JPH08271930A - Production of thin-film transistor - Google Patents

Abstract

PURPOSE: To provide thin-film transistors which are simple in structure, are not affected by stray transistors, etc., and make it possible to obtain images good for mixing when used for an image display device by forming drain electrodes between source electrodes and source bus lines. CONSTITUTION: Semiconductor layers of an (n) type or (p) type and transparent electrodes formed on the surface of an insulatable substrate are patterned to a prescribed shape, by which display pixels electrodes 15 and source bus lines 4 are formed. Second source electrodes 8 disposed nearly parallel with the source bus lines and source connecting electrodes 9 for connecting the second source electrodes 8 and the source bus lines 4 are formed in the positions near the left upper corners of the display pixel electrodes 15 of the source bus lines 4. The ends at the left upper corners of the display pixel electrodes 15 are elongated and disposed so as to be held between the source bus lines 4 and the second source electrodes 8, by which the drain electrodes 10 are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin film transistor for applying a voltage to a display pixel electrode of an image display device such as a liquid crystal display device.

[0002]

2. Description of the Related Art Recently, there has been a strong demand for development of thin displays such as OA equipment terminals and flat-screen televisions. As one of them, in a liquid crystal display device in which electrodes are arranged in rows and columns, active elements are provided at intersections of electrodes. Active matrix systems, which are arranged and drive liquid crystals, are being actively researched.

FIG. 16 is a typical equivalent circuit diagram of an active matrix type liquid crystal display device. (28) is a liquid crystal layer, and (29) is a capacitor for holding a voltage applied to the liquid crystal layer. However, the capacitor (29) may be omitted. (30) is a switching transistor for controlling the voltage for driving the liquid crystal layer. X ₁ , X ₂ ,
X ₃ , ... Are selection signal lines for controlling the gate of the switching transistor (30), and Y ₁ , Y ₂ , Y ₃ , ... are data lines for applying a voltage required to drive the liquid crystal. And are driven line-sequentially.

On the other hand, the structure of a thin film transistor used as a switching transistor is classified into a coplanar type structure, a stagger type structure and the like according to the positional relationship among a semiconductor layer, a gate electrode, a source electrode and a drain electrode. 17 is a sectional view of a coplanar type thin film transistor, FIG. 18 is a sectional view of a stagger type thin film transistor, and FIG. 19 is a plan view thereof. In the figure, the portions denoted by the same reference numerals indicate the same thin film transistor constituent elements.

(1) is an insulating substrate such as quartz or glass, on which a thin film transistor is formed. (2) is a semiconductor layer, such as polysilicon, amorphous silicon,
CdSe or the like is used. Reference numerals (6) and (10) respectively denote a source electrode and a drain electrode, which are usually wired with Al or the like.
(11) is a gate insulating film, which is formed of SiO ₂ , Si ₃ N _4, or the like. Reference numeral (12) is a gate electrode, which is wired by Al, Cr or the like. (31) is a protective film and (14) is a contact hole. (15) is a display pixel electrode made of a transparent conductive film.

Further, as shown in the plan view of FIG.
A thin film transistor having a simplified pattern structure is also known. This thin film transistor, as shown in the figure, after forming the source bus line (4), (5), the drain electrode (10), the display pixel electrode (15) with a transparent conductive film, a semiconductor, an insulating film,
The gate electrode (12) is formed by continuously forming a film and then etching the gate electrode (12) in a pattern.

By arranging the thin film transistors having the above-described structure so as to correspond to the respective pixels, it is possible to obtain a high-density display having a more excellent image quality as compared with a conventional panel using a dot matrix system or the like.

[0008]

As described above, by using a thin film transistor, a high-density liquid crystal display with good visibility can be realized. However, since one thin film transistor is required for each pixel, for example, 600 lines are required. In order to form a display of × 200 rows, it is necessary to form 120,000 thin film transistors in one substrate, and it is very difficult to form a large number of transistors without defects.

The types of defects of transistor defects include
Gate and source disconnection, gate-source short circuit, gate
There are short circuit between drains, short circuit between source and drain, defective transistor characteristics, etc.

The disconnection of the gate and the source occurs due to scratches during the process and poor step coverage of the crossover portion, which is a non-lighting line defect in a liquid crystal cell, but leads are taken out from both ends of the disconnection line. It is possible to eliminate display defects by repairing by connecting electrodes.

On the other hand, a gate-source short circuit occurs due to dust in the insulating film, etc., but if there is such a short circuit, the gate signal constantly escapes to the source line through the short circuit point, so that a voltage is always applied to the source. This is a lighting line defect. A gate-drain short-circuit also occurs due to the same reason, but since the gate voltage is applied to the drain through the short-circuit point regardless of the source signal, it is a point defect that always lights up. If the transistor characteristics are poor and a sufficient current does not flow even when the gate voltage is applied, the source signal voltage is not applied and a non-lighting defect occurs during selection.

A short circuit between the source and drain occurs due to etching residue of the source and drain electrodes, etc., but since the source signal is constantly applied to the drain electrode, it always causes a lighting point defect.

When the defect points of the above-mentioned defects are observed with a microscope after the defect inspection of the thin film transistor, the cause and the place of the defect such as foreign matter, pinhole, and etching residue can be confirmed in most cases.

Although the number of defects as described above varies depending on the process control, no line defect is allowed as a display.
Although it is necessary to make it about 0.01% or less as a point defect,
Currently, 0 in a board with more than 200 lines
〜A few line defects and 0.1-3% of point defects are often included, and the cell yield is low, which is a main problem that hinders the practical use of the active matrix type image display device. .

Further, the number of defects can be reduced by reducing the number of thin film transistor manufacturing processes, and a thin film transistor of a simplified process can be manufactured with two masks as shown in FIG. 20, which is advantageous for reducing the defect occurrence rate. Is a process.

However, as shown in FIG. 20, the drain current of the thin film transistor in the simplified process is the switching transistor 30 formed by the n-th source bus line 4 and the drain electrode 10 (source as shown). When the distance between the bus line (4) and the drain electrode (10) is L ₁ and the width of the gate electrode (12) is W, the channel width / channel length = W / L ₁ ) and the (n + 1) th source Bus line
Stray transistor (32) formed by (5) and drain electrode (10) (source bus line (5) and drain electrode (10)
The distance between the L _2, a channel width / channel length =
Affected by W / L ₂ ).

The drain current of the stray transistor 32 varies depending on the design value of the thin film transistor, but is usually 5 to 5 times the current value of the switching transistor.
This is 20%, which is not a big problem in the case of binary display, but in the case of gradation display, since a signal of an adjacent source line is picked up, clear display cannot be obtained, which is a problem.

On the other hand, since the shape of the transistor is smaller than the area of the display pixel, there is a problem that a sufficient current cannot be taken to operate the pixel.

The present invention has been made to solve the above-mentioned drawbacks of the conventional thin film transistor, and has a good production yield even when a large number of thin film transistors are formed on one insulating substrate, and An object of the present invention is to provide a thin film transistor which has a simple structure and is not affected by a stray transistor or the like and which can obtain a good image when used in an image display device.

[0020]

According to the present invention, a source bus line and a gate bus line are provided on an insulating substrate, a display pixel electrode is provided, and the display pixel electrode is provided to apply a voltage to the display pixel electrode. Connected via the drain electrode, the source electrode, in the method of manufacturing a thin film transistor provided with a gate electrode and a semiconductor layer, connected to the source bus line,
One or a plurality of source electrodes to which a voltage is applied from the source bus line is formed, and a drain electrode is formed between a pair of adjacent source electrodes formed of a plurality of the source electrodes, or the most source bus is formed. There is provided a method of manufacturing a thin film transistor, characterized in that the thin film transistor is formed between the source electrode located near the line and a source bus line which itself can act as a source electrode.

A typical example of a thin film transistor obtained by the method of manufacturing a thin film transistor according to the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an example of a thin film transistor obtained by the present invention, and FIG. 2 is a sectional view of the AA ′ plane.

In the figure, an insulating substrate such as quartz or glass
On the surface of (1), indium tin oxide (I
(TO) or the like made of a transparent conductive film, and on the surface thereof, polysilicon, amorphous silicon, Cd
A semiconductor layer 16 is formed by doping a semiconductor such as Se with P, As, B, or the like to be n-type or P-type, respectively.

The doped semiconductor layer (16) and the transparent electrode thus formed are simultaneously patterned into a shape as shown in FIG. 1 to form a display pixel electrode (15) and a source bus line (4). It At a position of the source bus line (4) near the upper left corner of the display pixel electrode (15), the second source electrode (8) provided substantially parallel to the source bus line (4) and A source connection electrode (9) connecting the second source electrode (8) and the source bus line (4) is formed. In addition, the end of the upper left corner of the display pixel electrode (15) is extended so as to be sandwiched between the source bus line (4) and the second source electrode (8) described above, and the drain electrode ( Ten)
Is formed.

On this substrate, a semiconductor layer (2) of polysilicon, amorphous silicon, CdSe or the like, and then SiO
₂ , gate insulating film made of Si ₃ N ₄ , SiON, etc.
1) Further, after forming a metal for the gate electrode such as Al and Cr, the metal layer, the insulating film layer and the semiconductor layer are continuously etched in the pattern of the gate electrode (12) of FIG.
(12), the insulating layer (11), and the semiconductor layer (2) are formed.

After that, the doped semiconductor layer on the display electrode source bus line and the like, which is exposed except the gate electrode pattern, is continuously removed by etching. A portion of the source bus line (4) that spatially intersects the gate electrode (12) functions as a first source electrode (7).

With this structure, the source signal is supplied to the drain electrode (10) from the first source electrode (7) and the second source electrode (8). That is, the above-mentioned ratio of the channel width to the channel length (W / L) of this thin film transistor is twice that of the conventional thin film transistor.

Further, in this case, since the drain electrode (10) is electrically cut off from the (n + 1) th source bus line (5) by the second source electrode (8), the (n + 1) th source bus line ( 5) and the stray transistor are not formed at all, and only the signal of the n-th source bus line (4) is supplied to the display pixel electrode (15), so that an accurate display can be obtained.

As the structure of the source electrode, as shown in FIG. 3, the first source electrode is the same as the second source electrode (8).
The shape of (7) can also be connected to the source connection electrode (9), and in this case, it is effective for repairing when there is a defect.

Although the description has been made above regarding the simplified pattern, the present invention is not limited to such a pattern and structure, and can be applied to conventional coplanar type and stagger type thin film transistors.

For example, in a thin film transistor having a coplanar structure, a drain electrode (10) is sandwiched by two source electrodes (7) and (8) provided so as to project at right angles to a source bus line (3) as shown in FIG. That has a drain electrode (10) sandwiched between source electrodes (8) that are provided so as to project in parallel with the source bus line (3) as shown in FIG. But it's okay.

With respect to these coplanar type and stagger type structures, the influence of the stray transistor is not the same as in the conventional simplified pattern, but the structure of the present invention allows the channel width and the channel length of the thin film transistor. Has a merit that the ratio (W / L) can be twice as high as that of the conventional one, and has a structure in which it is easy to take effective countermeasures when there is a defect.

Next, a method of repairing when the thin film transistor has a defect will be described. As a result of the inventors producing a large number of thin film transistor substrates, it has been found that the locations where various defects occur are random and the probability that adjacent thin film transistors become defective is extremely low. The present invention has been made in view of such facts. Among the above-mentioned defects, the source-gate short circuit has the highest probability of occurrence and becomes a serious defect of the lighting line defect, which is the main cause of the reduction in the production yield.

On the other hand, in the case where the thin film transistor has good characteristics and a sufficient drain current can be obtained even with a small W / L structure, and one of the two source / gate overlap portions, the reference numeral (17) shown in FIGS. If a short-circuit point such as shown in () is recognized, the source electrode (7) or (8) or the gate electrode (12) may be cut by some method, as indicated by reference numeral (18).

At this time, the source signal is input to the drain electrode only from the remaining source electrode (8) or (7), but if the performance of the thin film transistor is sufficient, there is no problem in the case of binary display. Further, even when the gradation display is performed, the gradation is slightly different from the original gradation, but in the case of a moving image, the difference is almost unrecognizable, and the image value can be remarkably improved as compared with the conventional line defect.

Further, as shown in FIG. 9, two source electrodes are provided.
Only one of (7 ') and (8) was electrically insulated, and as a result of the inspection, a source-gate short circuit defect was recognized as indicated by reference numeral (17) in FIG. The source electrode (8) of the thin film transistor is cut from the root as shown by the reference numeral (18), and the other source electrode (7 ') which has been electrically insulated until then is electrically connected by the reference numeral (19). It is also possible to connect to restore the function of the transistor, as shown by.

In the simplified pattern described above, the repaired pixel is affected by the stray transistor when the second source electrode (8) closer to the adjacent source bus line (5) is cut off. However, a small number of scattered repair pixels are difficult to distinguish from others, and the effect of the repair is as described above.

Although the above description has been made with respect to the simplified pattern, it is not limited to the structure of the thin film transistor and can be applied to a coplanar type or a stagger type.

Although the case where one pixel has one drain electrode has been described above, a thin film transistor having a simplified pattern having a plurality of drain electrodes will be described next.

When the performance of the thin film transistor is insufficient, as shown in FIG. 11, two source electrodes (7), (8), (34), (36), (37) for each pixel, It is effective to provide a plurality of thin film transistors composed of a plurality of drain electrodes (10), (35), (38) sandwiched by (39).

That is, the drain current obtained by providing a plurality of thin film transistors is twice the number of transistors as in the case of one transistor, and a sufficient drain current necessary for display can be obtained. When a defect is recognized in the thin film transistor in this structure, the defective thin film transistor can be electrically insulated and repaired by cutting the drain or source electrode as shown in FIG.

For example, as shown in the figure, a source-gate short circuit (17) occurs at the source electrode (34), and a gate-drain short circuit (20) occurs at the drain electrode (35),
When the (34) and the drain electrode (35) are cut as indicated by reference numerals (18) and (21) respectively, that is, when one of the three thin film transistors has a defect and is cut and separated, Since a drain current of 2/3 is obtained at the pixel electrode (15), the difference in display characteristics between the pixel and other pixels is smaller than that in the above case, and a higher quality image can be obtained. .

When the performance of the thin film transistor is sufficient, as shown in FIG. 13, a plurality of thin film transistors each having a plurality of drain electrodes sandwiched by two source electrodes for each pixel are provided, and the source electrode is provided. And the drain electrode are the source bus line and the display pixel electrode (1
The effect is further enhanced by including the thin film transistor (24) electrically insulated from 5).

That is, a sub-thin film transistor (24) that is electrically insulated is provided in addition to the main thin film transistor (23) electrically connected per pixel, and a defect is recognized in the main thin film transistor (23). When this occurs, as shown in FIG. 14, a part or both of the drain and source electrodes of the transistor (23) are cut as indicated by reference numerals (18) and (21), and the reference numeral (18) is obtained. , (21) electrically isolated state,
Next, the subordinate thin film transistor (2
By connecting the source electrode of 4) with the source connection electrode as shown by reference numeral (25) and connecting the drain electrode to the display pixel electrode (15) as shown by reference numeral (19), respectively,
The secondary thin film transistor (24) is activated.

In the case of the thin film transistor having the above structure, since the number of thin film transistors of the good pixel and the restored pixel can be made equal from the beginning, the display pixel electrode (1
The drain current supplied to 5) can be exactly the same, and
Since it is possible to receive the original source signal of the display pixel electrode (15), it is possible to manufacture a display pixel electrode having no defect on display.

The number of the plurality of thin film transistors in the present invention is not limited to the illustrated number, and the number of drain and source electrodes which are initially insulated is not limited to the illustrated number.

As the cutting method in the above-mentioned repairing step, there are a laser trimmer, a cutting method using an ultrasonic cutter and the like, but the cutting method is not limited to any method. Further, also in the method of connecting the drain electrode of the second transistor and the display pixel electrode, a method of attaching a fine conductor with a dispenser or the like,
Place a glass substrate coated with gold or aluminum on the thin film transistor substrate so that they face each other, and irradiate a laser that has been narrowed down to the desired size from the metal coated substrate side under normal pressure or reduced pressure, and place the metal at the desired location on the thin film transistor substrate There is a laser coating method for coating, but the method is not particularly limited.

[0047]

BEST MODE FOR CARRYING OUT THE INVENTION In the configuration example of the present invention whose configuration is shown in FIGS. 1 to 5, when a high potential voltage is applied to the gate electrode (12), the source bus lines (3), ( 4) a first source electrode (7) and a second source electrode connected to
A current flows from (8) to the drain electrode (10) through the semiconductor layer (2), and the display pixel electrode (15) connected to the drain electrode (10) is connected to the source bus lines (3) and (4). Becomes the same potential as
When the source bus lines (3) and (4) are at high potential,
A voltage between the display pixel electrode (15) and a common electrode (not shown) is applied, and in the case of a liquid crystal display device, the display pixel electrode (15)
The liquid crystal switch sandwiched between the common electrode and the common electrode is turned on, and the pixel corresponding to the display pixel electrode (15) is turned on to enter the display state.

When the source bus lines (3) and (4) are at low potential, the display pixel electrode (15) is also at low potential, the liquid crystal switch is not turned on, and the pixel corresponding to the display pixel electrode (15) is turned on. Turns off.

While the selection potential is being supplied to the other gate electrodes, a low potential is supplied to the gate electrode (12) to which a signal has already been supplied and the semiconductor layer (2) has a high resistance. 7), (8) and the drain electrode (10) are electrically separated, and the liquid crystal switch of the pixel corresponding to the display pixel electrode (15) continues the previous state due to the liquid crystal capacitance or the additional capacitance.

In the switching operation as described above,
As mentioned above, channel width / channel length (W /
L) is large, and the drain electrode (10) is the (n + 1) th source bus line by the second source electrode (8).
Since it is electrically cut off from (5), a sufficient drain current amount can be obtained, and the drain electrode (10) is (n
A good switching operation can be obtained without forming a stray transistor with the +1) th source bus line (5).

When a source-gate short circuit (17) as shown in FIGS. 6 and 7 occurs in the thin film transistor, as described above, the source electrode (7) or the gate electrode (12) is sourced, respectively. From the bus line (4) or the gate bus line, as shown by reference numeral (18) in the figure, it can be repaired by cutting and a normal switching operation can be obtained.

As shown in FIG. 9, the switching operation is the same in the case where only one source electrode (8) is connected to the source bus line (4), and the source-gate short circuit (17) Is generated on the source electrode (8), the source electrode (8) is disconnected from the source bus line (4) and the spare source electrode (7 ') is connected to the source bus line (4) to repair. The same is true that normal switching operation can be obtained.

As shown in FIG. 11, a plurality of drain electrodes (1
0), (35), and (38) each have two source electrodes (7), (8); (3
In the case of the configuration provided between 4), (36); (37), and (39), a sufficient drain current can be obtained and good display can be obtained.

As described above, the source-gate short circuit (1
7) or the gate-drain short circuit (20) occurs, the defective source electrode (34) or drain electrode
The defect can be repaired by cutting (35) as indicated by reference numerals (18) and (21), respectively.

As shown in FIG. 13, also in the case where a spare thin film transistor (24) is provided, the switching operation of the thin film transistor and the repairing method when a defect occurs are the same. In this case, as described above,
Even when repaired, a stable display can be obtained because the drain current amount is the same as before repair.

As described above, the thin film transistor of the present invention repairs even when a defect occurs in a certain display pixel so that the voltage from the original source bus line for applying the voltage to the pixel can be applied. Therefore, as compared with the method of applying the voltage from the adjacent source bus line, the defect can be more completely removed and repaired. Next, an example of manufacturing and repairing the thin film transistor of the present invention will be described.

[0057]

【Example】

(Example 1) First, a thickness of 10 was formed on a glass substrate of 50 mm square.
After coating 00Å ITO and 500Å n ⁺ a-Si,
As shown in FIG. 1, the source bus lines (4) and (5) and the source connection electrode (9), the source electrode (8) and the drain electrode (1
0), the display pixel electrode (15) was patterned. At that time, the drain electrode (10) was formed so as to be sandwiched between the two source electrodes (7) and (8).

Next, 2000 Å a-Si and 2000 Å SiON films were coated by P-CVD, and then 3000 Å aluminum for the gate electrode was coated. Aluminum and aS with the pattern of the gate electrode (12) using photoresist
i, SiON film is etched and then n ^{+ a} − on ITO
The Si film was also etched to complete a 200 × 200 pixel thin film transistor.

When the characteristics of the thin film transistor formed on the substrate in this way were measured, the drain current value was about twice that of the conventional simplified pattern, and the thin film transistor characteristics of a certain pixel showed that the adjacent source bus line Was not affected by the signal. When a liquid crystal display panel was assembled by coating a polyimide alignment film on the above substrate and a lighting test was performed, a clearer and more accurate image than the conventional one was obtained even when gradation display was performed. There were four lighting line defects caused by the gate short circuit and two lighting defects caused by the gate drain short circuit.

Example 2 As shown in FIG. 3, the drain electrode (10) was replaced with the source connection electrode with the same film structure as in Example 1.
After making a thin film transistor with a structure sandwiched between two source electrodes (7) and (8) connected to (9), all thin film transistors were inspected and a short circuit between the source and gate was found at three locations.
A gate-drain short circuit was observed at the location.

Observation of a thin film transistor having a short circuit between the source and the gate at three locations revealed that two locations were at the intersection of the gate electrode (12) and the first source electrode (7) and one location was the gate electrode (12).
A black foreign material was observed at the intersection of the second source electrode (8) and the. The root of the source electrode where foreign matter is recognized is cut with a laser trimmer as shown by reference numeral (18) in FIG.
(9) and electrically isolated from the source bus line (4).
After that, a liquid crystal display panel was prepared in the same manner as in Example 1 and a lighting test was performed. As a result, there was no lighting point defect caused by the source-gate short circuit, and the lighting point caused by the gate-drain short circuit. It was improved to the situation where there was only one defect.

Although the contrast of the repaired pixel is lower than that of the other pixels when carefully observed from a close distance, the difference is hardly perceptible when observed from a distance of 30 cm from the normal operating distance, and an image is not obtained. I knew there was no problem.

(Embodiment 3) With the same film structure as in Embodiment 1, as shown in FIG. 13, two source electrodes (7), () in which the drain electrode (10) is connected to the source connection electrode (9) Three thin film transistors with a structure sandwiched between 8) are provided for each pixel, and the two source electrodes (7), (8) and drain of only the main thin film transistor (23) closest to the source bus line (4) among them are provided. The electrodes (10) are connected to the source bus line (4) and the display pixel electrode (15) respectively, and other sub-thin film transistors (24)
The source / drain electrodes of were prepared in an electrically insulated state.

When the thin film transistors on all the substrates thus produced were inspected, three source-gate short circuits and two gate-drain short circuits were found. The two source electrodes of the thin film transistor with the short circuit between the source and the gate are connected as shown by the reference numeral (18) in FIG. 14, and the drain electrodes of the thin film transistor with the short circuit between the gate and the drain are connected as shown by the reference numeral (21). The electrode (9) and the display pixel electrode (15) were cut by the laser trimmer method.

Next, the insulated source connection electrode of the first subordinate thin film transistor (26) in the pixel and the source connection electrode (9) of the main thin film transistor (23) are connected to each other,
Also, after aiming the laser trimmer in the form of connecting the insulated drain electrode and the display pixel electrode (15),
A glass substrate coated with 5000 Å gold was placed on the thin film transistor substrate so that the gold coating surface was in contact with the substrate, and laser irradiation was performed under reduced pressure.

As a result, as shown by reference numerals (25) and (19) in FIG. 14, the gold of the portion irradiated by the laser is evaporated and redeposited on the thin film transistor substrate, so that the first sub-thin film transistor is formed. The source electrode and the drain electrode of (26) were connected.

In the re-inspection after the repair process, the source-gate short-circuit at two places and the gate-drain short-circuit at two places should have good characteristics by using the first sub-thin film transistor (26). However, there was a source-gate short circuit in the first sub-thin film transistor (26) in one thin film transistor. Therefore, the source electrode of the subordinate first thin film transistor (26) is
After cutting as indicated by reference numeral (18) in FIG. 15, the source connection electrode and the drain electrode of the subordinate second thin film transistor (27) are connected to the source connection electrode and the display pixel as indicated by reference numerals (25) and (22). It was connected to the electrode (15).

As a result, a normal drain current can be supplied to the display pixel electrode (15) of the pixel from the subordinate second thin film transistor (27).

When a liquid crystal display panel was prepared by the above-mentioned method and a lighting test was conducted on the thin film transistor which had been subjected to this repairing step, no point defect or line defect was observed, and even if it was carefully observed, there was no defect. I was able to get the display.

[0070]

In the thin film transistor according to the present invention, since the drain electrode is formed between the two source electrodes, the drain current can sufficiently flow and the influence of the stray transistor can be reduced. It is possible not to receive it at all.

Further, since a plurality of thin film transistors are provided, and when the main thin film transistor is defective, the sub-thin film transistor can be used to supply an accurate source signal to the display pixel electrode, the defect-free thin film transistor substrate This makes it possible to fabricate the device, significantly improves the production yield of the device, and thus greatly contributes to the reduction of the production cost.

Further, after the defect is repaired, the voltage can be applied to the display pixel electrode from the same source bus line as before the repair, so that the repair can be completed without any noticeable trace of repair.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a thin film transistor of the invention.

FIG. 2 is a cross-sectional view showing an example of a thin film transistor of the invention.

FIG. 3 is a plan view showing another example of the thin film transistor of the invention.

FIG. 4 is a plan view showing a third example (reference example) of a thin film transistor.

FIG. 5 is a plan view showing a fourth example (reference example) of a thin film transistor.

FIG. 6 is a plan view showing a repairing method when a source-gate short circuit is found in the thin film transistor of the present invention.

FIG. 7 is a plan view showing a repairing method when a source-gate short circuit is found in the thin film transistor of the present invention.

FIG. 8 is a plan view showing a repairing method when a source-gate short circuit is found in the thin film transistor of the present invention.

FIG. 9 is a plan view showing a fifth example of the thin film transistor of the invention.

10 is a plan view showing a repairing method when a source-gate short circuit is found in the thin film transistor of FIG.

FIG. 11 is a plan view showing a sixth example of the thin film transistor of the invention.

FIG. 12 is a plan view showing a repairing method when the thin film transistor of FIG. 11 has a defect.

FIG. 13 is a plan view showing a sixth example of the thin film transistor of the invention.

FIG. 14 is a plan view showing a repairing method when a defect is found in the thin film transistor of FIG.

FIG. 15 is a plan view showing a re-repairing method when a further defect is found in the repaired thin film transistor.

FIG. 16 is a typical equivalent circuit of an active matrix type liquid crystal display device.

FIG. 17 is a conventional coplanar thin film transistor.

FIG. 18 is a cross-sectional view of a conventional inverted stagger type thin film transistor.

FIG. 19 is a plan view of each of the conventional inverted stagger type thin film transistors.

FIG. 20 is a plan view of a conventional thin film transistor having a simplified pattern.

[Explanation of symbols]

 1: Insulating substrate 2: Semiconductor layer 3: Source bus line 4: Nth source bus line 5: (n + 1) th source bus line 6: Source electrode 7: First source electrode 8: Second source electrode 9: Source connection electrode 10: Drain electrode 11: Gate insulating film 12: Gate electrode 13: Gate bus line 14: Contact hole 15: Display pixel electrode 16: Doped semiconductor layer 17: Source-gate short-circuit point 20: Gate Short-circuit point between drains 23: main thin film transistor 24: secondary thin film transistor 26: first secondary thin film transistor 27: second secondary thin film transistor 28: liquid crystal layer 29: capacitor 30: switching transistor 31: protective film 32: stray transistor

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[Procedure amendment]

[Submission date] May 24, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

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[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

However, as shown in FIG. 20, the drain current of the thin film transistor in the simplified process is the switching transistor 30 formed by the n-th source bus line 4 and the drain electrode 10 (source as shown). When the distance between the bus line (4) and the drain electrode (10) is L ₁ and the width of the gate electrode (12) is W, in addition to the channel width / channel length = W / L ₁ , the (n + 1) th position The stray transistor (32) formed by the source bus line (5) and the drain electrode (10) of
The distance between (10) as L _2, a channel width / channel length = W / L ₂₎ affected.

Claims (11)

[Claims] 1. A source bus line and a gate bus line are provided on an insulating substrate, a display pixel electrode is provided, and the display pixel electrode is connected to the display pixel electrode through a drain electrode to apply a voltage to the display pixel electrode. In a method of manufacturing a thin film transistor having a source electrode, a gate electrode, and a semiconductor layer, one or more source electrodes connected to the source bus line to which a voltage is applied are formed, and the drain electrode is It is formed between a pair of adjacent ones of the plurality of formed source electrodes, or between the source electrode located closest to the source bus line and the source bus line which itself can act as the source electrode. A method of manufacturing a thin film transistor, which comprises forming the thin film transistor. 2. A single drain electrode is formed between the source electrode located closest to the source bus line and the source bus line which itself can act as a source electrode. Method of manufacturing thin film transistor of. 3. A source electrode which is not connected to a source bus line and a drain which is not connected to the display pixel electrode. 2. The method of manufacturing a thin film transistor according to claim 1, further comprising arranging subordinate thin film transistors formed of electrodes in parallel. 4. The method of manufacturing a thin film transistor according to claim 1, wherein a drain electrode is provided between a pair of adjoining ones of the plurality of source electrodes, and a plurality of drain electrodes are provided. 5. Two drain electrodes and four source electrodes are provided.
The thin film transistor manufacturing method according to claim 1, wherein the thin film transistor is formed. 6. Three drain electrodes and six source electrodes
The thin film transistor manufacturing method according to claim 1, wherein the thin film transistor is formed. 7. The method of manufacturing a thin film transistor according to claim 1, wherein the source electrode is formed substantially parallel to the source bus line. 8. The method of manufacturing a thin film transistor according to claim 1, wherein the source electrode is formed substantially parallel to the gate bus line. 9. The method of manufacturing a thin film transistor according to claim 1, wherein a gate bus line is arranged so as to cross the source electrode. 10. The method of manufacturing a thin film transistor according to claim 1, wherein the source bus line, the source electrode, the drain electrode, and the display pixel electrode are formed of a transparent conductive film. 11. The method of manufacturing a thin film transistor according to claim 1, further comprising forming a preliminary source electrode between the drain electrode and the source bus line.