JP3266217B2 - Liquid crystal substrate foreign matter inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign substance inspection apparatus for a liquid crystal substrate, and more particularly to a foreign substance inspection apparatus capable of effectively detecting a foreign substance in a foreign substance inspection of a substrate of an active matrix LCD having a TFT (thin film transistor). .

[0002]

2. Description of the Related Art On a substrate of an active matrix LCD, fine patterns of TFTs and transparent electrodes are formed on the surface similarly to a semiconductor wafer. In addition, color liquid crystal substrates (LC
D substrate), a finer filter pattern is formed. Foreign matter adhering to the surface of these substrates deteriorates the quality and damages the TFT and the alignment film, causing pixel defects. Therefore, as in the case of a semiconductor wafer, foreign matter is regarded as a problem, and it is necessary to inspect each step in the process of manufacturing a liquid crystal substrate. Semiconductor wafer foreign matter inspection equipment
There are various types, and the technology is in the direction of detecting finer foreign matter, but the foreign matter inspection device for the liquid crystal substrate is still groping, and the inspection method dedicated to the liquid crystal substrate is clearly established as a technology. Do not mean.

[0003]

Therefore, it is desirable that the technique of the wafer foreign substance inspection apparatus can be used as it is for the foreign substance inspection of the liquid crystal substrate, but it is not so simple because the actually formed pattern is different. As a technique of a wafer foreign matter inspection apparatus, a laser beam is irradiated on the surface of a wafer, scattered light scattered by the foreign matter is received, foreign matter is detected, and the detection signal is processed by an appropriate processing circuit. Foreign matter data is displayed on a map on a display device.
When this was actually used as a foreign substance inspection apparatus for a liquid crystal substrate, it was found that foreign substance detection sensitivity could not be obtained as in a foreign substance inspection apparatus for a wafer.

[0004] The possible reason is that TFT
Is thicker and has a larger step than the LSI pattern formed on the wafer. The edge of a pattern formed is coarser than that of an LSI pattern. T
A transparent electrode film on which no FT pattern is formed (ITO
Film, indium tin oxide electrode film) exists in a large area, and the reflectivity is low here. And so on. That is, the higher the reflectivity of the background on which the foreign matter is placed, the higher the scattered light, but the reflectivity of the ITO film is low, and the foreign matter present here has a relatively low level of the scattered light. . On the other hand, on the TFT side, the 30
There are more than twice the reflectance. Therefore, the scattered light of the foreign matter on the TFT is large. Further, when the light is scattered at the corners of the TFT pattern, particularly when the light is scattered at the corners of the Al wiring in the TFT pattern, the level of the scattered light is higher than that of the foreign matter. The scattering at the corners of the ITO film also has a large step, and its level is higher than that of the foreign matter in this region. The range of foreign matter detection includes both the TFT formation region and the ITO film region. Even if foreign matter is present in the ITO film, the range from the corner of the ITO film or the corner of the TFT formation region is large. The scattered light is large, especially at the corner of the TFT, which is 10 times or more that of the foreign matter in the form of an ITO film. For this reason, it is not possible to select an appropriate sensitivity for detecting foreign matter on the ITO film. Also,
The foreign matter in the TFT area also has a large scattering from the corners, and thus it is difficult to detect the foreign matter. In liquid crystal substrates, a rectangular pattern with a high step is basically used, and since many patterns are arranged, there are many corners and there is a lot of scattering there, and a simple and effective means for removing this scattered light is presently available. I can't find it.

However, it takes time and expense to develop a new apparatus for inspecting foreign substances on a liquid crystal substrate. Therefore, it is desirable to inspect foreign substances on a liquid crystal substrate by using a conventional technique for inspecting foreign substances on a wafer as much as possible. . The present invention solves the above-mentioned drawbacks of the prior art, and relates to a liquid crystal substrate having a large number of rectangular patterns having large steps and in which strong scattering with respect to irradiation light occurs at corners of the pattern. An object of the present invention is to provide a foreign substance inspection device for a liquid crystal substrate which detects a foreign substance by scattered light.

[0006]

The object of the present invention for achieving the above object is as follows.
Two laser beams of different wavelengths are obliquely tilted at substantially the same elevation angle with one side of a rectangular pattern formed on the substrate facing each other in a state where the irradiation angle projected on the horizontal plane is approximately 45 degrees. Irradiation receives each scattered light above the irradiation point, separates each scattered light and detects it with a sensor. When the respective detection levels are substantially equal, it is determined that a foreign substance exists.

[0007]

As described above, when two laser beams are irradiated while facing each other at an equal angle of approximately 45 degrees, the forward scattering of the foreign matter that has received the two laser beams is substantially equal, so the scattered light above the irradiation point is obtained. Are approximately equal, but at the corners of the pattern, one of the two laser beams hits a right angle and the other is nearly parallel, so the forward scattered light of the right-angled laser beam is Although it is large, the forward scattered light of the laser beam hit in parallel is small. Thus, there is a difference between them, and their scattered light levels are not equal. Although there is a difference in the level of scattered light between the ITO film region and the TFT region, the above relationship is the same for both the ITO film and the TFT region. Thus, the foreign matter and the pattern can be detected separately in both the ITO film region and the TFT region.

[0008]

FIG. 1 is a block diagram of an inspection apparatus to which a foreign substance inspection apparatus for a liquid crystal substrate according to one embodiment of the present invention is applied, and FIG. 2 is an explanatory diagram of the detection principle. In FIG. 1, reference numeral 1 denotes an LCD substrate, on which two laser beam irradiation systems 2 and 3 are provided so as to be obliquely opposed to the LCD substrate 1. The irradiation system 2 includes a laser diode (LD) 2a, a focusing lens 2b, and a mirror 2c, and has an elevation angle of 35 degrees with respect to the surface of the LCD substrate 1 and an X-axis (positive direction) when projected onto the substrate (XY plane). An inspection point P on the LCD substrate 1 is irradiated with a laser beam having a wavelength λ _{1 at} an angle of 45 ° to the inspection point P. The irradiation system 3 includes a laser diode (L
D) A wavelength λ that is composed of 3a, a focusing lens 3b, and a mirror 3c, and has an elevation angle of 35 degrees and an angle of 135 degrees with the X axis (positive axis) when projected onto a substrate (XY plane). _The inspection point P is irradiated with the _second laser beam. Therefore, irradiation systems 2 and 3 when projected onto a substrate (XY plane)
Are arranged on both sides at an angle of 45 degrees with respect to the Y axis (positive axis) and face each other. The X axis and the Y axis correspond to the horizontal side and the vertical side of the LCD substrate 1, respectively.

Reference numeral 4 denotes an objective optical system disposed above the inspection point P. The objective lens 4a, the focusing lens 4b, the mirror 4c, the slit 4d, the lens 4e, the dichroic mirror 4f, a photoelectric conversion sensor 4g such as a CCD, and the like. 4h. The dichroic mirror 4f separates the wavelengths λ ₁ and λ ₂ , sends the scattered light of the wavelength λ ₁ corresponding to the irradiation system 2 to the sensor 4g, and sends the scattered light of the wavelength λ ₂ corresponding to the irradiation system 3 to the sensor 4h. Send out. Reference numeral 5 denotes a microscope observation optical system, which includes a mirror 5a indicated by a dotted line, lenses 5b and 5c, mirrors 5d and 5e, and an observation optical device 5f. The mirror 5a is inserted into the optical path of the objective optical system 4 as necessary. Further, an optical system indicated by a dotted line is inserted.

Reference numeral 6 denotes a detection circuit, which is an amplifier (AMP) 6a for receiving a detection signal from the sensor 4g and amplifying a signal equal to or higher than a predetermined threshold THa, and a predetermined threshold THb for receiving a detection signal from the sensor 4h. An amplifier (AMP) 6b for amplifying the above signals, and an amplifier 6
It comprises a dividing circuit 6c for dividing the value of a by the value of the amplifier 6b, and a foreign matter determining circuit 6d which receives the output of the dividing circuit 6c and determines whether or not the foreign matter exists. Note that each of the threshold values THa,
THb level adjustment is possible. Further, the foreign matter determination circuit 6d may be constituted by an analog level determination circuit or an A / D conversion circuit and a microprocessor having a determination program.

Next, the detection principle of the present invention will be described with reference to FIG. The pattern formed on the LCD substrate 1 is such that pixels for display are arranged corresponding to each side of the rectangular substrate, and thus a substantially rectangular ITO film pattern is arranged vertically and horizontally. As shown in FIG. 2A, the pattern 7 for forming one pixel has a TFT forming region 9 at one corner of the ITO film 8, and the ITO film 8 is connected to the source of the TFT region 9. Al wirings SL and AL constituting signal lines and address lines are provided around the outside.

As shown in FIG. 1B, the laser beam A from the irradiation system 2 having the wavelength λ _{1 and} the laser beam B from the irradiation system 3 having the wavelength λ ₂ are 45 degrees with respect to the pattern 7 of the pixel. Irradiation at opposite angles. As a result, with respect to the foreign material 10, the scattered light A + B of the laser beams A and B is incident on the objective lens 4a of the objective optical system 4. Therefore, the outputs of the sensors 4g and 4h become substantially equal, and when they become equal to or more than a certain value exceeding the threshold values THa and THb, they are amplified by the amplifiers 6a and 6b and input to the division circuit 6c. At this time, the result obtained by dividing each input signal by the division circuit 6c becomes substantially 1. The foreign matter determination circuit 6d determines that the foreign matter is present when the output of the division circuit 6c is "1" or substantially "1".

As shown in FIG. 1C, when a laser beam A and a laser beam B are irradiated to a corner portion of the pattern 7, a beam irradiated in parallel with a beam irradiated at a right angle to the corner. Divided into The corner portion of the pattern 7 is actually slightly rounded like the foreign material, and is similar to the case where the laser beam A or B irradiated at right angles is applied to the foreign material. As a result, either the scattered light A of the laser beam A or the scattered light B of the laser beam B enters the objective optical system 4 in a large amount. Therefore, the sensors 4g and 4g
As for the output of h, one of them becomes strong and the other becomes weak. When only one output exceeds the threshold, the dividing circuit 6c
Results in "0" or "$". Further, even when both of them exceed the threshold values THa and THb,
It becomes a value other than "1". If the values of the threshold values THa and THb are selected, only one of them can be output. As a result, the result of the division by the dividing circuit 6c can be made substantially "0" or "∞", so that when the output of the dividing circuit 6c is "1" or almost "1", it is detected as a foreign substance. can do.

As shown in FIG. 1D, when the laser beam A and the laser beam B are irradiated on the side of the pattern 7, the irradiation angle with respect to the side is 45 degrees.
The scattered light incident on the objective optical system 4 is small or almost non-existent. Therefore, the outputs of the sensors 4g and 4h are both weak. If the values of the threshold values THa and THb are selected, the detection signal becomes less than this value. As a result, these outputs do not occur. The selection of the threshold values THa and THb can be made compatible with the selection of the threshold value that makes only one of the outputs valid, since the threshold values THa and THb need only be set to a certain value or more. As a result, the division circuit 6c
The result of dividing by "1" or almost "1"
It is either "0" or "$". “0” or “∞”
In this case, since the pattern becomes a pattern, almost "1" or "1" can be determined and detected as a foreign substance.

As described above, the elevation angle of the irradiation system with respect to the LCD substrate in the embodiment is not limited to 35 degrees. In the embodiment, the division circuit detects whether or not the detection levels of the scattered light by the light receiving sensor are equal. For this, various level comparison circuits including an analog comparator can be used.

[0016]

As described above, in the apparatus for inspecting foreign matter on a liquid crystal substrate according to the present invention, two laser beams are irradiated so as to face each other at an equal angle. The forward scattering of the foreign matter is almost equal, and at the corners of the pattern, one of the two laser beams hits a right angle and the other becomes nearly parallel, so that the laser beam hit at the right angle The forward scattered light is large, and the forward scattered light of the laser beam hit in parallel is small. Therefore, there is a difference between them and they are not equal, so that the foreign matter and the pattern can be detected separately in both the ITO film region and the TFT region.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an inspection apparatus to which a foreign substance inspection apparatus for a liquid crystal substrate according to an embodiment of the present invention is applied.

FIG. 2 is an explanatory view of the detection principle, and (a)
Is an explanatory view of a pixel pattern, (b) is an explanatory view of a scattering state of a foreign substance, (c) is an explanatory view of a scattering state of a corner portion of the pattern,
(D) is an explanatory view of a scattering state of a side portion of the pattern.

[Explanation of symbols]

1 ... LCD substrate, 2,3 ... irradiation system, 4 ... objective optical system, 5
... Microscope observation optical system, 6 ... Detection circuit, 7 ... Pattern for forming one pixel, 8 ... ITO film, 9 ... TFT formation area, 10 ...
Foreign matter.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/13 101 G01N 21/88

Claims (2)

(57) [Claims] An irradiation angle when projected on a surface of a substrate on which a rectangular pattern is arranged is one of the rectangular patterns.
The two laser beams having different wavelengths facing each other with a normal line at the irradiation point interposed therebetween at an angle of approximately 45 degrees with respect to the two sides are obliquely applied to the surface of the substrate at substantially equal elevation angles. First and second irradiation systems, each of which receives scattered light above the irradiation point, separates the scattered light into each of the different wavelengths, and separates the scattered light with the first and second photoelectric conversion sensors. Foreign matter on a liquid crystal substrate, comprising: a detection optical system that receives light to generate respective detection signals; and a detection circuit that detects whether the levels of the detection signals obtained by the first and second photoelectric conversion sensors are substantially equal. Inspection equipment. 2. The detection circuit receives first and second detection signals obtained from first and second photoelectric conversion sensors, and first and second amplification circuits having a predetermined threshold value for the detection signals. 2. The liquid crystal substrate foreign matter inspection apparatus according to claim 1, further comprising a division circuit or an analog comparison circuit which receives the outputs of the first and second amplifier circuits and detects whether or not these outputs are substantially equal.