JPH11218545A - Capacitive acceleration sensor and detection method - Google Patents

Abstract

(57) Abstract: To provide a small-sized, high-sensitivity capacitive acceleration sensor having a large electrode area. A support plate (12) of a semiconductor substrate (10) is a frame (1).
3 are supported at both ends, and are flexed and deformed in an arch shape by receiving acceleration. The central portion of the movable plate 16 that maintains the planar shape is locally connected and supported at the central portion of the support plate via the column portion 14, and when the support plate is bent, the movable plate is displaced in parallel in the thickness direction. However, the planar shape is maintained. Therefore, the second electrode 21 and the second electrode 21 are provided on the movable plate and the support plate facing the movable plate.
When the first electrode 20 is formed, the distance between the electrodes changes with the deformation of the support plate, and the capacitance generated between the electrodes also changes. Since the support plate and the movable plate are vertically stacked, the dead space occupied by the conventional beams and the like is eliminated, and the occupancy of the electrode area in the planar shape of the sensor chip increases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type acceleration sensor and a detection method.

[0002]

2. Description of the Related Art A conventional capacitance type acceleration sensor has been disclosed in, for example, Japanese Patent Application Laid-Open No. 8-236786, and its basic structure is shown in FIG. That is, the silicon substrate 2 is joined to the fixed substrate 1 to be integrated. The silicon substrate 2 supports a weight 5 with a cantilever 4 with respect to the surrounding frame 3, and a predetermined gap is secured between the weight 5 and the fixed substrate 1. When the cantilever 4 bends, the distance (gap) between the opposing surfaces of the weight 5 and the fixed substrate 1 changes. Then, the facing surface of the weight 5 becomes the movable electrode 6, and the fixed electrode 7 is formed on the surface of the fixed substrate 1 facing the movable electrode 6.

In such a configuration, when acceleration is applied to the sensor, the weight 5 receiving the acceleration attempts to displace in the direction in which the acceleration is received, and the displacement is permitted by bending the cantilever 4. Therefore, since a capacitance corresponding to the distance between the electrodes is generated between the electrodes 6 and 7, the capacitance associated with the displacement of the weight 5 also changes. Since the displacement amount of the weight 5 is uniquely determined according to the magnitude of the acceleration, the acceleration can be measured from the change or the absolute amount of the capacitance.

On the other hand, an acceleration sensor disclosed in, for example, Japanese Patent Application Laid-Open No. H8-236787 has a structure other than the general structure described above. As shown in FIG. 2, there is a sensor in which a weight 5 provided with a movable electrode 6 is elastically supported by a spring-like supporting portion 8 extending from all sides. In this case, when the acceleration is applied, the weight 5 is displaced in parallel, so that the distance between the electrodes 6 and 7 also changes uniformly.

[0005]

The above conventional sensor structure has the following problems. That is, in the general type shown in FIG. 1, the weight 5 is supported by the cantilever 4 and the weight 5 is
Is displaced, it is necessary to lengthen the cantilever 4 in order to increase the displacement amount and widen the sensitivity / measurement range.
In this case, an installation space for the cantilever 4 is required in addition to the size of the electrode portion (weight 5), which increases the chip size and the cost. Moreover, when considering the planar shape, the occupancy of the cantilever 4 and the space formed between the frame 3 and the weight 5 associated with the cantilever 4 is increased, and the size and shape of the sensor chip are increased. The electrode area for detecting the capacitance cannot be made large, which is a bottleneck for improving the sensitivity.

Further, the displacement of the weight 5 becomes larger at the tip (opposite side of the cantilever 4) because the weight 5 rotates around the cantilever 4 as a center of rotation. That is, the parallel displacement cannot be performed, and the sensitivity also decreases in that respect. Then, because of such rotation, the distance between the electrodes does not change much near the cantilever 4. In other words, in the region near half of the two electrodes 6 and 7 facing each other, even if the weight 5 is displaced, the distance between the electrodes does not change so much, and the capacitance is a parasitic capacitance. Such a point also causes a decrease in sensitivity.

On the other hand, in the sensor shown in FIG. 2, since the electrodes are displaced in parallel as compared with the general sensor shown in FIG. 1, problems such as parasitic capacitance are suppressed. But weight 5
And the supporting portion 8 are formed of the same material so as to be on the same plane by using an epitaxial growth technique. Then, since the epitaxially grown portion is elongated and etched to form the weight 5 and the support portion 8, the spring elastic coefficient of the support portion 8 may vary greatly. Then, the variation in the elastic coefficient is caused by the difference in the reaction force from the support portion 8 when the weight 5 is directly subjected to the acceleration, so that the parallel displacement is hardly caused, and the characteristic is varied. further,
Since the support portion 8 and the weight 5 are provided in the same plane, the support portion 8 needs to have a certain length in order to secure a certain spring elastic coefficient. There is still the problem that the area, and thus the electrode area, cannot be made large and the sensitivity is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to solve the above-mentioned problems, to increase the electrode area while reducing the chip size, and to provide a counter electrode. The parallel displacement area can be widened, the occurrence of parasitic capacitance can be suppressed as much as possible, the sensitivity can be increased and the measurement range can be widened, and the linearity of input / output characteristics can be improved. An object of the present invention is to provide a capacitance type acceleration sensor and a detection method.

[0009]

In order to achieve the above-mentioned object, in a capacitance type acceleration sensor according to the present invention, a frame (in the embodiment, a flat rectangular shape and an endless shape). (Which may correspond to the first semiconductor substrate 10 in the embodiment) provided with an elastically deformable support plate that is supported at both ends with respect to the first semiconductor substrate 10. A column provided on the surface of the plate, a movable plate connected to the column and displaced with the elastic deformation of the support plate, a substrate (including the support plate and / or a surrounding frame portion) and the movable plate First and second electrodes provided on the opposing surfaces, respectively, and means for extracting a signal based on capacitance generated between the first and second electrodes to the outside are provided (claim 1). In the embodiment, the pillar portion is formed of an insulating film as a separate member from the movable plate and the support plate. However, the present invention is not limited thereto, and may be formed integrally with one member.

The "support plate" in the present invention may be made thin by necessity of being elastically deformable. For example, the "support plate" can be formed by thinning a silicon wafer or the like by etching or the like, but is not limited to this. For example, if an elastically deformable film is manufactured by forming a predetermined material, the film is supported at both ends, and if the movable plate is also displaced according to the deformation of the film. , Regardless of whether the member is referred to as a “plate” or a “film”
It is included in the support plate in the present invention (the same applies hereinafter).

Another solution is to provide a substrate having an elastically deformable support plate supported at both ends with respect to a frame, and a support plate connected to the support plate and maintaining the initial shape. A movable plate that moves in parallel with the deformation of the substrate, first and second electrodes respectively provided on the opposing surfaces of the substrate and the movable plate, and a signal based on capacitance generated between the first and second electrodes. (A second aspect). That is, the support plate and the movable plate may be connected directly or indirectly.

Another solution is to provide a substrate, a movable plate, and a column connecting them, so that the periphery of the substrate to which the column is connected is made thinner than the outer periphery. In addition, a plurality of slits are formed at predetermined intervals in the thinned portion, and a region between the plurality of slits is provided with a support plate capable of elastic deformation, and the support plate is deformed. The movable plate may be displaced, and first and second electrodes may be provided on opposing surfaces of the substrate and the movable plate, respectively.

In each of the above structures, the movable plate and the support plate move in conjunction with each other in response to the acceleration, thereby causing a change in the sensor gap. That is, when the support plate is to be displaced in the direction in which the acceleration is applied, since the both ends are connected to the frame, the center portion tends to be displaced in the direction of the acceleration. Since both side edges of the support plate are separated from the frame body by forming slits and are in a free state, the support plate eventually deforms into an arch shape. With this deformation, the movable plate connected to the support via the pillar also moves.
At this time, since the periphery (outer periphery) of the movable plate is open, the movable plate is displaced while maintaining the shape in the no-load state (reference state). Therefore, the distance from the movable plate in the region around the support plate and in the region facing the substrate increases. Thus, by providing electrodes on the movable plate and the substrate, the displacement of the gap, that is, the acceleration, can be grasped as a change in capacitance.

Since the support plate and the movable plate are arranged so as to overlap in the direction of displacement, the conventional cantilever 4 (FIG. 1)
(See FIG. 2) and the support portion 8 (see FIG. 2), the weight supporting member is not coplanar with the weight, so that the occupation ratio of the electrode area in the planar shape of the sensor chip is increased, and the sensor chip is downsized. And the detection sensitivity is improved.

Further, since the support plate and the movable plate are connected via the column provided at the center, the portion where the gap change is large is the peripheral region, so that the region where the gap change is the largest can be obtained. it can. This is also a factor for improving the sensor characteristics and increasing the sensitivity.

The substrate can be formed of, for example, a semiconductor substrate. Further, the movable plate can be formed using a semiconductor substrate (including not only a semiconductor wafer but also a substrate on which a semiconductor is formed), a glass substrate, or the like. In the case where a semiconductor substrate is used, the cost can be significantly reduced because the glass substrate is not used.

Another solution is to provide a substrate provided with an elastically deformable support plate supported at both ends with respect to a frame, and an outer periphery of the support plate on the surface of the substrate (in the embodiment, A first electrode provided on the support plate side portion of the frame).
A movable plate connected to the support plate and moving with the deformation of the support plate while maintaining a parallel state with respect to the first electrode; and a second plate provided at a portion of the movable plate facing the first electrode. An electrode and means for extracting a signal based on the capacitance generated between the first and second electrodes to the outside can be provided (claim 3). This way,
Since the first and second electrodes are displaced in parallel, the linearity of the sensor output with respect to the applied acceleration (input) is improved.

The detection method according to the present invention includes:
A base having an elastically deformable support plate that is supported at both ends with respect to the frame (corresponding to the “semiconductor substrate 10” in the embodiment), and is connected to the support plate and moves while deforming the support plate A movable plate is provided, and first and second electrodes are provided on the opposing surfaces of the base and the movable plate (the base side may be any part of the support plate and / or the non-formed portion) (provided with electrodes) The portion may be the entire surface or a part of the opposing surface), by detecting a signal based on the capacitance generated between the two electrodes due to the relative position of the two electrodes that changes with the displacement of the support plate. The amount of displacement of the support plate or the physical amount applied to the support plate is detected (claim 5).

Further, in the present invention, the movable plate is displaced by receiving acceleration when the support plate is elastically deformed by the acceleration received by the sensor and the movable plate is also displaced following the elastic deformation. Various operating principles, such as the case where the movable plate receiving the acceleration attempts to displace in the direction of the acceleration, and the support plate elastically deforms to allow the displacement of the movable plate, and the case where both occur at the same time Occurs.
In other words, in the present invention, regardless of the master-slave relationship between the movable plate and the support plate, the point is that when the acceleration is applied, both the movable plate and the support plate may be displaced and deformed. Accordingly, claims such as “a movable plate that is displaced with elastic deformation of the support plate” and “displacement of the movable plate as the support plate is deformed” in the claims mean that such elements are included.

If the following means are taken as a more preferable structure of the present invention, more advantageous effects can be obtained in addition to the functions and effects based on the basic structure described above.
That is, for example, the movable plate has a planar shape larger than the support plate, and at least a part of the second electrode formed on the movable plate is configured to face the substrate surface outside the support plate. be able to. With such a configuration, the surface of the substrate on which the support plate is not formed does not change even when an acceleration is applied. Further, the movable plate does not bend as described above. Therefore, since the first and second electrodes facing each other at the outer portion of the support plate form a parallel displacement region, the linearity of the input / output characteristics is improved. Further, since the bonding portion can be widened, sufficient capacitance can be obtained with a smaller support plate, and the chip size can be reduced. Also, by reducing the size of the support plate, the support plate spring coefficient increases, and as a result, the response speed increases.

[0021] The distance between the substrate and the movable plate around the column may be wider than the distance between the substrate and the movable plate near the periphery of the movable plate. In other words, the gap around the column does not change much even when acceleration is applied. Therefore, when an electrode is provided in such a portion, the capacitance does not change in that portion, and the portion becomes a parasitic capacitance. Therefore, the parasitic capacitance is reduced by widening the gap in the region where the capacitance change is small, and as a result, the linearity of the input / output characteristics is improved.

In order to further improve the effect, it is preferable to provide a through hole in the movable plate around the column, for example. This further reduces the parasitic capacitance. Further, when the through-hole is provided, the through-hole serves as an air passage, so that responsiveness is improved.

Further, the first and second electrodes may be provided only in a region where the support plate is not formed and a region opposed thereto. By doing so, the parasitic capacitance is further eliminated, and the linearity is improved.

On the other hand, an insulating film may be provided on at least one of the opposing surfaces of the movable plate and the substrate. That is, in the present invention, the gap moves in the direction in which the gap widens, but even if the movable plate and the support plate (substrate) come into contact with each other, there is no risk of short-circuiting, and the resistance to humidity and the like is improved. Also, at this time,
When an insulating film having a higher dielectric constant than air is used, the capacitance is increased and the sensitivity is improved. In the case where the object is to improve the sensitivity, the insulating film is not necessarily required as long as it is a high dielectric material. When such a material having a high dielectric constant is formed only on the peripheral portion of the movable portion (the region where the parallel displacement occurs), the capacitance increases only in the region where the parallel displacement occurs, the parasitic capacitance decreases, and the sensitivity improves.

Further, the means for extracting the signal based on the capacitance to the outside has a lead wire connected to the movable plate, and has a cutout cut into a predetermined position of the movable plate up to the vicinity of the pillar. A part may be provided, and a part of the lead wire may be disposed in the front notch, and one end of the lead wire may be connected to the vicinity of the pillar part on the back side of the notch. With this configuration, no extra stress is applied to the movable plate as compared with the case where the wiring is drawn out from the end of the movable plate, so that stable characteristics can be detected.

Further, the means for extracting the signal based on the capacitance to the outside has an extraction wiring connected to the movable plate, and the dummy wiring has a point symmetry with the extraction wiring with respect to the column. (Same substance, same shape) may be provided. With such a configuration, since the stress generated by the lead wiring is symmetrically applied to the movable plate, the inclination of the movable plate,
Twist and the like can be suppressed.

Further, the means for extracting the signal based on the capacitance to the outside may have an extraction wiring connected to the movable plate, and the stress of the extraction wiring may be smaller than that of the movable plate. As a method of reducing the stress, for example, a method of reducing the thickness or manufacturing a lead wiring using a material having low rigidity can be used. With this configuration,
Since the stress (spring force) generated by the lead wiring is less likely to affect the displacement of the support plate, the sensitivity and the responsiveness are improved.

[0028]

FIG. 3 shows a first embodiment of a capacitive acceleration sensor according to the present invention. As shown in the figure, a thin supporting plate 12 is provided by removing a central portion of a lower end of a first semiconductor substrate 10 made of silicon, and a periphery of the supporting plate 12 becomes a frame 13. The lower surface of the frame 13 serves as a die bonding portion 13a. Further, a slit 11 is formed along a pair of opposite sides of the support plate 12, and the slit 11 allows the pair of opposite sides of the support plate 12 and the frame 1 to be formed.
3 are separated. Therefore, the support plate 12 is in a state of being supported at both ends, both ends of which are connected to the frame 13. And since it is made thin, it can be elastically deformed. For example, when a force in the thickness direction is applied to the central portion of the support plate 12, the connecting portions with the frame 13 at both ends cannot be moved. Deforms and the central part is displaced in the direction of force,
It will expand into a semi-cylindrical shape.

A movable plate 16 is connected to the center of the upper surface of the support plate 12 via a pillar 14 made of an insulator. The movable plate 16 is also composed of a second semiconductor substrate 18 made of silicon. Further, the movable plate 16 is formed of a flat plate having a substantially square shape in a plane, and floats in the air almost independently from the surroundings (strictly, while being connected to the support plate 12 via the column portion 14, It is connected to a wire pad via a lead wire described later).

Accordingly, the support plate 12 and the movable plate 16 are in an insulated state, and the upper surface of the support plate 12 becomes the first electrode 20,
The lower surface of the movable plate 16 becomes the second electrode 21. Then, a capacitance corresponding to the distance is generated between the electrodes 20 and 21.
Such a configuration is a basic configuration, and in a reference state where no acceleration is applied, as shown in the drawing, the movable plate 16 and the support plate 12
Both of them maintain a substantially horizontal state, and the distance between the electrodes 20 and 21 is the height of the column portion 14.

When an upward acceleration is applied to the lower surface of the support plate 12 from this state, as shown in FIG. 4, the support plate 12 is displaced and bent into an upwardly convex arch shape. Then, since the movable plate 16 that keeps the planar shape is only locally supported at the center of the support plate 12 at the center thereof through the column portion 14, the support plate 12 is bent and deformed in an arch shape. At times, the movable plate 16 is displaced in parallel in the thickness direction while maintaining the planar shape. As a result, the support plate 1
Since the space between the peripheral edge of the second and the movable plate 16 is widened, the gap between the two electrodes 20 and 21 in that part is widened, and the capacitance generated between the two electrodes 20 and 21 changes. Then, the applied acceleration can be measured based on the changed capacitance.

It should be noted that the gap between the electrodes 20 and 21 that changes based on the displacement of the support plate 12 is the periphery of the support plate 12 having a large area. That is, in the displacement of the weight 5 supported by the conventional cantilever 4 shown in FIG. 1, the gap does not change much in a region (area) almost half of the weight 5, but in the present embodiment, the gap is formed in an arch shape. Because of the change, the region where the gap does not change much can be reduced, the amount of change in the capacitance also increases, and the sensitivity becomes high. Furthermore, the movable plate 1
The support plate 12 for supporting the electrode 6 is placed on a different surface, that is, in the displacement direction (vertical direction), so that the occupation ratio of the electrode area to the chip size (planar area) can be increased, and the sensor can be downsized. In addition, it is possible to improve characteristics and sensitivity. In addition, in the conventional acceleration sensor, the cantilever 4 and the supporting portion 8 for displacing the weight 5 have only a supporting function (the supporting portion 8 also has a wiring extracting function), and a function of detecting the capacitance. However, in the present embodiment, since the first electrode 20 is provided on the surface of the support plate 12 as described above, there is an advantage that the space provided with the support plate 12 does not become a dead space for capacitance detection. . Further, since both the support plate 12 and the movable plate 16 are formed using a conductive semiconductor substrate, they are not affected by thermal distortion after joining.

In order to manufacture the support plate 12 as described above, for example, as shown in FIG. 5, a P-type silicon wafer 10 'is used as a first semiconductor substrate, and its upper surface is doped with phosphorus or the like. An n region 10a having a predetermined depth is formed. At this time, the depth of the dope is set to the thickness of the support plate 12 to be finally formed.
Is formed on the entire surface. Therefore, in the doped state, the upper surface of the silicon wafer 10 'is P-type silicon only in the slit forming region, and the n-region 10a
Becomes

Then, on the lower surface of the silicon wafer 10 ',
An oxide film or a nitride film R is provided by patterning. This installation position is the lower surface of the frame 13, that is, the area where the die bond portion 13a is formed. When anisotropic etching is performed on the wafer in this state, the P-type silicon portion not covered with the oxide film or the nitride film R is etched. Then, since the doped n region 10a serves as an etch stop layer, as shown in FIG. 6, the central portion of the lower surface which is not covered with the oxide film or the nitride film is removed to form the support plate 12. Moreover, the P-type silicon wafer 1
The two strip-shaped portions not doped with phosphorus on the upper surface side of 0 'are also removed, so that the slit 11 is formed. As a result, the support plate 12 that is supported on both sides of the frame 13 is formed. In the illustrated example, the manufacturing process has been described by focusing on the portion of the first semiconductor substrate 10 having the support plate 12, but actually, the insulating layer and the semiconductor wafer are further provided on the upper surface from the state shown in FIG. The step of manufacturing the support plate 12 as shown in FIG. 6 is performed at the time of or near the final process.

On the other hand, in the present embodiment, since both the support plate 12 (first electrode 20) and the movable plate 16 (second electrode 21) are formed of a semiconductor (silicon) substrate, both electrodes 20, 2 are formed.
The following structure was further adopted in order to correctly generate the capacitance between the electrodes and to take out the generated capacitance.

That is, when the two semiconductor substrates 10 and 18 are joined, the insulating film 22 is interposed therebetween.
Each of the substrates 10 and 18 was connected to the insulating film 22.
As the insulating film 22, for example, the first semiconductor substrate 1
The oxide film can be formed by patterning the oxide film on the upper surface of the insulating layer 22, and the above-described column portion 14 can be manufactured using the insulating film 22.

Further, in order to prevent the electrodes 20 and 21 from contacting and short-circuiting, the movable plate 16, that is, the bonding surface side surface (the lower surface in the figure) of the second semiconductor substrate 18 is made of an insulating protective film. 24. As a result, even if the movable plate 16 contacts the support plate 12 by mistake, the protective film 24
Does not cause a short circuit. Also, the second semiconductor substrate 18
Similarly, an insulating protective film 25 is also formed on the non-joining surface side surface to prevent a short circuit.

A mechanism for taking out the capacitance generated between the electrodes 20 and 21 to the outside is as follows.
On the 0 side, aluminum 22 is formed by forming a hole 22a in a part of the insulating film 22 to expose the lower first semiconductor substrate 10 and electrically connecting to the exposed first semiconductor substrate 10. The wire pad 26 is formed by sputtering. As a result, the first electrode 20 is electrically connected to the wire pad 26 via the support plate 12 and the first semiconductor substrate 10. By connecting the bonding wire to the wire pad 26, the first electrode 20 is connected to an external device. it can.

The second electrode 21 is connected to the first semiconductor substrate 1 via a lead-out line 27 formed integrally with the movable plate 16.
The terminal portion 28 is connected to a terminal portion 28 formed above the zero frame 13 and a hole 25a is formed in a part of the protective film 25 formed on the upper surface of the terminal portion 28, and the terminal portion 28 located below the hole 25a. Is exposed, and aluminum or the like is sputtered so as to be electrically connected to the exposed terminal portion 28 to form a wire pad 29. As a result, the second electrode 21 is electrically connected to the wire pad 29 through the above-described path. Therefore, by connecting a bonding wire to the wire pad 29, the second electrode 21 can be connected to an external device.

Further, an insulating film 22 is formed on the upper surface of the frame 13.
The frame 30 is formed via the. Protective films 24 and 25 are formed on both upper and lower surfaces of the frame 30. The frame 30 is arranged so as to surround the periphery of the movable plate 16, and by providing the frame 30, collision of any object on the side surface of the movable plate 16 is suppressed as much as possible. Then, the movable plate 16, the lead wiring 27, the terminal 28, and the frame 30 are formed by the second semiconductor substrate 18. That is, the second semiconductor substrate 18 can be simultaneously formed by etching and patterning. On the other hand, the second semiconductor substrate 18
Since the lead-out wiring 27 is manufactured more rigidly than a conventional bonding wire or the like, it is necessary to prevent the lead-out wiring 27 from affecting the displacement of the movable plate 16.

Therefore, in this embodiment, the rigidity of the lead wiring 27 itself is reduced by making the lead wiring 27 elongated. Moreover, by making the length as long as possible, the elastic restoring force does not work when the movable plate 16 is displaced. That is, as shown in FIG. 3B, one end 27a of the lead-out wiring 27 is connected near one vertex of the movable plate 16, and the lead-out wiring 27 is arranged in parallel with one side of the movable plate 16 and the other end 27b. Is extended to the vicinity of another vertex of the movable plate 16. More preferably, the movable plate 1 is further extended.
6 may be formed along two adjacent sides (the lead-out wiring is bent in the middle).

FIGS. 7 and 8 show a second embodiment of the present invention. This embodiment is basically the same as the above-described first embodiment, except that the dimension of the support plate 12 is smaller than that of the movable electrode 16. And the first
The electrode 20 has a surface facing the second electrode 21, that is, a part 20 b of the upper surface of the frame 13 of the first semiconductor substrate 10, as well as the upper surface 20 a of the support plate 12.

With this configuration, as can be seen from a comparison between FIG. 7A and FIG. 8, the support plate 12 which is supported at both ends by the acceleration being applied so that both sides are free by the slit 11 is formed by the arch. Electrodes 20 and 21
When the gap between the electrodes changes, in many areas (between the electrode portion 20b formed on the upper surface of the frame 13 and the second electrode 21), the distance between the electrodes is displaced in parallel, so that the input / output characteristics (acceleration) The area in which the linearity of the capacitance (change of the capacitance with respect to the change) can be obtained is widened.

Since the sensitivity is high even when the area of the support plate 12 is reduced, the width of the frame 13 can be increased, and the width of the die bonding portion 13a can be increased. Therefore, even if the sensor is miniaturized, the die bonding portion 1 for ensuring surface mounting while obtaining desired sensor characteristics is obtained.
Since the width of 3a can be secured, further miniaturization becomes possible. The other configuration and operation and effect are the same as those of the above-described first embodiment, and therefore, are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 9 shows a third embodiment.
This embodiment is based on the above-described second embodiment, and further improves the withstand voltage. That is, the insulating film 31 is formed so as to cover the upper surface of the electrode portion 20b located on the upper surface of the frame 13. By providing the insulating film 31, the protective film 2 is provided between the electrodes 20 and 21.
4 and the insulating film 31 exist, so that the
A short circuit between 0 and 21 is prevented. Note that the other configuration and operation and effect are the same as those of the above-described second embodiment, and thus the description thereof is omitted.

The insulating film 31 is made of SiN
It is preferable to use an insulating film having a high dielectric constant such as a film. In other words, even when the physical distance is equal to the gap of the support plate 12 and the gap of the frame 13 (reference state), the capacitance generated in the gap of the frame 13 increases.
Therefore, the capacitance can be increased only in the region where the gap interval changes due to the parallel displacement, so that the sensitivity can be increased and the linearity of the input / output characteristics can be improved.

In this structure, for example, an SiN film is deposited on the entire upper surface of the first semiconductor substrate 10 and an area other than a necessary area is removed by dry etching or the like to form the insulating film 3.
1 can be formed. Thereafter, the sensor of the present embodiment can be configured by forming the insulating film 22 (the pillar portion 14) and processing the same as a normal process such as bonding the second semiconductor substrate 18.

FIG. 10 shows a fourth embodiment of the present invention. In the present embodiment, the groove 32 is formed in a region around the column 14 on the lower surface of the movable plate 16 based on the first embodiment described above. That is, as is clear from FIG. 4, the amount of change in the inter-electrode distance around the pillar 14 due to the displacement of the support plate 12 is small. Therefore, considering the capacitance generated between the electrodes 20 and 21 of the entire sensor,
The capacitance generated in the area around the pillar portion 14 does not change much even when an acceleration is applied, and becomes a parasitic capacitance. Therefore, by forming the groove 32 as shown in the drawing, widening the gap in the region, and reducing the capacitance generated at the electrode portion opposed to the groove 32, the parasitic capacitance is reduced and the input / output is reduced. The linearity of characteristics was improved.

The type in which the grooves 32 are provided to reduce the parasitic capacitance is not limited to the illustrated type. For example, as shown in FIG. The groove 32 is formed including the connecting part,
The column portion 14 may be connected to a substantially central position of the groove 32. Further, as shown in FIGS. 12A and 12B, a groove 33 may be provided on the support plate 12 side. Furthermore,
It is also possible to implement them by appropriately combining them.

Further, in the case of the structure shown in FIGS. 11 and 12 (B), since the pillar 14 only needs to be located substantially at the center in the grooves 32 and 34, FIGS. 10 and 12 (A). Assembling can be performed easily as compared with those of the above. 10 and FIG.
In order to form the shape as shown in FIG. 1, a predetermined position (the portion where the groove 32 is formed) on the lower surface of the second semiconductor substrate 18 is removed in advance by etching, and then a protective film is formed. The first semiconductor substrate 10 can be easily manufactured.

Further, the fourth embodiment can be applied to the second embodiment (a type in which the area of the support plate is reduced and the distance between the electrodes is parallel-displaced is increased). As an example, as shown in FIG. 13, a groove 32 is formed around the pillar portion 14 on the lower surface of the movable plate 16.
Can be formed. Of course, although illustration is omitted,
As shown in FIG. 11, a groove may be provided in the center of the lower surface of the movable plate 16, and the upper end of the column portion 14 may be joined in the groove. Further, as shown in FIG. 14, a groove 33 may be provided in a central portion of the upper surface of the support plate 12, and the lower end of the column portion 14 may be connected in the groove 33. Of course, although not shown, a groove may be provided only around the pillar portion 14 as shown in FIG.

In each of the embodiments shown in FIGS. 10 to 14 and the modified examples not shown,
As shown in FIG. 3B and FIG.
A set of slits 11 as shown in FIG. 2B is formed, and the support plate 12 can be elastically deformed and bent in an arch shape.

FIG. 15 shows a fifth embodiment of the present invention. In the present embodiment, the linearity of input / output characteristics is further improved based on the second embodiment. That is, the through hole 35 is provided in a portion of the movable plate 16 facing the support plate 12. Accordingly, the column portion 14 and the movable plate 16 are connected by a cross-shaped beam 36. The through hole 35 can be manufactured at the same time that the movable plate 16 is formed by etching the second semiconductor substrate 18.

In this configuration, since there is almost no conductor (only the beam portion 36) in the portion facing the support plate 12, the first electrode 20 formed on the first semiconductor substrate 10 side
Only the upper surface portion of the frame body 13 that is not displaced (or most). Therefore, the parasitic capacitance is further reduced as compared with the above-described fourth embodiment, and almost all of the electrodes become parallel-displaced portions. Thereby, the linearity of the input / output characteristics is further improved.

Furthermore, in the present embodiment, the provision of the through hole 35 provides an air escape passage when the support plate 12 and thus the movable plate 16 are displaced, so that the air resistance during movement is small and the displacement is smooth. It is also possible to exhibit a secondary effect that even small acceleration, high frequency and / or momentary acceleration can be accurately detected. Note that the other configuration, operation, and effect are the same as those of the above-described embodiment (particularly, the second embodiment), and thus detailed description thereof will be omitted.

FIG. 16 shows a sixth embodiment of the present invention. This embodiment also improves the linearity of the input / output characteristics. As shown in the figure, unlike the above-described embodiments, the second electrode 38 is
A metal such as aluminum is formed on the surface of the protective film 24 formed on the lower surface of the substrate by sputtering or the like. The second electrode 38 is formed on a portion of the lower surface of the movable plate 16 that faces the frame 13 of the first semiconductor substrate 10.

With this configuration, the movable plate 16 formed of the second semiconductor substrate 18 becomes electrically non-conductive with the second electrode 38. Is held, that is, the function of displacing the second electrode 38 in parallel is provided.
Since the second electrode 38 is not provided around the column portion 14 on the lower surface of the movable plate 16, no capacitance is generated between the movable plate 16 and the upper surface of the support plate 12. is there). Accordingly, the capacitance is generated between the second electrode 38 that is displaced in parallel when acceleration is applied and the first electrode 20 that is formed on the frame 13 that faces (does not displace) the input / output characteristics. The linearity is improved.

FIG. 17 shows a seventh embodiment of the present invention. The present embodiment relates to an improvement in a lead-out structure for conducting the second electrode to a wire pad 29 for drawing out to the outside. As a specific sensor structure, any of the above-described first to fifth embodiments can be applied. That is, in each of the above embodiments, the movable plate 1
In the present embodiment, the dummy wiring 39 is provided point-symmetrically with respect to the lead wiring 27 (the center of the movable plate 16: with reference to the column part 14). The dummy wiring 39 connects the side edge of the movable plate 16 to a pattern 40 formed at a predetermined position on the second semiconductor substrate 18. This pattern 40 corresponds to frame 3
0 is insulated.

With this configuration, when the movable plate 16 is displaced, the same reaction force as the reaction force received from the extraction wiring 27 is also received from the dummy wiring 39. Therefore, the movable plate 1
Since the reaction force is applied to the entire plate 6 substantially uniformly, the movable plate 16 is not tilted or twisted. Therefore, the displacement is ensured while maintaining the parallel state of both electrodes. Although the wiring is provided in two places in the figure, for example, if the wiring is provided in four places in a swastika shape, the effect is further increased.

FIG. 18 shows an eighth embodiment of the present invention. The present embodiment is the same as the seventh embodiment in that the extraction wiring 27 and the dummy wiring 39 are arranged point-symmetrically, but each of the wirings 27 and 39 and the movable plate 16 are arranged.
The connection point with is different. That is, the movable plate 16
A band-shaped notch 16a is provided from the midpoint of each of the pair of opposite sides to the center. The back side of the notch 16a is
It is located on the pillar portion 14. Then, the lead wiring 27 and the dummy wiring 39 are inserted and arranged in the cutout portion 16 a and connected near the center of the movable plate 16. Thus, each of the wirings 2 near the pillar 14 that moves with the displacement of the support plate 12 is formed.
7 and 39 are connected, and near the connection point, there is little change in the gap, so that the reaction force on the support plate 12 side via the column portion 14 can be small. And the wiring 27,
The stress 39 is applied only to the vicinity of the column portion 14, and it is not necessary to consider the distortion and the like of the movable plate 16. Furthermore, both wirings 2
Even if the shape of 7, 39 is a single band, a sufficient length can be secured. Therefore, unlike the above-described embodiments, there is no need to extend the lead wiring 27 or the like along the gap between the movable plate 16 and the frame 30, so that the distance between the movable plate 16 and the frame 30 is reduced. And downsizing can be achieved.

FIG. 19 shows a ninth embodiment of the present invention. The present embodiment is a further improvement of the above-described eighth embodiment, in which the two wirings 2 that enter the notch 16a provided in the movable plate 16 and are connected near the pillar 14 are connected.
7, 39 are formed to extend a predetermined distance along the periphery of the movable plate 16 (two adjacent sides). Thereby, each wiring 2
7, 39 become parallel to the three sides of the movable plate 16, and the total extension distance becomes longer. Therefore, in the present embodiment, by making the two wirings 27 and 39 point-symmetric in the same manner as in the above-described seventh embodiment, the reaction force against the movable plate 16 is equalized. Similarly, by connecting near the pillar portion 14, the effect of reducing the generated reaction force itself is exhibited, and by increasing the length of both wires 27, 39, the stress of the wires 27, 29 is reduced. Thus, the movable plate 16 can be displaced in parallel more smoothly.

FIG. 20 shows a tenth embodiment of the present invention. This embodiment is also an improvement of the extraction wiring 27 and can be applied to each of the above embodiments. That is, the lead wiring 27 is made thinner than the movable plate 16.
By doing so, the stress of the lead wiring 27 is reduced, and the influence of the stress on the movable plate 16 is reduced. In order to manufacture a sensor having such a structure, for example, before joining the second semiconductor substrate 18 to the first semiconductor substrate 10, the region where the lead wiring 27 is formed on the joining surface side of the second semiconductor substrate 18 is dry-etched or the like. Etching to make it thinner. Thereafter, the two semiconductor substrates can be bonded by fusion bonding, and can be manufactured by performing a normal manufacturing process.

In each of the above-described embodiments, the lead wiring for leading the second electrode 21 (movable plate 16) to the outside is provided in the second semiconductor substrate 18 for manufacturing the movable plate 16.
However, the present invention is not limited to this, and connection may be made using another member such as a bonding wire 43 as shown in FIG. In this example, a wire pad 44 is provided on the upper surface of the movable plate 16 (if a protective film is provided, a hole is formed in a corresponding portion of the protective film), and the wire pad 44 and the electrode pad 29 are provided.
Are connected to both ends of the bonding wire 43. The use of the bonding wire 43 in this manner is preferable in that the influence of the stress of the lead-out wiring is eliminated as in the above embodiments. In this case, if wire bonding is performed before forming the support plate, bonding can be easily performed.

FIGS. 22 and 23 show an eleventh embodiment of the present invention. In the present embodiment, unlike the above embodiments, the movable plate 46 is formed using a glass substrate. That is, first, the first support plate 47 is formed.
An insulating film 49 is formed on the entire upper surface of the semiconductor substrate 48. Then, a wiring pattern 50 is formed by sputtering aluminum or the like at a predetermined position on the upper surface of the insulating film 49, and one end 50a of the wiring pattern 50 is widened to form a wire pad.

On the other hand, at the center of the lower surface of the movable plate 46, a convex portion 46a is provided.
To form Then, aluminum or the like is sputtered on the periphery of the lower surface side of the movable plate 46, that is, on the portion of the first semiconductor substrate 48 facing the frame 51 to form a second electrode 53, and the second electrode 53 is formed continuously with the second electrode 53. A wiring pattern 55 extending to the protrusion 46a is also formed at the same time. An interconnection portion 57 is provided at the other end 50b of the wiring pattern 50, and the projection 46a is joined to the interconnection portion 57. Since the interconnection portion 57 is formed of aluminum, the second electrode 5
3 is a wiring pattern 50 → interconnection part 57 →
Conduction is made to the wire pad 50a through the wiring pattern 55. Then, a pillar portion is formed by the convex portion 46a and the interconnection portion 57. By using the interconnection in this manner, the periphery of the movable plate 46 can be set in a free state, so that no stress is applied to the movable plate 46 and the occurrence of distortion can be suppressed as much as possible.

The upper surface of the frame 51 of the first semiconductor substrate 48 facing the second electrode 53 becomes the first electrode 58, and a capacitance is generated between the two electrodes 53, 58 according to the distance between the gaps. The first electrode 58 is electrically connected to the outside through a wire pad 60 formed by sputtering aluminum on the first semiconductor substrate 48 exposed through a hole 49 a formed at a predetermined position in the insulating film 49. It becomes possible.

FIG. 24 shows a twelfth embodiment of the present invention. In the present embodiment, the cover 61 is formed so as to cover the space above the movable plate 16 based on each of the above embodiments. With such a configuration, entry of dust and the like into the gap can be prevented. When the cover 61 is formed by appropriately etching a semiconductor substrate such as silicon, the cover 61 can be manufactured by a series of processes in a semiconductor process.

To manufacture the sensors having the above-described configurations,
For example, a first semiconductor substrate and a second semiconductor substrate are respectively formed from separate silicon wafers. For example, after forming a pillar on the first semiconductor substrate, a second semiconductor substrate is formed on the upper surface of the pillar.
After bonding the semiconductor substrate, the semiconductor substrate can be manufactured using a semiconductor process by performing patterning by etching.

As another method, it can be manufactured, for example, by the method shown in FIG. That is, the following method is used to form a counter electrode using a conductive thin film deposited on a substrate on which a support plate is to be provided, using surface microtechnology. (1) First, a silicon wafer 1 serving as a first semiconductor substrate
On the 0 ', a SiN film or the like is deposited, and the SiN is etched to form the pillars 14 and the like. (2) An oxide film 62 is deposited on a portion to be a gap.
This oxide film becomes a sacrificial layer. (3) The oxide film located above the pillars 14 is removed, polysilicon is deposited, and the movable plate 16 and the lead-out wiring are patterned. Of course, a protective film is also formed before and after the deposition of polysilicon. Thereby, the intermediate product of FIG. 25A can be formed. (4) The oxide film (sacrificial layer) manufactured in the process (2) is etched by wet etching to form a gap as described above. Thereby, the intermediate product of FIG. 25B can be formed. (5) A support plate 12 is formed by forming a pad for wire bonding and etching a predetermined position on the lower surface of the silicon wafer. Thus, a sensor as shown in FIG. 25C is manufactured. If a sensor chip is made by such a process, it can be made with one wafer, which leads to cost reduction.

Further, in the above step (3), the movable plate (second electrode) and the lead-out wiring are both formed of polysilicon. For example, the movable plate is made of single crystal silicon, and the lead-out wiring part is formed by surface microtechnology. Therefore, if the gate electrode is made of polysilicon, the rigidity of the movable plate> the rigidity of the lead-out wiring is satisfied, and a structure in which the influence of the stress generated by the lead-out wiring is hardly applied to the counter electrode can be obtained.

[0071]

According to the capacitance type acceleration sensor and the detection method of the present invention, the change in capacitance due to the deformation of the support plate can be maximized in a large area on the peripheral side of the support plate. As a result, the change in the sensor output with respect to the change in the physical quantity to be measured increases, and the sensitivity becomes high. Since the support plate and the movable plate are arranged so as to overlap in the displacement direction, the occupancy of the electrode area with respect to the sensor chip can be increased, and the sensitivity can be improved while miniaturizing the sensor. it can. Furthermore, in order to widen the measurement range, it is necessary to increase the displaceable distance of the movable plate. Then, in order to greatly displace the weight in the conventional structure in which the weight and the beam (supporting portion) are formed on the same plane, it is necessary to lengthen the beam and the like. Invite. However, in the present invention, even if the support plate is enlarged to increase the displacement of the movable plate, the occupancy of the electrode area is not affected. Therefore, the measurement range can be increased without lowering the sensitivity.

Further, when the electrodes are formed around the substrate with the support plate, that is, in a region where the support plate is not formed, the distance between the electrodes is displaced in parallel at that portion, so that the linearity of the input / output characteristics is reduced. Good, the width of the die bond portion can be made sufficient, and downsizing can be achieved. Further, if the distance between the gaps near the pillar portion (including the substantial distance in consideration of the dielectric constant) is increased, the parasitic capacitance can be reduced, and the linearity of the input / output characteristics can be improved. Furthermore, if the structure of the lead wiring is devised, the stress on the movable plate can be reduced or adverse effects can be eliminated, so that the characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a conventional capacitance type acceleration sensor.

FIG. 2 is a sectional view showing an example of a conventional capacitance type acceleration sensor.

FIG. 3 is a diagram showing a first embodiment of a capacitive acceleration sensor according to the present invention.

FIG. 4 is a diagram showing a first embodiment of a capacitive acceleration sensor according to the present invention.

FIG. 5 is a diagram illustrating an example of a manufacturing process of a substrate having a support plate.

FIG. 6 is a diagram illustrating an example of a manufacturing process of a substrate having a support plate.

FIG. 7 is a diagram showing a second embodiment of the capacitive acceleration sensor according to the present invention.

FIG. 8 is a diagram showing a second embodiment of the capacitive acceleration sensor according to the present invention.

FIG. 9 is a diagram showing a third embodiment of the capacitive acceleration sensor according to the present invention.

FIG. 10 shows a fourth example of the capacitive acceleration sensor according to the present invention.
It is a figure showing an embodiment.

FIG. 11 shows a fourth example of the capacitive acceleration sensor according to the present invention.
FIG. 14 is a diagram showing a modification of the embodiment.

FIG. 12 shows a fourth example of the capacitive acceleration sensor according to the present invention.
FIG. 14 is a diagram showing a modification of the embodiment.

FIG. 13 shows a fourth example of the capacitive acceleration sensor according to the present invention.
FIG. 14 is a diagram showing a modification of the embodiment.

FIG. 14 shows a fourth example of the capacitive acceleration sensor according to the present invention.
FIG. 14 is a diagram showing a modification of the embodiment.

FIG. 15 shows a fifth example of the capacitive acceleration sensor according to the present invention.
It is a figure showing an embodiment.

FIG. 16 shows a sixth example of the capacitive acceleration sensor according to the present invention.
It is a figure showing an embodiment.

FIG. 17 shows a seventh example of the capacitive acceleration sensor according to the present invention.
It is a figure showing an embodiment.

FIG. 18 shows an eighth example of the capacitive acceleration sensor according to the present invention.
It is a figure showing an embodiment.

FIG. 19 is a diagram illustrating a ninth capacitive acceleration sensor according to the present invention.
It is a figure showing an embodiment.

FIG. 20 shows a first example of the capacitance type acceleration sensor according to the present invention.
0 is a diagram showing an embodiment of the present invention. FIG.

FIG. 21 shows a first example of a capacitive acceleration sensor according to the present invention.
FIG. 14 is a diagram illustrating a modification of the embodiment of FIG.

FIG. 22 shows a first example of the capacitance type acceleration sensor according to the present invention.
It is a figure showing one embodiment.

FIG. 23 shows a first example of the capacitance type acceleration sensor according to the present invention.
It is a figure showing one embodiment.

FIG. 24 shows a first example of a capacitive acceleration sensor according to the present invention.
FIG. 8 is a diagram showing a second embodiment.

FIG. 25 is a diagram illustrating an example of a manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 First semiconductor substrate 11 Slit 12 Support plate 13 Frame 13a Die bond part 14 Column part 16 Movable plate 18 Second semiconductor substrate 20 First electrode 21 Second electrode 22 Insulating film 24, 25 Protective film 27 Lead-out wiring 39 Dummy wiring

Claims (5)

[Claims] A substrate provided with an elastically deformable support plate supported at both ends with respect to a frame; a column provided on a surface of the support plate; and a column connected to the column, A movable plate that is displaced with elastic deformation;
An electrostatic capacitance type acceleration sensor comprising: a second electrode; and means for extracting a signal based on an electrostatic capacitance generated between the first and second electrodes to the outside. 2. A substrate having an elastically deformable support plate supported at both ends with respect to a frame, and a movable member connected to the support plate and moving in parallel with deformation of the support plate while maintaining an initial shape. A plate, and first and second surfaces respectively provided on opposing surfaces of the substrate and the movable plate.
An electrostatic capacitance type acceleration sensor comprising: a second electrode; and means for extracting a signal based on an electrostatic capacitance generated between the first and second electrodes to the outside. 3. A substrate having an elastically deformable support plate supported on both sides of a frame, a first electrode provided on an outer periphery of the support plate on the surface of the substrate, and connected to the support plate. A movable plate that moves with the deformation of the support plate while maintaining a parallel state with respect to the first electrode; a second electrode provided at a portion of the movable plate facing the first electrode; A means for taking out a signal based on the capacitance generated between the first and second electrodes to the outside. 4. It has a substrate, a movable plate, and a column connecting them, and the periphery of the substrate to which the column is connected is made thinner and thinner than the outer periphery. A plurality of slits are formed in the portion at predetermined intervals, a support plate capable of elastically deforming an area sandwiched by the plurality of slits is provided, and the movable plate is displaced while the support plate is deformed. A capacitance type acceleration sensor, wherein first and second electrodes are provided on opposing surfaces of the substrate and the movable plate, respectively. 5. A base having an elastically deformable support plate supported on both sides of the frame and a movable plate connected to the support plate and moving as the support plate deforms, First and second electrodes are provided on the opposing surfaces of the base and the movable plate, respectively, and a signal based on a capacitance generated between the two electrodes according to a relative position of the two electrodes that changes with the displacement of the support plate. Detecting the acceleration applied to the support plate and the movable plate by detecting the acceleration.