JPH06160420A - Semiconductor acceleration sensor and its manufacture - Google Patents

Abstract

PURPOSE:To provide a semiconductor acceleration sensor which does not require any special sealing process and in which a pressure-reduced or desired atmosphere can be formed. CONSTITUTION:A diffusion layer (shown by the hatching in the figure) is formed by doping a prescribed part on the surface of a silicon plate 11 mounted with mobile electrodes 17 and 18 with phosphor and used for forming wiring 21 used for leading out the electrodes 17 and 18. Then another diffusion layer insulated from the wiring layer is formed on the surface of the plate 11 and used for forming the wiring of a first fixed electrode 19 formed on a glass plate 12. In addition, a connecting line 27 is formed by vapor-depositing a metal on a step section 26 formed on the lower surface of the plate 11 and a through hole 13a is formed through the glass plate 13. The upper end of wiring 28 formed on the internal surface of the hole 13a by sputtering (in a pressure- reduced state) is connected to the line 27 over the entire periphery of the hole 13a. Therefore, the wiring process and sealing of the hole 13a can be performed at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration sensor and a method for manufacturing the same, and more particularly to improvement of a wiring lead-out structure for each electrode.

[0002]

2. Description of the Related Art In a capacitance type semiconductor acceleration sensor used for vehicle body control or engine control of an automobile, glass plates 2 are arranged on both upper and lower sides of a silicon plate 1 which generally constitutes a movable electrode, as shown in FIG. To do. At this time, a predetermined gap is formed between the movable electrode and the facing surface of the glass plate 2,
The movable electrode is allowed to swing. And this glass plate 2
The fixed electrode is formed by aluminum vapor deposition or the like on a predetermined position of the inner surface of, ie, the surface facing the movable electrode. When the movable electrode swings as described above, the gap between the movable electrode and the fixed electrode changes, and the electrostatic capacitance generated between both electrodes changes.

In order to detect such a change in capacitance, it is necessary to lead out the wiring (electrode lead) connected to both electrodes to the outside. However, such a lead-out should be continuous on the fixed electrode side, for example. The aluminum wiring 3 is formed on the upper surface of the glass plate 2 below. Then, a predetermined portion of the silicon plate 1 is cut off to expose the end 3a of the aluminum wiring 3 to be a pad for taking out, and the silicon plate 1
A concave groove 1a is formed in a portion of the lower surface corresponding to the aluminum wiring 3, and the lower surface other than the concave groove 1a is joined to the lower glass plate 2.

However, with the structure as it is, it is difficult to match the inner shape of the concave groove 1a formed in the silicon plate 1 with the outer shape of the aluminum wiring 3, so that the width and depth of the concave groove 1a are The width and height of the aluminum wiring 3 are set to be larger than the width and height of the aluminum wiring 3 by one or more, and a gap is generated between the two as shown in FIG. Therefore, there is a risk that dust, etc. may enter inside through the gap,
It may cause a failure.

Therefore, through holes 1b and 2a vertically penetrating through the silicon plate 1 and the upper glass plate 2 at predetermined positions.
And the plates 1 and 2 are stacked and arranged, and then the through holes 1b,
2a is filled with an adhesive (resin) or the like and hermetically sealed.

[0006]

However, in the above-mentioned structure, an extra process of encapsulating an adhesive is required for sealing, and workability is poor. Further, the aluminum wiring 3 is wiring on the fixed electrode side, but when used as an actual sensor, wiring from the movable electrode formed on the silicon plate 1 (since silicon has conductivity, the silicon plate itself Is used for wiring). Since such wiring is formed on the upper surface of the silicon plate 2, the upper surface (front surface) of the silicon plate 2 exposed by further cutting off a part of the upper glass plate 2 is used as a pad 4 for extraction (same as above). See FIG. That is, since the height positions of the pads 3a and 4 are different from each other, workability of wire bonding for connecting to an external circuit or the like at the time of mounting is poor.

Further, since the pressure of air changes depending on the temperature, it is preferable to depressurize the inside of the sensor or to enclose an atmosphere which has little influence. However, in the above sensor, the inside of the sensor is in communication with the outside through the gap formed between the aluminum wiring 3 and the concave groove 1a of the silicon plate 1, and even if the inside of the sensor is sealed after manufacturing as described above, the inside of the sensor is in a depressurized state, etc. However, there is air in the sensor, and the accuracy of the sensor deteriorates under the influence of the air.

The present invention has been made in view of the above background, and it is an object of the present invention that a special process for sealing is unnecessary, and further, the inside of the sensor can be depressurized and a desired atmosphere can be obtained. A further object of the present invention is to provide a semiconductor acceleration sensor and a method of manufacturing the same, in which pads for taking out electrode wirings can be formed on the same surface as necessary.

[0009]

In order to achieve the above object, in a semiconductor acceleration sensor according to the present invention, insulating substrates are arranged on both sides of a semiconductor substrate on which movable electrodes that are displaced according to acceleration are formed, and , A fixed electrode is formed on a predetermined plate of the insulating substrate with a predetermined gap from the movable electrode, and acceleration is detected from a change in electrostatic capacitance between the movable electrode and the fixed electrode caused by the displacement. In the semiconductor acceleration sensor, the end of the metallic coating formed on the entire inner circumference of the through hole formed in the insulating substrate is connected to the metallic connecting line formed on the semiconductor substrate facing the through hole. The connection was made and the connection site was arranged endlessly. Further, the fixed electrode formed on the insulating substrate having the through hole was connected to the connecting wire.

As a method of manufacturing a semiconductor acceleration sensor having such a structure, an insulating substrate having at least the through hole is bonded to a semiconductor substrate having a predetermined structure and another insulating substrate, and then pressure reduction or That is, it has a process of forming a predetermined metal coating on the entire inner circumference of the through hole under a predetermined atmosphere.

[0011]

The metal coating is formed on the entire inner peripheral surface of the through hole, and the end portion of the metal coating is connected to the metallic connecting wire formed at the facing portion of the semiconductor substrate. The metallic connection wire is in electrical connection with the fixed electrode provided on the insulating substrate having the through hole formed therein. Therefore, by forming the metal film in the through hole, the wiring process for taking out the fixed electrode to the outside of the sensor through the metallic connecting wire and the metal film is completed. Further, as described above, since the connecting portion between the metal coating and the connecting wire is endless, the through hole is closed. That is, the wiring process and the sensor sealing process described above are performed at the same time, which eliminates the need for a special work for forming the sealing structure. Further, if the formation of such a metal film is performed in a predetermined gas atmosphere, the inside of the sensor can be filled with the relevant gas, and if it is performed in a depressurized state (including vacuum), the inside of the sensor is depressurized and thermally A stable semiconductor acceleration sensor is manufactured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a semiconductor acceleration sensor and a method of manufacturing the same according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a sectional view of a first embodiment of an acceleration sensor according to the present invention, FIG. 2 is a plan view of each plate, and FIGS. 3 and 4 are enlarged views of predetermined portions. As shown in the figure, glass plates 12 and 13 as substrates are arranged on both upper and lower sides of a P-type silicon plate 11 which is a semiconductor substrate. In this example, the silicon plate 11 and the lower glass plate 13 have substantially the same planar shape, and the upper glass plate 12 has a short planar rectangular shape in which one side is removed from the same planar shape. ing.

Further, the silicon plate 11 has a shape in which a weight portion 16 is swingably connected to the center of a frame body 14 having a substantially rectangular shape in a plane through a beam portion 15, and the upper surface side of the weight portion 16 is It becomes the first movable electrode 17, and the lower surface side becomes the second movable electrode 18. Further, corresponding to the electrodes 17 and 18, at a predetermined position on the inner surface of the glass plates 12 and 13, a metal such as aluminum is deposited (or sputtered (hereinafter the same)), or the like.
First and second fixed electrodes 19 and 20 having a predetermined shape are formed. Then, the acceleration is detected from the difference between the electrostatic capacities generated between the upper and lower electrodes,
The basic configuration described above is the same as that of a conventional differential type semiconductor acceleration sensor.

Here, in the present invention, first, FIG.
As shown in (B), phosphorus is doped at a predetermined portion of the upper surface of the silicon plate 11 to form a diffusion layer (shown by hatching in each figure). And, as you can see from the figure,
The diffusion layer is formed on the entire upper surface of the weight portion 16 and the beam portion 15.
Has formed throughout. Regarding the beam portion 15, a predetermined portion of P-type silicon is removed from the lower side of the silicon plate 11 to the diffusion layer by electrochemically etching a portion corresponding to the beam portion 15, whereby the beam portion 15 is diffused. It consists of only layers. With this configuration,
Since the thickness of the beam portion 15 is the same as the thickness of the diffusion layer, the thickness is accurately controlled, the elastic coefficient of the beam portion 15 does not vary, and the quality is made uniform.

The diffusion layer formed on the upper surface of the weight portion 16 serves as the first movable electrode 17. Further, the diffusion layer is formed as it is in a narrow width extending toward the side edge of the silicon plate 11 to form the wiring 21, and the pad 22 for taking out the wiring is formed on the upper surface of the end portion by metal deposition.

As shown in FIG. 3, the second movable electrode 18 formed below the weight portion 16 is formed by depositing metal on the entire lower surface of the weight portion 16 to form a metal coating. is doing. The end of the metal coating is extended and connected to the lower surface of the beam portion 15. As a result, the first and second movable electrodes 17 and 18 are short-circuited in the diffusion layer to have the same potential, and the second movable electrode 18 is also externally formed via the wiring 21 and the pad 22 formed of the diffusion layer. Can be taken out. That is, both movable electrodes 17 and 1
8 serves as a common electrode.

On the other hand, when taking out the first fixed electrode 19,
This is performed through the wiring 23 formed of another elongated rectangular diffusion layer formed on the upper surface of the silicon plate 11. That is, the pads 2 are formed on both ends of the wiring 23 by metal deposition.
4, 25 are formed, one pad 24 serves as a wiring take-out pad, and the other pad 25 is pressure-bonded to the extending portion 19a of the first fixed electrode 19 and is electrically mechanically connected. As a result, the first fixed electrode 19 can be connected to an external circuit or the like via the extraction pad 24.

Further, the second fixed electrode 20 is taken out by the structure shown below. That is, FIG.
As shown in (C), a part of the second fixed electrode 20 becomes an extended portion 20a extended in an elongated rectangular shape.
The end portion of 0a is pressure-bonded to the connecting wire 27 made of metal vapor deposition provided on the surface of the stepped portion 26 formed on the lower surface of the silicon plate 11 (on the side of the frame 14 with respect to the beam portion 15), and electromechanically It is connected. Further, the connecting line 27 is arranged so as to face a through hole 13a formed at a predetermined position of the lower glass plate 13 as shown in an enlarged view in FIG.

The upper end 28a of the wiring 28, which is a metallic coating deposited on the inner peripheral surface of the through hole 13a, is connected to the connecting line 27 over the entire circumference (endless shape). In this way, the upper end 28a of the wiring 28 formed over the entire inner circumference of the through hole 13a is connected to the connecting line 27 over the entire circumference, whereby the through hole 13a is sealed. That is, the semiconductor acceleration sensor is automatically sealed by the connection of the wiring. The other end of the wiring 28 is extended to a predetermined portion on the lower surface side of the glass plate 13 to form a pad 29 for taking out.

Here, the connection (manufacturing) method in the vicinity of the through hole 13a will be described. The through hole 13a is formed in a predetermined portion of the glass plate 13 by ultrasonic processing or the like.
Then, the glass plates 12 and 1 on which the above-mentioned various wirings and pads (excluding the wiring 28 formed in the through hole 13a) are formed.
3 and the silicon plate 11 are laminated and integrated by anodic bonding. At the time of this joining, the various wirings and the like that face each other are automatically brought into close contact and electromechanical connection is established.

Further, the wiring 21 of both movable electrodes 17 and 18 and the wiring 23 of the first fixed electrode 19 are formed by the diffusion layer as described above, and the surface thereof is the other silicon plate 1.
Since it is processed so as to be flush with the upper surface of No. 1, when anodic bonding between the silicon plate 11 and the upper glass plate 12 is performed,
Both plates 11 and 12 are in surface contact with each other to be integrated and sealed.

That is, by the joining process of both plates, the wiring process of both movable electrodes 17 and 18 and the first fixed electrode 19 (connection to the pads 22 and 24 for taking out) and the sealing process of the sensor are automatically performed at the same time. Is performed (no special sealing process is required). And the pad 2 for taking out both electrodes
Since 2 and 24 are located on the same plane, the wire bonding process for connecting to an external circuit can be easily performed.

Then, in this state, metal deposition (sputtering) is performed on a predetermined portion near the through hole 13a. As a result, not only the entire inner peripheral surface of the through hole 13a but also the vapor deposition portion up to the connecting line 27 located above the through hole 13a is arranged, and the desired wiring 28 is formed. If the wiring 28 is formed in a vacuum (predetermined decompression) state, the inside of the sensor is also decompressed, and the wiring 28 is formed in that state to seal the through hole 13a (opening portion). The state is maintained. This improves the characteristics of the semiconductor acceleration sensor. Further, if the wiring 28 is manufactured in an atmosphere of a desired gas, it is possible to easily fill the sensor with the desired gas.

FIG. 5 shows a second embodiment of the present invention.
As shown in the drawing, in this embodiment, unlike the above-described first embodiment, the extraction pad 30 of the lower second fixed electrode 20 is also positioned on the same plane as the other pads 22, 24. ing. That is, a diffusion layer is formed on the silicon plate 11 'at a predetermined position (a position different from the wiring 21 for both the movable electrodes 17 and 18 and the wiring 23 for the first fixed electrode 19) to form the wiring 31. Then, the pad 30 is formed by depositing metal on the upper surface of one end (exposed side end) of the wiring 31.

Then, a recess 32 is formed at a predetermined position of a step 26 'formed on the lower surface of the silicon plate 11' on the side of the frame 14 ', and the wiring 31 is formed on the inner surface of the recess 32. It is connected to the diffusion layer. This recess 32 also has a step 26 '.
This can be easily performed by electrochemically etching a predetermined portion of P to remove the P-type silicon portion, and the diffusion layer can be exposed.

Further, metal is vapor-deposited on the inner peripheral surface of the recess 32, the exposed portion of the diffusion layer and the predetermined portion of the step portion 26 'to form a connecting line 33, and the connecting line 33 and the second portion are formed. The extension portion 20a of the fixed electrode 20 is brought into close contact (this close contact process is also automatically performed by anodic bonding between the silicon plate 11 'and the glass plate 13'). As a result, the second fixed electrode 20 has the connection line 33 and the wiring 31 formed by the metal deposition.
It is linked to the pad 32 through the and can be taken out to the outside.

With this structure, the three pads 22, 24, 30 are located on the same plane,
Not only the subsequent wire bonding process and the like become easy, but also the process of making holes in the glass plate is not necessary, which greatly simplifies the manufacturing process. The rest of the configuration and operation are similar to those of the above-described first embodiment, and therefore their explanations are omitted.

FIG. 6 shows a third embodiment of the present invention. In this embodiment, unlike the above-described embodiments, both movable electrodes 17 ', 18' and the first and second fixed electrodes 1 are provided.
Three pads for taking out 9'and 20 'are formed on the surface of the glass plate 12 ". First, the basic structure in this example will be described. In each of the above embodiments, the beam portion 15' is located on the lower side. In the reverse arrangement of the example, metal evaporation is performed on the upper surface of the weight portion 16 'to form the first movable electrode 17'. Then, the end of the metal evaporation is extended to extend the beam portion 1.
By connecting to the diffusion layer forming 5 ', the first and second movable electrodes 17' and 18 'are made to have the same potential. It is located up to the step portion 35 formed on the upper surface of the plate 11 ″.

Then, the wiring 37 which is a metallic coating formed by sputtering on the inner surface of the first through hole 12 "a formed at a predetermined portion of the upper glass plate 12" and the end portion 36 of the metal vapor deposition are provided. Then, the second fixed electrode 20 in the first embodiment is connected in the same manner as the wiring extraction and sealing mechanism. As a result, the first through hole 12 ″ a is sealed. Then, the outer end portion of the wiring 37 (the glass plate 1) is sealed.
The 2 ″ upper surface side) serves as the extraction pad 38.

In the same way as above, the wiring of the first fixed electrode 19 'formed on the upper glass plate 12 "is taken out, and its extension 19'a is first formed on the step 35 of the silicon plate 11". Wiring 41, which is a metallic coating formed by sputtering on the entire inner circumference of the connecting wire 40 and the second through hole 12 "b formed in the glass plate 12"
This is done by connecting and. Then, the end portion of the wiring 41 becomes a pad 42 for taking out.

Further, the wiring of the second fixed electrode 20 'is taken out from the glass plate 1 as shown in the enlarged view of FIG.
A second through hole 44 that is vertically continuous is formed in a predetermined plate of the 2 ″ and the silicon plate 11 ″. Then, a wiring 45, which is a metallic coating, is formed on the inner peripheral surface of the third through hole 44 by sputtering, and the lower end 45a of the wiring 45 serves as an extension 20'a of the second fixed electrode 20 '. Are integrated and connected, and the third through hole 44 is sealed together with the electromechanical connection process. Then, the upper end of the wiring 45 is extendedly arranged on the upper surface of the glass plate 12 ″ to form a take-out pad 46.

Then, each of the above-mentioned through holes 12 "a, 1"
The wirings 37, 41, 45 formed in the 2 ″ b, 44 are formed by anodic bonding of the respective plates in the same manner as in the above-described embodiments.
It is performed by sputtering under reduced pressure or a predetermined atmosphere. Since the other configurations and operations are the same as those of the above-described embodiments, the description thereof will be omitted.

[0033]

As described above, in the semiconductor acceleration sensor and the method of manufacturing the same according to the present invention, the wiring drawing process for each electrode and the sealing process can be performed at the same time, and a special process for the sealing process is unnecessary. Therefore, the manufacturing process is simplified.
Moreover, since they can be performed simultaneously, for example, by performing the sealing process in a depressurized state or in a predetermined gas atmosphere, it is possible to easily depressurize the inside of the sensor and fill a desired gas.

When there are a plurality of fixed electrodes, at least one of the fixed electrodes and the end of the wiring with the movable electrode (the connection with the external circuit) can be arranged in the same plane, and mounting The connection process (wire bonding process, etc.) with an external circuit or the like at that time is simplified.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a semiconductor acceleration sensor according to the present invention.

FIG. 2A is a plan view showing the upper glass plate. (B) is a plan view showing the silicon plate.
(C) is a plan view showing the lower glass plate.

FIG. 3 is a perspective view showing a weight portion (movable electrode) formed on a silicon plate.

FIG. 4 is an enlarged cross-sectional view showing a main part of a wiring connection portion.

FIG. 5 is a diagram showing a second embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 6 is a diagram showing a third embodiment of the semiconductor acceleration sensor according to the present invention.

FIG. 7 is a diagram showing a conventional example.

[Explanation of symbols]

11, 11 ', 11 "Silicon plate (semiconductor substrate) 12, 12', 12", 13, 13 ', 13 "Glass plate (insulating substrate) 13a, 12" a, 12 "b Through hole formed in glass plate 16, 16 'Weight portion 17, 17' First movable electrode 18, 18 'Second movable electrode 19, 19' First fixed electrode 20, 20 'Second fixed electrode 21, 23, 31 Wiring (diffusion) Layers) 27, 36, 40 Connection lines 28, 31, 37, 41, 45 Wiring (metallic coating) 32 Recesses 44 Glass plate, through hole formed in communication with a silicon plate

Claims (6)

[Claims] 1. An insulating substrate is arranged on both sides of a semiconductor substrate on which a movable electrode that is displaced according to acceleration is formed, and a fixed electrode is provided on a predetermined plate of the insulating substrate with a predetermined gap from the movable electrode. And a semiconductor acceleration sensor that detects acceleration from a change in electrostatic capacitance between the movable electrode and the fixed electrode that accompanies the displacement, and is formed on the entire inner circumference of a through hole formed in the insulating substrate. The end portion of the formed metallic coating is connected to a metallic connecting line formed on the semiconductor substrate facing the through hole, and the connecting portion is arranged endlessly, and the through hole is provided. A semiconductor acceleration sensor in which the fixed electrode formed on an insulating substrate is connected to the connecting wire. 2. A semiconductor substrate in which movable electrodes are formed on both surfaces of a weight portion that is integrally connected to a frame body through a beam portion and that is displaced according to acceleration, and a predetermined gap between the movable electrodes. In a semiconductor acceleration sensor having fixed electrodes opposed to each other with an insulating substrate such as a glass plate arranged so as to sandwich the semiconductor substrate, at a predetermined position on the same surface of the semiconductor substrate, insulating In this state, a plurality of diffusion layers are formed, the movable electrode and the one fixed electrode are connected to each diffusion layer, and the other fixed electrode is formed on an insulating substrate provided with the fixed electrode. An end portion of the metallic coating formed on the entire inner circumference of the through hole is connected to a metallic connecting line formed on the semiconductor substrate facing the through hole, and the connecting portion is arranged endlessly, And the penetration A semiconductor acceleration sensor in which the fixed electrode formed on an insulating substrate having a hole is connected to the connecting line. 3. A semiconductor substrate on which movable electrodes are formed on both surfaces of a weight portion that is integrally connected to a frame body through a beam portion and that is displaced according to acceleration, and a predetermined gap between the movable electrodes. In a semiconductor acceleration sensor having fixed electrodes opposed to each other with an insulating substrate such as a glass plate arranged so as to sandwich the semiconductor substrate, at a predetermined position on the same surface of the semiconductor substrate, insulating A plurality of diffusion layers are formed in a state, the movable electrode and the one fixed electrode are connected to each of the diffusion layers, and a recess is formed on the surface on the opposite side of the semiconductor substrate so that the back surface side of the other diffusion layer is formed. A semiconductor acceleration which is exposed and is connected to the metallic coating on the inner peripheral surface of the recess and the back side of the other diffusion layer, and the other fixed electrode is connected to the metallic coating provided in the recess. Sensor. 4. A semiconductor substrate having movable electrodes formed on both surfaces of a weight portion that is integrally connected to a frame body through a beam portion and that is displaced according to acceleration, and a predetermined gap between the movable electrodes. A semiconductor acceleration sensor having fixed electrodes opposed to each other with an insulating substrate such as a glass plate arranged so as to sandwich the semiconductor substrate, wherein a plurality of through holes are provided at predetermined positions of the one insulating substrate. Of the plurality of through holes, the end of the metallic coating formed on the entire inner surface of the predetermined through hole is connected to the metallic wiring connected to the movable electrode, and The end portion of the metallic coating formed on the entire circumference is connected to the metallic connecting line formed on the semiconductor substrate facing the through hole and is formed on the one insulating substrate provided with the through hole. The fixed electrode is connected to the connecting wire. A through hole is formed in the semiconductor substrate while being connected to another through hole, and the ends of the metallic coatings provided on the entire inner surfaces of both through holes in the connected state are connected to the other fixed electrode. A semiconductor acceleration sensor which is connected to the formed metallic wiring and has endless connection portions at the end portions of the metal coating formed in the through holes. 5. One of the movable electrodes is formed of a diffusion layer formed on one surface of the weight portion, and the other movable electrode is formed of a metal film formed on the other surface of the weight portion. The semiconductor acceleration sensor according to any one of claims 1 to 5, further comprising: extending an end portion of a metal coating film forming another movable electrode and connecting the extended metal film to the diffusion layer. 6. The method for manufacturing a semiconductor acceleration sensor according to claim 1, wherein the semiconductor substrate has at least the through hole and a predetermined configuration. And a method for manufacturing a semiconductor acceleration sensor, which comprises a process of bonding a predetermined insulating film to another insulating substrate, and then forming a predetermined metal film on the entire inner surface of the through hole under reduced pressure or a predetermined atmosphere.