JPH0254137A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To measure differential pressure with high accuracy by relaxing stress at the change time of static pressure and that at the change time of temp. by providing a bonding ring zone surrounding a thin diaphragm and concentric thereto to the surface opposed to a pedestal of the thick part of a chip. CONSTITUTION:Since the bonding region of the thin diaphragm of a chip 2 and a pedestal 3 is a concentric circle and symmetry is held, the effect of the stress change caused by a change of temp. or static pressure on the stress sensor 4 provided to the diaphragm 1 is reduced and the zero shift signal due to the change of temp. or static pressure can be miniaturized. Further, the bonding area of the diaphragm 1 of the chip 2 and the pedestal 3 can be set to an area optimum to patterning on the side of the chip 2. Further, since an electrostatic adhesive method is used as the bonding method of the diaphragm 1 of the chip 1 and the pedestal 3, the chip 2 can be certainly fixed in spite of a slight bonding area. Furthermore, since electrostatic adhesion is performed between wafers, the bonding part of an individual sensor is uniformly bonded.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a semiconductor pressure sensor, and particularly has excellent zero point temperature characteristics and small two-temperature hysteresis.

The present invention relates to a semiconductor pressure sensor that can obtain a stable signal with a good S/N ratio even when outputting low sensitivity.

BACKGROUND OF THE INVENTION Conventionally known semiconductor pressure sensors use a diaphragm that responds to a pressure difference across its sides. The diaphragm consists of a chip consisting of a single crystal semiconductor substrate with a stress sensor placed on one surface of the diaphragm. And stress sensors commonly used for this purpose exhibit piezoresistive properties, whereby the resistance of the stress sensor changes with the stress experienced by the sensor as the stress within the chip changes. A circular cavity is also formed in the other surface of the chip to form a diaphragm. A cylindrical tube is then joined to the other surface of the chip so as to surround the circular cavity.

Typically, a chip consisting of a square single crystal semiconductor substrate with a circular thin diaphragm is used. this is,
This is because many of these square chips are easily obtained by cutting or slicing crystal wafers. In addition, when bonding a chip to an envelope, a pedestal with the same coefficient of thermal expansion as the chip is used, but this pedestal is also obtained by drilling a hole in the wafer, adhering it to a semiconductor (silicon) wafer, and then cutting it. Depends on what you're doing. The adhesive part connects the entire thick wall to the pedestal. Further, at the bonding interface of the thick part of the chip, the original single crystal or oxide film of the chip is uniformly broken.

However, in conventional semiconductor pressure sensors, the shape of the joint area with the pedestal is not symmetrical with the shape of the diaphragm, so when the ambient temperature of the semiconductor pressure sensor changes, the difference in material between the pedestal and the chip Thermal strain occurs in the diaphragm.

Furthermore, temperature non-uniformity due to stress itself generating heat changes the offset voltage of the sensor itself. In addition, static pressure (
When the pressure (common to both sides of the diaphragm) changes, it generates a false or spurious signal of zero shift. Because of this zero shift phenomenon, compensation of electrical signals is required in all differential pressure determinations that require high accuracy.

(Problems to be Solved by the Invention) Conventionally, therefore, a cylindrical tube shaped to match a circular thin-walled diaphragm is used as a pedestal.

Moreover, the electrostatic adhesion process used to bond the pedestal and the chip must be performed for each sensor individually, and there is a further problem in that the yield of hermetic sealing and the uniformity of bonding are reduced.

The purpose of the present invention is to reduce stress when static pressure changes +? It is an object of the present invention to provide an inexpensive and highly reliable semiconductor pressure sensor that is capable of alleviating stress when changing degrees, has a small amount of zero shift, and can perform highly sensitive and highly accurate differential pressure 4pj determination. .

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the object described in 1, the present invention uses a rectangular single-crystal semiconductor with a circular thin-walled diaphragm that responds to the pressure difference on both sides of the diaphragm. In a semiconductor pressure sensor consisting of a chip made of a substrate and a rectangular pedestal that is bonded to the chip by electrostatic adhesion at its thick part, a surface of the thick part of the chip surrounding a thin diaphragm that faces the pedestal, A joining ring is provided surrounding and concentric with the thin-walled diaphragm.

(Function) Therefore, in the semiconductor pressure sensor of the present invention, due to the reduction in the area and symmetry of the joint portion between the chip and the pedestal, changes in stress caused by changes in temperature and static pressure can be applied to the stress sensor on the thin diaphragm. This minimizes zero shift signals due to temperature and static pressure changes. Further, the pedestal can be made into a semiconductor pressure sensor in which a large number of circular holes are regularly punched in a large thick plate made of a Biolex glass wafer to form a chip having the above-mentioned bonding surface.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

1 and 2 are diagrams showing an example of the structure of a semiconductor pressure sensor according to the present invention, in which FIG. 1 is a plan view thereof, and FIG. 2 is a sectional view taken along the line A--A in FIG. 1.

In the figure, the semiconductor pressure sensor of this embodiment includes a chip 2 made of a rectangular single-crystal semiconductor (silicon, etc.) substrate having a circular thin-walled diaphragm 1 that responds to a pressure difference on both sides, and It is composed of a rectangular pedestal 3 joined at a portion 2a. Further, four stress sensors 4 are arranged on one surface of the thin diaphragm 1 around the thin diaphragm 1 to sense the stress applied to the thin diaphragm 1. This stress sensor 4 is formed by diffusion of an impurity such as boron, for example, by ion implantation into the surface of the chip 2 at an optimal location in the surface area determined by the shape of the sensor. This stress sensor 4 also exhibits piezoresistive characteristics, the resistance of which changes depending on the stress experienced by the sensor. Furthermore, a circular cavity 5 is formed in the surface of the chip 2 opposite to the surface on which the stress sensor 4 is disposed.

On the other hand, the pedestal 3 has a circular pressure channel 6 in its center, and the chip 2 on the opposite side of the surface on which the stress sensor 4 is arranged.
connected to the surface of In addition, a bonding ring 7 surrounding and concentric with the thin diaphragm 1 is provided by photolithography in the bonding region of the thick portion 2a of the chip 2 surrounding the thin diaphragm 1, which is the surface facing the pedestal 3. ing. For example, silicon other than bonding ring band 7 is
Etch the joint by 2μm to make it high.Here,
The pedestal 3 is made of Pyrex glass, for example, and the chip 2
It is bonded to the surface by electrostatic adhesion. As shown in FIG. 3, this Pyrex glass is made by forming a large number of circular holes, which will become pressure-conducting passages 6, regularly at intervals equal to the size of the chip 2 in advance in a thick plate that is approximately the same size as the wafer of the chip 2. The wafers are then bonded together by electrostatic adhesion and then diced into chips for semiconductor pressure sensors on both sides.

Note that the bonding ring band 7 is made of the same material as the single crystal semiconductor (silicon etc.) substrate or coated with an oxide film.

In the semiconductor pressure sensor configured as described above, the bonding area between the thin diaphragm 1 of the chip 2 and the pedestal 3 is concentric and symmetrical, so changes in stress due to changes in temperature and static pressure are The effect on the stress sensor 4 on the thin diaphragm 1 is reduced, thereby minimizing the zero shift signal caused by changes in temperature or static pressure. Further, the bonding area between the thin diaphragm 1 of the chip 2 and the base 3 can be optimized by patterning the chip 2 side. Furthermore, since the thin diaphragm 1 of the chip 2 and the pedestal 3 are joined together by electrostatic adhesion, which has an extremely strong adhesive strength, the chip 2 can be reliably fixed even with a small joining area. Furthermore, since electrostatic adhesion is performed between wafers, the bonding portions of individual semiconductor pressure sensors are bonded uniformly, and the bonding portions of individual semiconductor pressure sensors after dicing are uniform throughout. Moreover, the yield of hermetic sealing is also improved.

That is, to explain in more detail, since the joint area between the thin diaphragm 1 of the chip 2 and the pedestal 3 is small, thermal strain does not affect the circular thin diaphragm 1 much when the static pressure changes by 4 degrees, so zero shift occurs. quantity decreases.

In addition, thermal stress is less generated, and the stress generated due to changes in static pressure due to the difference in materials between the chip 2 and the pedestal 3 is alleviated at the joint, so zero shift characteristics can also be improved. Furthermore, it goes without saying that the area should be determined so that the strength of the bonded part due to excessive pressure can be maintained until the thin-walled diaphragm 1 is destroyed. In this case, a chain acid chain having an inner radius of 1.8 mm and an outer radius of 1.95 mm is sufficient. Such positioning is a specialty of photolithography, and as a result, there is an advantage that alignment errors during bonding will not be reflected in the misalignment between the thin diaphragm 1 and the bonding area of each sensor. Furthermore, since wafer-to-wafer bonding is possible, the assembly process can be simplified. The above-mentioned process takes advantage of the advantages of the semiconductor process, and is
L. It can contribute to lower prices.

As mentioned above, in the semiconductor pressure sensor of this example,
A joining ring band 7 having a joining step of several microns is formed on the surface of the thick wall portion 2a of the knob 2 surrounding the circular thin diaphragm 1 facing the pedestal 3, thereby reducing the joining area between the chip 2 and the pedestal 3. However, since the wafers are bonded using electrostatic adhesion, stress caused by static pressure changes and temperature changes can be alleviated, resulting in low cost, low zero shift, and uniform characteristics. It becomes possible to

Furthermore, since the zero shift characteristic, which conventionally required a difficult electric signal compensation circuit, can be achieved by several sounds, it is possible to perform differential pressure M1 determination with higher sensitivity and accuracy.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and for example, a semiconductor absolute pressure sensor may be manufactured by using a circular thin-walled diaphragm and a pedestal in a circular hole to form a vacuum chamber between the circular cavity and the pedestal. It is also possible to do this.

Further, in the above embodiment, the stress sensor is arranged around the circular thin diaphragm 1, but it goes without saying that the arrangement is not limited to this.

〔Effect of the invention〕

As explained above, according to the present invention, there is a chip made of a rectangular single-crystal semiconductor substrate having a circular thin-walled diaphragm that responds to the pressure difference applied to both sides, and a In a semiconductor pressure sensor composed of a rectangular pedestal and a rectangular pedestal joined by adhesive, a thick part of the chip surrounding a thin diaphragm has a surface facing the pedestal,
By providing a joint ring surrounding and concentric with the thin diaphragm, it is possible to alleviate stress caused by changes in static pressure and temperature, and to achieve high sensitivity and precision with less zero shift W. It is possible to provide an inexpensive and highly reliable semiconductor pressure sensor that is capable of determining the differential pressure M1.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of a semiconductor pressure sensor according to the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. It is a flowchart for explaining a process. 1... Thin diaphragm, 2... Chip, 2a...
・Thick part, 3...Pedestal, 4...Stress sensor 5・
...Circular cavity, 6...Pressure passage, 7...Joint ring zone. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) Consisting of a chip made of a rectangular single-crystal semiconductor substrate with a circular thin-walled diaphragm that responds to the pressure difference applied to both sides, and a rectangular pedestal that is bonded to this chip by electrostatic adhesion at its thick part. A semiconductor pressure sensor characterized in that a joint ring surrounding and concentric with the thin-walled diaphragm is provided on a surface of the thick-walled portion of the chip surrounding the thin-walled diaphragm that faces the pedestal. . (2) The semiconductor pressure sensor according to claim 1, wherein the bonding ring is made of the same material as the rectangular single crystal semiconductor substrate or coated with an oxide film, and the pedestal is made of Pyrex glass.