JPH09148255A - How to clean the inside of the reaction vessel - Google Patents

Abstract

(57) Abstract: A cleaning method using a fluorine-based gas, in which the fluorine-based substance remaining in the reaction vessel is efficiently removed to shorten the downtime of the apparatus and to reduce the processing time. (EN) Provided is a method for cleaning the inside of a reaction container, which can surely improve reproducibility and which does not cause a new problem of contamination. SOLUTION: A fluorine-based gas is introduced into the reaction container for cleaning, and then pure water gas is introduced into the reaction container to positively react with the residual fluorine-based substance to be exhausted and removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine-based gas for a reaction product deposited in a reaction vessel during the operation of a plasma processing apparatus such as a CVD apparatus, a PVD apparatus and an etching apparatus used for manufacturing semiconductor elements and the like. The present invention relates to a method for cleaning the inside of a reaction container which is removed by.

[0002]

2. Description of the Related Art In a plasma processing apparatus used for manufacturing a semiconductor device or the like, when the reaction products adhering to the inside of a reaction vessel increase, this becomes a dust source and causes a particle defect which causes a defect of the semiconductor device. Cause problems. Therefore, in a predetermined cleaning cycle, the deposits of reaction products are removed by plasma cleaning. In this plasma cleaning, a cleaning gas is introduced in a state where the inside of the reaction container is kept in a vacuum to generate plasma, and the plasma is reacted with the adhering substances to be removed. As the cleaning gas, NF ₃ ,
Fluorine-based gases such as SF ₆ , CF ₄ and C ₂ F ₆ are often used.

However, there has been a problem that after plasma cleaning with a fluorine-based gas, a fluorine-based compound or a decomposed product of the fluorine-based compound is adsorbed and remains on a wall of the reaction container or parts inside the reaction container.

If this fluorine-based substance remains in the reaction vessel, the degree of vacuum in the reaction vessel deteriorates, and the reproducibility of processing before and after cleaning deteriorates. For example, in the case of film formation, residual fluorine is mixed into the film, resulting in deterioration of film characteristics.

Also, during maintenance, the inside of the reaction vessel may be opened to the atmosphere. At this time, if the fluorine-based substance remains in the reaction container, a high concentration of hydrofluoric acid is generated by the remaining fluorine-based substance, which adversely affects the human body.

For these reasons, the residual fluorine-based substance is removed by introducing air into the reaction vessel and evacuating it.

[0007]

However, the method for removing the residual fluorine-containing substance by introducing the atmosphere into the reaction vessel and exhausting the atmosphere is not always stable in the effect, There was a problem not.
This prolongs equipment downtime and hinders improved process reproducibility. Further, there is a problem that there is a possibility of new contamination that the inside of the reaction vessel is contaminated by the substance contained in the atmosphere.

The present invention has been made to solve the above problems, and it is possible to efficiently remove the residual fluorine-based substance, shorten the downtime of the apparatus, and reliably improve the reproducibility of the processing. Moreover, it is an object of the present invention to provide a new method for cleaning the inside of a reaction vessel without the problem of contamination.

[0009]

The present inventor has found that water (H
It was confirmed that the residual fluorine-based substance could be removed by introducing the ₂ O) gas into the reaction vessel and exhausting it. Moreover, according to this method, the residual fluorine-based substance can be removed more efficiently than in the case of the conventional introduction into the atmosphere.

That is, the method for cleaning the inside of the reaction vessel according to the present invention is a reaction for removing the fluorine-based residual substance remaining in the reaction vessel after cleaning the deposit adhered in the reaction vessel with the fluorine-based gas. A method for cleaning the inside of a container is characterized by flowing a gas of water to remove residual fluorine-based substances.

In the above method of introducing air into the reaction container, it is presumed that the residual fluorine-based substance reacts with moisture in the atmosphere and the reaction product is removed by exhaust.

Therefore, when an appropriate amount of water is introduced into the reaction vessel by the method of the present invention, the number of water molecules can be increased more reliably and in a large amount as compared with the introduction into the atmosphere. Therefore, the fluorine-based residual substance can be reliably and efficiently removed.

Further, according to the method of the present invention, the gas of clean water can be flowed in the state where the inside of the reaction vessel is hermetically sealed from the atmosphere, so that the problem of new contamination due to introduction into the atmosphere does not occur.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention is used for ECR for forming TiN film.
The case of application to a plasma CVD apparatus will be described as an example.

FIG. 1 shows a TiN film-forming E to which the present invention is applied.
FIG. 1 is a schematic vertical sectional view of a CR plasma CVD apparatus, which is equipped with a mechanism for introducing pure water into a reaction container.

The reaction container 10 includes a plasma chamber 11 and a reaction chamber 1.
Consists of two. The microwave power supply window 15 has an RF power source 22.
The RF electrode 14 connected to is provided to prevent the TiN from adhering to the microwave introduction window 15 and preventing the microwave from being transmitted.

First, a method of forming a TiN film will be described. The inside of the reaction vessel 10 is exhausted from the exhaust port 21. H ₂ , Ar, and N ₂ gas are introduced into the plasma chamber 11 through the gas introduction pipe 19, and TiCl 3 is introduced into the reaction chamber 12 through the gas introduction pipe 20.
₄ Gas is introduced. A direct current is supplied to the magnetic field generating coil 1 to form a magnetic field in the plasma chamber 11. A microwave generated by a microwave oscillator (not shown) is supplied from the microwave introduction window 15 to the plasma chamber 1 through the waveguide 13.
Install within 1. Plasma is generated by ECR excitation,
A TiN film is formed on the sample S on the sample table 18.

Next, a plasma cleaning method of the reaction product attached to the inside of the reaction vessel 10 at the time of forming the TiN film will be described. The inside of the reaction vessel 10 is evacuated. NF ₃ gas and Ar gas are introduced into the plasma chamber 11 through the gas introduction pipe 19. NF ₃ gas is a cleaning gas, and A
The r gas is for stabilizing the plasma. As described above, a magnetic field is formed in the plasma chamber 11 by the magnetic field generation coil 1, microwaves are introduced into the plasma chamber 11, ECR plasma is generated, and deposits attached to the inside of the reaction vessel 10 are removed. Remove. During the plasma cleaning with the NF ₃ gas, the sample stage 18 and the wall of the reaction container 10 are usually heated.

However, immediately after the plasma cleaning with the NF ₃ gas, a large amount of the fluorine-based substance generated by the decomposition of NF ₃ in the plasma remains in the reaction vessel 10.

Water is introduced to remove the fluorine-based residual substance.

The pure water introduction mechanism shown in FIG. 1 is an example of a mechanism for introducing pure water into the reaction vessel 1. A pure water tank 27 storing pure water 28 is connected to the reaction vessel 10 through a heating pipe 25. A liquid mass flow controller 26 for controlling the flow rate of pure water is provided in the heating pipe 25.

The introduction and exhaust of pure water into the reaction vessel 10 can be performed as follows. The inside of the reaction vessel 10 is evacuated to a vacuum through the exhaust port 21. An exhaust valve (not shown) provided between the exhaust port 21 of the reaction container 10 and a vacuum pump (not shown) is closed to keep the inside of the reaction container 10 in that state. While controlling the flow rate from the pure water tank 27 by the liquid mass flow controller 26, the heating pipe 2
Pure water 28 is introduced into the reaction vessel 10 through 5. Since the inside of the reaction container 10 is maintained in vacuum, the pure water 28 introduced is vaporized in the middle of the heating pipe 25 from the liquid mass flow controller 26 to the reaction container 10 and is supplied into the reaction container 10 as a gas. . When the inside of the reaction container 10 reaches a predetermined pressure, the supply of pure water is stopped, the exhaust valve (not shown) is opened, and the exhaust of the reaction container 10 is started. The reaction product of the water gas and the fluorine-based residual substance in the reaction vessel is exhausted. In this way, fluorine-based residual substances can be reduced.

To further reduce the fluorine-based residual substance,
The introduction and exhaust of pure water may be repeated several times.

In the above method, pure water was introduced with the exhaust valve closed, but if the flow rate of pure water is small, pure water may be supplied while exhausting with the exhaust valve open. .

FIG. 2 is a schematic partial sectional view showing another mechanism for introducing pure water into the reaction vessel. A pure water tank 27 storing pure water 28 is connected to the reaction vessel 10 through a heating pipe 25. The pure water tank 27 has a structure that can be hermetically sealed, and includes a heater 30 that heats the pure water 28. A gas mass flow controller 29 for controlling the flow rate of pure water is provided in the heating pipe 25.

The introduction and exhaust of pure water into the reaction vessel 10 can be performed as follows. The inside of the reaction vessel 10 is evacuated to a vacuum. The pure water tank 23 is heated, and the pure water 27
Of the heating pipe 25 while controlling the flow rate of the pure water in the form of gas that is vaporized by the gas mass flow controller 29.
It is introduced into the reaction vessel 10 through. Water gas is supplied into the reaction vessel 10 to generate a reaction product with the fluorine-based substance, which is exhausted to reduce the residual fluorine-based substance. According to this method, the fluorine-based substance can be continuously reduced, so that the remaining fluorine-based substance can be reduced by flowing the water gas for a predetermined time.

After the inside of the reaction vessel 10 is evacuated to vacuum, an exhaust valve (not shown) is closed, pure water gas is introduced until the inside of the reaction vessel 10 reaches a predetermined pressure, and then the exhaust valve. (Not shown) may be opened to exhaust the gas of water and the reaction product of the fluorine-based substance in the reaction vessel.

In introducing water according to the present invention, it is preferable to use pure water (with a resistance value of 2 MΩ or more). Sample table 18
The wall of the reaction vessel 10 is preferably heated to, for example, 80 ° C. or higher. The sample table 18 and the reaction container 1
It is preferable that the heating of the No. 0 wall is always performed during each treatment. For example, in a TiN film forming apparatus, it is preferable to always perform the TiN film forming process and the NF ₃ gas plasma cleaning process.

The appropriate flow rate of the pure water to be introduced may be determined depending on the internal volume of the reaction container, the pressure, and the open / close state of the exhaust valve. This is because the greater the flow rate, the greater the effect of removing the residual substance, but if the flow rate is too high, problems such as difficulty in vaporization occur. In the above-mentioned TiN film forming ECR plasma CVD apparatus, a flow rate of about 0.5 to 5 sccm may be used.

When introducing water according to the present invention, a gas such as N ₂ or Ar may be flown at the same time.

In the cleaning method of the present invention, as long as plasma cleaning is performed using a fluorine-based gas,
It can be applied to any device such as a CVD device, a PVD device, and an etching device. For example, in addition to the TiN CVD apparatus, there are a SiO ₂ CVD apparatus and a Poly-Si etching apparatus.

The cleaning method of the present invention can be used not only for NF ₃ gas plasma cleaning but also for plasma cleaning of fluorine-based gas such as SF ₆ , CF ₄ and C ₂ F ₆ . It can also be used for ClF ₃ plasma rescreening. In short, it can be applied to cleaning in which a fluorine-based residual substance is generated.

[0033]

EXAMPLES The present invention is applied to ECR plasma CVD for TiN film formation.
An embodiment adapted to the apparatus will be described. The device to which the present invention is applied is the device shown in FIG.

Through the processes of forming a TiN film on a Si wafer, performing plasma cleaning with NF ₃ gas, and removing residual fluorine-containing substances by introducing pure water, the sample stage 18 is kept at 600 ° C. and the wall of the reaction vessel 10 is kept at all times. Heated to 100 ° C.
The humidity in the atmosphere was about 40%.

(Measurement 1) After forming a TiN film, NF ₃
Plasma cleaning with gas is performed, and the following a, b,
After removing the fluorine-based residual substance of c, Ti
An N film was formed. Re-deposition was started for 3 hours after the plasma cleaning with NF ₃ gas was completed. And T
The film quality of the iN film was measured, and the change in film quality before and after the measurement was evaluated.

A. Only vacuum exhaust.

B. The process of introducing atmospheric air with the exhaust valve closed and returning to atmospheric pressure, opening the exhaust valve and performing vacuum exhaust was repeated 10 times, and finally vacuum exhaust (atmospheric cycle flow).

C. 0.12k with exhaust valve closed
After introducing pure water to a pressure of gf / cm ² , purging with N ₂ to atmospheric pressure, opening the exhaust valve, and performing vacuum exhaust was repeated 10 times, and finally vacuum exhaust (pure water cycle flow). The liquid flow rate of pure water at the time of introducing pure water was 1 ccm. The resistance value of pure water is 2 MΩ. The heating pipe 25 was heated to 60 ° C.

The TiN film forming conditions and the NF ₃ plasma cleaning conditions are shown below.

<TiN film forming conditions> TiCl ₄ / N ₂ / H ₂ / Ar: 20/8/26/75 sccm Microwave power: 2800w Microwave window RF power: 200w Film forming time: 5 minutes <NF ₃ plasma cleaning Conditions> NF ₃ / Ar: 250/50 sccm Microwave power: 2000 w Cleaning time: 30 minutes FIG. 3 is a diagram showing measurement results of the specific resistance value of the TiN film. FIG. 4 is a diagram showing the measurement results of the film stress of the TiN film. The specific resistance value was measured with a 4-terminal meter, and the film stress was measured with a stress tester.

In the case of a (vacuum exhaust only), both the specific resistance value and the film stress after the treatment greatly changed from those before the treatment. FIG.
Shows secondary ion mass spectrometry (SIMS) of TiN film before treatment
6 shows the result of measurement, and FIG. 6 shows the result of measurement of the TiN film immediately after the treatment by secondary ion mass spectrometry. T immediately after processing
Since the iN film contains a large amount of fluorine (F) element, it can be seen that the fluorine-based substance remaining during plasma cleaning is taken into the film during film formation, which causes a change in film quality. In the case of a, about 10 dummy film formations are required to restore the film quality to the same level as before plasma cleaning.

In b (atmosphere cycle flow), compared with a, the film quality is recovered faster after plasma cleaning, but 5 to 6 dummy film formations are required.

In c (pure water cycle flow), the film quality is almost the same as that before the plasma cleaning immediately after the processing. FIG. 7 shows the results of measurement of the film immediately after treatment by secondary ion mass spectrometry. The content of the fluorine (F) element is slightly higher than the content before the plasma cleaning, but it is significantly lower than that of FIG. 6 which is the result of a. From this,
It was found that the introduction of pure water gas was extremely effective in removing the residual fluorine.

(Measurement 2) After TiN / Ti film formation was performed on 25 Si wafers, plasma cleaning with NF ₃ gas was performed. After that, the residual fluorine-containing substance is removed under the following three conditions, and hydrofluoric acid (HF) in the reaction vessel is used.
The concentration was detected with a gas detector.

A. A cycle flow (atmospheric cycle flow) in which the atmosphere is introduced with the exhaust valve closed and returned to atmospheric pressure, then the exhaust valve is opened and vacuum exhaust is repeated.

B. 0.12k with exhaust valve closed
A cycle flow (pure water cycle flow) by repeating the steps of introducing pure water to a pressure of gf / cm ² , purging with N ₂ to atmospheric pressure, opening an exhaust valve, and performing vacuum exhaust.

C. With the exhaust valve opened, that is, while exhausting with an exhaust pump, pure water is introduced at a liquid flow rate of 1 ccm for 5 minutes, then the exhaust valve is closed, N ₂ is purged to atmospheric pressure, and vacuum exhaust is performed. Repeated cycle flow (pure water cycle flow).

The TiN / Ti film forming conditions and NF are as follows.
₃ Shows plasma cleaning conditions.

<Ti film forming condition> TiCl ₄ / H ₂ / Ar: 10/50/75 sccm Microwave power: 2800w Microwave window RF power: 200w Film forming time: 2 minutes <TiN film forming condition> TiCl ₄ / N _{2 / H 2 / Ar: 20} /8/26 / 75sccm microwave power: 2800W micro Namimado RF power: 200 w deposition time: 5 minutes <NF ₃ plasma cleaning _{conditions> NF 3 / Ar: 250 /} 50sccm microwave power : 2000 w Cleaning time: 10 minutes FIG. 8 is a graph of the detection result of the hydrofluoric acid concentration. The horizontal axis plots the number of cycle flows, and the vertical axis plots the detection time of hydrofluoric acid. The numbers in the figure are the detected hydrofluoric acid concentration (ppm)
It is. When the concentration of hydrofluoric acid tends to increase to 30 ppm or more, the detection time when the concentration of hydrofluoric acid becomes 30 ppm or more is measured, and when the concentration of hydrofluoric acid tends to reach 30 ppm or less in a short time, the detection time 5 The hydrofluoric acid concentration was measured in minutes. The solid line in the figure indicates that the concentration of hydrofluoric acid in A is 30.
The detection time of not less than ppm is shown, and the dotted line in the figure shows the detection time of B having a hydrofluoric acid concentration of not less than 30 ppm.

In B (pure water cycle flow) and C (pure water cycle flow), the hydrofluoric acid concentration decreased with a smaller number of flows than the conventional method A (atmosphere cycle flow). That is, it was found that B and C can open the inside of the reaction vessel to the atmosphere in a shorter time than A. In particular, it has been found that B (pure water cycle flow) can sufficiently lower the hydrofluoric acid concentration by a quarter of the number of times of flow as compared with A (atmosphere cycle flow) which is a conventional method.

From this result, it was confirmed that the residual fluorine can be removed more efficiently by performing the cycle flow with pure water, and the down time can be shortened because the reaction vessel can be maintained in a short time.

[0052]

As described above, according to the present invention, the residual fluorine-containing substance can be efficiently removed and there is no new problem of contamination, so that the downtime of the apparatus can be shortened.
The reproducibility of the processing can be surely improved.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of an ECR plasma CVD apparatus for TiN film formation to which the present invention is applied.

FIG. 2 is a schematic partial cross-sectional view showing another mechanism for introducing pure water into the reaction container of the present invention.

FIG. 3 is a result of measuring the specific resistance value of the TiN film before and after the plasma cleaning and the fluorine-based residual substance removal treatment.

FIG. 4 shows measurement results of film stress of the TiN film before and after plasma cleaning and fluorine-based residual substance removal processing.

FIG. 5 is a result of secondary ion mass spectrometry of the TiN film before plasma cleaning.

FIG. 6 is a result of secondary ion mass spectrometry of the first TiN film after the plasma cleaning and the process a (vacuum exhaust only).

FIG. 7 shows the secondary ion mass spectrometry result of the first TiN film after the plasma cleaning and the c treatment (pure water gas flow).

FIG. 8 shows the results of measuring the concentration of hydrofluoric acid in the reaction container by various cycle flows after plasma cleaning.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic field generation coil 10 Reaction container 11 Plasma chamber 12 Reaction chamber 13 Waveguide 14 RF electrode 15 Microwave introduction window 16 Plasma outlet 18 Sample stage 19 Gas introduction pipe 20 Gas introduction pipe 21 Exhaust port 22 RF power supply 25 Heating pipe 26 Liquid mass flow controller 27 Pure water tank 28 Pure water 29 Gas mass flow controller 30 Heater

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H01L 21/304 341 H01L 21/304 341Z 21/31 21/31 C

Claims (1)

[Claims] 1. A fluorine-based gas is introduced into a reaction vessel for cleaning, and then water (H ₂ O) gas is introduced into the reaction vessel to remove a fluorine-based residual substance remaining in the reaction vessel. A method for cleaning the inside of a reaction container, which is characterized in that: