β · v _b .

Therefore, the output of the third differential amplifier circuit 105, which operates by receiving the signal outputs of the first differential amplifier circuit 103 and the second differential amplifier circuit 104, is 2V _B.

Here, when the pressure in the pressure guiding tube portion 26 becomes larger than that in the pressure guiding tube portion 25, the first mode in the completely opposite mode to that described above is obtained.
The outputs of the first and second bridge circuits 101 and 102 are 2 V _B , but the output of the third differential amplifier circuit 105 is unchanged.

Therefore, the output of the pressure sensor 1 due to the generation of the differential pressure between the pressure guiding tube portion 25 and the pressure guiding tube portion 26 is always a value twice as large as that of one diaphragm.

Next, the case where an external force other than pressure is applied will be described.
Now, when the pressure sensor 1 is vibrated, the diaphragm
When vibrating in the non-movable direction of 4a, 5a, the diaphragms 4a, 5a naturally do not respond, so no output is produced.

However, when the pressure sensor 1 is vibrated in the movable direction of the diaphragms 4a and 5a, the diaphragm 4a and the diaphragm 5a are distorted in the same amount and in the same direction at the same time. Therefore, when the output V _B to the first bridge circuit 101 has occurred, the output V _B is generated in the second bridge circuit 102.

As described above, the outputs of the first and second bridge circuits 101 and 102 are amplified to V _B by the first and second differential amplifier circuits 103 and 104 with a predetermined amplification factor, and then the third differential amplifier circuit. Input to 105.

However, the same value V _B is applied to both the (+) terminal and the (−) terminal of the third differential amplifier circuit 105 at the same time.
The differential amplifier circuit 105 does not output. Therefore, there is no output from the pressure sensor 1.

Here, if the output of the first bridge circuit 101 and the output of the second bridge circuit 102 are completely equal, it is as described above, but if equality is lost even a little, the third differential amplifier circuit 105. Is output according to the vibration, and the pressure sensor 1 is also output.

Therefore, it is essential to complete the equality of the output of the first bridge circuit 101 and the output of the second bridge circuit 102.
Therefore, the diaphragm 4a and the diaphragm 5a must have the same shape and electrical characteristics.

By the way, in the semiconductor chips 4 and 5 that operate as described above, the wiring portion 41 of the piezoresistive element provided on the diaphragms 4a and 5a that comes into contact with the pressure medium is formed of a semiconductor, and the gold electrode 42 and the gold wire 8 are both Since it has corrosion resistance, it has sufficient corrosion resistance even if the pressure medium comes into contact with them.

[Effect of device]

As described above, according to the present invention, the two diaphragms for detecting the differential pressure between the first and second pressure chambers and the third and fourth pressure chambers formed in the case have the same shape and the same characteristics. The wiring part that forms a bridge circuit by connecting the piezoresistive element provided on the lever diaphragm is made into a semiconductor,
Since the electrode and the wire for connecting the wiring portion to the terminal are the gold electrode and the gold wire, respectively, there is an effect that they do not corrode even if they are touched by the pressure medium and have sufficient corrosion resistance.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a pressure sensor according to an embodiment of the present invention, FIG. 2 is a sectional view taken in the direction perpendicular to FIG. 1 of the same embodiment, and FIG. 3 is one semiconductor chip in the same embodiment. FIG. 4 is a plan view of the portion of FIG. 4, and FIG. 4 is an electric circuit diagram of the control unit in the above embodiment. 1 ... Pressure sensor, 2, 3 ... Case, 4,5 ... Semiconductor chip, 4a, 5a ... Diaphragm, 7 ... Terminal, 8 ...
… Gold wire, 21 …… first pressure chamber, 22 …… second pressure chamber, 23 …… third pressure chamber, 24 …… fourth pressure chamber, 25 ……
Impulse tube part, 40 ... Piezoresistive element, 41 ... Semiconductor, 42 ...
... gold electrode, 101 ... first bridge circuit, 102 ... second bridge circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. A first and a fourth pressure chamber communicating with a first pressure guiding pipe portion formed in a case, and a second and a third pressure chamber communicating with a second pressure guiding pipe portion formed in the case. The pressure chamber, the partition wall of the first pressure chamber and the partition wall of the second pressure chamber, and the partition wall of the third and fourth pressure chambers are arranged on the semiconductor chip to have the same shape and the same electrical characteristics. When the first and second diaphragms have and the first and second diaphragms formed on the first and second diaphragms respond to the differential pressure generated in the first and second pressure guiding tube portions, Piezoresistive elements are connected in the semiconductor wiring section in order to output signals of the same value and opposite phases.
A pressure sensor comprising a second bridge circuit, a gold electrode provided on each of the semiconductor chips and connected to the wiring portion, and a gold wire connected between the gold electrode and the terminal.