JPH11337433A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cracks in a supporting substrate due to the thermal contraction of solder and to provide a semiconductor pressure sensor with high reliability. SOLUTION: A semiconductor pressure sensor is formed by supporting and housing a semiconductor pressure sensor chip 1 with a diaphragm 11, which is formed in a thin-walled shape by the formation of a recessed part, in a package 3 via a supporting substrate with a through hole and by introducing pressure to the diaphragm 11 via the through hole. In the semiconductor pressure sensor, the supporting substrate is formed in a laminated structure by joining the first glass supporting substrate 2 to the second supporting substrate 20 formed of semiconductor material more resistant to cracks than glass. The upper surface of the first supporting substrate 2 is joined to the semiconductor pressure sensor chip 1, the lower surface of the first supporting substrate 2 is joined to the upper surface of the second supporting substrate 20, and the lower surface of the second supporting substrate 20 is joined to the package 3 by solder.

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 in which a semiconductor pressure sensor chip having a diaphragm is housed in a package via a support substrate.

[0002]

2. Description of the Related Art Generally, a semiconductor pressure sensor measures a pressure in a minute pressure region, and as shown in FIG. 6, has a diaphragm 11 formed thin by forming a concave portion in a silicon substrate. Semiconductor pressure sensor chip 1
Is joined by anodic bonding or the like to one surface of a support substrate 2 having a through hole 2a and forming a pedestal, and the other surface of the support substrate 2 is joined to a plastic package 3 in which a pressure introducing tube 31 is disposed centered. As a result, the semiconductor pressure sensor chip 1 is supported and accommodated in the concave portion of the package 3.

The support substrate 2 serves to relieve stress applied from the package 3 or the like to the semiconductor pressure sensor chip 1, and is made of glass or silicon substrate having a thermal expansion coefficient close to that of the silicon substrate forming the semiconductor pressure sensor chip 1. Is used.

The bonding between the support substrate 2 and the package 3 is performed by solder 6. In order to improve the joint with the solder 6,
A plating layer 32 made of a material which is easily eutectic bonded to the solder 6 is formed on a bonding surface of the package 3 with the support substrate 2.
A metal thin film layer 21 made of a material that can be easily eutectic-bonded to the solder 6 is formed on the bonding surface of the support substrate 2 with the package 3.

[0005] The electrode pads 13 on the surface of the semiconductor pressure sensor chip 1 and the leads 4 are connected by gold or aluminum wires 5. A plurality of piezoresistors 12 are formed on the surface of the semiconductor pressure sensor chip 1 by diffusion, and a plurality of piezoresistors 12 are connected to each other to form a Wheatstone bridge circuit. By supplying a current or the like to the Wheatstone bridge circuit from the lead 4 and detecting a change in the resistance value of the piezoresistor 12 as a change in voltage, a change in pressure transmitted through the pressure introducing pipe 31 is extracted as a change in an electrical signal. be able to.

[0006]

However, in the above-described semiconductor pressure sensor, it is necessary to perform the bonding with the solder 6 at a temperature higher than the melting point of the solder 6. At this temperature, the solder 6, the package 3, the support substrate 2, and the semiconductor pressure sensor chip 1 do not exert any stress on each other, but are at a temperature higher than the melting point (generally higher than 200 ° C.). Therefore, as the semiconductor pressure sensor cools down to the temperature at which it is used, solder 6
Since the physical characteristics of the semiconductor substrate and the support substrate 2 to which the semiconductor pressure sensor chip 1 is bonded are different, forces are exerted on each other.

In general, the thermal expansion coefficient of the solder 6 is larger than that of the semiconductor pressure sensor chip 1 and the supporting substrate 2, and the solder 6 is at a room temperature level.
And the support substrate 2 is more contracted. As the solder 6 shrinks, the stress from the solder 6 acts to compress the support substrate 2 joined to the semiconductor pressure sensor chip 1 made of a silicon substrate, and cracks such as cracks occur in the support substrate 2. Cause. If environmental stress (for example, temperature change from high temperature to low temperature or temperature change from low temperature to high temperature) is repeatedly applied during actual use, cracks grow and eventually cannot withstand a predetermined pressure,
There was a problem of destruction.

The present invention has been made in view of the above points, and an object of the present invention is to provide a highly reliable semiconductor pressure sensor that prevents a support substrate from cracking due to thermal contraction of solder. It is in.

[0009]

According to the first aspect of the present invention,
A semiconductor pressure sensor chip having a diaphragm formed in a thin shape by forming a concave portion is supported and housed in a package via a support substrate having a through hole, and pressure is introduced into the diaphragm through the through hole. In the semiconductor pressure sensor configured as described above, the support substrate has a laminated structure in which a first support substrate made of glass and a second support substrate made of a semiconductor material that is less likely to break than glass are joined. The upper surface of the support substrate is joined to the semiconductor pressure sensor chip, the lower surface of the first support substrate is joined to the upper surface of the second support substrate, and the lower surface of the second support substrate is joined to the package by soldering. It is characterized by the following.

According to a second aspect of the present invention, in the first aspect of the present invention, the first support substrate and the semiconductor pressure sensor chip are joined, and the first support substrate and the second support substrate are joined. For anodic bonding, and the two anodic bondings are performed simultaneously.

[0011]

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 sectional view of a semiconductor pressure sensor according to one embodiment of the present invention. In the semiconductor pressure sensor according to the present embodiment, as shown in FIG. 2B, a piezoresistor 12 is formed by diffusion and an electrode pad 13 is formed on the surface of a silicon single crystal substrate as shown in FIG. 2A. Then, as shown in FIG. 2C, the semiconductor pressure sensor chip 1 is manufactured by forming a concave portion by forming a concave portion by anisotropically etching the rear surface side and forming a thin diaphragm 11.

One surface (upper surface) of a support substrate 2 as a first support substrate is joined to the lower surface of the semiconductor pressure sensor chip 1. The other surface (lower surface) of the support substrate 2 and the second surface
And one surface (upper surface) of the support substrate 20 as the support substrate. That is, the semiconductor pressure sensor chip 1
Is joined to the laminated structure of the two support substrates 2 and 20. The support substrate 2 is made of glass and has a through hole 2a. The support substrate 20 is made of a material that is harder to break than the glass support substrate 2, for example, a silicon substrate.
It has a through hole 20a having substantially the same shape as the through hole 2a. 2
The two support substrates 2 and 20 are joined in an arrangement such that the through holes 2a and 20a communicate with each other. The supporting substrate 2 is shown in FIG.
By applying ultrasonic processing to the glass substrate as shown in FIG. 3A, a through hole 2a as shown in FIG. 3B is formed. As shown in FIG. 4B, the support substrate 20 is formed by forming a metal thin film layer 21 of Au or the like by sputtering on a silicon single crystal substrate as shown in FIG. As a result, as shown in FIG.
The through hole 20a is formed. The through hole 2a is connected to the diaphragm 11, and the through hole 20a is connected to the pressure introducing pipe 31.

The support substrate 20 is joined to the die 33 of the plastic package 3 in which the pressure introducing tube 31 is disposed at the center, so that the semiconductor pressure sensor chip 1 is supported and stored in the recess of the package 3. It has become.

The bonding between the support substrate 20 and the die 33 of the package 3 is performed by the solder 6. In order to improve the bonding with the solder 6, a plating layer 32 as a metal thin film made of a material that can be easily eutectic bonded with the solder 6 is formed on a bonding surface of the die 33 of the package 3 with the supporting substrate 20. Substrate 2
0 of the package 3 with the die 33 (support substrate 20
A metal thin film layer 21 made of a material that can be easily eutectically bonded to the solder 6 is formed on the lower surface of the solder 6. For example, when Au-Si solder is used as the solder 6 as a structure that can be easily soldered, the material of the metal thin film layer 21 is A
u is used. Au plating is also applied to the plating layer 32 formed on the die 33 of the package 3.

If the metal thin film layer 21 is composed of a plurality of metal films, the adhesion between the solder 6 and the support substrate 20 is improved, and the metal 6 is hardly peeled off.

The electrode pads 13 on the surface of the semiconductor pressure sensor chip 1 and the leads 4 are connected by gold or aluminum wires 5. A plurality of piezoresistors 12 are formed on the surface of the semiconductor pressure sensor chip 1 by diffusion, and a plurality of piezoresistors 12 are connected to each other to form a Wheatstone bridge circuit. By supplying a current or the like to the Wheatstone bridge circuit from the lead 4 and detecting a change in the resistance value of the piezoresistor 12 as a change in voltage, the pressure change transmitted to the diaphragm 11 via the pressure introducing pipe 31 and the through holes 20a and 2a. Can be extracted as a change in an electrical signal.

According to the present embodiment, even when the solder 6 is thermally contracted due to a temperature change, the support substrate 20 made of a material that is harder to break than glass is interposed between the solder 6 and the glass support substrate 2. , The support substrate 20 becomes a buffer layer,
The thermal stress from the solder 6 is absorbed by the support substrate 20 and becomes difficult to be transmitted to the support substrate 2, so that the support substrate 2 can be prevented from cracking such as cracking. Therefore, even when environmental stress (for example, a temperature change from a high temperature to a low temperature or a temperature change from a low temperature to a high temperature) is repeatedly applied during actual use, it is possible to prevent the support substrate 2 from being broken due to crack growth.

FIG. 5 is a sectional view showing a semiconductor pressure sensor chip and a supporting substrate of a semiconductor pressure sensor according to the present invention.
It shows a bonding method with 0. The bonding between the semiconductor pressure sensor chip 1 and the supporting substrate 2 and the bonding between the supporting substrate 2 and the supporting substrate 20 are performed by simultaneously performing anodic bonding. In other words, as shown in FIG. 5A, the semiconductor pressure sensor chip 1, the support substrate 2, and the support substrate 20 manufactured by the method described with reference to FIGS. By applying a bias in an atmosphere of 400 ° C. and performing anodic bonding, the semiconductor pressure sensor chip 1 and the two support substrates 2 and 20 can be bonded together as shown in FIG. 5B. You can.

By using such a joining method, the number of steps can be minimized.

[0020]

As described above, according to the first aspect of the present invention, the semiconductor pressure sensor chip having the diaphragm formed thin by forming the concave portion is connected to the semiconductor pressure sensor chip via the supporting substrate having the through hole. , Stored in the package,
In a semiconductor pressure sensor in which pressure is introduced into the diaphragm through the through hole, the support substrate is made of a first support substrate made of glass and a second support substrate made of a semiconductor material that is less likely to break than glass. A first support substrate is bonded to the semiconductor pressure sensor chip, a lower surface of the first support substrate is bonded to an upper surface of the second support substrate, and a second support substrate is formed. Is bonded to the package by solder, so that even if the solder is thermally contracted due to a temperature change, the second material made of a material that is less likely to break than glass between the solder and the first support substrate made of glass. The support substrate is interposed, the second support substrate serves as a buffer layer, and thermal stress from the solder is absorbed and hardly transmitted to the first support substrate, cracks such as cracks can be prevented, and high reliability is achieved. Conductor pressure sensors could be provided.

According to the second aspect of the present invention, in the first aspect of the present invention, the first support substrate and the semiconductor pressure sensor chip are joined together, and the first support substrate and the second support substrate are connected to each other. Since the anodic bonding is performed at the same time as the anodic bonding, the increase in the number of steps can be minimized.

[Brief description of the drawings]

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

FIG. 2 is a process chart showing a method for manufacturing the semiconductor pressure sensor chip according to the above.

FIG. 3 is a process chart showing a method for manufacturing a first support substrate according to the semiconductor pressure sensor of FIG. 1;

FIG. 4 is a process chart showing a method for manufacturing a second support substrate according to the semiconductor pressure sensor of FIG. 1;

FIG. 5 is a cross-sectional view showing a method of joining a semiconductor pressure sensor chip and two support substrates according to the semiconductor pressure sensor of FIG. 1;

FIG. 6 is a sectional view of a semiconductor pressure sensor according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor pressure sensor chip 2, 20 Support substrate 2a, 20a Through-hole 3 Package 4 Lead 5 Wire 6 Solder 11 Diaphragm 12 Piezoresistance 13 Electrode pad 21 Metal thin film layer 31 Pressure introduction pipe 32 Plating layer 33 Package die

Claims (2)

[Claims] 1. A semiconductor pressure sensor chip having a thin-walled diaphragm formed by forming a recess is supported and housed in a package via a support substrate having a through-hole, and the diaphragm is inserted through the through-hole. In a semiconductor pressure sensor in which pressure is introduced into a semiconductor device, the support substrate is formed by joining a first support substrate made of glass and a second support substrate made of a semiconductor material that is less likely to break than glass. The upper surface of the first support substrate is joined to the semiconductor pressure sensor chip, the lower surface of the first support substrate is joined to the upper surface of the second support substrate, and the lower surface of the second support substrate is joined to the package by soldering. A semiconductor pressure sensor characterized in that: 2. The anodic bonding between the first supporting substrate and the semiconductor pressure sensor chip and the anodic bonding between the first supporting substrate and the second supporting substrate, and the two anodic bondings are performed simultaneously. The semiconductor pressure sensor according to claim 1, wherein: