JP4426202B2 - Acceleration sensor and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an acceleration sensor for detecting an acceleration by detecting a change in capacitance or the like, and a method for manufacturing the same.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-351876 [Patent Document 2]
JP, 2002-134659, A The substrate which forms a capacitance type semiconductor acceleration sensor conventionally, as shown in Drawing 6, the electrode for sensors etc. which are not illustrated on the surface of glass substrate 4, and the electrode of an external circuit board, A lead electrode 2 for connecting the wire and other electrodes and wiring patterns (not shown) are formed of an aluminum thin film or the like, and a number of predetermined weights 1, hollow portions 3, electrodes, and the like are formed on the surface of the glass substrate 4 vertically and horizontally. Some silicon wafers 6 are integrated by anodic bonding. The individual sensor chips 5 cut out from the silicon wafer 6 are drawn electrodes for connecting a sensor electrode (not shown) provided on the main body 7 or the glass substrate 4 by the silicon wafer 6 and an electrode of an external circuit board. 2 is provided on the surface of the glass substrate 4 exposed at the pair of edge portions of the main body portion 7 of each sensor chip 5.
[0003]
This acceleration sensor substrate is formed with a groove-like long hole 8 that exposes the extraction electrode 2 when the silicon wafer 6 is bonded to the glass substrate 4 by etching or the like in advance, and the extraction electrode 2 is formed in this groove shape. A silicon wafer 6 is anodically bonded to the surface of the glass substrate 4 so as to be exposed from the long hole 8. Thereafter, each sensor chip 5 was divided as shown by a two-dot chain line in FIG.
[0004]
Note that, as disclosed in Patent Documents 1 and 2, the extraction electrode 2 can be bonded to another circuit board in the thickness direction of the glass substrate 4 through a through-hole that is in contact with the surface-side electrode. This is also proposed by the present applicant.
[0005]
[Problems to be solved by the invention]
In the case of the acceleration sensor shown in FIGS. 5 and 6 of the above prior art, in the state where the silicon wafer 6 and the glass substrate 4 are anodically bonded, there is an internal stress on the bonding surface and a non-uniform stress in the plane direction in the substrate Will occur. This internal stress remains even after being divided into individual sensor chips, causing subtle strains in the sensor chip. That is, in the case of the conventional example, since the groove-like long hole 8 is formed in one direction, the anisotropy in the surface direction depends on the direction of the groove-like long hole 8 and the direction perpendicular thereto. As a result, the individual sensor chips 5 remain strained even after being divided.
[0006]
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide an acceleration sensor having a simple structure and causing no distortion in a substrate, and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
According to the present invention, the main body constituting the acceleration sensor is formed by etching from a silicon wafer, the silicon wafer on which the main body is formed is anodically bonded to a large insulating substrate, and then divided into individual sensor chips. In the method of manufacturing an acceleration sensor for forming an acceleration sensor, the main body is a square hollow rectangular tube, and the main body is formed with respect to four sides of the portion of the silicon wafer that forms the main body when the main body is formed. A rectangular through-hole is formed in a portion of each of the main body portions where the four sides are located in the state of the silicon wafer so that a part of each side of the portion is cut out. A part of each of the four sides is cut off to form a cut portion having a symmetrical and equal shape on both of the four sides, and a corner inside the cut portion is chamfered or rounded. As described above, the through hole of the silicon wafer is formed, and when the main body is formed, a beam is integrally extended from the four inner walls of the main body into the hollow portion of the main body. And a trapezoidal electrode part integrally projecting in four directions around the weight, and the weight of the hollow part and the electrode part are vertically and vertically with respect to the central axis of the main body part. The silicon wafer formed symmetrically in the lateral direction and having the main body formed thereon is anodically bonded to the insulating substrate, and in this state, each electrode individually formed on the surface of the insulating substrate, and the silicon wafer The weight and each electrode part are faced to each other, the lead electrode connected to each electrode on the insulating substrate is exposed in the through hole of the silicon wafer, and a cover is closely attached to the upper surface opening of the main body part. Secure and then insulation above The plate and the silicon wafer for each individual sensor chips, a manufacturing method of an acceleration sensor is divided into vertically and horizontally, across the hole.
[0008]
The opening of the hollow portion of the main body is sealed with a cover lid such as a glass plate or a silicon plate, and the inside of the main body is formed in a vacuum-tight state.
[0009]
The present invention also provides an acceleration sensor formed by the above manufacturing method. Further, the inside of the main body is evacuated by sealing the ventilation portion between the main body and the insulating substrate in a vacuum.
[0010]
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 acceleration sensor 10 according to this embodiment includes an insulating substrate 12 such as a glass plate and a capacitance formed on the center of the surface of the insulating substrate 12. A square electrode 14 to be formed and a trapezoidal electrode 16 which is formed on each of the four sides and similarly forms a capacitance are provided. The surface of the insulating substrate 12 is further provided with a wiring pattern (not shown) connected to the square electrode 14 and the trapezoidal electrode 16 and an extraction electrode 20 connected to the wiring pattern. The extraction electrode 20 is located in the vicinity of the edge of the central portion of each of the four sides of the insulating substrate 12. Each of the electrodes 14, 16, 20 and the wiring pattern is formed of a metal thin film such as aluminum or gold.
[0011]
A main body 22 made of silicon is bonded to the surface of the insulating substrate 12. As shown in FIGS. 1 and 2, the main body portion 22 is formed in a thin rectangular tube shape, and is formed in a shape in which a part of each side is cut into a rectangular shape. The four cutouts 24 are formed in such a size that the extraction electrodes 20 are exposed in a state where the main body 22 is bonded to the insulating substrate 12.
[0012]
In the hollow portion 25 of the main body portion 22, a beam 30 is integrally extended from the vicinity of the lower surface of each of the four inner walls 22 a of the main body portion 22, and a weight 26 is integrally provided at the distal end portion of the beam 30. Around the weight 26, trapezoidal electrode portions 28 are integrally projected in four directions. The weight 26, the electrode portion 28, and the beam 30 are integrally formed of a silicon semiconductor that is a constituent material of the main body portion 22. The beam 30 extends along the side wall 22a on one side from the vicinity of the lower surface of the inner wall 22a of the main body 22 and is bent at 45 ° before it hits another inner wall 22a that is orthogonal to the beam. Heading to the center, the tip is connected to the lower part of the weight 26 integrally. Four beams 30 are similarly extended from four sides of the inner wall 22 a of the main body 22 and connected to the weight 26.
[0013]
The main body 22 is formed in a p-type or n-type semiconductor by doping a silicon wafer substrate with a predetermined impurity. The upper surface opening of the main body 22 has a cover 32 such as a glass plate or a silicon plate fixed in an airtight state with a low melting point glass or the like, and seals the inside of the hollow portion 25 of the main body 22 together with the insulating substrate 12. .
[0014]
Then, the lower surface of the weight 26 and the square electrode 14 face each other at a predetermined interval to form a capacitance, and the acceleration in the direction perpendicular to the insulating substrate 12 is detected. The four electrode portions 28 of the weight 26 face the trapezoidal electrode 16 at a predetermined interval to form a capacitance, and detect acceleration in a direction parallel to the surface of the insulating substrate 12.
[0015]
First, as shown in FIGS. 2 and 3, the manufacturing method of the acceleration sensor 10 of this embodiment is a through-hole through which the extraction electrode 20 is exposed when the silicon wafer 36 is bonded to the insulating substrate 12 made of a glass plate. A rectangular hole 38, the hollow portion 25, and the weight 26 are formed in advance by etching or the like, and the extraction electrode 20 is formed so as to be exposed from the rectangular hole 38. The rectangular holes 38 are formed so as to be located on the four sides of the hollow portion 25.
[0016]
Next, the insulating substrate 12 made of a glass plate is integrally adhered to the back side of the silicon wafer 36 by anodic bonding. The anodic bonding is performed by applying a voltage of about 1 kV at a temperature of about 400 ° C. At this time, a wiring pattern of a feedthrough portion (not shown) is sandwiched between the main body portion 22 and the insulating substrate 12, and a gap of the ventilation portion is left. As will be described later, the gap between the ventilation portions is filled with an adhesive later.
[0017]
In addition, a low melting point glass plate or a silicon plate covering lid 32 is placed on the end face of the upper surface opening of the main body portion 22 and fixed in close contact in a vacuum. Further, the gap of the ventilation portion of the feedthrough portion due to the wiring pattern between the insulating substrate 12 and the main body portion 22 is filled with an adhesive in a vacuum, and the hollow portion 25 is sealed in a vacuum state. The adhesive used at this time is a thermosetting resin adhesive or an ultraviolet curable resin adhesive with a small amount of volatile components.
[0018]
Thereafter, the insulating substrate 12 and the silicon wafer 36 are divided for each sensor chip 40 as shown by a two-dot chain line in FIG. At this time, the rectangular hole 38 is divided at the center in the longitudinal direction, and becomes a cut portion 24 formed on each side of each sensor chip 40.
[0019]
In the acceleration sensor 10 of the present invention, the rectangular holes 38 are formed in the silicon wafer 36 forming the main body portion 22 in the four sides along with the hollow portion 25 of the main body portion 22 so as to surround the four sides of the main body portion 22 and the weight 26. The stress generated in the silicon wafer 36 after anodic bonding of the insulating substrate 12 and the silicon wafer 36 is extremely small. Further, the cut portions 24 by the rectangular holes 38 are formed on the four sides of the rectangular main body portion 22 and are formed in symmetrical shapes both vertically and horizontally as shown in FIG. 2, so that the thermal expansion of the insulating substrate 12 and the silicon wafer 36 is achieved. A uniform force does not act on the main body portion 22 due to a difference in coefficient, a joining condition, or the like, so that it is difficult to cause distortion as a whole.
[0020]
The rectangular hole 38 may have a shape with a corner cut as shown in FIG. This further relaxes the stress concentration at the corners and suppresses the cause of strain. Accordingly, the corners of the rectangular hole 38 may be rounded, and the rectangular hole 38 may be changed to an ellipse or an ellipse. Further, the cover lid may be bonded to the main body part in a vacuum, or may be bonded in the air, and at least if the gap of the ventilation part of the feedthrough part is closed in a vacuum and the inside of the main body part is formed in a vacuum. Good.
[0021]
【The invention's effect】
The acceleration sensor according to the present invention and the manufacturing method thereof are more precise because the cut portions are symmetrically formed in all directions, there is little distortion, and there is no biased directional strain or internal stress even on the substrate of each sensor chip. Measurement is possible. Further, the shape of the sensor chip can be made substantially square, the projected area can be reduced, and the volume can be suppressed.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an acceleration sensor according to an embodiment of the present invention.
FIG. 2 is a plan view of an acceleration sensor according to an embodiment of the present invention.
FIG. 3 is a plan view of a silicon wafer of the acceleration sensor according to the embodiment of the present invention.
FIG. 4 is a plan view of a silicon wafer of an acceleration sensor according to another embodiment of the present invention.
FIG. 5 is a plan view of the entire silicon wafer of a conventional acceleration sensor.
FIG. 6 is a plan view of a silicon wafer of a conventional acceleration sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Acceleration sensor 12 Insulating substrate 14 Square electrode 16 Trapezoid electrode 20 Extraction electrode 22 Main body part 24 Cutting part 26 Weight 28 Electrode part 30 Beam 32 Cover lid 36 Silicon wafer 38 Rectangular hole 40 Sensor chip

Claims (2)

The main body constituting the acceleration sensor is formed by etching from a silicon wafer, the silicon wafer on which the main body is formed is anodically bonded to a large insulating substrate, and then divided into individual sensor chips to form an acceleration sensor. In the manufacturing method of the acceleration sensor
The main body is a square hollow square tube, and when the main body is formed, part of each side of the main body is cut off with respect to the four sides of the silicon wafer forming the main body. In the state of the silicon wafer, rectangular through holes are formed in the portions where the four sides of each of the main body portions are located, and by this through hole, a part of the four sides of the main body portion is cut off and the four sides are symmetrical. Forming the through hole of the silicon wafer so as to form a cut portion of equal shape and chamfered or rounded the inner corner of the cut portion,
During the formation of the main body, a beam is integrally extended from the four inner walls of the main body into the hollow portion of the main body, and a weight is integrally provided at the tip of the beam, and the surroundings of the weight In four directions, a trapezoidal electrode part is integrally projected, and the weight of the hollow part and the electrode part are formed symmetrically in the longitudinal and transverse directions with respect to the central axis of the main body part,
The silicon wafer on which the main body portion is formed is anodically bonded to the insulating substrate, and in this state, each electrode individually formed on the surface of the insulating substrate, the weight of the silicon wafer, and each electrode portion are respectively connected. The lead-out electrode connected to each electrode on the insulating substrate is exposed in the through hole of the silicon wafer,
A cover lid is adhered and fixed to the upper surface opening of the main body,
Thereafter, the method of manufacturing an acceleration sensor, wherein the insulating substrate and the silicon wafer are divided vertically and horizontally so as to traverse the through-holes for each sensor chip. An acceleration sensor formed by the manufacturing method according to claim 1.

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