JPH0723905B2 - Defect detection circuit for active matrix substrate - Google Patents

Description

The present invention relates to an address detection circuit for a row signal and a column signal line in which an intersection leak of an active matrix substrate has occurred.

The intersection leak of the row signal and column signal lines of the active matrix substrate is caused by the direct leak caused by the leak or the short between the lines and the leak caused by the short or the short between the gate and the source of the switching transistor. There is an indirect leak. Therefore, in order to remove the active matrix substrate having such a defect, the absolute address of the row signal and the column signal line in which the intersection leak (hereinafter, referred to as SG leak) occurs is detected to judge the pass / fail or You have to make corrections.

FIG. 1 shows a schematic diagram of a conventional method for detecting an SG leak generation line. In the figure, 101 is a part of the active matrix substrate, 102 is a row signal side shift register that constitutes a row signal drive circuit, 103 is a column signal side shift register that constitutes a column signal drive circuit, and 104 is a row. An analog switch controlled by the signal side shift register, 105 is an analog switch controlled by the column signal side shift register, 106 is a DC power supply, and 107
Is an ammeter. One terminals of the row signal and column signal line side analog switches are connected in parallel and connected to a DC power supply. An ammeter is connected between the DC power supply and the analog switch. Then, the other terminal of the analog switch and the bonding pad of the active matrix substrate are electrically connected, for example, via a probe card, and the SG leak is detected by the following method.

First, the presence or absence of SG leak of the active matrix substrate is checked. All analog switches on the row signal and column signal sides are turned on, a DC voltage is applied, and the measured value after a fixed time is compared with a reference value to detect SG leak. here,
The reason why the current value after a fixed time is viewed is that stray capacitance exists between the line intersections. However, the stray capacitance per intersection is about 10 ^-3 pF (assuming that the interlayer SiO ₂ film is 8000 Å), and even at the intersection of 60 x 60 lines = 3600, it is on the order of about pF after the intersection, which has almost no effect on the actual measurement. Absent. If there is no SG leak, the measurement ends.

Secondly, either the row signal or the column signal line is sequentially scanned to detect the row signal or the column signal line address in which the SG leak has occurred. For example, when scanning the row signal line side, the analog switch on the row signal side is reset, then the row signal lines are selected row by row, and the current after a fixed time between the column signal line and the selected row signal line is selected. Compare the value with the reference value. this,
Continue until the SG leak line is detected.

Thirdly, the column signal lines are sequentially scanned with respect to the row signal lines in which the SG leak has been detected, and the column signal line address of the SG leak location is detected. The analog switch on the column signal side is reset, then the column signal lines are selected column by column, and the current value after a fixed time between the row signal line detected in the second and the selected column signal line is compared with the reference value. . Then, the scan is continued until the SG leak line can be detected.

The address of the SG leak is detected as described above. Further, considering the case where there are a plurality of SG leaks, the second and third detections are executed until the end of each signal line.

By the way, considering the detection time required for this, for example,
Set the row signal line and column signal line to 60 x 60 lines, and set the time from applying voltage to each signal line to measurement.
Assuming that 0.2 second is set and SG leak is detected by the above detection method, the time required for the above measurement is simply S
-0.2 seconds for 0 G leak, 24 seconds for 1 leak,
36 seconds for two, 132 seconds for 10. However, at present, more measurement time is required. That is, since the current measurement is conventionally performed as shown in FIG. 1, it is not possible to know whether or not the SG leak exists when first performing the above-described first inspection. Therefore, it is necessary to set the ammeter measuring range to a large value so that the ammeter is not destroyed even if a large current flows due to leakage.

For example, if the line resistance R ₁ of each signal line is 10 ³ Ω and the resistance at the intersection of the column signal line and the row signal line is Rc, Rc ≈ 10 ¹³ Ω if there is no leak, and Rc if there is a leak. ≒
It becomes 0Ω. Therefore, assuming that the resistance of each line when measuring each line is Ri, Ri will be Ri = R ₁ + Rc (1) ≈ Rc to 10 ¹³ Ω: no leakage R ₁ to 10 ³ Ω: leakage. Therefore, if the voltage applied to each line is Vi
= 10V, the current I flowing through each line is I = 10 ^-12 A: No Lark (2) 10 ^-2 A: There is a leak, and it can be seen that the current value is completely different between leak and non-leak. Therefore, at the start of measurement, set the ammeter to a larger range so that the ammeter will not be destroyed even if there is a leak, and gradually switch the range to measure an accurate current value. Will be done.

Therefore, when inspecting leakage by current measurement,
This kind of ammeter operation is required repeatedly for the measurement of each line, and the actual measurement time is many times longer than the simple measurement time calculated above.

As described above, detection of SG leak by current measurement requires a very long detection time, and although it is good in the case of manufacturing a prototype, the detection time is long in the case of mass production. Is an obstacle, and we cannot hope to improve mass productivity.

The present invention eliminates such drawbacks, and an object thereof is to provide a detection circuit capable of detecting an SG leak location in a short time.

An embodiment according to the present invention is shown in FIG. 201 in the figure
Is a part of the active matrix substrate, 202 is a row signal side shift register which constitutes a row signal drive circuit, 203 is a column signal side shift register which constitutes a column signal drive circuit, 20
Reference numeral 4 denotes a tri-state buffer controlled by the row signal side shift register, which indicates a first selection circuit group described in the claims. Reference numeral 205 denotes an analog switch controlled by the column signal shift register, which indicates a second selection circuit group described in the claims. One terminal of the analog switch 205 is connected to the column signal line of the active matrix substrate, and the other terminal is connected to the common bus line 209. And analog switch 205
Are opened and closed by the output of the column signal side shift register.
206 is a switching relay, and 207 and 208 are comparators for voltage comparison (comparing means described in claims) and reference voltage sources. The input side of the tri-state buffer 204 is connected in parallel so that the output of the tri-state buffer 204 becomes high level, and one terminal of the analog switch 205 is also connected in parallel via the common bus line 209.
Connected to 06. The output of the tri-state buffer 204 and the other terminal of the analog switch 205 are electrically connected to the bonding pad of the active matrix substrate as is conventionally done.

Next, a method of detecting an SG leak point according to this embodiment will be described.

First, a voltage is applied between the row signal line and the column signal line of the active substrate. All outputs of the transition buffer 204 are set to high level, all analog switches 205 are turned on, the switching relay 206 is tilted to the GND side and left for a certain period of time.

Secondly, the presence or absence of SG leak is checked. Switching relay
When 206 is pushed to the comparator side, the voltage Vo at the input terminal on one side of the comparator 207 becomes equal to the output voltage of the tri-state buffer 204.
i, the resistance in the active matrix substrate is Ri, the comparator 207
If the bias resistance of is R ₀ , then V ₀ = R ₀ 〜 (Ri + Ro)) Vi (3). That is, the result of the comparison between the voltage V ₀ and the reference voltage E is obtained by the comparator, and in this embodiment, if the output of the comparator is low level, SG leak has occurred, and the output of the comparator is Is high level, the SG leak does not occur and the measurement is completed.

Thirdly, either the row signal or the column signal line is sequentially scanned to detect the row signal or the column signal line address in which the SG leak has occurred. For example, when scanning the row signal line, Turn on all the analog switches on the signal side, and then check the output level of the comparator while selecting row signal lines row by row. And S
-Repeat scanning until G leak line is detected.

Fourthly, for the row signal side line in which the SG leak is detected, the column signal line is sequentially scanned with the row signal line selected, and the column signal line address of the SG leak location is detected. To do. First, the analog switch on the column signal side is reset, and then the output level of the comparator is checked while sequentially turning on the column signal line for each column. And
The scan is repeated until the SG leak line is detected.

Furthermore, considering the case where there are a plurality of SG leaks, the third and fourth
By repeating the above process until the end of each signal line, all addresses at the SG leak location are detected.

Here, as in the case of the conventional example, let us look at what kind of voltage comparison is made in the present application. The voltage V ₀ input to the comparator is as shown in the equation (3), but here, the bias resistance R ₀ of the comparator is R ₀ = 10 ⁶⁰ Ω (of course, the set value depends on the measuring instrument and panel. Different), the resistance Ri of each line can be calculated by equation (1) when leaking and when not leaking.
Therefore, if the output voltage Vi is Vi = 10V, V ₀ with and without leakage is as follows according to the equation (3).

a) In case of no leak, V ₀ = 10 ^-6 V b) In case of leak V ₀ = 10V Therefore, the output of the comparator is a) In case of no leak, Vi−V ₀ = 10−10 ^{-6 to} 10V: High b) If there is a leak, Vi-V ₀ = 10-10 to 0V: Low, and the leak can be detected simply by distinguishing between high (10V) and low (0V). Become. In other words, there is no need to switch the measurement range of the ammeter to perform the measurement, unlike the measurement using the ammeter.

Therefore, the inspection can be performed in a time close to the simple measurement time obtained at the beginning.

As described above, in the present application, the current comparison, which must be inspected by switching the measurement range because it is not known what kind of measurement value will be output, is the voltage comparison capable of predicting the output value as shown in Expression (3). This makes it possible to significantly reduce the detection time.

[Brief description of drawings]

FIG. 1 is a schematic view of a conventional SG leak line detection method. FIG. 2 is a schematic diagram of an embodiment of the present invention.

Claims (1)

[Claims] 1. A plurality of row signal lines and a plurality of column signal lines are arranged so as to intersect with each other on an insulating substrate, and a thin film transistor is formed near an intersection of the row signal lines and the column signal lines. In the defect location detection circuit of the active matrix substrate, the defect location detection circuit includes a row signal line drive circuit connected to the row signal line, a column signal line drive circuit connected to the column signal line, and the row. A first selection circuit group connected between a signal line and each output terminal of the row signal line drive circuit, and connected between the column signal line and each output terminal of the column signal line drive circuit. The second selection circuit group includes a second selection circuit group and a comparison unit that compares an output value of the second selection circuit group with a reference voltage. The first selection circuit group outputs a row selection signal of the row signal line drive circuit. Row signal selected based on A constant DC voltage is applied to the line, the second selection circuit group outputs the output of the selected column signal line to the common bus line based on the column selection signal of the column signal line drive circuit, and the comparison means. Is a defect location detection circuit for an active matrix substrate, which outputs a difference between a voltage obtained by dividing the output of the common bus line by a bias resistor and the reference voltage as an output value of the comparison means.