JP2010212226A - Plasma electrode, plasma generation nozzle using the same, plasma generator, and work treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a long life of a plasma electrode which is made of a metal rod, and generates plasma by receiving microwave propagated through a waveguide from a microwave generator on one side of the rod, and by making discharge between an electrode formed concentrically on the ground side on the other end side. <P>SOLUTION: The plasma generating nozzle 30 has an antenna 41 portion on the upper side of a plasma electrode 40 of rod shape which is arranged in a waveguide space H of a waveguide 20 and receives microwave, and the lower side of the plasma electrode 40 working as an inner electrode 42 with an outer electrode 31 arranged concentrically to it, and the treating gas supplied from a gas supply hole 35 into the internal space 32 between these is turned into plasma by the microwave. A ceramic flame spray layer 49 is formed at the lower end 421 of the inner electrode 42. Thereby, the ceramic flame spray layer 49 is adhered to the lower end 421 and covers stably the lower end 421, and can suppress evaporation and oxidation of the metal substrate against discharge. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma electrode used for a plasma generation nozzle of a plasma generation apparatus, and the plasma generation nozzle, plasma generation apparatus, and work processing apparatus using the plasma electrode.

  A microwave generated by a microwave generating means such as a magnetron is received via a waveguide, and a processing gas supplied from the outside is turned into a plasma by the energy of the microwave and irradiated to the object to be processed. A plasma generating nozzle has been proposed in, for example, Patent Document 1 by the present applicant. FIG. 8 is a simplified cross-sectional view of the prior art plasma generating nozzle. According to this, a cylindrical outer electrode 102 serving as a nozzle is attached to the bottom plate 101 a of the waveguide 101, and the rod-shaped inner electrode is inserted from the inspection hole 101 c formed in the top plate 101 b of the waveguide 101. 103 is fitted. The inner electrode 103, which is a plasma electrode, is supported by being insulated from the outer electrode 102 by a cylindrical holding member 104 made of PTFE (polytetrafluoroethylene) or the like, and the cap 105 of the inspection hole 101c. By removing the, the inner electrode 103 can be replaced integrally with the holding member 104. The processing gas is supplied from the outside through the opening 102a formed in the outer electrode 102.

JP 2008-300283 A

  Although the above-described conventional technique allows the inner electrode 103 to be easily replaced, there is a problem that the inner electrode 103 itself has a short life. Specifically, first, as the electrode material as described above, it is possible to select brass, aluminum, silver, copper or the like that is easily processed and has conductivity. Plasma ignition can be performed without any problem by the rod electrodes made of these materials. However, there is a problem in that the electrode tip 103a that becomes high temperature due to discharge evaporates, and the particles contaminate the workpiece.

  Therefore, although the processing becomes difficult as the electrode material, by using tungsten having a high melting point and boiling point, it is possible to suppress metal evaporation while maintaining plasma ignitability. However, this time, tungsten oxide powder is generated, the amount of particles is still large, and it is at a level that can be used only in a clean room for a short time.

  An object of the present invention is to provide a plasma electrode capable of extending the life, a plasma generating nozzle, a plasma generating apparatus, and a workpiece processing apparatus using the plasma electrode.

  The plasma electrode of the present invention is a plasma electrode that generates plasma by performing discharge with an electrode on the ground side. The plasma electrode is formed in a rod shape, receives microwaves on one side of the rod, and receives the microwave on the other end side. It has the electroconductive base material part which performs the said discharge, and the ceramic sprayed layer provided in the surface layer of the said other end side at least.

  According to said structure, a ceramic sprayed layer closely_contact | adheres to the other end side of a rod-shaped base material part, covers this other end side stably, and suppresses evaporation and oxidation of this base material with respect to the said discharge. be able to. Thereby, the life of the plasma electrode can be extended.

  Moreover, the plasma electrode of the present invention is characterized in that the base portion is made of titanium and the ceramic sprayed layer is made of alumina.

  According to said structure, a thermal expansion coefficient is used as a base material part corresponding to the ceramic sprayed layer which adhere | attaches the other end side of the said base material part with respect to discharge, and can cover this other end side stably. Titanium close to is used. Therefore, in the plasma electrode which becomes high temperature, damage due to temperature stress of the ceramic sprayed layer can be suppressed, and a longer life can be achieved.

  Furthermore, the plasma electrode of the present invention further includes a coating layer coated on the surface of the base material portion and having higher conductivity than the base material portion, and the ceramic sprayed layer is laminated on the coating layer. It is characterized by being.

  According to the above configuration, in consideration of the fact that the microwave current flowing back and forth in the plasma electrode from the reception of the microwave to the actual plasma ignition flows through the surface layer of the plasma electrode due to the skin effect, The ceramic sprayed layer is laminated (film formation) on a base material portion such as titanium coated with a layer made of a material such as gold having higher conductivity than the base material portion. Therefore, generation of Joule heat due to the loss of the plasma electrode until plasma ignition can be suppressed.

  Moreover, in the plasma electrode of this invention, it has a recessed part in the end surface center of the other end side of the said base material part, It is characterized by the above-mentioned.

  According to the above configuration, when the end surface of the rod-shaped base portion is cut into a flat surface with a lathe or the like, a protrusion is left in the center, whereas the center is not a flat surface, Engrave to be.

  Therefore, if the protrusion is left, an electric field concentrates on the portion, and the ceramic sprayed layer may be damaged. However, such a problem is eliminated and the life of the plasma electrode is extended. Can be achieved.

  Furthermore, a plasma generating nozzle according to the present invention includes an inner electrode composed of the plasma electrode, a cylindrical shape, a concentric arrangement with the inner electrode, an outer electrode that is grounded, and the inner electrode. And an annular plasma outlet formed by the outer electrode.

  According to the above configuration, by using a concentric inner electrode and outer electrode and applying an electric field by a microwave between both electrodes, it is possible to generate glow discharge instead of arc discharge. Therefore, by supplying the processing gas from the external supply pipe between the concentric electrodes, the processing gas can be turned into plasma and irradiated to the workpiece as the object to be processed from the annular plasma outlet.

  Further, the plasma generator of the present invention provides microwave generation means for generating a microwave, a waveguide for propagating the microwave, and energy of the microwave to a predetermined processing gas, and the processing gas is converted into plasma. The plasma generating nozzle is configured to discharge the plasma, and one end of the plasma electrode is grounded in the plasma generating nozzle.

  According to said structure, an electric field concentration part is not formed in an antenna in a waveguide, and the glow discharge in a waveguide can be prevented.

  Furthermore, in the plasma generator of the present invention, when the wavelength of the microwave propagating through the antenna is λ, the length from the ground point of the antenna to the other end is (2n−1) λ / 4 ( However, n is an integer) or a length in the vicinity thereof.

  According to the above configuration, the antenna having one end grounded electrically resonates with a length that is an odd multiple of a quarter wavelength of the received microwave. Therefore, as described above, the length of the antenna from the ground point is set to (2n-1) λ / 4 or a length in the vicinity thereof, so that the electric field strength at the other end can be increased. And plasma can be generated efficiently.

  In the plasma generator of the present invention, a holding member that is formed in a cylindrical shape with an insulating material and holds the inner electrode in the outer electrode, and a wall surface on which the outer electrode is attached in the waveguide An inspection port formed on the opposite wall surface, into which the inner electrode held by the holding member can be loosely inserted, and a fixture that covers the inspection port, and at least a portion of the holding member in the waveguide is As a grip portion, it is formed to extend on the opposite wall surface of the waveguide, and one end of the plasma electrode is suspended from the fixture so that the one end is grounded via the fixture. It is characterized by that.

  According to the above configuration, by removing the fixture from the waveguide, the inner electrode can be removed from the holding member, and the plasma generating nozzle can be compared with the case where the replacement is performed from the irradiated object (workpiece) side. There is no need to remove the attached waveguide, and the replacement can be performed very easily. In addition, the operator can replace the inner electrode without gripping the inner electrode by gripping the extended grip portion of the holding member and touching the inner electrode with a hand or a tool. And can be replaced without using a dedicated tool. The inner electrode can also be grounded from a fixture that suspends the inner electrode.

  Furthermore, a workpiece processing apparatus according to the present invention includes the plasma generation device and a workpiece processing unit that processes the workpiece with a plasma process gas generated by the plasma generation nozzle.

  Therefore, it is possible to realize a long-life work processing apparatus.

  According to the plasma electrode of the present invention, the ceramic sprayed layer adheres closely to the other end side of the rod-shaped base material portion and stably covers the other end side, and the base material portion is evaporated or oxidized against discharge. Can be suppressed. Thereby, the life of the plasma electrode can be extended.

  Further, according to the plasma generating nozzle of the present invention, by supplying a processing gas from an external supply pipe between concentric electrodes, the processing gas is turned into plasma, and a workpiece that becomes an object to be processed from an annular plasma outlet. Can be irradiated.

  Furthermore, according to the plasma generation apparatus of the present invention, no electric field concentration portion is formed in the antenna in the waveguide, and glow discharge in the waveguide can be prevented.

  Moreover, the workpiece | work processing apparatus of this invention is provided with the said plasma generator and the workpiece | work process part which processes a workpiece | work with the plasma-ized process gas generated with the said plasma generation nozzle as mentioned above.

  Therefore, a long-life work processing apparatus can be realized.

It is a schematic structure figure showing the work processing device concerning one embodiment of the present invention. It is sectional drawing of the plasma generation nozzle which concerns on one Embodiment of this invention. It is an exploded view of the component of the said plasma generation nozzle. It is a schematic diagram which shows the coupling relationship of an antenna and a microwave. It is sectional drawing of the plasma generation nozzle which concerns on the other embodiment of this invention. It is sectional drawing of the plasma generation nozzle which concerns on other form of implementation of this invention. It is a perspective view which expands and shows the difference of the plasma electrode end surface of the plasma generation nozzle of FIG. 1 and the plasma generation nozzle of FIG. 1 is a cross-sectional view of a typical prior art plasma generating nozzle.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram showing a work processing apparatus S according to an embodiment of the present invention. The work processing apparatus S includes a plasma generation unit PU (plasma generation apparatus) that generates plasma gas and a chamber T (work processing unit) into which the plasma gas is introduced. In the chamber T, for example, sterilization of medical instruments, removal of organic contaminants such as a semiconductor substrate, surface modification, and the like are performed with the plasmaized gas.

  The plasma generation unit PU is a unit capable of generating plasma at normal temperature and pressure using microwaves, and is generally a microwave generation device 10 (microwave generation means) that generates a microwave μ having a predetermined wavelength. ), A waveguide 20 connected to the microwave generator 10 and propagating the microwave μ, and a plasma generation nozzle 30 provided in the waveguide 20.

  The microwave generator 10 generates a microwave μ of 2.45 GHz, for example, and propagates the microwave μ to the inside of the waveguide 20. For this reason, the microwave generator 10 includes a microwave generation source such as a magnetron that generates a microwave, an amplifier that adjusts the intensity of the microwave generated by the microwave generation source to a predetermined output intensity, and a microwave. And a microwave transmission antenna that emits the light into the inside of the waveguide 20. In the plasma generation unit PU according to the present embodiment, for example, a continuously variable microwave generator 10 that can output microwave energy of 1 W to 3 kW is preferably used.

  The waveguide 20 is made of, for example, a nonmagnetic metal (aluminum or the like), has a rectangular cross section, and propagates the microwave μ generated by the microwave generator 10 toward the plasma generator 30. The waveguide 20 can be constituted by a rectangular tube-like assembly using an upper plate, a lower plate, and two side plates made of, for example, a metal flat plate. You may form by extrusion molding, the bending process of a plate-shaped member, etc. irrespective of the assembly of such a flat plate. In addition, the waveguide is not limited to a rectangular cross section, and for example, a waveguide having an elliptical cross section can be used. Furthermore, not only a nonmagnetic metal but a waveguide can be comprised with the various members which have a waveguide effect | action.

  The plasma generating nozzle 30 applies microwave μ energy to an appropriate processing gas, and converts the processing gas into plasma and emits it. The plasma generating nozzle 30 includes a rod-shaped plasma electrode 40 that receives the microwave μ. The upper side of the plasma electrode 40 is introduced into the inside of the waveguide 20 to become the antenna 41, and the lower side is projected to the outside of the waveguide 20 to become the inner electrode 42. The plasma generating nozzle 30 will be described in detail later with reference to FIGS.

  In such a plasma generation unit PU, in addition to the above-described components, a sliding short that reflects the microwave μ on the far end side of the waveguide 20, and a reflection micro of the microwave μ that is emitted to the waveguide 20. A circulator that separates the wave so as not to return to the microwave generator 10, a dummy load that absorbs the reflected microwave separated by the circulator, and a stub tuner that performs impedance matching may be provided.

  The chamber T is a chamber for performing a sterilization process on the workpiece W. The chamber T includes a chamber body 50 and a work tray 51 that is housed in the chamber body 50 and on which the workpiece W is placed.

  The chamber main body 50 is provided with an introduction hole 52 for the gas G that has been converted to plasma, and an inlet 54 and an outlet 55 for ventilating the processed gas. Connected to the gas introduction hole 52 is a stainless tube 53 for guiding the gas G generated by the plasma generation unit 30 to the inside of the chamber body 50. The work tray 51 is made of, for example, a mesh metal tray.

  An example of a usage mode of the workpiece processing apparatus S configured as described above is as follows. For example, a work W such as a medical instrument is placed on the work tray 51 and stored in the chamber body 50. Thereafter, the microwave generator 10 is activated to generate the microwave μ, and the processing gas is supplied to the plasma generation nozzle 30. As the processing gas here, a gas obtained by mixing an excitation gas such as oxygen, hydrogen, nitrogen, argon, or flon with a mist having a hydrogen component such as aqueous hydrogen peroxide, aqueous ammonia, or water can be used.

  The microwave μ is received by the plasma electrode 40 inside the waveguide 20. The received energy of the microwave μ is consumed for converting the processing gas into plasma, and thereby the plasma G is generated by the plasma generation nozzle 30. The gas G is introduced into the chamber body 50 through the stainless tube 53. The gas G contains a highly reactive hydroxyl radical, oxygen radical, and the like due to the plasma, and acts on the microorganisms adhering to the workpiece W to kill them.

  Next, the detailed structure of the plasma generating nozzle 30 will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the plasma generating nozzle 30 according to the embodiment of the present invention, and FIG. 3 is an exploded view of the components of the plasma generating nozzle 30. The plasma generating nozzle 30 includes a plasma electrode 40, an outer electrode 31, a base 25, and a fixture 44.

  As described above, the plasma electrode 40 is arranged in such a manner that the antenna 41 side penetrates the internal space (waveguide space) H of the waveguide 20 and the inner electrode 42 side protrudes outside the waveguide 20. Has been. The waveguide 20 is a waveguide having a rectangular cross section as described above, which includes an upper surface plate 21 and a lower surface plate 22 that face each other in the vertical direction, and a pair of side surface plates 23 and 24 that face each other in the left-right direction. In detail, the plasma electrode 40 is such that the antenna 41 side penetrates the internal space H of the waveguide 20 and penetrates the top plate 21 with respect to such a waveguide 20, and the tip protrudes to the outside. In addition, the inner electrode 42 side is disposed so as to penetrate the lower surface plate 22 and protrude to the outside by a predetermined length and be surrounded by the cylindrical outer electrode 31.

  The plasma electrode 40 is held by a cylindrical holding member 43. The holding member 43 serves to position the plasma electrode 40 and to prevent the plasma electrode 40 from coming into contact with the waveguide 20 and the outer electrode 31 at portions other than the ground point P described later. The holding member 43 is a microwave permeable member, and is formed of an insulating material. Preferably, a heat-resistant resin such as polypropylene resin or fluorine resin, for example, a low dielectric constant insulating material such as PTFE (polytetrafluoroethylene) or ceramic can be used.

  The holding member 43 includes a solid portion 431 that is in close contact with the outer periphery near the center in the longitudinal direction of the plasma electrode 40, and a hollow portion 432 that is disposed with a space 433 disposed on the outer periphery of the antenna 41 portion of the plasma electrode 40. Prepare. The solid portion 431 holds the plasma electrode 40 and prevents contact with the lower surface plate 22 of the waveguide 20, and the hollow portion 432 prevents the plasma electrode 40 from contacting the upper surface plate 21 and the base 25. . The holding member 43 is assembled so as to penetrate the waveguide 20 in the vertical direction, and an upper end 434 protrudes upward from the upper surface plate 21 and a lower end 435 protrudes downward from the lower surface plate 22.

  The outer electrode 31 is made of a metal block, and the inner electrode 42 of the plasma electrode 40 is concentrically disposed in the inner space 32 to form a cylindrical space between the inner electrode 42 and the outer space. It is possible to form a gas flow therethrough. The outer electrode 31 is attached to the waveguide 20 so that its upper end surface 33 is in contact with the outer surface of the lower surface plate 22 of the waveguide 20, and the lower end 435 side of the holding member 43 enters the upper part of the internal space 32. .

  The outer electrode 31 is provided with a gas supply hole 35 (gas supply unit) for supplying a processing gas. The gas supply hole 35 communicates with the internal space 32 and is connected to a gas supply pipe (not shown). A recess 36 for attaching a cooling pipe (not shown) is provided on the side peripheral wall of the outer electrode 31. The cooling pipe is for cooling the outer electrode 31 that becomes high temperature due to generation of plasma.

  As described above, the plasma electrode 40 is used as the inner electrode 42, the outer electrode 31 is concentrically grounded, and has an annular plasma outlet, so that an electric field by microwave μ is applied between the electrodes 31 and 42. Then, not arc discharge but glow discharge can be generated. Therefore, by supplying a processing gas from an external supply pipe between the concentric electrodes 31 and 42, the processing gas is turned into plasma and irradiated to the workpiece W as a workpiece from the annular plasma outlet. be able to.

  The base 25 is provided for mounting the fixture 44, and is attached to the outer surface of the upper surface plate 21 of the waveguide 20. The base 25 is a cylindrical member having a through hole 251, and the upper end 434 side of the holding member 43 is accommodated in the through hole 251.

  The fixture 44 is a member that is formed of a metal material and holds the projecting portion of the plasma electrode 40 from the upper surface plate 21 to suspend the plasma electrode 40. The fixing tool 44 penetrates the support portion 442 in the up-down direction, a circular flange portion 441 that is closely fixed to the upper surface of the base 25 with a screw or the like, a support portion 442 that projects from the center of the flange portion 441. A holding hole 443 and a stop hole 444 provided on the peripheral surface of the support portion 442 and communicating with the holding hole 443 are provided.

  The antenna 41 of the plasma electrode 40 is inserted into the holding hole 443 in a sliding contact state. An unillustrated set screw is screwed into the set hole 444 so that the antenna 41 side of the plasma electrode 40 is fixed (suspended) to the fixture 44. When the plasma generating nozzle 30 is assembled, the plasma electrode 40 to which the holding member 43 is attached is fixed to the fixture 44 in advance, and this is fitted into the portion of the waveguide 20 where the base 25 is mounted. It is possible to take a method of fixing the fixing tool 44 to. When replacing the plasma electrode 40, the fixture 44 may be removed from the base 25 and the fixture 44 may be extracted together with the plasma electrode 40.

  In the plasma generating nozzle 30 configured as described above, in this embodiment, the antenna 41 of the plasma electrode 40 is grounded. Specifically, as schematically shown in FIG. 2, a fixture 44 that suspends and fixes the antenna 41 side of the plasma electrode 40 is grounded. The plasma electrode 40 is not in contact with another conductive member at a portion other than the fixing portion by the fixing tool 44. For this reason, the plasma electrode 40 functions as a one-end grounded antenna having a grounding point P as a fixing portion by the fixture 44. The ground point in the antenna 41 may be set as appropriate. For example, the ground point is formed by conducting the antenna 41 to the waveguide 20 at a position below the fixing portion by the fixture 44. Also good.

  Here, the length L of the plasma electrode 40 in the direction from the ground point P to the inner electrode 42 is defined as the wavelength of the microwave propagating through the plasma electrode 40 that has received the microwave μ having the wavelength λ 0 in the waveguide 20. Sometimes it is chosen to have a length of 3λ / 4.

  FIG. 4 is a schematic diagram showing the coupling relationship between the plasma electrode 40 as described above and the microwave μ propagating through the plasma electrode 40. The plasma electrode 40 having one end grounded is electrically resonated with a length that is an odd multiple of a quarter wavelength of the received microwave. Therefore, the voltage distribution in the length direction of the plasma electrode 40, that is, in the protruding direction from the ground point P, is zero at the ground point P and the position of λ / 2, as shown in FIG. The curve becomes the maximum at the position of 3λ / 4. For this reason, the electric field intensity in the inner electrode 42 can be increased by setting the length L of the plasma electrode 40 from the ground point P to 3λ / 4 as described above. Thereby, high energy can be given to the processing gas passing near the inner electrode 42, and plasma can be generated efficiently.

  Here, since the resonance appears with a length that is an odd multiple of the quarter wavelength, the length L of the plasma electrode 40 can be set by the following general formula.

L = (2n−1) λ / 4 (where n is an integer)
If a relatively strong electric field strength can be obtained even if the length L ′ is slightly deviated from the length L derived from the above general formula, the plasma electrode 40 is set to the length L ′. Also good.

  According to the plasma generation nozzle 30 configured as described above, when the microwave μ is propagated into the waveguide 20, the microwave μ is received by the plasma electrode 40. As a result, an electric field concentration portion is formed in the vicinity of the inner electrode 42 of the plasma electrode 40. In this state, when processing gas is supplied from the gas supply hole 35 of the outer electrode 31, the processing gas is excited in the vicinity of the inner electrode 42 to generate plasma (ionized gas). The processing gas G thus converted into plasma is emitted from the lower end of the cylindrical space 32 of the outer electrode 31 as a plume by the gas flow provided from the gas supply hole 35.

  According to the plasma generation nozzle 30 according to the present embodiment described above, the antenna 41 side of the plasma electrode 40 is introduced into the waveguide 20 to receive the microwave μ propagating in the waveguide 20. However, since the antenna 41 is grounded, an electric field concentration portion is not formed in the plasma electrode 40 in the waveguide 20. Therefore, no glow discharge occurs in the waveguide 20. On the other hand, the inner electrode 42 is a protruding end from the ground point P, and the length L from the ground point P is selected to be 3λ / 4, so that it becomes an electric field concentration portion. For this reason, the energy for turning the processing gas into plasma can be reliably applied to the inner electrode 42. Therefore, it is possible to reliably generate plasma on the side of the inner electrode 42 that should originally generate plasma. Further, when the plasma electrode 40 is attached to the waveguide 20, it is possible to eliminate the need for severe adjustment management for avoiding the discharge in the waveguide.

  In addition, the plasma electrode 40 is held in the outer electrode 31 via a holding member 43 that is insulative and formed in a cylindrical shape, and the hollow portion 432 in the waveguide 20 of the holding member 43 is gripped. On the other hand, a through-hole 251 serving as an inspection port is formed in the base 25, and the tip of the antenna 41 is suspended from a fixture 44 covering the through-hole 251 so that the fixture 44 is guided through the waveguide. The plasma electrode 40 can be detached from the holding member 43 by removing from the waveguide 20, and the waveguide 20 to which the plasma generating nozzle 30 is attached is compared to the case where the plasma electrode 40 is exchanged from the irradiated object (work W) side. There is no need to remove the battery, and the replacement can be performed very easily. Further, the operator can replace the plasma electrode 40 without gripping the holding member 43 and touching the plasma electrode 40 with a hand or a tool, thereby preventing the plasma electrode 40 from being damaged. Can be exchanged without using a dedicated tool. The plasma electrode 40 can also be grounded from a fixture 44 that suspends the plasma electrode 40.

  In the plasma generating nozzle 30 configured as described above, it should be noted that the plasma electrode 40 is a rod-shaped base member 401 that is electrically conductive with respect to the lower electrode 31. That is, a ceramic sprayed layer 49 is formed on the surface layer of the end 421.

  The thermal spraying is a kind of method for treating the surface of a material by heating and melting the material, spraying the material onto a work piece (base material), and forming a film. As a heat source for heating, a high-temperature combustion flame, plasma, or the like can be used. The material (spraying material) is formed into droplets by this heat source and sprayed onto the substrate or coating. In addition, since the adhesion strength between the base material and the thermal spray particles is smaller than that of welding or the like, it is necessary to roughen the surface of the base material portion 401 by blasting before construction and to improve the adhesion strength by mechanical meshing. is there. Further, as in the case of painting or the like, masking can be applied only to a specific part of the object as shown in FIGS.

  With this configuration, the ceramic sprayed layer 49 is in close contact with the lower end 421 of the inner electrode 42 and stably covers the lower end 421, and against the discharge, the base material portion 401 (inner electrode 42). Evaporation and oxidation can be suppressed. Thereby, the life of the plasma electrode 40 can be extended. Further, by using such a plasma generating nozzle 30, the work processing apparatus S can also have a long life.

  Preferably, the base material portion 401 is made of titanium, and the ceramic sprayed layer 49 is made of alumina. This corresponds to the ceramic sprayed layer 49 that can tightly adhere to the lower end 421 of the inner electrode 42 and stably cover the lower end 421 with respect to the discharge. This is because close titanium is used. With this configuration, damage to the ceramic sprayed layer 49 due to temperature stress can be suppressed in the plasma electrode 40 that is at a high temperature, and a longer life can be achieved.

  Specifically, by using tungsten having a high melting point and boiling point as compared with the case where a highly conductive metal such as brass, aluminum, silver, copper or the like is used as the base part 401 as described above, the electrode The evaporation of the metal can be suppressed and the life can be extended. However, as described above, tungsten oxide powder is generated. Therefore, as a general method for preventing oxidation, by impregnating the tungsten surface with carbon of about several μm, the energy of the microwave received by the antenna 40 is set to 100 W for a while, for about 300 hours. The generation of particles can be suppressed as follows. However, when that time passes, the carbonized layer is gradually peeled off, and the oxidized powder is generated.

  On the other hand, when the alumina ceramic sprayed layer 49 was formed on the titanium base material 401 as in the present embodiment, a lifetime exceeding 2000 hours could be secured. Table 1 shows the experimental results of the present inventors. As described above, the microwave energy was 100 W, the processing gas used was clean dry air, and the flow rate was 15 LPM. Evaluation is the presence or absence of adhesion of the deposit on the electrode tip (the deposit jumps out of the nozzle and adheres to the workpiece).

(Embodiment 2)
FIG. 5 is a cross-sectional view of a plasma generating nozzle 30a according to another embodiment of the present invention. The plasma generation nozzle 30a is similar to the plasma generation nozzle 30 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that in this plasma generating nozzle 30a, the plasma electrode 40a is formed by coating the base material portion 401 with a coat layer 402 having higher conductivity than the base material portion 401, and further laminating the ceramic sprayed layer 49. (Film formation).

  This is because, as described above, the ceramic sprayed layer 49 is formed to suppress the particles, so that the life of the plasma electrode 40 exceeding 2000 hours can be realized. However, when the plasma is ignited from the extinguished state, the microwave μ This is because the microwave current that travels within the plasma electrode 40 from the reception of the plasma to the actual plasma ignition becomes Joule heat due to the resistance component in the plasma electrode 40a, leading to deterioration (melting and scorching) of the holding member 43. is there.

  As described above, the base material portion 401 is titanium having a thermal expansion coefficient close to that of alumina of the thermal spray layer 49, and the coating layer 402 is, for example, a gold layer and is coated to a thickness of 1 μm or more. The microwave current until ignition flows through the surface layer of the plasma electrode 40a, 2 to 3 μm, due to the skin effect. With this configuration, it is possible to suppress the deterioration of the holding member 43 due to repeated plasma ignition, and to realize a longer life of the plasma electrode 40a.

  Table 2 shows the experimental results of the inventors. The experimental conditions were the same as in Table 1 above, and an operation of turning off for 30 seconds after adding 30 seconds was added. The holding member 43 is made of PTFE (polytetrafluoroethylene). As can be understood from this experimental result, without coating, scorching occurs from several tens of times, and even if it can be used for a long time, 1000 times is the limit, but by applying the coating, it exceeds 4000 times. However, there is no change and the durability can be remarkably improved.

(Embodiment 3)
FIG. 6 is a cross-sectional view of a plasma generating nozzle 30b according to still another embodiment of the present invention. The plasma generation nozzle 30b is similar to the plasma generation nozzle 30 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that in this plasma generating nozzle 30b, a recess 422 is formed in the center of the end surface of the lower end 421 of the inner electrode 42 of the plasma electrode 40b.

  As described above, when the base portion 401 of the plasma electrode 40b is made of titanium and the end surface of the lower end 421 of the inner electrode 42 is machined into a flat surface with a lathe or the like, it is enlarged in FIG. This is because the protrusion 423 is left in the center as shown. If the protrusion 423 is left, the electric field concentrates on this portion, and the ceramic sprayed layer 49 made of alumina is melted or cracked. Therefore, as shown in an enlarged view in FIG. 7B, in order to remove the protrusion 423, the center of the end surface of the lower end 421 is carved to form the recess 422.

  As a result, the electric field concentrating portion is distributed to the outer peripheral edge 424 of the lower end 421 and the edge 425 of the recess 422, and the temperature rise of the lower end 421 is suppressed to damage the ceramic sprayed layer 49. Can be prevented and a longer life can be achieved. The outer peripheral edge 424 and the end edge 425 may be chamfered.

The plasma generation nozzles 30, 30a, 30b, the plasma generation unit PU, and the work processing apparatus S according to one embodiment of the present invention have been described above. However, the present invention is not limited to this, and for example, the following embodiment Can take.
(1) In the above embodiment, an example in which one plasma generating nozzle 30 is attached to the waveguide 20 has been shown, but a plurality of nozzles may be provided. In that case, the plurality of plasma generating nozzles 30 may not be arranged in a straight line in the straight waveguide 20 but may be provided in two rows in a staggered manner or in parallel. Such nozzle arrangement can be realized by optimizing the width of the waveguide 20, the arrangement pitch of the plasma generating nozzles 30, the wavelength of the microwave, and the like.
(2) In the said embodiment, the sterilizer was illustrated as an example of the workpiece | work processing apparatus S to which plasma generation unit PU is applied. In addition, the plasma generation unit PU can be used for other work processing apparatuses, for example, etching processing apparatuses and film forming apparatuses for semiconductor substrates such as semiconductor wafers, glass substrate and printed substrate cleaning processing apparatuses such as plasma display panels, and protein decomposition. The present invention can also be suitably applied to devices and the like.

DESCRIPTION OF SYMBOLS 10 Microwave generator 20 Waveguide 25 Base 30,30a, 30b Plasma generating nozzle 31 Outer electrode 32 Internal space 35 Gas supply hole 40, 40a, 40b Plasma electrode 401 Base material part 402 Coat layer 41 Antenna 42 Inner electrode 421 Below End 423 Recess 424 Outer peripheral edge 425 End edge 43 Holding member 44 Fixing tool 49 Ceramic sprayed layer S Work processing device PU Plasma generating unit (plasma generating device)
T Sterilization chamber W Workpiece

Claims (9)

In the plasma electrode that generates plasma by performing discharge with the electrode on the ground side,
A conductive base material formed in a rod shape, receiving microwaves on one side of the rod and performing the discharge on the other end side;
It has a ceramic sprayed layer provided in the surface layer of the said other end side at least, The plasma electrode characterized by the above-mentioned.   The plasma electrode according to claim 1, wherein the base material portion is made of titanium, and the ceramic sprayed layer is made of alumina. A coating layer coated on the surface of the base material portion and having higher conductivity than the base material portion;
The plasma electrode according to claim 1 or 2, wherein the ceramic sprayed layer is laminated on the coat layer.   The plasma electrode according to any one of claims 1 to 3, wherein the plasma electrode has a recess in the center of the end surface on the other end side of the base portion. An inner electrode comprising the plasma electrode according to any one of claims 1 to 4,
An outer electrode which is formed in a cylindrical shape and is concentrically arranged with the inner electrode and is grounded;
A plasma generating nozzle having an annular plasma outlet formed by the inner electrode and the outer electrode. Microwave generation means for generating microwaves;
A waveguide propagating the microwave;
The plasma generating nozzle according to claim 5, wherein the microwave energy is given to a predetermined processing gas, and the processing gas is turned into plasma and released.
In the plasma generation nozzle, one end of the plasma electrode is grounded. When the wavelength of the microwave propagating through the antenna is λ,
The length from the grounding point of the antenna to the other end is (2n-1) λ / 4 (where n is an integer) or a length in the vicinity thereof. Plasma generator. A holding member that is formed in a cylindrical shape with an insulating material and holds the inner electrode in the outer electrode;
An inspection port that is formed on the wall surface opposite to the wall surface to which the outer electrode is attached in the waveguide, and in which the inner electrode held by the holding member can be loosely inserted,
A fixing tool that covers the inspection port;
At least a part of the holding member in the waveguide is formed as a grip portion so as to extend to the opposite wall surface of the waveguide.
The plasma generator according to claim 6 or 7, wherein one end of the plasma electrode is suspended from the fixture, and the one end is grounded via the fixture. A plasma generator according to any one of claims 6 to 8,
A work processing apparatus, comprising: a work processing unit configured to process a work with a plasma processing gas generated by the plasma generating nozzle.

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