JPH05343327A - Film-forming method - Google Patents

Abstract

PURPOSE:To form a good-quality film with high productivity by keeping a film-formed substrate in a water-vapor atmosphere under 0.1-10Torr pressure, while the temperature of the film-formed substrate is raised from room temperature to film-forming temperature, and thereafter by starting film forming in a film-forming method through an atomic layer deposition method. CONSTITUTION:A rotator holding a sample S is placed in a reaction chamber 30 and rotated at 60rpm at the time of film forming or temperature rise. The inside of the reaction chamber 30 is exhausted of the air by a turbo-molecular pump VP to high vacuum. While the temperature of the reaction chamber rises from room temperature to 500 deg.C film-forming temperature, water vapor is caused to continue to flow through control valve V2 from an inlet N2 and adjusted by an orifice valve OF so that the pressure in the reaction chamber is 1Torr. In this case, Ar gas is used as the carrier gas of water vapor and the flow rate of the Ar gas is 200SCCM. At the time of film forming, the control valve V1 is opened and a fixed quantity of TMA gas 32 is introduced by the use of Ar gas as carrier gas. The flow rates of raw material gases are 100SCCM in the case of H2O gas and 40SCCM in the case of TMA gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic layer deposition method which is one of film forming techniques. With the advancement of thin film utilization technology in recent years, improvement of film quality such as crystallinity and uniformity of thin film is required. In particular, a method that can control the growth of semiconductor thin films that compose functional devices using the quantum size effect at the single atomic layer level is required, and semiconductor thin films with good crystallinity are being formed by the atomic layer deposition method. ..

Further, not only a semiconductor thin film, but also an insulating film can form a high quality thin film. For example, the insulation film of a thin-film EL (electroluminescence) panel is required to have a high breakdown voltage, no defects, and a long life, and it is necessary to realize a high-quality film quality that does not contain impurities or film defects in the thin film.

In the atomic layer deposition method, when forming a thin film, a plurality of gases as raw materials are alternately switched and introduced into the thin film forming region to form one layer at a single atomic layer level.
A high quality thin film can be formed.

[0004]

2. Description of the Related Art In the conventional atomic layer deposition method, the source gas is not introduced into the growth chamber when the temperature of the deposition target substrate is raised to the deposition temperature, and the source gas is not supplied until the deposition temperature is reached. The method of introducing and starting film formation was adopted.

There is also a method of making a water vapor atmosphere while the temperature is rising. Even when this method is used, the water vapor pressure is 10 ^-2.
It was performed at a relatively low pressure below Torr. The thin film transistor (TFT) gate has a two-layer structure in which titanium (Ti) is coated on the underlying aluminum (Al) film, and as long as plasma vapor deposition (CVD) method is used for the gate insulating film. Was unreliable. When the gate insulating film is formed, the resist used for patterning the gate may remain and cause serious defects.

[0006]

The film quality of the thin film (ALD film) formed by the conventional atomic layer deposition method is not stable, and white turbidity or dot-like unevenness often occurs. Also, like this
Even if a TFT-type LCD (liquid crystal display) gate insulating film is formed with an ALD film to create an evaluation element and the TFT characteristics are measured, dielectric breakdown, threshold voltage shift, etc. due to the withstand voltage test still occur. It was

Further, since the conventional gate has a two-layer structure of Ti / Al and the manufacturing process is complicated, it is desired to prepare a TFT having a single-layer gate. The present invention improves the above problems,
It is an object of the present invention to enable high quality film formation with high productivity.

[0008]

[Means for Solving the Problems] 1)
A film forming method by an atomic layer deposition method in which a film forming substrate is alternately exposed to a plurality of source gas atmospheres, wherein the film forming substrate is heated while the temperature of the film forming substrate is raised from room temperature to the film forming temperature. Film forming method in which the pressure is kept in a steam atmosphere of 0.1 to 10 Torr, and then film formation is started, or 2) the film forming apparatus described in 1) above, in which an inert gas is added to the steam atmosphere, or 3 The film-forming substrate is an insulating substrate on which metal film wiring is arranged, and the film-forming apparatus described in 1) or 2) above is used to grow an insulating film thereon.

[0009]

[Function] In the film formation by the atomic layer deposition method, the nucleus growth in the initial stage of the film formation controls the subsequent film formation state. It is often not difficult to set film formation conditions after the middle period. However, even if the initial conditions are reliably set, defects such as white turbidity and uneven film formation often occur, and the process before the start of film formation is important.

Therefore, conventionally, when the temperature is increased before film formation, the temperature is raised in a low-pressure steam atmosphere as described above to oxidize the surface when Al or the like is used for the gate material, and AL with few defects that facilitates nuclear growth
I tried to grow D film.

However, when the temperature is raised in a steam atmosphere,
When the water vapor pressure is as low as 10 ^-2 Torr or less, it promotes abnormal growth of alumina nuclei. Therefore, it was found from the experiments by the present inventor that a relatively high pressure of 0.1 to 10 Torr suppresses abnormal growth of alumina nuclei and enables film formation with good film quality. At this time, the inert gas (He, Ar, Ne, K
(r, Xe, etc.) may be added to adjust the water vapor pressure.

The limit of the water vapor pressure was determined experimentally by confirming the presence of cloudiness and defects in the grown film. When this alumina ALD film is used as the gate insulating film of a TFT LCD panel, the gate can have a single-layer structure of Al. The reason is that the alumina ALD film and the Al gate have good adhesion and good coverage. As a result, the breakdown voltage of the gate insulating film is higher than when other materials are used, and LC
It is possible to prevent pixel defects of the D panel, especially point defects.

Further, the resist residue generated when patterning the gate is also removed by a sulfuric acid type etchant before forming the alumina ALD film, so that the reliability of the gate insulating film can be improved.

[0014]

1 is a perspective view of an ALD device for explaining an embodiment of the present invention. In the figure, in the reaction chamber 30, there is a rotor for holding the sample S, which is rotated at 60 rpm during film formation or temperature rise. In the reaction chamber (growth chamber),
The turbo molecular pump VP evacuates to a high vacuum. While increasing the temperature from room temperature to 500 ℃, control valve V2
Steam continues to flow from the inlet N2 through the orifice valve OF
The pressure inside the reaction chamber was adjusted to 1 Torr. At this time, argon (Ar) gas was used as the carrier gas for water vapor, and the flow rate was 200 SCCM.

At the time of film formation, the control valve V1 is opened,
Tetramethylaluminum (TM) using Ar gas as carrier gas
A) A certain amount of gas 32 was introduced. The flow rate of the source gas is H ₂ O
Gas is 100 SCCM and TMA gas is 40 SCCM. Ar gas 31 is used as a barrier gas by controlling the control valve V0 to flow 350 SCCM in a curtain shape from the inlet N0 so that the raw material gases do not mix and react in the gas phase.

Each source gas is heated by a heater before being introduced into the reaction chamber. The heating temperature is 80 ° C for H ₂ O gas and 65 ° C for TMA gas. As the sample of the example, an Al glass film was formed on an insulating glass substrate, and an alumina ALD film was formed thereon. Before and after film formation, a sulfuric acid-based etchant was used to remove the resist residue, and some were not.

It took 5400 rotations at the above-mentioned number of rotations to form an ALD film of about 4000Å. A 500N silicon nitride (SiN) film was grown on this ALD film by the plasma CVD method to form a gate insulating film (interlayer insulating film).

2 (A) and 2 (B) are sectional views of the TFTs of the embodiment and the conventional example. In the figure, 1 is a glass substrate, 2 is a gate bus line GB of the embodiment, an Al film, 2A and 2B are a conventional gate bus line GB, an Al film, a Ti film, 3 and 4 are gate insulating films of the embodiment. Alumina ALD film, SiN film,
3'and 4 are conventional gate insulating films, SiO ₂ film, SiN film, 5
Is a channel layer which is an amorphous silicon (a-Si) layer, 6 is a contact layer which is an n ⁺ type a-Si layer, 7 is a source / drain electrode which is a titanium (Ti) film, 8 is a channel protective film which is a SiN film, and 9 is a drain In the bus line DB, an Al film and 10 are pixel electrodes (ITO transparent electrodes).

On the substrate, the gate bus line connecting the gates of the respective TFTs is orthogonal to the drain bus line DB connecting the drains of the respective TFTs or the source bus line connecting the sources of the respective TFTs forms a gate insulating film. Are located through.

[0020]

According to the present invention, an ALD film having good film quality can be obtained. When the present invention is applied to the manufacture of a TFT type LCD panel, the alumina nuclei are not grown abnormally at the interface between the gate electrode or the gate bus line and the interlayer insulating film (gate insulating film) before the ALD film formation. The formation of ALD film with good quality is obtained.

The ALD film formed by the method shown in the example has a cloudiness, which is more turbid than that without heating in a steam atmosphere or with heating in a low-pressure steam atmosphere.
A film without unevenness in film thickness and dot defects was obtained. In addition, the panel formed of the ALD film of the example has a high withstand voltage, and
A product with good characteristics and no display unevenness was obtained.

Further, a film of which the resist residue was removed with a sulfuric acid-based etchant before the film formation was able to obtain a higher quality film than the film of which the resist residue was not removed.

[Brief description of drawings]

FIG. 1 is a perspective view of an ALD device illustrating an embodiment of the present invention.

FIG. 2 is a sectional view of a TFT according to an example and a conventional example.

[Explanation of symbols]

1 glass substrate 2 Al film on the gate bus line GB of the embodiment 2A, 2B Al film on the gate bus line GB of the conventional example,
Ti film 3, 4 Alumina ALD for each of the gate insulating films of the examples
Film, SiN film 3 ', 4 Conventional gate insulating film SiO ₂ film, SiN film 5 Channel layer a-Si layer 6 Contact layer n ⁺ type a-Si layer 7 Source drain electrode Ti film 8 Channel protection Film is SiN film 9 Drain bus line DB is Al film 10 Pixel electrode (ITO transparent electrode)

Claims (3)

[Claims] 1. A film forming method by an atomic layer deposition method in which a film formation substrate is alternately exposed to a plurality of source gas atmospheres, and the temperature of the film formation substrate is raised from room temperature to a film formation temperature. A film forming method characterized in that the film formation substrate is kept in a water vapor atmosphere having a pressure of 0.1 to 10 Torr, and then film formation is started. 2. The film forming apparatus according to claim 1, wherein an inert gas is added to the water vapor atmosphere. 3. The film forming apparatus according to claim 1, wherein the film formation substrate is an insulating substrate on which metal film wiring is arranged, and an insulating film is grown on the insulating substrate.