JPH0272392A - Inspecting and correcting method for active matrix type display device - Google Patents

Abstract

PURPOSE:To surely inspect the defective mode and defective position of a display device substrate without using any special means newly by using a picture element auxiliary capacitor common electrode as a measurement terminal. CONSTITUTION:An auxiliary capacitor 14 and a liquid crystal cell 6 are arranged in parallel and led out by the auxiliary capacitor common electrode 7, and the potential is fixed. In this structure, a voltage applied to the liquid crystal cell 6 is written in the auxiliary capacitor 14 at the same time. The electrostatic capacity of the auxiliary capacitor 14 is large or several times as large as that of the liquid crystal cell 6 and compensates the leak current of the liquid crystal cell 6 or a switching element 2, so it is evident that the voltage applied to the liquid crystal cell 6 is held normally and the reliability of the display quality is improved; and this auxiliary capacitor is formed in the produced liquid crystal display device. Then a current signal which is charged into or discharged from the auxiliary capacitor 14 through the switching element 2 is observed. Consequently, the operation of the switching element 2 and an active matrix 1 can be surely evaluated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flat display device, and more particularly to a method for inspecting and repairing an active matrix type display device having an auxiliary capacitor.

[Conventional technology]

An active matrix that combines a switching element such as TPT with a liquid crystal or electroluminescence is described in +3, J. Lecher et al., Proceedings, I.E.E. 59 y' 1566
(1971) (Proc, IEEE59.1566(
Since its announcement in 1971, research has continued into various methods, and liquid crystal displays have reached the stage of practical use.

The basic configuration of the pixel section is such that one TPT is provided in one pixel to drive a liquid crystal or the like.

FIG. 8 shows a specific configuration diagram. A TPT switching element 2 made of polycrystalline silicon or amorphous silicon is mounted on a transparent active matrix substrate 1 such as glass.
are arranged in each pixel and connected in a matrix by signal lines 3 and scanning lines 4. A liquid crystal cell 6 is formed by sealing liquid crystal between the active matrix substrate 1 and the common electrode 5 of the counter substrate.

Display is performed by sequentially applying signals to the scanning line 4, applying a signal voltage to the signal line 3, and applying a voltage to the liquid crystal cell 6 to control the light transmittance.

FIG. 9 shows a cross-sectional shape near the switching element 2 of the pixel. For example, polycrystalline silicon 7 is formed on the active matrix substrate 1 and processed into an island shape. Gate insulating film 8.
A polycrystalline silicon gate 9, a train electrode 11, a source electrode 12, an insulating film 10, and a transparent electrode 13 are formed.

In the active matrix type liquid crystal display device as described above, for example, about 100,000 switching elements 2 and about 650 scanning lines 4 and signal lines 3 are formed in a display area of 5 inches diagonally. In such large substrates, it is difficult to achieve defect-free production, and yield becomes an issue. For example, T.P.
When a defect occurs in the T element, a point defect occurs. Further, if a wire breakage or the like occurs, a line defect occurs and the commercial value as a display element is lost.

In order to know the existence of these defects, there is a method of laminating a counter glass on an active matrix substrate, sealing liquid crystal to form a display shape, and then visually or optically measuring the presence of the defects.

Alternatively, as described in Japanese Patent Application Laid-Open No. 57-38498, there is a method of detecting short circuits between wirings by measuring the amount of change in the amount of charge accumulated in the parasitic capacitance attached to pixels or wirings. Proposed.

[Problem to be solved by the invention]

In the first conventional technique, it is possible to determine the presence or absence of a defect, but it is very difficult to correct it. Moreover, a wasteful liquid crystal process is performed on defective liquid crystals, which causes a decrease in productivity.

In addition, although the latter method makes it possible to inspect the TPT substrate before filling the liquid crystal, it is impossible to accurately know the TPT characteristics because it uses stray capacitance existing within the substrate. In addition, in order to accurately determine the characteristics of a TPT element, the most reliable method is to bring a probe into contact with the transparent electrode of the pixel section and measure the various characteristics. However, in displays with a large number of display pixels, This is not a practical method because the measurement time is long and mechanical contact with the probe or the like causes scratches on the surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inspection method that enables reliable inspection of a TPT board once it is completed, and that can determine the failure mode and position of the TPT substrate.

[Means to solve the problem]

The above object is achieved by using the pixel auxiliary capacitance common electrode built into the TPT substrate as the third measurement terminal.

[Effect]

The auxiliary capacitor is capacitively coupled to the switching element, and by observing the current signal that is charged and discharged to the auxiliary capacitor via the switching element, the operation of the switching element and the active matrix can be reliably evaluated.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

First, FIG. 1 shows the basic configuration of an active matrix substrate with auxiliary capacitance. An auxiliary capacitor 14 is arranged in parallel with the liquid crystal cell 6, and is drawn out to the outside by a auxiliary capacitor common electrode 17, and its potential is fixed. In this structure, the voltage applied to the liquid crystal cell 6 is simultaneously written into the auxiliary capacitor 14. Normally, the capacitance of the auxiliary capacitor 14 is several times larger than that of the liquid crystal cell 6, and it compensates for the leakage current of the liquid crystal cell 6 or the switching element 2, so that the voltage applied to the liquid crystal cell 6 is maintained normally and the display is displayed. This auxiliary capacitance is known to improve quality reliability, and commercialized liquid crystal display devices are provided with this auxiliary capacitance.

FIG. 2 shows a cross-sectional view of the vicinity of the switching element 2. As shown in FIG.

The structure of the TPT region is the same as that in FIG. 9, and the interlayer film 15
．． It is characterized by having an auxiliary capacitor transparent electrode 16 and an auxiliary capacitor common electrode 17.

FIG. 3 shows a schematic configuration of an active matrix substrate evaluation method for carrying out the present invention. The scanning line 4, the signal line 3, and the auxiliary capacitor common electrode 17 are connected to the evaluation device via a vertical scanning circuit 18 and a horizontal scanning circuit 19. The probe method, flexible wiring, etc. are used for connection. In this configuration, the characteristics of the active matrix substrate can be evaluated by evaluating the current waveform written in the auxiliary capacitor 14 based on the voltage waveform input to the auxiliary capacitor common electrode 17 while switching the switching element 2 by scanning.

FIG. 4 shows a specific method for evaluating characteristics of a switching element according to the present invention. A voltage is applied to the auxiliary capacitor 14 by the test voltage generator 21 . During this time, the gate voltage generator 22
turns the gate on. By measuring the current flowing in synchronization with this signal using the current measuring device 23, the characteristics of the switching element 2 can be evaluated.

FIG. 5 shows specific voltage and current waveforms in FIG. 4.

(a) Vt is the applied test voltage waveform. When (b) Va is applied while this voltage is applied, TPT
gate is turned on.

If the current waveform flowing at this time is (c) 11, it is normal TPT.
Showing operation. (d) In the case of Iz, current continues to flow even when Va is turned off, indicating a short-circuit between the source and drain.

(e) The waveform of Ia shows that no current flows,
Indicates an open state between the source and drain, or a break in the signal line or scanning line. The former and the latter can be separated by scanning and evaluating a plurality of TPTs.

For example, if evaluation is performed continuously by scanning in the Y direction, and the (,) mode continues with a specific position as a boundary, it can be seen that there is a disconnection at the boundary. (Q
) to (e) can be specifically determined by comparing the current values at the X or Y points.

If the interlayer film breakdown voltage of the auxiliary capacitor is poor, a large current with a waveform similar to (a) will flow due to the test voltage.
This current level can be detected. Furthermore, if the withstand voltage at the intersection of the signal line and the operation line is defective, a large current with a waveform synchronized with Va flows, and by detecting this current level, it can be detected along with its position. Furthermore, the retention characteristic of the switching element 2 charges the auxiliary capacitor.

The test can be performed by turning on the switching element again after holding it for a predetermined time and evaluating the voltage or current of the auxiliary capacitor. Note that the withstand voltage of the cross portion can be evaluated without using an auxiliary capacitor.

In the above embodiments, the test voltage was applied from the auxiliary capacitor common electrode side, but it is also possible to apply the test voltage from the signal line side and observe the current waveform from the auxiliary capacitor common electrode side. Furthermore, the test voltage and current waveform can be arbitrarily selected depending on the measurement method, measuring instrument, and evaluation target.

Next, referring to FIG. 6, an application example of the present invention will be described.

In this example, the vertical and horizontal circuits for driving the display portion are built into the same transparent substrate as the switching elements, and this circuit is characterized in that it is used for evaluation.

The measurement principle is the same as that described in FIGS. 4 and 5, but by using the built-in vertical scanning circuit 24 and built-in horizontal scanning circuit 25, the number of external connections to the evaluation device 20 can be reduced.
It is possible to increase inspection efficiency. In this case as well, the test signal may be input from either the auxiliary capacitor common electrode side or the built-in horizontal scanning circuit side. In addition to the circuit for driving the display area, it is also effective to provide auxiliary circuits, terminals, etc. to facilitate inspection. For example, the auxiliary capacitor common electrode can be divided into multiple blocks, and a circuit for scanning the blocks can be provided.

Next, as an example of application other than liquid crystal display devices, an electroluminescent (EL) element is shown in FIG. Similar to FIG. 2, a light emitting layer 26 and an upper transparent electrode 27 are formed on the source side transparent electrode 13 of a MOS type switching element.
An EL cell 28 is configured. In this case as well, it can be driven using an active matrix method like a liquid crystal cell. In addition, by forming an auxiliary capacitor, it is possible to improve the reliability and stability of display in the same way as a liquid crystal cell. In this example as well, similar tests can be carried out using the methods shown in FIGS. 3 to 6.

In the embodiments described above, a polycrystalline silicon MO3FET was described as a switching element, but semiconductor materials,
It is not limited to the structure of the switching element.

Furthermore, based on the failure mode and failure position obtained by the present invention, broken wires can be repaired and short circuits can be separated.

It is possible to make corrections such as separating the defective switching element and insulating the defective auxiliary capacitor with withstand voltage. For example, a cut portion of a wiring can be repaired by metal laser CVD or the like. A short circuit at the cross portion can be repaired by removing the upper wiring, local CVD of the interlayer insulating film, and connecting by rewiring the upper wiring. Defective switching elements can be cut and separated using a laser beam, focused ion beam, electron beam, or the like. An auxiliary capacitance section with a breakdown voltage defect can be corrected by removing the ring of the transparent electrode in the defective section using a laser beam or the like, or by forming an insulating film locally.

〔Effect of the invention〕

According to the present invention, the failure mode and failure position of a display device substrate can be reliably inspected without using any special means. As a result, it is also possible to correct defective parts.

[Brief explanation of the drawing]

1, 3, and 6 are conceptual plan views of an active matrix substrate for explaining the present invention, FIG. 2 is a cross-sectional view of the vicinity of a switching element for explaining the present invention, and FIG. FIG. 5 is a test voltage and current waveform diagram for explaining the present invention; FIG. 7 is a sectional view of the vicinity of a switching element showing an application example of the present invention; FIGS. 8 and 9 are A conceptual plan view of an active matrix substrate and a cross-sectional view of the vicinity of a switching element are shown for explaining a conventional example. DESCRIPTION OF SYMBOLS 1... Active matrix substrate, 2... Switching element, 13... Transparent electrode, 14... Auxiliary capacitor, 1
5...Interlayer film, 16...Auxiliary capacitance transparent electrode, 17...
Auxiliary capacitor common electrode. Fig. 4 Fig. 7 Fig. 5 (e) Fig. 3 Fig. 3 Fig. 7 Fig. 2g

Claims (1)

[Scope of Claims] 1. A method for testing an active matrix display device having an auxiliary capacitor, characterized in that a common electrode for the auxiliary capacitor is used as an electrode for testing the display device. 2. The method for inspecting an active matrix substrate according to item 1, wherein the auxiliary capacitor is composed of a pixel electrode and a single or plural independent auxiliary capacitor electrodes. 3. The method for inspecting an active matrix display device according to item 1 or 2, wherein the display device has a built-in drive circuit. 4. The method for testing an active matrix type substrate according to item 3, characterized in that a built-in drive circuit is used as a testing means. 5. The method for testing an active matrix substrate according to item 1, 2, 3, or 4, characterized by comprising an auxiliary circuit for testing, auxiliary means for testing terminals, etc. 6. A method for inspecting an active matrix substrate according to items 1 to 5, characterized in that failure modes such as disconnections and short circuits and their positions are detected. 7. In active matrix display devices, cross short circuits can be corrected by removing the upper layer conductor, repairing the insulating film,
A method for repairing an active matrix display device, characterized in that the repair method is performed by reconnecting an upper layer conductor. 8. An active matrix display device in which a short circuit in an auxiliary capacitance section is corrected by partially removing the upper electrode of the short section, further repairing the insulating film, or further re-forming the upper electrode. How to modify the device. 9. A method for repairing an active matrix display device, characterized in that the methods for repairing items 7 and 8 are performed based on the inspection results in item 6. 10. The switching elements in the first to ninth terms are
A method for inspecting and repairing an active matrix display device characterized by being a thin film transistor using a single crystal, polycrystalline or amorphous semiconductor. 11. The method for inspecting and repairing an active matrix display device according to item 10, wherein the semiconductor is silicon. 12. A method for inspecting and repairing an active matrix display device, wherein the display device according to items 1 to 11 uses liquid crystal. 13. A method for inspecting and repairing an active matrix display device, wherein the display device according to items 1 to 11 uses EL. 14. An active matrix display device characterized by having undergone the inspections and corrections described in Items 1 to 13. 15. An inspection and correction device for an active matrix display device, characterized by having the inspection, correction, and correction confirmation functions described in items 1 to 13.