JPH06167400A - Mechanical quantity sensor - Google Patents

Abstract

PURPOSE:To provide a mechanical quantity sensor which can be manufactured easily and can detect mechanical quantities simultaneously in the direction normal to a substrate and in the direction in parallel with the substrate. CONSTITUTION:A V-valley is made in a substrate 31 with electrodes 33, 35 being provided on the banks thereof and a beam structure 37 having profile corresponding to that of the V-valley is mounted on the substrate 31. Upon application of mechanical quantity from the outside, the beam structure 37 displaces regardless of the applying direction of mechanical quantity thus varying the capacitances between the beam structure 37 and the electrodes 33, 35. Magnitude of mechanical quantity can be determined basing on the variation of the capacitances.

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 more particularly to a mechanical quantity sensor for detecting a mechanical quantity such as an external force or acceleration and a suitable manufacturing method thereof.

[0002]

2. Description of the Related Art As a mechanical quantity sensor such as an acceleration sensor or an angular velocity sensor used in a machine tool or the like, a mechanical quantity sensor using a semiconductor as shown in FIG. The mechanical quantity sensor 10 has a structure in which a conductive beam-shaped structure 13 and a fixed electrode 15 are mounted on a substrate 11. The beam-shaped structure 13 is a rib-shaped structure having a plurality of arm portions 14, and the arm portion 1 located at the four corners of the plurality of arm portions 14
4 is supported on the substrate 11 by the support portion 17. On the other hand, the fixed electrode 15 is arranged so as to cross the arm 14 with the fingers.

Here, FIG. 6 is a cross-sectional view of the mechanical quantity sensor 10 shown in FIG. As shown in this FIG.
Since the arm portions 14 not located at the four corners are suspended on the substrate 11, they are displaced between the fixed electrodes 15. Therefore, when acceleration or the like is applied in the direction of the arrow in FIG. 5, the arm portion 14 suspended in the air is displaced in the direction of the arrow. When the arm portion 14 is displaced, the electrostatic capacitance between the arm portion 14 and the fixed electrode 15 changes. Therefore, by measuring the change in capacitance between the beam-shaped structure 13 and the fixed electrode 15, the magnitude of acceleration in the direction of the arrow in FIG. 5 can be detected. The detected change in capacitance is output as a signal to a detection circuit (not shown) via the metal wiring 19. As described above, in the mechanical quantity sensor of FIG. 5, the magnitude of the mechanical quantity such as acceleration can be obtained by detecting the change in the electrostatic capacitance between the beam-shaped structure 13 and the fixed electrode 15.

By the way, the mechanical quantity sensor 10 of the type as shown in FIG. 5 can detect the acceleration in the direction parallel to the substrate, but as a mechanical quantity sensor for detecting the acceleration in the direction perpendicular to the substrate. A mechanical quantity sensor 20 as shown in FIG. 7 can be considered. The mechanical quantity sensor 20 is constructed by forming a fixed electrode body 21 on a substrate 11 and a movable electrode body 23 facing the surface of the fixed electrode body 21 in the air. The movable electrode body 23 is supported on the substrate 11 by the support body 25. As shown in FIG. 8, which is a cross-sectional view, FIG.
In the mechanical quantity sensor 20, the movable conductor 23 is displaced in the vertical direction when acceleration acts in the vertical direction of the substrate 11, and the electrostatic capacitance between the movable conductor 23 and the fixed conductor 21 changes. Therefore, the acceleration in the vertical direction in FIG. 8 can be detected by causing the metal wiring 19 to output a signal from the change in the capacitance between them.

Since these mechanical quantity sensors have high accuracy and small temperature dependence, not only the acceleration sensor of a machine tool but also a force sensor used for measuring the weight of an object,
It can also be adopted as a pressure sensor for measuring the pressure of gas or liquid, an acceleration sensor used in automobiles, and the like.

[0006]

Here, in the conventional mechanical quantity sensor as described above, since the detection direction is structurally limited, the mechanical quantity in the horizontal direction and the mechanical quantity in the vertical direction are arranged on the substrate. There is a problem that a plurality of mechanical quantity sensors are required to detect both and at the same time.

Further, in the mechanical quantity sensor as described above, there is a problem that the processing method is difficult and it is difficult to improve the yield in manufacturing. That is,
In order to increase the sensitivity of the sensor, it is necessary to increase the capacitance of the detection part.Therefore, the distance between the beam-shaped structure and the fixed conductors should be reduced for that purpose, or the area of the opposite conductive parts A design to increase However, in order to implement such a design, it is necessary to make full use of a highly accurate photo-etching method and an advanced dry etching technique that requires precise control of etching conditions.
It becomes difficult to improve the yield.

The present invention has been made in view of the above problems, and an object thereof is to detect a mechanical quantity acting on a substrate from any direction and to easily manufacture it. It is to provide a quantity sensor.

[0009]

In order to solve the above problems, a mechanical quantity sensor according to the present invention comprises a substrate having an inclined surface and electrodes formed on the inclined surface, and a surface opposed to the inclined surface. A conductive beam-like structure that is displaced by a mechanical amount such as an external force, and detects the change in capacitance between the electrode and the beam-like structure to determine the mechanical amount as the beam-like structure. It is characterized in that it is detected as the amount of displacement of the body.

Further, in the method of manufacturing the mechanical quantity sensor as described above, the step of forming an inclined surface on the substrate, the step of forming an electrode on the inclined surface, and the electrode formed on the inclined surface. A step of forming a sacrificial layer on the substrate, a step of removing a part of the sacrificial layer to form a pattern corresponding to the beam-like structure, a step of forming a conductive layer on the pattern of the sacrificial layer, and a conductive layer And a step of forming a beam-like structure by removing a part of the above, and a step of removing the remaining sacrificial layer.

Further, the above-mentioned two mechanical quantity sensors are combined to form a mechanical quantity sensor assembly so that the detection directions form a predetermined angle with each other.

[0012]

In the mechanical quantity sensor of the present invention having the above configuration, when the beam-like structure is displaced by a mechanical quantity such as an external force or acceleration, the distance between the inclined surface of the substrate and the beam-like structure changes. Then, along with this, the capacitance between the electrode formed on the inclined surface and the beam-like structure changes. Then, it becomes possible to detect the mechanical quantity by detecting the change in the electrostatic capacitance. At that time, because the capacitance changes regardless of the direction of the mechanical quantity applied to the substrate, the mechanical quantity other than the direction orthogonal to the extension direction of the beam-shaped structure is detected. Therefore, the restriction on the detection direction is relaxed. Further, the electrostatic capacitance is a capacitance between the electrodes and the beam-shaped structure face-to-face, and can be set to be sufficiently large, so that the sensitivity of the sensor is improved.

Further, in the above-described method for manufacturing the mechanical quantity sensor, the sacrificial layer is formed on the substrate having the electrodes formed on the inclined surfaces, and the sacrificial layer is partially removed to correspond to the beam-like structure. A pattern is formed. Then, a conductive layer is formed on the pattern of the sacrificial layer, a part of the conductive layer is removed, and a beam-like structure is formed. Then, finally, all the sacrificial layers are removed. By such a method, it is possible to accurately and easily manufacture a beam-shaped structure which is opposed to the inclined surface at a predetermined distance and faces the surface.

Further, by combining two of the above mechanical quantity sensors so that the detection directions form a predetermined angle with each other to form a mechanical quantity sensor assembly, three-dimensional mechanical quantity detection having three detection directions becomes possible. Become.

[0015]

1 is a diagram showing the configuration of a mechanical quantity sensor according to a preferred embodiment of the present invention. The same components as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 1, the mechanical quantity sensor 30 according to the present embodiment has electrodes 33 and 35 formed on a slope formed by partially etching the surface of a silicon substrate 31 into a V shape. The beam-like structure 37 having an accordion shape is supported on the substrate 31 so as to face the slope. The beam-shaped structure 37 is provided on the substrate 31 by the support portion 39.
Supported above. In the embodiment, the electrodes 33 and 35 are formed by diffusing boron in the n-type silicon substrate 31. Electrode 33 or electrode 35 and beam-like structure 37
The change in the capacitance during the period is transmitted to the detection circuit 43 (not shown) by the metal wiring 41.

Here, FIG. 2 is a sectional view of the mechanical quantity sensor 30 shown in FIG. In the mechanical quantity sensor 30 according to the present embodiment, as shown in FIG. 2A, when the beam-shaped structure 37 is laterally displaced in the direction of the electrode 35 parallel to the surface of the substrate 31, The capacitance between the beam-shaped structure 37 and the electrode 33 increases as the beam-shaped structure 37 and the electrode 33 approach each other. On the contrary, the capacitance between the beam-like structure 37 and the electrode 35 is reduced. On the other hand, in the opposite direction, the beam-shaped structure 3
When 7 is displaced to the side of the electrode 33 (FIG. 2B), the change in capacitance is reversed, and the capacitance between the beam-like structure 37 and the electrode 35 increases, resulting in a beam-like structure. The capacitance between the body 37 and the electrode 33 is reduced. Further, as shown in FIG. 2C, when the beam-shaped structure 37 is displaced in the vertical direction,
The capacitance of the electrodes 33 and 35 decreases or increases at the same time. That is, in the mechanical quantity sensor 30 of the present embodiment, the capacitance becomes differential in the case of lateral displacement and becomes in-phase in the case of vertical displacement, and therefore reliability is improved by processing with a differential circuit or the like. It is possible to obtain a detection signal of high.

FIG. 3 shows a mechanical quantity sensor 30 shown in FIG.
Mechanical quantity sensor assembly 4 formed by combining two
It is a block diagram which shows the structure of 0. The mechanical quantity sensor assembly 40 has a configuration in which two mechanical quantity sensors 30a and 30b are two-dimensionally arranged such that the directions of the beam-shaped structures 37 are orthogonal to each other. If the extension direction of the beam-like structure 37 of the mechanical quantity sensor 30a is X, and that of the mechanical quantity sensor 30b is Y, and the direction orthogonal to both the X and Y directions is the Z direction, the mechanical quantity sensor 30a is The mechanical quantity sensor 30b detects the mechanical quantity in the Z direction, and detects the mechanical quantity in the Y direction and the Z direction. According to such a mechanical quantity sensor assembly 40, it is possible to detect mechanical quantities in all directions of the X direction, the Y direction, and the Z direction.

Next, FIG. 4 is a view for explaining the manufacturing process when manufacturing the mechanical quantity sensor shown in FIG. As shown in FIG. 4, the mechanical quantity sensor 30 according to the present embodiment.
Is the V-type on the n-type single crystal silicon substrate 31 (FIG. 3A).
Etching is performed so as to form the V-shaped valley 42 (FIG. 4B). The etching at this time is performed by, for example, a method of etching with an alkaline etching solution using the thermal oxide film as a mask. Next, boron is diffused to form the electrodes 33 and 35 (FIG. 4C). At this time, boron, which is an impurity, is also diffused into the supporting portion 36 of the beam-shaped structure 37. Further, the sacrificial layer 43 is formed on the substrate 31 on which the electrodes are formed (FIG. 4D). At this time,
The sacrificial layer 43 of the supporting portion 36 is removed by etching. PSG (phosphosilicate glass) is suitable as a constituent component of the sacrificial layer 43. Next, on the sacrificial layer 43, a conductive layer 4 made of polycrystalline silicon having conductivity is used.
5 is formed. At this time, since the sacrificial layer 43 of the supporting portion 36 has been removed, a part of the conductive layer 45 is immersed in the supporting portion 36 (FIG. 4E). Then, a part of the conductive layer 45 is removed to form the beam-shaped structure 37, and finally, the sacrifice layer 43 is removed by wet etching to configure the mechanical quantity sensor 30 of the present embodiment (see FIG. Four
(F)).

By such a method, the mechanical quantity sensor 30 according to the present embodiment can be constructed without using a high degree of dry etching or a highly accurate photographic etching method. A circuit can be formed together with the mechanical quantity sensor 30 on the silicon substrate 31.

Here, in this embodiment, a V-shaped valley 42 is formed.
Although two capacitors are provided to increase the capacitance, this number may be set as necessary in consideration of layout restrictions and target sensitivity. In addition, in the present embodiment, in order to form the inclined portion, a method of removing a part of the surface by etching to form the V-shaped valley 42 is used. However, for example, a mountain is formed to form the inclined portion. For example, even if the inclined portion is formed by another method, the same effect as that of the present embodiment can be achieved.

Further, although the silicon substrate is used as the substrate in this embodiment, a material such as ceramic may be used for the substrate. In that case, it is necessary to form a valley or the like on the ceramic substrate. Further, in this embodiment, in order to form the electrodes 33 and 35 on the substrate 31,
Although the impurities are diffused in the substrate 31, the electrodes may be formed using a conductor such as a metal within a process-possible range. In this respect, the same applies to the beam-shaped structure 37 and the like, and not limited to polycrystalline silicon, a conductor such as metal may be adopted.

It is also possible to detect the change in the resonance frequency by using the beam-like structure 37 as a vibrating body.

[0023]

As described above, in the mechanical quantity sensor according to the present invention, the electrode is formed on the inclined surface of the substrate and the beam-like structure is made to face this, so that a single mechanical quantity is obtained. The sensor can simultaneously detect the mechanical quantities in the vertical and parallel directions of the substrate. Further, since it is not necessary to use a high degree of dry etching or a highly accurate photo-etching method at the time of manufacturing, the manufacturing is simple and the yield can be improved. Then, the two-dimensional arrangement can eliminate the insensitive direction of the mechanical quantity.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a mechanical quantity sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the mechanical quantity sensor of FIG.

FIG. 3 is a layout view showing a configuration of a mechanical quantity sensor assembly according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a manufacturing process of the mechanical quantity sensor according to the embodiment.

FIG. 5 is a configuration diagram showing a configuration of a conventional mechanical quantity sensor using a semiconductor.

6 is a cross-sectional view of the mechanical quantity sensor of FIG.

FIG. 7 is a diagram showing another configuration of a conventional mechanical quantity sensor.

8 is a sectional view of the mechanical quantity sensor shown in FIG. 7. FIG.

[Explanation of symbols]

 30 mechanical quantity sensor 31 substrate 33, 35 electrode 37 beam structure 40 mechanical quantity sensor assembly

Claims (3)

[Claims] 1. A substrate having an inclined surface and an electrode formed on the inclined surface; and a conductive beam-like structure that faces the inclined surface and is displaced by a mechanical amount such as an external force. A mechanical quantity sensor that detects a mechanical quantity as a displacement quantity of the beam-like structure by detecting a change in capacitance between the electrode and the beam-like structure. 2. A step of forming an inclined surface on a substrate, a step of forming an electrode on the inclined surface, a step of forming a sacrificial layer on a substrate having an electrode formed on the inclined surface, and a sacrificial layer. Part of the conductive layer is removed to form a pattern corresponding to the beam-like structure, a conductive layer is formed on the sacrificial layer pattern, and a part of the conductive layer is removed to form the beam-like structure. 2. The method for manufacturing a mechanical quantity sensor according to claim 1, further comprising: a step of removing the remaining sacrificial layer. 3. A mechanical quantity sensor assembly formed by combining two mechanical quantity sensors according to claim 1 so that detection directions form a predetermined angle with each other.