JP4576962B2 - Defect inspection method and defect inspection apparatus - Google Patents

Description

  The present invention relates to a defect inspection method and a defect inspection apparatus capable of automatically detecting a defect in which a foreign object or the like is mixed into an object having a flat surface, in particular, a film thickness variation defect due to the foreign object.

  In recent years, display devices using a CRT (Cathode Ray Tube), liquid crystal, or the like have been devised to prevent or reduce reflection by applying an antireflection film on the surface of the screen. In the display device, “readability” is one of the most important quality characteristics, and the importance of the antireflection film for preventing the reflection of light in the display device is increasing year by year.

  The antireflection film is roughly classified into two types, AR (Anti-Refrection) and LR (Low-Refrection). AR is formed of a multilayer film and is relatively expensive, but has the highest antireflection effect. In general, the reflectance on the AR surface is about 0.5 to 1.0% on the average in the visible light range. On the other hand, LR is formed of a charcoal layer film and is inexpensive, although the antireflection effect is slightly inferior to AR. Generally, the reflectance on the LR surface is about 1.0 to 2.0% on the average in the visible wide range.

  AR is commercialized as an antireflection film in which an optical interference film is multilayer-deposited on a base film, and LR is commercialized as an antireflection film in which an optical interference film is applied on a base film. In the display device, the antireflection film exhibits an effect as an antireflection film by sticking the antireflection film in close contact with the surface so that bubbles are not mixed.

  Since the antireflection film uses the optical interference effect, an error in the film thickness of the optical interference film often becomes a problem. In general, the film thickness is a thickness around ¼ wavelength of visible light, and the interference wavelength is determined by the film thickness. Therefore, if the film thickness slightly varies locally on the surface of the antireflection film, the image transmitted from the display device only at that portion is distorted or the hue slightly changes. This is a typical defect in the antireflection film.

  Other defects in the antireflection film include scratches on the film surface and cosmetics. There are also defects such as scratches, dents and unevenness on the base film itself.

  There are many factors that cause the film thickness to fluctuate. When foreign matter adheres before or during the deposition (or application) of the optical interference film, pinhole-shaped protrusions are formed on the film surface at the foreign matter adhesion portion. In addition, the phenomenon that the film thickness changes like a skirt at the periphery of the foreign material adhering portion is caused.

The foreign matter is a very small object and does not have a certain hue such as black or transparent. Currently available film defect inspection apparatuses can identify a foreign object that is large and black, but cannot identify a minute object such as 100 μm or less. In addition, the technique which test | inspects the defect of the unevenness | corrugation of the coated surface is disclosed as a related technique which detects such a defect (refer patent document 1).
Japanese Unexamined Patent Publication No. 05-296941

  Here, in the above-described defects in the antireflection film, in particular, defects in film thickness fluctuation due to foreign matters are not easy to confirm even by a skilled person, and the price and mass production of the antireflection film are reduced. In order to carry out, it was difficult to inspect films having a thickness of 100 μm or less. In addition, it is usually difficult to automatically check for defects in the antireflection film, and as described above, it is difficult to inspect all of the large number of antireflection films. Several samples will be removed and checked. Therefore, the shipped antireflection film contains not a few defective films, and there is a problem that the defect rate of the antireflection film cannot be reduced. In addition, regardless of the above-described antireflection film, the same problem as described above also exists when inspecting whether or not foreign matter is mixed in a plane such as another film or sheet.

  Therefore, the present invention relates to a defect inspection method capable of automatically detecting a defect in which a foreign object or the like is mixed into an object having a flat surface, particularly a defect of film thickness variation on the flat surface due to the foreign material.

  The present invention has been made to solve the above-described problems, and is a defect inspection that inspects defects on the surface of the inspection object by irradiating the inspection object with inspection light and receiving reflected light from the inspection object. A defect inspection method for an apparatus, wherein the inspection object is irradiated with inspection light, reflected light that is polarized and separated at the inspection object is received, and light components of the received reflected light are photoelectrically converted to each polarization. In the defect inspection method, interference data indicating a component value is generated, and a defect on the surface of the inspection object is detected based on the interference data.

  In the defect inspection method, the present invention is characterized in that the inspection light is irradiated perpendicularly to the inspection object.

  According to the present invention, in the defect inspection method, the inspection light is directional light.

  According to the present invention, in the defect inspection method, the inspection light is diffuse light.

  According to the present invention, in the defect inspection method, the defect inspection apparatus is disposed at one of two symmetrical positions that form a predetermined angle from the perpendicular of the inspection object, and the light source of the inspection light is disposed at the other. Features.

  Further, the present invention provides the defect inspection method, wherein the inspection light is a light source of any one of a fluorescent lamp, a metal halide lamp, an ultraviolet lamp using any or all gases of rare gas, halogen gas, and mercury gas. It is characterized by being emitted light.

  In the defect inspection method, the present invention is characterized in that the ultraviolet light emitted from the ultraviolet light and serving as inspection light has a wavelength band of 200 nm to 450 nm.

  In the defect inspection method, the present invention is characterized in that a plurality of the defect inspection apparatuses are arranged to inspect a surface defect of the inspection object.

  Further, the present invention is characterized in that, in the defect inspection method, when the defect inspection apparatus detects that there is a defect on the surface of the inspection object, the defect portion of the inspection object is marked. .

  Further, the present invention is a defect inspection apparatus for inspecting a defect on the surface of the inspection object by irradiating the inspection object with inspection light and receiving reflected light from the inspection object, the inspection light being the inspection object Means for irradiating an object; means for receiving reflected light that has been polarized and separated at the inspection object; and means for generating interference data indicating the value of each polarization component by photoelectrically converting the light component of the received reflected light And a means for detecting a defect on the surface of the inspection object based on the interference data.

  According to the defect inspection method of the present invention, the inspection object is irradiated with the inspection light, the reflected light polarized and separated at the inspection object is received, the light component of the received reflected light is photoelectrically converted, and each polarization component is Interference data indicating a value is generated, and a defect on the surface of the inspection object is detected based on the interference data. Thereby, the effect that the defect which the foreign material etc. mixed into the test target object which has a plane, especially the defect of the film thickness fluctuation | variation on the plane by a foreign material can be detected automatically is acquired.

  Hereinafter, a defect inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the object to be inspected is an antireflection film, but other films or sheets may be used.

FIG. 1 is a diagram showing a configuration of the defect inspection apparatus according to the embodiment.
As shown in this figure, the defect inspection apparatus mainly includes a light source unit 1, a light extraction unit 2, imaging units 3 and 4, and a processing unit 5. The antireflection film 20 to be imaged is disposed on the back plate 6.

  In the light source unit 1, the coherent light output from the coherent light source 7 such as a laser light source is converted to P-polarized light by the change filter 8, passed through the mirror 9, and input to the scanning mirror 10. The scanning mirror 10 oscillates light in a direction perpendicular to the paper surface. This is made parallel by the fθ lens 11 and irradiated to the subject 20 through the half mirror 12. The above is the optical path a.

  In the light extraction unit 2, the reflected light from the subject 20 that becomes the path of the optical path b is made an appropriate light intensity through the filter 13, and then only the parallel light is extracted by the telecentric optical system 14. Next, it is separated into a P-polarized light component and an S-polarized light component by the polarizing beam splitter 15, and an image is formed on the light receivers 17 and 19 via the imaging lenses 16 and 18, respectively. In synchronization with the scanning mirror 10, photoelectric conversion is performed by the light receivers 17 and 19. It is desirable that the inner surface of the lens tube enclosing the light extraction unit 2 is subjected to stray light processing such as matte black coating or a brush structure using black hair.

  The light receivers 17 and 19 may be an imaging device such as a CCD, but it is easiest to use a photodiode (including a phototransistor) in order to synchronize with the scanning mirror 10. Further, the photodiodes may be arranged in an array by adding a simple device of the imaging system.

  The back plate 6 is for placing a subject such as an antireflection film 20. Although not shown, the back plate 6 is provided with a mechanism for fixing the antireflection film 20 so as not to loosen.

  The structure and characteristics of the antireflection film will be described with reference to FIG. This figure shows the structure of the LR film. In the LR film, an LR layer 61 is applied on a base film 62 having a thickness of about several μm. Since the film thickness of the LR layer 61 is in the vicinity of a quarter wavelength of the light to be used, it is approximately several tens to several hundreds of nm. The refractive index n1 of the LR layer 61 is desirably a low refractive index, and is about 1.2 to 1.4 depending on the composite material (having wavelength characteristics, and the refractive index tends to be large in the case of ultraviolet light). In general, the refractive index n2 of the base film 62 is generally set to the square value of the refractive index n1 of the LR layer 61.

  As described above, the LR film as the antireflection film has been described. The antireflection film has an effect as an antireflection film by being closely bonded to the target where the reflected light (reflectance) should be reduced at the refractive index interface 77 portion. Demonstrate.

  Next, an interference phenomenon in the case where the incident beam light 64 which is incoherent light on the LR film is irradiated to the incident optical axis 63 at an incident beam incident angle 65 (θ1) will be described. First, the incident beam light 64 is separated into the LR surface reflected light 66 and the LR incident light 67 by the refractive index interface 75. Both directions follow the Snell (Cartesian) law shown below.

  The intensities of the LR surface reflected light 66 and the LR incident light 67 are obtained by the following equations.

  Here, Ip is the incident beam light intensity, Rp is the reflected light intensity, Tp is the transmitted light intensity, Ap is the intensity of the light absorption component on the inner surface of the film, Dp is the intensity of the light scattering component, and n0 is the refractive index of air (= 1). .0).

  The LR incident light 67 passes through the LR layer 61 and is separated into the LR back surface reflected light 69 and the base material incident light 71 by the refractive index interface 76. Note that refraction and reflection are re-refracted every time they hit the interface, producing 1 to n-order light. Only the secondary reflected light 70, which is the secondary light, is shown, but in order to simplify the description, in the present embodiment, the secondary light and the subsequent light are ignored and only the primary light component is considered.

  The antireflection effect is generated by interference between the LR front surface reflected light 66 and the LR back surface reflected light 69. When the film thickness of the LR layer is d, the optical film thickness D is represented by the following formula.

  Here, θ1 is made sufficiently small,

  And approximate. When D = (2m−1) · λ / 4 is satisfied, the reflected light is weakened by interference. The reflectance Rmin at this time can be obtained by the following equation, where λ is the wavelength of incident light.

  When D = (2 m) · λ / 4 is satisfied, the reflected light is intensified by interference. The reflectance Umax at this time is obtained by the following equation.

  In the above equation, when n1 = 1.3, n2 = 1.69, and d = 100 [nm], the reflectivity R = 0.177 (with respect to light having wavelengths λ = 520 nm, 173 nm, and 104 nm) 1.7%), and for light having wavelengths λ = 260 nm, 130 nm, and 75 nm, the reflectance R is increased to 0.066 (6.6%). When the refractive index of the target medium to be bonded to the antireflection film is np, the reflectance R0 of the medium itself can be obtained by the following equation.

  If np = 1.5, R0 = 0.04 (4%), and if the value of D is selected and the value of Rmin is taken, the reflectivity is improved to about 2.4 times. Can do. In general, the wavelength λ is often based on 550 nm, which is the maximum human relative luminous sensitivity.

Next, a case where coherent light is incident on the antireflection film will be described.
The difference when incoherent light is incident is that the polarization planes of the LR front surface reflected light 66 and the LR back surface reflected light 69 are different. When the antireflection film is irradiated with the incident beam light 64 that is P-polarized with respect to the coherent light, the LR front surface reflected light 66 is P-polarized light and the LR back surface reflected light 69 is S-polarized light. Since the LR layer 61 has the optical film thickness D, this may be regarded as performing the same function as the quarter-wave plate. When the antireflection film is irradiated with the incident beam light 64 that is S-polarized with respect to the coherent light, the LR front surface reflected light 66 is S-polarized light and the LR back surface reflected light 69 is P-polarized light. The incident beam light 64 may be either P-polarized light or S-polarized light.

  The light passing through the optical path b takes the vector sum of the LR front surface reflected light 66 and the LR back surface reflected light 69. The light flux takes P-polarized light and S-polarized light components. The P-polarized light component is reflected light from the surface of the LR layer 61, and the S-polarized light component is reflected light from the surface of the base material layer 62. Thus, independent reflection characteristics can be obtained for each of the LR layer 61 and the base material layer 62.

  Next, the defect of an antireflection film is demonstrated using FIG. The defects are roughly classified into category A, which is a defect of the LR layer 61, and category B, which is a defect of the base film 62. FIG. 3 is a diagram modeling 10 defects. In the figure, the height direction is enlarged and displayed for the sake of explanation.

  First, as category A, an example of a defect that appears as a change in the level of the LR layer will be described. The defect 91 is an example of a defect in which the concave portion 110 of the base film 62 appears in the LR layer 61 as it is. The defect 92 is an example of a defect in which a concave portion is generated in the LR layer 61 although the base film 62 has no problem. The defect 93 is an example of a defect in which the convex portion 111 of the base film 62 appears on the LR layer 61 as it is. The defect 94 is an example of a defect in which the base film 62 has no problem but the LR layer 61 has a convex portion. The defect 95 is an example of a defect in which a convex portion is generated in the LR layer 61 as a result of the foreign material 112 being mixed, although the base film 62 has no problem. The defect 96 is an example of a defect in which a scratch or a scrap is generated on the LR layer 61.

  Next, as a category B, an example of a defect that has a defect in the substrate layer (substrate film) but does not appear as a change in the height of the LR layer will be described. The defect 97 is an example of a defect in which the foreign material 112 is mixed on the base film 62 but the unevenness is not generated on the LR layer 61. The defect 98 is an example of a defect in which the recess 110 is generated in the base film 62 but the unevenness is not generated on the LR layer 61. The defect 99 is an example of a defect in which the convex portion 111 is generated on the base film 62 but the unevenness is not generated on the LR layer 61. The defect 100 is an example of a defect in which scratches and rust are generated on the base film 62 but no irregularities are formed on the LR layer 61.

  As a first example of the shape of the defect, the shape of the defect 95 is shown in FIG. FIG. 5 is a cross-sectional view taken along the dotted line in FIG. The foreign matter defect 112 is very small, and the change in the film thickness tends to be relatively large in the defect range 115. However, the range of the defect range 115 does not necessarily have a smooth shape, but often has an irregular shape. For this reason, scattering occurs in this portion, regular reflection is performed at an unexpected angle, and optical path prediction of reflected light becomes difficult. Further, in the peripheral portion of the foreign substance defect 112, a relatively small change in film thickness is caused within a relatively large defect range 114. This forms the base of the contour line.

  FIG. 6 shows the shapes of the defects 93 and 94 as a second cross-sectional view of the shape of the defect. The defect portion generates Δθ (x, y) with respect to the surface of the LR layer 61 and forms a very gentle skirt. The defects 91 and 92 are not shown in the figure because they only differ in the direction in which the skirt is formed with respect to the height direction.

  The defects 91 to 95 cause a minute angle change 125 of Δθ (x, y) on the surface of the LR layer 61. Therefore, the regular reflection light 124 forms an angle 126 of 2Δθ (x, y) with respect to the optical axis 122 or the irradiation light 123. This is shown in FIG. By setting the aperture angle of the telecentric optical system 12 to 2Δθ (x, y) or less, the reflected light 124 is not imaged. The change in the shape of the surface of the LR layer 61 is detected by the difference in the P-polarized light component with respect to the difference. In addition, since the surface shape of the base material layer 62 changes, the defects 91, 93, and 95 can be detected by the difference in the S polarization component.

  The defect 96 can be detected in the same manner by the method using the defects 91 to 95. Although the shape of the surface of the LR layer 61 is changed, it is different in that scattered light is incident. A certain threshold value may be provided to determine whether or not scattered light enters.

  The defects 97 to 100 are not detected on the surface of the LR layer 61, but can be detected by the difference in the S-polarized light component reflected from the base material layer 62.

  As described above, the defect inspection apparatus is a method for detecting a change in the surface shape using the P-polarized component and the S-polarized component of the specularly reflected light by projecting light perpendicularly to the antireflection film (coaxial incident light). In addition, as shown in FIG. 8, there is a light source in one of two symmetric angles about the perpendicular at the inspection target point of the antireflection film, and a defect inspection apparatus is installed on the other side. In this case, a method of detecting a change in the surface shape by the P-polarized component and the S-polarized component of the light projected from the light source by the antireflection film may be used (in the case of inclined regular reflection). Here, when detecting a change in the surface shape of the antireflection film by inclined regular reflection, the angle formed between the perpendicular line at the inspection target point in the antireflection film and the direction of the light source is 0 to 10 ° (preferably 5 °). If the angle formed between the perpendicular and the direction of the defect inspection apparatus is 0 to 10 ° (preferably 5 °), interference reflected light on one side of the image captured by the defect inspection apparatus is scattered, and the image is unclear. Alternatively, disappearance can be prevented.

  Moreover, directional light (parallel light) is used as a light source for detecting a change in the surface shape of the antireflection film. This directional light (parallel light) is obtained by providing a slit plate (aperture) between the inspection object such as an antireflection film and the light source, or by providing a hemisphere, a semicircular lens, a Fresnel lens, etc. You can get it. As the light source, a general fluorescent lamp, a metal halide lamp, a rare gas, a halogen gas, a mercury gas, and an ultraviolet lamp using a mixed gas thereof can be used. In the case of using an ultraviolet lamp, an ultraviolet ray having a wavelength of 200 nm to 450 nm is used. In particular, in order to suppress safety, discoloration, and deterioration of an inspection object, an ultraviolet ray that generates a wavelength of 360 nm to 380 nm having a peak at around 38 nm. Use a light lamp.

  And when detecting the change in the surface shape of the antireflection film, a plurality of defect inspection devices are arranged side by side as shown in FIG. 9 to detect the change in the surface shape of the entire width of the antireflection film at once. be able to. And when the change in the surface shape can be detected in the defect inspection apparatus, the processing unit 5 instructs the defect check unit provided in the defect inspection apparatus to check using the ink or the like at the detection location, The defect check unit may add a check mark using ink.

  The processing unit of the above-described defect inspection apparatus has a computer system inside. The processes such as the above-described surface shape change detection process are stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing the program. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

It is a figure which shows the structure of the defect inspection apparatus of one Embodiment of this invention. It is a figure which shows the structure and characteristic of an antireflection film. It is a figure which shows the example of the defect of an antireflection film. It is a figure which shows the 1st example of the shape of a defect. It is the 1st sectional view of the shape of a defect. It is a 2nd sectional view of the shape of a defect. It is a figure which shows the regular reflection light in case the minute angle change has arisen on the surface. It is a figure which shows the example of inclination regular reflection. It is a figure which shows the mode at the time of arranging a plurality of defect inspection apparatuses.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source part, 2 ... Light extraction part, 3, 4 ... Imaging part, 5 ... Processing part, 6 ... Back plate, 20 ... Antireflection film

Claims (8)

In defect inspection method of the defect inspection apparatus irradiates an inspection light to the anti-reflection film having an optical interference film on a substrate film by receiving the reflected light from the antireflection film for inspecting defects of a surface of the antireflection film There,
Irradiate the antireflection film with the inspection light which is directional light ,
Receiving the reflected light polarized and separated in the antireflection film ,
Interferometric data indicating the value of each polarization component by photoelectrically converting the light component of the received reflected light,
A defect inspection method, wherein a defect on the surface of the antireflection film is detected based on the interference data. The defect inspection method according to claim 1, wherein the inspection light is irradiated perpendicularly to the antireflection film . 2. The defect inspection according to claim 1 , wherein the defect inspection apparatus is disposed at one of two symmetrical positions forming a predetermined angle from a perpendicular of the antireflection film , and the light source of the inspection light is disposed at the other. Method. The inspection light is light emitted by a light source of any one of a fluorescent lamp, a metal halide lamp, an ultraviolet lamp using any or all of rare gas, halogen gas, and mercury gas. The defect inspection method according to any one of claims 1 to 3 . The defect inspection method according to claim 4 , wherein the ultraviolet light that is emitted from the ultraviolet light and serves as inspection light has a wavelength band of 200 nm to 450 nm. Defect inspection method according to any one of claims 1 to 5, characterized in that the side by side a plurality of defect inspecting apparatus for inspecting defects of a surface of the antireflection film. Defects according to claims 1 to claim 6 wherein the defect inspection apparatus when it detects that there is a defect on the surface of the antireflection film, which is characterized in subjecting a mark defect of the antireflection film Inspection method. The defect inspection apparatus for inspecting a defect of a surface of the antireflection film by receiving the reflected light from the antireflection film is irradiated with inspection light antireflection film comprising an optical interfering film on the substrate film,
Means for irradiating the antireflection film with the inspection light which is directional light ;
Means for receiving the reflected light polarized and separated in the antireflection film ;
Means for photoelectrically converting the light component of the received reflected light to generate interference data indicating the value of each polarization component;
Means for detecting a surface defect of the antireflection film based on the interference data;
A defect inspection apparatus comprising:

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