JPH08285884A - Semiconductor capacitance type acceleration sensor - Google Patents

Abstract

PURPOSE: To obtain a semiconductor capacitance type acceleration sensor having structure suitable for miniaturization in which the process of assembling work can be simplified. CONSTITUTION: The capacitance between first and second electrodes 20, 21 formed on a first semiconductor substrate 12a and the opposing surface at the weight part 13 provided on a second semiconductor substrate 11 is detected. Since the first and second electrodes 20, 21 are connected with a plurality of lead-out electrodes on the first semiconductor substrate 11 signal can be taken out only from the lead-out electrode on the first semiconductor substrate 11 without leading out from the second semiconductor substrate 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type acceleration sensor using a semiconductor, and more particularly to a semiconductor capacitance type acceleration sensor suitably used for controlling a vehicle body of various vehicles such as automobiles.

[0002]

2. Description of the Related Art As a conventional acceleration sensor, for example, a structure shown in FIG. 10 has been proposed. This acceleration sensor is composed of an upper substrate 1 and a lower substrate 2 made of a silicon substrate. A weight portion 3 is provided on the upper substrate 1, and the weight portion 3 is supported by a support portion 5 via a cantilever 4. The lower end portion of the supporting portion 5 is fixed to the surface of the lower substrate 2 via the insulating film 5a, and the weight portion 3
Of the upper substrate 1 and the lower substrate 2 so that a slight gap D is provided between the end face 3a of the lower substrate 2 and the end face 2a of the lower substrate 2 on the upper substrate 1 side.
And are stuck. This acceleration sensor detects a change in electrostatic capacitance between the weight portion 3 and the lower substrate 2.

A wire 6 is bonded to an end surface of the upper substrate 1 opposite to the lower substrate 2 via an electrode 7, and
A wire 8 is bonded on the end surface 2a of the lower substrate 2 via an electrode 9, and the substrate 1,
2 are connected to external circuits respectively. In such an acceleration sensor, when acceleration is applied in the vertical direction in FIG. 10, the distance of the gap D changes, and an electrostatic capacitance that changes accordingly is detected by an external detection circuit via the wires 6 and 8. Then
This makes it possible to detect acceleration.

[0004]

In such an acceleration sensor, since the wires 6 and 8 for connecting the upper substrate 1 and the lower substrate 2 to the external circuit are formed at different heights, the acceleration sensor itself. The thickness is large, and the structure is not suitable for downsizing. Further, the wires 6 and 8 must be bonded at positions of different heights, which complicates the work process during assembly such as wire bonding.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a semiconductor capacitive acceleration sensor having a structure suitable for downsizing and simplifying the work process during assembly.

[0006]

According to the present invention, there is provided a first semiconductor substrate having first and second electrodes provided on one surface thereof,
A second semiconductor substrate provided to face the first semiconductor substrate, and the second semiconductor substrate includes:
A weight portion and a support portion arranged to face the first and second electrodes are provided, the weight portion is supported by the support portion via a cantilever, and the weight of the weight portion is provided on the surface of the first substrate. A plurality of extraction electrodes connected to the first and second electrodes are formed, and the capacitance of the facing surface of the first electrode and the weight portion and the capacitance of the facing surface of the second electrode and the weight portion. Is a semiconductor capacitance type acceleration sensor characterized by outputting a signal according to the above through an extraction electrode.

Still further, according to the present invention, wires are bonded to the plurality of extraction electrodes, and the capacitance of the facing surface of the first electrode and the weight portion and the facing surface of the second electrode and the weight portion. The semiconductor capacitive acceleration sensor is characterized in that it outputs a signal according to the electrostatic capacitance to the outside through the wire. The present invention also provides the first
On the surface of the semiconductor substrate, a signal processing circuit that processes a signal according to the capacitance of the facing surfaces of the first electrode and the weight portion and the capacitance of the facing surfaces of the second electrode and the weight portion is provided. It is a semiconductor capacitive acceleration sensor characterized by being formed.

The first and second semiconductor substrates of the present invention may be made of silicon.

[0009]

In the semiconductor capacitive acceleration sensor according to the present invention,
The first and second electrodes formed on the first semiconductor substrate and the electrostatic capacitance generated by the facing surface of the weight portion provided on the second semiconductor substrate facing the first and second electrodes are detected. . That is, since the facing surface of the weight portion is formed of the same semiconductor substrate, the capacitance of the facing surface of the first electrode and the weight portion and the capacitance of the facing surface of the second electrode and the weight portion. The signal corresponding to and can be detected by measuring the capacitance between the first and second electrodes. On the other hand, since the first and second electrodes are connected to the plurality of extraction electrodes on the first semiconductor substrate, the first and second electrodes are provided on the first semiconductor substrate without deriving a signal from the second semiconductor substrate. A signal corresponding to the capacitance can be output only by deriving a signal from the extraction electrode.

Since the signal corresponding to the electrostatic capacitance can be output only from the extraction electrode on the first semiconductor substrate, the signal corresponding to the electrostatic capacitance can be output on the surface of the first semiconductor substrate. By forming a signal processing circuit for processing, all signal processing can be performed on the first semiconductor substrate.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an acceleration sensor 10 according to an embodiment of the present invention.
2 is a sectional view taken along section line II-II of FIG. 1, and FIG. 3 is a sectional view taken along section line III-III of FIG. Hereinafter, the configuration of the acceleration sensor 10 will be described with reference to FIGS. The acceleration sensor 10 is composed of an upper substrate 11 and a lower substrate 12 made of a silicon substrate. A weight portion 13 is provided on the upper substrate 11, and the weight portion 13 cantilevers 14a, 14b, 14
It is supported by a supporting portion 15 provided around the weight portion 13 via c and 14d. The lower end portion 15a of the support portion 15 is fixed to the lower substrate 12 via the low melting point glass layer 16.

The surface 1 facing the upper substrate 11 of the lower substrate 12
A pair of electrodes 20 and 21 is formed on 2a, and a slight gap is provided between the end surface 13a of the weight portion 13 and these electrodes 20 and 21. This acceleration sensor detects a change in electrostatic capacitance between the weight portion 13 and the electrodes 20 and 21. As shown in FIG. 1, a cutout 22 is formed at the edge of the upper substrate 11 so that the edge of the surface 12a of the lower substrate 12 is exposed.
A plurality of extraction electrodes 25 are provided on the extraction electrode 25, and a plurality of wires 26 for connecting to an external circuit are provided on these extraction electrodes 25.
Are bonded.

A capacitor C1 is formed between the end surface 13a of the weight portion 13 and the electrode 20, and the weight portion 13 is formed.
A capacitor C2 is formed between the end surface 13a of the electrode and the electrode 21. Since the end surface 13a of the weight portion 13 is one surface of the silicon substrate, the capacitors C1 and C2 are connected in series via the end surface 13a. These two capacitors C1 and C2 are connected in series to a separately provided signal processing circuit 30, as shown in FIG.

In the acceleration sensor 10, when acceleration is applied in the vertical direction of FIG. 2, the distance between the end face 13a of the weight portion 13 and the electrodes 20 and 21 changes, and the electrostatic capacitances of the capacitors C1 and C2 change accordingly. The capacity is the signal processing circuit 30.
The acceleration can be detected by the output of the signal processing circuit 30. The two capacitors C
If the electrostatic capacities of 1 and C2 are C1 and C2 respectively,
The total capacitance C detected by the electrodes 20 and 21 is C = C1 · C2 / (C1 + C2) (1).

The signal processing circuit 30 may be provided outside the acceleration sensor 10 or may be formed as an IC inside the lower substrate 12. 5 is a plan view of the lower substrate 12, and FIG. 6 is a sectional view taken along the section line VI-VI of FIG. The lower substrate 12 is composed of a silicon substrate, and the electrodes 20 and 21 and the extraction electrode 25 are formed on the surface 12a by patterning with a metal material such as aluminum. Electrodes 20, 21
An integrated circuit section 31 (a hatched area in FIG. 5) is formed around the area by photolithography as in a normal IC. The signal processing circuit 30 may be formed in the integrated circuit unit 31, or other circuits may be formed.

The electrodes 20, 21 are connected to the connecting portions 20a, 2
Each of them is connected to a part of a circuit element (not shown) provided in the integrated circuit section 31 via 1a. Further, the extraction electrode 25 is also connected to a part of a circuit element (not shown) provided in the integrated circuit portion 31 via the connecting portion 25a. In this way, the electrodes 20 and 21 are connected to the extraction electrode 25 via the integrated circuit section 31.

Since the electrodes 21, 21 are provided on the lower substrate 12 in this manner, the capacitors C1, C2 are connected in series between the electrodes 20, 21 via the end face 13a, With this, by detecting the electrostatic capacitance between the electrodes 20 and 21, the total sum of the electrostatic capacitances of the capacitors C1 and C2 can be detected. On the other hand, electrode 2
Since 0 and 21 are connected to the extraction electrode 25 via the integrated circuit section 31, it is possible to extract a signal corresponding to the above-mentioned capacitance from the extraction electrode 25, and the acceleration is detected based on this signal. It

As described above, in the acceleration sensor of the present invention, the lead electrode is not provided on the upper substrate 11, and only the wire 26 is bonded to the lead electrode 25 formed on the lower electrode 12, so that the signal can be led to the outside. You can Therefore,
Since it is not necessary to bond a wire to the upper substrate 12, the thickness of the acceleration sensor 10 itself can be reduced by that much, and the configuration suitable for downsizing is achieved.

Further, since it is not necessary to bond the wire on the upper substrate 11 and it is sufficient to bond the wire 26 only to the extraction electrode 26 on the lower substrate 12, it is not necessary to bond the wire 26 at the positions of different heights. It is possible to simplify the work process during assembly such as bonding.
7 is a plan view of the upper substrate 11, and FIG. 8 is a sectional view taken along the section line VIII-VIII of FIG. On the upper substrate 11,
Substantially L-shaped holes 17a, 17b, 17c, 17d are formed, and the four cantilevers 14a, 14b, 1 are provided in a portion sandwiched by these holes 17a, 17b, 17c, 17d.
4c and 14d are formed. Weight portion 13 and support portion 1
5 is four cantilevers 14a, 14b, 14c,
14d is connected. In this way, the weight unit 13
It is supported by the support portion 15 via the four cantilevers 14a, 14b, 14c, 14d. The cantilevers 14a, 14b, 14c and 14d are the weight portions 13
The weight portion 13 is formed to be sufficiently thin as compared with the weight portion 13 so that it slightly bends when acceleration is applied in the thickness direction. In addition, the edge portion of the support portion 15 has the extraction electrode 2 provided on the lower substrate 12.
A notch 22 is formed to bond the wire to the wire 5.

As the upper substrate 11 and the lower substrate 12, for example, silicon substrates having a specific resistance of 0.1 Ωcm or less are used. In the upper substrate 11, substantially L-shaped holes 17a, 1
The shapes such as 7b, 17c and 17d are formed by etching a silicon wafer by ordinary photolithography. Specifically, potassium hydroxide (KOH)
Is formed by etching the wafer as an etching solution. In this case, the concentration of the etching solution is set to KOH: H ₂ 0 = 9: 1 to 4: 6, and heating is performed at 80 to 120 ° C. for etching. After that, the silicon wafer is diced into a predetermined shape so that the upper substrate 1 shown in FIGS.
1 is obtained.

On the other hand, on the lower substrate 12, the electrodes 20, 2
1, the extraction electrode 25, and the integrated circuit portion 30 are formed on a silicon wafer by ordinary photolithography. The electrode 30 has a width W = 0.5 mm and a length L = 1.0 m
m, thickness T = 1.0 μm, distance d between both electrodes 30 = 0.2
It is set to 5 mm. After that, the lower substrate 12 shown in FIGS. 5 and 6 is obtained by dicing the silicon wafer into a predetermined shape.

The upper substrate 11 and the lower substrate 12 thus obtained are attached to each other so that the lower end surface 13a of the weight portion 13 faces the lower substrate 12. At this time, the support portion 15
A low-melting point glass is used as an adhesive between the lower end portion 15a and the lower substrate 11. The adhesion of the two substrates is achieved by heating the low melting point glass at 300 ° C. for 10 hours. At this time, the thickness of the low melting point glass 16 is set so that the distance between the lower end surface 13a of the weight portion 13 and the surface of the electrode 30 is 1.0 μm.

In this embodiment, the cantilever is formed in a linear shape. However, the shape is not limited to this. For example, as shown in FIG.
You may form 0b, 40c, 40d. Further, in this embodiment, the two electrodes 20 and 21 are formed on the surface of the lower substrate 11, but the number of electrodes is not limited to two, and one electrode may be used, or three or more electrodes may be formed. May be.
Further, the silicon substrate is selected as the material for the upper substrate 10 and the lower substrate 11, but other semiconductor substrates such as gallium / arsenic substrate may be used.

[0024]

As described above, according to the present invention, the electrostatic charges can be obtained by only deriving the signal from the extraction electrode on the first semiconductor substrate without deriving the signal from the second semiconductor substrate. Since the signal corresponding to the capacitance can be output, the signal can be led to the outside only by bonding the wire to the extraction electrode on the first semiconductor substrate. Therefore, it is not necessary to bond the wire on the second semiconductor substrate, and the thickness of the semiconductor acceleration sensor itself can be reduced accordingly, and the configuration suitable for downsizing can be obtained.

Further, it is not necessary to bond the wire on the second semiconductor substrate, and it is sufficient to bond the wire only to the extraction electrode on the first semiconductor substrate. Therefore, it is not necessary to bond the wire at positions of different heights. It is possible to simplify the work process during assembly such as wire bonding.

[Brief description of drawings]

FIG. 1 is an acceleration sensor 10 according to an embodiment of the present invention.
Top view of

FIG. 2 is a sectional view taken along the section line II-II in FIG.

FIG. 3 is a sectional view taken along section line III-III in FIG.

FIG. 4 is a block diagram showing an electrical configuration of the acceleration sensor 10.

FIG. 5 is a plan view of the lower substrate 12.

6 is a sectional view of FIG. 6 taken along section line VI-VI of FIG.

FIG. 7 is a plan view of the upper substrate 11.

8 is a sectional view taken along the line VIII-VIII in FIG.

FIG. 9 is a plan view of an acceleration sensor according to another embodiment of the present invention.

FIG. 10 is a typical prior art cross-sectional view.

[Explanation of symbols]

 11 ... Upper substrate 12 ... Lower substrate 13 ... Weight part 13a ... End surface 14a, 14b, 14c, 14d ... Cantilever 15 ... Support part 20, 21 ... Electrode 26 ...・ Wire 30 ・ ・ ・ Signal processing circuit

Claims (4)

[Claims] 1. A first semiconductor substrate having first and second electrodes provided on one surface thereof, and a second semiconductor substrate provided so as to face the first semiconductor substrate. Then, the second semiconductor substrate is provided with a weight portion and a support portion arranged to face the first and second electrodes, and the weight portion is supported by the support portion via a cantilever. A plurality of extraction electrodes connected to the first and second electrodes are formed on the surface of the first semiconductor substrate,
A signal according to the capacitance of the facing surface of the first electrode and the weight portion and the capacitance of the facing surface of the second electrode and the weight portion is output via the extraction electrode. Semiconductor capacitive acceleration sensor. 2. A wire is bonded to the plurality of extraction electrodes, and a capacitance is provided between opposing surfaces of the first electrode and the weight portion and a capacitance of opposing surfaces of the second electrode and the weight portion. The semiconductor capacitive acceleration sensor according to claim 1, wherein a corresponding signal is output to the outside through the wire. 3. The surface of the first semiconductor substrate is responsive to the capacitance of the facing surface of the first electrode and the weight portion and the capacitance of the facing surface of the second electrode and the weight portion. The semiconductor capacitive acceleration sensor according to claim 1 or 2, wherein a signal processing circuit for processing a signal is formed. 4. The semiconductor capacitive acceleration sensor according to claim 1, wherein the first and second semiconductor substrates are made of silicon.