JPH06331648A - Acceleration sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance productivity in manufacturing acceleration sensors by preventing an etchant from entering and breaking the periphery of each groove during a second process in which fixed portions and movable portions are formed. CONSTITUTION:Fixed portions 32 and movable portions 34 are both formed from silicon materials and so can be formed by pluralities at a time using a silicon wafer. In a first etching process, a groove for making each fixed portion 32 and each movable portion 34 independent of each other and a guard groove for preventing the groove from communicating with its periphery are formed. In a second etching process, acceleration sensors 31 are partitioned from one another using guards 39 from the other side of the silicon wafer so as to prevent an etchant in each acceleration sensor 31 from entering the adjoining acceleration sensors 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor which is preferably used for detecting acceleration of a vehicle or the like and a method for manufacturing the same, and more particularly, an acceleration sensor which can improve the yield at the time of manufacturing and a method for manufacturing the same. Regarding

[0002]

2. Description of the Related Art Generally, an acceleration sensor used to detect the acceleration and the rotation direction of a vehicle or the like is one which detects it by utilizing the electrostatic capacitance between electrode plates.
No. 169 and Japanese Patent Laid-Open No. 232171/1987.

However, in these acceleration sensors, since the effective area between the electrodes of the fixed portion and the movable portion is small and the distance between them is large, the detection sensitivity is low and it is not possible to perform highly accurate acceleration detection. .

On the other hand, for example, in the acceleration sensor described in Japanese Patent Application Laid-Open No. 4-115165 (hereinafter referred to as "other prior art"), comb-shaped electrodes are used for the fixed electrode and the movable electrode to increase the effective area between the electrodes. The detection sensitivity is improved.

Another conventional acceleration sensor is a cantilever having one end fixed to a base and the other end serving as a weight capable of horizontally vibrating, and a movable side integrally formed with the cantilever. A comb-teeth-shaped electrode portion and a comb-teeth-shaped electrode portion on the fixed side which is meshed with the comb-teeth-shaped electrode portion on the movable side in a non-contact manner, and includes a comb-teeth fixed plate fixed to the base. When the acceleration is applied to the weight, the effective area of the comb-shaped electrode portion on the movable side and the comb-shaped electrode portion on the fixed side is changed, and this change is detected as a capacitance, which is determined according to the acceleration. A detection signal is obtained.

[0006] However, in the other conventional techniques, when each comb-toothed electrode portion is formed by utilizing the silicon etching processing technique, the etching process is performed only from one side surface of the silicon, so that each etching is performed. If the surface is tilted and the distance between the electrode portions is reduced, the electrode portions may come into contact with the other side surface portion of silicon, and the distance between the electrode portions cannot be reduced.

That is, a silicon wafer having a thickness of several hundreds of μm is normally used, and if this thickness is used as it is as the thickness dimension of each electrode portion, the etching surface is inclined and the separation dimension is reduced for the above reason. Becomes difficult. On the other hand, it is conceivable to use a silicon wafer having a thickness of about several tens of μm from the beginning, but in this case, the strength of the silicon wafer becomes weak and it is damaged during transportation.

Therefore, in order to solve the above-mentioned problems of the prior art, the present inventor previously examined an acceleration sensor and a manufacturing method thereof as shown in FIGS.
"Prior art").

That is, in FIGS. 10 to 20, 1 is an acceleration sensor, 2 is a glass substrate as an insulating substrate, and fixed parts 3, 3 and a movable part 5 which will be described later are formed on the glass substrate 2. There is. Further, a rectangular concave groove 2A is formed in the glass substrate 2, and the mass portion 8 of the movable portion 5 and the movable side comb-shaped electrode 9 located on the concave groove 2A are indicated by arrows A.
It can be displaced in any direction (direction in which acceleration is applied).

Reference numerals 3 and 3 denote a pair of fixing portions made of a silicon material having a low resistance. The fixing portions 3 are located on the left and right sides of the glass substrate 2 and are spaced apart from each other, and inner surfaces facing each other. Is a plurality of (for example, five) thin plate-like electrode plates 4
A, 4A, ... Are formed so as to project, and each of the electrode plates 4A constitutes fixed side comb-shaped electrodes 4 and 4 as fixed electrodes.

Reference numeral 5 denotes a movable portion formed of a silicon material having a low resistance. The movable portion 5 is separated from the front and rear of the glass substrate 2 by supporting portions 6 and 6 fixed to the glass substrate 2. , Supported by beams 7 on each of the support portions 6,
A mass portion 8 disposed between the fixing portions 3 and a plurality (for example, five) of thin plate-shaped electrode plates 9A, 9A, ... Each of the beams 7 is formed in a thin plate shape so as to displace the mass portion 8 in the arrow A direction. The electrode plates 9A of the movable comb-shaped electrodes 9 face the electrode plates 4A of the fixed comb-shaped electrodes 4 with a minute gap therebetween.

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

First, reference numeral 11 in FIG. 12 denotes a silicon wafer as a silicon plate, and the silicon wafer 11 is formed into a disk shape having a diameter of 7.5 to 15.5 (cm) and a thickness of about 300 μm. There is.

Next, since the fixed portion 3 and the movable portion 5 are separately formed on one side surface of the silicon wafer 11, the groove 1 is formed.
After masking parts other than 2, RIE (reactive ion etching) as dry etching is performed from the one side surface for a predetermined time by the first etching step.
Alternatively, anisotropic etching is performed as wet etching to form a groove 12 having a predetermined depth as shown in FIG. As shown in FIGS. 18 and 20, in order to form a plurality of acceleration sensors 1 at one time on the silicon wafer 11, the grooves 12 are all in communication with one side surface of the silicon wafer 11.

On the other hand, as shown in FIG. 14, a disk-shaped glass substrate 13 having the same size as the silicon wafer 11 is prepared, and one side surface of the glass substrate 13 is subjected to glass etching (glass etching step). By doing so,
A rectangular concave portion 13A (concave groove 2A) such as 5 is formed.

Next, in the joining step shown in FIG. 16, the silicon wafer 11 having the groove 12 formed in the first etching step as shown in FIG. 13 is inverted so that one side surface faces downward, and a concave portion 13A is formed. One side surface of the silicon wafer 11 is anodically bonded to one side surface of the formed glass substrate 13 to integrate the silicon wafer 11 and the glass substrate 13.

Further, in the second etching process shown in FIG. 17, the thickness of the silicon wafer 11 is reduced.
RIE or wet etching is performed from the other side surface of the silicon wafer 11 and etching is performed until the groove 12 penetrates (that is, the silicon wafer 11 is melted to the level of the groove 12 from the upper side and removed), thereby accelerating the acceleration sensor. A plurality of fixed portions 3 and movable portions 5 that become 1 are formed on the glass substrate 13 (see FIGS. 18 and 20). In the movable part 5, only the support parts 6 and 6 are fixed on the glass substrate 13, and the beams 7, 7 and the mass part 8 and the movable side comb-shaped electrodes 9, 9 are located on the concave part 13A. The beam 8 is movable in the direction of arrow A by each beam 7.

Then, as shown in FIG. 20, a plurality of acceleration sensors 1 formed on the glass substrate 13 are cut in a size of a chip (5 mm square) at a position indicated by a dotted line so that a single manufacturing process is performed. For example, 52 acceleration sensors 1 are manufactured.

In the acceleration sensor 1 of the prior art constructed as described above, when the acceleration in the direction of the arrow A is applied from the outside, the mass portion 8 is displaced with respect to each support portion 6 via each beam 7 and the movable side. Since each electrode plate 9A of the comb-shaped electrode 9 approaches or separates from each electrode plate 4A of the fixed-side comb-shaped electrode 4, the displacement of the separation dimension at this time is regarded as a change in the capacitance, and an external signal processing (not shown) is performed. The signal processing circuit outputs a signal corresponding to the acceleration based on the change in the electrostatic capacitance.

In the acceleration sensor 1, the electrode plates 9 of the movable side comb-shaped electrode 9 and the fixed side comb-shaped electrode 4 are arranged.
Acceleration is detected as a change in electrostatic capacitance between A and 4A, and since the electrode plates 9A and 4A are electrically connected in parallel, the electrostatic capacitance between the electrode plates 9A and 4A is Acceleration can be detected from the total capacitance that is the sum of the respective values, the detection sensitivity can be increased, and the acceleration detection accuracy can be improved.

Further, in the method of manufacturing the acceleration sensor 1 according to the prior art, for example, the fixed portion 3 and the movable portion 5 are formed by thinning the silicon wafer 11 having a thickness of 300 μm to several tens of μm in the second etching step. Since the thicknesses of the fixed portion 3, the movable portion 5, etc. are determined based on the depth dimension of the groove 12 formed in the first etching step, the depth dimension of the groove 12 is adjusted. By doing so, the effective area of each electrode plate 4A, 9A can be adjusted. Further, since the one side surface and the other side surface of the silicon wafer 11 are respectively subjected to the etching processing in the first and second etching steps, the thickness of the silicon wafer 11 can be thinned on the glass substrate 13, and the comb-shaped electrode can be formed. The distance between the electrode plates 4A and 9A of 4 and 9 can be secured as a minute gap.

[0022]

By the way, in the above-mentioned prior art, when the etching rate of the silicon wafer 11 varies in the corresponding portion of each acceleration sensor 1 in the second etching step, the groove 12 penetrates quickly. There are places where it does not penetrate. Then, in the second etching step, the etching agent (plasma in the case of RIE, etching solution in the case of wet etching) is applied to the portion of the other acceleration sensor 1 from the portion of the groove 12 that penetrates quickly. Infiltrate through.

That is, taking the acceleration sensors 1 and 1 positioned front and rear as shown in FIG. 19 as an example, there is no partition between the acceleration sensors 1 and one acceleration sensor 1 side to the other acceleration sensor 1 side. When the etching agent penetrates in the direction of the arrow B in the direction shown by the arrow, the excessive amount of the etching agent is supplied to the other acceleration sensor 1 side, and the electrode plates 4A and 9A formed in a thin plate shape.
Also, there is a problem of breaking or deforming the beam 7 or the like.
As a result, of the plurality of acceleration sensors 1, 1, ... Produced from the silicon wafer 11, most of the acceleration sensors 1 become defective products, which deteriorates the yield and remarkably lowers the productivity.

The present invention has been made in view of the above-mentioned problems of the prior art. For example, an acceleration sensor which can improve the yield when manufacturing an acceleration sensor from a silicon wafer and can significantly improve the productivity, It is an object to provide a manufacturing method thereof.

[0025]

In order to solve the above-mentioned problems, an acceleration sensor according to the present invention is formed on an insulating substrate and a silicon plate provided on the insulating substrate and separated from each other by etching a silicon plate. A fixed electrode and a movable part, and a fixed electrode is integrally formed on the fixed part,
The movable portion has a movable electrode facing the fixed electrode via a minute gap, a mass portion for moving the movable electrode toward and away from the fixed electrode by an external acceleration, and a beam for the mass portion. And a supporting portion that displaceably supports the mass portion and the movable electrode on the insulating substrate. A feature of the configuration adopted by the present invention is that a guard surrounding the fixed portion and the movable portion is formed on the insulating substrate.

In this case, the movable electrode of the movable portion is formed by a plurality of electrode plates protruding in a comb shape from the mass portion,
It is preferable that the fixed electrode of the fixed portion is formed by a plurality of comb-shaped electrode plates facing each electrode plate of the movable electrode with a minute gap therebetween.

Further, in the method of manufacturing the acceleration sensor according to the present invention, the silicon plate is etched from one side,
A first etching step of forming a groove for separating the fixed portion and the movable portion on one side surface of the silicon plate; and, after forming the groove on the silicon plate, the other side surface of the silicon plate faces upward. The silicon plate is inverted, and a bonding step of bonding one side surface of the silicon plate to the insulating substrate, and an etching process from the other side surface of the silicon plate in a state where the silicon plate is bonded to the insulating substrate, A second etching step of separately forming a fixed portion and a movable portion on the silicon plate, wherein in the first etching step, the fixed portion and the movable portion are surrounded from one side on one side surface of the silicon plate. A guard groove is formed on the insulating substrate, and a guard groove is formed around the fixed portion and the movable portion and is separated from the fixed portion and the movable portion in the second etching step, and is joined to the insulating substrate. In the door.

[0028]

As described above, by forming the guards surrounding the fixed part and the movable part on the insulating substrate, the individual acceleration sensors can be partitioned by the respective guards. liquid)
Can be prevented from penetrating from one acceleration sensor portion to the fixed portion and the movable portion of the other acceleration sensor, and the problem due to the variation in etching rate can be reliably eliminated.

By forming the movable electrode of the movable portion and the fixed electrode of the fixed portion as comb-shaped electrodes,
The effective area between the electrodes can be increased, and the respective electrode plates can be opposed to each other through a minute gap.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 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 prior art are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 31 denotes an acceleration sensor according to the present embodiment, the acceleration sensor 31 having substantially the same structure as the acceleration sensor 1 according to the prior art, and a fixing portion 32 to be described later on a glass substrate 2 as an insulating substrate. , 32 and movable part 3
4 and the like are integrally formed.

Reference numerals 32 and 32 denote fixed portions, and each fixed portion 3
Reference numeral 2 has fixed-side comb-shaped electrodes 33, 33 as fixed electrodes, which are formed separately on the left and right sides of the glass substrate 2, and have a plurality of thin plate-shaped electrode plates 33A, 33 on the inner surfaces facing each other.
A, ... are projected.

Reference numeral 34 denotes a movable portion, which is a support portion 35 which is arranged in front of and behind the glass substrate 2 and is spaced apart from each other.
35, a mass portion 37 supported by the supporting portions 35 via beams 36, 36, and arranged between the fixing portions 32, and a thin plate protruding from the mass portion 37 in the left and right directions. Side comb-shaped electrode 3 having electrode plates 38A, 38A, ...
8 and 38 are integrally formed.

Reference numeral 39 denotes a guard of this embodiment, which is located on the glass substrate 2 and is formed of a silicon material in a rectangular shape so as to surround the fixed portion 32 and the movable portion 34 from the periphery. The height is fixed part 32 and movable part 3
It is almost the same height as 4.

The acceleration sensor 31 of this embodiment has the above-mentioned structure. Next, a method of manufacturing the acceleration sensor 31 will be described with reference to FIGS.

First, after masking a portion of the silicon wafer 41 as a silicon plate other than the groove 42 and the guard groove 43 for forming the guard 39 on one side surface, a first etching step is performed for a predetermined time from the one side surface. In the meantime, RIE (reactive ion etching) as dry etching or anisotropic etching as wet etching is performed to form the groove 42 and the guard groove 43 having a predetermined depth as shown in FIG. In addition, each acceleration sensor 31
The groove 42 in which the fixed portion 32 and the movable portion 34 are formed is
Each of them is surrounded by the guard groove 43.

Next, in the bonding step shown in FIG. 5, the silicon wafer 41 of FIG. 4 is inverted so that one side surface faces downward, and one of the silicon wafer 41 is placed on the glass substrate 13 having the recess 13A on one side surface. The side surfaces are anodically bonded to integrate the silicon wafer 41 and the glass substrate 13.

Further, in the second etching step shown in FIG. 6, RIE or wet etching is performed from the other side surface of the silicon wafer 41, and etching is performed until the groove 42 and the guard groove 43 are penetrated (that is, FIG. 5). By melting and removing the silicon wafer 41 from the upper side up to the level of the thickness T indicated by the dotted line in FIG.
A plurality of fixed portions 32, movable portions 34, and guards 39 that will become the above are formed on the glass substrate 13 (see FIGS. 7 and 9). After that, the glass substrate 13 is cut along the dotted line in FIG. 7 to manufacture a plurality of acceleration sensors 31.

As shown in FIGS. 7, 8 and 9, the guard 39 formed in this way is used for each acceleration sensor 31.
The (fixed part 32 and the movable part 34) are surrounded by being partitioned from each other. As a result, the etching rate varies in the second etching step, and before the groove 42 of one acceleration sensor 31 penetrates, the other acceleration sensor 3
Even when the first groove 42 penetrates, the etching agent from the other acceleration sensor 31 can be surely prevented from entering the one acceleration sensor 31 by the guard 39. It becomes possible to contain it.

Therefore, according to the present embodiment, since each acceleration sensor 31 is individually partitioned by the guard 39, one acceleration from the other acceleration sensor 31 side due to variation in etching rate in the second etching step. It is possible to reliably prevent the etching agent from being excessively supplied into the sensor 31, and to fix the fixing portion 3 of the acceleration sensor 31.
2. It is possible to effectively prevent the movable portion 34 from being damaged by the etching agent at this time. Thereby, the yield in the manufacturing process of the acceleration sensor 31 can be increased,
The productivity of the acceleration sensor 31 can be greatly improved.

In the above embodiment, as shown in FIG. 1, the guard 39 is left around the acceleration sensor 31, but the present invention is not limited to this, and the guard 39 is used when the glass substrate 13 is cut. It may be cut off from the acceleration sensor 31. It is also possible to package the acceleration sensor 31 by raising the guard 39 and joining the cover. In this case, the portion of the guard 39 is masked during the second etching step, and the guard groove 43 is formed. Only the part needs to be etched to penetrate. Further, the guard groove 43
It is also possible to form two of them and form the guard 39 separately for each acceleration sensor 31.

Further, in the above-mentioned embodiment, it is described that either dry etching or wet etching is selected in the first and second etching steps. However, dry etching is used particularly in view of processing accuracy. It is preferable to use wet etching from the viewpoint of cost.

Further, the acceleration sensor 31 of the above embodiment.
Describes that the fixed electrode of the fixed portion 32 is the fixed-side comb-shaped electrode 33, the movable electrode of the movable portion 34 is the movable-side comb-shaped electrode 38, and the electrode plates 33A and 38A are opposed to each other through a minute gap. However, the present invention is not limited to this, a general insulating substrate, a movable part having a base end side fixed on the insulating substrate, and a free end side having a mass part to be a movable electrode, and a moving direction of the mass part. You may use for the acceleration sensor which formed the fixed part used as a fixed electrode.

[0044]

As described above in detail, according to the present invention, the guard surrounding the fixed portion and the movable portion is formed on the insulating substrate, and the acceleration sensors are partitioned by the guard. It is possible to reliably prevent the etching agent from penetrating from one acceleration sensor to the other acceleration sensor side during manufacturing, and prevent the etching agent from being excessively supplied into the acceleration sensor and damaging the fixed parts and movable parts. However, the yield at the time of manufacturing can be effectively improved, and the productivity can be significantly increased.

If the movable electrode of the movable portion and the fixed electrode of the fixed portion are formed in a comb shape from a plurality of electrode plates, respectively, the effective area between the electrodes can be surely increased, and the electrostatic capacitance against acceleration can be increased. Can be increased, and the detection sensitivity of the acceleration sensor can be improved.

Further, according to the manufacturing method of the present invention, the thickness of the fixed portion and the movable portion formed of the silicon plate on the insulating substrate can be reduced, and the fixed electrode of the fixed portion and the movable electrode of the movable portion can be made thinner. The separation dimension can be reliably ensured as a minute gap.

[Brief description of drawings]

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

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

FIG. 3 is a vertical cross-sectional view of a silicon wafer used to form a fixed portion, a movable portion, and a guard of an acceleration sensor.

FIG. 4 is a vertical cross-sectional view showing a state in which a groove is formed on one side surface of a silicon wafer by a first etching process.

5 is a vertical cross-sectional view showing a state in which one side surface of a silicon wafer and a glass substrate are bonded by a bonding process following the first etching process in FIG.

6 is a vertical cross-sectional view showing a state in which a fixed part, a movable part and a guard are formed on a silicon wafer by a second etching process following the bonding process shown in FIG. 5, as viewed from the direction of arrows VI-VI in FIG. 7. is there.

7 is a plan view showing a fixed portion, a movable portion, and a guard formed on a glass substrate by the second etching process shown in FIG.

8 is a vertical cross-sectional view as seen from the direction of arrows VIII-VIII in FIG.

FIG. 9 is a plan view showing a state in which a fixed portion, a movable portion, and a guard are formed on a glass plate with a silicon wafer.

FIG. 10 is a plan view showing an acceleration sensor according to the prior art.

11 is a vertical cross-sectional view as seen from the direction of arrow XI-XI in FIG.

FIG. 12 is a vertical cross-sectional view of a silicon wafer used to form a fixed portion and a movable portion of an acceleration sensor.

FIG. 13 is a vertical cross-sectional view showing a state in which a groove is formed on one side surface of a silicon wafer by the first etching process.

FIG. 14 is a vertical sectional view showing a glass substrate of an acceleration sensor.

FIG. 15 is a vertical cross-sectional view showing a state in which a groove is formed in a glass substrate by a glass etching process.

16 is a vertical cross-sectional view showing a state in which one side surface of the silicon wafer and the glass substrate are bonded by the bonding process following the first etching process of FIG. 13 and the glass etching process of FIG. 15.

17 is a vertical cross-sectional view showing a state in which a fixed portion and a movable portion are formed on a silicon wafer by a second etching step following the joining step shown in FIG. 16 as seen from the direction of arrows XVII-XVII in FIG. 18.

FIG. 18 shows a second etching process according to FIG.
It is a top view which shows the fixed part and movable part which were formed on the glass substrate.

19 is a vertical cross-sectional view as seen from the direction of arrows XIX-XIX in FIG.

FIG. 20 is a plan view showing a state where a fixed portion and a movable portion are formed on a glass plate with a silicon wafer.

[Explanation of symbols]

 2 (13) Glass substrate (insulating substrate) 31 Acceleration sensor 32 Fixed part 33 Fixed side comb-shaped electrode (fixed electrode) 34 Movable part 35 Support part 36 Beam 37 Mass part 38 Movable side comb-shaped electrode (movable electrode) 39 Guard 41 Silicon wafer (silicon plate) 42 groove 43 groove for guard

Claims (3)

[Claims] 1. An insulating substrate, provided on the insulating substrate,
A fixed part and a movable part are formed separately from each other by etching a silicon plate, and a fixed electrode is integrally formed on the fixed part, and the fixed part and a minute gap are formed in the movable part. And a mass portion that moves the movable electrode toward and away from the fixed electrode by an external acceleration, and a mass portion that is connected to the mass portion through a beam to insulate the mass portion and the movable electrode from each other. In an acceleration sensor integrally formed with a support portion that is displaceably supported on a substrate, a guard surrounding the fixed portion and the movable portion is formed on the insulating substrate. Sensor. 2. The movable electrode of the movable part is formed by a plurality of electrode plates protruding in a comb shape from the mass part, and the fixed electrode of the fixed part is formed with a minute gap between each electrode plate of the movable electrode. The acceleration sensor according to claim 1, wherein the acceleration sensor is formed by a plurality of comb-shaped electrode plates facing each other. 3. A first etching step of etching a silicon plate from one side surface to form a groove on one side surface of the silicon plate for separating a fixed part and a movable part, and the groove on the silicon plate. After forming, the silicon plate is turned over so that the other side surface of the silicon plate is on the upper side, and one side surface of the silicon plate is bonded to the insulating substrate, and the silicon plate is bonded to the insulating substrate. The second side of the silicon plate, the second side of the silicon plate is subjected to an etching treatment from the other side of the silicon plate to form a fixed portion and a movable portion separately from each other. A guard groove is formed on one side surface of the fixed portion and the movable portion so as to surround the fixed portion and the movable portion from the periphery, and is positioned around the fixed portion and the movable portion in the second etching step. A method of manufacturing an acceleration sensor, which comprises a guard separated from the above and bonded on the insulating substrate.