Abstract:
An inspecting apparatus for a glass substrate detects blurs of a green color filter layer, a blue color filter layer, a column spacer layer, a pixel layer of a thin film transistor, or the like, which are generally hardly inspected. The inspecting apparatus for a glass substrate includes: a first illumination unit supplying reflective light to a surface of the substrate to inspect whether the surface of the substrate is defective or not; a second illumination unit supplying transmissive light from a rear side of the substrate to inspect whether the interior of the substrate is defective or not; a latticed rear plate provided on a rear surface of the substrate; and a driving interferometer system generating a phase difference of light by driving such that a driving guide is moved along the rear plate or the rear plate itself is moved.

Description:
This nonprovisional application claims priority under 35 U.S.C. § 119( a ) on Patent Application No. 2007-0030285 filed in Republic of Korea on Mar. 28, 2007, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an inspecting apparatus for a glass substrate to inspect whether a surface of a substrate is defective or not with naked eyes. 
     2. Related Art 
     In general, in fabricating a large-scale substrate such as semiconductor wafer or a liquid crystal display (LCD), a plasma display panel (PDP), an organic electro-luminescence display, and the like, the displays are inspected with naked eyes to detect debris, spots, or blurs that may remain on the substrates. In this case, an illumination device that uniformly illuminates the entirety of the substrate is used to facilitate detection of defects. The configuration of the related art inspecting apparatus for a glass substrate will now be described. 
       FIG. 1   a  is a view schematically showing the related art inspecting apparatus for a glass substrate, and  FIG. 1   b  is a view substantially illustrating detection of light reflected by an upper illumination unit by an inspector. 
     First, with reference to  FIG. 1   a , the related art inspecting apparatus for a glass substrate comprises an upper illumination unit  30  and a rear illumination unit  40  which are, respectively, disposed at an upper side and a rear side of a glass substrate  10 , an inspection target. An inspector  50  detects a defect of the glass substrate  10  by means of a reflective light L 1  irradiated from the upper illumination unit  30  and a transmissive light L 2  irradiated from the rear illumination unit  40 . The glass substrate  10  is fixed by clampers  20  and comprises pattern regions such as a color filter region, a column spacer region, a pixel region, etc. formed on a front surface thereof. The inspector  50  is in front of the glass substrate  10  and checks whether the front surface of the glass substrate  10  is defective or not. 
     As shown in  FIG. 1   b , the upper illumination unit  30  comprises a light source  31 , a reflecting unit  32 , a condensing unit  33 , and a scattering (diffusion) unit  34 . When light is first generated from the light source  31 , it is reflected to the condensing unit  33  by means of the reflecting unit  32 , transmitted through the condensing unit  33  and the scattering unit  34 , and then irradiated to the glass substrate  10 , the inspection target. The light reflected by the glass substrate  10  proceeds to the naked eyes of the inspector  50 . Then, the inspector  50  observes the reflected light to check whether the glass substrate  10  is defective or not. 
     The inspecting method is performed such that mura, namely, blurs, present on the glass substrate  10  is checked by the naked eyes of the inspector based on the difference between the strength and a reflection angle of light reflected from a flawless surface of the glass substrate  10  and those of light reflected from a defective surface of the glass substrate  10 . However, the related art inspecting apparatus for the glass substrate has a problem in that, actually, it is not easy to properly inspect the glass substrate  10  because of the difference in thickness of pigments or an overlay in forming color filters. Namely, the pigments for forming red, green, and blue color filters, column spacers, or pixels of a TFT substrate make it difficult to detect blurs, such as overlay blurs, namely, butterfly blurs, that affect the characteristics of the viewing angle. For instance, the butterfly blurs can be detected, provided two or more layers are stacked, so after all the follow-up layer processes are performed, the butterfly blurs are inspected. In other words, the butterfly blurs cannot be detected until the follow-up layer processes are performed, resulting in a loss of production because the follow-up processes should be necessarily performed. 
     In an effort to solve this problem, pigments were formed or a pixel layered pattern was formed on a metal-deposited glass substrate and then a sampling inspection was performed. However, in case of using the metal-deposited glass substrate such as a TFT gate pattern, the blurs with respect to the pixels, the column spacers or the pigments of the color filters can be well seen, but disadvantageously, the sampling and the glass substrate should be separately fabricated, causing much loss in terms of production and costs. 
     BASIC SUMMARY OF THE INVENTION 
     An object of this invention is to provide an inspecting apparatus for a glass substrate capable of effectively detecting blurs (spots) generated on a green color filter layer, a blue color filter layer, a column spacer layer, a thin film transistor (TFT) layer, and so on, which have not been possibly inspected because of pigments used for fabricating a liquid crystal display (LCD) and structural weaknesses. 
     Another object of this invention is to provide an inspecting apparatus for a glass substrate capable of effectively detecting blurs (spots) of stacked layers caused by a thickness difference or overlay of pigments or blurs (spots) sensitive to light scattering (diffusion) characteristics to thus improve a production yield and quality of an LCD. 
     In an aspect, an inspecting apparatus for a glass substrate includes: a first illumination unit supplying reflective light to a surface of the substrate to inspect whether the surface of the substrate is defective or not; a second illumination unit supplying transmissive light from a rear side of the substrate to inspect whether the interior of the substrate is defective or not; a rear plate provided on a rear surface of the substrate; and a driving guide disposed on a rear surface of the rear plate and generating a phase difference between the light provided from the first illumination unit and the light provided from the second illumination unit. The driving guide may move up and down (vertically) or left and right (horizontally) along the rear surface of the rear plate, and interfere with or scatter (diffuse) light provided from the first and second illumination units if the glass substrate is defective. 
     In another aspect, an inspecting apparatus for a glass substrate includes: a first illumination unit supplying reflective light to a surface of the substrate to inspect whether the surface of the substrate is defective or not; a second illumination unit that supplies transmissive light from a rear side of the substrate to inspect whether the interior of the substrate is defective or not; and a rear plate disposed on a rear surface of the substrate and generating a phase difference between the light provided from the first illumination unit and the light provided from the second illumination unit. The rear plate may move up and down (vertically) or left and right (horizontally) along the rear surface of the rear plate, and interfere with or scatter (diffuse) light provided from the first and second illumination units if the glass substrate is defective. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The implementation of this document will be described in detail with reference to the following drawings in which like numerals refer to like elements. 
         FIG. 1   a  is view schematically illustrating an inspecting apparatus for a glass substrate according to the related art. 
         FIG. 1   b  is a view substantially illustrating detection of light reflected by an upper illumination unit by an inspector. 
         FIG. 2   a  is a plan view showing an inspecting apparatus for a glass substrate to which this document is applied. 
         FIG. 2   b  is a view showing a mura defect that may be detected in inspecting the substrate. 
         FIG. 3  is a view for explaining a driving principle of the inspecting apparatus for a glass substrate according to a first embodiment of the invention. 
         FIG. 4  is view for explaining a principle for detecting blurs existing on the glass substrate by using the inspecting apparatus according to the first embodiment of the invention. 
         FIG. 5  is a view for explaining a driving principle of the inspecting apparatus for a glass substrate according to a second embodiment of the invention. 
         FIG. 6  is view for explaining a principle for detecting blurs existing on the glass substrate by using the inspecting apparatus according to the second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The foregoing and other objects, features, aspects and advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings. The same reference numerals denote the same elements throughout the specification. 
     The inspecting apparatus for a glass substrate according to the embodiments of the invention will now be described with reference to the accompanying drawings. 
     The invention provides a structure for remarkably improving mura detection capabilities of an inspecting apparatus for a glass substrate, namely, of a macro-inspecting apparatus for inspecting unspecified defects of a surface of the glass substrate. 
       FIG. 2   a  is a plan view showing an inspecting apparatus for a glass substrate to which this document is applied, and  FIG. 2   b  is a view showing a mura defect that may be detected in inspecting the substrate. 
     As shown in  FIG. 2   a , the inspecting apparatus for a glass substrate according to the embodiments of the invention can easily detect an overlay blur of patterns or a mura defect generated due to a thickness difference of the patterns by using hologram light and polarization characteristics implemented by a rear plate  300  with a lattice pattern and a driving interferometer system  400 . 
     Here, the rear plate  300  may be disposed on a rear surface of a glass substrate  100 , an inspection target, and serve to fixedly clamp the glass substrate  100 . 
     The rear plate  300  has the lattice pattern and may also serve as a surface plate chuck for adsorbing the glass substrate  100  in a vacuum state. 
     The driving interferometer system  400  may generate a phase difference of light irradiated to the rear plate  300 . As shown, the driving interferometer system  400  may be provided in a plate form on the rear surface of the rear plate  300 , and generates a phase difference of light while being moved vertically or horizontally, or may generate a phase difference of light by moving the rear plate  300  vertically or horizontally. 
     In this manner, the driving interferometer system  400  may be divided into two types according to its driving method for generating the phase difference of light. 
     In the inspecting apparatus for a glass substrate according to the embodiments of the invention, when light, which is to be irradiated to the glass substrate  100 , passes through the rear plate  300 , it is reflected by the rear plate  300 . At this time, the reflective light reflected by the glass substrate  100  and the reflective light reflected by the rear plate  300  are interfered with each other due to their phase difference to generate hologram light. 
     In general, refractive index of light varies depending on types of media through which the light transmits. Thus, the reflection angle of the light reflected by a layer on the glass substrate  100  and that reflected by the rear plate  300  are different from each other, thereby making the phase difference therebetween. 
     The optical interference due to the phase difference may occur due to blurs or a thickness difference of pattern regions such as a color filter formation layer, a column spacer formation layer, a TFT formation layer, or the like, on the glass substrate  100 , and the hologram light may appear like a rainbow pattern due to the optical interference as shown in  FIG. 2   b . Thus, the mura defect existing on the glass substrate  100  can be detected. 
     Compared with the related art inspecting apparatus for a glass substrate that allows observation of only the reflected light on the surface of the substrate, the inspecting apparatus for a glass substrate according to the embodiments of the invention employs the rear plate  300  which reflects light incident on the surface and the driving interferometer system  400  which moves a separate driving guide on the rear side of the rear plate  300  or moves the rear plate  300 . That is, by using the phase difference between the reflective light from the surface of the glass substrate  100  and the reflective light by the rear plate  300  and the driving interferometer system  400 , the defect detection capabilities with respect to the blurs resulting from the overlay, namely, the butterfly blurs due to the overlap of pixels can be enhanced. 
     The embodiments of the invention will now be described based on the two types of driving methods of the interferometer system  400 . 
     A First Embodiment 
       FIG. 3  is a view for explaining a driving principle of the inspecting apparatus for a glass substrate according to a first embodiment of the invention, and  FIG. 4  is view for explaining a principle for detecting blurs existing on the glass substrate by using the inspecting apparatus according to the first embodiment of the invention. 
     The inspecting apparatus for a glass substrate according to the first embodiment of the invention has such a structure that the driving interferometer system  400  for generating a light phase difference is provided on the rear surface of the rear plate. 
     First, with reference to  FIG. 3 , the inspecting apparatus for a glass substrate according to the first embodiment of the invention comprises an upper illumination unit  330  that provides a reflective light source to the surface of the glass substrate  310  to be inspected, a rear illumination unit  340  that provides a transmissive light source from a rear side of the glass substrate  310 , a rear plate  360  provided on a rear surface of the glass substrate  310 , and a driving guide  370  provided on a rear surface of the rear plate  360 . 
     The glass substrate  310  is fixed to the rear plate  360  by means of clampers  320  and comprises pattern region  310   a  such as a plurality of color filter regions, column spacer regions, pixel regions for forming TFTs, and the like, formed on a front surface of the glass substrate  310 . 
     The glass substrate  310  may be a color filter substrate for use in a liquid crystal display (LCD) comprising red, green, and blue color filters. 
     The upper illumination unit  330  may be installed at an upper side of the glass substrate  310  and provides a reflective light source to the surface of the glass substrate  310  to inspect a defect that may exist on the surface of the glass substrate  310 . 
     The upper illumination unit  330  may comprise a light source (not shown), a reflecting unit (not shown), a condensing unit (not shown), and a scattering (diffusion) unit (not shown). 
     The light source generates light to be irradiated on the surface of the glass substrate  310 . The reflecting unit reflects light generated from the light source to change a path of the light to the condensing unit. The condensing unit condenses light irradiated from the reflecting unit. The scattering unit allows light to be transmitted therethrough as it is or scattered according to whether or not power is applied, to thus facilitate detection of blurs of the glass substrate  310 . 
     The rear illumination unit  340  is positioned at a rear side of the glass substrate  310 , and irradiates a transmissive light to the surface of the glass substrate  310  to inspect whether the interior of the glass substrate  310  is defective or not. 
     The rear illumination unit  340  comprises a light source for generating the transmissive light, and the light source of the rear illumination unit  340  is provided to be moved in a forward/backward direction of the glass substrate  310 . 
     The reason of driving the light source of the rear illumination unit  340  in the forward/backward direction is as follows. 
     As the glass substrate  310 , the inspection target, is enlarged in size, the rear illumination unit  340  should be separated by more than a certain distance from the glass substrate  310  to secure a rotation radius of the glass substrate  310 . In this respect, however, when the rear illumination unit  340  is separated by more than the certain distance from the glass substrate  310 , the illuminance relatively is weakened in inspecting the interior of the glass substrate  310  as to whether it is defective or not. Thus, the light source needs to come closer to the glass substrate  310  to inspect the glass substrate  310 , for which, thus, the light source of the rear illumination unit  340  is provided to be movable in the forward/backward direction. 
     The rear plate  360  has the lattice form and a reflection plate disposed on the rear surface of the glass substrate  310  to reflect light outputted from the rear surface of the glass substrate  310 . 
     For instance, if the glass substrate  310  is a color filter substrate, the rear plate  360  would serve to reflect light which has passed through pigments that form the color filters after being provided from the upper illumination unit  330 , so that blurs generated due to the thickness difference of the pigments can be detected. 
     The rear plate  360  may be made of a metallic material and have high transmittance and high reflectance in terms of its material characteristics. Specifically, the metallic material may be aluminum (Al) or chromium (Cr), etc. 
     The lattice pattern of the rear plate  360  may have various sizes. But in order to detect blurs and thickness difference of the pixel regions that form the TFTs as well as the multiple color filter regions and column spacer regions, the rear plate  360  may have a size equivalent to the region where the gate pattern of the TFT is formed. 
     The rear plate  360  is fastened to the glass substrate  310  by means of the clampers  320 , and in this case, the rear plate  360  may be fastened to the glass substrate  310  with a certain distance therebetween or may be tightly attached to the glass substrate  310 . 
     In addition, the rear plate  360  may also serve as a surface plate chuck that adsorbs the glass substrate  310  to be inspected in a vacuum state. 
     The driving guide  370  may be disposed on a rear surface of the rear plate  360  to generate a phase difference between light provided from the upper illumination unit  330  and that provided from the rear illumination unit  340 . 
     The driving guide  370  may be moved up and down (vertically) or left and right (horizontally), may have a plate shape, and may be made of the metallic material such as the rear plate  360 . 
     For example, the driving guide  370  may comprise a first driving guide  370   a  that is moved horizontally along the rear surface of the rear plate  360  and a second driving guide  370   b  that is moved vertically along the rear surface of the rear plate  360 . 
     Light irradiated to the first driving guide  370   a  and the second driving guide  370   b  proceeds to the rear plate  360  and is then reflected to the glass substrate  310 , and at this time, the light is interfered and scattered because of the vertical or horizontal movement of the first and second driving guides  370   a  and  370   b.    
     Here, the light irradiated to the first and second driving guides  370   a  and  370   b  is provided by the upper illumination unit  330  and the rear illumination unit  340 . In particular, the light provided from the upper illumination unit  330  is light which has passed through the glass substrate  310  and the rear plate  360  after being provided from the upper illumination unit  330 . 
     Accordingly, the inspecting apparatus for a glass substrate according to the first embodiment of the invention performs inspecting on the glass substrate  310  while moving the driving guide  370  vertically or horizontally along the rear surface of the rear plate  360  in a state that the glass substrate  310  is fixed to the rear plate  360  in the vacuum state. 
     If the glass substrate  310  is defective, as shown in  FIG. 4 , a reflective light R 1  reflected by the glass substrate  310  and a reflective light R 2  reflected by the rear plate  360  and the driving guide  370  have different phases, making the two lights interfered with each other to generate hologram light in the shape of rainbow, or the like. 
     If the glass substrate  310  is normal or flawless, there is no phase difference between a reflective light R 3  reflected by the glass substrate  310  and a reflective light R 4  reflected by the rear plate  360  and the driving guide  370 , so there is no optical interference nor light scattering. 
     In this manner, a mura defect of the glass substrate  310  can be detected. 
     With reference to  FIG. 4 , if the glass substrate  310  is a color filter substrate, a plurality of black matrixes  312  are formed at uniform distance on a substrate  311 , and red (R), green (G), and blue (B) pigments are formed to form color filters between the black matrixes  312 . 
     In this case, the characteristics of the red (R), green (G), and blue (B) pigments may cause the overlay and the thickness difference of the pigments to create a mura defect, which, however, can be effectively detected in the manner as described above. 
     In addition, by observing the phenomenon of the pattern phase difference based on the latticed rear plate  360 , the particular mura, which can be possibly inspected after layers are stacked, such as the butterfly blurs can be detected at an earlier stage. 
     In addition, a defect of a non-metallic layer such as the pixel layer of the TFT can be also detected. 
     According to the first embodiment of the invention, the same detection effect as that of the related art method that performs the sampling inspection by using the glass substrate with the gate metal pattern deposited thereon can be obtained, and moreover, the costs for fabricating the glass substrate and sampling can be reduced compared with the related art method. 
     The Second Embodiment 
       FIG. 5  is a view for explaining a driving principle of the inspecting apparatus for a glass substrate according to a second embodiment of the invention, and  FIG. 6  is view for explaining a principle for detecting blurs existing on the glass substrate by using the inspecting apparatus according to the second embodiment of the invention. 
     With reference to  FIG. 5 , an inspecting apparatus for a glass substrate according to the second embodiment of the invention comprises an upper illumination unit  530  that provides a reflective light source to a surface of a glass substrate  510  to be inspected, a rear illumination unit  540  that provides a transmissive light source from a rear side of the glass substrate  510 , and a rear plate  560  provided on a rear surface of the glass substrate  510 . 
     The glass substrate  510  may be fixed on a frame of the inspecting apparatus by means of clampers  520 , and comprise pattern regions  510   a  such as a plurality of color filter regions, column spacer regions, pixel regions for forming TFTs, or the like, on its front surface. 
     The glass substrate  510  may be a color filter substrate for use in an LCD comprising red (R), green (G), and blue (B) color filters. 
     The upper illumination unit  530  is installed at an upper side of the glass substrate  510  and provides a reflective light source to the surface of the glass substrate  510  to inspect whether the surface of the glass substrate  510  is defective or not. 
     The rear illumination unit  540  is positioned at a rear side of the glass substrate  510  and irradiates transmissive light to the rear surface of the glass surface  510  to inspect whether the interior of the glass substrate  510  is defective or not. 
     Here, the upper illumination unit  530  and the rear illumination unit  540  according to the second embodiment of the invention are the same as the upper illumination unit  330  and the rear illumination unit  340  as shown in  FIG. 3  according to the first embodiment of the invention, so its description will be omitted. 
     The rear plate  560  according to the second embodiment of the invention may have a lattice form, may be disposed on the rear surface of the glass substrate  510 , and reflect light outputted from the rear surface of the glass substrate  510 . For example, if the glass substrate  510  is a color filter substrate, the rear plate  560  serves to reflect light which has passed through pigments for formation of color filters after being provided from the upper illumination unit  530 , to detect blurs generated due to a thickness difference of the pigments. 
     Also, the rear plate  560  generates a phase difference between the light provided from the upper illumination unit  530  and the light provided from the rear illumination unit  540 , to generate optical interference and light scattering. 
     For this purpose, the rear plate  560  may be made of a metallic material with high reflectance and transmittance, and may be configured to be moved up and down (vertically) or right and left (horizontally) along the rear surface of the glass substrate  510 . 
     In this case, the rear plate  560  may be separated by about 10 cm from the glass substrate  510  and moved vertically or horizontally within the distance of 10 cm. 
     Specifically, the metallic material may be aluminum (Al) or chromium (Cr), etc. 
     The lattice pattern of the rear plate  560  may have various sizes, but in order to detect blurs and the thickness difference of the pixel regions that form the TFTs as well as at the multiple color filter regions and column spacer regions, the rear plate  560  may have a size equivalent to the region where the gate pattern of the TFT is formed. 
     Accordingly, in the second embodiment of the invention, without such a driving guide disposed on the rear surface of the rear plate as in the first embodiment of the invention, the rear plate  560  is separated by a certain distance from the glass substrate  510  and moved vertically or horizontally to inspect the glass substrate  510 . 
     The inspecting operation is performed by using optical interference and light scattering, during which, as mentioned, the rear plate  560  is moved vertically or horizontally without using any driving guide. 
     That is, with reference to  FIG. 6 , if the glass substrate  510  is a color filter substrate, a plurality of black matrixes  512  are formed at uniform distance on a substrate  511 , and red (R), green (G), and blue (B) pigments are formed between the black matrixes  512  to form the color filters. 
     In this case, if there is a defect due to an overlay and thickness difference according to the characteristics of the red (R), green (G), and blue (B) pigments, a reflective light R′  1  reflected by the glass substrate  510  and a reflective light R′ 2  reflected by the rear plate  560  which is moved vertically or horizontally would have different phases, causing the two lights to be interfered with each other and scattered to generate hologram light having a rainbow shape or the like. 
     If, however, the glass substrate  510  is normal or flawless, there is no phase difference between a reflective light R′ 3  reflected by the glass substrate  510  and a reflective light R′ 4  reflected by the rear plate  560 , so there is no optical interference nor light scattering. 
     Accordingly, the mura defect that may be present on the glass substrate  510  can be detected. 
     In this manner, a defect of the non-metallic layer such as the pixel layer of the TFT, as well as the particular mura defect according to the stacked structure such as the overlay blurs, can be detected at an earlier stage. 
     As described above, the inspecting apparatus according to the embodiments of the invention has the advantages in that whether the green color filter layer, the blue color filter layer, the column spacer layer, the TFT layer, or the like, is defective or not can be detected, compared with the related art in which it is not possible to inspect the green color filter layer, the blue color filter layer, the column spacer layer, the TFT layer, or the like, because of the pigments used for fabricating the LCD or its structural weaknesses. 
     In particular, the improvement of the detection capabilities with respect to blurs of the stacked layers and blurs sensitive to light scattering characteristics such as the blues due to the thickness difference or overlay of the pigments can lead to enhancement of the production yield and quality of the LCD. 
     Also, by effectively disposing the inspecting apparatus for a glass substrate according to the embodiments of the invention and the existing inspecting apparatus for a substrate, the detection capabilities can be further improved at a relatively low investment cost and the efficiency of a production line can be enhanced. 
     In addition, by improving the detection capability with respect to particular mura defects in the process of fabricating the LCD, the inspecting apparatus for a glass substrate according to the invention can be utilized for a process monitoring and inspecting process. 
     It will be apparent to those skilled in the art that various modifications and variation can be made in the invention without departing from the spirit or scope of the invention. Thus, it is intended that the invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.