JPH10281732A - Dimension measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sustain the accuracy of calculating dimensions based on the image data of an object by scanning the object at a constant speed regardless of the weight thereof. SOLUTION: A laser beam 10 from a laser light source 4 is swept in the X direction by means of an X direction galvanomirror 5 and the laser beam 10 reflected thereon is swept in the Y direction by means of a Y direction galvanomirror 6 in order to scan a mask (object) 1 two-dimensionally by means of the laser beam 10. Intensity of the laser beam 10 reflected on the mask 1 is detected by a light receiving element 9 in order to obtain one-dimensional image data which are recorded sequentially on an image memory 13 and a two-dimensional image data is generated on the image memory 13. Subsequently, an image processing section 15 extracts the outline of a mask pattern from the two-dimensional image data and calculates the line width based on the number of pixels between the extracted outlines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting two-dimensional image data of an object to be measured by detecting reflected light of light illuminating the object to be measured, and obtaining the dimensions of the object from the image data. More specifically, the present invention relates to a dimension measuring apparatus capable of performing highly accurate dimension measurement without being affected by weight fluctuation of an object to be measured.

[0002]

2. Description of the Related Art Conventionally, as a dimension measuring device used for measuring a minute dimension such as a line width of a mask pattern,
An image processing type dimension measuring device for detecting the reflected light of the light irradiated to the object to obtain enlarged two-dimensional image information of the object to be measured and calculating the dimension of the object to be measured from the two-dimensional image information. Is known (see Japanese Patent Application Laid-Open No. 4-278555, etc.). Conventionally, an image processing type dimension measuring apparatus as described above has a configuration in which scanning is performed by moving an object to be measured placed on a stage to obtain two-dimensional image information of the object to be measured. was there.

[0003]

However, as described above, in the case of the configuration in which the scanning is performed by moving the measurement object, the movement of the measurement object changes depending on the weight of the measurement object, and the constant In some cases, the scanning speed cannot be maintained. When the scanning speed changes, there is a problem in that the actual dimensions are the same, but the images are photographed in different dimensions on the image information. Was being maintained.

Further, when measuring the line width of a mask pattern, if the line width direction intersects the scanning direction (X direction or Y direction) at a certain angle, the dimension along the X direction or Y direction is obtained. When the calculation is performed, a measurement error occurs according to the angle, and there is a problem that the line width cannot be measured with high accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to address the above-mentioned problems and to provide a dimension measuring apparatus capable of measuring dimensions in the same calibration state without being affected by the weight of an object to be measured. . A further object of the present invention is to provide a dimension measuring device capable of measuring a dimension with high accuracy even at a measurement site crossing at an angle with respect to the X direction or the Y direction.

[0006]

In order to achieve the above object, a dimension measuring apparatus according to the present invention comprises a light source for emitting a light beam, a light source for deflecting the light beam from the light source, and a measurement target mounted on a stage. X direction scanning means for scanning an object in the X direction, Y direction scanning means for deflecting a light beam from the light source and scanning the object to be measured in the Y direction,
The light beam is two-dimensionally scanned on the object by the light detection unit that detects reflected light of the light beam applied to the object, and the X-direction scanning unit and the Y-direction scanning unit. Imaging means for obtaining two-dimensional image data of the object based on the detection result by the light detecting means at the time; and calculating dimensions of the object based on the two-dimensional image data obtained by the imaging means. And dimension calculation means.

Preferably, the light beam is a laser beam. The X-direction scanning means and Y
The direction scanning means may be constituted by a galvanomirror.

Further, an angle discriminating means for discriminating an intersection angle of the dimension measuring portion in the object to be measured in the X and Y directions based on the two-dimensional image data obtained by the image pickup means, and the stage is driven to rotate. Stage rotation drive means, and rotation control means for rotating the stage by the stage rotation drive means by the intersection angle determined by the angle determination means to match the dimension measurement portion of the workpiece with the X direction or Y direction. Should be provided.

[0009]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a dimension measuring device according to the present invention. This dimension measuring device calculates a line width of a pattern on a mask 1 as an object to be measured based on two-dimensional image data obtained by imaging the mask 1.

In FIG. 1, a mask 1 as an object to be measured (sample) is an XYθ stage (hereinafter abbreviated as a stage).
2 is placed. The stage 2 is configured to be movable in the X and Y directions (a direction orthogonal to the X direction) constituting a horizontal plane and to be rotatable on the same plane. It is supposed to be. The detailed configuration of the stage control unit 3 will be described later.

On the other hand, a laser light source (light source) 4, an X-direction galvanometer mirror (galvanometer mirror) 5, a Y-direction galvanometer mirror (galvanometer) in order to scan a portion of the mask 1 where the dimension measurement is to be performed to obtain a two-dimensional image. A mirror) 6, a prism 7, an objective lens 8, and a light receiving element (line sensor) 9 having photoelectric conversion elements arranged in the X direction.

A laser beam 10 emitted from the laser light source 4 is applied to an X-direction galvanometer mirror 5 and reflected. The reflected laser beam 10 is applied to a Y-direction galvanometer mirror 6 and reflected. The mask 1 on the stage 2 is irradiated via the lens 8. The laser beam 10 reflected by the mask 1 passes through an objective lens 8 for enlarging the reflected light image, is then polarized by a prism 7 and forms an image on a light receiving surface of the light receiving element 9 (light detecting means). Each element (pixel) 9 outputs an electric signal corresponding to the intensity of incident light, so that one-dimensional image data of the mask 1 can be obtained.

Here, the X-direction galvanometer mirror 5 and the Y-direction galvanometer mirror 6 are driven and controlled by galvanometer mirror controllers 11 and 12, respectively. The X-direction galvanometer mirror 5 causes the laser beam 10 to move in the X direction by its vibration. Scanning (X-direction scanning means), and the Y-direction galvanometer mirror 6 scans the laser beam 10 in the Y-direction by its vibration (Y-direction scanning means). As a result, the laser beam 10 moves the mask 1 in the X-direction and Y-direction. The two-dimensional image data of the mask 1 is obtained as a set of one-dimensional image data obtained by the light receiving element 9 (see FIG. 3).

FIG. 3 shows the laser beam 10 in the X direction and Y direction.
It shows the state of an output signal from the light receiving element 9 when a direction scan is performed. Specifically, when a laser beam is scanned in the X direction crossing two parallel patterns, the pattern portion is high. Is output from the light receiving element 9,
By repeatedly performing such scanning in the X direction while gradually shifting the scanning in the Y direction, a state in which two-dimensional image data, that is, two parallel patterns are captured is shown.

The objective lens 8 has an automatic focusing mechanism.
A focus 16 is automatically provided in response to a change in the optical path length caused by the scanning of the laser beam 10.

The one-dimensional image data from the light receiving element 9 is sequentially recorded in the image memory 13 in FIG. 1, and two-dimensional image data of the measurement site of the mask 1 is generated on the image memory 13 (imaging means). Then, the two-dimensional image data is displayed on a monitor 14, and a measurement dimension is calculated by an arithmetic processing unit 15 (dimension calculating means) based on the two-dimensional image data recorded in the image memory 13. The obtained dimensional data is displayed on the monitor 14.

FIG. 2 is a block diagram showing the details of the stage control unit 3, and shows a laser beam from a laser light source 21.
After being polarized by the mirror 23, the light 22 enters the prism 24 and is separated, and supplied to the X-axis interferometer 25 and the Y-axis interferometer 26. The X-axis interferometer 25 and the Y-axis interferometer 26 detect the positions of the stage 2 in the X direction and the Y direction. Is input to The servo controller 28 includes the X-axis interferometer 25,
Upon receiving the measurement result by the Y-axis interferometer 26, an X servo 29 for driving the stage 2 in the X direction, a Y servo 30 for driving the stage 2 in the Y direction, and a θ servo for rotating and driving the stage 2
Control 31. X servo 29 and Y servo 30 are X, Y
The θ servo 31 corresponds to the direction driving means, and the θ servo 31 corresponds to the stage rotation driving means.

In the dimension measuring apparatus having the above configuration, first,
The portion of the mask pattern to be measured on the mask 1 is within the imaging range of the imaging scanning system including the laser light source 4, the X-direction galvanometer mirror 5, the Y-direction galvanometer mirror 6, the prism 7, the objective lens 8, the light receiving element 9, and the like. As described above, the stage 2 is moved in the X and Y directions by the stage control unit 3. Then, in a state where the position of the stage 2 is fixed, the laser beam 10 is two-dimensionally scanned by the X-direction galvanometer mirror 5 and the Y-direction galvanometer mirror 6, and a light receiving element is formed based on the reflected light from the mask 1 at this time. 1 obtained by 9
The two-dimensional image data is generated by sequentially recording the two-dimensional image data in the image memory 13.

The two-dimensional image data recorded in the image memory 13 includes an image in which the pattern portion and the transmissive portion are represented as a light-dark difference due to the difference in reflectance between the pattern portion and the transmissive portion of the mask 1. Become. Therefore, the image processing unit 15 outputs a signal for each element (pixel) of the light receiving element 9 to 2
The contour line of the pattern portion is extracted by, for example, converting to a value, the number of pixels between the contour lines is counted in the X direction or the Y direction, and the pattern is calculated based on the count value and a predetermined length per pixel. Calculate the line width (dimension calculating means).

According to the above configuration, the laser beam 10 is scanned in the X and Y directions with the mask 1 as the object to be measured fixed to obtain two-dimensional image data of the measurement site. Even when the weight of the object (mask 1) changes, the scanning speed does not change, and the dimensions can be measured with high accuracy based on the number of pixels on the two-dimensional image data.

On the image data obtained by two-dimensional scanning of the laser beam 10, if the pattern portion is oblique as shown in FIG. 4 (the contour of the pattern is in the X direction and the Y direction). At an angle θ),
When the line width is calculated in the X direction or the Y direction, the intersection angle θ
Will be caused.

Therefore, in this embodiment, when the contour line of the pattern portion extracted as described above has a certain angle θ with respect to the X and Y directions (see FIG. 4), From the angle θ (angle determination means),
The stage 2 is rotated by the calculated angle (rotation control means) so that the contour of the angle pattern matches the X direction or the Y direction (see FIG. 4). Then, the laser beam 10 is scanned again to obtain image data, and the number of pixels between contour lines that match in the X direction or the Y direction is counted to measure the line width. According to the above configuration, since the dimension measurement can be performed with the direction of the pattern line width always being adjusted to the X direction or the Y direction, the pattern line width can be measured with high accuracy regardless of the pattern direction.

In the above embodiment, the pattern line width is measured using the mask 1 as an object to be measured.
For example, a semiconductor substrate manufactured using the mask 1 may be used as an object to be measured, and the object to be measured is not limited to the mask 1. Although a laser beam is used as the light beam in the above description, a light source other than a laser may be used. However, by using a laser beam, the spot diameter can be reduced, and thus dimensional measurement can be performed with high accuracy.

[0024]

The present invention has been configured as described above.
By scanning the light beam with the object to be measured in a fixed state to obtain image data of the object to be measured, and calculating the dimensions based on the image data, a constant value is obtained without being affected by the weight fluctuation of the object to be measured. The object to be measured can be imaged at the scanning speed, and the dimension can be measured in the same calibration state without being affected by the weight of the object to be measured.

Further, by scanning the object to be measured with the laser beam, the object to be measured can be scanned with a small spot diameter and the dimension can be measured with high accuracy. Furthermore, by scanning the light beam in the X and Y directions with a galvanometer mirror,
Highly reliable optical scanning can be performed. Also,
Even when the measurement site has a certain angle with respect to the X and Y directions, such as an angle pattern of a mask, by rotating the stage, the measurement site is adjusted to the X direction or the Y direction before imaging. Thereby, dimension measurement can be performed with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing details of a stage control unit in the embodiment.

FIG. 3 is a diagram showing a state of scanning in an X direction and a Y direction in the embodiment.

FIG. 4 is a diagram showing a procedure of measuring a line width of an angle pattern in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mask (measured object) 2 ... Stage 3 ... Stage control part 4 ... Laser light source (light source) 5 ... X direction galvanometer mirror (X direction scanning means) 6 ... Y direction galvanometer mirror (Y direction scanning means) 7 ... Prism 8 Objective lens 9 Light receiving element (light detecting means) 10 Laser beam (light beam) 11, 12 Galvano mirror control unit 13 Image memory 14 Monitor 15 Operation processing unit (dimension calculating means) 16 Auto focus mechanism

Claims (4)

[Claims] A light source for emitting a light beam; X-direction scanning means for deflecting the light beam from the light source to scan an object to be measured placed on a stage in an X direction; Y-direction scanning means for deflecting a beam to scan the object in the Y direction, light detecting means for detecting reflected light of the light beam applied to the object, and X-direction scanning means Imaging means for obtaining two-dimensional image data of the object to be measured based on a detection result by the light detecting means when the light beam is two-dimensionally scanned on the object to be measured by a Y-direction scanning means; and A dimension calculation unit configured to calculate a dimension of the object to be measured based on the two-dimensional image data obtained by the imaging unit. 2. The dimension measuring apparatus according to claim 1, wherein said light beam is a laser beam. 3. The apparatus according to claim 1, wherein said X-direction scanning means and said Y-direction scanning means are constituted by galvanometer mirrors.
Or the dimension measuring device according to 2. 4. An angle discriminating means for discriminating an intersection angle of the dimension measuring portion in the object to be measured in the X and Y directions based on the two-dimensional image data obtained by the image pickup means, and the stage is rotationally driven. Stage rotation drive means, and rotation control means for rotating the stage by the stage rotation drive means by the intersection angle determined by the angle determination means to match the dimension measurement portion of the workpiece with the X direction or Y direction. The dimension measuring device according to any one of claims 1 to 3, further comprising: