JP3505369B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a device for protecting a surge invading a terminal in a liquid crystal display device including a driving circuit and made of TFTs. is there.

[0002]

2. Description of the Related Art Recently, as liquid crystal display devices, attention has been paid to low power consumption, thinness and light weight, high-definition images, etc., and liquid crystal display devices employing TFTs have been actively researched. In particular, aS
Although i and poly-Si are the main components, poly-Si has been focused and put to practical use from the viewpoint of mobility, aperture ratio, number of process steps, and the like.

For example, FIG. 4 is a schematic plan view of a liquid crystal display device, in which a plurality of wiring lines extending left and right are gate lines 10 and a plurality of wiring lines extending vertically are drain lines 11. is there. The gate lines and the drain lines form matrix-shaped intersections, and the display electrodes 12 and the TFTs 13 electrically connected to the display electrodes 12 form a pair to form a display area.

On the other hand, the glass substrate 14 on which these are formed
Terminals 15 are arranged as a group on one side of the liquid crystal display device, and a driving circuit for driving the liquid crystal display device, here, the precharge driver 1 is provided between the terminal group 15 ... And the display area.
6 is formed, and the drain driver 1 is provided on the opposite side.
7 are formed. Further, gate drivers 18 are formed on the left and right sides.

The gate driver 18 has wirings 19 and 2 to which a vertical clock signal and a vertical start signal are input.
0, wirings 21, 22 and 23 to which a horizontal clock signal, a horizontal start signal and a video signal are input to the drain driver 17, and wirings to which a precharge signal and a gate control signal are input to the precharge driver 16. 24 and 25 extend around the substrate 14 and are connected to the terminals 15.

When the vicinity of the terminal 15 of the substrate 14 having these structures is enlarged, the structure as shown in FIG. 5 is formed, and a protection transistor for surge absorption is formed at the terminal, which is equivalently shown in FIG. Is. Here, the solid line is the drain electrode of the TFT forming the display area, that is, Al.
Further, the alternate long and short dash line is formed in the lower layer of Al of poly-Si which becomes the semiconductor layer of the TFT which constitutes the display area. Also,
The alternate long and two short dashes line is Cr that constitutes the gate of the TFT and is arranged in the lower layer of poly-Si. Further, the portion indicated by X is a contact.

First, the wiring 30 is formed by extending the terminal 15 of FIG. 4 and is made of Al.
In order to avoid the intersection with the ground line Vss after passing through 1, the Cr wiring 32 extended to the lower layer is used for crossover. Further, a Cr gate 35 is formed so as to extend from one region of the Vss line to the upper Al wiring 34 through the poly Si resistor 33 and then extend to the lower layer. Further, on the upper layer of the Cr gate 35, the semiconductor layer 37 of the transistor 36 for absorbing surge, that is, poly-Si is formed. Also, the drain electrode 3 of the transistor 36
A transistor 40 is formed from 8 through a poly-Si resistor 39, and a gate 44 of the transistor 40 is connected to an extended wiring 30 'from the terminal. The extended wiring 30' is connected to a semiconductor layer 45 made of poly-Si. I have a contact. Further, this extended wiring 30 'has a poly-Si resistor 42, is extended to a lower layer by a Cr wiring 43 in order to avoid crossing with the power supply line VDD, is cross-overed, and is extended wiring 30''.
For example, it has been extended to precharge drivers.

[0008]

In this structure, the poly-Si resistors 31 and 42 are provided for blunting the waveform when an abnormal pulse (surge) is applied. If it is too large, the poly-Si resistance is melted and the extended wirings 30 and 30 ′ or the extended wirings 30 and 30 ″ are disconnected, and the terminals provided in front of the extended wiring 30 are broken. There is a problem in that the signal input to is not transmitted to the wiring 30 ″ and thus does not function as a liquid crystal display device.

[0009]

The present invention has been made in view of the above-mentioned problems, and firstly, the first line intersecting the power supply line and the ground line is formed in a layer lower than the first line. A gate material to be formed into a crossover structure, and a first wiring extending between the two intersections,
The problem is solved by using an electrode made of an Al electrode and integrally formed so as to project from the first wiring as the common electrode of the first bottom gate type TFT and the second bottom gate type TFT. is there.

Since the active element connected to the display electrode, which is the bottom gate in this case, is used, it is possible to reduce the resistance value of the wiring extending from the terminal by using a gate material having a resistance value lower than that of poly-Si. Yes, and contacts C1 and C
Since the common electrode can be formed immediately after taking only the space for 2, the poly-Si10 forming the semiconductor layer of the transistor can be formed.
It can be melt-fused on the side of 9, 112.

Secondly, the wiring intersecting the power supply line and the ground line has a crossover structure with a gate material formed in a layer lower than the wiring, and in the wiring to which the video signal is input, the power supply line is used. This is solved by forming a crossover structure with the gate material formed in the lower layer for the ground line and the ground line. Generally, Cr, tantalum, etc. are used as the gate material, and poly-Si
Although the resistance value is smaller than that of Al, the resistance value is higher than that of Al, so that there is a problem that the most important video signal for display is dulled. However, if the wiring is made of Al and the power supply line VDD and the ground line Vss have a crossover structure using a gate material, the extended wiring can further reduce its resistance value and, at the same time, the video signal You can also suppress blunting.

Thirdly, Cr is excellent as a gate material because it is excellent in corrosion resistance and the like and has a relatively small resistance value. If this is used as a crossover material, it can be realized without increasing the number of steps. Fourth, extended wiring and V
By forming a non-doped semiconductor layer at the intersection of the DD line, the extended wiring and the Vss line, it is possible to prevent the surge from entering the drive circuit without passing through the transistor.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, the conventional example has been described, but the planar arrangement will be described with reference to FIG. A plurality of wirings extending to the left and right are the gate lines 10 made of Cr, and a plurality of wirings extending vertically are the drain lines 11 made of Al. And two kinds of lines 10, 1
1, the intersections are formed in a matrix, and the display electrodes 12 each made of ITO and the TFTs 13 electrically connected to the display electrodes 12 form a pair to form a display area.

On the other hand, the glass substrate 14 on which these are formed
Terminals 15 are arranged as a group on one side of the liquid crystal display device, and a driving circuit for driving the liquid crystal display device, here, the precharge driver 1 is provided between the terminal group 15 ... And the display area.
6 is formed, and the drain driver 1 is provided on the opposite side.
7 are formed. Further, gate drivers 18 are formed on the left and right sides. However, the positions of the drain driver and the precharge driver may be exchanged, or the gate driver may be formed integrally on one side.

Then, the Al wiring 1 to which the vertical clock signal and the vertical start signal are inputted to the gate driver 18.
Reference numerals 9 and 20 denote drain drivers 17 and Al wirings 21, 22, and 23 to which a horizontal clock signal, a horizontal start signal, and a video signal are input. Precharge drivers 16 receive precharge signals and gate control signals. The Al wirings 24 and 25 are connected to the terminal 15 while rotating around the substrate 14.

Before explaining the pattern of FIG. 1, the sectional structure of the liquid crystal display device will be described. An alkali-free glass 50 is used as the first transparent substrate, on which a gate 51 of a transistor and a gate line integral therewith are formed, and an auxiliary capacitance electrode 52 of the same material is formed. Here, the corrosion resistance and the resistance value are taken into consideration, Cr is adopted, and the taper structure is adopted considering the film breakage on this.

Further, Si is formed on the entire surface by plasma CVD.
An oxide film 53 and a Si nitride film 54 are formed, and a poly-Si 55 patterned so as to extend to the transistor region and the auxiliary capacitance region is provided. Here, the impurity P is introduced into the poly-Si, and the low concentration N− type source / drain regions 57 and 58 and the high concentration N + type contact region 5 are formed.
9 and 60 are formed. Further, the channel region 56 of the transistor is provided with a mask 61 of Si oxide film in order to prevent this impurity.

Here, the auxiliary capacitance is a poly-Si N + type contact region 6 extending to the auxiliary capacitance electrode 52.
0, a storage capacitor electrode 52 and an insulating layer 53 made of Cr,
It is composed of 54. Furthermore, plasma CVD on the entire surface
The Si oxide film 62 and the Si nitride film 63 by the method
A part of the contact region 59 is opened to form a contact hole, and an Al drain electrode 64 is provided.
In addition, a flattening film 65 that fills the irregularities having the structure described above is provided on the entire surface, and a display electrode 66 made of ITO is provided through a contact hole where a part of the contact region 60 is exposed.
Is provided.

On the other hand, on the second transparent substrate 70, IT
A counter electrode 67 made of O is provided. Also, here, for color display, R, G, B color filters 6
8 is provided in a region corresponding to the display electrode 66, and a light shielding film 69 is provided around the region. Further, if necessary, it may be provided before the counter electrode 67 is provided in order to flatten the unevenness.

Alignment films 71 and 72 are provided on the transparent substrates 50 and 70 having the above-mentioned structure, the transparent substrates are arranged to face each other, and a sealing material is provided between them, which is a part of the sealing material. Liquid crystal is injected through the injection hole to complete the liquid crystal display device. The point of the present invention is how to construct a transistor for surge absorption by utilizing the material used for the configuration of FIG. 3, and a specific example thereof will be described below.
Will be described with reference to.

First, the relationship between the transistor 101 connected to the terminal 100 and the extended wiring 104 '' will be described. Similar to the conventional example, it is manufactured using the constituent elements of FIG. 3, the solid line is Al, the one-dot chain line is poly-Si, and the two-dot chain line is C.
It consists of r. The terminal 100 may be composed of an Al electrode, and Cr may be laminated on the lower layer or ITO may be laminated on the upper layer. The Al extended wiring 104 electrically connected to the terminal 100 is connected via a lower layer extended wiring 105 made of Cr,
This extended wiring 10 is connected to the extended wiring 104 ′ of Al.
4'is again connected to the Al extended wiring 104 '' via the Cr lower layer extended wiring 106.

Insulating layers 53 and 54 of FIG. 3 are provided on the upper layers of the lower layer extended wirings 105 and 106, and the Vss line of Al and Al extending from the top to the bottom with respect to the paper surface of FIG.
VDD line is provided. When the Vss line crosses the lower layer extended wiring 105, the gate of the transistor 107, here the Cr gate 108, is connected, and the Cr gate 108 is covered with the semiconductor layer 109 made of poly-Si. . Here, the transistor is N
Since it is a channel, N-type impurities are introduced except for the region corresponding to the gate 108. And poly-Si
The insulating layer 62, 63 shown in FIG. The Vss line of Al is provided as a source electrode, and a part of the extended wiring 104 'is provided so as to project in parallel with the VDD line, and the Al electrode 110 serves as a drain electrode and is in contact with the semiconductor layer through the contact hole. Also V
When the DD line crosses the lower layer extended wiring 106, the gate of the transistor 101, here the Cr gate 111, is connected. On top of this Cr gate 111, poly S
A semiconductor layer 112 of i is covered. Since the transistor is a P-channel type here, the gate 11
P-type impurities are introduced except for the region corresponding to 1. The insulating layer 6 shown in FIG. 3 is formed on the poly-Si 112.
2, 63 are covered, the Al VDD line serves as a source electrode, and the Al electrode 110 in which a part of the extended wiring 104 ′ extends serves as a drain electrode, and contacts the semiconductor layer through a contact hole. There is.

The feature of the present invention is that the extended wirings 104 to 10 are provided.
At 4 ″, without using poly-Si resistor, transistor 1
The noise is absorbed by 01 and 107. Instead of using poly-Si as a resistor, a gate material is used where crossover is required. In addition, Al electrode 1
10 extends in parallel with the VDD line and has a contact hole C
After passing the height of 1 and C2
Since it is formed as a common electrode of Nos. 1 and 107, the surge can be absorbed by the transistor without being blown out at the extended wirings 104 to 104 ″. In addition, even if a surge that melts the poly-Si resistance as in the conventional case enters, the semiconductor layer (poly-Si) of the transistor melts and the signal applied to the terminal is connected to the extended wiring. Is transmitted to the drive circuit. Therefore, the displayable normal operation period can be extended.

On the other hand, the transistor connected to the terminal 102 and its configuration will be described. The Al extension wiring 120 extending to the drive circuit is extended to the drive circuit integrally with the common electrode 121 without providing a lower layer wiring. On the contrary, the Vss line of Al and the VDD line of Al are connected via the lower wirings 122 and 123 of Cr. Further, the Cr gate of the transistor 124 is formed after the Cr lower layer wiring 122 contacts the upper layer Vss line. Insulating layers 53 and 54 are formed on the Cr gate.
And a poly-Si layer 125 to be a semiconductor layer of the transistor is formed thereon. Then, again the insulating layer 6
The Vss line provided on the upper layer via the electrodes 2, 63 serves as the source electrode, and the common electrode 121 serves as the drain electrode, and is in contact with the semiconductor layer through the contact hole. Further, the VDD line also crosses over via the lower layer wiring 123, and the VDD line rising to the upper layer again is C.
It is in contact with the r gate 126. The insulating layers 53 and 54 are formed on the gate of the transistor 124, and the insulating layers 62 and 63 are formed on the semiconductor layer 127.

In this structure, the extended wiring 120 extending from the terminal 102 to the drive circuit is not crossed over to the lower layer, but instead the Vss line and the VDD line are crossed over to the lower layer. Therefore, the extended wirings 104 to 1 above
The resistance value can be further reduced as compared with 04 ″. Therefore, unlike the conventional structure, since the poly-Si resistance is not adopted, the extended wiring is not easily blown out, and even if a surge that blows out the poly-Si resistance as in the conventional case enters, the transistor Only the semiconductor layer is destroyed, and the signal applied to the terminal is transmitted to the drive circuit in the extended wiring. Therefore, the displayable normal operation period can be extended.

In the present invention, since the fluctuations of Vss and VDD and the fluctuations of the video signal are the most important, the terminal for receiving the video signal adopts the structure described in the terminal 102 below, and otherwise Employs the structure described for terminal 100 above. In fact, it is designed so that the poly-Si semiconductor layer melts when an abnormal pulse enters the protective transistor. However, since the wiring between the terminal and the drive circuit extends around the panel as shown in FIG. 4, the waveform is blunted by the time it reaches the drive circuit, and the drive circuit is hardly destroyed.

Further, the intersection of the Cr and Al wirings in FIG.
Poly-Si is formed. By installing this poly-Si, sparks at this intersection can be prevented.

[0028]

As is apparent from the above description, the first
In addition, a resistance value can be lowered by forming the extended wiring that intersects the power supply line and the ground line into a crossover structure with a gate material formed in a layer lower than the extended wiring, and the common electrode Since it is in the immediate vicinity, it is possible to prevent the extended wiring between the terminal and the drive circuit from being blown.

In particular, the active element connected to the display electrode is
Since it is a bottom gate, by using a gate material having a resistance value lower than that of poly-Si, it is possible to prevent melting of the extended wiring extended from the terminal. Secondly, the extended wiring that intersects the power supply line and the ground line has a crossover structure with a gate material formed in a layer lower than the extended wiring, and the extended wiring connected to a terminal to which a video signal is input. In the wiring, the power supply line and the ground line have a crossover structure with the gate material formed in the lower layer, so that the video signal can be protected without blunting.

As the gate material, Cr, tantalum or the like is generally used, and its resistance value is smaller than that of poly-Si, but its resistance value is higher than that of Al, so that the most important video signal for display is lost. Although there is a problem, the extended wiring remains Al and the power supply line VDD and ground line V
If ss is made to have a crossover structure using a gate material, the extended wiring is not melted and the video signal is not dulled.

Thirdly, Cr is excellent as a gate material because it is excellent in corrosion resistance and the like and has a relatively small resistance value. If it is used as a crossover material, it can be realized without increasing the number of steps. Fourth, extended wiring and V
By forming a non-doped semiconductor layer at the intersection of the DD line, the extended wiring and the Vss line, it is possible to prevent the surge from entering the drive circuit without passing through the transistor.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a protective element used in a liquid crystal display device of the present invention.

FIG. 2 is a diagram illustrating an equivalent circuit of FIG.

FIG. 3 is a cross-sectional view illustrating a liquid crystal display device.

FIG. 4 is a diagram illustrating a substrate on a side where a transistor of a liquid crystal display device is formed.

FIG. 5 is a diagram illustrating a conventional protection element.

FIG. 6 is a diagram illustrating an equivalent circuit of FIG.

Claims (3)

(57) [Claims] 1. A first transparent substrate, a display region which is provided on the first transparent substrate, and which includes a plurality of bottom gate type TFTs and a plurality of display electrodes connected thereto, and one of the first transparent substrate. A plurality of terminals formed on a side edge, a driving circuit provided between the plurality of terminals and the display region, a wiring electrically connecting the terminals and the driving circuit, and a crossing of the wiring. Between a power line of the same layer and a ground line of the same layer, a first bottom gate type TFT for surge absorption connected between the wiring and the power line, and between the wiring and the ground line The connected second bottom-gate TFT for absorbing surge, the second transparent substrate, the counter electrode provided on the second transparent substrate, the first transparent substrate and the second transparent substrate. The alignment film provided and the first In a liquid crystal display device having a liquid crystal sealed between a transparent substrate and the second transparent substrate via a sealing material, the wiring connected to the terminal for inputting a video signal.
Power line and ground line corresponding to the intersection with
Is connected by the gate material formed below this wiring
It is, in the intersections of the power supply line and the ground line
Connected to the above-mentioned terminal to input other than the corresponding video signal.
The wiring is connected with the gate material in the layer below this wiring.
Are continued, a first wiring extending between the second intersection of the first intersections of the power supply lines the ground line is made of Al electrode protrudes from said first wiring The electrodes integrally provided are the first bottom gate type TFT and the second bottom gate type TFT.
The liquid crystal display device, which is used as a common electrode of the bottom gate type TFT. 2. The liquid according to claim 1, wherein the gate is made of Cr.
Crystal display device. 3. A non-doped semiconductor layer at the intersection.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed.