JPH10144666A - Method of cleaning plasma treating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the time required to clean a C film contg. F, deposited on the interior of a vacuum vessel. SOLUTION: After forming a CF film e.g. by a plasma treating apparatus, an O2 cleaning gas is fed into the vacuum vessel 2 to clean the CF film deposited on the interior of this vessel such that a plasma of the O2 gas is produced to physically or chemically break the C-C or C-F bond of the CF film surface by the active species of O caused by the plasma and O2 gas penetrates the broken parts of the film and reacts with C of the film to produce CO2 , resulting in scattering while F scatters as F2 , thus the CF film is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method for a plasma processing apparatus for performing a plasma processing on a substrate to be processed such as a semiconductor wafer.

[0002]

2. Description of the Related Art Aluminum wiring is mainly used as a wiring pattern of an integrated circuit, and an SiO ₂ film or a SiOF film is used as an interlayer insulating film for insulating the aluminum wiring. Has good film quality,
For example, ECR (El
electron Cyclotron Resonance
e) There is a tendency to use plasma treatment.

FIG. 19 shows an example of a plasma processing apparatus for performing this ECR plasma processing.
The microwaves of, for example, 2.45 GHz are supplied through the waveguide 11 and have a predetermined size, for example, 875 μm.
A Gaussian magnetic field is applied by the electromagnetic coil 12, and the interaction (resonance) between the microwave and the magnetic field causes a plasma gas such as an Ar gas or an O ₂ gas, or a reactive gas introduced into the film formation chamber 1B, for example. The SiH ₄ gas is turned into plasma, and active species of the SiH ₄ gas are formed by this plasma to form Al
A thin film is formed on the surface of the semiconductor wafer W mounted on the mounting table 13 made of N (aluminum nitride).

In such a plasma processing apparatus,
When a film forming process such as a SiO ₂ film is performed, these films also adhere to the wall surface of the film forming chamber 1B and the periphery of the mounting table 13, but the film forming process proceeds, and the film has a certain thickness. In this case, the adhered film is peeled off, causing particles. Therefore, after performing a film forming process of the SiO ₂ film or the SiOF film, a predetermined cleaning is performed to remove the adhered film. I have.

For example, the cleaning for removing the SiO ₂ film and the SiOF film is performed, for example, for about 20 minutes every time 12 wafers W are formed, and CF ₄ gas or NF _{3 is} used as the cleaning gas. An F-based gas such as a gas is introduced into the vacuum vessel, the gas is activated by plasma, and the activated species reacts with the adhered film and is removed.

[0006]

SUMMARY OF THE INVENTION By the way, SiO ₂
Although the film has a dielectric constant of about 4 and the SiOF film has a dielectric constant of about 3.5, the demand for high-speed devices has increased in recent years, and as a result, an interlayer insulating film having a low dielectric constant has been required. Therefore, as such an interlayer insulating film having a low dielectric constant, a fluorine-added carbon film (hereinafter referred to as CF) capable of achieving a dielectric constant of 2.5 or less.
Membrane)).

This CF film can also be formed by the above-mentioned plasma processing apparatus. However, when the CF film is removed by cleaning, if an F-based gas such as the CF ₄ gas or the NF ₃ gas is used, the CF ₄ gas is removed. With only NF ₃ gas, the cleaning speed hardly progresses, and with only NF ₃ gas, the cleaning speed is considerably slow, and the processing takes a long time of about 90 minutes. If the cleaning takes a long time in this way,
Since the thinning is performed during the film forming process, there is a problem that the throughput of the film forming process is deteriorated.

At the time of cleaning, the mounting table 13 is exposed to the plasma, but since the CF film is not originally adhered to the surface of the mounting table 13, the surface of the mounting table 13 is directly hit by the plasma. And get rough. When the surface of the mounting table 13 becomes rough, unevenness is generated on the surface of the mounting table, and the suction force of the wafer W and the heat conduction to the wafer W are partially changed. It changes in the latter period, and the reproducibility of the process deteriorates. Therefore, there is a problem that the in-plane uniformity of the film thickness of the formed film is deteriorated and the uniformity of the film thickness between the surfaces is deteriorated.

Further, if the surface of the mounting table 13 is roughened, particles may be generated when the wafer W is mounted on or removed from the mounting table 13 in a subsequent film forming process. There is also a problem that the life of the expensive mounting table 13 is shortened. For example, when a particularly strong plasma is generated to increase the cleaning speed, there is a problem because the surface of the mounting table is greatly deteriorated.

Further, at the time of cleaning, an operator visually checks the inside of the film forming chamber 1B through the viewing window 14 formed on the side wall of the film forming chamber 1B and checks whether or not the film remains. In this case, the end of the process is determined. However, in such a method, the determination of the end is inaccurate because the method often depends on the experience of the operator. For this reason, the decision at the end is too early and the membrane remains,
In order to avoid this, the judgment at the end is delayed, and the
There is a problem in that the processing time becomes too long, and as a result, the throughput of the film forming process deteriorates.

The present invention has been made under such circumstances, and an object of the present invention is to reduce the time required for cleaning a carbon film containing fluorine adhering to the inside of a vacuum vessel. Another object of the present invention is to provide a method of cleaning a plasma processing apparatus, which can protect a mounting table when cleaning an adhered film. .

[0012]

According to the present invention, a processing gas is converted into plasma in a vacuum vessel having a mounting table for a substrate to be processed, and the plasma is applied to the substrate by the plasma. In a plasma processing apparatus for forming a carbon film, a cleaning gas containing oxygen gas is turned into plasma, and the plasma is used to remove the fluorine-added carbon film adhered to the inside of the vacuum vessel.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a cleaning method for a plasma processing apparatus according to the present invention will be described. The present inventors have developed CF attached to the inside of a vacuum vessel of a plasma processing apparatus.
In cleaning for removing the film, various gases were examined as a cleaning gas, and it was found that oxygen (O ₂ ) gas was effective. In this embodiment, cleaning of a plasma processing apparatus having a CF film attached thereto is performed using O ₂ gas as a cleaning gas.

First, an example of a plasma processing apparatus for forming a CF film on a substrate to be processed will be described with reference to FIG. This plasma processing apparatus is an apparatus using ECR (Electron Cyclotron Resonance). In the figure, reference numeral 2 denotes a vacuum vessel formed of, for example, aluminum or the like. This vacuum vessel 2 is connected to a cylindrical plasma chamber 21 located above and in communication with a lower cylindrical plasma chamber 21 for generating plasma. And a cylindrical film forming chamber 22 having a larger inner diameter.

The upper end surface of the vacuum vessel 2 is formed by a transmission window 23 for transmitting microwaves. On the upper surface of the transmission window 23, for example, 2.45 GH
A waveguide 31 for supplying microwaves of z is provided, and the other end of the waveguide 31 is connected to a microwave oscillator 32. In this example, the waveguide 31 and the microwave oscillator 32 constitute a high-frequency supply unit.

A ring-shaped main solenoid coil 33 (hereinafter referred to as a main coil 33) is disposed near the outer periphery of the side wall defining the plasma chamber 21 as magnetic field forming means in close proximity thereto. For example, a magnetic field of 875 gauss can be formed from above to below. A ring-shaped sub solenoid coil 34 (hereinafter, referred to as a sub coil 34) is disposed below the bottom wall of the film forming chamber 22.

On the side wall that partitions the plasma chamber 21,
The plasma gas nozzles 24 are provided evenly along the circumferential direction. A plasma gas source and a cleaning gas source (not shown) are connected to the nozzle 24 so that the plasma gas and the cleaning gas can be uniformly supplied to the upper portion in the plasma chamber 21. Although only two nozzles 24 are shown in the figure to avoid complication of the drawing, more nozzles 24 are actually provided.

On the other hand, in the film forming chamber 22, for example, C ₄ F ₈ gas and C ₄
A ring-shaped gas ring 25 having a gas outlet 25a for introducing ₂ H ₄ gas is provided.
The gas ring 25 is connected to a reactive gas source (not shown), for example, a C ₄ F ₈ gas source and a C ₂ H ₄ gas source.
A mounting table 4 for mounting a substrate to be processed, for example, a semiconductor wafer W (hereinafter, referred to as a wafer W), is provided at substantially the center of the film forming chamber 22 so as to be able to move up and down. The mounting table 4 has a main body 41 made of, for example, aluminum or the like provided with a ceramic body 42 having a built-in heater, and the mounting surface is configured as an electrostatic chuck. Further, the ceramic electrostatic chuck 42 of the mounting table 4 has a built-in electrode 43 for applying a bias for drawing ions into the wafer W, and the electrode 43 is connected to, for example, a high-frequency power supply 44 for drawing plasma. Furthermore, an exhaust port (not shown) is formed at the bottom of the film forming chamber 22.

Next, a description will be given of a process of forming a CF film using the above-described apparatus. First, a wafer W having, for example, an aluminum wiring formed on its surface is loaded from a load lock chamber (not shown) and placed on the mounting table 4. Subsequently, the inside of the vacuum vessel 2 is evacuated to a predetermined degree of vacuum, a plasma gas such as an Ar gas is introduced from the plasma gas nozzle 24 into the plasma chamber 21, and a film forming gas such as an Ar gas is introduced from the gas ring 25 into the film forming chamber 22. C ₄ F ₈ gas and C ₂ H ₄ gas are introduced at flow rates of 60 sccm and 30 sccm, respectively. Then, the inside of the vacuum vessel 2 is set to a process pressure of 0.2 P, for example.
a, and 13.56 MHz, 150
A bias voltage of 0 W is applied, and the surface temperature of the mounting table 4 is set to 320 ° C.

2.45 GH from microwave oscillator 32
The high frequency (microwave) of z is conveyed through the waveguide 31, passes through the transmission window 23, and is introduced into the plasma chamber 21.
In the plasma chamber 21, a mirror magnetic field generated by the main coil 33 and the sub-coil 34 is applied with a strength of 875 gauss, and the interaction between the magnetic field and the microwave generates electron cyclotron resonance. By A
The r gas is converted into plasma and the density is increased.

The plasma flow flowing from the plasma chamber 21 into the film forming chamber 22 activates the C ₄ F ₈ gas and the C ₂ H ₄ gas supplied thereto to form active species.

On the other hand, active species transported onto wafer W are CF
A film is formed as a film. At this time, Ar ions drawn into the wafer W by a bias voltage for plasma pulling in are formed.
The CF film formed at the corners of the pattern on the surface of the wafer W is scraped off by the sputter etching action, and while widening the frontage, the CF film is formed from the bottom of the pattern groove, and the CF film is embedded in the recess without voids.

Subsequently, with such a plasma processing apparatus,
The cleaning performed after performing such a film forming process will be described. When a predetermined film forming process is performed on the wafer W, the CF also reaches a place where the film forming gas reaches, for example, around the wafer W on the surface of the mounting table 4, an outer peripheral portion of the mounting table 4, and around the gas outlet 25 a. The film adheres. Cleaning is a process performed to remove the CF film adhered to the inside of the vacuum vessel 2 as described above.
This is performed after performing the film forming process on the two wafers W.

Specifically, after unloading the twelfth wafer W from the vacuum vessel 2, O ₂ gas is introduced into the plasma chamber 21 from the plasma gas nozzle 24 as a cleaning gas at a flow rate of, for example, 200 sccm, and This is performed by introducing a microwave of 2.45 GHz from the oscillator 32 and applying a magnetic field with a strength of 875 gauss by operating the main coil 33 and the sub coil 34, for example.

The mirror will be described later in the inside of the deposition chamber 22 when such - a magnetic field is formed, occurs electron cyclotron resonance in interaction between the magnetic field and the microwave, O ₂ gas is converted to plasma by the resonance, And the density is increased. Then, active species of O, such as O radicals and ions, generated by the plasma, react with the CF film attached to the gas outlet 25a and the periphery of the mounting table 4, and convert the CF film into, for example, CO ₂ gas or F ₂ gas. It is decomposed and scattered, and removed to the outside of the film forming chamber 22 through an exhaust port (not shown).

Here, a description will be given of an experimental example performed to confirm the effect of the present embodiment. Using the plasma processing apparatus shown in FIG. 1 as an experimental device, O ₂ and O ₂ gas from the plasma gas nozzle 24 to the wafer W to the CF film placed on the mounting table introduces was deposited at a flow rate of 200sccm Etching was performed by using the plasma, and the etching rate at this time was calculated to obtain the removal amount of the CF film. Here, other conditions include a pressure of 0.1 P
a, a mirror magnetic field was used and microwave power was changed.
The same experiment was performed when NF ₃ gas was introduced at a flow rate of 200 sccm instead of O ₂ gas. The result is shown in FIG.

From the results shown in FIG. 2, it was confirmed that the etching rate was considerably larger when the O ₂ gas was used than when the NF ₃ gas was used, whereby the O ₂ gas was converted to the NF ₃ gas. It was recognized that the CF film removal rate was higher than that.

In the plasma processing apparatus shown in FIG. 1, a 5-μm CF film is formed on an 8-inch wafer W under a pressure of 0.2 Pa and a microwave power of 2700 W, and then an O ₂ gas is used as a cleaning gas. 200sc
When the CF film was cleaned under the conditions of a pressure of 0.1 Pa, a microwave power of 2500 W, and a mirror magnetic field, the CF film was completely removed after 30 minutes, and NF was removed. ₃ It is recognized that the cleaning time is reduced to 1/10 to 1/5 as compared with the case where cleaning is performed by introducing a gas at a flow rate of 200 sccm.
From these results, it was confirmed that O ₂ gas was effective for cleaning the CF film.

The reason why the O ₂ gas is effective for cleaning the CF film is considered to be due to the following reasons. That is, when an O ₂ gas is used as a cleaning gas, the active species of O generated by plasma hitting the surface of the CF film physically causes the CC bond or CF bond on the CF film surface to physically. At the same time, the C—C bond and the like are also broken by a chemical reaction of generating CO ₂ between the active species of O and C (carbon) of the CF film. Then, O ₂ enters the inside of the CF film from this cut, and cuts the CC bond and the CF bond inside the CF film. As described above, the active species of O react with C of the CF film to generate CO ₂ gas, while F (fluorine) is presumed to generate F ₂ gas. Is thought to be removed.

On the other hand, when NF ₃ gas is used as the cleaning gas, the active species of F generated by the plasma breaks the CC bond or CF bond on the CF film surface, and these bonds are cut. After that, F is scattered as F ₂ gas or NF ₃ gas, and C is supposed to be scattered as CF ₄ gas, thereby removing the CF film.

It is considered that the generation of CO ₂ by the reaction between O and C is more likely to occur than the generation of CF ₄ by the reaction of F and C. For this reason, it is considered that the active species of O is liable to break the CC bond or CF bond inside the CF film by generating CO ₂ , so that it is easier to enter the CF film than F. As described above, the cleaning rate of the O ₂ gas is higher than that of the NF ₃ gas, because the C—C bond and the C—F bond are more likely to be cut off than the NF ₃ gas, and the O ₂ gas easily enters the CF film. As a result, it is assumed that the cleaning time is shortened.

As described above, in this embodiment, since the O ₂ gas is used as the cleaning gas for the CF film, the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is shortened. The throughput of the treatment can be improved.

Next, another example of the present embodiment will be described. In this example, the power density of the microwave at the time of cleaning is 1 in the cleaning method of the above-described embodiment.
It is set to 0 kW / m ³ or more. The microwave power density is calculated by dividing the microwave power by the volume of the vacuum vessel 2. For example, if the microwave power is 2000 W and the volume of the vacuum vessel 2 is 0.2 m ³ , the microwave power density is 10 kW / m ³ .

From the experiment shown in FIG. 2 above, it was confirmed that the etching rate of the CF film was increased when the microwave power was increased. Therefore, the present inventors changed the power density of the microwave to clear the CF film. It was confirmed that the cleaning speed was increased when the microwave power density was 10 kW / m ³ or more.

Now, an experimental example performed by the present inventors will be described. As the experimental apparatus, the plasma processing apparatus shown in FIG. 1 was used, and the pressure was 0.2 Pa, the power was 2700 W, and the power density was 1
Under a 3.5 kW / m ³ microwave, a 10 μm CF film was formed on an 8-inch wafer W, and then a clear film was formed.
O ₂ gas was introduced as a cleaning gas at a flow rate of 200 sccm, and the CF film was cleaned by changing the power density of the microwave. At this time, the pressure was set to 0.2 Pa,
The test was performed by forming a magnetic field. The cleaning condition was visually observed, and the time until the CF film was removed was measured. The result is shown in FIG. The SiO ₂ film is 10 μm
After forming the film, NF ₃ gas and N ₂ gas are used as cleaning gases.
The same experiment was performed when the gas was introduced at a flow rate of 500 sccm. The result is shown in FIG.

According to the results shown in FIG. 3, when the SiO ₂ film is cleaned with the NF ₃ gas and the N ₂ gas, the cleaning is performed even if the microwave power density is increased from 6 kW / m ³ to 10 kW / m ^3. The time can be reduced by only 5 minutes, whereas when the CF film is cleaned with O ₂ gas, 6 kW when the microwave power density is 10 kW / m ³ or more.
/ M ³ , the cleaning time is shortened by 20 minutes and the cleaning time is reduced to ／ or less. Therefore, when cleaning the CF film, the cleaning time is shorter than that of the SiO ₂ film. It was confirmed that the influence of the microwave power density was large.

When cleaning the CF film by increasing the microwave power density from 9 kW / m ³ to 10 kW / m ³ , the cleaning time is reduced by 10 minutes, whereas the cleaning time is reduced by 10 kW / m ^3. Even if it is increased from 10 kW / m ³ to ³ kW / m ³ , the shortening time is 3 minutes, and the degree of shortening becomes small.
It is considered desirable to set the kW / m ³ or more.

The effect of the microwave power density on the cleaning of the CF film is considered to be due to the following reasons. The higher the microwave power density, the higher the plasma density, and the higher the plasma density, the higher the O 2 activated by the plasma.
The energy of the active species is increased. Here, among the active species of O, the energies are different from each other, and some of the active species reach the adhered CF film and contribute to the removal of the CF film, while others have a small energy and cannot reach the CF film. Therefore, as described above, if the energy of the active species is increased, it is possible to reach the CF film on which more active species are attached.

In the cleaning with O ₂ gas, as described above, the active species of O generated by the plasma physically break the CC bond and CF bond on the CF film surface,
It is considered that the generation proceeds by chemically cutting by generating O _2. However, when the density of the plasma itself is increased and the energy of the activated species of O is increased, the activated species of O reaching the CF film are reduced. This increases both the physical and chemical cutting forces. Therefore, it is presumed that the CC bond and the like are more easily broken, and the O ₂ gas is more likely to enter the inside of the CF film, thereby promoting the progress of the cleaning process.

On the other hand, when cleaning the SiO ₂ film,
It is considered that the Si—O bond on the surface of the O ₂ film is cleaved by a chemical reaction with an active species of F obtained by activating NF ₃ . Accordingly, when the microwave power density increases and the plasma density increases, the energy of F activated by the plasma increases, so that the cleaning speed increases, but the physical force affects the SiO ₂ film. Since there is no cleaning, the degree of promotion of cleaning is reduced accordingly.

As described above, in this example, since the microwave power density is set to 10 kW / m ³ or more in the cleaning of the CF film, the cleaning time of the CF film adhered inside the vacuum vessel 2 is further reduced. Thus, the throughput of the film forming process can be further improved.

Next, still another example of the present embodiment will be described. In this example, the magnetic field at the time of cleaning is set to a divergent magnetic field in the cleaning method of the above embodiment. Here, the mirror magnetic field and the diverging magnetic field will be described with reference to FIG.
As shown in (a), the magnetic field M is confined around the mounting table 4 and is formed by operating the main coil 33 and the sub coil 34. On the other hand, as shown in FIG. 4B, the divergent magnetic field forms a magnetic field M that spreads downward around the mounting table 4 and is formed by operating only the main coil 33.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, a 10 μm CF film was formed on an 8-inch wafer W under microwave power of 2700 W, and O ₂ gas was used as a cleaning gas at a flow rate of 200 sccm. The cleaning was performed on the CF film by changing the magnetic field to a mirror magnetic field and a divergent magnetic field under a pressure of 20 Pa and a microwave power of 2500 W. At this time, the mirror magnetic field was such that the main coil 33 current was 200 A and the sub coil 34 current was 2 A.
The divergent magnetic field was formed with the main coil 33 current at 200 A and the sub coil 34 current at 0 A. The cleaning condition was visually observed, and the time required for the CF film to be removed from the vicinity of the gas outlet 25a and the surface and the outer peripheral portion of the mounting table 4 (the peripheral portion of the mounting table 4) was measured. A similar experiment was performed with the pressure changed to 0.2 Pa. The result is shown in FIG.

According to the results shown in FIG. 5, in the diverging magnetic field, the cleaning time around the mounting table is much shorter than the mirror magnetic field, and the cleaning time around the gas outlet 25a takes longer than the mirror magnetic field. Clear around mounting table
When the cleaning is completed, the cleaning around the gas outlet 25a has already been completed. As a result, it has been recognized that the diverging magnetic field has a shorter cleaning time than the mirror magnetic field. Further, when the pressure is set to 0.2 Pa, the cleaning time around the mounting table is reduced by 20 minutes as compared with the case of 20 Pa, so that the cleaning time of the CF film is reduced as the pressure becomes lower. Inferred.

The reason for this is that, as described above, when the CF film is cleaned with the O ₂ gas, the plasma density becomes C
Since it greatly affects the physical and chemical cutting force such as the CC bond of the F film, it is considered that such a difference in the plasma density causes a large difference in the cleaning speed.
That is, since the plasma density increases as the magnetic flux density increases, the plasma is generated over the entire inside of the vacuum vessel 2.
In the case of the mirror magnetic field, the plasma region is formed so as to be confined in the vicinity of the upper portion of the mounting table, and in the case of the divergent magnetic field, the plasma region is formed so as to spread downward around the mounting table 4. Here, the plasma region means that the plasma is ECR
Means a region which is confined and increased in density, and in regions other than this region, the plasma density is extremely low.

Therefore, in the vicinity of the gas outlet 25a, the divergent magnetic field has a lower magnetic flux density and a lower cleaning speed. However, in this part, the magnetic field is confined to some extent even in the divergent magnetic field, and the plasma density is originally high, so it is considered that the cleaning time is not so long.

On the other hand, although the vicinity of the mounting table exists in the plasma region with the diverging magnetic field, the plasma diverges downward with the diverging magnetic field, and the plasma density decreases as it goes downward. . Therefore, the magnetic flux density around the mounting table is small, and the plasma density is
Since the temperature is lower than the vicinity of 5a, it is considered that the cleaning time is longer than that of the gas outlet 25a. On the other hand, in the mirror magnetic field, the periphery of the mounting table 4 is out of the plasma region and the plasma density becomes considerably low.
The running time will be quite long.

The reason why the cleaning time is further reduced when the pressure is reduced is considered to be as follows. That is, at low pressure, the mean free path of O ions becomes longer and the energy of the ions increases, so that the ion sputtering efficiency increases. As described above, the C—F film has a C—C bond or a C—C bond.
Since it is necessary to physically break the F bond, the more ions with high energy, the higher the cleaning speed.

Since the cleaning time was shortened by the divergent magnetic field, the magnetic field was changed to a mirror magnetic field and a divergent magnetic field even when the SiO ₂ film was cleaned with NF ₃ gas and N ₂ gas. When the cleaning time was measured in this manner, no reduction in the cleaning time was observed due to such a change in the magnetic field.

It is considered that the influence of the magnetic field on the cleaning is different between the CF film and the SiO ₂ film because the way of the cleaning progresses. As described above, in the cleaning of the O ₂ gas, the plasma density greatly affects the cleaning speed, and the cleaning does not easily progress in a portion far from the plasma region where the plasma density is extremely low. On the other hand, in the cleaning of the SiO ₂ film, the mechanism is not clear because the plasma density does not significantly affect the cleaning by the active species of F, as described above, but the cleaning is performed even in a portion where the plasma density is low. Is thought to progress. As described above, in the cleaning of the CF film, the influence of the plasma density is considerably larger than that of the SiO ₂ film, and it is presumed that the influence of the magnetic field becomes larger.

In the above example, in this example, a cusp magnetic field may be formed by flowing a current from the sub-coil 34 in a direction opposite to that of the main coil 33 instead of the diverging magnetic field. Also in the case of the cusp magnetic field, the plasma density around the mounting table can be increased.

As described above, in this example, a diverging magnetic field and a cusp magnetic field are formed in the cleaning of the CF film with the O ₂ gas, so that the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is further reduced. Thereby, the throughput of the film forming process can be further improved.

Next, still another example of the present embodiment will be described. In this example, in the cleaning method of the above-described embodiment, a microwave at the time of cleaning is supplied in a pulse form. Here, supplying the microwave in a pulse shape means that a microwave of 2.45 GHz of, for example, 2700 W oscillated from the microwave oscillator 32 is turned on with a pulse of, for example, a frequency of 100 to 5000 Hz.
It means turning off, that is, modulating the microwave with a pulse. The pulse duty ratio is, for example, 40
６０60% can be set. When a microwave is supplied in a pulse form as in the above, plasma having a high energy can be generated, so that the cleaning speed can be increased.

Here, an experimental example performed by the present inventors will be described. A plasma processing apparatus shown in FIG. 1 was used as an experimental apparatus, and a pressure of 500 Pa and a mirror magnetic field (main coil 3) were used.
Under the conditions of 3 current 200A, sub coil 34 current 200A) and temperature 350 ° C, microwave of 2700W and 2.45GHz is supplied while turning on and off at a frequency of 100 to 5000Hz and a duty ratio of 0.4 to 0.6. Then, an O ₂ gas is introduced as a cleaning gas at a flow rate of 500 sccm, the wafer W on which the CF film is formed is etched, and the etching rate at this time is calculated to remove the CF film. I asked. The same experiment was performed when a microwave of 2700 W was continuously supplied.

According to this experiment, the cleaning rate (etching rate) when microwaves were supplied in a pulsed manner was
G) While it was 8000 angstroms / min, it was confirmed to be 4000 angstroms / min when supplied continuously, and the removal rate of the CF film was obtained by supplying microwaves in a pulsed manner. Was found to be larger.

Therefore, in the plasma processing apparatus shown in FIG. 1, a CF film is formed to a thickness of 5 μm on an 8-inch wafer W under the conditions of a pressure of 0.2 Pa and a microwave power of 2700 W. Under the conditions,
2700 W, 2.45 GHz microwave at frequency 10
It was supplied at 0-5000 Hz with a duty ratio of 0.4-0.6 while being turned on and off, and O ₂ gas was introduced as a cleaning gas at a flow rate of 500 sccm to clean the CF film. The cleaning time was about 6 minutes. On the other hand, microwave of 2700W is continuously supplied,
Otherwise, when the cleaning time was measured under the same conditions, the cleaning time was 12 minutes. From these results, it was confirmed that the cleaning time was shortened by about 6 minutes when the microwaves were supplied in a pulsed form compared to when the microwaves were supplied continuously.

The reason why the cleaning time is shortened when the microwave is supplied in a pulsed manner is considered to be as follows. That is, the microwave power is determined by (the number of electrons) × (the energy of the electrons), but the energy of the electrons is considerably high at the beginning of the supply of the microwave because the number of the electrons is small. The avalanche phenomenon increases exponentially, so it drops rapidly and stabilizes. Therefore, when microwaves are supplied in pulse form,
As shown in FIGS. 6A and 6B, high-energy electrons are supplied for each pulse, so that a high-energy plasma is continuously generated. FIG. 6
FIG. 3C shows, for comparison, changes in electron energy when microwaves are continuously supplied as in the prior art.
When the energy of the plasma increases as in this example, the energy of the active species activated by the plasma also increases, so that the number of active species reaching the CF film adhered in the vacuum vessel 2 increases. As a result, the cleaning speed increases.

As described above, in this example, the microwave is supplied in a pulsed manner in the cleaning of the CF film by the O ₂ gas, so that the cleaning time of the CF film adhered inside the vacuum vessel 2 is further reduced. Thus, the throughput of the film forming process can be further improved.

Next, still another example of the present embodiment will be described. In this example, in the cleaning method of the above-described embodiment, for example, cleaning is performed every time one wafer W is formed. If the cleaning is performed every time one wafer W is formed, the amount of the CF film adhered in the vacuum vessel 2 is small, so that one cleaning time is considerably long, for example, about 15 seconds. Be shorter.

After the wafer W on which film formation has been completed is carried out and before the next wafer W is carried in, in order to remove the electric charge remaining on the mounting table 4, for example, a charge elimination process using O ₂ plasma is performed, for example, 10 times. However, if cleaning is performed with O ₂ gas every time one wafer W is formed, the cleaning time is longer than the charge elimination time. That is, it is not necessary to perform only the charge removal processing separately from the cleaning. For this reason, the total processing time for processing the same number of wafers W is simpler than the case where cleaning is performed after depositing 25 wafers W while performing static elimination processing when exchanging the wafers W, for example. In the calculation, (the static elimination processing time) × (the number of wafers W) can be reduced, thereby improving the throughput.

Further, when cleaning is performed after 25 wafers W are formed, if the amount of the CF film adhering to the inside of the vacuum vessel 2 increases, the internal state of the vacuum vessel 2 changes and the adhering CF film changes. The film quality of the film changes, and the film adheres more firmly. This makes it difficult to remove the CF film. Therefore, compared to a case where cleaning is performed each time one wafer W is formed, total cleaning is performed.
The ninging takes a long time. Thus, the wafer W
When cleaning is performed each time one film is formed,
Since the cleaning time of the barrel can be shortened, the throughput can be further improved.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, a CF film is formed on an 8-inch wafer W under a pressure of 0.2 Pa and a microwave power of 2700 W. - the O ₂ gas was introduced at a flow rate of 500sccm as Ningugasu, pressure 500 Pa,
CF under the condition of divergent magnetic field and microwave power of 2700 W
The film was cleaned, and the total processing time when 25 wafers W were formed was measured. Also, under the same conditions, the total processing time when cleaning was performed after film formation on 25 wafers W while performing static elimination processing for 10 seconds when replacing the wafer W was measured. .

According to the results of this experiment, when cleaning is performed every time one wafer W is formed, the cleaning is about 15 seconds on average and the total processing time is 68 minutes 4
In contrast to 5 seconds, when cleaning is performed after 25 wafers W are formed, the cleaning time is about 30 minutes, and the total processing time is 92 minutes 3
It was confirmed to be 0 seconds.

As described above, in this example, the cleaning is performed each time one wafer W is formed in the cleaning of the CF film with the O ₂ gas, so that the total processing time can be reduced. Therefore, the throughput of the film forming process can be further improved.

In the above embodiment, in the cleaning, a plasma gas, for example, an Ar gas may be supplied simultaneously with the cleaning gas. In the film forming process, the CF film adheres not only to the mounting table 4 and the periphery of the gas outlet 25 a but also to the inner wall surface of the vacuum vessel 2. Since the film is weaker and thinner than the CF film adhering to the periphery and the amount is small, the cleaning of the inner wall of the vacuum vessel 2 has already been completed when the cleaning around the mounting table 4 is completed. State.

Next, another embodiment of the present invention will be described. The present embodiment is different from the above-described embodiment in that O ₂ gas is used as a cleaning gas in combination with H ₂ gas or a gas containing F such as CF ₄ gas or NF ₃ gas. is there. Here, O ₂ gas and H ₂
The gas or the like may be supplied at the same time, or the O ₂ gas may be supplied first, and then the H ₂ gas or the like may be supplied.

Next, experimental examples performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, a CF film was formed to a thickness of 10 μm on an 8-inch wafer W under a microwave power of 2700 W, and then a pressure of 0.2 Pa, a microwave power of 2500 W and a mirror were used. Under a magnetic field condition, a cleaning gas is introduced to clean the CF film.
Was performed.

As the cleaning gas, only O ₂ gas (flow rate 200 sccm), O ₂ gas + H ₂ gas (O ₂ gas flow rate 200 sccm, H ₂ gas flow rate 100 s)
ccm), O ₂ gas + CF ₄ gas (O ₂ gas flow rate 200
sccm, CF ₄ gas flow rate 200 sccm), O ₂ gas + NF ₃ gas (O ₂ gas flow rate 200 sccm, NF ₃ gas flow rate 200 sccm) were used. Then, the cleaning condition was visually observed, and the time until the CF film was removed was measured. This result is shown in FIG.

When O ₂ gas is first introduced as a cleaning gas and then NF ₃ gas is introduced (O ₂ gas flow rate 200 sccm, NF ₃ gas flow rate 500 sccm)
And when NF ₃ gas + N ₂ gas is introduced (O ₂ gas flow rate 200 sccm, NF ₃ gas flow rate 500 sccm, N 2
The same experiment was performed with _two gas flow rates of 500 sccm). At this time, the pressure was set to 0.2 Pa when the O ₂ gas was introduced, and was set to 120 Pa when the NF ₃ gas or the like was introduced. The result is shown in FIG.

According to the results of this experiment, the cleaning speed was increased by combining H ₂ gas and F containing gas with O ₂ gas as the cleaning gas, and the cleaning time was longer than when only O ₂ gas was used. It was confirmed that can be shortened. Thus O ₂ than O ₂ gas alone
The reason why the cleaning speed is increased by the combination of the gas and the H ₂ gas is that the active species of O is the C type of the CF film as described above.
The reaction to generate CO ₂ and the active species H so generates the HF reacts with F in the CF film, C-C bonds and CF bonds are considered to be because susceptible to cleavage.

Since the cleaning speed is increased by the combination of the O ₂ gas and the gas containing F as compared with the O ₂ gas alone, the cleaning by the active species of F affects the plasma density as described above. Is smaller than the active species of O, the mechanism is not clear where the plasma density is extremely low outside the plasma region due to the mirror magnetic field, such as around the mounting table 4, but the F is higher than that of the active species of O. It is considered that the active species has a higher cleaning speed. At this time, the combination of O ₂ gas and NF ₃ gas is particularly preferable because in the case of the combination of O ₂ gas and H ₂ gas or the combination of O ₂ gas and CF ₄ gas, the cleaning gases react with each other and H ₂ O This is thought to be due to the fact that these gases are liable to react with each other in the combination of the O ₂ gas and the NF ₃ gas, while they easily generate CO ₂ and CO ₂ .

In this experiment, by visual observation,
In the case of NF ₃ gas, the cleaning speed around the gas outlet 25a is low, but in the case of O ₂ gas or a gas obtained by combining O ₂ gas and H ₂ gas, the cleaning speed of this portion is high. It was confirmed that the cleaning speed around the mounting table 4 was high with NF ₃ gas. In the cleaning, C adhered from the upper side inside the vacuum vessel 2.
It was confirmed that the F film was removed, and the removed CF film may be re-adhered on the lower side. From these results, it is considered that it is desirable to first clean the inner wall portion of the gas ring 25 with a gas containing O ₂ gas, and then to clean around the mounting table 4 with a gas containing F, especially NF ₃ gas. Can be

As described above, in the present embodiment, CF
Since a gas containing O ₂ gas, H ₂ gas and F is used as a cleaning gas for the film, the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is shortened. Put can be improved.

Next, still another embodiment of the present invention will be described. The present embodiment has been made by paying attention to the fact that a combination of O ₂ gas and H ₂ gas is effective for cleaning, and different points from the above-described embodiment are as follows.
That is, a liquid or gas of H ₂ O is introduced into the vacuum vessel 2 at the time of cleaning. Here, H ₂ O may be supplied alone or in combination with a plasma gas such as O ₂ gas or Ar gas.

First, a plasma processing apparatus in which the cleaning of this embodiment is performed will be described with reference to FIGS. The plasma processing apparatus shown in FIG. 8 is intended to introduce of H ₂ O in a gaseous state, the plasma processing apparatus includes a side wall upper portion of the H ₂ O vessel 51 and the plasma chamber 21 that of H ₂ O liquid state is stored Are connected by a H ₂ O supply pipe 52 in which a mass flow 53 is interposed in the middle. The other structure is the same as that of the plasma processing apparatus shown in FIG. 1 described above. In such a plasma processing apparatus, the pressure of the plasma chamber 21 is, for example, about 0.2 Pa and the H ₂ O container 51 during cleaning. because much lower than, H ₂ O in H ₂ O container 51 becomes vaporized steam H ₂ O supply pipe 5
2. It is supplied to the plasma chamber 21 via the mass flow 53 at a flow rate of, for example, 0.01 sccm. And this H ₂
The O gas is turned into plasma in the plasma chamber 21 to become active species of H and O, and reacts with C and F of the CF film to form CO gas.
_The cleaning is advanced by generating ₂ or HF.

[0076] The plasma processing apparatus shown in FIG. 9 also H ₂ O
The is intended to be introduced in a gaseous state, this plasma processing apparatus, by connecting the plasma gas source 54 through the gas supply pipe 55 in H ₂ O container 51, the plasma of H ₂ O in H ₂ O container 51 A plasma gas such as an Ar gas or an O ₂ gas is supplied from the gas source 54 and supplied into the plasma chamber 21 while the plasma gas contains H ₂ O gas as humidity. In such a plasma processing apparatus, H ₂ O is supplied together with the plasma gas at a flow rate of, for example, 300 sccm.
Here, it is converted into plasma and reacts with C and F of the CF film to advance cleaning.

The plasma processing apparatus shown in FIG. 10 also introduces H ₂ O in a gaseous state. In this plasma processing apparatus, for example, a heater 56 is provided around an H ₂ O container 51 and H ₂ O is provided. A heater 57 is wound around the supply pipe 52, and H ₂ O in the H ₂ O container 51 is heated to forcibly vaporize and supply the H ₂ O into the plasma chamber 21. In such a plasma processing apparatus, H ₂ O is supplied to the plasma chamber 21 at a flow rate of, for example, 100 sccm, where it is turned into plasma and reacts with C and F of the CF film to advance cleaning.

The plasma processing apparatus shown in FIG. 11 introduces H ₂ O in a liquid state. In the figure, reference numeral 59 denotes a liquid mass flow, and the end of the H ₂ O supply pipe 58 connecting the H ₂ O container 51 and the plasma chamber 21 on the H ₂ O container 51 side is H ₂ O.
It is provided so as to enter the inside of H ₂ O in the container 51. The H in the inside of the ₂ O container 51 has been applied pressure by, for example, N ₂ gas, thereby the liquid state H ₂
O is supplied through the H ₂ O supply pipe 58 to, for example, 0.01 sccm.
Is supplied into the plasma chamber 21 at a flow rate of? Since the pressure inside the plasma chamber 21 is, for example, about 0.2 Pa,
H ₂ O in a liquid state is vaporized as soon as it is supplied into the plasma chamber 21, is converted into plasma here, reacts with C and F of the CF film, and advances cleaning.

Next, an experimental example conducted by the present inventors will be described. As an experimental apparatus, a plasma processing apparatus shown in FIG. 10 was used, and a pressure of 500 Pa, a divergent magnetic field, and microwave power 2
At 500 W, O ₂ gas and Ar gas are supplied as plasma gases at a flow rate of 200 sccm and 150 sccm, respectively, and gaseous H ₂ O is supplied at a changed flow rate, and the wafer W on which a CF film is formed is supplied. Was etched, and the etching rate at this time was calculated to obtain the removal amount of the CF film. The result is shown in FIG.

[0080] The results of FIG. 12, increasing the flow rate of H ₂ O until the flow rate was 100sccm, the etching rate in accordance with the increase of the flow rate - from that bets becomes larger, the supply of H ₂ O It was recognized that the removal rate of the CF film was increased.

Subsequently, in the plasma processing apparatus shown in FIG. 11, a CF film is formed to a thickness of 5 μm on an 8-inch wafer W under the conditions of a pressure of 0.2 Pa and a microwave power of 2700 W.
After forming the film, the pressure is 500 Pa and the microwave power is 2500
W, under the condition of diverging magnetic field, O ₂ as plasma gas
Gas and Ar gas at 200 sccm and 150 sccc respectively
m ₂ , and gaseous H ₂ O is supplied for 60 seconds.
When the cleaning was performed at a flow rate of ccm and the CF film was cleaned, the cleaning time was about 5 minutes, which is smaller than the case where only the O ₂ gas was introduced as the cleaning gas to perform cleaning. -It was confirmed that the shortening time was shortened.

As described above, in this embodiment, since the cleaning is performed by introducing H ₂ O, the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is shortened. Can be improved. By introducing H ₂ O, O ₂ gas and H ₂
The introduction operation is easier than in the case where the gas is separately introduced, and the handling is convenient because safe H ₂ O is used.

Next, another embodiment of the present invention will be described.
Will be described. This embodiment is different from the above-described embodiment.
Is that O is used as a cleaning gas._TwoInstead of gas,
CO _TwoGas, N_TwoO gas, N_FourO_TwoGas or CO gas
It is to use.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, after forming a CF film of 5 μm on an 8-inch wafer W under a microwave power of 2800 W, a pressure of 0.18 Pa, a microwave power of 2500 W, and a divergent magnetic field Under the conditions described above, 20 CO ₂ gas was used as a cleaning gas.
C was introduced at a flow rate of 0 sccm and adhered inside the vacuum vessel 2.
The F film was cleaned. The cleaning condition is visually observed, and the vicinity of the gas outlet 25a and the mounting table 4 are checked.
The time until the CF film was removed was measured with respect to the peripheral portion. The cleaning gas is N ₂ O gas, N ₄ O
The same experiment was performed when _two gases, CO gas and O ₂ gas were used. FIG. 13 shows the result.

According to the results of this experiment, the use of CO ₂ gas, N ₂ O gas, N ₄ O ₂ gas or CO gas as the cleaning gas makes it possible to reduce the gas outlet 25a and the mounting table 4 as compared with the case of using O ₂ gas. It was confirmed that the peripheral cleaning speed was increased and the cleaning time could be reduced. Thus, CO ₂ gas and N ₂ O are better than O ₂ gas.
The reason why the cleaning speed of gas, N ₄ O ₂ gas, CO gas, etc. is increased is that CO ₂ gas or CO gas reacts with F of the CF film to generate CF _4, and N ₂ O gas, N ₄
O ₂ gas reacts with F to generate NF ₃ , so that these gases react more easily with F than O ₂ gas, and therefore, the residue of F attached to the vacuum vessel 2 is easily removed. Conceivable.

As described above, in this embodiment, CO ₂ gas, N ₂ O gas, N ₄ O ₂ gas and C
Since O gas is used, C adhered inside the vacuum vessel 2
The cleaning time of the F film is reduced, thereby improving the throughput of the film forming process.

Next, still another embodiment of the present invention will be described. This embodiment is different from the above-described embodiment in that cleaning is performed after a cleaning wafer serving as a protection plate for protecting the surface of the mounting table is mounted on the mounting table 4. The cleaning wafer is made of, for example, a material that is not etched by a cleaning gas, such as AlN or Al ₂ O ₃ , and has the same size as the wafer W to be formed, for example, 8 inches. A transport arm (not shown) for carrying the cleaning wafer into and out of the vacuum vessel 2 is provided outside the vacuum vessel 2, and a cleaning wafer cassette (not shown) for mounting the cleaning wafer is provided. Have been.

In this embodiment, after the film formation processing of the wafer W is completed, the wafer W is unloaded from the vacuum vessel 2, the cleaning wafer is taken out from the cleaning wafer cassette and loaded into the vacuum vessel 2. Then, it is mounted on the mounting table 4. Then, predetermined cleaning is performed in a state where the cleaning wafer is mounted on the surface of the mounting table 4.

When the cleaning is performed in this manner, the surface of the mounting table 4 is protected by the cleaning wafer, so that the surface of the mounting table 4 is not exposed to the plasma during the cleaning. There is no danger of being beaten and rough. Here, in this example, the surface of the mounting table 4 is formed to be, for example, about 2 mm larger than the outer periphery of the processing wafer W, and a CF film adheres to a region protruding from the wafer W during the film forming process. Since the CF film does not adhere to the region where the wafer W is placed, the processing wafer W
By cleaning with a cleaning wafer having the same size as that of the above, the area where the CF film is not adhered is protected from the plasma, and the area where the CF film is adhered is exposed to the plasma and adhered. The CF film is removed. The present invention is also effective when the wafer is larger than the mounting table 4.

If the surface of the mounting table 4 becomes rough, irregularities are formed on the surface, and the heat conduction to the wafer W and the attraction force of the wafer W are partially changed. However, in the present embodiment, since the surface of the mounting table 4 is not rough as described above, the change in the heat conduction and the attraction force of the wafer W can be suppressed. Therefore, the thickness of the CF film to be formed can be made more uniform,
Further, since there is no possibility that the reproducibility is deteriorated during the process, the uniformity of the film thickness between the surfaces can be improved.

Since the surface of the mounting table 4 is not roughened, the life of the expensive mounting table 4 can be extended. More clean
The surface of the cleaning wafer is roughened by being hit by the plasma. However, since the cleaning wafer is made of a material which is not etched by the cleaning gas as described above, there is no possibility that particles will be generated from the roughened surface.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, an SiO ₂ film of 1 μm was formed on an 8-inch wafer W under a microwave power of 2300 W.
Each time a film is formed, an 8-inch cleaning wafer is placed on a mounting table, and under the conditions of a pressure of 200 Pa, a microwave power of 1200 W, and a diverging magnetic field, NF ₃ gas and N ₂ gas as cleaning gas. Was introduced at a flow rate of 500 sccm, and cleaning was performed for 15 minutes. In this manner, the film forming process is performed on 120 wafers W, and the temperature of the wafer W and the SiO
_The thickness of the _two films was measured. The same experiment was performed when no cleaning wafer was placed. FIG. 14 shows the maximum and minimum values of the wafer temperature and the film thickness.

According to the experimental results, when the cleaning wafer is mounted on the mounting table, the difference between the wafer temperature and the maximum value and the minimum value of the film thickness is smaller than when the cleaning wafer is not mounted. It has been confirmed that the uniformity of the film thickness can be improved in the film forming process by protecting the surface of the mounting table with the wafer. As described above, the present embodiment is not limited to the cleaning of the SiO ₂ film, but may be a CF film or a SiOF film.
The present invention can be applied to cleaning of a film.

Next, still another embodiment of the present invention will be described. This embodiment is different from the above-described embodiment in that, as shown in FIG. 15, the emission intensity is detected via an optical fiber 62 outside a viewing window 22a formed on the side wall of the film forming chamber 22. Of the film forming chamber 22
The end of the cleaning is determined by measuring the luminescence intensity of the active species. The viewing window 22a is made of a material that transmits light, for example, quartz (SiO ₂ ), calcium fluoride (CaF ₂ ), or the like.
The emission intensity of the active species, for example, O, C, F, or the like in 2 is detected by the spectroscope 61. Other configurations are the same as those of the plasma processing apparatus shown in FIG.

The operation of such a plasma processing apparatus will be described in the case where the CF film is cleaned with O ₂ gas. At the time of cleaning with O ₂ gas, for example, the spectroscope 61 continuously measures the emission intensity of the active species of O in the film forming chamber 22. Here, in the film forming chamber 22, O,
Various activated species (CF, C, C ₂ , C ₂ ) generated by the decomposition of the CF film itself and the reaction between the CF film and O
O, CO ₂ , and F) are present, but when the emission intensity of the active species of O is measured, as shown in FIG. 16, the active species of O has a peak specific to a wavelength such as 777 nm or 616 nm. Therefore, for example, the wavelength 7 having the highest peak value in the spectroscope 61 is obtained.
By measuring the emission intensity at 77 nm, it is possible to selectively detect only the emission intensity of the O active species. The emission intensity is proportional to the amount of O. The emission intensity increases as the amount of O increases, and the emission intensity decreases as the amount of O decreases.

As the cleaning proceeds, the emission intensity of the active species of O gradually increases as shown by the curve A in FIG. 17 and becomes substantially constant after the time T. That is, the amount of O increases as the cleaning time increases, and becomes substantially constant after the time T. This is because at the beginning of cleaning, a part of the generated active species of O is consumed for removing the CF film.
When the cleaning proceeds to some extent and the remaining amount of the CF film decreases, the amount of the active species of O consumed by the removal of the CF film decreases, so the amount of the active species of O remaining in the film forming chamber 22 When the CF film is completely removed, the consumption of the active species of O becomes zero, and the generated active species of O remain as it is, so that the amount of O becomes constant. is there. Therefore, the time until the amount of active species becomes constant is the time required for cleaning, and this time T is the end point of cleaning.

On the other hand, the curve B in FIG. 17 is the emission intensity of the active species originating from the CF film, for example, the active species of CF, C, C ₂ , CO, CO ₂ , and F. As it progresses, it gradually decreases in contrast to O, and becomes zero after the time T. That is, a large amount of C is initially used for cleaning.
Since the F film is present, the amount of these active species is large, but when the cleaning proceeds to some extent and the remaining amount of the CF film decreases, the amount gradually decreases accordingly, and the CF film is completely removed. Then it becomes zero. Therefore, in this case, the time required for the cleaning until the active species amount becomes zero is the time required for cleaning, and this time T is the end point of the cleaning.

FIG. 18 shows the emission intensity at a wavelength of 777 nm of the active species of O actually measured at the time of cleaning. As described above, since the emission intensity of the active species of O gradually increases, the cleaning is terminated when the emission intensity becomes constant. Here, the end point of the cleaning is determined, for example, by observing the level of the detected value of the light emission intensity, and setting a program for setting the light emission intensity constant when the detected value falls within a certain range in advance. You.

As described above, in the plasma processing apparatus of the present embodiment, the end point of the cleaning is determined by detecting the emission intensity of the active species of O existing in the film forming chamber 22. The end point can be determined more accurately than when the end point of the cleaning is visually determined. For this reason, the CF film is not left in the film forming chamber 22 by mistake in determining the end point, and the cleaning is not continued even though the CF film has already been removed. Can be improved.

As described above, in the present embodiment, the light emission intensity of the active species caused by the CF film is detected to clear the light.
The end point of the cleaning may be determined, or when a gas other than the O ₂ gas is used as the cleaning gas,
The emission intensity of the active species of this gas may be detected. This embodiment can be applied not only to cleaning of a CF film formed by ECR plasma processing but also to cleaning of a CF film formed by plasma. Further, the present invention can be applied to cleaning of a SiO ₂ film or a SiOF film.

[0101]

According to the present invention, the time required for cleaning the carbon film containing fluorine adhered to the inside of the vacuum vessel can be shortened, and the surface of the mounting table can be cleaned at the time of cleaning. Can be protected.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a plasma processing apparatus in which cleaning according to an embodiment of the present invention is performed.

FIG. 2 is a characteristic diagram of etching of a CF film by an O ₂ gas.

FIG. 3 is a table showing results of an experiment for confirming the effect of microwave power density on cleaning of O ₂ gas in a CF film.

FIG. 4 is an explanatory diagram showing a mirror magnetic field and a divergent magnetic field.

FIG. 5 is a table showing results of an experiment for confirming the effect of a magnetic field on cleaning of an O ₂ gas in a CF film.

FIG. 6 is a characteristic diagram showing electron energy when a microwave is supplied in a pulsed manner.

FIG. 7 is a table showing results of an experiment for confirming the effect of a cleaning gas on cleaning of a CF film.

FIG. 8 is a cross-sectional view illustrating a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 9 is a cross-sectional view showing another example of a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 10 is a cross-sectional view showing another example of a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 11 is a cross-sectional view showing another example of a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 12 is a characteristic diagram of etching of a CF film by H ₂ O gas.

FIG. 13 is a table showing results of an experiment for confirming the influence of a cleaning gas on cleaning of a CF film.

FIG. 14 is a table showing results of an experiment for confirming the effect of a cleaning wafer on cleaning of a CF film.

FIG. 15 is a sectional view showing a plasma processing apparatus according to still another embodiment of the present invention.

FIG. 16 is a characteristic diagram showing emission intensity of O plasma.

FIG. 17 is a characteristic diagram showing emission intensity of active species at the time of cleaning the CF film.

FIG. 18 is a characteristic diagram showing measurement results of emission intensity of O plasma during cleaning of a CF film.

FIG. 19 is a sectional view showing a conventional plasma processing apparatus.

[Explanation of symbols]

2 the vacuum chamber 21 plasma chamber 22 the film forming chamber 23 transmission window 31 waveguide 33 main coil 34 sub-coils 4 mounting table 51 H ₂ O container 52 H ₂ O supply pipe 53 mass flow - 61 spectrograph 62 optical fiber

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 18, 1997

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Cleaning method for plasma processing apparatus

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method for a plasma processing apparatus for performing a plasma processing on a substrate to be processed such as a semiconductor wafer.

[0002]

2. Description of the Related Art Aluminum wiring is mainly used as a wiring pattern of an integrated circuit, and an SiO ₂ film or a SiOF film is used as an interlayer insulating film for insulating the aluminum wiring. Has good film quality,
For example, ECR (El
electron Cyclotron Resonance
e) There is a tendency to use plasma treatment.

FIG. 19 shows an example of a plasma processing apparatus for performing this ECR plasma processing.
The microwaves of, for example, 2.45 GHz are supplied through the waveguide 11 and have a predetermined size, for example, 875 μm.
A Gaussian magnetic field is applied by the electromagnetic coil 12, and the interaction (resonance) between the microwave and the magnetic field causes a plasma gas such as an Ar gas or an O ₂ gas, or a reactive gas introduced into the film formation chamber 1B, for example. The SiH ₄ gas is turned into plasma, and active species of the SiH ₄ gas are formed by this plasma to form Al
A thin film is formed on the surface of the semiconductor wafer W mounted on the mounting table 13 made of N (aluminum nitride).

In such a plasma processing apparatus,
When a film forming process such as a SiO ₂ film is performed, these films also adhere to the wall surface of the film forming chamber 1B and the periphery of the mounting table 13, but the film forming process proceeds, and the film has a certain thickness. In this case, the adhered film is peeled off, causing particles. Therefore, after performing a film forming process of the SiO ₂ film or the SiOF film, a predetermined cleaning is performed to remove the adhered film. I have.

For example, the cleaning for removing the SiO ₂ film and the SiOF film is performed, for example, for about 20 minutes every time 12 wafers W are formed, and CF ₄ gas or NF _{3 is} used as the cleaning gas. An F-based gas such as a gas is introduced into the vacuum vessel, the gas is activated by plasma, and the activated species reacts with the adhered film and is removed.

[0006]

SUMMARY OF THE INVENTION By the way, SiO ₂
Although the film has a dielectric constant of about 4 and the SiOF film has a dielectric constant of about 3.5, the demand for high-speed devices has increased in recent years. Therefore, as such an interlayer insulating film having a low dielectric constant, a fluorine-added carbon film (hereinafter referred to as CF) capable of achieving a dielectric constant of 2.5 or less.
Membrane)).

This CF film can also be formed by the above-mentioned plasma processing apparatus. However, when the CF film is removed by cleaning, if an F-based gas such as the CF ₄ gas or the NF ₃ gas is used, the CF ₄ gas is removed. With only NF ₃ gas, the cleaning speed hardly progresses, and with only NF ₃ gas, the cleaning speed is considerably slow, and the processing takes a long time of about 90 minutes. If the cleaning takes a long time in this way,
Since the thinning is performed during the film forming process, there is a problem that the throughput of the film forming process is deteriorated.

At the time of cleaning, the mounting table 13 is exposed to the plasma, but since the CF film is not originally adhered to the surface of the mounting table 13, the surface of the mounting table 13 is directly hit by the plasma. And get rough. When the surface of the mounting table 13 becomes rough, unevenness is generated on the surface of the mounting table, and the suction force of the wafer W and the heat conduction to the wafer W are partially changed. It changes in the latter period, and the reproducibility of the process deteriorates. Therefore, there is a problem that the in-plane uniformity of the film thickness of the formed film is deteriorated and the uniformity of the film thickness between the surfaces is deteriorated.

Further, if the surface of the mounting table 13 is roughened, particles may be generated when the wafer W is mounted on or removed from the mounting table 13 in a subsequent film forming process. There is also a problem that the life of the expensive mounting table 13 is shortened. For example, when a particularly strong plasma is generated to increase the cleaning speed, there is a problem because the surface of the mounting table is greatly deteriorated.

Further, at the time of cleaning, an operator visually checks the inside of the film forming chamber 1B through the viewing window 14 formed on the side wall of the film forming chamber 1B and checks whether or not the film remains. In this case, the end of the process is determined. However, in such a method, the determination of the end is inaccurate because the method often depends on the experience of the operator. For this reason, the decision at the end is too early and the membrane remains,
In order to avoid this, the judgment at the end is delayed, and the
There is a problem in that the processing time becomes too long, and as a result, the throughput of the film forming process deteriorates.

The present invention has been made under such circumstances, and an object of the present invention is to reduce the time required for cleaning a carbon film containing fluorine adhering to the inside of a vacuum vessel. processing apparatus chestnut - is to provide a training method.

[0012]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a vacuum
Place the substrate to be processed on the mounting table provided in the container,
The film gas is turned into plasma, and the plasma
Film forming process for forming a fluorine-added carbon film on a substrate
And then for oxygen plasma generation in the vacuum vessel
The gas is turned into plasma, and the plasma is
Cleaner for removing fluorine-added carbon film adhering inside
And a charging step. Here the film formation
For example, the gas is turned into plasma by depositing the gas into a microwave and
By plasmatization by the interaction of the fields
In this case, the unit volume (1 cubic
The power of microwave per Torr) is set to 10kW or more.
It is desirable to do. Also, turning the deposition gas into plasma
Area facing the processing surface of the processing substrate by the field forming means
A magnetic field is formed so that lines of magnetic force run from
Into a plasma due to the interaction between the magnetic field and the electric field.
In this case, in this case,
In the cleaning step, the lines of magnetic force near the substrate to be processed are
Adjust the magnetic field so that it spreads wider than during the film deposition process
It is desirable to do it. Further adjustment of the magnetic field in this case
The magnetic field forming means surrounds the central axis of each substrate to be processed.
And a first coil provided above the substrate to be processed.
And a second side provided below or beside the substrate to be processed.
And a current flowing through the second coil.
Make it smaller than plasma processing (including zero) or reverse
It is desirable to carry out by flowing a current in the direction. Sa
In addition, AC power is applied to the oxygen plasma generation gas to
Plasma is generated and the plasma is added
When cleaning is performed after removing the cleaning film,
In the cleaning, the AC power is set higher than the frequency of the AC power.
What to do while turning on and off with low frequency pulses
Is desirable. Here, the cleaning process is performed for one sheet to be processed.
It may be performed every time a film formation process is performed on a substrate.
No. The oxygen plasma generating gas may be oxygen gas, acid gas, or the like.
Gas consisting of hydrogen gas and hydrogen gas, oxygen gas and fluorine
Gas containing oxygen and gas containing oxygen and fluorine
Water, water vapor, gas of carbon and oxygen compounds, nitrogen and oxygen
Is desirable. Also cleanin
The oxygen plasma generating gas composed of oxygen gas
Used, then oxygen consisting of a gas of a compound of oxygen and fluorine
This may be performed using a plasma generation gas.
Further, in the present invention, during the cleaning process,
Of the active species generated in
Detects the emission intensity of a specific wavelength of light,
It is desirable to judge the end of cleaning based on
No.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a cleaning method for a plasma processing apparatus according to the present invention will be described. The present inventors have developed CF attached to the inside of a vacuum vessel of a plasma processing apparatus.
In cleaning for removing the film, various gases were examined as a cleaning gas, and it was found that oxygen (O ₂ ) gas was effective. In this embodiment, cleaning of a plasma processing apparatus having a CF film attached thereto is performed using O ₂ gas as a cleaning gas.

First, an example of a plasma processing apparatus for forming a CF film on a substrate to be processed will be described with reference to FIG. This plasma processing apparatus is an apparatus using ECR (Electron Cyclotron Resonance). In the figure, reference numeral 2 denotes a vacuum vessel formed of, for example, aluminum or the like. This vacuum vessel 2 is connected to a cylindrical plasma chamber 21 located above and in communication with a lower cylindrical plasma chamber 21 for generating plasma. And a cylindrical film forming chamber 22 having a larger inner diameter.

The upper end surface of the vacuum vessel 2 is formed by a transmission window 23 for transmitting microwaves. On the upper surface of the transmission window 23, for example, 2.45 GH
A waveguide 31 for supplying microwaves of z is provided, and the other end of the waveguide 31 is connected to a microwave oscillator 32. In this example, the waveguide 31 and the microwave oscillator 32 constitute a high-frequency supply unit.

A ring-shaped main solenoid coil 33 (hereinafter referred to as a main coil 33) is disposed near the outer periphery of the side wall defining the plasma chamber 21 as magnetic field forming means in close proximity thereto. For example, a magnetic field of 875 gauss can be formed from above to below. A ring-shaped sub solenoid coil 34 (hereinafter, referred to as a sub coil 34) is disposed below the bottom wall of the film forming chamber 22.

On the side wall that partitions the plasma chamber 21,
The plasma gas nozzles 24 are provided evenly along the circumferential direction. A plasma gas source and a cleaning gas source (not shown) are connected to the nozzle 24 so that the plasma gas and the cleaning gas can be uniformly supplied to the upper portion in the plasma chamber 21. Although only two nozzles 24 are shown in the figure to avoid complication of the drawing, more nozzles 24 are actually provided.

On the other hand, in the film forming chamber 22, for example, C ₄ F ₈ gas and C ₄
A ring-shaped gas ring 25 having a gas outlet 25a for introducing ₂ H ₄ gas is provided.
The gas ring 25 is connected to a reactive gas source (not shown), for example, a C ₄ F ₈ gas source and a C ₂ H ₄ gas source.
A mounting table 4 for mounting a substrate to be processed, for example, a semiconductor wafer W (hereinafter, referred to as a wafer W), is provided at substantially the center of the film forming chamber 22 so as to be able to move up and down. The mounting table 4 has a main body 41 made of, for example, aluminum or the like provided with a ceramic body 42 having a built-in heater, and the mounting surface is configured as an electrostatic chuck. Further, the ceramic electrostatic chuck 42 of the mounting table 4 has a built-in electrode 43 for applying a bias for drawing ions into the wafer W, and the electrode 43 is connected to, for example, a high-frequency power supply 44 for drawing plasma. Furthermore, an exhaust port (not shown) is formed at the bottom of the film forming chamber 22.

Next, a description will be given of a process of forming a CF film using the above-described apparatus. First, a wafer W having, for example, an aluminum wiring formed on its surface is loaded from a load lock chamber (not shown) and placed on the mounting table 4. Subsequently, the inside of the vacuum vessel 2 is evacuated to a predetermined degree of vacuum, a plasma gas such as an Ar gas is introduced from the plasma gas nozzle 24 into the plasma chamber 21, and a film forming gas such as an Ar gas is introduced from the gas ring 25 into the film forming chamber 22. C ₄ F ₈ gas and C ₂ H ₄ gas are introduced at flow rates of 60 sccm and 30 sccm, respectively. Then, the inside of the vacuum vessel 2 is set to a process pressure of 0.2 P, for example.
a, and 13.56 MHz, 150
A bias voltage of 0 W is applied, and the surface temperature of the mounting table 4 is set to 320 ° C.

2.45 GH from microwave oscillator 32
The high frequency (microwave) of z is conveyed through the waveguide 31, passes through the transmission window 23, and is introduced into the plasma chamber 21.
In the plasma chamber 21, a mirror magnetic field generated by the main coil 33 and the sub-coil 34 is applied with a strength of 875 gauss, and the interaction between the magnetic field and the microwave generates electron cyclotron resonance. By A
The r gas is converted into plasma and the density is increased.

The plasma flow flowing from the plasma chamber 21 into the film forming chamber 22 activates the C ₄ F ₈ gas and the C ₂ F ₄ gas supplied thereto ( to form plasma) and activates the active species.
(Plasma) is formed.

On the other hand, active species transported onto wafer W are CF
A film is formed as a film. At this time, Ar ions drawn into the wafer W by a bias voltage for plasma pulling in are formed.
The CF film formed at the corners of the pattern on the surface of the wafer W is scraped off by the sputter etching action, and while widening the frontage, the CF film is formed from the bottom of the pattern groove, and the CF film is embedded in the recess without voids.

Subsequently, with such a plasma processing apparatus,
The cleaning performed after performing such a film forming process will be described. When a predetermined film forming process is performed on the wafer W, the CF also reaches a place where the film forming gas reaches, for example, around the wafer W on the surface of the mounting table 4, an outer peripheral portion of the mounting table 4, and around the gas outlet 25 a. The film adheres. Cleaning is a process performed to remove the CF film adhered to the inside of the vacuum vessel 2 as described above.
This is performed after performing the film forming process on the two wafers W.

Specifically, after the twelfth wafer W has been carried out of the vacuum chamber 2, the cleaning gas (oxygen plasma generation gas) is introduced into the plasma chamber 21 from the plasma gas nozzle 24.
At the same time, O ₂ gas is introduced at a flow rate of, for example, 200 sccm and a microwave of 2.45 GHz is introduced from the microwave oscillator 32.
And operating the sub-coil 34 to apply a magnetic field with a strength of 875 gauss.

The mirror will be described later in the inside of the deposition chamber 22 when such - a magnetic field is formed, occurs electron cyclotron resonance in interaction between the magnetic field and the microwave, O ₂ gas is converted to plasma by the resonance, And the density is increased. Then, active species (plasma) of O, such as radicals or ions of O, generated by the plasma, react with the CF film adhered to the gas outlet 25a and the periphery of the mounting table 4, and convert the CF film to, for example, CO ₂ gas or F ₂ gas. _The gas is decomposed into _two gases, scattered, and removed to the outside of the film forming chamber 22 through an exhaust port (not shown).

Here, a description will be given of an experimental example performed to confirm the effect of the present embodiment. Using the plasma processing apparatus shown in FIG. 1 as an experimental device, O ₂ and O ₂ gas from the plasma gas nozzle 24 to the wafer W to the CF film placed on the mounting table introduces was deposited at a flow rate of 200sccm Etching was performed by using the plasma, and the etching rate at this time was calculated to obtain the removal amount of the CF film. Here, other conditions include a pressure of 0.1 P
a, a mirror magnetic field was used and microwave power was changed.
The same experiment was performed when NF ₃ gas was introduced at a flow rate of 200 sccm instead of O ₂ gas. The result is shown in FIG.

From the results shown in FIG. 2, it was confirmed that the etching rate was considerably larger when the O ₂ gas was used than when the NF ₃ gas was used, whereby the O ₂ gas was converted to the NF ₃ gas. It was recognized that the CF film removal rate was higher than that.

In the plasma processing apparatus shown in FIG. 1, a 5-μm CF film is formed on an 8-inch wafer W under a pressure of 0.2 Pa and a microwave power of 2700 W, and then an O ₂ gas is used as a cleaning gas. 200sc
When the CF film was cleaned under the conditions of a pressure of 0.1 Pa, a microwave power of 2500 W, and a mirror magnetic field, the CF film was completely removed after 30 minutes, and NF was removed. ₃ It is recognized that the cleaning time is reduced to 1/10 to 1/5 as compared with the case where cleaning is performed by introducing a gas at a flow rate of 200 sccm.
From these results, it was confirmed that O ₂ gas was effective for cleaning the CF film.

The reason why the O ₂ gas is effective for cleaning the CF film is considered to be due to the following reasons. That is, when an O ₂ gas is used as a cleaning gas, the active species of O generated by plasma hitting the surface of the CF film physically causes the CC bond or CF bond on the CF film surface to physically. At the same time, the C—C bond and the like are also broken by a chemical reaction of generating CO ₂ between the active species of O and C (carbon) of the CF film. Then, O ₂ enters the inside of the CF film from this cut, and cuts the CC bond and the CF bond inside the CF film. As described above, the active species of O react with C of the CF film to generate CO ₂ gas, while F (fluorine) is presumed to generate F ₂ gas. Is thought to be removed.

On the other hand, when NF ₃ gas is used as the cleaning gas, the active species of F generated by the plasma breaks the CC bond or CF bond on the CF film surface, and these bonds are cut. After that, F is scattered as F ₂ gas or NF ₃ gas, and C is supposed to be scattered as CF ₄ gas, thereby removing the CF film.

It is considered that the generation of CO ₂ by the reaction between O and C is more likely to occur than the generation of CF ₄ by the reaction of F and C. For this reason, it is considered that the active species of O is liable to break the CC bond or CF bond inside the CF film by generating CO ₂ , so that it is easier to enter the CF film than F. As described above, the O ₂ gas has a CC bond and a CF bond at the time of cleaning, as compared with the NF ₃ gas.
Easy to cut, chestnut to easily enter the interior of the CF film - training speed is increased, as a result chestnut - training time is presumed to be shorter.

As described above, in this embodiment, since the O ₂ gas is used as the cleaning gas for the CF film, the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is shortened. The throughput of the treatment can be improved.

Next, another example of the present embodiment will be described. In this example, the power density of the microwave at the time of cleaning is 1 in the cleaning method of the above-described embodiment.
It is set to 0 kW / m ³ or more. The microwave power density is calculated by dividing the microwave power by the volume of the vacuum vessel 2. For example, if the microwave power is 2000 W and the volume of the vacuum vessel 2 is 0.2 m ³ , the microwave power density is 10 kW / m ³ .

From the experiment shown in FIG. 2 above, it was confirmed that the etching rate of the CF film was increased when the microwave power was increased. Therefore, the present inventors changed the power density of the microwave to clear the CF film. It was confirmed that the cleaning speed was increased when the microwave power density was 10 kW / m ³ or more.

Now, an experimental example performed by the present inventors will be described. As the experimental apparatus, the plasma processing apparatus shown in FIG. 1 was used, and the pressure was 0.2 Pa, the power was 2700 W, and the power density was 1
Under a 3.5 kW / m ³ microwave, a 10 μm CF film was formed on an 8-inch wafer W, and then a clear film was formed.
O ₂ gas was introduced as a cleaning gas at a flow rate of 200 sccm, and the CF film was cleaned by changing the power density of the microwave. At this time, the pressure was set to 0.2 Pa,
The test was performed by forming a magnetic field. The cleaning condition was visually observed, and the time until the CF film was removed was measured. The result is shown in FIG. The SiO ₂ film is 10 μm
After forming the film, NF ₃ gas and N ₂ gas are used as cleaning gases.
The same experiment was performed when the gas was introduced at a flow rate of 500 sccm. The result is shown in FIG.

According to the results shown in FIG. 3, when the SiO ₂ film is cleaned with the NF ₃ gas and the N ₂ gas, the cleaning is performed even if the microwave power density is increased from 6 kW / m ³ to 10 kW / m ^3. The time can be reduced by only 5 minutes, whereas when the CF film is cleaned with O ₂ gas, 6 kW when the microwave power density is 10 kW / m ³ or more.
/ M ³ , the cleaning time is shortened by 20 minutes and the cleaning time is reduced to ／ or less. Therefore, when cleaning the CF film, the cleaning time is shorter than that of the SiO ₂ film. It was confirmed that the influence of the microwave power density was large.

When cleaning the CF film by increasing the microwave power density from 9 kW / m ³ to 10 kW / m ³ , the cleaning time is shortened by 10 minutes, whereas the cleaning time is reduced by 10 kW / m ^3. Even if it is increased from 10 kW / m ³ to 10 kW / m ³ , the shortening time is 3 minutes, and the degree of shortening becomes small.
It is considered that it is desirable to set W / m ³ or more.

The effect of the microwave power density on the cleaning of the CF film is considered to be due to the following reasons. The higher the microwave power density, the higher the plasma density, and the higher the plasma density, the higher the O 2 activated by the plasma.
The energy of the active species is increased. Here, among the active species of O, the energies are different from each other, and some of the active species reach the adhered CF film and contribute to the removal of the CF film, while others have a small energy and cannot reach the CF film. Therefore, as described above, if the energy of the active species is increased, it is possible to reach the CF film on which more active species are attached.

In the cleaning with O ₂ gas, as described above, the active species of O generated by the plasma physically break the CC bond and CF bond on the CF film surface,
It is considered that the generation proceeds by chemically cutting by generating O _2. However, when the density of the plasma itself is increased and the energy of the activated species of O is increased, the activated species of O reaching the CF film are reduced. This increases both the physical and chemical cutting forces. Therefore, it is presumed that the CC bond and the like are more easily broken, and the O ₂ gas is more likely to enter the inside of the CF film, thereby promoting the progress of the cleaning process.

On the other hand, when cleaning the SiO ₂ film,
It is considered that the Si—O bond on the surface of the O ₂ film is cleaved by a chemical reaction with an active species of F obtained by activating NF ₃ . Accordingly, when the microwave power density increases and the plasma density increases, the energy of F activated by the plasma increases, so that the cleaning speed increases, but the physical force affects the SiO ₂ film. Since there is no cleaning, the degree of promotion of cleaning is reduced accordingly.

As described above, in this example, since the microwave power density is set to 10 kW / m ³ or more in the cleaning of the CF film, the cleaning time of the CF film adhered inside the vacuum vessel 2 is further reduced. Thus, the throughput of the film forming process can be further improved.

Next, still another example of the present embodiment will be described. In this example, the magnetic field at the time of cleaning is set to a divergent magnetic field in the cleaning method of the above embodiment. Here, the mirror magnetic field and the diverging magnetic field will be described with reference to FIG.
As shown in (a), the magnetic field M is confined around the mounting table 4 and is formed by operating the main coil 33 and the sub coil 34. On the other hand, as shown in FIG. 4B, the divergent magnetic field forms a magnetic field M so as to spread downward around the mounting table 4 and includes a sub- coil .
The current that flows through 34 is smaller than that during the film forming process, and is formed, for example, by operating only main coil 33.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, a 10 μm CF film was formed on an 8-inch wafer W under microwave power of 2700 W, and O ₂ gas was used as a cleaning gas at a flow rate of 200 sccm. The cleaning was performed on the CF film by changing the magnetic field to a mirror magnetic field and a divergent magnetic field under a pressure of 20 Pa and a microwave power of 2500 W. At this time, the mirror magnetic field was such that the main coil 33 current was 200 A and the sub coil 34 current was 2 A.
The divergent magnetic field was formed with the main coil 33 current at 200 A and the sub coil 34 current at 0 A. The cleaning condition was visually observed, and the time required for the CF film to be removed from the vicinity of the gas outlet 25a and the surface and the outer peripheral portion of the mounting table 4 (the peripheral portion of the mounting table 4) was measured. A similar experiment was performed with the pressure changed to 0.2 Pa. The result is shown in FIG.

According to the results shown in FIG. 5, in the diverging magnetic field, the cleaning time around the mounting table is much shorter than the mirror magnetic field, and the cleaning time around the gas outlet 25a takes longer than the mirror magnetic field. Clear around mounting table
When the cleaning is completed, the cleaning around the gas outlet 25a has already been completed. As a result, it has been recognized that the diverging magnetic field has a shorter cleaning time than the mirror magnetic field. Further, when the pressure is set to 0.2 Pa, the cleaning time around the mounting table is reduced by 20 minutes as compared with the case of 20 Pa, so that the cleaning time of the CF film is reduced as the pressure becomes lower. Inferred.

The reason for this is that, as described above, when the CF film is cleaned with the O ₂ gas, the plasma density becomes C
Since it greatly affects the physical and chemical cutting force such as the CC bond of the F film, it is considered that such a difference in the plasma density causes a large difference in the cleaning speed.
That is, since the plasma density increases as the magnetic flux density increases, the plasma is generated over the entire inside of the vacuum vessel 2.
In the case of the mirror magnetic field, the plasma region is formed so as to be confined in the vicinity of the upper portion of the mounting table, and in the case of the divergent magnetic field, the plasma region is formed so as to spread downward around the mounting table 4. Here, the plasma region means that the plasma is ECR
Means a region which is confined and increased in density, and in regions other than this region, the plasma density is extremely low.

Therefore, in the vicinity of the gas outlet 25a, the divergent magnetic field has a lower magnetic flux density and a lower cleaning speed. However, in this part, the magnetic field is confined to some extent even in the divergent magnetic field, and the plasma density is originally high, so it is considered that the cleaning time is not so long.

On the other hand, although the vicinity of the mounting table exists in the plasma region with the diverging magnetic field, the plasma diverges downward with the diverging magnetic field, and the plasma density decreases as it goes downward. . Therefore, the magnetic flux density around the mounting table is small, and the plasma density is
Since the temperature is lower than the vicinity of 5a, it is considered that the cleaning time is longer than that of the gas outlet 25a. On the other hand, in the mirror magnetic field, the periphery of the mounting table 4 is out of the plasma region and the plasma density becomes considerably low.
The running time will be quite long.

The reason why the cleaning time is further reduced when the pressure is reduced is considered to be as follows. That is, at low pressure, the mean free path of O ions becomes longer and the energy of the ions increases, so that the ion sputtering efficiency increases. As described above, the C—F film has a C—C bond or a C—C bond.
Since it is necessary to physically break the F bond, the more ions with high energy, the higher the cleaning speed.

Since the cleaning time was shortened by the divergent magnetic field, the magnetic field was changed to a mirror magnetic field and a divergent magnetic field even when the SiO ₂ film was cleaned with NF ₃ gas and N ₂ gas. When the cleaning time was measured in this manner, no reduction in the cleaning time was observed due to such a change in the magnetic field.

It is considered that the influence of the magnetic field on the cleaning is different between the CF film and the SiO ₂ film because the way of the cleaning progresses. As described above, in the cleaning of the O ₂ gas, the plasma density greatly affects the cleaning speed, and the cleaning does not easily progress in a portion far from the plasma region where the plasma density is extremely low. On the other hand, in the cleaning of the SiO ₂ film, the mechanism is not clear because the plasma density does not significantly affect the cleaning by the active species of F, as described above, but the cleaning is performed even in a portion where the plasma density is low. Is thought to progress. As described above, in the cleaning of the CF film, the influence of the plasma density is considerably larger than that of the SiO ₂ film, and it is presumed that the influence of the magnetic field becomes larger.

In the above example, in this example, a cusp magnetic field may be formed by flowing a current from the sub-coil 34 in a direction opposite to that of the main coil 33 instead of the diverging magnetic field. Also in the case of the cusp magnetic field, the plasma density around the mounting table can be increased.

As described above, in this example, a diverging magnetic field and a cusp magnetic field are formed in the cleaning of the CF film with the O ₂ gas, so that the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is further reduced. Thereby, the throughput of the film forming process can be further improved.

Next, still another example of the present embodiment will be described. In this example, in the cleaning method of the above-described embodiment, a microwave at the time of cleaning is supplied in a pulse form. Here, supplying the microwave in a pulse shape means that a microwave of 2.45 GHz of, for example, 2700 W oscillated from the microwave oscillator 32 is turned on with a pulse of, for example, a frequency of 100 to 5000 Hz.
It means turning off, that is, modulating the microwave with a pulse. The pulse duty ratio is, for example, 40
６０60% can be set. High Supplying microwaves pulsed energy as this - it is possible to generate a plasma having, chestnut - can be increased training speed.

Here, an experimental example performed by the present inventors will be described. A plasma processing apparatus shown in FIG. 1 was used as an experimental apparatus, and a pressure of 500 Pa and a mirror magnetic field (main coil 3) were used.
Under the conditions of 3 current 200A, sub coil 34 current 200A) and temperature 350 ° C, microwave of 2700W and 2.45GHz is supplied while turning on and off at a frequency of 100 to 5000Hz and a duty ratio of 0.4 to 0.6. Then, an O ₂ gas is introduced as a cleaning gas at a flow rate of 500 sccm, the wafer W on which the CF film is formed is etched, and the etching rate at this time is calculated to remove the CF film. I asked. The same experiment was performed when a microwave of 2700 W was continuously supplied.

According to this experiment, the cleaning rate (etching rate) when microwaves were supplied in a pulsed manner was
G) While it was 8000 angstroms / min, it was confirmed to be 4000 angstroms / min when supplied continuously, and the removal rate of the CF film was obtained by supplying microwaves in a pulsed manner. Was found to be larger.

Therefore, in the plasma processing apparatus shown in FIG. 1, a CF film is formed to a thickness of 5 μm on an 8-inch wafer W under the conditions of a pressure of 0.2 Pa and a microwave power of 2700 W. Under the conditions,
2700 W, 2.45 GHz microwave at frequency 10
It was supplied at 0-5000 Hz with a duty ratio of 0.4-0.6 while being turned on and off, and O ₂ gas was introduced as a cleaning gas at a flow rate of 500 sccm to clean the CF film. The cleaning time was about 6 minutes. On the other hand, microwave of 2700W is continuously supplied,
Otherwise, when the cleaning time was measured under the same conditions, the cleaning time was 12 minutes. From these results, it was confirmed that the cleaning time was shortened by about 6 minutes when the microwaves were supplied in a pulsed form compared to when the microwaves were supplied continuously.

The reason why the cleaning time is shortened when the microwave is supplied in a pulsed manner is considered to be as follows. That is, the microwave power is determined by (the number of electrons) × (the energy of the electrons), but the energy of the electrons is considerably high at the beginning of the supply of the microwave because the number of the electrons is small. The avalanche phenomenon increases exponentially, so it drops rapidly and stabilizes. Therefore, when microwaves are supplied in pulse form,
As shown in FIGS. 6A and 6B, high-energy electrons are supplied for each pulse, so that a high-energy plasma is continuously generated. FIG. 6
FIG. 3C shows, for comparison, changes in electron energy when microwaves are continuously supplied as in the prior art.
When the energy of the plasma increases as in this example, the energy of the active species activated by the plasma also increases, so that the number of active species reaching the CF film adhered in the vacuum vessel 2 increases. As a result, the cleaning speed increases.

As described above, in this example, the microwave is supplied in a pulsed manner in the cleaning of the CF film by the O ₂ gas, so that the cleaning time of the CF film adhered inside the vacuum vessel 2 is further reduced. Thus, the throughput of the film forming process can be further improved.

Next, still another example of the present embodiment will be described. In this example, in the cleaning method of the above-described embodiment, for example, cleaning is performed every time one wafer W is formed. If the cleaning is performed every time one wafer W is formed, the amount of the CF film adhered in the vacuum vessel 2 is small, so that one cleaning time is considerably long, for example, about 15 seconds. Be shorter.

After the wafer W on which film formation has been completed is carried out and before the next wafer W is carried in, in order to remove the electric charge remaining on the mounting table 4, for example, a charge elimination process using O ₂ plasma is performed, for example, 10 times. However, if cleaning is performed with O ₂ gas every time one wafer W is formed, the cleaning time is longer than the charge elimination time. That is, it is not necessary to perform only the charge removal processing separately from the cleaning. For this reason, the total processing time for processing the same number of wafers W is simpler than the case where cleaning is performed after depositing 25 wafers W while performing static elimination processing when exchanging the wafers W, for example. In the calculation, (the static elimination processing time) × (the number of wafers W) can be reduced, thereby improving the throughput.

Further, when cleaning is performed after 25 wafers W are formed, if the amount of the CF film adhering to the inside of the vacuum vessel 2 increases, the internal state of the vacuum vessel 2 changes and the adhering CF film changes. The film quality of the film changes, and the film adheres more firmly. This makes it difficult to remove the CF film. Therefore, compared to a case where cleaning is performed each time one wafer W is formed, total cleaning is performed.
The ninging takes a long time. Thus, the wafer W
When cleaning is performed each time one film is formed,
Since the cleaning time of the barrel can be shortened, the throughput can be further improved.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, a CF film is formed on an 8-inch wafer W under a pressure of 0.2 Pa and a microwave power of 2700 W. - the O ₂ gas was introduced at a flow rate of 500sccm as Ningugasu, pressure 500 Pa,
CF under the condition of divergent magnetic field and microwave power of 2700 W
The film was cleaned, and the total processing time when 25 wafers W were formed was measured. Also, under the same conditions, the total processing time when cleaning was performed after film formation on 25 wafers W while performing static elimination processing for 10 seconds when replacing the wafer W was measured. .

According to the results of this experiment, when cleaning is performed every time one wafer W is formed, the cleaning is about 15 seconds on average and the total processing time is 68 minutes 4
In contrast to 5 seconds, when cleaning is performed after 25 wafers W are formed, the cleaning time is about 30 minutes, and the total processing time is 92 minutes 3
It was confirmed to be 0 seconds.

As described above, in this example, the cleaning is performed each time one wafer W is formed in the cleaning of the CF film with the O ₂ gas, so that the total processing time can be reduced. Therefore, the throughput of the film forming process can be further improved.

In the above embodiment, in the cleaning, a plasma gas, for example, an Ar gas may be supplied simultaneously with the cleaning gas. In the film forming process, the CF film adheres not only to the mounting table 4 and the periphery of the gas outlet 25 a but also to the inner wall surface of the vacuum vessel 2. Since the film is weaker and thinner than the CF film adhering to the periphery and the amount is small, the cleaning of the inner wall of the vacuum vessel 2 has already been completed when the cleaning around the mounting table 4 is completed. State.

Next, another embodiment of the present invention will be described. The present embodiment is different from the above-described embodiment in that O ₂ gas is used as a cleaning gas in combination with H ₂ gas or a gas containing F such as CF ₄ gas or NF ₃ gas. is there. Here, O ₂ gas and H ₂
The gas or the like may be supplied at the same time, or the O ₂ gas may be supplied first, and then the H ₂ gas or the like may be supplied.

Next, experimental examples performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, a CF film was formed to a thickness of 10 μm on an 8-inch wafer W under a microwave power of 2700 W, and then a pressure of 0.2 Pa, a microwave power of 2500 W and a mirror were used. Under a magnetic field condition, a cleaning gas is introduced to clean the CF film.
Was performed.

As the cleaning gas, only O ₂ gas (flow rate 200 sccm), O ₂ gas + H ₂ gas (O ₂ gas flow rate 200 sccm, H ₂ gas flow rate 100 s)
ccm), O ₂ gas + CF ₄ gas (O ₂ gas flow rate 200
sccm, CF ₄ gas flow rate 200 sccm), O ₂ gas + NF ₃ gas (O ₂ gas flow rate 200 sccm, NF ₃ gas flow rate 200 sccm) were used. Then, the cleaning condition was visually observed, and the time until the CF film was removed was measured. This result is shown in FIG.

When O ₂ gas is first introduced as a cleaning gas and then NF ₃ gas is introduced (O ₂ gas flow rate 200 sccm, NF ₃ gas flow rate 500 sccm)
And when NF ₃ gas + N ₂ gas is introduced (O ₂ gas flow rate 200 sccm, NF ₃ gas flow rate 500 sccm, N 2
The same experiment was performed with _two gas flow rates of 500 sccm). At this time, the pressure was set to 0.2 Pa when the O ₂ gas was introduced, and was set to 120 Pa when the NF ₃ gas or the like was introduced. The result is shown in FIG.

According to the results of this experiment, the cleaning speed was increased by combining H ₂ gas and F containing gas with O ₂ gas as the cleaning gas, and the cleaning time was longer than when only O ₂ gas was used. It was confirmed that can be shortened. Thus O ₂ than O ₂ gas alone
The reason why the cleaning speed is increased by the combination of the gas and the H ₂ gas is that the active species of O is the C type of the CF film as described above.
The reaction to generate CO ₂ and the active species H so generates the HF reacts with F in the CF film, C-C bonds and CF bonds are considered to be because susceptible to cleavage.

Since the cleaning speed is increased by the combination of the O ₂ gas and the gas containing F as compared with the O ₂ gas alone, the cleaning by the active species of F affects the plasma density as described above. Is smaller than the active species of O, the mechanism is not clear where the plasma density is extremely low outside the plasma region due to the mirror magnetic field, such as around the mounting table 4, but the F is higher than that of the active species of O. It is considered that the active species has a higher cleaning speed. At this time, the combination of O ₂ gas and NF ₃ gas is particularly preferable because in the case of the combination of O ₂ gas and H ₂ gas or the combination of O ₂ gas and CF ₄ gas, the cleaning gases react with each other and H ₂ O This is thought to be due to the fact that these gases are liable to react with each other in the combination of the O ₂ gas and the NF ₃ gas, while they easily generate CO ₂ and CO ₂ .

In this experiment, by visual observation,
In the case of NF ₃ gas, the cleaning speed around the gas outlet 25a is low, but in the case of O ₂ gas or a gas obtained by combining O ₂ gas and H ₂ gas, the cleaning speed of this portion is high. It was confirmed that the cleaning speed around the mounting table 4 was high with NF ₃ gas. In the cleaning, C adhered from the upper side inside the vacuum vessel 2.
It was confirmed that the F film was removed, and the removed CF film may be re-adhered on the lower side. From these results, it is considered that it is desirable to first clean the inner wall portion of the gas ring 25 with a gas containing O ₂ gas, and then to clean around the mounting table 4 with a gas containing F, especially NF ₃ gas. Can be

As described above, in the present embodiment, CF
Since a gas containing O ₂ gas, H ₂ gas and F is used as a cleaning gas for the film, the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is shortened. Put can be improved.

Next, still another embodiment of the present invention will be described. The present embodiment has been made by paying attention to the fact that a combination of O ₂ gas and H ₂ gas is effective for cleaning, and different points from the above-described embodiment are as follows.
H ₂ O liquid or gas (water vapor) during cleaning
Is introduced into the vacuum vessel 2. Where H ₂
O may be supplied alone, O ₂ gas or A
It may be supplied in combination with a plasma gas such as r gas.

First, a plasma processing apparatus in which the cleaning of this embodiment is performed will be described with reference to FIGS. The plasma processing apparatus shown in FIG. 8 is intended to introduce of H ₂ O in a gaseous state, the plasma processing apparatus includes a side wall upper portion of the H ₂ O vessel 51 and the plasma chamber 21 that of H ₂ O liquid state is stored Are connected by a H ₂ O supply pipe 52 in which a mass flow 53 is interposed in the middle. The other structure is the same as that of the plasma processing apparatus shown in FIG. 1 described above. In such a plasma processing apparatus, the pressure of the plasma chamber 21 is, for example, about 0.2 Pa and the H ₂ O container 51 during cleaning. because much lower than, H ₂ O in H ₂ O container 51 becomes vaporized steam H ₂ O supply pipe 5
2. It is supplied to the plasma chamber 21 via the mass flow 53 at a flow rate of, for example, 0.01 sccm. And this H ₂
The O gas is turned into plasma in the plasma chamber 21 to become active species of H and O, and reacts with C and F of the CF film to form CO gas.
_The cleaning is advanced by generating ₂ or HF.

[0076] The plasma processing apparatus shown in FIG. 9 also H ₂ O
The is intended to be introduced in a gaseous state, this plasma processing apparatus, by connecting the plasma gas source 54 through the gas supply pipe 55 in H ₂ O container 51, the plasma of H ₂ O in H ₂ O container 51 A plasma gas such as an Ar gas or an O ₂ gas is supplied from the gas source 54 and supplied into the plasma chamber 21 while the plasma gas contains H ₂ O gas as humidity. In such a plasma processing apparatus, H ₂ O is supplied together with the plasma gas at a flow rate of, for example, 300 sccm.
Here, it is converted into plasma and reacts with C and F of the CF film to advance cleaning.

The plasma processing apparatus shown in FIG. 10 also introduces H ₂ O in a gaseous state. In this plasma processing apparatus, for example, a heater 56 is provided around an H ₂ O container 51 and H ₂ O is provided. A heater 57 is wound around the supply pipe 52, and H ₂ O in the H ₂ O container 51 is heated to forcibly vaporize and supply the H ₂ O into the plasma chamber 21. In such a plasma processing apparatus, H ₂ O is supplied to the plasma chamber 21 at a flow rate of, for example, 100 sccm, where it is turned into plasma and reacts with C and F of the CF film to advance cleaning.

The plasma processing apparatus shown in FIG. 11 introduces H ₂ O in a liquid state. In the figure, reference numeral 59 denotes a liquid mass flow, and the end of the H ₂ O supply pipe 58 connecting the H ₂ O container 51 and the plasma chamber 21 on the H ₂ O container 51 side is H ₂ O.
It is provided so as to enter the inside of H ₂ O in the container 51. The H in the inside of the ₂ O container 51 has been applied pressure by, for example, N ₂ gas, thereby the liquid state H ₂
O is supplied through the H ₂ O supply pipe 58 to, for example, 0.01 sccm.
Is supplied into the plasma chamber 21 at a flow rate of? Since the pressure inside the plasma chamber 21 is, for example, about 0.2 Pa,
H ₂ O in a liquid state is vaporized as soon as it is supplied into the plasma chamber 21, is converted into plasma here, reacts with C and F of the CF film, and advances cleaning.

Next, an experimental example conducted by the present inventors will be described. As an experimental apparatus, a plasma processing apparatus shown in FIG. 10 was used, and a pressure of 500 Pa, a divergent magnetic field, and microwave power 2
At 500 W, O ₂ gas and Ar gas are supplied as plasma gases at a flow rate of 200 sccm and 150 sccm, respectively, and gaseous H ₂ O is supplied at a changed flow rate, and the wafer W on which a CF film is formed is supplied. Was etched, and the etching rate at this time was calculated to obtain the removal amount of the CF film. The result is shown in FIG.

[0080] The results of FIG. 12, increasing the flow rate of H ₂ O until the flow rate was 100sccm, the etching rate in accordance with the increase of the flow rate - from that bets becomes larger, the supply of H ₂ O It was recognized that the removal rate of the CF film was increased.

Subsequently, in the plasma processing apparatus shown in FIG. 11, a CF film is formed to a thickness of 5 μm on an 8-inch wafer W under the conditions of a pressure of 0.2 Pa and a microwave power of 2700 W.
After forming the film, the pressure is 500 Pa and the microwave power is 2500
W, under the condition of diverging magnetic field, O ₂ as plasma gas
Gas and Ar gas at 200 sccm and 150 sccc respectively
m ₂ , and gaseous H ₂ O is supplied for 60 seconds.
When the cleaning was performed at a flow rate of ccm and the CF film was cleaned, the cleaning time was about 5 minutes, which is smaller than the case where only the O ₂ gas was introduced as the cleaning gas to perform cleaning. -It was confirmed that the shortening time was shortened.

As described above, in this embodiment, since the cleaning is performed by introducing H ₂ O, the cleaning time of the CF film adhered to the inside of the vacuum vessel 2 is shortened. Can be improved. By introducing H ₂ O, O ₂ gas and H ₂
The introduction operation is easier than in the case where the gas is separately introduced, and the handling is convenient because safe H ₂ O is used.

Next, still another embodiment of the present invention will be described. This embodiment is different from the above-described embodiment in that instead of O ₂ gas as a cleaning gas,
CO ₂ gas, N ₂ O gas, is to use N ₄ O ₂ gas and CO gas.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, after forming a CF film of 5 μm on an 8-inch wafer W under a microwave power of 2800 W, a pressure of 0.18 Pa, a microwave power of 2500 W, and a divergent magnetic field Under the conditions described above, 20 CO ₂ gas was used as a cleaning gas.
C was introduced at a flow rate of 0 sccm and adhered inside the vacuum vessel 2.
The F film was cleaned. The cleaning condition is visually observed, and the vicinity of the gas outlet 25a and the mounting table 4 are checked.
The time until the CF film was removed was measured with respect to the peripheral portion. The cleaning gas is N ₂ O gas, N ₄ O
The same experiment was performed when _two gases, CO gas and O ₂ gas were used. FIG. 13 shows the result.

According to the results of this experiment, the use of CO ₂ gas, N ₂ O gas, N ₄ O ₂ gas or CO gas as the cleaning gas makes it possible to reduce the gas outlet 25a and the mounting table 4 as compared with the case of using O ₂ gas. It was confirmed that the peripheral cleaning speed was increased and the cleaning time could be reduced. Thus, CO ₂ gas and N ₂ O are better than O ₂ gas.
The reason why the cleaning speed of gas, N ₄ O ₂ gas, CO gas, etc. is increased is that CO ₂ gas or CO gas reacts with F of the CF film to generate CF _4, and N ₂ O gas, N ₄
O ₂ gas reacts with F to generate NF ₃ , so that these gases react more easily with F than O ₂ gas, and therefore, the residue of F attached to the vacuum vessel 2 is easily removed. Conceivable.

As described above, in this embodiment, CO ₂ gas, N ₂ O gas, N ₄ O ₂ gas and C
Since O gas is used, C adhered inside the vacuum vessel 2
The cleaning time of the F film is reduced, thereby improving the throughput of the film forming process.

Next, still another embodiment of the present invention will be described. This embodiment is different from the above-described embodiment in that cleaning is performed after a cleaning wafer serving as a protection plate for protecting the surface of the mounting table is mounted on the mounting table 4. The cleaning wafer is made of, for example, a material that is not etched by a cleaning gas, such as AlN or Al ₂ O ₃ , and has the same size as the wafer W to be formed, for example, 8 inches. A transport arm (not shown) for carrying the cleaning wafer into and out of the vacuum vessel 2 is provided outside the vacuum vessel 2, and a cleaning wafer cassette (not shown) for mounting the cleaning wafer is provided. Have been.

In this embodiment, after the film formation processing of the wafer W is completed, the wafer W is unloaded from the vacuum vessel 2, the cleaning wafer is taken out from the cleaning wafer cassette and loaded into the vacuum vessel 2. Then, it is mounted on the mounting table 4. Then, predetermined cleaning is performed in a state where the cleaning wafer is mounted on the surface of the mounting table 4.

When the cleaning is performed in this manner, the surface of the mounting table 4 is protected by the cleaning wafer, so that the surface of the mounting table 4 is not exposed to the plasma during the cleaning. There is no danger of being beaten and rough. Here, in this example, the surface of the mounting table 4 is formed to be, for example, about 2 mm larger than the outer periphery of the processing wafer W, and a CF film adheres to a region protruding from the wafer W during the film forming process. Since the CF film does not adhere to the region where the wafer W is placed, the processing wafer W
By cleaning with a cleaning wafer having the same size as that of the above, the area where the CF film is not adhered is protected from the plasma, and the area where the CF film is adhered is exposed to the plasma and adhered. The CF film is removed. The present invention is also effective when the wafer is larger than the mounting table 4.

If the surface of the mounting table 4 becomes rough, irregularities are formed on the surface, and the heat conduction to the wafer W and the attraction force of the wafer W are partially changed. However, in the present embodiment, since the surface of the mounting table 4 is not rough as described above, the change in the heat conduction and the attraction force of the wafer W can be suppressed. Therefore, the thickness of the CF film to be formed can be made more uniform,
Further, since there is no possibility that the reproducibility is deteriorated during the process, the uniformity of the film thickness between the surfaces can be improved.

Since the surface of the mounting table 4 is not roughened, the life of the expensive mounting table 4 can be extended. More clean
The surface of the cleaning wafer is roughened by being hit by the plasma. However, since the cleaning wafer is made of a material which is not etched by the cleaning gas as described above, there is no possibility that particles will be generated from the roughened surface.

Here, an experimental example performed by the present inventors will be described. Using a plasma processing apparatus shown in FIG. 1 as an experimental apparatus, an SiO ₂ film of 1 μm was formed on an 8-inch wafer W under a microwave power of 2300 W.
Each time a film is formed, an 8-inch cleaning wafer is placed on a mounting table, and under the conditions of a pressure of 200 Pa, a microwave power of 1200 W, and a diverging magnetic field, NF ₃ gas and N ₂ gas as cleaning gas. Was introduced at a flow rate of 500 sccm, and cleaning was performed for 15 minutes. In this manner, the film forming process is performed on 120 wafers W, and the temperature of the wafer W and the SiO
_The thickness of the _two films was measured. The same experiment was performed when no cleaning wafer was placed. FIG. 14 shows the maximum and minimum values of the wafer temperature and the film thickness.

According to the experimental results, when the cleaning wafer is mounted on the mounting table, the difference between the wafer temperature and the maximum value and the minimum value of the film thickness is smaller than when the cleaning wafer is not mounted. It has been confirmed that the uniformity of the film thickness can be improved in the film forming process by protecting the surface of the mounting table with the wafer. As described above, the present embodiment is not limited to the cleaning of the SiO ₂ film, but may be a CF film or a SiOF film.
The present invention can be applied to cleaning of a film.

Next, still another embodiment of the present invention will be described. This embodiment is different from the above-described embodiment in that, as shown in FIG. 15, the emission intensity is detected via an optical fiber 62 outside a viewing window 22a formed on the side wall of the film forming chamber 22. Of the film forming chamber 22
The end of the cleaning is determined by measuring the luminescence intensity of the active species. The viewing window 22a is made of a material that transmits light, for example, quartz (SiO ₂ ), calcium fluoride (CaF ₂ ), or the like.
The emission intensity of the active species, for example, O, C, F, or the like in 2 is detected by the spectroscope 61. Other configurations are the same as those of the plasma processing apparatus shown in FIG.

The operation of such a plasma processing apparatus will be described in the case where the CF film is cleaned with O ₂ gas. At the time of cleaning with O ₂ gas, for example, the spectroscope 61 continuously measures the emission intensity of the active species of O in the film forming chamber 22. Here, in the film forming chamber 22, O,
Various activated species (CF, C, C ₂ , C ₂ ) generated by the decomposition of the CF film itself and the reaction between the CF film and O
O, CO ₂ , and F) are present, but when the emission intensity of the active species of O is measured, as shown in FIG. 16, the active species of O has a peak specific to a wavelength such as 777 nm or 616 nm. Therefore, for example, the wavelength 7 having the highest peak value in the spectroscope 61 is obtained.
By measuring the emission intensity at 77 nm, it is possible to selectively detect only the emission intensity of the O active species. The emission intensity is proportional to the amount of O. The emission intensity increases as the amount of O increases, and the emission intensity decreases as the amount of O decreases.

As the cleaning proceeds, the emission intensity of the active species of O gradually increases as shown by the curve A in FIG. 17 and becomes substantially constant after the time T. That is, the amount of O increases as the cleaning time increases, and becomes substantially constant after the time T. This is because at the beginning of cleaning, a part of the generated active species of O is consumed for removing the CF film.
When the cleaning proceeds to some extent and the remaining amount of the CF film decreases, the amount of the active species of O consumed by the removal of the CF film decreases, so the amount of the active species of O remaining in the film forming chamber 22 When the CF film is completely removed, the consumption of the active species of O becomes zero, and the generated active species of O remain as it is, so that the amount of O becomes constant. is there. Therefore, the time until the amount of active species becomes constant is the time required for cleaning, and this time T is the end point of cleaning.

On the other hand, the curve B in FIG. 17 is the emission intensity of the active species originating from the CF film, for example, the active species of CF, C, C ₂ , CO, CO ₂ , and F. As it progresses, it gradually decreases in contrast to O, and becomes zero after the time T. That is, a large amount of C is initially used for cleaning.
Since the F film is present, the amount of these active species is large, but when the cleaning proceeds to some extent and the remaining amount of the CF film decreases, the amount gradually decreases accordingly, and the CF film is completely removed. Then it becomes zero. Therefore, in this case, the time required for the cleaning until the active species amount becomes zero is the time required for cleaning, and this time T is the end point of the cleaning.

FIG. 18 shows the emission intensity at a wavelength of 777 nm of the active species of O actually measured at the time of cleaning. As described above, since the emission intensity of the active species of O gradually increases, the cleaning is terminated when the emission intensity becomes constant. Here, the end point of the cleaning is determined, for example, by observing the level of the detected value of the light emission intensity, and setting a program for setting the light emission intensity constant when the detected value falls within a certain range in advance. You.

As described above, in the plasma processing apparatus of the present embodiment, the end point of the cleaning is determined by detecting the emission intensity of the active species of O existing in the film forming chamber 22. The end point can be determined more accurately than when the end point of the cleaning is visually determined. For this reason, the CF film is not left in the film forming chamber 22 by mistake in determining the end point, and the cleaning is not continued even though the CF film has already been removed. Can be improved.

As described above, in the present embodiment, the light emission intensity of the active species caused by the CF film is detected to clear the light.
The end point of the cleaning may be determined, or when a gas other than the O ₂ gas is used as the cleaning gas,
The emission intensity of the active species of this gas may be detected. This embodiment can be applied not only to cleaning of a CF film formed by ECR plasma processing but also to cleaning of a CF film formed by plasma. Further, the present invention can be applied to cleaning of a SiO ₂ film or a SiOF film.

[0101]

According to the present invention, mosquitoes containing fluorine attached to the inside of the vacuum chamber - Bonn film chestnut - as possible out to shorten the time required for training.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a plasma processing apparatus in which cleaning according to an embodiment of the present invention is performed.

FIG. 2 is a characteristic diagram of etching of a CF film by an O ₂ gas.

FIG. 3 is a table showing results of an experiment for confirming the effect of microwave power density on cleaning of O ₂ gas in a CF film.

FIG. 4 is an explanatory diagram showing a mirror magnetic field and a divergent magnetic field.

FIG. 5 is a table showing results of an experiment for confirming the effect of a magnetic field on cleaning of an O ₂ gas in a CF film.

FIG. 6 is a characteristic diagram showing electron energy when a microwave is supplied in a pulsed manner.

FIG. 7 is a table showing results of an experiment for confirming the effect of a cleaning gas on cleaning of a CF film.

FIG. 8 is a cross-sectional view illustrating a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 9 is a cross-sectional view showing another example of a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 10 is a cross-sectional view showing another example of a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 11 is a cross-sectional view showing another example of a plasma processing apparatus in which cleaning according to another embodiment of the present invention is performed.

FIG. 12 is a characteristic diagram of etching of a CF film by H ₂ O gas.

FIG. 13 is a table showing results of an experiment for confirming the influence of a cleaning gas on cleaning of a CF film.

FIG. 14 is a table showing results of an experiment for confirming the effect of a cleaning wafer on cleaning of a CF film.

FIG. 15 is a sectional view showing a plasma processing apparatus according to still another embodiment of the present invention.

FIG. 16 is a characteristic diagram showing emission intensity of O plasma.

FIG. 17 is a characteristic diagram showing emission intensity of active species at the time of cleaning the CF film.

FIG. 18 is a characteristic diagram showing measurement results of emission intensity of O plasma during cleaning of a CF film.

FIG. 19 is a sectional view showing a conventional plasma processing apparatus.

[EXPLANATION OF SYMBOLS] 2 vacuum chamber 21 plasma chamber 22 the film forming chamber 23 transmission window 31 waveguide 33 main coil 34 sub-coils 4 mounting table 51 H ₂ O container 52 H ₂ O supply pipe 53 mass flow - 61 spectrograph 62 optical fiber

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Risa Nakase 1-2-4, Shiroyamacho, Tsukui-gun, Kanagawa Prefecture Inside the Sagami Office of Tokyo Electron Tohoku Co., Ltd. (72) Inventor Yoko Naito, Shiroyamacho Machiya, Tsukui-gun, Kanagawa Prefecture 1-2-141 Tokyo Electron Tohoku Co., Ltd. Sagami Business Office (72) Inventor Masaki Tozawa 1-2-41 Shiroyama Machiya, Tsukui-gun, Kanagawa Prefecture Tokyo Electron Tohoku Co., Ltd. Sagami Business Office (72) Inventor Hirata Masafumi 1-2-141 Machiya, Shiroyama-cho, Tsukui-gun, Kanagawa Prefecture Inside the Tokyo Electron Tohoku Co., Ltd. Sagami Office

Claims (1)

[Claims] A plasma processing apparatus for converting a processing gas into a plasma in a vacuum vessel having a mounting table for a substrate to be processed therein, and forming a fluorine-added carbon film on the substrate by the plasma. 3. The cleaning method for a plasma processing apparatus according to claim 1, wherein the cleaning gas containing oxygen gas is turned into plasma, and the plasma removes the fluorine-added carbon film adhered inside the vacuum vessel.