JP3189506B2 - Acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor suitably used for detecting acceleration of a vehicle or the like.
In particular, the present invention relates to an acceleration sensor capable of improving the yield during manufacturing.

[0002]

2. Description of the Related Art In general, an acceleration sensor used to detect the acceleration or the direction of rotation of a vehicle or the like has a fixed electrode on an insulating substrate and a movable electrode disposed to face the fixed electrode. When the acceleration is applied, a change in the distance between the movable electrode and the fixed electrode in accordance with the acceleration is detected as a change in capacitance.
There are known acceleration sensors as shown in FIGS.

First, in FIGS. 10 to 12, reference numeral 1 denotes an acceleration sensor according to the prior art.
Denotes a glass substrate 2 as an insulating substrate on which a concave portion 2A is formed.
And a pair of fixed parts 3 and 3 provided on the glass substrate 2 so as to sandwich the recess 2 </ b> A, and a movable part 4 provided between the fixed parts 3.

Here, since each of the fixed part 3 and the movable electrode 4 is formed separately from a single low-resistance silicon wafer 10 to be described later by etching, each of them has conductivity. The opposed end faces of the pair of fixing portions 3 sandwiching the recess 2A are formed integrally with the fixing portions 3 as fixed electrodes 3A.

The movable portion 4 has a support portion 5 fixed to the glass substrate 2 on the base end side and serving as a fixed end. A beam 6 and a beam 6 are provided on the distal end side of the support portion 5. And a mass 7 serving as a free end that can be displaced therethrough. here,
Since the movable part 4 is also formed of the same silicon wafer 10 as the fixed part 3, it has conductivity. The mass part 7 has movable electrodes 7A, 7A whose facing end faces on the fixed electrode 3A side are movable parts 7A. And are formed integrally. The mass portion 7 thus formed is positioned above the concave portion 2A of the glass substrate 2 and supported by the support portion 5 and the beam 6 in a state where it can be displaced in the direction of arrow A between the fixed portions 3. Have been.

Next, a method of manufacturing the acceleration sensor 1 according to the prior art will be described with reference to FIGS.

In FIG. 13, reference numeral 10 denotes a silicon wafer as a silicon plate. The front and back (one side and the other side) of the silicon wafer 10 are (110) planes, for example, low resistance (0.01 to 0.02 Ωcm). ) With a diameter of about 7.5 to 15
cm and a thickness of about 300 μm.

Reference numeral 11 denotes a glass substrate as an insulating substrate. The glass substrate 11 is formed to have the same diameter as or larger than the size of the silicon wafer 10, and one side of the glass substrate 11 is made of hydrofluoric acid or the like. Glass etching (glass etching step) is performed to obtain a rectangular recess 11A.
(2A) and 11A (2A) are formed.

Next, in the bonding step shown in FIG. 14, the other side of the silicon wafer 10 and one side of the glass substrate 11 are bonded.

Next, in the patterning step shown in FIG. 15, in order to form the fixing parts 3 and the mass parts 7 on the silicon wafer 10, the fixing parts 3 and the mass parts 7 on the surface of the silicon wafer 10 are formed. A few μm of SiN (or SiO ₂ ) is
Are formed from the thin films of the above.

In a first etching step shown in FIG. 16, wet etching using KOH or the like is performed from one side surface of the silicon wafer 10 to process the silicon wafer 10 in a vertical direction. Let it separate.
Thereafter, a cleaning step using pure water is performed to remove an etching solution such as KOH, and then a drying step for drying the pure water is performed.

Further, in the second etching step shown in FIG. 17, RIE (reactive ion etching) is performed from one side, and the fixed part 3 and the mass part 7 separated in the first etching step are formed on one side. The remaining mask films 12 are removed.

Thus, a plurality of acceleration sensors 1 can be formed on the glass substrate 11 by the manufacturing method shown in FIGS. 13 to 17, and cut at the position shown by the two-dot chain line (for example, the size of the chip angle) in FIG. For example, a plurality of acceleration sensors 1 can be manufactured at one time.

The acceleration sensor 1 manufactured as described above
When an external acceleration is applied in the direction of arrow A shown in FIG. 10, the mass 7 is displaced via the beam 6, and the mass 7
Since it approaches or separates from the right fixing portions 3 and 3, the displacement of the separation dimension at this time is fixed by the fixed electrode 3A and the movable electrode 7A.
The change in the capacitance between the two is output to an external signal processing circuit (not shown), and the signal processing circuit outputs a signal corresponding to the acceleration based on the change in the capacitance.

[0015]

In the prior art described above, after the first etching step for separating and forming the fixing part 3 and the mass part 7, the glass substrate 2 and the silicon wafer 10 are cleaned with pure water. A step and a drying step for drying these are required. Here, after the cleaning step,
Pure water (water) used in the washing process between the fixing part 3 and the mass part 7
Remains, the mass part 7 easily sticks to the fixing part 3 via the water, and the fixing part 3 and the mass part 7 approach each other as the water evaporates in the drying step, and the fixing part 3 and the mass part 7 Are inseparable from each other.

If the fixed portion 3 and the mass portion 7 are in close contact with each other, the fixed electrode 3A and the movable electrode 7A are in close contact with each other and cannot be used as a product.
However, there is a problem that the production yield is lowered and the productivity is lowered.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an acceleration sensor capable of preventing the occurrence of defective products in a washing step and a drying step and improving the yield. Aim.

[0018]

In order to solve the above problems SUMMARY OF THE INVENTION, the configuration of the invention of claim 1 is employed, an insulating substrate and, the
Formed on a low-resistance silicon plate provided on an insulating substrate
A movable section and a fixed section.
A supporting portion fixed on the edge substrate and one end connected to the supporting portion;
Beam and the other end of the beam
And a mass portion arranged opposite to the fixing portion,
The mass part is displaced according to the acceleration when the acceleration acts.
And the capacitance between the mass part and the opposing surface of the fixed part is
In the changing acceleration sensor, the mass part and the fixed part
The at least one surface of the opposing surfaces of the parts, provided projecting towards the opposing <br/> other surface, the projection portion for chromatic <br/> a raised portion in a substantially triangular pyramid shape integral, the mass Between the part and the fixed part
It is characterized by ensuring a minute gap between them. Also,
According to a second aspect of the present invention, there is provided an insulating substrate, and an insulating substrate provided on the insulating substrate.
Moving parts and fixed parts made of low-resistance silicon plate
And a plurality of thin plates formed integrally with the fixing portion.
The movable part is fixed on the insulating substrate.
A supported support and a beam having one end connected to the support
Is connected to the other end of the beam,
Mass part displaced according to the degree, the mass part is
Integrated so that it faces the electrode plate of the fixed part with a small gap
Having a plurality of thin plate-shaped electrode plates protruding from
Of the opposing surfaces of the fixed portion electrode plate and the fixed portion electrode plate.
At least one side protrudes toward the other side,
A projection with a generally triangular pyramid
A small gap between the mass part and the fixed part
And an electrostatic force between the electrode plate of the mass part and the electrode plate of the fixed part.
The configuration is such that a change in capacitance is detected.

[0019]

[Action] In the invention described in claim 1, in the drying step, the fixed part
It is interposed water between parts by weight, of a substantially triangular pyramid projection portion
The protruding part is in point contact with the surface of the other
Fixed because a small gap is secured between the fixed part and the mass part
Or parts by mass sticks to part, fixing part and parts by weight in the drying step
As the water evaporates during this time, the fixed portion and the mass portion come close to each other and can be prevented from being in close contact with each other. According to the second aspect of the present invention,
Of the opposing surfaces of the electrode plate of the
At least one side protrudes toward the other side,
Protruding part having a raised part in a substantially triangular pyramid is provided integrally
Therefore, the part of the protrusion that protrudes in a substantially triangular pyramid shape
Point contact with the other electrode plate, and a small gap between each electrode plate
Can be secured. For this reason, the electrode plate of the fixed part
Prevents the mass electrode plate from sticking or sticking
You.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An acceleration sensor according to an embodiment of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those of the above-described conventional technology are denoted by the same reference numerals, and description thereof will be omitted.

FIGS. 1 to 7 show a first embodiment of the present invention.

In the drawing, reference numeral 21 denotes an acceleration sensor according to the present embodiment. The acceleration sensor 21 has a glass substrate 2 and a glass substrate 2 similar to the acceleration sensor 1 according to the prior art.
It is roughly composed of a pair of fixed parts 22 and 22 and a movable part 24 described later provided above.

Reference numerals 22 and 22 denote fixing portions according to the present embodiment. Each of the fixing portions 22 is etched together with the movable portion 24 from a single low-resistance silicon wafer 10 in substantially the same manner as the above-described fixing portion 3 of the prior art. Each of the fixing portions 22 is formed by processing, and each of the fixing portions 22 itself has conductivity, and the opposite end surfaces of the fixing portions 22 are integrally formed as fixed electrodes 22A, but each of the fixing portions 22 has the same surface as the fixed electrode 22A. Are formed integrally with each other.

Reference numerals 23, 23 denote projections formed on the fixing portions 22. The projections 23 are, as shown in FIGS. 2 and 7, inner end faces of the fixing portions 22 (the same surface as the fixed electrode 22A). ) Are provided at a distance from each other, and each projection 23 extends from one side to the other side and has a columnar portion 23A having a triangular cross section.
And a mass portion 2 described below, which is located on the other side of the columnar portion 23A.
And a substantially triangular pyramid-shaped protruding portion 23B protruding to the seventh side. Then, each columnar portion 23A and the raised portion 23B
Is sharp toward the mass portion 27 side, even if the mass portion 27 is greatly displaced toward one of the fixed portions 22 in the washing step and the drying step, each columnar portion 23A or each raised portion 23B is Are in point contact with each other to secure a minute gap between the electrodes.

Reference numeral 24 denotes a movable portion according to the present embodiment. The movable portion 24 is formed integrally with a support portion 25, a beam 26, and a mass portion 27 in substantially the same manner as the movable portion 4 described in the prior art. The part 24 is formed by etching the same single low-resistance silicon wafer 10 as the fixing part 22. The mass portion 27 itself has conductivity, and the opposed end surfaces of the mass portion 27 on the fixed electrode 22A side are movable electrodes 27.
A and 27A are integrally formed with the mass portion 27.

28, 28 are movable electrodes 2 of the mass part 27;
7A shows other projections projecting from the same plane as FIG. 7A. Each projection 28 is formed from a columnar portion 28A and a raised portion 28B almost in the same manner as the projection 23 of the fixing portion 22 as shown in FIG. The projections 28 are located between the projections 23 and protrude from the mass 27 toward the fixed part 22.

Here, a method of forming each of the projections 23 by etching will be described with reference to FIGS. The description of the same steps as those in the method of manufacturing the acceleration sensor 1 according to the related art described above is omitted.

First, FIG. 3 shows a patterning step. In this patterning step, as described in the prior art, mask films 29, 29,.
Are formed, but the projections 23 are formed on each of the mask films 29.
Is formed at a position where a rectangular projection 29A is to be formed as shown in FIG.
Is provided.

Then, in the first etching step, wet etching with KOH or the like is performed from one side surface of the silicon wafer 10 to process the silicon wafer 10 in the vertical direction.

At this time, as described in the related art, the side surfaces of the fixing portions 22 and the mass portions 27 become the (111) plane, and are not etched in the direction perpendicular to the (111) plane due to the anisotropy of silicon.

However, since another surface of silicon appears at the corner of the convex portion 29A of the mask film 29, the slope is formed so as to lag the (110) plane with respect to this surface as shown in FIG. When the etching is performed for a predetermined period of time, as shown in FIG. 6, a projection 23 composed of a columnar portion 23A and a raised portion 23B is formed so as to project from the (111) plane.

Then, RIE (reactive ion etching) is performed from one side in the second etching step, and the mask film 29 remaining on one side of the fixing portion 22 is removed.
As shown in FIG. 7, a protrusion 23 is formed on the same surface of the fixed part 22 as the fixed electrode 22A.

The movable portion 27A is also provided on the mass portion 27.
Each projection 28 can be formed on the same surface as above.

Then, as described in the prior art, the acceleration sensor 21 is manufactured through a washing step and a drying step.

The acceleration sensor 21 according to the present embodiment has the above configuration, and its basic operation is not particularly different from that of the prior art.

However, in the present embodiment, when the silicon wafer 10 is vertically processed from one side surface by performing wet etching with KOH or the like, a square convex portion 29A is provided in the mask film 29 on the silicon wafer 10. Fixed part 2
2, 22 and the mass portion 27, each projection 23 projecting from each fixed portion 22 side toward the mass portion 27 side,
And the projections 28 projecting from the side 7 toward the respective fixing portions 22 are formed.
Even if water is interposed between the movable electrode 27A and the movable electrode 27A of the mass portion 27, the sharp projections 23 and 28 abut against each other's electrode surface to secure a minute gap. By allowing water to escape from the gap, the movable electrode 27A sticks to the fixed electrode 22A,
It is possible to prevent the fixed portion 22 and the mass portion 27 from approaching each other as the water evaporates between the portions A and 27A, and to prevent the fixed portion 22 and the mass portion 27 from intimately contacting each other.

Therefore, according to the present invention, the occurrence of defective products can be prevented, and the yield can be greatly improved.

Next, FIGS. 8 and 9 show a second embodiment of the present invention. The feature of this embodiment is that a comb-shaped electrode is used for a fixed electrode and a movable electrode, and the effective area of each electrode is increased. This is to improve the detection sensitivity.

In FIG. 8, reference numeral 31 denotes an acceleration sensor;
Denotes a glass substrate as an insulating substrate, and the glass substrate 3
2 is formed with a rectangular recess 32A.
Fixed portions 33, 33 and a movable portion 35, which will be described later, are formed separately from each other by etching a single low-resistance silicon wafer.

Reference numerals 33, 33 denote a pair of fixing portions, each of which is spaced apart to the left and right of the glass substrate 32, and a thin plate-like electrode plate 34
A, 34A,... Are formed in a plurality (for example, five), and each of the electrode plates 34A is a fixed side comb-shaped electrode 3 as a fixed electrode.
4 and 34 respectively.

Reference numeral 35 denotes a movable portion. The movable portion 35 is separated from the glass substrate 32 in front of and behind the glass substrate 32 and fixed to the glass substrate 32.
A mass portion 38 supported between the fixing portions 33 and a plurality of (for example, five) thin plate-shaped members protruding left and right from the mass portion 38, respectively; And the movable side comb-shaped electrodes 39, 39 as movable electrodes having the electrode plates 39A, 39A,.
7 is formed in a thin plate shape so as to support the mass portion 38 so as to be displaceable in the direction of arrow B. The electrode plates 39A of the movable comb electrodes 39 are opposed to the electrode plates 34A of the fixed comb electrodes 34 via a minute gap.

.., 40, 40,...
4 shows projecting portions protruding from the respective electrode plates 34A constituting the fourth electrode plate 39A on the side of the movable comb-shaped electrode 39 facing each other, and the respective projecting portions 40 are described in the first embodiment. A substantially triangular pyramid-shaped protruding portion which is formed to protrude from the side surface of each electrode plate 34A and protrudes toward each electrode plate 39A by etching as in the case of each protrusion 23 (28).
Have .

, 41, 41,...
9 shows protrusions formed so as to protrude from the respective electrode plates 39A constituting the electrode 9 to the electrode plate 34A on the side of the fixed-side comb-shaped electrode 34, and the respective protrusions 41 are formed in the same manner as the respective protrusions 40. , Formed so as to project between the respective projections 40 ,
It has a substantially triangular pyramid-shaped protruding portion protruding toward the electrode plate 34A .

The acceleration sensor 31 according to this embodiment configured as described above is manufactured through a cleaning step, a drying step, etc. after the etching step, similarly to the acceleration sensor 21 according to the first embodiment described above. , Each electrode plate 34
By providing the projections 40 and 41 on A and 39A,
The same operation and effect as those of the first embodiment can be obtained. In particular, in the acceleration sensor 31 of the present embodiment, the acceleration is detected as a change in the capacitance between the electrode plates 39A and 34A of the movable-side comb-shaped electrode 39 and the fixed-side comb-shaped electrode 34. Since the electrodes 39A and 34A are electrically connected in parallel, the capacitance between the electrode plates 39A and 34A can be set to a large value. Sensitivity can be increased and acceleration detection accuracy can be improved.

In the first embodiment, each fixing part 2
2. The fixed electrode 22A is formed integrally with the fixed part 22 by forming the mass part 27 from the low-resistance silicon wafer 10, and the movable electrode 27A is formed integrally with the movable part 27. However, the present invention is not limited to this. For example, each fixed portion and mass portion are formed from a high-resistance silicon wafer, and a thin film or the like for imparting conductivity is separately provided on the opposite end surface of each fixed portion and mass portion, and the fixed electrode and the movable electrode are provided. May be formed.

In each of the above embodiments, the projections are formed on both the fixed electrode side and the movable electrode side. However, the present invention is not limited to this, and the projections may be formed on the fixed electrode side or the movable electrode side. It may be provided on any one of the electrodes.

[0047]

As described above in detail, according to the first aspect of the present invention, the opposing surfaces of the fixed portion and the mass portion which oppose each other.
Among the at least one surface, protruding towards the other plane, substantially
Since a protrusion which have a raised portion on the triangular pyramid is formed integrally, at the time of manufacturing the acceleration sensor, even water between the fixed portion and the mass portion after the cleaning process is carried out dry in a state interposed, Of the protrusions provided between them, the protrusions
The raised part is in point contact with the other surface and abuts,
It is possible to secure a minute gap between the parts. others
Because, fixing unit and quality by escape of water from this small gap
It is possible to prevent the mass portions from sticking to each other, to suppress the occurrence of defective products, and to greatly improve the yield. In addition, claim 2
According to the invention, the electrode plate of the mass part and the electrode plate of the fixed part are opposed to each other.
At least one of the surfaces
A protrusion with a generally triangular pyramid-shaped protruding portion
Since the raised part is provided integrally, the protruding part has a substantially triangular pyramid shape.
The raised portion makes point contact with the other electrode plate,
A minute gap can be secured between the electrode plates. In addition, each
The capacitance between the plates can be set to a large value,
When detecting acceleration from changes in capacitance,
The acceleration detection accuracy can be improved.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a main part in the direction of arrows II-II in FIG.

FIG. 3 is an enlarged sectional view showing a state in which a mask film is formed on one side surface of a silicon wafer by a patterning process.

FIG. 4 is an enlarged perspective view showing a mask film.

FIG. 5 is an enlarged perspective view showing a process in which a protrusion is formed on a fixing portion in a first etching step.

FIG. 6 is an enlarged perspective view similar to FIG. 5, showing a state in which a protrusion is formed on a fixing portion.

FIG. 7 is an enlarged perspective view similar to FIG. 5, showing a state in which a mask film has been removed from a fixing portion in a second etching step.

FIG. 8 is an enlarged plan view of an acceleration sensor according to a second embodiment of the present invention as viewed from above.

FIG. 9 is an enlarged view of a main part in FIG.

FIG. 10 is a perspective view showing an entire acceleration sensor according to the related art.

FIG. 11 is an enlarged view of the acceleration sensor shown in FIG. 10 as viewed from above.

12 is a sectional view taken in the direction of arrows XII-XII in FIG. 11;

FIG. 13 is a longitudinal sectional view showing a silicon wafer and a glass substrate for manufacturing the acceleration sensor.

FIG. 14 is a longitudinal sectional view showing a state in which one side surface of a silicon wafer and a glass substrate are joined by a joining step.

FIG. 15 is a longitudinal sectional view showing a state where a mask film is formed on one side surface of a silicon wafer by a patterning step.

FIG. 16 is a longitudinal sectional view showing a state where the silicon wafer is separated into a fixed part and a mass part by a first etching step.

FIG. 17 is a longitudinal sectional view showing a state where the mask film has been removed from one side surface of the fixed part and the mass part in the second etching step.

[Explanation of symbols]

 21, 31 Acceleration sensor 2, 32 Glass substrate (insulating substrate) 2A, 32A Concave portion 10 Silicon wafer (silicon plate) 22, 33 Fixing portion 22A Fixed electrode 23, 28, 40, 41 Projecting portion 23A, 28A Columnar portion 23B, 28B Raised portion 24, 35 Movable portion 25, 36 Supporting portion 26, 37 Beam 27 Mass 27A Movable electrode 34 Fixed-side comb-shaped electrode (fixed electrode) 38 Mass 39 Combined movable-side electrode (movable electrode)

Continuation of front page (56) References JP-A-4-116465 (JP, A) JP-A-4-244968 (JP, A) JP-A-4-115165 (JP, A) JP-A-4-232875 (JP) JP-A-5-94937 (JP, A) JP-A-3-1486872 (JP, A) JP-A-6-151889 (JP, A) Table 4-4-504003 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G01P 15/08-15/125

Claims (2)

(57) [Claims] 1. An insulating substrate, and an insulating substrate provided on the insulating substrate .
And a movable portion and a fixed portion formed of a low resistance silicon plate, front Symbol movable portion, a support portion fixed to the insulating substrate,
A beam whose one end is connected to the support portion, is disposed opposite to the fixed portion through the fine small clearance is communicated <br/> forming the other end of the beams
Mass part, and when the acceleration acts , the mass part is displaced in accordance with the acceleration.
And the capacitance between the mass part and the opposing surface of the fixed part is
In the acceleration sensor changes, on at least one surface of the opposing surfaces of the fixed portion and the weight portion protrudes toward the other surface facing, substantially triangular pyramid
A protrusion which have a raised portion on Jo provided integrally, the quality
An acceleration sensor , wherein a minute gap is secured between a measuring part and the fixed part . 2. An insulating substrate, and an insulating substrate provided on the insulating substrate.
Movable and fixed parts made of low resistance silicon plate
The fixing portion comprises a plurality of thin plate-like electrode plates integrally formed so as to protrude.
The movable part has a support fixed on the insulating substrate.
Part, a beam having one end connected to the support part, and the other end of the beam
When the acceleration acts, it is displaced according to the acceleration
Mass part which faces the electrode plate of the fixed part via a minute gap.
To form a plurality of thin plate-shaped electrode plates
Has, opposing surfaces of the fixed portion of the electrode plate and the electrode plate of the mass portion
At least on one side, facing the other side
One projection that has a portion that protrudes and is
Provided on the body, the minute gap between the mass part and the fixed part
Secure and between the electrode plate of the mass part and the electrode plate of the fixed part
An acceleration sensor configured to detect a change in capacitance .