JP2010177420A - Microwave plasma processing apparatus, dielectric board for microwave plasma processing apparatus, and microwave feeding method of microwave plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave plasma processing apparatus, in which microwave propagation characteristics are not adversely affected even when an inner conductor of a coaxial waveguide is thermally expanded or shrunk. <P>SOLUTION: The inner conductor 22 consists of a dielectric board side inner conductor portion 22b that is connected to at least one of a dielectric board 26 and a slot board 27, and a mode transformer side inner conductor portion 22a that is connected to a mode transformer 29 or a rectangular waveguide 21. The mode transformer side inner conductor portion 22a is separated from the dielectric board side inner conductor portion 22b, and a clearance is provided between the inner conductor portions. Thermal expansion or shrinkage of the inner conductor 22 just causes the clearance between the dielectric board side inner conductor portion 22b and the mode transformer side inner conductor portion 22a to be changed. This structure prevents stress caused by thermal expansion or shrinkage from occurring at the dielectric board side inner conductor portion 22b, thereby avoiding deformation of the dielectric board 26 and/or the slot board 27 connected to the dielectric board side inner conductor portion 22b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a microwave plasma processing apparatus that performs plasma processing on an object to be processed such as a semiconductor wafer, a liquid crystal substrate, and an organic EL element using plasma generated using microwaves.

  Plasma treatment is widely used in processes such as etching and thin film deposition in semiconductor manufacturing processes. In recent years, the process rules (IC line width) of semiconductors constituting an LSI have been increasingly miniaturized from the viewpoint of high integration, high speed, and low power consumption of the LSI. When the distance between the wirings is shortened, the conventional interlayer insulating film cannot be insulated, and there is a possibility of interfering with a signal of an adjacent wiring. In order to solve this interference, an insulating film having a low dielectric constant (Low-k) is required. However, in parallel plate type and inductively coupled plasma processing apparatuses that have been widely used in the past, the electron temperature is high, which damages the insulating film having a low dielectric constant. For example, when a CF film containing carbon and fluorine, which is known as an insulating film having a low dielectric constant, is used, the dielectric constant of the insulating film increases due to plasma processing damage.

  Furthermore, the size of semiconductor wafers has been increased, and accordingly, it has been demanded to uniformly process large-diameter semiconductor wafers without deviation.

  Therefore, in recent years, a microwave plasma processing apparatus using RLSA (Radial Line Slot Antenna) capable of uniformly forming high density and low electron temperature plasma has attracted attention (see, for example, Patent Document 1). A microwave plasma treatment apparatus radiates microwaves into a processing container from a planar microwave antenna having a number of slots arranged to emit uniform microwaves, and gas in the processing container is generated by an electric field of the microwaves. Is ionized to excite the plasma. According to this microwave plasma processing apparatus, since a high plasma density can be realized in a wide region directly under the antenna, it is possible to perform uniform plasma processing in a short time. Moreover, since plasma having a low electron temperature can be generated, there is an advantage that damage to the substrate to be processed can be reduced.

  As shown in FIG. 1, in this microwave plasma processing apparatus, the opening of the ceiling portion of the processing container 1 is closed by a dielectric window 2. A microwave antenna 3 is placed on the dielectric window 2. A microwave generator is connected to the rectangular waveguide 4. The microwaves emitted from the microwave generator are propagated through the rectangular waveguide and then converted into the coaxial mode by the mode converter 5. The mode-converted microwave propagates up and down the coaxial waveguide 6. The microwave propagated through the coaxial waveguide 6 propagates in the radial direction through the disk-shaped dielectric plate 7. The microwave whose wavelength is compressed in the dielectric plate 7 and resonates passes through the slot of the slot plate 8 made of a conductive material, and is radiated into the processing container 1 through the dielectric window 2.

  The coaxial waveguide 6 includes an inner conductor 6a and an outer conductor 6b surrounding the inner conductor 6a. An upper end portion of the inner conductor 6 a is coupled to the mode converter 5. The lower end portion of the inner conductor 6a is electrically coupled to the slot plate 8 with screws or the like. The microwave propagates in an annular coaxial waveguide between the outer peripheral surface of the inner conductor 6a and the inner peripheral surface of the outer conductor 6b.

JP 2002-35550 A

  When heat is generated by the excited plasma, heat is transferred to the microwave antenna 3 through the dielectric window 2. When a temperature difference occurs between the inner conductor 6a and the outer conductor 6b of the coaxial waveguide 6, as shown in FIG. 2, the extension amount of the inner conductor 6a and the extension amount of the outer conductor 6b due to heat are different. The slot plate 8 coupled to the inner conductor 6a is displaced in the vertical direction. One of the reasons is that the rigidity of the slot plate 8 itself is low and the inner conductor 6a is long. When the slot plate 8 is displaced in the vertical direction, a gap is formed between the slot plate 8 and the dielectric plate 7 or the slot plate 8 is pressed against the dielectric plate 7. This disturbs the waveguide, making it difficult to generate a uniform plasma and adversely affecting the process. If the amount of elongation due to thermal expansion of the inner conductor 6a and the outer conductor 6b is the same, the position of the slot plate 8 can be made constant. However, it is difficult to control the amount of elongation due to thermal expansion of the inner conductor 6a and the outer conductor 6b to be the same. Further, the inner conductor 6a not only extends, but may be bent with the mode converter 5 and the slot plate 8 as fixed ends. If the inner conductor 6a bends, the distribution of the microwave propagating through the coaxial waveguide 6 will be disturbed.

  On the other hand, as shown in FIG. 3, a microwave plasma treatment is performed by patterning a conductive film 9 such as plating as a slot plate on the dielectric plate 7 and electrically connecting the inner conductor 6a to the conductive film 9 on the lower surface of the dielectric plate. Devices are also known. However, even in this plasma processing apparatus, when the inner conductor 6a expands or contracts due to heat, the electric contact plate 6c at the lower end of the inner conductor 6a is deformed, or the conductive film 9 on the lower surface of the electric contact plate 6c and the dielectric plate 7 is used. There is a problem that electrical contact with the battery becomes insufficient.

  Accordingly, the present invention provides a microwave plasma processing apparatus and a dielectric plate for the microwave plasma processing apparatus that do not adversely affect the propagation characteristics of the microwave even if the inner conductor of the coaxial waveguide is thermally expanded or contracted. And it aims at providing the microwave electric power feeding method of a microwave plasma processing apparatus.

  In order to solve the above problems, according to one embodiment of the present invention, a processing container in which a ceiling portion is defined by a dielectric window, a gas exhaust system that decompresses the processing container, and a plasma excitation gas is supplied to the processing container. A microwave plasma processing apparatus comprising: a gas supply unit configured to operate; and a microwave antenna mounted on the dielectric window of the processing container and configured to supply microwaves into the processing container. A coaxial waveguide for propagating microwaves, a dielectric plate for propagating microwaves in the radial direction and compressing the wavelength of the microwaves, and a slot plate having slots for transmitting the microwaves, the coaxial waveguide Includes an inner conductor and an outer conductor surrounding the inner conductor, and the inner conductor is connected to at least one of the dielectric plate and the slot plate, and an inner conductor on the dielectric plate side; Serial separated from the inner conductor of the dielectric plate side, the a microwave plasma processing apparatus comprising, a remainder of the inner conductor which space is opened between the inner conductor of the dielectric plate side.

  Another aspect of the present invention is a coaxial waveguide including an inner conductor and an outer conductor surrounding the inner conductor, which is used in a microwave plasma processing apparatus for plasma-treating an object to be processed with plasma generated using microwaves. A dielectric plate that propagates the microwave propagated in the radial direction and shortens the wavelength, and an inner conductor on the dielectric plate side is integrated with the dielectric plate, and the dielectric is made into the microwave plasma. When incorporated in a processing apparatus, the inner conductor comprises a microwave composed of an inner conductor on the dielectric plate side and a remaining inner conductor arranged with a space from the inner conductor on the dielectric plate side. A dielectric plate for a plasma processing apparatus.

  According to still another aspect of the present invention, a microwave propagating in a rectangular waveguide is mode-converted by a mode converter and propagated to a coaxial waveguide including an inner conductor and an outer conductor surrounding the inner conductor. In the microwave power feeding method of the microwave plasma processing apparatus, in which the microwave propagated through the tube is propagated in the radial direction by the dielectric plate and the wavelength is compressed, the microwave is connected to the mode converter on the mode converter side And a microwave power supply method for a microwave plasma processing apparatus that propagates around the inner conductor on the dielectric plate side that is spaced from the inner conductor on the mode converter side.

  The inner conductor of the coaxial waveguide is separated into the inner conductor on the dielectric plate side and the remaining inner conductor (the inner conductor on the mode converter side), and only the inner conductor on the dielectric plate side is used as the dielectric plate or slot plate. Even if the inner conductor is thermally expanded or contracted, the gap between the inner conductor on the dielectric plate side and the remaining inner conductor only changes, and the inner conductor on the dielectric plate side is thermally expanded.・ Prevents stress from thermal shrinkage. Since it is possible to prevent the dielectric plate and the slot plate connected to the inner conductor on the dielectric plate side from being deformed, the microwave propagation characteristics are not adversely affected.

Sectional view of a conventional microwave plasma processing apparatus Detailed view showing a coaxial waveguide of a conventional microwave plasma processing apparatus Sectional view of a conventional microwave plasma processing apparatus in which a conductive film as a slot plate is patterned on a dielectric plate Sectional drawing of the microwave plasma processing apparatus of one Embodiment of this invention Detailed view of coaxial waveguide Sectional drawing which shows the other example (modification 1) of the inner conductor by the side of a dielectric plate, and a dielectric plate The figure which shows the dielectric plate to which the conductive film adheres Sectional drawing which shows further another example (modification 2) of the inner conductor on the dielectric plate side and the dielectric plate Sectional drawing which shows the example which formed the electrically conductive film in the internal peripheral surface of the hole of a dielectric material board in the modification 2. Sectional drawing which shows further another example (modification 3) of the inner conductor on the dielectric plate side and the dielectric plate Sectional drawing which shows further another example (modification 4) of the inner conductor on the dielectric plate side and the dielectric plate The figure which shows the coaxial waveguide of an Example Graph showing the relationship between electromagnetic wave frequency and transmission ratio when using the coaxial waveguide of the example

  Hereinafter, an embodiment of a microwave plasma processing apparatus of the present invention will be described with reference to the accompanying drawings. FIG. 4 shows an overall configuration diagram of the microwave plasma processing apparatus.

The microwave plasma processing apparatus is composed of a processing container 11 partitioned by an outer wall, and aluminum nitride (AlN) or alumina (Al ₂ O ₃ ) provided in the processing container 11 and holding a substrate to be processed by an electrostatic chuck. A holding table 16. In the processing container 11, exhaust ports are uniformly formed in the circumferential direction in an annular space surrounding the holding table. The processing container 11 is evacuated and decompressed by a vacuum pump through an exhaust port.

The processing vessel 11 is made of stainless steel containing aluminum (Al), preferably aluminum (Al), and a protective film made of aluminum oxide (Al ₂ O ₃ ) may be formed on the inner wall surface by oxidation treatment. A dielectric window 12 made of a dielectric such as alumina (Al ₂ O ₃ ) or quartz is provided as a part of the outer wall on the ceiling of the processing vessel 11. The dielectric window 12 is attached to the side wall of the processing container 11 via a seal ring 13. The dielectric window 12 is fixed to the processing container 11 by a dielectric window pressing ring 14 attached to the upper part of the side wall of the processing container 11. The dielectric window pressing ring 14 is made of aluminum (Al) or stainless steel containing aluminum (Al) in the same manner as the processing container 11.

On the side wall of the processing vessel 11, for example, an annular gas supply unit 15 for supplying plasma excitation gas into the processing vessel 11 is provided. A gas supply system is connected to the gas supply unit 15. A plasma excitation gas such as Ar gas or Kr gas, or a processing gas corresponding to the type of plasma processing is supplied from the gas supply unit to the processing vessel 11. Such plasma treatment includes radical oxidation treatment, radical nitridation treatment, radical oxynitridation treatment, plasma CVD treatment and the like. A fluorocarbon gas such as C ₄ F ₈ , C ₅ F _8, or C ₄ F ₆ , an F-based or Cl-based etching gas is supplied from the gas supply unit, and a high-frequency voltage is applied to the holding table 16 from a high-frequency power source. As a result, the substrate is processed.

  On the side wall of the processing container 11, a loading / unloading port (not shown) for loading and unloading the substrate to be processed is provided. The carry-in / out port is opened and closed by a gate valve.

  On the dielectric window 12, a microwave antenna 18 for exciting the plasma excitation gas in the processing vessel 11 is placed. The microwave antenna includes a rectangular waveguide 21, a coaxial waveguide 24, a cooling plate 25, a dielectric plate 26 and a slot plate 27. A microwave generator such as a magnetron is connected to the rectangular waveguide 21 via a matching unit. The microwave generator generates microwaves having frequencies of 2.45 GHz, 8.35 GHz, 1.98 GHz, 915 MHz, and the like, for example. The matching unit propagates the microwave generated from the microwave generator to the dielectric plate 26 via the rectangular waveguide 21 and the coaxial waveguide 24.

  The rectangular waveguide 21 extending in the horizontal direction is connected to the upper end portion of the coaxial waveguide 24 extending in the vertical direction. The coaxial waveguide 24 includes an inner conductor 22 extending in the vertical direction and a cylindrical outer conductor 23 surrounding the inner conductor 22. A coaxial waveguide 20 having an annular cross section is formed between the inner conductor 22 and the outer conductor 23. The inner conductor 22 and the outer conductor 23 are made of, for example, silver plated copper. A conical mode converter 29 is provided at the connection between the rectangular waveguide 21 and the coaxial waveguide 24. The microwave propagating through the rectangular waveguide 21 is converted into a coaxial mode by the mode converter 29 and propagates up and down the coaxial waveguide 20.

The microwave propagated in the vertical direction through the coaxial waveguide 24 propagates through the disk-shaped dielectric plate 26 in the radial direction. The dielectric plate 26 is made of a dielectric such as alumina (Al ₂ O ₃ ) or quartz. On the upper surface of the dielectric plate 26, a cooling plate 25 made of metal such as aluminum (Al) for cooling the dielectric plate 26 is provided. A cooling water passage 25 a is formed in the cooling plate 25. The dielectric plate 26 is cooled by flowing cooling water through the cooling water passage 25a. A slot plate 27 made of a conductive material such as a copper plate is provided on the lower surface of the dielectric plate 26.

Microwaves are electromagnetic waves that propagate while the electric and magnetic fields change very quickly. A slot plate 27 made of metal is provided on the lower surface of the dielectric plate 26, and a cooling plate 25 made of metal is provided on the upper surface of the dielectric plate 26. The microwaves that hit the metal surface do not enter the metal, but a current flows through the very surface, and most of the light is reflected. Therefore, the microwave that has entered the dielectric plate 26 from the coaxial waveguide 20 propagates in the dielectric plate 26 in the radial direction while reflecting the slot plate 27 and the cooling plate 25. Further, when entering the dielectric plate 26 from the coaxial waveguide 20, the microwave medium is changed from air to a dielectric, so that the wavelength of the microwave is compressed. The thickness of the dielectric plate 26 is determined so as to propagate in the TE mode (so that the electric field can be generated only in the thickness direction). If it is 1/4 or less of the wavelength of the microwave in the dielectric plate 26, there is no problem. About 3~6mm is optimum thickness in the case of alumina (Al ₂ O _3).

  The slot plate 27 has a number of slots through which microwaves are transmitted. The microwaves resonated in the dielectric plate 26 pass through a number of slots of the slot plate 27 and are radiated into the processing container 11 through the dielectric window 12.

  The microwave antenna 18 is fixed to the dielectric window 12 by an antenna holder 30 attached to the dielectric window holder 14. The antenna holder 30 is made of aluminum (Al) or stainless steel containing aluminum (Al) in the same manner as the processing container 11. An electromagnetic shielding elastic body 31 is provided between the cooling plate 25 and the antenna holder 30. The electromagnetic shielding elastic body 31 has a function of electromagnetic shielding and a function of pressing the microwave antenna 18 against the dielectric window 12. The microwaves that pass through the slots of the slot plate 27 are not all absorbed by the plasma, but part of them leak out to the outside through a small gap between the slot plate 27 and the dielectric window 12. The electromagnetic shielding elastic body 31 shields the leaked microwave. If the microwave antenna 18 is merely placed on the dielectric window 12, a gap is generated between the microwave antenna 18 and the dielectric window 12 due to thermal expansion. In order to prevent the generation of a gap, the electromagnetic shielding elastic body 31 presses the microwave antenna 18 against the dielectric window 12 with a strong force.

  As shown in FIG. 5, the inner conductor 22 constituting the coaxial waveguide 24 is connected to the inner conductor 22b on the dielectric plate side connected to the slot plate, and the mode converter 29 or the rectangular waveguide 21. The inner conductor 22a on the mode converter side which is the remaining inner conductor is separated. The inner conductor 22a on the mode converter side extends vertically downward from the mode converter 29. A flange portion 32a protruding in a disk shape may be provided in the axial direction of the inner conductor 22a on the mode converter side.

  The inner conductor 22b on the dielectric plate side extends in the vertical direction. The inner conductor 22 b on the dielectric plate side penetrates the slot plate 27 and the dielectric plate 26. A slot center fixing plate 33 is provided at the lower end of the inner conductor 22b on the dielectric plate side. The slot center fixing plate 33 is coupled to the slot plate 27 with screws or the like. A flange portion 32b projecting in a disk shape is provided on the upper portion of the inner conductor 22b on the dielectric plate side. In FIG. 5, there are shown gaps between the dielectric plate 26 and the slot plate 27 and between the slot plate 27 and the dielectric window 12. There are no gaps.

  A space is provided between the lower end of the inner conductor 22a on the mode converter side and the upper end of the inner conductor 22b on the dielectric plate side. This space may be filled with air or a vacuum. In order to prevent transmission of force, there is no inclusion between the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side. That is, the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side are physically discontinuous. A gap between the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side is set to 3 to 5 mm, for example. If it is less than 3 mm, the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side may be in physical contact with each other due to thermal expansion. If it exceeds 5 mm, the length a of the inner conductor 22b on the dielectric plate side, which will be described later, necessary for uniform propagation of microwaves cannot be secured sufficiently.

  The inner conductor 22 of the coaxial waveguide 24 is separated into the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side, and the inner conductor 22b on the dielectric plate side is connected to the slot plate 27. Even if the inner conductor 22 is thermally expanded or contracted, only the gap between the inner conductor 22b on the dielectric plate side and the inner conductor 22a on the mode converter side changes, and the inner conductor 22b on the dielectric plate side changes. It is possible to prevent the occurrence of stress due to thermal expansion and contraction. Since the slot plate 27 connected to the inner conductor 22b on the dielectric plate side can be prevented from being deformed, the microwave propagation characteristics are not adversely affected.

  If the inner conductor 22 a on the mode converter side and the inner conductor 22 b on the dielectric plate side are physically continuous, the microwave propagates around these inner conductors 22. However, if a gap is formed between the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side as in this embodiment, the microwave is reflected in the gap. Flange portions 32a and 32b are provided to correct the reflection of the microwave and shape the microwave. When the microwave propagates around the inner conductor 22, a current due to the microwave electric field and a displacement current accompanying a change in the electric field flow on the surface of the inner conductor 22. In response to this displacement current, the flange portion functions like a capacitor 32a, 32b (a range surrounded by a two-dot chain line in the figure), and a high-frequency displacement current flows in the gap. For this reason, the high-frequency displacement current is not interrupted by the gap, and the impedance does not change rapidly in the gap. Microwaves are attenuated by adjusting the size of the gap and the flange portions 32a and 32b (for example, by reducing the gap between the outer diameter of the flange portions 32a and 32b and the outer conductor 23 by the amount of the gap). It is possible to propagate in the coaxial waveguide 20 without doing so.

  The length a of the inner conductor 22b on the dielectric plate side is preferably in the range from 1/4 to 1 wavelength of the microwave wavelength in the coaxial waveguide 24. Here, the length a of the inner conductor 22b on the dielectric plate side is the length of the portion where the inner conductor 22b on the dielectric plate side functions as the inner conductor of the coaxial waveguide 24. Specifically, This is the height from the upper surface of the dielectric plate 26 to the lower end of the flange portion 32b. If a gap is made between the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side, the microwave is once disturbed in the gap. By making the length of the inner conductor 22b on the dielectric plate side 1/4 or more of the wavelength of the microwave and propagating the microwave along the inner conductor 22b, the disturbance of the microwave can be corrected. Even if the center deviation between the inner conductor 22a on the mode converter side and the inner conductor 22b on the dielectric plate side occurs, the microwave is propagated along the inner conductor 22b on the dielectric plate side, Since the disturbance of the microwave caused by the deviation can be corrected, a highly symmetrical microwave distribution is formed. If the length of the inner conductor 22b on the dielectric plate side exceeds one wavelength, the inner conductor 22b itself on the dielectric plate side is heated by microwaves, which may cause problems such as breakage.

FIG. 6 shows another example (Modification 1) of the inner conductor 22b and the dielectric plate 26 on the dielectric plate side. The inner conductor 22b on the dielectric plate side in this example is made of a dielectric material such as alumina (Al ₂ O ₃ ) or quartz, and a conductive film 36 having conductivity is formed on the surface thereof. The conductive film 36 is formed, for example, by plating a metal. The inner conductor 22 b on the dielectric plate side is fitted into the hole 26 a in the center of the dielectric plate 26. The inner conductor 22 b on the dielectric plate side is integrated with the dielectric plate 26. Specifically, the inner conductor 22b on the dielectric plate side is integrated with the dielectric plate 26 by press fitting, brazing, diffusion bonding, melting, or other methods. Current flows only on the surface of the metal due to the microwave.

  FIG. 7 shows a detailed view of the dielectric plate 26 on which the conductive film 38 is formed. A conductive film 38 made of a metal layer is plated on the upper surface, the lower surface and the outer peripheral surface of the dielectric plate 26, for example. A hole 26 a connected to the inner conductor 22 b on the dielectric plate side is opened at the center of the dielectric plate 26. The conductive film 38 on the lower surface of the dielectric plate 26 is electrically connected to the inner conductor 22b on the dielectric plate side, and the conductive film 38 on the upper surface of the dielectric plate 26 is connected to the coaxial waveguide 24 via the cooling plate 25. Is electrically connected to the outer conductor 23 (see FIG. 6).

  In the conductive film 38 on the lower surface side of the dielectric plate 26, a large number of slots 38a that transmit microwaves are formed. A pair of adjacent slots 38a are arranged in a T shape so as to be orthogonal to each other. The many slots 38a are arranged concentrically on the conductive film 38, for example. The length and arrangement of the slots 38 a are appropriately determined according to the wavelength of the microwave compressed by the dielectric plate 26 so that a strong electric field is radiated from the slot 38 a to the processing container 11. The shape of the slot 38a may be an arc shape in addition to the linear shape, and the arrangement of the slots 38a may be a spiral shape or a radial shape in addition to a concentric shape.

The positioning accuracy of the centers of the outer conductor 23, the inner conductor 22 and the dielectric plate 26 is required to be 50 microns or less. However, at present, it is difficult to perform positioning with an accuracy of 50 microns or less, and these positional shifts cause machine differences (differences between apparatuses performing the same process). By integrating the inner conductor 22b on the dielectric plate side with the dielectric plate 26, the positioning accuracy of the center of the dielectric plate 26 and the feeding portion is improved, and the amount of thermal expansion at the time of temperature rise is the same. The uniformity of the plasma generated by the microwave can be improved without disturbing the propagation path of the microwave. Furthermore, if the dielectric plate 26 and the inner conductor 22b on the dielectric plate side are integrally formed of a dielectric made of the same material such as alumina (Al ₂ O ₃ ) or quartz, the coefficient of thermal expansion is the same. Even when warm, the amount of thermal expansion is the same, no gaps are generated, and the microwave can be supplied uniformly without disturbing the microwave propagation path.

  When the inner conductor 22b on the dielectric plate side is integrated with the dielectric plate 26, if there is a difference in thermal expansion between them, the inner conductor 22b and the dielectric plate 26 on the dielectric plate side may break. The inner conductor 22b on the dielectric plate side is made of the same material as that of the dielectric plate 26 or a material having substantially the same thermal expansion coefficient instead of metal, so that the crack can be prevented.

  FIG. 8 shows still another example (Modification 2) of the inner conductor 22b and the dielectric plate 26 on the dielectric plate side. The dielectric plate 26 of this example is provided with a neck portion 26 b protruding to the coaxial waveguide 20 of the coaxial waveguide 24. A conical tapered portion 26c is formed in the lower portion of the hole 26a of the dielectric plate 26. A conductive film 38 is formed on the outer peripheral surface of the neck portion 26 b of the dielectric plate 26 and the tapered portion 26 c on the lower surface of the dielectric plate 26. In the hole 26a of the dielectric plate 26, the inner conductor 22b on the dielectric plate side having a conductive surface is fitted. The conductive film 36 of the inner conductor 22 b on the dielectric plate side is electrically connected to the conductive film 38 on the lower surface of the dielectric plate 26. The conductive film 38 on the outer peripheral surface of the neck portion 26 b of the dielectric plate 26 is electrically connected to the cooling plate 25. By providing the neck 26b on the dielectric plate 26, not only can the dielectric plate 26 and the inner conductor 22b on the dielectric plate side be fitted, but the dielectric plate 26 and the cooling plate 25 can be fitted. Can do.

  As shown in FIG. 9, a conductive film 38 may be formed on the inner peripheral surface of the hole 26 a of the dielectric plate 26. The conductive film 38 may be formed on a part of the inner peripheral surface of the hole 26a. By forming the conductive film 38 on the inner peripheral surface of the hole 26a, electrical contact between the inner conductor 22b and the conductive film 38 can be strengthened.

  Also in this example, it is desirable that the length a of the inner conductor 22b on the dielectric plate side is within a range from 1/4 to 1 wavelength of the microwave wavelength in the coaxial waveguide 24. Here, the length a of the inner conductor 22b on the dielectric plate side is the height from the upper surface of the dielectric plate 26 in contact with the cooling plate 25 to the lower end of the flange portion 32b. Note that the wavelength of the microwave differs between when propagating through the air and when propagating through the dielectric at the boundary between the air and the dielectric. The length a of the inner conductor 22b on the dielectric plate side is represented by a wavelength obtained by adding the wavelength when propagating through the air and the wavelength when propagating through the dielectric.

  FIG. 10 shows still another example (Modification 3) of the inner conductor 22b and the dielectric plate 26 on the dielectric plate side. A conical tapered portion 40 is formed on the upper surface of the neck portion 26b of the dielectric plate 26 of this example. Due to the tapered portion 40, the protruding height of the neck portion 26b on the outer peripheral side becomes higher than that on the inner peripheral side. The protruding height b of the outer peripheral surface of the neck portion 26 b of the dielectric plate 26 is preferably not less than ¼ of the wavelength of the microwave in the coaxial waveguide 24.

  The outer peripheral surface of the neck portion 26 b of the dielectric plate 26 is electrically connected to the cooling plate 25. A slight gap is generated between the upper end 39 of the outer peripheral surface of the neck portion 26 b of the dielectric plate 26 and the cooling plate 25. If this gap becomes uneven in the circumferential direction, the microwaves are not evenly distributed in the circumferential direction. By setting the protruding height b of the outer peripheral surface of the neck portion 26b of the dielectric plate 26 to ¼ or more of the wavelength of the microwave, the gap can be kept away from the dielectric plate 26. Then, the microwave disturbance can be corrected by propagating the microwave along the conductive film 38 of the neck portion 26b having a length of 1/4 or more of the wavelength of the microwave. Further, by reversing the inclination of the taper portion 40 on the upper surface of the neck portion 26b and the taper portion 26c on the lower surface of the dielectric plate 26, the reflection of microwaves at the taper portion 40 of the neck portion 26b and the lower surface of the dielectric plate 26 are reduced. The reflection of the microwaves at the taper portion 26c can be canceled out, and the loss of the microwaves can be reduced.

  In this example as well, the length of the inner conductor 22b on the dielectric plate side is preferably within a range from 1/4 to 1 wavelength of the microwave wavelength in the coaxial waveguide 24. When propagating through the air and when propagating through the dielectric, the wavelength of the microwave differs at the boundary between the air and the dielectric. The length a of the inner conductor 22b on the dielectric plate side is equal to the wavelength when propagating through the air at the center of the taper portion 40 ((inner diameter of the taper portion 40 + outer diameter of the taper portion 40) / 2). And the sum of the wavelengths when propagating through the dielectric.

FIG. 11 shows still another example (Modification 4) of the inner conductor 22b and the dielectric plate 26 on the dielectric plate side. A cylindrical outer conductor block 42 having a conductive surface is fitted to the outer conductor 23 of the coaxial waveguide 24 (more precisely, the cooling plate 25 constituting the outer conductor 23). The outer conductor block 42 is made of a dielectric such as alumina (Al ₂ O ₃ ) or quartz, and a conductive film 43 having conductivity is formed on the surface thereof. The dielectric plate 26 has a neck portion 26b protruding between the inner conductor 22b and the outer conductor block 42 on the dielectric plate side. The outer conductor block 42 is fitted on the outer peripheral surface of the neck portion 26b of the dielectric plate 26, and the outer conductor block 42 and the dielectric plate 26 are integrated. An inner conductor 22b on the dielectric plate side is integrated with the dielectric plate. Therefore, in this example, the inner conductor 22b on the dielectric plate side, the dielectric plate 26, and the outer conductor block 42 are integrated. The outer peripheral surface of the outer conductor block 42 is electrically connected to the cooling plate 25, and the lower surface of the outer conductor block 42 is electrically connected to the conductive film 38 on the upper surface of the dielectric plate 26. The conductive film 36 of the inner conductor 22b on the dielectric plate side is electrically connected to the conductive film 38 on the lower surface of the dielectric plate 26.

  A gap 45 having a depth of about λ / 2 is formed in the upper portion of the outer conductor block 42 (the portion in contact with the cooling plate 25). This is because when the inner surface of the outer conductor 23 and the outer conductor block 42 are connected to each other, heat (Joule heat) is generated due to contact resistance or the like when a microwave current flows. Since this portion has a large current value, the amount of heat generation increases and the heat load increases, which may cause damage. Therefore, the gap 45 is provided so that the outer conductor 23 and the outer conductor block 42 are in contact with each other at a position where the distance of the gap 45 from the inner surface of the outer conductor is about λ / 4.

  The length b of the outer conductor block 42 in the axial direction is preferably set to ¼ or more of the microwave wavelength in the coaxial waveguide 24. In this way, a gap formed between the upper end of the outer conductor block 42 and the cooling plate 25 can be kept away from the dielectric plate 26 by a quarter or more of the microwave wavelength. For this reason, the disturbance of the microwave caused by passing through the gap can be corrected. An O-ring 44 is mounted between the outer peripheral surface of the outer conductor block 42 and the inner peripheral surface of the cutout portion 25d of the cooling plate 25 in order to make the gap generated between them uniform in the circumferential direction.

  Also in this example, it is desirable that the length of the inner conductor 22b on the dielectric plate side is in a range from 1/4 to 1 wavelength of the microwave wavelength in the coaxial waveguide 24. The axial length b of the outer conductor block 42 and the length a of the inner conductor 22b on the dielectric plate side are the sum of the wavelength when propagating through the air and the wavelength when propagating through the dielectric plate 26. Expressed in wavelength.

  The inner conductor and the outer conductor shown in FIG. 12 were manufactured, and the microwave was propagated to the coaxial waveguide between the inner conductor and the outer conductor. As shown in FIG. It was found that microwaves were transmitted with almost no loss to electromagnetic waves of 2.4 to 2.6 GHz.

  In addition, this invention is not restricted to the said embodiment, In the range which does not change the summary of this invention, it can change variously. For example, a passage through which cooling gas or cooling water flows may be provided in the inner conductor on the mode converter side and the inner conductor on the dielectric plate side, and these inner conductors may be cooled.

  The conductive film attached to the dielectric plate and the inner conductor on the dielectric plate side may be formed by a technique such as thermal spraying or vapor deposition in addition to plating.

  Even if there is no electromagnetic shielding elastic body that presses the cooling plate and dielectric plate against the dielectric window for holding the antenna, the periphery of the cooling plate and dielectric plate is evacuated so that they are in close contact with the dielectric window. Also good.

  Further, a plasma excitation gas supply path for supplying a plasma excitation gas into the processing container may be formed in the dielectric window, and an intermediate shower head for supplying the processing gas may be provided between the dielectric window and the substrate to be processed. Good.

DESCRIPTION OF SYMBOLS 11 ... Processing container 12 ... Dielectric window 15 ... Gas supply part 18 ... Microwave antenna 20 ... Coaxial waveguide 21 ... Rectangular waveguide 22 ... Inner conductor 22a ... Inner conductor (remaining inner conductor) on the mode converter side
22b ... Inner conductor 23 on the dielectric plate side ... Outer conductor 24 ... Coaxial waveguide 25 ... Cooling plate 26 ... Dielectric plate 26b ... Neck portion 27 ... Slot plate 29 ... Mode converter 32a ... Flange portion 32b ... Flange portion 38 ... Conductive film 42 ... outer conductor block

Claims (11)

A processing container having a ceiling defined by a dielectric window, a gas exhaust system for depressurizing the processing container, a gas supply unit for supplying plasma excitation gas to the processing container, and the dielectric window of the processing container In a microwave plasma processing apparatus comprising: a microwave antenna that is mounted and that supplies a microwave to the processing container;
The microwave antenna includes a coaxial waveguide that propagates the microwave, a dielectric plate that propagates the microwave in the radial direction and compresses the wavelength of the microwave, and a slot plate having a slot that transmits the microwave, Including
The coaxial waveguide includes an inner conductor and an outer conductor surrounding the inner conductor,
The inner conductor is separated from the inner conductor on the dielectric plate side connected to at least one of the dielectric plate and the slot plate, and the inner conductor on the dielectric plate side, And a remaining inner conductor in which a space is left between. The microwave antenna further includes a rectangular waveguide that propagates the microwave, and a mode converter that converts a mode of the microwave that propagates through the rectangular waveguide,
The microwave plasma processing apparatus according to claim 1, wherein the remaining inner conductor is connected to the mode converter or the rectangular waveguide.   The microwave plasma processing apparatus according to claim 1, wherein the slot plate is made of a conductive film attached to the dielectric plate.   4. The microwave plasma processing apparatus according to claim 1, wherein the inner conductor on the dielectric plate side is integrated with the dielectric plate.   The inner conductor on the dielectric plate side is made of the same material as that of the dielectric plate or a material having substantially the same thermal expansion coefficient, and has conductivity on the surface thereof. Microwave plasma processing equipment.   6. The microwave plasma processing apparatus according to claim 1, wherein the inner conductor on the dielectric plate side and the remaining inner conductor are provided with flange portions projecting outward.   7. The length of the inner conductor on the dielectric plate side is in a range from 1/4 to 1 wavelength of the microwave wavelength in the coaxial waveguide. The microwave plasma processing apparatus as described. The dielectric plate has a neck protruding into the coaxial waveguide;
The outer peripheral surface of the neck has conductivity,
The protruding height of the outer peripheral surface of the neck protruding into the coaxial waveguide is ¼ or more of the wavelength of the microwave in the coaxial waveguide. Microwave plasma processing equipment. The outer conductor of the coaxial waveguide is fitted with a cylindrical outer conductor block having a conductive surface.
The dielectric plate has a neck portion protruding between the inner conductor and the outer conductor block,
9. The microwave plasma processing apparatus according to claim 1, wherein the length of the outer conductor block in the axial direction is ¼ or more of the wavelength of the microwave in the coaxial waveguide. . Used in a microwave plasma processing apparatus that plasma-processes an object to be processed with plasma generated using microwaves, and the microwaves propagated through a coaxial waveguide including an inner conductor and an outer conductor surrounding the inner conductor in the radial direction. A dielectric plate that propagates to the wavelength and shortens the wavelength,
An inner conductor on the dielectric plate side is integrated with the dielectric plate,
When the dielectric is incorporated in the microwave plasma processing apparatus, the inner conductor includes the inner conductor on the dielectric plate side and the remaining inner conductor arranged with a space from the inner conductor on the dielectric plate side. And a dielectric plate for a microwave plasma processing apparatus. Microwaves propagating in the rectangular waveguide are mode-converted by a mode converter, propagated to the coaxial waveguide including the inner conductor and the outer conductor surrounding the inner conductor, and the microwave propagated through the coaxial waveguide is dielectric. In a microwave power feeding method of a microwave plasma processing apparatus that propagates in a radial direction with a plate and compresses a wavelength,
The microwaves surround the inner conductor on the mode converter side connected to the mode converter, and the inner conductor on the dielectric plate side arranged with a space from the inner conductor on the mode converter side. Microwave power supply method for microwave plasma processing apparatus propagating through the surface.

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