JPH04326032A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To realize a higher accuracy, a simplification of construction and a lower cost by reducing limit due to a pressure medium to be detected to improve endurance and reliability for a long time. CONSTITUTION:A semiconductor chip 1 is bonded on a glass base 2 and moreover, the glass base 2 is bonded on a container 3 on which a stem 4 is fastened. A transparent silicone gel area 6 is formed on the semiconductor chip 1 after a wire bonding is performed with a gold wire 8 and then, a black silicone gel area 7 is formed on the perimeter thereof.

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, and more particularly to a semiconductor pressure sensor that can improve reliability with respect to a pressure medium.

0002

2. Description of the Related Art As a semiconductor pressure sensor, for example, one in which a strain gauge bridge is integrally formed on the surface of a single crystal silicon chip which also serves as a diaphragm by diffusion of impurities is known.

Conventionally, two types of semiconductor pressure sensors are known: a double diaphragm type and a reverse pressure type, which are used to detect various liquid pressures such as water pressure and oil pressure. In the double diaphragm method, silicone oil is filled between a semiconductor chip on which a gauge resistor is formed and a rubber or stainless steel diaphragm to seal it, and pressure is applied to the semiconductor chip through the rubber or stainless steel diaphragm. It is a method of communication. The reverse pressure method is a method in which pressure is applied from the back surface of a semiconductor chip on which a gauge resistor is formed.

0004

Problems to be solved by the above-mentioned double diaphragm type semiconductor pressure sensor will be explained. In the case of a double diaphragm type semiconductor pressure sensor using a rubber diaphragm, there are the following problems. Long-term reliability cannot be ensured because the silicone oil penetrates the rubber and leaks to the outside. External gases may penetrate the rubber diaphragm and enter the silicone oil, changing the temperature characteristics of the sensor.

[0005] In addition, 2
In the case of a heavy diaphragm type semiconductor pressure sensor, there are the following problems. Due to residual stress in the welded part of the stainless steel diaphragm and internal stress caused by the deformation of the stainless steel diaphragm due to expansion and contraction of the silicone oil due to temperature changes, there is a risk that accuracy will decrease, especially in the low pressure range.

Both the rubber diaphragm and the stainless steel diaphragm in the double diaphragm type semiconductor pressure sensor have the following problems in common. Since pressure is transmitted through a rubber diaphragm or a stainless steel diaphragm, it is affected by the characteristics of the diaphragm material and the temperature characteristics of silicone oil, so it is not easy to obtain sufficient accuracy. Due to its complex structure, it is difficult to manufacture at low cost.

On the other hand, the above-mentioned reverse pressure type semiconductor pressure sensor has the following problems. When pressure is applied, a tensile load is applied to the adhesive surface of the semiconductor chip to the support member, making it difficult to obtain sufficient durability. Since the pressure receiving area is narrow and pressure is introduced through the small pressure introduction hole, the pressure introduction hole is easily clogged with dirt. Since the pressure medium to be detected comes into direct contact with the back surface of the semiconductor chip, it cannot be used directly for pressure detection when the pressure medium to be detected is a conductive liquid such as tap water.

The present invention has been made in view of the above circumstances, and has few limitations due to the pressure medium to be detected, excellent durability and long-term reliability, high precision, and simple structure and low cost. The purpose of this invention is to provide a semiconductor pressure sensor.

[0009]

[Means for Solving the Problems] A semiconductor pressure sensor according to the present invention covers a gauge resistance surface of a semiconductor chip with a first gel region made of transparent silicone gel, and further surrounds the first gel region. It is characterized in that it is covered with a second gel region made of silicone gel mixed with a filler exhibiting light-shielding properties.

0010

[Operation] In the semiconductor pressure sensor of the present invention, the gauge resistance surface of the semiconductor chip is covered with double gel regions, and the first gel region of these double gel regions is made of transparent silicone gel. The second gel region that further covers the area is made of silicone gel mixed with a filler that exhibits light-shielding properties, so the structure is simple, water can be used as the pressure medium to be detected, and it is durable and long-term. It has excellent reliability, high precision, and can be constructed at low cost. Furthermore, if the second gel region is made of fluorosilicone gel mixed with a filler exhibiting light-blocking properties, the oil resistance, solvent resistance, gasoline resistance, etc. of the pressure-receiving surface are further improved, and a wider range of coverage can be achieved. It can correspond to the detection pressure medium.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional configuration of a semiconductor pressure sensor according to a first embodiment of the present invention. A first embodiment of the present invention shown in FIG. 1 is an absolute pressure type semiconductor pressure sensor.

The semiconductor pressure sensor shown in FIG. 1 has a semiconductor chip 1, a glass pedestal 2, a container 3, a stem 4, a sealing material 5, a transparent silicone gel region 6, a black silicone gel region 7, and a gold wire 8. .

The semiconductor chip 1 is a diaphragm type semiconductor pressure sensor chip that converts pressure into an electrical signal by utilizing, for example, the piezoresistance effect of a semiconductor diffused resistor. The glass pedestal 2 is made of, for example, borosilicate glass, and supports and fixes the semiconductor chip 1. The semiconductor chip 1 is designed to form a bridge with a strain gauge with a very high strain rate and easily respond to stress, so mechanical coupling with other parts affects detection accuracy. . Therefore, a material with a small difference in coefficient of thermal expansion from the semiconductor chip 1 is selected for the glass pedestal 2, and the semiconductor chip 1 and the glass pedestal 2 are
is hermetically sealed. For fixing the semiconductor chip 1 to the glass pedestal 2, low melting point glass is used as an adhesive to avoid distortion during bonding.

The container 3 is made of metal or the like and has an opening on the top surface. The glass pedestal 3 is airtightly fixed to the container 3 using low melting point glass or the like to prevent distortion during adhesion. The stem 4 serves as a power supply terminal and an output terminal of the semiconductor chip 1, and is hermetically fixed to the container 3 using a sealing material 5. In this state, the semiconductor chip 1 and the stem 4 are electrically connected by wire bonding using the gold wire 8, for example.

A transparent silicone gel is deposited on the gauge resistance surface of the semiconductor chip 1 to form a transparent silicone gel region 6 as a first gel region. The periphery of the transparent silicone gel region 6 in the container 3 is filled with silicone gel colored black by mixing a filler such as carbon as a filler exhibiting a light-shielding property, and the second gel region is colored black. A silicone gel region 7 is formed.

In manufacturing, first, the semiconductor chip 1 is bonded to a glass pedestal 2, and then the glass pedestal 2 is bonded to the container 3 to which the stem 4 is fixed, and wire bonding is performed with a gold wire 8. After a transparent silicone gel region 6 is formed on the semiconductor chip 1, a black silicone gel region 7 is formed around it.

In this way, an absolute pressure type semiconductor pressure sensor is constructed. When using this semiconductor pressure sensor, the pressure to be detected is applied to the opening of the container 3 by a pressure medium. This pressure causes distortion in the semiconductor chip 1 via the transparent silicone gel region 6 and the black silicone gel region 7, which is detected.

In this case, the transparent silicone gel region 6 contributes to moisture proofing, waterproofing, and protecting the electrical characteristics of the semiconductor chip, and the black silicone gel region 7 contributes to light shielding.

If the semiconductor chip 1 is covered only with the transparent silicone gel region 6 without providing the black silicone gel region 7, the properties of the transparent silicone gel will deteriorate due to light, especially ultraviolet rays, and the pressure on the semiconductor chip 1 will deteriorate. Since detection is obstructed, a problem arises in durability, but such a problem can be effectively solved by configuring as in this embodiment.

For reference, experimental water resistance data are shown below. Samples were prepared in which the same semiconductor chip as described above was covered only with transparent silicone gel, when it was covered only with black silicone gel, and when it was configured as in this example. The above sample was installed on the floor and the water resistance was compared.

As a result, in the case of using only black silicone gel, corrosion occurred in the aluminum wiring of the semiconductor chip after 100 hours, whereas in the case of using only transparent silicone gel and in the case of this example, corrosion occurred even after 1000 hours. No abnormality occurred in the sensor characteristics.

According to the semiconductor pressure sensor of the first embodiment of the present invention, the following effects can be obtained. Since the surface of the semiconductor chip 1 is treated with a transparent silicone gel region 6 to be waterproof and moisture-proof, water can be used as a pressure medium. Since the pressure receiving surface of the pressure sensor is shielded from light by the black silicone gel region 7, there is no problem with durability even if it is used in a place exposed to light. Since the actual pressure receiving area of the pressure sensor is wide, there is no risk of clogging due to adhesion of dust or the like, which would occur when the pressure medium is introduced through a narrow pipe. Since the container 3 is filled with silicone gel, impact resistance is improved, and heat resistance and cold resistance are also improved. Since the pressure to be detected is applied from the front surface of the semiconductor chip 1, the withstand pressure against the detected pressure is improved compared to a method such as a reverse pressure method in which pressure is applied from the back surface of the semiconductor chip 1 by the pressure to be detected. Since the structure is simple, it can be manufactured at low cost.

Furthermore, as an additional effect of mixing the filler into the silicone gel in the black silicone gel region 7, the coefficient of thermal expansion is reduced, the influence of thermal changes on the detection pressure is reduced, and the detection accuracy is improved. .

[0024] In addition to carbon, an inorganic pigment or the like may be used as the filler mixed in the silicone gel in the second gel region, and the color is not limited to black; Since it is sufficient to exhibit the desired light-shielding properties, a sufficient effect can be obtained even when red iron oxide, white carbon, or the like is used.

In the first embodiment described above, an absolute pressure type semiconductor pressure sensor has been described, but the present invention can also be applied to a relative pressure (differential pressure) type semiconductor pressure sensor. FIG. 2 shows a cross-sectional configuration of a semiconductor pressure sensor according to a second embodiment of the present invention. The second embodiment of the present invention shown in FIG.
The embodiment is a relative pressure type semiconductor pressure sensor.

The semiconductor pressure sensor shown in FIG. 2 differs from the structure shown in FIG. 1 in that a pressure introduction path for applying a reference pressure is provided on the back surface of the semiconductor chip 1 in order to detect relative pressure. That is, the difference between FIG. 2 and FIG. 1 is as follows.
A through hole is provided in the center of the glass pedestal 11, and a pressure introducing pipe 13 communicating with the through hole of the glass pedestal 11 is hermetically fixed to the bottom of the container 12 together with the stem 4 by a sealing material 5. The pressure introduction path is formed by the through hole of the glass pedestal 11 and the pressure introduction pipe 13.

The relative pressure type semiconductor pressure sensor configured as described above receives a reference reference pressure from the back surface of the semiconductor chip 1 through the pressure introduction path formed by the through hole of the glass pedestal 11 and the pressure introduction pipe 13. , a pressure to be detected is applied to the surface of the semiconductor chip 1 from the opening of the container 12 through the black silicone gel region 7 which is the second gel region and the transparent silicone gel region 6 which is the first gel region. By applying pressure, pressure is detected. In this case, the detected pressure detected by the semiconductor chip 1 is a relative pressure with respect to the reference pressure, that is, a differential pressure.

It goes without saying that the relative pressure type semiconductor pressure sensor according to the second embodiment can also provide the same effects as the absolute pressure type semiconductor pressure sensor according to the first embodiment. Also, in the relative pressure type semiconductor pressure sensor according to the second embodiment, an inorganic pigment or the like may be used in addition to carbon as a filler mixed into the silicone gel in the second gel region, and the color is also black. However, the material is not limited to the above, as long as it exhibits light-shielding properties capable of absorbing or reflecting ultraviolet rays, sufficient effects can be obtained even when red iron oxide, white carbon, etc. are used.

Next, a third embodiment of the present invention will be described in which the absolute pressure type semiconductor pressure sensor according to the first embodiment shown in FIG. 1 is further improved in water resistance, oil resistance, solvent resistance, and gasoline resistance. The configuration of such a semiconductor pressure sensor is shown in FIG.

The configuration shown in FIG. 3 differs from FIG. 1 in that the second gel region is made of fluorosilicone gel colored black by mixing filler such as carbon as a filler exhibiting light-shielding properties. This is the point where the black fluorosilicone gel region 21 is formed. In this case, the black fluorosilicone gel region 21 contributes to light shielding, oil resistance, solvent resistance, gasoline resistance, etc.

Experimental data regarding the water resistance of the semiconductor pressure sensor of the third embodiment are almost the same as the water resistance data of the semiconductor pressure sensor of the first embodiment described above. Also, experimental data regarding comparison of oil resistance and solvent resistance between the fluorosilicone gel used in the second gel region in this third example and the silicone gel used in the second gel region in the first example. are shown in Table 1. In Table 1, “◎
” mark indicates that there is little swelling due to oil or solvent and can be used, “○” mark indicates that there is little swelling due to oil or solvent and it can be used, and “x” mark indicates that there is little swelling due to oil or solvent and it can be used. Or, the swelling caused by the solvent is so great that it cannot be used.

[0032]

[Table 1]

Next, in order to confirm the effect of the configuration of this third embodiment, transparent silicone gel, black silicone gel, transparent fluorosilicone gel, black fluorosilicone gel, and transparent silicone gel as shown in FIG. Table 2 shows the results of coating with black fluorosilicone gel and measuring the gauge resistance and withstand voltage characteristics of the substrate before and after coating in each case.

[0034]

[Table 2]

The semiconductor pressure sensor according to the third embodiment provides the following effects. Since the surface of the semiconductor chip 1 is treated with a transparent silicone gel region 6 to be waterproof and moisture-proof, water can be used as a pressure medium. Since the pressure receiving surface of the pressure sensor is shielded from light by the black fluorosilicone gel region 21, there is no problem with durability even if it is used in a place exposed to light. Since the actual pressure receiving area of the pressure sensor is wide, there is no risk of clogging due to adhesion of dust or the like, which would occur when the pressure medium is introduced through a narrow pipe. Since the container 3 is filled with silicone gel, impact resistance is improved, and heat resistance and cold resistance are also improved. Since the pressure to be detected is applied from the front surface of the semiconductor chip 1, the withstand pressure against the detected pressure is improved compared to a method such as a reverse pressure method in which pressure is applied from the back surface of the semiconductor chip 1 by the pressure to be detected. Since the structure is simple, it can be manufactured at low cost. Since the pressure receiving surface of the pressure sensor is filled with fluorosilicone gel, it is possible to detect pressure using oil, gasoline, and various solvents as pressure media. Furthermore, as an additional effect of mixing the filler into the fluorosilicone gel in the black fluorosilicone gel region 21, the coefficient of thermal expansion is reduced, the influence of thermal changes on the detection pressure is reduced, and detection accuracy is improved.

Note that, as in the case of the first embodiment, the second
In addition to carbon, inorganic pigments, etc. may be used as the filler mixed in the silicone gel in the gel region, and the color is not limited to black; Therefore, sufficient effects can be obtained even if red iron oxide, white carbon, etc. are used.

In the third embodiment described above, an absolute pressure type semiconductor pressure sensor has been described, but the present invention can also be applied to a relative pressure type semiconductor pressure sensor. FIG. 4 shows the fourth embodiment of the present invention.
3 shows a cross-sectional configuration of a relative pressure type semiconductor pressure sensor according to an embodiment of the present invention.

The semiconductor pressure sensor shown in FIG. 4 has almost the same configuration as the semiconductor pressure sensor shown in FIG. 2, and the semiconductor pressure sensor shown in FIG. 4 differs from the semiconductor pressure sensor shown in FIG. The gel region is made into a black fluorosilicone gel region 21 composed of a fluorosilicone gel colored black by mixing a filler such as carbon as a filler exhibiting light-shielding properties. It goes without saying that the relative pressure type semiconductor pressure sensor according to the fourth embodiment can also provide the same effects as the absolute pressure type semiconductor pressure sensor according to the third embodiment.

Furthermore, the present invention can be implemented with various modifications without changing the gist thereof. For example, Figure 5
A fifth embodiment of the present invention shown in FIG. 1 is a semiconductor pressure sensor having a flat shape, in which the container 31 is made of synthetic resin and has a flat shape as a whole, and the stem 31 has a shape in which the portion protruding to the outside of the container 31 is bent. It is said that In this case, stem 31
is inserted into the mold when molding the container 31, making the sealing material 5 unnecessary. The other configurations in this fifth embodiment are almost the same as those in FIG. 1, and FIGS.
Of course, modifications such as the following are also possible.

[0040]

As described above, according to the present invention, the gauge resistance surface of a semiconductor chip is covered with a double gel region,
The first gel region of these double gel regions is made of transparent silicone gel, and the second gel region covering it is made of silicone gel mixed with a filler exhibiting light-shielding properties. It is possible to provide a semiconductor pressure sensor that is less limited by the detection pressure medium, has excellent durability and long-term reliability, is highly accurate, has a simple structure, and is inexpensive.

[Brief explanation of drawings]

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

FIG. 2 is a sectional view showing the configuration of a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing the configuration of a semiconductor pressure sensor according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing the configuration of a semiconductor pressure sensor according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view showing the configuration of a semiconductor pressure sensor according to a fifth embodiment of the present invention.

[Explanation of symbols]

1...Semiconductor chip, 2,11...Glass pedestal, 3,12,
31... Container, 4, 32... Stem, 5... Sealing material, 6... First
gel region, 7, 21...second gel region, 13...pressure introduction pipe.

Claims (2)

[Claims] 1. In a semiconductor pressure sensor, a gauge resistance surface of a semiconductor chip is covered with a first gel region made of transparent silicone gel, and a filler exhibiting light-shielding properties is mixed around the first gel region. A semiconductor pressure sensor characterized in that it is covered with a second gel region made of silicone gel. 2. The semiconductor pressure sensor according to claim 1, wherein the second gel region is a fluorosilicone gel region made of fluorosilicone gel mixed with a filler exhibiting light-shielding properties.