JPH07128360A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To provide a semiconductor acceleration sensor in which leak current is prevented between a sensing element and a stripper to which voltage is applied when a drive voltage is applied for the purpose of self-diagnosis. CONSTITUTION:A recess 10 for preventing current leak between the semiconductor substrate parts of a sensing element A and an upper stopper B at the time of self-diagnosis by ensuring a sufficient spatial distance and creeping distance is formed around the upper stopper B on the joint face side thereof.

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 A conventional semiconductor acceleration sensor of this type is
As shown in FIG. 2, a weight portion 1, a flexible portion 3 that is integrally connected to the weight portion 1 at one end and is fixed to one side of the frame-shaped support portion 2 at the other end, and which is linked to the movement of the weight portion 1. The supporting unit 2 is formed by processing a Si semiconductor substrate, and a gauge resistor 4 for extracting a voltage proportional to the applied acceleration as an output is provided on the bending unit 3 and the sensing unit A and the sensing element A are provided above and below the sensing unit A. The upper and lower stoppers B and C, which are respectively located and are joined to the support portion 2 and regulate so that the weight portion 1 is not displaced by a certain value or more when an excessive acceleration is applied, have a basic configuration. The sensing element A has a rectangular shape, the supporting portion 2 surrounds the periphery of the weight portion 1, and the stoppers B and C also have a rectangular shape.

More specifically, the upper and lower parts of the weight portion 1 and the support portion 2 will be described.
Thermal oxidation of the surface (SiO₂, Si₃N _FourEtc.) Insulating film such as film
7 is formed, and also on the joint surface of the upper and lower stoppers B and C.
A similar insulating film 7'is formed, and the insulating films 7 and 7'on each bonding surface are formed.
The spaces are joined by a metal film 6 of Au, AuGe or the like. Also
On the insulating film 7 on the upper surface of the weight portion 1 facing the upper stopper B
Similarly, a metal film 5 is formed on the
The metal film 5 is electrically connected to the semiconductor substrate via the conductor 8.
There is. On the other hand, a metal film is also formed on the insulating film 7 on the upper surface of the supporting portion 2.
9 is formed, and this metal film 9 is used as the Si half that constitutes the supporting portion 2.
It is electrically connected to the conductor substrate through the conductor 8 '.

When the positive electrode of the DC power source E is connected to the metal film 9 and the negative electrode is connected to the Si semiconductor substrate forming the upper stopper B, and a driving voltage is applied between the sensing element A and the upper stopper B, the voltage is applied. It is possible to generate an electrostatic force between the weight portion 1 and the upper stopper B in proportion to the square of Due to this electrostatic force, the weight portion 1 moves toward the upper stopper B side as if acceleration is applied, and bends the bending portion 3.

In other words, by applying a drive voltage, the same state as that in which acceleration is applied to the weight portion 1 is created, and the operation diagnosis is made by observing the change in the electrical conductivity of the gauge resistor 4 according to the bending of the bending portion 3 at this time. Can be done. In this way, the structure for applying the drive voltage between the upper stopper B and the weight portion 1 to cause the same behavior as when the acceleration is applied to the weight portion 1 becomes the self-diagnosis means.

[0006]

By the way, the main premise for the self-diagnosis means to be established is that a drive voltage can be reliably applied between the sensing element A and the upper stopper B, and the self-diagnosis drive voltage can be electrically applied within the self-diagnosis drive voltage range. There is complete insulation. However, in the conventional example, although the insulation is secured by the insulating film 7 ′ on the joint surface of the upper stopper B to the sensing element A, there is a problem that the current is likely to leak around the upper stopper B for the following reasons (1) to (3). It was

At the time of self-diagnosis drive, a relatively high voltage of several tens of V is generally applied. Since the end surface of the sensor chip is a surface cut by dicing, it is not insulated. The insulating film thickness is at most about 1 μm, and therefore the clearance between the end faces of the sensing element A and the upper stopper B is about 4 to 5 μm even if the metal film of the bonding layer is taken into consideration. As shown in FIG. If there is only a gap, there will be no leakage, but in reality, foreign matter, especially silicon shavings during dicing, etc., may enter the gap, and if cleaning cannot be completed, a creeping distance of 2 μm may occur. It is easy to leak.

The end surface is chipped during dicing. When the crack reaches the metal film, it tends to leak along the surface. The present invention has been made in view of the above problems, and an object thereof is to generate a leak current between a sensing element and a stopper to which a voltage is applied when a drive voltage for self-diagnosis is applied. In order to provide a semiconductor acceleration sensor that prevents the above.

[0009]

In order to achieve the above object, according to the present invention, a weight portion formed by processing a semiconductor substrate and one end of the weight portion are integrally connected and the other end is integrally supported by a supporting portion. A sensing unit that includes a bending portion that bends in response to the movement of the weight portion and the support portion, and has a unit that takes out a voltage proportional to the applied acceleration as an output, and is located above and below the sensing element. , A voltage is applied between one of the upper and lower stoppers, the sensing element, and the stopper, which is joined to the support portion and regulates the weight portion so as not to be displaced by a certain value or more when excessive acceleration is applied. A semiconductor acceleration sensor equipped with self-diagnosis means for confirming whether the sensing element is functioning normally by generating an electrostatic force between the weight portion and the stopper. In, and forming a lower recess the joint surfaces around the bonding surface side of the stopper comprising a voltage application target of the self-diagnosis means.

[0010]

According to the invention of claim 1, since the recess lower than the joint surface is formed around the joint surface side of the stopper to which the voltage is applied by the self-diagnosis means, the semiconductor substrate portion of the sensing element and the voltage application are formed. It is possible to secure a sufficient space distance and creepage distance between the target stopper and the semiconductor substrate portion, and to apply a self-diagnostic drive voltage of several tens of volts between the target stopper and the sensing element. However, it is possible to prevent a leak current from occurring.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a sectional structure of this embodiment, which is basically the same as the conventional example shown in FIG. 2, but in order to solve the conventional problems in the self-diagnosis means, the upper stopper B is used in this embodiment. The periphery of the joint surface side is recessed to form a recess 10 that is one step lower than the joint surface.

Then, the DC film E is applied to the metal film 9 of the supporting portion 2.
When the driving voltage is applied between the sensing element A and the upper stopper B by connecting the positive electrode of the above and the negative electrode of the Si semiconductor substrate forming the upper stopper B, electrostatic force is generated between the sensing element A and the upper stopper B and the weight portion 1. Although it can be generated between the upper stopper B and the operation diagnosis as in the conventional case, the semiconductor acceleration sensor of the present invention uses the recess 10 to detect the semiconductor substrate portion of the sensing element A and the upper stopper B. Since a sufficient space distance and creepage distance from the semiconductor substrate portion can be secured, current leakage does not occur during self-diagnosis.

The method used for the concave processing may be any processing method such as etching processing with KOH or the like, or other mechanical processing. Needless to say, when applying the self-diagnosis drive voltage between the sensing element A and the lower stopper C, it is sufficient to form a recess around the joint surface side of the lower stopper C.

[0014]

According to the present invention, since the recess lower than the joint surface is formed around the joint surface side of the stopper to which the voltage is applied by the self-diagnosis means, the semiconductor substrate portion of the sensing element and the target of voltage application. It is possible to secure a sufficient space distance and creepage distance between the stopper and the semiconductor substrate portion, and even if a self-diagnostic drive voltage of several tens of volts is applied between the stopper and the sensing element to which the voltage is applied. There is an effect that it is possible to prevent the occurrence of a leak current.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional example.

[Explanation of symbols]

 A Sensing element B Upper stopper C Lower stopper E DC power supply 1 Weight part 2 Support part 3 Bending part 9 Metal film 10 Recess

Claims (1)

[Claims] 1. A weight portion formed by processing a semiconductor substrate, and a bending portion which is integrally connected to the weight portion at one end thereof and is integrally supported at the other end by a supporting portion so as to bend in association with the movement of the weight portion. A sensing unit comprising the supporting part and having means for taking out a voltage proportional to the applied acceleration as an output, which are respectively located above and below the sensing element and are joined to the supporting part when an excessive acceleration is applied. A voltage is applied between the upper and lower stoppers that regulate the weight portion so that it does not displace by a certain value or more, and either the sensing element or the stopper to generate an electrostatic force between the weight portion and the stopper. In a semiconductor acceleration sensor having a self-diagnosis means for confirming whether or not the sensing element is functioning normally, the voltage application target by the self-diagnosis means is not applied. The semiconductor acceleration sensor, characterized in that the formation of the lower recess the joint surfaces around the bonding surface side of the stopper.