JP3191898B2 - Inspection method for thin film transistor array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor array used for an active matrix type liquid crystal display device and the like.
The inspection method.

[0002]

2. Description of the Related Art In recent years, a technique for forming a thin film transistor using an amorphous silicon film or a polycrystalline silicon film on a large area substrate has been developed, and an active matrix type liquid crystal display device in which a pixel electrode is selected by using the thin film transistor as a switching element is put into practical use. Has been Further, a liquid crystal display device using a thin film transistor using a polycrystalline silicon film to form a drive circuit, and using a thin film transistor array with a built-in peripheral circuit formed on the same substrate as the thin film transistor as a switching element is being put into practical use. However, since the number of elements in a thin film transistor array used for a liquid crystal display device is several hundred thousand, the inspection method thereof has been variously studied.

[0003] A conventional thin film transistor array and a method of inspecting the same will be described below by taking a liquid crystal display device as an example.

FIG. 4A is a diagram showing a circuit configuration for supplying a video signal to a video signal line of a conventional thin film transistor array, and FIG. 4B is a diagram showing a circuit configuration of a display section of the thin film transistor array. These figures show the main parts of an active matrix type liquid crystal display device.
1 is a horizontal scanning circuit composed of a shift register or the like, 2 is a video signal line, 3 is an analog switch for switching a video signal, 4 is a video signal line, 5 is a vertical scanning line, and 6 is a pixel for supplying a video signal to a pixel described later. A transistor 7 is an auxiliary capacitor for holding a video signal, and 8 is a pixel transistor 6
A pixel electrode connected to the drain of the pixel, 9 is a counter electrode, 10
Is a liquid crystal, 11 is an inspection transistor used only when inspecting the thin film transistor array, 12 is a common source line connected to the source of the inspection transistor 11 in common and drawn out, and 13 is a drain of the inspection transistor 11. This is a common drain line that is connected in common and drawn out. In these drawings, a vertical scanning circuit for supplying a signal to the vertical scanning line 5 is omitted for simplicity. In a thin film transistor array using an amorphous silicon film as a semiconductor film,
Since the mobility of the channel portion is small, the driving circuit cannot be formed on the same substrate, and the portion shown in FIG. 4A and the vertical scanning circuit are externally attached, and only the display portion shown in FIG. It is formed on a substrate as a thin film transistor array. On the other hand, in a thin film transistor array using a polycrystalline silicon film as a semiconductor film or a single crystal silicon film that is single-crystallized by laser annealing or the like, since the mobility of a channel portion is large, a peripheral driving circuit is also provided on the substrate at the same time. Can be formed.

The operation of the thin film transistor array configured as described above will be described below.

As shown in FIG. 4A, the gate electrode of the analog switch 3 which is an N-type transistor is connected to the output terminals 1 to n of the horizontal scanning circuit 1, and the source electrode is connected to the video signal line 2.
In addition, the drain electrode is connected to the video signal line 4. In addition, as shown in FIG. 4B, the display section of the liquid crystal display device has a pixel transistor 6 formed at the intersection of the video signal line 4 and the vertical scanning line 5, and its gate electrode is connected to the vertical scanning line 5.
The source electrode is connected to the video signal line 4 and the drain electrode is connected to the pixel electrode 8. Although the details are omitted in FIG. 4B and shown in an equivalent circuit, the pixel electrode 8 and the counter electrode 9 are electrically opposed to each other with the liquid crystal 10 interposed therebetween.

The video signals V 1, V 2, and V 3 are commonly connected for every three video signal lines 4. The video signal lines 4 are selected and supplied by a signal from the horizontal scanning circuit 1. The vertical scanning line 5 is selected by a signal from a vertical scanning circuit (not shown) in synchronization with the video signal, the pixel transistor 6 is turned on, and the video signal is supplied to the pixel electrode 8.

Next, a method of inspecting the thin film transistor array having the above configuration will be described.

In the thin-film transistor array having the circuit configuration shown in FIGS.
A voltage between the common scanning line and the common drain line is applied, and the inspection transistor 11 is turned on by an output from the horizontal scanning circuit 1 while measuring a current. At this time, if a current flows, the inspection transistor 11 is turned on, and as a result, there is no disconnection in the signal line. However, if no current flows, there is a disconnection somewhere in the signal line. However, the condition is that the inspection transistor 11 operates normally.

[0010]

However, in the above-mentioned conventional structure, the area of the substrate of the thin film transistor array is increased because the inspection transistor is built in,
If there is a leak in the gate of the inspection transistor, the normal operation of the thin film transistor array is hindered, and there is an additional problem that the yield of the thin film transistor array is reduced because of the addition of extra components.

The present invention solves the above-mentioned conventional problems, and provides a thin film transistor array and an inspection method thereof capable of performing inspections other than disconnection and short circuit of signal lines without increasing the substrate area of the thin film transistor array. The purpose is to do.

[0012]

[MEANS FOR SOLVING THE PROBLEMS] To achieve this object
The thin film transistor array has a configuration in which a capacitance element is provided between an end of a signal line and a common line, and the inspection method of the thin film transistor array of the present invention charges a capacitance element through an input terminal of a signal line. Then, the voltage or the current at the input end of the signal line is measured after a certain time has elapsed . Multiple parallel
Signal line, scanning that is electrically insulated from and crosses the signal line
Line and the intersection of the signal line and the scanning line.
The source is connected to the signal line and the gate is connected to the scanning line
Transistors formed on a substrate,
A capacitive element is inserted and connected between the end of the signal line and the common line.
A thin film transistor array, the method comprising:
Charges the capacitive element via the input end of the line
Measure the voltage or current at the input end of the signal line later
This is a method for inspecting a thin film transistor array. Also the signal
After charging the capacitive element while switching the lines, the voltage or
2. The thin film transistor array according to claim 1, wherein current is measured.
Is the inspection method. Also, while switching the scanning line,
4. The thin film tiger according to claim 2, wherein the current is measured.
This is an inspection method for transistor arrays.

[0013]

With this configuration, when the signal line is disconnected, the capacitance element is not charged, so that the current at the time of measurement decreases, and the ratio of the capacitance of the capacitance element to the stray capacitance of the signal line is appropriately adjusted. In this case, disconnection near the end of the signal line can be easily detected. Also, after charging for a certain period of time, by measuring the voltage at the input end of the signal line,
A short circuit between signal lines, a short circuit of a transistor connected to the signal line, and the like can be detected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thin film transistor array and an inspection method thereof according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1A shows a circuit configuration for supplying a video signal to a video signal line in a thin film transistor array according to a first embodiment of the present invention, and FIG. 1B shows a display section of the thin film transistor array. FIG. 3 is a diagram showing a circuit configuration of FIG.
In these figures, the same parts as those in the conventional example shown in FIGS. 4A and 4B are denoted by the same reference numerals, and description thereof will be omitted. In these figures, reference numeral 14 denotes a capacitive element connected to the end of the video signal line 4, and 15 denotes a power supply line to which the capacitive element 14 is connected. The capacitance of the capacitance element 14 is appropriately equal to the stray capacitance of the video signal line 4, but is not particularly concerned with this value. A vertical scanning circuit for supplying a drive signal to the vertical scanning line 5 is not shown. In the present embodiment, one terminal is connected to the power supply line 15 while the other terminal of the capacitive element 14 connected to the end of the video signal line 4 is connected to the power supply line 15. It doesn't matter.

The above thin film transistor array is shown in FIG.
The circuit portion for supplying the video signal to the video signal line shown in FIG. 1A and the display portion shown in FIG. 1B are described separately. However, when the pixel transistor 6 is formed of an amorphous silicon film, The circuit for supplying the video signal and the scanning signal is an external circuit, but when the pixel transistor 6 is formed of a polycrystalline silicon film or a single crystal silicon film, the video signal and the pixel signal are simultaneously output. In addition, a circuit portion for supplying a scanning signal can be formed over the same substrate. Further, the capacitor 14 can be easily formed over the substrate in the step of forming the thin film transistor.

The normal operation of the above-mentioned thin film transistor array is the same as that of the conventional example shown in FIGS.

Next, a method of inspecting a thin film transistor array according to an embodiment of the present invention will be described. FIG. 2 is a diagram illustrating a step of charging a capacitive element in the method of testing a thin film transistor array of the present invention, and FIG. 3 is a diagram illustrating a step of voltage measurement in the method of testing a thin film transistor array of the present invention. In these drawings, only the horizontal scanning circuit and the analog switch of the thin film transistor array shown in FIGS. 1A and 1B are shown, and the display unit and the vertical scanning circuit are not shown. In FIGS. 2 and 3, 21, 22, 2
3 is a video signal input terminal, 24 is a voltage source, 25 is a transistor showing a circuit for measurement, 26 is a power supply of the transistor 25, 27 is a resistor, and 28 is an output terminal of the transistor 25.

First, as shown in FIG.
A voltage is applied from a voltage source 24 to the video signal line 4 via 1 to 23 to charge the capacitive element 14 shown in FIG. Next, as shown in FIG. 3, a measuring circuit is connected in place of the voltage source 24, and the horizontal scanning circuit 1 is scanned while measuring the output obtained at the output terminal 28 of the transistor 25, and the potential of each video signal line 4 is measured. Is measured. At this time, the measurement is performed by sequentially switching the video signal input terminals 21 to 23. If the video signal line 4 is normal, the voltage charged in the capacitor 14 is applied to the gate of the transistor 25 and the output terminal 2
8 is at a low level, and if the video signal line 4 is disconnected or the video signal lines 4 are short-circuited, the transistor 25
Since no predetermined voltage is applied to the gate of the transistor 25, the transistor 25 does not turn on and the output of the output terminal 28 is at a high level. This inspection method can be used to check for broken signal lines,
In addition to the short circuit, a short circuit between the source and the drain or a short circuit between the source and the gate of the transistor 6 of the display unit whose source is connected to the video signal line 4 can be inspected.

In the above inspection method, no voltage is applied to the scanning line 5 and the transistor 6 in the display section is not turned on. However, the above inspection is performed by selecting the scanning line 5 and turning on the transistor 6. The transistor 6 in the display portion can be inspected. That is, the scanning line 5 is selected, the transistor 6 in one column is turned on, the video signal line 4 is selected by the horizontal scanning circuit 1, and a voltage is applied through the video signal input terminals 21 to 23 as shown in FIG. Apply. Next, FIG.
By measuring the voltage or the current by the method described in (1), it is possible to identify the fault location.

[0021]

According to the present invention, there is provided an excellent thin film transistor array in which a capacitive element is inserted between an end of a signal line of a thin film transistor array and a power supply line to detect a disconnection or short circuit of a signal line and a defect of a transistor in a display portion . An inspection method can be realized .

[Brief description of the drawings]

1A is a diagram illustrating a circuit configuration for supplying a video signal to a video signal line in one embodiment of a thin film transistor array according to the present invention; FIG. 1B is a diagram illustrating a circuit configuration of a display unit of the thin film transistor array;

FIG. 2 is a diagram for explaining a step of charging a capacitive element in an embodiment of the method for inspecting a thin film transistor array of the present invention.

FIG. 3 is a diagram for explaining a voltage measurement step in an embodiment of the method for inspecting a thin film transistor array of the present invention.

4A is a diagram showing a circuit configuration for supplying a video signal to a video signal line of a conventional thin film transistor array. FIG. 4B is a diagram showing a circuit configuration of a display unit of the thin film transistor array.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Horizontal scanning circuit 2 Video signal line 3 Analog switch 4 Video signal line 5 Vertical scanning line 6 Pixel transistor 7 Auxiliary capacitance 8 Pixel electrode 9 Counter electrode 10 Liquid crystal 11 Inspection transistor 12 Common source line 13 Common drain line 14 Capacitance element 15 Power supply Line 21, 22, 23 Video signal input terminal 24 Voltage source 25 Transistor 26 Power supply 27 Resistance 28 Output terminal

Continuation of the front page (56) References JP-A-5-5866 (JP, A) JP-A-5-289102 (JP, A) JP-A-62-151769 (JP, A) JP-A-50-17599 (JP, A) , A) JP-A-5-313132 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/136 G02F 1/133 550 G09G 3/36

Claims (3)

(57) [Claims] A plurality of parallel signal lines, scanning lines electrically insulated from and intersecting with the signal lines, and at intersections between the signal lines and the scanning lines, a source scans the signal line and a gate scans the signal line. A thin film transistor array in which transistors respectively connected to the lines are formed on a substrate, and a capacitive element is inserted and connected between an end of each of the signal lines and a common line.
Is a method of inspecting a capacitor via an input end of a signal line.
Charge the element, and after a certain period of time,
Of the thin film transistor array that measures the voltage or current
Inspection methods. Wherein after charging the capacitor by switching the signal line, the inspection method of a thin film transistor array according to claim 1, wherein measuring the voltage or current. 3. A process according to claim 2 or 3 test method of thin film transistor array according to measure a voltage or current while switching the scan line.