JP2003332586A - External force sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a diaphragm accurately and efficiently by providing a frame- like etching stopper in an insulating layer of an SOI substrate and forming a cavity inside thereof. <P>SOLUTION: A frame-like etching stopper 7 is provided in the SOI substrate 2 using a material not corroded with etching liquid for the insulating layer 4 and a piezoelectric resistive element 8 is provided at a part of an active layer 5 inside the etching stopper 7. On the other hand, a cavity 11 is formed inside the etching stopper 7 by etching the insulating layer 4 through a through hole 10 of a supporting layer 3 so that a part of the active layer 5 above the cavity 11 serves as the diaphragm 12. Since the shape of the cavity 11 can be formed accurately at the time of etching the insulating layer 4 without controlling a etching time or the like, an error in the characteristic of the pressure sensor 1 due to the variation of the shape of the diaphragm 12 can be prevented from occurring. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external force sensor suitably used for detecting an external force such as pressure, load, vibration or the like by utilizing flexural deformation of a thin portion (diaphragm portion) provided on an SOI substrate. And a manufacturing method thereof.

[0002]

2. Description of the Related Art Generally, as an external force sensor, there is an external force sensor that detects a flexural deformation amount when a silicon substrate is flexibly deformed by an external force, for example, by using a piezoresistor. As such an external force sensor, an SOI substrate (Silicon) is used.
A semiconductor type pressure sensor using an On Insulator is known (for example, JP 2001-3049 A).
95, etc.).

In this type of conventional pressure sensor, for example, the support layer and the active layer of the SOI substrate are formed of a single crystal silicon material, and the insulating layer sandwiched between these two layers is silicon oxide or the like. Is formed of an insulating material. The insulating layer of the SOI substrate is provided with a flat cavity extending horizontally between the support layer and the active layer. In this case, the cavity of the insulating layer is formed by etching the insulating layer through a through hole or the like provided in the support layer and removing a part of the insulating layer within a predetermined range. is there.

As a result, in the active layer, a portion of the active layer located on the surface side of the cavity is a thin-walled diaphragm portion as compared with the thickness of the entire substrate, and the diaphragm portion is flexibly deformed by pressure applied from the outside. ing. Further, the diaphragm portion is provided with a flexure detection element such as a piezoresistor that detects the flexural deformation amount as pressure.

Here, when the SOI substrate is subjected to etching to form a cavity, for example, the support layer made of a single crystal silicon material or the like and the active layer are not eroded, but only the insulating layer made of silicon oxide or the like is eroded. Prepare an etching solution that does this. Then, the etching liquid is brought into contact with the insulating layer through the through hole of the supporting layer, and only the insulating layer is selectively removed to form a cavity.

In this case, the cavity of the insulating layer is formed in a wider range as the contact time (etching time) between the etching liquid and the insulating layer is longer, and therefore the area of the diaphragm portion is larger as the etching time is longer. Therefore, in the conventional technique, the diaphragm portion is formed to have a predetermined size by appropriately setting the etching time of the insulating layer and the like.

[0007]

By the way, in the above-mentioned conventional technique, the diaphragm portion is formed in a predetermined size according to, for example, the etching time of the insulating layer. However, when etching the insulating layer, the etching rate is likely to change depending on conditions such as the type, concentration and temperature of the etching solution. Even if these conditions are kept constant, when the insulating layer is gradually eroded and the cavity expands, for example, an inactive etching solution containing a large amount of the dissolved material of the insulating layer stays in the flat cavity. By doing so, the etching rate may become unstable.

Therefore, in the prior art, even if the etching time of the insulating layer is properly set, it is difficult to control the etching rate accurately, and therefore, for example, the size and shape of the diaphragm portion are likely to vary. Therefore, the relationship between the pressure applied to the diaphragm portion and the amount of flexural deformation (sensor characteristics) may deviate from the design reference characteristics or the like, and there is a problem that the detection accuracy or reliability of the sensor decreases.

The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to control the size, shape, etc. of an insulating layer of an SOI substrate when the thin portion is formed by etching. An object of the present invention is to provide an external force sensor that can be accurately formed and can improve detection accuracy and reliability, and a manufacturing method thereof.

[0010]

In order to solve the above-mentioned problems, an external force sensor according to the invention of claim 1 is a three-layer structure in which an insulating layer is sandwiched between a support layer made of a silicon material and an active layer. The SOI substrate, the etching stopper formed in a frame shape using a material different from the insulating layer and provided in at least the insulating layer among the three layers of the SOI substrate, and the etching stopper at a position corresponding to the inside of the etching stopper. A bending detection element provided in the active layer, a through hole formed through the support layer at a position corresponding to the inside of the etching stopper, and a portion of the insulating layer located inside the etching stopper. A cavity formed by etching through the through hole, and a thin-walled portion formed by using a portion of the active layer corresponding to the cavity and flexibly deformed by an external force. It has adopted the Ranaru configuration.

With this structure, when the external force sensor is manufactured, an etching stopper can be formed in advance on, for example, the insulating layer of the SOI substrate, and the etching stopper forms a cavity in the insulating layer. Can surround the site. Then, by bringing the etching liquid into contact with the inside portion of the etching stopper in the insulating layer, only this inside portion can be selectively eroded, and the erosion due to the etching liquid can be prevented from spreading to the outside of the etching stopper.

Therefore, when the cavity is formed in the insulating layer, the position and shape of the cavity can be accurately set by the etching stopper by simply bringing the etching solution into contact with the insulating layer, and the thin portion is formed with high dimensional accuracy. can do.

According to the second aspect of the present invention, the SOI substrate is provided with a frame-shaped groove that penetrates the active layer and the insulating layer in the plate thickness direction at a position surrounding the thin portion and reaches the support layer. The etching stopper is arranged in the frame-shaped groove.

As a result, a frame-shaped groove can be formed on the SOI substrate from the thin active layer side to the support layer through the insulating layer, and an etching stopper can be provided in the frame-shaped groove to form a support layer. A predetermined portion of the insulating layer sandwiched between the active layer and the active layer can be easily surrounded by the etching stopper. Further, since the etching stopper can be extended from the insulating layer to both sides in the plate thickness direction and can be arranged so as to straddle the boundary surface between the support layer and the active layer, when the insulating layer is etched, it is present inside the etching stopper. It is possible to prevent the etching solution that is used to leak outside through these interfaces.

Further, since the etching stopper can be exposed on the surface side (active layer side) of the substrate, the position of the thin portion formed inside can be confirmed from the surface side of the substrate by the etching stopper. For this reason,
When the bending detection element is formed in the thin portion, the thin portion and the bending detection element can be accurately aligned with each other with the etching stopper as a reference.

Further, the shape of the thin portion is not restricted by the shape of the through hole formed on the back side of the substrate,
Since it can be set according to the frame shape of the etching stopper,
For example, it is possible to easily form a thin-walled portion having a square shape with rounded corners or a circular shape. This allows
When the thin-walled portion is flexibly deformed, stress concentration can be prevented from occurring at the corners and the like, and the durability (breakdown pressure resistance) of the thin-walled portion can be enhanced.

According to the third aspect of the invention, the insulating layer is made of silicon oxide, and the etching stopper is made of silicon nitride, single crystal silicon or polycrystalline silicon.

As a result, the insulating layer can be etched using an etching solution such as diluted hydrofluoric acid, and the etching stopper can be formed using a material that is not corroded by the etching solution. When a material such as single crystal silicon or polycrystalline silicon is used as the etching stopper, for example, an etching stopper having a thermal expansion coefficient substantially equal to that of the support layer or active layer of the SOI substrate is integrated with these layers. Can be bonded to each other and the bonding strength between them can be increased.

The method of manufacturing an external force sensor according to a fourth aspect of the present invention has a three-layer SOI substrate formed by sandwiching an insulating layer between a support layer made of a silicon material and an active layer. Frame-shaped groove forming step of forming a frame-shaped groove that penetrates the active layer and the insulating layer of the SOI substrate in the plate thickness direction to reach the support layer, and the frame-shaped groove using a material different from that of the insulating layer An etching stopper forming step of providing a frame-shaped etching stopper therein; an element forming step of providing a bending detection element in a portion of the active layer corresponding to the inside of the etching stopper; and a position corresponding to the inside of the etching stopper. A step of forming a through hole in the support layer is performed, and a portion of the insulating layer located inside the etching stopper is etched through the through hole to form a cavity. And a cavity forming step of, constituting a thin portion flexural deformation by an external force the portion corresponding to the cavity of the active layer.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an external force sensor and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 to 11 show a first embodiment, and in this embodiment, a pressure sensor will be described as an example of the external force sensor.

Reference numeral 1 is a pressure sensor, 2 is an SOI substrate (hereinafter referred to as substrate 2) which constitutes the main body of the pressure sensor,
As shown in FIGS. 1 and 2, the substrate 2 is formed of a support layer 3 made of, for example, a single crystal silicon material or the like, and an insulating material such as silicon oxide, and bonded to the surface side of the support layer 3. It is composed of an insulating layer 4 and an active layer 5 made of a single crystal silicon material or the like to be thinner than the supporting layer 3 and joined to the surface side of the insulating layer 4. The insulating layer 4 also has a boundary surface 4 </ b> A located between the insulating layer 4 and the support layer 3 and a boundary surface 4 </ b> B located between the active layer 5.

Reference numeral 6 is a frame-shaped groove provided in the substrate 2 for disposing an etching stopper 7 which will be described later.
Is a quadrangle that opens to the surface side of the active layer 5, penetrates the active layer 5 and the insulating layer 4 in the plate thickness direction to reach the support layer 3, and surrounds a cavity 11 and a diaphragm portion 12 described later. It extends like a frame.

Reference numeral 7 denotes an etching stopper provided in the frame-shaped concave groove 6 of the substrate 2. The etching stopper 7 is shown in FIG.
As shown in FIG. 3, the cavity 11 of the substrate 2 is formed in a rectangular frame shape by using a material different from that of the insulating layer 4 as described later.
It is arranged to surround.

The etching stopper 7 is made up of the active layer 5
And the insulating layer 4 to reach the support layer 3 and extend from the insulating layer 4 to both sides in the plate thickness direction so as to straddle the boundary surfaces 4A and 4B. As a result, the etching stopper 7
The insulating layer 4 located outside and the cavity 11 located inside
(Etching removal portion 15B2 of substrate material 15 described later)
Is closed in a liquid tight state.

Here, as the material forming the etching stopper 7, a material having resistance to the etching liquid for the insulating layer 4 is used. In the present embodiment, since the insulating layer 4 made of silicon oxide or the like is etched using an etching solution such as diluted hydrofluoric acid in the cavity forming step shown in FIG. , For example, silicon nitride is used.

As a result, the etching stopper 7 etches the insulating layer 15B of the substrate material 15 to form the cavity 1.
1 is formed, the etching process range is limited to the etching removal portion 15B2, and the etching stopper 7
The cavity 11 (diaphragm portion 12) is accurately formed at a predetermined position and shape by preventing the insulating layer 15B from being eroded on the outside.

Reference numeral 8 denotes, for example, four piezoresistive elements as deflection detecting elements provided on the active layer 5 of the substrate 2. Each piezoresistive element 8 injects impurity ions into the surface side of the active layer 5, for example. As a result, a diaphragm portion 12 which will be described later is formed inside the etching stopper 7 in an elongated linear shape.
Are arranged on all four sides. And the piezoresistive element 8
Is to be flexibly deformed together with the diaphragm portion 12, the resistance value of the piezoresistive element 8 is changed according to the deformation amount, and the change in resistance value at this time is output as a pressure detection signal.

Reference numeral 9 denotes an insulating film provided on the back surface side of the support layer 3 using, for example, a material such as silicon oxide. Reference numeral 10 denotes an anisotropic etching process or the like on the support layer 3 using the insulating film 9 as a mask. The through hole 10 is formed in a substantially rectangular shape, and the through hole 10 penetrates the support layer 3 in the plate thickness direction at a position corresponding to the inside of the etching stopper 7.

Reference numeral 11 denotes a rectangular cavity provided in the insulating layer 4, which is a flat space inside the etching stopper 7 that extends horizontally between the support layer 3 and the active layer 5. Etching removal portion 15B of substrate material 15
It is formed by removing 2 by etching. As a result, the positions and shapes of the cavity 11 and the diaphragm portion 12 are determined by the etching stopper 7. Further, a through hole 10 of the support layer 3 is opened at approximately the center of the cavity 11, and the cavity 11 communicates with the back surface side of the substrate 2 through the through hole 10.

Reference numeral 12 denotes a diaphragm portion as a thin portion arranged on the surface side of the substrate 2, and the diaphragm portion 12 is
The active layer 5 is formed by using a quadrangular portion located on the surface side of the cavity 11, and has a smaller thickness than the thickness of the substrate 2 as a whole. The diaphragm portion 12 bends and deforms in the plate thickness direction when pressure is applied from the outside.

Reference numeral 13 denotes an insulating protective film provided on the surface side of the active layer 5. The protective film 13 is made of an insulating material such as silicon oxide or silicon nitride, and covers each piezoresistive element 8 or the like. To protect.

Reference numeral 14 is a plurality of wiring patterns provided on the insulating protection film 13, and each wiring pattern 14 is formed of a metal material such as aluminum and is connected to both ends of each piezoresistive element 8. The detection signal is output to an external signal processing circuit (not shown) or the like.

The pressure sensor 1 according to this embodiment has the structure as described above, and its operation will be described below.

First, the cavities 11 on the front and back sides of the substrate 2
When a pressure difference occurs between the piezoresistive element 8 and the piezoresistive element 8, the diaphragm portion 12 flexibly deforms together with the piezoresistive element 8 according to the pressure difference, and the resistance value of the piezoresistive element 8 changes according to the deformation amount. As a result, a detection signal is output from the piezoresistive element 8 to the external signal processing circuit via the wiring pattern 14 or the like, so that the pressure can be detected using this detection signal.

Next, a method of manufacturing the pressure sensor 1 according to the present embodiment will be described with reference to FIGS.

First, in the frame-shaped groove forming step shown in FIGS. 4 and 5, a substrate material 15 which is a material of the SOI substrate 2 is prepared. In this case, the support layer 15A, the insulating layer 15B and the active layer 15C of the substrate material 15 become the support layer 3, the insulating layer 4 and the active layer 5 of the SOI substrate 2, respectively. Then, as shown in FIG. 4, a coating film 16 made of, for example, a resist material is provided on the front surface side of the substrate material 15, and the coating film 16 is provided.
The frame-shaped groove 6 is formed by means of photolithography or the like.
A rectangular opening 16A corresponding to the planar shape of is provided.

Then, as shown in FIG. 5, by using the film 16 as a mask for etching, for example, dry etching using a fluorine-based plasma gas is performed on the surface side of the substrate material 15 to form an active layer 15C. Insulation layer 15B
A frame-shaped groove 6 is formed to penetrate through and reach the support layer 15A.

[0039] In this case, when the support layer 15A and the active layer 15C made of silicon material such as single crystal is etched, for example Freon gas _(CF 4), using a mixed gas of Freon and oxygen _(CF 4 + _{O 2),} etc. When the insulating layer 15B made of silicon oxide or the like is etched, for example, Freon gas or a mixed gas of this with hydrogen (CF) is used.
₄ + H ₂ ) or the like is used.

Next, in the etching stopper forming step shown in FIGS. 6 and 7, first, as shown in FIG.
D (Chemical Vapor Deposition)
on) method or the like to form a silicon nitride film 17 on the front surface side of the substrate material 15. As a result, the silicon nitride of the coating film 17 is also filled in the frame-shaped concave groove 6.

Then, as shown in FIG. 7, processing such as dry etching using a fluorine-based plasma gas or surface polishing is applied to the surface side of the substrate material 15 to form the coating film 1.
The etching stopper 7 is formed by removing a portion of the portion 7 that is disposed outside the frame-shaped groove 6.

As a result, the insulating layer 15B is located outside the etching stopper 7 and serves as the insulating layer 4 of the pressure sensor 1, and the insulating layer 15B is located inside the etching stopper 7 and is removed in a cavity forming step described later. It is in a state of being partitioned by the etching removal portion 15B2.

Next, in the element forming step shown in FIG. 8, the film 18 made of, for example, a resist material is aligned with the position of the frame-shaped groove 6 and the substrate material 15 is formed in substantially the same manner as the film 16.
Provided on the front side of. Then, using the coating film 18 as a mask, the active layer 15C of the substrate material 15 is subjected to ion implantation, thermal diffusion, etc., so that each piezoresistive element 8 is formed in the active layer 15C.
To form.

Next, in the through hole forming step shown in FIG. 9, first, the insulating film 9 is provided on the back side of the substrate material 15, and the insulating film 9 is used as a mask to subject the support layer 15A to anisotropic etching or the like. . As a result, the through hole 10 is formed in the support layer 15A, and the etching removal portion 15B2 of the insulating layer 15B is exposed at the position of the through hole 10.

Then, in the cavity forming step shown in FIG.
Then, for example, an etching solution such as diluted hydrofluoric acid is used for the through hole 1.
By contacting the etching removal portion 15B2 of the insulating layer 15B from 0, the etching removal portion 15B2 is eroded by the etching liquid and completely removed, and the etching stopper 7
To form a cavity 11 surrounded by.

As a result, the active layer 1 is formed on the substrate material 15.
Since the thin diaphragm portion 12 is formed by using the portion of 5C located on the surface side of the cavity 11, the position and shape of the diaphragm portion 12 can be accurately determined by the etching stopper 7, and high dimensional accuracy can be obtained. The diaphragm portion 12 can be easily formed.

In this case, since the etching stopper 7 is formed so as to surround the etching removed portion 15B2 by using silicon nitride or the like which is not corroded by the etching solution, the etching stopper 7 is not corroded by the etching solution.
Can be prevented from spreading outside. Therefore, it is possible to selectively remove only the etching removal portion 15B2 of the insulating layer 15B by merely bringing the etching liquid into contact with the insulating layer 15B from the through hole 10.

Next, in the wiring pattern forming step shown in FIG. 11, an insulating protective film 13 is first provided on the front surface side of the substrate material 15, and a through hole or the like through which the piezoresistive element 8 is exposed is formed in this insulating protective film 13. . Then, a pressure sensor is formed by forming a metal film on the surface side of the insulating protective film 13 using a method such as a sputtering method or a CVD method, and performing etching or the like on the metal film to form each wiring pattern 14. 1 can be manufactured.

Thus, according to the present embodiment, the substrate 2
Since the frame-shaped etching stopper 7 is provided in the pressure sensor 1, the etching stopper 7 can be easily formed at the time of manufacturing the pressure sensor 1 by using a material such as silicon nitride that is not corroded by an etching solution such as diluted hydrofluoric acid. The substrate material 15 (insulating layer 15
The etching removal portion 15B2 of B) can be surrounded.

Then, in the cavity forming step, the etching solution is brought into contact with the etching removal portion 15B2 through the through hole 10 of the support layer 15A, so that the insulating layer 15B is formed.
Only the predetermined etching removal portion 15B2 can be selectively eroded and removed, and the etching stopper 7 can reliably prevent the erosion by the etching solution from spreading to the outer portion 15B1 of the insulating layer 15B.

As a result, in the cavity forming step, the position and shape of the cavity 11 can be accurately set by the etching stopper 7 simply by bringing the etching liquid into contact with the etching removal portion 15B2. The diaphragm portion 12 can be easily formed with high dimensional accuracy without strictly controlling time, speed, and the like.

Therefore, for example, the relationship between the amount of flexural deformation of the diaphragm portion 12 and the pressure can be stably aligned with respect to the design reference characteristics and the like, and there is an error in the characteristics of the sensor due to variations in the shape of the diaphragm portion 12. The pressure sensor 1 can be prevented from being generated, the detection accuracy and reliability thereof can be improved, and the accurate pressure sensor 1 can be efficiently manufactured.

In this case, in the frame-shaped groove forming step, the substrate 2
Since the frame-shaped groove 6 that penetrates the active layer 5 and the insulating layer 4 and reaches the support layer 3 is provided in the above, and the etching stopper 7 is provided in the frame-shaped groove 6 in the etching stopper forming step,
At the time of manufacturing the sensor, even if the insulating layer 15B of the substrate material 15 is sandwiched between the support layer 15A and the active layer 15C, the etching removal portion 15B2 can be easily surrounded by the etching stopper 7. .

Further, by using the frame-shaped concave groove 6, the etching stopper 7 can be extended from the insulating layer 4 to both sides in the plate thickness direction, and the boundary surface 4 between the support layer 3 and the active layer 5 can be extended.
It can be arranged so as to straddle A and 4B. As a result, at the time of etching processing, the etching liquid existing inside the etching stopper 7 is allowed to pass through the boundary surfaces 4A and 4B.
It is possible to reliably prevent the leakage through the outside.

Further, since the etching stopper 7 can be exposed to the surface side of the active layer 5 by using the frame-shaped groove 6, the position of the diaphragm portion 12 formed inside the etching stopper 7 can be controlled by the etching stopper 7. It can be confirmed from the surface side of 2. Therefore, in the element forming step, the piezoresistive element 8 and the diaphragm portion 12 can be accurately aligned with each other with the etching stopper 7 as a reference, and the detection accuracy of the pressure sensor 1 can be improved.

Next, FIG. 12 shows a second embodiment according to the present invention, which is characterized in that a single crystal or polycrystal silicon material is used as an etching stopper. In this embodiment, the same components as those in the first embodiment are designated by the same reference numerals,
The description will be omitted.

Reference numeral 21 is a pressure sensor.
In the same manner as in the first embodiment, is composed of the SOI substrate 2, the frame-shaped groove 6, the piezoresistive element 8, the diaphragm portion 12, the etching stopper 22 and the like.

However, the etching stopper 22 is formed by using, for example, single crystal silicon or polycrystal silicon having resistance to an etching solution such as dilute hydrofluoric acid, whereby the support layer 3 and the active layer 5 of the substrate 2 are formed. It is joined and fixed integrally with.

Thus, in this embodiment having such a configuration, it is possible to obtain substantially the same operational effects as those of the first embodiment. In particular, in this embodiment, since the etching stopper 22 is made of a monocrystalline or polycrystalline silicon material or the like, for example, the etching stopper having a thermal expansion coefficient substantially equal to that of the support layer 3 of the substrate 2, the active layer 5, etc. 22 can be integrally bonded to these layers 3 and 5, so that stress or the like due to temperature change can be prevented from occurring between them, and the bonding strength between the substrate 2 and the etching stopper 22 can be increased.

Further, since the supporting layer 3 and the active layer 5 can be held at the same potential by the etching stopper 22 having a certain degree of conductivity, the active layer 5 of the substrate 2 can be etched by connecting it to an external earth or the like. The support layer 3 can also be held at the ground potential via the stopper 22.
As a result, the potentials of the support layer 3 and the active layer 5 can be fixed by a simple wiring structure without connecting a special ground wiring or the like to the support layer 3, and fluctuations in the potential are prevented to stabilize the pressure detection operation. be able to.

In each of the above embodiments, the etching stoppers 7 and 2 are used when the insulating layer 4 made of silicon oxide or the like is eroded by an etching solution such as diluted hydrofluoric acid.
As the second structure, silicon nitride, single crystal silicon or polycrystalline silicon is used. However, in the present invention,
The material of the insulating layer and the etching stopper, the kind of the etching solution, etc. are not limited to the embodiment, and various insulating materials including, for example, silicon nitride, and conductive materials such as a polycrystalline silicon layer are used. You can Then, in this case, an etching stopper formed of a material different from that of the insulating layer and an etching solution that corrodes only the insulating layer excluding the etching stopper may be selected.

Further, in the embodiment, the etching stoppers 7 and 22 are formed in a rectangular frame shape. However, the present invention is not limited to this, and the etching stopper may have a smooth shape such as a square shape with rounded corners, a circular shape, or an elliptical shape. This makes it possible to easily form a diaphragm portion having a smooth contour according to the frame shape of the etching stopper.
When the diaphragm portion is flexibly deformed, stress concentration can be prevented from occurring at the corners and the like, and the durability (breakdown pressure resistance) of the diaphragm portion can be increased.

Further, in the embodiment, the pressure sensor 1 is described as an example. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to an external force sensor that detects various external forces including load, vibration, acceleration, and the like.

[Brief description of drawings]

FIG. 1 is a front view showing a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the pressure sensor as seen from the direction of arrows II-II in FIG.

3 is a cross-sectional view of the pressure sensor as seen from the direction of arrows III-III in FIG.

FIG. 4 is a cross-sectional view showing a state in which a coating film is provided on the front surface side of the SOI substrate for performing a frame-shaped groove forming step at the time of manufacturing the pressure sensor.

5 is a cross-sectional view showing a state in which a frame-shaped groove is formed in the SOI substrate by using the film in FIG. 4 as a mask in the frame-shaped groove forming step.

FIG. 6 is a cross-sectional view showing a state in which a silicon nitride film serving as an etching stopper is formed on the surface side of the SOI substrate by the etching stopper forming step.

FIG. 7 is a cross-sectional view showing a state in which an etching stopper is formed by processing the film in FIG.

FIG. 8 is a cross-sectional view showing a state in which a deflection detecting element is formed on an active layer of an SOI substrate by an element forming process.

FIG. 9 is a cross-sectional view showing a state in which a through hole is formed in the support layer of the SOI substrate by the through hole forming step.

FIG. 10 is a cross-sectional view showing a state in which an insulating layer of an SOI substrate is etched by a cavity forming step.

FIG. 11 is a cross-sectional view showing a state in which a wiring pattern is formed on the front surface side of the SOI substrate by the wiring pattern forming step.

FIG. 12 is a sectional view of a pressure sensor according to a second embodiment of the present invention seen from the same position as in FIG.

[Explanation of symbols]

1,21 Pressure sensor 2 SOI substrate 3,15A support layer 4,15B insulation layer 5,15C active layer 6 Frame-shaped groove 7,22 Etching stopper 8 Piezoresistive element (deflection detection element) 10 through holes 11 cavities 12 Diaphragm part (thin part) 15 Substrate material (SOI substrate)

Continued front page    F term (reference) 2F055 AA40 BB20 CC02 DD05 EE14                       FF11 FF43 GG01 GG15                 4M112 AA01 AA02 BA01 CA01 CA03                       CA08 CA16 DA03 DA04 DA06                       DA09 DA10 DA12 DA15 DA18                       EA03 EA04 EA06 EA07 EA11                       FA01 FA05 FA07 FA09 FA20

Claims (4)

[Claims] 1. An SOI substrate having three layers formed by sandwiching an insulating layer between a support layer made of a silicon material and an active layer, and the insulating layer provided on at least the insulating layer of the three layers of the SOI substrate. An etching stopper formed in a frame shape using a different material, a bending detection element provided in the active layer at a position corresponding to the inside of the etching stopper, and the support at a position corresponding to the inside of the etching stopper. A through hole formed through the layer; a cavity formed by etching a portion of the insulating layer located inside the etching stopper through the through hole; An external force sensor comprising a thin portion formed by using a portion corresponding to a cavity and flexibly deformed by an external force. 2. The SOI substrate is provided with a frame-shaped groove that penetrates the active layer and the insulating layer in the plate thickness direction to reach the support layer at a position surrounding the thin portion, and the etching stopper is The external force sensor according to claim 1, wherein the external force sensor is provided in the frame-shaped concave groove. 3. The external force sensor according to claim 1, wherein the insulating layer is made of silicon oxide, and the etching stopper is made of silicon nitride, single crystal silicon or polycrystalline silicon. 4. A three-layer SOI substrate having an insulating layer sandwiched between a support layer made of a silicon material and an active layer, wherein the active layer and the insulating layer of the SOI substrate are arranged in the plate thickness direction. A frame-shaped groove forming step of forming a frame-shaped groove that penetrates and reaches the support layer; and an etching stopper forming step of providing a frame-shaped etching stopper in the frame-shaped groove using a material different from that of the insulating layer. An element forming step of providing a deflection detecting element in a portion of the active layer corresponding to the inside of the etching stopper, and a through hole forming step of forming a through hole in the support layer at a position corresponding to the inside of the etching stopper. A cavity forming step of forming a cavity by etching a portion of the insulating layer located inside the etching stopper through the through hole. Production method of the external force sensor comprising constituting the portion corresponding to the cavity as a thin portion which deformed by an external force.