JP2996165B2 - Shape measuring method and shape measuring device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape measuring method and a shape measuring apparatus using the same, for example, by measuring the surface of an object to be measured having a continuous curved surface such as a lens surface or a mirror surface.
The difference (error shape) between the measured data and the design shape when measured as a set of coordinate points by the dimensional coordinate measuring device is obtained, and the shape of the measured object is measured with high accuracy.

[0002]

2. Description of the Related Art Conventionally, a contact probe has been frequently used as a three-dimensional coordinate measuring device for three-dimensionally measuring the surface shape of an object to be measured. FIG. 7 is a schematic view of a main part of a three-dimensional shape measuring apparatus for three-dimensionally measuring the shape of the DUT 1 using a conventional contact probe.

In FIG. 1, a device under test 1 is mounted on a base 2. A contact probe 6 having a sphere 6a at the tip is attached to moving members 3, 4, and 5 provided so as to be movable in three dimensions of X, Y, and Z. And contact probe 6
The surface 6a of the object to be measured is traced by the sphere 6a.

FIG. 2 is an enlarged explanatory view of the sphere 6a provided at the tip of the contact probe 6 and the surface 1a of the measured object at this time.

FIG. 1 shows how a contact type probe 6 having a sphere 6a having a radius R traces the surface 1a of an object to be measured and measures coordinate points. As shown in the figure, the surface 1a of the object to be measured is moved while the sphere 6a of the probe 6 is brought into contact with the surface 1a of the object to be measured, and the position of the probe 6 at that time is measured at a position such as a linear scale (not shown). Measured by means. The position measured at this time, that is, the value of the coordinates, is the center position of the sphere 6a at the tip, not the coordinates on the surface 1a of the measured object.

FIG. 3 is a schematic diagram showing a trace locus 16 and a measurement point 17 on the surface 1a of the object to be measured when FIG. 2 is viewed from above (in the z-axis direction). As shown in the figure, the measurement points 17 are a group of points arranged at random. An order is assigned to this point group, and the position is set as a position vector P _{i, j} .

In a measuring method using a contact probe as shown in FIGS. 2 and 3, a coordinate system (hereinafter, referred to as a "coordinate system of an object to be measured") defining the shape of the object 1 and a measuring apparatus are used. Coordinate system (hereinafter referred to as “device coordinate system”)
Are generally different due to mounting errors (setting errors) of the DUT 1. Therefore, when calculating the error shape by subtracting the design shape from the measurement point group measured in the device coordinate system, the measurement point group on the shape in the device coordinate system is coordinate-transformed into a representation on the shape of the object coordinate system. There is a need.

An error (deviation) from a preset position when the object to be measured is mounted at a predetermined position in order to measure the shape of the object to be measured is called an attachment error or a setting error.
Hereinafter, this coordinate conversion is referred to as “attachment error correction” or “setting error correction” of the device under test. In general, there are six types of setting errors in a three-dimensional space: three positional errors (for example, positional displacement errors in the X, Y, and Z directions) and three angular errors (for example, rotational errors about the X, Y, and Z axes). In other words, "setting error" with 6 degrees of freedom
There is.

In the shape measuring apparatus shown in FIG. 7, the measurement data P _{i, j} measured by the coordinate capturing means 7 based on the movement of the contact type probe 6 is led to the setting error correcting means 8, and the setting error is obtained. The error shape is determined by subtracting the design shape from the error. As a setting error correction method, a method using a least squares method is known. The setting error calculating means 8 calculates the setting error and the error shape Q _{i, j} from the design data,
Among them, for example, the error shape Q _{i, j} is stored in the storage / save unit 9 or displayed on the display unit 10.

[0010]

When the shape of the device under test 1 is measured by the shape measuring device shown in FIG. 7, abnormal measurement data is included in the measurement data at each measurement point (coordinate point) P _{i, j.} Is present for the following reason, and the shape measurement accuracy deteriorates. First, a projection-like error is added upward (in the Z direction) due to dust adhering to the surface 1a of the measured object or the sphere 6a at the tip of the probe. In addition, errors occur due to temporary vibration and electrical noise.

The setting error calculated from the coordinate point P _{i, j} including such an error includes a shape measurement error.
Then, an error is also included in the error shape calculated from the setting error including the shape measurement error, and the shape measurement accuracy is deteriorated.

According to the present invention, coordinate points (point groups) that generate abnormal measurement data (abnormal data) are extracted from coordinate points when measuring the surface of an object to be measured, a setting error is correctly calculated, and It is an object of the present invention to provide a shape measuring method capable of measuring the shape of an object with high accuracy and a shape measuring apparatus using the same.

In addition, the present invention complements data at a point cloud where abnormal data is generated by extracting abnormal data by a simple method, or extracting abnormal data, and correctly calculating a setting error. An object of the present invention is to provide a shape measuring method capable of measuring the shape of an object with high accuracy and a shape measuring device using the same.

[0014]

According to the shape measuring method of the present invention, there is provided: (1-1) a setting error calculating means for setting a setting error by means of a setting error calculating means based on measurement data from a shape measuring means for obtaining a shape of a plurality of point groups of an object to be measured. Is corrected, the error shape of the measured object is obtained from the difference between the obtained measurement data and the design data, abnormal data is extracted based on the error shape, the position coordinates are marked, and the marked position coordinates are calculated. The method is characterized in that a step of re-inputting the measurement data at the plurality of removed point groups to the setting error calculating means, correcting the setting error, and obtaining an error shape of the measured object is used.

In particular, (1-1-1) the abnormal data extracting means is arranged such that a maximum value of a difference between one point and an adjacent point exceeds a predetermined constant in the point group of the error shape of the measured object. In this case, one point is extracted as abnormal data.

(1-2) The setting error is corrected by the setting error calculating means from the measured data from the shape measuring means for obtaining the shape of the measured object at a plurality of point groups, and the measured data and the design data obtained therefrom are corrected. The error shape of the measured object is obtained from the difference, the abnormal data is extracted from the error shape by the abnormal data extracting means, the position coordinates are marked, and the measurement data at a plurality of point groups excluding the marked position coordinates are obtained. The setting error is again input to the setting error calculating means, the setting error is corrected, the error shape of the measured object is obtained, the obtained error shape is input to the extraction position complementing means, and the abnormal data is obtained by the extraction position complementing means. That the data at the position where the abnormal data has occurred is used instead of the normal data surrounding the position where the abnormal data has occurred and used as measurement data. It is set to.

(1-3) The shape at a plurality of point groups on the surface of the object to be measured is measured by the shape measuring means, and the measured data at the plurality of point groups from the shape measuring means is read by the coordinate data taking means. The flag is set to 1 or more by the capture and flag setting means, and then the setting error, which is the attitude difference when the object to be measured is placed at a predetermined position, is corrected by the setting error calculation means from the measurement data from the coordinate data capture means. The error shape of the measured object is obtained from the difference between the measured data thus obtained and the design data, and the value of the error shape from the setting error calculation means is determined by the flag determination means when the flag is 1 or more. And then extract the abnormal data by the abnormal data extracting means, and calculate the setting error again using the measured data of the plurality of point groups excluding the point group where the abnormal data has occurred. A step of obtaining an error shape again from the difference between the measurement data in which the setting error has been corrected by the step and the design data, and when the flag becomes 0, the data at the position where the abnormal data has occurred is extracted by the extraction position complementing means. Instead, a process is used in which measurement data is supplemented from normal data around the position where the abnormal data has occurred.

The shape measuring apparatus according to the present invention is characterized in that the shape of an object to be measured is obtained by using any one of the above-mentioned constituent features (1-1) to (1-3). And

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of the present invention. FIG. 2 is a schematic diagram showing a state where the surface 1a of the object is traced by a sphere 6a at the tip of the contact probe 6 of FIG. 1, FIG. 3 is a schematic diagram showing measurement points on the surface of the object, and FIG. Is an explanatory diagram of adjacent points of the error shape on the surface of the measured object, FIG. 5 is an explanatory diagram of measurement points indicating abnormal data in the error shape, and FIG. 6 is a flowchart of a method of complementing the abnormal data in the present embodiment.

In FIG. 1, the DUT 1 is mounted on a base 2, a Y slide 3 is provided on the base 2 so as to be movable in the Y direction, and an X slide 4 is provided on the Y slide 3 so as to be movable in the X direction. The X slide 4 is provided with a Z slide 5 movably in the Z direction, and the Z slide 5 is provided with a contact probe 6. The contact probe 6 has a sphere 6a at its tip, and a control circuit (not shown) for controlling the positions of the X, Y, and Z slides 3, 4, and 5 so that the sphere 6a traces on the surface 1a of the workpiece. ing.

The positions of the X, Y, and Z slides 3, 4, and 5 are measured on a linear scale. The center position of the sphere 6a is calculated from the position of the X, Y, Z slide measured by the linear scale or the like by the coordinate data capturing means 7, and this is used as the measurement data of the point group P _{i, j} .

On the other hand, the flag setting means 11 sets a flag for controlling the operation flow to "1". The measurement data of the point group P _{i, j} is derived from the coordinate data acquisition means 7 to the setting error calculation means 8, the setting error is calculated, the corrected measurement data is obtained, and the design shape is calculated based on the corrected measurement data. Is subtracted to obtain an error shape Q _{i, j} .
That is, an error shape which is a difference between the set shape and specific measurement data is obtained. This method of calculating the setting error at this time is performed by the method described above. The error shape Q _{i, j} from the setting error calculating means 8 is reset by the flag determining means 12 to a value obtained by subtracting 1 from the flag by the flag subtracting means 13 if the flag is larger than 0, and the error shape is changed to the abnormal data. A mark is added to the point group where the abnormal data is found by guiding to the extracting means 14, and all marked positions (coordinate points) are output as mark position data.

The measurement data of the mark position is led again to the setting error calculating means 8, and the setting error is calculated for the measurement data of the point group excluding the mark position, and the setting error and the error shape are calculated again.

Then, since the flag is subtracted by 1 and becomes 0, the flag determination means 12 guides the error shape to the extraction position complementing means 15 and appropriately complements the measurement data of the marked point group. After that, the measurement result is led to the storage means 9 and the display means 10. Although 1 is set by the flag setting means 11, a numerical value of 2 or more may be set. According to this, the procedure is repeated the number of times, and the calculation accuracy can be further improved.

Next, the operation of the abnormal data extracting means 14 and the extraction position complementing means 15 will be described. First, a case where abnormal data is generated as shown in FIG. 5 will be described. FIG. 5 shows measurement points at which the difference from the design value (design shape), that is, the error shape of some point groups greatly deviates from the design value, is referred to as an abnormal measurement point. In such a case, the same result is not obtained even if the shape is measured again at the same place under the same measurement conditions, and in most cases, the measurement is unstable without reproducibility. Also, the difference between these abnormal measurement points and normal measurement points ranges from tens of nanometers to several microns. In particular, when the difference is small, it is indistinguishable from the measured data before the subtraction of the design shape obtained by the coordinate data capturing means 7 because a large change in the design shape is added.

Therefore, the abnormal data extracting means 14 is preferably arranged after the setting error correcting means 8. FIG. 4 shows the arrangement of adjacent measurement points of the error shape. In the figure, since the measurement points are arranged two-dimensionally, they are distinguished by two subscripts, and their position vectors are represented by Q _{i, j} and the like.

Since the abnormal measurement point as shown in FIG. 5 is greatly different from the surroundings, the maximum value of the difference from the surrounding eight points is calculated as in the following equation, and the value obtained by the calculation is defined as a predetermined evaluation value. By determining whether the point is exceeded, it is determined whether the point is an abnormal measurement point. f _{i, j} = max (| Q _{i-1, j + 1} -Q _{i, j} |, | Q _{i, j + 1} -Q _{i, j} |, | Q _{i + 1, j + 1-}
Q _{i, j} |, | Q _{i-1, j} -Q _{i, j} |, | Q _{i + 1, j} -Q _{i, j} |, | Q _{i-1, j-1} -Q _{i, j} |,
| Q _{i, j-1} -Q _{i, j} |, | Q _{i + 1, j-1} -Q _{i, j} |) Since there are no neighboring eight points around, In that case, it takes the maximum value at the point that exists. The evaluation value used for the determination is appropriately determined in view of the magnitude of the shape error of the measured object. For example, when measuring the shape of the lens surface where the error is expected to be 100 nm or less, the value may be set to 100 nm. The above formula is calculated for all measurement points, and the evaluation values are compared. If the evaluation values are exceeded, the data is regarded as abnormal data and marked.

As described above, when the absolute value of the difference between one point and an adjacent point in the point group of the error shape exceeds a predetermined constant, the abnormal data extracting means in this embodiment Is marked. An abnormal measurement point indicates a value far apart from a normal measurement point, and is determined by monitoring the magnitude of the difference between adjacent points.

Next, the operation of the extraction position complementing means 15 will be described with reference to FIG.
This will be described with reference to the flowchart of FIG. First, the data of the marked abnormal measurement point is discarded. Next, if necessary, the marked point group is appropriately complemented while checking the surrounding point group. First, the subscripts i and j are changed for all the measurement areas _{, and} when the mark is attached to Q _{i, j} , the counter n is set to 0.
Is set to 0, a variable Q is set to 0, and i1 is changed from im to i + m for one or more constants m, and j1
Is changed from j−m to j + m. If Q _{i1 and j1} are not marked, they are added to Q, and 1 is added to n. At the end of this loop, if n is not zero, Q _{i, j}
Is substituted for Q / n. If n is zero, there are no normal points around, so do nothing and go to the next step. The above operation is performed for all the measurement areas. And no more Q
Repeat until _{i and j} no longer change.

As described above, in the present embodiment, the extraction position complementing means substitutes the average value of the values of one unmarked point group adjacent to one point marked in the error-shaped point group into the data of the one point. Is repeated until there are no more marked positions. As a result, without using abnormal data, measurement results are obtained only from surrounding normal measurement points and complemented to obtain an error shape, thereby improving measurement accuracy.

If the shape measuring apparatus of the present invention is used in, for example, a process of manufacturing a device (semiconductor device),
The device can be easily manufactured.

[0032]

According to the present invention, by utilizing each step as described above, the coordinate points (abnormal data) which generate abnormal measurement data (abnormal data) among the coordinate points when measuring the surface of the workpiece are measured. (Point group) is extracted, a setting error is correctly calculated, and a shape measuring method and a shape measuring apparatus using the same capable of measuring the shape of an object to be measured with high accuracy can be achieved.

Further, according to the present invention, the abnormal data is extracted by a simple method, or the abnormal data is extracted, and the setting error is correctly calculated, thereby complementing the data in the point group that generates the abnormal data. It is possible to achieve a shape measuring method and a shape measuring apparatus using the same, which can measure the shape of an object to be measured with high accuracy.

In addition, the present invention has the following effects.

(A) The setting error can be accurately calculated even when abnormal measurement points are mixed. Therefore, it is possible to perform shape measurement with higher accuracy than in the case where a result of an error shape distorted due to an abnormal measurement point is conventionally given. Further, even if there is an abnormal measurement point, the necessity of re-measurement can be reduced, and the operation efficiency of the measurement device can be improved.

(B) High-precision shape measurement is possible even when there is an influence of an object to be measured, which is a main cause of an abnormal measurement point, or dust attached to a sphere at the tip of the probe. Therefore, since the conditions for the measurement environment can be relaxed,
It is possible to reduce the installation cost of the measuring device.

Further, in addition to the effects (a) and (b), (c) abnormal data can be extracted by a simple method.

(D) After removing an abnormal measurement point, the point is complemented from surrounding data, so that a smooth measurement result can be obtained.

(E) The abnormal data can be complemented by a simple method. And the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state in which the surface of the object to be measured 1a is traced by a sphere 6a at the tip of the contact probe 6 of FIG.

FIG. 3 is a schematic diagram showing measurement points on the surface of an object to be measured.

FIG. 4 is an explanatory diagram of adjacent points of an error shape on the surface of a measured object.

FIG. 5 is an explanatory diagram of measurement points indicating abnormal data among error shapes.

FIG. 6 is a flowchart of a method for complementing abnormal data in the embodiment.

FIG. 7 is a schematic diagram of a main part of a conventional shape measuring apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DUT 2 Base 3 Y slide 4 X slide 5 Z slide 6 Probe 6a Sphere at the tip of probe 7 Coordinate data capture device 8 Setting error calculation device 9 Storage device 10 Display device 11 Flag setting device 12 Flag judgment device 13 Flag subtraction device 14 Abnormal data extraction device 15 Extraction position complementing device 16 Probe scanning locus 17 Measurement point

Claims (5)

(57) [Claims] 1. A setting error calculating means for correcting a setting error based on measurement data from a shape measuring means for obtaining a shape of a plurality of point groups of an object to be measured, and a setting error is calculated based on a difference between the obtained measurement data and the design data. The error shape of the measured object is obtained, abnormal data is extracted based on the error shape, the position coordinates are marked, and the measurement data at a plurality of point groups excluding the marked position coordinates is again set in the setting error calculating means. And a step of correcting a setting error by inputting the error to a device to obtain an error shape of the object to be measured. 2. The method according to claim 1, wherein when the maximum value of the difference between one point and an adjacent point exceeds a predetermined constant in the point group of the error shape of the device under test, 2. The shape measuring method according to claim 1, wherein the data is extracted as abnormal data. 3. A setting error is corrected by a setting error calculating means from measurement data from a shape measuring means for obtaining a shape of a plurality of point clouds of the object to be measured, and a setting error is calculated from a difference between the obtained measurement data and the design data. The error shape of the measured object is determined, the abnormal data is extracted from the error shape by the abnormal data extracting means, the position coordinates are marked, and the measurement data at a plurality of point groups excluding the marked position coordinates is set again. Correcting the setting error by inputting to the error calculating means, obtaining the error shape of the measured object, inputting the obtained error shape to the extraction position complementing means, and generating the abnormal data by the extraction position complementing means. A method characterized by using a process of removing position data and supplementing it with normal data around the position where the abnormal data occurs to obtain measurement data instead. Condition measurement method. 4. A shape measuring means for measuring a shape at a plurality of point groups on the surface of the object to be measured, and measurement data at the plurality of point groups from the shape measuring means are taken in by coordinate data taking means, and a flag is read. The setting means sets a flag to 1 or more, and then the setting data calculating means corrects the setting error, which is the attitude difference when the object is placed at a predetermined position, from the measurement data from the coordinate data taking means. And the design data, the error shape of the DUT is obtained, and the value of the error shape from the setting error calculation means is subtracted by one from the value of the flag when the flag is one or more by the flag determination means. Later, the abnormal data is extracted by the abnormal data extracting means, and the setting error calculating means again uses the measurement data of the plurality of point groups excluding the point group where the abnormal data has occurred. A step of obtaining an error shape again from the difference between the measurement data and the design data in which the setting error has been corrected, and, when the flag becomes 0, the data at the position where the abnormal data has occurred is extracted by the extraction position complementing means. Instead, a shape measurement method is characterized in that a step of using measurement data as a complement to normal data around a position where the abnormal data is generated is used. 5. A shape measuring apparatus for measuring a shape of an object to be measured by using the shape measuring method according to claim 1.