JPH10206169A - Capacitance-type external-force detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a capacitance-type external-force detector which enhances the detecting sensitivity of an external force by a method wherein a parasitic capacitance generated from a silicon substrate is reduced. SOLUTION: Separating grooves 38 are formed on a silicon substrate 22, pad formation parts 36 in which output electrode pads 37 are formed are separated electrically from electrode supports 27 at a detection part 23 and from circuit formation parts 31 in which capacitance-to-voltage conversion circuits 32 are formed. Thereby, the area of the electrode supports 27 and that of the circuit formation parts 31 are reduced, and a parasitic capacitance component which is mixed with a capacitance detected by detecting electrodes 29 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type external force detecting device for detecting an external force such as acceleration, angular velocity or the like as a change in capacitance.

[0002]

2. Description of the Related Art In general, a capacitance type external force detecting device for detecting acceleration and angular velocity acting on a vehicle and the like and detecting camera shake is known from, for example, Japanese Patent Application Laid-Open No. 4-242114. Such a capacitance type external force detection device includes a detection unit that detects an external force as a change in capacitance,
And a capacitance-voltage conversion circuit for converting a change in capacitance detected by the detection unit into a voltage signal.

FIGS. 14 and 1 show an example of an angular velocity detecting device as an example of a conventional capacitance type external force detecting device.
This will be described with reference to FIG.

[0004] Reference numeral 1 denotes an angular velocity detecting device as a conventional capacitance type external force detecting device.
As described later, the sensor chip 2 includes a sensor chip 2 provided with a detection unit 4 and a conversion circuit chip 12 provided with a capacitance-voltage conversion circuit 14.

A sensor chip 2 is formed as a separate chip from the conversion circuit chip 12, as shown in FIG.

Reference numeral 3 denotes a silicon substrate constituting the sensor chip 2. The silicon substrate 3 includes a front side silicon layer 3A made of a silicon material, a back side silicon layer 3B made of a silicon material, and a front side silicon layer 3A. It is provided between the back side silicon layer 3B and the insulating layer 3C made of silicon oxide or the like. The surface side silicon layer 3A of the silicon substrate 3 is made to have a low resistance by doping impurities such as phosphorus and boron.

Reference numeral 4 denotes a silicon layer 3 on the front side of the silicon substrate 3.
A detection unit provided by performing etching on A, wherein the detection unit 4 is located at the center of the silicon substrate 3 and is provided so as to be capable of vibrating in a direction parallel to the silicon substrate 3; The electrode supports 6, 6,... Provided at four places around the vibrator 5 and fixed to the silicon substrate 3 are provided.
It is roughly composed of

Here, the vibrator 5 has four support beams 7,
Are supported on the silicon substrate 3 by. Then, as shown in FIG. 15, the vibrator 5 floats above the silicon substrate 3 by removing a part of the insulating layer 3C of the silicon substrate 3 by etching. This allows the vibrator 5 to vibrate in the X and Y directions indicated by arrows in FIG. Also, comb-shaped electrodes 5A, 5A,... Are provided on each side of the vibrator 5.

On the other hand, each electrode support 6 has a comb-shaped electrode 6
A, 6A,... Are provided, and the comb-shaped electrodes 6A are engaged with the respective comb-shaped electrodes 5A of the vibrator 5 in a separated state.

Here, in FIG. 14, the comb-shaped electrodes 5A and 6A located on the upper side and the comb-shaped electrodes 5A located on the lower side are shown.
A and 6A constitute the drive electrode 8, respectively. These drive electrodes 8 vibrate the vibrator 5 in the direction indicated by the arrow Y in FIG. 14 by generating an electrostatic force between the comb-shaped electrodes 5A and 6A.

In FIG. 14, the comb electrodes 5A and 6A located on the left side and the comb electrodes 5A located on the right side
A and 6A constitute the detection electrode 9, respectively. When the vibrator 5 vibrates in the X direction indicated by the arrow in FIG.
This is to detect a change in capacitance occurring between A and A.

Reference numerals 10 and 10 denote input electrode pads provided on the surface of each of the electrode supports 6 located on the upper and lower sides in FIG. 14, and the input electrode pads 10 are used to vibrate the vibrator 5. The oscillation circuit which outputs the drive signal of the above is connected via a wire (neither is shown).

Numerals 11 and 11 denote output electrode pads provided on the surface of each electrode support 6 located on the left and right sides in FIG. 14, respectively.
The change of the capacitance detected by the above is output.

A conversion circuit chip 12 is formed as a separate chip from the sensor chip 2.

Reference numeral 13 denotes a circuit board constituting the conversion circuit chip 12, and 14 denotes a capacitance-voltage conversion circuit provided on the circuit board 13. The capacitance-voltage conversion circuit 14 is detected by each detection electrode 9 of the detection unit 4. This is a circuit for converting the change in the capacitance to a voltage, and is configured by, for example, a capacitor bridge circuit or a switched capacitor circuit.

Reference numerals 15, 15,... Denote input electrode pads provided on the circuit board 13.
Is for receiving a change in capacitance detected by each detection electrode 9 and output from the output electrode pad 11 of the sensor chip 2 and inputting the change in capacitance to the capacitance-voltage conversion circuit 14. .

Reference numerals 16 and 16 denote output electrode pads for outputting a voltage signal output from the capacitance-voltage conversion circuit 14 to a signal processing circuit (not shown) provided outside.

Reference numeral 17 denotes a wire for electrically connecting one of the output electrode pads 11 of the sensor chip 2 to the input electrode pad 15 of the conversion circuit chip 12, and the end of the wire 17 is connected to the output electrode pad of the sensor chip 2. 11, are connected to the input electrode pads 15 of the conversion circuit chip 12 by solders 18, 18, respectively.

The other output electrode pad 11 of the sensor chip 2 is provided with a wire for connecting to the other input electrode pad 15 of the conversion circuit chip 12, and each input electrode pad 10 of the sensor chip 2 is provided with a wire. In addition, wires for connecting to an oscillation circuit are provided, and wires for connecting to an external signal processing circuit are provided on each output electrode pad 16 of the conversion circuit chip 12, respectively.
In FIG. 15, the description of these wires is omitted.

The angular velocity detecting device 1 according to the prior art has the above-described configuration, and its operation will be described below.

That is, when a drive signal is supplied from an oscillation circuit (not shown) to the input electrode pad 10 of the sensor chip 2, an electrostatic force is generated between the comb electrodes 5A and 6A constituting each drive electrode 8. The vibrator 5 vibrates in the direction indicated by the arrow Y in FIG. When the angular velocity Ω around the ZZ axis in FIG. 15 acts while the vibrator 5 is vibrating in this manner, the vibrator 5 vibrates in the direction indicated by the arrow X due to Coriolis force. As a result, the separation distance between the comb-shaped electrodes 5A and 6A constituting each detection electrode 9 changes, so that the capacitance between the comb-shaped electrodes 5A and 6A changes. As a result, a change in capacitance detected by each detection electrode 9 is output from the output electrode pad 11 of the sensor chip 2.

The change in the capacitance output from the output electrode pad 11 of the sensor chip 2 is input to the input electrode pad 15 of the conversion circuit chip 12 via the wire 17, and the capacitance voltage is output from the input electrode pad 15. Conversion circuit 14
Is input to Then, the change in the capacitance is converted into a voltage signal by the capacitance-voltage conversion circuit 14 and output from each output electrode pad 16 to an external signal processing circuit. Then, the angular velocity is obtained by an external signal processing circuit.

[0023]

In the above-described angular velocity detecting device 1 according to the prior art, the sensor chip 2 and the conversion circuit chip 12 are connected by wires 17 or the like, and are detected by the respective detecting electrodes 9 of the sensor chip 2. The change in the capacitance is output to the capacitance-voltage conversion circuit 14 of the conversion circuit chip 12 via the wire 17 or the like. For this reason, each electrode support 6 provided on the sensor chip 2 has a wire 1
An output electrode pad 11 is provided for connecting the first electrode 7 and the like. Therefore, it is necessary to increase the area of each electrode support 6 in order to provide the output electrode pad 11.

That is, the vibrator 5 which is a component of the detection unit 4
Can be finely formed by micromachining technology, while the output electrode pad 11
It is difficult to reduce the size as in the case of the vibrator 5 for reasons such as securing the bonding area. Therefore, the output electrode pad 11
Is provided on each electrode support 6, the area of each electrode support 6 is greatly increased.

However, when the area of each electrode support 6 of the detection section 4 increases, the silicon layer 3 on the front side of the silicon substrate 3
The parasitic capacitance generated between A and the backside silicon layer 3B increases. That is, as shown in FIG.
Has a configuration in which an insulating layer 3C is provided between the front-side silicon layer 3A and the back-side silicon layer 3B, so that a parasitic capacitance is formed between the front-side silicon layer 3A and the back-side silicon layer 3B. Occurs. This parasitic capacitance increases as the area of the front side silicon layer 3A and the back side silicon layer 3B increases.

Therefore, when the area of each electrode support 6 increases, the parasitic capacitance generated between the front side silicon layer 3A and the back side silicon layer 3B constituting each electrode support 6 increases, and this parasitic capacitance is reduced. There is a problem that the increase decreases the detection sensitivity of the angular velocity.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a capacitance type external force detecting device capable of reducing parasitic capacitance generated from a silicon substrate and improving external force detection sensitivity. It is intended to be.

[0028]

According to a first aspect of the present invention, there is provided a silicon substrate having an insulating layer interposed between a front side silicon layer and a back side silicon layer; A detection unit provided on the front surface silicon layer of the substrate and detecting an external force by a change in capacitance; and a detection unit provided on the front surface silicon layer of the silicon substrate and detecting a change in the capacitance output from the detection unit. A capacitance-voltage conversion circuit for converting a signal into a signal, and an output electrode provided on the surface-side silicon layer of the silicon substrate, for outputting a voltage signal output from the capacitance-voltage conversion circuit to an external signal processing circuit, The silicon substrate is provided with an insulating portion for electrically separating the surface-side silicon layer provided with the detection unit and the capacitance-voltage conversion circuit from the surface-side silicon layer provided with the output electrode. Lies in the fact.

With this configuration, the area of the front-side silicon layer provided with the detection unit and the capacitance-voltage conversion circuit can be reduced, and the front-side silicon layer provided with the detection unit and the capacitance-voltage conversion circuit can be reduced. Parasitic capacitance generated between the silicon layer and the backside silicon layer can be reduced.

Further, by integrally providing the detection section and the capacitance-voltage conversion circuit on the surface side silicon layer of the silicon substrate, an electrode for connecting the detection section and the capacitance-voltage conversion circuit is provided.
Wiring and the like can be eliminated. Therefore, the area of the front-side silicon layer on which the detection unit and the capacitance conversion circuit are provided can be reduced, and the parasitic capacitance generated between the front-side silicon layer and the back-side silicon layer can be reduced.

According to a second aspect of the present invention, the insulating portion is formed by a vertical groove extending from the silicon layer on the front surface side of the silicon substrate to the insulating layer of the silicon substrate. This makes it possible to easily separate the front-side silicon layer provided with the detection unit and the like from the front-side silicon layer provided with the output electrode.

Further, as in the invention according to claim 3, the vertical groove can be provided by removing a part of the surface side silicon layer of the silicon substrate by anisotropic etching.

Further, as in the invention according to claim 4, the insulating portion is constituted by a vertical groove reaching the insulating layer of the silicon substrate on the silicon layer on the surface side of the silicon substrate, and an insulating film is formed on the groove surface of the vertical groove. It is also possible to provide a structure in which a buried member is buried in the vertical groove provided with the insulating film.

On the other hand, the invention according to claim 5 resides in that the capacitance-voltage conversion circuit is constituted by a source follower circuit using a junction field effect transistor. With this configuration, the change in the capacitance output from the detection unit can be efficiently converted into a voltage signal by the source follower circuit, and the detection sensitivity of the external force can be increased.

[0035]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIGS. 1 to 11 show the first embodiment of the present invention.
An angular velocity detecting device is shown as an example of the capacitance type external force detecting device according to the embodiment.

Reference numeral 21 denotes an angular velocity detecting device as a capacitance type external force detecting device according to the present embodiment. Reference numeral 22 denotes a silicon substrate that constitutes the angular velocity detecting device 21. The silicon substrate 22 includes a surface-side silicon layer 22A made of a silicon material and a silicon substrate 22A, like the silicon substrate 3 of the angular velocity detecting device 1 according to the related art. Back silicon layer 22B, and an insulating layer 22C made of silicon oxide or the like provided between the front silicon layer 22A and the back silicon layer 22B. The surface side silicon layer 22A of the silicon substrate 22 is made to have a low resistance by doping impurities such as phosphorus and boron.

Reference numeral 23 denotes a detection unit provided on the front surface side silicon layer 22A of the silicon substrate 22 and detects an angular velocity by a change in capacitance. The detection unit 23 is substantially the same as the detection unit 4 according to the prior art. A vibrator 24 that can vibrate in a direction parallel to the silicon substrate 22 and four support beams 25 for supporting the vibrator 24 on the silicon substrate 22.
And driving electrode support members 26, 26 disposed above and below the vibrator 24 in FIG. Also,
As in the prior art, a comb-shaped electrode 24A,
Are provided, and each electrode support 26 is provided with a comb-shaped electrode 26A. The comb-shaped electrodes 24A and 26A are engaged with each other while being separated from each other.

Reference numerals 27, 27 denote detection electrode supports disposed on the left and right sides of the vibrator 24 in FIG. 1. Each of the electrode supports 27 has the same configuration as the driving electrode support 26. Comb-shaped electrodes 27A, 27A are provided, and each of the comb-shaped electrodes 27A is engaged with each of the comb-shaped electrodes 24A of the vibrator 24 while being separated from each other.

Here, each electrode support 27 is formed in, for example, an elongated rectangular shape by etching the surface side silicon layer 22A of the silicon substrate 22, as shown in FIG. That is, each electrode support 27 is formed so as to have a minimum area sufficient to support each comb-shaped electrode 27A, and has a smaller area than each electrode support 6 according to the related art. It has been significantly reduced.

Reference numerals 28, 28 denote drive electrodes for vibrating the vibrator 24 in the direction indicated by the arrow Y in FIG. 1 by electrostatic force. Each of the drive electrodes 28 is a respective comb-like electrode 24A provided on the vibrator 24. And each comb-shaped electrode 26 </ b> A provided on each electrode support 26.

Reference numerals 29, 29 denote detection electrodes for detecting the angular velocity as a change in capacitance. Each of the detection electrodes 29 is provided on each of the comb electrodes 24A provided on the vibrator 24 and on each of the electrode supports 27. Each comb-shaped electrode 27A is constituted. Each detection electrode 29 detects a change in capacitance between each of the comb-shaped electrodes 24A and 27A when the vibrator 24 is displaced in the direction indicated by the arrow X in FIG. 1 due to Coriolis force. .

Reference numerals 30, 30 denote input electrode pads provided on the surface of each of the driving electrode supports 26. Each of the input electrode pads 30 has an oscillation for outputting a driving signal for vibrating the vibrator 24. The circuits are connected via wires (neither shown).

Reference numerals 31 and 31 denote circuit forming portions provided outside the respective electrode supports 27. Each of the circuit forming portions 31 is formed on the front surface side silicon layer 22A of the silicon substrate 22,
It is integrated with each electrode support 27. Each of the circuit forming sections 31 has a capacitance-voltage conversion circuit 32 described later. Here, each circuit forming section 31 is formed with a minimum area sufficient to form the capacitance-voltage conversion circuit 32.

Numerals 32 and 32 denote capacitance-voltage conversion circuits provided in each circuit forming section 31, respectively.
Is a junction field effect transistor 33 as shown in FIG.
(Hereinafter, referred to as a “junction FET 33”).

That is, one side of each capacitance-voltage conversion circuit 32 is connected to a junction type FET 33 whose gate terminal G is connected to the detection electrode 29 of the detection section 23 and whose drain terminal D is connected to a power supply electrode pad 37A described later. FET 33 is connected to the source terminal S, and the other side is connected to a ground electrode pad 37C described later.
, And one side is a junction type FET 33
And the resistance element 35 connected to the source terminal S of the junction type FET 33 on the other side. The source terminal S of the junction FET 33 is connected to a signal output electrode pad 37B described later.

Each capacitance-voltage conversion circuit 32 converts a change in capacitance detected by the detection electrode 29 of the detection unit 23 into a voltage signal.

Numerals 36 and 36 denote pad forming portions provided outside the circuit forming portions 31.
Is formed by the surface side silicon layer 22A of the silicon substrate 22.

Reference numerals 37, 37 denote output electrode pads as output electrodes provided on the surface of each circuit forming portion 31. The output electrode pads 37 are a power supply electrode pad 37A, a signal output electrode pad 37B, and a ground electrode pad. The power supply electrode pad 37A is connected to a drain terminal D of a junction type FET 33 included in the capacitance-voltage conversion circuit 32 via a wiring 40A described later, as shown in FIGS. The signal output electrode pad 37B is connected to the wiring 40
It is connected to the source terminal S of the junction FET 33 via B. The ground electrode pad 37C is connected to the wiring 40C.
Is connected to one end of the resistance element 34 via the
The other end of 4 is connected to wiring 40B.

A wire or the like is connected to each output electrode pad 37, and is connected to a ground terminal such as a power supply and a signal processing circuit provided outside (neither is shown).

Numerals 38 and 38 denote separation grooves as insulating portions provided between the respective circuit forming portions 31 and the respective pad forming portions 36. The respective separating grooves 38 correspond to the circuit forming portion 31 and the respective pad forming portions. 36 is formed as a vertical groove having a V-shaped cross-section by removing the surface-side silicon layer 22A located between the groove 36 and the base layer 36 by anisotropic etching. The bottom of each separation groove 38 reaches the insulating layer 22C of the silicon substrate 22, and the surface side silicon layer 22A is electrically separated (insulated) between the circuit forming portion 31 and the pad forming portion 36. I have.

Reference numerals 39, 39 designate insulating films provided along the respective groove surfaces (side surfaces and bottom surfaces in the separating grooves 38) of the respective separating grooves 38, and the respective insulating films 39 are formed of silicon oxide or the like. . Further, each of the insulating films 39 has a corresponding one of the circuit forming portions 31,
The surface of each pad forming portion 36 is also covered.

Reference numerals 40A, 40B, and 40C denote each circuit forming section 3.
1 is a wiring connecting the capacitance-voltage conversion circuit 32 provided in 1 and each output electrode pad 37 provided in each pad forming section 36, and each of the wirings 40A, 40B, 40C is made of, for example, aluminum, polysilicon or the like. It is formed of a conductive material and provided on the insulating film 39. Further, as shown in FIG. 4, each of the wirings 40A and 40B is bent in a V-shape along each groove surface of each separation groove 38.

The angular velocity detecting device 21 according to the present embodiment has the above-described configuration. Next, a method of manufacturing the angular velocity detecting device 21 will be described.

First, as shown in FIG. 6, an insulating layer 22 is provided between the front side silicon layer 22A and the back side silicon layer 22B.
A silicon substrate 22 provided with C is prepared. And
The surface-side silicon layer 22A is doped with an impurity such as phosphorus or boron to lower the resistance of the surface-side silicon layer 22A.

In the separation groove forming step, as shown in FIG.
The separation groove 3 is formed in the silicon layer 22A on the surface of the silicon substrate 22.
8, 38 are formed. That is, after the silicon oxide film 41 is formed on the front surface side silicon layer 22A, the silicon oxide film 41 where the separation grooves 38 are formed is removed using a BHF (buffer hydrofluoric acid) solution or the like. Then, using the silicon oxide film 41 as a mask, anisotropic etching is performed on the front-side silicon layer 22A, and the front-side silicon layer 22A where the separation groove 38 is to be formed is completely removed until it reaches the insulating layer 22C. The anisotropic etching includes TMA
A silicon etchant such as H is used. This allows
The silicon substrate 22 is formed with V-shaped separation grooves 38, 38, each groove surface of which is inclined.

In the circuit forming step, as shown in FIG. 8, the junction type FET 3 is placed at a predetermined position on the surface side silicon layer 22A.
3 and the like are formed.

In the electrode forming step, as shown in FIG. 9, insulating films 39, 39 are formed on the respective isolation grooves 38 formed in the silicon substrate 22, and the output electrode pads 37 are formed on the insulating films 39. And wirings 40A, 40B and 40C are formed (see FIG. 2). At this time, the wirings 40A and 40B are formed in a V-shape along each groove surface of each separation groove 38.

In the detection section forming step, as shown in FIG. 10, etching (RIE or the like) is performed on the silicon layer 22A on the front surface of the silicon substrate 22 using a resist as a mask, and the vibrator 24 of the detection section 23 The electrode support 27, the comb-shaped electrodes 24A, 27A, the respective circuit forming portions 31, the respective pad forming portions 36, and the like are formed. Then, as shown in FIG.
The insulating layer 22C located below the vibrator 24 is removed by etching using a BHF solution or the like.

Thus, the angular velocity detecting device 21 is manufactured. The order of the separation groove forming step, the circuit forming step, and the detecting section forming step is not limited to this. For example, after forming the detecting section 23 in the detecting section forming step first,
Each isolation groove 38 may be formed by an isolation groove forming step, and then the capacitance-voltage conversion circuit 32 may be formed by a circuit forming step.

Next, the angular velocity detecting device 21 according to the present embodiment
Will be described. That is, the vibrator 24 is vibrated in the direction indicated by the arrow Y in FIG. In this state, when the angular velocity Ω around the ZZ axis in FIG. 3 acts, the vibrator 24 is displaced in the direction indicated by the arrow X in FIG. 1 due to the Coriolis force. As a result, the capacitance between the comb electrodes 24A and 27A constituting each detection electrode 29 changes, and this change in the capacitance is input to the capacitance-voltage conversion circuit 32.

As a result, the voltage at the gate terminal G of the junction FET 33 provided in the capacitance-voltage conversion circuit 32 shown in FIG.
A current flows between the terminal and the source terminal S. As a result, the voltage of the source terminal S of the junction FET 33 changes in accordance with the change in the capacitance detected by the detection electrode 29.

The source terminal S of the junction type FET 33
Is output to the signal output electrode pad 37B via the wiring 40B as a voltage signal, and is output from the signal output electrode pad 37B to an externally provided signal processing circuit or the like. Then, the angular velocity is obtained by a signal processing circuit or the like.

Here, the capacitance detected from each detection electrode 29 of the detection unit 23 includes a parasitic capacitance generated between the front side silicon layer 22A and the back side silicon layer 22B of the silicon substrate 22, and the parasitic capacitance is generated. An increase in the capacitance causes a decrease in the angular velocity detection sensitivity.

However, in the angular velocity detecting device 21 according to the present embodiment, each output electrode pad 37 requiring a relatively large area is provided on each pad forming portion 36, and each pad forming portion 36 is connected to each separation groove. 38, each electrode support 2
7 and each circuit forming section 31. Thereby, the area of each electrode support 27 and each circuit forming portion 31 can be reduced, and the surface side silicon layer 22A and the back side silicon layer 22B constituting each electrode support 27 and each circuit forming portion 31 can be reduced. The parasitic capacitance generated therebetween can be reduced.

Therefore, the parasitic capacitance component mixed in the capacitance detected from each detection electrode 29 can be reduced, and the detection sensitivity of the angular velocity can be improved.

Thus, according to the present embodiment, each isolation groove 38 is provided in the silicon substrate 22, and each pad formation section 36 provided with each output electrode pad 37 is replaced with each electrode support 27 and each circuit formation section 31. Since it is configured to be electrically separated (insulated) from the above, the parasitic capacitance component mixed in the capacitance detected by each detection electrode 29 of the detection unit 23 can be reduced, and the detection sensitivity of the angular velocity can be improved. be able to.

In particular, according to the present embodiment, the silicon substrate 2
By performing anisotropic etching on the surface-side silicon layer 22A of No. 2, each separation groove 38 can be easily formed, thereby preventing a complicated manufacturing operation and an increase in manufacturing cost.

Further, by forming each separation groove 38 by anisotropic etching, each groove surface of each separation groove 38 is
As shown in FIG. 4, it can be inclined in a V-shape. As a result, the wirings 40A, 40A
B can be easily formed.

Further, according to the present embodiment, since the capacitance-voltage conversion circuit 32 is formed integrally with the detection section 23 of the silicon substrate 22, the angular velocity detection device 21 can be reduced in size as a whole. it can. Furthermore, by integrating the detection unit 23 and the capacitance-voltage conversion circuit 32, it is possible to eliminate electrodes, wires, and the like that connect the detection unit and the capacitance-voltage conversion circuit as in the related art. Thus, the area of the circuit forming section 31 provided with the electrode supports 27 of the detection section 23 and the capacitance-voltage conversion circuit 32 can be significantly reduced, and the parasitic capacitance can be reduced.

Further, the detecting section 23 and the capacitance-voltage converting circuit 3
By forming 2 on a single silicon substrate 22, the distance between each detection electrode 29 of the detection unit 23 and the input terminal of the capacitance-voltage conversion circuit 32 (gate terminal G of the junction FET 33) can be shortened. External noise input to the capacitance-voltage conversion circuit 32 can be significantly reduced.

Further, according to the present embodiment, since each capacitance-voltage conversion circuit 32 is constituted by a source follower circuit using a junction type FET 33, the change of the capacitance detected from each detection electrode 29 of the detection unit 23 is changed. Can be efficiently converted to a voltage signal. In particular, the gate terminal G of the junction FET 33 is directly connected to the electrode support 27 of the detection unit 23. That is, the gate terminal G is integrated with the electrode support 27. As a result, the signal path from the detection electrode 29 provided on the electrode support 27 to the gate terminal G of the junction type FET 33 can be made very short, and external noise is mixed in the capacitance detected by the detection electrode 29. Can be suppressed.

Next, an angular velocity detecting device will be described as an example of a capacitance type external force detecting device according to a second embodiment of the present invention, and will be described with reference to FIGS. The features of this embodiment are as follows.
The insulating portion is constituted by a vertical groove extending in a direction orthogonal to the silicon substrate on the front surface side silicon layer of the silicon substrate and reaching the insulating layer of the silicon substrate, and an insulating film is provided on a groove surface of the vertical groove, The structure is such that silicon is buried in a vertical groove provided with a film. In this embodiment, the same components as those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

That is, reference numeral 51 denotes an angular velocity detecting device as a capacitance type external force detecting device according to the present embodiment. 52, 52
Indicates a separation groove as an insulating portion provided between each circuit formation portion 31 and each pad formation portion 36, and each separation groove 52
Is formed by removing a part of the surface-side silicon layer 22A of the silicon substrate 22 of the angular velocity detecting device 51 by means such as dry etching. Each separation groove 52 is a vertical groove extending in a direction orthogonal to the silicon substrate 22, and the bottom thereof is formed on the insulating layer 22 of the silicon substrate 22.
C has been reached.

Reference numerals 53, 53 denote insulating films provided along the respective groove surfaces of the respective separating grooves 52. The respective insulating films 53 are formed of silicon oxide or the like. Further, each insulating film 53 also covers the surface of each circuit forming section 31 and each pad forming section 36.

An embedding member 54 made of polysilicon or the like is embedded in each separation groove 52. As a result, although the respective circuit forming portions 31 and the respective pad forming portions 36 are electrically insulated, the surface of each of the circuit forming portions 31 and the surface of each of the pad forming portions 36 are continuous in a flat state with no steps. Are connected.

Are provided in each circuit forming section 31, and each capacitance-voltage conversion circuit 32 and each output electrode pad 37
And a plurality of the wirings 55 are provided so as to correspond to the respective output electrode pads 37 as in the first embodiment described above.

According to the present embodiment configured as described above, each pad forming section 36 can be electrically separated from each electrode support 27 of the detecting section 23 and the circuit forming section 31. Thereby, the parasitic capacitance component mixed in the capacitance detected by each detection electrode 29 of the detection unit 23 can be reduced, and the detection sensitivity of the angular velocity can be improved.

In each of the above embodiments, the separation groove 38 (52) is provided as an insulating portion. However, the present invention is not limited to this, and the insulating portion may be formed by another trench technique.

In each of the above embodiments, the angular velocity detector 21 (51) having the detector 23 as shown in FIG. 1 has been described as an example.
The shape and arrangement of each electrode support 26, 27, the electrodes 24A, 2
The shape and the like of 6A and 27A are not limited to this.

In each of the above embodiments, the capacitance-voltage conversion circuit 32 is described as being constituted by a source follower circuit using a junction type FET 33. However, the present invention is not limited to this, and the capacitance-voltage conversion circuit may be a capacitor bridge circuit. , A switched capacitor circuit or the like.

Further, in each of the above embodiments, the angular velocity detecting device 21 (51) has been described as an example of the capacitance type external force detecting device. However, the present invention is not limited to this, and the acceleration detecting device for detecting acceleration is not limited thereto. And the like.

[0083]

As described in detail above, according to the first aspect of the present invention, a silicon substrate having an insulating layer interposed between a front side silicon layer and a back side silicon layer, and a front side of the silicon substrate A detection unit provided on the silicon layer and detecting an external force by a change in capacitance; and a detection unit provided on the surface-side silicon layer of the silicon substrate and converting a change in capacitance output from the detection unit into a voltage signal. A capacitance-voltage conversion circuit, and an output electrode provided on a silicon layer on the surface side of the silicon substrate, for outputting a voltage signal output from the capacitance-voltage conversion circuit to an external signal processing circuit; Has a configuration in which an insulating portion is provided to electrically separate the surface-side silicon layer provided with the detection unit and the capacitance-voltage conversion circuit from the surface-side silicon layer provided with the output electrode. Can amount-voltage conversion circuit is to reduce the area of the surface silicon layer formed, the detection unit can reduce parasitic capacitance occurring between the surface-side silicon layer and the back-side silicon layer provided.

Therefore, it is possible to reduce the parasitic capacitance component mixed in the capacitance output from the detection unit, and it is possible to improve the detection sensitivity of the external force.

According to the second aspect of the present invention, since the insulating portion is constituted by the vertical groove extending to the insulating layer of the silicon substrate on the surface side silicon layer of the silicon substrate, the insulating portion can be easily formed, The surface-side silicon layer provided with the portions and the like and the surface-side silicon layer provided with the output electrode can be reliably separated.

According to the third aspect of the present invention, the vertical groove as the insulating portion is provided by removing a part of the silicon layer on the front surface side of the silicon substrate by anisotropic etching. Can be easily formed,
It is possible to prevent the manufacture of the capacitance type external force detection device from becoming complicated.

According to the fourth aspect of the present invention, the insulating portion is formed by a vertical groove reaching the insulating layer of the silicon substrate on the silicon layer on the surface side of the silicon substrate, and an insulating film is provided on the groove surface of the vertical groove. Since the embedding member is buried in the vertical groove provided with the insulating film, the surface-side silicon layer provided with the detection unit and the like and the surface-side silicon layer provided with the output electrode are separated. Separation can be reliably performed. Also,
Since silicon is buried in the vertical groove, the surface of the silicon layer on the surface side where the insulating portion is formed can be flattened. Thus, wiring and the like can be easily provided on the insulating portion.

According to the fifth aspect of the present invention, since the capacitance-voltage conversion circuit is constituted by the source follower circuit using the junction type field effect transistor, the change in the capacitance output from the detection unit can be efficiently performed by the voltage signal. And the detection sensitivity of external force can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing an angular velocity detecting device according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view showing a main part in FIG. 1;

FIG. 3 is a cross-sectional view of the angular velocity detecting device in FIG. 1 as viewed from the direction of arrows III-III.

FIG. 4 is an enlarged sectional view showing a main part of the angular velocity detecting device in FIG. 3;

FIG. 5 is a circuit diagram showing a capacitance-voltage conversion circuit according to a first embodiment of the present invention.

FIG. 6 is a sectional view showing a silicon substrate used for manufacturing the angular velocity detecting device according to the first embodiment.

FIG. 7 is a sectional view showing a separation groove forming step.

FIG. 8 is a cross-sectional view showing a circuit forming step.

FIG. 9 is a sectional view showing an electrode forming step.

FIG. 10 is a cross-sectional view illustrating a detection portion forming step.

FIG. 11 is a cross-sectional view showing a state in which an insulating film located below a vibrator has been removed in a detecting portion forming step.

FIG. 12 is a sectional view showing an angular velocity detecting device according to a second embodiment of the present invention.

FIG. 13 is an enlarged sectional view showing a main part in FIG. 12;

FIG. 14 is a plan view showing a conventional angular velocity detecting device.

FIG. 15 is a cross-sectional view of the angular velocity detecting device in FIG. 14 as viewed from the direction of arrows XV-XV.

[Explanation of symbols]

 21, 51 Angular velocity detector 22 Silicon substrate 22A Front side silicon layer 22B Back side silicon layer 22C Insulating layer 23 Detecting part 27 Electrode support 31 Circuit forming part 32 Capacitance voltage conversion circuit 33 Junction field effect transistor 36 Pad forming part 37 Output Electrode pad (output electrode) 38, 52 Separation groove 39, 53 Insulating film 54 Embedded member

Claims (5)

[Claims] 1. A silicon substrate having an insulating layer interposed between a front-side silicon layer and a back-side silicon layer, and an external force provided on the front-side silicon layer of the silicon substrate for detecting an external force by a change in capacitance. A detection unit, a capacitance-voltage conversion circuit provided on the front surface side silicon layer of the silicon substrate, and configured to convert a change in capacitance output from the detection unit into a voltage signal; and a capacitance-voltage conversion circuit provided on the front surface silicon layer of the silicon substrate. And an output electrode for outputting a voltage signal output from the capacitance-voltage conversion circuit to an external signal processing circuit. The silicon substrate has a surface on which the detection unit and the capacitance-voltage conversion circuit are provided. An electrostatic capacitance type external force detecting device having a configuration in which an insulating portion for electrically separating a silicon layer and a surface side silicon layer provided with the output electrode is provided. 2. The electrostatic capacitance type external force detecting device according to claim 1, wherein said insulating portion is formed by a vertical groove extending to an insulating layer of said silicon substrate in a silicon layer on a surface side of said silicon substrate. 3. The electrostatic capacitance type external force detecting device according to claim 2, wherein the vertical groove is provided by removing a part of a surface side silicon layer of the silicon substrate by anisotropic etching. 4. The insulating portion is constituted by a vertical groove reaching the insulating layer of the silicon substrate in a silicon layer on a front surface side of the silicon substrate, and an insulating film is provided on a groove surface of the vertical groove. The electrostatic capacitance type external force detection device according to claim 1, wherein the embedded member is embedded in the provided vertical groove. 5. The capacitance type external force detection device according to claim 1, wherein said capacitance-voltage conversion circuit comprises a source follower circuit using a junction type field effect transistor.