JPH078743U - Semiconductor pressure sensor - Google Patents

Abstract

(57) [Summary] [Purpose] The number of hermetic seals is reduced by eliminating the lead wire of the guard ring that protects the output terminal of the wheelstone bridge from leak current. [Structure] A pressure measuring wheel stone bridge 10 composed of four strain gauges 9 on a semiconductor substrate, and a second wheel stone bridge 2 also composed of four strain gauges 25.
6 is formed. The second wheelstone bridge 26
It is formed outside the pressure measuring wheel stone bridge 10 and outside the diaphragm of the semiconductor substrate. Both bridges 10 and 26 are connected in parallel to the power supply line 27, and the second wheelstone bridge 2
The output terminals 28a and 28b of 6 are leads 29a and 29b to guard rings 12a and 12b surrounding the output terminals 15a and 15b of the wheel stone bridge 10 for pressure measurement.
Connected by.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a semiconductor pressure sensor used for a differential pressure transmitter for detecting a pressure difference between two points which is a process variable and a pressure transmitter for measuring a pressure in a pipe.

[0002]

[Prior art]

 The differential pressure transmitter used to control various process fluids measures the flow rate of the fluid in the pipe.Therefore, this type of conventional differential pressure transmitter has barrier diaphragms installed on both sides of the detector body. By applying fluid pressure between two points, the movement of the internal sealing liquid inside the detector body due to the displacement of these diaphragms is guided to the semiconductor pressure sensor that is provided by partitioning the enclosed circuit, and the distortion of this sensor is converted into an electrical signal. It is configured to convert and take out (eg, Jikken 4-16920, etc.).

FIG. 2 is a sectional view of a detecting portion of a conventional differential pressure transmitter, FIG. 3 is a diagram showing a bridge circuit of a semiconductor pressure sensor, and FIG. 4 is a sectional view of a gauge portion. In these figures, 1 is a header cover integrally provided on the upper surface of a detector body (not shown), and 2 is a semiconductor pressure provided in an upper chamber 3 provided on the upper surface of the head cover 1. A sensor 4 is a lid for hermetically sealing the upper chamber 2, 5 is a nut member for fixing the lid 4 to the header cover 1, and 6a and 6b are enclosing circuits in which an encapsulating liquid 7 such as silicon oil is enclosed.

The semiconductor pressure sensor 2 generally uses a Si (silicon) semiconductor diaphragm. This Si diaphragm type semiconductor pressure sensor 2 acts as a piezoresistive region by impurity diffusion or ion implantation technology on the surface of a substrate (hereinafter referred to as a semiconductor substrate) 8 made of a semiconductor crystal as shown in FIGS. 2 and 3. The four strain gauges 9 are formed, and the gauges 9 are bridge-connected to form the wheel stone bridge 10 for pressure measurement, and the electrical contact wiring layer 11 and the guard ring 12a are formed by vapor deposition of Al or the like. , 12b are formed, and a central portion of the back surface of the substrate is removed by etching to form a thin portion having a thickness of about 20 μm to 50 μm, that is, a diaphragm 13, which is measured on the front and back surfaces of the diaphragm 13. The pressures Hp and Lp between the two power points are sealed in a barrier diaphragm and encapsulation circuits 6a and 6b (not shown), respectively. When it is added through the filled inner sealing liquid 7, the diaphragm 13 is displaced and the specific resistance of the gauge 9 is changed. Therefore, the pressure measuring wheel stone bridge 10 differentially outputs the output voltage V0 according to the resistance change at this time. Then, the output voltage V0 is guided to the oscillator 14, amplified by the amplifier, and then transmitted remotely.

The guard rings 12 a and 12 b are formed by vapor deposition of Al or the like in order to prevent the drift of the output voltage V 0 of the Wheelston bridge 10 due to the leak current from the strain gauge 9. The output terminals 15a and 15b are surrounded and are held at substantially the same potential as those of the output terminals 15a and 15b. The guard rings 12a and 12b are electrically insulated by the strain gauge 9 and the insulating layer 16. An applied voltage VB (for example, 5 V) is applied to the wheel stone bridge 10, and the lead wires 17 of the wheel stone bridge 10 and the lead wires 18 of the guard rings 12a and 12b are provided on the lid 4. The lead wire insertion hole 19 is penetrated and connected to the oscillator 14, and the lead wire insertion hole 19 is sealed by a hermetic seal 20. In FIG. 2, reference numeral 21 is a silicon base fixed to the inner bottom surface of the upper chamber 3.

[0006]

[Problems to be solved by the device]

 As described above, in the conventional semiconductor pressure sensor 2, the output terminals 15a, 15b of the wheel stone bridge 10 are protected from the leak current by the guard rings 12a, 12b, and the lead wires 17, 18 are provided on the lid 4. It was led out from the wire insertion hole 19 and the lead wire insertion hole 19 was sealed by a hermetic seal 20. However, in such a configuration, since one end of the lead wire 18 is connected to the guard rings 12a and 12b by wire bonding, the number of lead wires led out from the upper chamber 3 to the outside is increased, in other words, the lid 4 is connected. There is a problem that the number of lead wire insertion holes 19 and hermetic seals 20 formed is increased, and the work of sealing the lead wire insertion holes 19 is troublesome.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to eliminate a lead wire of a guard ring that protects an output terminal of a wheelstone bridge from a leak current. , To provide a semiconductor pressure sensor capable of reducing the number of hermetic seals.

[0008]

[Means for Solving the Problems]

 In order to solve the above object, the present invention is formed by connecting a diaphragm formed on one surface of a substrate made of silicon single crystal, a plurality of strain gauges diffused and formed on the diaphragm, and connecting these strain gauges. In a semiconductor pressure sensor having a pressure measuring wheel stone bridge and a guard ring provided around the output terminal of the pressure measuring wheel stone bridge, a second wheel formed by another strain gauge on the outer substrate of the diaphragm. A stone bridge is formed, and the second wheel stone bridge and the pressure measuring wheel stone bridge are connected in parallel, and the output terminal of the second wheel stone bridge is connected to the guard ring. .

[0009]

[Action]

 In the present invention, the pressure detecting wheel stone bridge and the second wheel stone bridge are connected in parallel, and the output terminal of the second wheel stone bridge is connected to the guard ring, so that the lead of the guard ring is connected. Make lines unnecessary.

[0010]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is a bridge circuit diagram showing an embodiment of a semiconductor pressure sensor according to the present invention. It should be noted that, in the drawings, the same components as those in FIGS. 2 to 4 are denoted by the same reference numerals, and the description thereof will be omitted. In this figure, in this embodiment, four strain gauges 9 are diffused and formed on a diaphragm 13 (see FIG. 2) of a substrate 8 made of a silicon single crystal, and the strain gauges 9 are connected to each other for pressure measurement. In addition to forming the wheel stone bridge 10, four strain gauges 25 are also formed outside the pressure measuring wheel stone bridge 10 by diffusion, ion implantation, etc., and these strain gauges 25 are connected to form a second strain gauge 25. A wheelstone bridge 26 is formed, the second wheelstone bridge 26 and the pressure measuring wheelstone bridge 10 are connected in parallel to the power supply line 27, and the output terminal 28a of the second wheelstone bridge 26 is 28b corresponding to leads 29a and 29b formed on the diaphragm 13 by vapor deposition or the like. Doringu 12a, is obtained by respectively connecting to 12b. The second wheel stone bridge 26 is formed simultaneously with the pressure measuring wheel stone bridge 10. The second wheelstone bridge 26 is formed on the outer peripheral surface of the upper surface of the semiconductor substrate 8 so as to be located outside the diaphragm 13. This is to prevent the strain gauge 25 from changing its resistance due to the displacement of the diaphragm 13 during pressure measurement. Other configurations are similar to those of the conventional structure shown in FIGS.

Thus, in such a configuration, the pressure measuring wheel stone bridge 10 and the second wheel stone bridge 26 are formed on the semiconductor substrate 8, and these bridges are arranged in parallel to the power supply line 27. Since the output terminals 28a and 28b of the second wheelstone bridge 26 and the guard rings 12a and 12b are electrically connected together, the lead wires 18 of the guard rings 12a and 12b in the conventional structure shown in FIG. 3 are unnecessary. Therefore, it is not necessary to form a lead wire insertion hole through which the lead wire 18 is inserted in the lid 14 or to seal the lead wire insertion hole with a hermetic seal. Therefore, the work of sealing the lead wire insertion hole is easy, and the sealing performance of the enclosed liquid 7 by the lid 4 is improved. Further, the guard rings 12a and 12b can surely prevent the leak current from flowing into the output terminals 15a and 15b of the measuring wheel stone bridge 10, and prevent the drift of the output voltage V0.

[0012]

[Effect of device]

 As described above, according to the semiconductor pressure sensor of the present invention, the pressure measuring wheel stone bridge and the second wheel stone bridge located on the outer substrate of the diaphragm are formed on the semiconductor substrate. Connected in parallel to the power supply line, surrounding each output terminal of the pressure measuring wheel stone bridge with a guard ring, and connecting each output terminal of the second wheel stone bridge to the corresponding guard ring. Therefore, it is not necessary to connect the lead wire to the guard ring, and therefore the number of hermetic seals can be reduced in the differential pressure transmitter or pressure transmitter filled with the internal sealing liquid, and the seal of the lead wire insertion hole can be reduced. The work is simple and the reliability of encapsulating liquid can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a bridge circuit of a semiconductor pressure sensor according to the present invention.

FIG. 2 is a sectional view of a detection portion of a differential pressure transmitter including a conventional semiconductor pressure sensor.

FIG. 3 is a diagram showing a bridge circuit of the sensor.

FIG. 4 is a cross-sectional view of a gauge section.

[Explanation of symbols]

 2 semiconductor pressure sensor 8 semiconductor substrate 9 strain gauge 10 pressure measuring wheel stone bridge 12a, 12b guard ring 13 diaphragm 15a, 15b output terminal 17 lead wire 18 lead wire 25 strain gauge 26 second wheel stone bridge 28a, 28b output terminal 29a, 29b lead

Claims (1)

[Scope of utility model registration request] 1. A diaphragm formed on one surface of a substrate made of a silicon single crystal, a plurality of strain gauges diffused and formed on the diaphragm, and a wheel stone for pressure measurement formed by connecting these strain gauges. In a semiconductor pressure sensor having a bridge and a guard ring provided around an output terminal of the pressure measuring wheel stone bridge, a second wheel stone bridge formed by another strain gauge is formed on the outer substrate of the diaphragm. A semiconductor pressure sensor characterized in that the second wheelstone bridge and the pressure measuring wheelstone bridge are connected in parallel, and an output terminal of the second wheelstone bridge is connected to the guard ring.