WO2010095328A1

WO2010095328A1 - Line width measuring apparatus and light quantity adjusting method

Info

Publication number: WO2010095328A1
Application number: PCT/JP2009/070183
Authority: WO
Inventors: 大野上
Original assignee: 株式会社日立国際電気
Priority date: 2009-02-20
Filing date: 2009-12-01
Publication date: 2010-08-26
Also published as: JP2010190843A

Abstract

A system for measuring the reduced light quantity of a lamp is configured in a measuring system, since the light quantity required for measurement cannot be ensured when the light quantity of the lamp is reduced, the light quantity required for the measurement is ensured by controlling the transmissivity of light emitted from a light source corresponding to the reduced quantity, and the measurement is continued. The reduced light quantity of the lamp is measured by providing an optical path with a reflecting mirror and using video signals of a CCTV camera. Furthermore, illuminance characteristics of an illuminating device are stored in an image processing unit, and the light quantity of the illuminating device is controlled so as to obtain the light quantity required for measurement using the stored information.

Description

Line width measuring device, light intensity adjustment method

The present invention relates to a line width measuring apparatus and a light amount adjusting method, and in particular, irradiates light onto a pattern formed on a transparent substrate such as glass, and obtains a pattern image obtained through a microscope, such as a CCD (Charge-Coupled Device). The present invention relates to a line width measuring apparatus that measures an image obtained by processing an image captured by a camera using an image sensor, and a light amount adjusting method that is employed in the line width measuring apparatus.

In the manufacturing process of a TFT (Thin Film Transistor) substrate, a line width measuring device is used. A configuration example of this line width measuring apparatus will be described with reference to FIG. FIG. 6 shows an image obtained by irradiating a pattern formed on a transparent substrate such as glass with transmission illumination or reflection illumination and capturing a pattern image obtained through a microscope with a camera using an image sensor such as a CCD. It is the schematic which shows the structural example of the LCD (Liquid * Crystal * Display) line | wire width measuring apparatus for processing and measuring a dimension.

In the figure, the line width measuring apparatus of this example includes a CCTV (Closed-circuit Television) camera 1 equipped with an image sensor such as a CCD, an automatic light adjustment adapter 2, a straight tube 3, a light projecting tube 4, and a revolver. 5, an objective lens 6, a light guide 7 that guides light to be measured, a sample stage 8 for mounting a sample to be measured, and a video signal that is an imaging result of the CCTV camera 1 is displayed on a monitor. The image processing unit 10 that converts to a possible format, a monitor 11 for displaying the imaging result of the CCTV camera 1, and a reflected illumination light source unit 12 that emits light to irradiate the sample stage 8 are configured. A sample 9 as a line width measurement target is placed on the sample table 8. The reflected illumination light source unit 12 includes a diaphragm plate 13 and a lamp 14 as a light emission source.

The light emitted from the lamp 14 passes through the diaphragm plate 13 and is emitted from the reflected illumination light source unit 12. Since the aperture plate 13 can change the light transmittance stepwise, the brightness of the light output from the reflected illumination light source unit 12 can be changed by controlling the aperture plate 13.

Further, a microscope is constituted by the straight tube 3, the light projecting tube 4, the revolver 5, and the objective lens 6. In addition, since other optical components used for reflection illumination etc., such as a beam splitter and a half mirror, are known, description and illustration were abbreviate | omitted. The image processing unit 10 is a PC (Personal Computer), for example, and performs line width measurement by processing an image acquired by the CCTV camera 1. In addition, the image processing unit 10 controls the entire LCD line width measuring apparatus for line width measurement. Illustration of control signals for control and wiring for acquiring control information is omitted.

In FIG. 6, the light output from the exit of the reflected illumination light source unit 12 passes through the light guide 7, the light projecting tube 4, and the objective lens 6, and is applied to the sample 9 mounted on the sample table 8. Used as reflected illumination. The CCTV camera 1 for measurement captures an image of the sample magnified with a microscope and outputs it to the image processing unit 10.

The image processing unit 10 takes in the captured image of the CCTV camera 1 and displays the luminance waveform of the image on the monitor 11. The image processing unit 10 has a function of setting parameters necessary for measurement. For example, the automatic light adjustment adapter 2 is controlled so that the amount of light reaching the image sensor (CCD) of the CCTV camera 1 for measurement from the automatic light adjustment adapter 2 is adjusted to a specified value. The light emitted from the reflected illumination light source unit 12 is collected by the objective lens 6 and the spot-like light is irradiated onto the sample 9 mounted on the sample stage 8.

If the sample 9 cannot withstand the energy of the collected light, the sample 9 will be damaged. In order to prevent this, the amount of light output from the reflected illumination light source unit 12 is controlled by controlling the aperture plate 13 built in the reflected illumination light source unit 12 according to a command value from the image processing unit 10 and changing the transmittance. Is set so that the energy of the light collected by the objective lens 6 does not damage the sample 9, and the peak of the white level of the video signal that can be measured in this state is 0.7 V or higher. The camera sensitivity of the CCTV camera 1 is adjusted in advance.

By the way, in Patent Document 1, the line width is measured using reflected light from a measurement object. Moreover, in patent document 2, the line width is measured using the transmitted light with respect to a measuring object and the reflected light from a measuring object.

Here, with reference to FIG. 7, the principle of measuring the line width of a measurement sample using reflected light will be described. (A) of FIG. 7 is a measurement sample, and the pattern 50 is formed on the glass substrate. The pattern 50 is irradiated with light, and the line width of the pattern 50 is measured by the scanning line Li.

FIG. 7B shows a luminance waveform obtained when the glass substrate of the measurement sample and the pattern 50 are crossed by the scanning line Li by the camera. In the luminance distribution, the maximum luminance level 51 is set to 100%, the minimum luminance level 52 is set to 0%, and the positional difference between the a-th pixel and the b-th pixel corresponding to the luminance level 53 of the intermediate luminance level 50% is Nab. To do. A coefficient determined by the measurement magnification of the camera and the object distance from the camera to the measurement sample is k. At this time, the line width X of the pattern 50 of the measurement sample can be obtained by the following equation (1).
X = k × Nab (1)
Here, measurement of the line width of the measurement sample using transmitted light with respect to the measurement object and reflected light from the measurement object will be described. FIG. 8 is a diagram for explaining a luminance waveform obtained when a measurement sample is illuminated with reflected light and transmitted light.

In FIG. 8, the measurement sample consists of a metal pattern (non-transparent) 32 formed on the glass 31. When the line width of the metal pattern (non-transparent) 32 is actually measured by turning on the reflected illumination and the transmitted illumination at the same time, the reflected illumination and the transmitted illumination are turned on at the same time. The luminance waveform obtained and the luminance waveform obtained only by transmitted illumination will be described separately. In fact, as described above, there are cases where measurement is performed using only reflected illumination, and cases where measurement is performed using only transmitted illumination.

In the case of only reflected illumination, when the metal pattern (non-transparent) 32 side is illuminated with reflected light 33 from a reflection light source (not shown), the reflected light reflected by the measurement sample is measured. The light is incident on a camera (not shown) via an ND (NeutralityDensity) filter (a filter whose transmittance changes continuously) located in an automatic light adjustment adapter (not shown) located above the sample. The luminance waveform 34 obtained as the output of the camera is (b), and the ND filter in the automatic dimming adapter is adjusted so that the peak of the luminance waveform 34 becomes a specified value (video signal 0.7 V).

In the case of only transmitted illumination, as shown in FIG. 5C, the side opposite to the side where the metal pattern (non-transmitted) 32 is formed on the glass 31 is illuminated with transmitted light 35 from a not-shown transmitted light source. Then, the transmitted light that has passed through the measurement sample enters the camera via the ND filter in the automatic light adjustment adapter located above the measurement sample. The luminance waveform 36 obtained as the output of the camera is (d), and the transmitted light 35 from the transmissive light source is adjusted so that the peak of the luminance waveform 36 becomes a specified value (video signal 0.7V).

Therefore, as shown in (e), when the reflected light 33 and the transmitted light 35 are turned on at the same time, the simultaneous lighting luminance waveform 37 obtained as the output of the camera is as shown in (f). That is, by combining (b) and (d), the peak due to the reflected light 33 and the peak due to the transmitted light 35 have the same specified value (video signal 0.7 V), and the peak due to the reflected light and the metal pattern (non-transparent) 32 The contrast between the bottom of the groove based on the inclined portion of the groove and the contrast between the bottom of the groove and the peak due to the transmitted light are the same, and the luminance waveform according to the shape of the inclined portion of the metal pattern (non-transparent) 32 Can be obtained.

Note that with respect to the transmissive light source, the light collected by the lens used for transmissive illumination is larger than the spot diameter of the objective lens, does not damage the sample, and it is not necessary to suppress the amount of illumination light.

JP 2003-279318 A JP 2006-194593 A

As is generally known, the brightness of the lamp decreases with the lighting time. For this reason, the amount of light necessary for measurement (for example, a white level peak of 0.7 V) cannot be obtained after a lapse of time. Further, depending on the use environment, the lamp 14 may cause a chemical reaction with substances in the atmosphere, and the amount of light generated from the lamp 14 may be significantly reduced. In the line width measuring apparatus described in the background art, the light transmittance by the diaphragm plate 13 is fixedly used in accordance with the magnification of the objective lens 6. For this reason, when the light amount of the lamp 14 is reduced, the light amount necessary for measurement cannot be obtained and measurement is impossible.

The reflected illumination light source unit 12 used in the line width measuring device of the LCD substrate has a light amount that is reduced by 40% from the initial illuminance after a lighting time of 2000 hours. The sensitivity of the CCTV camera is set so that the light collected by the objective lens at the initial illuminance can be measured at an illuminance that does not damage the sample. The measurement cannot be continued.

The present invention has been made to solve the above-described problems of the prior art, and the purpose thereof is a line capable of ensuring the amount of light necessary for measurement and continuing the measurement even when the light amount of the lamp is reduced. It is providing the light quantity adjustment method employ | adopted as a width | variety measuring apparatus and a line | wire width measuring apparatus.

The present invention is a line width measuring device that irradiates a measurement target with light from a lamp and measures the line width of the measurement target based on the imaging result, and is provided in an optical path for imaging the measurement target. A light reflecting means for reflecting the light from the lamp, and a light quantity control means for controlling the light quantity of the light irradiated from the lamp to the measurement object in accordance with the light quantity of the reflected light from the light reflecting means. A characteristic line width measuring apparatus is provided. Equipped with a reflecting mirror as a light reflecting means in the optical path, using the video signal of CCTV camera etc., measure the amount of light reduction of the lamp, and the amount of light of the lighting device so that the amount of light necessary for line width measurement can be obtained By controlling the above, it is possible to secure the amount of light necessary for the line width measurement and appropriately continue the line width measurement.

The light amount control means may include a diaphragm plate capable of changing the transmittance of light from the lamp, and may change the transmittance according to the measurement result of the light amount of the reflected light. By controlling the diaphragm plate according to the measurement result of the reflected light amount and increasing the transmittance of the diaphragm plate by the reduced amount, the light amount necessary for line width measurement is ensured even if the lamp light amount decreases. The line width measurement can be continued stably.

The light quantity control means includes a correction table regarding a correspondence relationship between the light quantity and the transmittance, and controls the diaphragm plate according to the transmittance obtained by referring to the correction table based on the light quantity based on the measurement result. May be. By using the correction table, it is possible to appropriately control the light amount of the illumination device even when the relationship between the aperture plate command value and the transmittance is not regular.

It is desirable to increase the transmittance according to a decrease in the amount of light due to the measurement result. By measuring the amount of light reduction of the lamp and controlling the amount of light in the lighting device so that the amount of light necessary for line width measurement is obtained, the amount of light necessary for line width measurement can be secured and the line width measurement can be continued properly. .

The light reflecting means may be a reflecting mirror provided at a position of an objective lens close to the measurement target. By providing a reflecting mirror in the optical path for imaging the measurement target, the amount of light reduction of the lamp can be easily measured.

The image sensor used for measuring the line width of the measurement target may also be used for measuring the amount of reflected light by the light reflecting means. By using the image pickup device provided originally, there is no need to add an element for measuring the amount of reflected light.

Further, the present invention is a light amount adjustment method in a line width measuring apparatus for measuring a line width of a measurement object based on an image obtained by irradiating the measurement object with light from a lamp and photographing the measurement object. According to the step of setting the light reflecting means at the position of the adjacent objective lens, the step of measuring the amount of reflected light of the light irradiated on the set light reflecting means, and the measurement result of the amount of reflected light And a step of controlling the amount of light radiated from the lamp to the measurement object. By measuring the amount of light reflected by the light reflecting means provided in the optical path for imaging the measurement target, the amount of light that has been reduced is grasped, and the amount of light that has fallen is increased by increasing the transmittance of the diaphragm plate. Even if this occurs, the amount of light necessary for the line width measurement can be secured and the line width measurement can be continued stably.

According to the present invention, the amount of light reflected by the light reflecting means provided in the optical path for imaging the object to be measured is measured to grasp the amount of decrease, and the transmittance of the diaphragm plate is increased by the amount of decrease. Thus, even when the light amount of the lamp is reduced, the light amount necessary for the line width measurement can be secured and the line width measurement can be continued stably.

It is a figure which shows the structural example of the line | wire width measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the more concrete structure of the line | wire width measuring apparatus of FIG. It is a flowchart which shows the light quantity adjustment method used in the line | wire width measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship between a diaphragm board command value and the transmittance | permeability. It is a figure which shows the structural example of a correction table. It is a figure which shows the structure of a general line | wire width measuring apparatus. It is a figure for demonstrating the principle which measures the line | wire width of a measurement sample using reflected light. It is a figure for demonstrating the principle which measures the line | wire width of a measurement sample using reflected light and transmitted light.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.

FIG. 1 is a diagram showing a configuration example of a line width measuring apparatus according to an embodiment of the present invention. Referring to the drawing, in the line width measuring apparatus of this example, a reflecting mirror 15 is provided at the position of the objective lens of the revolver 5. The amount of light reflected by the reflecting mirror 15 is measured, and the amount of light emitted from the reflective illumination light source unit 12 to the measurement sample is controlled.

In other words, in this apparatus, in the line width measuring apparatus that irradiates the measurement target with the light from the lamp and measures the line width of the measurement target based on the imaging result, the light from the lamp is placed in the optical path for imaging the measurement target. The light reflecting means for reflecting the light is provided, and the amount of light emitted from the lamp to the measuring object is controlled according to the amount of reflected light.

The path of light emitted from the lamp 14 in the reflected illumination light source unit 12 will be described. The light 100 emitted from the lamp 14 sequentially passes through the aperture plate 13, the light guide 7, and the light projecting tube 4, is reflected by the half mirror in the light projecting tube 4, and strikes the reflecting mirror 15. The light is reflected by the reflecting mirror 15. The reflected light 101 from the reflecting mirror 15 reaches the CCTV camera 1 through the path of the light projecting tube 4, the straight tube 3, and the automatic light adjustment adapter 2. The level of the video signal of the CCTV camera 1 corresponds to the amount of light. Here, for example, if the illuminance of the lamp 14 decreases by 30%, the level of the video signal also decreases by 30%. Therefore, if the level of the video signal is measured by the image processing unit 10, it is possible to grasp how much the illuminance of the lamp 14 has decreased. And if the transmittance | permeability of the aperture plate 13 is raised according to the illumination fall amount of the lamp | ramp 14, the light quantity irradiated from the reflective illumination light source unit 12 can be kept constant.

For example, if the reduction in the amount of light is 30% as a result of the measurement, assuming that the transmittance is 40% at the initial illuminance, the transmittance of the diaphragm plate 13 is about 57% (= 40 × 100 / (100-30). )), The same brightness as 40% of the initial lamp illuminance can be obtained. Therefore, by measuring the amount of light from the lamp, the amount of decrease can be grasped, and by increasing the transmittance of the diaphragm plate by the amount of decrease, stable line width measurement can be performed. That is, the illuminance on the measurement sample can be kept constant by controlling the amount of light transmitted through the diaphragm according to the measurement result of the illuminance.

As described above, a reflection mirror, which is a light reflecting means, is provided in the optical path, and the amount of light reduction of the lamp is measured using a video signal from a CCTV camera or the like, so that the amount of light necessary for line width measurement can be obtained. By controlling the amount of light of the illumination device, the amount of light necessary for line width measurement can be ensured and appropriate measurement can be continued.

In this apparatus, the image sensor used for measuring the line width of the measurement object is also used for measuring the amount of reflected light by the reflecting mirror. By using the image pickup element provided originally, it is not necessary to add a new element for measuring the amount of reflected light.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. In this figure, in the present apparatus, the reflecting mirror 15 can be set in the optical path instead of the objective lens 6 by controlling the revolver 5. That is, the reflecting mirror 15 can be provided at the position of the objective lens 6 that is close to the sample 9 to be measured and used for measuring the line width. If the reflecting mirror 15 is provided at the position of the objective lens 6 and the reflected light is measured, it is possible to grasp how much the illuminance of the lamp 14 has decreased. Then, by increasing the transmittance of the diaphragm plate 13 according to the illuminance reduction amount of the lamp 14, the amount of light emitted from the reflected illumination light source unit 12 can be kept constant.

(Light intensity adjustment method)
Here, with reference to FIG. 3, the light amount adjustment method employed in the present apparatus will be described. In the figure, first, in order to measure the amount of decrease in illuminance of the lamp 14, the revolver 5 is controlled so that the reflecting mirror 15 enters the optical path for imaging the measurement target (step S301).

Next, based on the video signal level of the CCTV camera 1 due to the light reflected by the reflecting mirror 15, the amount of decrease in illuminance of the lamp 14 currently used is measured (step S302). Then, by comparing and calculating the transmittance of the diaphragm plate 13 for preventing the light condensed by the objective lens 6 from damaging the sample 9 and the illuminance reduction amount of the lamp 14 measured this time, it is adapted to the current lamp state. The transmittance to be calculated is calculated, and the light transmittance by the diaphragm plate 13 is controlled according to the transmittance (step S303). With this series of operations, the amount of light necessary for line width measurement can be secured.

Thereafter, the revolver 5 is controlled and set so that the objective lens 6 enters the optical path for imaging the measurement target (step S304). This makes it possible to measure the line width while keeping the illuminance constant (step S305).

Thereafter, the above steps are repeated. However, since the line width can be measured if the lamp light quantity reduction is about 5%, the measurement of the illuminance reduction quantity and the light quantity adjustment need not always be performed, and may be performed at a certain interval.

(Relationship between aperture plate command value and transmittance)
The image processing unit 10 controls the diaphragm plate 13 of the reflected illumination light source unit 12 by a digital signal. This digital signal is, for example, 7 bits, and 128-step command values from “0” to “127” can be sent from the image processing unit 10 by a combination of “0” and “1”.

The reflected illumination light source unit 12 controls the diaphragm plate 13 according to the 128-step command values from “0” to “127”. The relationship between the aperture plate command value and the transmittance is, for example, as shown in FIG. In FIG. 4, the horizontal axis of the graph is the aperture plate command value, and the vertical axis is the transmittance.

Referring to FIG. 4, for example, when the command value given from the image processing unit 10 is “71”, the transmittance of the reflected illumination light source unit 12 is 21% from the graph (the command value “127” is 100%). Case). As can be seen from the graph, since there is no regularity in the relationship between the aperture plate command value and the transmittance, the aperture plate command value for increasing the transmittance to compensate for the decrease even if the amount of decrease in illuminance can be measured. It cannot be obtained by simple calculation. For example, when the transmittance is 57%, referring to the graph of FIG. 4, the aperture plate command value is “115”.

Since there is no regularity in the relationship between the aperture plate command value and the transmittance in this way, the relationship between the aperture plate command value and the transmittance shown in FIG. 4 is registered in advance as a correction table in the image processing unit 10. A diaphragm plate command value is calculated from the transmittance to be set based on this correction table. This correction table is, for example, as shown in FIG. By referring to the information of the registered correction table, the diaphragm plate 13 in the reflected illumination light source unit 12 is controlled.

(Summary)
As described above, in this apparatus, the amount of light emitted from the lamp to the measurement object is controlled in accordance with the amount of reflected light from the reflecting mirror provided in the optical path. That is, by measuring the amount of light from the lamp, the amount of reduction is grasped, and by increasing the transmittance of the diaphragm plate by the amount of reduction, stable line width measurement is possible. That is, the illuminance on the measurement sample can be kept constant by controlling the amount of light transmitted through the diaphragm according to the measurement result of the illuminance. Thereby, even if the light amount of the lamp is reduced, the light amount necessary for the line width measurement can be secured and the measurement can be continued satisfactorily.

Further, in this apparatus, the illuminance characteristics of the lighting device are stored as a correction table in the image processing unit, and the light amount of the lighting device is controlled so as to obtain a light amount necessary for measurement using the information. As a result, even when the light amount of the lamp is reduced, the light amount necessary for the line width measurement can be maintained appropriately and the measurement can be continued satisfactorily.

The present invention can be used to secure a light quantity necessary for measurement when an illumination lamp used for reflection illumination of a liquid crystal line width measuring device is consumed.

DESCRIPTION OF SYMBOLS 1 CCTV camera 2 Automatic light control adapter 3 Straight pipe 4 Projection tube 5 Revolver 6 Objective lens 7 Light guide 8 Sample stand 9 Sample 10 Image processing unit 11 Monitor 12 Reflection illumination light source unit 13 Aperture plate 14 Lamp 15 Reflector

Claims

A line width measuring device for irradiating a measurement target with light from a lamp and measuring a line width of the measurement target based on an imaging result thereof, provided in an optical path for imaging of the measurement target, from the lamp A light reflecting means for reflecting the light of the light and a light quantity control means for controlling the light quantity of the light irradiated from the lamp to the measurement object according to the light quantity of the reflected light by the light reflecting means. Width measuring device.
The light quantity control means includes a diaphragm plate that can change the transmittance of light from the lamp, and changes the transmittance according to the measurement result of the light quantity of the reflected light. Line width measuring device.
The light quantity control means includes a correction table regarding a correspondence relationship between the light quantity and the transmittance, and controls the diaphragm plate according to the transmittance obtained by referring to the correction table based on the light quantity based on the measurement result. The line width measuring apparatus according to claim 2.
The line width measuring device according to claim 2 or 3, wherein the transmittance is increased in accordance with a decrease in light amount due to the measurement result.
The line width measuring device according to any one of claims 1 to 4, wherein the light reflecting means is a reflecting mirror provided at a position of an objective lens close to the measuring object.
The line according to any one of claims 1 to 5, wherein the imaging device used for measuring the line width of the measurement target is also used for measuring the amount of reflected light by the light reflecting means. Width measuring device.
A method for adjusting the amount of light in a line width measuring apparatus for measuring a line width of a measurement object based on an image obtained by irradiating the measurement object with light from a lamp and photographing the position of the objective lens adjacent to the measurement object A step of setting the light reflecting means, a step of measuring the amount of reflected light of the light irradiated on the set light reflecting means, and the measurement object from the lamp according to the measurement result of the amount of reflected light And a step of controlling the amount of light emitted to the light source.