JPH0696864A - Display device and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a dielectric breakdown between a metal wire and a transparent electrode by connecting conducting layers between picture elements with the metal wire via contact holes formed on an insulating layer on the conducting layer. CONSTITUTION:A ground (GND) electrode 8 connected to the ground level via the third and fourth insulating layers 7, 9 is provided between a thin film EL element and a thin film transistor. The electrode 8 is separately formed for each EL element, and a GND wire 18 is formed in the auxiliary scanning direction on the uppermost fifth insulating layer 20 of laminated insulating layers to connect each electrode 8 in the auxiliary scanning direction. The electrode 8 of each picture element is connected to the GND wire 18 via contact holes (a), (b) provided on insulating layers of the fourth insulating layer 9 and a gate insulating layer 12 and the fifth insulating layer 20. Insulating layers 5, 7, 9, 12, 20 are provided between the wire 18 and a transparent electrode 2 at a sufficient interval without being affected by irregularities of the transparent electrode 2 and a step between a metal electrode 6 and a luminescent layer 4, the withstand voltage of the insulating layers is improved, and the dielectric breakdown can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TFT drive active matrix type display device in which thin film EL elements are arranged in a matrix and driven by using thin film transistors (TFTs), and in particular, a ground separating the thin film EL elements from the thin film transistors. The present invention relates to a display device in which an electrode is an individual electrode for each pixel and the connection structure of each ground electrode is improved to improve the yield, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a display device using a thin film EL element has electrodes arranged in a matrix in the X and Y directions, and a voltage is applied to the electrodes in the X and Y directions from a driving circuit to emit light from pixels. A display device having a simple matrix structure is known.

However, in a simple matrix display device, when the number of pixels is as large as 2000 × 2000, the problem of crosstalk becomes large, making it difficult to cause many pixels to emit light, and red or blue light emission with low brightness. When using a color EL device as a display,
Since it has to be driven at a frequency corresponding to a color having low luminance, it has been difficult to colorize a display device using an EL element.

Therefore, an active matrix driving method has been considered in which a thin film transistor is used for each pixel so that the ON state of the pixel can be maintained between frames. In this method, the driving frequency and the frame of each pixel are
Since the EL frequency is independently controlled, the EL element can be driven at a high frequency, and red or blue light-emitting color EL elements having relatively low brightness can also be used as a display.

This TFT-driven active matrix type display device will be described. This display device is provided with a circuit for holding a signal in which a pixel is selected for each pixel (1 bit). By selecting light emission or non-light emission of each pixel by a signal line formed in a matrix. , Drives the entire display.

Next, the 1-bit EL drive circuit of the conventional display device will be described with reference to the EL drive circuit diagram of FIG. This EL drive circuit includes a first switching element Q1 composed of a thin film transistor (TFT).
A storage capacitor CS having one terminal connected to the source terminal S1 side of the switching element Q1 and a gate terminal G2 of the source terminal S of the first switching element Q1.
A second switching element Q2, which is connected to 1 and whose source terminal S2 is connected to the other terminal of the storage capacitor CS, and one terminal of which is the drain electrode of the second switching element Q2. It is composed of a thin film EL element CEL connected to D2 and the other terminal of which is connected to the EL drive power source Va, and a dividing capacitor CDV connected in parallel with the second switching element Q2.

The first switching element Q1 is turned on in response to the switching signal SCAN applied to the gate terminal G1, and the first switching element Q1 is turned on / off to charge the storage capacitor CS in response to the light emission signal DATA. It is designed to discharge. The second switching element Q2 is turned on when the discharge voltage from the storage capacitor CS is applied to the gate terminal G2, and the thin film EL element CEL is caused to emit light by the EL drive power source Va. The dividing capacitor CDV divides the voltage of the EL driving power source Va by the thin film EL element CEL and the dividing capacitor CDV when the second switching element Q2 is turned off.
The second switching element Q2 is provided so that the withstand voltage can be designed to be low.

When the thin film EL element and the thin film transistor are combined to form an active matrix type display, a structure in which the thin film EL element and the thin film transistor are arranged side by side and a thin film transistor on which the thin film EL element is formed are laminated. A type structure is possible. In that case, considering the display quality of the display device, the higher the aperture ratio that represents the ratio of the area of the light emitting portion to the total area including the non-light emitting portion and the light emitting portion, the higher the display quality, and the higher the aperture ratio. A laminated active matrix display is desired.

Next, the structure of one bit of the above-mentioned laminated TFT driving active matrix type display device will be described with reference to FIGS. 5 is a plan view of a conventional display device, and FIG.
FIG. 6 is a cross-sectional explanatory view of a portion BB ′ of FIG.

As shown in FIG. 5, in one bit (one pixel), a first switching element Q1, a second switching element Q2, a storage capacitor CS, a dividing capacitor CDV, and a thin film EL element. And CEL.

As shown in FIG. 6, a transparent electrode 2 made of indium tin oxide (ITO) or the like, a first insulating layer 3 made of a silicon nitride film (SiNx), on a transparent substrate 1 made of glass or the like, A thin film EL element CEL including a light emitting layer 4 of zinc manganese sulfide (ZnS: Mn), a second insulating layer 5 of SiNx, and a metal electrode 6 of chromium (Cr) or the like is formed.
A ground (G) is formed on the metal electrode 6 via a third insulating layer 7.
A ground (GND) electrode 8'connected to the ND) level is formed, and a portion sandwiching this third insulating layer 7 between the metal electrode 6 and the ground electrode 8'forms a divided capacitor CDV.

Further, two TFTs, a first switching element Q1 and a second switching element Q2, and a storage capacitor C are provided on the ground electrode 8'through a fourth insulating layer 9.
S is formed. The storage capacitor CS is formed by sandwiching the fourth insulating layer 9 between the ground electrode 8'and the electrode layer 10.

The TFTs of the two switching elements Q are composed of the gate electrode 11 and the gate insulating layer 1 on the fourth insulating layer 9.
2. The semiconductor active layer 13 and the channel protection film 14 are sequentially stacked, and the ohmic contact layer 15 and the diffusion prevention layer 16 are formed with the channel protection film 14 sandwiched therebetween. Here, the divided ohmic contact layer 15 and the diffusion prevention layer 16 are divided.
Form the source / drain electrodes. A wiring layer 17 for connecting the switching element Q to the storage capacitor CS and the like is formed.

In the structure of such a display device, a ground electrode 8'connected to the ground level is provided between the thin film EL element and the thin film transistor.
This ground electrode 8'is applied to the thin film EL element 200
In order to prevent the gate voltage of the thin film transistor provided above the thin film EL element from being affected by the AC voltage of V and preventing normal ON / OFF driving from becoming impossible, a thin film EL element and a thin film transistor are provided between the thin film EL element and the thin film transistor. It is arranged. This ground electrode 8'can shield each signal of the device from the AC voltage for EL driving.

When a plurality of 1-bit laminated type thin film EL elements and thin film transistors are arranged in a matrix form in the main scanning direction and the sub scanning direction as shown in the plan view of FIG. 7, a thin film transistor driven active matrix type display is provided. The device is formed.

Next, the outline of the conventional display device will be described with reference to FIG. 7. The data line (DATA LINE) for pixel selection has a shape extending in the sub-scanning direction of the pixel, and the light emitting portion of the thin film EL element. And the scan line (SCAN LINE) for line selection extends in the main scanning direction of the pixel, and is arranged between the light emitting unit and the light emitting unit of the thin film EL element. I was trying to do it.

The ground electrode 8'is formed so as to shield the TFT and DATA LINE from the transparent electrode 2 of ITO so as to shield the operation of the TFT from the AC voltage driving the thin film EL element. It is a common electrode in the scanning direction. Further, the ITO transparent electrode 2 is also formed in a strip shape in the main scanning direction.

In the above-mentioned conventional display device, the first insulating layer 3, the second insulating layer 5, and the third insulating layer 7 are provided between the ground electrode 8'and the transparent electrode 2 so as to interpose the second insulating layer 3 and the transparent electrode 2.
An AC voltage of 00 V is applied, and the strength of the electric field between the ground electrode 8 ′ and the transparent electrode 2 constitutes S which constitutes each insulating layer.
If the withstand voltage characteristic of iNx is about 4 MV / cm, the withstand voltage of the insulating layer will be sufficient and dielectric breakdown will not occur.

[0019]

However, in the above-mentioned conventional active matrix type display device driven by thin film transistors, the metal electrode 6 and the light emitting layer 4 to be the upper electrode of the thin film EL element are individually formed for each pixel and are adjacent to each other. Since there is a step at the end between pixels, the film thickness of the second insulating layer 5 and the film thickness of the third insulating layer 7 in the vicinity of the step portion are thin in the step of laminating the insulating layer. In addition, since the ITO transparent electrode 2 has an uneven surface property, a portion having a small film thickness is formed in the first insulating layer 3, and especially the ground indicated by an arrow in FIG. There is a problem that dielectric breakdown easily occurs in a portion between the electrode 8'and the transparent electrode 2, resulting in poor yield.

The present invention has been made in view of the above circumstances, in which the ground electrode is formed as an individual electrode for each pixel,
The ground electrodes are connected to each other between adjacent pixels by using the ground wiring on the uppermost layer of the insulating layers laminated via the contact holes, thereby sufficiently separating the ITO transparent electrode and the ground electrode. By avoiding dielectric breakdown,
An object of the present invention is to provide a display device capable of improving yield and a manufacturing method thereof.

[0021]

According to a first aspect of the present invention for solving the above-mentioned conventional problems, a thin film EL element having pixels arranged individually in a matrix, and the thin film EL element are driven. A thin film transistor formed on the thin film EL element via a conductive layer having a constant potential, wherein the conductive layer is formed in an individual shape for each pixel and is stacked on the conductive layer. The metal wiring for connecting the conductive layer between the pixels is provided through a contact hole formed in the insulating layer.

According to a second aspect of the present invention for solving the above-mentioned conventional problems, in a method of manufacturing a display device, thin film EL elements are arranged in a matrix in individual pixels, and a constant potential is provided on the thin film EL element. A conductive layer of each pixel is formed in an individual shape, an insulating layer is laminated on the conductive layer, a contact hole is formed on the insulating layer, and the contact hole is formed between the pixels via the contact hole. It is characterized in that a metal wiring for connecting the conductive layers is formed.

[0023]

According to the first aspect of the invention, the thin film E is provided for each pixel.
A thin film transistor is laminated on the L element, and a conductive layer having a constant potential provided between the thin film EL element and the thin film transistor is formed into an individual shape for each pixel, and a contact hole formed in an insulating layer on the conductive layer is used. Since the display device in which the conductive layer between the pixels is connected by the metal wiring is used, an insulating layer on the conductive layer can be interposed between the metal wiring and the thin film EL element. A sufficient distance from the transparent electrode can be secured, and the metal wiring and thin film EL
It is possible to prevent dielectric breakdown between the element and the transparent electrode and improve the yield.

According to the second aspect of the invention, the thin film EL elements are arranged in a matrix in individual pixels, and a conductive layer having a constant potential is formed on the thin film EL element in an individual shape for each pixel. The insulating layer is laminated on the insulating layer to form a contact hole on the insulating layer, and the metal wiring connecting the conductive layers between the pixels is formed through the contact hole. Since the metal wiring can be manufactured in the same process as the wiring connected to the electrode of the thin film transistor and the data line of the display device, which are formed by being laminated on the display device, the display device capable of preventing dielectric breakdown can be easily manufactured.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. 1 is a partial plan view of a display device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a portion AA 'in FIG. It should be noted that portions having the same configurations as those in FIG. 5 and FIG.

In one pixel of the display device of the present embodiment, as shown in FIG.
, A second switching element Q2, a storage capacitor CS, a dividing capacitor CDV, and a thin film EL element CEL.

Then, a data line for pixel selection (DA
TA LINE) is a shape extending in the sub-scanning direction of the pixel,
It is arranged between the light emitting portion of the thin film EL element and the scan line (SC for line selection).
AN LINE) is a shape that extends in the main scanning direction of pixels,
It was arranged between the light emitting portions of the thin film EL element.

Next, each part constituting one pixel of the display device of this embodiment will be described with reference to FIG. As shown in FIG. 2, the thin film EL element CEL comprises a transparent substrate 1 made of glass or the like, a transparent electrode 2 made of indium tin oxide (ITO), a first insulating layer 3 made of a silicon nitride film (SiNx), and a sulfide. Zinc manganese (ZnS: Mn) light emitting layer 4, S
iNx second insulating layer 5, chromium (Cr) metal electrode 6
Are sequentially laminated.

A Cr ground electrode 8 connected to the ground (GND) level via a third insulating layer 7 of SiNx is formed on the metal electrode 6, and the third insulating layer 7 is formed.
The portion sandwiched between the metal electrode 6 and the ground electrode 8 forms a divided capacitor CDV.

Further, a fourth layer of SiNx is formed on the ground electrode 8.
Through the insulating layer 9 of the first switching element Q1 and the second switching element Q1.
Two thin film transistors (T
FT) and a storage capacitor CS are formed. The storage capacitor CS is constructed by sandwiching the fourth insulating layer 9 between the ground electrode 8 and the electrode layer 10.

TFT which is two switching elements Q
Is formed on the fourth insulating layer 9 by the Cr gate electrode 11 and Si.
Nx gate insulating layer 12, intrinsic amorphous silicon (ia-Si) semiconductor active layer 13, Si
Nx channel protective films 14 are sequentially stacked, and n + amorphous silicon (n + a- is sandwiched between the channel protective films 14).
This is an inverted stagger type thin film transistor in which an ohmic contact layer 15 of Si) and a diffusion prevention layer 16 of Cr are formed. Here, the divided ohmic contact layer 15 and the diffusion prevention layer 16 form source / drain electrodes, a fifth insulating layer 20 of SiNx is laminated on this thin film transistor, and the switching element Q and the storage capacitor CS, etc. The wiring layer 17 for connecting the above is formed of aluminum (Al) or the like on the fifth insulating layer 20.

Further, in the structure of the display device, the ground (GND) electrode 8 connected to the ground level via the third insulating layer 7 and the fourth insulating layer 9 is provided between the thin film EL element and the thin film transistor. Has been. The ground electrode 8 is the thin film EL in this embodiment.
A ground (GND) wiring 18 of Al or the like is formed on the uppermost layer (upper part of the fifth insulating layer 20) of the stacked insulating layers in order to connect each ground electrode 8 in the sub-scanning direction separately formed for each element. It is formed in the sub-scanning direction. Ground wiring 1
Reference numeral 8 connects the ground electrode 8 of each pixel through the contact holes a and b provided on the fourth insulating layer 9, the insulating layer formed by the gate insulating layer 12 and the fifth insulating layer 20. ing.

Here, each ground electrode 8 serves as one electrode of the dividing capacitor CDV and the storage capacitor CS, and is provided on the upper portion of the thin film EL element by the AC voltage of 200V applied to the thin film EL element. It is arranged between the thin film EL element and the thin film transistor in order to prevent the gate voltage applied to the gate electrode 11 of the TFT from being affected and the normal ON / OFF driving being disabled. With this ground electrode 8, each signal of the device can be shielded from the AC voltage for EL driving.

If one thin film EL element pixel in which the thin film transistors are laminated is arranged in a matrix form in the main scanning direction and the sub scanning direction as shown in the plan view of FIG. 3, an active matrix for driving the thin film transistor of this embodiment is formed. Mold display device is formed.

The display device of this embodiment is
As shown in FIG. 3, scan lines (SCAN LIN
E) is formed between adjacent pixels of the thin film EL element with Cr or the like in the main scanning direction, and is arranged on the fourth insulating layer 9. In addition, the data line (DATA LI
NE) is disposed between adjacent pixels, is formed in the sub-scanning direction by Al or the like on the uppermost layer (upper part of the fifth insulating layer 20) of the laminated insulating layers, and is connected to the drain electrode of the TFT of the switching element Q1. It is configured to be. And GN
As with the data line (DATA LINE), the D wiring 18 connects the GND electrode 8 of each pixel in the sub-scanning direction.
It is formed by l.

According to the display device of this embodiment, G
Since the GND wiring 18 for connecting the ND electrode 8 is provided in the uppermost layer of the laminated insulating layers, it is directly influenced by the surface property of the unevenness of the transparent electrode 2 and the step difference of the metal electrode 6 and the light emitting layer 4. The second insulating layer 5, the third insulating layer 7, and the fourth insulating layer between the GND wiring 18 and the transparent electrode 2, and the GND wiring 18 and the transparent electrode 2 are sufficiently separated from each other. 9, insulating layer by gate insulating layer 12, fifth insulating layer 2
Since there are five insulating layers of 0, the withstand voltage of the insulating layer is improved, and dielectric breakdown can be prevented.

Next, a method of manufacturing the display device of this embodiment will be described with reference to FIG. On the glass substrate 1, ITO of a transparent electrode material is 0.1 μm by using a sputtering device.
The transparent electrode 2 is formed by a photolithography process after depositing a film of about m. Next, the first insulating layer under the thin film EL element
In order to form the insulating layer 3 of SiNx, a film of about 0.3 μm is deposited using SiNx. Then, ZnS: Mn that is the light emitting layer 4 is deposited to a thickness of about 0.4 μm using an EB vapor deposition device, and the light emitting layer 4 is formed by a photolithography process. Next, in order to form the second insulating layer 5 to be the insulating layer above the thin film EL element, SiNx is deposited to a thickness of about 0.3 μm by using a sputtering device, and the second layer is formed by photolithography process.
Both the insulating layer 5 and the first insulating layer 3 are simultaneously etched to form a contact hole (not shown) for connecting the transparent electrode 2 and the wiring from the driving power source Va. Then, Cr is deposited to a thickness of about 0.1 μm using a sputtering device, and the metal electrode 6 is formed by a photolithography process.

Next, SiNx is deposited to a thickness of about 0.8 μm by using a sputtering device, and a third insulating layer 7 is formed by using a photolithography process. A contact hole (not shown) for connecting the metal electrode 6 and the drain electrode D2 of the TFT of the switching element Q2 is formed in the third insulating layer 7.

Then, Cr is added to 0.1 using a sputtering device.
The film is deposited to a thickness of about μm, and the GND electrode 8 is formed by a photolithography process. Here, the GND electrode 8 is formed so as to have a predetermined shape that shields the gate electrode of the TFT from the transparent electrode 2.
In order to prevent the end of the GND electrode 8 from protruding beyond the end of the metal electrode 6 of the thin film EL element,
It is formed so as to be an individual electrode inside the metal electrode 6.

Next, SiNx is deposited to a thickness of about 0.4 μm using a sputtering apparatus, and a fourth layer is formed by a photolithography process.
The insulating layer 9 is formed into a predetermined shape. Here, contact holes a and b for connecting the GND wiring 18 to each GND electrode 8 are formed on the fourth insulating layer 9, and further, the source electrode S2 of the TFT of the switching element Q2 is the GND electrode. A contact hole (not shown) is formed for connecting with 8.

The TFT gates of the switching elements Q1 and Q2
Electrode 11, scan line and contact hole a,
Cr used as a metal layer for connection in b is deposited to a thickness of about 0.05 μm by using a sputtering device, and a metal for connection in the gate electrode 11, scan line and contact holes a and b is formed by a photolithography process. Form the layers. At this time, the scan line is arranged so as to pass between adjacent pixels of the thin film EL element.

Next, the SiNx layer to be the gate insulating layer 12 is made to have a thickness of about 0.3 μm, and i-a-S to be the semiconductor active layer 13 is formed.
The i layer (i layer) is about 0.1 μm, the SiNx layer to be the channel protection film 14 is about 0.15 μm, and plasma CVD is performed.
Continuous film formation is performed using the device. Then, the channel protection film 14 is formed by the photolithography process.

Next, n + of the ohmic contact layer 16 is formed.
An a-Si layer (n + layer) is deposited to a thickness of about 0.15 μm using a plasma CVD apparatus. Then, the n + layer and the i layer are simultaneously etched by a photolithography process. Then, the gate insulating layer 12 is etched by a photolithography process to form contact holes a and b for connecting the scan line and the GND electrode 8.

Further, Cr which becomes the diffusion prevention layer 16 of the TFT.
Is deposited to a thickness of about 0.15 .mu.m using a sputtering apparatus, and a metal layer for connection with the source / drain electrodes and the contact holes a and b is formed by a photolithography process. Then, after depositing a SiNx layer to be the fifth insulating layer 20 to a thickness of about 1.0 .mu.m and forming contact holes a, b, etc. by a photolithography process, the data line and the wiring layer 17, and the Al of the GND wiring 18 are formed. Is deposited to a thickness of about 1.0 μm using a sputtering device, and a data line, a wiring layer 17, and a GND wiring 18 are formed by a photolithography process. At this time, the data line arranges the adjacent pixels of the thin film EL element in the sub-scanning direction, and the GND wiring 18 also similarly connects the adjacent pixels in the sub-scanning direction in the sub-scanning direction via the contact holes a and b. The electrodes 8 are arranged so as to be connected. In this way, the display device of this embodiment is manufactured.

According to the manufacturing method of the display device of the present embodiment, the data line and the wiring layer 17 as well as the G of the individual electrode are formed.
Since the GND wirings 18 connecting the ND electrodes 8 can be simultaneously formed, there is an effect that a display device capable of preventing dielectric breakdown can be easily manufactured.

[0046]

According to the first aspect of the present invention, a thin film transistor is laminated on a thin film EL element for each pixel to form a thin film EL element.
A conductive layer with a constant potential provided between the element and the thin film transistor is formed into an individual shape for each pixel, and the conductive layer between the pixels is connected by metal wiring through a contact hole formed in the insulating layer on the conductive layer. Since the display device is used, since an insulating layer on the conductive layer can be interposed between the metal wiring and the thin film EL element, a sufficient distance can be secured between the metal wiring and the transparent electrode of the thin film EL element. Further, there is an effect that the dielectric breakdown between the metal wiring and the transparent electrode of the thin film EL element can be prevented and the yield can be improved.

According to the second aspect of the present invention, the thin film EL elements are arranged in a matrix in individual pixels, and a conductive layer having a constant potential is formed on the thin film EL element in an individual shape for each pixel. The insulating layer is laminated on the insulating layer to form a contact hole on the insulating layer, and the metal wiring connecting the conductive layers between the pixels is formed through the contact hole. Since the metal wiring can be manufactured in the same process as the wiring connected to the electrode of the thin film transistor and the data line of the display device, which are formed by stacking on the display device, it is possible to easily manufacture the display device capable of preventing dielectric breakdown.

[Brief description of drawings]

FIG. 1 is a partial plan view of a display device according to an exemplary embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view of a portion AA ′ in FIG.

FIG. 3 is a plan external view of the display device according to the present embodiment.

FIG. 4 is a 1-bit EL of a conventional display device.
It is a drive circuit diagram.

FIG. 5 is a partial plan view of a conventional display device.

FIG. 6 is a cross-sectional explanatory view of a portion BB ′ in FIG.

FIG. 7 is a plan external view of a conventional display device.

[Explanation of symbols]

1 ... Substrate, 2 ... Transparent electrode, 3 ... First insulating layer, 4
... Light-emitting layer, 5 ... Second insulating layer, 6 ... Metal electrode, 7
... third insulating layer, 8 ... ground electrode, 9 ... fourth insulating layer, 10 ... electrode layer, 11 ... gate electrode, 12 ...
Gate insulating layer, 13 ... Semiconductor active layer, 14 ... Channel protective film, 15 ... Ohmic contact layer, 16 ... Diffusion prevention layer, 17 ... Wiring layer, 18 ... Connection line, 20 ...
Fifth insulating layer

Claims (2)

[Claims] 1. A thin film EL element having individual pixels arranged in a matrix and a thin film transistor formed by driving the thin film EL element and laminating the thin film EL element via a conductive layer having a constant potential. In the display device having, the conductive layer is formed in an individual shape for each pixel, and the conductive layer between the pixels is connected via a contact hole formed in an insulating layer laminated on the conductive layer. A display device provided with metal wiring for connection. 2. A thin film EL element is arranged in a matrix in individual pixels, a conductive layer having a constant potential is formed on the thin film EL element in an individual shape for each pixel, and an insulating layer is laminated on the conductive layer. Then, a contact hole is formed on the insulating layer, and a metal wiring for connecting the conductive layer between the pixels is formed via the contact hole.