JP2007205743A - Colored film thickness variations inspection method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variation inspection method and apparatus which avoids variations in inspection sensitivity caused by a difference in transmittance by the color of a resist to detect variations in colored film thickness with high precision. <P>SOLUTION: An imaging device with increased near-infrared region sensitivity is used. Light providing optical transmittance of 50% or more for the entire colored film and providing a half-value width of 30 nm or less for a central value of 800 nm to 900 nm, as a wavelength region in which the imaging device has its sensitivity, is irradiated to a substrate to be inspected 3. On the basis of an interference phenomenon caused by the phase difference between reflected light by the surface of the colored film, and reflected light passed through the colored film and reflected by a boundary with the substrate interface of the substrate to be inspected 3, a change in the colored film thickness is imaged as light and shade of the reflected light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a colored film thickness unevenness inspection method and apparatus capable of accurately detecting a colored film thickness unevenness of a substrate on which a multicolored colored film pattern is formed, which is suitable for use in, for example, a color filter.

  In recent years, color filters for liquid crystal displays and organic EL are factors that greatly affect the display characteristics of the display, and therefore their inspection has become very important. Inspecting minute pattern defects and foreign substance adhesion defects, the contrast of the defective part is relatively high, and automation of inspection by machine vision has advanced. On the other hand, when viewed locally, the area where the difference from the normal part is at an acceptable level is gathered locally, so defects that appear as unevenness have low contrast, so automatic inspection is difficult and the ratio of relying on visual inspection is high Is the current situation. The most common cause of uneven defects is due to slight differences in the thickness of the colored film.

  Conventionally, in the color filter unevenness inspection, orange light from a sodium lamp is used, and inspection is performed by visually observing or imaging an interference fringe generated due to a slight difference in the colored film thickness. In order to observe the interference fringes resulting from the difference in the colored film thickness with high contrast, it is important that the light transmittance used is high and the light wavelength range is narrow. A sodium lamp has a luminance spectrum at 590 nm and has a characteristic that the transmittance of the colored film Red and Green is relatively high. Therefore, the sodium lamp is suitable for observation of interference fringes. There is a problem of difficulty.

Also, as a countermeasure against the difficulty of blue inspection with a sodium light source, a method of using a light source having a peak at 490 nm in combination with a conventional light source having an emission peak near 590 nm as disclosed in Patent Document 1 is disclosed. ing.
JP 2005-207829 A

  In the conventional method for inspecting colored film thickness unevenness, it is necessary to change the light source and image twice, which causes a problem that increases inspection time and inspection cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a nonuniformity inspection method capable of detecting unevenness in colored film thickness with high accuracy by avoiding variations in inspection sensitivity resulting from a difference in transmittance depending on resist colors. To provide an apparatus.

  In order to solve the above-mentioned problems, the present invention provides that the light transmittance of all the used colored films is 50% or more with respect to a substrate to be inspected on which a pattern of colored films of a plurality of colors is formed, and an imaging device As a wavelength region having a sensitivity, a light from a light source having a central value of 800 nm to 900 nm and a half-value width of 30 nm or less is irradiated, reflected light on the surface of the colored film, and a boundary with the substrate interface through the colored film Based on the interference phenomenon caused by the phase difference from the reflected light reflected by the light, the change in the colored film thickness is imaged as the shade of the reflected light.

  Further, in order to solve the above problems, the present invention irradiates light from a light source onto a plurality of colored films formed on a substrate, images changes in the colored film as shades of reflected light, and captures the image. A colored film thickness non-uniformity inspection apparatus for inspecting the colored film thickness unevenness of the colored film, wherein the light transmittance of all the colored films is 50% or more, and the wavelength range is half from the central value of 800 nm to 900 nm. An illumination unit that irradiates the colored film formed on the substrate with light having a value width of 30 nm or less, reflected light that is reflected by the surface of the colored film, and reflected light that is transmitted through the colored film and reflected by the substrate interface And an imaging unit having sensitivity in the wavelength range that captures the change in the colored film thickness as the density of reflected light based on the interference phenomenon caused by the phase difference.

  According to the present invention, there is an effect that unevenness inspection with high accuracy can be performed by avoiding variations in inspection sensitivity caused by differences in transmittance depending on resist colors.

  The interference fringe has a phase difference corresponding to the film thickness between the light reflected on the film surface when light is incident on the film surface and the light transmitted through the film and reflected on the boundary surface with the substrate. It is observed by the intensity of the specific wavelength depending on the film thickness. Therefore, interference is unlikely to occur when the transmittance of the membrane is low. FIG. 2 is a characteristic diagram showing an example of the spectral transmittance of Red, Green, and Blue of the color filter. It can be seen that any resist has a transmittance of 90% or more at 850 nm or more. A sodium lamp having a luminance spectrum at 590 nm has a low blue transmittance and the interference fringe cannot be observed. This problem can be solved by using light in the wavelength region of 850 nm or more.

  The characteristic of the sodium lamp is a steep emission line spectrum around 590 nm. The wavelength range of incident light affects the ease of observation of interference fringes. FIG. 3 is a characteristic diagram in which the reflection intensity for each film thickness is calculated when the wavelength range of light irradiated around 850 nm is changed stepwise from 100 nm to 10 nm. As can be seen, the narrower the wavelength range of the irradiated light, the greater the difference in reflection intensity due to interference caused by the difference in film thickness, and an image with good contrast can be obtained when captured as an image.

  In addition, the intensity of the specific wavelength of the reflected light due to the interference generates a local maximum / minimum or a local minimum / maximum at an integral multiple of the wavelength and an integer +0.5 times, so that the interference period becomes longer as the wavelength becomes longer. In other words, the longer the wavelength, the less the reflection intensity changes even if the film thickness is different, and the interference cannot be observed with good contrast. It can be said that the wavelength of about 800 to 900 nm is most suitable under the condition that the film thickness of the color filter is 1 to 2 μm, the film refractive index is 1.6, and the glass substrate refractive index is about 1.5.

  Next, as an image pickup device, a CCD device camera is generally used in automatic inspection. Originally, the CCD element has sensitivity not only in the visible range but also in the near infrared range. FIG. 4 is a characteristic diagram showing the spectral sensitivity characteristic of NC300AIR manufactured by Takenaka System Equipment as an example of a general CCD camera. The vertical axis is a value normalized with 1 being the highest sensitivity. However, light in the near-infrared region, which has a wavelength longer than that of visible light, is not sufficiently sensitive because it is photoelectrically converted in the deep part of the semiconductor silicon. It is difficult to collect the sensor well, and sufficient sensitivity cannot be obtained. In view of this, image sensors with high near-infrared sensitivity have been put into practical use by adopting an FT method capable of a high aperture ratio, so that they can be used for imaging with low illuminance or a short exposure time. . FIG. 5 is a characteristic diagram showing the spectral sensitivity characteristics of an image sensor LC99115 from Sanyo Electric as an example of an image sensor with improved sensitivity in the near infrared region. By adopting these image sensors, an automatic inspection system can be constructed at a cost that is not significantly different from conventional automatic inspection systems using visible light.

  Considering all the conditions such as the spectral transmittance of the color filter, the light source, and the image sensor, it is desirable to irradiate with a light source that has a center value of 800 to 900 nm and a half-value width of 30 nm or less.

Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a configuration of a colored film thickness unevenness inspection apparatus according to the first embodiment. As a candidate of the light source 1 that emits light in the near infrared region, there is an LED (Light Emitting Diode). It is used as a vehicle number reading camera light source and an infrared surveillance camera light source, and has a narrow wavelength range. FIG. 6 is a characteristic diagram showing an example of spectral radiation characteristics of an LED that emits near infrared rays. Further, as another light source 1 candidate, a halogen bulb also emits near infrared light, although the wavelength range is wide. FIG. 7 is a characteristic diagram showing the spectral radiation characteristics of this halogen bulb.

  As shown in FIG. 1, when the light emitted from the light source 1 is broadband, the target substrate 3 is irradiated via the bandpass filter 2. The band pass filter 2 desirably has a center wavelength of 800 nm to 900 nm and a half width of about 30 nm.

  As shown in FIG. 1, the imaging unit 5 is installed at an angle of regular reflection with the illumination unit including the light source 1 and the bandpass filter 2. The incident angle α is preferably 10 ° to 40 °. If the angle is larger than that, the surface reflection component becomes too large, and the component that is transmitted and reflected decreases, so that it becomes difficult to observe the interference phenomenon. Based on the interference phenomenon caused by the phase difference between the light incident from the illuminating part and the light reflected by the colored film surface and the light transmitted through the colored film and reflected by the glass substrate interface, A video signal in which the change in the colored film thickness is captured as the shade of reflected light is obtained. That is, when different film thicknesses are imaged, a difference in reflection intensity occurs, and a video signal is obtained in which the change in film thickness is captured as the density of reflected light.

  In recent years, since the inspection target substrate 3 has been increased in size, a line scanning camera is often used as the imaging unit 5. Therefore, the inspection target substrate 3 is imaged while being transported by the transport mechanism 4. This is subjected to A / D conversion, and the digital data is detected by using software on the computer 6 or dedicated hardware.

  When an image having a high contrast between the uneven portion and the normal portion is obtained, a method disclosed in Japanese Patent Application Laid-Open No. 2000-113188 can be applied to a method for detecting unevenness from the image, and the description thereof is omitted.

As described above, according to the first embodiment, an imaging device with increased sensitivity in the near infrared region is used, the light transmittance of all the colored films is 50% or more, and the imaging device has sensitivity. As the wavelength range, the inspection target substrate 3 is irradiated with light having a central value of 800 nm to 900 nm and a half-value width of 30 nm or less, and the reflected light on the colored film surface and the substrate interface of the inspection target substrate 3 are transmitted through the colored film Since the change in the colored film thickness is imaged as the shade of the reflected light based on the interference phenomenon caused by the phase difference with the reflected light reflected at the boundary with the automatic inspection using conventional visible light There is an effect that it is possible to provide a non-uniformity inspection method and apparatus capable of detecting a non-uniform color film thickness with high accuracy while avoiding variations in inspection sensitivity caused by a difference in transmittance depending on resist colors at a cost that is not significantly different from the system.
Further, by narrowing the wavelength range of the light irradiated around 850 nm, the difference in the reflection intensity due to the interference caused by the film thickness difference can be increased, and the colored film thickness nonuniformity inspection method that can obtain an image with enhanced contrast And there is an effect that can provide a device.

It is a schematic diagram which shows the structure of the colored film thickness nonuniformity inspection apparatus of Example 1 of this invention. It is a characteristic view showing an example of spectral transmittance of Red, Green, Blue of the color filter. It is the characteristic view which calculated the reflection intensity for every film thickness when the wavelength range of the light irradiated centering on 850 nm was changed in steps from 100 nm to 10 nm. It is a characteristic view which shows the spectral sensitivity characteristic of NC300AIR made from Takenaka system equipment as an example of a general CCD camera. It is a characteristic view which shows the spectral sensitivity characteristic of the image pick-up element LC99115 of Sanyo Electric. It is a characteristic view which shows an example of the spectral radiation characteristic of LED which discharge | releases near infrared rays. It is a characteristic view which shows the spectral radiation characteristic of a halogen bulb.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Band pass filter, 3 ... Board | substrate to be examined, 5 ... Imaging part, 6 ... Computer.

Claims (2)

  For a substrate to be inspected on which a pattern of colored films of multiple colors is formed, the light transmittance of all the used colored films is 50% or more, and the central value is 800 nm as a wavelength range in which the imaging device has sensitivity. The phase difference between the reflected light reflected from the surface of the colored film and the reflected light transmitted through the colored film and reflected at the boundary with the substrate interface is irradiated with light from a light source having a half-width of 30 nm or less at 900 nm Based on the interference phenomenon caused by the above, a variation in the colored film thickness is picked up by the image sensor as the intensity of reflected light, and the colored film thickness unevenness is detected from the captured image. Inspection method. Irradiates light from a light source onto multiple colored films formed on the substrate, images changes in the colored film as shades of reflected light, and inspects the colored film for unevenness of the colored film based on the image An apparatus for inspecting colored film thickness unevenness,
An illuminating unit that irradiates the colored film formed on the substrate with light having a light transmittance of 50% or more for all the colored films, a wavelength range of 800 nm to 900 nm, and a half-value width of 30 nm or less;
Based on the interference phenomenon caused by the phase difference between the reflected light reflected on the surface of the colored film and the reflected light transmitted through the colored film and reflected at the substrate interface, the change in the colored film thickness is defined as the shade of the reflected light. An imaging unit having a sensitivity in the wavelength range for imaging,
A colored film thickness nonuniformity inspection apparatus characterized by comprising:

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