JP4472745B2 - Liquid crystal display device having TFT array substrate including thin film transistor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a liquid crystal display device using a thin film transistor (hereinafter referred to as TFT).

  In a matrix type liquid crystal display device, a display material such as liquid crystal is held between two substrates, a TFT array substrate and a counter substrate, which are usually provided with TFTs made of a semiconductor thin film (hereinafter referred to as a semiconductor film). The display material is configured so that a voltage is selectively applied to each pixel. A counter electrode, a color filter, a black matrix, and the like are provided on the counter substrate. A liquid crystal display device (Liquid Crystal Display, hereinafter abbreviated as LCD) using such a TFT array substrate is hereinafter referred to as TFT-LCD.

  The TFT array substrate is provided with at least TFT and pixel electrodes composed of a gate electrode, a source electrode, a drain electrode, and a semiconductor film in an array for each element on an insulating substrate made of glass or the like. Accordingly, a storage capacitor is provided, and a plurality of signal lines such as gate lines and source lines are provided between the respective pixels in parallel with each other to form a display region. Further, outside the display area, input terminals and driving circuits for driving the TFTs are provided corresponding to the respective signal lines.

  In order to manufacture a liquid crystal device using such a TFT array substrate, a TFT, a gate (a gate electrode and a gate wiring are simply referred to as a gate), a source / drain (a source electrode and a source wiring are combined) on a glass substrate. The drain electrode is also simply referred to as the drain, and the source and drain are referred to as source / drain) and other common wirings are formed in an array to form a display area, and input terminals, spares Wiring and driving circuits are arranged around the display area. At this time, a conductive thin film (hereinafter referred to as a conductive film) or an insulating thin film (hereinafter referred to as an insulating film) is provided as necessary in order to develop each function. A counter electrode is provided on the counter substrate, and a color filter and a black matrix are provided.

  After the TFT array substrate and the counter substrate are fabricated, the two substrates are bonded together in a state having a desired gap so that the liquid crystal material can be injected between the two substrates. An LCD is manufactured by injecting a liquid crystal material into the gap.

  Various semiconductor devices and the like are provided on the TFT array substrate and the counter substrate used in the LCD by utilizing thin film technology. In these semiconductor devices, a semiconductor film, an insulating film, and a conductive film are formed, and a contact hole penetrating the interlayer insulating film and the semiconductor film is further formed for electrical connection between the layers.

  In TFT-LCD, in order to prevent signal delay in gate wiring and source / drain wiring due to increase in size or resolution, electrically low resistance alloy material mainly composed of Al or Al is used. It is desirable from the viewpoint of characteristics and process, but when the second electrode made of ITO or the like that becomes a transparent pixel electrode is brought into contact with the first electrode made of pure Al or Al alloy, the contact resistance is It was as high as 1E10 to 1E12Ω, and good contact characteristics could not be obtained.

  Therefore, a TFT that directly contacts (connects) a first electrode made of pure Al or an Al alloy and a second electrode made of a transparent conductive film such as ITO which becomes a pixel electrode through a contact hole opened in the insulating film. It was impossible to realize an array substrate.

  As a method for solving this problem, in order to obtain a good contact in the prior art, the first electrode is formed on pure Al or an Al alloy as disclosed in, for example, JP-A-4-253342, 4-305627, and 8-18058. In addition, a two-layer structure in which Cr, Ti, Mo, Cu, Ni, or the like is formed is used.

  Thus, in the conventional manufacturing method, the contact resistance between the second electrode made of ITO or the like and the first electrode made of pure Al or Al alloy is as high as 1 × 10E10 to 1 × 10E12Ω, and a good contact resistance is obtained. I could n’t. Also, if the first electrode has a two-layer structure made of different materials in order to obtain good contact, the same chemical solution and simultaneous etching are impossible, and two etching steps with two types of chemical solutions are required. Therefore, the process was complicated. The present invention provides a low-resistance Al wiring material by obtaining a good contact resistance at the contact portion between the second electrode and the first electrode and having a two-layer structure in which the first electrode can be etched simultaneously with the same chemical And a liquid crystal display device using a high-performance thin film transistor capable of reducing the production cost and improving the productivity.

A liquid crystal display device according to claim 1 of the present invention includes:
A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate and comprising at least two layers;
At least a second electrode formed on the insulating film,
The first electrode is composed of a lower first layer made of pure Al, and a second layer made by adding an impurity made of at least one of N and Si to pure Al,
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected;
In the insulating film composed of at least two layers, the layer in contact with the first electrode is formed by a plasma CVD method in a mixed gas obtained by further adding CF ₄ gas to a SiH ₄ + H ₂ + NH ₃ + N ₂ mixed gas . It is formed with a deposited silicon nitride film,
A second layer of the first electrode obtained by adding an impurity composed of at least one of N and Si to the pure Al is formed by diffusion of N element and Si element from the silicon nitride film. .
A liquid crystal display device according to claim 2 of the present invention is provided.
A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate and comprising at least two layers;
At least a second electrode formed on the insulating film,
The first electrode comprises a first lower layer made of an Al alloy and a second layer obtained by adding an impurity made of at least one of N and Si to the Al alloy;
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected;
In the insulating film composed of at least two layers, the layer in contact with the first electrode is formed by a plasma CVD method in a mixed gas obtained by further adding CF ₄ gas to a SiH ₄ + H ₂ + NH ₃ + N ₂ mixed gas . It is formed with a deposited silicon nitride film,
A second layer of the first electrode obtained by adding an impurity composed of at least one of N and Si to the Al alloy is formed by diffusion of N element and Si element from the silicon nitride film. .

A liquid crystal display device according to claim 3 of the present invention is provided.
3. The liquid crystal display device according to claim 1, wherein an electrical resistance value of a surface portion of the second layer of the first electrode obtained by adding an impurity composed of at least one of N and Si to the pure Al or Al alloy. Is configured to be 350 to 800Ω per 50 μm area .
The manufacturing method according to claim 4 of the present invention is:
A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate;
Including at least a second electrode formed on the insulating film and including at least a first layer and a second layer;
The first electrode comprises a first lower layer made of an Al alloy and a second layer obtained by adding an impurity made of at least one of N and O to the Al alloy;
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected, and the first layer of the second electrode connected to the second layer of the first electrode is the second layer of the second electrode. in the liquid crystal display device having the TFT array substrate amount of oxygen element include a thin film transistor has less than layer,
The first layer of the pixel electrode is formed by a sputtering method using only pure Ar gas, and then the second layer of the pixel electrode is formed using Ar + O ₂ gas.
Including things.
The manufacturing method according to claim 5 of the present invention is:
A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate;
Including at least a second electrode formed on the insulating film and including at least a first layer and a second layer;
The first electrode comprises a first lower layer made of an Al alloy and a second layer obtained by adding an impurity made of at least one of N and O to the Al alloy;
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected, and the first layer of the second electrode connected to the second layer of the first electrode is the second layer of the second electrode. A method of manufacturing a liquid crystal display device having a TFT array substrate including a thin film transistor having a smaller amount of oxygen element than a layer,
The first layer of the pixel electrode is formed by a sputtering method using only pure Ar gas, and then the second layer of the pixel electrode is formed using Ar + O ₂ gas.
Including things.
The manufacturing method according to claim 6 of the present invention is:
A thickness of the first layer and the second layer of the pixel electrode is about 500 mm.

In the liquid crystal display device according to claim 1 of the present invention, the layer in which the insulating film is in contact with the first electrode contains more nitrogen element than the other layers in the insulating film, and the second electrode and the second electrode of the first electrode. Since it has a TFT array substrate including a thin film transistor in which layers are electrically connected, a high aperture ratio and high performance display characteristics can be obtained by using a thin film transistor that can realize a low contact resistance directly with ITO or the like. It has the effect of obtaining an excellent liquid crystal display device that can be realized at low cost with higher productivity than conventional devices. Further, by mixing CF ₄ gas, the first layer of the gate insulating film and the second layer of the gate insulating film can be formed as a silicon nitride film rich in N element and chemically unstable. The second layer of the first electrode to which elements are easily diffused and Si and N elements are efficiently added can be formed.

  The liquid crystal display device according to claim 2 of the present invention is characterized in that the layer connected to the second layer of the first electrode in the second electrode has a smaller amount of oxygen element than the other layers in the second electrode. Since it has a TFT array substrate containing thin film transistors, it has high aperture ratio and high performance display characteristics using thin film transistors that can realize low contact resistance directly with ITO etc., and is more productive than conventional devices There is an effect that an excellent liquid crystal display device that can be realized well at low cost is obtained. Further, by reducing the amount of O element in the initial ITO film in contact with the first electrode made of pure Al or Al alloy in this way, AlxOy formation at the first electrode interface due to O element diffusion can be suppressed, It has an effect that a low contact resistance value of several hundreds to several kiloΩ can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Embodiment 1
1, 2 and 3 are process cross-sectional explanatory views showing the TFT portion and the terminal portion of the TFT array substrate according to the present invention in the order of the manufacturing process. 1, 2, and 3, 21 is a TFT portion, 22 is a terminal portion, 1 is a transparent insulating substrate, 2 is a first electrode (the first electrode of the TFT portion is a gate electrode) 1 is a first layer, 3 is a second layer of the first electrode, 4 is a gate insulating film, 5 is a semiconductor layer a-Si film, 6 is a semiconductor layer n + a-Si film, 7 is a first layer of the first electrode (the first electrode of the TFT portion is a source / drain electrode), 8 is a second layer of the first electrode, 9 is an interlayer insulating film, and 10 is a contact hole. Yes, 11 is a second electrode (pixel electrode). The TFT portion 21 is provided in the vicinity of the intersecting portion of the gate wiring and the source wiring (both not shown) on the TFT array substrate, and constitutes a switching element for driving the liquid crystal, and the terminal portion 22 is a gate. This is a portion that is extended outside the display panel and extends from the display panel, and is used for inputting a signal to the gate electrode from the outside.

This embodiment will be described in the order of manufacturing. A pure Al or Al alloy (first electrode material) film is formed on the transparent insulating substrate 1 by sputtering or the like, and after resist patterning by photolithography, phosphoric acid, nitric acid and acetic acid based etching solutions Etching is performed to form a gate wiring (not shown), a gate electrode (first electrode), and a terminal portion (see FIG. 1A). The first layer 2 of the first electrode (gate electrode), which is the lower layer film, and the second layer 3 of the first electrode (gate electrode), which is the upper layer film, are features of the present invention and will be described in detail later. To do. Next, a gate insulating film 4 made of silicon nitride (SiNx) or silicon oxide (SiO ₂ ) is formed to a thickness of about 4000 mm using a chemical vapor deposition method (hereinafter referred to as CVD), and a semiconductor layer is formed. Then, the semiconductor layer a-Si film 5 (thickness of about 1500 mm) and the low-resistance semiconductor layer n + a-Si film 6 (thickness of about 300 mm) are sequentially formed (see FIG. 1B).

  Further, about 3000 liters of pure Al or Al alloy as the first electrode material is formed again by sputtering, and patterning is performed to form the channel portion and source / drain electrode portion of the transistor. The two-layer structure of the first layer 7 of the first electrode (source / drain electrode) as the lower layer and the second layer 8 of the first electrode (source / drain electrode) as the upper layer is a feature of the present invention. Yes, the formation method will be described later (see FIG. 2A).

  Next, after forming the interlayer insulating film 9, the contact hole 10 is formed by patterning. Contact holes are formed in the gate terminal portion and the drain electrode portion of the TFT. Here, the interlayer insulating film 9 can be formed of, for example, a silicon nitride film by CVD or an acrylic transparent resin, or a combination of both (see FIG. 2B).

  Finally, an ITO film (indium tin oxide) having a thickness of about 1000 mm is formed using a sputtering method as a transparent conductive film and patterned to form a pixel electrode (second electrode) 11 to obtain a TFT array substrate. The pixel electrode 11 includes a gate electrode made of a first electrode material and an upper layer film of a source / drain electrode through a contact hole 10 of an interlayer insulating film, that is, a second layer 3 of a first electrode (gate electrode), a first electrode It is electrically connected to the second layer 8 of (source / drain electrode).

In the present embodiment, when the gate electrode and the terminal portion are formed using pure Al or an Al alloy of the first electrode material by sputtering, first the first layer of the first electrode is used using pure Ar gas. 2 was formed to a thickness of about 2000 mm, and then the second layer 3 of the first electrode was continuously formed to a thickness of about 250 mm using an Ar + N ₂ mixed gas. As the second Al film, a film to which nitrogen (N) element is added is formed by reactive sputtering with N ₂ gas. In the case of the source / drain electrodes, the same method is applied, and the first layer 7 (about 2000 mm) of the second electrode, which is a lower layer film of pure Al or Al alloy, and the upper layer film to which nitrogen (N) element is added. A second layer 8 (about 250 cm) of the second electrode is formed.

  Table 1 shows the film formation conditions applied to this embodiment. The electrical resistance value (contact resistance) of the contact surface portion between the first electrode made of pure Al or Al alloy and the second electrode made of a transparent conductive film such as ITO in the contact hole 10 of the TFT array substrate thus manufactured. Value) was about 50 μm □ at the minimum value and about 350Ω, indicating a good value.

  In addition, the contact resistance value after heat treatment at 250 ° C. for 60 minutes on this TFT array substrate is about 750Ω, and the contact resistance value is about 800Ω even after heat treatment at 300 ° C. for 60 minutes. Compared to 1E10 to 1E12Ω in the case, the heat resistance was extremely low.

  Note that the parameter values of the film formation conditions in Table 1 are uniquely optimized by the apparatus, and are not limited to these values. However, as the tendency of the contact resistance value with respect to the parameter value, the contact resistance value tended to decrease as the second layer deposition pressure increased.

  Further, the thickness of the second layer of the first electrode for obtaining good contact resistance is 250 mm in this embodiment, but is not limited to this, and may be 50 to 1000 mm. This is because it is difficult to suppress the diffusion of O at the ITO / Al interface at 50 mm or less, and the resistance value of the entire electrode is high at 1000 mm or more, and it is not possible to enjoy the merit of reducing the resistance of the wiring by using Al. It is. Furthermore, 100 to 500cm is more preferable.

In this embodiment, when the gate electrode, the terminal portion, and the source / drain electrode are formed using pure Al or an Al alloy as the first electrode material by sputtering, first Ar gas is used to form the first electrode. The second layer was formed by depositing the layer and then the second layer was deposited using an Ar + N ₂ mixed gas. The initial gas was pure Ar, and the amount of N ₂ gas added was gradually increased. It may be formed by continuous sputtering. In this case, the film has a continuous composition profile in which the nitrogen (N) element addition amount increases toward the upper layer part (contact surface part with the second electrode) of the Al film.

  Moreover, as Al used as the base material of the first electrode material, in addition to pure Al, an Al alloy containing Al as a main component can be used. The element added to the Al alloy is preferably Cu, Si, or a rare earth element from the viewpoint of suppressing hillocks and improving corrosion resistance. However, in order to take advantage of the electrical low resistance of Al, the added amount has a specific resistance of 10 μΩ · It is preferable to suppress to a level not exceeding cm.

However, in the case of a two-layer structure film in which the upper layer portion of the film is partially capped with an aluminum nitride (AlNx) film by Ar + N ₂ mixed gas sputtering as in this embodiment, simultaneous etching is performed. Even when pure Al is used, the generation of hillocks can be prevented, and the corrosion resistance can be improved. For this reason, it is a significant feature of this embodiment that a highly reliable TFT array can be realized without using an Al alloy having particularly excellent hillock resistance.

  Hereinafter, in the second to tenth embodiments, the second layer of the first electrode Al for obtaining a low contact resistance between the Al film of the first electrode material and the ITO film of the second electrode material in the first embodiment will be described. Processes other than the forming method and the effects of the invention are all the same as in the first embodiment. Therefore, only the method for forming the second layer of the first electrode Al is described.

Embodiment 2
In the TFT array manufacturing process of FIGS. 1, 2 and 3, the first electrode is formed by depositing pure Al or an Al alloy in pure Ar gas using a sputtering method, and then using an ion doping method or an ion implantation method. A second layer in which nitrogen (N) ions are implanted and N is added, that is, the second layer 3 of the first electrode and the second layer 8 of the second electrode are formed, and then patterned to form an electrode. . The dose was 5E16 to 1E17 / cm ³ .

  Further, even when the ion species are B ions and P ions, the same contact reduction effect can be obtained although not as remarkable as in the case of N ions.

Embodiment 3
FIG. 4 is an explanatory cross-sectional view showing the structure of the TFT portion and the terminal portion according to this embodiment. In FIG. 4, 12 is the second layer of the contact portion in the gate electrode, 13 is the second layer of the contact portion in the source / drain electrode, 42 and 47 are the first electrodes, and other symbols are shown in FIG. And in common. In the TFT array manufacturing process of FIG. 1, a first electrode made of pure Al or an Al alloy is formed by patterning after being formed by sputtering using pure Ar gas. After the interlayer insulating film 9 is formed and the contact hole 10 is opened, N ions are implanted using an ion doping method after the contact hole 10 is opened, and N ions are added to the contact surface of each first electrode. Form a layer. Therefore, in the present embodiment, as shown in FIG. 2, the second layer of the first electrode, that is, the second layer 12 of the contact portion in the gate electrode and the second layer 13 of the contact portion in the source / drain electrode are the second electrode. The structure is formed only in the contact portion connected to the pixel electrode 11 made of an ITO film.

Embodiment 4
In the TFT manufacturing processes of the second and third embodiments, the second layer of the first electrode made of pure Al or Al alloy was formed by heat treatment (annealing) in a nitriding gas atmosphere instead of ion doping. .

The heat treatment was performed under conditions of a temperature of 300 to 450 ° C. and a time of 30 to 90 minutes, and N ₂ gas or NH ₃ gas was used as a nitriding gas. In addition, gases such as methyl hydrazine, hydrazine, and ethyl aniline can be used. In this case, it is possible to efficiently form the second layer on which AlNx is formed by low-temperature and short-time heat treatment. is there.

Embodiment 5
In the TFT manufacturing processes of the second and third embodiments, the second layer of the first electrode made of pure Al or Al alloy was formed by N ₂ plasma treatment instead of ion doping. The plasma processing conditions were as follows: Power 500 W in PE or RIE mode, N ₂ gas pressure 7 to 500 Pa, and processing time 15 to 60 seconds. Note that the parameter values of the film forming conditions are also uniquely optimized by the processing apparatus, and are not limited to these values.

Embodiment 6
In the TFT manufacturing process according to the second and third embodiments, the second layer of the first electrode made of pure Al or Al alloy is immersed in ammonia water NH ₄ OH to immerse the first electrode into NH ₄ OH. ₄ Formed by soaking in OH. Further, after immersion in NH ₄ OH, heat treatment may be performed in a nitriding gas atmosphere as in the fourth embodiment.

Embodiment 7
In the TFT manufacturing process shown in the first embodiment, in the formation of the first electrode made of pure Al or an Al alloy, the first layer is first formed by sputtering using pure Ar gas, and then Ar + NH _{3 is formed.} After the second layer was formed by reactive sputtering using a mixed gas, patterning was performed to form an electrode.

In addition, when Ar + O ₂ , Ar + N ₂ + CO ₂ , Ar + N ₂ CF ₄ is used as a mixed gas for forming the second layer, SiH ₄ is further added to these gases. The low contact resistance effect was also obtained. Therefore, even when N, O, or N + C + O + Si is added as an impurity to the second layer of Al, the effects of the present invention can be sufficiently obtained.

Embodiment 8
In the TFT manufacturing process shown in the first embodiment, gates formed on the first electrode in the first electrode (gate electrode, source / drain electrode) made of pure Al or an Al alloy by sputtering using pure Ar gas, respectively. As the insulating film and the interlayer insulating film, a silicon nitride film is formed by a plasma CVD method using a mixed gas of SiH ₄ + H ₂ + NH ₃ + N ₂ , and Si and N elements are added by utilizing interface diffusion. A second layer of electrodes was formed.

Embodiment 9
FIG. 5 is a cross-sectional explanatory view of the TFT portion and the terminal portion according to the ninth embodiment of the present invention, 14 is the first layer of the gate insulating film, 15 is the second layer of the gate insulating film, Is the first layer of the interlayer insulating film, 17 is the second layer of the interlayer insulating film, and the other symbols are the same as in FIGS.

In the eighth embodiment, at least two silicon nitride films are formed on the first electrode made of pure Al or Al alloy as shown in FIG. 5, and the initial film is formed by SiH ₄ + H _{2 by} plasma CVD. A mixed gas obtained by adding CF ₄ to a + NH ₃ + N ₂ mixed gas is used. By mixing CF ₄ gas, the first layer 14 of the gate insulating film and the second layer 16 of the gate insulating film can be formed as a silicon nitride film rich in N element and chemically unstable. The second layer of the first electrode to which elements are easily diffused and Si and N elements are efficiently added can be formed.

Embodiment 10
In the TFT array manufacturing process according to the eighth embodiment, the gate insulating film and the interlayer insulating film are made of silicon oxide SiO _2, and the second layer of the first electrode is formed by adding Si and O elements by interfacial diffusion. The contact resistance reduction effect can be obtained.

Embodiment 11
FIG. 6 is a cross-sectional explanatory view of a TFT portion and a terminal portion according to the eleventh embodiment of the present invention, 18 is a first layer of pixel electrodes made of ITO, and 19 is a second layer of pixel electrodes made of ITO. Other symbols are the same as those in FIGS. In the TFT array manufacturing process of Embodiment 1 shown in FIG. 1, the pixel electrode 11 which is a second electrode made of a transparent conductive oxide film such as the ITO film of FIG. The first layer 18 is formed by a sputtering method using only pure Ar gas, and then the second layer 19 of the pixel electrode is formed by a conventional method using Ar + O ₂ gas. .

  Thus, by reducing the amount of O element in the initial ITO film in contact with the first electrode made of pure Al or Al alloy, AlxOy formation at the first electrode interface due to O element diffusion can be suppressed, and several hundred A low contact resistance value of up to several kilo ohms can be realized.

  Note that the thickness of the first layer of the second electrode made of ITO or the like is preferably about 100 to 500 mm. This is because if the thickness is less than 100 mm, the contact reducing effect is not sufficient, and the ITO film with few O elements has high specific resistance and low transmittance. Because it will let you.

In the first to eleventh embodiments, pure Al or an Al alloy is used as the first electrode material, and an ITO film is used as the second electrode material. There is no limitation to the electrode material, for example, Ta as the first electrode material, and other transparent oxidation based on any of In ₂ O ₃ , SnO ₂ , ZnO _2, etc. as the second electrode material Even when a conductive film is used, the same effect can be obtained.

Embodiment 12
A TFT array substrate formed according to any one of the first to eleventh embodiments described above is used, and this is bonded to a counter substrate having a counter electrode, a color filter, and the like, and a liquid crystal material is injected and held to provide a TFT active matrix type. A liquid crystal display device (TFT-LCD device) was obtained. In other words, according to the present embodiment, Al which is a low resistance wiring is used for the wiring and electrodes of the TFT array substrate, and the pixel electrode made of the ITO transparent film is formed without providing another metal layer mainly composed of other than Al. Since it has a structure in direct contact with Al, it was possible to obtain an excellent liquid crystal display device having a high aperture ratio and high performance, and capable of being implemented with higher productivity and lower cost than conventional devices. .

FIG. 3 is an explanatory cross-sectional view showing the structure of the TFT portion and the terminal portion according to the first embodiment of the present invention. FIG. 3 is an explanatory cross-sectional view showing the structure of the TFT portion and the terminal portion according to the first embodiment of the present invention. FIG. 3 is an explanatory cross-sectional view showing the structure of the TFT portion and the terminal portion according to the first embodiment of the present invention. It is end surface explanatory drawing which shows the structure of the TFT part and terminal part concerning Embodiment 3 of this invention. It is sectional explanatory drawing which shows the structure of TFT concerning Embodiment 9 of this invention. It is sectional explanatory drawing which shows the structure of TFT concerning Embodiment 11 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent insulating substrate, 2, 7 1st layer of 1st electrode, 3, 8 2nd layer of 1st electrode,
4 gate insulating film, 5 semiconductor layer a-si film, 6 semiconductor layer n + a-Si film,
9 Interlayer insulating film, 10 contact hole, 11 pixel electrode,
12 a second layer of the contact portion in the gate electrode;
13 Second layer of contact portion in source / drain electrode,
14 gate insulation film first layer, 15 gate insulation film second layer,
16 first layer of interlayer insulating film, 17 second layer of interlayer insulating film, 18 first layer of pixel electrode,
19 Second layer of pixel electrodes, 42 First electrode.

Claims (6)

A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate and comprising at least two layers;
At least a second electrode formed on the insulating film,
The first electrode is composed of a lower first layer made of pure Al, and a second layer made by adding an impurity made of at least one of N and Si to pure Al,
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected;
In the insulating film composed of at least two layers, the layer in contact with the first electrode is formed by a plasma CVD method in a mixed gas obtained by further adding CF ₄ gas to a SiH ₄ + H ₂ + NH ₃ + N ₂ mixed gas . It is formed with a deposited silicon nitride film,
A thin film transistor in which the second layer of the first electrode obtained by adding an impurity composed of at least one of N and Si to the pure Al is formed by diffusion of N element and Si element from the silicon nitride film is included. A liquid crystal display device having a TFT array substrate. A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate and comprising at least two layers;
At least a second electrode formed on the insulating film,
The first electrode comprises a first lower layer made of an Al alloy and a second layer obtained by adding an impurity made of at least one of N and Si to the Al alloy;
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected;
In the insulating film composed of at least two layers, the layer in contact with the first electrode is formed by a plasma CVD method in a mixed gas obtained by further adding CF ₄ gas to a SiH ₄ + H ₂ + NH ₃ + N ₂ mixed gas . It is formed with a deposited silicon nitride film,
The second layer of the first electrode formed by adding an impurity composed of at least one of N and Si to the Al alloy includes a thin film transistor formed by diffusion of an N element and an Si element from the silicon nitride film A liquid crystal display device having a TFT array substrate. The electrical resistance value of the surface portion of the second layer of the first electrode obtained by adding an impurity composed of at least one of N and Si to the pure Al or Al alloy is 350 to 800Ω per 50 μm area. The liquid crystal display device according to claim 1 or 2, comprising the liquid crystal display device. A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate;
Ri Do two layers of at least first and second layers are formed on the insulating film includes at least a second electrode that acts as a pixel electrode,
The first electrode is composed of a lower first layer made of pure Al and a second layer made by adding an impurity made of at least one of N and O to pure Al;
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected, and the first layer of the second electrode connected to the second layer of the first electrode is the second layer of the second electrode. a process for preparing a liquid crystal display device having the TFT array substrate amount of oxygen element include a thin film transistor has less than layer,
The first layer of the pixel electrode is formed by a sputtering method using only pure Ar gas, and then the second layer of the pixel electrode is formed using Ar + O ₂ gas.
The manufacturing method of the liquid crystal display device including this . A gate, a source and a drain which are first electrodes formed on a transparent insulating substrate;
An insulating film formed to cover the first electrode and the transparent insulating substrate;
Including at least a second electrode formed on the insulating film and including at least a first layer and a second layer;
The first electrode comprises a first lower layer made of an Al alloy and a second layer obtained by adding an impurity made of at least one of N and O to the Al alloy;
The second electrode comprises a transparent film electrode;
The second electrode and the second layer of the first electrode are electrically connected, and the first layer of the second electrode connected to the second layer of the first electrode is the second layer of the second electrode. a process for preparing a liquid crystal display device having the TFT array substrate amount of oxygen element include a thin film transistor has less than layer,
The first layer of the pixel electrode is formed by a sputtering method using only pure Ar gas, and then the second layer of the pixel electrode is formed using Ar + O ₂ gas.
The manufacturing method of the liquid crystal display device including this. 6. The method of manufacturing a liquid crystal display device according to claim 4, wherein the first layer and the second layer of the pixel electrode have a thickness of about 500 mm.

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