JPH07263709A - Dynamic quantity sensor and airbag system - Google Patents

Abstract

PURPOSE:To cut down the cost of the title system in which a dynamical variable sensor is used by a method wherein the continuity from the inside of a hermeticaly sealed detection part is obtained by having a low-priced, highly reliable and highly efficient structure. CONSTITUTION:A weight 3, which moves up and down by accelerated inertia, an elastic part 4 which supports the weight and a conductive pole 6 are formed by anisotropic etching an intermediate conductor 2 consisting of n-type single crystal. An upper electrode 5b, consisting of two-layer structure of aluminum and molibdenum, is formed on the upper insulator 1a opposing to the weight 3 using a photolithographic processing in such a manner that the upper electrode 5b is conductive to the conductive pole 6. A lower insulator 1b consists of a Pyrex 7740 same as the upper insulator 1a, and a lower electrode 5a is formed by the material and process same as the upper electrode 5b. In order to obtain conduction from the internal part of a sensor, aluminum conductors 8a, 8b, 10a and 10b are formed by a vapor deposition method and a sputtering method wherein a metal mask is used on the surface of impurity layers 7a, 7b, hole parts 9a and 9b, and the upper insulator 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical quantity sensor, and a structure, a manufacturing method, and a vehicle body control system using the mechanical quantity sensor for the purpose of detecting the mechanical quantity used in aircrafts, home appliances and automobiles. ， Anti-lock brake system, especially for automobile airbag system.

[0002]

2. Description of the Related Art As a conventional technique, for example, Japanese Patent Laid-Open No. 5-528
There is a capacitive acceleration sensor described in Japanese Patent Publication No. 67.
This device has a silicon substrate on which a vibrating mass is formed, which is moved by inertial force due to acceleration and supported by a beam having elasticity from the surroundings, and a vibrating mass and a minute gap on an insulating substrate formed on an insulating material. The present invention relates to a capacitive acceleration sensor in which a fixed electrode facing each other is formed, and acceleration is measured by a change in electrostatic capacitance between the vibration mass and the fixed electrode.

In the above-mentioned prior art, from a sensor hermetically sealed by attaching a lead wire using chrome copper gold and conductive epoxy vapor-deposited in fine holes formed in glass through an n + layer diffused on the surface of a silicon substrate. Achieved the electrical wiring (feed-through).

[0004]

The first problem of the above-mentioned prior art is that the entire surface of the silicon substrate including the vibrating mass surface is n.
+ Since the diffusion layer is formed, the etching rate during anisotropic etching of the vibrating mass surface changes and it becomes extremely difficult to control the interelectrode gap. It is well known that in a capacitive sensor, the air gap between the vibrating mass and the fixed electrode has a great influence on the linearity, temperature characteristics, and sensitivity.

The second problem of the above-mentioned prior art is that the hole opening is chipped because the hole is formed in the glass by a physical processing method such as electrolytic discharge machining. Therefore, the vapor-deposited film formed in the holes has a conduction failure at the chipped portions of the holes, and the conduction from the n + layer of the silicon substrate cannot be obtained, but the conduction is achieved by the lead wire using the conductive epoxy.

[0006]

The present invention was devised to solve the above-mentioned problems, and the first feature is
A weight conductor for detecting a mechanical quantity and an elastic part for supporting the weight, a middle conductor having an impurity layer uniformly formed on the surface of the airtight joint, an upper insulator having a through hole, and a lower insulator. In the mechanical quantity sensor having the above-mentioned middle conductor, the upper insulator and the lower insulator are airtightly joined, and conduction is made by the conductor formed in the hole and the upper insulator from the inside of the sensor through the impurity layer of the middle conductor. is there.

The second feature is that the middle conductor is formed of a P-type silicon substrate having no diffusion layer on its surface.

The third feature is that the hole portion of the upper insulator is processed after the airtight bonding, and the hollow portion which is continuous with the hole portion is provided in the middle conductor.

The fourth feature is that after the hole portion of the upper insulator is processed, the hole opening portion is polished to remove the chipped portion.

A fifth feature is the structure and manufacturing method of the airtight acceleration sensor achieved by the above invention, and the airbag system to which the airtight acceleration sensor according to the present invention is applied.

[0011]

The action of the first feature is that since a uniform impurity layer is formed in the middle conductor of the joint interface, there is no step at the joint interface and perfect airtight sealing is possible, and at the same time impurity diffusion is performed. When anisotropically etching the surface of a weight having no layer, variations in etching rate due to impurity diffusion can be avoided, and a highly accurate interelectrode gap can be formed. The action of the second characteristic is to reduce the number of steps, achieve hermetic sealing, and avoid etching variations by using a P-type silicon substrate for the middle conductor and eliminating the diffusion layer. Incidentally, an ohmic junction between a P-type semiconductor and a metal without a p + diffusion layer is known.

The operation of the third feature is that the hole of the upper insulator can be prevented from being chipped by processing the hole of the upper insulator after airtight bonding. If there is no lack of holes, which was the cause of poor conduction, conduction can be obtained only by the vapor-deposited metal film without sealing the conductive epoxy and lead wires in the holes, reducing the number of processes and reducing poor conduction. Etc. are achieved.

The fourth feature of the present invention is that after the holes of the upper insulator are processed, the hole openings are polished to remove the chipped portions, so that conduction can be obtained only by the vapor-deposited metal film, and the conductivity is improved. Elimination of epoxy and lead wires, reduction of the number of processes, and reduction of conduction defects are achieved.

A fifth feature is that the acceleration sensor to which the airtightly sealed structure obtained by the above feature and the low-priced and highly reliable feed-through portion are applied has the airtightness in the acceleration detection portion, so The degree of freedom is improved, and inexpensive materials such as plastic can be used. Further, since such an acceleration sensor can be integrated into a package similar to a general IC, for example, when the acceleration sensor of the present invention is used for a control unit used in an airbag system, a general device is used for mounting on the unit substrate. Because it can be used, mass production and equipment cost reduction effects are significant.

[0015]

EXAMPLE An example of a mechanical quantity sensor according to the present invention, that is, a capacitance type acceleration sensor will be described below.

FIG. 1 is a sectional view of a first embodiment of the acceleration detector of the present invention.

The weight 3 which moves up and down due to the inertia caused by acceleration, the elastic portion 4 which supports the weight, and the conductive columns 6 form the middle conductor 2 made of n-type silicon single crystal by anisotropic etching. Prior to etching, a mask such as an oxide film is formed by photolithography and phosphorus is diffused at the junction to form n + -type uniform impurity layers 7a and 7b. Pyrex 7 whose coefficient of thermal expansion is almost equal to that of silicon
Holes 9a and 9b are formed from the upper insulator 1a made of 740 by sandblasting using a metal mask. After the holes 9a and 9b are formed in the upper insulator 1a, the chipping of the opening formed during the hole processing is polished as shown in FIG. An upper electrode 5b having a two-layer structure of aluminum / molybdenum is formed on the upper insulator 1a so as to face the weight 3 by photolithography so as to be electrically connected to the conductive pillar 6. The lower insulator 1b is made of Pyrex 7740 like the upper insulator 1a, and the lower electrode 5a is also the upper electrode 5a.
It is formed by the same material and process as b. The middle conductor 2 and the upper insulator 1a and the lower insulator 1b are airtightly joined by anodic bonding. In order to obtain conduction from the inside of the sensor, the impurity layers 7a and 7b, the holes 9a and 9b, the conductors 8a and 8b made of aluminum by the vapor deposition method using the metal mask on the surface of the upper insulator 1a, the sputtering method, and the conductors. Form 10a and 10b.

FIG. 3 shows a second embodiment of the acceleration detector according to the present invention. The holes 9a and 9b of the upper insulator 1a are processed by sandblasting after the middle conductor 2 and the upper and lower insulators 1a and 1b are anodically bonded. Since the upper insulator 1a and the middle conductor 2 are anodically bonded, the holes 9a and 9b are formed integrally with the recess of the middle conductor. At this time, the hole 9
No chipping occurs in the openings of a and 9b. This is a fact obtained by experiment. Generally, when a brittle material such as glass is processed by a physical means such as sandblasting, electrolytic discharge machining, ultrasonic machining, it is inevitable to eliminate the occurrence of chipping of the opening when the hole penetrates. In the present invention, it is avoided by joining a rigid material to the hole penetrating side during hole processing.

FIG. 4 shows a third embodiment of the acceleration detector according to the present invention. The middle insulator 2 is made of p-type silicon single crystal. The holes 9a and 9b are formed after anodic bonding as in the embodiment of FIG. Through the holes 9a, 9b extending to the middle conductor, conductors 8a, 8b, 10a made of aluminum,
Electrical conduction from the inside of the acceleration detector is obtained by 10b. Here, the ohmic contact itself between the p-type semiconductor and the metal is a well-known method.

FIG. 5 shows a first embodiment of a method of processing an acceleration detector according to the present invention. (1) The hole 9 is formed by sandblasting the upper insulator 1a made of Pyrex glass.
After the formation of a and 9b, the upper insulator 1a is subjected to double-sided mirror polishing to remove the chipped portion. The upper electrode 5b is formed on the upper insulator 1a after the polishing process. (2) The middle conductor 2, on which the weight 3, elastic portion 4, and conductive column 6 are formed by anisotropic etching
The lower insulator 1b having the lower electrode 5a and the upper insulator 1a are aligned. (3) The middle conductor 2, the lower insulator 1b, and the upper insulator 1a are anodically bonded.
(4) The conductors 8a, 8b, 10a, 10b made of aluminum are formed by sputtering, vapor deposition or the like using a metal mask or the like.

FIG. 6 shows a second embodiment of the method for processing the acceleration detector according to the present invention.

(1) The upper electrode 5b is formed on the upper insulator 1a made of Pyrex glass. A weight 3, an elastic portion 4, and a conductive column 6 are formed on the middle conductor 2 by anisotropic etching. The lower electrode 5a is formed on the lower insulator 1b.
(2) After the middle conductor 2, the upper insulator 1a, and the lower insulator 1b are aligned, anodic bonding is performed. (3) The holes 9a and 9b are formed by sandblasting. (4) The conductors 8a, 8b, 10a, 10b made of aluminum are formed by sputtering, vapor deposition or the like using a metal mask or the like.

FIG. 7 shows a fourth embodiment of the acceleration detector according to the present invention. The cross-sectional structures of the plan view are A-A and B-, respectively.
B and C-C are shown. In this embodiment, the electrodes 5b, 5a formed on the inner surface of the laminated structure are drawn out through the conductive columns 6a, 6b and the holes 8 and the inside of the laminated body is hermetically sealed.

The manufacturing process of the above device and the electrode drawing method will be described below. A weight 3 and conductive columns 6a and 6b that are displaced by an external force are manufactured on the middle conductor 2 by an anisotropic etching process technique, and these are connected and supported by the middle conductor 2 by an elastic body 4. On the other hand, electrodes 5b, 5a made of metal thin film electrodes are formed on the upper insulator 1a and the lower insulator 1b. The process here is performed individually. Next, by the glass / silicon anodic bonding technique, the middle conductor 2, the upper insulator 1a, and the lower insulator 1b are simultaneously joined in three layers to form a laminated structure. At this time, the weight 3 is not joined because there is a gap between the upper insulator 1a and the lower insulator 1b, but the conductive columns 6a and 6b are joined to the upper and lower insulators, so that this portion is airtight. In addition, the lower electrode 5a formed on the lower insulator 1b in this process is sandwiched by a part of the conductive column 6a and mechanically contacts by the bonding force, and these are brought into conduction. Therefore, when a through hole consisting of a hole 9 is provided in the portion of the upper insulator 1a where the conductive pillar 6b is located, and the conductors 8 and 10 are formed on the inner surface of the through hole and the outer periphery thereof by sputtering or vapor deposition, the lower electrode 5a becomes conductive. It is connected to the conductors 10 and 8 through the pillars 6a so as to ensure airtightness and can be drawn out to the outside. Furthermore,
The elastic body 4 that connects and supports the conductive columns 6a and 6b is melted and cut through the upper insulator 1a to form an independent system electrode.

According to this embodiment, the anodic bonding between the middle conductor 2 and the upper and lower insulators 1a and 1b is required only once, and an airtight device can be obtained. Therefore, a device mounting method for an environment such as humidity can also be used. It can be simplified, and thereby high reliability and cost reduction can be achieved, and the manufacturing process can be facilitated.

FIG. 8 shows a fifth embodiment of the acceleration detector according to the present invention. The difference from FIG. 7 is that the central conductor 2 has an electronic circuit 3
It has 0. By incorporating the electronic circuit 30 in the middle conductor 2, the stray capacitance between the acceleration detector and the electronic circuit 30 can be reduced, and a highly accurate acceleration sensor can be provided.

FIG. 9 shows an embodiment of the mounting method of the acceleration detector according to the present invention. 100 is an acceleration detector, 110 is a control IC unit, 120 is a substrate, and 130 is a conducting wire. The acceleration detector 100 is connected to a control IC unit 110 that drives the acceleration detector 100 via a conductor 130, and is connected to a substrate 120.

FIG. 10 shows an embodiment of the configuration of the acceleration sensor according to the present invention. 100 is an acceleration detector, 200 is a control circuit unit, and 300 is an acceleration sensor. Acceleration detector
Since 100 has the airtightness in the acceleration detecting portion as described above, the degree of freedom of the sensor package is improved, and an inexpensive material such as plastic can be used. Further, such an acceleration sensor can be integrated into a package similar to a general IC. FIG. 11 shows an embodiment of the airbag system configuration according to the present invention.

Reference numeral 300 is an acceleration sensor, 400 is a control unit, 410 is a diagnostic unit, 420 is an airbag starting unit, 430 is a fail-safe function unit, and 500 is an airbag. When a control unit that uses the acceleration sensor 300 of the present invention in an airbag system is used, the mounting of the unit substrate can use a general apparatus, and thus the mass production effect and the facility cost reduction effect are great.

[0030]

Since the present invention is constructed as described above, it has the following effects.

According to the first aspect of the present invention, since a uniform impurity layer is formed on the middle conductor of the junction interface, there is no step at the junction interface, and complete airtight sealing is possible, and at the same time the impurity diffusion layer is formed. When anisotropically etching the surface of a weight without a gap, variations in etching rate due to impurity diffusion can be avoided, and a highly accurate interelectrode gap can be formed.

According to the second invention, by using the P-type silicon substrate for the middle conductor and eliminating the diffusion layer, it is possible to reduce the number of steps, achieve hermetic sealing, and avoid etching variations.

According to the third aspect of the invention, it is possible to prevent chipping of the opening of the hole by processing the hole of the upper insulator after the airtight bonding. When the chipping of the hole that was the cause of the conduction failure disappears, conduction can be obtained only by the vapor-deposited metal film without sealing the conductive epoxy and the lead wire in the hole,
A reduction in the number of processes and a reduction in conduction defects are achieved.

According to the fourth aspect of the invention, after the hole portion of the upper insulator is processed, the hole opening portion is polished and the chipped portion is removed to obtain conduction only by the vapor-deposited metal film. Also, the elimination of lead wires, the reduction of the number of processes, and the reduction of conduction defects are achieved.

According to the fifth aspect of the invention, the acceleration sensor to which the airtightly sealed structure obtained by the above-mentioned features and the low-priced and highly reliable feed-through section are applied has the acceleration detecting section having airtightness. The degree of freedom of the package is improved, and an inexpensive material such as plastic can be used. Further, since such an acceleration sensor can be integrated into a package similar to a general IC, for example, when the acceleration sensor of the present invention is used for a control unit used in an airbag system, a general device is used for mounting on the unit substrate. Because it can be used, mass production and equipment cost reduction effects are significant.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of an acceleration detector according to the present invention.

FIG. 2 is a structural diagram of a hole portion of the acceleration detector according to the present invention.

FIG. 3 is a diagram showing a second embodiment of the acceleration detector according to the present invention.

FIG. 4 is a diagram showing a third embodiment of the acceleration detector according to the present invention.

FIG. 5 is a diagram showing a first embodiment of a method for processing an acceleration detector according to the present invention.

FIG. 6 is a diagram showing a second embodiment of the method of processing the acceleration detector according to the present invention.

FIG. 7 is a diagram showing a fourth embodiment of the acceleration detector according to the present invention.

FIG. 8 is a diagram showing a fifth embodiment of the acceleration detector according to the present invention.

FIG. 9 is a diagram showing an embodiment of a mounting method of an acceleration detector according to the present invention.

FIG. 10 is a diagram showing an example of an acceleration sensor configuration according to the present invention.

FIG. 11 is a diagram showing an embodiment of an airbag system configuration according to the present invention.

[Explanation of symbols]

1a ... upper insulator, 1b ... lower insulator, 2 ... middle conductor, 3 ... weight, 4 ... elastic part, 5a ... lower electrode, 5b ... upper electrode, 6 ... conductive pillar, 7a, 7b ... impurity layer, 8a, 8b,
10a, 10b, 20 ... Conductor, 9a, 9b ... Hole part, 3
0 ... Electronic circuit section, 100 ... Acceleration detector, 110 ... Control IC section, 120 ... Board, 130 ... Conductive wire, 200 ... Control circuit section, 300 ... Acceleration sensor, 400 ... Control unit, 410 ... Diagnostic section, 420 ... Air Bag starter,
430 ... Fail-safe function part, 500 ... Air bag.

Front page continuation (72) Inventor Masayoshi Suzuki 2520 Takaba, Katsuta-shi, Ibaraki Hitachi, Ltd. Automotive Equipment Division (72) Inventor Norio Ichikawa 2477 Kashima Yatsu, Katsuta-shi, Ibaraki 3 Hitachi Automotive Engineering Co., Ltd. (72) Inventor Masahide Hayashi 2520 Takaba, Katsuta City, Ibaraki Prefecture Hitachi Automotive Systems Division, Hitachi Ltd.

Claims (11)

[Claims] 1. A middle conductor having a weight for detecting a mechanical quantity and an elastic portion for supporting the weight and having an impurity layer uniformly formed on a bonding surface, an upper insulator having a through hole, and a lower portion. In a mechanical sensor having an insulator, the middle conductor, the upper insulator, and the lower insulator are hermetically bonded to each other, and the conductor formed in the hole and the upper insulator is conducted from inside the sensor through the impurity layer of the middle conductor. A mechanical quantity sensor characterized by taking. 2. A middle conductor made of a P-type silicon single crystal having a weight for detecting a mechanical quantity and an elastic portion for supporting the weight, an upper insulator having a through hole, and a lower insulator. In the mechanical quantity sensor having, the middle conductor, the upper insulator, and the lower insulator are hermetically joined to each other, and conduction is established by the conductor formed in the hole and the upper insulator layer through the hole from inside the sensor. And a mechanical sensor. 3. A mechanical quantity sensor according to claim 1, wherein the middle conductor has a recess continuous with the hole formed in the upper insulator. 4. A mechanical quantity sensor according to claim 1, wherein the opening of the hole formed in the upper insulator is polished. 5. The method according to claim 1 or 2, wherein (1) a hole is formed in the upper insulator (2) the middle conductor and the upper insulator and the lower insulator are hermetically joined. A mechanical quantity sensor characterized by being formed by. 6. The method according to claim 3, wherein (1) the middle conductor is bonded to the upper insulator and the lower insulator in an airtight manner. (2) The hole of the upper insulator and the recess of the middle conductor are simultaneously processed. ) And (2), the mechanical quantity sensor characterized by the above-mentioned. 7. The method according to claim 4, wherein (1) a hole is formed in the upper insulator, (2) an opening of the hole in the upper insulator is polished, and (3) a middle conductor, an upper insulator and a lower portion. A mechanical quantity sensor characterized by being formed in the above (1) to (3) for hermetically bonding an insulator. 8. A mechanical quantity sensor according to claim 1, wherein the middle conductor has an electronic circuit section. 9. A mechanical quantity sensor according to claim 1, wherein the mechanical quantity sensor is connected to the control IC section by a conductive wire. 10. An acceleration sensor comprising the mechanical quantity sensor according to any one of claims 1 to 9 and a control circuit section, which is used for the purpose of measuring acceleration. 11. An airbag system comprising the mechanical quantity sensor according to any one of claims 1 to 10 and a control unit.