JPH03259184A - Inspection device for thin film transistor substrate - Google Patents

Abstract

PURPOSE:To detect a defect of the thin film transistor(TFT) substrate in a short time without damaging the substrate by providing a means which applies a voltage between scanning lines and signal lines of the TFT substrate and a means which detects a magnetic field produced with currents flowing through the scanning lines and signal lines. CONSTITUTION:A probe 7 is applied to the probe terminal 14 of the TFT sub strate 1 and the voltage from a power source 4 is applied between the scanning lines 8 and signal lines 9, so that a current flows through a short-circuit defect between the scanning lines 8 and signal lines 9. A magnetic head 3 is put close to an electric conductor part where the current flows to obtain a voltage which is proportional to the level of the current as the output of the magnetic head 3. A comparator 5 compares the amplitude of the obtained output voltage with a reference value to detect the electric conductor being connected directly to the short-circuit defect when the output voltage is larger than the reference value. Consequently, the defect due to the short circuit of the electric conductor of the TFT substrate can be detected speedily and the inspection is performed without damaging the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inspection device for thin film transistor substrates used in liquid crystal displays and the like.

[Conventional technology]

A part of the structure of the thin film transistor substrate to be inspected is shown in the plan view of FIG. The thin film transistor substrate has a plurality of scanning lines 8, signal lines 9, thin film transistors 1.0, and pixel electrodes]1 formed on a glass substrate 12 using a thin film process.

In the thin film transistor substrate described above, defects are likely to occur due to short circuits between scanning lines and signal lines due to dust, hole resist defects, etc. during the manufacturing process.

For this purpose, it is necessary to detect defects, separate good products from defective products, and furthermore detect the location of defects.

It is necessary to correct the defects using a laser or the like. Generally, an electrical method is used to detect defects. For example, to detect short line defect positions between the scanning line and the signal line 6, place the probe 4 on one scanning line, touch all the signal lines, and sequentially apply the probe 20 on the scanning line. Measure the electrical resistance between the signal line and the signal line. 5''Repeat 1 for all scan lines, -
In addition, it is possible to detect the position of the short circuit defect, that is, the position of the defective pixel. However, with this method, it is necessary to measure the electrical resistance as many times as the product of the number of scanning lines and the number of signal lines, and for thin film transistor substrates used in liquid crystal displays etc. The measurement will be immersed. Therefore, the measurement requires a huge amount of time and is not practical. Multiple measurements 1. Damage to the end-f portion of the probe, scanning line, and signal line UJ due to J is also a problem. The electrical method described in item 1-1 is a method in which, for example, multiple probes are applied simultaneously and the inspection is performed while electrically switching the scanning line or signal line to be inspected, and the inspection time can be reduced to a certain extent by However, it is inevitable that it will take a long time. Furthermore, the electrical inspection method described in -1- is based on a thin film transistor substrate on which two or more transistors are formed for each pixel electrode (Fig. (showing an enlarged view of the substrate), it is possible to detect defective pixels, but there is a problem in that it is not possible to specify which transistor has a defect.

Active matrix substrates and electrochromic display panels, as shown in Figure 8, have been proposed as a way to shorten the enormous amount of inspection time. A method for detecting defects based on the coloring state of the coloring film of an electrochromic panel is disclosed in Japanese Patent Application Laid-Open No. 1999-1991. It is described in the publication No.-154092. Although the figure illustrates a case in which the pixel electrode moving element is a diode, the principle is the same in the case of a transistor. ”−
According to the power distribution method, the coloring film of the electrochromic display panel becomes non-colored or colored depending on the conduction state of the pixel electrode of each pixel electrode, making it possible to identify defective pixels. However, in the above method, it is necessary to conductively connect the pixel electrode of the active matrix substrate and the coloring film of the electrochromic display panel via an electrolyte, so if a liquid electrolyte is used, the active matrix substrate There is a problem of contamination. Furthermore, even when a solid electrolyte 14' is used, physical contact with the metal wire tends to cause damage to the reactor polymer I/RIX substrate, and errors in defect inspection due to poor conductivity are likely to occur. There are problems such as.

[Problem to be solved by the invention]

As described above, with the prior art, it has been impossible to detect defects in thin film transistor substrates in a short time and without causing damage to the substrate. Furthermore, even if it is possible to identify the pixel in which the defect exists, it is impossible to identify which transistor has the defect if multiple thin film transistors are formed for each pixel. Met.

The present invention eliminates defects in thin film transistor substrates in a short time.
The purpose of the present invention is to provide a thin film transistor that can detect a defect without damaging the substrate, and even when multiple thin film transistors are formed for each pixel, it is possible to identify which transistor has a defect. to obtain the substrate,
For other purposes. 1 [Means for solving the problem] -1- The first method is to apply a voltage between a scanning line and a signal line of a thin film transistor substrate, and a current flowing through the scanning line and the signal line. This is achieved by comprising means for detecting the generated magnetic field.

Also. A plurality of +- transistors are formed for each pixel of the liquid crystal display on the thin film transistor substrate.
, one of the plurality of transistors corresponding to one pixel,
Even if the scanning line and signal line are short-circuited at the same time in two or more transistors, a wiring portion of at least 20 μm is provided on the scanning line or signal line for each transistor so that the current flowing into each short-circuit point can flow independently.
It is possible to achieve more than 'i'. .

[Effect]

In a normal thin film transistor substrate, the resistance value between the scanning line and the signal line is on the order of megaohm b. Even when a voltage of approximately 1.0 volts is applied between the scanning line and the signal line, almost no current flows.

On the other hand, if there is a short-circuit defect between the scanning line and the signal line in the thin film transistor substrate, current flows through this short-circuit defect. When a current flows through a wire, a concentric magnetic field with a strength proportional to the magnitude of the current is formed around the wire.For this reason, all scanning lines and signal lines are electrically connected. In this state, when a voltage is applied between the scanning line and the signal line 2 and the magnetic field formed around each scanning line and signal line is detected, it is detected that the scanning line and signal line are directly connected to the short-circuited defective part. can do.

If there are only 7 short-circuit defects on the film transistor substrate, the number of scan lines and signal lines to be detected is 1 each.
This intersection point can be identified as the location of the defective pixel. When there are two short-circuit defects, two scanning lines and two signal lines are detected, and four intersections are detected as defect candidates. By detecting the magnetic field caused by the current flowing through each transistor for each detected defect candidate pixel LJ, only true defects can be detected5.If there are three or more defects, the same method can be used. method can detect only true defects.

Thin film transistor substrate numbers, in which two or more transistors are formed for each pixel of a liquid crystal display, are 7 and 1.
Even if the scanning line and signal line of multiple transistors corresponding to pixels 1 and J are short-circuited at the same time, each transistor has a wiring section that allows current to flow into each short-circuit point independently. - By forming short-circuit lines with a length of at least 20 μm or over scanning lines or signal lines, the magnetic field generated by the current flowing through each short-circuit point can be independently detected, making it possible to detect defective pixels. It is possible to identify which transistor has a defect among the multiple transistors detected.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of a thin film transistor substrate inspection apparatus according to the present invention, FIG. 2 is a plan view showing an example of the configuration of a thin film transistor substrate used for inspection, and FIG. 13 is a diagram showing defects according to the present invention. Explanatory diagram of transistor identification method, 4th
The figure is an enlarged plan view of an example of a thin film transistor substrate according to the present invention, FIG. 5 is a plan view showing another example of a thin film transistor substrate according to the present invention, and FIG. It is a TqZ plane view.

In FIG. 1, a thin film transistor substrate 1 is placed and fixed on an XY stage 2 capable of attracting the substrate 2, and a magnetic head 3 is opposed to the thin film transistor substrate 1.

As shown in FIG. 2, the thin film I-transistor substrate used for inspection includes a plurality of scanning lines 8, signal lines 9, and thin film transistors]
0. The pixel electrodes 11 are formed on each of the glass substrates 12 by a thin film process, and all the scanning line terminals are
5 and a signal line terminal 16 are electrically connected to each other by a test wiring 13. This electrical connection may be made in multiple blocks. ” - When the probe 7 is applied to the probe terminal 24 of the thin film transistor substrate and a voltage is applied from the power supply 4 between the scanning line 8 and the signal line 9, a short circuit defect between the scanning line 8 and the signal line 9 is detected. A current flows through it.

When the generation chamber I'-1 of the power source 4 is set to AC voltage, the current flowing through the short-circuit defective part and the magnetic field formed by the current change with time, so that the current flows
When the magnetic head 3 is brought close to the wiring part where the magnetic head 3 is located, a voltage proportional to the magnitude of the current is obtained at the output of the F magnetic head 3. The amplitude of the obtained output voltage is compared with a reference value by a comparator 5, and if the output voltage is larger than the reference value, it is detected that the wiring is directly connected to the short circuit defect. The thin film transistor substrate 1 and the magnetic head 3 are
It is also possible to inspect them in close contact or at intervals. Due to the spacing 7, the possibility of contamination or damage during inspection of the thin film L-transistor substrate 1 can be completely eliminated.

However, when the above-mentioned interval is widened, the applied voltage or its frequency necessary for inspection increases.

In the embodiment described above, the magnetic field formed by the current is changed over time by using an alternating current voltage as the applied voltage, thereby making it possible to detect the magnetic field while the magnetic head 3 is stationary.

However, by changing the applied voltage to DC voltage, the XY sweeper 2 to which the thin film 1... Yo ℃
, the above magnetic conduction (He)... 3) change the magnetic flux interlinking with the coil existing inside 3 over time, and the direct current 1;-yo.
Detection of two magnetic legs in three-pronged life? ), = we can do it. All scanning lines ε3 and signal lines 9. To detect the presence of scan line 8 and signal line 9 which are directly connected to short-term defects present on the board under the condition that voltage is applied to the scan line terminal 1! The area inside the area where the thin film I/transistor 10 and the pixel electrode 1J are formed, the area outside the area where the thin film I/transistor 10 and the pixel electrode 1J are formed, is also shown in FIG. If the wiring portion existing in the shown area 151 and the area] 61 is sequentially inspected and scanned by the magnetic head !3, then ), if the applied voltage is an AC voltage, On the other hand, since the magnetic field can be detected even when the magnetic head 3 is stationary, there is no particular restriction on the scanning speed by the magnetic head 3. Compare the output voltage 1L obtained from 7 with the reference value 7, upper δ) 4 If the output voltage is greater than the reference value, determine that the scanning line or believe line is directly connected to the short circuit defect. If there are only 12 short circuit defects in the board,
Each of the detected scanning lines and signal lines is a - line, and their intersection can be identified as the position of the defective pixel at 17. If there are N short-circuit defects, the number of scanning lines and signal lines to be detected is a maximum of N, and these NXN intersections become candidates for defective pixels.

In FIG. 3, a method for identifying a true defective pixel will be explained using an example in which there are two short-circuit defects.

In the figure, thin film transistors 1012 and 103
3, there is a short-circuit defect between the scanning line and the signal line (corresponding to the gate line and drain line inside the transistor). For this reason,
By scanning the area 15] and the area 161 shown in FIG. 2 with a magnetic head, the scanning line 81.83 and the signal line 92.93 are detected as being directly connected to the short circuit defect. Therefore, the thin film transistors 10.12.1013, 1032.1. ,03
3 is a defect candidate. To detect two true defects from the four defect candidates, it is sufficient to check whether current flows through each transistor. For example, in the scan line 81-11m, a current flows between the gate line connection of the transistor 1012 and the gate line connection of the transistor 101:3. If not, it can be determined that there is a major defect U in the transistor 1012 &: and that the transistor 1013 is normal.

On the contrary, on the scanning line 8], the gate of l transistor]012 is
If a current flows between the connection to the gate line and the connection to the gate line of transistor 1013, a defect exists in transistor 1.013 [55, transistor 1012
By performing the same inspection on the 6 scanning lines 83 that can be determined to be normal, it is possible to identify either 4 defect candidates or 122 true defects. The test to find out whether current is flowing through the
This can be done using the magnetic head 3 described above. Also,
To check whether current is flowing through each transistor,
This can be done for both scanning lines and signal lines.

In the above embodiment, the short circuit between the scanning line and the signal line has been described as occurring only inside each transistor. However, in reality, there is a possibility that a short-circuit defect may occur at a portion where each scanning line and signal line intersect (for example, portion A in FIG. 3). Even in such a case, after detecting the scanning line or signal line directly connected to the short circuit defect, just as in the example above,
Detecting parts where current is flowing and parts where current is not flowing along the scanning line or signal line 1.
The true defect location can be identified.

The current flowing through the wiring is detected by a magnetic head, and the highest sensitivity is obtained when the direction of the wiring and the length direction of the gap in the magnetic head are perpendicular to each other. Most of the wiring on the thin film transistor substrate is formed in the X or Y direction, so the length directions of the gaps are perpendicular to each other and 2
, the current flowing through the wiring in the X or Y direction,
If the inspection is performed using two magnetic heads set to detect with the highest sensitivity, the inspection can be done in a short time.

FIG. 4 is a part of an enlarged view of an example of a thin film transistor substrate according to the present invention.
This is a case in which two transistors 9 and a pixel electrode are formed. Corresponding to one pixel, even if the scanning line and signal line (corresponding to the gate line and train line inside the transistor) are short-circuited simultaneously in three transistors, the current flowing into each short-circuit point will be independent of each other: Since wiring portions 901, 902, 903 through which 1+, J can flow are present on the signal line for each transistor, each short circuit point 1
:The magnetic fields generated by the flowing current can be detected independently. For example, for a board in which the scanning line and the signal line are simultaneously short-circuited inside the transistors 10b and loe,
Consider the case where a voltage is applied between the scanning line and the signal line as shown in FIG. In this case, the current flows from the right side of the scanning line 8 in FIG. )
flows.

Therefore, by inspecting each of the wiring portions 901, 902, and 903 with a magnetic head, it is possible to detect that current is flowing through the wiring portions 902 and 903, and to identify defective transistors 10b and 10c. Note that the wiring portion 901.

902 and 903 is desirably at least 20 μm or more in order to facilitate detection by a magnetic head. The wiring portion may be present in either a signal line (train line) or a scanning line (gate line).

FIG. 5 is a part of an enlarged view showing another example of a thin film transistor substrate according to the present invention, and similarly to FIG. 4, it shows a case where three transistors and a pixel electrode are formed for each pixel of a liquid crystal display. There is. The same numbers as in FIG. 4 are given to the wiring portions for identifying defective transistors. 1 [Effects of the Invention] As described above, the thin film transistor substrate inspection apparatus according to the present invention is provided with means for applying a voltage between the scanning line and the signal line of the thin film transistor substrate, and the scanning line and the signal line shown in - Equipped with a means to detect the magnetic field generated by the current flowing in the J knee], it is possible to quickly detect defects caused by short circuits in the wiring of thin film transistor substrates, allowing board defect inspection to be performed in an extremely short time. be able to. In addition, since contact with a probe for defect inspection can be carried out using a specially provided inspection terminal even though the number of times is extremely small, there is no risk of damaging the thin film transistor substrate. Furthermore, according to the present invention, it is possible to identify defective l-transistors, which was previously impossible, on a substrate on which a plurality of transistors and pixel electrodes are formed for each pixel of a liquid crystal display. It becomes easier to modify existing substrates. As described above, according to the present invention, thin film transistor substrates can be inspected in an extremely short period of time, and this is effective in improving the yield and quality control of thin film transistor substrates, as well as reducing product costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of an inspection apparatus for thin film transistor substrates according to the present invention, FIG. 2 is a plan view showing an example of the structure of a thin film transistor substrate used for inspection, and FIG. 3 is a diagram showing a method for identifying defective transistors according to the present invention. 4 is an enlarged plan view showing an example of a thin film transistor substrate according to the present invention, FIG. 5 is a plan view showing another example of the above-mentioned thin film transistor substrate, and FIG. 6 is an inspection target according to the present invention. FIG. 7 is an enlarged view of a conventional thin film transistor substrate on which a plurality of transistors are formed for each pixel electrode, and FIG. 8 is a plan view of a conventional thin film transistor substrate structure.・A diagram showing the configuration of a transistor board inspection device, (a
) is an explanatory cross-sectional view, and (b) is a plan view of the substrate. 1. Thin film transistor substrate 3... To magnetic head 8.81 84... Scanning lines 9.91-94... Signal lines 10.1011-1013.1021-1023.10
31-1033, 10a-10e...thin film transistor

Claims (6)

[Claims] 1. An inspection device for a thin film transistor substrate, comprising means for applying a voltage between a scanning line and a signal line of a thin film transistor substrate, and a means for detecting a magnetic field generated by a current flowing through the scanning line and the signal line. 2. 2. The thin film transistor substrate inspection apparatus according to claim 1, wherein the means for detecting the magnetic field generated by the current uses a magnetic head. 3. 2. The thin film transistor substrate inspection apparatus according to claim 1, wherein the applied voltage is an alternating current voltage. 4. 2. The thin film transistor substrate inspection apparatus according to claim 1, wherein the applied voltage is a direct current voltage and moves the thin film transistor substrate and the magnetic head relative to each other. 5. If the magnetic field generated by the current flowing through the scanning line and the signal line is larger than a reference value, the scanning line and the signal line are detected as a defective scanning line and a defective signal line, respectively, and then the detected N defective scanning lines are detected. Claims characterized in that N×M intersections between a line and M defective signal lines are taken as defect candidates, and only the defect candidate portions are inspected in detail to detect true defects. 2. The thin film transistor substrate inspection device according to claim 1 or 2. 6. The above-mentioned thin film transistor substrate forms a plurality of transistors for each pixel of the liquid crystal display, and even if the scanning line and the signal line are short-circuited at the same time, even if the scanning line and the signal line are short-circuited at the same time, each short-circuit point is The wiring portion where the incoming current flows independently is at least 20 μm for each transistor on the scanning line or signal line.
An inspection apparatus for a thin film transistor substrate according to claim 1, characterized in that the above exists.