WO2010064352A1 - Line width measuring method - Google Patents

Abstract

There has been such a problem that in a pattern formed of a transparent film, a phenomenon wherein a contrast change varies depending on the area is generated and that a pattern which does not accord with a luminance change pattern cannot be measured.  Provided is a line width measuring method which can perform measurement even in the case where the contrast change of the transparent film pattern is changed. A plurality of luminance change patterns are registered corresponding to contrast changes of the transparent film, measuring conditions which correspond to each of the registered luminance change patterns are set, and measurement is performed under the measuring conditions.

Description

Line width measurement method

The present invention relates to an inspection apparatus or a measurement apparatus, and in particular, to liquid crystal line width measurement used in a manufacturing process of a liquid crystal (LCD) panel substrate such as a TFT (Thin Film Transistor) substrate.

An outline of the LCD substrate automatic line width measuring apparatus will be described with reference to FIG. FIG. 1 shows a pattern image obtained through a microscope by irradiating a pattern formed on a transparent substrate such as glass with transmission illumination or reflection illumination, and imaging with a camera using an image sensor such as a CCD (Charge Coupled Device). It is a figure for demonstrating the structure of the test | inspection apparatus for image-processing the measured image and measuring a dimension. 1 is a CCTV camera, 2 is an automatic light adjustment adapter, 3 is a straight tube, 4 is a light projection tube, 5 is a revolver, 6 is an objective lens, 7 is a light guide, and 8 is a sample for mounting a sample to be measured. Table, 9 is a transmission illumination head, 10 is a light guide, 11 is a reflection illumination light source unit, 12 is a transmission illumination light source unit, 13 is an image processing unit, and 14 is a monitor. The straight tube 3, the light projecting tube 4, the revolver 5, and the objective lens 6 constitute a microscope. In addition, since other optical components used for reflection illumination etc., such as a half mirror, are known, description and illustration were abbreviate | omitted.

The image processing unit 13 is, for example, a PC (Personal Computer) or the like. The image processing unit 13 processes the image acquired by the CCTV camera 1 to measure the line width, and the entire LCD line width measuring device is used for the line width measurement. Although control is performed, control signal signals for control and wiring for acquiring control information are omitted.

In FIG. 1, when using reflected illumination, light output from the exit of the reflected illumination light source unit 11 passes through the light guide 7, the light projecting tube 4, and the objective lens 6 and passes through the sample table 8. The sample mounted above is irradiated and used as reflected illumination. Further, when using transmitted illumination, the light output from the exit of the transmitted illumination light source unit 12 passes through the light guide 10 and the transmitted illumination head 9 and is used as transmitted illumination by irradiating the sample from the back surface. .

The CCTV camera 1 for measurement captures an image of the sample magnified with a microscope and outputs it to the image processing unit 13. The image processing device 13 captures the captured image of the CCTV camera 1 and displays the luminance waveform of the image on the monitor 14. The image processing unit 13 has a function of setting parameters necessary for measurement. For example, the automatic light adjustment adapter 2 is controlled, and the automatic light adjustment adapter 2 adjusts so that the amount of light reaching the imaging device (CCD) of the CCTV camera 1 for measurement becomes a specified value.

Next, a state in which the low contrast pattern width of the transparent film is measured using the reflected illumination will be described with reference to FIG. FIG. 2 is a diagram for explaining the difference in luminance waveform under three conditions with different contrasts in a nearly transparent pattern (hereinafter referred to as a transparent film) formed on a sample by reflected illumination. 15a, 15b, 15c, and 16 are transparent films, 17 is a glass substrate, 18, 19, 23, 24, 28, and 29 are reflected light, 20, 25, and 30 are luminance waveforms, 21, 22, 26, 27 , 31 and 32 are luminance change sections.
In FIG. 2A, the length of the upward portion of the arrow of the reflected light 18 is the reflectance 18 of the transparent film 16, and the length of the upward portion of the arrow of the reflected light 19 is the reflection of the transparent film 15a. In FIG. 2 (b), the length of the upward portion of the arrow of the reflected light 23 is the reflectance 23 of the transparent film 16, and the length of the upward portion of the arrow of the reflected light 24 is FIG. 2C shows the relative reflectance 23 of the transparent film 15b. In FIG. 2C, the length of the upward portion of the arrow of the reflected light 28 is above the arrow of the reflectance 28 of the transparent film 16 and the arrow of the reflected light 29. The length of the direction portion relatively indicates the reflectance 29 of the transparent film 15c.
In the case of reflected illumination, light is irradiated from the upper side (upward direction) of the glass substrate 17.
2 (a) to 2 (c), the upper figure is a transparent film 16 on a glass substrate 17, and transparent films (samples) 15a, 15b, which are objects to be measured, formed on the transparent film 16. Or it is sectional drawing which showed a part of 15c and reflected light typically, and the lower figure shows the luminance waveform of the said part. The transparent films 15a to 15c and the transparent film 16 are transparent films frequently used in the liquid crystal pattern manufacturing process, and are usually formed on the glass substrate 17.

FIG. 2A shows a case where the reflectance 19 of the transparent film 15a is smaller than the reflectance 18 of the underlying transparent film 16 (reflectance 19 <reflectance 18). FIG. 2B shows a case where the reflectance of the transparent film 15b is larger than the reflectance of the underlying transparent film 16 (reflectance 19> reflectance 18). FIG. 2C shows a case where the reflectance 19 of the transparent film 15c and the reflectance 18 of the underlying transparent film 16 are substantially the same (reflectance 19≈reflectance 18).
In FIG. 2, when using reflective illumination, the amount of light reflected on the surface of the transparent film differs depending on the difference between the reflectance of the transparent films 15 a to 15 c and the reflectance of the transparent film 16. This is expressed by the length of the upward arrow in FIG. When the luminance waveform is displayed from the image of the measurement camera (see FIG. 1) attached to the microscope, the luminance waveform 20, 25, or 30 in FIG.

As shown in FIG. 2A, when the amount of light reflected on the surfaces of the transparent film 15a and the transparent film 16 has a relationship of reflectance 19 <reflectance 18, the luminance waveform 20 is a luminance changing portion 21. 22, the white-black-white state changes from the left of the figure with or without the transparent film 15 a as a boundary.
In addition, as shown in FIG. 2B, when the amount of light reflected on the surfaces of the transparent film 15b and the transparent film 16 has a relationship of reflectance 24> reflectance 23, the luminance waveform 25 changes in luminance. As can be seen from the portions 26 and 27, the black-white-black state changes from the left in the figure with or without the transparent film 15b.
Further, as shown in FIG. 2C, when the amount of light reflected on the surfaces of the transparent film 15c and the transparent film 16 has a relationship of reflectance 29≈reflectance 28, the luminance waveform 30 has a luminance change. As can be seen from the portions 31 and 32, a V-shaped luminance change appears with or without the transparent film 15c.

Further, the state of measuring the low contrast pattern width of the transparent film using transmitted illumination is as follows in FIG. FIG. 3 is a diagram for explaining a difference in luminance waveform under two conditions with different contrasts in a nearly transparent pattern (hereinafter referred to as a transparent film) formed on a sample by transmitted illumination. 33a, 33b, and 34 are transparent films, 35 is a glass substrate, 36, 37, 41, and 42 are transmitted light, 38 and 43 are luminance waveforms, and 39, 40, 44, and 45 are luminance change portions.
The length of the arrow of the transmitted light 37 is the transmittance 37 when passing through the glass substrate 35, the transparent film 34, and the transparent film 33a, and the length of the arrow of the transmitted light 36 is the glass substrate 35 and the transparent film 34. The transmittance 36 when passing through and the length of the arrow of the transmitted light 42 are the transmittance 42 when passing through the glass substrate 35, the transparent film 34 and the transparent film 33 b, and the length of the arrow of the transmitted light 41. Shows relatively the transmittance 42 when passing through the glass substrate 35 and the transparent film 34.
3 (a) and 3 (b), the upper figure shows the transparent film 34 on the glass substrate 35 and the transparent film (sample) 33a or 3b that is the object to be measured formed on the transparent film 34. A sectional view schematically showing a part and reflected light, and the lower figure shows a luminance waveform of the part. The transparent films 33 a and 33 b and the transparent film 34 are transparent films that are frequently used in the manufacturing process of the liquid crystal pattern, and are usually formed on the glass substrate 35.

FIG. 3A shows that when the transparent film 33a is thick, the transmittance 37 is smaller than the transmittance 36 of the underlying transparent film 34 (transmittance 37 <transmittance 36). In FIG. 3B, since the transparent film 33b is relatively thin, the transmittance 42 of the transparent film 33b and the transmittance 41 of the underlying transparent film 34 are substantially the same (reflectance 42≈reflection). Rate 41).
In the case of transmitted illumination, uniform light is irradiated from the lower side (downward direction) of the glass substrate. Therefore, the image of the camera for measurement attached to the microscope observes the light that has passed through the glass substrate 35 and the transparent film 34, or the light that has further passed through the transparent films (samples) 33a and 33b that are objects to be measured. Will do. For this reason, a luminance change according to the transmittance of the transparent film 34 and the transparent film 33a or 33b appears.

In FIG. 3, when transmitted illumination is used, the amount of light transmitted through the glass substrate and the transparent film differs depending on the difference between the transmittances of the transparent films 33a and 33b and the transmittance of the transparent film 34. This is expressed by the length of the upward arrow in FIG. When the luminance waveform is displayed from the image of the measurement camera (see FIG. 1) attached to the microscope, the luminance waveform 38 or 43 in FIG. 3 is obtained.

That is, when the length of the arrow shown in FIGS. 3A and 3B is regarded as the transmittance as in FIG. 2, in FIG. 3A, in FIG. When the amount of light transmitted through the transparent film 33a is in the relationship of transmittance 37 <transmittance 36, the luminance waveform 38 is determined by the presence or absence of the transparent film 33a, as can be seen from the luminance changing portions 39 and 40. It changes from left to right in the form of white-black-white.
In addition, as shown in FIG. 3B, when the amount of light passing through the glass substrate 35 and passing through the transparent film 34 and the transparent film 33b has a relationship of transmittance 42≈transmittance 41, the luminance waveform 43 is As can be seen from the luminance change portions 44 and 45, a V-shaped luminance change appears with or without the transparent film 33b.

JP 2005-283319 A

The edge recognition by the measurement program in the image processing unit (see FIG. 1) will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of a registered pattern of luminance change in the measurement program. 46a, 46b, and 46c are registered patterns of luminance change.
With respect to the above-described conventional example, the edge recognition by the measurement program in the image processing unit (see FIG. 1) indicates that the luminance change of the edge to be measured is the luminance change registration pattern 46a of FIG. White-black, black-white of the luminance change registration pattern 46b in FIG. 4B, one of the luminance changes on the left side of the V shape and the right side of the V shape of the luminance change registration pattern 46c in FIG. Set as.

For this reason, the conventional line width measuring apparatus cannot measure when the set luminance change pattern and the actual luminance change are different. In addition, even if it is the same board | substrate, such a phenomenon changes the mode of a brightness | luminance change because the film thickness of a transparent film is not uniform for every place. For this reason, the pattern formed of the transparent film has a phenomenon in which the change in contrast differs depending on the location, and a pattern that does not coincide with the pattern of luminance change cannot be measured.
An object of the present invention is to provide a line width measurement method capable of performing measurement even when a change in contrast of a transparent film pattern changes.

In order to achieve the above object, the line width measurement method of the present invention registers a plurality of luminance change patterns in accordance with the contrast change of the transparent film, and sets measurement conditions corresponding to the registered luminance change patterns. If set and image processing is performed under the measurement conditions, and the measurement is OK by the image processing, the measurement result that is OK is adopted.

According to the present invention, it is possible to realize a measurable line width measuring method even when the contrast of the pattern of the transparent film that is the object to be inspected changes.

The block diagram for demonstrating schematic structure of an LCD substrate line | wire width measuring apparatus. The figure for demonstrating the difference in the contrast of the transparent film by the conventional reflective illumination. The figure for demonstrating the difference in the contrast of the transparent film by the conventional transmitted illumination. The figure which shows the example of a registration pattern of the brightness change in a measurement program. The figure which shows the several brightness | luminance change pattern of one Example of this invention. The flowchart for demonstrating the processing operation of one Example of the line | wire width measuring method of this invention.

An embodiment of the present invention will be described below with reference to FIG. FIG. 5 is a diagram for explaining the difference in luminance waveform under three conditions with different contrasts for a nearly transparent pattern (hereinafter referred to as a transparent film) formed on a sample by reflected illumination; and It is a figure which shows the several brightness | luminance change pattern registered of one Example of this invention. 47a, 47b, 47c and 48 are transparent films, 49 is a glass substrate, 50, 51, 55, 56, 60 and 61 are reflected light, 52, 57 and 62 are luminance waveforms (luminance change patterns), 53, Reference numerals 54, 58, 59, 63, and 64 denote luminance changing portions.
Similar to FIG. 2, in the case of reflective illumination, light is irradiated from the upper side (upward direction) of the glass substrate 49.
5 (a) to 5 (c), the upper figure shows a transparent film 48 on a glass substrate 49, and transparent films (samples) 47a, 47b, which are objects to be measured, formed on the transparent film 48. Or it is sectional drawing which showed a part of 47c and reflected light typically, and the lower figure shows the luminance waveform of the said part. The transparent films 47a to 47c and the transparent film 48 are transparent films frequently used in the liquid crystal pattern manufacturing process, and are usually formed on the glass substrate 49.

In FIG. 5, when the pattern to be measured of the sample composed of the transparent films 47a to 47c, the transparent film 48, and the glass substrate 49 is measured with reflected illumination, the transparent film 48 and the transparent film 47a are measured as described in the prior art. The tendency of the luminance waveform obtained from the camera for measurement (see FIG. 1) varies depending on the difference in reflectance of .about.47c.
This is expressed by the length of the upward arrow in FIG. When the luminance waveform is displayed from the image of the measurement camera (see FIG. 1) attached to the microscope, the luminance waveform 52, 57, or 62 in FIG. 5 is obtained.

As shown in FIG. 5A, when the amount of light reflected on the surfaces of the transparent film 47a and the transparent film 48 is in the relationship of reflectance 51 <reflectance 50, the luminance waveform 52 has a luminance changing portion 53. , 54, white-black-white changes from the left in the figure with or without the transparent film 47a.
Further, as shown in FIG. 5B, when the amount of light reflected on the surfaces of the transparent film 47b and the transparent film 48 has a relationship of reflectance 56> reflectance 55, the luminance waveform 57 is a luminance change. As can be seen from the portions 58 and 59, the state changes from black to white to black from the left in the figure with or without the transparent film 47b.
Further, as shown in FIG. 5C, when the amount of light reflected on the surfaces of the transparent film 47c and the transparent film 48 has a relationship of reflectance 61≈reflectance 60, the luminance waveform 62 has a luminance change. As can be seen from the parts 63 and 64, a V-shaped luminance change appears with or without the transparent film 47c.

As described above, the tendency of the luminance waveform obtained from the camera for measurement differs depending on the magnitude relationship between the reflectances of the transparent films 47a to 47c and the transparent film 48. In the present invention, measurement conditions 1 to 3 that can measure the patterns of the luminance waveform 52 (white-black-white), the luminance waveform 57 (black-white-black), and the luminance waveform 62 (V-shaped-V-shaped) are imaged in advance. Measurement is performed by setting the processing unit and performing image processing under the measurement conditions 1 to 3.

Normally, under the measurement condition 3 for the luminance waveform in FIG. 5C, the contrast change is small, so that the luminance signal changes only at the edge slope. For this reason, the threshold value recognized as a luminance waveform is set lower than in the case of measurement condition 1 (FIG. 5A) and measurement condition 2 (FIG. 5B). However, erroneous measurement (measurement of a portion different from the edge) may occur by setting the threshold value low. For this reason, in the measurement conditions 1 and 2, etc., the threshold is set to a value at which no erroneous measurement occurs, and the measurement is performed before the measurement condition 3. Thus, it is possible to prevent erroneous measurement to some extent.
Even in the measurement condition 3, even if the threshold value is set small, the luminance waveform at the edge portion once decreases and then increases, so that erroneous measurement can be reduced. If the luminance waveform at the edge portion once decreases and does not increase, measurement is impossible and the object to be measured can be set to NG.

Note that the measurement method of the present invention can be realized by the measurement program of the image processing unit and a plurality of registered patterns in the line width measurement apparatus described in FIG.

An algorithm for measurement according to the present invention will be described with reference to FIG. FIG. 6 is a flowchart for explaining the processing operation of an embodiment of the line width measuring method of the present invention. 6 is executed by the image processing unit (see FIG. 1) according to the embodiment of FIG.
First, as described with reference to FIG. 5, three types of luminance change patterns are set based on the magnitude relationship between reflectance or transmittance (for example, luminance waveforms 52, 57, and 62 in FIG. 5). Then, measurement conditions 1 to 3 corresponding to those luminance waveforms are set. In this embodiment, an edge is detected for each luminance change pattern, an image processing window having a predetermined size is set around the detected edge, and the luminance pattern is registered in the set window. Yes.

First, before the image processing of the present invention, an image for measuring a pattern to be measured is acquired and measurement is started.
In step 601, measurement condition 1 is selected, and the process proceeds to step 602.
In step 602, line width measurement is executed from the acquired image according to the selected measurement condition 1, and the process proceeds to step 603.
In step 603, it is determined whether or not the next measurement condition for which the measurement process has not been completed for the target image is set. If not, the process proceeds to step 605. If it is set, the process proceeds to step 604.
In step 604, the next measurement condition is selected, and the process returns to step 602.

In step 605, the number n indicating the measurement condition is set to 1 (n = 1), and the process proceeds to step 606.
In step 606, it is determined whether measurement is possible under measurement condition n (measurement is OK) or not (measurement is NG). If the determination is successful, the process proceeds to step 609. If not, the process proceeds to step 607. .
In step 607, it is determined whether or not there is a next measurement condition that has not been determined in step 606. If not, the process proceeds to step 610. If there is a next measurement condition, the process proceeds to step 608. .

In step 608, 1 is added to the number n indicating the measurement condition to set a new n (n = n + 1), and the process proceeds to step 606.
In step 609, the measurement result of measurement condition n is adopted and the measurement is terminated.
In step 610, since the measurement could not be performed, an error code is set and the measurement process is terminated.

As described above, measurement is performed under all conditions. Checks are performed in order from measurement condition 1. If the measurement is OK, the result is adopted, and if it is NG, the result of measurement condition 2 which is the next measurement condition is confirmed. Similarly, if the measurement is NG, the measurement result of measurement condition 3 is confirmed.
In this way, for the set number of measurement conditions (3 conditions in the case of FIGS. 5 and 6), whether the measurement is OK or NG is sequentially confirmed, and the measurement value that is OK in the determination is adopted. is there.

In the embodiment of FIG. 6, a method for determining whether the measurement is OK or NG will be briefly described.
(1) A luminance waveform is obtained from the acquired image, an edge is recognized from the luminance waveform, and a preset slice level position (pixel address) is calculated for the recognized edge portion (two points).
(2) The pixel length between two slice level positions (pixel addresses) is calculated.
(3) Histogram processing.
(4) Convert the pixel dimensions into measured values.
If the processes (1) to (4) are normally executed, the measurement is determined to be OK, and if the processes are not normally executed, the measurement is determined to be NG.

According to the above-described embodiment, the line width measurement image processing software for the line width measurement of the line width measurement apparatus performs the measurement of the pattern in which the contrast is not stable in the line width measurement of the pattern having a different subject contrast. Is possible.
In the embodiment of FIG. 6, the measurement values that can be measured after measurement under all measurement conditions are adopted, but when measurement is successful, measurement is not performed under the following measurement conditions, and measurement is performed. You may end.

In the above embodiment, there are three types of registered luminance waveform patterns and corresponding measurement conditions. However, it is not necessary to limit to three types, and there may be a plurality of measurement conditions for the luminance waveform pattern 1.
For example, when the registered luminance waveform pattern has a magnitude relationship, the brightness waveform pattern may be further differentiated by two times or an arbitrary magnification. Also, a plurality of measurement conditions may be provided for one registered luminance waveform pattern by making the measurement condition parameters different, such as the slice level and the brightness change.

1: CCTV camera, 2: automatic dimming adapter, 3: straight tube, 4: floodlight tube, 5: revolver, 6: objective lens, 7: light guide, 8: sample stage, 9: transmission illumination head, 10: light Guide: 11: Reflection illumination light source unit, 12: Transmission illumination light source unit, 13: Image processing unit, 14: Monitor, 15a, 15b, 15c, 16: Transparent film, 17: Glass substrate, 18, 19, 23, 24, 28, 29: Reflected light, 20, 25, 30: Luminance waveform, 21, 22, 26, 27, 31, 32: Luminance changing portion, 33a, 33b, 34: Transparent film, 35: Glass substrate, 36, 37, 41, 42: Transmitted light, 38, 43: Luminance waveform, 39, 40, 44, 45: Luminance changing part, 46a, 46b, 46c: Registration pattern of luminance change 47a, 47b, 47c, 48: transparent film, 49: glass substrate, 50, 51, 55, 56, 60, 61: reflected light, 52, 57, 62: luminance waveform (luminance change pattern), 53, 54, 58 , 59, 63, 64: luminance change portions.

Claims (1)

1. Line width characterized by registering multiple brightness change patterns according to the contrast change of the transparent film, setting measurement conditions corresponding to each of the registered multiple brightness change patterns, and measuring under multiple measurement conditions Measuring method.

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