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Microwave plasma treatment apparatus NEW コモンズ

外国特許コード F180009577
整理番号 2017000348
掲載日 2018年11月5日
出願国 欧州特許庁(EPO)
出願番号 16755415
公報番号 3264866
出願日 平成28年2月22日(2016.2.22)
公報発行日 平成30年1月3日(2018.1.3)
国際出願番号 JP2016055064
国際公開番号 WO2016136669
国際出願日 平成28年2月22日(2016.2.22)
国際公開日 平成28年9月1日(2016.9.1)
優先権データ
  • 特願2015-038677 (2015.2.27) JP
  • 2016JP55064 (2016.2.22) WO
発明の名称 (英語) Microwave plasma treatment apparatus NEW コモンズ
発明の概要(英語) [Problem] To provide a microwave plasma treatment apparatus that is not provided with complicated, long gas flow paths inside a dielectric substrate, to stabilize generation and retention of a plasma, and can generate a highly uniform, high-density, stable low-temperature plasma not only at low atmospheric pressures but also at middle atmospheric pressures and high atmospheric pressures.
[Solution] In a micro plasma treatment apparatus including a dielectric substrate, a microwave introducing section, a microstrip line, an earth conductor, a gas inlet, a plasma generating section, and a nozzle for blowing out a plasma, the gas inlet is provided at the earth conductor or the microstrip line, and the gas inlet is provided with a diameter preferably smaller than a cut-off wavelength determined depending on a cross-section of the gas inlet, to prevent leakage of a microwave.
従来技術、競合技術の概要(英語) Background Art
In recent years, plasma treatment techniques have become indispensable in many fields of materials development and production technology.Plasma can generate high density radicals while keeping a high non-thermal equilibrium.Therefore, plasma is widely used in low temperature dry process technology.
Plasma jet is used as one of plasma sources at low atmospheric pressures (1 torr or lower) and pressures between middle atmospheric pressures (from 1 torr through 100 torr) and the atmospheric pressure.Plasma jet is a plasma blown out from a nozzle of an apparatus.Therefore, plasma jet is useful for applying CVD (chemical vapor deposition), etching, ashing, (resist ashing treatment), plasma nitriding and treatments such as air cleaning and sterilization/disinfection to a treatment target substrate such as a wafer using a plasma.
Currently, for generating a plasma jet, a method using a direct-current arc discharge or a direct-current pulse discharge is well-known.However, the method using a direct-current arc discharge or a direct-current pulse discharge has various problems such as that electrodes easily deteriorate and that reactive gases cannot be used.
Further, a method using a dielectric barrier discharge is well-known.However, the method using a dielectric barrier discharge has various problems such as that a filament-shaped discharge is generated and that high density radicals cannot be generated.
Furthermore, an electrodeless plasma jet generating apparatus is also known.For example, there has been proposed an inductive-coupling thermal plasma generating apparatus using a high frequency in a VHF band (from 30 MHz through 300 MHz) (see PTL 1).However, the proposed plasma jet generating apparatus has complicated impedance matching, cannot be upsized due to a structural problem, and has various limitations and problems in the production and operation of the apparatus because the apparatus uses a high-voltage electric circuit.
Meanwhile, there are the following advantages in the generation of a plasma jet using a microwave.
(1) A microwave power source is inexpensive.
(2) Electrodeless operation is possible and a life duration for which a discharge is retained is long.
(3) Impedance matching is possible with simple elements.
(4) Efficiency of coupling between a microwave and a plasma is good.
(5) Radiation loss to the outside is low, and power can be concentrated to where it is needed.
(6) A stable, high-density plasma is generated in a wide pressure range including the atmospheric pressure.

However, an existing plasma generating apparatus using a microwave power uses a waveguide, which is a metal tube, as a microwave transmission line, and has problems such as that the microwave transmission circuit is structurally large and expensive, and that operation at a low power is difficult.
Recently, there have been proposed methods for producing a plasma jet generating apparatus using a microstrip line, which is a low-power microwave transmission line, instead of the existing waveguide (see PTLs 2 and 3 and NPLs 1 and 2).
FIG. 15 illustrates a perspective view of an example of an existing plasma jet generating apparatus using a microstrip line.This apparatus includes: a microwave introducing section 13 provided on a cross-section at one end of a dielectric substrate 1; a taper section 14 formed toward the other end of the dielectric substrate 1; gas flow paths 23 formed inside the dielectric substrate 1; a microstrip line 11 for microwave power transmission provided on one surface of the dielectric substrate 1; an earth conductor 12 covering the other surface of the dielectric substrate 1; a plasma generating section 25 provided between the microstrip line 11 and the earth conductor 12; and a nozzle 24 configured to discharge a plasma.
In the plasma get generating apparatus, gases are introduced from two gas inlets 22 and 22 provided on the side surfaces of the dielectric substrate 1, pass through the gas flow paths 23 and 23, and merge at the plasma generating section 25, to be blown out from the nozzle 24 having a width of 10 mm to the outside of the dielectric substrate 1.
A microwave (2.45 GHz) power is introduced into the dielectric substrate 1 through a coaxial microwave connect 31, propagates between the microstrip line 11 and the earth conductor 12, and concentrates to the plasma generating section 25.As a result, a plasma is generated and blown out to the outside of the dielectric substrate 1 from the nozzle 24 together with the gas flow.
Meanwhile, in order to improve productivity in the plasma processes, development of a plasma jet having a wide width and capable of applying plasma treatment to a large area is strongly demanded.Structurally, it is possible to upsize the plasma generating apparatus using a microstrip line described above, by arraying microstrip lines based on their shared use of, for example, the dielectric substrate and the earth conductor (see PTL 2).Therefore, future prospects are expected for the apparatus.
Citation List
Patent Literature
PTL 1: Japanese Patent Application Laid-Open (JP-A) No. 2003-109795
PTL 2: JP-A No. 2007-299720
PTL 3: JP-A No. 2008-282784

Non-Patent Literature
NPL 1: Susanne Schemer, et. al., "An improved microstrip plasma for optical emission spectrometry of gaseous species", Spectrochimica Acta Part B: Atomic Spectroscopy, Vol. 56, pp. 1585-1596 (2003).
NPL 2: Jaeho Kim, et. al., "Microwave-excited atmospheric-pressure plasma jets using a microstrip line", Applied Physics Letters, Vol. 93, 191505 (2008).

特許請求の範囲(英語) [claim1]
1. A microwave plasma treatment apparatus, comprising:
a dielectric substrate;
a microstrip line provided from one end to the other end of a first surface of the dielectric substrate, the first surface being any one of a front surface and a back surface of the dielectric substrate;
an earth conductor provided from one end to the other end of a second surface of the dielectric substrate opposite to the first surface;
a microwave introducing section provided at one end of the dielectric substrate and configured to introduce a microwave to between the microstrip line and the earth conductor;
a plasma generating section that is a space in which a plasma is generated by the microwave introduced from the microwave introducing section, and is a space provided between the microstrip line and the earth conductor;
a gas inlet provided at the earth conductor or the microstrip line and configured to supply a gas to the plasma generating section; and
a nozzle configured to discharge the plasma generated by the gas supplied to the plasma generating section and the microwave from the other end of the dielectric substrate.
[claim2]
2. The microwave plasma treatment apparatus according to claim 1,
wherein a diameter of the gas inlet is smaller than a cut-off wavelength determined depending on a cross-section of the gas inlet.
[claim3]
3. The microwave plasma treatment apparatus according to claim 1 or 2,
wherein the first surface or the second surface of the dielectric substrate is provided with a groove in which the microstrip line or the earth conductor is embedded.
[claim4]
4. The microwave plasma treatment apparatus according to any one of claims 1 to 3,
wherein the dielectric substrate comprises a taper section having a shape gradually decreasing in thickness toward the other end of the dielectric substrate.
[claim5]
5. The microwave plasma treatment apparatus according to any one of claims 1 to 4,
wherein the earth conductor or the microstrip line is provided with 2 or more gas inlets to which gases of different kinds are supplied, to vary a plasma discharge characteristic or a plasma treatment characteristic.
[claim6]
6. The microwave plasma treatment apparatus according to claim 5,
wherein the earth conductor or the microstrip line is provided with 2 or more gas inlets, any one of which is provided with a liquid material vaporizing/supplying unit.
[claim7]
7. The microwave plasma treatment apparatus according to any one of claims 1 to 6, comprising:
a second dielectric substrate provided in contact with a surface of the dielectric substrate provided with the microstrip line;
a second earth conductor provided from one end to the other end of the second dielectric substrate;
a second plasma generating section that is a space provided between the microstrip line and the second earth conductor;
a second gas inlet provided at the second earth conductor to supply a gas to the second plasma generating section;
a second gas supplying unit provided to supply a gas to the second gas inlet; and
a second nozzle configured to discharge a plasma generated by the gas supplied to the second plasma generating section and a microwave from the other end of the second dielectric substrate.
[claim8]
8. A microwave plasma treatment apparatus, comprising:
a plurality of microwave plasma apparatuses,
wherein each of the plurality of microwave plasma apparatuses is the microwave plasma apparatus according to any one of claims 1 to 7,
wherein the plurality of microwave plasma apparatuses are configured to be arranged side by side based on shared use of the dielectric substrate and the earth conductor, to generate a long, elongate plasma.
[claim9]
9. The microwave plasma treatment apparatus according to any one of claims 1 to 8,
wherein the microwave plasma treatment apparatus is configured to be supplied with a rare gas, or a reactive gas, or a mixture gas of a rare gas and a reactive gas to generate a plasma at a low atmospheric pressure, or a middle atmospheric pressure, or a high atmospheric pressure.
  • 出願人(英語)
  • NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE AND TECHNOLOGY
  • 発明者(英語)
  • KIM JAEHO
  • SAKAKITA HAJIME
国際特許分類(IPC)
指定国 Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
参考情報 (研究プロジェクト等) Innovative Plasma Processing Group, AIST

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