JPH0750006B2 - Semiconductor pressure sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor used for detecting intake air pressure, atmospheric pressure or exhaust pressure of an internal combustion engine such as an automobile.

2. Description of the Related Art In recent years, with the tightening of exhaust gas regulations for automobiles and the like, it is necessary to control engine engines for automobiles so that the best combustion state can always be obtained regardless of the operating state. Therefore, as a part of this, a pressure converter is used to detect the intake pressure of the engine and convert it into an electrical signal,
This signal can be used to electronically control the amount of fuel supplied, to control the ignition timing to maintain the combustion condition of the engine in an optimal state, or to detect changes in atmospheric pressure and perform altitude correction. It has been adopted.

By the way, a pressure transducer used for such an automobile is required to have excellent earthquake resistance and the like, and a semiconductor strain gauge type pressure sensor has come to be widely adopted as a pressure transducer that meets the demand. Along with this, various improved pressure sensors have been proposed.

Hereinafter, an example of a chip configuration of a conventional pressure sensor will be described with reference to the drawings.

FIG. 5 is a schematic configuration diagram of a conventional semiconductor pressure sensor.
In FIG. 5, 101 is a stem and 102 is a pedestal fixed on the stem 101 with a bonding agent 103. 104 is a diaphragm
With a silicon diaphragm chip having 106, a pressure detecting Wheatstone bridge resistor is provided on the diaphragm 106 and mounted on the pedestal 102. Reference numeral 105 is a notch groove provided in the pedestal 102 to relieve thermal stress from the stem 101. 107 is a lead pin penetrating the pedestal 102.
The gap with 102 is hermetically sealed with glass 115. Reference numeral 108 is a conductive wire that connects the bridge electrode of the silicon diaphragm chip 104 and the lead pin 107. Reference numeral 109 is a cap that covers the silicon diaphragm chip 104 and the pedestal 102 mounted on the stem 101 from the outside to form a vacuum chamber 113, and a sealing hole 111 is provided in the upper portion. Reference numeral 114 denotes a pipe for introducing pressure that guides fluid to the lower surface of the silicon diaphragm chip 104 through the stem 101 and the pedestal 102, and is fixed to the lower surface of the stem 101 by means such as brazing. The pedestal 102 is formed of a material having a thermal expansion coefficient similar to that of the silicon diaphragm chip 104, and relaxes the thermal stress from the stem 101 together with the cutout groove 105.

And when assembling the conventional semiconductor pressure sensor,
Before attaching the cap 109 to the stem 101,
A pedestal 102, a silicon diaphragm chip 104, a mounting lead pin 107, a wire 108 and a pressure introducing pipe 11 on the 101 side.
Attach 4 etc. Next, the cap 109 is attached to the stem 101 in a state where the sealing hole 111 is not sealed, and the outer periphery 110 of the stem 101 is sealed and joined by means such as pressure welding or welding. After this bonding, the air in the cap 109 is evacuated in a vacuum, and at the same time, the sealing hole 111 is hermetically sealed with solder 112.
Then, the vacuum chamber 113 is formed in the cap 109 and assembled.

Therefore, in this semiconductor pressure sensor, the diaphragm 106 of the silicon diaphragm chip 104 is attached to the vacuum chamber 11
Since it is housed in 3, the fluid introduced from the pressure introduction pipe 114 can be measured in absolute pressure using this vacuum pressure as a reference pressure.

Problems to be Solved by the Invention However, in the pressure transducer using the conventional semiconductor pressure sensor, the influence of thermal stress exerted on the silicon diaphragm chip 104 from the stem 101 and the bonding agent 103 between the pedestal 102 and the stem 101 is large. This thermal stress strains the silicon diaphragm chip 104. Therefore, the diaphragm 106
The value of the Wheatstone bridge resistance formed on the surface varies depending on the temperature, and the pressure detection characteristics also vary greatly with it. This problem is mainly due to the difference in the thermal expansion coefficient of the silicon diaphragm chip 104, the stem 101, the pedestal 102, and the bonding agent 310.

Therefore, in the structure of the conventional semiconductor pressure sensor, as described above, the pedestal 102 is made of a material having a thermal expansion coefficient as close as possible to the silicon diaphragm chip 104, and the pedestal 102 is used for the purpose of relaxing the thermal stress from the stem 101. The thickness of the base is increased, or the pedestal 102 is provided with a cutout groove 105. As a result, the workability of the pedestal 102 is poor, and the number of joints is large, resulting in poor workability, high cost, and low reliability.

The present invention solves such conventional problems,
An object of the present invention is to provide a semiconductor pressure sensor capable of improving pressure detection characteristics and simplifying the structure to improve reliability, stabilize quality, and reduce cost.

Means for Solving the Problems In order to achieve the above object, the present invention provides a pressure-sensitive diaphragm chip made of single crystal silicon having a pressure-sensitive diaphragm having a Wheatstone bridge resistance, and a pressure-sensitive diaphragm chip similar to the pressure-sensitive diaphragm chip. The pressure-sensitive diaphragm is provided with a cap that is molded from a glass material having a thermal expansion coefficient and is sealed to one side of the pressure-sensitive diaphragm chip by anodic bonding to form a vacuum chamber, and a through hole corresponding to the pressure-sensitive diaphragm. A pressure-sensitive diaphragm chip surface opposite to the cap, which is formed of a glass material having a thermal expansion coefficient similar to that of the chip, and a pedestal for sealing the anode surface of the pressure-sensitive diaphragm chip. A structure in which the cap is passed under the anode bonding surface in the diaphragm chip layer and led out to the outside. Is.

Therefore, according to the present invention, a glass material having a thermal expansion coefficient similar to that of the pressure-sensitive diaphragm chip is used as the material of the pedestal and the cap, and the anodic bonding in which the dissimilar metal layer is not present on the bonding surface is used as the bonding means. Therefore, when the temperature changes, the influence of the thermal stress from the pedestal and the cap exerted on the pressure-sensitive diaphragm chip is eliminated. Therefore, there is no difference in fluctuation of the Wheatstone bridge resistance system formed on the pressure-sensitive diaphragm surface due to thermal stress.

Further, since the signal extraction to the outside from the Wheatstone bridge resistor formed on the pressure-sensitive diaphragm surface passes under the anode bonding surface of the cap in the pressure-sensitive diaphragm chip layer, it was necessary in the conventional structure. No need for hermetic sealing.

Embodiment FIG. 1 to FIG. 4 show the construction of an embodiment of the present invention. 1 to 4, reference numeral 1 denotes a pressure-sensitive diaphragm chip made of a planar square single crystal silicon material, and a pressure-sensitive diaphragm 2 is provided at the center. The pressure-sensitive diaphragm 2 is provided with a pressure-detecting Wheatstone bridge resistor 3, and the signal lead-out line 4 of this Wheatstone bridge resistor 3 is spread to spread inside the P ⁺ layer of the pressure-sensitive diaphragm chip 1. Is forming. Further, the pressure-sensitive diaphragm chip 1 is provided with aluminum electrodes 5 exposed at the four corners, and the other end of the signal output line 4 is connected to the aluminum electrodes 5. Reference numeral 6 denotes a cap made of a glass material having a thermal expansion coefficient similar to that of the pressure-sensitive diaphragm chip 1, and is hermetically sealed and bonded in vacuum on the upper surface of the pressure-sensitive diaphragm chip 1 by anodic bonding or the like without dissimilar metal layers. A vacuum chamber 7 is formed on the upper surface of the pressure-sensitive diaphragm chip 1 as a reference pressure for pressure measurement. The cap 4 is sealed and joined with the aluminum electrode 5 of the pressure-sensitive diaphragm chip 1 exposed to the outside, and the signal extractor 4 is in a state of passing under the capper 4. Reference numeral 8 is a pedestal made of a glass material having a thermal expansion coefficient similar to that of the pressure-sensitive diaphragm chip 1, and a through hole 9 corresponding to the pressure-sensitive diaphragm 2 is integrally provided. Then, on the upper surface of the pedestal 8, the surface of the pressure-sensitive diaphragm chip 1 on the opposite side where the pressure-sensitive diaphragm 2 is made to correspond to the through hole 9 is sealed-bonded by anodic bonding or the like without interposing different metal layers. There is. The lower side of the pedestal 8 is joined to the substrate 11 by the silicon glue 10.
The substrate 11 is made of alumina or the like and has a through hole 12 corresponding to a portion to which the pedestal 8 is joined, and a signal amplification circuit and a temperature compensation circuit are formed around the upper surface of the portion to which the pedestal 8 is joined. is doing. Reference numeral 13 is a pressure introducing pipe having a pressure introducing hole 14 formed in the center thereof, and is sealed and joined to the lower surface of the pedestal 8 joined to the substrate 11 through the through hole 12. Reference numeral 15 is a bonding wire that electrically connects the aluminum electrode 5 and the circuit on the substrate 11. The temperature characteristics of the sensor are adjusted on the substrate 11 after mounting the pressure-sensitive diaphragm chip 1 by means such as trimming. Reference numeral 16 is a relatively soft silicon gel made of a silicon potting agent provided on the substrate 11 so as to cover and protect the entire pressure-sensitive diaphragm chip 1, the cap 6 and the wires 15 mounted on the substrate 11 via the pedestal 8. Is.

It should be noted that the substrate 11 is formed into a wafer by continuously providing a plurality of portions corresponding to the respective semiconductor pressure sensors, and is divided into individual parts after incorporating the above-mentioned components, and the substrate 11 required by each semiconductor pressure sensor individually. Is formed. Also, a plurality of pressure-sensitive diaphragm chips 1, caps 6, and pedestals 8 are each formed in a continuous state in the form of a wafer, and after being bonded to each other, they are integrally divided and mounted on the substrate 11.

Next, the pressure measuring method and operation of the above embodiment will be described.

In the above embodiment, for example, when measuring the intake air pressure of the internal combustion engine, the other end of the pressure introducing pipe 13 is connected to the intake hole of the intake manifold, and the fluid from the manifold intake hole passes through the hole 14 and the through hole 9 to form the pressure sensitive diaphragm. Get it in 2. Then, the fluid introduced through the pressure introduction pipe 13 gives strain to the pressure-sensitive diaphragm 2. This distortion changes the value of the pressure detecting Wheatstone bridge resistance formed on the pressure sensitive diaphragm 2, and this signal changes to the signal output line 4,
It is taken out to the circuit on the substrate 11 through the aluminum electrode 5 and the wire 15. By knowing this resistance value, the pressure in the intake manifold can be measured, and since the reference pressure is 0 when the vacuum chamber 7 is formed, it can be measured as an absolute pressure.

Therefore, in the semiconductor pressure sensor of the above embodiment, the base 8
The cap 6 has a coefficient of thermal expansion similar to that of the pressure-sensitive diaphragm chip 1, but a lath material is used, and anodic bonding in which a dissimilar metal layer is not present on the bonding surface is used as a bonding means for these, so that the temperature At the time of change, the influence of thermal stress exerted on the pressure-sensitive diaphragm chip 1 from the pedestal 8 and the cap 6 is eliminated. As a result, there is no difference in fluctuation of the Wheatstone bridge resistance system formed on the pressure-sensitive diaphragm 2 due to thermal stress, and the characteristics of the semiconductor pressure sensor are stabilized.

Further, since the external signal is taken out from the Wheatstone bridge resistor 3 formed on the pressure-sensitive diaphragm 2, it passes under the anodic bonding surface of the cap 6 in the layer of the pressure-sensitive diaphragm chip 1, so that the conventional structure is used. The hermetic sealing that was needed is no longer necessary. As a result, the reliability of vacuum sealing can be improved, the size can be reduced, and the cost can be reduced.

Further, the pressure-sensitive diaphragm chip 1 is mounted on the substrate via the base 8.
The structure is such that the aluminum electrode 5 formed directly on the pressure sensitive diaphragm chip 11 and the electrode of the hybrid integrated circuit formed on the substrate 11 are directly bonded with the wire 15 and then covered with the soft silicon potting agent. Therefore, the stem in the conventional structure becomes unnecessary, and the cap can be omitted. As a result, miniaturization and cost reduction are further improved.

Further, since the pressure-sensitive diaphragm chip 1, the pedestal 8 and the cap 6 are collectively formed in a wafer state after anodic bonding in a vacuum, the wafer is individually cut and divided, so that the vacuum sealing work can be performed. This simplifies and improves the efficiency of assembly work.

Further, the pressure-sensitive diaphragm chip 1 is mounted on the substrate 11 via the base 8.
Since a silicon glue is used as a means for mounting on top, the thermal stress from the substrate 11 to the pressure sensitive diaphragm 2 is relieved. As a result, there is no difference in thermal stress of the Wheatstone bridge resistance system, and the characteristics of the pressure sensor are further improved.

As is apparent from the above embodiments, the present invention uses a glass material having a thermal expansion coefficient similar to that of the pressure-sensitive diaphragm chip as the material of the pedestal and the cap, and the dissimilar metal on the bonding surface as the bonding means for these materials. Since the anodic bonding without the interposition of layers is used, the influence of the thermal stress from the pedestal and the cap exerted on the pressure-sensitive diaphragm chip when the temperature changes is eliminated. As a result, the fluctuation difference due to the thermal stress in the Wheatstone bridge resistance system formed on the pressure-sensitive diaphragm is eliminated, and the characteristics of the semiconductor pressure sensor are stabilized.

In addition, the external signal output from the Wheatstone bridge resistor formed on the pressure-sensitive diaphragm passes under the anodic bonding surface of the cap within the layer of the pressure-sensitive diaphragm chip, so the hermetic structure required in the conventional structure is used. No need for sealing. As a result, the reliability of vacuum sealing can be improved, the size can be reduced, and the cost can be reduced.

[Brief description of drawings]

1 is a plan view of a semiconductor pressure sensor according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is taken along the line BB of FIG. A sectional view, FIG. 4 is an enlarged sectional view showing a main part of the same sensor, and FIG. 5 is a sectional view showing an example of a conventional semiconductor pressure sensor. 1 ... Pressure-sensitive diaphragm chip, 2 ... Pressure-sensitive diaphragm, 3 ... Pressure detection Wheatstone bridge resistor, 4 ...
… Signal extraction line, 5 …… Aluminum electrode, 6 …… Cap, 7 …… Vacuum chamber, 8 …… Pedestal, 9,12 …… Through hole, 10 …… Silicon glue, 11 …… Substrate, 13 …… Pressure Introducing pipe, 15 …… wire, 16 …… silicon gel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Morikawa Takashi Morikawa 4-3-1, Tsunashima-higashi, Kohoku-ku, Yokohama-shi, Kanagawa Matsushita Communication Industrial Co., Ltd. (72) Kazuhiko Mizojiri, Tsunashima-higashi, Kohoku-ku, Yokohama-shi, Kanagawa 3-3-1 Matsushita Communication Industrial Co., Ltd. (72) Inventor Naoyuki Tsuda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd. (72) Kazuyoshi Fukuda 1006 Kadoma, Kadoma City, Osaka Matsushita Electronics Industry Within the corporation

Claims (5)

[Claims] 1. A pressure-sensitive diaphragm chip made of single crystal silicon having a pressure-sensitive diaphragm having a Wheatstone bridge resistance, and a glass material having a thermal expansion coefficient similar to that of the pressure-sensitive diaphragm chip. Molded from a glass material having a thermal expansion coefficient similar to that of the pressure-sensitive diaphragm chip by providing a cap that is anodically bonded to one side of the diaphragm chip to form a vacuum chamber and a through hole corresponding to the pressure-sensitive diaphragm. And a pedestal for anode-sealing the pressure-sensitive diaphragm chip surface on the side opposite to the cap, and a signal lead-out line of the Wheatstone bridge resistance is formed on the anode bonding surface of the cap in the pressure-sensitive diaphragm chip layer. A semiconductor pressure sensor configured to pass through the bottom and lead out to the outside. 2. The pressure-sensitive diaphragm chip has a rectangular plate shape, and the end portions of the signal output lines are connected to aluminum electrodes formed at the four corners of the pressure-sensitive diaphragm chip, respectively. The semiconductor pressure sensor according to claim (1). 3. The pedestal is directly bonded and mounted by a silicon glue on a hybrid integrated circuit forming a widening circuit and a temperature compensation circuit of the semiconductor pressure sensor, and the aluminum electrode on the pressure sensitive diaphragm and the hybrid. The semiconductor pressure sensor according to claim (2), characterized in that the wiring with the electrode formed on the integrated circuit is directly wire-bonded. 4. The semiconductor pressure sensor according to claim 3, wherein the wire-bonded portion and the pressure-sensitive diaphragm chip portion are covered with a silicon potting agent. 5. The pressure-sensitive diaphragm chip is formed in a wafer shape in which a plurality of the pressure-sensitive diaphragm chip portions are continuously formed, and a plurality of the pressure-sensitive diaphragm chip portions are integrated simultaneously in the wafer-shaped pressure-sensitive diaphragm chip state. The semiconductor pressure sensor according to claim (1), characterized in that the semiconductor pressure sensor is formed into a sheet and is then individually cut.