JPH10274580A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor that can heighten the output of a full scale voltage characteristic without reducing the thickness of a diaphragm. SOLUTION: A semiconductor sensor consists of a semiconductor substrate with a diaphragm 1a formed in thin-walled shape by forming a recessed part, and a plurality of piezoresistances 2 formed at the diaphragm 1a. Two semiconductor pressure sensors of such constitution are formed, and the recessed parts of two semiconductor pressure sensors are opposedly arranged to form a closed void part 7. The face side, different from the face with the closed void part 7 formed, of one diaphragm 1a is made reference pressure, and pressure is applied from the face side, different from the face with the closed void part 7 formed, of the other diaphragm 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm type semiconductor pressure sensor using a piezoresistor, and more particularly to a high output full scale voltage.

[0002]

2. Description of the Related Art A diaphragm type semiconductor pressure sensor using a piezoresistor made of a semiconductor such as silicon has advantages that it is excellent in mass productivity, that it can be miniaturized, that it is easy to perform fine processing, and that it has high detection sensitivity. It is widely used because it has good reproducibility of characteristics and high reliability.

[0003] A conventional semiconductor pressure sensor is formed on a semiconductor substrate using silicon micromachining technology. FIG.
FIG. 2 is a schematic cross-sectional view showing a semiconductor pressure sensor according to a conventional example, in which a concave portion is formed by etching a substantially central portion of one main surface of a semiconductor substrate 1 such as silicon, and a diaphragm 1a formed of a thin portion and a diaphragm 1a. Is formed.

[0006] Four piezoresistors 2 are formed on a diaphragm 1 a on two main surfaces of the semiconductor substrate 1, and wirings 3 are formed so as to be electrically connected to the four piezoresistors 2.

As an example of a method of forming the piezoresistor 2, there is a method in which low-concentration boron (B) is formed by performing ion implantation and thermal diffusion treatment. One example of a method of forming the wiring 7 is as follows. There is a method of forming by performing thermal diffusion in a boron (B) atmosphere.

A silicon oxide film 4 and a silicon nitride film 5 are formed on two main surfaces of the semiconductor substrate 1,
Contact holes (not shown) are formed in the silicon oxide film 4 and the silicon nitride film 5 at desired positions on the wiring 3, and an electrode 6 made of aluminum (Al) or the like is formed so as to fill the contact holes. 6 and wiring 3
And are electrically connected. The four piezoresistors 2 constitute a Wheatstone bridge structure by the wiring 3 and the electrode 6.

[0007] The semiconductor pressure sensor has a diaphragm 1
When a pressure is applied to the diaphragm a, a stress generated in the flexed diaphragm 1a is detected as a change in resistance value due to a piezoresistance effect of a piezoresistor 2 formed on the diaphragm 1a to detect the pressure. I have.

[0008]

However, in the semiconductor pressure sensor having the above-described structure, the full-scale voltage of the element alone is on the order of several tens mV to one hundred and several tens mV, and the full-scale voltage higher than this is higher. In order to obtain the above, it is necessary to further reduce the thickness of the diaphragm 1a, which causes a problem such as deterioration of the mechanical strength of the element itself.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor capable of increasing the output of full-scale voltage characteristics without reducing the thickness of a diaphragm. It is to provide a pressure sensor.

[0010]

According to the first aspect of the present invention,
A semiconductor pressure sensor comprising: a semiconductor substrate having a diaphragm formed in a thin shape by forming a concave portion; and a plurality of piezo resistors formed in the diaphragm, wherein the piezo resistors constitute a bridge circuit. A closed cavity is formed by arranging a concave portion of each of the two semiconductor substrates to face each other, and a surface of one of the diaphragms, which is different from the surface on which the cavity is formed, is set to a reference pressure, and the other diaphragm Wherein pressure is applied from a surface different from the surface on which the gap is formed.

According to a second aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, the two semiconductor substrates are arranged with their concave portions opposed to each other via a lead frame having an opening at a substantially center. To form a closed void portion.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIGS. 1A and 1B are schematic views showing a semiconductor pressure sensor according to an embodiment of the present invention, wherein FIG. 1A is a schematic cross-sectional view, and FIG. 1B shows a state where the semiconductor pressure sensor is arranged inside a package body 11. FIG. 3C is a schematic plan view showing a state where the semiconductor pressure sensor is mounted on the lead frame 8. The schematic cross-sectional view of the semiconductor pressure sensor in FIG. 1 is the same as that of the semiconductor pressure sensor shown in FIG. 3 as a conventional example, and therefore, the same portions are denoted by the same reference numerals and description thereof is omitted here. The semiconductor pressure sensor according to the present embodiment is obtained by bonding the semiconductor pressure sensor shown in FIG. 3 as a conventional example using a wafer bonding technique such that the surfaces of the semiconductor substrate 1 where the concave portions are formed face each other, and closes substantially at the center. The formed void 7 is formed.

Then, lead terminals 9 are formed on both sides,
The bonded substrate is inserted into the opening 8a of the lead frame 8 made of an insulating material and has an opening 8a at a substantially central portion, and is fixed with an adhesive or the like. Perform bonding.

Finally, the semiconductor pressure sensor formed as described above is arranged inside the package body 11 having the pressure introducing hole 11a. At this time, the lead terminals 9 are configured to be drawn out of the package body 11.

At this time, a surface of the one diaphragm 1a, which is different from the surface on which the closed gap 7 is formed, is set to the reference pressure, and a pressure is applied to the other diaphragm 1a.

Therefore, in this embodiment, the diaphragm 1 is operated by the pressure applied to one of the semiconductor pressure sensors.
a when the diaphragm 1a of the other semiconductor pressure sensor flexes in the opposite direction through the gap 7 closed by bonding and the output voltage from the bridge circuit formed by the piezoresistor 2 By obtaining the sum with the output voltage from the bridge circuit constituted by the piezoresistor 2, the characteristics of the full-scale voltage can be increased without reducing the thickness of the diaphragm 1a.

In this embodiment, the closed space 7 is formed by bonding the surfaces of the semiconductor substrate 1 on which the concave portions are formed. However, the present invention is not limited to this. As shown in FIG. 2, on the surface of the semiconductor substrate 1 shown in FIG. 3 where the concave portion is formed, the gap 7 closed by sandwiching the lead frame 8 having the opening 8a at the approximate center is formed. The same effect can be obtained even if it is formed.

[0018]

According to a first aspect of the present invention, there is provided a semiconductor substrate having a diaphragm formed in a thin shape by forming a concave portion, and a plurality of piezoresistors formed in the diaphragm. In a semiconductor pressure sensor comprising a bridge circuit, a closed cavity is formed by arranging concave portions of two semiconductor substrates to face each other, and a surface different from a surface on which a cavity of one of the diaphragms is formed. Side is set to the reference pressure, and pressure is applied from a surface side different from the surface on which the gap portion of the other diaphragm is formed, so that when the diaphragm is bent by the pressure applied to one semiconductor pressure sensor , The output voltage from the bridge circuit constituted by the piezoresistor, and the diagram of the other semiconductor pressure sensor through the gap closed by bonding. By obtaining the sum of the output voltage from the bridge circuit constituted by the piezoresistor when the ram is bent in the opposite direction, the characteristics of the full-scale voltage can be increased without reducing the thickness of the diaphragm. The semiconductor pressure sensor which can be provided.

According to a second aspect of the present invention, in the semiconductor pressure sensor according to the first aspect, the two semiconductor substrates are arranged so that the concave portions are opposed to each other via a lead frame having an opening at substantially the center. Since a closed gap is formed, when the diaphragm is bent by the pressure applied to one of the semiconductor pressure sensors, the output voltage from the bridge circuit formed by the piezoresistor is closed by bonding. When the diaphragm of the other semiconductor pressure sensor bends in the opposite direction through the gap, the sum of the output voltage from the bridge circuit formed by the piezoresistor is obtained, without reducing the thickness of the diaphragm. The output of the full-scale voltage characteristic can be increased.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic views showing a semiconductor pressure sensor according to an embodiment of the present invention, wherein FIG. 1A is a schematic sectional view, and FIG. 1B shows a state where the semiconductor pressure sensor is arranged inside a package body. It is a schematic sectional view, (c) is a schematic plan view showing the state where the semiconductor pressure sensor was mounted on the lead frame.

FIG. 2 is a schematic cross-sectional view showing a state where a semiconductor pressure sensor according to another embodiment of the present invention is disposed inside a package body.

FIG. 3 is a schematic sectional view showing a semiconductor pressure sensor according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 1a Diaphragm 1b Supporting part 2 Piezoresistor 3 Wiring 4 Silicon oxide film 5 Silicon nitride film 6 Electrode 7 Closed void 8 Lead frame 8a Opening 9 Lead terminal 10 Wire 11 Package body 11a Pressure introduction hole

Claims (2)

[Claims] A semiconductor substrate having a diaphragm formed in a thin shape by forming a concave portion, and a plurality of piezoresistors formed in the diaphragm;
In the semiconductor pressure sensor in which the piezoresistors constitute a bridge circuit, closed voids are formed by arranging recesses of the two semiconductor substrates to face each other,
A surface side different from the surface on which the gap portion of one diaphragm is formed is set to a reference pressure, and pressure is applied from a surface side different from the surface on which the gap portion is formed on the other diaphragm. Semiconductor pressure sensor. 2. The semiconductor device according to claim 1, wherein the two semiconductor substrates are arranged with a concave portion facing each other via a lead frame having an opening at a substantially center to form a closed void. The semiconductor pressure sensor according to claim 1, wherein