JPH09203748A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a processing circuit to be constructed of simple circuits without being affected by floating capacitance by forming a thin-film magnetic resistance element on the planar portion of a weight part, and providing upper and lower insulating substrates with an external magnetic substance used to apply a magnetic field to the element. SOLUTION: Upper and lower insulating substrates 2, 3 are bonded to the upper and lower surfaces of a silicon substrate 1 on which a weight part 4 and a beam part 9 are formed, and a thin-film magnetic resistance element 6 is formed on the planar portion of the weight part 4. An external magnetic substance 7 used to apply a magnetic field to the element 6 is secured to at least one of the substrates 2, 3. When external acceleration is applied, the weight part 4 is varied in its cross direction, i.e., vertical direction, and the element 6 formed on the planar portion also moves vertically. Therefore, the intensity of the magnetic field received from the external magnetic substance 7 is varied, and this intensity variation is detected as variation of the resistance value of the element 6 itself to calculate the acceleration. Hence a processing circuit can be constructed of simple circuits without being affected by floating capacitance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration sensor used for collision detection or attitude control of an automobile, and more particularly to a magnetic actuation type semiconductor acceleration sensor having a silicon diaphragm and a thin film magnetoresistive element. Regarding sensors.

[0002]

2. Description of the Related Art An example of such a conventional semiconductor acceleration sensor is shown in FIG.

The sensor chip of this semiconductor acceleration sensor includes a silicon substrate 1a having a movable electrode (weight portion) 4a and a beam portion 9a formed thereon, and an upper insulating substrate 2a above and below the silicon substrate 1a.
And the lower insulating substrate 3a are closely joined by means such as electrostatic joining.

Reference numerals 5a and 6a denote stepped portions, 9a denotes beam portions, and 8
Reference numerals 1a and 82a denote fixed electrodes.

The principle of detecting the applied acceleration is that the movable electrode (weight part) 4a is displaced by the acceleration, whereby the capacitance values of the upper and lower capacitor parts inside the sensor change, and this is converted into a circuit. (C-F converter etc.).

[0006]

However, in the above-mentioned conventional semiconductor acceleration sensor, since the sensor chip is of the electrostatic capacitance type, the movable electrode (weight part) and the fixed electrode part of the lead are taken out, for example, fixed. There is a problem in that the price of the sensor chip becomes expensive because it is necessary to take measures against the influence of stray capacitance, such as taking out through holes from the electrodes.

A CV converter circuit for converting the capacitance of the sensor chip into a voltage or the like is generally used on the dedicated IC circuit board, but this circuit is a circuit system including an oscillation circuit. However, there is also a problem that the circuit configuration is complicated and the price is expensive.

An object of the present invention is to provide a semiconductor acceleration sensor which is not affected by stray capacitance and can be realized by a simple circuit as a processing circuit. Therefore, the characteristics are stable and the price is low.

[0009]

In order to solve the above problems, the present invention is not affected by the stray capacitance, and the detection circuit method is simple, and the detection accuracy is good. As a cheap method, a silicon substrate (a weight part and a beam part are formed), a thin film magnetoresistive element formed on the surface of the weight part in the substrate, and an external magnetic element fixed on an insulating substrate. The present invention provides a magnetically actuated semiconductor acceleration sensor composed of a body (magnetic field generation source).

That is, according to the present invention, the upper insulating substrate and the lower insulating substrate are bonded to the upper and lower surfaces of the silicon substrate on which the weight portion and the beam portion are formed, respectively, and the flat portion of the weight portion of the silicon substrate is joined. A stripe-shaped thin film magnetoresistive element is formed, and an external magnetic body for applying a magnetic field to the thin film magnetoresistive element is provided on at least one of the upper insulating substrate and the lower insulating substrate. The semiconductor acceleration sensor having

Further, according to the present invention, in the upper insulating substrate and the lower insulating substrate, a predetermined step portion is provided on the flat surface on the side facing the weight portion,
A semiconductor acceleration sensor is obtained in which an external magnetic body for generating a magnetic field is fixed to a flat surface portion, a side surface portion, or any other portion of at least one of the upper insulating substrate and the lower insulating substrate.

Further, according to the present invention, the weight portion and the beam portion are formed by etching the silicon substrate on one side, and at least one side of the silicon substrate is flat, and the thin film magnetic layer is formed on the flat surface. A semiconductor acceleration sensor having a resistance element is obtained.

[0013]

When an external acceleration is applied, the weight portion of the silicon substrate is displaced in the thickness direction, that is, the vertical direction, and the thin film magnetoresistive element formed on the flat portion of the weight portion is also moved vertically. The strength of the magnetic field being received changes. The change in the magnetic field is detected as a change in the resistance value of the thin film magnetoresistive element itself to detect the acceleration.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A semiconductor acceleration sensor according to an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 and 2, the semiconductor acceleration sensor of this embodiment has a silicon substrate 1, on which a weight portion 4 and a beam portion 9 are formed. The upper insulating substrate 2 and the lower insulating substrate 3 are precisely joined to each other by means of electrostatic joining or the like.

A thin film magnetoresistive element 6 made of a material such as Fe-Ni is provided in a stripe shape on the plane portion of the weight portion 4, and the conductive lead portion 11 thereof has a silicon substrate 1
It is formed on one of the planes and is led to the external connection terminal 10. Here, the thin film magnetoresistive element 6 is contained in the plane of the weight portion 4 and does not straddle the beam portion 9.

When an external acceleration is applied, the weight portion 4
However, the thin-film magnetoresistive element 6 moves up and down in the thickness direction, and the thin-film magnetoresistive element 6 moves in the same manner.

In the upper insulating substrate 2 and the lower insulating substrate 3,
A predetermined step 51 is formed on the flat surface portion near the weight portion 4 in the vicinity thereof.
And 52 are provided (about 50 to 100 μm), and the weight portion 4 moves in the steps 51 and 52.

On the other hand, the upper insulating substrate 2 and the lower insulating substrate 3
An external magnetic body 7 as a magnetic source is fixed to the outer flat surface portion, the side surface portion, and any other location.

In the embodiment shown in FIGS. 1 and 2, the external magnetic body 7 is fixed to the outer flat surface portion of the upper insulating substrate 2. A magnetic flux is generated from the external magnetic body 7, and the magnetic flux is applied in a plane portion of the thin film magnetoresistive element 6 in a direction substantially orthogonal to the stripe longitudinal direction. In this way, applying the magnetic flux in the orthogonal direction is the most efficient arrangement in terms of the detection sensitivity of the magnetoresistive element 6. That is, the arrangement is such that the largest variation in resistance can be obtained.

In general, the thin film magnetoresistive element 6 has a characteristic that the resistance value shifts in the negative direction as the intensity of the applied magnetic flux increases. Therefore, in the arrangement of each component as shown in FIGS. 1 and 2, when the weight portion 4 is displaced upward, the intensity of the magnetic flux received by the thin film magnetoresistive element 6 changes in the increasing direction. Therefore, as is clear from the characteristic diagram of the resistance value of the thin film magnetoresistive element shown in FIG. 3 versus the applied magnetic field,
The resistance value of the element itself changes in the decreasing direction.

The thin film magnetoresistive element 6 is connected to a processing circuit (not shown) in the subsequent stage, and a discriminator circuit such as a comparator can output a detection output at a predetermined resistance value. Acceleration can be detected.

In the semiconductor acceleration sensor of the present embodiment, the displacement of the weight portion 4 is detected by the magnetic actuation type utilizing the thin film magnetoresistive element 6, so that unlike the conventional capacitance type semiconductor acceleration sensor, Little affected by stray capacitance.

Further, in the case of the semiconductor acceleration sensor of this embodiment, since the physical quantity to be detected is a change in resistance value, a relatively simple DC amplification circuit can be used and the processing circuit can be inexpensive.

[0025]

As described above, in the semiconductor acceleration sensor of the present invention, the displacement of the weight portion is detected by the magnetic actuation type utilizing the thin film magnetoresistive element. Unlike the one, it is hardly affected by the stray capacitance.

Further, since the physical quantity to be detected is a change in resistance value, a relatively simple DC amplification circuit can be used,
The processing circuit is inexpensive.

Therefore, according to the present invention, the characteristics are stable and hardly affected by the stray capacitance, and the processing circuit can be realized by a simple circuit. Therefore, the characteristics are stable.
A low-priced semiconductor acceleration sensor can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor acceleration sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the semiconductor acceleration sensor shown in FIG.

FIG. 3 is a diagram showing a resistance value-magnetic field strength characteristic of a magnetoresistive element.

FIG. 4 is a diagram showing an example of a conventional semiconductor acceleration sensor.

[Explanation of symbols]

1, 1a Silicon substrate 2, 2a Upper insulating substrate 3, 3a Lower insulating substrate 4 Weight portion 4a Movable electrode portion 5a, 6a, 51, 52 Step portion 6 Thin film magnetoresistive element 7 External magnetic body (magnetic field generation source) 9, 9a Beam part 10 External connection terminal 11 Conductive lead part 81a, 82a Fixed electrode

Claims (3)

[Claims] 1. An upper insulating substrate and a lower insulating substrate are respectively bonded to upper and lower surfaces of a silicon substrate on which a weight portion and a beam portion are formed, and a striped thin film magnetic film is formed on a flat portion of the weight portion of the silicon substrate. A semiconductor acceleration sensor, wherein a resistance element is formed, and an external magnetic body that applies a magnetic field to the thin film magnetoresistive element is provided on at least one of the upper insulating substrate and the lower insulating substrate. 2. The semiconductor acceleration sensor according to claim 1, wherein, in the upper insulating substrate and the lower insulating substrate, a predetermined step portion is provided on a flat surface on a side facing the weight portion, A semiconductor acceleration sensor, wherein an external magnetic body for generating a magnetic field is fixed to a flat surface portion, a side surface portion, or any other portion of at least one of the upper insulating substrate and the lower insulating substrate. 3. The semiconductor acceleration sensor according to claim 1, wherein the weight portion and the beam portion are formed by etching one side of the silicon substrate, and at least one side of the silicon substrate is flat. A semiconductor acceleration sensor, wherein the thin-film magnetoresistive element is formed on the.