JP3944509B2 - Tilt sensor - Google Patents

Description

  The present invention relates to a tilt sensor that accurately measures the tilt of a processing apparatus that performs wafer processing and precise processing in a semiconductor factory, for example.

  There are tilt sensors that use a laser and those that measure the amount of displacement of the mass point, and those that measure the amount of displacement of the mass point have a simple structure and are often used for small ones.

Examples of such a technique include those disclosed in Patent Document 1 and Patent Document 2.
Patent Publication No. 160097 JP 2002-243757 A

  The one disclosed in Patent Document 1 suppresses gyro drift, and is provided with a piezoelectric element on each surface of a triangular prism-like vibration body 14.

  However, the device described in Patent Document 1 detects the vibration of the triangular prism-shaped vibration body 14 with a piezoelectric element, and the triangular column-shaped vibration body 14 is not greatly displaced by a very small acceleration. It is difficult to detect with an element and is not suitable for detecting the direction of minute gravitational acceleration.

  In addition, what is disclosed in Patent Document 2 uses a piezoelectric element in which stress applied by acceleration is opposite to each other, and increases the sensitivity by detecting a phase difference of an oscillation circuit including the piezoelectric element.

However, there is no idea of increasing the sensitivity of the element itself. For this reason, there is a problem that it is difficult to detect an extremely small change in the direction of acceleration and use it in, for example, an inclinometer.
The present invention is a kind of such a tilt sensor, and provides a sensor that has extremely high detection sensitivity and can be easily mass-produced. In addition, the present invention provides an extremely sensitive tilt sensor using such a tilt sensor.

  In order to solve the above-described problems, the present invention has a displacement portion that is displaced with respect to the fixed portion, and the displacement portion is displaced due to a change in the direction of gravitational acceleration. The displacement amount of the displacement part was measured by the change in capacitance.

  Since the tilt sensor according to the present invention is configured as described above, increasing the mass of the transition portion can be easily adapted to increase sensitivity. Further, the spring constant of the narrow portion can be reduced, and this can also increase the sensitivity.

  When the fixed portion, the displacement portion, and the narrow portion are integrally formed, for example, by etching a crystal plate or the like, each of the above portions can be configured at a time, and productivity can be improved.

  Furthermore, when three fixed parts, a displacement part, and a narrow part are integrally formed using a trigonal crystal, it is possible to easily obtain a point-symmetrical position that is exactly 120 degrees apart. Can do. Alternatively, when four fixed parts, a displacement part, and a narrow part are integrally formed using a cubic crystal, it is possible to easily obtain a point-symmetrical position that is shifted by 90 degrees. Can do.

  The invention according to claim 1 of the present invention has a displacement portion that is displaced with respect to the fixed portion, and the displacement portion is displaced by gravitational acceleration, and the electrostatic capacitance between the fixed portion and the displacement portion associated therewith is changed. Since the displacement amount of the displacement portion is measured by the change, the displacement portion is displaced by a slight acceleration, and the displacement can be detected by a change in the gravitational acceleration direction between the fixed portion and the displacement portion.

Embodiments of the tilt sensor of the present invention will be described in detail below with reference to the drawings. The tilt sensor of the present invention basically has the structure shown in FIG. That is, the fixed portion 2 and the displacement portion 3 are formed by etching the substrate 1 such as quartz.
The fixed portion 2 and the displacement portion 3 are connected by a narrow portion 4, and the narrow portion 4 is also formed by etching the single substrate 1 together with the fixed portion 2 and the displacement portion 3. Accordingly, when acceleration is applied to the fixed portion 2 and the displacement portion 3, the narrow portion 4 is bent by the mass of the displacement portion 3, and the lower end of the displacement portion 3 swings in the direction of the arrow in FIG.

  A plurality of grooves 5 are formed at the lower end of the displacement portion 3, and a comb-like facing portion 6 inserted into the groove 5 is formed in the fixed portion 2. Further, as shown in FIG. 2, a displacement electrode 7 is formed on the side surface of the groove 5, and a fixed electrode 8 facing the displacement electrode 7 is formed on the side surface of the facing portion 6.

  As shown in FIGS. 1 and 2, conductive thin films 9 and 10 are connected to the displacement electrode 7 and the fixed electrode 8, respectively, and connection terminals 11 and 12 are provided to the conductive thin films 9 and 10, respectively.

  In the tilt sensor of the first embodiment, when gravitational acceleration is applied, the narrow portion 4 is curved and the lower end of the displacement portion 3 is displaced in any of the arrow directions in FIG. As a result, the distance between the displacement electrode 7 and the fixed electrode 8 changes, and the capacitance between them changes. By detecting this change in capacitance, the displacement amount of the displacement electrode 7 can be detected, and the inclination angle applied to the inclination sensor can be detected by the mass of the displacement portion 3 and the spring constant of the narrow portion 4. it can.

  Next, a second embodiment of the present invention will be described. In the second embodiment, the narrow portion 4 is formed long as shown in FIG. Further, five sets of grooves 5 and comb-like facing portions 6 are formed. Displacement electrode 7 and fixed electrode 8 similar to those shown in FIG. 2 are formed in groove 5 and facing portion 6, and conductive thin films 9 and 10 are connected to displacement electrode 7 and fixed electrode 8. 9 and 10 are provided with connection terminals 11 and 12, respectively.

  As a result, as shown in FIG. 4, five capacitors constituted by the displacement electrode 7 and the fixed electrode 8 are connected in parallel, and the parallel circuit of this capacitor is connected to the outside by the connection terminals 11 and 12.

  Since the narrow portion 4 is formed long and the number of the displacement electrodes 7 and the fixed electrodes 8 is large in the second embodiment, the sensitivity can be significantly improved as compared with the first embodiment. In the second embodiment, five sets of grooves 5 and comb-like facing portions 6 are formed, but the number may be further increased.

Next, as shown in FIG. 6 , a description will be given of a third embodiment in which two detectors 14 and 15 are formed on a single crystal substrate 13 so as to be rotated by 90 degrees each other.

  For example, when a cubic crystal substrate such as silicon is used and the two detection units 14 and 15 are formed by etching, each detection unit can be formed at the position of a point object that is accurately rotated 90 degrees. Here, each detection part 14 and 15 is the shape shown in FIG. 3, respectively.

  In the third embodiment, each of the detection units 14 and 15 is accurately shifted by 90 degrees, and the direction of gravity acceleration from the direction perpendicular to the surface of the substrate 13, that is, the inclination angle, is from which direction. Even if it exists, it is possible to detect the direction and size.

Next, a description will be given of the fourth embodiment in which a single substrate 16 made of quartz two detection portions 17 and 18 are formed such that the relationship displaced 120 degrees from one another as shown in FIG.

  Quartz constitutes a trigonal crystal. For this reason, when the detection parts 17 and 18 are made by etching, the respective detection parts 17 and 18 are made at the position of the point object that is accurately rotated by 120 degrees. Here, each of the detection units 17 and 18 has the shape shown in FIG.

  In the fourth embodiment, each of the detection units 17 and 18 is accurately deviated by 120 degrees, and the direction of gravity acceleration from the direction perpendicular to the surface of the substrate 16, that is, the inclination angle, is from which direction. Even if it exists, it is possible to detect the direction and size.

  Furthermore, a sensor with higher performance can be configured by disposing the three detectors 17, 18, and 19 with an accurate displacement of 120 degrees as in the fourth embodiment.

  The third embodiment described above has two detectors 14 and 15 that are accurately shifted by 90 degrees, and the fourth embodiment has two or three detectors 17, 18, and that are accurately shifted by 120 degrees. 19. Therefore, in both the third embodiment and the fourth embodiment, it is possible to know from which direction the direction of the gravitational acceleration is applied from the data of the respective detection units.

  Therefore, the inclination angle can be known from the magnitude and direction of the gravitational acceleration. For this reason, a precise inclination sensor can be obtained by applying the inclination sensor of the present invention.

  Furthermore, Example 5 which is a structural example for implement | achieving a highly accurate sensor is shown in FIG. In addition to the electrodes 7-1 and 8-1 constituting the first capacitance similar to those in FIG. 2, electrodes 7-2 and 8-2 constituting the second capacitance are provided. When the displacement portion is displaced in the direction of the arrow by acceleration, the first capacitance increases and the second capacitance decreases. By detecting the acceleration from the result of subtracting the second capacitance from the first capacitance, a sensor that is stable and accurate with respect to disturbances other than temperature and acceleration to be detected can be realized.

  Further, FIG. 8 shows the configuration of the sixth embodiment that facilitates the manufacture of the sensor that detects acceleration from the difference between the two sets of capacitances and provides an inexpensive sensor. In FIG. 7, it is necessary to separate the electrodes 7-1 and 7-2, and 8-1 and 8-2, but high-level manufacturing technology is required for separating the electrodes in a fine structure. The FIG. 8 illustrates a configuration in which it is not necessary to separate electrodes in a fine portion.

  The 1st electrostatic capacitance part comprised by the displacement part electrode 9-1 and the fixed part electrode 10-1, and the 2nd electrostatic capacity part comprised by the displacement part electrode 9-2 and the fixed part electrode 10-2 Consists of. In the first capacitance portion, the gap of 5-1-2 is sufficiently larger than the gap of 5-1-1. Therefore, the first capacitance is substantially 5-1-1. Determined by the gap. Therefore, it is not necessary to separate the electrode of the displacement part, and it is not necessary to separate the electrode of the fixed part. Similarly, since the gap of 5-2-2 is sufficiently larger than that of 5-2-1, the second capacitance is determined by the gap of 5-2-1. 9-1 and 9-2, and 10-1 and 10-2 are separated at a portion that is not a fine portion.

  When the displacement portion is displaced in the direction of the arrow due to acceleration, the first capacitance increases and the second capacitance decreases. The acceleration can be detected from the result of subtracting the second capacitance from the first capacitance.

  By adopting such a configuration, it is not necessary to separate the electrodes at fine portions, so that manufacture is facilitated and an inexpensive sensor can be provided.

  The present invention provides a highly sensitive tilt sensor that is excellent in mass productivity and can be mass-produced using a semiconductor manufacturing process.

It is a front view which shows Example 1 of the inclination sensor of this invention. It is an enlarged front view which shows a part of inclination sensor of this invention. It is a front view which shows Example 2 of the inclination sensor of this invention. It is a circuit diagram which shows the equivalent circuit of the inclination sensor of this invention. It is a front view which shows Example 3 of the inclination sensor of this invention. It is a front view which shows Example 4 of the inclination sensor of this invention. It is an enlarged front view which shows Example 5 of the inclination sensor of this invention. It is an enlarged front view which shows Example 6 of the inclination sensor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Fixed part 3 Displacement part 4 Narrow part 5 Groove 6 Opposing part 7 Displacement electrode 8 Fixed electrode 9, 10 Conductive thin film 11, 12 Connection terminal 13 Substrate 14, 15 Detection part 16 Substrate 17, 18, 19 Detection part

Claims (13)

A displacement portion that is displaced with respect to the fixed portion, the fixed portion is provided with a plurality of fixed portion electrodes, the displacement portion is provided with a plurality of displacement portion electrodes, and each of the fixed portion electrode and the displacement portion electrode They are positioned alternately and face each other, and the displacement part is displaced by gravitational acceleration, and the displacement of the displacement part is measured by the change in capacitance between the fixed part electrode and the displacement part electrode. In the first electrostatic capacitance section in which the odd-numbered displacement electrodes are composed of the odd-numbered fixed electrodes, the other gap is sufficiently larger than the one gap, and the even-numbered displacement electrodes are even-numbered. In the second capacitance portion configured with the second fixed electrode, one gap is sufficiently larger than the other gap, and the displacement of the displacement portion is changed from the capacitance of the first capacitance portion. so as to obtain the result of subtracting the volume of the second capacitance section, Tilt sensors as the displacement amount of substantially displacing portion electrode is determined by the capacitance variation due to substantially smaller clearance by Les. The tilt sensor according to claim 1, wherein the displacement portion is coupled to the fixed portion by a narrow portion. The inclination sensor according to claim 2, wherein the fixed portion, the displacement portion, and the narrow portion are each integrally formed. 4. The tilt sensor according to claim 3, wherein the fixed portion, the displacement portion, and the narrow portion are integrally formed from a single crystal plate. The inclination sensor according to claim 4, wherein the plurality of inclination sensors having the fixed portion, the displacement portion, and the narrow portion are arranged so as to have an angle of 90 degrees with each other. The tilt sensor according to claim 4, wherein the crystal plate is formed of a trigonal crystal. The tilt sensor according to claim 6, wherein the crystal plate is formed of α crystal. The inclination sensor according to claim 6 or 7, wherein two or three inclination sensors each having a fixed portion, a displacement portion, and a narrow portion are arranged so as to have an angle of 120 degrees with respect to each other. The tilt sensor according to claim 4, wherein the crystal plate is formed of a cubic crystal. 10. The tilt acceleration sensor according to claim 9, wherein the crystal plate is made of silicon crystal. The inclination sensor according to claim 3, further comprising a metal electrode at a portion where the fixed portion and the displacement portion are opposed to each other. The tilt sensor according to claim 9, wherein a metal electrode is provided on the X plane of the crystal. The inclination according to claim 4, wherein the acceleration is measured from a difference between the capacitance portion on the side where the displacement is increased by the acceleration and the capacitance is increased by the acceleration and the capacitance on the side where the capacitance is decreased by the acceleration. Sensor.

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