JP4095280B2 - Acceleration sensor element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor acceleration sensor element that detects acceleration by capacitance .
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, as a substrate provided with conductive wiring in the thickness direction of a glass substrate, there is a substrate using a conductive resin shown in FIG. In this substrate, a metal thin film layer 3 is formed by vapor-depositing aluminum or the like in a through hole 2 formed in a predetermined portion of the glass substrate 1, and a conductive resin is formed in the through hole 2 as shown in FIG. There was a substrate in which the paste 4 was filled and the conductive resin paste 4 was baked as shown in FIG. 5B to form the wiring 5 in the thickness direction using the conductive resin 4a. Further, as shown in FIGS. 6A and 6B, a through hole 2 in which a metal thin film 3 is formed is provided at a predetermined portion of the glass substrate 1, and a ball of solder 6 is placed on the through hole 2 and heated. In some cases, solder 6 was melt-filled in the through holes 2 to form the thickness direction wiring 7.
[0003]
Furthermore, when forming the glass block 8 for the glass substrate, as shown in FIG. 7A, metal wirings 9 such as tungsten wires are provided at equal intervals in the glass block 8, and the glass block 8 is solidified. 7 (b), the glass block 8 was sliced together with the metal wiring 9 into a thin glass substrate 1 to form a substrate having wiring in the thickness direction.
[0004]
[Problems to be solved by the invention]
In the case of using the conductive resin shown in FIG. 5 of the above prior art, the conductive resin 4 a after baking contracts and a gap is formed between the metal thin film 3. Therefore, it is not suitable for a substrate of an electronic element such as an acceleration sensor that requires airtightness between the front and back of the glass substrate 1.
[0005]
Further, in the case where the solder 6 is filled in the through hole of the glass substrate 1 shown in FIG. 6, in the manufacturing process or use environment of the electronic element provided on the glass substrate 1, the environment becomes higher than the melting point of the solder 6. There was a limitation when it could not be used, and particularly when the temperature was high in the manufacturing process.
[0006]
Further, in the case of the glass substrate 1 shown in FIG. 7, as shown in FIG. 7 (c), after slicing to the thin glass substrate 1, the surface is polished and finished. There is a problem that the metal wiring 9 protrudes from the surface of the glass substrate 1 due to the difference in the manner of wear. Therefore, in this case, the surface property of the glass substrate 1 on which the electronic element is mounted is poor, and there is a problem in the mountability when another electronic component is attached to the glass substrate 1 or when the glass substrate 1 is attached to the circuit substrate surface. It was.
[0007]
Further, as disclosed in Japanese Patent Laid-Open No. 11-351876, in a manufacturing method of an angular velocity sensor in which the inside is kept in a vacuum, an exhaust hole is provided in one of the substrates constituting the sensor, and the inside of the sensor is evacuated. There has also been proposed a method in which the hole is sealed with a metal thin film, solder, low melting point glass, or the like. In this case, however, the exhaust hole communicates with the inside of the sensor. When the exhaust hole is closed after evacuation, impurities or gas of the sealing material may enter the sensor. The reliability of hermetic sealing is not high.
[0008]
The present invention has been made in view of the above-mentioned problems of the prior art, and can obtain the conductivity in the thickness direction of the substrate with a simple process, has little thermal distortion, and ensures airtightness between the front and back of the substrate. An object of the present invention is to provide a semiconductor acceleration sensor element that can be small and can accurately detect acceleration .
[0009]
[Means for Solving the Problems]
In the present invention, a semiconductor thin plate having a predetermined electrode shape for acceleration detection is laminated on an insulating substrate, and a through hole reaching the semiconductor thin plate from the opposite side of the laminated surface of the semiconductor thin plate of the substrate is formed. An electronic device substrate having a back electrode in contact with the inside of the through hole and the semiconductor thin plate is formed on the back surface side of the substrate, and an acceleration sensor is provided to face the semiconductor thin plate on the surface side of the electronic device substrate. The acceleration sensor faces the semiconductor thin plate, and includes a weight portion, a frame-like case portion in which the weight portion is integrally formed and housed inside, and electrodes facing the semiconductor thin plate provided on four sides of the weight portion. And the weight portion are integrally formed to extend toward the four corners of the case , bend in a letter shape when viewed from the corner , and adjacent to the case portion along the case portion. It extends to the corner portion And a said record-shaped beam portion that is connected to the corner portion adjacent to the casing portion, the electrode of the acceleration sensor is also connected to the back surface electrode of the holes, the back surface electrode of the holes in the rear surface side of the substrate Thus, the acceleration sensor element can be connected to an external circuit board.
[0010]
The acceleration sensor is formed in an airtight state in a vacuum state within a case portion provided on the substrate. Furthermore, a semiconductor thin plate having a predetermined electrode shape is adhered and laminated on an insulating substrate by anodic bonding, and a through hole is formed so that the semiconductor thin plate is exposed from the opposite side of the laminated surface of the semiconductor thin plate of the substrate, The case part is joined in an airtight manner so as to surround the peripheral part of the substrate and the semiconductor thin plate, and includes a back electrode in contact with the through hole and the exposed semiconductor thin plate, and a glass plate is provided in the upper surface opening of the case part. The inside of the case part is sealed in an airtight state, and the weight part and the electrode part of the acceleration sensor are sealed in a vacuum state .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment of the present invention. An electronic element substrate 10 according to this embodiment has a thickness of an insulating substrate 11 at a predetermined electrode drawing position of an insulating substrate 11 such as a glass plate. A through hole 12 formed in the direction is formed. A metal thin film 14, which is a conductive thin film, is provided on the inner surface of the through hole 12, and the metal thin film 14 is connected to a back electrode 16 including a wiring pattern on the back surface side of the insulating substrate 11. The metal thin film 14 is made of a metal such as Al, Cr, or Au.
[0012]
On the surface side of the insulating substrate 11, a square electrode 20 a that detects acceleration in a direction perpendicular to the substrate is formed at the center, and each of the four electrodes detects acceleration in a direction parallel to the substrate surface. A semiconductor thin plate 20 provided with a trapezoidal electrode 20b and further divided into a rectangular frame portion 20c around it is laminated. The semiconductor thin plate 20 is formed of a silicon wafer substrate having a thickness of about 200 μm, and is formed into a p-type or n-type semiconductor by doping predetermined impurities. The portions of the insulating substrate 11 and the semiconductor thin plate 20 are in close contact with each other by anodic bonding.
[0013]
The acceleration sensor 22 according to this embodiment has a weight portion 24 of the acceleration sensor 22 facing the semiconductor thin plate 20 of the insulating substrate 11 and a frame-shaped case portion 26 in which the weight portion 24 is integrally formed and accommodated inside. Is provided. The case portion 26 is also formed as a p-type or n-type semiconductor by doping a silicon wafer substrate having a thickness of about 500 μm with a predetermined impurity. The weight portion 24 faces the square electrode 20a at the center of the semiconductor thin plate 20, and electrode portions 28 are formed on four sides of the weight portion 24. The electrode unit 28 faces the trapezoidal electrode 20b in parallel. From the weight portion 24, a beam portion 30 that supports the weight portion 24 is integrally formed and extends in a letter shape, and is connected to the four corners of the case portion 26. The bottom surface of the case portion 26 is positioned below the bottom surface of the weight portion 24 and is in close contact with the frame portion 20c of the semiconductor thin plate 20 in an airtight state by Au solder, high-temperature solder, or the like.
[0014]
A glass plate 32 is in close contact with the upper surface of the case portion 26 so as to close the upper surface opening. The glass plate 32 is joined to the case portion 26 by a low melting point glass or the like in an airtight state. The electrode part 28 of the acceleration sensor 22 is also connected to the back electrode 16 of the through hole 12 through the case part 26.
[0015]
In the manufacturing method of the acceleration sensor 22 of this embodiment, as shown in FIG. 4A, first, a semiconductor thin plate 20 of, for example, a p-type silicon substrate is etched to form a square electrode 20a, a trapezoidal electrode 20b, and a frame portion 20c. To do. At this time, a groove-like portion 34 that divides each portion is formed by etching, and a part of the surface side is left so that the groove-like portion 34 does not penetrate so that each portion does not fall apart. Next, as shown in FIG. 4B, an insulating substrate 11 such as glass on the back surface side is integrally adhered by anodic bonding. The anodic bonding is performed by applying a voltage of about 1 kV at a temperature of about 400 ° C. Next, as shown in FIG. 1C, the remaining portion on the surface side of the semiconductor thin plate 20 is etched, and the square electrode 20a, the trapezoidal electrode 20b, and the frame portion 20c are separated by the groove-shaped portion 34, respectively. To.
[0016]
Thereafter, as shown in FIGS. 3B and 4D, the through holes 12 are formed from the back side of the insulating substrate 11 by sandblasting. The through hole 12 penetrates the insulating substrate 11 and is slightly shaved without penetrating the semiconductor thin plate 20 so that the semiconductor thin plate 20 is exposed in the through hole 12.
[0017]
In addition, the silicon substrate forming the case portion 26 is etched to integrally form the weight portion 24, the electrode portion 28, and the beam portion 30. When the glass plate 32 is brought into close contact with the case portion 26 in advance, the glass plate 32 can be brought into close contact with the case portion 26 by anodic bonding. Then, as shown in FIG. 4E, the case portion 26 is brought into close contact with the electronic element substrate 10 in a vacuum by Au brazing or high-temperature solder, thereby forming the inside of the case portion 26 in a vacuum state. Further, after forming the case portion 26, the case portion 26 may be brought into close contact with the electronic element substrate 10 by Au soldering or high-temperature soldering, and then the glass plate 32 may be brought into close contact with the opening of the case portion 26. In this case, it joins by low melting glass.
[0018]
Note that the through holes 12 may be formed after the case portion 26 is bonded to the insulating substrate 11. And after forming the through-hole 12, the back surface electrode 16 containing wiring is formed by mask vapor deposition, sputtering, etc. FIG.
[0019]
The acceleration sensor 22 using the electronic element substrate 10 of the present invention can easily and reliably perform hermetic sealing in the sensor, the manufacturing process is simple, and the manufacturing cost can be reduced. Since each electrode 20a, 20b in the acceleration sensor 22 is formed by the semiconductor thin plate 20 in close contact with the insulating substrate 11, the coefficient of thermal expansion between the semiconductor case portion 26 and the semiconductor thin plate 20 is fixed. There is no difference, and the stress strain between the two can be greatly reduced. Further, the beam portion 30 supporting the weight portion 24 extends in a letter shape, the arm length is long, the acceleration detection sensitivity is high, and the outer shape can be small. Furthermore, the electronic device substrate 10 is internally briefly each electrode 20a while maintaining the vacuum state, the opposite side of 20b, it is possible to directly form the back surface electrode 16, the acceleration sensor 22 downsizing This point Greatly contributes to.
[0020]
The insulating substrate of the acceleration sensor according to the present invention may be made of silicon, ceramics, or the like depending on the application in addition to the glass-based material. Moreover, you may comprise a back surface electrode with conductors other than a metal thin film.
[0021]
【The invention's effect】
According to the acceleration sensor element of the present invention, electrical conduction between the front and back sides of the substrate can be achieved, and the inside of the acceleration sensor provided on the surface of the substrate can be easily provided in an airtight state. Can be maintained. In addition , the length of the beam can be increased with respect to the weight portion, and the conflicting problems of reducing the outer shape and increasing the detection sensitivity can be solved, and a highly sensitive acceleration sensor can be formed. In addition, an acceleration sensor that can be easily mounted on the surface can be provided. Thus, greatly contributes to the improvement of implementation density of the compact and the circuit board of the acceleration sensor. Furthermore, the size can be easily reduced, and the number of substrates that can be taken from one wafer can be increased, thereby reducing the cost.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a semiconductor acceleration sensor element according to an embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view showing a semiconductor acceleration sensor element according to one embodiment of the present invention.
FIGS. 3A and 3B are a plan view and a bottom view of an electronic device substrate according to an embodiment of the present invention. FIGS.
FIG. 4 is a longitudinal sectional view showing a schematic manufacturing process of the semiconductor acceleration sensor according to the embodiment of the present invention.
FIG. 5 is a longitudinal sectional view showing a conventional substrate for electronic devices.
FIG. 6 is a longitudinal sectional view showing another electronic device substrate according to the prior art.
FIG. 7 is a schematic view showing a manufacturing process of still another electronic device substrate according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Substrate for electronic devices 11 Insulating substrate 12 Through-hole 14 Metal thin film 16 Back electrode 20 Semiconductor thin plate 20a Square electrode 20b Trapezoid electrode 20c Frame part 22 Acceleration sensor 24 Weight part 28 Electrode part 30 Beam part 32 Glass plate

Claims (3)

A semiconductor thin plate having a predetermined electrode shape for acceleration detection is laminated on an insulating substrate, and a through hole reaching the semiconductor thin plate from the side opposite to the laminated surface of the semiconductor thin plate of the substrate is formed. The electronic element substrate is provided with a back electrode in contact with the semiconductor thin plate in the through hole, and an acceleration sensor is provided facing the semiconductor thin plate on the surface side of the electronic element substrate. Facing the semiconductor thin plate, a weight portion, a frame-shaped case portion in which the weight portion is integrally formed and accommodated inside, an electrode portion provided on four sides of the weight portion and facing the semiconductor thin plate, and The weight part is integrally supported and extends toward the four corners of the case , bends in a letter shape when viewed from the corner, and extends to the next corner along the case part. The above case It said a record-shaped beam portion that is connected to the corners of the neighboring electrodes of the acceleration sensor is also connected to the back electrode of the through hole, of the substrate at the rear surface side of the outside by the back electrode of the hole An acceleration sensor element characterized in that it can be connected to a circuit board. 2. The acceleration sensor element according to claim 1, wherein the acceleration sensor is formed in an airtight state in a vacuum state within a case portion provided on the substrate. A semiconductor thin plate having a predetermined electrode shape is adhered and laminated on an insulating substrate by anodic bonding, and a through hole is formed so that the semiconductor thin plate is exposed from the side opposite to the laminated surface of the semiconductor thin plate of the substrate. The case portion is joined in an airtight manner so as to surround the peripheral portion of the semiconductor thin plate, and includes a back electrode in contact with the through hole and the exposed semiconductor thin plate, and a glass plate is joined to the upper surface opening of the case portion. 3. The acceleration sensor element according to claim 2, wherein the inside of the case portion is hermetically sealed and the weight portion and the electrode portion of the acceleration sensor are sealed in a vacuum state .

Images