JP2013024701A - Position sensor, measuring system, and plane stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the displacement of an object to be measured with a simple structure using electrostatic capacitance.SOLUTION: The present invention provides a position sensor 100 for measuring the position of a moving stage. The position sensor 100 comprises: first movable electrodes 131 partially inserted between a first pair of fixed opposite electrodes 111 and 121; second movable electrodes 132 partially inserted between a second pair of fixed opposite electrodes 112 and 122; and third movable electrodes 133 partially inserted between a third pair of fixed opposite electrodes 113 and 123. The first opposite electrodes are disposed in a position shifted in a first direction with respect to the second opposite electrodes, and the third opposite electrodes are disposed in a position shifted in a second direction with respect to the first opposite electrodes.

Description

  The present invention relates to a capacitance type position sensor, and more particularly to a position sensor for a planar stage that utilizes a change in capacitance caused by a change in the facing area of electrodes.

  An XY stage is used as a positioning device such as an industrial robot or a semiconductor manufacturing device. The XY stage includes a planar linear motor that drives the moving stage in the X-axis (left and right) direction and the Y-axis (vertical) direction, and a position sensor that measures the position of the moving stage. As the position sensor, for example, an optical system (for example, Patent Document 1) using an optical sensor such as a laser length measuring device is widely used. However, the optical method requires a plurality of expensive optical sensors, and the optical sensors have to be arranged outside the movable range of the moving stage, which has been a factor in increasing the size. On the other hand, as a position sensor, a capacitive sensor has also been proposed (Patent Document 2). In Patent Document 2, the rotation angle θ about the axis in the direction perpendicular to the X axis, the Y axis, and the XY plane is based on each capacitance change caused by the variation in the facing area between the moving electrode and the plurality of fixed electrodes. A position sensor capable of measuring the above has been proposed.

JP 2006-194672 A JP 2005-168154 A

  However, it is difficult for a position sensor that measures the position based on the capacitance to detect a minute movement of the moving stage based on a change in the facing area. This is because it is difficult to increase the SN ratio because the change in capacitance due to the movement of the moving stage is small.

  The present invention was created in order to solve at least a part of the above-described conventional problems, and an object of the present invention is to provide a technique for measuring the displacement of a measurement target with a simple configuration using capacitance. And

  Hereinafter, effective means for solving the above-described problems will be described while showing effects and the like as necessary.

  Means 1. In a planar stage having a fixed part and a moving stage that moves relative to the fixed part in a plane, the position sensor measures the position of the moving stage, and is connected to the fixed part, A fixed electrode portion having a first fixed counter electrode pair, a second fixed counter electrode pair, and a third fixed counter electrode pair facing each other at an interval; and connected to the moving stage; A first movable electrode partially inserted between the fixed counter electrode pair, a second movable electrode partially inserted between the second fixed counter electrode pair, and the third A movable electrode portion having a third movable electrode partially inserted between the fixed counter electrode pair, wherein the first fixed counter electrode pair extends in the first direction. Counter electrode, and the second fixed counter electrode pair is formed on the first side. And the third fixed counter electrode pair has a third counter electrode extending in a second direction intersecting the first direction, and The first counter electrode has a first capacitance that changes according to an insertion state of the first movable electrode, and the second counter electrode is in an insertion state of the second movable electrode. The third counter electrode has a third capacitance that changes according to an insertion state of the third movable electrode, and the third counter electrode has a second capacitance that changes in accordance with an insertion state of the third movable electrode. The counter electrode is disposed at a position shifted in the first direction with respect to the second counter electrode, and the third counter electrode is shifted in the second direction with respect to the first counter electrode. Position sensor that is placed at the position.

  The position sensor of the means 1 has a first counter electrode extending in a first direction and a second counter electrode extending in parallel thereto, which are shifted in the first direction relative to each other. Since they are arranged at the positions, the electrostatic capacity changes in the opposite directions due to the rotation of the moving stage. The rotation angle of the moving stage can be detected as a difference in capacitance between the first counter electrode and the second counter electrode by using the change in capacitance in the reverse direction. On the other hand, the translational movement of the moving stage in the second direction can be detected by canceling the influence of the rotational movement as the sum of the first counter electrode and the second counter electrode. The translational movement of the moving stage in the first direction can be detected by correcting the influence of the rotational movement on the change in the capacitance of the third counter electrode.

  The change in capacitance changes according to the state of insertion of the movable electrodes (first and second movable electrodes) into the fixed counter electrodes (first and second counter electrodes). According to the present inventor, the capacitance changes in accordance with a change in the relative positional relationship in the plane of the fixed counter electrode and the movable electrode (for example, in the XY plane), while being perpendicular to the plane ( It has been found that there is no change in principle depending on the change in the positional relationship in the Z-axis direction). This finding shows that in the region where the movable electrode is inserted, the distance obtained by subtracting the thickness of the movable electrode from the distance between the fixed counter electrodes is equivalent to the distance between the counter electrodes which is a determinant of the capacitance of the fixed counter electrode. It is based on the point.

  Accordingly, the present inventor only needs to make the parallelism (uniformity of the gap) between the fixed counter electrodes and the parallelism (thickness uniformity) of the movable electrodes highly accurate. It was found that it does not depend on errors. As a result, the trade-off problem between the measurable displacement amount and the tolerance for assembly of the counter electrode is solved.

  Mean 2. The position sensor according to means 1, wherein the first counter electrode is a comb-like electrode in which a first comb-like electrode group, which is a plurality of electrode elements extending in parallel with each other, is connected to each other. And the second counter electrode includes a comb-like electrode to which a second comb electrode group, which is a plurality of electrode elements extending in parallel with each other, is connected to each other, and the third counter electrode The counter electrode includes a comb-like electrode in which a third comb electrode group, which is a plurality of electrode elements extending in parallel with each other, is connected to each other.

  In the position sensor of the means 2, each of the first to third counter electrodes has a comb-like electrode in which a plurality of comb-teeth electrode groups that are parallel to each other are connected to each other. Therefore, it is possible to increase the change in capacitance with the movement of the moving stage. Thereby, the detection accuracy with respect to the minute movement of the moving stage can be improved.

  Means 3. The position sensor according to means 1 or 2, wherein the fixed electrode portion includes a fourth counter electrode connected to the fixed portion and facing each other at the predetermined interval, and the movable electrode portion Is a position sensor having a fourth movable electrode connected to the moving stage and entirely inserted between the fourth counter electrodes within a range of movement set in advance on the moving stage.

  Since the position sensor of the means 3 has the fourth movable electrode that is entirely inserted between the fourth fixed counter electrode pair within the range of movement set in advance on the moving stage, it is set in advance on the moving stage. Thus, a correction capacitor whose capacitance does not change due to the movement being performed is provided. The correction capacitor can be used for applications in which detection accuracy is increased by compensating for a change in capacitance caused by an environmental change such as temperature.

  Means 4. The position sensor according to means 1 or 2, wherein the fixed electrode portion includes a fifth counter electrode connected to the fixed portion and facing each other at the predetermined interval, and the movable electrode portion Is a position sensor having a fifth movable electrode connected to the moving stage and having a region facing the entirety of the fifth counter electrode within a range of movement set in advance on the moving stage.

  The position sensor of the means 4 has a fifth movable electrode having a region facing the whole of the fifth fixed counter electrode within the range of movement set in advance on the moving stage. In some movements, a correction capacitor whose capacitance does not change is provided. The correction capacitor can be used for applications in which detection accuracy is increased by compensating for a change in capacitance caused by an environmental change such as temperature.

  Means 5. The position sensor according to any one of means 1 to 4, wherein the first direction intersects the second direction substantially perpendicularly.

  In the position sensor of the means 5, since the first direction intersects the second direction substantially perpendicularly, the displacement in the first direction and the displacement in the second direction can be separated and directly detected. .

  Means 6. A measuring system for measuring a position of the moving stage in a flat stage having a fixed portion and a moving stage that moves relative to the fixed portion in a plane, and is any one of means 1 to 5. A first capacitance of the first counter electrode, a second capacitance of the second counter electrode, and a third capacitance of the third counter electrode. A displacement in the second direction is measured based on a capacitance detection unit to be detected and the sum of the first capacitance and the second capacitance, and the first capacitance and the second capacitance are measured. A measurement system comprising: a measurement unit that measures a rotation angle of the movable stage based on a difference in capacitance and measures a displacement in the first direction based on the third capacitance and the difference.

  In the means 6, the present invention is embodied as a measurement system that effectively uses the position sensor described in any one of the means 1 to 5.

  Mean 7 A planar stage, a movable stage that moves relative to the stationary part in a plane; a measurement system according to means 6; and the movable stage in the plane based on the measurement value. A planar stage comprising: a planar linear motor for driving.

  In the means 7, the present invention is embodied as a planar stage that effectively uses the measurement system described in the means 6.

  Means 8. The stage according to claim 7, wherein the planar linear motor supports the movement stage in a direction perpendicular to the plane to allow movement in the plane without contact with the fixed portion. A flat stage equipped with.

  The means 8 includes an air bearing that allows movement in a plane by a plane linear motor supporting the movement stage in a direction perpendicular to the plane, so that the movement stage is supported in a non-contact manner and has little hysteresis. Can be easily realized. Since the air bearing is lifted by air pressure, the design is facilitated by allowing the height and inclination of the moving stage in the Z-axis direction when floating. Each of the above-described means does not affect the position detection accuracy due to an assembly error between the fixed counter electrode and the fixed electrode, and therefore, preferable characteristics of the air bearing can be effectively used.

  The present invention can be realized not only in the form of a position sensor, a measurement system, and a planar stage, but also in the form of a measurement method, a computer program for realizing the measurement system, and a recording medium for storing the program.

Sectional drawing which shows the cross section of the plane stage 10 in embodiment of this invention. The top view of the fixed counter electrode plate 120 in embodiment of this invention. The top view of the movable electrode 130 in embodiment of this invention. Explanatory drawing which shows the structure of the electrode pattern in embodiment of this invention. Explanatory drawing showing the schematic diagram and calculation formula which show the measurement principle in embodiment of this invention. The schematic diagram which shows a mode that the displacement and rotation angle (theta) of the Y-axis direction in embodiment of this invention are measured. The schematic diagram which shows a mode that the displacement of the X-axis direction in embodiment of this invention is detected. The graph which shows the electrostatic capacitance of the comb-tooth electrodes 113 and 123 for measuring the displacement of the X-axis direction in embodiment of this invention.

In the present embodiment, a planar stage including a position sensor that measures translational movement in the X-axis direction and Y-axis direction of the moving stage and a rotation angle θ is embodied. Hereinafter, embodiments embodying the present invention will be described in the following order.
A. Planar stage configuration:
B. Measuring method of moving stage:
C. Variations:

A. Planar stage configuration:
FIG. 1 is a cross-sectional view showing a cross section of a planar stage 10 in an embodiment of the present invention. The planar stage 10 is a device for finely adjusting the position and orientation of a workpiece when handling a wafer (not shown) as a workpiece. The flat stage 10 includes a fixed part 200 fixed to a manufacturing facility (not shown) and a movable part 30 that moves relative to the fixed part 200. The fixed part 200 and the movable part 30 both have a square shape in plan view (XY plane). The fixed part 200 is configured with a larger outer dimension than the movable part 30.

  The fixing part 200 includes a rectangular tube-shaped square tube part 210 that is hollow inside, a square bottom part 220 that constitutes the bottom of the square tube part 210, and a hole that is a through hole formed in the square bottom part 220. 230, a stator unit 240 constituting a stator of the electromagnetic linear motor, a levitation unit 250, and a position sensor 100. On the other hand, the movable portion 30 is a prismatic chuck base 31 for mounting a wafer chuck (not shown) for attracting a workpiece such as a semiconductor wafer, a cylindrical stepped shaft portion 32, and a movable electromagnetic linear motor. And a mover unit 33 constituting a child.

  The stator unit 240 has a base portion 241 formed of a magnetic material. The base portion 241 has a plurality of cylindrical magnetic core portions 244a, 244b and the like protruding as part of the base portion 241. Ring coils 242a, 242b and the like are mounted on the outer sides of the plurality of magnetic core portions 244a and 244b, respectively. Magnet portions 243a, 243b, etc., which are permanent magnets, are mounted on the end sides of the plurality of magnetic core portions 244a, 244b, etc. The plurality of magnetic core portions 244a and 244b and the like can drive the movable portion 30 in the XY plane by operating a current flowing through the coils 242a and 242b and the like. The magnet parts 243a, 243b, etc. fulfill the function of attracting and lifting the movable part 30 in the Z-axis direction.

  The mover unit 33 includes magnetic projections 34a, 34b and the like facing the Z axis direction on the plurality of magnetic core portions 244a, 244b and the like. Since the protrusions 34a, 34b, etc. are magnetic, they are attracted in the Z-axis direction by the magnets 243a, 243b, etc., and are driven in the XY plane by a magnetic field generated by the coils 242a, 242b, etc.

  The levitation unit 250 is an air for moving the movable part 30 attracted by the magnet parts 243a, 243b and the like downward by a minute amount from the fixed part 200 to realize a smooth movement of the movable part 30 in the XY plane. It is a bearing. The levitation unit 250 ejects compressed air from the porous member 252 to form an air layer with the chuck base 31, thereby separating the movable part 30 from the fixed part 200 downward. The compressed air is supplied to the porous member 252 through three annular air flow paths 253, 254, 255 formed in the floating unit main body 251.

  Thus, the movable part 30 can be in a non-contact state separated from the fixed part 200 by the attraction force of the magnet parts 243a, 243b and the like and the aerodynamic force by the levitation unit 250, and can realize minute driving with low hysteresis. .

  The position sensor 100 is a sensor for measuring the translational displacement and the rotation angle θ of the movable part 30 with respect to the fixed part 200. The position sensor 100 includes a movable electrode 130 attached to the movable part 30 and a fixed electrode part attached to the fixed part 200. The fixed electrode section includes a pair of fixed counter electrode plates 110 and 120 having a square outer shape in plan view, an additional electrode plate 160, a first separation member 140, and a second separation member 150. The movable electrode 130 is also referred to as a movable electrode portion.

  The pair of fixed counter electrode plates 110 and 120 and the additional electrode plate 160 have a square outer shape in plan view (XY plane). A part of the movable electrode 130 is inserted between a pair of fixed counter electrode plates 110 and 120, and the outer shape of the square is slightly smaller than the fixed counter electrode plates 110 and 120 and the additional electrode plate 160 (plan view of the XY plane). )have. The first separation member 140 is a member for ensuring a separation distance between the pair of fixed counter electrode plates 110 and 120. The second separation member 150 is a member for ensuring a separation distance between the fixed counter electrode plate 110 and the additional electrode plate 160.

  The additional electrode plate 160 is fixed to the square tube portion 210 of the fixed portion 200 by abutting against a flat surface 211 formed in the lumen portion of the square tube portion 210. The fixed counter electrode plate 110 is fixed to the additional electrode plate 160 with a predetermined separation interval being secured via the second separation member 150. The fixed counter electrode plate 120 is fixed to the fixed counter electrode plate 110 with a predetermined separation interval being secured via the first separation member 140. The levitation unit 250 is fixed to the square tube portion 210 via the fixed counter electrode plate 120.

  With such a configuration, the pair of fixed counter electrode plates 110 and 120 move relative to the movable electrode 130 in the XY plane in accordance with the movement of the movable unit 30 with respect to the fixed unit 200.

  A grounded shield electrode is formed on the upper surface of the additional electrode plate 160 and the lower surface of the fixed counter electrode plate 120, respectively. Thereby, the position sensor 100 can implement | achieve a highly accurate measurement, suppressing the influence from an external electric field or a magnetic field. On the other hand, a pair of counter electrodes (not shown) for forming a correction capacitor are formed on the lower surface of the additional electrode plate 160 and the upper surface of the fixed counter electrode plate 110.

  The correction capacitor is a capacitor whose capacitance does not change due to the movement of the movable unit 30 set in advance. The correction capacitor can be used for applications in which detection accuracy is increased by compensating for a change in capacitance caused by an environmental change such as temperature.

  FIG. 2 is a plan view (upper surface) of the fixed counter electrode plate 120 according to the embodiment of the present invention. FIG. 3 is a plan view (upper surface) of the movable electrode 130 in the embodiment of the present invention. On the fixed counter electrode plate 120, an electrode pattern having three comb-tooth electrodes 121 to 123 and a correction counter electrode plate 114 is formed on the surface. On the lower surface of the fixed counter electrode plate 110, an electrode pattern having a shape facing the electrode pattern of the fixed counter electrode plate 120 is formed. Thereby, the counter electrode pattern shown by FIG. 2 by planar view can be comprised.

  As described above, the correction capacitor is formed on the pair of fixed counter electrode plates 110 and 120 without using the above-described additional electrode plate 160 as shown in FIGS. You may make it comprise using the electrode plate 114. FIG. Specifically, for example, the correction counter electrode plate 114 is formed by the pair of fixed counter electrode plates 110 and 120, while the correction counter electrode plate 114 is within the range of movement set in advance by the movable unit 30. In addition, a small movable electrode 138 configured so as to be always inserted as a whole may be formed on the movable electrode 130. The correction counter electrode plate 114 is also referred to as a fourth counter electrode. The movable electrode 138 is also called a fourth movable electrode.

  On the contrary, the correction counter electrode plate is made smaller, while the movable electrode is configured to have a wide area facing the entire correction counter electrode plate within the range of movement set in advance by the movable portion 30. May be. In this case, the correction counter electrode plate is also referred to as a fifth counter electrode. The movable electrode is also called a fifth movable electrode.

  An electrode pattern having three electrode element groups 131 to 133 and a correction movable electrode 138 is formed on the upper surface of the movable electrode 130. On the lower surface of the movable electrode 130, the same electrode pattern as that of the upper surface of the movable electrode 130 is formed in plan view. The electrode pattern on the upper surface of the movable electrode 130 and the electrode pattern on the lower surface of the movable electrode 130 are electrically connected to each other.

  The comb-tooth electrode 123 is a moving electrode used for measuring displacement in the X-axis direction. The comb electrode 123 includes four electrode elements 123a, 123b, 123c, and 123d extending at equal intervals in a direction perpendicular to the X-axis direction, and the four electrode elements 123a, 123b, 123c, and 123d. And a connection element 123e that is electrically connected to the.

  On the other hand, on the lower surface of the fixed counter electrode plate 110, a comb electrode 113 (not shown) having a shape facing the comb electrode 123 is formed. The comb-teeth electrode 113 is connected to the four electrode elements 113a, 113b, 113c, and 113d that face the four electrode elements 123a, 123b, 123c, and 123d of the comb-teeth electrode 123 and the connection element 123e, respectively. Element 113e (both not shown).

  The two comb-shaped electrodes 121 and 122 are paired with each other, and are electrodes on the moving side used for measuring the displacement in the Y-axis direction and the rotation angle θ around the Z-axis. The comb-tooth electrode 121 includes four electrode elements 121a, 121b, 121c, and 121d extending at equal intervals in a direction perpendicular to the Y-axis direction, and the four electrode elements 121a, 121b, 121c, and 121d. And a connection element 121e that is electrically connected to the. The comb electrode 122 includes four electrode elements 122a, 122b, 122c, and 122d extending at equal intervals in a direction perpendicular to the Y-axis direction, and the four electrode elements 122a, 122b, 122c, and 122d. And a connection element 122e that is electrically connected to the terminal.

  On the other hand, a comb electrode 111 (not shown) having a shape facing the comb electrode 121 is formed on the lower surface of the fixed counter electrode plate 110. The comb-tooth electrode 111 is connected to the four electrode elements 111a, 111b, 111c, and 111d that face the four electrode elements 121a, 121b, 121c, and 121d of the comb-tooth electrode 121 and the connection element 121e, respectively. It has an element 111e (both not shown).

  Further, a comb-tooth electrode 112 (not shown) having a shape facing the comb-tooth electrode 122 is formed on the lower surface of the fixed counter electrode plate 110. The comb electrode 112 is connected to the four electrode elements 112a, 112b, 112c, and 112d facing the four electrode elements 122a, 122b, 122c, and 122d of the comb electrode 122 and the connection element 122e, respectively. Element 112e and (both not shown) are included.

  On the other hand, the electrode element group 133 of the movable electrode 130 is a plurality of fixed-side electrode elements used for measuring displacement in the X-axis direction. The electrode element group 133 includes four electrode elements 133a, 133b, 133c, and 133d that extend at equal intervals in a direction perpendicular to the X-axis direction. The four electrode elements 133a, 133b, 133c, and 133d all have a width of W in the Y-axis direction.

  On the other hand, the electrode element groups 131 and 132 of the movable electrode 130 are a pair of electrode elements on the moving side that are used to measure the displacement in the Y-axis direction and the rotation angle θ around the Z-axis. The electrode element group 131 includes four electrode elements 131a, 131b, 131c, and 131d extending at equal intervals in a direction perpendicular to the Y-axis direction. All of the four electrode elements 131a, 131b, 131c, and 131d have a width of W in the X-axis direction. The electrode element group 132 includes four electrode elements 132a, 132b, 132c, and 132d that extend at equal intervals in a direction perpendicular to the Y-axis direction. All of the four electrode elements 132a, 132b, 132c, and 132d have a width of W in the X-axis direction.

  Such an electrode pattern can be formed, for example, by metal vapor deposition or mounting of a metal plate. The electrical connection between the upper surface side and the lower surface side of the movable electrode 130 can be realized by a via hole penetrating the movable electrode 130, for example.

  Note that the direction in which the four electrode elements 121a, 121b, 121c, and 121d extend is referred to as a first direction. The direction in which the four electrode elements 123a, 123b, 123c, and 123d extend is referred to as a second direction.

  The combination of the four electrode elements 121a, 121b, 121c, and 121d and the electrode elements 111a, 111b, 111c, and 111d that face each other is referred to as a first counter electrode. The combination of the four electrode elements 122a, 122b, 122c, and 122d and the electrode elements 112a, 112b, 112c, and 112d that face each other is referred to as a second counter electrode. The combination of the four electrode elements 123a, 123b, 123c, and 123d and the electrode elements 113a, 113b, 113c, and 113d that face each other is called a third counter electrode.

  FIG. 4 is an explanatory diagram showing the configuration of the electrode pattern in the embodiment of the present invention. FIG. 4 is a diagram in which each electrode pattern of the pair of fixed counter electrode plates 110 and 120 and the movable electrode 130 inserted therein is projected onto the XY plane. FIG. 4 shows an initial position, that is, an initial state in which the displacement and rotation of the movable part 30 with respect to the fixed part 200 are zero. As can be seen from FIG. 4, these electrode patterns constitute three sets of electrode units. The three sets of electrode units include an X-axis displacement measurement electrode unit 50, a Y-axis displacement and rotation angle θ measurement electrode unit 60, and a correction electrode unit 70.

  The X-axis displacement measuring electrode unit 50 includes comb electrodes 113 and 123 and an electrode element group 133 disposed therebetween. In the initial position, each of the electrode elements 133a, 133b, 133c, and 133d of the electrode element group 133 overlaps the electrode elements 123a, 123b, 123c, and 123d of the comb electrode 123 by half in the XY plane. ing. Specifically, for example, half of the electrode element 133a overlaps with the electrode element 123a of the comb electrode 123 in the X-axis direction.

  Specifically, when the movable portion 30 moves in the X-axis direction, the electrode elements 133a, 133b, 133c, and 133d of the electrode element group 133 also move in the X-axis direction together, and the electrode elements 123a of the comb-tooth electrode 123, The facing area with each of 123b, 123c, and 123d is reduced. Thereby, since the electrostatic capacitance of a pair of comb-tooth electrodes 113 and 123 (corresponding to the third counter electrode) decreases, the displacement of the movable portion 30 in the X-axis direction can be detected.

  On the other hand, in the initial position, each of the electrode elements 133a, 133b, 133c, and 133d of the electrode element group 133 is disposed at the center of the electrode elements 123a, 123b, 123c, and 123d of the comb electrode 123 in the Y-axis direction. It is in the state. The electrode elements 123a, 123b, 123c, and 123d are arranged such that the opposing areas do not change even if each of the electrode elements 133a, 133b, 133c, and 133d is displaced by δ in the Y-axis direction. And longer than 133d. Thereby, the displacement of the movable part 30 in the X-axis direction can be accurately detected without being affected by the displacement of the movable part 30 in the Y-axis direction.

  The electrode unit 60 for measuring the Y-axis displacement and the rotation angle θ has an offset amount N corresponding to the Y-axis direction line passing through the centroid P of the pair of fixed counter electrode plates 110 and 120. It is constituted as a pair of symmetrical electrodes separated only by each other. That is, the comb-tooth electrode 121 and the comb-tooth electrode 122 are configured as a pair of electrodes that are symmetrical with respect to a line in the Y-axis direction. The comb electrode 121 and the comb electrode 122 have a relative positional relationship with respect to the electrode elements 131 and 132, respectively, similar to the positional relationship between the comb electrode 123 and the electrode element group 133 described above.

  The comb electrode 123 and the electrode element group 133 are arranged at a position obtained by rotating the centroid P by 90 degrees clockwise with respect to the comb electrode 121 and the electrode element 131. That is, the comb-tooth electrode 123 and the electrode element group 133 are arranged at positions where their ends are separated by an offset amount N with respect to the line in the X-axis direction passing through the centroid P of the fixed counter electrode plates 110 and 120. It is comprised as a made electrode.

  Such an electrode configuration makes it possible to detect the capacitance for accurately measuring the displacement and the rotation angle of the movable part 30 effectively by the following method. A method for detecting the Y-axis displacement and the rotation angle θ and a method for eliminating the influence of the rotation angle θ on the X-axis displacement will be described later.

B. Measuring method of moving stage:
FIG. 5 is an explanatory diagram showing a schematic diagram and a calculation formula showing the measurement principle in the embodiment of the present invention. FIG. 5 shows a schematic diagram illustrating a configuration of a capacitor Cx having a measurement capacitance Cmes and a circuit diagram illustrating an equivalent circuit of the capacitor Cx. The capacitor Cx is equivalent to a circuit in which a capacitor C ₃ is connected in parallel to a series circuit of _two capacitors C ₁ and C ₂ .

Capacitance Cmes of the condenser Cx is the capacitance _{C 12} of the pair of comb electrodes 113 and 123 and the areas S1 of overlap electrode element group 133 and 135 facing each other (overlapping region), a pair of comb electrodes 113 , 123 is the sum of the capacitance C ₃ of the non-overlapping region S2 (non-overlapping region). The capacitance _{C 12} of the overlapping areas S1 becomes a capacitance of the series circuit of the capacitor _C 1, _{C 2,} can be calculated by the formula F1. On the other hand, the electrostatic capacitance C ₃ non-overlapping region S2 can be a capacitor having a plurality of dielectric having a dielectric constant different, is calculated by the formula F2. Therefore, the capacitance Cmes of the condenser Cx can be calculated as the sum of the capacitance C ₁₂ of the overlap region, the capacitance C ₃ non-overlapping regions (see equation F3).

The capacitance of the overlapping region S1 is determined by the area S1 of the overlapping region S1 of the electrode element group 133 and the dielectric constant ε1 of the dielectric (for example, air). The overlap area S1 is determined as a product of the insertion amount L of the electrode element group 133, the width W of the electrode element group 133 (see FIGS. 3 and 5), and the number of electrode elements (four in this example). Thus, the capacitance C ₁₂ of the overlap region, while dependent on the sum of the inter-electrode distance from formula F1 d1, d3, seen to be independent of the respective inter-electrode distance d1, d3.

On the other hand, the capacitance C ₃ of the non-overlapping region is calculated by subtracting the area of the non-overlapping region (calculated by subtracting the overlapping region area), the separation distance of each pair of comb electrodes 113 and 123, and the dielectric ( For example, the dielectric constant ε1 of air) and the dielectric constant ε2 of the non-electrode portion of the movable electrode 130 are determined. Since such a capacitor is known to be equivalent to a series capacitor for each of a plurality of dielectrics having different dielectric constants, it can be calculated by the calculation formula F2. As described above, the capacitance C ₃ of the non-overlapping region depends on the sum of the interelectrode distances d1 and d3 (or the thickness d2 of the movable electrode 130) from the calculation formula F2, and on the interelectrode distances d1 and d3. It turns out that is independent.

  Thus, in this embodiment, since the electrostatic capacitance of the non-overlapping region does not depend on the position of the movable electrode 130 in the Z-axis direction, only the uniformity of the distance between the pair of comb electrodes 113 and 123 is highly accurate. You can see that

  The sum of the inter-electrode distances d1 and d2 is a value obtained by subtracting the distance between the electrode element groups 133 and 135 from the distance between the comb-tooth electrode 113 and the comb-tooth electrode 123. Therefore, in the present embodiment, only the uniformity of the distance between the fixed counter electrodes and the uniformity of the thickness of the movable electrode 130 need only be highly accurate, and depend on the assembly error between the fixed counter electrode plates 110 and 120 and the movable electrode 130. I found it not. As a result, the trade-off problem between the measurement accuracy and the tolerance for assembly of the capacitor electrode is solved.

  The electrode element 133 is also called a third movable electrode together with the electrode element group 135 on the lower surface of the movable electrode 130. The electrode element 131 is also called a first movable electrode together with an electrode element group (not shown) on the lower surface of the movable electrode 130. The electrode element 132 is also called a second movable electrode together with an electrode element group (not shown) on the lower surface of the movable electrode 130.

  FIG. 6 is a schematic diagram showing how the displacement in the Y-axis direction and the rotation angle θ are measured in the embodiment of the present invention. FIG. 6A shows a state where the rotation angle θ of the movable part 30 is zero. FIG. 6B shows a state where the movable part 30 is rotating. As can be seen from FIG. 6A, when the movable portion 30 is not rotating, the displacement in the Y-axis direction is a combination of the pair of comb electrodes 111 and 121 and the electrode element group 131 (hereinafter, the left electrode). And a combination of a pair of comb electrodes 112 and 122 and an electrode element group 132 (hereinafter also referred to as a right electrode group). The displacement in the Y-axis direction can be measured basically in the same way as the displacement in the X-axis direction.

  On the other hand, the rotation angle θ around the Z axis can be measured based on the difference in capacitance between the left electrode group and the right electrode group. This is because the rotation of the movable portion 30 causes the capacitance change in the opposite direction between the left electrode group and the right electrode group. Specifically, due to counterclockwise rotation, the overlapping region area S increases in the left electrode group, while the overlapping region area S decreases in the right electrode group.

  Furthermore, the left electrode group and the right electrode group are arranged symmetrically with respect to the line in the Y-axis direction passing through the centroid P of the fixed counter electrode plates 110 and 120 in the direction in which each electrode group extends as described above. Yes. With such a symmetrical arrangement, the sum of the capacitance Cy1 of the left electrode group and the capacitance Cy2 of the right electrode group can be used for measuring the displacement in the Y-axis direction by eliminating the influence caused by the rotation angle θ. . This is because the increase in the capacitance Cy1 of the left electrode group caused by the rotation angle θ coincides with the decrease in the capacitance Cy2 of the left electrode group caused by the rotation angle θ. .

  On the other hand, the amount of increase in the capacitance Cy1 of the left electrode group caused by the rotation angle θ can also be used for measuring the displacement in the X-axis direction. This is because the comb-tooth electrode 123 and the electrode element group 133 are arranged in the same shape at a position obtained by rotating the centroid P by 90 degrees clockwise with respect to the comb-tooth electrode 121 and the electrode element 131. In other words, the comb-tooth electrode 123 and the electrode element group 133 are located at positions where their ends are separated by an offset amount N with respect to the line in the X-axis direction passing through the centroid P of the fixed counter electrode plates 110 and 120. This is because it is configured as an arranged electrode.

  The pair of comb electrodes 111 and 121 is also referred to as a first fixed counter electrode pair. The pair of comb electrodes 112 and 122 is also referred to as a second fixed counter electrode pair. The pair of comb electrodes 113 and 123 is also referred to as a third fixed counter electrode pair. The electrostatic capacity Cy1 of the pair of comb electrodes 111 and 121 is also referred to as a first electrostatic capacity. The electrostatic capacity Cy2 of the pair of comb electrodes 112 and 122 is also called a second electrostatic capacity. The capacitance Cx of the pair of comb electrodes 113 and 123 is also referred to as a third capacitance.

  FIG. 7 is a schematic diagram illustrating how the displacement in the X-axis direction is detected in the embodiment of the present invention. FIG. 8 is a graph showing the capacitance of the pair of comb electrodes 113 and 123 facing each other for measuring the displacement in the X-axis direction in the embodiment of the present invention. A line L1 indicates the capacitance when the movable unit 30 is not rotating (FIGS. 7A to 7C). A line L2 indicates the capacitance when the movable unit 30 is rotated (FIGS. 7D to 7F).

  FIG. 7A shows a state where the electrode element group 133 of the movable portion 30 is displaced to the negative side in the X-axis direction, and the capacitance corresponds to the point P1 in FIG. FIG. 7B shows an initial state in which the movable unit 30 is neither rotated nor displaced, and the capacitance corresponds to the point P2 in FIG. FIG. 7C shows a state in which the movable unit 30 is displaced to the positive side in the X-axis direction, and the capacitance corresponds to the point P3 in FIG. FIG. 7D shows a state where the movable portion 30 is rotating and displaced to the negative side, and the capacitance corresponds to the point P4 in FIG. FIG. 7E shows a state where the movable unit 30 is rotating, and the capacitance corresponds to a point P5 in FIG. FIG. 7F shows a state where the movable part 30 is rotating and displaced to the positive side, and the capacitance corresponds to the point P6 in FIG.

  As can be seen from FIGS. 7 and 8, it can be seen that the displacement of the movable portion 30 in the X-axis direction has a linear relationship with the capacitance regardless of whether the movable portion 30 is rotated. This is because the two lines L1 and L2 are both straight lines. On the other hand, it can be seen that the change in capacitance due to the rotation of the movable part 30 is constant regardless of the displacement of the movable part 30 in the X-axis direction. This is because the two lines L1 and L2 are straight lines at positions shifted by a certain offset amount.

Thus, in this embodiment, the movement of the movable part 30 can be directly measured using the following detection values of the following position sensor 100.
(1) Rotation angle θ: Difference between the capacitance Cy1 of the left electrode group and the capacitance Cy2 of the right electrode group of the electrode unit 60 (see FIG. 4)
(2) Displacement in the X-axis direction: half the difference between the capacitance Cx of the comb electrodes 113 and 123, the capacitance Cy1 of the left electrode group, and the capacitance Cy2 of the right electrode group (for the left electrode group)
(3) Displacement in the Y-axis direction: the sum of the capacitance Cy1 of the left electrode group and the capacitance Cy2 of the right electrode group.

  The present embodiment can achieve the following effects.

  (1) The position sensor 100 of the present embodiment solves the trade-off problem between the measurable displacement amount and the assembly tolerance of the capacitor electrode, and thereby has an ideal linear characteristic as a sensor. Yes. In the present embodiment, only the parallelism (uniformity of spacing) between the fixed counter electrodes and the parallelism (thickness uniformity) of the movable electrodes need to be highly accurate. For example, the pair of fixed counter electrode plates 110 and 120 This is because the relative assembling error between the separation interval and the movable electrode 130 does not affect the measurement accuracy.

  (2) The position sensor 100 of this embodiment has an advantage that the parallelism of the counter electrode (for example, the fixed counter electrode) and the accuracy of the thickness of the movable electrode can be easily realized by general machining.

C. Variations:
The embodiment is not limited to the above contents, and may be implemented as follows, for example.

  (1) In the above embodiment, each electrode element of the electrode unit 50 and the electrode unit 60 extends in a direction substantially perpendicular to each other in the XY plane, but does not necessarily have to extend substantially perpendicular to each other. If it extends in a direction crossing each other, it can be measured. However, extending perpendicularly to each other has the advantage that the displacement of each axis can be detected directly and independently.

  (2) In the above embodiment, a configuration in which the movable electrode is inserted into the fixed counter electrode pair is employed. However, the present invention is not limited to such a configuration. For example, a fixed electrode may be inserted into the movable counter electrode pair. However, the above embodiment only needs to detect the capacitance of the fixed-side counter electrode, and does not require wiring on the movable-side electrode side. Therefore, it is caused by obstruction of movement of the moving stage caused by wiring or movement of the movable-side electrode. This also has the advantage of avoiding problems with wiring.

  (3) Although mounted as a position sensor in the above embodiment, the present invention is a measurement system, a measurement system, and a drive device including an electronic circuit that outputs a measurement value based on the capacitance of the position sensor, for example. It is also possible to configure as a planar linear motor having the above or a planar stage including these. Further, the present invention can be realized in the form of a measurement method, a computer program for realizing the measurement system, a recording medium for storing the program, and the like.

  DESCRIPTION OF SYMBOLS 10 ... Planar stage, 30 ... Fixed part, 50 ... X-axis displacement measuring electrode unit, 60 ... Measuring electrode unit, 70 ... Correction electrode unit, 100 ... Position sensor, 110 ... Fixed counter electrode, 111 ... Comb electrode 112 ... Comb electrode, 113 ... Comb electrode, 114 ... Moving electrode for correction, 120 ... Fixed counter electrode, 121 ... Comb electrode, 122 ... Comb electrode, 123 ... Comb electrode, 130 ... Fixed electrode, 140 ... separation member, 200 ... moving part, 240 ... mover unit, 250 ... floating unit.

Claims (8)

In a planar stage having a fixed part and a moving stage that moves relative to the fixed part in a plane, the position sensor measures the position of the moving stage,
A fixed electrode portion having a first fixed counter electrode pair, a second fixed counter electrode pair, and a third fixed counter electrode pair connected to the fixed portion and facing each other at a predetermined interval;
A first movable electrode connected to the moving stage and partially inserted between the first fixed counter electrode pair and partially inserted between the second fixed counter electrode pair. A movable electrode portion having a second movable electrode and a third movable electrode partially inserted between the third fixed counter electrode pair;
With
The first fixed counter electrode pair includes a first counter electrode extending in a first direction,
The second fixed counter electrode pair includes a second counter electrode extending in parallel with the first direction,
The third fixed counter electrode pair includes a third counter electrode extending in a second direction intersecting the first direction,
The first counter electrode has a first capacitance that changes according to an insertion state of the first movable electrode,
The second counter electrode has a second capacitance that changes according to an insertion state of the second movable electrode,
The third counter electrode has a third capacitance that changes according to an insertion state of the third movable electrode,
The first counter electrode is disposed at a position shifted in the first direction with respect to the second counter electrode;
The third sensor is a position sensor arranged at a position shifted in the second direction with respect to the first counter electrode. The position sensor according to claim 1,
The first counter electrode includes a comb-like electrode to which a first comb electrode group that is a plurality of electrode elements extending in parallel to each other is connected to each other,
The second counter electrode includes a comb-like electrode in which a second comb electrode group that is a plurality of electrode elements extending in parallel to each other is connected to each other,
The third counter electrode is a position sensor including a comb-like electrode in which a third comb electrode group which is a plurality of electrode elements extending in parallel to each other is connected to each other. The position sensor according to claim 1 or 2,
The fixed electrode portion includes a fourth counter electrode connected to the fixed portion and facing each other at the predetermined interval,
The movable electrode portion is connected to the movable stage, and has a fourth movable electrode that is entirely inserted between the fourth counter electrodes within a range of movement set in advance on the movable stage. Sensor. The position sensor according to claim 1 or 2,
The fixed electrode portion has a fifth counter electrode connected to the fixed portion and facing each other at the predetermined interval,
The movable electrode unit is connected to the movable stage, and a position sensor having a fifth movable electrode having a region facing the entire fifth counter electrode within a range of movement set in advance on the movable stage. . The position sensor according to any one of claims 1 to 4,
The position sensor in which the first direction intersects the second direction substantially perpendicularly. In a planar stage having a fixed part and a moving stage that moves relative to the fixed part in a plane, the measuring system measures the position of the moving stage,
The position sensor according to any one of claims 1 to 5,
A capacitance detection unit that detects a first capacitance of the first counter electrode, a second capacitance of the second counter electrode, and a third capacitance of the third counter electrode. When,
The displacement in the second direction is measured based on the sum of the first capacitance and the second capacitance, and the moving stage is based on the difference between the first capacitance and the second capacitance. A measurement unit that measures a rotation angle of the first direction based on the third capacitance and the difference;
Measuring system. A planar stage,
A fixed part;
A moving stage that moves relative to the fixed part in a plane;
A measurement system according to claim 6;
A planar linear motor that drives the moving stage in the plane based on the measured value;
A plane stage comprising The stage according to claim 7, wherein
The planar linear motor includes an air bearing that supports movement in the plane in a non-contact manner with respect to the fixed portion by supporting the movable stage in a direction perpendicular to the plane.

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