JP2009281768A - Measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring apparatus which uses effectively only advantages of a level and the multipoint method in the measurement of a long cross-sectional linear shape or planar shape, allowing a large-area surface under measurement to be measured quickly and with high precision. <P>SOLUTION: The apparatus scans and measures a linear shape by relatively moving a stage on which a sample under measurement is mounted and a sensor holder holding a multipoint method probe. The level is provided which can measure the inclination angle in the scanning direction of the moving sensor holder or stage. The inclination angle of the moving object is measured by the level at the start point and end point of the scanning movement, thereby allowing the zero-point adjustment error of the multipoint method probe to be calibrated in-situ. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a measurement technique, and more particularly, to a measurement apparatus that measures a straight shape, a surface shape, and a moving straight motion error of a large-sized object with high accuracy.

In order to measure a surface shape or a cross-sectional linear shape, a comparative measurement with a standard straight ruler is often performed. Alternatively, on the basis of the linearity of the optical axis, a method of calculating the linear shape by measuring the inclination of the mirror on the table that is in contact with the surface to be measured at two points in the scanning direction with an autocollimator. Further, when the reference cannot be used, a method of separating the motion error and the shape error by a multipoint method using a multipoint probe is used (see Patent Document 1). In addition, using a spirit level, measure the slope between the points where the lower surface of the spirit level contacts the surface to be measured at the required location on the surface to be measured, and calculate the linear shape or surface shape from the measurement results. Used.
JP 2008-8879 A

  As the measuring object of straight shape or planar shape becomes larger, the reference ruler becomes longer and it becomes difficult to create it. In addition, the accuracy of the optical axis reference cannot be maintained due to the influence of light fluctuation in the air. Therefore, the necessity of the multipoint method is increased. However, the multipoint method has a problem of a parabola error due to a zero point adjustment error, and the longer the length is, the larger the parabola error becomes.

  On the other hand, with the level, since the direction of gravity is taken as a reference, it is possible to perform theoretically stable measurements even for long lengths. The response speed is slow, it is difficult to measure quickly while moving, and the time taken to measure the inclination of a large number of points on a large plane is also long.

  In view of such a problem, the present invention can effectively use only the advantage of a level and multipoint method in measuring a long straight line shape and a surface shape, and can measure a large area to be measured quickly and with high accuracy. It aims at providing a measuring device.

  The measuring apparatus of the present invention is an apparatus for scanning and measuring a linear shape by moving a stage on which a sample to be measured and a sensor holder holding a multipoint probe move relative to each other. A level that can measure the tilt angle of the stage (hereinafter referred to as the moving object) in the scanning direction is provided, and the inclination of the moving object at the start and end points of the scanning movement is measured by the level. Thus, the zero-point adjustment error of the multipoint probe is calibrated in situ.

  The straight shape and the motion straight shape are separately measured by the multipoint method, but if the multipoint probe has a zero point adjustment error, the motion straight shape also includes a parabolic error. By the way, when the parabola is differentiated once and the inclination is obtained, the inclination changes linearly. Therefore, if an error generated in the difference in inclination at both ends of the motion straight shape is known, a parabola error is obtained.

  In other words, if the inclination on the moving moving object side can be measured correctly when the movement start point and end point in shape measurement are stationary, it is included in the difference between the inclinations of both ends of the movement straight shape measured and evaluated by the multipoint probe. It is possible to extract the effect of parabolic error due to zero adjustment error of the method probe. As a result, the so-called in-situ calibration can be realized in which the zero point of the multipoint probe can be calibrated from the target shape measurement data itself. Previously, it was necessary to calibrate the zero point error by measuring a known reference shape and then scan and measure the target surface to be measured using the multipoint method. In addition to speeding up the measurement, it is possible to reduce errors such as drift over time.

  Based on this concept, the present invention correctly measures the tilt of the moving object at both ends of the scanning movement by fixing the level that can correctly measure the tilt of the moving object in the direction of gravity to the moving object in multipoint measurement. Suggest to do.

The principle of the present invention will be described with reference to the drawings. FIG. 1A schematically shows a parabolic shape caused by a zero adjustment point error of the multipoint probe, and FIG. 1B schematically shows a change in inclination along the scanning line, which is the basis of the parabolic shape. Here, parabolic shape caused by the zeroing point error, the moving direction when the x-direction, when the zero point adjustment error and alpha, expressed by ^{h (x) = αx 2/} 2. Maximum the height h _max = αL ^2/8 at the measurement total length L.

The difference ΔEφ in the inclination of the moving object between the scanning start point and the end point can be measured from the reading of the level indicator at rest. On the other hand, the difference Δμ in inclination between the scanning start point and the end point obtained with the multipoint method probe includes an error by a difference Δh ′ at both ends of a value h ′ corresponding to a single derivative of a parabola caused by a zero point error. . From this, the following relationship is obtained.
Δμ = ΔEφ + Δh ′
Therefore,
Δh ′ = Δμ−ΔEφ
It becomes. Here, Δh ′ = αL,
α = Δh ′ / L
Is obtained.

Further, in order to simplify the explanation of the principle of zero point adjustment error calibration using a level, a two-point angle method is selected and explained as a multipoint method. FIG. 2 shows a principle diagram of straight shape measurement using an angle two-point probe composed of two angle sensors AS1 and AS2. Here, an example is shown in which the stage STX on which the sample SP to be measured is mounted is a moving object. The interval between the two angle sensors AS1 and AS2 scanned in the x direction is d, and the outputs of the angle sensors AS1 and AS2 are μ1 (x) and μ2 (x + d), respectively. If the shape of the surface to be measured in the sample SP to be measured is f (x), the derivative thereof is f ′ (x), and the pitching of the motion during relative scanning is e _φ (x), the outputs of the angle sensors AS1 and AS2 Equations (1) and (2) are obtained as follows. However, α represents the difference between the zeros of the two angle sensors AS1, AS2, that is, the zero point adjustment error.
μ1 (x) = f ′ (x) + e _φ (x) (1)
μ2 (x) = f ′ (x + d) + e _φ (x) + α (2)

Here, the output of the angle sensor AS1 at the position where the probe (AS1, AS2) is shifted by d in the x direction is:
μ1 (x + d) = f ′ (x + d) + e _φ (x + d) (3)
It becomes.

Furthermore, from the equations (2) and (3), μ1 (x + d) −μ2 (x) = e _φ (x + d) −e _φ (x) −α (4)
Get.

If the measurement total length L is dN and the i-th point is x _i , the slopes at the points of x ₁ = 0 and x _N = d (N−1) are e _φ (0) and e _φ (N−1). When the moving straight shape is obtained by the sequential method, the following is obtained.
Σ {μ1 (x + d) −μ2 (x)} = e _φ (N−1) −e _φ (0) − (N−1) α (5)

On the other hand, the difference Derutaifai slope at both ends measured by Level EL, since the _{ΔEφ = {e φ (N-} 1) -e φ (0)}, the zero point adjustment error α is determined as follows .
α = [Σ {μ1 (x + d) −μ2 (x)} − ΔEφ] / (N−1) (6)
Therefore, from equations (5) and (6), it is possible to correctly obtain the moving straight shape e _φ (x) of the moving object while eliminating the zero point adjustment error α. Furthermore, the shape of the surface to be measured in the sample SP to be measured can be accurately obtained from the equation (1).

  In the measuring apparatus of the type in which the stage STX on which the object SP to be measured shown in FIG. In principle, the moving stage STX and the sample SP to be measured are not deformed even if the posture is changed. However, as the stage length becomes longer, there is a possibility that the stage STX and the sample SP to be measured are deformed along with the position change. It is also preferable to arrange the level of at a position along the object SP to be measured. Further, since the indication value of the level EL changes in the direction of gravity, it is necessary to correct the value of the level according to the curvature of the earth. Approximately, the reading of the level EL changes by about 0.03 seconds with a movement of 1 m.

  Note that the posture may change before the start of scanning movement of the stage STX, such as when the moving stage STX is supported by a static pressure bearing. In such a case, the reading of the level EL at the time of rest is taken and the outputs of the sensors AS1 and AS2 of the multipoint probe are taken simultaneously. It is necessary to correct the change in posture at the beginning. This is the same when the posture of the stage STX continues to change after the scanning movement is finished. It is necessary to correct the change.

  FIG. 3 shows a measuring apparatus that scans a surface to be measured in the y direction by attaching a multipoint probe and a level EL2 using a tool axis that moves along the y-direction guide SY of the portal machine tool as a sensor holder. This is an embodiment corresponding to claim 2.

  At this time, in the planar shape measuring apparatus in which the stage STX loaded with the sample SP to be measured moves and scans in the x direction, the level EL1 is also attached to the stage STX. As the multipoint probe, as shown in FIG. 3 (b), the angle two-point method using the measurement values of the two-dimensional angle sensor ASxy1 and the angle sensor ASx2 for detecting the tilt in the x direction is established for scanning in the x direction. In the y-direction scanning, a two-point angle method using measurement values of the two-dimensional angle sensor ASxy1 and the angle sensor ASy2 that detects the inclination in the y direction is established.

  The moving object can move in two-dimensional directions perpendicular to each other, and the level is a two-dimensional level that can measure the tilt in the two-dimensional direction. At least three points of the start and end points of the two-dimensional scanning movement It is preferable to calibrate the zero point adjustment error of the two-dimensional multi-point probe in situ by measuring the two-dimensional inclination of the moving object at the same position. Further, the multipoint probe may be a displacement three-point probe using three displacement sensors arranged on one scanning line, an angle two-point probe using two angle sensors arranged on one scanning line, or one It is preferable that the mixing method probe is composed of two displacement sensors and one angle sensor arranged on the scanning line. Furthermore, the multipoint probe measures a two-dimensional multipoint probe that measures four to five points arranged two-dimensionally, or measures the tilt angles of three to four points arranged two-dimensionally. It is a two-dimensional multi-point probe using an angle sensor or a two-dimensional multi-point probe based on a three-dimensionally arranged displacement and an angle sensor that measures an inclination angle in two orthogonal directions at least at one point. preferable.

It is a figure which shows the relationship of the zero point adjustment error between the sensors of the multipoint method made into the calibration object by this invention, and the parabolic error by it. It is a figure which shows the outline | summary of the measurement of the straight shape measuring system of an angle 2 point method as an example of a multipoint method. It is a figure which shows the Example corresponding to Claim 2.

Explanation of symbols

α: Zero point adjustment error hmax of multipoint method hmax: Maximum value of parabola error caused by zero point adjustment error Δh ′: Difference in slope at both ends of parabola error
AS1, AS2, ASxy1 angle sensors
EL, EL1, EL2 level
SH Sensor holder
STX stage for specimen loading
SY Scanning direction in y direction
SP Sample to be measured
f (x) Straight shape of sample to be measured
e _φ (x) Pitching during scanning

Claims (5)

  In an apparatus for scanning and measuring a linear shape by moving a stage on which a sample to be measured and a sensor holder holding a multipoint probe move relative to each other, a moving sensor holder or stage (hereinafter referred to as a moving object) Multi-point method by measuring the inclination of the moving object at the start and end points of the scanning movement by the level. A measuring apparatus characterized by in-situ calibration of a zero adjustment error of a probe.   In measurement by two-dimensional relative scanning movement, each of the stage on which the sample to be measured is placed and the sensor holder holding the multipoint probe are used to scan the level in one of two orthogonal directions. The in-situ calibration of the zero-point adjustment error of the multipoint probe by being on the moving object side, and measuring the two-dimensional surface shape and the movement straightness in two directions. The measuring device described.   The moving object is movable in two-dimensional directions perpendicular to each other, and the level is a two-dimensional level capable of measuring a tilt in a two-dimensional direction, and at least three points of a two-dimensional scanning movement start point and end point The measuring apparatus according to claim 1 or 2, wherein a zero-point adjustment error of a two-dimensional multipoint probe is calibrated in situ by measuring a two-dimensional inclination of a moving-side object.   The multipoint probe is a displacement three-point probe using three displacement sensors arranged on one scan line, or an angle two-point probe using two angle sensors arranged on one scan line, or one scan. The measuring apparatus according to any one of claims 1 to 3, wherein the measuring apparatus is a mixing method probe using two displacement sensors and one angle sensor arranged on a line.   The multipoint probe measures a two-dimensional multipoint probe that measures four to five points arranged two-dimensionally, or an angle that measures an inclination angle of three to four points arranged two-dimensionally A two-dimensional multi-point probe using a sensor, or a two-dimensional multi-point probe based on a two-dimensionally arranged three-point displacement and an angle sensor that measures an inclination angle in two orthogonal directions at at least one point. The measuring apparatus according to claim 1, wherein the measuring apparatus is characterized.