JP6128639B2 - Measuring method - Google Patents

Description

  The present invention relates to a measuring method for measuring the straight shape of a long object.

  The need to measure long straight shapes and large area planar shapes with high precision is increasing due to the increase in the length of precision coating tools, the enlargement of wafers, and the increase in the area of LCD screens. The certainty of the metrics given is no longer limited. Therefore, there is a need for a measurement method based on mathematically given standards that does not rely on physical standards.

  In the patent document 1, the present applicant effectively uses only the advantage of the level and the multipoint method in measuring the long cross-sectional straight line shape and surface shape, and quickly and accurately measures a large surface to be measured. A measuring device that can be used is proposed.

JP 2009-281768

  By the way, when a long sample such as a rod-shaped object is shifted in a predetermined direction with respect to the sensor and the straight shape is measured from the difference between the measurement results before and after the shift, it is shifted when the long sample is shifted. Since the rigid inclination of the lens leads to a parabola error, high-precision posture measurement is required for measuring a long straight shape. When considering the accuracy limit of the attitude sensor, the parabolic error has a higher effect of suppressing the parabolic error as the shift amount is larger.

  However, when the shift amount is large, the density of the measurement points of the straight shape is lowered, and there is a drawback that it is necessary to combine the result with a smaller shift amount (small shift). In addition, it takes time and labor to move a long sample greatly, and the total measurement time becomes longer. For high-accuracy measurement, the environment such as temperature at the required level of the measurement system during that time is stable. It becomes difficult to keep.

  The present invention has been made in view of the problems of the prior art, and introduces a small shift of the sensor so that a large shift of a long sample is unnecessary, and when two sensors can be used, It is an object of the present invention to provide a measurement method that can perform two scanning measurements before and after the shift in one time.

The measuring method according to claim 1 performs relative scanning by relatively moving a holder on which a displacement sensor is mounted and a stage on which a long object is placed in a scanning direction to obtain an output value from the displacement sensor. A measuring method for measuring the straight shape of the long object,
The displacement sensor measures a surface to be measured of the long object to obtain a first output value, and further shifts the displacement sensor with respect to the holder in the scanning direction by the distance d, Measure the surface of the object to be measured and obtain the second output value (first step)
The stage of mounting the elongate object, said shifted by distance d in the scanning direction with respect to the displacement the holder sensor mounting, in the displacement sensor, in a position to obtain a first output value Measure the measurement surface of the long object to obtain a third output value (second step),
A measurement error component is obtained from the first output value and the third output value, and the difference between both ends of the total movement direction of the posture angle (pitching) in the scanning movement direction of the stage on which the long object is placed. Is measured by a posture sensor, and based on the output value and the first to third output values, the posture change at the time of relative scanning of the stage on which the long object is placed with respect to the holder is corrected. On the other hand, the straight shape of the long object is obtained (third step).

According to the present invention, the measurement error component is obtained from the first output value and the third output value, and the movement direction of the posture angle (pitching) in the scanning movement direction of the stage on which the long object is placed. At the time of relative scanning of the stage on which the long object is placed with respect to the holder , based on the output value and the first to third output values, by measuring the difference between both ends of the total length with the attitude sensor. Since the straight shape of the long object is obtained while correcting the posture change of the long object, a large shift of the long object is unnecessary, the number of displacement sensors is small, and a highly accurate measurement can be realized with a compact measuring device. .

According to a second aspect of the present invention, there is provided a measurement method in which a holder to which a first displacement sensor and a second displacement sensor arranged at an interval d in the scanning direction are attached and a stage on which a long object is placed are relative to each other in the scanning direction. It is a measurement method for measuring the straight shape of the long object by performing relative scanning by moving and obtaining output values from the first displacement sensor and the second displacement sensor,
The first displacement sensor measures the surface to be measured of the long object to obtain a first output value, the second displacement sensor measures the surface to be measured of the long object, and the second Obtain the output value (first step),
The stage on which the long object is placed is shifted with respect to the holder by the distance d in the scanning direction, and the first displacement sensor obtains the second output value at the position where the second output value is obtained. Measure the surface to be measured to obtain the third output value (second step)
A measurement error component is obtained from the first output value and the third output value, and the difference between both ends of the total movement direction of the posture angle (pitching) in the scanning movement direction of the stage on which the long object is placed. Is measured by an attitude sensor, and the change in attitude during scanning of the stage on which the long object is placed is corrected based on the output value and the first to third output values. A straight shape of the scale object is obtained (third step).

According to the present invention, the measurement error component is obtained from the first output value and the third output value, and the movement direction of the posture angle (pitching) in the scanning movement direction of the stage on which the long object is placed. The difference between the two ends of the total length is measured by the posture sensor, and the posture change at the time of scanning the stage on which the long object is placed is based on the output value and the first to third output values. Since the straight shape of the long object is obtained while correcting, a large shift of the long object is unnecessary, and high-precision measurement can be realized with a compact measuring apparatus. In the relative scanning, the displacement sensor side may be moved, or the long object side may be moved.

  The present invention provides a measurement method that introduces a small shift of the sensor, eliminates the need for a large shift of the sample, and can perform two scanning measurements before and after the shift of the sensor once when two sensors can be used. can do.

It is a perspective view of a measuring device which can realize the measuring method of the present invention. It is a perspective view of a measuring device which can realize the measuring method of the present invention. It is a perspective view of the measuring device concerning another embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are perspective views of a measuring apparatus capable of realizing the measuring method of the present invention. The relative movement direction of the displacement sensor AS and the linear motion stage STX is the X direction, the vertical direction is the Z direction, and the direction orthogonal to the X direction and the Z direction is the Y direction.

  As shown in FIG. 1, in a measuring apparatus in which a linear motion stage STX carrying a sample SP to be measured, which is a long object, moves with respect to a surface plate or the like (not shown), the same linear motion as the sample SP to be measured A level EL is installed on the stage STX. Theoretically, the linear motion stage STX and the sample SP to be measured are not deformed even if the posture is changed, but may be deformed with a change in position as the stage length becomes longer. It is also preferable to arrange a plurality of levels at positions along the sample 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.

  In the present embodiment, the level EL is arranged on the posture table SB placed on the linear motion stage STX with two-point support. The reason will be described. In this measurement method, it is necessary to detect the rigid offset and posture change (pitching) of the sample SP being scanned from the scanning measurement data of the sample SP to be measured. Usually, this movement is almost the same as the scanning stage. However, if it becomes a long stage, elastic deformation during movement may occur. If the level EL is placed directly on the stage, a local inclination due to elastic deformation is detected, and there is a possibility that the pitching of the sample cannot be accurately detected. Ideally, the sample SP to be measured is supported at two points and the level EL is fixed to the sample SP to be used. However, in consideration of the workpiece, it may not be easily fixed. Therefore, it is preferable to place the level EL on the attitude sensor table SB supported at two points at the same position as the sample SP to be measured so as to generate the same pitching as the sample SP supported at two points. Obviously, when the level EL can be fixed to the sample SP to be measured, the posture table SB is not necessary. In addition, when two points to be measured SP cannot be supported, a level EL may be provided in the vicinity of both ends of the scanning measurement range.

  In some cases, such as when the moving linear motion stage STX is supported by a static pressure bearing, the posture may change before the scanning movement of the linear motion stage STX starts. In such a case, the reading of the level EL at rest is taken, and at the same time, two outputs are taken from the displacement sensor of the multipoint probe, and the posture indicated by the reading of the level EL at rest and the actual movement scanning are performed. It is necessary to correct the change in posture at the beginning. The same applies to the case where the posture of the linear motion stage STX continues to change after the scanning movement is finished. The posture at the same position is read with a multipoint probe until the posture indicated by the level EL is stabilized, and after the scanning is finished. It is necessary to correct the posture change.

  Here, a case where the sample SP to be measured is mounted on the linear motion stage STX for scanning and measured by a single displacement sensor AS (referred to as relative scanning) will be described as an example. Prior to the measurement, the displacement sensor AS supported by a holder HLD fixed to a not-shown surface plate or the like is shifted by a distance d in the scanning direction (the moving direction of the linear motion stage STX, that is, the X direction). Two outputs are obtained from the displacement sensor AS that measures the shape of the measurement target surface of the measurement sample SP.

(First step)
By shifting the displacement sensor AS in the scanning direction with respect to the holder HLD while the linear motion stage STX is stationary, the output m ₁ of the displacement sensor AS (first output value of the first displacement sensor), m ₂ (second output value of the second displacement sensor) can be expressed by the following equation. As shown in FIG. 3, when two displacement sensors (the first displacement sensor AS1 and the second displacement sensor AS2 fixed to the holder HLD at a distance d in the scanning direction) can be used, the shift of the displacement sensor is unnecessary. Therefore, the first step of obtaining the first output value and the second output value can be completed once.
m ₁ (x) = f (x) + e _z (x) (1)
m ₂ (x) = f (x + d) + e _z (x) + d · e _p (x) + z ₂ (2)

(Second process)
Next, as shown in FIG. 2, after moving the sample SP to be measured together with the linear motion stage STX in the scanning direction by an interval d, the output m ₃ (third output value of the third displacement sensor) of the displacement sensor AS is It can be expressed by the following formula.
m ₃ (x) = f (x) + e _z (x) + d · e _p (x) + z ₂ + z ₃ + αx (3)

Where x is the position coordinate in the scanning direction, f (x) is the shape of the surface to be measured of the sample SP to be measured, and e _z (x) and e _p (x) are the sensor sensitivity directions in the scanning motion (z direction), respectively. Error and pitching error, z ₂ is the zero point movement amount of the displacement sensor in the z direction accompanying the displacement sensor shift, z ₃ is the z direction offset of the sample SP to be measured during the movement (scanning) of the sample SP to be measured, α is an inclination angle of the sample SP to be measured at the time of scanning.

Here, since the displacement sensor AS measures the shape of the measurement surface of the measurement sample SP before the shift in the first step, f (x) is obtained from the equations (1) and (3). It disappears and the following equation is obtained as the measurement error.
Δm ₁₃ (x) = m ₃ (x) −m ₁ (x) = d · e _p (x) + z ₂ + z ₃ + αx (4)

Furthermore, when the relative scanning range full length is L, it can be expressed as follows.
Δm ₁₃ (L) −Δm ₁₃ (0) = d {e _p (L) −e _p (0)} + α · L (5)

(3rd process)
Since Equation (5) of the first term on the right side of _{{e p (L) -e p} (0)} is the pitching error (the difference at both ends of the moving direction entire length of the attitude angle of the scanning motion direction (pitching)) It can be known by an attitude sensor (for example, a level EL) placed on the attitude sensor base SB on the linear motion stage STX. Therefore, the coefficient α can be determined as shown in Expression (6) from Expression (5).
α = [Δm ₁₃ (L) −Δm ₁₃ (0) −d {e _p (L) −e _p (0)}] / L (6)

When the coefficient α is determined, a difference regarding f (x) can be obtained from the equations (2) and (3).
Δf (x) = f (x + d) −f (x) = m ₂ (x) −m ₃ (x) + z ₃ + αx (7)

From the difference at the interval d, the required shape f (x) is obtained sequentially by various methods such as the transfer function method. However, due to the influence of unknown z ₃ , an inclination is added to the obtained straight shape, but this is not a problem because it is removed when displaying the straight shape with both end heights aligned.

  In order to eliminate the influence of surface roughness so that the displacement sensor output at x = 0 and x = L is less likely to cause an error, only the both ends of the sample SP to be measured are polished, or the polished surface is polished to the sample to be measured. A device such as addition to both ends of the SP is also preferable. In addition, since it is difficult to accurately shift the large sample SP to be scanned in the scanning direction at the interval d, the output of the displacement sensor AS is output in the order of equations (3), (2), and (1) with the measurement order reversed. It is also preferable to obtain a device that shifts the displacement sensor AS in accordance with the interval after scanning the sample SP to be measured and determines the exact shift interval.

AS Displacement sensor EL Level spirit HLD Holder SB Attitude sensor stand SP Sample to be measured STX Linear motion stage

Claims (2)

Relative scanning is performed by obtaining the output value from the displacement sensor by relatively moving the holder with the displacement sensor and the stage on which the long object is placed in the scanning direction, and measuring the straight shape of the long object. Measuring method
The displacement sensor measures a surface to be measured of the long object to obtain a first output value, and further shifts the displacement sensor with respect to the holder in the scanning direction by the distance d, Measure the surface of the object to be measured and obtain the second output value (first step)
The stage of mounting the elongate object, said shifted by distance d in the scanning direction with respect to the displacement the holder sensor mounting, in the displacement sensor, in a position to obtain a first output value Measure the measurement surface of the long object to obtain a third output value (second step),
A measurement error component is obtained from the first output value and the third output value, and the difference between both ends of the total movement direction of the posture angle (pitching) in the scanning movement direction of the stage on which the long object is placed. Is measured by a posture sensor, and based on the output value and the first to third output values, the posture change at the time of relative scanning of the stage on which the long object is placed with respect to the holder is corrected. On the other hand, a measuring method characterized by obtaining a straight shape of the long object (third step). A holder on which a first displacement sensor and a second displacement sensor arranged at an interval d in the scanning direction and a stage on which a long object is placed are relatively moved in the scanning direction to move the first displacement sensor and the first displacement sensor. A measurement method for performing a relative scan by obtaining an output value from a two-displacement sensor and measuring a straight shape of the long object,
The first displacement sensor measures the surface to be measured of the long object to obtain a first output value, the second displacement sensor measures the surface to be measured of the long object, and the second Obtain the output value (first step),
The stage on which the long object is placed is shifted with respect to the holder by the distance d in the scanning direction, and the first displacement sensor obtains the second output value at the position where the second output value is obtained. Measure the surface to be measured to obtain the third output value (second step)
A measurement error component is obtained from the first output value and the third output value, and the difference between both ends of the total movement direction of the posture angle (pitching) in the scanning movement direction of the stage on which the long object is placed. Is measured by an attitude sensor, and the change in attitude during scanning of the stage on which the long object is placed is corrected based on the output value and the first to third output values. A measurement method characterized by obtaining a straight shape of a scale object (third step).

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