JPH0748147B2 - Manufacturing method of active matrix substrate - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, and more particularly, to a method for manufacturing an active matrix substrate which enables effective detection and repair of point defects in an image display device of active matrix organization. It is about.

2. Description of the Related Art Advances in fine processing technology, liquid crystal materials, and packaging technology in recent years have made it possible to obtain a television image on a commercial base, which is a small size of about 2 to 6 inches, but is practically unproblematic for a liquid crystal panel. It was Configure the LCD panel 2
Color display is easily realized by forming an RGB colored layer on one of the glass plates, and a so-called active type liquid crystal panel with a built-in switching element for each picture element has less crosstalk. Images with a high contrast ratio are guaranteed.

Such a liquid crystal panel has 120-240 scanning lines,
A standard matrix of 240-720 signal lines is used. For example, as shown in FIG. 5, switching elements and picture element electrodes are formed in a matrix on one glass substrate 2 constituting a liquid crystal panel 1. COG (Chip-On-Glass) for directly connecting the semiconductor integrated circuit chip 3 that supplies a drive signal to the electrode terminal group 6 of the scanning lines formed on the active matrix substrate 2
Or a method of fixing a connection film 4 having a terminal group (not shown) of gold-plated copper foil on the basis of a polyimide-based resin thin film as a base while pressing the electrode terminal group 5 of the signal line with an adhesive. An electric signal is supplied to the image display unit by the mounting means. Here, for convenience, two mounting methods are illustrated at the same time, but it goes without saying that either mounting method is actually selected. Numerals 7 and 8 are wiring paths for connecting between the image display portion in the center of the liquid crystal panel 1 and the electrode terminal groups 5 and 6 of the signal line and the scanning line, which are not necessarily made of the same conductive material as the electrode terminal group. There is no.

In the figure, 9 is another glass substrate having a transparent conductive counter electrode common to all picture elements, and two glass substrates 2 and 9 are predetermined by a spacer such as quartz fiber or plastic beads. Formed with a distance, the gap is a closed space sealed with a sealing material and a sealing material, and the closed space is filled with liquid crystal. In order to realize a color display, an organic thin film containing one or both of a dye or a pigment called a coloring layer is attached to the closed space side of the glass plate 9 to provide a color display function, and thus the glass substrate 9 is colored. Called a filter. Depending on the properties of the liquid crystal material, a polarizing plate is attached to either the upper surface of the glass substrate 9 or the lower surface of the glass substrate 2 or both surfaces, and the liquid crystal panel 1 functions as an electro-optical element.

FIG. 6 is an equivalent circuit diagram of an active liquid crystal panel in which an insulated gate transistor 10 is arranged as a switching element for each pixel. The element drawn by the solid line is formed on one glass substrate 2, and the element drawn by the broken line is formed on the other glass substrate 9. Scan line 11 and signal line 12
Is a thin film transistor 1 using, for example, amorphous silicon as a semiconductor layer and a silicon nitride film (Si ₃ N ₄ ) as a gate insulating film.
Simultaneously with the formation of 0, it is formed on the glass substrate 2. The liquid crystal cell 13 includes a transparent conductive pixel electrode 14 formed on the glass substrate 2, a transparent conductive counter electrode 15 formed on the color filter 9, and a closed glass plate composed of two glass plates. It is composed of liquid crystal that fills the space, and is electrically treated like a capacitor. In addition, in order to align the liquid crystal molecules in a predetermined direction, it is necessary to form an alignment film on the counter electrode and the pixel electrode, but the detailed description thereof is omitted here.

As described above, the colored layer made of colored photosensitive gelatin or colored photosensitive resin is arranged in the three primary colors RGB corresponding to the pixel electrodes on the closed space side of the color filter 9 according to a predetermined arrangement. The counter electrode 15 common to all the pixel electrodes is formed on the coloring layer in order to avoid voltage distribution loss due to the presence of the coloring layer.

In FIG. 6, the storage capacitor 16 is not always an essential component for an active liquid crystal panel, but it improves the utilization efficiency of the driving signal source, suppresses the stray parasitic capacitance failure, and operates at high temperature. Image flicker
It is effective for prevention and is appropriately adopted. 17 is a conductive path common to all storage capacitors 16, typically the counter electrode 15
And the conductive path 17 are connected and used.

As is well known, since an image display device is an object that is identified by a highly sensitive sensor, which is human vision, there are very severe restrictions on various image defects, not to mention line defects but point defects. Even in that case, it is very difficult to compare with CRT, in other words, it is a device with low yield and difficult to make. Further technological development will be needed in order for the yield to become extremely high and active type liquid crystal panels to be provided in a state close to that of non-inspection, and it will take some time, and similar to the silicon-based semiconductor process. As long as the manufacturing method is continued, no matter how much the yield is improved, it cannot be said to be 100% non-defective product.

A line defect is a defect that appears as a line on the screen, literally, and the reason for its occurrence is clearly caused by the causes described below.
(1) The scanning line or the signal line was broken on the way,
Mainly, (2) an electric signal does not reach the scanning line or the signal line, (3) the scanning line and the signal line are short-circuited, (4) a plurality of scanning lines or the signal line is short-circuited, etc. It is a factor.

Such a line defect is relatively easy to detect even before the two glass plates are bonded to each other to form a liquid crystal panel, that is, even in the state of the active matrix substrate, and the defect can be apparently made defect-free. It is possible. For example, in the case of disconnection, in addition to normal connection to electrode lines such as scanning lines and signal lines, the same signal may be applied from the other end via a relief line. On the other hand, if the short-circuited portion is cut with a laser or the like and converted into a broken wire of any of the electrode wires, a treatment equivalent to the broken wire can be performed.

On the other hand, the point defect inspection is equivalent to a full-bit inspection when compared to a semiconductor memory, and although it varies depending on the device structure, it is not hard to imagine that the inspection time is generally long and difficult. In fact, at the present time, it is the fact that point defects are also checked from the aspect of quality at the time of image inspection in the final process, and an inspection machine that can effectively detect point defects during the manufacturing process has not yet been put to practical use. Not not. It is an urgent task to reduce the point defects to improve the image quality.

FIG. 7 shows an equivalent circuit of an example of a first improvement measure implemented to reduce the influence of the above point defect on the display image. This is because an insulated gate type transistor, which is a switching element that constitutes a unit pixel, and a pixel electrode are divided into a plurality (two in FIG. 7) and arranged, and at least one set of insulated gate type transistors and picture elements is arranged. This is intended to ensure the display function with the element electrodes. It is easy to understand that in this improvement measure, the deterioration of the display image due to the point defect that cannot be controlled by the electric signal is alleviated as compared with the surrounding pixel in which the plurality of pixel electrodes are normally operating. See. The degree of relaxation is more effective as the number of divided picture elements is larger. However, when the number of divisions is increased, the space for separating the elements does not contribute to the display, and the reduction of the aperture ratio is inevitable, so that it is obviously restricted. In addition, although the white spot defect is alleviated in the case of the normally black display method, it is always lit when there is no signal, so it is very noticeable unless the pixel is very small, and the degree of relaxation of the black spot defect is high. It is unavoidable that the effect is evaluated low compared with.

In the configuration shown in FIG. 7, it is easy to shift the unit picture elements every other row by half a pitch as shown in FIG. 8 and arrange the RGB colored layers on the color filter in a delta (triangle) arrangement. There is an advantage that the apparent resolution can be secured even when the number is small. The disadvantage is that which of the two sets loses the display function cannot be identified unless a liquid crystal panel is used.

FIG. 9 shows an equivalent circuit of the second modification. This is two insulated gate transistors 10-1 and 10 in a unit pixel.
-2 are arranged diagonally, and one pixel electrode 13 is shared by two insulated gate transistors and driven. As an advantage, writing to the pixel electrode is maintained in the normal direction even when the current supply capability of any of the insulated gate transistors decreases. In addition, the two insulated gate transistors form a closed loop in series, and the electrical characteristics of the insulated gate transistor can be electrically inspected from the outside. In this case, if it is cut off from the regular wiring with a cutting means such as a laser, the same measure as described above can be taken.

The drawbacks of the above improvement measures are that the arrangement of the colored layers is limited to the oblique arrangement as shown in FIG. 10 in the case of displaying a color image, and the interference fringes are conspicuous when the number of picture elements is small. Next, in a strict sense, normal writing is not performed in the picture element in which the current supply capability of the insulated gate transistor has deteriorated, and it is visually deceptive due to the color signal of the adjacent picture element. It will be difficult to obtain a quality image. Therefore, even if it is acceptable as a television image, there remains a doubt as a display for OA that displays characters and figures.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above-mentioned first improvement measure, even if a plurality of insulated gate transistors, which are switching elements, are arranged to provide redundancy with respect to reduction in current capacity, the insulated gate transistors are provided. The problem that cannot be controlled due to an internal short-circuit cannot be detected in the active matrix substrate state, and eventually the presence of white spot defects cannot be detected if an image is displayed on a liquid crystal panel. I can't say.

Also, by irradiating the liquid crystal panel with a laser to separate the insulated gate transistor having an internal short circuit from the pixel electrode, it is possible to convert a white dot defect into a black dot defect although the success rate is low. When a plurality of type transistors are arranged, it is completely meaningless unless it is known which insulated gate type transistor the internal short circuit exists.

In the second improvement measure, even when a point defect occurs, a defect that is not displayed with a regular color signal cannot be corrected, and further improvement is required. Further, in this case, the insulated gate transistor does not form a closed loop by simply dividing the pixel electrode, which has the same drawbacks as in the first improved example. Even if the pixel electrode is divided, the pixel electrodes are connected. There is no point in splitting it.

Means for Solving the Problems The present invention has been made in view of the above-mentioned current situation, and scan lines and signals are provided so that the electrical characteristics of an insulated gate transistor, which is a switching element, can be evaluated on an active matrix substrate. Two sets of insulated gate transistors and pixel electrodes are diagonally arranged at each intersection with a line, and a temporary electrical connection is made between the two insulated gate transistors for driving using removable wiring materials. Then, the insulated gate transistor is electrically inspected to detect the position of the defective insulated gate transistor which is the main cause of point defects. Then, it is determined based on the information on the position and type of the characteristic defect whether or not to advance the active matrix substrate in the panel assembling process. Prior to proceeding to the panel assembly process, the temporary connection made of removable wiring material and the normal wiring are released so as not to adversely affect the normal wiring, and further, there is an internal short circuit by using a cutting means such as a laser. By disconnecting the insulated gate transistor and the pixel electrode from the defective characteristic, an active matrix substrate in which point defects are repaired is obtained.

In a further improved manufacturing method, the pixel electrode is formed after the electrical inspection of the two insulated gate transistors is completed, and the defective insulated gate transistors are selectively excluded so that only normal insulated gate transistors are formed. By forming the pixel electrode on the pixel electrode, it becomes possible to suppress the generation of point defects with extremely high accuracy.

The insulating gate type transistor for driving is formed as an active matrix substrate in a state of being temporarily connected using a removable wiring material between the two insulating gate type transistors so as to form a closed loop. Therefore, it is possible to inspect the transistor characteristics of all insulated gate transistors electrically independently from the outside. Therefore, the insulating gate type transistor for driving which has a defective characteristic or an internal short circuit is separated from the pixel electrode to promote the mitigation or suppression of the point defect. Since the wiring material used for the temporary connection is removed by an etching method selected so as not to affect other elements after the electrical inspection of the insulated gate transistor is completed, a secondary defect does not occur.

Practical Example FIG. 1 is an equivalent circuit of a liquid crystal panel having an active matrix configuration according to the first example of the present invention. As can be seen from the comparison with the conventional example in FIG. 9, the first address (n, m)
Once the active matrix substrate in which the connection line 20 is formed between the drain electrode of the insulated gate transistor 10-1 and the drain electrode of the second insulated gate transistor 10-2 at the address (n + 1, m + 1) , Electrical inspection in the inspection process. After the electrical inspection of the insulated gate transistor is completed, for example, the opening 21 formed including the connection line 20.
A pair of the pixel electrode and the insulated gate transistor is independent by means such as partially removing the connection line inside.

The insulated gate transistor 10 has a function of alternatingly charging and discharging the liquid crystal cell 13 as a switching element, and its source and drain cannot be uniquely defined, but here it is customary to supply a video signal. The one connected to the signal line is defined as the source, and the one connected to the pixel electrode is defined as the drain.

According to the circuit configuration of FIG. 1, the first driving insulated gate transistor 10-1 at the address (n, m) connected to the scanning line and the signal line at the address (n, m) is connected to the connection line 20. Via (n +
(N + 1, m) connected to the scan line and signal line at address 1, m + 1
A closed loop having a common drain with the second insulated gate transistor 10-2 at address +1) is formed. Therefore, if a DC voltage is applied between the two signal lines 12 (m) and 12 (m + 1) and the current value flowing therethrough is measured, the scanning with the two scanning lines 11 (n) The quality of the two insulated gate transistors can be determined by the magnitude of the DC voltage applied to the line 11 (n + 1). For example, a voltage sufficient to turn on the first insulated gate transistor 10-1 is applied to the scanning line 11 (n), and the second insulated gate transistor 10-2 is turned on to the scanning line 11 (n + 1). If a current flows between the signal lines 12 (m) and 12 (m + 1) when a voltage that does not apply is applied, it can be seen that the source and drain of the second insulated gate transistor 10-2 are short-circuited. . Also, although stochastic is extremely low, the source and drain of both of the insulated gate transistors are short-circuited as long as a current is flowing though a voltage that does not turn on is applied to the two scanning lines. Because you can see that In this way, if the scanning lines and the signal lines are combined two by two, the characteristics and internal short circuit of all the first insulated gate type transistors and the second insulated gate type transistors can be inspected.

The failure modes of the insulated gate transistor 10 are roughly classified into 1) the drain current is small with respect to a predetermined gate voltage, 2) the drain current constantly flows too much, 3) the gate and the drain are short-circuited (leakage), 4) There are four items, that is, the gate and the source are short-circuited (leakage). In the image display of the normally black display method,
In the case of 1), it becomes a black dot defect, in the cases of 2) and 3) it becomes a white dot defect, and in the case of 4), it becomes a cross-shaped line defect.

In the case of 1), the cause of the point defects irregularly occurring on each substrate is that the electrical contact between the pixel electrode, the insulated gate transistor and the source / drain wiring is unstable or lost. In some cases, the function of the insulated gate transistor may not be sufficiently exhibited due to the lack of the semiconductor layer. In case 2), the insulated gate transistor is turned off.
There are cases where the leakage current between the source and drain is too large and there is a case where the source and drain are short-circuited.
The former, which occurs as an abnormal film quality of the semiconductor layer in all insulated gate transistors, cannot cause point defects that occur irregularly on each substrate, and it is necessary to separately manage it by inspecting the monitor transistor. is there.

If all the defects of the insulated gate transistor can be known together with the generation address, the progress to the panel assembling process is determined as a good product, a defective product, or a recyclable product according to preset judgment criteria, and an expensive color filter is wasted. It can be avoided to consume. Since the unit pixel includes two driving insulated gate transistors in the first embodiment, as a reproducible failure mode, a cutting means such as a laser is used for the short circuit of 3) and 4). The target is a treatment for converting a white spot defect into a black spot defect. Needless to say, in the short circuit of 4), either the scanning line or the signal line must be cut to be converted into a disconnection, and a method for relieving the disconnection must be prepared at the same time.

It is difficult to say that the structure and manufacturing method of the insulated gate transistor have been established yet. Therefore, various structures and manufacturing methods of the active matrix substrate are conceivable.
An example of the pattern layout diagram corresponding to the figure is shown in FIG. A source line 22 and a drain line 23 made of, for example, Al are branched from the signal line 12. The drain wiring 28 is connected to the pixel electrode 14 below the insulating layer through an opening 24 formed in the insulating layer. The connection 20 between the drain electrode or the pixel electrode of the first and second insulated gate transistors 10-1 and 10-2 is formed by the connection pattern 25 made of, for example, Cr and formed in the same step as the scanning line 11. , The drain wiring 23 through the openings 26 and 27 formed in the insulating layer on the connection pattern 25.
And the adjacent picture element electrode 14-1.
The release of the connection 20 is achieved by removing the Cr exposed by the opening 21 on the connection pattern 25 formed at the same time as the openings 26, 27 with a Cr etching liquid containing cerium nitrate as a main component. The Cr etching liquid has a low acidity of PH5-6 and does not corrode the signal line and source / drain wiring made of Al.

A structure in which the pixel electrode 14 and the drain wiring 23 are directly connected instead of being connected via the opening 24 is also possible, and the connection pattern 25 is made of a material different from that of the scanning line 11. Although it is possible to do so, the above-mentioned process is optimal in the sense that the number of manufacturing steps does not increase.

FIG. 3 shows a pattern layout diagram of a unit picture element corresponding to the second embodiment of the present invention.

The connection pattern 28 corresponds to the connection pattern 25 of FIG.
An active substrate is manufactured by connecting the drain wirings of the first and second insulated gate transistors. As described above, after applying the electric signal from the outside to measure the characteristics of all the insulated gate transistors, the connection pattern material in the opening 21 formed on the connection pattern 28 is removed first,
The second insulated gate transistors 10-1 and 10-2 are made independent. After that, the pixel electrodes 14-1 and 14-2 are formed. To alleviate the point defect by avoiding the electrical connection between the defectively insulated gate transistor and the pixel electrode. There are two ways.

One method is to use insulated gate transistors 10-1, 10-
The second drain wiring is removed by a cutting means such as a laser, and then the pixel electrodes 14-1 and 14-2 are formed.
This has the advantage that it can be performed in parallel during electrical testing of insulated gate transistors, but there is no risk of side effects that occur during laser irradiation, such as scattered substances causing short circuits or protrusions elsewhere. It can not be said.

Another method is to form the pixel electrodes 14-1 and 14-2 having a missing portion on the basis of the electrical inspection result of the insulated gate transistor, and then to form the insulated gate transistors 10-1 and 10-2 and the pixel electrode 14 -1, 14-2 to avoid the connection. This can be easily performed by adopting a positive type photosensitive resin in the selective formation of the pixel electrodes and performing spot exposure corresponding to the electrical inspection result of the insulated gate transistor. Although it is troublesome to store and transfer the electrical inspection result of the insulated gate transistor so that it can be used at the time of spot exposure, there is no possibility of causing side effects such as laser cutting.

In FIG. 3, the pixel electrodes are shown by dotted lines in order to clearly show that the pixel electrodes are formed after the electrical inspection of the insulated gate transistor. It goes without saying that 29 is the drain electrode of the insulated gate transistor and must be of a material and structure that ensures ohmic contact with the pixel electrode.

FIG. 4 is a layout view of the colored layers on the color filter corresponding to the active substrate in each embodiment of the present invention. As can be seen from the comparison with FIG. 10, two colored layers located diagonally are one. Since the pixels are formed, the interference fringes are visually inconspicuous.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to electrically inspect all insulated gate transistors for driving, which are the main cause of point defects, in manufacturing an active matrix substrate that constitutes a liquid crystal panel. Two sets of insulated gate transistors and pixel electrodes are arranged at each intersection of the scanning line and the signal line, and the drain electrodes of the insulated gate transistors can be removed so that the two sets of insulated gate transistors form a closed loop. The pixel electrode is formed by excluding defective insulated gate type transistors after electrical inspection of the insulated gate type transistors as a further advanced manufacturing method. As a result, it is possible to roughly estimate the occurrence of point defects before converting the active matrix substrate into a liquid crystal panel, avoid the loss of wasted expensive color filters, and its industrial value is immeasurable. There is no such thing. Further, by forming the unit pixel with two sets of insulated gate transistors and pixel electrodes, the relaxation of point defects is promoted. Furthermore, because one pixel can be composed of two colored layers located diagonally,
The interference fringes are visually inconspicuous. In the most advanced form, the pixel electrode driven by the poorly-insulated insulated gate transistor loses its display capability, so that the alleviation of point defects is further promoted. In addition, excellent effects such as ensuring color reproducibility of display image quality at the point defect occurrence portion were obtained.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of an active matrix substrate according to the first embodiment of the present invention, FIG. 2 is a pattern layout diagram within a unit pixel in the same embodiment, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a layout view of patterns in FIG. 4, FIG. 4 is a layout view of colored layers on a color filter corresponding to each embodiment of the present invention, and FIG.
FIG. 6 is a perspective view showing mounting means on a liquid crystal panel, FIG. 6 is an equivalent circuit diagram of a conventional active type liquid crystal panel, and FIG. 7 is an equivalent circuit diagram of a liquid crystal panel in a first improvement measure against point defects. FIG. 8 is a layout view of the colored layer on the color filter, FIG. 9 is an equivalent circuit diagram of the liquid crystal panel in the second improvement measure against the point defect, and FIG. 10 is a layout view of the colored layer on the color filter. . 1 ... Liquid crystal panel, 2 ... Active matrix substrate,
9 ... Color filter, 10 ... Insulated gate type transistor, 11 ... Scan line, 12 ... Signal line, 13 ... Liquid crystal cell, 14
…… Pixel electrode, 15 …… Counter electrode, 20 …… Connecting wire, 21 ……
Opening, 22 …… Source wiring, 23 …… Drain wiring, 25,
28 …… connection pattern, 29 …… drain electrode.

Claims (4)

[Claims] 1. A pair of first and second driving insulated gate transistors and a pixel for sharing a gate electrode and a source electrode at each intersection of a scanning line (nth) and a signal line (mth). An electrode, and a drain electrode or pixel electrode of the first insulated gate transistor at address (n, m) and (n + 1, m +
1) The drain electrode or picture element electrode of the second insulated gate type transistor at the address is connected by a removable wiring material, each insulated gate type transistor is electrically inspected, and after the inspection is completed, the connection is released and the characteristics are A method for manufacturing an active matrix substrate, characterized in that the connection between a defective driving insulated gate transistor and a pixel electrode is released. 2. A pair of first and second driving insulated gate transistors having a common gate electrode and source electrode are formed at each intersection of a scanning line (nth) and a signal line (mth). ,
The drain electrode of the first insulated gate type transistor at the address (n, m) and the drain electrode of the second insulated gate type transistor at the address (n + 1, m + 1) are connected by a removable wiring material, and each insulated gate type The transistor is electrically inspected, the connection is released after the inspection is completed, and the pixel electrodes corresponding to all the insulated gate type transistors except the driving insulated gate type transistor with defective characteristics are formed. Matrix substrate manufacturing method. 3. The active matrix substrate according to claim 2, wherein a part of the pixel electrode is formed so as not to connect the pixel electrode to the insulated gate transistor having a poor characteristic. Manufacturing method. 4. The pixel electrode is formed after the defective insulating gate transistor is separated from the normal wiring by laser irradiation so that the pixel electrode and the defective insulating gate transistor are not connected to each other. The method for manufacturing an active matrix substrate according to claim 2.