JP2000040830A - Mechanical sensor and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent malfunctions such as sticking or the like from being generated in a beam structure. SOLUTION: A beam structure 2A having movable electrodes 7a and 7b is supported on the upper surface of a substrate 1 so that they can move in the direction parallel to the surface of the substrate 1 with a prescribed space. Fixed electrodes 9a, 9b, and 11a are fixed on the upper surface of the substrate 1 and are arranged in face with the movable electrodes 7a and 7b. As a result, the displacement of the beam structure 2A and that of the movable electrodes 7a and 7b, are detected dependently on the applied acceleration. Each side of the movable electrodes 7a and 7b, which face with the fixed electrodes 9a, 9b, and 11a, has the shape of a taper. Each facing inside distance between the movable electrodes 7a and 7b face, and the fixed electrodes 9a, 9b, and 11a, is various depending on the direction of movement of the beam structure 2A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic quantity sensor, and more particularly, to a dynamic quantity sensor for detecting, for example, acceleration, yaw rate, and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a semiconductor acceleration sensor, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent Publication No. 21022, etc., there is known a method of having a beam structure that moves when subjected to acceleration and detecting the movement of the beam structure using opposing electrodes (fixed and movable electrodes). Have been.

[0003] The present inventors have further studied the acceleration sensor and found that sticking (adhesion) and warping are likely to occur in the beam structure, and the sensor function may be impaired.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a dynamic quantity sensor in which a problem such as sticking does not easily occur in a beam structure, and a method of manufacturing the same.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, the distance between the movable electrode and the fixed electrode in the moving direction of the beam structure in the plane facing each other is different. I let you. Therefore, the sticking area on the electrode facing surface, where sticking occurs, is reduced, and the sticking force is reduced, so that the structure is easily released.

Here, as set forth in claim 2, at least one of the surfaces facing the movable electrode and the fixed electrode has a tapered shape in which the separation distance in the facing surface gradually changes. As described in the third aspect, at least one of the surfaces of the movable electrode and the fixed electrode facing each other is formed to have irregularities by repeating forward taper and reverse taper. This is practically preferable.

For example, by forming a tapered shape, the residual portion of the stress which causes the warpage can be reduced, and the occurrence of the warp can be suppressed. According to the method of manufacturing a physical quantity sensor according to claim 4, the thin film for the sacrificial layer and the first insulator thin film are laminated on the first semiconductor substrate, and the thin film for the sacrificial layer and the first insulator thin film are laminated. An opening is formed in the anchor portion forming region in the laminate with the above. Then, a conductive thin film is formed in a predetermined region on the first insulating thin film including the opening, and a second insulating thin film is formed on the first insulating thin film including on the conductive thin film. Further, the bonding thin film is formed on the second insulator thin film, and the surface of the bonding thin film is flattened. Subsequently, the surface of the bonding thin film is bonded to the second semiconductor substrate, and the first semiconductor substrate is polished to a desired thickness.

Next, an unnecessary region between the movable electrode forming portion and the fixed electrode forming portion in the first semiconductor substrate is removed by changing the separation distance in a direction parallel to the surface of the substrate in the opposing surface. Is done. Then, the sacrificial layer thin film in a predetermined region is removed by wet etching, and the beam structure made of the first semiconductor substrate becomes a movable structure. As a result, the structure according to claim 1 is obtained.

According to the method of manufacturing a physical quantity sensor according to the fifth aspect, the groove is formed in the air gap forming region between the movable electrode forming portion and the fixed electrode forming portion in the first semiconductor substrate.
In the opposing inner wall surfaces, they are formed with different separation distances in a direction parallel to the surface of the substrate. Then, the thin film for the sacrificial layer and the first insulator thin film are laminated on the first semiconductor substrate including the groove, and the anchor portion forming region in the laminate of the thin film for the sacrificial layer and the first insulator thin film is opened. Is done. Further, a conductive thin film is formed in a predetermined region on the first insulating thin film including the opening, and a second insulating thin film is formed on the first insulating thin film including on the conductive thin film. Subsequently, a bonding thin film is formed on the second insulator thin film,
The surface of the bonding thin film is flattened, and the surface of the bonding thin film and the second semiconductor substrate are bonded. Next, the first semiconductor substrate is polished to a desired thickness, and the sacrificial layer thin film in a predetermined region is removed by wet etching, so that the beam structure made of the first semiconductor substrate has a movable structure. As a result, the structure according to claim 1 is obtained.

Here, as described in claim 6, it is practically preferable that the separation distance is made different by performing groove processing while changing the etching conditions.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the present invention is applied to a semiconductor acceleration sensor. More specifically, the present invention is applied to a servo-controlled differential capacitive semiconductor acceleration sensor. FIG. 1 is a plan view of a semiconductor acceleration sensor according to the present embodiment,
FIG. 2 is an enlarged view of an element portion (beam structure 2A) in FIG. 1, and FIG. 3 is a sectional view taken along line AA in FIG.

In FIG. 3, a beam structure 2A made of single crystal silicon is arranged on the upper surface of a substrate 1. As shown in FIGS. 2 and 3, the beam structure 2A is bridged by four anchors 3a, 3b, 3c, 3d protruding from the substrate 1 side, and is disposed at a predetermined interval on the upper surface of the substrate 1. Have been. The anchor portions 3a to 3d are made of a polysilicon thin film. Anchor 3a and anchor 3b
A beam portion 4 is provided between the anchor portions 3c and 3d, and a beam portion 5 is provided between the anchor portions 3c and 3d.

A rectangular mass part (mass part) 6 is provided between the beam part 4 and the beam part 5. Mass part 6
Is provided with a through hole 6a penetrating vertically. By providing the through holes 6a, it is possible to make it easier for the etchant to enter at the time of etching the sacrificial layer.

Further, four movable electrodes 7a, 7 are provided from one side (left side in FIG. 2) of the mass section 6.
b, 7c and 7d protrude. These movable electrodes 7a to 7
d has a rod shape and extends in parallel at equal intervals. Further, four movable electrodes 8a, 8b, 8c, 8d protrude from the other side surface (the right side surface in FIG. 2) of the mass portion 6. The movable electrodes 8a to 8d have a rod shape and extend in parallel at equal intervals. Here, the beam parts 4 and 5, the mass part 6, and the movable electrodes 7a to 7d and 8a to 8d are
4 (see FIG. 3) is movable by partially or entirely removing it by etching.

On the upper surface of the substrate 1, four first fixed electrodes 9a, 9b, 9c, 9d and a second fixed electrode 11
a, 11b, 11c, and 11d are fixed. The first fixed electrodes 9a to 9d are supported by anchor portions 10a, 10b, 10c, and 10d protruding from the substrate 1 side, and are provided on one side surface of each movable electrode (bar-shaped portion) 7a to 7d of the beam structure 2A. They are arranged facing each other. Further, the second fixed electrodes 11a to 11d are supported by anchor portions 12a, 12b, 12c, and 12d protruding from the substrate 1 side, and the other of the movable electrodes (bar-shaped portions) 7a to 7d of the beam structure 2A. It is arranged facing the side surface.

Similarly, first fixed electrodes 13a, 13b, 13c, 13d and second fixed electrodes 15a, 15b, 15c, 15d are fixed on the upper surface of the substrate 1. The first fixed electrodes 13a to 13d are anchor portions 14a, 14
b, 14c, 14d, and the beam structure 2A
Of the movable electrodes (bar-shaped portions) 8a to 8d. Also, the second fixed electrodes 15a to 15a
5d are anchor portions 16a, 16 protruding from the substrate 1 side.
b, 16c, 16d, and the beam structure 2
The movable electrodes A (bar-shaped portions) 8a to 8d are arranged so as to face the other side surfaces.

As shown in FIG. 1, anchors 17a, 17b, 17 projecting from the substrate 1 are provided on the upper surface of the substrate 1.
c, electrode extraction portions 18a, 18b, 18c supported by
Are formed thereon, and electrode pads (bonding pads) 19a, 19b, 19c made of aluminum electrodes are further formed thereon.
Are formed. The electrode portions 20a, 20b, 20c are anchor portions 17a, 17b, 17c, and electrode extraction portions 18a,
18b, 18c and electrode pads 19a, 19b, 19c, and the electrode portion 20d is composed of the fixed portion 2B (see FIG. 3) and the electrode pad 19d.

The substrate 1 is a silicon substrate 2 as shown in FIG.
2, a bonding thin film (polysilicon thin film) 23, an insulating thin film (silicon oxide film) 24, an insulating thin film 25, a conductive thin film (for example, a polysilicon thin film doped with an impurity such as phosphorus) 26, and an insulator. A thin film 27 is laminated on the conductive thin film 27, and the conductive thin film 26 is covered with insulating thin films 25 and 27. Here, the insulator thin films 25, 2
Reference numeral 7 denotes a thin film (for example, a silicon nitride film) which is hardly eroded by an etching solution used for etching the above-described sacrificial layer. That is, in this example, H is used as the etching solution.
F (hydrogen hydrogen liquid) is used, and the silicon nitride film has a smaller amount of erosion than the silicon oxide film and is suitable for manufacturing a sensor.

The conductive thin film 26 forms the anchor portions 3a, 10a, 10b, 12a as shown in FIG. Also, the anchor portions 3b to 3d, 10c, 10d, 12b and
12d, 14a to 14d, 16a to 16d, 17a to 1
7c is also formed of the conductive thin film 26.

The conductive thin film 26 is formed on the first fixed electrode 9.
a to 9d and the electrode extraction portion 18a, the first fixed electrode 13
a to 13d and the electrode extraction portion 18a, the second fixed electrode 1
Wirings for electrically connecting between 1a to 11d and the electrode extraction portion 18c and between the second fixed electrodes 15a to 15d and the electrode extraction portion 18c are formed, respectively, and a lower electrode (fixed electrode for canceling electrostatic force). 28 are formed. The lower electrode 28 is formed in a region facing the beam structure 2A on the upper surface of the substrate 1 as shown in FIG.

As shown in FIGS. 1 and 2, the fixed electrodes 9a to 9d are connected to an electrode extraction portion 18a through a wiring pattern 29 and an anchor portion 17a. Pad) 1
9a is provided. The fixed electrodes 11a to 11d are connected to the wiring pattern 30,
The electrode pad 19c is provided on the upper surface thereof by being connected to the electrode take-out portion 18c through c. Fixed electrodes 13a-1
3d is also the electrode extraction portion 18 through the wiring pattern 31.
a and the electrode pads 19a and the fixed electrodes 15a to
15d is connected to the electrode extraction portion 18c and the electrode pad 19c through the wiring pattern 32. Beam structure 2A
Is connected to the electrode extraction portion 18b and the electrode pad 19b through the wiring pattern 33 and the anchor portion 17b. Here, the electrode pad 19d is for taking a surface potential, and more specifically, the beam structure 2A and the fixed electrodes (9a to 9d, 11a to 11d, 13a) in one silicon substrate.
To 13d, 15a to 15d), and an electrode extraction part (18a to 1
This is for taking the potential of the part except for 8c).

In the above configuration, a first capacitor is formed between the movable electrodes 7a to 7d of the beam structure 2A and the first fixed electrodes 9a to 9d, and the first capacitor is formed between the movable electrodes 7a to 7d of the beam structure 2A. A second capacitor is formed between the second fixed electrodes 11a to 11d. Similarly, a first capacitor is provided between the movable electrodes 8a to 8d of the beam structure 2A and the first fixed electrodes 13a to 13d, and the movable electrodes 8a to 8d and the second fixed electrode 15a of the beam structure 2A are also provided. To 15d to form a second capacitor.

The acceleration acting on the beam structure 2A can be detected based on the capacitances of the first and second capacitors. More specifically, two differential capacitances are formed by the movable electrode and the fixed electrode, and the servo operation is performed so that the two capacitances become equal.

FIG. 4 is an enlarged view of a section of the fixed electrode and the movable electrode of FIG. In FIG. 4, the movable electrode 35
And the fixed electrode 36 are opposed to each other, the beam structure 2
The separation distances d1 and d2 in the moving direction of A are different.
Specifically, the surface where the movable electrode 35 and the fixed electrode 36 face each other has a tapered shape in which the separation distance in the facing surface gradually changes. That is, the beam structure 2 at the upper end of FIG.
The separation distance in the movement direction of A is the smallest, d1, and the separation distance in the movement direction of the beam structure 2A at the lower end is d2, the largest. Therefore, as shown in FIG. 3, the beam structure 2A including the movable electrodes (7a to 7d, 8a to 8d) and the fixed electrodes (9a to 9d, 11a to 11d, 13a to 13).
By adopting an appropriate tapered shape in d, 15a to 15d), the sticking area on the electrode facing surface that causes sticking is reduced. This makes it easier to release with reduced sticking power.

Furthermore, by making the electrode shape tapered,
The area of the lower end face of the beam structure 2A, which is the residual portion of the stress, is reduced, and the occurrence of warpage is suppressed. Thereby, a desired sensor shape is obtained. More specifically, for example, in a structure having a cross-sectional shape drawn by imaginary lines 100 and 200 in FIG. 4, a case where a large amount of residual stress causing warpage is generated on the fixed / movable electrodes 35 and 36 on the substrate 1 side. As shown by a solid line in FIG. 4, the trapezoidal shape with the lower side narrowed, that is, by reducing the width W on the substrate 1 side with respect to the electrodes 100 and 200 having a rectangular cross section, warpage can be suppressed. Will be possible.

Next, a method of manufacturing the semiconductor acceleration sensor thus configured will be described with reference to FIGS. First, as shown in FIG. 5, a single crystal silicon substrate 40 is prepared as a first semiconductor substrate. Then, a trench 41 is formed in the silicon substrate 40 by trench etching. The groove 41 is used as an alignment mark of a stopper and a mask at the time of polishing described later.

Further, as shown in FIG. 6, the surface of the silicon substrate 40 is doped with impurities by ion implantation or the like.
The low resistance region 42 is formed. Then, as shown in FIG. 7, a silicon oxide film 43 as a sacrificial layer thin film is formed by CVD.
Then, the surface of the silicon oxide film 43 is flattened.

Subsequently, as shown in FIG. 8, the silicon oxide film 43 is partially etched through photolithography to form a concave portion 44. Thereafter, as shown in FIG. 9, a silicon nitride film (first insulating thin film) 45 is formed to increase the surface irregularities and to use it as an etching stopper at the time of etching the sacrificial layer.

Then, as shown in FIG. 10, openings 46a, 46b, 46c, 46d are formed in the anchor formation region by dry etching or the like through photolithography on the stacked body of the silicon oxide film 43 and the silicon nitride film 45. I do. The openings 46a to 46d are for connecting the beam structure and the lower electrode, and for connecting the fixed electrode / electrode extraction portion and the wiring pattern.

Subsequently, as shown in FIG.
A polysilicon thin film 47 is formed on the silicon nitride film 45 including 6a to 46d, then impurities are introduced by phosphorus diffusion or the like. Thin film) 47
a, 47b, 47c and 47d are formed.

Then, as shown in FIG. 12, a silicon nitride film 48 and a silicon oxide film 49 as a second insulator thin film are sequentially formed on the polysilicon thin films 47a to 47d and the silicon nitride film 45.

Further, as shown in FIG. 13, a polysilicon thin film 50 as a bonding thin film is formed on the silicon oxide film 49.
Then, as shown in FIG. 14, the surface of the polysilicon thin film 50 is flattened by mechanical polishing or the like for bonding.

Thereafter, as shown in FIG. 15, a single-crystal silicon substrate (support substrate) 51 different from the silicon substrate 40 is prepared, and the surface of the polysilicon thin film 50 and the silicon substrate 51 as the second semiconductor substrate are formed. Paste.

Then, as shown in FIG. 16, the silicon substrates 40 and 51 are turned upside down, and as shown in FIG. 17, the silicon substrate 40 side is thinned by mechanical polishing or the like. At this time, polishing is performed until a layer of the silicon oxide film 43 in the groove 41 appears. When the polishing is performed until the layer of the silicon oxide film 43 appears as described above, the hardness in the polishing changes, so that the end point of the polishing can be easily detected.

Thereafter, as shown in FIG. 18, after forming a silicon oxide film 52 as an interlayer insulating film, impurities are doped by ion implantation or the like. Thus, the low resistance layer 53 is formed on the surface of the silicon substrate 40. And
A contact hole 54 is formed, and an aluminum electrode 55 is formed through film formation and photolithography as shown in FIG. After that, the fixed part 2B including the fixed electrode and the beam movable body 2
A groove 56 for defining A is formed. This groove 56
The groove 56 is formed in an unnecessary area between the movable electrode forming part and the fixed electrode forming part in the silicon substrate 40, and the groove 56 has an inner wall surface which is gradually separated in a direction parallel to the surface of the substrate 40. Is tapered. Regarding the formation of the groove 56, more specifically, the groove 56 is formed into a sectional shape shown in FIG. 19 by selecting and using a desired gas type as a condition for dry etching.

Finally, as shown in FIG. 20, the silicon oxide films 43 and 52 are removed by etching with an HF-based etchant, and the beam structure having movable electrodes is made movable. That is, the silicon oxide film 43 in a predetermined region is removed by sacrifice layer etching using an etchant, and the silicon substrate 4 is removed.
The beam structure made of zero is a movable structure. At this time, a sublimating agent such as paradichlorobenzene is used to prevent the movable portion from adhering to the substrate during the drying process after the etching.

In this manner, a semiconductor acceleration sensor having the cross section of the fixed electrode and the movable electrode shown in FIG. 4 can be formed. As described above, this embodiment has the following features. (A) As shown in FIG. 4, the movable electrode 35 and the fixed electrode 36
Are different in the moving direction of the beam structure 2A in the plane in which. Therefore, it is possible to provide a structure in which the sticking area on the opposing surface of the electrode, which is a site where sticking occurs, is reduced, and the sticking force is reduced to facilitate release. More specifically, at least one of the surfaces of the movable electrode 35 and the fixed electrode 36 facing each other has a tapered shape in which the separation distance in the facing surface gradually changes.

Further, as shown in FIG. 4, by forming the opposing surface of the electrode in a tapered shape, the residual portion of the stress which causes the warpage can be reduced, and the warpage can be suppressed. (B) As a manufacturing method, as shown in FIG. 9, a sacrificial layer thin film 43 and an insulator thin film 45 are stacked on a silicon substrate 40, and as shown in FIG. Anchor part formation region 46 in a laminate with 45
a, 46b, 46c and 46d are opened, and as shown in FIG. 11, conductive thin films 47a, 47b, 47c and 47d are formed in predetermined regions on the insulating thin film 45 including the openings 46a to 46d.
Are formed, and as shown in FIG.
7d, the insulator thin films 48, 4
9 is formed, and as shown in FIG.
9 and the surface of the bonding thin film 50 is flattened as shown in FIG.
As shown in FIG. 5, the surface of the bonding thin film 50 is bonded to the silicon substrate 51, and the silicon substrate 40 is polished to a desired thickness as shown in FIG. Unnecessary regions between the electrode forming portion and the fixed electrode forming portion are removed by changing the separation distance in a direction parallel to the surface of the substrate in the opposing surfaces, and predetermined portions are wet-etched as shown in FIG. By removing the sacrificial layer thin film 43 in the region, the beam structure made of the silicon substrate 40 was made a movable structure. As a result, it is possible to obtain the sensor structure of (a), and to obtain a structure in which the wiring for the movable electrode extends from the anchor portion of the beam structure and the wiring for the fixed electrode extends from the anchor portion of the fixed electrode. It is preferable as a method for producing. (Second Embodiment) Next, a second embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

In the first embodiment described above, FIG.
9, that is, the fixed portion 2 including the fixed electrode
The etching for defining B and the beam structure 2A was performed at the end of the process. In the present embodiment, this process is performed simultaneously with the trench etching described with reference to FIG. this,
This will be described in detail with reference to FIGS.

First, as shown in FIG. 21, a groove 60 for defining the fixed portion 2B including the fixed electrode and the beam structure 2A is formed in the single crystal silicon substrate 40. In other words, the groove 60 is formed in the air gap forming region between the movable electrode forming portion and the fixed electrode forming portion in the silicon substrate 40, and is formed in the surface of the opposing inner wall in the surface of the substrate 40. It is formed in a tapered shape with a different separation distance in a direction parallel to the surface.

Then, as shown in FIG. 22, an impurity is doped into the surface of the silicon substrate 40 by ion implantation or the like to form a low-resistance region 42, and as shown in FIG. The film 43 is formed by a CVD method or the like, and the surface of the silicon oxide film 43 is flattened.

Further, as shown in FIG. 24, after the silicon oxide film 43 is partially etched through photolithography to form a concave portion 44, a silicon nitride film 45 is formed as shown in FIG. Then, as shown in FIG. 26, the openings 46a, 46b,
46c and 46d are formed, and as shown in FIG. 27, a polysilicon thin film 47 is formed on the silicon nitride film 45 including the openings 46a to 46d, and then impurities are introduced by phosphorus diffusion or the like. Through photolithography, anchor portions, wiring, lower electrode patterns 47a, 47b,
47c and 47d are formed.

Then, as shown in FIG. 28, a silicon nitride film 48 and a silicon oxide film 49 are formed on the polysilicon thin film 47 and the silicon nitride film 45, and as shown in FIG. Then, a polysilicon thin film 50 is formed as a bonding thin film, and the surface of the polysilicon thin film 50 is flattened by mechanical polishing or the like for bonding as shown in FIG.

Thereafter, as shown in FIG. 31, the surface of the polysilicon thin film 50 is bonded to a silicon substrate 51 as a second semiconductor substrate, and the silicon substrates 40 and 51 are turned upside down as shown in FIG. , As shown in FIG.
The silicon substrate 40 is thinned by mechanical polishing or the like. Thereafter, as shown in FIG. 34, after forming a silicon oxide film 52 as an interlayer insulating film, impurities are doped by ion implantation or the like. Then, a contact hole 54 is formed, and as shown in FIG. 35, an aluminum electrode 55 is formed through film formation and photolithography, and as shown in FIG.
Silicon oxide films 43 and 52 by HF-based etchant
Is removed by etching to make the beam structure having a movable electrode movable.

As described above, this embodiment has the following features. (A) As shown in FIG. 21, a groove 60 is formed in an air gap forming region of a silicon substrate 40 between a movable electrode forming portion and a fixed electrode forming portion, in a direction parallel to the surface of the substrate in the opposed inner wall surface. Are formed with different separation distances.
Then, as shown in FIG. 25, the sacrificial layer thin film 43 and the insulator thin film 45 are laminated on the substrate 40 including the groove 60,
As shown in FIG. 26, the sacrificial layer thin film 43 and the insulator thin film 4
5. Anchor part formation regions 46a to 46 in the laminate with No. 5
d, and openings 46a-46 as shown in FIG.
The conductive thin film 47 is formed in a predetermined region on the insulating thin film 45 containing d.
a to 47d are formed, and as shown in FIG. 28, insulating thin films 48 and 49 are formed on the insulating thin film 45 including on the conductive thin films 47a to 47d, and as shown in FIGS. The lamination thin film 50 is formed on the body thin films 48 and 49, and the surface of the lamination thin film 50 is flattened. As shown in FIG.
And the silicon substrate 4 as shown in FIG.
0 is polished to a desired thickness, and as shown in FIG. 36, a predetermined region of the sacrificial layer thin film 43 is removed by wet etching to make the beam structure made of the silicon substrate 40 a movable structure. As a result, the sensor structure shown in FIG. 3 is obtained.

In addition to those described above, the present invention may be implemented as follows. FIG. 3 shows a structure in a plane facing the movable electrode 35 and the fixed electrode 36 in place of FIG.
As shown in FIG. 7, a reverse taper may be used. That is, FIG.
The separation distance in the movement direction of the beam structure 2A at the lower end of 7 is d11, which is the shortest, and the separation distance in the movement direction of the beam structure 2A at the upper end is d10, the largest. The groove having such a tapered shape is obtained by selecting and using a desired gas type as a condition for dry etching. In this case, the portion where the stress remains at the upper end can be reduced, and the occurrence of warpage can be suppressed. That is, in FIG.
In a structure having a cross-sectional shape drawn at 0 and 200, if a large amount of residual stress causing warpage occurs on the non-substrate side of the fixed / movable electrodes 35 and 36, as shown by a solid line in FIG. If a trapezoidal shape with a narrow upper side is used (a beam width W on the side opposite to the substrate is narrowed), warpage can be suppressed.

It should be noted that the tapered shape shown in FIG.
Regarding the taper shape shown in FIG. 7, a sensor may be actually manufactured, and a taper shape for suppressing the occurrence of warpage may be determined from the result.

Further, as shown in FIG. 38, the forward / reverse taper (the combination of a forward taper and a reverse taper) with the center approached.
It may be. That is, the distances d20 and d21 at the upper and lower ends are made smaller than the distance d22 at the center.

Alternatively, as shown in FIG. 39, a forward / reverse taper (a combination of a forward taper and a reverse taper) in which the upper and lower ends are close to each other may be used. That is, the distance d3 between the upper and lower ends
The distance d32 at the center is made smaller than 0 and d31.

Alternatively, as shown in FIG. 40, irregularities are formed by continuously repeating a forward taper and a reverse taper. Here, the groove shapes shown in FIGS. 38 to 40 can be realized by performing groove processing while changing the conditions of dry etching.
For example, the changing conditions include gas type, gas flow rate, substrate temperature, and power. In this way, by performing the groove processing while changing the etching conditions, the separation distance d can be varied.

In FIG. 4, the movable electrode 35 and the fixed electrode 3
6 are both tapered surfaces, but only one may be a tapered surface (or an uneven surface or the like).
Further, the present invention is not limited to the above-described acceleration sensor, and can be applied to a dynamic quantity sensor such as a yaw rate sensor.

[Brief description of the drawings]

FIG. 1 is a diagram showing a planar configuration of a semiconductor acceleration sensor according to an embodiment.

FIG. 2 is an enlarged view of an element part in FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a partially enlarged view of a cross section of the acceleration sensor according to the embodiment.

FIG. 5 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 6 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 7 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 8 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 9 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 10 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 11 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 12 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 13 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 14 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 15 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 16 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 17 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 18 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 19 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 20 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 21 is a sectional view showing a manufacturing process of the acceleration sensor according to the second embodiment.

FIG. 22 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 23 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 24 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 25 is a sectional view showing a manufacturing process of the acceleration sensor.

FIG. 26 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 27 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 28 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 29 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 30 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 31 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 32 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 33 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 34 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 35 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 36 is a sectional view showing the manufacturing process of the acceleration sensor.

FIG. 37 is a cross-sectional view of another example of an acceleration sensor.

FIG. 38 is a cross-sectional view of another acceleration sensor.

FIG. 39 is a cross-sectional view of another example of an acceleration sensor.

FIG. 40 is a sectional view of another example of an acceleration sensor.

[Description of Signs] 1 ... substrate, 2A ... beam structure, 7a, 7b, 7c, 7d ...
Movable electrode, 8a, 8b, 8c, 8d ... movable electrode, 9a,
9b, 9c, 9d: first fixed electrodes, 11a, 11b,
11c, 11d: second fixed electrodes, 13a, 13b, 1
3c, 13d: first fixed electrodes, 15a, 15b, 15
c, 15d: second fixed electrode, 40: silicon substrate, 4
DESCRIPTION OF SYMBOLS 1 ... groove | channel, 43 ... silicon oxide film, 45 ... silicon nitride film, 46a-46d ... opening part, 47a-47d ... polysilicon thin film, 48 ... silicon nitride film, 50 ... polysilicon thin film, 51 ... silicon substrate, 56 ... Groove, 60 ... groove.

Continued on the front page (72) Inventor Shoichi Yamauchi 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 4M112 AA02 BA07 CA22 CA26 CA36 DA03 DA04 DA05 DA18 EA03 EA04 FA07

Claims (6)

[Claims] 1. A substrate, a beam structure supported on a top surface of the substrate at a predetermined interval so as to be movable in a direction parallel to the surface of the substrate and having a movable electrode, and fixed to the top surface of the substrate; A fixed electrode disposed to face the movable electrode of the beam structure and detecting a displacement of the beam structure accompanying the application of the mechanical amount together with the movable electrode. A distance between the beam structure and the fixed electrode in a direction in which the beam structure moves in a plane facing the fixed electrode. 2. The physical quantity sensor according to claim 1, wherein at least one of the surfaces facing the movable electrode and the fixed electrode has a tapered shape in which a separation distance in the surface facing the movable electrode gradually changes. . 3. The physical quantity sensor according to claim 1, wherein at least one of the surfaces of the movable electrode and the fixed electrode facing each other has a concave / convex portion formed by repeating a forward taper and a reverse taper. 4. A substrate, a beam structure having a movable electrode supported on the upper surface of the substrate at a predetermined interval so as to be movable in a direction parallel to the surface of the substrate, and fixed to the upper surface of the substrate; A fixed electrode for being disposed opposite to the movable electrode of the beam structure and detecting the displacement of the beam structure accompanying the application of the mechanical amount together with the movable electrode, comprising: Laminating a sacrificial layer thin film and a first insulator thin film on a first semiconductor substrate, and opening an anchor portion forming region in a laminate of the sacrificial layer thin film and the first insulator thin film Forming a conductive thin film in a predetermined region on the first insulating thin film including the opening; and forming a second insulating thin film on the first insulating thin film including on the conductive thin film Forming a thin film for lamination on the second insulator thin film. Forming a surface of the bonding thin film, flattening the surface of the bonding thin film, bonding the surface of the bonding thin film to a second semiconductor substrate, and forming the first semiconductor substrate to a desired thickness. Polishing, and an unnecessary region between the movable electrode forming portion and the fixed electrode forming portion in the first semiconductor substrate, in which the separation distance in the direction parallel to the surface of the substrate in the opposing surface is made different. A physical quantity sensor comprising: a removing step; and a step of removing the thin film for the sacrificial layer in a predetermined region by wet etching to make the beam structure made of the first semiconductor substrate a movable structure. Manufacturing method. 5. A substrate, a beam structure having a movable electrode supported on the upper surface of the substrate at a predetermined interval so as to be movable in a direction parallel to the surface of the substrate, and fixed to the upper surface of the substrate; A fixed electrode for being disposed opposite to the movable electrode of the beam structure and detecting the displacement of the beam structure accompanying the application of the mechanical amount together with the movable electrode, comprising: Grooves are formed in the air gap forming region between the movable electrode forming portion and the fixed electrode forming portion in the first semiconductor substrate at different distances in the direction parallel to the surface of the substrate in the inner wall surfaces facing each other. A step of laminating a sacrificial layer thin film and a first insulator thin film on the first semiconductor substrate including the groove, and a step of laminating the sacrificial layer thin film and the first insulator thin film. A step of opening an anchor portion forming area; Forming a conductive thin film on a predetermined region on the first insulating thin film including the opening; forming a second insulating thin film on the first insulating thin film including on the conductive thin film; Performing a bonding thin film on the second insulating thin film and flattening the surface of the bonding thin film; and performing a bonding between the surface of the bonding thin film and a second semiconductor substrate. Bonding the first semiconductor substrate to a desired thickness; removing the sacrificial layer thin film in a predetermined region by wet etching to form a beam structure made of the first semiconductor substrate. A method of manufacturing a mechanical quantity sensor, comprising: a step of forming a movable structure. 6. The method for manufacturing a physical quantity sensor according to claim 4, wherein the separation distance is varied by performing groove processing while changing etching conditions.