JPH0771918A - Dimension measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent errors in measured values due to displacement of the imaging means due to changes over time. An illumination optical system that irradiates a sample 10 having a high step pattern and a low step pattern with light, an objective lens 9 that collects a light beam from the sample surface, and an objective lens 9 that is disposed behind the objective lens 9. Half mirror 7 for splitting the light flux of objective lens 9, imaging lens 6 for focusing one light flux split by this half mirror 7, and imaging for focusing the other light flux split by half mirror 7. An optical system, an imaging unit 5 for photoelectrically converting a sample image by the imaging lens 6, an imaging unit 15 for photoelectrically converting a sample image by the imaging optical system, and a sample formed between the sample 10 and the half mirror 7. The transparent reference plate 17 arranged at the positions of the ten intermediate images and provided with the reference marks 17a and 17b, the distance between the high step pattern image and the reference mark image, and the distance between the low step pattern image and the reference mark image, respectively. Seeking Further, there is provided a signal processing means 16 for measuring the dimension between the high step pattern and the low step pattern by obtaining the difference between the two distances.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimension measuring device,
In particular, the present invention relates to a dimension measuring device that measures a dimension between a high step pattern and a low step pattern.

[0002]

2. Description of the Related Art FIG. 4 is an overall configuration diagram of a conventional dimension measuring apparatus. A conventional dimension measuring apparatus includes an illumination optical system that irradiates a sample 110 held by a sample holder 111 with light, an objective lens 109 that collects reflected light from the sample surface, and a light flux that exits the objective lens 109. Half mirror 10 to split
7, a first imaging optical system 106 that forms an image of the light beam that has passed through the half mirror 107, a second imaging optical system 112 that forms an image of the light beam that is reflected by the half mirror 107, and a first connection. First image pickup means 105 for photoelectrically converting the sample image formed by the image optical system 106, and second image pickup means 1 for photoelectrically converting the sample image formed by the second image forming optical system 112.
15 and signal processing means 116 for superimposing both sample images obtained by the first and second imaging means 105 and 115 and measuring the dimensions of the high step pattern and the low step pattern on the sample 110. .

The light from the light source 101 forming the illumination optical system is condensed by the condenser lens 102, the illumination diaphragm 103, and the projection lens 1.
An image is formed on the pupil plane of the objective lens 109 via 04 and the half mirror 108 to form Koehler illumination.

The image of the sample 110 is magnified by the objective lens 109, divided by the half mirror 107 through the half mirror 108. The luminous flux transmitted through the half mirror 107 is the first
The light flux imaged on the first image pickup means 105 by the image forming lens forming the second image forming optical system 106 and reflected by the half mirror 107 is the aperture stop and the image forming lens forming the second image forming optical system 112. Thus, an image is formed on the second image pickup means 115.

The respective sample images formed on the first and second image pickup means 105 and 115 are photoelectrically converted, and both sample images are superposed on each other by the signal processing means 116 to form a high step pattern on the sample 110 and a low step pattern. The dimension with the step pattern is measured.

[0006]

By the way, in the above-mentioned conventional example, a sample image having a large NA is formed on the first image pickup means 105, and a sample image having a small NA is formed on the second image pickup means 115, respectively. In some cases, the image pickup means may be selected according to the step pattern of the sample 110, or the first image pickup means 105 may directly project the sample image, and the second image pickup means 115 may pass through the polarizing plate. In some cases, a sample image is formed.

However, in the above-mentioned conventional example, if a positional shift occurs due to secular change between the first and second image pickup means 105 and 115 or between the first and second image forming optical systems 106 and 112. However, there is a problem that a measurement error occurs when the measurement values are calculated by combining both sample images obtained by the first and second imaging means 105 and 115.

The present invention has been made in view of such circumstances, and an object thereof is to provide a dimension measuring device capable of preventing an error in a measured value due to a positional shift of an image pickup means or the like due to secular change or the like. Is.

[0009]

In order to solve the above-mentioned problems, a dimension measuring apparatus according to the present invention comprises an illumination optical system for irradiating a sample surface having first and second patterns with light, and the sample surface. An objective lens for condensing a light beam from the objective lens, a light beam splitting unit disposed behind the objective lens for splitting the light beam of the objective lens into two, and an image forming one of the light beams split by the light beam splitting unit. One image forming system, a second image forming system for forming an image of the other light beam divided by the light beam dividing means, and a first image forming device for photoelectrically converting a sample image by the first image forming system.
Of the sample formed between the sample and the light beam splitting means, the dimension measuring apparatus including: the image capturing means and the second image capturing means for photoelectrically converting the sample image by the second image forming system. The transparent reference plate, which is arranged at the position of the intermediate image and is provided with the reference mark, the distance between the first pattern image and the reference mark image which are respectively formed by the first image forming system, and the second image formation. Dimension measuring means for determining the distance between the second pattern image formed by the system and the reference mark image, and for determining the difference between the two distances to measure the dimension between the first and second patterns. Is equipped with.

[0010]

[Function] The index mark is imprinted on the sample image by the reference plate,
Since the distance between the patterns is measured with reference to the index mark in the image obtained by the first and second image pickup means,
It is possible to prevent an error in the measured value due to the positional deviation of the image pickup means or the like due to secular change.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of a dimension measuring apparatus according to an embodiment of the present invention.

A condenser lens 2 for converging illumination light is arranged in front of the light source 1, and an illumination diaphragm 3 for limiting the numerical aperture is arranged in front of the condenser lens 2. The light source 1 is provided in front of the illumination diaphragm 3 on the pupil plane of an objective lens 9 described later.
A projection lens 4 for forming an image of
A half mirror 8 that bends the illumination light at a right angle is arranged in front of. The reflected light reflected by the half mirror 8 passes through the objective lens 9 and the sample 10 held by the sample holder 11
It is illuminated on top and is what we call Koehler lighting.

A reference plate 17 is arranged above the half mirror 8 and at the position of the intermediate image formed by the objective lens 9. As shown in FIG. 2, the reference plate 17 is formed by vapor-depositing two linear index marks 17a and 17b which are orthogonal to each other with an extension line on a disk-shaped transparent glass plate.

Above the reference plate 17, a half mirror 7 for splitting the light beam emitted from the reference plate 17 is arranged, and an image forming lens 6 is arranged on one of the divided optical paths.
Forms an image on the imaging means 5. On the other divided optical path, a relay lens 12 forming a plane conjugate with the pupil plane of the objective lens 9, an image forming diaphragm 13 arranged at a position conjugate with the pupil plane of the objective lens 9, and an image on the image pickup means 15. Imaging lens 14 that connects
Are arranged. The image pickup means 5 and 15 photoelectrically convert the sample image, respectively. The image pickup means 5 and 15 are signal processing means 16
And the signal processing means 16 is connected to the image pickup means 5, respectively.
Based on the image signal from 15, the dimensions of the high step pattern 10a and the low step pattern 10b on the sample 10 are measured.

Next, the operation of this dimension measuring device will be described.

Illumination light from the light source 1 is condensed by the condenser lens 2.
After being condensed by the illumination diaphragm 3 and the numerical aperture thereof being limited, the projection lens 4 forms an image of the light source 1 on the pupil plane of the objective lens 9. At this time, the illumination light emitted from the projection lens 4 is bent at a right angle by the half mirror 8. The illumination light is the objective lens 9
The sample 10 is irradiated with the light through.

Reflected light (scattered light) from the sample 10 passes through the reference plate 17 through the objective lens 9 and the half mirror 8. When transmitting through the reference plate 17, the index mark 17 is displayed on the sample image.
a and 17b are imprinted and enter the half mirror 7.

The reflected light that has passed through the reference plate 17 passes through the half mirror 7 and reaches the image forming lens 6, where the image of the sample is formed on the image pickup means 5.

Part of the reflected light of the sample 10 is a half mirror 7.
Then, the relay lens 12 forms a plane conjugate with the pupil plane of the objective lens 9. The numerical aperture is limited by the image forming diaphragm 13 arranged at a position conjugate with the pupil plane of the objective lens 9, and the reflected light whose numerical aperture is limited is formed into a sample image on the image pickup means 15 by the image forming lens 14.

The sample image is photoelectrically converted by the image pickup means 5 and 15, and the image signal is sent to the signal processing means 16. The image pickup means 5 and 15 are respectively connected to the signal processing means, and the measurement in the signal processing means 16 is performed by the image signal from the image pickup means 5 for the low step pattern 10a of the sample 10 by the control signal from the control device (not shown). For the high step pattern 10b, the image signal from the image pickup means 15 is used. The signal processing means 16 first obtains the distance between the index mark 17a and the low step pattern 10a, then obtains the distance between the index mark 17a and the high step pattern 10b, and finally, from both distances, the low step pattern 10a and the high step pattern 10a. Find the distance from 10b. Since the distance between the patterns 10a and 10b is measured with the index mark 17a as a reference in this way, the image pickup means 5 due to secular change or the like.
It is possible to prevent an error in the measured value due to the positional deviation of the optical system 15 and the optical system.

In the above-mentioned embodiment, the index mark 17a is used.
However, the index mark 17b is used when measuring in the Y direction.

Further, in the above-described embodiment, the present invention is applied to the low step pattern 10a and the high step pattern 10 which are parallel to each other.
Although the case where it is applied to the dimension measurement between b is described, it is also applicable to the dimension measurement of a so-called box type pattern in which one pattern is surrounded by the other pattern.

Furthermore, in the above-described embodiment, the two patterns 10a and 10b are shown as the patterns having different steps, but the apparatus of this embodiment is used even if the two patterns have the same step size. It goes without saying that it can be measured by

[0025]

As described above, according to the dimension measuring apparatus of the present invention, it is possible to prevent an error in the measurement value due to the positional deviation of the first and second image pickup means and the like due to aging and the like.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a dimension measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a reference plate.

FIG. 3 is a diagram showing an image obtained by an image pickup means.

FIG. 4 is an overall configuration diagram of a conventional dimension measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 condenser lens 3 illumination diaphragm 4 projection lens 5,15 imaging means 6,14 imaging lens 7,8 half mirror 9 objective lens 10 sample 12 relay lens 13 imaging diaphragm 16 signal processing means 17 reference plate 17a, 17b index mark

Claims (1)

[Claims] 1. An illumination optical system for irradiating a sample surface on which the first and second patterns are provided with light, an objective lens for condensing a light beam from the sample surface, and an objective lens disposed behind the objective lens. A light beam splitting means for splitting the light flux of the objective lens into two, a first image-forming system for focusing one light flux split by the light flux splitting means, and the other light flux split by the light flux splitting means. A second imaging system for forming an image, a first imaging unit for photoelectrically converting a sample image by the first imaging system, and a second imaging for photoelectrically converting a sample image by the second imaging system. And a transparent reference plate provided with a reference mark at a position of an intermediate image of the sample formed between the sample and the light beam splitting means, and the first measuring device. First pattern image and base formed by the imaging system, respectively The distance between the mark image and the distance between the second pattern image formed by the second image forming system and the reference mark image are obtained, and the difference between the distances is obtained to obtain the first and second images. And a dimension measuring means for measuring the dimension between the patterns.