JPH08122825A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a picture element electrode of desirable shape with less undesirable etching of the picture element due to electrocorrosion and without increasing the number of steps, by using indium oxide as the picture element. CONSTITUTION: Picture elements which are composed of a thin film transistor and a picture element electrode connected with the thin film transistor electrically are plural matrix arranged. On this occasion. the thin film transistor and the connecting electrode for connecting the picture element electrode are formed by aluminum or a metal whose main component is aluminum. and the picture element electrode is formed by indium oxide. And at least one element among scandium, silicon. copper. tungsten, and nickel other than aluminum is added to aluminum or the metal whose main component is aluminum. Thereby, ionization tendency of aluminum for constituting wiring is changed and electrocorrosion is hard to be generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device which mainly uses aluminum as a wiring material.

[0002]

2. Description of the Related Art At present, active matrix type liquid crystal display devices are being increased in display screen size and resolution. On the other hand, each pixel of the active matrix type liquid crystal display device is provided with a pixel electrode and a thin film transistor connected to the pixel electrode. A scanning line for selecting a display pixel is connected to the gate of the thin film transistor, and a signal line for transmitting a data signal such as a gradation signal is connected to the drain (or source). Also,
The source (or drain) of the thin film transistor has I
Pixel electrodes made of TO (indium tin oxide) are connected via metal electrodes in order to reduce the contact resistance. Metals such as tantalum and chromium are used for these scanning lines and signal lines.

However, as the display screen becomes larger and the resolution becomes higher, the wiring such as the scanning line and the signal line becomes longer,
Thin things are needed. Therefore, in order to accurately transmit a signal required for each pixel, it is required to reduce the resistance of the wiring, and for that reason, the wiring is provided using aluminum whose electric resistance is lower than that of chromium or tantalum. There is.

FIG. 1 shows the structure of a pixel portion of a conventional active matrix circuit using aluminum wiring. An active matrix circuit configured using aluminum wiring is provided on a substrate 1 having an insulating surface such as glass,
Source (drain) region 2, channel forming region 3, drain (source) region 4, gate insulating film 5, gate electrode 6
A thin film transistor composed of (signal line), a first interlayer insulating film 7, a pixel connecting electrode 8 (source (drain) electrode), a drain (source) electrode 9, and a second interlayer insulating film 1.
0, the pixel electrode 11 is provided. Pixel connection electrode 8
Is made of aluminum and electrically connects the source (drain) region and the pixel electrode. The pixel electrode 11 is
An ITO (indium tin oxide) film is formed and patterned.

[0005]

[Problems of the Prior Art] However, I which becomes the pixel electrode 11
During the patterning process of the TO film, the photoresist 12
After development, the ITO film was sometimes removed up to the region 13 inside the portion masked with the resist. Further, also in the subsequent etching process,
The ITO film may be unnecessarily removed to the inner side by the portion masked with the resist, and the initially intended pixel electrode shape may not be obtained. In the worst case, the pixel electrode 11 and the pixel connection electrode 8 may not be formed. Sometimes the connection was broken.

In an active matrix type liquid crystal display device having ITO and aluminum wiring, in a resist developing process and an etching process when patterning pixel electrodes,
It is considered that the reason why the pixel electrode is removed more than necessary is that electrochemical etching, so-called electrolytic corrosion, is performed between aluminum and ITO. In this electrolytic corrosion, a potential difference occurs between aluminum and ITO due to different redox potentials of aluminum and ITO through a developing solution or an etching solution, which is an electrolyte liquid, whereby ions are eluted in the liquid. It is believed that this is because of the resulting etching. But aluminum and I
Between TO and TO, for example, it is often observed that ITO is removed even when aluminum is not in contact with the electrolyte liquid at all, and there is a point where the principle is unclear.

In order to prevent this electrolytic corrosion, it is considered to provide a metal film of titanium or the like on aluminum, but this leads to an increase in the number of steps, which causes a decrease in productivity and an increase in cost, which is preferable. Absent,.

[0008]

SUMMARY OF THE INVENTION According to the present invention, in an active matrix type liquid crystal display device using aluminum wiring, undesired deformation of the pixel electrode is prevented in the resist developing process and the etching process when patterning the pixel electrode. The aim is to get a preventive configuration.

[0009]

In order to solve the above problems, one of the inventions disclosed in this specification is that a pixel including a thin film transistor and a pixel electrode electrically connected to the thin film transistor is provided. An active matrix type liquid crystal display device having a plurality of matrix arrangements,
The liquid crystal display device is characterized in that the connection electrode connecting the thin film transistor and the pixel electrode is made of aluminum or a metal containing aluminum as a main component, and the pixel electrode is made of indium oxide. .

Another aspect of the invention disclosed in this specification is an active matrix type liquid crystal in which a plurality of pixels, each of which is composed of a thin film transistor and a pixel electrode electrically connected to the thin film transistor, are arranged in a matrix. In the display device, the connection electrode connecting the thin film transistor and the pixel electrode is made of aluminum or a metal containing aluminum as a main component, and the pixel electrode is made of indium oxide, and the aluminum or The metal containing aluminum as a main component is a liquid crystal display device in which at least one element of scandium, silicon, copper, tungsten, and nickel is added to aluminum.

Another aspect of the invention disclosed in this specification is an active matrix type liquid crystal in which a plurality of pixels, each of which is composed of a thin film transistor and a pixel electrode electrically connected to the thin film transistor, are arranged in a matrix. In the display device, the connection electrode connecting the thin film transistor and the pixel electrode includes aluminum or a metal containing aluminum as a main component, and any one of titanium, molybdenum, and chromium provided on the metal. And a thin film made of indium oxide, and the pixel electrode is made of indium oxide.

In the present invention, indium oxide (In ₂ O ₃ ) is used in place of conventional ITO (indium tin oxide) as a pixel electrode of an active matrix type liquid crystal display device using aluminum wiring as a wiring material. It is a thing.

[0013]

As a result of earnest research, the applicant of the present invention uses indium oxide as a pixel electrode to perform pixel electrode patterning when manufacturing an active matrix type liquid crystal display device using aluminum for an electrode in contact with the pixel electrode. It was discovered that in the resist developing step and the etching step, the undesired etching of the pixel electrode due to the above-mentioned electrolytic corrosion reaction can be extremely reduced. Although it is unclear why this is the case, it is considered that the use of indium oxide for the pixel electrode causes the potential difference due to contact with the electrolytic solution and other conditions to make it difficult to cause electrolytic corrosion. Therefore, a pixel electrode having a desired shape can be obtained without increasing the number of steps.

Further, in the above structure, it was discovered that electrolytic corrosion can be further prevented by adding a trace amount of a metal such as scandium, silicon, copper, or tungsten to the aluminum forming the wiring. This is considered to be because the addition of the above-mentioned metal changes the ionization tendency of aluminum forming the wiring and makes electrolytic corrosion less likely to occur.

Further, in the above structure, it was discovered that the electrolytic corrosion reaction can be further suppressed by providing a film of titanium, molybdenum, chromium or the like on the aluminum wiring. It is considered that this is because the potential difference between the metal forming the film provided on the aluminum wiring and the indium oxide film is reduced by doing so. In particular, molybdenum is more preferable because it can be etched with a fluorine-based etchant (in dry etching) like aluminum, so that the etching process can be simplified.

[0016]

EXAMPLE This example is a monolithic active matrix circuit for a liquid crystal display device in which a peripheral circuit and an active matrix circuit are provided on the same glass substrate and uses indium oxide as a pixel electrode. An example of producing The manufacturing process of this example is shown in FIG. A CMOS circuit is adopted as the peripheral circuit of this embodiment, but for simplicity, the peripheral circuit TFT is NTFT in FIG.
Show only. In FIG. 2, the left side shows the peripheral logic circuit,
The right side shows the matrix circuit as a representative.

Corning # 7059 (thickness 1.1 m
A base silicon oxide film 202 having a thickness of 2000 Å was formed on a glass substrate 201 (e.g., 300 × 400 mm) by a plasma CVD method. Monosilane (SiH ₄ ) and dinitrogen monoxide (N ₂ O) are used as source gases for the plasma CVD method.
The substrate temperature during film formation was set to 380 to 500 ° C., for example, 430 ° C. The silicon oxide film 202 thus formed had a relatively low etching rate and was a hard film. This is because dinitrogen monoxide was used as the source gas, so that the film became a silicon oxynitride film containing 1 to 10% of nitrogen. A typical etching rate is a hydrofluoric acid / ammonium fluoride / acetic acid ratio of 1: 50: 5.
The etching rate of acetic acid buffered hydrofluoric acid (ABHF), which was 0, at 23 ° C. was 800 to 1100 Å / min.

After that, a thickness of 5 is obtained by the plasma CVD method.
A 00Å amorphous silicon film was formed. further,
By performing thermal annealing at 550 ° C. for 1 hour in an oxidizing atmosphere, an extremely thin (estimated to be 40 to 100 Å) silicon oxide film was formed on the surface of the amorphous silicon film. Then, an extremely thin film of nickel acetate was formed by spin coating. Here, 1-100p
A pm nickel acetate aqueous solution was used. The thin silicon oxide film was first formed on the surface of the amorphous silicon film so that the aqueous solution can be uniformly spread on the surface of the amorphous silicon film.

Next, thermal annealing was performed at 550 ° C. for 4 hours in a nitrogen atmosphere. Nickel acetate decomposes into nickel at about 400 ° C., but since the nickel acetate thin film is in close contact with the amorphous silicon film, nickel penetrates into the amorphous silicon by this thermal annealing process and crystallizes it. It became a crystalline silicon region. Then, the silicon film was irradiated with XeCl excimer laser light (wavelength 308 nm). In this embodiment, the energy density of the laser is 250 to 300 mJ /
It was set to cm ² . As a result, the crystallinity of crystalline silicon was further improved.

Further, in order to alleviate the stress strain due to laser irradiation, thermal annealing was performed again. In this embodiment, thermal annealing is performed at 550 ° C. for 4 hours. Then, the silicon film is etched to form an island-shaped active layer 203,
Formed 204. Then, a 1200 Å thick silicon oxide film 205 was formed as a gate insulating film by a sputtering method.

Further, the thickness is 4000 by the sputtering method.
An aluminum film of Å (containing 0.2 to 0.3% by weight of scandium) was formed. Then, the surface thereof was anodized to form an aluminum oxide film (not shown) having a thickness of 100 to 300Å. Due to the presence of the aluminum oxide film, the adhesion to the photoresist is good, and by suppressing the leakage of current from the photoresist, it is possible to form the porous anodic oxide only on the side surface in the subsequent anodic oxidation process. Was effective in. Then, a photoresist (for example, OFPR800 /
30 cp) was formed by spin coating. This is patterned and etched to form the gate electrodes 209, 2
11, the gate line 210 was formed. The gate electrode 209 of the peripheral circuit, the gate line 210, and the gate electrode 211 of the matrix circuit are electrically insulated. The photoresist masks 206, 207, and 208 used for etching were left as they were. (Fig. 2 (A))

Next, a porous anodic oxidation is carried out by passing a current through the gate line 210 (that is, the gate electrode 211) with the photoresist mask attached, and the porous anodic oxide 212 is formed on the side surfaces of the gate line and the gate electrode. 213 was formed. The anodic oxidation may be performed using a 3 to 20% aqueous solution of citric acid or oxalic acid, phosphoric acid, chromic acid, sulfuric acid, or the like, and applying a constant current of 10 to 30 V to the gate electrode. In this example, the voltage was set to 10 V in an oxalic acid solution (30 ° C.) having a pH of 0.9 to 1.0, and 20 to 40.
Minutes, anodized. The thickness of the anodic oxide was controlled by the anodic oxidation time. When anodic oxidation is performed in such an acidic solution, a porous anodic oxide is produced. In this embodiment, the thickness of the porous anodic oxide is 3000 to 10000.
Å, for example, 5000 Å. (FIG. 2 (B))

Further, this time, the photoresist mask is peeled off, a current is applied to the gate line 210 to perform barrier type anodic oxidation, and a dense barrier type anodic oxide film 214 is formed on the side surfaces and upper surfaces of the gate line and the gate electrode. 215 to thickness 1
200Å formed. (Fig. 2 (C))

Next, the silicon oxide film 2 is formed by a dry etching method using the porous anodic oxides 212 and 213 as masks.
05 was etched to form gate insulating films 217 and 218. In this etching, a plasma mode of isotropic etching or a reactive ion etching mode of anisotropic etching may be used. However, it is important to prevent the active layer from being excessively etched by sufficiently increasing the selection ratio of silicon to silicon oxide. For example, if CF ₄ is used as an etching gas, the anodic oxide will not be etched and the silicon oxide film 2
Only 05 is etched. Moreover, the silicon oxide films 217 and 218 under the porous anodic oxides 212 and 213 remained without being etched. (Fig. 2 (D))

Further, only the porous anodic oxide was etched using a mixed solution of phosphoric acid, acetic acid and nitric acid (aluminum mixed acid). Aluminum mixed acid etches porous anodic oxide, but barely etches barrier type anodic oxide coatings 214, 215. However, since aluminum is etched, in order to protect the gate electrode of the peripheral circuit part,
The peripheral circuit portion was masked with photoresist.

Then, using this gate insulating film, impurities (phosphorus and boron, only NMOS is shown in the figure, only boron was actually doped) were introduced into the active layer by ion doping. . Taking phosphorus doping as an example, first, phosphorus ions are implanted with a relatively high acceleration voltage of 5 × 10 ^{14 to} 5 × 10 ¹⁵ atoms / cm ² at a relatively low acceleration voltage of 10 to 30 keV. At this time, since the accelerating voltage is low, the ion penetration depth is shallow, and phosphorus is implanted mainly in the regions 219 and 220 where silicon is exposed.

Next, phosphorus ions were implanted at a relatively high acceleration voltage of 60 to 95 keV and at a relatively low dose of 1 × 10 ¹² to 1 × 10 ¹⁴ atoms / cm ² . At this time, since the acceleration voltage is high, ions penetrate deeply, and phosphorus is also implanted into the region 221 covered with the gate insulating film. As a result, the heavily doped phosphorus regions 219 and 220 are formed.
A low-concentration phosphorus-doped region 221 was formed. That is, the pixel TFT could have a so-called double drain structure. The same applies to boron. In addition, activation of impurities after doping was also performed by laser annealing. (Fig. 2 (E))

After that, as a first interlayer insulator, a silicon oxide film having a thickness of 200 Å and a thickness of 4 are formed by a plasma CVD method.
A multilayer film 222 of a silicon nitride film having a thickness of 000 Å was deposited, and this was etched by a dry etching method to form contact holes 223, 224, 225, 226, 227. (Fig. 2 (F))

Then, an aluminum film of 5000 Å was formed by the sputtering method. At this time, for the aluminum film, scandium, silicon, copper, tungsten,
Electrolytic corrosion can be further prevented by adding at least one element of nickel. The amount of each element added is
About 0.18 atomic% of scandium, about 2 atomic% of silicon, about 1 atomic% of copper, about 6 atomic% of tungsten, and about 3 atomic% of nickel were preferable. At this time, by further providing a film of titanium, molybdenum, chromium or the like in a thickness of about 200 to 500 Å by a sputtering method or the like, electrolytic corrosion of the pixel electrode can be further prevented. Especially molybdenum
In the case of dry etching, since etching can be performed with a fluorine-based gas like aluminum provided earlier, the number of steps can be reduced as compared with other metals, which is preferable.
This aluminum film or a laminated film of the aluminum film and another metal film was etched to form aluminum electrodes / wirings 228, 229, 230 and 231. The aluminum electrode 231 is a connection electrode that connects the TFT and the pixel electrode.

Further, as a second interlayer insulator, a silicon oxide film 232 having a thickness of 2000 Å is formed by a plasma CVD method.
Was deposited, and a contact hole was formed in the drain side electrode 231 of the pixel TFT.

Next, in order to provide a pixel electrode, an indium oxide film having a thickness of 2000 Å was provided by a sputtering method. The substrate temperature was 50 to 150 ° C., and the pressure was 3 × 10 ⁻³ Torr in a chamber (not shown) by a reactive sputtering method using argon and oxygen. Then, a photoresist was formed in order to form the indium oxide film on the pattern of the pixel electrode. At this time, the indium oxide film was not removed in the developing step. further,
The indium oxide film masked by the photoresist was etched. Etching is hydrochloric acid: nitric acid: water =
An etching solution having a mixing ratio of 1: 0.03: 1 was used, the temperature of the etching solution was 25 ° C., and the etching rate was 160.
It was 0Å / min. In this etching process,
A desired pixel electrode pattern was obtained, and the inside of the region masked by the photoresist was not etched. In this way, the pixel electrode 233 made of indium oxide was provided.

As described above, aluminum is used as an electrode,
A pixel electrode having a desired shape could be obtained in a monolithic active matrix circuit having wiring. (Fig. 2 (G))

[0033]

According to the present invention, it is possible to obtain an active matrix type display device using aluminum as a wiring material, in which the pixel electrodes are not unnecessarily deformed or removed in the resist developing process and the etching process. The present invention contributes to higher resolution and larger size of an active matrix liquid crystal display device.

[Brief description of drawings]

FIG. 1 shows a configuration of a pixel portion of a conventional active matrix circuit using aluminum wiring.

FIG. 2 shows a manufacturing process of an example.

[Explanation of symbols]

 1 substrate 2 source (drain) region 3 channel formation region 4 drain (source) region 5 gate insulating film 6 gate electrode 7 first interlayer insulating film 8 pixel connection electrode (source (drain) electrode) 9 drain (source) electrode 10 Second interlayer insulating film 11 Pixel electrode 12 Photoresist 13 Region inside the portion masked with resist 231 Pixel connection electrode (source (drain) electrode) 233 Pixel electrode made of indium oxide

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/336

Claims (3)

[Claims] 1. An active matrix liquid crystal display device in which a plurality of pixels, each composed of a thin film transistor and a pixel electrode electrically connected to the thin film transistor, are arranged in a matrix. The liquid crystal display device, wherein the connection electrode connecting to the electrode is made of aluminum or a metal containing aluminum as a main component, and the pixel electrode is made of indium oxide. 2. An active matrix liquid crystal display device in which a plurality of pixels, each of which is composed of a thin film transistor and a pixel electrode electrically connected to the thin film transistor, are arranged in a matrix. The connection electrode connecting to the electrode is made of aluminum or a metal containing aluminum as a main component, the pixel electrode is made of indium oxide, and the aluminum or a metal containing aluminum as a main component is different from aluminum. , Scandium, silicon,
A liquid crystal display device, to which at least one element of copper, tungsten, and nickel is added. 3. An active matrix liquid crystal display device in which a plurality of pixels, each of which is composed of a thin film transistor and a pixel electrode electrically connected to the thin film transistor, are arranged in a matrix. The connection electrode connecting to the electrode is composed of aluminum or a metal containing aluminum as a main component, and a thin film made of any one of titanium, molybdenum, and chromium provided on the metal. The electrode is composed of indium oxide, wherein the liquid crystal display device is characterized.