JPH04260374A - Image display device and its manufacture - Google Patents

Abstract

PURPOSE:To enable short-circuiting between vertical signal lines and that of a vertical signal line and a picture element electrode to be eliminated and picture quality to be improved in an image display device. CONSTITUTION:A picture element electrode 6 which is extended from a drain region of a thin-film transistor 2 consists of a single layer and is formed on an insulating substrate 1 through a first insulating film 5. A second insulation film 8 is formed on the picture element electrode 6 and the first insulating film 5 where no picture element electrode 6 is formed and the first and second insulating films 5 and 8 are etched simultaneously, thus enabling a window for the source region to be provided. A vertical signal line 7 is provided at that window.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device formed using thin film transistors on an insulating substrate and a method for manufacturing the same.

0002

2. Description of the Related Art A conventional image display device will be explained below. FIG. 3 shows a cross-sectional structure of a pixel portion of a conventional liquid crystal image display device. As shown in the figure, a switching thin film transistor (hereinafter referred to as TF) made of polysilicon is mounted on a quartz substrate 11.
A gate electrode 14 made of polysilicon is provided on the TFT 12 with a gate oxide film 13 interposed therebetween. 15 is BPSG (boron-phosphosilicate glass)
The pixel electrode 16 made of polysilicon and aluminum for contact are connected to the drain region of the insulating film. In the source region, an Al (aluminum) signal line 17 is connected via a polysilicon layer similarly to the drain region.
is provided, and SOG (Spin-on-Glave) is provided on the entire surface.
ss) A protective film consisting of a film 18 is formed.

0003

[Problems to be Solved by the Invention] In such a conventional image display device, after forming a polysilicon pixel electrode,
There is a problem in that the polysilicon pixel electrode is also etched during etching to remove silicon residue when forming the l wiring.

The present invention solves the above problems and has a structure in which a second insulating film is provided on a pixel electrode formed of a polysilicon thin film, and when removing silicon residue after Al etching, polysilicon is removed. An object of the present invention is to provide an image display device in which silicon pixel electrodes are not etched, and a method for manufacturing the same.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides that a pixel electrode extending from the drain region of a thin film transistor is made of a single layer by directly contacting the drain region through a contact window, and the pixel electrode is made of a single layer. the second on the electrode
An insulating film is provided, and a vertical signal line is provided connected to a source region through a contact window formed in the first and second insulating films.

[0006]

[Operation] Since the present invention forms the second insulating film on the polysilicon pixel electrode with the above-described structure, the Al vertical signal line is deposited and etched after the second insulating film is formed on the pixel electrode. In order to do this, not only is the polysilicon pixel electrode not damaged, but also A
Short-circuits between vertical signal lines and short-circuits between Al vertical signal lines and polysilicon pixel electrodes are also eliminated.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional structural diagram of an image display device according to an embodiment of the present invention. 1 is a quartz substrate, 2 is a polysilicon TFT, 3 is a gate oxide film, 4 is a gate electrode, 5 is a BPSG film, 6 is a polysilicon pixel electrode, 7 is an Al (aluminum) vertical signal line, and 8 is an NSG (non-doped) 9 is an SOG film.

Next, a method for manufacturing an image display device according to the present invention will be explained. As shown in FIG. 2(a), a polysilicon film of 1800 Å is grown on a quartz substrate 1 by low pressure CVD, and etched leaving only the portion that will become the TFT 2. Next, as shown in FIG. 2(b), a gate oxide film 3 with a thickness of 1200 Å and a gate electrode 4 made of polysilicon are patterned. Then, impurities such as phosphorus ions are implanted using self-alignment. Next, as shown in FIG. 2C, a first insulating film 5 made of a BPSG film with a thickness of 9000 Å is grown, a contact hole is made in the drain region, and a polysilicon pixel electrode with a thickness of 500 Å is grown. Further, phosphorus ions are implanted into the entire surface of the polysilicon pixel electrode 6 and patterned into the shape of the electrode. Next, as shown in Figure 2(d), N
A second insulating film 8 made of SG with a thickness of 500 Å is grown,
After forming a contact hole at once by combining the first and second insulating films on the source region, Al(Al-Si:0.
A vertical signal line 7 is formed by etching. Further, the remaining silicon is removed by wet or dry etching. Finally, an SOG film 9 is applied to the entire surface to form pixels as shown in FIG.

The pixel portion formed as described above uses a polysilicon thin film as the pixel electrode. Since the electrode is provided on the first insulating film 5, the electrode is located closer to the liquid crystal part than a conventional pixel electrode, and an electric field can be effectively applied to the liquid crystal. Further, a second insulating film 8 is formed on the pixel electrode.
By providing the polysilicon pixel electrode 6, the polysilicon pixel electrode 6 will not be etched by wet etching when removing the silicon residue after Al etching, and furthermore, the Since there is no Al, there is no large step part, and the orientation of the liquid crystal in the pixel area is improved, improving the quality of the displayed image.

Note that in this embodiment, polysilicon TFT
2 has a single gate, but other configurations may be used. Furthermore, polysilicon TFT2 may be a P-channel transistor. Further, the first and second insulating films are not limited to those in the embodiment. Further, the polysilicon pixel electrode 6 may have a large number of holes formed in a mesh shape or may be formed in a stripe shape in order to improve transmittance.

0012

As described above, in the present invention, the pixel electrode extending from the drain region of a thin film transistor is in direct contact with the drain region through the contact window, and is formed of a single layer, and a second insulating layer is formed on the pixel electrode. The structure includes a vertical signal line connected to the source region through a contact window formed in the first and second insulating films.
Wet etching when removing silicon residue after aluminum etching eliminates damage to the polysilicon electrode, and since there is no aluminum in the drain area where it connects to the pixel electrode, there is no large step part, and the alignment of the liquid crystal is improved. Therefore, an image display device with improved image quality can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a pixel portion of an image display device according to an embodiment of the present invention.

[Fig. 2] Cross-sectional view showing the manufacturing process of the image display device

[Figure 3
] Cross-sectional view of a conventional image display device

[Explanation of symbols]

1 Quartz substrate (insulating substrate) 2 Polysilicon TFT (thin film transistor) 3
Gate oxide film 4 Gate electrode 5 BPSG film (first insulating film) 6 Polysilicon pixel electrode (pixel electrode) 7 Al vertical signal line (vertical signal line) 8 NSG film (second insulating film) 9 SOG film (protection film)

Claims (2)

[Claims] 1. A thin film transistor formed on an insulating substrate, a vertical signal line connected to a source region of the thin film transistor, and a vertical signal line extending from a drain region of the thin film transistor and formed through a first insulating film. an image display device having at least a pixel electrode, the pixel electrode extending from the drain region of the thin film transistor is in direct contact with the drain region through a contact window and is formed of a single layer, and a second insulating layer is provided on the pixel electrode. An image display device characterized in that a film is provided, and the vertical signal line is connected to the source region through a contact window formed in the first and second insulating films. 2. A step of forming a polysilicon thin film to serve as a thin film transistor region on an insulating substrate, a step of forming a gate electrode on a predetermined portion of the polysilicon thin film via a gate insulating film, and masking the gate electrode. a step of implanting impurities to form a source region and a drain region, and a first step of implanting impurities on the insulating substrate, polysilicon thin film, etc.
forming a contact window in a portion of the first insulating film corresponding to the drain region;
A process of forming polysilicon connected to the drain region through the contact window and implanting impurities to form a pattern of a polysilicon pixel electrode, and forming a second insulating film on the pixel electrode and the first insulating film, etc. a step of forming a contact window in a portion of the first and second insulating films corresponding to the source region; and a step of patterning a vertical signal line connected to the source region through the contact window. , its vertical signal line and the second
A method for manufacturing an image display device, comprising at least the step of forming a protective film on an insulating film or the like.