JPH09326384A - Plasma processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a plasma processing system in which the labor and the cost of maintenance is reduced while enhancing the safety without sacrifice of the rate of operation by eliminating a troublesome periodic cleaning, e.g. dry cleaning, and to suppress generation of particle simply at low cost. SOLUTION: A reactive gas is introduced into a vacuum vessel 11A and applied with energy in order to generate a plasma and a silicon substrate 25, for example, arranged on a substrate holder 22 in the vacuum vessel 11A is processed with active species, e.g. ions or radicals, contained in the plasma. The surface of the inner structural member of the vacuum vessel 11A exposed to the plasma is coated, at least partially, with a layer of fluoride principally comprising aluminum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to an improvement in a structure for suppressing dust generated during plasma processing in a plasma processing apparatus such as a dry etching apparatus or a plasma CVD apparatus for processing a semiconductor substrate.

[0002]

2. Description of the Related Art Plasma processing by various methods is adopted in an etching process and a film forming process in a semiconductor device manufacturing process. Various reactive gases are used in these plasma treatments. It is desired that each reactive gas react stoichiometrically completely depending on its purpose. However, in reality, a part of the reactive gas is exhausted unreacted or an unnecessary reaction product is generated. The reaction product is
It adheres to the inner wall surface of the vacuum container that is exposed to plasma,
It grows as a deposited film.

Conventionally, when dry etching a SiO ₂ film, a Si ₂ N ₄ film or another Si-based compound formed on a semiconductor substrate, a reactive gas such as CF ₄ ,
C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , CHF ₃ , CH ₂ F ₂
Etc. are used. These reactive gases are turned into plasma, and as a result, active species such as ions and radicals are produced.

For example, SiO ₂ exposed in a predetermined pattern
When the substrate on which the film is formed is treated with the plasma of the reactive gas, the Si ₂ O ₃ film and the active species generated by the plasma cause a physicochemical reaction to produce Si.
O ₂ is converted to a volatile gas such as SiF ₄ and CO ₂ and is removed from the substrate. Further, the volatile gas is sequentially discharged from the vacuum container to the outside. Thus, the SiO ₂ film on the substrate is dry-etched.

On the other hand, the active species is SiO 2.
_{2 When} recombined without reacting with the membrane, C _X F _Y , C _X
A fluorocarbon polymer such as F _Y O _Z is generated.
The generated fluorocarbon polymer becomes a reaction product remaining in the vacuum container, and most of them are on the inner wall surface of the vacuum container or the surface of each internal member, that is, the surface of the member forming the internal structure of the vacuum container. Deposit to form a fluorocarbon film. This fluorocarbon film gradually grows with the progress of the etching process, and the amount of adhesion (film thickness) increases. The fluorocarbon film is eventually peeled off from the inner surface of the vacuum container or the like. Therefore, the fluorocarbon film becomes a particle source that contaminates the substrate.

Therefore, conventionally, in order to remove the fluorocarbon film, the inner surface of the vacuum container and the surface of each member inside the vacuum container have been regularly cleaned in order to remove the fluorocarbon film. As a conventional cleaning method, generally, the inside of the vacuum container is placed in an atmospheric state, the film attached to the inner surface or the like is scraped off, and a wet cleaning method of performing a wiping operation using an organic solvent such as alcohol, or a vacuum container is used. There is a dry cleaning method in which an O ₂ gas is introduced into plasma and the O radicals that are active species generated are used to decompose the fluorocarbon film.

In addition, a treatment may be adopted from the beginning so that the fluorocarbon film is not formed on the inner surface of the vacuum container. For example, heating the vacuum container during the etching process with a heater prevents the fluorocarbon polymer from adhering to the inner surface of the vacuum container.

As prior art documents relating to the background art related to the present invention, Japanese Patent Laid-Open Nos. 61-133386 (1st document), 61-289934 (2nd document) and 6
3-29514 (3rd document), Japanese Examined Patent Publication No. 63-45
No. 466 (4th document) can be mentioned. First
The literature discloses a configuration in which a detachable alumina coating member is provided along the inner surface of a vacuum container of a plasma etching apparatus. With this configuration, it is possible to prevent the release of iron, nickel, etc. from the vacuum container made of stainless steel. The second document shows a structure in which a portion such as the inner wall of the reaction chamber is covered with an alumina material in a dry etching apparatus, thereby suppressing generation of a polymer during etching. The third document shows a configuration in which a cover made of fluororesin or the like is used to cover the back space of the electrode in a dry etching processing apparatus or the like. In this configuration, foreign matter is deposited on the cover and foreign matter is deposited in a narrow back space. Prevents and simplifies cleaning. The fourth document shows a structure in which a ceramic coating is formed on the inner surface of an aluminum vacuum chamber by a dry etching apparatus or the like, and with this structure, corrosion of the aluminum vacuum chamber during dry etching is prevented.

[0009]

In the above wet cleaning method, the etching apparatus is stopped, the vacuum container is vented (opened to the atmosphere), the internal member is removed to scrape off the attached film, and then the organic material such as alcohol is removed. It was wiped off with a solvent. Therefore, the etching process is interrupted during cleaning. When the cleaning work is completed, it is necessary to assemble the removed member, evacuate the vacuum container, and check the etching characteristics with the dummy wafer. As described above, according to the wet cleaning method, a great amount of time and labor are required, which causes a decrease in the operating rate of the etching apparatus and poses a problem that productivity is significantly impaired.

In the dry cleaning method, it is not necessary to open the vacuum container to the atmosphere and remove the internal members, which is itself efficient. However, if the fluorocarbon film is thickly deposited, it is difficult to completely remove it. Further, depending on the location in the vacuum container, there is a place where it is difficult to remove by dry cleaning, so there is a problem that wet cleaning must be used together. Further, during dry cleaning, the fluorocarbon film is decomposed and F radicals are simultaneously generated. When the members in the vacuum container are made of Si, C, a polymer material, or the like, these members react with F radicals during dry cleaning and are etched at high speed. For this reason, the above-mentioned member is worn out sharply each time dry cleaning is performed, the life is shortened, and the replacement frequency is increased. In such a case, the problem that the maintenance cost becomes high is also raised.

It is also possible to heat the vacuum container with a heater or the like during the etching process so that the fluorocarbon film is not formed. However, on the other hand, a heater, a control mechanism, a power source, etc. are required as auxiliary equipment for the etching apparatus. Therefore, the device configuration becomes complicated, the device becomes large and the cost increases, and the safety in handling is impaired.

The object of the present invention is to solve the above-mentioned problems, and it does not require any troublesome periodical cleaning such as wet cleaning or dry cleaning, does not lower the operation rate of the apparatus, and requires less labor for maintenance. Another object of the present invention is to provide a plasma processing apparatus which can reduce particle generation at low cost, high safety, and extremely simple and inexpensive.

[0013]

A plasma processing apparatus according to the present invention (corresponding to claim 1) introduces a reactive gas into a vacuum container and applies energy to the reactive gas to generate plasma. Is a device for processing a silicon substrate or the like placed on a substrate holder in a vacuum container with active species such as ions and radicals contained in this plasma, and the internal structure of the vacuum container is formed. At least a part of the surface of the member exposed to the plasma is configured to be covered with a layer of fluoride containing aluminum as a main component.

In the present invention described above, the fluoride layer containing aluminum as a main component utilizes the experimentally found action of suppressing the deposition of the fluorocarbon polymer. By covering the surface for generating plasma with the above-mentioned fluoride layer, it is possible to reduce the deposition of the fluorocarbon film by plasma treatment such as dry etching.

In the above structure, preferably, the fluoride layer is made of a fluoride itself containing aluminum as a main component, and the fluoride covers the surface of the member.

In the above structure, preferably, the fluoride layer is formed by subjecting the surface of the member to a fluorination treatment.

In the above structure, preferably, the member is formed of an alloy or metal compound containing aluminum, and the fluorination treatment is performed on this alloy or metal compound.

In the above structure, preferably, the member is formed of alumite, and the fluorination treatment is performed on this alumite.

In the above structure, preferably, the member is formed of a ceramic containing aluminum, and the fluorination treatment is performed on this ceramic.

In the above structure, preferably, at least a part of the surface of the member is made of aluminum fluoride.

[0021]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Through experiments and research on the subject matter of the present invention, the following new facts have been found regarding fluorides containing aluminum as a main component. The details will be described with reference to the outline of the experimental plasma device and the sample details and the comparison table regarding the adhesion amount.

First, in order to evaluate a material to which a fluorocarbon polymer does not adhere in the plasma treatment, a sample of SUS316 having a size of about 30 mm ² whose surface is not subjected to a fluorination treatment, that is, a Ni system is used. 5 samples subjected to the plating treatment, and then 5 samples subjected to further fluorination treatment to the same plated sample were prepared to make a total of 10 types of samples. The detailed contents of these samples are described in the column of sample details in Table 1 shown below. In the column of sample details in Table 1, the upper column shows five kinds of samples "without fluorination treatment" and the middle column shows five kinds of samples with "fluorination treatment". In the lower part of the column of sample details,
For the purpose of comparison, which will be described later, members existing inside the vacuum container of the plasma processing apparatus (components of the plasma processing apparatus),
That is, the inner wall surface of the vacuum container, the surface of the silicon (Si) substrate, and the surface of the electrode cover (alumina) are described.

[0024]

[Table 1]

The above-mentioned 10 kinds of samples were placed in an experimental plasma processing apparatus, a fluorocarbon film was formed on each sample, and the adhesion amount (film thickness) of each was measured to evaluate the adhesion of the fluorocarbon film. It was

FIG. 1 shows a schematic configuration of the plasma processing apparatus used in the experiment. In FIG. 1, a plasma generation chamber 12 communicating with the internal space of the vacuum container is provided on the upper wall of the vacuum container 11, and a substrate stage 13 is provided on the lower wall thereof. The vacuum container 11 further has a gas inlet 14 for introducing a required gas into the internal space, a pressure control system 15 for adjusting the internal space to a desired pressure, and the internal space kept at a desired reduced pressure state. A gas exhaust system (not shown) is provided.

A loop-shaped antenna 16 is arranged around the plasma generating chamber 12. The antenna 16 is supplied with high frequency power of 13.56 MHz from a high frequency power supply 18 via an impedance matching device 17. This high-frequency power is transmitted via the antenna 16 to the plasma generation chamber 12
And is used as electric power to generate plasma. A magnetic field generating coil 19 is further arranged around the outside of the plasma generating chamber 12. A coil power supply 20 is connected to the magnetic field generating coil 19.

In the substrate stage 13, the substrate holder 22 is provided with the insulator 21 interposed between the substrate stage 13 and the lower wall of the vacuum container 11. The substrate holder 22 also functions as an electrode, and a cooling medium passage 23 is formed therein. A ring-shaped electrode cover 24 is arranged on the upper surface of the substrate holder 22. The electrode cover 24 is arranged around the substrate mounting portion 22a, and when viewed from above, the electrode cover 24 surrounds the substrate 25 mounted on the substrate mounting portion 22a.

In the above plasma processing apparatus, for example,
The total flow rate from the gas inlet 14 to the inside of the vacuum container 11 is 50
C ₄ F ₈ and CH ₂ F with sccm (flow ratio 1: 1)
₂ is introduced, and the vacuum container 11 is operated by the pressure control system 15.
The internal pressure of is controlled to be a constant pressure of 10 mTorr. Further, a DC voltage is applied to the magnetic field generating coil 19 by the coil power source 20 and adjusted so that the coil current value is about 40A.

Subsequently, 1 kW of high frequency power (13.56 MHz) is applied to the antenna 16 from the high frequency power supply 18. As a result, plasma is generated in the plasma generation chamber 12.

Under the above conditions, a polycrystalline Si film or SiO ₂
When the film etc. were dry-etched, it was found that the film was hardly etched. Therefore, since the active species generated by the plasma are kept in an unreacted state, the above conditions are
It was confirmed that the conditions were such that the fluorocarbon film was easily formed.

Next, a substrate 2 having a diameter of 6 inches, in which a sample material 26 containing all of the 10 kinds of samples shown in Table 1 above is placed on the substrate mounting portion 22a of the substrate holder 22 in the vacuum container 11
5 was placed, the above plasma was intermittently generated, and the plasma treatment was performed for about 3 hours in total.

Then, the adhered amount of the fluorocarbon film was measured with a height gauge for each sample on the substrate 25 taken out. The results at this time are shown in the column of the attached amount in Table 1 above. In the column of the amount of the fluorocarbon film deposited, the upper column shows the deposited amount of each of the 5 samples without "fluorination", the middle column shows the deposited amount of each of the 5 samples with "fluorination", and the lower column shows the plasma. The amount of adhesion on each component of the processing apparatus and the substrate 25 is shown. The values in the column of the adhered amount are all shown by measuring 5 times and averaging them.

As is clear from the numerical values of the adhesion amount in Table 1 above, the adhesion amount of the sample "without fluorination" is 0.014 to
The value included in the range of 0.042 mm is taken, and the average value thereof is 0.027 mm. Further, the adhered amount of the sample "with the fluorination treatment" takes a value included in the range of 0.002 to 0.008 mm, and the average value thereof is 0.005 mm.

From the above, when the amounts of the adhered fluorocarbon films of the respective samples were compared, it was found that the amount of the adhered amount of the sample subjected to the fluorination treatment was smaller than that of the sample only subjected to the Ni plating treatment. . Particularly, among them, the amount of adhesion of the sample which was subjected to the fluorination treatment after the Ni pure plating treatment was
Despite the condition that the fluorocarbon film is very easily deposited, it was 0.002 mm. This value is the limit of measurement, and it is considered that the fluorocarbon film is hardly formed on the surface of this sample.

These samples which have been subjected to the fluorination treatment are prepared by, for example, adding 1 to 20% fluorine gas diluted with nitrogen gas.
The sample was thermally decomposed at a temperature of 50 to 400 ° C. and the sample was heated to 400 ° C. in the atmosphere for about 2 hours. It is considered that by performing this treatment, thermodynamically stable Ni fluoride is uniformly formed on the sample surface, and the subsequent reaction with F is suppressed.

When the adhesion amount of the fluorocarbon film deposited on the inner wall surface of the vacuum container 11 exposed to the plasma, the surface of the Si substrate 25, and the surface of the electrode cover 24 and the like located on the outer periphery thereof is examined, Although there were some partial differences, the amount of adhesion reached 0.6 to 1.0 mm. Usually, when the adhered amount of the fluorocarbon film starts to exceed 1.0 mm, a crack is generated on the surface thereof, and eventually it becomes flakes and peels off. This is the source of so-called particles.

Next, in the plasma processing apparatus, paying attention to materials for forming members such as the inner wall surface of the vacuum container 11, the substrate holder 22, the electrode cover 24, etc., where the fluorocarbon film is likely to be deposited by being exposed to plasma. 1) Aluminum-containing materials (aluminum materials: including aluminum-containing alloys and metal compounds), (2) alumite (oxalic acid-based treatment), (3) alumite (sulfuric acid-based treatment), (4) alumina, (5) AlN (nickel aluminum), (6) Six types of ceramics containing aluminum such as sapphire, and six types of samples "fluoridation-free" for these six types of samples. It was made. Similar to the above-mentioned samples, plasma treatment was performed on these samples as well, and the adhesion amount of the fluorocarbon film was examined. The results are shown in Table 2 below. All of these adhesion amounts are also shown by taking the average value of the five measurements.

[0039]

[Table 2]

As is clear from Table 2 above, the fluorocarbon film is deposited on all the samples that have not been subjected to the fluorination treatment, and the adhesion amount is measured to be 0.2 to 0.5 m.
A film having a thickness included in the range of m was formed.

On the other hand, when the adhesion amount of the sample subjected to the fluorination treatment was measured, it was all less than 0.01 mm. Therefore, as in the case of the Ni plating described above, the fluorocarbon film was not formed. Can be considered

As a result of the above experiment, it was confirmed that the formation of the fluorocarbon film was suppressed by performing the fluorination treatment.

Next, based on the above experimental results, for example, in an actual dry etching apparatus, a part or all of the surface exposed to plasma in the member forming the internal structure of the vacuum container was fluorinated. An example of the form will be described with reference to FIG. In the embodiment of FIG. 2, at least the inner wall surface of the vacuum container 11A and the electrode cover 24A.
The surface of has been fluorinated. In FIG. 2, the configuration of the other parts is the same as in the case of FIG.

In FIG. 2, an alumite fluoride layer 31 is formed on the inner wall surface of a vacuum container 11A made of aluminum, and an alumina fluoride layer 32 is formed on the surface of an electrode cover 24A made of alumina. here,
Under the etching conditions applied in the above-mentioned experiment, only the gas flow rate ratio is returned to 3: 2 which is the ratio in the actual dry etching, and the etching process with a required time of 5 minutes / time is repeated 10,000 times to deposit the fluorocarbon film. Was evaluated.

In the above evaluation, the adhered amounts of the fluorocarbon film on the surfaces of the alumite fluoride layer 31 and the alumina fluoride layer 32 according to the present embodiment were measured, respectively.
Both were 0.2 mm or less.

On the other hand, in the conventional dry etching process,
Cleaning was performed when the adhered amount of the fluorocarbon film exceeded 1 mm. Therefore, it was necessary to perform the cleaning at least about 8 to 10 times in 10,000 times of the dry etching treatment. When calculated backward from this, it is easily expected that the adhered amount of the fluorocarbon film will be about 8 to 10 mm by the conventional dry etching process.

According to the above comparison results, when the structure according to the present invention is applied, it is possible to make the adhesion amount of the fluorocarbon film at least 1/40 to 1/50 of the conventional adhesion amount.

As described above, since part or all of the surface exposed to the plasma in the plasma processing apparatus is composed of the surface that has been subjected to the fluorination treatment, the deposition of the fluorocarbon film can be sufficiently suppressed.

In the above embodiment, a member made of aluminum (vacuum container 11A) is fluorinated to form an alumite fluoride layer on its inner surface, and a member made of alumina (electrode cover 24A) is used. Although the alumina fluoride layer was formed on the surface by performing the fluorination treatment, similarly, other materials subjected to the fluorination treatment shown in Table 2 above can be used for the surface exposed to the plasma. . Thus, in general, a part or all of the surface exposed to plasma is covered with the fluoride layer containing aluminum as the main component, whereby the effect of the present invention that the deposition of the fluorocarbon film is sufficiently suppressed can be achieved. When the surface exposed to plasma is covered with a fluoride layer containing aluminum as a main component, the surface itself can be covered with fluoride itself containing aluminum as a main component.

[0050]

As is apparent from the above description, according to the present invention, in a vacuum vessel in which plasma treatment is performed, a part or all of the surface of the member forming the internal structure exposed to plasma is mainly made of aluminum. Since it is covered with a layer of fluoride as a component, it is possible to sufficiently suppress the deposition of the fluorocarbon film on the above-mentioned surface exposed to plasma, and therefore, no troublesome wet cleaning or dry cleaning is required. In addition, it is possible to reduce maintenance labor and cost without lowering the operation rate of the device, to have a safety problem, and to suppress the particle generation amount very simply and at low cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional configuration diagram showing an internal structure of an experimental plasma processing apparatus.

FIG. 2 is a schematic cross-sectional configuration diagram showing an internal structure of the plasma processing apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 11, 11A Vacuum container 12 Plasma generation chamber 13 Substrate stage 14 Gas inlet 15 Pressure control system 16 Antenna 19 Magnetic field generation coil 21 Insulator 22 Substrate holder 23 Coolant passage 24, 24A Electrode cover 25 Substrate 26 Sample material 31 Anodized fluorine Fluoride layer 32 Alumina fluoride layer

Front page continued (72) Inventor Kunio Kashiwa 1-13-9 Shibadaimon, Minato-ku, Tokyo Within Showa Denko KK (72) Inventor Takanori Kodama 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Denko KK Kawasaki Factory (72) Inventor Hiroyasu Taguchi 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Denko KK Kawasaki Factory

Claims (7)

[Claims] 1. A plasma processing apparatus for introducing a reactive gas into a vacuum container, applying energy to the reactive gas to generate plasma, and processing the substrate arranged in the vacuum container with the plasma. A plasma processing apparatus, wherein in the vacuum container, at least a part of a surface of the member forming the internal structure exposed to the plasma is covered with a layer of fluoride containing aluminum as a main component. 2. The plasma processing apparatus according to claim 1, wherein the fluoride layer is fluoride itself, and the fluoride covers the surface of the member. 3. The plasma processing apparatus according to claim 1, wherein the fluoride layer is formed by subjecting the surface of the member to a fluorination process. 4. The plasma processing apparatus according to claim 3, wherein the member is formed of an alloy or metal compound containing aluminum, and the fluorination treatment is performed on the alloy or metal compound. 5. The plasma processing apparatus according to claim 3, wherein the member is made of alumite, and the fluorination treatment is performed on the alumite. 6. The plasma processing apparatus according to claim 3, wherein the member is formed of a ceramic containing aluminum, and the fluorination treatment is performed on the ceramic. 7. The plasma processing apparatus according to claim 1, wherein at least a part of the surface of the member is formed of aluminum fluoride.