JPH07113817A - Acceleration sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a semiconductor capacitance type acceleration sensor having a highly reliable through hole portion with high manufacturing yield. [Structure] A three-layer structure in which a mass part (movable electrode) 2 and a single crystal silicon plate 1 on which a cantilever 3 is formed are sandwiched by glass plates 4 and 5 having fixed electrodes 6 and 7, and a fixed electrode 6 In the acceleration sensor including the through hole portion 9 in the connection path to the wire bonding pad 11, the conductive film reinforcing portion is provided in a part of the electrode lead portion 8 including the through hole portion 9. [Effect] The conductive film can be sufficiently secured on the inner wall of the through hole portion 9 provided between the connection paths to the wire bonding pad 11 without increasing the thickness of the fixed electrode 6 more than necessary. It is possible to suppress the occurrence of wire breakage and connection failure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor capacitance type acceleration sensor, and more particularly to an acceleration sensor suitable for being mounted on an automobile and used for airbag control and vehicle body attitude control.

[0002]

2. Description of the Related Art In recent years, with increasing interest in vehicle body attitude control systems such as airbag systems and active suspension systems for automobiles, various acceleration sensors have been proposed.
One of them is a capacitance detection type acceleration sensor based on semiconductor technology. As a conventional technique of this type of acceleration sensor, for example, there is one described in Japanese Patent Laid-Open No. 4-16769, and the acceleration sensor according to this conventional technique includes an upper glass plate provided with a fixed electrode and a mass part ( Movable electrode part)
Of a laminated structure consisting of three layers of a silicon plate on which is formed a fixed glass plate and a lower glass plate on which a fixed electrode is formed. A connection path with the connection terminal is provided.

The term "through hole portion" as used herein means that a through hole is provided in a plate-shaped dielectric material, and a conductive film is formed on the inner surface of the plate-shaped dielectric material. It is meant to provide a conductive path between the faces.

Other conventional techniques for providing a connecting path by providing through holes include those disclosed in, for example, JP-A-61-166082 and JP-A-55-86165. Is a structure in which a plurality of conductive layers and insulating layers are stacked, a through hole is provided in an edge layer stacked on the conductive layer, and by stacking a conductive layer on the structure, a lower conductive layer and an upper conductive layer are stacked. The connection path is given to.

[0005]

In the above-mentioned prior art, no particular consideration is given to the optimum film thickness of the fixed electrode and the connection path, and in the acceleration sensor in which the gap between the fixed electrode and the movable electrode is about 1 to 5 μm. When the film thickness of the fixed electrode is increased, the variation in film thickness affects the detection accuracy of the sensor, and when the film thickness of the connection path is decreased, the film thickness inside the through hole provided on the glass plate becomes insufficient. However, there is a problem that connection failure or disconnection may occur.

That is, in such an acceleration sensor,
Sputtering or vapor deposition is used to form the fixed electrode, but at this time, in the above-mentioned conventional technique, as shown in FIG. 3, the film thickness of the electrode lead portion 8 continuously formed from the fixed electrode 6 is changed. On the other hand, since the conductive film inside the through-hole portion 9 is formed thin, disconnection of the connection path and contact failure occur.

On the other hand, if the conductive film inside the through-hole portion 9 is formed to have a sufficient thickness to ensure conduction,
When viewed on a wafer-by-wafer basis, the thickness of the fixed electrode 6 varies greatly, and it becomes difficult to manage the gap between the fixed electrode and the movable electrode. In addition, this FIG.
It is an enlarged view of a portion A surrounded by a broken line in (a).

An object of the present invention is to provide an acceleration sensor which does not lower the detection accuracy of the sensor, eliminates the risk of disconnection in the through hole portion, and can sufficiently improve the manufacturing yield and reliability. To provide.

[0009]

SUMMARY OF THE INVENTION The above-mentioned object is to stack two sides of a semiconductor plate-shaped member, in which a mass portion serving as a movable electrode is formed, on at least one side of which two glass plates are formed, and to fix the above-mentioned fixed plate. In a semiconductor capacitance type acceleration sensor having a through hole portion penetrating the glass plate in a connection path between an electrode and an external terminal, a film of the connection path in the vicinity of the through hole portion with respect to a film thickness of the fixed electrode. This is achieved by making the thickness thicker.

[0010]

[Function] The fixed electrode portion formed of the thin conductive film has a uniform thickness, and the electrode lead portion (connection path) formed of the thick conductive film has an inner wall surface of the through hole portion where it is difficult to secure the film thickness. Also works to secure a sufficient film thickness.

Therefore, by limiting the film thickness of the fixed electrode, it is possible to suppress the variation in the distance between the movable electrode and the fixed electrode caused by the variation in the film thickness within the wafer, and to reduce the film thickness of the electrode lead portion (connection path). By increasing the thickness, a sufficient film thickness can be secured even on the inner wall surface of the through hole portion, and the risk of disconnection or contact failure can be sufficiently eliminated.

[0012]

EXAMPLE An acceleration sensor according to the present invention will be described below.
This will be described in detail with reference to the illustrated embodiment.

FIG. 1 shows an embodiment of the present invention, and FIG. 1 (a) is a sectional view and FIG. 1 (b) is a front view thereof. In these figures, 1 is a silicon plate, Reference numeral 4 denotes an upper glass plate, and 5 denotes a lower glass plate, which are laminated to form an acceleration sensor.

The upper glass plate 4 and the lower glass plate 5 are respectively provided with an upper fixed electrode 6 and a lower fixed electrode 7 made of a thin film of a conductive material such as aluminum (Al). These are formed by photolithography after forming a film on the entire surface of each glass plate 4, 5 by sputtering or vapor deposition.

The silicon plate 1 is made of single crystal silicon and has a mass portion 2 also serving as a movable electrode and a cantilever 3.
Are formed, but these are formed by etching to which a micromachining technique is applied.

The glass plates 4 and 5 and the silicon plate 1 are laminated with the silicon plate 1 sandwiched in the middle so that the fixed electrodes 6 and 7 face the mass part 2.
Can be assembled.

Anodic bonding is usually used for bonding these three layers.

Returning to FIG. 1, 8 is an electrode lead, 9 is a through hole portion, 10 is a filler, and 11, 12, and 13 are wire bonding pads.

Of these wire bonding pads, the wire bonding pad 11 is first provided on the surface of the upper glass plate 4 (the upper surface in the figure), and then the wire bonding pad 12 is formed on the silicon plate 1. The wire bonding pads 13 are provided on the upper side surface and on the upper surface of the lower glass plate 5, respectively, and the wire bonding pads 11 serve as terminals for connecting the upper fixed electrode 6 to the outside. The wire bonding pad 12 serves as a terminal for connecting the mass portion 2 which also serves as a movable electrode, and the wire bonding pad 13 serves as a terminal for connecting the lower fixed electrode 7 to the outside.

Here, first, the mass portion 2 also serving as a movable electrode.
The connection path from the wire bonding pad 12 to the wire bonding pad 12 is formed as it is because the wire bonding pad 12 is directly provided on the upper surface of the silicon plate 1.

Further, the lower fixed electrode 7 is provided with a lower electrode connecting path (not shown in the figure) on the lower glass plate 5, whereby the lower fixed electrode 7 is provided. Are directly connected to the wire bonding pad 13.

However, the connection between the upper fixed electrode 6 and the wire bonding pad 11 is provided on different surfaces of the upper glass plate 4, respectively.
It is necessary to connect through the through-hole portion 9. Therefore, first, the upper fixed electrode 6 and the lower electrode lead-out portion of the through-hole portion 9 are connected by the electrode lead 8, and the through-hole portion 9 is further connected. A connection path is obtained by connecting the upper electrode lead-out part of the wire bonding pad 11 to the wire bonding pad 11, so that the signal from the upper fixed electrode 6 is taken out to the wire bonding pad 11. In addition, the inside of this through hole portion 9,
A part of the space between the upper glass plate 4 and the silicon plate 1 is filled with a filler 10 made of a suitable material such as a silicone resin, and has a structure for preventing water or foreign matter from entering from the outside.

FIG. 2A is an enlarged view of a portion A surrounded by a broken line in FIG. 1. As is apparent from FIG. 2A, this embodiment will be described with reference to FIG. Unlike the case of the prior art described above, the electrode lead reinforcing portion 14 in which the film thickness of the electrode lead portion 8 is increased is formed in the portion including the through hole portion 9.

According to the embodiment shown in FIG. 2A, the inner wall surface of the through-hole portion 9 is formed on the entire surface of the upper glass plate 4 on which the fixed electrode 6 is formed (the lower surface in FIG. 2A). A conductive film having a film thickness sufficient to ensure electrical continuity, for example, 1 μm or more on the surface on which the fixed electrode 6 is formed, and the conductive film is removed using photolithography technology while leaving the electrode lead reinforcing portion 14. In addition, since a fixed electrode is formed on the entire surface of the same surface, a thin conductive film is formed so that variation in film thickness does not occur.
For example, it is formed by forming a film having a thickness of 0.1 μm to 0.5 μm and removing the conductive film by using a photolithography technique while leaving the fixed electrode 6, the electrode lead portion 8 and the electrode lead reinforcing portion 14.

Next, in FIG. 2B, the fixed electrode 6 and the electrode lead portion 8 are first formed in the procedure shown in FIG. 2A, and then the electrode is formed by mask sputtering or mask vapor deposition. The lead reinforcing portion 14 is formed.

As described above, by providing the electrode lead reinforcing portion 14 in the portion of the electrode lead portion 8 that extends over the through hole portion 9, there is no wire breakage or contact failure in the through hole portion while suppressing the film thickness variation of the fixed electrode 6. can do.

[0027]

According to the present invention, even if a through-hole portion is used for extracting a signal from the fixed electrode, there is no fear of disconnection or connection failure, and it is effective in improving reliability, and the fixed electrode and the movable electrode are effective. It is also effective in improving the measurement accuracy of the sensor and in improving the yield because it is possible to reduce the variation in the interval.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an acceleration sensor according to the present invention.

FIG. 2 is an enlarged view of a through hole portion according to an embodiment of the present invention.

FIG. 3 is an enlarged view of a through hole portion showing a conventional example of an acceleration sensor.

[Explanation of symbols]

1 ... Silicon plate, 2 ... Mass part (movable electrode), 3 ... Cantilever, 4 ... Upper glass plate, 5 ... Lower glass plate, 6
... Upper fixed electrode, 7 ... Lower fixed electrode, 8 ... Upper electrode lead, 9 ... Through hole part, 10 ... Filler, 11,1
2, 13 ... Wire bonding pads, 14 ... Electrode lead reinforcing portions.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahide Hayashi 2520 Takaba, Katsuta City, Ibaraki Prefecture Hitachi Ltd. Automotive Equipment Division

Claims (2)

[Claims] Claim: What is claimed is: 1. A semiconductor plate-shaped member having a mass portion to be a movable electrode, and both surfaces thereof are laminated with two glass plates having a fixed electrode formed on at least one side thereof, and a connection between the fixed electrode and an external terminal is formed. In a semiconductor electrostatic capacitance type acceleration sensor having a through hole penetrating the glass plate in a path, in a connection path formed continuously with the fixed electrode, a portion where a conductive material is overlapped and thickened at a portion including the through hole. An acceleration sensor comprising: 2. A semiconductor plate-shaped member on which a mass portion serving as a movable electrode is formed is laminated on at least one side of two glass plates on which fixed electrodes are formed, and a connection between the fixed electrode and an external terminal is formed. A semiconductor capacitance type acceleration sensor having a through hole penetrating the glass plate in a path, wherein the connection path is thicker than the fixed electrode.