JP2000046523A - Measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance accuracy of measurement by making a planar measuring table for mounting a thin article to be measured of ceramic thereby suppressing undulation of the measuring table. SOLUTION: The measuring equipment 1 comprises a planar ceramic measuring table 2. Fine ceramic having rigidity high enough not to cause deformation through aging, e.g. ceramic for stretch, is preferably employed. A pair of sliding rails 11 are arranged in back forth direction on the left and right of the measuring table 2. A gate type movable bridge 3 sliding on the sliding rails 11 is fixed with CCD camera 4 reciprocal in the left/right direction in order to pick up the image of an article to be measured vertically from above. Since the ceramic measuring table 2 has smaller undulation as compared with an aluminum or glass measuring table and reduce aging, undulation is not required to be regulated by moving a supporting member up and down.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for measuring the size of various parts of an object to be measured such as a thin rigid plate using optical means such as a CCD camera.

[0002]

2. Description of the Related Art Conventionally, in the case of a liquid crystal substrate which is repeatedly manufactured by exposure, in order to measure whether a pattern size of a mask or a substrate is formed as designed by each exposure, the pattern of the mask or the substrate is measured. Is placed on a flat measurement table, and the CCD camera is moved in the X-Y direction while capturing the pattern with the CCD camera from above.
2. Description of the Related Art Measuring apparatuses for accurately measuring the dimensions of various portions of a mask or substrate pattern from a moving distance of a camera are known.

[0003]

The measuring table is approximately one meter square and preferably as flat as possible. The measuring table of the conventional measuring device is made of aluminum or glass, and the surface roughness is easily 1
Although it can be reduced to μm or less, there is a problem that undulation is increased. The object to be measured has a small rigidity because it is thin like the above-mentioned substrate, and when the object to be measured is placed on the measurement table, the object to be measured is partially bent according to the undulation of the bed. For example, the curvature radius of the undulation of the measurement table is approximately 666.7 m, the undulation is 30 μm, and the thickness of the measurement table is 1.1 μm.
Assuming that the object to be measured is placed on the
0.33μ due to bending of the object to be measured for a distance of 0mm
An error of m occurs. Therefore, a plurality of vertically movable correction pins are provided below the measurement table at predetermined intervals, and the concave portion of the measurement table is pushed up by the correction pins to reduce the undulation on the upper surface of the measurement table.
However, the undulation of the measurement table cannot be corrected to several tens μm or less by correcting the undulation of the measurement table with the correction pin. Also, when the ambient temperature at the time of measurement changes, aluminum, in particular, thermally expands or contracts, and the undulation changes. Further, if the residual stress in the measurement table is not sufficiently removed, the undulation that the residual stress is released with time changes.
Further, the undulation of the measurement table is irregularly generated depending on the location of the measurement table and changes with time, so that the reproducibility of the error due to the bending of the measured object is extremely low.

[0004] In view of the above problems, an object of the present invention is to provide a measuring apparatus in which the swell of a measuring table is small.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises a flat measuring table on which a thin measuring object is placed, and the measuring object mounted on the measuring table. In the measuring device for optically measuring the dimensions of the above, the measuring table is made of ceramics.

[0006] Ceramics can be processed with less undulation than conventional materials such as aluminum and glass, and are hardly changed in shape due to temperature change, and have little change over time.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 1 denotes a measuring device having a flat plate-shaped measuring table 2 made of ceramics. Ceramics for forming the measurement table 2 may be any of high-performance ceramics, so-called fine ceramics, that have high rigidity and do not change shape over time. It is desirable to use ceramics used for the straight edge). A pair of sliding rails 1 is provided on the left and right sides of the measurement table 2 with the measurement table 2 interposed therebetween.
1 are provided in parallel with each other so as to be long in the front-rear direction. A gate-shaped movable bridge 3 sliding on the sliding rail 11
The movable bridge 3 is provided with a CCD camera 4 that can reciprocate in the left-right direction. The CCD camera 4 captures an image of an object to be measured placed on the measurement table 2 from vertically above. The CCD camera 4 can be freely moved in the X and Y directions by a measuring device 5 composed of an external computer, and the moving amount is input to the control device 5 from a rotary encoder or a potentiometer (not shown). For example, when measuring the distance between two points on an object to be measured, the CCD camera 4 is moved to a position vertically above one of the measurement points, and the coordinates of the measurement point are stored. Subsequently, the CCD camera 4 is moved to a position vertically above the other measurement point to obtain the coordinates of the other measurement point. Then, the distance between the two measurement points is obtained from the coordinates of the fixed points on both sides.

Since the measuring table 2 is made of ceramics, the undulation height ε shown in FIG. 2 is smaller than the undulation height of a conventional aluminum or glass measuring table. In the present embodiment, the radius of curvature of the undulation generated on the measurement table 2 is approximately 4000 m and ε is 5 μm.
When an object to be measured D having a thickness of 1.1 mm is placed on the measuring table 2, 400 m above the object to be measured bent along the undulation
The error due to deflection for a distance of m is 0.055 μm, which is 1/6 that of the conventional measurement table.
become. In FIG. 2, reference numeral 21 denotes a support member that supports the measurement table 2 from below at predetermined intervals and prevents bending of the measurement table 2 due to its own weight. Since the change with time of the measurement table 2 is extremely small, there is no need to adjust the swell by moving the support member 21 in the vertical direction.

[0009]

As is apparent from the above description, according to the present invention, since the measurement table on which the object to be measured is placed is formed of ceramics, the undulation of the measurement table can be reduced, and the undulation can be reduced. Thereby, the measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a sectional view of a measurement table.

[Explanation of symbols]

 1 Measuring device 2 Measuring table 4 CCD camera 5 Control device

Claims (1)

[Claims] 1. A measuring apparatus comprising: a plate-shaped measurement table on which a thin object to be measured is mounted, and optically measuring a dimension of the object to be mounted mounted on the measurement table; A measuring device characterized by being made of ceramics.