JPH06301054A - Production of thin-film transistor array substrate for liquid crystal display device - Google Patents

Abstract

PURPOSE:To save a patterning stage for a high melting metallic layer and to form scanning lines in common use as gate lines by forming an alloy layer at the boundary between a metallic layer essentially consisting of aluminum and the high melting metallic layer formed on the surface of this metallic layer and simultaneously converting this high melting metallic layer to an oxide layer. CONSTITUTION:The aluminum 2 is deposited by a sputtering method on a glass substrate 1 with an SiO2 layer by a plasma CVD method and is patterned to the shape of the scanning lines. A molybdenum-tantalum alloy layer 11 is deposited on a substrate 1 formed with the aluminum layer 2. This substrate is annealed to form the aluminum alloyed layer 3 and the metal oxide layer 12 on the aluminum surface. Only the metal oxide layer 12 is thereafter removed by a dry etching method. The alloy layer, therefore, eventually remains on the scanning line surface consisting of the metallic layer essentially composed of the aluminum and the generation of the hillock of the aluminum is prevented by this alloy layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin film transistor array substrate, and more particularly to a method of manufacturing a scanning line structure of a thin film transistor array substrate used in a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices are widely used as display devices for office automation equipment such as Japanese word processors and personal computers because they have the great advantages of thinness, light weight, and low power consumption. There is a strong demand for improvements in manufacturing technology and productivity. Especially,
Such as a thin film transistor (hereinafter abbreviated as TFT)
The active matrix type liquid crystal display device in which the 3-terminal element is connected to each of the display pixels as a switch has a higher contrast ratio than other liquid crystal display devices.
The TFT array substrate used has been attracting attention because of its remarkably excellent response speed and the fact that conventional semiconductor manufacturing techniques can be applied to manufacturing, and active research and development of the TFT array substrate used.

On the other hand, the display screen of the liquid crystal display device is required to have a large screen and high definition. Along with this, the TFT array substrate used in such a liquid crystal display device has a long scanning line, and the line width of the scanning line is narrowed by making the aperture ratio of the pixel substantially constant. As a result, the resistance of the scanning line becomes high. When the resistance of the scanning line becomes high, the waveform of the scanning signal is distorted and the signal propagation delay occurs. This appears as non-uniformity of the image, resulting in deterioration of the image quality of the display screen. To solve this problem, it is necessary to reduce the resistance of the scanning line. Aluminum (Al), a low resistance metal
However, when aluminum alone is used, hillocks are generated in the heat treatment process during the manufacturing process, and there is a problem that the interlayer insulation between the scan line and the signal line is greatly reduced. Conventionally, in order to solve this problem, a T having a structure in which a refractory metal is laminated on aluminum to form a scanning line.
There is an FT array substrate.

The structure and manufacturing method of such a conventional TFT array substrate will be described with reference to FIG. Figure 2
FIG. 4 is a diagram showing a cross-sectional structure of a typical inverted staggered type TFT of a conventional TFT array substrate. An aluminum (Al) film 2 is formed on an insulating substrate 1 made of glass or the like and patterned. Next, a molybdenum-tantalum alloy (MoTa) layer 11 is formed and patterned so as to cover aluminum (Al) to form a scanning line which also serves as a gate electrode. Next, S
The iO _x layer and SiN _x layer are used as the gate insulating layers 13 and 4, and the semiconductor layer 5 is made of amorphous silicon (a-
The Si) layer and the protective layer 6 are sequentially laminated and patterned. After that, a low resistance amorphous silicon (n ⁺ a-Si) layer 7 is formed and patterned. After that, the display electrode 8 is replaced with ITO.
A film is formed by a sputtering method using (indium tin oxide layer) and patterned. After that, a signal line 10 also serving as a source electrode and a drain electrode 9 connected to the display electrode are formed by using aluminum by a sputtering method. In this way, a TFT array substrate is obtained.

An alignment film is formed on the TFT array substrate thus manufactured, and a rear glass substrate having a light-shielding film, a counter electrode and an alignment film formed in this order on the surface is made to face the alignment film, and a gap is formed between them. A liquid crystal composition is sealed to form a liquid crystal cell, and an external circuit is connected to such a liquid crystal cell and housed in a case to form a liquid crystal display device.

[0006]

However, in order to prevent aluminum hillocks, the scanning line which also serves as the gate electrode is formed of aluminum and molybdenum-tantalum alloy (M
If the laminated structure of the (oTa) layer is used, the patterning process is required twice, which complicates the manufacturing process.

Further, if aluminum is used as the scanning line, not only is it impossible to prevent interlayer dielectric breakdown due to hillocks,
There is a problem that the scanning line is broken due to being attacked by chemical treatment such as buffer hydrofluoric acid or aqua regia in a later step.

The present invention has been made to solve the above problems, and a simple TFT array substrate for a liquid crystal display device in which hillock does not occur even when aluminum is used as the low resistance scanning line and the array process conformity is high. It aims at providing the manufacturing method of.

[0009]

A method of manufacturing a TFT array substrate for a liquid crystal display device according to the present invention comprises a step of forming a scanning line also serving as a gate electrode on an insulating substrate, and a step of forming a predetermined insulating layer on the gate electrode. In the method of manufacturing a thin film transistor array substrate for a liquid crystal display device, which comprises a step of forming a semiconductor layer by a step of forming a signal line also serving as a source electrode and a drain electrode connected to the display electrode on the semiconductor layer, The process of forming a scanning line that also serves as an electrode
The step of laminating the refractory metal layer on the surface of the metal layer containing aluminum as a main component, and forming the alloy layer at the interface between the surface of the metal layer containing aluminum as a main component and the refractory metal layer, and at the same time forming the refractory metal layer. The method is characterized by comprising a step of forming an oxide layer and a step of removing the oxide layer from the insulating substrate.

The metal layer containing aluminum as a main component according to the present invention may be an aluminum metal simple substance, and an aluminum alloy may be used as long as the conductivity is not impaired. For example, 1 atomic% copper (Cu), silicon
An aluminum alloy containing (Si) 0.5 atom% can be used.

The refractory metal to be laminated on the metal layer containing aluminum as a main component is tantalum (Ta), titanium (Ti), chromium (Cr), tungsten (W), niobium (Nb),
Metals such as molybdenum (Mo) and alloys combining these are particularly preferably used.

The method for forming the metal layer containing aluminum as a main component and the refractory metal layer is not particularly limited, and a known method such as a sputtering method can be used.

The step of forming the alloy layer at the laminated interface and simultaneously making the refractory metal layer on the surface into the oxide layer according to the present invention is performed by performing thermal annealing under atmospheric pressure or reduced pressure after forming the laminated film. . The conditions of thermal annealing are
The thermal annealing temperature is preferably 600 ° C. or lower because the lower layer is a metal layer containing aluminum as a main component, although it varies depending on the kind of the high melting point metal to be laminated and the layer thickness. The conditions for oxidizing the refractory metal layer at the same time as the thermal annealing are not particularly limited as long as the refractory metal layer on the surface on which the alloy layer is not formed can be oxidized.

The refractory metal oxide layer formed on the surface is
The aluminum layer is removed from the alloy layer formed on the surface of the metal layer and the insulating substrate. As a means for removing, various etching methods can be used, but a dry etching processing method capable of easily removing the oxide layer is particularly preferable. As the dry etching processing method, excitation gas etching, plasma etching, reactive ion etching, sputter etching, reactive ion beam etching, ion beam etching, or the like can be used.

According to the present invention, a step of forming a semiconductor layer on a gate electrode via a predetermined insulating layer and a drain electrode connected to a signal line also serving as a source electrode and a display electrode are formed on the semiconductor layer. A known means can be used for the step, and there is no particular limitation. For example, a SiO _x layer, a SiN _x layer, or the like can be used as the gate insulating layer, and single crystal silicon, polycrystalline silicon, amorphous silicon, or the like can be used as the semiconductor layer. Further, a low resistance amorphous silicon layer or the like can be used as an ohmic contact layer such as a semiconductor layer and a source electrode. Further, as a method of forming the gate insulating layer and the semiconductor layer, a known method such as a plasma CVD method or a photolithography method used for a TFT array substrate for a liquid crystal display device can be used.

[0016]

Function: The refractory metal oxide layer is removed from the substrate surface by a dry etching method or the like. Therefore, the formed alloy layer remains on the surface of the scanning line made of a metal layer containing aluminum as a main component. If an alloy layer is present on the surface, aluminum hillocks will not occur. Further, this alloy layer has high chemical resistance, and short-circuiting between layers such as scanning lines and signal lines and disconnection of scanning lines do not occur.

Further, the patterning process of the refractory metal layer is not necessary, and the manufacturing process is shortened.

[0018]

The manufacturing process of the TFT array substrate for a liquid crystal display device of the present invention will be described in detail below with reference to FIG. Figure 1
(E) is a diagram showing a cross-sectional structure of an inverted staggered TFT. An aluminum (Al) layer 2 is formed by sputtering on a glass substrate 1 having a SiO _x layer formed by plasma CVD.
200nm deposition and patterning in scanning line shape (Fig. 1
(A)). A molybdenum-tantalum alloy (MoTa) layer 11 having a thickness of 100 nm is deposited on the substrate 1 on which the aluminum layer 2 is formed (FIG. 1B). This substrate is annealed in an annealing furnace at 400 ° C. and 0.1 Pa for 1 hour to form an aluminum alloying layer 3 and a metal oxide layer 12 on the aluminum surface (FIG. 1 (c)). After that, only the metal oxide layer 12 is removed by the dry etching method (FIG. 1D). Subsequently, the gate insulating layers 13 and 4 composed of a SiO _x layer and a SiN _x layer are deposited by a plasma CVD method, and further, an amorphous silicon (a-Si) layer 5 and a SiN _x layer 6 are deposited continuously.
The upper SiN _x layer 6 is patterned. After pretreatment, n ⁺ a-
The Si layer 7 is deposited by the plasma CVD method and patterned. A display electrode (transparent pixel electrode) 8 is formed using ITO (indium tin oxide layer). Then, the opening of the scanning line pad is formed with an HF etching solution. The reaction product generated on the scan line of the opening is removed with concentrated nitric acid. Next, aluminum is deposited by the sputtering method to form the source electrode 9 and the drain electrode 10. The n ⁺ a-Si layer on the back channel is removed by reactive ion etching (RIE) to obtain a TFT array substrate for a liquid crystal display device (FIG. 1 (e)).

The scanning line resistance of the obtained TFT array substrate had an average scanning line width of 10 μm and a scanning line length of 20 cm.
Was about 3 kΩ. This is molybdenum
Approximate resistance of 9 kΩ when the tantalum alloy layer is 300 nm thick
It is one-third.

Since the scanning line of this embodiment was not attacked by any of buffer hydrofluoric acid, aqua regia system, and phosphoric acid / nitric acid system, no disconnection occurred. In addition, no interlayer short circuit due to aluminum hillocks occurred.

[0021]

According to the method of manufacturing a TFT array substrate for a liquid crystal display device of the present invention, a step of forming a scanning line which also serves as a gate electrode comprises laminating a refractory metal layer on the surface of a metal layer containing aluminum as a main component. A step of forming an alloy layer at the interface between the surface of the metal layer containing aluminum as a main component and the refractory metal layer, and at the same time using the refractory metal layer as an oxide layer, and removing this oxide layer from the insulating substrate Since it includes the step of performing, the patterning step of the refractory metal layer is not necessary,
The manufacturing process is shortened.

On the other hand, the TFT array substrate obtained by this method can eliminate the interlayer short circuit due to the hillock of aluminum. Further, since the alloy layer is formed on the surface of the metal layer containing aluminum as the main component, the chemical resistance is excellent and the disconnection of the scanning line due to the chemical liquid can be prevented. Furthermore, since the wiring material is mainly composed of aluminum, the scanning line resistance has a low resistance value. As a result, the liquid crystal display device using the TFT array substrate obtained by the method of the present invention can easily have a large screen and high definition.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a TFT array substrate for a liquid crystal display device of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of a conventional TFT array substrate.

[Explanation of symbols]

1 ... Insulation substrate, 2 ... Aluminum layer, 3 ...
Aluminum alloyed layer, 4 ... Gate insulating layer, 5 ...
… Amorphous silicon (a-Si) layer, 6 ………… SiN
_x layer, 7 ………… n ⁺ a-Si layer, 8 ………… Display electrode, 9 ……
Source electrode, 10 Drain electrode, 11 Molybdenum / tantalum alloy layer, 12 Metal oxide layer,
13 ... Gate insulating layer.

Claims (1)

[Claims] 1. A step of forming a scanning line also serving as a gate electrode on an insulating substrate, a step of forming a semiconductor layer on the gate electrode via a predetermined insulating layer, and a step of also serving as a source electrode on the semiconductor layer. In a method of manufacturing a thin film transistor array substrate for a liquid crystal display device, which comprises a step of forming a signal line and a drain electrode connected to a display electrode, the step of forming a scanning line also serving as the gate electrode is mainly composed of aluminum. Stacking a refractory metal layer on the surface of the metal layer, forming an alloy layer at the interface between the surface of the metal layer and the refractory metal layer, and simultaneously forming the refractory metal layer as an oxide layer, A method of manufacturing a thin film transistor array substrate for a liquid crystal display device, comprising a step of removing an oxide layer from the insulating substrate.