JPH04299231A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To enable miniaturization of a simple construction by providing a semiconductor pressure sensor itself with an excessive pressure protection mechanism. CONSTITUTION:This sensor is made up of a flat moncrystalline silicon wafer 24 and monocrystalline silicon wafers 21 and 29 having recesses 22 and 30 on the surface thereof. The monocrystalline silicon wafers 21 and 29 are joined on both sides of the flat monocrystalline silicon wafer 24 respectively being faced by the recesses 22 and 30 and holes 33 and 34 are formed in the recesses 22 and 30 to introduct a pressure.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to semiconductor pressure sensors and, more particularly, to improved overpressure protection in differential pressure transmitters.

0002

2. Description of the Related Art FIG. 4 is a block diagram of an example of a conventional semiconductor pressure sensor. In the figure, 1 is the body, and the lower part 2
and upper part 3 are formed. A first seal diaphragm 4 is provided on one side of the lower part 2, on which the measured pressure PL on the low pressure side acts, and on the other side, the measured pressure PH on the high pressure side is provided.
A second sealing diaphragm 5 is provided, on which an overpressure protection diaphragm 6 is provided. In the upper part 3 is a capacitance detection type semiconductor sensor diaphragm 7.
is provided. The semiconductor sensor diaphragm 7 is
It is composed of a moving electrode 8 and two fixed electrodes 9 and 10 formed to face both sides of the moving electrode 8. The overpressure protection diaphragm 6 in the lower part 2 and the semiconductor sensor diaphragm 7 in the upper part 3 are connected to the measured pressures PL and PH.
Passages 11 and 12 each filled with an enclosed liquid that transmits
are connected and integrated.

In the above configuration, the two measurement pressures PL and PH applied to each seal diaphragm 4 and 5 are applied to semiconductor sensor diaphragm 7 via the sealed liquid filled in each passage 11 and 12, and the moving electrode 8 Displace. Thereby, a displacement proportional to the differential pressure between the two measured pressures PL and PH is detected as a change in capacitance between the moving electrode 8 and the fixed electrodes 9 and 10, and is converted into an electrical signal.

[0004] When excessive pressure is applied to the seal diaphragm 4 or 5, an overpressure protection diaphragm 6
operates to alleviate excessive pressure changes in order to protect the semiconductor sensor diaphragm 7 from excessive pressure.

[0005]

[Problems to be Solved by the Invention] However, according to such a conventional configuration, the semiconductor sensor diaphragm 7
An overpressure protection diaphragm 6 must be provided separately in order to protect the motor from overpressure, resulting in a problem that the structure becomes large.

The present invention has been made in view of the above problems, and its object is to provide a semiconductor pressure sensor which is equipped with an overpressure protection mechanism, has a simple structure, and can be miniaturized. It's about doing.

[0007]

[Means for Solving the Problems] The present invention, which solves the above problems, consists of a flat single-crystal silicon wafer and two single-crystal silicon wafers each having a recess formed on the surface thereof. Each single-crystal silicon wafer is bonded to a single-crystal silicon wafer having a shape such that depressions face each other on both sides, and a hole for introducing pressure is formed in each depression.

[0008]

[Operation] The flat silicon wafer bends in response to the difference in pressure introduced into the pressure introduction holes of the silicon wafers on both sides. When the pressure on one side becomes large, it is pressed against the wall of the opposing silicon wafer and is protected from damage due to excessive pressure.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 are explanatory diagrams of steps for manufacturing an embodiment of a semiconductor pressure sensor according to the present invention (steps A to D are shown in FIG. 1, and steps E and F are shown in FIG. 2). be. (Step A) After forming a depression 22 with a depth of several μm on the surface of the first single crystal silicon wafer 21, the surface is oxidized to
A SiO2 film 23 having a thickness of about 0 nm is formed. Note that the depression 22 may be circular or rectangular. (Step B) A SiO2 film with a thickness of about 100 nm is formed on the surface of the first silicon wafer 21 by oxidizing the surface.
For example, second n-type single crystal silicon wafers 24 having a film 25 formed thereon are stacked and heated to about 1000° C. to bond the two silicon wafers 21 and 24 together. (Step C) The second silicon wafer 24 is mechanically or chemically scraped to a desired thickness (several μm to several tens of μm), and the surface is diffused to attach a p-type diffused resistor 26 that functions as a gauge and an electrode. A resistor 27 is formed, and then the surface is oxidized to form a SiO2 film 28 with a thickness of about 100 nm. (Step D) After forming a depression 30 with a depth of several μm in the same shape as the depression 22 of the first silicon wafer 21 on the surface of the third single crystal silicon wafer 29, the surface is oxidized to
A SiO2 film 31 with a thickness of about 100 nm is prepared, and the SiO2 film 28 formed in step C is stacked on the surface of the SiO2 film 28 so that the depressions 22 and 30 face each other, and is heated to about 1000°C and attached. match. (Step E) A portion of the third silicon wafer 29 located above the end of the diffused resistor 27 is removed by etching with, for example, hydrazine to expose the SiO2 film 31. And S
Holes are made in the iO2 films 31 and 28 to expose the ends of the diffused resistor 27, and an electrode layer 32 of, for example, Al is formed and one end thereof is connected. The other end of the electrode layer 32 is connected to a wire bonding pad (not shown). (Step F) After that, a hole 33 is made in a portion of the first silicon wafer 21 so as to communicate with the depression 22, and a hole 34 is also made in a portion of the third silicon wafer 28 so as to communicate with the depression 30. This causes the second silicon wafer 24 to function as a diaphragm.

FIG. 3 is a conceptual diagram of a semiconductor pressure sensor according to the present invention manufactured through the steps shown in FIG. In the figure, the parts indicated by arrows A to D are fixed, and pressure PL is introduced through the hole 33 formed in the first silicon wafer 21, and pressure PH is introduced through the hole 34 formed in the third silicon wafer 29. As a result, the second silicon wafer 24 flexes in response to the pressure difference therebetween and functions as a diaphragm. By detecting the amount of deflection of the second silicon wafer 24 as a change in the resistance value of a piezoresistor, for example, an output corresponding to the differential pressure can be obtained.

[0012] Here, when one pressure becomes large, the second silicon wafer 24 is pressed against the wall of the opposing silicon wafer 21 or 29, and is protected from damage due to excessive pressure.

That is, with this configuration, a diaphragm for overpressure protection as in the prior art is not required, so the overall structure can be simplified and made smaller.

[0014] In order to detect the deflection of the diaphragm, an electrode may be formed on the diaphragm portion and detected as a change in capacitance, or a beam may be formed on the diaphragm portion and detected as a change in vibration of the beam. Good too.

[0015] Furthermore, the silicon wafers may be bonded by anodic bonding or bonding using low melting point glass.

[0016]

As described above in detail, according to the present invention, the following effects can be obtained.

That is, the semiconductor pressure sensor of the present invention has the following features:
The structure is equipped with an overpressure protection mechanism,
The overall structure is simplified and can be made smaller.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a process for manufacturing an embodiment of a semiconductor pressure sensor according to the present invention.

FIG. 2 is an explanatory diagram of a process for manufacturing an embodiment of a semiconductor pressure sensor according to the present invention.

FIG. 3 is a conceptual configuration diagram of a semiconductor pressure sensor according to the present invention manufactured through the steps shown in FIG. 1;

FIG. 4 is a configuration diagram of an example of a conventional semiconductor pressure sensor.

[Explanation of symbols]

21 First single crystal silicon wafer 22, 30
Hollow 24 Second single crystal silicon wafer 29 Third single crystal silicon wafer 33, 34 Pressure introduction hole

Claims (1)

[Claims] 1. Consisting of a flat single-crystal silicon wafer and two single-crystal silicon wafers each having a depression formed on its surface, the flat single-crystal silicon wafer having depressions facing each other on both sides. A semiconductor pressure sensor characterized in that single crystal silicon wafers are bonded to each other, and a hole for introducing pressure is formed in each recess.