JP3178431B2 - Cleaning method for plasma CVD apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for cleaning a plasma CVD apparatus.

[0002]

2. Description of the Related Art In a plasma CVD apparatus, fluorine is adhered to the inner wall of a chamber after a film is formed on a substrate, and it is necessary to remove the fluorine.

Conventionally, in the technique of self-cleaning a chamber of a plasma CVD apparatus, there is a problem that the characteristics of a transistor change due to a fluorine-based gas remaining in the chamber after cleaning.

In order to solve the above problem, Japanese Patent Publication No. 7-1
No. 00865 proposes a method of performing plasma treatment with a mixed gas of hydrogen and nitrogen after cleaning NF ₃ . Further, in JP-A-63-267430, after the cleaning NF _3, a method of performing hydrogen plasma treatment has been proposed.

[0005]

SUMMARY OF THE INVENTION However, Japanese Patent Publication No. 7-100865 and Japanese Patent Application Laid-Open No. 63-267430.
In the method disclosed in Japanese Patent Laid-Open Publication No. H06-187, hydrogen and nitrogen do not sufficiently decompose into a highly reactive radical state, so that the reaction with fluorine adsorbed in the chamber hardly occurs, and the fluorine removal rate deteriorates. Therefore, there is a problem that the plasma processing time becomes long.

For this reason, Japanese Patent Application Laid-Open No. 3-130368 discloses that after cleaning NF ₃ , a reducing gas (hydrogen,
Silane, phosphine, etc.).

However, in the method disclosed in Japanese Patent Application Laid-Open No. 3-130368, for example, when silane is used, hydrogen radicals are generated, but amorphous silicon having a weaker adhesive force than a nitride film is formed on the inner wall of the chamber. Since the film is formed on the inner wall of the chamber, there is a problem that the film is easily peeled off from the inner wall of the chamber during the film forming process.

Therefore, the method disclosed in Japanese Patent Application Laid-Open No. 3-130368 has a problem that frequent gas cleaning must be performed.

Furthermore, Japanese Patent Publication No. 3-48268 proposes a plasma-less treatment using a mixed gas of hydrogen and a rare gas such as argon or helium after ClF-based gas cleaning.

However, the gas cleaning of ClF system is
Since inexpensive aluminum or stainless steel is etched, there is a problem that the apparatus itself becomes expensive.

Japanese Patent Application Laid-Open No. 2-240267 proposes a method of pre-coating the inside of a chamber with a plasma silicon nitride film after cleaning instead of post-processing after cleaning.

However, in the method disclosed in Japanese Patent Application Laid-Open No. 2-240267, there is a problem that the tact time becomes long because the film thickness to be coated must be increased.

An object of the present invention is to provide a method for cleaning a plasma CVD apparatus which reduces the influence of residual gas on a transistor in a short cycle time.

[0014]

[0015]

[0016]

[0017]

In order to achieve the above object,
The method of cleaning a plasma CVD apparatus according to the present invention is a method of performing plasma cleaning using a fluorine-based gas in a film formation chamber of a plasma CVD apparatus, wherein the film formation chamber is formed using a fluorine-based gas. After plasma cleaning, fluorine adhering to the inside of the film formation chamber after the cleaning is removed by discharge using a gas obtained by adding a rare gas to hydrogen, and furthermore, Si-
A nitride film having a H / N—H bond number ratio of 1.5 to 5 is grown, fluorine adhering to the chamber is taken in, and F adhering to the chamber is removed.

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

(Embodiment 1) FIG. 1 is a flowchart showing a method of cleaning a plasma CVD apparatus according to Embodiment 1 of the present invention in the order of steps.

As shown in FIG. 1, the cleaning method of the plasma CVD apparatus according to the first embodiment of the present invention
A glass substrate is carried into a film formation chamber of a plasma CVD apparatus.

Next, a silane gas or the like is introduced into the film forming chamber, and an amorphous silicon film and a silicon nitride film are formed on the glass substrate using the silane gas and the like.

After the film formation on the glass substrate is completed, the process gas is exhausted from the chamber to 1 Pa or less, and after the evacuation is completed, the glass substrate is carried out of the film formation chamber.

Subsequently, NF is used as a cleaning gas.
₃ is introduced into the film formation chamber at 500 SCCM.
At this time, pressure control in the film formation chamber is not performed, and the orifice opening for pressure control is set to 100%.

When the gas flow rate into the film forming chamber is stabilized, 2000 W of a high frequency power supply (RF) is applied.

[0025] Upon starting the RF applied to the film forming chamber, typically ^{_{NF 3 + e - → NF 2}} + F * + e - Si + 4F * → SiF 4 ↑ that a chemical reaction takes place, on the inner wall of the film forming chamber The attached silicon film is etched.

Here, when the removal of the silicon film adhered to the inner wall of the film formation chamber is completed, the above reaction is completed. Therefore, only the above reaction occurs, and the silicon film adhered to the inner wall of the film formation chamber is removed. Etching is completed.

Since the completion of the etching of the silicon film adhered to the inner wall of the film forming chamber is monitored by the pressure, it is possible to always perform a constant etching regardless of the amount of the silicon film adhered to the inner wall of the film forming chamber. Become.

When the etching of the silicon film adhered to the inner wall of the film forming chamber is completed, the RF is stopped, then the supply of NF ₃ is stopped, and the inside of the film forming chamber is set at 1P.
Vacuum to below a.

In this case, since a large amount of F adheres to the inside of the film forming chamber, the following removal process is performed.

First, 20 hours of hydrogen was placed in a film forming chamber.
00 SCCM and Ar are introduced at 100 SCCM, respectively. At this time, the pressure is controlled to 100 Pa.

When the gas flow rate to the film forming chamber is stabilized, 1000 W of a high frequency power supply (RF) is applied.

[0032] Upon starting the RF ^{_{applied, H 2 + e - → H}} * + H + + e - F + H * → HF ↑ that a chemical reaction takes place, it is possible to remove the F remaining in the film forming chamber.

This process is performed for 5 minutes, and after completion, the RF
Is stopped, the supply of H ₂ and Ar is stopped, and the inside of the film forming chamber is evacuated to 1 Pa or less to complete the cleaning process.

After the completion of the cleaning described above, the glass substrate is carried into the film forming chamber again, and the film formation is started.

The process of removing F adhered to the inside of the film forming chamber is performed by discharging only hydrogen,
FIG. 2 shows the results of SIMS analysis of the F concentration in the amorphous silicon film after the cleaning process for the case where He was added and the case where He was added to hydrogen.

In this case, the deposited film in the film forming chamber is a film formed by laminating a laminated film of an amorphous silicon film and a silicon nitride film to a thickness of 2 μm. Other than the gas flow rate, it is set constant.

As is clear from FIG . 2 , while the concentration of F in the film is 1.0 * E19 atms / cc or more in the case of only hydrogen, the concentration of F in the film is increased by adding a rare gas. Was reduced to 5 * E18 atms / cc or less.

In the first embodiment shown in FIG. 1, (hydrogen + A
Although the case where the discharge is performed for 5 minutes under r) has been described, depending on the discharge conditions such as the applied power of the high frequency power supply (RF) and the flow rate ratio of Ar and hydrogen, the F concentration in the film can be reduced to 5 times in a shorter time. * Needless to say, it can be removed to E18 atms / cc or less.

As shown in FIG. 2, by performing the cleaning method according to the first embodiment of the present invention, it is possible to remove fluorine adhering to the inner wall of the film forming chamber.

The reason is that the density of hydrogen radicals is increased by adding a rare gas as compared with the hydrogen discharge treatment, so that F attached to the chamber can be efficiently removed as HF.

There is also an effect that F can be effectively removed by the sputtering effect of the rare gas.

(Embodiment 2) FIG. 4 is a flowchart showing a method of cleaning a plasma CVD apparatus according to Embodiment 2 of the present invention in the order of steps.

The cleaning method of the plasma CVD apparatus according to the second embodiment of the present invention shown in FIG. 4 is the same as that of the first embodiment up to the processing step of discharging hydrogen + rare gas.

Plasma CVD according to Embodiment 2 of the present invention
In the apparatus cleaning method, as a discharge treatment of hydrogen + rare gas, hydrogen + Ar discharge is performed for 5 minutes, and then silane 3 is discharged.
00SCCM, ammonia 300SCCM, nitrogen 500
0SCCM, RF power 1000W, pressure 10
Under a condition of 0 Pa, a nitride film is formed to a thickness of 1000 °.

FIG. 5 shows the result of measuring the F concentration in the film by SIMS analysis in the method of the second embodiment of the present invention in the same manner as in the first embodiment.

As is clear from FIG. 5, when the (hydrogen + Ar treatment) + nitride film is formed, the F concentration in the film becomes 1 * E1.
8 atms / cc or less.

Here, the hydrogen concentration in the nitride film is set to F
Investigation by T-IT showed that the nitride film Si-H / N-H
The ratio of the number of bonds was found to be 1.8.

FIG. 3 shows the result of forming films having different ratios of Si—H / NH bonds from 1 to 4 to the same thickness as the nitride film.

As a result, when the ratio of the number of Si—H / N—H bonds was 1.5 or more, the F concentration in the film by SIMS analysis was 1 *
E18 atms / cc or less.

As described above, the discharge treatment of hydrogen and rare gas,
By combining the formation of a nitride film having a Si—H / N—H bond number ratio of 1.5 or more, the F concentration in the film can be more efficiently reduced.

Here, when only the nitride film processing is performed without performing the hydrogen + rare gas discharge processing, as shown in FIG.
It is not suitable for mass production because the thickness of the nitride film becomes 18 atms / cc or the F concentration in the film does not decrease sufficiently.

[0052]

As described above, according to the present invention, the density of hydrogen radicals can be increased and F attached to the chamber can be efficiently removed as HF.

Further, F can be effectively removed by the sputtering effect of the rare gas.

Further, a discharge treatment of hydrogen + rare gas and Si
By combining the formation of a nitride film with a ratio of the number of -H / N-H bonds of 1.5 or more, the F concentration in the film can be more efficiently reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a cleaning method of a plasma CVD apparatus according to Embodiment 1 of the present invention in the order of steps.

FIG. 2 is a characteristic diagram illustrating an effect of a cleaning method of a plasma CVD apparatus according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram illustrating an effect of a cleaning method for a plasma CVD apparatus according to an embodiment of the present invention.

FIG. 4 is a flowchart showing a cleaning method of a plasma CVD apparatus according to Embodiment 2 of the present invention in the order of steps.

FIG. 5 is a characteristic diagram showing the effect of the cleaning method of the plasma CVD apparatus according to the embodiment of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/205 C23C 16/44 C23F 4/00 H01L 21/3065

Claims (1)

(57) [Claims] 1. A method for plasma-cleaning the inside of a film forming chamber of a plasma CVD apparatus using a fluorine-based gas, wherein the film-forming chamber is plasma-cleaned using a fluorine-based gas and then diluted with hydrogen. Fluorine adhering to the inside of the film formation chamber after the cleaning is removed by the discharge using the gas to which the gas is added, and the nitride film having a Si—H / N—H bond number ratio of 1.5 to 5 is further provided. A method for cleaning a plasma CVD apparatus, comprising growing fluorine, taking in fluorine adhering in a chamber, and removing F adhering to the chamber.