JP2851495B2 - Active matrix substrate manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an active matrix substrate using thin film transistors as active elements for driving picture element electrodes.

[0002]

2. Description of the Related Art In an active matrix type liquid crystal display device using the above-mentioned thin film transistor (hereinafter referred to as TFT), insertion of a TFT reduces crosstalk between picture elements and does not limit the number of scanning lines. There are advantages. Therefore, compared to a simple matrix type display device,
A large-capacity, high-quality display can be obtained.

For this reason, active matrix substrates used in active matrix type liquid crystal display devices have been actively studied.

FIG. 6 shows a conventional active matrix type liquid crystal display device. This liquid crystal display device has a glass substrate 6
01, a display portion 602, a scanning line driving portion 603, and a signal line driving portion 604 are formed. Display part 602
Are formed with a scanning line 605 and a signal line 606, a display TFT 607 for driving each picture element is formed at an intersection thereof, a liquid crystal layer 608 and a charge storage storage capacitor 609.
It is connected to the. Further, a driving TFT for driving the display portion is formed in each of the scanning line driving portion 603 and the signal line driving portion 604.

As a TFT used for the active matrix substrate as described above, a thin film transistor (hereinafter a-SiT) using a semiconductor layer made of amorphous silicon is used.
FT), a thin film transistor using a semiconductor layer made of polycrystalline silicon (hereinafter referred to as p-Si TFT), a thin film transistor using a semiconductor layer made of crystalline silicon (hereinafter referred to as c-Si TFT), and the like. .

Here, polycrystalline silicon has various crystal orientations in the same film, and crystalline silicon refers to a single crystal having the same crystal orientation.

[0007]

The above a-S
i TFT has a field effect mobility of about 1 cm ₂ / v
alts · sec or less. For this reason, there is no problem when used as a display TFT for driving a picture element, but the performance is insufficient when used as a TFT for driving a display portion. Therefore, it is difficult to form the display TFT and the display portion driving TFT on the same substrate. Even if it can be formed, only 300 scanning line driving circuits can be made monolithic.

On the other hand, p-Si TFT and c-Si TFT
Since the TFT has a large grain size, the field-effect mobility is 30 to 600 cm ₂ / volts · sec.
And is excellent. Therefore, not only the scanning line driving circuit,
It can also be used for a signal line driver circuit. However, these TFTs have a more difficult manufacturing process than a-Si TFTs. For example, a high-temperature process (600 ° C. or higher) is required, and the process is complicated when manufacturing by solid phase growth, laser annealing, or the like. Therefore, it is difficult to increase the area of the substrate, and the manufacturing cost increases.

In the case of a p-Si TFT, particularly when used as a display TFT for driving a picture element,
In order to prevent leakage current between crystal grains, an annealing process, a hydrogen process, and the like are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a high performance active matrix substrate provided with a display TFT for driving picture elements and a TFT for driving a display section on the same substrate. Inexpensively.

[0011]

[0012]

[0013]

Means for Solving the Problems] active matrix of the present invention
In the method for manufacturing a liquid crystal substrate, a display unit including at least a display pixel electrode, a display thin film transistor, a scan line, and a signal line, and one or more drive circuits for driving the display unit are provided side by side on the same substrate. In the method for manufacturing an active matrix substrate in which the driving circuit has a driving thin film transistor, a step of forming a semiconductor layer of each thin film transistor from amorphous silicon, and heating the semiconductor layer of the driving thin film transistor by a high-frequency induction heating method Treating the semiconductor layer with polycrystalline silicon or crystalline silicon, thereby achieving the above object.

[0014]

[0015]

In the present invention, since the high frequency induction heating method is used,
The area to be crystallized is located at the installation position of the high-frequency induction heating coil.
Can be more easily controlled, for example, formed on the substrate
Scan lines and signal lines while avoiding the display
Only the portion can be heated. Therefore, the display
Of the thin film transistor semiconductor layer
For heating scan lines and signal lines by heat treatment
Excellent thin film transistor semiconductor layer with excellent field effect mobility
Can be polycrystalline silicon or crystalline silicon
Become. Moreover, according to the high-frequency induction heating method,
Depending on the conditions of the source, crystallization temperature, etc.
Can finely control the formation of crystalline silicon
You. As a result, the same manufacturing process
Inexpensive utilizing the characteristics of thin film transistors in each part
To manufacture high-performance active matrix substrates
It becomes possible.

[0016]

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a liquid crystal display device formed using an active matrix substrate according to an embodiment of the present invention.

In this liquid crystal display device, a display portion 102 is formed on a glass substrate 101, and a scanning line drive portion 103 and a signal line drive portion 104 are formed as display portion drive portions. A scanning line 105 and a signal line 106 are formed in the display portion 102, and an a-Si TFT 107 which is an active element for driving a picture element is formed in a crossing portion thereof, and is connected to a liquid crystal layer 108 and a storage capacitor 109 for holding a charge. Have been. On the other hand, the p-Si TFT or c-SiTF is provided in the scanning line driving portion 103 and the signal line driving portion 104.
T is formed.

The above p-Si TFT or c-Si T
Depending on the carrier transfer capability of the semiconductor layer in the FT,
It is also possible to form only the scanning line driving circuit on the same substrate and form the signal line driving circuit on another substrate (Si wafer) and connect it to the liquid crystal display device.

The charge storage capacitor may not be added in some cases, or the next scan line may be used without providing a storage capacitor wiring.

FIGS. 2A and 2B show an example of an equivalent circuit of a signal line driving portion.

This part is composed of a shift register 210, an analog switch 211, an output buffer part 212 and a hold capacitor 213.
An iTFT or c-Si TFT 204, 205 and a line memory 203 are formed. In this figure, 201 is a power supply, 202 is an analog switch, 204
Denotes a multi-level line, 206 denotes an output, 207 denotes a matrix switch, 208 denotes a ground line, and 209 denotes a multi-level selector.

FIG. 3 shows an example of an equivalent circuit of a scanning line driving portion.

In this part, the shift register 30
1 and the output buffer 302 are constituted by p-Si TFTs or c-Si TFTs. 3, 303 and 309 are start pulses, 304 and 306 are clock signals, 305 is an inverter, 30
7 denotes a power supply voltage, 308 denotes an output terminal, and 310 denotes a ground.

A method for manufacturing the liquid crystal display device having the above-described configuration will be described below.

First, as shown in FIG. 4A, tantalum is sputter-deposited on a glass substrate 401 so as to have a film thickness of 300.
It is formed into a thin film of 0 Å. Thereafter, patterning is performed by a photolithographic technique, and the gate wiring 40 is formed.
2. Formed on the storage capacitor wiring 403. At this time, the gate electrode 409 is also formed in the display portion driving portion.

Next, the surface of the tantalum film is oxidized by anodic oxidation to form a tantalum oxide (Ta ₂ O ₅ ) layer 404 as required.

Further, as shown in FIG. 4 (b), both the display portion and the display portion drive portion are made of a 3000 angstrom thick silicon nitride (SiN) film by a plasma CVD method.
x) Layer 405, intrinsic amorphous silicon (a-Si (i)) layer 40 having a thickness of 100 to 2000 Å
6 and n-type amorphous silicon (a-Si
(N ⁺ )) Deposit layer 407.

Next, as shown in FIG. 4C, the display drive section is heated by the high-frequency induction coil 408 connected to the high-frequency power supply 410 to heat the gate electrode 409. As a result, aS on the gate electrode 409
The i (i) layer 406 and the a-Si (n ⁺ ) layer 407 are heat-annealed and crystallized, and as shown in FIG. 4D, the p-Si or c-Si semiconductor layers 412, 413
Becomes

The region to be crystallized can be controlled by the installation position of the high-frequency induction heating coil 408, and for example, can be configured as shown in FIG. In this configuration, the scanning line driving portion 10 formed on the substrate 401
3 and only the signal line driving portion 104 is heated,
A coil 408 is provided.
Is not provided. Therefore, after this heat treatment,
The semiconductor layers 406 and 407 of the display TFT remain a-Si. By changing the installation position of the high-frequency induction heating coil 408, a part of the semiconductor layer of the display TFT may be a p-Si or c-Si semiconductor layer, or a part of the TFT for driving the display unit may be a-Si. It is also possible to leave the semiconductor layer as it is.

Further, the material, resistance, thickness, etc. of the gate electrode 409 and the coil for high-frequency induction heating need to be prepared so that high-frequency induction heating can be performed. For example, as a material of the gate electrode 409, Ta, Al, Cr, Nb, Ti,
Alloys such as TaMo, W, Mo, Pt, and Au can be used, and Cu, Au, Ag, and oxide superconducting materials can be used as the coil material. The formation of p-Si or c-Si can be controlled by conditions such as crystallization temperature and a high-frequency power supply. In this embodiment, Cu is used as the coil 408 and 1 kW (power of the high-frequency power source, frequency 1
MHz or more).

Next, as shown in FIG. 4E, the a-Si (i) layer 4 in the display portion is formed by photolithography.
06 and the a-Si (n ⁺ ) layer 407 and the p-Si or c-Si semiconductor layers 412 and 413 are patterned in an island shape. Thereafter, a source electrode 414 and a drain electrode 415 are formed by sputtering and depositing titanium (Ti) to a thickness of 3000 angstrom and patterning by photolithography.

Next, the n-type semiconductor layers 407 and 413 are shown in FIG.
The TFT is formed by etching with the pattern shown in FIG.

Further, for the display portion, an ITO film for a pixel electrode is further sputter-deposited to a thickness of 1000 Å and patterned by a photolithographic method to form a pixel electrode 416 and a source wiring 417.

Next, as shown in FIG. 4F, a protective film 418 is formed by depositing silicon nitride (SiNx) to a thickness of 3000 angstrom by a plasma CVD method, and a light shielding film 419 is formed thereon. To obtain an active matrix substrate.

Further, after bonding the substrate and a counter glass substrate 422 on which a transparent electrode 420 made of ITO and an alignment film 421 are formed, a liquid crystal 423 is placed between the substrates.
To form a liquid crystal display device.

The a-Si crystallization process by the high-frequency induction heating method may use a method other than the above-mentioned process as long as it is before the liquid crystal is injected. For example, crystallization can be performed when the TFT is completed.

As described above, for the display portion,
A-Si TFTs for display are formed for driving picture elements,
As for the display portion driving portion, a liquid crystal display device in which a driving p-Si TFT or a c-Si TFT is formed is obtained.

In this embodiment, heating at about 1000 ° C. is obtained, and the semiconductor layers 412, 4
13 became a p-Si semiconductor layer or a c-Si semiconductor layer. This allows the field effect mobility to be 30 cm ₂ /
V · s, and the driver circuits for driving 480 scanning lines and the driver circuits for driving 240 signal lines could be made monolithic.

The display TFT for driving the picture element is a
−Si TFT remains, and it is easy to increase off-resistance.

In this embodiment, the reverse stagger type TF
Although T was used, a coplanar type may also be used. In the positive stagger type, a-Si crystallization is performed in a state where the TFT is completed. In the case of a reverse stagger type TFT, induction heating is desirable because it can be easily performed using a gate electrode metal.

[0043]

As described above, according to the present invention,
According to the method of manufacturing a matrix substrate, high-frequency induction heating
Method, the area to be crystallized is
Can be easily controlled by the installation position of the
For example, avoiding the display area formed on the substrate,
In addition, only the driving portion of the signal line can be heated. Obedience
Therefore, the semiconductor layer of the thin film transistor in the display portion is made amorphous.
Keep the silicon and scan lines and signals by heat treatment.
Field effect transfer of semiconductor layer of thin film transistor for driving line
Polycrystalline silicon or crystalline silicon with excellent mobility
be able to. Moreover, according to the high-frequency induction heating method,
Polycrystalline silicon depending on conditions such as frequency power supply and crystallization temperature
Fine-grained control of silicon or crystalline silicon formation.
Wear. As a result, on the same substrate, the same manufacturing process
It is safe to make full use of the characteristics of thin film transistors in each part.
To manufacture high-performance, high-performance active matrix substrates
Can be.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a liquid crystal display device formed using an active matrix substrate according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of an equivalent circuit of a signal line driving portion.

FIG. 3 is a diagram illustrating an example of an equivalent circuit of a scanning line driving portion.

FIG. 4 is a diagram showing a manufacturing process of the active matrix substrate of the present invention.

FIG. 5 is a diagram illustrating an example of a system configuration of a high-frequency induction heating process in the embodiment.

FIG. 6 is a diagram showing a conventional liquid crystal display device.

[Explanation of symbols]

Reference Signs List 102 Display part 103 Scan line driving part 104 Signal line driving part 107 a-Si TFT 406 Intrinsic amorphous silicon (a-Si
(I)) Layer 407 n-type amorphous silicon (a-Si
(N ⁺ )) layer 408 High frequency induction heating coil 410 High frequency power supply 412 p-Si (i) or c-Si (i) layer 413 p-Si (n ⁺ ) or c-Si (n ⁺ ) layer

Continuing on the front page (72) Inventor Kiyoshi Nakazawa 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Makoto Miyago 22-22 Nagaikecho, Abeno-ku, Osaka-shi Osaka Prefecture Inside Sharp Corporation (72 ) Inventor Yoshiharu Kataoka 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Inside Sharp Corporation (56) References JP-A-4-184424 (JP, A) JP-A-63-11989 (JP, A) JP-A Heisei 6-45607 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/136 500

Claims (1)

(57) [Claims] To 1. A same substrate, at least the display pixel electrodes, display thin film transistor, a display unit composed of scanning lines and signal lines, one or more drive circuits for driving the display unit is arranged, A method of manufacturing an active matrix substrate in which the driving circuit has a driving thin film transistor, the method comprising: forming a semiconductor layer of each thin film transistor from amorphous silicon; and heating the semiconductor layer of the driving thin film transistor by high-frequency induction heating.
Subjected to heat treatment by law, active and a step of the material of the semiconductor layer and the polycrystalline silicon or crystalline silicon
A method for manufacturing a matrix substrate .