JPH09189544A - Method for measuring shape and apparatus for measuring shape using the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly calculate a setting error and highly accurately measure a shape of an object to be measured, by obtaining an error shape of the object from a difference between measuring data and design data and extracting abnormal data based on the error shape. SOLUTION: Measuring data of a point group Pi ,j are introduced to a setting error-calculating means 8 from a coordinate data-taking means 7, thereby to calculate a setting error. A design shape is subtracted based on corrected measuring data, whereby an error shape Qi ,j is obtained. In calculating the setting error, if a flag of the error shape Qi ,j from the setting error-calculating means 8 is detected to be larger than 0 by a flag-judging means 12, a value subtracted 1 from the flag by a flag-subtracting means 13 is reset, and the error shape is guided to an abnormal data-extracting means 14, where a point group in which abnormal data are discovered is marked and output as marked position data. The error shape is guided from the flag-judging means 12 to an extraction position-complementing means 15, so that measuring data of the marked point group are complemented.

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 shape measuring method. For example, the surface of an object to be measured having a continuous curved surface such as a lens surface or a mirror surface is
The difference (error shape) between the measurement data and the design shape when measured as a group of coordinate points by the dimensional coordinate measuring apparatus 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 widely used as a three-dimensional coordinate measuring apparatus 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 that three-dimensionally measures the shape of the DUT 1 using a conventional contact probe.

In FIG. 1, the device under test 1 is attached to a base 2. Further, the contact type probe 6 having a sphere 6a at its 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 spherical body 6a.

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

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

FIG. 3 is a schematic view showing a trace locus 16 and a measurement point 17 on the surface 1a of the object to be measured as viewed from above (z-axis direction) in FIG. As shown in the figure, the measurement points 17 are a set of randomly arranged points. This point group is given an order, and its position is defined as a position vector P _{i, j} .

In a measuring method using a contact type probe as shown in FIGS. 2 and 3, a coordinate system (hereinafter referred to as "measurement object coordinate system") for defining the shape of the DUT 1 and a measuring device. Coordinate system (hereinafter referred to as "apparatus coordinate system")
Are generally different because of the mounting error (setting error) of the DUT 1. Therefore, when the design shape is subtracted from the measurement point group measured in the device coordinate system and the error shape is calculated, the coordinate of the shape measurement point group in this device coordinate system is converted into the shape representation in 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 installation error or a setting error.
Hereinafter, this coordinate conversion will be referred to as "correction of mounting error" or "correction of setting error" of the object to be measured. Generally, there are a total of 6 types of setting errors in a three-dimensional space, including three position errors (for example, positional deviation errors in the X, Y, and Z directions) and three angular errors (for example, rotation errors around the X, Y, and Z axes). That is, "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 fetching means 7 based on the movement of the contact type probe 6 is guided to the setting error correcting means 8 to obtain the setting error, and the setting error is obtained. The design shape is further subtracted to obtain the error shape. As this setting error correction method, a method using the least squares method is known. The setting error calculation means 8 calculates the setting error and the error shape Q _{i, j} from the design data,
Of these, for example, the error shape Q _{i, j} is stored in the storage means 9 or displayed on the display means 10.

[0010]

When the shape of the object to be measured 1 is measured by the shape measuring apparatus shown in FIG. 7, the measured data at each measurement point (coordinate point) P _{i, j} is abnormal measurement data. Since there are measurement points having “” for the following reason, the accuracy of shape measurement deteriorates. First, a projection-like error is added upward (Z direction) by dust adhering to the surface 1a of the object to be measured or the sphere 6a at the tip of the probe. Also, errors occur due to temporary vibrations and electrical noise.

The setting error calculated from the coordinate point P _{i, j} including such an error includes a shape measurement error.
Then, the error shape calculated from the setting error including the shape measurement error also contains an error, which deteriorates the shape measurement accuracy.

The present invention extracts coordinate points (point groups) that generate abnormal measurement data (abnormal data) from the coordinate points when measuring the surface of the object to be measured, correctly calculates the setting error, and An object of the present invention is to provide a shape measuring method capable of measuring the shape of a measurement object with high accuracy and a shape measuring apparatus using the shape measuring method.

In addition to the above, the present invention extracts abnormal data by a simple method, or extracts abnormal data and correctly calculates the setting error, thereby complementing the data at the point group where the abnormal data is generated and measuring the measured data. 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 apparatus using the shape measuring method.

[0014]

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

In particular, (1-1-1) the abnormal data extracting means has a maximum value of a difference between one point and an adjacent point in the error shape point group of the object to be measured exceeding a predetermined constant. If there is, one of the points is extracted as abnormal data.

(1-2) The setting error is corrected by the setting error calculating means from the measurement data from the shape measuring means for obtaining the shapes of the object to be measured at a plurality of point groups, and the measurement data and the design data obtained from this are corrected. The error shape of the object to be measured is obtained from the difference, the abnormal data is extracted from the error shape by the abnormal data extraction means, the position coordinates thereof are marked, and the measurement data at a plurality of point groups excluding the marked position coordinates are obtained. It is input to the setting error calculating means again to correct the setting error to obtain the error shape of the object to be measured, and the obtained error shape is input to the extraction position complementing means. Is used to replace the normal position data around the position where the abnormal data is generated with the measured data. It is set to.

(1-3) The shape measuring means measures the shapes of a plurality of point groups on the surface of the object to be measured, and the coordinate data fetching means measures the measurement data of the plurality of point groups from the shape measuring means. The flag is set to 1 or more by the fetching and flag setting means, and the setting error calculation means corrects the setting error which is the attitude difference when the measured object is placed at the predetermined position from the measurement data from the coordinate data fetching means. The error shape of the object to be measured is obtained from the difference between the measured data and the design data, and the value of the error shape from the setting error calculation means is 1 from the value of the flag when the flag is 1 or more by the flag determination means. After extracting the abnormal data, the abnormal data is extracted by the abnormal data extracting means, and the setting error is calculated again by using the measurement data of a plurality of point groups excluding the point group in which the abnormal data occurs. The step of obtaining the error shape again from the difference between the measurement data and the design data in which the setting error is corrected by the step, and when the flag becomes 0, the extraction position complementing means is used to send the data of the position where the abnormal data has occurred. Instead of that, a process of complementing normal data around the position where the abnormal data is generated to obtain measurement data is used.

The shape measuring apparatus of the present invention is characterized in that the shape of an object to be measured is obtained by using the shape measuring method according to any one of the above-mentioned constitutional requirements (1-1) to (1-3). I am trying.

[0019]

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

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

The positions of the X, Y, Z slides 3, 4, and 5 are measured with a linear scale. The center position of the sphere 6a is calculated from the position of the X, Y, Z slides measured by the coordinate data capturing means 7 using a linear scale or the like, 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 flow of operation 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 to calculate the setting error, and the corrected measurement data is obtained from this, and the design shape is based on this corrected measurement data. To obtain the error shape Q _{i, j} .
That is, the error shape, which is the difference between the set shape and the specific measurement data, is obtained. Further, this method of calculating the setting error at this time is performed by the method described above. For the error shape Q _{i, j} from the setting error calculation means 8, if the flag is larger than 0 by the flag determination means 12, the flag subtraction means 13 resets the flag to a value obtained by subtracting 1 from the flag, and the error shape is determined as abnormal data. The extraction means 14 guides a mark to the point group where abnormal data is found, and outputs all marked positions (coordinate points) as mark position data.

The measurement data of the mark position is again guided to the setting error calculation means 8, and this time, 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, the flag judging means 12 subtracts 1 from the flag this time and becomes 0, so the error shape is guided to the extraction position complementing means 15 and the measurement data of the marked point group is appropriately complemented. After that, the measurement result is led to the storage means 9 and the display means 10. Further, 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 for that number of times, and the calculation accuracy can be further improved.

Next, the operations of the abnormal data extracting means 14 and the extraction position complementing means 15 will be described. First, a case where abnormal data occurs as shown in FIG. 5 will be described. FIG. 5 shows measurement points where the difference from the design value (design shape), that is, the error shape of a part of the point group deviates significantly from the design value, and these point groups are called abnormal measurement points. In such a case, even if the shape is measured again at the same place under the same measurement condition, the same result cannot be obtained, and in most cases, the reproducibility is unstable. Further, the difference between these abnormal measurement points and normal measurement points ranges from several tens of nanometers to several microns. Especially when the difference is small, it cannot be distinguished at all from the measured data obtained by the coordinate data fetching means 7 before the design shape is subtracted, because a large change in the design shape is added.

Therefore, the abnormal data extraction means 14 is preferably arranged after the setting error correction 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 the position vector is expressed as Q _{i, j} .

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 8 points is calculated by the following equation and the value is set to a preset evaluation value. By determining whether or not it exceeds, it is determined whether or not 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 8 adjacent points around, In that case, it takes the maximum value at the existing point. The evaluation value used for the determination is appropriately determined depending on the size of the shape error of the object to be measured. For example, when the shape of the lens surface is expected to have an error of 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, it is regarded as abnormal data and marked.

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

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. First, the data of the marked abnormal measurement points is discarded. Then, if necessary, the marked point group is appropriately complemented while looking at the surrounding point group. First, when the subscripts i and j are changed for all the measurement areas and Q _{i, j} is marked, the counter n is set to 0.
, A variable Q is set to 0, i1 is changed from i−m to i + m for a constant m of 1 or more, and j1
Is changed from j−m to j + m, and if Q _{i1, j1} is not marked, it is added to Q and n is incremented by 1. At the end of this loop, if n is not zero, then Q _{i, j}
Substitute Q / n for If n is zero, there is no normal point around, so proceed without doing anything. The above operation is performed for all measurement regions. And no more Q
Repeat until _{i and j} do not change.

As described above, in the present embodiment, the extraction position complementing means substitutes the average value of the unmarked point groups adjacent to one point marked in the error shape point group into the data of the one point. Repeat until the marked position disappears. As a result, the measurement accuracy is improved by obtaining the measurement result from only the normal measurement points in the periphery and complementing the error shape without using abnormal data.

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

[0032]

As described above, according to the present invention, by utilizing each process as described above, coordinate points (abnormal data) that generate abnormal measurement data (abnormal data) among the coordinate points when measuring the surface of the object to be measured ( It is possible to achieve a shape measuring method and a shape measuring apparatus using the same which can accurately measure the shape of an object to be measured by extracting a point cloud), calculating a setting error correctly.

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 which generates the abnormal data, A shape measuring method and a shape measuring apparatus using the shape measuring method capable of measuring the shape of an object to be measured with high accuracy can be achieved.

Besides, according to the present invention, there are the following effects.

(B) The setting error can be calculated accurately even when abnormal measurement points are mixed. Therefore, it is possible to measure the shape with higher accuracy than in the case where the result of the error shape distorted due to an abnormal measurement point is conventionally given. Further, it becomes possible to reduce the necessity of re-measurement even if there is an abnormal measurement point, and it is possible to improve the operational efficiency of the measuring device.

(B) It is possible to perform highly accurate shape measurement even if there is an influence of an object to be measured, which is a main cause of an abnormal measuring point, or dust attached to a sphere at the tip of the probe. Therefore, it is possible to loosen the conditions for the measurement environment,
It is possible to reduce the installation cost of the measuring device.

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

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

(E) Abnormal data can be complemented by a simple method. And so on.

[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 view showing a state in which a surface 6a of the object to be measured is traced by a spherical body 6a at the tip of the contact type probe 6 of FIG.

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

FIG. 4 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.

FIG. 6 is a flowchart of an abnormal data complementing method according to the present embodiment.

FIG. 7 is a schematic view of a main part of a conventional shape measuring device.

[Explanation of symbols]

 1 Object to be Measured 2 Base 3 Y Slide 4 X Slide 5 Z Slide 6 Probe 6a Sphere at Tip of Probe 7 Coordinate Data Capture Device 8 Setting Error Calculator 9 Memory Saving Device 10 Display Device 11 Flag Setting Device 12 Flag Judging Device 13 Flag subtracting device 14 Abnormal data extracting device 15 Extraction position complementing device 16 Probe scanning locus 17 Measuring point

Claims (5)

[Claims] 1. A setting error calculation means corrects a setting error from measurement data from a shape measuring means for obtaining shapes of a plurality of point groups of an object to be measured, and a difference between the measured data and design data obtained from the setting error is used to detect the difference. The error shape of the measurement object is obtained, abnormal data is extracted based on the error shape, the position coordinates thereof are marked, and the measurement data at a plurality of point groups excluding the marked position coordinates are again set by the setting error calculation means. A shape measuring method characterized by using a step of inputting into the step (1) to correct a setting error and obtaining an error shape of the object to be measured. 2. The abnormal data extracting means selects one point in the error shape point group of the object to be measured when the maximum value of the difference between the point and the adjacent point exceeds a predetermined constant. The shape measurement method according to claim 1, wherein the shape measurement is performed as abnormal data. 3. The setting error is corrected by the setting error calculation means from the measurement data from the shape measuring means for obtaining the shapes of the object to be measured at a plurality of point groups, and the difference between the measured data and the design data obtained from the setting error is corrected. The error shape of the measured object is obtained, the abnormal data extracting means extracts the abnormal data from the error shape, the position coordinates are marked, and the measurement data at a plurality of point groups excluding the marked position coordinates are again set. The error shape of the object to be measured is obtained by inputting it to the error calculating means to correct the setting error, the obtained error shape is inputted to the extraction position complementing means, and the abnormal data is generated by the extraction position complementing means. The method is characterized in that a step of using the position data to replace the normal data around the position where the abnormal data is generated to obtain measurement data is used instead. Condition measurement method. 4. The shape measuring means measures the shape of a plurality of point groups on the surface of the object to be measured, the measurement data of the plurality of point groups from the shape measuring means is fetched by the coordinate data fetching means, and a flag is set. Measurement data obtained by setting a flag to 1 or more by the setting means and then correcting the setting error which is the attitude difference when the object to be measured is placed at a predetermined position by the setting error calculation means from the measurement data from the coordinate data fetching means. Then, the error shape of the object to be measured is obtained from the difference from the design data, and the value of the error shape from the setting error calculation means is subtracted from the value of the flag when the flag is 1 or more by the flag determination means. After that, the abnormal data is extracted by the abnormal data extracting means, and the measured data of a plurality of point groups excluding the point cloud in which the abnormal data is generated is used again by the setting error calculating means. A step of obtaining an error shape again from the difference between the measurement data corrected for the setting error and the design data, and when the flag becomes 0, the extraction position complementing means is used to pass the data of the position where the abnormal data has occurred, Instead, a shape measuring method is characterized in that a process of complementing normal data around a position where the abnormal data is generated to obtain measurement data is used. 5. A shape measuring device, characterized in that the shape measuring method according to claim 1 is used to measure the shape of an object to be measured.