JPH09162409A - Manufacturing method for semiconductor device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of a hole due to migration even when wiring width is narrowed and film is thinned down, with the use of aluminum based metal as a gate electrode of a thin film transistor. SOLUTION: A pixel electrode 2 and a silicon oxide film 3 are formed on a glass substrate 1, and a gate electrode 4 consisting of a pure a aluminum thin film is formed into a specified pattern. The anodic oxidation of the gate electrode 4 is performed, and an aluminum oxide film 5 is formed. The substrate temperature is raised to 150 deg.C or above, and a tantalum oxide thin film is formed as an oxide thin film 6 in the atmosphere containing oxygen plasma, by reactive sputtering, and then, heat treatment is performed at the temperature of the substrate when sputtering or above, in the atmosphere containing the oxygen plasma. After a silicon nitride film 7, a semiconductor layer 8 and a channel protecting film 9 are formed, the channel protecting film 9 is formed into a specified pattern. After and ohmic contact layer 10 is formed, a source- drain electrode 11 in which the pixel electrode 2 and a drain electrode are electrically connected is formed.

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 a semiconductor device and a method for manufacturing a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, the size of TFT liquid crystal display devices has been increased.
There is an increasing demand for large display capacity and high brightness. A display having a size of about 17 inches and a display capacity of about 1000 × 900 lines has been manufactured. A problem at this time is that the glass substrate becomes larger with the increase in size, and the pitch between pixels becomes smaller as the display capacitance becomes larger. Therefore, a low-resistance wiring electrode is required to narrow the width of the gate line. . Therefore, a laminated structure of aluminum and chromium or a laminated structure of aluminum alloy and tantalum is conventionally used as the wiring electrode.

However, in this laminated structure, the wiring width becomes wide due to the pattern alignment accuracy in the photolithography, and the pixel electrode cannot be made wide. Therefore, the transmittance becomes low, and there are major problems in power consumption and display quality. Occur. On the other hand, when an aluminum-based alloy is used for the wiring electrode, the light-shielding effect of the transistor part becomes insufficient because a hole through which light passes through the electrode may be opened due to so-called migration, and the transistor is turned off (almost current flows). Even if it is not), the photoirradiation deterioration phenomenon occurs due to the photoconduction phenomenon. In particular, when manufacturing a thin film transistor using amorphous silicon, in a transistor structure in which an aluminum-based metal is used as a wiring electrode that also serves as a light-shielding layer, the thickness of the wiring electrode is adjusted to prevent light from entering the semiconductor layer. It was thick.

[0004]

However, when the film thickness of the wiring electrode is large, stains due to liquid residue or the like may be generated in a process using a liquid such as a cleaning process or an etching process in the process of manufacturing a semiconductor device. This will cause redeposition of dust and lead to defective patterns. In order to solve this, it is necessary to reduce the unevenness of the substrate surface to a flattened structure and to reduce the wiring width, thin the film thickness, and reduce the electric resistance. Indispensable.

An object of the present invention is to use an aluminum-based metal as a metal wiring such as a gate electrode of a thin film transistor, and to suppress the generation of holes due to migration even if the wiring width is narrow and the film thickness is thin. Is to provide a method for manufacturing the same. Another object of the present invention is to use an aluminum-based metal for a gate electrode of a thin film transistor used as a switching element, and to suppress generation of holes due to migration even if the wiring width is narrow and the film thickness is thin. Is to provide a method for manufacturing the same.

[0006]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein a metal wiring containing aluminum as a main component is formed on an insulating substrate, and then the metal wiring is anodized to form an anodized film. Then, after forming an oxide thin film on the anodic oxide film by sputtering at a substrate temperature of 150 ° C. or higher in an oxygen plasma atmosphere, it is continuously heated in an oxygen plasma atmosphere at a temperature higher than the substrate temperature during sputtering. Characterized by heat treatment. As a result, the internal stress of the metal wiring containing aluminum as a main component is relaxed and the water content of the anodic oxide film is removed, the occurrence of migration is suppressed, and even if the wiring width is narrow and the film thickness is thin, holes due to migration are generated. It is possible to realize a low resistance metal wiring with few defects such as.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
A step of forming a gate electrode containing aluminum as a main component on an insulating substrate; a step of anodizing the gate electrode to form an anodic oxide film; and a step of sputtering at a substrate temperature of 150 ° C. or higher in an oxygen plasma atmosphere. After forming an oxide thin film on the anodic oxide film, continuously performing a heat treatment in an oxygen plasma atmosphere at a temperature equal to or higher than the substrate temperature during sputtering, and forming a semiconductor layer on the oxide thin film via an insulating film The method is characterized by including a step and a step of forming a source / drain electrode on the semiconductor layer. As a result, the internal stress of the gate electrode composed mainly of aluminum is relaxed and the water content of the anodic oxide film is removed, the occurrence of migration is suppressed, and even if the wiring width is narrow and the film thickness is thin, holes due to migration are generated. It is possible to form a low-resistance gate electrode with few defects such as, and to realize a highly reliable thin film transistor.

According to a third aspect of the invention, there is provided a method of manufacturing a semiconductor device.
In the method for manufacturing a semiconductor device according to claim 1 or 2, the oxide thin film is a thin film of an oxide containing at least one of aluminum, tantalum, titanium and silicon or a perovskite oxide. By using these, a good semiconductor device can be realized.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device in which a liquid crystal layer is sandwiched between an array substrate having pixel electrodes and thin film transistors formed in a matrix, and a counter substrate having counter electrodes. A method of manufacturing, wherein the thin film transistor is formed by the method of manufacturing a semiconductor device according to claim 2. This makes it possible to form a low-resistance gate electrode with few defects such as holes due to migration even if the wiring width is narrow and the film thickness is thin, and realizes a highly reliable thin film transistor, high yield, high performance, and high reliability. The liquid crystal display device can be realized.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 7 are process sectional views showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. Here, as the semiconductor device,
A method of manufacturing an array substrate of a liquid crystal display device in which pixel electrodes and thin film transistors are formed in a matrix will be described. 1 to 7, 1 is a glass substrate, 2 is a pixel electrode made of an indium tin oxide (ITO) thin film, 3 is a silicon oxide film, 4 is a gate electrode made of a pure aluminum thin film, and 5 is a gate electrode 4 as an anode. An aluminum oxide film (anodic oxide film) formed on the surface by oxidation, 6 is an oxide thin film formed by a sputtering method, 7 is a silicon nitride film,
8 is a semiconductor layer made of an amorphous silicon (a-Si) film, 9 is a channel protective film made of a silicon nitride film,
10 is an ohmic contact layer made of an n ⁺ type a-Si film, 11 is a titanium thin film 11a and an aluminum thin film 11b.
And 12 are contact holes, and 13 is a protective insulating film made of a silicon nitride film.

First, as shown in FIG. 1, an ITO thin film was formed on a glass substrate 1 by a DC sputtering method, and then a transparent pixel electrode 2 was formed in a predetermined pattern by a wet etching method. Next, as shown in FIG. 2, the silicon oxide film 3 is formed on the interface between the pixel electrode 2 of the ITO thin film and the gate electrode 4 of the pure aluminum thin film to be formed next.
Was formed to a thickness of about 100 nm to prevent occurrence of defects in the gate electrode patterning process. After that, a pure aluminum thin film was formed by DC sputtering to have a thickness of 133 to 400 nm, and a gate electrode 4 was formed into a predetermined pattern by wet etching. At this time, the etching solution was a phosphoric acid: nitric acid: acetic acid: water system.

Next, as shown in FIG. 3, a resist pattern is formed in a portion of the gate electrode 4 where a contact hole will be formed in a later step and the electrode will be taken out, and a portion of the gate electrode 4 where the resist pattern is not formed is formed. Anodization is performed to form an aluminum oxide film 5 with a film thickness of 100 to 200 nm. The electrolytic solution used for anodic oxidation was a solution having a volume ratio of about 1% by weight citric acid aqueous solution or tartaric acid aqueous solution to ethylene glycol of 3: 7. The unevenness on the surface of the substrate is 166 to 466 nm. The residual film of aluminum metal forming the gate electrode 4 changes from 66 nm to 267 nm.

Next, as shown in FIG. 4, a tantalum oxide thin film was formed at a substrate temperature of 150 ° C. or higher as the oxide thin film 6 using the sputtering method. This oxide thin film 6
The method of forming the above will be described in detail with reference to FIG. FIG. 8 is a schematic cross-sectional view of a main part of an in-line type sputtering apparatus in which the substrate moves during sputtering.
A glass substrate (hereinafter abbreviated as “substrate”) on which the silicon oxide film 3, the gate electrode 4 and the aluminum oxide film 5 are formed, 21 is a vacuum chamber, 22 is an argon gas inlet, 23 is an oxygen gas inlet, and 24 is a vacuum. Exhaust system, 25 is a target, 26 is a deposition preventive plate, 27 is a magnet, 28 is an insulating shield, 29 and 30 are heaters for heating the substrate 1,
Reference numeral 31 is an atmosphere containing oxygen plasma.

Here, tantalum metal is used as the target 25, and a mixed gas of argon and oxygen is used as the sputtering gas. The substrate 1 moves in the direction of the arrow x in the vacuum chamber 21, and at the time of sputtering, the substrate temperature is raised to 150 ° C. or higher by the heater 29 in the film formation region A, and reactive sputtering is performed in the atmosphere 31 containing oxygen plasma. Form a tantalum oxide thin film. continue,
In the heat treatment region B, the substrate 1 is heat-treated by the heater 30 in the atmosphere 31 containing oxygen plasma at a temperature equal to or higher than the substrate temperature at the time of sputtering. As described above, the surface of the substrate 1 is exposed to the atmosphere 31 containing oxygen plasma during and after the film formation.

Next, the silicon nitride film 7 having a thickness of 200 to 300 nm is formed by a plasma CVD method, and a-S is formed as a semiconductor layer 8.
An i film was continuously formed to have a thickness of 50 to 200 nm, and a silicon nitride film as a channel protective film 9 for a transistor was continuously formed to have a thickness of 100 to 200 nm. After that, the channel protection film 9
Was selectively removed with a hydrofluoric acid-based etching solution to form a predetermined pattern, and the resist was removed.

Next, as shown in FIG. 5, the ohmic contact layer 1 is formed on the substrate whose surface oxide film has been removed with dilute hydrofluoric acid.
0 is an n ⁺ type a that is a silicon thin film to which phosphorus is added.
A -Si film was formed with a thickness of 50 nm. A contact hole 12 for electrically connecting the pixel electrode 2 and the drain electrode 11 (see FIG. 6) was formed in a predetermined pattern by an etching method. At this time, the silicon nitride film and the a-Si film in the extraction electrode portion corresponding to the connection terminal portion of the gate electrode 4 with the drive circuit were also removed.

Next, as shown in FIG. 6, a titanium thin film 11 is formed.
a and the aluminum thin film 11b were continuously formed by the DC sputtering method. Then, the aluminum thin film 11b is first formed into a predetermined pattern by the wet etching method or the dry etching method, and then the titanium thin film 11b is formed.
The ohmic contact layer 10 of a and n ⁺ type a-Si film and the semiconductor layer 8 of a-Si film were etched into a predetermined pattern. As a result, the source / drain electrodes 11 having a predetermined pattern are formed.

Finally, as shown in FIG. 7, the protective insulating film 1
As No. 3, a silicon nitride film was formed by the plasma CVD method, and a part on the pixel electrode 2 and a part on the extraction part of each of the gate electrode 4 and the source electrode 11 were removed by the dry etching method. As described above, an array substrate in which the pixel electrodes 2 and the thin film transistors are arranged in a matrix on the glass substrate 1 is manufactured, and the liquid crystal layer is sandwiched between the array substrate and the counter substrate on which the counter electrode is formed to form a liquid crystal display device. As a result of fabrication, good results were obtained with no defects in the transistor portion formed on the array substrate.

The gate electrode 4 is formed when the oxide thin film 6 is not formed and when the oxide thin film 6 is formed by changing the sputtering conditions (substrate temperature) and the amount of remaining aluminum metal film to be the gate electrode 4. Table 1 collectively shows the generation status of holes through which light is transmitted. Here, the substrate temperature is
The conditions were changed from room temperature (without heating) to 300 ° C.

[0020]

[Table 1]

In Table 1, ◯ indicates that no holes were observed, X indicates that holes were observed, and Δ indicates that holes were not observed or unstable. As shown in Table 1, when the oxide thin film 6 was not formed, a hole for transmitting light was opened inside the wiring of the gate electrode 4. Further, when the residual film amount of aluminum metal was 80 nm or less, the formation of holes became particularly remarkable. Further, when the oxide thin film 6 was formed by the sputtering method at the substrate temperature of 150 ° C. or higher, the generation of holes through which light was transmitted inside the gate electrode 4 drastically decreased. When the heat treatment was performed in the atmosphere without oxygen plasma or in a vacuum, it was not possible to prevent the generation of holes through which light was transmitted inside the gate electrode 4.

Incidentally, FIG. 9 shows a state in which a hole is formed inside the gate electrode 4. As shown in FIG. 9, when a hole 14 through which light passes inside the gate electrode 4 is generated, the glass substrate 1
Light energy reaches the semiconductor layer 8 from the side, and a so-called off-leakage state occurs in which a current flows due to a photoconductive effect even when the transistor is off, which causes abnormal transistor operation.

As described above, according to the embodiment of the present invention, on the surface of the gate electrode 4 made of aluminum metal,
An aluminum oxide film 5 is formed by anodic oxidation, an oxide thin film 6 is formed on the aluminum oxide film 5 by sputtering at a substrate temperature of 150 ° C. or higher in an oxygen plasma atmosphere, and continuously in an oxygen plasma atmosphere. By heat treatment at a temperature equal to or higher than the substrate temperature at the time of sputtering, relaxation of internal stress of the gate electrode 4 containing aluminum as a main component and anodic oxide film (aluminum oxide film 5)
The removal of the water content of the gate electrode 4 can suppress the occurrence of migration, and even if the width of the gate electrode 4 is narrow and the film thickness is thin, a wiring electrode with few defects such as holes due to migration can be realized, and as shown in FIG. Light energy does not reach the semiconductor layer 8 and the transistor does not operate abnormally. In this way, the transistor portion can be shielded from external light, the resistance of the wiring electrode can be reduced, and a highly reliable thin film transistor with few defects inside the electrode can be realized. Furthermore, a liquid crystal display device with high yield, high performance, and high reliability can be realized. In particular, when a liquid crystal display device is manufactured using a glass substrate having a size of 300 mm × 400 mm or more, a particular effect is exhibited. Further, it goes without saying that it can be applied to other electronic devices using thin film transistors.

Further, the effect of the present invention is not limited to the transistor structure described in the above embodiment.
Furthermore, although the pixel electrode 2 is formed before the gate electrode 4 is formed, the invention is not limited to this.
The same effect was obtained with the structure in which the pixel electrode is formed.
In addition, in the above embodiment, as the oxide thin film 6, in addition to tantalum oxide, aluminum oxide, silicon oxide, tantalum oxide containing barium, barium titanate, strontium titanate, zircon oxide, zirconate titanate. Barium acid, strontium zirconate titanate, strontium, barium, tin, titanium,
Similar good results were obtained in thin films of perovskite type oxides containing manganese, hafnium, zircon, tungsten and the like. However, although the ratio of oxygen to the metal element was slightly deviated from stoichiometry, this effect was not affected and good results were obtained.

Although a pure aluminum thin film is used as the gate electrode 4, the same result was obtained with an aluminum alloy. Even when a metal containing aluminum as a main component and containing tantalum, titanium, zirconium, or molybdenum is used for the gate electrode 4, the effect of suppressing the generation of holes inside the gate electrode 4 is It was obtained by forming the oxide thin film 6 by using the reactive sputtering method including, and a good thin film transistor could be manufactured. As the oxide thin film 6, a thin film of tantalum oxide, aluminum oxide, titanium oxide, silicon oxide, niobium oxide, zirconium oxide, or perovskite type oxide was obtained, and good results were obtained.

In the above embodiment, the metal wiring containing aluminum as a main component is applied to the gate electrode 4, but the present invention is not limited to this, and may be applied to the source / drain electrodes, or the transistor. It may be applied to other wirings other than.

[0027]

As described above, according to the present invention, the anodic oxide film is formed on the surface of the metal wiring mainly containing aluminum, and the substrate temperature is set to 150 ° C. in the oxygen plasma atmosphere on the anodic oxide film. By forming an oxide thin film by sputtering as described above and continuously performing heat treatment in an oxygen plasma atmosphere at a temperature equal to or higher than the substrate temperature at the time of sputtering, relaxation of internal stress of metal wiring containing aluminum as a main component and anodization By removing moisture from the film, the occurrence of migration can be suppressed, and a low-resistance metal wiring with few defects such as holes due to migration can be realized even if the wiring width is narrow and the film thickness is thin. By using this metal wiring as a gate electrode of a thin film transistor or the like, a highly reliable thin film transistor with few defects inside the electrode can be realized. Further, by applying it to a thin film transistor of a liquid crystal display device, a liquid crystal display device with high yield, high performance and high reliability can be realized. Further, it goes without saying that it can be applied to other electronic devices using thin film transistors.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing the method of manufacturing a semiconductor device according to the embodiment of the present invention.

FIG. 3 is a process cross-sectional view showing the method of manufacturing a semiconductor device according to the embodiment of the present invention.

FIG. 4 is a process cross-sectional view showing the method for manufacturing a semiconductor device according to the embodiment of the present invention.

FIG. 5 is a process sectional view showing the method for manufacturing the semiconductor device according to the embodiment of the present invention.

FIG. 6 is a process sectional view showing the method for manufacturing the semiconductor device in the embodiment of the present invention.

FIG. 7 is a process sectional view showing the method for manufacturing the semiconductor device according to the embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view of a main part of an in-line type sputtering apparatus used for forming an oxide thin film in the embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a state where holes are formed in the gate electrode of the thin film transistor according to the embodiment of the present invention.

[Explanation of symbols]

 1 glass substrate 2 pixel electrode 3 silicon oxide film 4 gate electrode 5 aluminum oxide film (anodic oxide film) 6 oxide thin film 7 silicon nitride film 8 semiconductor layer 9 channel protective film 10 ohmic contact layer 11 source / drain electrode 12 contact hole 13 Protective insulation film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuo Imada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A metal wiring containing aluminum as a main component is formed on an insulating substrate, the metal wiring is anodized to form an anodic oxide film, and then the substrate temperature is set to 150 ° C. in an oxygen plasma atmosphere. After the oxide thin film is formed on the anodic oxide film by sputtering as described above, a heat treatment is continuously performed in the oxygen plasma atmosphere at a temperature equal to or higher than the substrate temperature at the time of sputtering. 2. A step of forming a gate electrode containing aluminum as a main component on an insulating substrate, a step of anodizing the gate electrode to form an anodic oxide film, and a substrate temperature of 150 in an oxygen plasma atmosphere. A step of forming an oxide thin film on the anodized film by sputtering at a temperature of ℃ or higher, and then continuously performing heat treatment in the oxygen plasma atmosphere at a temperature equal to or higher than the substrate temperature at the time of sputtering; and insulating on the oxide thin film. A method of manufacturing a semiconductor device, comprising: a step of forming a semiconductor layer via a film; and a step of forming source / drain electrodes on the semiconductor layer. 3. The manufacturing of a semiconductor device according to claim 1, wherein the oxide thin film is a thin film of an oxide containing at least one of aluminum, tantalum, titanium and silicon or a perovskite type oxide. Method. 4. A method of manufacturing a liquid crystal display device, wherein a liquid crystal layer is sandwiched between an array substrate in which pixel electrodes and thin film transistors are formed in a matrix and an opposite substrate in which opposite electrodes are formed. A method for manufacturing a liquid crystal display device, which is formed by the method for manufacturing a semiconductor device according to claim 2.