PLASMA PROCESSING APPARATUS
The invention provides a plasma processing apparatus having a means for generating a plasma capable of correcting the eccentricity of the plasma diffused above the wafer caused by magnetic field or by vacuum eccentricity, comprising a vacuum processing chamber in which a sample is processed via plasma, a gas supply means for supplying gas into the vacuum processing chamber, a sample stage disposed within the vacuum processing chamber on which the sample is placed, an induction coil disposed outside the vacuum processing chamber, a radio frequency power supply for supplying radio frequency power to the induction coil, a Faraday shield being capacitively coupled with the plasma, and an eccentricity correction means disposed between the induction coil and a dielectric sealing window constituting an upper surface of the vacuum processing chamber, wherein the eccentricity correction means generates a plasma capable of correcting the eccentricity of the plasma.
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The present application is based on and claims priority of Japanese patent application No. 2010-269875 filed on Dec. 3, 2010, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to plasma processing apparatuses, and more specifically, relates to inductively coupled plasma processing apparatuses.
2. Description of the Related Art
In the field of semiconductor device fabrication, inductively coupled plasma processing apparatuses are used to perform etching and surface treatments. In this type of plasma processing apparatus, a few turns of induction coils are arranged on the outer side of a vacuum chamber of the apparatus and radio frequency current is supplied to the coils so as to feed power to generate plasma. At this time, stray capacitance occurs between the induction coils and plasma, causing local damages of the vacuum chamber. Japanese patent application laid-open publication No. 2007-158373 (patent document 1) discloses an apparatus capable of preventing this problem by disposing a Faraday shield composed of a conductor between the induction coils and plasma.
It is known that regardless of the type of inductively coupled plasma source being applied, the generated plasma becomes uneven along the circumferential direction of the induction coils, since uneven current distribution along the induction coils is unavoidable. This phenomenon causes the eccentricity of plasma in which the center axis of plasma diffused above the wafer is displaced from the center axis of the induction coils. Plasma eccentricity is also considered to be caused by the influence of magnetic fields, wherein Japanese patent application laid-open publication No. 2004-22988 (patent document 2) discloses an apparatus for covering the whole body of the plasma processing chamber with a magnetic member to shield the magnetic fields, thereby solving the above-mentioned problem of influence of magnetic fields.
The present inventors have also confirmed via experiment that eccentricity of distribution of plasma diffused above the wafer occurs by the influence of magnetic fields. In the experiment, plasma processing was performed by disposing an approximately 0.4 mT magnet to the outer circumference of the plasma processing chamber 1. As a result, it was discovered that a minute magnetic field as small as 0.4 mT created by the magnet caused the plasma distribution diffused above the wafer to be varied greatly. It has been recognized that plasma is possibly influenced by even a minute magnetic field as small as geomagnetism. The above-mentioned phenomenon may also be caused by the magnetic field created via a vacuum pressure gauge or a motor disposed on the processing apparatus. The eccentricity of plasma diffused above the wafer influenced by the magnetic field is caused by the generated plasma being diffused obliquely toward the wafer by the influence of the magnetic field. When etching is performed while the plasma diffused above the wafer has eccentricity, the uniformity and verticalness of the etching process is deteriorated. Demands are increasing for higher accuracy and higher speed of etching processes, and the influence of magnetic fields cannot be ignored in order to realize stable etching processes. The following three problems occur when the art disclosed in patent document 2 is adopted to solve the influence of magnetic fields. The first problem is the problem of performance. Plasma processing chambers must have openings for transferring samples to be processed or for evacuating processing gases, so that it is actually impossible to shield magnetic fields. Moreover, when the chamber is covered by a magnetic member, induction loss occurs within the magnetic member due to the induction magnetic field generated by the induction coils, according to which the plasma generating ability is deteriorated. The second problem is related to the mounting process. A significant change of design is required to cover the whole chamber with the magnetic member, and dangers during operation increase along with the increased chances of handling heavy loads during assembly. The third problem relates to costs. According to the art disclosed in patent document 2, a large amount of magnetic materials capable of covering the plasma processing chamber must be used, which requires a large amount of costs. These three problems are extremely serious in manufacturing mass production apparatuses. Other than the above-mentioned influence of magnetic fields, the eccentricity of plasma caused by the oblique diffusion of plasma mentioned above may also occur due to the eccentricity of vacuum within the plasma processing chamber 1. Thus, the present invention aims at solving the three problems mentioned above and the influence of vacuum eccentricity, not by shielding magnetic fields but by providing a plasma processing apparatus having a means for generating plasma capable of correcting the eccentricity of plasma diffused above the wafer caused by magnetic fields and vacuum eccentricity.
SUMMARY OF THE INVENTIONThe present invention provides a plasma processing apparatus comprising a vacuum processing chamber in which a sample is processed via plasma, a gas supply means for supplying gas into the vacuum processing chamber, a sample stage disposed within the vacuum processing chamber on which the sample is placed, an induction coil disposed outside the vacuum processing chamber, a radio frequency power supply for supplying radio frequency power to the induction coil, a Faraday shield being capacitively coupled with the plasma, and an eccentricity correction means disposed between the induction coil and a dielectric sealing window constituting an upper surface of the vacuum processing chamber, wherein the eccentricity correction means generates a plasma capable of correcting the eccentricity of the plasma.
The arrangement of the present invention enables to correct the eccentricity of plasma diffused above the wafer and to achieve the desired etching performance.
Now, a preferred embodiment of the present invention will be described in detail with reference to the drawings.
While feeding processing gas from a gas supply device 9 into the plasma processing chamber 1, the pressure within the plasma processing chamber 1 is decompressed to a predetermined pressure via a vacuum device 10. Processing gas is fed from the gas supply device 9 to the plasma processing chamber 1, and plasma is generated by the processing gas via the action of an electric field created via the Faraday shield 6 and the induction magnetic field created via the induction coils 4. A second radio frequency power supply 11 is connected to the sample stage 3. A bias power is applied from the second radio frequency power supply 11 to the sample stage 3 so as to draw ions existing within the plasma 5 toward the sample 2. The Faraday shield 6 is composed of a metallic conductor having vertical striped slits and arranged to be superposed to the window 1a. Thus, the present apparatus realizes a function to prevent local damages of the window 1a caused by the stray capacitance between the induction coils 4 and plasma 5, and a function to maintain the inner wall of the plasma processing chamber 1 to a most suitable condition by applying uniformly-sized capacitive coupling actively controlled via the matching box 7 to the plasma.
As shown in
The plasma processing apparatus of the present invention as described above enables to generate plasma capable of correcting the eccentricity of plasma diffused above the sample 2 caused by the influence of the magnetic field other than the induction magnetic field generated by the induction coils 4. This is due to the following operation of the present invention. As shown in
Next, the result of verification of the effect of the present invention via the etching rate will be described.
First, according to the prior art plasma processing apparatus as shown in
The present embodiment has been illustrated based on an example in which the location of eccentricity of the plasma diffused above the sample has been estimated based on the measurement of in-plane distribution of etching rate of the sample, but the estimation of location of eccentricity of the plasma diffused above the sample can also be performed based for example on ion current flux measurement or plasma density distribution measurement using probes.
As described above, the plasma processing apparatus according to the present invention provides an eccentricity correction means for generating a plasma capable of correcting the eccentricity of plasma diffused above the sample, thereby improving the eccentricity of plasma diffused above the sample caused by the influence of magnetic fields or by the eccentricity of vacuum within the plasma processing chamber.
Claims
1. A plasma processing apparatus comprising:
- a vacuum processing chamber in which a sample is processed via plasma;
- a gas supply means for supplying gas into the vacuum processing chamber;
- a sample stage disposed within the vacuum processing chamber on which the sample is placed;
- an induction coil disposed outside the vacuum processing chamber;
- a radio frequency power supply for supplying radio frequency power to the induction coil;
- a Faraday shield being capacitively coupled with the plasma; and
- an eccentricity correction means disposed between the induction coil and a dielectric sealing window constituting an upper surface of the vacuum processing chamber, wherein the eccentricity correction means generates a plasma capable of correcting the eccentricity of the plasma.
2. The plasma processing apparatus according to claim 1, wherein
- the eccentricity correction means comprises a conductor plate, wherein the conductor plate is in conduction with the Faraday shield.
3. The plasma processing apparatus according to claim 1, wherein
- the eccentricity correction means comprises a ring-shaped conductor, wherein the ring-shaped conductor is in conduction with the Faraday shield.
Type: Application
Filed: Feb 4, 2011
Publication Date: Jun 7, 2012
Applicant:
Inventors: Yusaku SAKKA (Shunan-shi), Ryoji NISHIO (Kudamatsu-shi), Tadayoshi KAWAGUCHI (Kudamatsu-shi)
Application Number: 13/020,929
International Classification: C23F 1/08 (20060101);