JP2009110802A - Plasma generator apparatus and workpiece treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma generator using microwaves in which occurrence of a discharging phenomenon inside a wave guide tube can be prevented simply and surely as well. <P>SOLUTION: The plasma generator PU is provided with a microwave generator 10, a wave guide tube 20 which is connected with the microwave generator 10 and transmits the microwaves μ, and a plasma generating portion 30 arranged in the wave guide tube 20. The plasma generating portion 30 has an antenna 40 of a rod shape for receiving the microwaves μ. The antenna 40 includes a side of a first end portion 41 introduced inside the wave guide tube 20 and a side of a second end portion 42 projected out of the wave guide tube 20. The first end portion 41 is grounded and energy of the microwave μ is given to treatment gas at the second end portion 42. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plasma generator capable of generating and releasing a plasma gas using microwave energy, and a work processing apparatus using the same.

  For example, a plasma gas may be used to sterilize medical instruments, remove organic contaminants such as a semiconductor substrate, or modify the surface. As a plasma generator for generating such plasma gas, the present applicant has previously proposed an apparatus disclosed in Patent Document 1.

This plasma generator is an atmospheric pressure plasma generator using microwaves as an energy source for generating plasma, and includes a waveguide for propagating microwaves, an inner electrode and an outer electrode attached to the waveguide. And a plasma generating nozzle. A part of the inner electrode protrudes into the waveguide so as to receive the microwave propagating through the waveguide. On the other hand, the outer electrode is grounded together with the waveguide, and is disposed around the inner electrode so that glow discharge can be generated between the tip of the inner electrode to which microwave energy is applied. A plasma gas is generated by supplying a predetermined processing gas between the inner electrode and the outer electrode.
JP 2007-220589 A

  In the plasma generator of Patent Literature 1, the inner electrode is rod-shaped and attached in a state in which one end side protrudes into the waveguide while being insulated from the waveguide and the outer electrode. One end projecting into the waveguide functions as an antenna portion that receives microwaves, and the other end functions as a portion that forms an outer electrode and a high electric field portion (glow discharge generating portion).

  However, when the above configuration is employed, glow discharge may occur between the inner electrode and the inner wall surface of the waveguide depending on the length of the inner electrode protruding into the waveguide. This means that glow discharge does not occur between the inner electrode and the outer electrode that should originally generate discharge, and plasma generation cannot be freely controlled. Therefore, very severe adjustment management is required for the length of the inner electrode protruding into the waveguide.

  The present invention has been made in view of the above problems, and provides a plasma generator capable of easily and reliably preventing the occurrence of a discharge phenomenon inside a waveguide, and a work processing apparatus using the plasma generator. Objective.

  A plasma generator according to one aspect of the present invention provides microwave generation means for generating microwaves, a waveguide for propagating the microwaves, applying energy of the microwaves to a predetermined gas, A plasma generating unit that emits the plasma and emits the plasma, and the plasma generating unit includes a rod-shaped antenna that receives the microwave, and the antenna has a first end portion that is introduced into the waveguide. And a second end side projecting to the outside of the waveguide, the first end is grounded, and the microwave energy is applied to the gas at the second end. (Claim 1).

  According to this configuration, the first end portion side of the antenna is introduced into the waveguide so as to receive the microwave propagating in the waveguide, but the first end portion is grounded. In the waveguide, no electric field concentration portion is formed on the antenna. Therefore, no glow discharge occurs in the waveguide. On the other hand, the second end portion is a far end from the ground point, and can be an electric field concentration portion. For this reason, the energy for making the said gas into plasma can be given in a 2nd edge part.

  In the above configuration, when the wavelength of the microwave propagating through the antenna is λ, the length from the ground point of the antenna to the second end portion is (2n−1) λ / 4 (where n is an integer) Or a length in the vicinity thereof (claim 2).

  An antenna with one end grounded electrically resonates with a length that is an odd multiple of a quarter wavelength of the received microwave. Therefore, by setting the length from the ground point of the antenna to a length of (2n-1) λ / 4 or a length in the vicinity thereof, the electric field strength at the second end can be increased. Plasma can be generated efficiently.

  In the above-described configuration, the plasma generation unit is arranged such that the first end side penetrates the inside of the waveguide, and the second end side protrudes outside the waveguide; A cylinder that is spaced apart around the second end of the antenna, and a gas supply that supplies the gas between the second end of the antenna and the cylinder. It is desirable that the plasma generating nozzle is included, and the plasmaized gas is discharged from the tip of the plasma generating nozzle.

  According to this configuration, gas is supplied from the gas supply unit to the annular space between the antenna and the cylindrical body, and microwave energy is applied to the gas at the second end portion of the antenna to form plasma, and the tip portion of the nozzle The gas converted into plasma can be released from the gas.

  In this case, the waveguide is a waveguide having a rectangular cross section, and includes a first face plate and a second face plate facing each other, and the first end portion side of the antenna is the interior of the waveguide. And the front end of the antenna protrudes to the outside through the first face plate, and the second end portion side of the antenna passes through the second face plate and protrudes to the outside by a predetermined length. And a fixing tool that holds the projection of the antenna from the first face plate and suspends the antenna without substantially contacting the first face plate and the second face plate. Desirable (Claim 4).

  According to this configuration, the antenna is suspended and supported by the fixture in such a manner as to penetrate the internal space of the waveguide and the second face plate from the first face plate side of the waveguide. Therefore, the antenna can be easily and reliably attached to the waveguide.

  In this case, the fixture is made of a conductive member, and the holding portion by the fixture is a grounding point of the antenna. When the wavelength of the microwave propagating through the antenna is λ, the grounding of the antenna is performed. It is desirable that the length from the point in the second end direction is (2n−1) λ / 4 (where n is an integer) or a length in the vicinity thereof (Claim 5).

  A workpiece processing apparatus according to another aspect of the present invention includes a plasma generator according to any one of claims 1 to 5, and a workpiece processing unit that processes a workpiece with a plasma gas generated in the plasma generator. (Claim 6).

  In the above-described configuration, it is desirable that the workpiece processing unit includes a sterilization chamber into which a plasma gas is introduced.

  According to the present invention, since one end (first end) of the antenna is grounded, no glow discharge occurs between the antenna and the inner surface of the waveguide inside the waveguide. Therefore, it is possible to reliably generate plasma on the other end (second end) side of the antenna that should originally generate plasma. In addition, when adjusting the antenna to the waveguide, severe adjustment management or the like can be eliminated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a sterilization apparatus S according to one embodiment of the present invention. The sterilizer S is composed of a plasma generation unit PU (plasma generator) that generates plasma gas and a sterilization chamber T into which the plasma gas is introduced.

  The plasma generation unit PU is a unit capable of generating plasma at room temperature and normal pressure using microwaves, and is generally a microwave generation device 10 (microwave generation means) that generates a microwave μ having a predetermined wavelength. The waveguide 20 is connected to the microwave generator 10 and propagates the microwave μ, and the plasma generator 30 is 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 generation unit 30 applies microwave μ energy to an appropriate processing gas, converts the processing gas into plasma, and discharges it. The plasma generator 30 includes a rod-shaped antenna 40 that receives the microwave μ. The antenna 40 is arranged such that the first end 41 side which is the upper end side is introduced into the waveguide 20 and the second end 42 side which is the lower end side protrudes outside the waveguide 20. Yes. The plasma generation unit 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 sterilization chamber T is a chamber for sterilizing the workpiece W. The sterilization 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 body 50 is provided with a gas introduction hole 52 and an inlet 54 and an outlet 55 for ventilation. Connected to the gas introduction hole 52 is a stainless tube 53 for guiding the gas G generated in the plasma generator 30 into the chamber body 50. The work tray 51 is made of, for example, a mesh metal tray.

  An example of the usage mode of the sterilizer 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 generator 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 antenna 40 inside the waveguide 20. The received energy of the microwave μ is consumed for converting the processing gas into plasma, whereby the plasma G is generated in the plasma generating unit 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 generation unit 30 will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the plasma generation unit 30, and FIG. 3 is an exploded view of the components of the plasma generation unit 30. The plasma generation unit 30 (plasma generation nozzle) includes an antenna 40, a cylindrical body 31, a base 25, and a fixture 44.

  The antenna 40 is made of a rod-shaped member made of a highly conductive metal such as copper, aluminum, or brass. The antenna 40 is arranged in such a manner that the first end 41 side passes through the internal space (waveguide space) H of the waveguide 20 and the second end 42 side protrudes outside the waveguide 20. Yes. The waveguide 20 has a rectangular cross section composed of an upper surface plate 21 (first surface plate) and a lower surface plate 22 (second surface plate) opposed in the up-down direction, and a pair of side surface plates 23, 24 opposed in the left-right direction. It is a waveguide. Specifically, the antenna 40 has a tip end (first end portion) with respect to such a waveguide 20 such that the first end 41 side penetrates the internal space H of the waveguide 20 and penetrates the upper surface plate 21. 41) protrudes to the outside, and the second end 42 side is disposed so as to penetrate the lower surface plate 22 and protrude to the outside by a predetermined length.

  The antenna 40 is held by a cylindrical holding member 43. The holding member 43 serves to position the antenna 40 and to prevent the antenna 40 from coming into contact with the waveguide 20 and the cylindrical body 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, or a low dielectric constant insulating material such as 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 antenna 40, and a hollow portion 432 that is disposed with a space 433 placed on the outer periphery of the upper portion of the antenna 40. The solid portion 431 holds the antenna 40 and prevents contact with the lower surface plate 22 of the waveguide 20, and the hollow portion 432 prevents the antenna 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 cylindrical body 31 forms a cylindrical space on the outer periphery on the second end portion 42 side of the antenna 40 so that a gas flow passing through the second end portion 42 can be formed. The cylindrical body 31 is made of a metal block and has a hollow hole 32 penetrating in the vertical direction near the center thereof. The cylindrical body 31 is attached to the waveguide 20 so that the upper end surface 33 thereof is in contact with the outer surface of the lower surface plate 22 of the waveguide 20. Further, the lower end 435 side of the holding member 43 enters the upper portion of the hollow hole 32, and the second end portion 42 side of the antenna 40 and the hollow hole 32 are assembled so as to be coaxial. A cylindrical space is formed between the hollow hole 32 and the antenna 40, and the second end portion 42 is substantially flush with the lower end surface 34 of the cylindrical body 31.

  The cylinder 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 hollow hole 32 and is connected to a gas supply pipe (not shown) so that the processing gas can be supplied to a cylindrical space formed between the hollow hole 32 and the antenna 40. Further, a concave portion 36 for attaching a cooling pipe (not shown) is provided on the side peripheral wall of the cylindrical body 31. The cooling pipe is for cooling the cylindrical body 31 that becomes high temperature due to generation of plasma.

  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 antenna 40 from the upper surface plate 21 to suspend the antenna 40. The fixing tool 44 includes a circular flange portion 441 that is tightly fixed to the upper surface of the base 25 with screws, a support portion 442 that protrudes from the center of the flange portion 441, a holding hole 443 that penetrates the support portion 442 in the vertical direction, And a stop hole 444 provided on the peripheral surface of the support portion 442 and communicating with the holding hole 443.

  The first end 41 of the antenna 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 first end side of the antenna 40 is fixed (suspended) to the fixture 44. When assembling the plasma generating unit 30, the antenna 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. A method of fixing the fixture 44 can be taken. When exchanging the antenna 40, the fixture 44 may be removed from the base 25 and the fixture 44 may be extracted together with the antenna 40.

  In the plasma generating unit 30 configured as described above, in the present embodiment, the first end 41 of the antenna 40 is grounded. Specifically, as schematically shown in FIG. 2, a fixture 44 that suspends and fixes the first end 41 side of the antenna 40 is grounded. The antenna 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 antenna 40 functions as a one-end grounded antenna in which the fixing portion by the fixing tool 44 is the ground point P. The grounding point at the first end 41 may be set as appropriate. For example, the grounding is performed by connecting the first end 41 to the waveguide 20 at a position below the fixing portion by the fixture 44. Points may be formed.

Here, the length L in the direction from the ground point P of the antenna 40 to the second end portion 42 is the wavelength of the microwave propagating through the antenna 40 that has received the microwave μ having the wavelength λ ₀ in the waveguide 20. When selected, a length of 3λ / 4 is selected.

  FIG. 4 is a schematic diagram showing the coupling relationship between the antenna 40 and the microwave propagating through the antenna 40. The antenna 40 grounded at one end is electrically resonated with a length that is an odd multiple of a quarter wavelength of the received microwave. Therefore, in the voltage distribution in the length direction of the antenna 40, that is, in the protruding direction from the ground point P, as shown in FIG. 4, the positions of the ground point P and λ / 2 are zero, and λ / 4 and 3λ / 4. It becomes the maximum curve at the position. Therefore, by setting the length L of the antenna 40 from the ground point P to 3λ / 4, the electric field strength at the second end portion 42 can be increased. Thereby, high energy can be given to the processing gas passing near the second end portion 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 antenna 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 antenna 40 may be set to the length L ′. good.

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

  According to the plasma generation unit PU according to the present embodiment described above, the first end 41 side of the antenna 40 is placed inside the waveguide 20 so as to receive the microwave μ propagating in the waveguide 20. Although introduced, since the first end portion 41 is grounded, an electric field concentration portion is not formed in the antenna 40 in the waveguide 20. Therefore, no glow discharge occurs in the waveguide 20. On the other hand, the second end portion 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 second end portion 42. Therefore, it is possible to reliably generate the plasma on the second end portion 42 side where the plasma should be originally generated. In addition, when the antenna 40 is attached to the waveguide 20, severe adjustment management for avoiding the in-waveguide discharge can be made unnecessary.

  As described above, the plasma generation unit PU and the sterilization apparatus S according to one embodiment of the present invention have been described. However, the present invention is not limited to this, and for example, the following embodiment can be taken.

(1) In the above embodiment, an example in which one antenna 40 is attached to the waveguide 20 has been described. However, a plurality of antennas 40 may be provided in the waveguide 20. 5 and 6 are plan views in plan view schematically showing an example of attachment of a plurality of antennas 40 to a waveguide. FIG. 5A shows an example in which two antennas 40 are arranged near the branch end of the T-branch waveguide 20A. FIG. 5B shows an example in which four antennas 40 are arranged near the branch end of the H branch waveguide 20B.

  FIG. 6 shows an example in which a plurality of antennas 40 are arranged in a linear waveguide 20C. FIG. 6A shows two antennas 40 arranged in parallel to the waveguide 20C, and FIG. Four antennas 40 are arranged in a staggered manner in the waveguide 20C, and FIG. 6C shows an example in which the four antennas 40 are arranged in series in the waveguide 20C. Such an arrangement of the antenna 40 can also be realized by optimizing the width of the waveguide 20, the arrangement pitch of the antenna 40, the wavelength of the microwave, and the like.

(2) In the above-described embodiment, the example in which the cylindrical body 31 arranged on the outer periphery of the antenna 40 is configured from a metal block has been described. In the present invention, since the cylindrical body 31 does not have to be used as an external conductor as in the case of Patent Document 1, the cylindrical body 31 may be made of a non-conductive material.

(3) In the said embodiment, the sterilizer S was illustrated as an example of the workpiece | work processing apparatus 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.

It is a schematic block diagram which shows the sterilizer which concerns on one Embodiment of this invention. It is sectional drawing of a plasma generation part. It is an exploded view of the component of a plasma generation part. It is a schematic diagram which shows the coupling relationship of an antenna and a microwave. It is a top view of the top view which shows typically the example of attachment to the waveguide of several antennas. It is a top view of the top view which shows typically the example of attachment to the waveguide of several antennas.

Explanation of symbols

10 Microwave generator (microwave generator)
20 Waveguide 21 Top plate (first face plate)
22 Bottom plate (second plate)
25 base 30 plasma generating part 31 cylinder 32 hollow hole 35 gas supply hole (gas supply part)
DESCRIPTION OF SYMBOLS 40 Antenna 41 1st end part 42 2nd end part 43 Holding member 44 Fixing tool S Sterilization apparatus (work processing apparatus)
PU plasma generation unit (plasma generator)
T Sterilization chamber W Workpiece

Claims (7)

Microwave generation means for generating microwaves;
A waveguide propagating the microwave;
A plasma generator that applies the energy of the microwave to a predetermined gas, and radiates the gas into a plasma; and
The plasma generator includes a rod-shaped antenna that receives the microwave,
The antenna includes a first end side introduced into the waveguide and a second end side protruding outside the waveguide;
The plasma generating apparatus, wherein the first end is grounded, and the microwave energy is applied to the gas at the second end. When the wavelength of the microwave propagating through the antenna is λ,
2. The length from the ground point of the antenna toward the second end portion is (2n−1) λ / 4 (where n is an integer) or a length in the vicinity thereof. The plasma generator described in 1. The plasma generator is
The antenna, wherein the first end side passes through the inside of the waveguide, and the second end side protrudes to the outside of the waveguide;
A cylindrical body spaced apart around the second end of the antenna;
A plasma supply nozzle comprising: a gas supply unit that supplies the gas between the second end side of the antenna and the cylindrical body;
The plasma generating apparatus according to claim 1, wherein a plasma gas is discharged from a tip portion of the plasma generating nozzle. The waveguide is a waveguide having a rectangular cross section, and includes a first face plate and a second face plate facing each other,
The first end side of the antenna penetrates the inside of the waveguide and is arranged so as to penetrate the first face plate and the tip protrudes to the outside. The second end side of the antenna is , Disposed so as to protrude through the second face plate to the outside by a predetermined length,
The apparatus further comprises a fixture that holds the protrusion of the antenna from the first face plate and suspends the antenna without substantially contacting the first face plate and the second face plate. Item 4. The plasma generator according to Item 3. The fixture is made of a conductive member, and the holding portion by the fixture is a grounding point of the antenna,
When the wavelength of the microwave propagating through the antenna is λ,
The length in the second end direction from the ground point of the antenna is (2n-1) λ / 4 (where n is an integer) or a length in the vicinity thereof. 5. The plasma generator according to 4. A plasma generator according to any one of claims 1 to 5;
A workpiece processing section for processing a workpiece with the plasmaized gas generated in the plasma generating section;
A work processing apparatus comprising:   The work processing apparatus according to claim 6, wherein the work processing unit includes a sterilization chamber into which a plasma gas is introduced.

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