JP2008026065A - Shape measuring apparatus and confocal microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape measuring apparatus and a laser microscope which, even when external mechanical vibrations and acoustic vibrations are propagated, are unaffected by the external vibrations. <P>SOLUTION: A light beam emitted by a light source (1) is projected onto a sample (9) through an objective lens (8). The surface of the sample is scanned by the light beam in a two-dimensional manner. An objective lens drive means (10) for moving the objective lens in its optical axis direction is provided, allowing the surface of the sample to be scanned, while the objective lens is moved in the optical axis direction, where the spacing between the objective lens (8) and the surface of the sample (9) is measured as Z-axis direction position information (12), and the measured spacing is used as the Z-axis direction position information. A signal processing circuit (20), using a brightness signal from a one-dimensional image sensor receiving reflected light from the surface of the sample and the position information from the spacing measuring means (12), outputs the two-dimensional image information of the sample and the height information of the surface of the sample. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a shape measuring apparatus, and more particularly to a shape measuring apparatus suitable for measuring the height of a protrusion existing on the surface of a sample that is easily affected by external vibration.

  In a manufacturing process of a color filter used in a liquid crystal display device, a defect inspection is performed on the manufactured color filter, and when a defect is detected, correction or defect removal is performed using a correction device. For example, there is a protrusion defect formed on the surface of the color filter as the type of defect, and when the protrusion defect is detected, the protrusion defect is corrected by tape polishing (for example, see Patent Document 1). When correcting this projection defect, it is necessary to determine the polishing amount. That is, if the polishing amount is insufficient, additional polishing is necessary, and if the polishing is excessive, there is a problem of scratching the glass substrate. For this reason, there is a strong demand for the development of a shape measuring apparatus that measures the height of the protrusion formed on the color filter with high accuracy.

  A shape measuring device using a confocal optical system is known as a method for measuring the height of a minute protrusion of about several μm (see, for example, Patent Document 2). In this known shape measuring device, an objective lens and a sample are used. The surface of the sample is two-dimensionally scanned with a light beam while changing the distance between and the reflected light from the sample is received by the photodetector, and the height from the position information in the optical axis direction of the objective lens that generates the maximum luminance value Information is output.

JP-A-6-313871 Japanese Patent Laid-Open No. 9-61720

  A shape measuring apparatus using a confocal optical system has an advantage that the height of a minute protrusion can be measured with high accuracy. However, since a color filter for a liquid crystal display device is large, a stage that supports the color filter has a size of about 1.5 m × 2 m, for example. In addition, since the defect is observed and discriminated by transmitted light, the stage is made of optically transparent glass. Such a glass stage is easily affected by external vibration, and the stage itself vibrates due to external mechanical vibration from the floor surface or acoustic vibration generated from the duct during measurement. On the other hand, when external vibration is transmitted during measurement, the surface of the color filter vibrates and the objective lens also vibrates, resulting in a measurement error. That is, in the conventional shape measuring apparatus using the confocal optical system, the position information in the optical axis direction of the objective lens is obtained from the movement amount of the objective lens or the movement amount of the stage. Vibrates, the actual distance between the objective lens and the surface of the color filter does not match the output position information. If the protrusion defects are tape-polished using the height information output in such a state, excessive polishing or insufficient polishing will occur.

  The effect of the external vibration described above is not only due to the shape measuring device, but also the two-dimensional scanning of the sample surface while displacing the relative distance between the objective lens and the sample surface, and the three-dimensional shape based on reflected light from the sample This also applies to laser microscopes that perform measurements.

  Accordingly, an object of the present invention is to realize a shape measuring apparatus and a laser microscope that are not affected by external vibration even when mechanical vibration or acoustic vibration is transmitted from the outside.

The shape measuring device according to the present invention is a shape measuring device for measuring the surface shape of a sample,
A two-dimensional scanning optical system that projects a light beam emitted from a light source toward a sample via an objective lens and two-dimensionally scans the surface of the sample with the light beam;
A stage that freely moves in an XY plane orthogonal to the optical axis of the objective lens and supports the sample;
Photodetection means for receiving reflected light from the sample surface and outputting a luminance signal;
Objective lens driving means for moving the objective lens along its optical axis (Z-axis) direction;
An interval measuring means for measuring an interval between the objective lens and the sample surface, and outputting as position information in the Z-axis direction;
Signal processing means for outputting height information of the sample surface using the luminance signal output from the light detection means and the position information output from the interval measurement means is provided.

  In the present invention, as the scan information in the Z-axis direction, the distance or distance between the objective lens and the sample surface is measured instead of detecting the feed amount of the objective lens and the movement amount of the stage. If the actual distance or distance between the objective lens and the sample surface is measured, even if the stage or objective lens vibrates in the Z-axis direction, displacement information in the Z-axis direction is always detected as actual position information. Position information in the Z-axis direction that is not affected by external vibration is detected.

  Various existing distance sensors can be used as the distance measuring means for measuring the distance between the objective lens and the sample surface, and the distance sensor can be integrally coupled to the objective lens barrel. As another method, an interval measuring device using the principle of optical lever can be used. For example, a laser beam emitted from a separately provided laser light source is optically coupled to the optical path of the objective lens via a coupling member such as a dichroic mirror or a half mirror, and projected toward the sample surface via the objective lens. To do. Reflected light from the sample surface is received by a one-dimensional image sensor through a coupling member. In this case, since the reflected light from the sample is displaced on the one-dimensional image sensor in accordance with the distance between the objective lens and the sample surface, the distance is measured based on the amount of displacement (for example, pixel number). In this case, since the objective lens is shared, there is an advantage that the interval between the parts scanned by the scanning beam is measured.

  In the present invention, since the distance between the objective lens and the sample surface is measured as position information in the Z-axis direction, even if the stage or the objective lens vibrates due to external vibration, the Z-axis direction is not affected by the vibration. Position information is output. As a result, when measuring the height of the protrusion defect formed on the surface of the color filter, more accurate height information can be output.

  FIG. 1 is a diagram showing an example of a shape measuring apparatus according to the present invention. A mercury lamp that emits white light is used as a light source, and a linear light beam emitted from the mercury lamp is emitted from the optical fiber 1 and used as a scanning beam. The light beam emitted from the optical fiber 1 is converted by the expander optical system 2 into a linear light beam extending in a direction perpendicular to the paper surface. The line-shaped light beam is reflected by the total reflection mirror 3, reflected by the half mirror 4 that functions as a beam splitter, and enters the galvanometer mirror 5. The galvanometer mirror 5 periodically deflects the incident line-shaped light beam at a predetermined frequency in a direction orthogonal to the extending direction.

  The light beam emitted from the galvanometer mirror 5 enters the objective lens 8 through the two relay lenses 6 and 7, becomes a converging line light beam, and enters the sample 9. Therefore, the sample surface is scanned two-dimensionally by the converging line light beam. In this example, a color filter used in a liquid crystal display device is used as a sample, the surface shape of the color filter is measured, and the height of the protrusion defect existing on the surface of the color filter is measured. A motor 10 is connected to the objective lens 8 via a head. Therefore, the objective lens can be moved in the optical axis direction by the motor 10, and Z-axis scanning is performed.

  The sample 9 is placed on a stage 11 made of transparent glass. The stage 11 is connected to an XY drive mechanism (not shown) and can freely move in a plane (XY plane) orthogonal to the optical axis (Z axis) of the objective lens 8. Therefore, the projection defect existing on the surface of the color filter is positioned in the field of view of the objective lens based on the address information of the projection defect detected by the defect detection device, and the projection defect and its periphery are scanned two-dimensionally with the light beam. Can do. In this example, defect detection, defect observation, and defect correction are performed in a state where a color filter as a sample is placed on the stage 9. Therefore, defect observation and defect correction are performed using the address information of the defect detected by the defect detection device.

  As described above, the stage 9 that supports the color filter is composed of a large glass substrate of about 1.5 m × 2.0 m, for example, and has a characteristic of being easily vibrated. For this reason, external vibration is transmitted through the gantry supporting the stage, and the surface of the color filter vibrates. Also, not only external mechanical vibration transmitted through the gantry but also easily affected by acoustic vibration due to duct noise, etc., if there is a noise source nearby, the stage and color filter are affected by acoustic vibration transmitted through the air. It will vibrate. On the other hand, if the stage or the objective lens vibrates during the measurement, the relative distance between the focal point of the scanning beam emitted from the objective lens and the color filter surface changes, and the output position information in the Z-axis direction and the actual sample or A situation occurs in which the position of the objective lens in the Z-axis direction does not correspond.

  In order to eliminate the above-described problems, the present invention does not detect the feed amount of the objective lens or the movement amount of the stage as the scan information in the Z-axis direction, but instead of detecting the actual distance between the objective lens and the sample surface. Measure distance. In other words, if the actual distance or distance between the objective lens and the sample surface is measured, even if the stage or objective lens vibrates in the Z-axis direction, displacement information in the Z-axis direction is always detected accurately. Therefore, position information in the Z-axis direction that is not affected by external vibration is detected.

  In order to detect the distance between the objective lens and the sample surface, the distance sensor 12 is integrally coupled to a support frame (lens barrel) of the objective lens 8. The distance sensor 12 is a sensor that measures the distance between the objective lens 8 and the surface of the sample 9, and for example, a laser displacement meter or a capacitance sensor can be used. The laser displacement meter is a displacement meter that uses the principle of optical lever, and includes a laser light source and a one-dimensional image sensor that receives reflected light from the sample surface. A light beam is projected from the laser light source, the reflected light from the sample surface is received by the one-dimensional image sensor, and the distance to the sample surface is measured based on the principle of triangulation using the output signal from the one-dimensional image sensor. The The distance information output from the distance sensor 12 is used as position information for the Z-axis direction scan. Thus, by using the distance information output from the distance sensor integrally coupled to the objective lens, the displacement information in the Z-axis direction that is not affected by external vibration is measured.

  The line-like reflected beam from the surface of the sample 9 is collected by the objective lens 8 and enters the galvanometer mirror 5 through the two relay lenses 7 and 6. The incident reflected beam is descanned by the galvanometer mirror 5, passes through the half mirror 4, and enters the one-dimensional image sensor 14 through the imaging lens 13. Since the incident line-shaped reflected beam is descanned by the galvanometer mirror 5, it becomes stationary on the light incident surface of the one-dimensional image sensor. The one-dimensional image sensor 14 has a plurality of light receiving elements arranged in a direction corresponding to the extending direction of the line-shaped light beam emitted from the optical fiber 1, and the amount of electric charge accumulated in each light receiving element is galvanomirror 5. Are read out in synchronism with the deflection frequency and output as a luminance signal. The one-dimensional image sensor 14 constitutes a confocal optical system because the frame located on the light incident surface performs the same function as a pinhole. The luminance signal output from the one-dimensional image sensor 14 is amplified by the amplifier 15 and supplied to the signal processing circuit 20.

  When capturing a two-dimensional image of a sample and measuring the shape, a two-dimensional image is captured a plurality of times while moving the objective lens in the optical axis direction, and the distance between the objective lens and the sample surface is measured. For example, when the objective lens is gradually lowered or raised from the reference position, the reflected light from the sample surface acts as a pinhole if the focal point of the light beam emitted from the objective lens is not located on the sample surface1 The light is shielded by the frame of the three-dimensional image sensor and a luminance signal having a low signal level is output. When the focal point of the light beam is positioned on the sample surface as the objective lens moves, a large amount of reflected light from the sample surface enters the light receiving element of the one-dimensional image sensor due to the principle of the confocal optical system. Therefore, while moving the objective lens in the optical axis direction, the maximum luminance value of the luminance signal output from the light detection means and the position information in the Z-axis direction that generates the maximum luminance value are detected, thereby focusing the sample surface. The obtained two-dimensional image is picked up and the position in the Z-axis direction of each part on the sample surface is detected.

  FIG. 2 is a diagram showing an example of a signal processing circuit. The signal processing circuit 20 receives the luminance signal from the one-dimensional image sensor 14 and the interval information output from the distance sensor 12 as position information in the Z-axis direction. The luminance signal from the one-dimensional image sensor 14 is amplified by the amplifier 15, converted into a digital signal by the A / D device 21, and supplied to the comparator 22 and the selector 23. The luminance information selected by the selector 23 is stored in the first frame memory 24. The luminance information stored in the first frame memory 24 is supplied to the comparator 22 and the selector 23. In the comparator 22, the newly input luminance value for each pixel is compared with the luminance value stored in the frame memory 24, and a selection signal for selecting the signal having the larger luminance value is output to the selector 23. The selector 23 selects the higher luminance signal based on the input selection signal and outputs it to the first frame memory 24. By reading the luminance information stored in the first frame memory, the two-dimensional image information of the sample is output.

  The output from the distance sensor 12 is converted into a digital signal by the A / D converter 25 and output to the second frame memory 26. The selection signal output from the comparator 22 is input to the second frame memory 26 as a write control signal. Therefore, the position information output from the distance sensor is written in the second frame memory 26 as position information in the Z-axis direction when the maximum luminance value is generated. The height information on the sample surface is output from the second frame memory 26.

  Next, a description will be given of a modified example of the interval measuring means for measuring the interval between the objective lens and the sample surface and outputting it as position information. FIG. 3 is a diagram showing a modification of the interval measuring means. In this example, the objective lens that projects the scanning beam toward the sample is also used as the scanning beam, and the distance between the objective lens and the sample surface is measured by the principle of optical lever. For example, a semiconductor laser 30 that emits a near-infrared laser beam of 830 μm is used. The measurement beam emitted from the laser 30 is reflected by the half mirror 31 and enters a dichroic mirror 32 disposed in the optical path of the objective lens 8. The dichroic mirror 32 functions as a coupling optical system, and has a characteristic of transmitting light having a wavelength of 830 μm or less and reflecting light having a wavelength of 830 μm or more. Accordingly, the measurement beam is reflected by the dichroic mirror 32 and enters the surface of the sample 9 through the objective lens 8. On the other hand, most of the scanning beam passes through the dichroic mirror 32 and is incident on the sample surface, and thus does not affect the shape measurement of the sample.

  The measurement beam is reflected by the sample surface, passes through the objective lens again, and is reflected by the dichroic mirror 32. Further, the light passes through the half mirror 31 and enters the one-dimensional image sensor 33. The one-dimensional image sensor 33 has a plurality of light receiving elements arranged in a direction parallel to the optical axis of the objective lens in the y direction (see FIG. 3). It is assumed that the objective lens 8 is lowered from the reference position indicated by the solid line by the distance Δz and displaced to the position indicated by the broken line. As the objective lens Δz is lowered, the measurement beam is displaced in the x direction on the sample surface, displaced by Δy in the y direction on the one-dimensional image sensor 33, and the measurement beam is incident on the pixel displaced by Δy. In this case, the relationship between the movement amount Δz of the objective lens and the number of moving pixels Δy of the one-dimensional image sensor is stored in advance, so that the objective lens is based on an output signal (for example, a pixel number) from the one-dimensional image sensor. And the sample surface is detected. In this example, since the measurement beam for interval measurement is incident on the sample surface in the vicinity of the scanning beam, an advantage that more accurate interval information can be obtained is achieved.

The present invention is not limited to the above-described embodiments, and various modifications and changes can be made. For example, in the above-described embodiments, the present invention has been described with reference to an example in which the present invention is applied to a shape measuring apparatus. The invention can be applied. When the present invention is applied to a two-dimensional scanning confocal microscope, it is possible to drive either the objective lens or the sample stage to change the distance between the objective lens and the sample surface. Even in this case, the distance between the objective lens and the sample surface is measured and used as position information in the Z-axis direction.
In addition, a configuration in which a linear light beam is periodically deflected in a direction orthogonal to its extending direction is adopted as a two-dimensional scanning optical system. It is also possible to scan the sample surface two-dimensionally by combining two beam deflectors.

It is a diagram which shows an example of the optical system of the formation measuring apparatus by this invention. It is a diagram which shows an example of a signal processing circuit. It is a diagram which shows the modification of a space | interval measurement means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Expander optical system 3 Total reflection mirror 4 Half mirror 5 Galvano mirror 6,7 Relay lens 8 Objective lens 9 Sample 10 Motor 11 Stage 12 Distance sensor 13 Imaging lens 14 One-dimensional image sensor 15 Amplifier 21, 25 A / D converter 22 comparator 23 selector 24 first frame memory 26 second frame memory

Claims (9)

A shape measuring device for measuring the surface shape of a sample,
A scanning optical system that projects a light beam emitted from a light source toward a sample via an objective lens, and scans the surface of the sample with the light beam;
A stage that freely moves in an XY plane orthogonal to the optical axis of the objective lens and supports the sample;
Photodetection means for receiving reflected light from the sample surface and outputting a luminance signal;
Objective lens driving means for moving the objective lens along its optical axis (Z-axis) direction;
An interval measuring means for measuring an interval between the objective lens and the sample surface, and outputting as position information in the Z-axis direction;
A shape measuring apparatus comprising signal processing means for outputting height information of a sample surface using a luminance signal outputted from the light detecting means and position information outputted from an interval measuring means.   2. The shape measuring apparatus according to claim 1, wherein the distance measuring means is constituted by a distance sensor that is integrally coupled to the objective lens and measures a distance between the objective lens and the sample surface. Shape measuring device.   3. The shape measuring apparatus according to claim 2, wherein the distance sensor includes means for projecting a light beam toward the sample surface and light detecting means for receiving reflected light from the sample surface. A shape measuring apparatus that outputs a displacement amount of an interval between an objective lens and a sample surface based on an output signal.   2. The shape measuring apparatus according to claim 1, wherein the distance measuring means includes a laser light source that generates a laser beam, a coupling member that couples the laser beam to the optical path of the objective lens, and an optical axis of the objective lens. A plurality of light receiving elements arranged along a direction, and a one-dimensional image sensor that receives a laser beam reflected by the sample surface, and an objective lens and the sample surface based on output information from the one-dimensional image sensor A shape measuring device comprising an interval measuring device for detecting an interval between the two.   5. The shape measurement scan according to claim 1, wherein the sample surface is two-dimensionally scanned while moving the objective lens in the optical axis direction, and the signal processing means has the objective lens in the optical axis direction. A first frame memory for storing the maximum luminance value of each pixel obtained during the movement along the line, and a second frame memory for storing position information in the Z-axis direction for generating the maximum luminance value. A shape measuring apparatus characterized by that.   6. The shape measuring apparatus according to claim 1, wherein the sample is a color filter, and a height of a protrusion existing on the surface of the color filter is detected.   The two-dimensional scanning optical system includes means for generating a line-shaped light beam, and beam deflecting means for periodically deflecting the line-shaped light beam in a direction orthogonal to the extending direction thereof. 7 is a one-dimensional image sensor having a plurality of light receiving elements arranged in a direction corresponding to the extending direction of the linear light beam. The shape measuring apparatus described. A two-dimensional scanning optical system that projects a light beam emitted from a light source toward a sample via an objective lens and two-dimensionally scans the surface of the sample with the light beam;
A stage for supporting the sample;
Photodetection means for receiving reflected light from the sample surface and outputting a luminance signal;
Driving means for relatively changing the distance between the objective lens and the sample surface;
An interval measuring means for measuring an interval between the objective lens and the sample surface, and outputting as position information in the Z-axis direction;
And a signal processing means for outputting two-dimensional image information and shape information of the sample surface using the luminance signal output from the light detection means and the position information output from the interval measurement means. Focus microscope. 9. The confocal microscope according to claim 8, wherein the two-dimensional scanning optical system includes a laser light source, a first beam deflecting device that periodically deflects a laser beam generated from the laser light source in a first direction, A second beam deflecting device that periodically deflects a laser beam emitted from one beam deflecting device in a second direction orthogonal to the first direction, and two-dimensionally scanning the sample surface with the laser beam; A confocal microscope.