JP3355916B2 - Micro G switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro G switch for use in various safety devices, and more particularly to a micro G switch used for an airbag system of an automobile.

[0002]

2. Description of the Related Art Conventionally, as this type of G switch (ie, acceleration switch), a mechanical G switch described in JP-A-6-43181 or TRANSDUCERS '87, pp410 has been proposed.
A micro G switch manufactured by microfabrication of a silicon plate described in U.S.-413 is known.

[0003]

The mechanical G switch has a problem that it is large in size and has no self-diagnosis function. Although the size of the micro G switch is small, there is also a problem that it does not have a self-diagnosis function. In addition, both could only detect acceleration in one direction. In particular, the latter type has the following other problems. A small acceleration (that is, G) could not be detected, and the sensitivity was low. It is easy to feel the acceleration of the component orthogonal to the acceleration in the direction to be detected, that is, the sensitivity to the other axis is large. The production yield was poor and there was no mass productivity. After the switch was turned on in response to the pulsed acceleration, this on state could not be maintained for a long time. In addition, when the switch is turned on and the acceleration becomes zero due to the problem of welding of the switch section, the reliability is lacking such that the switch can be shifted to the off state by itself.

An object of the present invention is to provide a high performance and high reliability micro G switch which is small in size and suitable for mass production.

[0005]

The object of the present invention is to provide silicon
Beam and movable mass obtained by fine processing, the movable mass
A movable contact provided on a part of the semiconductor, and a semiconductive member opposed to the movable contact
Fixed contact provided on the body substrate, formed on the semiconductor substrate
A MOS switch, and the fixed contact is connected to the MOS switch.
It is electrically connected to the switch gate electrode.
This is achieved by a micro G switch. Also,
The purpose of the above is to obtain a beam obtained by micromachining silicon.
A movable mass is provided on a semiconductor substrate so as to face the movable mass.
Fixed electrode, MOS switch formed on the semiconductor substrate
Wherein the fixed electrode is a gate of the MOS switch.
A microphone electrically connected to an electrode
This is achieved by the G switch.

[0006]

DETAILED DESCRIPTION OF THE INVENTION Next will be described in more detail with reference to examples or be resolved, as in the previous issue Gad. By forming a micro G switch by finely processing a silicon plate, the size of the G switch is reduced. The size of the control module for the airbag system can be reduced by integrating the micro G switch unit and the power element unit on the same silicon plate so that they can be mounted together with the crash sensor in the same package. By providing movable contacts on both sides of the movable mass supported by the beam and fixed contacts opposed to the movable contacts, it is possible to detect two-directional component accelerations (+ direction acceleration and-direction acceleration). By locating the center of gravity of the movable mass on the center axis of the beam, the sensitivity of the other axis can be made zero. By setting the thickness and width of the movable mass to be sufficiently larger than those of the beam, the sensitivity of the micro G switch is increased, and a small acceleration can be detected. A very small acceleration can be detected by forming a MOS switch on the silicon plate, making the conductor electrically connected to the gate of the MOS switch facing the movable mass, and controlling the potential of the gate according to the acceleration. I made it possible. Prevents welding between the movable electrode and the fixed electrode by forming a function in the silicon plate to limit the current flowing through the switch to a certain value or less, or by configuring the movable contact and the fixed contact with a high melting point metal material A highly reliable G switch can be obtained. Is the G switch operable by providing an electrode for self-diagnosis facing the movable mass and displacing the movable mass with electrostatic force? Is not it? Enabled self-diagnosis. By finely processing the thickness and width of the movable mass and the beam with high precision, the magnitude of the acceleration to be detected can be kept within a certain narrow area, and the yield in manufacturing can be improved. By providing an electrode for pre-biasing and by the value of the voltage applied to this electrode, the magnitude of the acceleration at which the movable mass starts to be displaced can be adjusted to a constant value, and the production yield can be further increased. . It is possible to optimize the damping amount of the movable mass and the beam system by providing an air circulation groove or an air circulation hole in the movable mass, or arranging the second movable mass and the beam between the movable mass and the beam. That is, the state where the switch is on can be maintained for a long time even after the acceleration becomes zero. In addition, by providing a function for maintaining the ON state of the MOS switch for a long time in the silicon plate, the state where the switch is on can be similarly maintained for a long time even after the acceleration becomes zero.

Next, an embodiment of a micro G switch according to the present invention is shown in FIG. The micro G switch is composed of a laminated body of a glass plate 1, a silicon plate 2, and a glass plate 3, and forms a beam 4 and a movable mass 5 by finely processing the silicon plate 2 by etching. The movable mass 5 is supported by the beam 4, and a movable contact 14 is provided on a part of the movable mass 5.
The fixed contact 1 is provided on the bottom of the glass plate 1 so as to face the movable contact 14.
5 are arranged. The fixed contact 15 is electrically connected to the upper surface of the glass plate 1 via a wiring lead 12 formed on the bottom surface of the glass plate 1, a three-dimensional pillar 13 made of silicon, and a wiring lead 9 formed on the inner surface of a through hole 7 formed on the glass plate 1. Drawn to. Here, the three-dimensional column 13 is a columnar member obtained by etching the silicon plate 2, is mechanically separated from the frame 16, and is electrically insulated from the movable mass 5. Similarly, the movable contact 14 is electrically connected to the upper surface of the glass plate 1 via the movable mass 5, the beam 4, the frame 16 of the silicon plate 2, and the wiring lead 8 formed on the inner surface of the through hole 6 formed in the glass plate 1. Has been drawn out. When an acceleration of a component perpendicular to the surface of the movable mass 5 acts, the movable mass 5 supported by the beam 4 is displaced to bring the movable contact 14 and the fixed contact 15 into contact. As a result, both contacts are electrically connected, and the magnitude of the acceleration acting on the micro G switch can be detected. As shown in the figure, the beam 4 is formed on the center of gravity of the movable mass 5, and a micro G switch having extremely low sensitivity to other axes can be obtained. By setting the thickness of the beam 4 to a sufficiently small value relative to the thickness of the movable mass 5, the movable contact 14 can contact the fixed contact 15 with a small acceleration. That is, a highly sensitive micro G switch can be obtained. Further, by finely processing the thickness and width of the movable mass 5 and the beam 4 by etching with high precision, the magnitude of the acceleration to be detected can be held within a certain narrow area, and the micro G switch is manufactured. The yield of time can be improved. The laminate composed of the glass plate 1, the silicon plate 2 and the glass plate 3 is obtained by bonding the glass plate 1 and the glass plate 3 to both surfaces of the silicon plate 2 by well-known anodic bonding. At this time, the dimensions of the gap 17 between the movable mass 5 and the glass plate 1 and the gap 18 between the movable mass 5 and the glass plate 3 are as small as about several microns. The movable mass 5 is attracted to either the glass plate 1 or the glass plate 3 by the electrostatic force due to the voltage, and adheres to the glass plate. To prevent this, metal thin films 10 and 11 electrically connected to the silicon plate 2 are formed on the surface of the glass plate facing the movable mass 5 by sputtering, vapor deposition, or the like. The potential difference between the glass plate 1 and the glass plate 3 was made zero to prevent the electrostatic force from acting.

FIG. 2 shows another embodiment of the micro G switch according to the present invention. From this figure, the same elements as those in FIG. 1 are denoted by the same reference numerals. In addition, numbers that are not used for elements that are not used in the description are omitted. This drawing shows an embodiment in which the surface of the movable mass 5 is deeply etched to increase the size of the gaps 17, 18 between the movable mass 5 and the upper and lower glass plates. By doing so, the electrostatic force generated between the movable mass 5 and the upper and lower glass plates at the time of anodic bonding can be reduced, so that the metal thin films 10 and 11 as shown in FIG. 1 become unnecessary. Instead, the movable contact 14 is replaced with a minute projection 19 on the surface of the movable mass 5.
Is provided. In addition, a micro G switch capable of detecting acceleration components in two positive and negative directions can be provided by arranging a movable contact below the movable mass 5 and a fixed contact opposite to the movable contact on a lower glass plate.

Another embodiment of the micro G switch according to the present invention is shown in FIG. This figure is an example in which an electrode 22 for pre-bias is provided on the lower glass plate 3 so as to face the surface of the movable mass 5 having no movable contact. The pre-bias electrode 22 is connected to the glass plate via a wiring lead portion 23 provided around the three-dimensional column 13, a three-dimensional column 25, and a wiring lead portion 21 provided on the inner surface of the through hole 20 formed in the glass plate 1. 1 is electrically drawn to the upper surface. On the surface of the movable mass 5, an insulator protrusion 24 made of a thermal oxide film of silicon or the like is formed. The movable mass 5 is drawn toward the glass plate 3 so that the insulator protrusion 24 of the movable mass 5 comes into contact with the electrode 22 by the electrostatic force generated by the voltage applied to the electrode 22. The size of the gap 18 between the movable mass 5 and the electrode 22 is uniquely determined by the height of the projection 24 of the insulator. By adjusting the magnitude of the voltage applied to the pre-bias electrode 22 from the outside of the micro G switch via the lead part 21, the magnitude of the force that pulls the movable mass 5 toward the electrode 22 can be freely controlled. . As a result, the magnitude of the acceleration when the movable mass 5 separates from the electrode 22, that is, the magnitude of the acceleration when the movable contact and the fixed contact of the micro G switch come into contact (on state) can be accurately determined. A micro G switch with a high yield can be provided.

FIG. 4 shows another embodiment of the micro G switch according to the present invention. An electrode 26 for self-diagnosis is formed on the upper glass plate 1 facing the movable mass 5. Electrode 26
Is a wiring lead 2 provided so as to bypass the three-dimensional column 13
7, through the three-dimensional pillars 25 and the lead portions 21 provided on the inner surface of the through holes 20 formed in the glass plate 1,
Is electrically pulled out to the upper surface of the. Electrode 2 for self-diagnosis from the outside of the micro G switch through the lead portion 21
6 by applying a voltage to the movable mass 5 by electrostatic force.
To the electrode 26 side to bring the movable contact and the fixed contact of the micro G switch into contact (on state). As described above, is the state where the micro G switch can be actually operated by providing the self-diagnosis electrode 26 facing the movable mass 5 and displacing the movable mass 5 by electrostatic force? Is not it? Can actively self-diagnose.
For example, it is also possible to actively detect that dust or the like exists in the gap 17 and is inoperable.

Another embodiment of the micro G switch according to the present invention is shown in FIG. This figure is a schematic plan view of two silicon plates in the micro G switch shown in FIG. The movable mass 5 is supported by two beams 4, and a movable contact 14 is provided at the tip and center of the movable mass 5. The three-dimensional columns 13 and 25 are arranged as shown in the figure, and are mechanically separated from the frame 16 of the silicon plate 2 and are electrically insulated.
It should be noted that FIG. 4 which is a cross section of the micro G switch is schematically shown, and the positions of the three-dimensional columns 13 and 25 are different between FIGS. 4 and 5. The wiring lead portions below the through holes 6, 7, and 20 in the previous figure are 8, 9, and 21, respectively, and are formed by forming a thin metal film on the surface of a silicon member by sputtering or vapor deposition. When the micro G switch is particularly required to have responsiveness, a groove having a depth of several microns to several tens of microns as indicated by 28 may be formed on the surface of the movable mass 5 by etching. This is an air flow groove for improving the fluidity of air in the gap between the glass plate and the silicon plate and controlling the amount of air damping in this portion. It is possible to optimize the damping amount of the movable mass 5 and the beam 4 system, to improve the response of the micro G switch, or to keep the switch on for a long time even after the acceleration becomes zero. Can be done.

FIG. 6 shows an example of a mounting method of the micro G switch according to the present invention. This figure shows an example of a method for mounting a micro G switch on a control module for an airbag system of an automobile. Micro G
A method in which the lead portions 8 and 9 of the switch 200 are mechanically joined to conductive pad portions (not shown in the drawing!) On the surface of the module 31 by solder layers 29 and 30 and electrically connected. is there. Thus, by mounting the micro G switch directly on the module 31, the size of the control module for the airbag system can be reduced. FIG. 7 shows another embodiment of the micro G switch according to the present invention. This figure shows a micro G switch obtained by etching a sacrifice layer on an SOI substrate. Silicon plate 34 (substrate for element formation), thermal oxide film 33, silicon plate 3
This is a method in which a movable portion 44 composed of a movable mass and a beam is formed on the silicon plate 32 by silicon etching of the silicon plate 34 of the SOI substrate 2 (support substrate) and sacrificial layer etching of the thermal oxide film 33. Note that the SOI substrate is obtained by directly bonding an element formation substrate to a support substrate via a thermal oxide film and then polishing the element formation substrate on the upper surface to a desired thickness. The micro G switch is electrically connected to an external signal processing circuit and the like via lead portions 41, 42 and 43 wired in through holes 38, 39 and 40 formed in the glass plate 1 bonded on the silicon plate 34. Connected. Here, the wiring lead portions 42 and 43 are electrically connected to three-dimensional pillars 36 and 37 of silicon which are electrically insulated from the frame portion 35 of the silicon plate 34, respectively.
Further, as the SOI substrate, a substrate obtained by epitaxially growing polycrystalline silicon as an element formation substrate on a surface of a support substrate on which a thermal oxide film is formed may be used.

FIG. 8 is a schematic plan view of the silicon plate 34 in the micro G switch shown in FIG. The movable part 44 shown in the previous figure is a movable mass 4 supported by three beams 45.
6. Movable contacts 46, 49a are provided at the center portions on both sides of the movable mass 46, and fixed contacts 48, 49a are opposed thereto.
48a are arranged. The fixed contacts 48 and 48a are fixed to the fixed portions 47 and 5 which are integrated with the three-dimensional pillars 36 and 37, respectively.
0 is formed as shown in the figure. Here, the three-dimensional pillars 36 and 37 of the silicon are respectively
And are electrically insulated. The micro G switch shown in the figure detects the acceleration of a component parallel to the surface of the silicon substrate 34 and makes the movable contact 49 and the fixed contact 48 contact or the movable contact 49a and the fixed contact 48a. If the acceleration in the direction in which the movable contact 49 contacts the fixed contact 48 is defined as a positive direction, the acceleration in the direction in which the movable contact 49a contacts the fixed contact 48a is a negative direction. Thus, a micro G switch capable of detecting acceleration components in two directions, positive and negative, can be realized. Note that the wiring lead portions 41, 4
The movable contact and the fixed contact of the micro G switch section are electrically connected to an external signal processing circuit and the like via 2 and 43.

Another embodiment of the micro G switch according to the present invention is shown in FIG. This example differs from the switch shown in FIG. 7 in the method of drawing out the movable part and the lead. As in the case shown in FIG. 7, silicon etching of the silicon plate 34 of the SOI substrate including the silicon plate 34 (element forming substrate), the thermal oxide film 33, and the silicon plate 32 (support substrate) and the thermal oxide film 33 are performed. A movable portion 53 composed of a movable mass and a beam is formed on the silicon plate 32 by etching the portion with a sacrificial layer. A cap 51 made of glass, silicon, or the like is joined on the silicon plate 34 so as to seal the space 52 above the movable portion 53. The movable contact and the fixed contact provided in the space 52 are electrically connected to a pad 54 provided on the silicon plate 34 via a wiring lead 55 provided below the cap 51. The contact of the switch is connected via a pad 54 to a signal processing circuit outside the micro G switch.

FIG. 10 is a schematic plan view showing the vicinity of the movable portion 53 in the micro G switch shown in FIG. The movable part 53 in the previous figure is a movable mass 57 supported by two beams 56.
Consists of The beam 56 has a fixed end 64 and is firmly fixed on the thermal oxide film 33 shown in the previous figure. The movable mass 57 has a comb shape having convex portions 58 and 59.
Movable contacts 62, 62a are provided on the convex portion 58, and fixed contacts 61, 61a are arranged to face the movable contacts. The fixed contacts 61 and 61a are formed on the protrusions 60 of the fixed portion 63 fixed on the thermal oxide film. The micro G switch shown in this figure can detect positive and negative acceleration components parallel to the surface of the silicon plate 34 and orthogonal to the two beams 56. It should be noted that the wiring lead portions 55 and the pads 54 are not shown in this drawing.

FIG. 11 shows an example in which the micro G switch according to the present invention is applied to an integrated ignition device for an airbag system of an automobile. The micro G switch 65 has a resistor 6
6 and connected in series with the power supply Vs. This resistor 66 limits the current flowing through the micro G switch 65 to a certain value or less. As a result, a highly reliable micro G switch can be obtained because welding does not occur due to heat generation between the movable contact and the fixed contact. The resistor 66 may be formed by diffusion on the silicon plate described above, or may be provided by the elongated beam itself. PMOS switch 6 for power supply Vs, resistor 66 and micro G switch 65
7, a capacitor 68 and an NMOS power element 69 are connected as shown in the figure. A power element 71 and an inflator 74 are connected in series with the power element 69, and resistors 72 and 73 are connected in parallel with each power element. The resistors 72 and 73 allow a small current to flow through these portions to self-diagnose the operation state of the inflator 74. Now, when the acceleration exceeds a predetermined value, the micro G switch 65 detects this, and the movable contact and the fixed contact are turned on. Then, the potential at the point A decreases and the switch 6
7 is turned on, and then the potential at the point B increases to turn the power element 69 on. At this time, when the automobile causes a collision accident and the microcomputer 70 processes an output signal from a crash sensor (not shown) and detects the signal, the power element 71 is turned on. When the power elements 69 and 71 are simultaneously turned on, the inflator 74 ignites and activates the airbag to protect the occupant. It is not easy for the micro G switch to keep the switch on for a long time even after the acceleration becomes zero. In this case, even after the micro G switch 65 is turned off by the capacitor 68, the power element 69 can be substantially turned on. That is, even after the acceleration becomes zero, the state where the micro G switch 65 is apparently on can be maintained for a certain period. By doing so, the reliability of the airbag system can be improved.

FIG. 12 shows a mounting method of an integrated ignition device using the micro G switch according to the present invention. A micro G switch 65 on a substrate 75 such as ceramics,
A signal processing circuit 78 including a power element 69 and a resistor 66, a switch 67, a capacitor 68, and the like shown in FIG. A cap 77 is joined to the upper part of the substrate 75 to hermetically seal a space 76 in which the micro G switch 65 and the like are stored. This integrated ignition device is electrically connected to an external power supply and an inflator via pads 79 and 80 provided on a substrate 75. As a result, it is possible to provide a high-performance and highly reliable integrated ignition device that is small in size and suitable for mass production.

Another embodiment of the micro G switch according to the present invention is shown in FIG. This figure is an embodiment in which a second movable mass and a beam are arranged between the movable mass and the beam. That is,
The second movable mass 81 and the second beam 83 are provided between the movable masses 82 supported by the beam 4. After the acceleration is applied and the movable contact 14 formed on the surface of the movable mass 82 is turned on, the beams 4 and 83 are further deformed, and the entire surface of the movable mass 81 is brought into contact with the lower surface of the glass plate 1 soon. Due to the surface of the movable mass 81 and the damping effect of itself,
The state in which the movable contact is on can be maintained for a long time even after the acceleration becomes zero.

Another embodiment of the micro G switch according to the present invention is shown in FIG. This figure shows a micro G switch in which the gate electrode of a MOS switch is made movable and a composite micro G switch in which a power element portion is integrated on the same silicon plate. An n + region is formed by diffusion or ion implantation on the surface of the p-type silicon plate 84 passivated by the thermal oxide films 150 and 151 to form the source and drain portions of the power element and the micro G switch. And
86, 87 and 88 are a source electrode, a drain electrode and a gate electrode of the power element portion, respectively. 89, 9
Reference numerals 0 and 91 denote a source electrode, a drain electrode, and a gate electrode of the micro G switch unit, respectively. The value of the current flowing through the power element is several to several tens of amperes, whereas the value of the current flowing through the micro G switch is negligibly small. The gate electrode 91 of the micro G switch unit is a movable mass supported by the beam 92. The beam 92 is firmly fixed on the thermal oxide film 150 at its end 152. When an acceleration perpendicular to the surface of the silicon plate 84 acts, the size of the space 153 between the gate electrode 91 and the thermal oxide film 150 decreases. When the dimension value of the gap 153 becomes equal to or smaller than a predetermined value, the portion between the source electrode 89 and the drain electrode 90 of the micro G switch is turned on. Then, as described with reference to FIG. 11, the portion between the source electrode 86 and the drain electrode 87 of the power element portion can be turned on. The micro G switch section and the power element section are hermetically housed in a space 94 by a cap 85 joined to an upper portion of a silicon plate 84.
The composite micro G switch is electrically connected to an external signal processing circuit via a pad 93 formed on a silicon plate 84. As a result, a high performance and high reliability micro G switch having a small size, suitable for mass production, and high performance can be realized.

Another embodiment of the composite micro G switch according to the present invention is shown in FIG. The micro G switch of this embodiment has a structure in which a mechanical switch section and an electronic MOS switch section are separated. On the thermal oxide film 150 of the silicon plate 84, a movable mass 98 supported by a beam 99 firmly fixed at the end portion 100 is formed by a sacrificial layer etching technique. The mechanical switch section includes a movable mass 98 supported by the beam 99, a movable contact 97 formed on the movable mass 98, and a fixed contact 96 arranged to face the movable contact 97. The electronic MOS switch section includes a source electrode 89, a drain electrode 90, and a gate electrode 95. The gate electrode 95 and the fixed contact 96 are formed by the thermal oxide film 15.
When the composite micro G switch receives acceleration and the movable contact 97 and the fixed contact 96 come into contact with each other, the potential of the gate electrode 95 increases to turn on the MOS switch unit. As described above, a high voltage is previously supplied to the movable mass 98 from the power supply via the beam 99. When the movable contact 97 and the fixed contact 96 come into contact with each other, the MOS switch is turned on to operate the power element section. As described above, by forming the MOS switch on the silicon plate 84 and electrically connecting the gate electrode 95 of the MOS switch and the fixed contact 96, the current flowing through the mechanical switch unit is limited to a small value. Can be. By forming a function in the silicon plate to limit the current flowing through the switch to a certain value or less, or by forming the movable contact and the fixed contact with a high melting point metal material, the welding between the movable electrode and the fixed electrode is completely completed. And a highly reliable composite micro G switch can be obtained. Further, even after the acceleration becomes zero, the function of maintaining the ON state of the MOS switch for a long time can be easily integrated on the silicon plate 84.

Another embodiment of the composite micro G switch according to the present invention is shown in FIG. The micro G switch of the present embodiment also has a structure in which a mechanical switch section and an electronic MOS switch section are separated. A fixed electrode 101 is arranged so as to face the surface of the movable mass 98 supported by the beam 99, and the fixed electrode 101 and the gate electrode 95 of the MOS switch portion are electrically indirectly or directly connected on the thermal oxide film 150 or the like. Connection. The size of the gap 154 between the movable mass 98 and the fixed electrode 101 changes according to the acceleration acting on the micro G switch, and the capacitance of the gap 154 changes. Then, when acceleration acts on the micro G switch, the potential of the gate electrode 95 rises and the MOS switch is turned on. As described above, the MOS switch is formed on the silicon plate, and the conductor (fixed electrode) electrically connected to the gate electrode of the MOS switch is opposed to the movable mass, so that the potential of the gate electrode is changed according to the acceleration. Changes and the MOS switch is turned on.
A highly sensitive combined micro-G switch that operates at very low acceleration is obtained. The region diffused into the silicon plate 84 in opposition to the movable mass 98 may be used as a fixed electrode.

FIG. 17 shows a mounting method of the composite micro G switch according to the present invention. In this embodiment, the composite micro G switch 102 (described with reference to FIGS. 14 to 16) in which the micro G switch unit and the power element unit are integrated on the same silicon plate can be mounted together with the crash sensor 103 in the same package. It is like that. The composite micro G switch 102 and the crash sensor 103 are bonded to the ceramic substrate 113 with adhesives 104 and 105. Next, the structure of the crash sensor 103 will be briefly described. It has a structure in which silicon plates 106, 107 and 108 are laminated in layers via insulators 109 and 110 such as thermal oxide films, and a movable mass 111 internally supported by a beam is formed by fine processing. The acceleration at the time of a crash is detected in an analog manner from the change in the capacitance between the movable mass 111 and the silicon plates 106 and 108 arranged above and below. Cap 11 on ceramic substrate 113
2 are bonded with an adhesive 114 to hermetically seal the periphery of the switch and the sensor. Then, it is surface-mounted on the module substrate 115 of the airbag system via the conductive layer 116 of the ceramic substrate 113 using the solder layer 117. By being able to be mounted together with the crash sensor in the same package, the size of the control module for the airbag system can be reduced.

Another embodiment of the composite micro G switch according to the present invention is shown in FIG. In this embodiment, the silicon plate 8
4. The crash sensor 121 is integrated with the composite micro G switch 102 described with reference to FIGS. A void 118 is formed below the movable mass 120 by etching the thermal oxide film 150 of the SOI substrate by a sacrifice layer. The fixed end 119 of the beam (not shown in the figure) supporting the movable mass 120 is firmly fixed on the thermal oxide film 150. This is a crash sensor that detects an acceleration at the time of a crash in an analog manner from a change in capacitance between the movable mass 120 and the silicon plate 84. By integrating the composite micro G switch together with the crash sensor on the same silicon plate, the size of the control module for the airbag system can be further reduced.

[0024]

As described above, according to the present invention, a micro G which is small in size, suitable for mass production, and has high performance and high reliability.
Switch is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a micro G switch according to the present invention.

FIG. 2 is a diagram showing another embodiment of the micro G switch according to the present invention.

FIG. 3 is a diagram showing another embodiment of the micro G switch according to the present invention.

FIG. 4 is a diagram showing another embodiment of the micro G switch according to the present invention.

FIG. 5 is a diagram showing another embodiment of the micro G switch according to the present invention.

FIG. 6 is a diagram showing a mounting method of a micro G switch according to the present invention.

FIG. 7 is a diagram showing another embodiment of the micro G switch according to the present invention.

FIG. 8 is a diagram showing a schematic plan view of the micro G switch shown in the preceding figure.

FIG. 9 is a diagram showing another embodiment of the micro G switch according to the present invention.

FIG. 10 is a schematic plan view of a movable portion of the micro G switch shown in the previous figure.

FIG. 11 is a diagram showing an example of application to an integrated ignition device according to the present invention.

FIG. 12 is a diagram showing a mounting method of the integrated ignition device according to the present invention.

FIG. 13 is a diagram showing another embodiment of the micro G switch according to the present invention.

FIG. 14 is a diagram showing an embodiment of a composite micro G switch according to the present invention.

FIG. 15 is a diagram showing another embodiment of the composite micro G switch according to the present invention.

FIG. 16 is a diagram showing another embodiment of the composite micro G switch according to the present invention.

FIG. 17 is a diagram showing a mounting method of the composite micro G switch according to the present invention.

FIG. 18 is a diagram showing another embodiment of the composite micro G switch according to the present invention.

[Explanation of symbols]

1,3 ... glass plate, 2,32,34,84,106,1
07,108 ... silicon plate, 4,45,56,83,9
2,99 ... beam, 5,46,57,81,82,9
8, 111, 120 ... movable mass, 6, 7, 20, 38,
39,40 ... through-hole, 8,9,12,21,2
3, 27, 41, 42, 43, 55 ... wiring lead portion, 1
0, 11: metal thin film, 13, 25, 36, 37: solid pillar, 14, 49, 49a, 62, 62a, 97: movable contact, 15, 48, 48a, 61, 61a, 96: fixed contact, 16, 35 ... frame part, 17, 18, 118, 153
154: void, 19: minute projection, 22, 26: electrode,
24 ... Insulator protrusion, 28 ... Air flow groove, 29,30,
117: solder layer, 31: module, 33, 109, 1
10, 150, 151: thermal oxide film, 44, 53: movable part, 47, 50, 63: fixed part, 51, 77, 85, 1
12 ... cap, 52, 76, 94 ... space, 54, 7
9, 80, 93 ... pad, 58, 59 ... convex part, 60 ... protruding part, 64, 119 ... fixed end, 66 ... resistance, 65, 20
0: micro G switch, 66, 72, 73: resistor, 6
7 switch, 68 capacitor, 69, 71 power element, 70 microcomputer, 74 inflator, 75, 115 substrate, 78 signal processing circuit, 86,
89 ... source electrode, 87, 90 ... drain electrode, 88,
91, 95 ... gate electrode, 101 ... fixed electrode, 102 ...
Composite micro G switch, 103: crash sensor, 104, 105, 114: adhesive, 113: ceramic substrate, 116: conductive layer, 152: end.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Terumi Nakazawa 2520 Ojiko-ba, Hitachinaka-shi, Ibaraki Pref. Hitachi, Ltd. Automotive Equipment Division JP-A-5-273230 (JP, A) JP-A-5-10969 (JP, A) JP-A-7-263712 (JP, A) JP-A-6-308152 (JP, A) A) JP-A-6-222075 (JP, A) JP-A-6-34654 (JP, A) JP-A-7-245417 (JP, A) JP-A-6-37187 (JP, A) JP-A-6 -5582 (JP, A) JP-A-4-249727 (JP, A) JP-A-9-145740 (JP, A) JP-A-4-25764 (JP, A) JP-A-5-180866 (JP, A) ) JP-A-7-234244 (JP, A) WO 95/27216 (WO, A ) C. Robinson, D .; Overman, R .; Warner, T .; Blo mquist, Problems En countered In the D evelopment of a Mi croscale g-switch Using Three Design Approaches, TRANSD UCERS'87,410-413 (58) investigated the field (Int.Cl. ^7, DB name) G01P 15/00 -15/135 G01P 21/00

Claims (6)

(57) [Claims] 1. A beam and a movable mass obtained by finely processing silicon, a movable contact provided on a part of the movable mass, a fixed contact provided on a semiconductor substrate facing the movable contact, A micro G switch comprising a formed MOS switch, wherein the fixed contact is electrically connected to a gate electrode of the MOS switch. 2. A beam obtained by finely processing silicon, a movable mass, a fixed electrode provided on a semiconductor substrate facing the movable mass, and a MOS switch formed on the semiconductor substrate, wherein the fixed electrode is A micro G switch electrically connected to a gate electrode of a MOS switch. 3. A micro G switch according to claim 1 , wherein the micro G switch is hermetically mounted together with a semiconductor crash sensor in a ceramic package. Micro G switch in any one of claims 4] according to claim 1, characterized by being integrated on semiconductor type crash sensor co to the same silicon plate. 5. In any of claims 1, 2, micro G switch, characterized in that integrated in the semiconductor type crash sensor and power elements co to the same silicon plate. 6. The micro G according to claim 1 , wherein
A switch, and crash sensors, on the basis the air bag, and an output of the crash sensor and the micro-G switch, an air bag system that includes a inflation regulator for beating the air bag.