JP2000121662A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor in which an insulating film for inhibiting contact of a movable electrode with a fixed electrode is kept from dielectric breakdown due to discharge caused in anode joining. SOLUTION: A silicon substrate 2 having an overlap part 6 displaced by acceleration is anode joined to the upper surface of a glass substrate 1 having a fixed electrode 8 to be integrated. The overlap part and the fixed electrode are opposite to each other, and the opposite surface of the overlap part is taken as a movable electrode 7. On the surface of the glass substrate, an insulating layer 11 is provided through an electrode material 10 in a fixed electrode unformed area 8a in a position opposite to the movable electrode 7. Thus, when the overlap part is largely displaced, the movable electrode 7 and the insulating layer 11 first come into contact with each other so that both electrodes are kept from electric contact. Further, since the fixed electrode 8 and the insulating layer 11 are out of contact, in anode joining, discharge is caused between both electrodes, and at that time, high voltage is applied to the insulating layer 11 not to cause dielectric breakdown.

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.

[0002]

2. Description of the Related Art Semiconductor acceleration sensors are used for, for example, seismic detectors for detecting earthquake vibration, airbag systems for automobiles, and mechanical vibration / shock detectors for navigation systems.

The configuration of such a semiconductor acceleration sensor is as follows.
In general, a laminated structure is used in which a semiconductor substrate having a movable portion (referred to as a weight portion or the like) that is displaced by acceleration and a fixed substrate are joined, and a metal film is formed on the surface of the fixed substrate facing the movable portion. As a result, a fixed electrode is formed, and a movable electrode is formed on the surface of the movable portion facing the fixed electrode. Further, a silicon substrate is often used as a semiconductor substrate, and a glass substrate is used as a fixed substrate. In the case of such a combination, the two substrates are generally bonded by anodic bonding.

[0004] With this configuration, a capacitance corresponding to the distance is generated between the movable electrode and the fixed electrode. When the movable electrode is displaced by the acceleration, the distance also fluctuates, so that the capacitance also changes. That is, it functions as a variable capacitor. Therefore, the amount of displacement, and thus the acceleration, can be measured from the capacitance of the variable capacitor.

Furthermore, in order to prevent the fixed electrode and the movable electrode from contacting and conducting during the anodic bonding or during subsequent use, an insulating film is formed on the surface of the fixed electrode or the movable electrode. There are also things. As a type to which such an insulating film is added, a conventional type is disclosed, for example, in JP-A-4-32
773 discloses this. In the acceleration sensor disclosed in this publication, an insulating film is formed on the entire surface or a part of the fixed electrode facing the movable electrode. Thereby, even if the displacement amount of the movable part becomes large, the contact between the two electrodes can be prevented because the insulating layer is interposed between the movable electrode and the fixed electrode.

[0006]

However, the above-described conventional acceleration sensor has the following problems.
That is, the conventional insulating layer is formed on the electrode portion of the capacitor. Therefore, even if the movable part is drawn to the fixed electrode side by the electrostatic attractive force at the time of anodic bonding, the two electrodes do not come into direct contact with each other. However, a discharge may occur between the electrodes in combination with the approach of the distance between the two electrodes. Then, the discharge causes the electrode material to scatter on the insulating layer, and thereafter, there is a possibility that the displacement of the movable electrode is suppressed, or welding occurs, and a desired acceleration detection characteristic cannot be obtained. Further, the discharge may cause dielectric breakdown, and the effect of the insulating layer may be reduced or eliminated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to solve the above-mentioned problems, to suppress the contact between the movable electrode and the fixed electrode, and to reduce the contact. An object of the present invention is to provide a semiconductor acceleration sensor in which an insulating film is not broken down by a discharge generated at the time of anodic bonding or the like, and is easy to manufacture and has a high yield.

[0008]

In order to achieve the above-mentioned object, a semiconductor acceleration sensor according to the present invention comprises a semiconductor substrate having a movable portion which is displaced by receiving an acceleration, and a fixed substrate joined to the semiconductor substrate. A semiconductor acceleration sensor having a movable electrode provided on a surface of the movable portion facing the fixed substrate and a fixed electrode provided on a surface of the fixed substrate facing the movable electrode.

In the above-described sensor, an insulating layer is provided on a surface of the fixed substrate in a region where the fixed electrode is not formed and opposed to the movable portion, and when the movable portion is displaced. Furthermore, the movable electrode and the fixed electrode are configured not to be in electrical contact with each other due to the contact between the movable portion and the insulating layer (claim 1).

Further, as another solution, in the sensor based on the same premise as described above, an insulating layer is provided on a surface of the movable portion facing the fixed substrate and at a position facing a region where the fixed electrode is not formed. May be provided so that when the movable portion is displaced, the region where the fixed electrode is not formed is in contact with the insulating layer, so that the movable electrode and the fixed electrode do not come into electrical contact with each other (claim). Item 2).

If the acceleration applied to the sensor is larger than the allowable amount, the displacement of the movable part also increases, and the distance between the movable electrode and the fixed electrode becomes very short. Then, in the present invention,
An insulating layer is provided at a predetermined position on the fixed substrate (Claim 1) or the semiconductor substrate (Claim 2). Before the two electrodes come into contact with each other, the insulating layer comes into contact with the opposing substrate, and the displacement of the movable part is increased. To block. This prevents the movable electrode and the fixed electrode from contacting and conducting. Therefore, current does not flow due to conduction and the sensor does not break down. In addition, since the fixed electrode and the insulating layer are not in contact with each other, when performing anodic bonding or the like when bonding the two substrates, a discharge occurs between the two electrodes, and a current flows from the movable electrode to the fixed electrode via the insulating layer. The movable portion can have a desired displacement characteristic without flowing and without causing the electrode material to scatter on the insulating layer due to discharge. According to the same principle, no high voltage is applied to the insulating layer, and no dielectric breakdown occurs.

In the present invention, the insulating layer only needs to be in contact with the fixed electrode. Therefore, as shown in the embodiment,
On the surface of the glass substrate 1 which is a fixed substrate, an electrode material is provided in a region 8a where no fixed electrode is formed, in a state electrically separated from the fixed electrode, and an insulating layer is provided on the electrode material, In the case where an insulating layer is provided, the insulating layer may be in contact with the above-mentioned electrode material, or may not be provided with such an electrode material.

However, as described in the embodiment, it is more preferable to provide an electrode material. That is, when the electrode material is provided in the region where the fixed electrode is not formed, the thickness of the insulating layer can be reduced by the thickness of the electrode material. Therefore, the processing time for depositing or etching the insulating layer can be shortened, and the processing time can be reduced in such a short time, so that the manufacturing efficiency can be improved and the amount of material required for manufacturing the insulating layer can be reduced. Cost can be reduced.
Further, since the processing time is shortened in this manner, an insulating film necessary for forming an insulating layer is formed, a resist film for patterning the insulating film is formed, and each film is patterned. Damage to the substrate caused when performing various types of etching can be minimized. Therefore, it is possible to reduce the occurrence of inconveniences caused by this step, and to improve the yield. This can be said when the insulating layer is formed on either the fixed substrate or the semiconductor substrate.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a semiconductor acceleration sensor according to the present invention will be described below with reference to the accompanying drawings. 1 and 2 show a first embodiment of the present invention. As shown in FIG.
A silicon substrate 2 as a semiconductor substrate is formed on the upper surface of
Both are integrated by anodic bonding.

The silicon substrate 2 is partially etched to form a substantially rectangular support frame 4 around the periphery thereof, and the weight 6 is cantilevered inside the support frame 4 via a thin beam 5. So that they are integrally formed. The lower surface of the weight 6 becomes the movable electrode 7. The lower surface of the weight 6 is
It is shaved by a predetermined amount and is separated from the surface of the glass substrate 1 by a certain distance. Therefore, when acceleration is applied, the beam 5 is bent, and the weight 6 is displaced.

On the other hand, a fixed electrode 8 is formed on a portion of the glass substrate 1 facing the movable electrode 7 by vapor deposition or sputtering and patterning. Thereby, a capacitance corresponding to the distance is generated between the movable electrode 7 and the fixed electrode 8. Then, as described above, when the acceleration is applied, the movable electrode 7 is displaced, so that the distance between the electrodes is changed, and the capacitance is also changed. Therefore, in order to take out such a change in the capacitance, the terminal pad provided at a predetermined position of the sensor is electrically connected to the two electrodes.

That is, as shown in FIG. 2 (b), a lead pattern 9a is provided on the surface of the glass substrate 1 so as to be continuous with the fixed electrode 8, and is movable to a position electrically separated from the fixed electrode 8. An extraction pattern 9b for the electrode 7 is provided. Then, the extraction pattern 9b comes into contact with the support frame 4 of the silicon substrate 2. Further, both of the extraction patterns 9a and 9b are exposed to the outside of the silicon substrate 2, and the exposed tips serve as terminal pads. Thereby, the withdrawal pattern 9a becomes
Since it is electrically connected to the fixed electrode 8 and the extraction pattern 9b is electrically connected to the movable electrode 7 via the silicon substrate 2, the connection between the electrodes 7 and 8 via the electrode pads provided at the tips of the extraction patterns 9a and 9b. The signal based on the capacitance generated in the above can be taken out to the outside. Note that each of the above-described configurations is the same as the conventional one, and thus detailed description thereof is omitted.

In the present invention, as shown in FIG. 2, an electrode material 1 is provided on the surface of glass substrate 1 (the surface facing the movable electrode).
0 is formed, and an insulating layer 11 is provided on the upper surface of the electrode material 10. As shown in FIG. 1B, the positions where the electrode material 10 and the insulating layer 11 are formed are formed around a fixed electrode 8 and in a fixed electrode-free area 8 a which is electrically separated from the fixed electrode 8. ing. Further, as shown in FIG. 1A, the electrode material 10 and the fixed electrode 8 are formed to have the same thickness.
Since the insulating layer 11 is provided on the electrode material 10, the upper surface of the insulating layer 11 is higher (closer to the movable electrode 7) than the upper surface of the fixed electrode 8. Further, the insulating layer 11 can be formed of an oxide film such as silicon oxide. Of course, it may be other than an oxide film.

With this configuration, as shown in FIG. 3, even if a large acceleration is applied and the movable electrode 7 is greatly displaced, the weight portion 6 (the movable electrode 7) contacts the insulating layer 11 before coming into contact with the fixed electrode 8. Since they are in contact with each other, a short circuit between the electrodes 7 and 8 can be suppressed. Therefore, when the sensor is used, it is possible to prevent the electrodes from contacting each other and causing a current to flow. Further, even if a discharge may occur between the electrodes during anodic bonding or the like, since the electrode material 10 is separated from the fixed electrode 8, no current flows on the electrode material 10 side, and the insulating layer 4 can also prevent dielectric breakdown.

Since the electrode material 10 can be manufactured by the same process as the fixed electrode 8 by patterning, the electrode material 10 can be manufactured in a different process from the conventional acceleration sensor manufacturing process (type in which an insulating layer is provided on the fixed electrode). The numbers are the same. The insulating layer 11 can be manufactured by etching (patterning) after deposition.

FIG. 4 shows a main part of a second embodiment of the present invention. That is, in this embodiment, unlike the above-described first embodiment, the insulating layer 11 is directly deposited at a predetermined position on the surface of the glass substrate 1 (the formation location is the same as in the first embodiment). It is formed by doing. Even with such a configuration, the same operation and effect as described above can be exerted, conduction between the movable electrode 7 and the fixed electrode 8 can be prevented, and breakage of the insulating layer 11 due to discharge at the time of anodic bonding or the like can be suppressed. The other configuration and operation and effect are the same as those of the above-described first embodiment, and therefore, are denoted by the same reference numerals, and detailed description thereof will be omitted.

It is preferable to form the insulating layer 11 on the electrode material 10 as in the first embodiment, since damage to the substrate during patterning of the insulating layer 11 can be avoided. When the height position of the surface of the insulating layer 11 is higher than the surface of the fixed electrode 8 by a predetermined amount, the surface of the electrode material 10 and the surface of the fixed electrode 8 already match (in the case of the same formation). Therefore, the film thickness when the insulating layer 11 is formed can be small. Accordingly, the deposition time for forming the insulating layer can be shortened, and the etching time can be shortened. Therefore, there is an advantage that the time for the entire manufacturing process can be shortened. This means that even if the electrode material 10 and the fixed electrode 8 are separately formed, the thickness of the insulating layer 11 is reduced by at least the thickness of the electrode material 10. From such a point, a more preferable embodiment has a structure in which the electrode material 10 is formed and the insulating layer 11 is formed thereon as in the first embodiment.

In each of the above-described embodiments, the insulating layer 11 (electrode material 10) is provided with a plurality of fixed electrode non-formed regions 8a in a part of the periphery of the fixed electrode 8, and
Although the insulating layer 11 and the like are scattered in the unformed region 8a, the present invention is not limited to this. For example, as shown in FIG. The layer 11 may be formed. In the illustrated example, the insulating layer 11 is formed directly on the upper surface of the glass substrate 1. However, similarly to the first embodiment, an electrode material (which is electrically separated from the fixed electrode 8) is formed thereunder. Of course) may be formed.

FIG. 6 shows a third embodiment of the present invention. In each of the above-described embodiments and modified examples, the insulating layer is provided on the glass substrate 1 side, but in the present embodiment, the insulating layer 11 'is provided on the movable portion (weight portion 6, movable electrode 7) side.
Is formed. As shown in the figure, in the present embodiment, similarly to the first embodiment, an electrode material 10 is formed on the surface of a glass substrate 1 in a non-contact state with a fixed electrode 8, and the electrode material 10 An insulating layer 11 'is provided on the surface of the facing weight portion 6.
Is formed.

As a result, although not shown, when the weight portion 6 is largely displaced (in a direction approaching the fixed electrode 8), the insulating layer 11 'and the electrode material 10 first come into contact with each other. 8 does not touch. Also, even if there is a discharge during the anodic bonding, the insulating layer 11 and the fixed electrode 8
Are electrically separated and non-conductive, so that occurrence of dielectric breakdown can be suppressed as much as possible. The other configuration and operation and effect are the same as those of the above-described first embodiment, and therefore, are denoted by the same reference numerals, and detailed description thereof will be omitted.

Further, as shown in FIG. 7, even in the type in which the insulating layer 11 'is provided on the weight portion 6 side, the electrode material may not be provided on the glass substrate 1 side. In this case,
On the surface of the glass substrate 1 facing the insulating layer 11 ', a fixed electrode non-formed region 8a is provided, and even if the weight 6 is largely displaced and the insulating layer 11' comes into contact with the glass substrate 1. , So as not to come into contact with the fixed electrode 8. The other configuration and operation and effect are the same as those of the above-described first embodiment, and therefore, are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 8 shows a fourth embodiment of the present invention. In each of the above-described embodiments, the insulating layers 11, 1
Although the mounting position of 1 ′ differs between the glass substrate 1 and the weight portion 6, the region where the insulating layer 11 is formed or the insulating layer 1
This is the same in that the fixed electrode 8 is not formed in the region facing 1 '. As shown in the drawings, the fixed electrode non-formed region 8a in each embodiment has a shape in which a part of the periphery thereof is notched in a concave shape.

On the other hand, in the present embodiment, the window 8b is formed at a predetermined position in the fixed electrode 8 instead of the cutout, and the electrode material 10 is placed in the window 8b. And an insulating layer 11 is formed on the electrode material 10.
By doing so, the fixed electrode is arranged around the insulating layer 11, but the basic operation and effect are the same as in the first embodiment.

The other constructions and functions and effects are the same as those of the first embodiment, and therefore the same reference numerals are given and the detailed description is omitted. Although the example shown in FIG. 8 is based on the first embodiment, it is needless to say that a window part is formed in a part of the fixed electrode similarly to the second and third embodiments. It is needless to say that a structure provided with is provided.

FIG. 9 shows a fifth embodiment of the present invention. In the present embodiment, unlike the above-described embodiments, an example in which the present invention is applied to a type in which the same potential electrode 12 is formed around the fixed electrode 8 is shown. That is, the same potential electrode 12 is pattern-formed on the surface of the glass substrate 1 so as to surround the fixed electrode 8. The pattern shape of the same potential electrode 12 is such that the main body portion 1 has a substantially rectangular shape and covers substantially the entire circumference at a predetermined distance from the outer periphery of the fixed electrode 8.
2a and a connection portion 12b extending from the main body portion 12a toward the support frame. And the body part 1
2 a is cut off at the portion of the extraction pattern 9 a connected to the fixed electrode 8 to insulate it from the fixed electrode 8. In other words, it is not strictly a square shape but a partially open shape. The connecting portion 12b is formed on the silicon substrate 2
To come into contact with the support frame.

Thus, when the glass substrate 1 and the silicon substrate 2 are brought into contact, the portion of the same potential electrode 12 is conducted to the silicon substrate 2. Therefore, since the movable electrode 7 and the same potential electrode 8 are conducted, there is no potential difference between the movable electrode 7 and the same potential electrode 12, and the potential is the same. As a result, even when the weight portion 6 (movable electrode 7) is drawn and the same potential electrode 12 and the movable electrode 7 are brought into contact with each other at the time of anodic bonding or the like, no current flows and the effect of suppressing the welding between the electrodes can be achieved. .

However, even if the potentials are actually the same, the potential distribution is not uniform and a slight potential difference occurs due to the positional relationship. is there. Therefore, as shown, a window 12a is formed at a predetermined position of the same potential electrode 12, and the same potential electrode 1 is formed in the window 12a.
The electrode material 10 is provided in a state electrically separated from the electrode material 2, and the insulating layer 11 is provided on the electrode material 10.
Thus, if the potential distribution at the same potential electrode 12 varies, even if the insulating layer 11 and the movable electrode 7 come into contact with each other, the potential distribution via the insulating layer 11 will be based on the same principle as in each of the above-described embodiments. No current flows from the movable electrode 7 to the same potential electrode 12 side, and the problem of dielectric breakdown at the time of discharge or the like can be suppressed.

The reason why the electrode material 10 is provided as shown in the drawing is to obtain the same effect as that of the first embodiment described above. If such a merit is unnecessary, the electrode material is not necessarily provided. You may. Also, an insulating layer may be provided on the surface side of the weight portion 6 facing the window portion 12a formed in the same potential electrode 12.

[0034]

As described above, in the semiconductor acceleration sensor according to the present invention, the insulating layer is provided on the surface of the movable part and / or the fixed electrode on the joint surface side. Since the surface facing the layer is in contact, contact between the movable electrode and the fixed electrode can be suppressed as much as possible. In addition, since the insulating layer is formed in a region where the fixed electrode is not formed (claim 1) or on the surface of the movable portion facing the non-formed region (claim 2), the insulating layer comes into contact with the fixed electrode. The dielectric breakdown does not occur due to discharge generated during anodic bonding or the like.

[Brief description of the drawings]

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

FIG. 2A is an enlarged sectional view of a main part of the first embodiment. (B) is a plan view showing the surface of the glass substrate.

FIG. 3 is a diagram illustrating the operation of the first embodiment.

FIG. 4A is an enlarged sectional view of a main part showing a second embodiment of the semiconductor acceleration sensor according to the present invention. (B) is a plan view showing the surface of the glass substrate.

FIG. 5 is a plan view illustrating a surface of a glass substrate according to a modification of the second embodiment.

FIG. 6 (a) is an enlarged sectional view of a main part showing a third embodiment of the semiconductor acceleration sensor according to the present invention. (B) is a plan view showing the surface of the glass substrate.

FIG. 7A is an enlarged sectional view of a main part showing a modification of the third embodiment of the semiconductor acceleration sensor according to the present invention.
(B) is a plan view showing the surface of the glass substrate.

FIG. 8A is an enlarged sectional view of a main part showing a fourth embodiment of the semiconductor acceleration sensor according to the present invention. (B) is a plan view showing the surface of the glass substrate.

FIG. 9A is an enlarged sectional view of a main part of a semiconductor acceleration sensor according to a fifth embodiment of the present invention. (B) is a plan view showing the surface of the glass substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate (fixed substrate) 2 Silicon substrate (semiconductor substrate) 4 Support frame 5 Beam part 6 Weight part (movable part) 7 Movable electrode 8 Fixed electrode 9a, 9b Lead-out pattern 10 Electrode material 11, 11 'Insulating layer 12 Same potential electrode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masatoshi Oba 10F, Hanazono Todocho, Ukyo-ku, Kyoto-shi, Japan OMRON Corporation F-term (reference) 4M112 AA02 BA07 CA23 CA36 DA18 EA02 EA13

Claims (2)

[Claims] 1. A semiconductor substrate having a movable portion that is displaced by receiving an acceleration, and a fixed substrate joined to the semiconductor substrate, wherein a movable electrode is provided on a surface of the movable portion facing the fixed substrate, In a semiconductor acceleration sensor having a fixed electrode provided on the surface of the fixed substrate facing the movable electrode, an insulating region is provided on the surface of the fixed substrate, in a region where the fixed electrode is not formed, and at a position facing the movable portion. A semiconductor acceleration sensor, wherein a layer is provided, and when the movable part is displaced, the movable part and the insulating layer are in contact with each other so that the movable electrode and the fixed electrode are not in electrical contact with each other. . 2. A semiconductor device comprising: a semiconductor substrate having a movable portion that is displaced by receiving an acceleration; and a fixed substrate joined to the semiconductor substrate, wherein a movable electrode is provided on a surface of the movable portion facing the fixed substrate. In a semiconductor acceleration sensor having a fixed electrode provided on a surface of the fixed substrate facing the movable electrode, an insulation is provided at a position on the surface of the movable portion facing the fixed substrate and facing a region where the fixed electrode is not formed. A layer is provided, and when the movable section is displaced, the movable electrode and the fixed electrode are configured so as not to electrically contact with each other by contacting the insulating layer and the region where the fixed electrode is not formed. Semiconductor acceleration sensor.