JPH10185719A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor for detecting a small pressure change. SOLUTION: A semiconductor pressure sensor is formed by incorporating a semiconductor element, where piezoresistance is formed on a diaphragm 11, into a package 7 with a pressure introduction hole 71 and detects the change in the piezoresistance according to the distortion of the diaphragm 11 due to a pressure that is introduced from the pressure introduction hole 71. The sensor has two semiconductor elements 1a and 1b and a mounting part 72 on the inner surface of the package 7. The electrode of the semiconductor elements 1a and 1b and an external terminal 4 are connected by performing the face-down bonding of the two semiconductor elements 1a and 1b from both upper and lower directions of the mounting part 72 while the surfaces of their diaphragms 11 face each other and at the same time the semiconductor elements 1a and 1b are adhered and fixed to the mounting part, a pressure from the pressure introduction hole is directly applied to the diaphragm 11 of one semiconductor element 1a, and a pressure is applied to the diaphragm 11 of the other semiconductor element 1b via an air hole 73 that is formed in the mounting part 72.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor pressure sensor having a diaphragm structure formed on a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, this type of semiconductor pressure sensor has a diaphragm structure having a diaphragm 11 by forming a piezoresistor on the front side of a silicon substrate and anisotropically etching the back side. The semiconductor element 1 formed with 12 is fixed to the package 2 having the pressure introducing hole 21 and the external terminal 4 is connected to the electrode on the semiconductor element 1 by wire bonding the wire 3. . The diaphragm 11 is distorted by the pressure introduced through the pressure introducing hole 21 and the pressure is detected by detecting the resistance value of the piezo resistor which changes according to the distortion of the diaphragm 11. If you configure a Wheatstone bridge with piezo resistance,
A change in pressure can be detected as a change in output voltage by changing the resistance balance of the piezoresistor of the Wheatstone bridge due to a change in the resistance value of the piezoresistor. In addition, 5
Is a silicone resin, and 6 is a lid of the package 2.

[0003]

However, in the above-described semiconductor pressure sensor, since only one semiconductor element 1 having the diaphragm structure 12 is incorporated in one package 2, a very small pressure change is caused. Could not be detected. In other words, there is a problem that a pressure change involving only a change in the output voltage at the error level cannot be detected.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor pressure sensor capable of detecting a small pressure change.

[0005]

According to a first aspect of the present invention, there is provided a semiconductor pressure sensor, wherein a diaphragm is formed by anisotropically etching a semiconductor substrate, and a semiconductor element having a piezoresistor formed in the diaphragm is provided with a pressure introducing hole. A semiconductor pressure sensor that detects a pressure by detecting a change in a resistance value of a piezoresistor in accordance with distortion of the diaphragm due to pressure introduced from the pressure introduction hole.
And a mounting portion protruding from the inner peripheral surface of the package, and the two semiconductor elements are face-down bonded with both diaphragm surfaces facing each other from both upper and lower directions of the mounting section, thereby forming an electrode of the semiconductor element. An external terminal is connected and the semiconductor element is tightly fixed to the mounting portion. Pressure from the pressure introduction hole is directly applied to the diaphragm of one semiconductor element, and the mounting portion is applied to the diaphragm of the other semiconductor element. The pressure is applied through the air holes formed in the fin.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a cross-sectional state of a semiconductor pressure sensor according to an example of an embodiment of the present invention. Reference numeral 7 denotes a pre-mold package having a pressure introduction hole 71 at a lower portion, and a mounting portion
2 are protruding. A semiconductor element 1 having a diaphragm structure formed by anisotropically etching a silicon substrate on each of an upper surface side and a lower surface side of the mounting portion 72.
A and 1b are closely fixed with the diaphragm surfaces forming the piezoresistors facing each other. The electrodes of the semiconductor elements 1a and 1b and the external terminals 4 are connected by face-down bonding 9 using bumps. An air hole 73 is formed in the mounting portion 72, and the portions of the diaphragm structure 12 of the semiconductor elements 1 a and 1 b are maintained at the same pressure via the air hole 73. Therefore, a change in the pressure of the outside air introduced from the pressure introducing hole 71 is equally applied to both of the semiconductor elements 1a and 1b, so that both diaphragms can be distorted. In addition, 8
Denotes a lid of the pre-mold package 7.

The diaphragm 11 of the semiconductor elements 1a and 1b
The piezoresistors 10 formed above are arranged, for example, as shown in FIG. 2, and each piezoresistor 10 is connected to form a Wheatstone bridge as shown in FIG.
When the diaphragm 11 of the semiconductor elements 1a and 1b receives pressure and generates distortion, the resistance value of the piezoresistor 10 changes and the resistance balance changes.
The pressure change can be detected by monitoring the change in the voltage between C and D when a very small current flows between them. here,
The output voltages of the semiconductor elements 1a and 1b are connected in series. The pressure change is detected by monitoring the voltage change of the sum of the output voltages of the two semiconductor elements 1a and 1b.

According to this embodiment, the two semiconductor elements 1a and 1b are connected to the external terminals 4 by face-down bonding 9 using bumps.
And the diaphragms are arranged so that equal pressure is applied to each of the diaphragms and tightly fixed, so that output voltages corresponding to the pressures of the semiconductor elements 1a and 1b are connected in series and output. By doing so, twice the output can be obtained as compared with the case of one semiconductor element 1 for the same pressure, and the sensitivity is doubled. Therefore, a small pressure change can be detected.

[0009]

As described above, according to the first aspect of the present invention, a diaphragm is formed by anisotropically etching a semiconductor substrate, and a semiconductor element having a piezoresistor formed in the diaphragm is connected to a pressure introducing hole. In a semiconductor pressure sensor that is incorporated in a package having, and detects a pressure by detecting a change in the resistance value of a piezoresistor according to the distortion of the diaphragm due to the pressure introduced from the pressure introducing hole, the semiconductor element includes: Two mounting parts are provided on the inner peripheral surface of the package, and the two semiconductor elements are face-down bonded from both the upper and lower sides of the mounting part with their diaphragm surfaces facing each other, thereby forming electrodes of the semiconductor elements. And an external terminal, and the semiconductor element is tightly fixed to the mounting portion. The pressure from the pressure introduction hole is directly applied to the diaphragm of the semiconductor element, and the pressure is applied to the diaphragm of the other semiconductor element via the air hole formed in the mounting portion. If the output voltage corresponding to the pressure of the semiconductor element is connected in series and output, twice the output can be obtained for the same pressure as compared with the case of one semiconductor element 1. Thus, a semiconductor pressure sensor capable of detecting a small pressure change can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional state of a semiconductor pressure sensor according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an upper surface state of the semiconductor element according to the above.

FIG. 3 is a circuit diagram showing a Wheatstone bridge according to the above.

FIG. 4 is a schematic diagram showing a cross-sectional state of a semiconductor pressure sensor according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a, 1b Semiconductor element 2, 7 Package 3 Wire 4 External terminal 5 Silicon resin 6, 8 Lid 9 Face down bonding 10 Piezo resistance 11 Diaphragm 12 Diaphragm structure 21, 71 Pressure introduction hole 72 Attachment part 73 Air hole

Claims (1)

[Claims] 1. A semiconductor device having a diaphragm formed by anisotropically etching a semiconductor substrate and having a piezoresistor formed in the diaphragm incorporated in a package having a pressure introducing hole. In a semiconductor pressure sensor for detecting pressure by detecting a change in the resistance value of a piezoresistor in accordance with distortion of the diaphragm due to the applied pressure, two of the semiconductor elements are provided, and a mounting portion protrudes from the inner peripheral surface of the package. And connecting the electrodes of the semiconductor element to external terminals by face-down bonding the two semiconductor elements from both upper and lower directions of the mounting part with their respective diaphragm surfaces facing each other, and attaching the semiconductor element to the mounting part. And the pressure introducing hole is provided in the diaphragm of one of the semiconductor elements. A semiconductor pressure sensor, wherein pressure is applied directly to the diaphragm of the other semiconductor element through an air hole formed in the mounting portion.