Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
1998-09-21
2002-09-03
Chen, Bret (Department: 1762)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C216S067000, C427S534000
Reexamination Certificate
active
06443165
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a method for cleaning a plasma treatment system for carrying out the plasma treatment of a substrate to be treated, such as a semiconductor wafer, and a plasma treatment system.
BACKGROUND ART
Typically, an interconnection layer of aluminum is used as a metallization pattern of an integrated circuit, and an SiO
2
or SiOF film is used as an interlayer insulator film for insulating the interconnection layer. As a method for depositing these layer and films, there is a tendency to use, e.g., the ECR (Electron Cyclotron Resonance) plasma treatment, which utilizes the combination of a microwave with a magnetic field, since the quality of films deposited by the method is good.
FIG. 28
shows an example of a plasma treatment system for carrying out the ECR plasma treatment. A microwave of, e.g., 2.45 GHz, is supplied into a plasma production chamber
1
A via a waveguide
11
. Simultaneously, a magnetic field of a predetermined magnitude, e.g., 875 gausses, is applied into the plasma production chamber
1
A by means of an electromagnetic coil
121
. Thus, the interaction (resonance) between the microwave and the magnetic field produces a plasma of a plasma gas, such as Ar or O
2
gas, and a plasma of a reactive gas, such as SiH
4
gas, which is introduced into a thin film deposition chamber
1
B. These plasmas form an active species of SiH
4
gas to deposit a thin film on the surface of a semiconductor waver W transferred onto a transfer table
13
of AlN (aluminum nitride).
In such a plasma treatment system, when the deposition treatment of an SiO
2
film and so forth is carried out, these films are adhered to the side wall of the thin film deposition chamber
1
B and the surrounding portion of the transfer table
13
. When the thin film deposition treatment proceeds to allow the film to have a certain thickness, the adhered film is peeled off to cause particles. Therefore, after the deposition treatment of the SiO
2
or SiOF film is carried out, a predetermined cleaning is carried out to remove the adhered film.
For example, the cleaning for removing the SiO
2
or SiOF film is carried out for, e.g., about 20 minutes, each time the deposition on, e.g., 12 wafers W, is carried out. As a cleaning gas, a F containing gas, such as CF
4
or NF
3
gas, is introduced into a vacuum vessel, and this gas is activated by a plasma to allow the active species to react with the adhered film to remove the adhered film.
After the cleaning is completed, a predetermined precoat is carried out in order to prevent particles remaining on the inner wall of the vacuum vessel
10
from scattering and so forth. This precoat is a treatment for depositing a precoat film on the inner wall of the vacuum vessel
10
. For example, in the case of the deposition treatment of an SiO
2
film or the like, the precoat film is formed of an SiO
2
or SiF
4
film.
By the way, the SiO
2
film has a dielectric constant of about 4, and the SiOF film has a dielectric constant of about 3.5. In recent years, a demand for higher speed devices has been raised, so that a demand for interlayer insulator films having a low dielectric constant has been made. Therefore, as such an interlayer insulator film having a low dielectric constant, a fluorine containing carbon film (which will be hereinafter referred to as a “CF film”) capable of having a dielectric constant of 2.5 or less has been widely noticed.
This CF film can be also deposited by the above described plasma treatment system. However, if the F containing gas, such as CF
4
or NF
3
gas, is used to carry out the cleaning of the CF film, the cleaning hardly progresses when only CF
4
gas is used. In addition, when only NF
3
gas is used, the cleaning rate is very slow, and the treatment takes a long time, about 90 minutes. Thus, if the cleaning takes a long time, there is a problem in that the throughput in the thin film deposition treatment deteriorates since the cleaning is carried out during the thin film deposition treatment.
In addition, when the cleaning is carried out, the transfer table
13
is exposed to plasma. However, since the CF film is not originally adhered to the surface of the transfer table
13
, the surface of the transfer table
13
is directly struck with plasma to become rough. Thus, when the surface of the transfer table
13
becomes rough, the surface of the transfer table has irregularities, so that the absorbing force onto the wafer W and the thermal conduction into the wafer Ware partially changed. In addition, the thin film deposition treatment changes between the initial and later stages of the process, so that the reproducibility of the process deteriorates. Therefore, there is a problem in that the inplane uniformity of the thickness of the deposited film deteriorates or the face-to-face uniformity of the thickness thereof deteriorates.
Moreover, if the surface of the transfer table
13
becomes rough, there are also problems in that the rough surface of the transfer table
13
may cause particles when the wafer W is loaded onto the transfer table
13
to carry out the subsequent thin film deposition treatment or unloaded from the transfer table
13
, and that the life of the expensive transfer table
13
may be reduced. For example, when a particularly strong plasma is intended to be produced to increase the cleaning rate, there is a problem in that the surface of the transfer table deteriorates considerably.
In addition, when the cleaning is carried out, an operator observes the interior of the thin film deposition chamber
1
B via a peep hole
14
, which is formed in the side wall of the thin film deposition chamber
1
B, to determine the finish time of the treatment by recognizing whether the film remains. According to such a method, the determination of the finish time may be incorrect since it is relied upon the experience of the operator. Consequently, there are problems in that the determined finish time is too early so that the film remains, and that in order to prevent the determination of the early finish time, the determined finish time is late so that the cleaning time is too long, thereby reducing the throughput in the thin film deposition treatment.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a method for cleaning a plasma treatment system, which can shorten the time required for the cleaning of a fluorine containing carbon film adhered in a vacuum vessel. It is another object of the present invention to provide a method for cleaning a plasma treatment system, which can protect a transfer table when the cleaning of an adhered film is carried out.
In addition, the CF film can be also deposited by means of the above described plasma treatment system. However, if the precoat film is formed of an SiO
2
or SiOF film when the deposition treatment of the CF film is carried out, there is a problem in that the precoat film is easy to react with a raw material gas of the CF film, e.g., a CF gas, such as C
4
F
8
gas, to produce particles, and the precoat used for the deposition treatment of the CF film has many unknown components.
It is therefore another object of the present invention to provide a plasma treatment method, which can carry out a stable thin film deposition on a substrate to be treated, by reducing particles in a vacuum vessel.
DISCLOSURE OF THE INVENTION
According to the present invention, a plasma treatment system cleaning method comprises: a thin film deposition step of transferring a substrate to be treated, onto a transfer table provided in a vacuum vessel, and producing a plasma of a thin film deposition gas to deposit a fluorine containing carbon film on the substrate by means of the plasma of the thin film deposition gas; and a cleaning step of producing a plasma of an oxygen plasma producing gas in the vacuum vessel, and removing the fluorine containing carbon film adhered in the vacuum vessel, by means of the plasma of the oxygen plasma producing gas. The plasma production of the thin film dep
Akahori Takashi
Hirata Tadashi
Ishizuka Shuichi
Naito Yoko
Nakase Risa
Chen Bret
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
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