JPH04299837A - Manufacture of active matrix liquid-crystal display - Google Patents

Abstract

PURPOSE:To manufacture a liquid-crystal display which does not contain any surface defect by removing particles, foreign bodies and the like. CONSTITUTION:A first gate insulating film is formed; after that, a substrate is irradiated with ultraviolet rays; ozone is generated; particles which have been produced during the formation of the first gate insulating film, organic foreign bodies due to a cleaning defect and the like are oxidized and decomposed. A second gate insulating film and a semiconductor layer are formed; after that, ultraviolet rays are irradiated again; particles, foreign bodies and the like are oxidized and decomposed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an active matrix liquid crystal display, and more particularly, to a method for manufacturing an active matrix liquid crystal display characterized by a method for manufacturing an amorphous silicon thin film transistor array substrate.

0002

2. Description of the Related Art FIG. 3 is a cross-sectional view of an active matrix liquid crystal display incorporating a thin film transistor (hereinafter referred to as "a-SiTFT") using amorphous silicon, and FIG. 4 shows a conventional manufacturing process of an a-SiTFT array substrate. FIG. Hereinafter, a method for manufacturing a conventional active matrix liquid crystal display will be described with reference to FIGS. 3 and 4.

First, as shown in FIG. 4(a), a
The iTFT substrate (lower substrate) is made by depositing a metal layer of chromium (Cr), tantalum (Ta), and molybdenum (Mo) on the glass substrate 1 by sputtering or vapor deposition.
The gate electrode 2 is formed by depositing a film of about μm and then processing it into a predetermined shape by photolithography etching.

Thereafter, as shown in FIG. 4(b), a predetermined portion of the gate electrode film is anodized to a predetermined thickness to form tantalum oxide (TaO), which will become the first gate insulating film.
x) 3 is formed to a film thickness of 0.1 to 0.3 μm. In addition,
The dielectric constant of the chemically formed film at this time is 25 to 30. Then, as shown in Figure 4(c), a plasma CVD method (hereinafter referred to as "PCVD") using NH3 and SiH4 gases as main components was applied.
A silicon nitride film (SiNx) is deposited to a thickness of 0 using
．． It is deposited to a thickness of 1 to 0.4 μm over the entire surface of the substrate.

Next, as shown in FIG. 4(d), SiH4
A-Si is deposited to a thickness of 0.05 to 0.2 μm and n+ type a-Si to form an ohmic contact is deposited to a thickness of 0.003 to 0.005 μm over the entire surface of the substrate by a PCVD method using gas as the main component. Then, by processing them into a predetermined shape, the gate insulating film 4, the a-Si semiconductor layer 5, and the n-Si semiconductor layer 5 are formed.
A + type a-Si layer 6 is formed.

Next, as shown in FIG. 4(e), aluminum (Al), chromium (Cr), nichrome (NiCr)
A metal layer of 0.3
The source electrode 7 and the drain electrode 8 are formed by forming a film with a thickness of about 1.0 μm and processing it into a predetermined shape. Then, as shown in FIG. 4(f), an insulating film made of silicon nitride film (SiNx) or the like is formed by the PCVD method,
The surface protective film 9 is formed by processing into a predetermined shape including a contact hole for connecting a source electrode made of Al, Cr, NiCr, etc. and an ITO film to be described later.

Finally, as shown in FIG. 4(g), ITO
A film (In2O3 +SnO2) is formed to a thickness of about 0.1 μm by sputtering or vapor deposition, and then processed into a predetermined shape to form a transparent electrode 9 that will serve as a display electrode. By two-dimensionally arranging the above a-SiTFTs with transparent electrodes, an a-SiTFT array substrate is completed. Then, an organic film made of polyimide having a thickness of 0.1 μm is formed on this TFT array substrate, and a rubbing treatment is performed to form an alignment treatment film. Thereafter, in order to form and maintain uniform cell spacing, spacers 11 having a diameter of 3 to 10 μm are sprinkled on the alignment film to complete the lower substrate.

On the other hand, the upper substrate (counter electrode side) is formed as shown below. First, a black matrix layer 13 is formed on a glass substrate 12 to prevent light leakage and improve contrast. Next, the colored layer 14 is formed by printing, electrodeposition, or other processing. Next, after forming a flattening layer 15 thereon, a counter transparent electrode 16 made of an ITO film with a thickness of about 0.1 μm is formed into a predetermined shape by sputtering or vapor deposition and processing. Further, an organic film made of polyimide having a thickness of about 0.1 μm is formed on the counter electrode 16, and a rubbing process is performed to form an alignment film 17. Furthermore, a sealing layer 18 with a film thickness of 5 to 20 μm is formed in a predetermined pattern by a thick film screen printing method using a material in which a spacer is mixed into a polymeric insulating material (such as an epoxy material). The board is completed.

When the upper and lower substrates are completed, the upper and lower substrates are aligned and bonded together with the sealing layer in between, and the sealing layers are heated and cured by being fixed under pressure. Furthermore, after the inside of the seal layer is vacuum degassed, liquid crystal 19 is injected through a predetermined injection port. Finally, the injection port is sealed and the polarizing film 20 is pasted at a predetermined position, thereby completing a liquid crystal display using an a-SiTFT.

0010

[Problems to be Solved by the Invention] However, in the method for manufacturing an active matrix liquid crystal display having the above structure, as the surface screen becomes larger and the display capacity increases, particles during film formation and foreign matter due to poor cleaning during the process are produced. For these reasons, the insulating layer and semiconductor layer of the TFT tend to bulge, and the drain electrode tends to open due to reduced adhesion between the semiconductor layer and the electrode layer. As a result, display defects (line defects, point defects) occur in the liquid crystal display, resulting in a problem of deterioration in display quality.

[0011] The present invention solves the above conventional problems, and
An object of the present invention is to provide a method for manufacturing an active matrix liquid crystal display with excellent display quality and free from drain line defects due to particles, organic foreign matter, etc.

0012

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a structure in which a gate electrode, a first gate insulating film, a second gate insulating film, and an amorphous silicon semiconductor layer are sequentially formed on a transparent insulating substrate. , source-drain electrode, transparent electrode,
In a method for manufacturing an active matrix liquid crystal display that manufactures an amorphous silicon thin film transistor array on which a surface protective film is formed, when forming a second gate insulating film, a semiconductor layer, or a source and drain electrode, the substrate is irradiated with ultraviolet rays. particles in the film,
Due to poor cleaning during the process, transparent resin-like organic foreign matter and resist residue are oxidized and decomposed.

[0013]

[Operation] According to the present invention, since the method for manufacturing an active matrix liquid crystal display is configured as described above, when forming the second gate insulating film, the semiconductor layer, or the source-drain electrode, the substrate is irradiated with ultraviolet rays. The generated ozone oxidizes and decomposes particles during film formation, transparent resin-like organic foreign matter and resist residue due to poor cleaning during the process.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a diagram according to an embodiment of the present invention.
- It is a flowchart of the manufacturing process of a SiTFT array substrate. Hereinafter, a method for manufacturing an active matrix liquid crystal display according to an embodiment of the present invention will be explained based on FIGS. 1 and 3. The film forming conditions (method, atmosphere, film thickness, etc.) in this embodiment are the same as in the conventional example. Therefore, some of the descriptions will be omitted to avoid duplication.

First, as shown in FIG. 1(a), a tantalum (Ta) film is formed on a glass substrate 1, and then processed into a predetermined shape by photolithography to form a gate electrode 2. . After that, as shown in FIG. 1(b),
By anodizing a predetermined portion of the gate electrode film 2 to a predetermined thickness, a tantalum oxide film (TaOx) 3, which will become a first gate insulating film, is formed. At this time, the dielectric constant of the chemically formed film is 25 to 30.

Next, before forming the second gate insulating film 4, the a-Si semiconductor layer 5, and the n+ type a-Si layer 6, it is heated at a power density (1.2 W/cm2 to 2.4 W/cm2). The substrate surface is irradiated with ultraviolet light for a certain period of time (15 to 30 minutes). Ozone generated from the surrounding oxygen when irradiated with ultraviolet rays causes a chemical reaction (oxidative decomposition) of particles, transparent resin-like organic foreign matter caused by poor cleaning, and resist residue. After blowing nitrogen gas onto the substrate surface to remove decomposed particles and organic foreign matter, the second gate insulating film 4 is formed as shown in FIG. 1(d). )
As shown in FIG.
A Si layer 6 is formed.

Then, by processing them into a predetermined shape, the gate insulating film 4, the a-Si semiconductor layer 5, and the n+
A type a-Si layer 6 is formed. Next, after film formation, the same power density as before (1.2W/cm2 ~ 2.4Wc
m2) is irradiated with ultraviolet rays for a certain period of time (15 to 30 minutes) to generate ozone, which oxidizes and decomposes organic foreign matter adhering to the substrate surface and removes it, keeping the surface clean and then depositing the film. Improves adhesion to metal films made of aluminum (Al), chromium (Cr), nichrome (NiCr), etc.

It goes without saying that the above power density and time are preferably short and low power from the viewpoint of process throughput and cost. However, the power density is 1.2W
/cm2 or less and the time is less than 15 minutes, it is impossible to completely remove particles, transparent resin-like organic foreign matter due to poor cleaning, resist residuals, etc. Next, as shown in FIG. 1E, a source electrode 7 and a drain electrode 8 are formed by processing a metal layer such as Al, Cr, or NiCr into a predetermined shape.

Then, as shown in FIG. 1(f), the PCV
An insulating film made of a silicon nitride film (SiNx) or the like is formed using the D method, and processed into a predetermined shape including a contact hole for connecting a source electrode made of Al, Cr, NiCr, etc. and an ITO film described later. By doing so, a surface protection film 9 is formed. Finally, as shown in Figure 1(g),
An ITO film (In2O3 +SnO2) is formed by sputtering or vapor deposition, and processed into a predetermined shape to form a transparent electrode 10 that becomes a display electrode. By arranging the above a-Si TFTs with transparent electrodes two-dimensionally, a-
The SiTFT array substrate is completed.

Thereafter, the lower substrate is coated with an alignment film and spacers using conventional techniques. On the other hand, for the counter electrode substrate (upper substrate), a counter transparent electrode, a black matrix layer, and an alignment film are sequentially formed using a conventional technique. All subsequent cell assembly steps are the same as in the prior art. In this way, a liquid crystal display is completed.

FIG. 2 shows a-
SiTFT and a-SiT manufactured by conventional manufacturing method
FIG. 3 is a characteristic diagram showing the operation of FT. The horizontal axis in the figure is the gate voltage VG, with each division being 5V. The vertical axis on the right side is the drain current ID, and the current value increases ten times with each increment. a1 indicates the drain current manufactured by the conventional technique, and b1 indicates the drain current ID manufactured by the present embodiment. The left vertical axis is the square root of the drain current ID, and the scale is equally spaced, a
2 shows the one manufactured by the conventional technique, and b2 shows the one manufactured by the present example.

As is clear from the figure, in the embodiment of the present invention, compared to the conventional example, Ion can be increased because the drain current is large when the gate voltage is positive, and Ion can be increased when the gate voltage is negative. Since the drain current of is small, IOf
In addition, since the gate voltage at which the drain current becomes 0 is low, the threshold voltage (Vth) can be reduced.
can be reduced.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0024]

As explained in detail above, according to the present invention, by performing ultraviolet irradiation, particles during film formation, transparent resin-like organic foreign matter and resist residue due to poor cleaning during the process can be removed. Since it is removed by oxidative decomposition, the following effects are achieved. (1) It can reduce film defects caused by particles during the process, transparent resin-like organic foreign matter due to poor cleaning, resist residue, etc., and the occurrence of opens and shorts in gate electrodes and drain electrodes, improving yields. do.

(2) Since the adhesion between the films is improved, peeling between the films can be prevented when processing into a predetermined shape by photolithography etching or the like. Therefore, an active matrix liquid crystal display with good display characteristics without display defects such as line defects caused by open gate electrodes or drain electrodes can be obtained. (3) By irradiating the film interface between the first gate insulating film and the second gate insulating film with ultraviolet rays, a clean interface can be formed.

(4) Contact resistance between the semiconductor layer and the drain electrode can be reduced by ultraviolet irradiation. (5) An active matrix liquid crystal display having a large on-current Ion, a small off-current Ioff, and a small threshold voltage Vth can be obtained.

[Brief explanation of drawings]

FIG. 1 is a flow diagram of a manufacturing process of an a-Si TFT array substrate according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the operation of an a-SiTFT according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of an active matrix liquid crystal display.

FIG. 4 is a flow diagram of a conventional a-SiTFT array substrate manufacturing process.

[Explanation of symbols]

1 Glass substrate 2 Gate electrode 3 First gate insulating film 4 Second gate insulating film 5 a-Si semiconductor layer 6 n+ type a-Si layer 7 Source electrode 8 Drain electrode 9 Surface protective film 10 Transparent electrode

Claims (3)

[Claims] 1. A gate electrode, a first gate insulating film, a second gate insulating film, an amorphous silicon semiconductor layer, a source-drain electrode, a transparent electrode,
In the method for manufacturing an active matrix liquid crystal display, which manufactures an amorphous silicon thin film transistor array on which a surface protection film is formed, the second gate insulating film;
An active matrix characterized in that when forming an amorphous silicon semiconductor layer or a source-drain electrode, the substrate is irradiated with ultraviolet rays to oxidize and decompose particles generated during the film formation process and foreign matter due to poor cleaning. Method of manufacturing liquid crystal displays. [Claim 2] Ultraviolet irradiation density is 1.2 W/cm2
Claim 1 characterized in that it is ~2.4 W/cm2.
The method of manufacturing the active matrix liquid crystal display described. 3. The method for manufacturing an active matrix liquid crystal display according to claim 1, wherein the ultraviolet irradiation time is 15 minutes to 30 minutes.