JPH03249625A - Repairing method for defect of active matrix substrate - Google Patents

Abstract

PURPOSE:To repair a defect without causing neither an increase in parasitic capacity nor a decrease in opening rate by preparing a specific thin film transistor(TFT) for repair in advance and connecting the TFT for repair to the removal track of a defective TFT. CONSTITUTION:A semiconductor substrate is stuck on a support substrate 11 across an insulating thin film 12 previously and made into a thin film. Then while a semiconductor thin film 14 is used as an operating semiconductor layer, a thin film transistor(TFT) and connection pads 15 led out of a gate electrode G, a source electrode S, and a drain electrode D are formed. Further, the TFT and the support substrate on the reverse surface of a connection pad formation area are removed to obtain the TFT for repair. Then an active matrix substrate 2 is inspected and when a defect of the TFT is detected, the defect is removed and the TFT 1 for repair is connected to the removal track. Consequently, the defect of the active matrix liquid crystal substrate can be repaired without causing neither the increase in the parasitic capacity nor the decrease in the opening rate.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for repairing defects in an active matrix display device, in which driving thin film transistors are provided in correspondence with pixels, and the switching action of the thin film transistors is used to write and hold a voltage to a liquid crystal cell. The purpose of the present invention is to provide a thin film transistor that makes it possible to repair defects in active matrix liquid crystal display devices without increasing parasitic capacitance or decreasing the aperture ratio. A repair thin film transistor is formed which is composed of a semiconductor thin film obtained as an active semiconductor layer and has electrode pads led out from each electrode, and further, a support substrate on the back surface of the repair thin film transistor forming area is removed. A module substrate is prepared, and an active matrix substrate with display electrodes arranged in a matrix on the surface and thin film transistors corresponding to the display electrodes is inspected, detected defective thin film transistors are removed, and the removed thin film transistors are removed. The repairing thin film transistor is connected to the removal trace via the electrode pad.

[Industrial application field]

The present invention relates to a method for repairing defects in an active matrix display device, in which drive thin film transistors are arranged corresponding to pixels, and the switching action of the thin film transistors is used to write and hold a voltage to a liquid crystal cell.

Active matrix display devices, together with simple matrix display devices, are used as thin display devices for information terminals, and liquid crystal is used as the display medium.

Comparing the characteristics of the two, the active matrix type can perform the same operation as driving a large number of pixels individually, so even if the number of lines increases as the display capacity increases, the simple matrix type The drive ratio is reduced, and problems such as contrast reduction and viewing angle phenomena do not occur. For this reason, active matrix liquid crystal display devices can provide a color display comparable to that of a cathode ray tube (CRT), and are increasingly being used as thin flat displays.

However, in active matrix display devices, it is necessary to form a switching element for each pixel, resulting in a huge number of elements and a complex structure, resulting in lower manufacturing yields and higher costs. .

[Conventional technology]

A method for repairing point defects in conventional active matrix liquid crystal display panels has been to use a redundant configuration in which a plurality of thin film transistors are provided for each pixel.

That is, as shown in FIG. 4, a plurality of pixel driving thin film transistors T (two examples are shown in the figure) are provided for each of a large number of pixels arranged in a matrix, and defects occur. The thin film transistors were cut and separated, and the remaining thin film transistors were used to drive the pixels.

In the figure, E is the display electrode, SB is the scan canvas, and DB is the display electrode.
is the data bus.

[Problem to be solved by the invention]

In the conventional defect repair method using the above-mentioned redundant configuration, it is difficult to identify the defective thin film transistor.Secondly, since each pixel is provided with a plurality of thin film transistors T that can be driven by one, Parasitic capacitance increases,
Furthermore, there were other problems such as a decrease in the aperture ratio.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for repairing defects in an active matrix liquid crystal display device, which makes it possible to repair defects in an active matrix liquid crystal display device without increasing parasitic capacitance or reducing aperture ratio.

[Means to solve the problem] The present invention will be explained with reference to FIGS. 1 and 2.

FIG. 1 is a cross-sectional view taken along arrow 1-1 in FIG. 2, and FIG. 2 is a plan view showing one repair thin film transistor according to the present invention.

In the figure, 1 is a repair thin film transistor, and 2 is an active matrix substrate.

A semiconductor substrate is previously attached onto the support substrate 11 with an insulating thin film 12 interposed therebetween, and this is made into a thin film. This semiconductor thin film 14
A thin film transistor is formed using the thin film transistor as an active semiconductor layer, and connection pads 15 led out from the gate electrode G, source electrode S, and drain electrode of this thin film transistor are formed. Furthermore, the support substrate on the back surface of the thin film transistor and the connection pad formation area is removed to obtain a repair thin film transistor l according to the present invention. Here, the insulating thin film 12 may be removed from the back surface of the connection pad 15.

On the other hand, the active matrix substrate 2 has display electrodes (not shown) arranged in a matrix on the surface of an insulating substrate 21 such as a glass substrate, as in the case of a normal substrate.
A thin film transistor (not shown) is provided corresponding to the display electrode. This active matrix substrate 2 is inspected, and if a defective thin film transistor is detected, it is removed using a laser beam or the like.

Next, the repairing thin film transistor 1 is connected to the area where the thin film transistor on the active matrix substrate 2 has been removed. For this purpose, the electrode pads 15 are stacked on the corresponding connection electrodes 22 of the active matrix substrate 2,
Connect the two.

Note that the connection electrode 22 may be a connection-only electrode provided on the active matrix substrate 2, or may be connected to the gate pass line, drain pass line, and display electrode to which each electrode of the removed defective thin film transistor was connected. A predetermined location may also be used.

Furthermore, the connection between the connection pad 15 and the connection electrode 22 can be easily achieved by applying a laser beam or applying ultrasonic waves.

Finally, the repair thin film transistor 1 is separated from the support substrate 11 using a laser beam or the like.

[For production]

In this way, according to the method for repairing defects in active matrix substrates using repair thin film transistors, each pixel on the active matrix substrate only needs to be provided with one driving thin film transistor. Can be easily detected.

Further, it is possible to suppress an increase in parasitic capacitance and a decrease in aperture ratio due to a plurality of thin film transistors being provided in a normal part, which are problems in a normal redundant configuration.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In this example, a single-crystal Si thin film is formed on an insulating film.
Ol (Silicon On In5ulator)
This method uses techniques for forming substrates, such as the wafer bonding method (Nikkei Microdevice March 1988 issue).

82-98), graphoepitaxy method, etc. can be used.

In this example, approximately 4 μm thick film was formed on a silicon wafer.
through the film, S with a thickness of about 0.5 μm
If! A film is formed, and using this Sol substrate, a repair module substrate including a large number of repair thin film transistors is manufactured. Then, this repairing thin film transistor is connected to the spot where the defective thin film transistor was removed on the active matrix substrate to repair the defect.

That is, as shown in FIG. 3(a), Si is used as a support substrate.
A substrate 11 is used. The surface of this Si substrate 11 is oxidized to form a SiO film 12 with a thickness of approximately 4 μm.

Next, a Si single crystal substrate is bonded onto this SiO□ film 12 using a wafer bonding method, and then the thickness of the Si single crystal substrate is reduced by polishing and etching to form a Si thin film 14 with a thickness of approximately 0.5 μm. do.

Next, as shown in FIG. 3(b), the above 5iii# film 1
4 is removed in a net shape, leaving small pieces of the 5iil film 14 in a matrix shape. Then, a thin film transistor is formed using each of them. In the figure, 15 is a connection pad, G is a gate electrode, S is a source electrode, and D is a drain electrode. In addition, three regions 41 to 42 are depicted in the Si thin film 14, and these are a high-resistance channel region 41 and n-type source and drain regions 42 and 43 into which n-type impurities are introduced, respectively. .

The gate electrode G, the source electrode S, and the drain electrode extend from the corresponding regions 41, 42, and 43 to outside the small piece of the Si thin film 14, and the connecting pads 15 are placed on top of them.
form.

Next, plasma etching is performed from the back surface of the Si substrate 11 using CFz +Ot as a reaction gas, and as shown in FIG. 3(C).
As shown in FIG. 2, the Si substrate 11 on the back surface of the region where the thin film transistor and its connection pad are formed is removed.

The above describes the I! for active matrix defect repair according to the present invention. l) The transistor 1 is completed.

In this embodiment described above, as shown in FIG. 3(d),
A repair module substrate 3 is obtained in which one repair thin film transistor 1 is supported in each opening of the mesh-like Si substrate 11.

After aligning this repair thin film transistor with the spot where the defective thin film transistor was removed in the active matrix substrate, the connection pad 15 is connected to a predetermined part of the active matrix substrate using ultrasonic waves or a laser beam.
[see FIG. 1], the connected repair thin film transistor 1 is separated from the repair module substrate 3.

According to this embodiment described above, even if there is a defective thin film transistor in the active matrix substrate, it can be easily repaired. Therefore, there is no need to adopt a redundant configuration, and only one thin film transistor needs to be disposed in each pixel, which not only facilitates identification of defective locations but also prevents increase in parasitic capacitance.

In the above embodiment, a Si substrate was used as the support substrate 11, but if a Si substrate is used, various properties such as expansion coefficient match those of a Si single crystal substrate, so the manufacturing process is easier. However, it is not necessarily limited to a Si substrate, and an insulating substrate such as a glass substrate may be used.

Furthermore, although the Si single crystal substrate was used as the starting material for the semiconductor ff1lW14 which becomes the active semiconductor layer, it may be a polycrystalline substrate, an amorphous substrate, or a semiconductor other than Si. , should be selected in consideration of the relationship with the configuration of the active matrix substrate.

〔Effect of the invention〕

As explained above, according to the present invention, defective thin film transistors in an active matrix substrate can be easily detected and repaired, and an increase in parasitic capacitance due to providing a plurality of thin film transistors in each pixel can be avoided. Since this does not occur, manufacturing yield can be improved without deteriorating display characteristics.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the configuration of the present invention, FIG. 3 is a detailed explanatory diagram of the present invention, and FIG. 4 is an explanatory diagram of problems in the conventional technology. In the figure, 1 is a thin film transistor for repair, 2 is an active matrix substrate, 3 is a repair module substrate, 11
12 is a supporting substrate (Si substrate), 12 is an insulating thin film (Sin,
14 is a semiconductor thin film (Si single crystal thin film), 15 is a connection pad, 22 is a connection electrode, G is a gate electrode, S is a source electrode, and D is a drain electrode. -koL''#+Name of the present invention January figure Figure 2 'lI/&4

Claims (2)

[Claims] (1) Electrode pads (15) formed from a semiconductor thin film (14) pasted in advance on a support substrate (11) via an insulating thin film (12) as an active semiconductor layer, and led out from each electrode. A repair module substrate (3) is prepared by forming a repair thin film transistor (1) comprising a repair thin film transistor (1) and removing a support substrate on the back surface of the repair thin film transistor forming area, and having display electrodes arranged in a matrix on the front surface. The active matrix substrate (2) on which thin film transistors are arranged and arranged in correspondence with the display electrodes is inspected, the detected defective thin film transistors are removed, and the repair thin film transistors are placed on the electrode pads on the remains of the removed thin film transistors. A method for repairing defects in an active matrix substrate, characterized by connecting via a (2) The semiconductor thin film (14) pasted on the support substrate (11) in advance is configured as an active semiconductor layer, and is drawn out from each electrode with a dimensional relationship corresponding to the thin film transistor on the active matrix substrate to be repaired. An active matrix substrate characterized in that it has a plurality of repair thin film transistors (1) each having a plurality of electrode pads (15), and the supporting substrate is provided with a cutout for separating the repair thin film transistors. module board for defect repair.