Plasma processing apparatus

A plasma processing apparatus is provided that is configured to supply a gas into a chamber, generate a plasma from the gas using a power of an electromagnetic wave, and perform a predetermined plasma process on a substrate that is held by a mounting table. The plasma processing apparatus includes a dielectric window through which the electromagnetic wave that is output from an electromagnetic wave generator is propagated and transmitted into the chamber, a support member that supports the dielectric window, a partition member that separates a space where the support member is arranged from a plasma generation space and includes a protrusion abutting against the dielectric window, and a conductive member that is arranged between the partition member and the dielectric window and is protected from being exposed to the plasma generation space by the protrusion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma processing apparatus.

2. Description of the Related Art

Techniques are known for controlling the generation of plasma in a plasma processing apparatus that supplies a gas into a chamber, generates plasma from the gas using a high frequency power, and performs a predetermined plasma process on a substrate that is held by a mounting table.

For example, Japanese Laid-Open Patent Publication No. 2001-185542 (Patent Document 1) discloses an apparatus including a current path correction means for correcting a part of a high frequency current path that is formed by a high frequency bias applied to a wafer and is near an outer periphery of the wafer, wherein the current path part is forced toward an opposing electrode surface facing the wafer. As an example of the current path correction means, a conductive member is disposed near a wall at a lower part of a dielectric body.

However, according to Patent Document 1, the conductive member is configured to correct a current path in order to control a plasma generation region within the chamber and improve plasma processing in-plane uniformity of a wafer. On the other hand, Patent Document 1 does not contemplate measures for suppressing the occurrence of abnormal discharge within the chamber.

When abnormal discharge occurs within the chamber, the chamber may be damaged and particles may be generated from the chamber walls. The particles may be dispersed on a wafer while a plasma process is performed thereon, and short-circuits may occur in the wirings formed on the wafer, for example.

SUMMARY OF THE INVENTION

An aspect of the present invention is directed to suppressing the occurrence of abnormal discharge within the chamber of a plasma processing apparatus by suppressing the propagation of electromagnetic waves.

According to one embodiment of the present invention, a plasma processing apparatus is provided that is configured to supply a gas into a chamber, generate a plasma from the gas using a power of an electromagnetic wave, and perform a predetermined plasma process on a substrate that is held by a mounting table. The plasma processing apparatus includes a dielectric window through which the electromagnetic wave that is output from an electromagnetic wave generator is propagated and transmitted into the chamber, a support member that supports the dielectric window, a partition member that separates a space where the support member is arranged from a plasma generation space and includes a protrusion abutting against the dielectric window, and a conductive member that is arranged between the partition member and the dielectric window and is protected from being exposed to the plasma generation space by the protrusion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be described with reference to the accompanying drawings. Note that in the following descriptions and drawings, elements having substantially the same features are given the same reference numbers and overlapping descriptions thereof may be omitted.

[Overall Configuration of Plasma Processing Apparatus]

First, an overall configuration of a plasma processing apparatus31according to an embodiment of the present invention will be described with reference toFIG. 1.FIG. 1is a cross-sectional view of the plasma processing apparatus31according to an embodiment of the present invention. In the present embodiment, a plasma processing apparatus using a radial line slot antenna is illustrated as an example of the plasma processing apparatus31. Another example of the plasma processing apparatus31includes an electron cyclotron resonance (ECR) plasma apparatus. The plasma processing apparatus31may be any apparatus that supplies a gas into a chamber, generates a plasma from the gas using the power of electromagnetic waves, and performs a predetermined plasma process on a wafer W that is held by a mounting table34.

The plasma processing apparatus31includes a chamber32for performing a plasma process such as etching on a semiconductor wafer (hereinafter also referred to as “wafer W”) and a gas supply unit33for supplying gas into the chamber32.

The plasma processing apparatus31also includes a plasma generating mechanism39for generating a plasma within the chamber32using microwaves, and a high frequency power source58for supplying high frequency power for applying an RF (radio frequency) bias to the wafer W that is held by the mounting table34.

A ring-shaped focus ring110is arranged at the outer edge side of the mounting table34. The front surface of the focus ring110is coated with a coating film111. Further, the back surface of the focus ring110is coated with a coating film112. Note that in embodiments of the present invention, at least one of the front surface and the back surface of the focus ring110is coated with a coating film.

The overall operations of the plasma processing apparatus31are controlled by a control unit28. The control unit28may control overall operations of the plasma processing apparatus31by controlling the gas flow rate of the gas supply unit33, the pressure in the chamber32, and the high frequency power supplied to the mounting table34, for example.

The chamber32may be made of aluminum (Al) that has been alumite-treated (anodized), for example. The chamber32is connected to ground. The chamber32includes a bottom part41that is disposed at the lower side of the mounting table34, and a side wall42extending upwardly from the outer periphery of the bottom part41. The sidewall42is cylindrical. An exhaust hole43that penetrates through a portion of the bottom part41is arranged at the bottom part41of the chamber32.

The upper side of the chamber32is open. As illustrated inFIG. 1andFIG. 3A, which is an enlarged view of a region A ofFIG. 1, the opening of the chamber32is sealed by a support member44, a dielectric window36, and an O-ring45. The support member44is arranged on an upper portion of the side wall42of the chamber32. The dielectric window36is arranged at a ceiling portion of the chamber32, and the O-ring45is a sealing member that is interposed between the dielectric window36and the support member44.

The outer edge of the dielectric window36is supported by the support member44. The support member44is made of a metal such as aluminum. The support member44constitutes a part of a lid of the upper opening of the chamber32.

A metal plate102and a partition member103are arranged at the lower side of an outer edge portion of the dielectric window36. The partition member103is made of a dielectric material such as quartz and is supported by the dielectric window36(or the inner wall of the chamber32). An installation member101is arranged to extend below the support member44. The installation member101acts as a receiving member for receiving particles that may be generated within a space U where the support member44is arranged and thereby prevents the particles from being scattered into a plasma generation space P. Note that a small space is provided between the partition member103and the installation member101.

Referring back toFIG. 1, the gas supply unit33includes a first gas supply unit46for introducing a gas toward the center of the wafer W, and a second gas supply unit47for introducing a gas to the outer side of the wafer W. The first gas supply unit46includes a gas supply hole30that is provided at a position recessed from a lower face48of the dielectric window36. The first gas supply unit46supplies a gas for plasma excitation from the gas supply hole30while adjusting the flow rate of the gas by a gas supply system49that is connected to the first gas supply unit46. The second gas supply unit47includes a plurality of gas supply holes50that are arranged at an upper side portion of the side wall42for supplying a gas for plasma excitation into the chamber32. The gas supply holes50are arranged at equal intervals around the circumferential direction of the chamber32.

The mounting table34includes an electrode to which a high frequency power for biasing is applied from a high frequency power source58via a matching unit59. The high frequency power source58may be capable of outputting a high frequency of 13.56 MHz at a predetermined power (biasing power), for example. The matching unit59accommodates a matching box (not shown) for matching the impedance at the high frequency power source58and the impedance at the plasma side (load side). The matching box includes a blocking capacitor (not shown) for generating a self-biasing voltage.

An electrostatic chuck34ais arranged on the mounting table34. The electrostatic chuck34ais capable of electrostatically attracting the wafer W. Note that in some embodiments, the electrostatic chuck34adoes not have to be provided on the mounting table34. In this case, the wafer W may be held directly by the mounting table34, for example.

The mounting table34is supported by an insulating cylindrical support51that extends vertically upward from the lower side of the bottom part41. The exhaust hole43is arranged to penetrate through a portion of the bottom part41of the chamber32along the outer periphery of the cylindrical support51. An exhaust system (not shown) is connected to the bottom side of the exhaust hole43via an exhaust pipe. The exhaust system includes a vacuum pump such as a turbo molecular pump (not shown). The exhaust system is capable of reducing the pressure within the chamber32to a predetermined pressure.

The plasma generating mechanism39is provided outside the chamber32and includes a microwave generator35for generating microwaves for plasma excitation. The microwave generator35is an example of an electromagnetic wave generator, and the microwave output by the microwave generator35is an example of an electromagnetic wave.

Also, the plasma generating mechanism39includes the dielectric window36that is disposed at a position facing the mounting table34. Microwaves output by the microwave generator35are propagated by the dielectric window36and transmitted into the chamber32. The plasma generating mechanism39also includes a slot antenna37that is arranged on the upper side of the dielectric window36. The slot antenna37includes a plurality of slots for radiating microwaves to the dielectric window36. Also, the plasma generating mechanism39may include a dielectric member38that is arranged on the upper side of the slot antenna37and is configured to propagate microwaves introduced from a coaxial waveguide56(described below) in the radial direction.

The microwave generator35includes a matching circuit53and is connected to the coaxial waveguide56via a mode transducer54and a waveguide55. For example, microwaves in the TE mode that are generated by the microwave generator35may pass through the waveguide55to be converted into the TEM mode by the mode converter54and propagated through the coaxial waveguide56. The frequency of the microwaves to be generated by the microwave generator35may be set to 2.45 GHz, for example.

The dielectric window36is substantially disc-shaped and may be made of a dielectric material such as quartz or alumina. An annular concave part57is provided at a portion of the lower face48of the dielectric window36. The concave part57has tapered side walls in order to facilitate the generation of standing waves with the introduced microwaves. By arranging the concave part57, a plasma may be efficiently generated by microwaves at the lower side of the dielectric window36.

The slot antenna37is a thin plate having a circular shape. As illustrated inFIG. 2, the plurality of slots40are arranged into pairs, and the slots40of each pair are set apart by a predetermined interval and are orthogonal to each other. The pairs of the slots40are arranged at predetermined intervals along the circumferential direction. The pairs of the slots40are also arranged at predetermined intervals along the radial direction.

Referring back toFIG. 1, the microwaves generated by the microwave generator35are propagated through the coaxial waveguide56. The microwaves are spread radially outward within a region between a cooling jacket52and the slot antenna37and are radiated to the dielectric window36from the plurality of slots40arranged in the slot antenna37. The microwaves transmitted through the dielectric window36generate an electric field directly below the dielectric window36and cause the generation of a plasma within the chamber32. Note that a circulation path60for circulating a coolant is formed within the cooling jacket52.

When a plasma is generated in the plasma processing apparatus31, a plasma generation space is created just below the lower face48of the dielectric window36, more specifically, in a region located several centimeters below the lower face48of the dielectric window36. Also, a so-called plasma diffusion area where the plasma generated at the plasma generation space is diffused is created in a region located vertically below the plasma generation space. In the present embodiment, the plasma generation space P includes such a plasma diffusion area. The plasma generation space P is distinguished and separated from the space U where the support member44is arranged by the partition member103.

The control unit28includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and is configured to control plasma processing such as etching according to predetermined procedures set up in a recipe that is stored in the RAM, for example. Note that the functions of the control unit28may be implemented using software, hardware, or a combination thereof.

When performing a predetermined plasma process such as etching in the plasma processing apparatus31having the above configuration, first, the wafer W is transferred into the chamber32and is held on the electrostatic chuck34athat is arranged on the mounting table34. Then, a plasma is generated from a gas using high frequency power, and a plasma process such as etching is performed on the wafer W with the generated plasma. After the plasma process is completed, the wafer W is unloaded from the chamber32.

[Configuration for Suppressing Abnormal Discharge at Outer Edge of Dielectric Window]

In the following, a configuration for suppressing abnormal discharge at the outer edge of the dielectric window36is described with reference toFIGS. 3A and 3B.FIG. 3Aillustrates an exemplary configuration of an outer edge portion of the dielectric window36of the plasma processing apparatus31according to the present embodiment.FIG. 3Billustrates a comparative example of the dielectric window36of the plasma processing apparatus31.

As illustrated inFIG. 3A, the metal plate102and the partition member103are arranged at a lower portion of the outer edge of the dielectric window36. The upper face of the metal plate102comes into contact with the lower face of the dielectric window36, and the lower face of the metal plate102comes into contact with the upper face of the partition member103. In this way, the metal plate102can reflect microwaves transmitted through the dielectric window36.

The partition member103separates the plasma generation space P from the space U where the support member44is arranged. The partition member103includes a protrusion103a. The protrusion103acovers the inner diameter side of the metal plate102so as not to expose the metal plate102to the plasma generation space P, and has an upper portion abutting against the dielectric window36. Note that in some embodiments, the partition member103may be integrally formed with the dielectric window36via the protrusion103a. In such a case, the metal plate102may be inserted between the dielectric window36and the partition member103to abut against the protrusion103a.

InFIG. 3B, the metal plate102is not provided, and as such, microwaves output from the microwave generator35are transmitted through the dielectric window36and are supplied not only to the plasma generating space P but also to the space U where the support member44is arranged. As a result, abnormal discharge occurs in a gap between the support member44and a partition part36aof the dielectric window36. Also, the microwaves propagate through a gap between the installation member101and the partition part36aand enter the space U where the support member44is arranged to thereby cause abnormal discharge in the space U where the support member44is arranged. When abnormal discharge occurs in the chamber32, the chamber32may be damaged, and particles of yttria and aluminum may be generated from the wall surface of the chamber32causing metal contamination within the chamber32. Particles generated in the space U may be scattered into the plasma generation space P, and when the particles reach the wafer W during a plasma process, they may affect the wafer W by causing short-circuits in the wirings formed on the wafer W, for example. This may lead to a decrease in yield, for example.

On the other hand, in the present embodiment, the metal plate102is arranged between the plasma generation space P and the space U where the support member44is arranged as illustrated inFIG. 3A. Thus, microwaves propagating through the dielectric window36are reflected by the metal plate102to be prevented from passing through the partition member103. In this way, microwaves may be prevented from entering the space U from the dielectric window36and/or entering the space U through the lower portion of the partition member103, and the occurrence of abnormal discharge in the space U where the support member44is arranged may be suppressed. As a result, damage to the chamber32and parts within the chamber32may be prevented. In this way, a decrease in yield may be prevented, and the product life of the chamber32and parts within the chamber32may be enhanced.

In the present embodiment, the metal plate102is made of aluminum. The metal plate102is an example of a conductive member arranged between the partition member103and the dielectric window36. The conductive member that is disposed between the partition member103and the dielectric window36may be a metallic conductive member or a non-metallic conductive member. Examples of metals that may be used as the metallic conductive member include aluminum and the like. Examples of materials that may be used as the non-metallic conductive member include silicon (Si), germanium (Ge), silicon carbide (SiC), and conductive plastics. The conductive member may be formed by thermal spraying. For example, the conductive member may be a sprayed film formed by coating a conductive material such as silicon or aluminum on the dielectric window36by thermal spraying. In the present embodiment, aluminum is sprayed on the dielectric window36to form a thin and uniform metal plate102.

Also, the metal plate102is arranged to be protected from being exposed to the plasma generation space P by the protrusion103athat is formed into a ring-shape extending along the plasma generation space P side of the partition member103. When the metal plate102is exposed to the plasma generation space P, dust from the metal plate102may cause contamination within the chamber32. Thus, in the present embodiment, the protrusion103ais arranged at the partition member103to thereby prevent the metal plate102from being directly exposed to the plasma generation space P, and in this way, metal contamination within the chamber32may be prevented.

The metal plate102is arranged to be in contact with the support member44. Thus, the metal plate102is connected to ground via the support member44and the chamber32. As a result, a charge held by the metal plate102may be flown toward the ground side, and a potential difference between the metal plate102and the support member44may be set to 0 such that the occurrence of a DC discharge may be prevented. Note, however, that the metal plate102does not necessarily have to be connected to ground.

The partition member103is L-shaped and is arranged to hold the metal plate102while being supported by the dielectric window36(or the inner wall of the chamber32). An inner corner103bof the partition member103is arranged to be close to the metal plate102. Note that abnormal discharge is more likely to occur at pointed portions. Thus, the inner corner103bof the partition member103is brought close to the lower face of the metal plate102. Because microwaves are reflected by the metal plate102, an electric field at the inner corner103bof the partition member103may be weakened. In this way, the occurrence of abnormal discharge due to electric field concentration at the inner corner103bof the partition member103may be suppressed.

The surface of the support member44may be coated with a quartz coating film, for example. In this way, the occurrence of abnormal discharge in the space U may be further suppressed.

As illustrated in the lower part ofFIG. 4, a distance D of the gap between the protrusion103aand the metal plate102(conductive member) is designed to be a distance over which multipactor discharge would not occur. Here, multipactor discharge refers to an electron avalanche phenomenon that is caused by repeated secondary electron emissions.

The table ofFIG. 4indicates calculations of the distance D of the gap between the dielectric window36made of quartz and the conductive member over which multipactor discharge would not occur.

When silicon (Si) is used as the material of the conductive member, the distance D over which multipactor discharge would not occur is less than 0.68 mm, meaning the gap between the protrusion103aand the conductive member has to be no more than 0.68 mm. When quartz (SiO2) is used as the material of the conductive member, the distance D over which multipactor discharge would not occur is less than 0.39 mm, meaning the gap has to be even smaller.

Based on the above, silicon may preferably be used over quartz as the material of the conductive member. Also, when the conductive member is made of silicon, the power loss of microwaves in the conductive member may be greater as compared to that in the metal plate102made of aluminum. This suggests that the microwaves may be absorbed by the silicon of the conductive member.

In the following, the principle of multipactor discharge will be described with reference toFIGS. 5A-5D. As described above, multipactor discharge is caused by the repetition of secondary electron emissions.

(Condition for Repeated Secondary Electron Emissions)

For example, as illustrated inFIG. 5A, dielectric plates forming a pair of electrodes facing each other may be spaced apart by the distance D, and an electromagnetic wave of a frequency f (high frequency wave or microwave) may be applied between the electrodes. A secondary electron emitted from one electrode surface is incident on the other electrode surface without colliding with ions in the space between the electrodes. Such secondary electron emissions occur repeatedly, and electron discharge (multipactor discharge) occurs as a result of the repetition of the secondary electron emissions.

Assuming an electric field of V×sin(2πft+θ) is applied between the electrodes, the following formula (1) is satisfied.

In the above formula (1), “t” represents the time, and “x” represents the distance between the electrodes.

By integrating the above formula (1), the following formula (2) may be obtained.

Further, by integrating the above formula (2), the following formula (3) may be obtained.

Assuming x=0 and dx/dt=0 when t=0, and x=D when t=NT/2, by applying the above conditions to formula (3), the following formula (4) may be obtained.

V=(f⁢⁢D)2N⁢⁢π·-me⁢⁢cos⁡(θ)(4)
Here, N represents the number of secondary electron emissions. For example, as illustrated inFIG. 5A, when an electron is incident on one of the opposing faces of the electrodes and causes a secondary electron emission, the number N of secondary electron emissions is equal to “1”. When the electron is further incident on the other one of the opposing faces of the electrodes to cause a further secondary electron emission, the number N of the secondary electron emissions is equal to “2”. For example, if the electron is incident five times on the opposing faces of the electrodes, the number N of the secondary electron emission is equal to “5”. The present calculation is performed assuming an electron reaches an opposing electrode face in N/2 (odd number) cycles. That is, the calculation is performed assuming x=D when t=(N/2)×T cycles.

In order to prompt the repetition of secondary electron emissions, microwaves have to work on the electric field between the electrodes in a timely manner. That is, in the above formula (4), the electric field V between the electrodes is a function of fD (where “f” is the frequency of the microwave and “D” is the distance between the electrodes).

FIG. 5Bis a graph representing fD on the horizontal axis and the electric field V between the electrodes on the vertical axis. As a condition for repeating secondary electron emissions within the possible value range of the product of the frequency f of the microwave and the distance D between the electrodes in the graph ofFIG. 5B, the electric field V has to be maintained between a maximum value Vg max 0of the electric field and a minimum value Vg minof the electric field calculated from formula (4). Thus, within the possible value range of fD shown inFIG. 5B, a discharge region corresponds to a region defined by the maximum value of Vg max 0of the electric field and the minimum value Vg minof the electric field.

The maximum value Vg max 0of the electric field calculated from formula (4) may be defined by the following formula (5). The minimum value Vg minof the electric field calculated from formula (4) may be defined by the following formula (6).

As shown inFIG. 5C, in the present example, the emission energy E0is set to 1 eV, an oscillation period of an electron before hitting a wall as a data sampling period ΔD is set to 0.0025 mm, and the frequency f of the high frequency wave is set to 2.45 GHz.

FIG. 5Dis a graph showing the multipactor discharge regions when the number N of the secondary electron emissions is equal to 1, 3, 5, and 7 calculated from the above formulas (5) and (6). As can be appreciated fromFIG. 5D, the amplitude V of the voltage across the opposing faces of the electrodes increases as the number (odd number) N of secondary electron emissions increases. According to these calculation results, in a case where multipactor discharge is the dominant discharge occurring between electrodes having a gap (distance D) of 2.5 mm, the amplitude V of the voltage across the opposing faces may be estimated to be about 400 V.

(Occurrence Condition for Secondary Electron Emission)

In the following, an occurrence condition for secondary electron emission will be described. By applying the condition dx/dt=0 when t=0 to formula (2), the following formulas (7) and (8) may be obtained.

In this case, by substituting the amplitude V of the voltage across the electrodes with the maximum value Vg max 0of the amplitude of the voltage (V=Vg max 0) into formula (5), the following formulas (9) and (10) are satisfied when the minimum emission energy E1at which the secondary electron emission coefficient becomes 1 is less than or equal to the maximum value Emaxof the emission energy (E1≤Emax). Here, the emission energy E1is the energy at which the number of incident electrons and the number of secondary electrons that are emitted are equal which corresponds to the minimum energy that can cause multipactor discharge.

Multipactor discharge occurs only in a region where the secondary electron emission coefficient is greater than 1. When the space (gap) between opposing members is too small, acceleration of the electrons by the electric field may be inadequate such that multipactor discharge would not occur. Thus, the distance between members abutting against the dielectric window36through which microwaves are transmitted is preferably arranged to be as small as possible.

As shown inFIGS. 6A and 6B, provided emission energy E1and emission energy E2represent energies at which the secondary electron emission coefficient δ is equal to 1, and E1≤E≤E2, multipactor discharge would not occur if the secondary electron emission coefficient δ for the emission energy E is less than or equal to 1. That is, multipactor discharge would not occur if the maximum value Emaxof the emission energy E that satisfies the condition E1≤E≤E2as illustrated inFIG. 6Bis less than or equal to 1.

The secondary electron emission coefficient δ is determined by the material of the electrodes. For example, if the electrodes are made of aluminum, the maximum value δmaxof the secondary electron emission coefficient is 1, and the maximum value Emaxof the emission energy is 300 eV, which is equal to the emission energy E1=300 eV and the emission energy E2=300 eV. According to the above, when the opposing electrodes are made of aluminum, the secondary electron emission coefficient δ is less than or equal to 1 regardless of the incident energy E of the electrons, and as such, multipactor discharge would not occur.

It can be appreciated that multipactor discharge is less likely to occur when the secondary electron emission coefficient δ approximates 1.

On the other hand, for example, when the opposing electrodes are made of quartz, the maximum value δmaxof the secondary electron emission coefficient may be from 2.1 to 4, and the maximum value Emaxof the emission energy is 400 eV. Thus, multipactor discharge is more likely to occur when the electrodes are made of quartz as compared to a case where the electrodes are made of aluminum or silicon.

[Configuration for Suppressing Abnormal Discharge at Focus Ring]

In the following, a configuration for suppressing abnormal discharge at the focus ring110will be described with reference toFIGS. 7 and 8.FIG. 7is an enlarged view of a region B ofFIG. 1illustrating an exemplary configuration of the focus ring110.FIG. 8is an enlarged view of the region B illustrating another exemplary configuration of the focus ring110.

In the plasma processing apparatus31that generates a plasma using microwaves, the microwaves are propagated up to the vicinity of a boundary between the focus ring110and the electrostatic chuck34aon the mounting table34. As a result, abnormal discharge may occur at a gap between the focus ring110and the electrostatic chuck34a, and the plasma processing apparatus31may be damaged. For example, particles may be generated, and the product life of the parts within the plasma processing apparatus31may be reduced. Thus, the occurrence of abnormal discharge in the gap between the electrostatic chuck34aand the focus ring110is preferably suppressed along with the suppression of abnormal discharge at the outer edge of the dielectric window36as described above.

In one preferred embodiment, the front surface and the back surface of the focus ring110may respectively be coated with the coating film111and the coating film112as illustrated inFIG. 7. In another embodiment, only the back surface of the focus ring110may be coated with the coating film112as illustrated inFIG. 8. In another embodiment, only the front surface of the focus ring110may be coated with the coating film111, for example. Also, in some embodiments, in addition to coating at least one of the front surface and the back surface of the focus ring110, one or more side faces of the focus ring110may be coated with a coating film.

Metallic conductive members or non-metallic conductive members may be used as the coating films111and112. For example, a metal such as aluminum may be used as the metallic conductive member. Also, materials such as silicon (Si), germanium (Ge), silicon carbide (SiC), and conductive plastics may be used as the non-metallic conductive member. The coating films111and112may be formed by thermal spraying. For example, the coating films111and112may be sprayed films formed by coating aluminum or silicon on the focus ring110by thermal spraying. In the present embodiment, aluminum is sprayed on the focus ring110to form thin and uniform coating films111and112.

In this way, microwaves may be reflected by the coating films111and112, and propagation of the microwaves into the gap between the electrostatic chuck34aand the focus ring110may be prevented. In turn, the occurrence of abnormal discharge in the gap between the electrostatic chuck34aand the focus ring110may be suppressed. As a result, metal contamination within the chamber32caused by the generation of particles at the back surface of the focus ring110may be prevented. Also, the product life of the parts within the chamber32may be prolonged.

Further, as illustrated inFIGS. 7 and 8, a screw113for fixing the electrostatic chuck34aon the mounting table34may be formed by a conductive member such as a metal, and the screw113may be connected to the chamber32. In this way, the coating film112may be connected to ground via the screw113and the chamber32. As a result, an electric charge held by the coating film112may be flown toward the ground side, and the potential difference between the coating film112and the electrostatic chuck34amay be set to 0 to prevent the occurrence of a DC discharge. Note, however, that the coating film112does not necessarily have to be connected to ground.

As described above, in the plasma processing apparatus31according to the present embodiment, microwaves may be reflected by the ring-shaped metal plate102arranged at the lower side of the outer edge portion of the dielectric window36. As a result, the occurrence of abnormal discharge in the vicinity of the outer edge of the dielectric window36may be prevented.

Further, in the plasma processing apparatus31according to the present embodiment, microwaves may be reflected by at least one of the coating film111arranged on the front surface of the focus ring110and the coating film112arranged on the back surface of the focus ring110. In this way, the occurrence of abnormal discharge in the gap between the focus ring110and the electrostatic chuck34amay be prevented.

Although illustrative embodiments of the plasma processing apparatus according to the present invention have been described above, a plasma processing apparatus according to the present invention is not limited to the above embodiments, and numerous variations and modifications may be made within the scope of the present invention. Also, two or more of the embodiments described above may be combined to the extent practicable.

For example, the plasma processing apparatus according to the present invention may include the metal plate102arranged on the dielectric window36as well as the coating film111arranged on the front surface of the focus ring110and/or the coating film112arranged on the back surface of the focus ring110. In other examples the plasma processing apparatus according to the present invention may only include the metal plate102or the coating film111and/or the coating film112.

Also, the substrate to be processed by the plasma processing apparatus according to the present invention is not limited to a semiconductor wafer. For example, the substrate may be a large-size substrate for a flat panel display, or a substrate for an EL (electroluminescence) element or a solar cell.

The present application is based on and claims priority to Japanese Patent Application No. 2014-218625 filed on Oct. 27, 2014, the entire contents of which are hereby incorporated by reference.