JPH09257642A - Glass substrate defect type determination method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To detect three kinds of defects existing in a glass substrate,
It is determined whether the type is a foreign substance, a scratch, or a bubble. SOLUTION: A wavelength band (for example, a white light flux and a red light flux) having different wavelength bands from the back side of the substrate 1 is about 2 with respect to the substrate 1.
Projecting respectively 0 ° angle of incidence theta ₁ and about 60 ° of the incident angle theta _2, the surface side of the substrate, providing a vertical light receiving system optical axis in the substrate, only the scattered light of each defect by the condenser lens Is collected, the scattered light is divided into white light and red light by the half mirror HM and the filters F _a and F _b , and the CCD sensors (A) and (B) receive each, and the output of both CCD sensors The intensities of the defect signals S _a and S _b are i _a and i _b , and the length and width of each defect obtained by image processing the defect signal S _a or S _b are L and W, and the ratio of both intensities i _a / i _b and L / W ratio L / W are
The foreign matters K _i , the scratches K _s , and the bubbles K _b are compared with the determination criteria R ₁ and R ₂ , respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of determining a defect type of a glass substrate, and more particularly to a method of determining the type of three types of defects existing on the front surface, back surface or inside of a glass substrate for a liquid crystal panel. .

[0002]

2. Description of the Related Art A TFT substrate that constitutes a liquid crystal panel is made of a glass substrate, and a large number of TFT elements are formed on the surface thereof. If there are defects such as scratches on this surface, the TFT element is not formed well in that portion, and therefore the TFT
Since it impairs the quality of the substrate, the defect inspection apparatus inspects for the presence of defects and takes necessary measures. In the defect inspection device, a laser beam is projected onto the glass substrate, the scattered light of the defect is received by a photodetector, the defect is detected, the size of the defect is calculated from the defect signal, and the defect is present in this. The defect data with the coordinate value added is output.

[0003]

There are various types of defects in a glass substrate (hereinafter simply referred to as a substrate), and typical ones are foreign substances existing on the front surface or the back surface of the substrate,
There are three types of scratches and bubbles. However, the foreign matter includes an adhering foreign matter to which dust or the like adheres and a fixed foreign matter to which the foreign matter adheres in the process of manufacturing the substrate. Scratch scratches occur during double-side polishing and handling of the substrate, and bubbles are generated inside the substrate during the manufacturing process. Of these, the adhered foreign matter can be removed by re-cleaning, and the adhered foreign matter can be removed by re-polishing, but scratches and air bubbles cannot. Therefore, it is necessary to know the type of each defect in manufacturing and managing the substrate. However, in the above-described defect inspection apparatus, these are not distinguished but are simply detected as defects. Therefore, effective means for determining the type of defect is required. An object of the present invention is to collectively detect three types of defects existing on a glass substrate and determine whether the type is a foreign substance, a scratch, or a bubble.

[0004]

SUMMARY OF THE INVENTION The present invention is a defect type determination method for a glass substrate which solves the above-mentioned problems, wherein at least two different wavelength bands are provided by a light projecting system provided on the back side of the substrate. The light beam is projected at a small incident angle and a large incident angle with respect to the inspection position of the substrate. A light receiving system whose optical axis is perpendicular to the substrate is provided on the surface side of the substrate, and the light collecting system has a narrow light receiving viewing angle condensing lens that collects the scattered light of each light beam and collects it. The scattered light emitted is divided into the above-mentioned different wavelength bands and received by the respective CCD image sensors. Output defect signal S _a of both the CCD image sensor, the intensity i _a of S _b, and the ratio i _a / i _b of i _b, defect signal S _a or the length of each defect found by the image processing S _b L and calculating the ratio L / W of the width W, both the ratio i _a / i _b, the criteria for L / W as R _1, R _2, each determined under the following _{conditions: (i a / i b>} R 1, _{L / W> R 2):} K s ......... condition _{(1) (i a / i} b> R 1, L / W ≦ R 2): K b ......... condition _{(2) (i a / i} b _{≦ R 1, L / W>} R 2): K s ......... condition _{(3) (i a / i} b ≦ R 1, L / W ≦ R 2): the K _i ......... condition (4), The foreign matter K _i , the scratch K _s , and the bubble K _b are determined.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the shapes of three types of defects and the directivity of scattered light will be described with reference to FIG. 1, and the principle of the defect type determination method of the present invention will be described with reference to FIGS. In FIG. 1, (a) illustrates the shape of each defect, and the foreign matter K
_{Many of i} have a granular shape with unevenness on the surface, and the sizes thereof are various, and those having a size larger than a certain size are harmful. The scratches K _s are usually formed by grooving the surface of the substrate 1, and the width and depth thereof are relatively small, but the scratches K _s longer than this are harmful.
The bubbles K _b are usually spherical or a deformation thereof, and their sizes are different, but if they are too large, they are harmful.
(b) illustrates the directional characteristics of each defect. When the light flux L is projected on each defect, each scatters scattered light according to the shape. The scattered light of the foreign matter K _i is scattered in the direction of the upper hemisphere with almost the same intensity regardless of the projection direction of the light flux L, that is, it is omnidirectional. Scattered light scratches K _s is closely related to the projection direction of the light beam L, the projection direction,
As shown in the figure, there is a strong vertical peak, and the lower the angle, the weaker the directivity. The scattered light of the bubble K _b has a direct relationship with the foreign matter K _i and the scratch K _s . The intensity of scattered light of each defect changes depending on its size, and the larger the size, the greater the intensity.

In FIG. 2, a small incident angle θ ₁ and a large incident angle θ ₂ are made from the back surface side of the substrate 1 to project, for example, a white light beam and a red light beam having different wavelength bands, respectively.
If there is a defect K on the surface of the substrate 1 or a defect K ′ on the back surface, these scatter scattered light. A light receiving system whose optical axis is perpendicular to the surface is provided on the surface side, and the light receiving viewing angle θ ₃ of the condensing lens is narrowed so that both light fluxes transmitted through the substrate 1 are not incident, and the defect K or K ' Only the scattered light is condensed, divided by the half mirror HM, one of the transmitted light is removed by the filter F _{A for} red color, the other reflected light is transmitted by the filter F _{B for} red color, and each is transmitted through the CCD image sensor ( Light is received by A) and (B). Both CCD (A),
The defect signals S _a and S _b output by (B) have their respective intensities i _a and i _b significantly changed due to the directivity depending on the type of defect and various sizes.

For the above defect signals S _a and S _b , the inventors of the present invention conducted a trial experiment using defect samples of each type. First, the defect signals S _a and S of each sample
_When the intensity ratio i _a / i _b of _b is taken, the difference in the size of each defect and the intensity change of both defect signals S _a and S _b due to the intensity variation of each luminous flux are canceled out, and the directional characteristic is extracted. It Next, the relationship between the intensity ratio i _a / i _b and the defect type was examined. As a result, most of the defects in which i _a / i _b is larger than the constant value R ₁ are scratches K _s or bubbles K _b , and the constant value R 1 is constant.
It was found that when it was ₁ or less, it was mostly foreign matter K _i or scratches K _s . By further advancing the experiment, the detection signal S _a or S _b is image-processed, and the length L and width W (illustrated in the margin of FIG. 2) of the defect K are calculated from each element e received by the CCD, and the ratio thereof is calculated. As a result of examining the relationship with the defect type by taking L / W, when L / W is larger than a constant value R ₂ , there are almost scratch scratches K _s , and when L / W is less than the constant value R ₂ , almost foreign matter K _i. Alternatively, it was confirmed that the bubbles were K _b .

Summarizing the results of both of the above-mentioned experiments, the above-mentioned respective judgment conditions are set with the above-mentioned constant values R ₁ and R ₂ as judgment criteria.
(1) to (4) were obtained, and it was found that it is possible to almost certainly determine whether the defect is the foreign matter K _i , the scratch K _s , or the bubble K _b . Figure 2 shows each judgment condition (1)
The execution order of (4) is shown. First, by strength comparison, i _a / i
_b and R ₁ are compared to determine whether (K _s OR K _b ) or (K _i OR K _s ), and L /
By W comparison, L / W and R ₂ are compared with each other, and K _i , K _s , and K _b are determined. FIG. 3 shows the distribution area of each defect determined as described above, where i _a / i
_{With b} as the ordinate and L / W as the abscissa, the foreign matter K _i , scratches K _s , and bubbles K _b are distributed as shown with respect to the criteria R ₁ and R ₂ .

Now, the above-mentioned defect type judging method has a drawback to be noted. That is, the present invention relates to the glass substrate 1
Three types of defects existing on the front surface, the back surface, or inside are detected and their types are determined. However, since the TFT is not formed on the back surface of the substrate, it is unnecessary to detect the defect on the back surface and to judge the type, and it is rather harmful for the management of the substrate 1 unless it is identified that this is the back surface side. With respect to such a defect, the inventor of the present invention has devised a means for discriminating between a front surface defect and a back surface defect, and separately filed a patent as "a front and back surface defect detection method for a glass substrate". By applying this front / back defect identification method to the substrate 1 whose defect type has been determined as described above, each defect (excluding internal bubbles) is identified as the front surface side or the back surface side, and the defect inspection is completed. Is.

[0010]

4 and 5 show an embodiment of the present invention, FIG. 4 is a block diagram of a defect detection / type determination device 10 to which the defect type determination method of the present invention is applied, and FIG. 5 is a defect type determination procedure. It is a flowchart showing. In FIG. 4, the defect detection / type determination device 10 includes a detection optical system 2, an XY stage 3, and a data processing unit 4. Substrate 1 is X
It is placed on the Y stage 3, and one end to the other end is step-moved in the X direction by the XY movement control circuit 3a.
Direction is sequentially moved, and step movement in the X direction is repeated to inspect the entire surface. The detection optical system 2 includes a light projecting system 21 and a light receiving system 22, and the light projecting system 21 is provided on the back surface side of the substrate 1.
It has four light sources 211, 212, 212, 212 composed of halogen lamps, and the white light flux of the light source 211 is focused by the focusing lens 213 so that the incident angle θ ₁ with respect to the inspection position of the substrate ₁ is about 20.
The white light flux of each of the other three light sources 212 is focused by each focusing lens 214, red is selected by the filter 215, and the incident angle θ ₂ is about 60 ° with respect to the inspection position. Is projected from three directions. Substrate 1
The surface defect K or the back surface defect K ′ that has come to the inspection position due to the step movement of 1 scatters the scattered light of the light flux.

The light receiving system 22 is provided on the front surface side of the substrate 1 with its optical axis perpendicular to the substrate 1, and its condensing lens 221.
Collects only the scattered light of the defects K and K ′ with the light-receiving viewing angle θ _{3 set} to about 15 ° so that each light beam transmitted through the substrate 1 does not enter. In this case, since the light beam is projected from four directions, the scattered light of each defect has a component directed vertically upward, and this component always enters the condenser lens 221. The scattered light thus collected is split by the half mirror 222, one of which removes the red light by the filter 223 and is received by the CCD (A) 224, and the other of which is transmitted by the filter 225 to the red light and C
The CD (B) 226 receives the light, and the defect signals S _a ,
S _b is output. The data processing unit 4 includes an image memory 41,
It includes a microprocessor (MPU) 42, a printer 43, and the like. In the image memory 41, the defect signals S _a and S _b output by both CCDs (A) and (B) by the step movement of the substrate 1,
It is updated and stored for each inspection position. The MPU 42 includes an intensity comparison program PG1, an image processing program PG2, and L / W.
Comparison program PG3, size calculation program PG4,
It has a control signal generation program PG5 and a data editing program PG6, and the judgment criteria R ₁ and R ₂ obtained in advance by trial experiments are set in PG1 and PG3, respectively. The PG 5 generates a control signal and supplies it to the XY movement control circuit 3a to perform the step movement of the substrate 1 described above.

The defect type determination procedure in the data processing unit 4 will be described below with reference to FIG. 4 and FIG. Image memory 41
Both defect signals S _a and S _b updated and stored in
Is read out and the intensity ratio i _a / i _b is calculated by the processing of PG1 (step in the flowchart) and compared with the determination standard R ₁ set therein. The comparison result is i
_a / i _b > R ₁ ; (YES) (K _s OR K _b ).
Then, the defect signal S _a or S _b is processed by the PG2 to calculate the defect length-width ratio L / W, which is compared with the judgment criterion R ₂ by the PG3.
L / W≤R ₂ ; _Kb when (NO), L / W> R ₂ ;
When (YES), it is determined to be K _s , each size is calculated by PG4, and the XY movement control circuit 3
The XY coordinate values of the defect given by a are added, and these and the defect type are edited by PG6,
It is output to 43 and printed. In the step
i _a / i _b ≤R ₁ ; when (NO), (K _i OR K _s ).
It is determined that L / W is calculated and L / W is calculated in the same manner as above.
And R ₂ are compared, and L / W> R ₂ ; (YES)
Is determined to be K _s , L / W ≦ R ₂ ; (NO) is determined to be K _i .
The XY coordinate values are added and the data is edited in sequence and printed on the printer 43.

[0013]

As described above, according to the defect type determining method of the present invention, the light beams of two different wavelength bands are projected to the glass substrate at different incident angles, and the scattered light of each defect is CCD by wavelength band. The intensity ratio i _a / i _{b of} the defect signals S _a and S _b received by the image sensor and output from each of them and the ratio L / W of the length L and the width W of each defect are calculated, and both ratios are constant. The results of trial experiments comparing the values R ₁ and R ₂ respectively, R ₁ and R
Based on this, a judgment condition based on ₂ is obtained, and based on this, it is possible to almost certainly judge and distinguish whether the three types of defects detected are foreign matter, scratches, or bubbles. The effects that contribute to the production and management of glass substrates for liquid crystals are excellent.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of shapes of three types of defects, (a) is an explanatory diagram of the defect shape, and (b) is an explanatory diagram of defect directional characteristics.

FIG. 2 is an explanatory diagram of the principle of the defect type determination method of the present invention.

FIG. 3 is a distribution diagram showing distribution areas of three types of defects determined by a defect type determination method.

FIG. 4 is a configuration diagram of an embodiment of a defect inspection apparatus to which the present invention is applied.

FIG. 5 is a flowchart showing a defect type determination procedure for FIG.

[Explanation of symbols]

1 ... Glass substrate for liquid crystal panel, 2 ... Detection optical system, 21 ...
Projection system, 211,212 ... Light source of halogen lamp, 213,214 ...
Focusing lens, 215 ... Red filter, 22 ... Light receiving system, 221 ...
Condensing lens, 222 ... Half mirror, 223, 225 ... Filter, 224, 226 ... CCD image sensor, 3 ... XY stage, 3a ... XY movement control circuit, 4 ... Data processing section, 41 ...
Image memory, 42 ... MPU, 43 ... Printer, 10 ... Defect inspection apparatus according to the present invention, K ... Front surface defect, K ′ ... Back surface defect, K _i ... Foreign matter, K _s ... Scratch scratch, K _b ... Bubble,
θ ₁ , θ ₂ ... Incident angle, θ ₃ ... Receiving viewing angle, S _a , S _b ... Defect signal, i _a , i _b ... Defect signal intensity, L ... Defect length, W ...
Defect width, R ₁ , R ₂ ... Judgment standard, PG1 to PG6 ... MP
U's program, ~ ... Step number in the flowchart.

Claims (1)

[Claims] 1. A glass substrate for a liquid crystal panel, which has three types of defects: a foreign substance K _i and a scratch K _s existing on the front surface or the back surface of a TFT, and a bubble K _b existing inside the glass substrate. In the type determination, the light projecting system provided on the back surface side of the glass substrate projects at least two light beams having different wavelength bands at a small incident angle and a large incident angle with respect to the inspection position of the glass substrate. , A light receiving system whose optical axis is perpendicular to the glass substrate is provided on the front surface side of the glass substrate, and the light receiving system has a narrow converging lens with a narrow light receiving visual angle from which each light beam is caused by each defect. Of the defect signals S _a and S _b output by both CCD image sensors. strength The ratio i _a / i _{b of the} degrees i _a and i _b and the ratio L / W of the length L and the width W of each defect obtained by image-processing the defect signal S _a or S _b are calculated. Both ratios i _a / i
_b, and criteria for L / W as R _1, R _2, respectively, each determined under the following _{conditions: (i a / i b>} R 1, L / W> R 2): K s ......... condition (1) _{(i a / i b> R} 1, L / W ≦ R 2): K b ......... condition _{(2) (i a / i} b ≦ R 1, L / W> R 2): K s ......... Condition (3) (i _a / i _b ≤R ₁ , L / W ≤R ₂ ): K _i ............ The condition K4 determines the foreign matter K _i , scratch scratch K _s , and bubble K _b , respectively. A method of determining a defect type of a glass substrate, comprising: