JP3218302B2 - Capacitive 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, and more particularly, to a capacitance type acceleration sensor provided with a fixed electrode and a movable electrode and detecting acceleration from a change in capacitance when a gap between the two electrodes changes. About.

[0002]

2. Description of the Related Art Generally, a capacitive acceleration sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-152369.
A sensor chip having a fixed electrode and a movable electrode is adhered on a substrate, and acceleration is detected from a change in capacitance between the fixed electrode and the movable electrode when a gap between the two electrodes changes. .

[0003]

However, in the above-mentioned conventional capacitive acceleration sensor, no consideration is given to adjusting the thickness of the adhesive layer when the sensor chip is adhered to the substrate, and the adhesive layer is not There is a disadvantage that it becomes thin. When the adhesive layer becomes thinner, the distance between the substrate and the sensor chip becomes narrower, so that when the substrate and the sensor chip thermally expand, the influence of the thermal expansion difference between the two appears. That is, due to the difference in the coefficient of thermal expansion between the substrate and the sensor chip, when the temperature changes, the amounts of expansion and contraction of the substrate and the sensor chip are different from each other, and the substrate and the sensor chip are warped. In particular, when warping deformation occurs in the sensor chip, the gap between the movable electrode and the fixed electrode provided inside changes, and a difference in capacitance that detects acceleration even when no acceleration is applied is detected. State, and as a result, the zero point shifts.

An object of the present invention is to provide a capacitive acceleration sensor in which the zero point does not shift even if the substrate and the sensor chip thermally expand due to a temperature change.

[0005]

[0006]

[0007]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
Further, the present invention includes a substrate, a sensor chip provided on the substrate, a fixed electrode and a movable electrode are arranged with a predetermined gap, between the two electrodes when the gap changes In a capacitive acceleration sensor for detecting acceleration from a change in capacitance, a conductor similar to a wiring formed on the substrate is provided.
A frame made of a material, which is larger than the sensor chip and has a closed shape is formed on the substrate, and the frame is filled with the adhesive, and the sensor chip is filled with the adhesive.
The cap is bonded and fixed .

[0008] The present invention also provides a substrate, and a device provided on the substrate.
Provided with a fixed electrode and the movable electrode and the sensor chip which is arranged with a predetermined gap, the capacitance type acceleration sensor for detecting acceleration from a change in capacitance between the two electrodes when the gap is changed In the above, the sensor on the substrate
As for the mounting position of the chip,
And the adhesive is filled in the recess.
Attach the sensor chip with the adhesive
It is fixed .

Further, the present invention comprises a substrate, and a sensor chip which is adhered and fixed on the substrate with an adhesive, and in which a fixed electrode and a movable electrode are arranged with a predetermined gap, wherein the gap is changed. A capacitance type acceleration sensor for detecting acceleration from a change in capacitance between the two electrodes when the plurality of projections are provided, wherein a plurality of projections are partially provided on the substrate corresponding to an outer peripheral portion of the sensor chip; Is filled with the adhesive, and a material having a linear expansion coefficient substantially equal to that of the adhesive is used as a material of the protrusion.

[0010]

[Function] If the thickness of the adhesive layer is made larger than the thickness capable of absorbing thermal deformation of the sensor chip and avoiding warpage of the sensor chip,
Even if there is a difference in the amount of expansion and contraction due to the difference in the coefficient of thermal expansion between the sensor chip and the substrate, the difference in the amount of expansion and contraction is absorbed by the adhesive layer, thereby preventing the sensor chip from being warped. For this reason, the change in the gap between the movable electrode and the fixed electrode provided on the sensor chip can be kept small, and the shift of the zero point of the capacitive acceleration sensor due to the temperature change can be prevented.

In order to keep the thickness of the adhesive layer large, there is provided means for preventing the adhesive for bonding and fixing the sensor chip onto the substrate from leaking out from the bonding surface to the outside. Specifically, a frame that is larger and closed than the sensor chip is formed on the substrate, and the frame is filled with an adhesive, or a recess is provided at the sensor chip mounting position on the substrate, and the adhesive is formed in the recess. By filling the adhesive, it is possible to prevent the adhesive from leaking outside from the adhesive surface. In addition,
The frame is made of the same conductive material as the wiring formed on the substrate.
If it is, manufacturing is easy. In addition, the depression is
It can be easily formed by not providing a protective film.

Further, a plurality of projections may be provided on the substrate corresponding to the outer peripheral portion of the sensor chip, and an adhesive may be filled in a space surrounded by these projections. With such a configuration, the sensor chip can be supported by the plurality of protrusions, and it is possible to prevent the adhesive layer from becoming thin due to the weight of the sensor chip. In this case, it is necessary to reduce the influence of the contraction of the adhesive by setting the coefficient of linear expansion of the material of the projection to be substantially equal to the coefficient of linear expansion of the adhesive.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view (BB section in FIG. 2) of a capacitive acceleration sensor, and FIG. (A-A cross section in FIG. 1).

The sensor chip 1 of the capacitive acceleration sensor comprises:
The movable electrode forming layer 12 is formed in a three-layer structure sandwiched between the fixed electrode forming layer 11 and the fixed electrode forming layer 13. A movable electrode 15 supported by a support member 16 is provided at the center of the movable electrode forming layer 12, and a pair of fixed electrodes 14 </ b> A and 14 </ b> B are provided on both surfaces of the movable electrode 15 at predetermined intervals on the fixed electrode forming layers 11 and 13. Are provided respectively.

When an acceleration in a direction perpendicular to the electrode surface is applied to the sensor chip 1, an inertial force is applied to the movable electrode 15, and the support member 16 is elastically deformed and the movable electrode 15 is displaced. The gap between the movable electrode 15 and the fixed electrode 14B changes, and the gap between the movable electrode 15 and the fixed electrode 14B also changes. The acceleration can be detected by detecting the change in the capacitance.

The movable electrode forming layer 12 is made of silicon single crystal as a material, and is formed into a shape as shown in FIG. 2 by processing the single crystal by etching.
Further, the fixed electrode forming layers 11 and 13 use glass as a material for the fixed portion. Then, the fixed electrode forming layer 1
The sensor chip 1 is integrally formed by sandwiching the movable electrode forming layer 12 from both sides by 1 and 13 and joining them by an anodic bonding method.

The sensor chip 1 is adhered and fixed on a substrate 4 by an adhesive 2. In order to prevent the adhesive 2 from leaking out of the bonding surface when the sensor chip 1 is bonded and fixed, a closed frame 3 is provided on the substrate 4 at the position where the sensor chip 1 is bonded.

Alumina is used as the material of the substrate 4 and silver palladium is used as the material of the frame 3. By doing so, the frame 3 can be formed only by performing screen printing on the substrate 4 in the same manner as the peripheral circuit, and there is no need to add a special process to the conventional manufacturing process, which is extremely advantageous in manufacturing.

Here, the features of the capacitive acceleration sensor of the present invention will be described in comparison with the conventional one. In the conventional capacitive acceleration sensor, when the sensor chip 1 is bonded to the substrate 4 as shown in FIGS. 4A and 4B, the thickness of the adhesive 2 is reduced due to the weight of the sensor chip 1. .
When the thickness of the adhesive 2 is reduced, the temperature is changed and the sensor chip 1 and the substrate 4 are strongly affected by the difference in thermal expansion, and as shown in FIG.
In addition, the substrate 4 is warped. In particular, when warpage deformation occurs in the sensor chip 1, even when no acceleration is applied, the inclination of the support member 16 of the sensor chip 1 changes and the movable electrode 15 is displaced. The gap changes, and a change in capacitance is output. That is, a zero point shift occurs.

On the other hand, in the capacitive acceleration sensor of the present invention, in the step of bonding the sensor chip 1 to the substrate 4, the frame 3 is previously provided on the substrate 4 as shown in FIG. When the liquid adhesive 2 is filled (or applied), the adhesive 2 does not flow out. Further, as shown in FIG.
Is placed on the adhesive 2, and even when the weight of the sensor chip 1 is applied to the adhesive 2, the surface tension of the adhesive 2
The sensor chip 1 can be floated on the surface of the adhesive 2. By curing the adhesive 2 in this state, an adhesive layer having a uniform and sufficient thickness can be formed. As described above, since it is possible to bond and fix the adhesive layer in a state where the thickness of the adhesive layer can be secured, warpage deformation of the sensor chip as shown in FIG. Does not occur.

In order to confirm the effects of the present invention, the relationship between the thickness of the adhesive and the amount of change in the gap between the movable electrode and the fixed electrode caused by a change in temperature was calculated by the finite element method. The result is shown in FIG. FIG. 5 shows that if the thickness of the adhesive is 10 μm or more, the change in the gap can be made 0.01 μm or less even when a temperature change of 60 ° C. is applied. When the measurement maximum acceleration is applied, that is, when the change in the gap at the time of full scale is set to 1 μm, the shift of the zero point due to the temperature change of 60 ° C. can be 1% or less of the full scale. 20
° C, the zero point shift is ± 1 even if the environmental temperature changes within ± 60 ° C, that is, -40 ° C to 80 ° C.
%, And practically sufficient accuracy can be ensured when general applications are considered.

A silver palladium conductor is used as the material of the frame,
By appropriately adjusting the viscosity of the conductor paste when printing the conductor on the substrate, the thickness of the fired frame is set to, for example, 14 ±
It can be controlled to 4 μm. That is, if the thickness of the frame is 1
Since the thickness can be set to 0 μm or more, the thickness of the adhesive can be secured to 10 μm or more.

According to the present embodiment, the shape of the frame 3 is
By making the frame into a closed, that is, unbroken frame that does not leak out, the thickness of the adhesive 2 can be made constant, and in the manufacturing process of bonding the sensor chip 1 to the substrate 4, Since the sensor chip 1 has a function of determining the bonding position and can prevent the sensor chip 1 from being bent and bonded, it is possible to reduce the occurrence of defective products in the sensor chip bonding process during mass production.

(Second Embodiment) FIGS. 6 and 7 show a second embodiment of the present invention. FIG. 6 is a longitudinal sectional view of a capacitive acceleration sensor (a sectional view taken along line DD in FIG. 7), and FIG. FIG. 7 is a transverse sectional view (a sectional view taken along line CC in FIG. 6).

The sensor chip 1 is formed in a three-layer structure and has a movable electrode 15 and fixed electrodes 14A and 14B therein as in the first embodiment. The feature of this embodiment is that the recess 4A is provided on the substrate 4 side, and the adhesive 2 for bonding and fixing the sensor chip 1 is filled in the recess 4A. By providing the recess 4A, the adhesive 2 can be prevented from leaking to the outside.

The substrate 4 is a wiring substrate provided with wiring, and a surface protective film 5 is provided on the surface thereof. However, the surface protective film 5 is not provided at a position where the sensor chip 1 is bonded. By doing so, the depression 4A can be formed. In forming the depressions 4A, if glass is used as the material of the surface protection film 5, a glass coating process after wiring formation can be used as in a conventional manufacturing process. Further, in this embodiment, the glass film thickness can be controlled to 14 μm ± 4 μm by adjusting the viscosity of the glass paste in the same manner as in the first embodiment, so that the adhesive layer can secure a greater thickness. , The zero point shift can be made sufficiently small for practical use.

According to the present embodiment, since the adhesive 2 can be prevented from leaking out, the adhesive 2 can be secured to a sufficient thickness, and the warpage of the sensor chip 1 as described above hardly occurs. A point shift can be prevented from occurring. Also, the formation of the recess 4A can be performed without adding a special process to the conventional manufacturing process, so that the effect of preventing the zero point shift can be improved without increasing the manufacturing cost.

(Third Embodiment) FIGS. 8 and 9 show a third embodiment of the present invention. FIG. 8 is a longitudinal sectional view (a sectional view taken along line FF in FIG. 9) of a capacitive acceleration sensor, and FIG. FIG. 9 is a transverse sectional view (EE section in FIG. 8).

The sensor chip 1 is formed in a three-layer structure and has a movable electrode 15 and fixed electrodes 14A and 14B therein as in the first and second embodiments. The feature of the present embodiment is that a projection 6 having a function of securing the thickness of the adhesive 2 is provided at a position on the substrate 4 where the sensor chip 1 is bonded, corresponding to the four corners of the lower surface of the sensor chip. The space is filled with the adhesive 2, and the protrusion 6 and the material of the adhesive 2 have the same linear expansion coefficient.

According to this embodiment, when the sensor chip 1 is bonded to the substrate 4, the protrusion 6 supports the sensor chip 1, so that the thickness of the adhesive 2 does not become thin due to the weight of the sensor chip 1. As shown in FIG. 10A and FIG. 10B, the thickness of the adhesive 2 can be secured at least by the height of the protrusion 6. However, this alone may cause a zero point shift due to a temperature change. It is adhesive 2
No consideration is given to their own expansion and contraction. In particular, when the adhesive 2 contracts at a low temperature, the protrusion 6
Where the protrusions 6 around the sensor chip 1 are not affected by the contraction of the adhesive 2 and the central portion is affected by the contraction of the adhesive 2. As a result, FIG. As shown in (c), warpage occurs such that the central portion of the sensor chip 1 bends toward the substrate 4 side. There is a problem that a zero point shift occurs due to the warpage deformation.

Therefore, in this embodiment, the protrusion 6 and the adhesive 2
By using the same material for the linear expansion coefficient of
To reduce the effect of warpage deformation. By eliminating the difference in thermal expansion between the protrusion 6 and the adhesive 2 in this manner, the expansion and contraction of the protrusion 6 and the adhesive 2 caused by a temperature change become the same, and as shown in FIG. Even if the sensor chip 1 contracts, it is possible to prevent the sensor chip 1 from being warped and to prevent a zero point shift due to a temperature change.

Silver palladium is used as the material of the projections 6. As a result, the projections 6 can be formed by screen printing similarly to the wiring of the peripheral circuit, which is extremely advantageous in productivity.

By using a polyimide resin, particularly PIQ, as the material of the adhesive 2, a linear expansion coefficient close to that of the above-mentioned projection material can be realized, and good adhesiveness can be secured.

It is sufficient that a plurality of protrusions 6 are provided not only at positions corresponding to the four corners of the lower surface of the sensor chip 1 but also at positions corresponding to the outer peripheral portion of the lower surface of the sensor chip 1.

[0035]

As described above, according to the present invention,
By maintaining a large layer thickness of the adhesive for bonding the sensor chip and the substrate, the distance between the sensor chip and the substrate can be increased, so that the sensor chip does not warp even when subjected to a temperature change, A capacitive acceleration sensor with a small zero point shift can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a capacitive acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the capacitive acceleration sensor of FIG.

FIG. 3 is an explanatory diagram showing an operation of the capacitive acceleration sensor of FIG. 1;

FIG. 4 is an explanatory view showing the operation of a conventional capacitive acceleration sensor.

FIG. 5 is a diagram showing a relationship between a gap between a movable electrode and a fixed electrode and a thickness of an adhesive.

FIG. 6 is a longitudinal sectional view of a capacitive acceleration sensor according to a second embodiment of the present invention.

FIG. 7 is a transverse sectional view of the capacitive acceleration sensor of FIG. 6;

FIG. 8 is a longitudinal sectional view of a capacitive acceleration sensor according to a third embodiment of the present invention.

9 is a cross-sectional view of the capacitive acceleration sensor of FIG.

FIG. 10 is an explanatory diagram showing an operation of the capacitive acceleration sensor of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor chip 2 Adhesive 3 Frame 4 Substrate 4A Depression 5 Surface protective film 6 Projection 11, 13 Fixed electrode formation layer 12 Movable electrode formation layer 14A, 14B Fixed electrode 15 Movable electrode 16 Support member

Continued on the front page (72) Inventor Akio Hogawa 502 Kandachicho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (56) References JP-A-4-47271 (JP, A) JP-A-1-251624 (JP, A) JP-A-2-125628 (JP, A) JP-A-4-1377041 ( JP, U) Hikaru 1-157424 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15/08 G01P 15/125 H01L 29/84

Claims (3)

(57) [Claims] 1. A semiconductor device comprising: a substrate; and a sensor chip provided on the substrate and having a fixed electrode and a movable electrode disposed with a predetermined gap therebetween, wherein a static capacitance between the two electrodes when the gap changes is provided. In a capacitive acceleration sensor that detects acceleration from a change in capacitance, the capacitive acceleration sensor is made of the same conductive material as the wiring formed on the substrate.
Ri, the frame of large and closed shape than the sensor chip is formed on the substrate, filling the adhesive in the frame
Attach the sensor chip with the adhesive
A capacitive acceleration sensor characterized by being fixed . 2. A semiconductor device comprising: a substrate; and a sensor chip provided on the substrate and having a fixed electrode and a movable electrode disposed with a predetermined gap therebetween, wherein a static gap between the two electrodes when the gap changes is provided. In a capacitive acceleration sensor for detecting acceleration from a change in capacitance , a table is provided on the substrate as a mounting position of the sensor chip.
A dent is formed without providing a surface protection film, and the dent is formed.
Is filled with the adhesive, and the adhesive
Wherein the sensor chip is bonded and fixed . 3. A sensor device comprising: a substrate; and a sensor chip which is bonded and fixed on the substrate with an adhesive, and in which a fixed electrode and a movable electrode are arranged with a predetermined gap. In a capacitive acceleration sensor for detecting acceleration from a change in capacitance between both electrodes, a plurality of projections are provided on the substrate corresponding to the outer peripheral portion of the sensor chip, and the projection is surrounded by the projections A capacitive acceleration sensor in which a space is filled with the adhesive and a material having a linear expansion coefficient substantially equal to that of the adhesive is used as a material of the protrusion.