Plasma generating unit, plasma processing apparatus, and plasma generating method

Abstract

A plasma generating unit, a plasma processing apparatus, and a plasma generating method are provided that are capable of improving the degree of freedom in the shape of a plasma generating surface. [Solution] The plasma generating unit U includes a dielectric 4 into which the tip of an inner conductor 30 of a coaxial tube 3 that transmits microwaves output from a microwave output section 1 is inserted, and generates a plasma wave by the microwaves transmitted by the coaxial tube 3. The dielectric 4 has a shape and dimensions that allow a standing wave to be generated inside as the microwaves of a predetermined wavelength output from the microwave output section 1 propagate inside, and the generated standing wave generates plasma on the surface of the dielectric 4.

Description

[Technical field]

[0001] The present application discloses a plasma generating unit for generating plasma, a plasma processing apparatus including such a plasma generating unit, and a plasma generating method using such a plasma processing apparatus. [Background technology]

[0002] Plasma processing apparatuses are used that perform plasma processing on a processing object using microwaves. For example, the inventors of the present application have proposed in Patent Document 1 a technology for generating surface wave excited plasma, which generates high density plasma in a reactor for generating surface waves, has a high processing speed, and is suitable for processing a large area. The method for generating surface wave excited plasma proposed in Patent Document 1 has a structure in which a reactor having a slot antenna in a waveguide is provided with a quartz dielectric between the reduced pressure side, and plasma is generated on the surface of the reactor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-348898 A Summary of the Invention [Problem to be solved by the invention]

[0004] As proposed in Patent Document 1, in technical fields such as surface treatment of processing objects, there is a demand for technology that improves the degree of freedom in the shape of the plasma generation surface, such as by expanding the plasma generation area.

[0005] The present application has been made in consideration of the above circumstances, and its main purpose is to disclose a plasma generating unit that can improve the freedom of shape of the plasma generating surface by propagating microwaves as standing waves within a dielectric.

[0006] Another object of the present invention is to provide a plasma processing apparatus and a plasma generating method using such a plasma generating unit. [Means for solving the problem]

[0007] In order to solve the above problems, the plasma generating unit disclosed in the present application is a plasma generating unit that includes a dielectric into which the tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output section is inserted, and generates plasma by the microwaves transmitted by the coaxial tube, wherein the dielectric is formed in a shape and dimensions that generate standing waves inside the dielectric as microwaves of a predetermined wavelength output from the microwave output section propagate therethrough, and the generated standing waves generate plasma on the surface of the dielectric.

[0008] In the plasma generating unit, the inner conductor is inserted so that a tip thereof is positioned at a node of a standing wave generated in the dielectric.

[0009] In the plasma generating unit, the dielectric body has a rectangular parallelepiped shape, and the inner conductor is inserted so as to be parallel to the shortest side of the dielectric body.

[0010] In addition, in the plasma generating unit, the rectangular parallelepiped dielectric is characterized in that the lengths of the long and short sides of the surface into which the tip of the inner conductor is inserted are N times (N is a natural number greater than or equal to 2) the half wavelength of the microwave propagating inside.

[0011] In addition, in the plasma generating unit, the dielectric is formed using alumina having a length in the insertion direction of the inner conductor of 17 to 19 mm or quartz glass having a length in the insertion direction of the inner conductor of 30 to 32 mm, and the metal casing has a cooling surface that contacts the dielectric and cools the dielectric in contact with it.

[0012] In the plasma generating unit, the dielectric body has a rectangular parallelepiped shape, and the inner conductor is inserted so as to be parallel to the longest side of the dielectric body.

[0013] The plasma generating unit is characterized in that a plurality of the dielectric bodies are arranged with gaps therebetween.

[0014] The plasma generating unit is also characterized in that it has a metal housing that covers the dielectric body and has a plurality of openings formed therein.

[0015] Furthermore, the plasma processing apparatus disclosed in the present application comprises the plasma generating unit, the plasma generating unit having a metal casing that covers the dielectric and has a portion that is open, and further comprising a processing chamber that contains the dielectric covered by the metal casing, and is characterized in that surface wave plasma is generated by radiating microwaves from the opening of the metal casing into the processing chamber, the pressure of which has been reduced to 30 to 300 Pa.

[0016] The plasma processing apparatus further comprises the plasma generating unit, the plasma generating unit having a metal casing that covers the dielectric and has a portion that is open, and further comprising a processing chamber that contains the dielectric covered by the metal casing, and is characterized in that volume wave plasma is generated by radiating microwaves from the opening of the metal casing into the processing chamber, the pressure of which is reduced to 20 Pa or less.

[0017] The plasma processing apparatus is also characterized in that it is designed so that the minimum value of the voltage standing wave ratio as viewed from the inner conductor into which the microwaves are introduced is 1.5 or less.

[0018] Furthermore, the plasma generation method disclosed in the present application is a plasma generation method that uses a microwave output unit that outputs microwaves of a predetermined wavelength, a coaxial tube that transmits the microwaves output from the microwave output unit, and a dielectric into which the tip of an inner conductor of the coaxial tube is inserted, and generates plasma by the microwaves transmitted by the coaxial tube, wherein the microwaves of the predetermined wavelength output from the microwave output unit propagate through the dielectric, generating standing waves within the dielectric, and the generated standing waves generate plasma on the surface of the dielectric. Effect of the Invention

[0019] The plasma generating unit and the like disclosed herein generate standing waves that propagate through a dielectric body using microwaves, and thus the plasma generating unit and the like disclosed herein exhibit excellent effects, such as improving the degree of freedom in designing the plasma generating surface, for example, by enlarging the plasma generation area. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic diagram illustrating an example of a plasma processing apparatus disclosed herein; [Diagram 2] 2 is a schematic cross-sectional view showing an enlarged schematic view of a portion of the plasma generating unit disclosed in the present application. [Diagram 3] 1 is a schematic perspective view showing an example of the structure of a dielectric and a peripheral portion provided in a plasma generating unit disclosed in the present application; [Figure 4] 1 is a schematic perspective view showing an example of the structure of a dielectric and a peripheral portion provided in a plasma generating unit disclosed in the present application; [Diagram 5] FIG. 1 is a perspective view conceptually illustrating an example of the behavior of microwaves. [Figure 6] FIG. 1 is a perspective view conceptually illustrating an example of the behavior of microwaves. [Figure 7] 1 is a cross-sectional view showing a schematic example of a structure of a dielectric and a peripheral portion provided in a plasma generating unit disclosed in the present application. [Figure 8]1 is an explanatory diagram illustrating an example of a relationship between an inner conductor, a dielectric, and a standing wave provided in a plasma generating unit disclosed in the present application. FIG. [Figure 9] FIG. 4 is an explanatory diagram showing some of the conditions for a simulation of the plasma generating unit disclosed herein. [Figure 10] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 11] FIG. 4 is an explanatory diagram showing some of the conditions for a simulation of the plasma generating unit disclosed herein. [Figure 12] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 13] FIG. 4 is an explanatory diagram showing some of the conditions for a simulation of the plasma generating unit disclosed herein. [Figure 14] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 15] 13 is an example of a simulation result of the electric field strength in the dielectric 4 in the plasma generating unit disclosed in the present application. [Figure 16] FIG. 4 is an explanatory diagram showing some of the conditions for a simulation of the plasma generating unit disclosed herein. [Figure 17] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 18] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 19] FIG. 2 is an explanatory diagram showing an example of simulation conditions for the plasma generating unit disclosed in the present application. [Figure 20] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 21] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 22]13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 23] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 24] FIG. 4 is an explanatory diagram showing some of the conditions for a simulation of the plasma generating unit disclosed herein. [Diagram 25] 13 is an example of a simulation result of the electric field strength in a dielectric material in the plasma generating unit disclosed in the present application. [Figure 26] 1 is a graph showing an example of the relationship between the number of teeth and the voltage standing wave ratio (VSWR) for a standing wave in a dielectric in a plasma generating unit disclosed in the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment will be described with reference to the drawings. The plasma generating unit disclosed in the present application is a system that generates plasma by microwaves. The plasma generating unit performs processing such as surface treatment of a processing object by irradiating the generated plasma to the processing object. Below, a plasma processing apparatus E including a plasma generating unit U shown in the drawings will be described with reference to the drawings.

[0022] 1 is a schematic diagram showing an example of a plasma processing apparatus E disclosed in the present application. The plasma processing apparatus E includes a plasma generating unit U, which irradiates a processing object W with plasma to perform various surface treatments such as reduction treatment, addition of hydroxyl groups, ashing, etc., as well as plasma CVD, etching, and addition of water-repellent groups.

[0023] The plasma processing apparatus E includes a microwave output unit 1 that outputs microwaves, and a waveguide 2 that transmits the microwaves output from the microwave output unit 1 to a plasma generating unit U. The plasma generating unit U includes a coaxial tube 3, a dielectric 4, and other components. The plasma processing apparatus E also includes a processing chamber 5 that performs various processes using the plasma generated in the plasma generating unit U. The microwave output unit 1 includes a power source and an oscillator such as a magnetron that generates microwaves using power applied from the power source, and outputs the microwaves oscillated by the oscillator. The waveguide 2 is a transmission medium that transmits the microwaves output from the microwave output unit 1 to the plasma generating unit U. The coaxial tube 3 is connected to the waveguide 2, and functions as an antenna that transmits the microwaves into the dielectric 4 through the internal conductor 30 contained therein and outputs the microwaves in the dielectric 4. The dielectric 4 is formed in a shape such as a rectangular parallelepiped, and is covered by a metal housing 40. A part of the bottom surface of the metal housing 40 is opened as an opening 400. Furthermore, the tip of the inner conductor 30 is inserted into the dielectric 4 as an antenna.

[0024] A transport conveyor 50 for transporting the processing object W is disposed in the processing chamber 5. A carry-in gate 51 that opens and closes to transport the processing object W to the transport conveyor 50 is provided on the wall of the processing chamber 5, and a carry-in conveyor 52 that passes the processing object W to the transport conveyor 50 through the carry-in gate 51 is provided outside the processing chamber 5. A carry-out gate 53 that opens and closes to transport the processing object W from the transport conveyor 50 is provided on the wall of the processing chamber 5 at a position opposite to the carry-in gate 51, and a carry-out conveyor 54 that receives and transports the processing object W passed from the transport conveyor 50 is provided outside the processing chamber 5. A gas supply unit 55 that supplies a processing gas for generating plasma into the processing chamber 5, and a gas exhaust unit 57 that is connected to a pressure reduction unit 56 such as a vacuum pump to exhaust gas from the processing chamber 5 are provided in the processing chamber 5. From the gas supply unit 55, a gas containing oxygen, hydrogen, argon, nitrogen, carbon fluoride, water vapor, or a mixture of these gases as a main component is supplied as a process gas.

[0025] FIG. 2 is a schematic cross-sectional view showing an enlarged portion of the plasma generating unit U disclosed herein. FIG. 3 is a schematic perspective view showing an example of the structure of the dielectric 4 and the surrounding part of the plasma generating unit U disclosed herein. FIG. 4 is a schematic perspective view showing an example of the structure of the dielectric 4 and the surrounding part of the plasma generating unit U disclosed herein. FIG. 2 shows an enlarged view of the tip of the inner conductor 30 of the coaxial tube 3 included in the plasma generating unit U included in the plasma processing device E illustrated in FIG. 1. FIG. 3 illustrates the dielectric 4 and the coaxial tube 3 included in the plasma generating unit U. FIG. 4 illustrates the dielectric 4, the metal housing 40, and the coaxial tube 3 included in the plasma generating unit U.

[0026] The dielectric 4 and its surrounding configuration will be further described with reference to Figures 1 to 4. The dielectric 4 is formed into a shape such as a rectangular parallelepiped, into which the tip of the inner conductor 30 of the coaxial tube 3 is inserted. The dielectric 4 is formed into a rectangular parallelepiped shape, the shortest in the thickness (height) direction (t direction), and the upper surface is rectangular, square, or the like in plan view. The dielectric 4 is formed using a material such as alumina with a dielectric constant of about 9.6, or quartz glass with a dielectric constant of about 3.6.

[0027] The inner conductor 30 of the coaxial tube 3 is formed in a tapered shape with an outer diameter that gradually decreases toward the tip side. The inner conductor 30 is inserted to a depth such that the tip is located at about 1 / 2 the position in the thickness direction from the upper surface of the dielectric 4. In the plasma processing apparatus E, the lower surface of the dielectric 4 becomes a reduced pressure space V by discharging gas from the processing chamber 5. In the embodiment illustrated in FIG. 1 to FIG. 4, the inner conductor 30 of the coaxial tube 3 is inserted at the position of the center of gravity of the upper surface of the dielectric 4. As will be described later, the plasma processing apparatus E disclosed in the present application may be inserted at a position other than the center of gravity of the upper surface as long as the tip of the inner conductor 30 is located at the node position of the standing wave generated inside the dielectric 4.

[0028] The metal housing 40 is formed using a material such as aluminum. The outer shape of the metal housing 40 is formed in a substantially rectangular parallelepiped shape, and the inner shape is formed in a shape that closely fits along the outer shape of the dielectric 4, covering the dielectric 4. A part or the whole of the lower surface of the metal housing 40 is opened as an opening 400, and the lower surface of the dielectric 4 is exposed. The metal housing 40 has a supply port 401 and an exhaust port 402 for a cooling medium such as water formed on the upper surface, and a circulation path (not shown) that circulates the cooling medium supplied from the supply port 401 and exhausts it from the exhaust port 402 is formed inside the upper surface. In the dielectric 4 covered by such a metal housing 40, the upper surface that closely fits the inner top surface of the metal housing 40 functions as a cooling surface, and the lower surface functions as a plasma generating surface.

[0029] 5 and 6 are perspective views conceptually showing an example of the behavior of microwaves. FIG. 5 and FIG. 6 are quoted from “FIG. 3: Electromagnetic field distribution in a rectangular parallelepiped cavity (single mode)” and “FIG. 4: Electromagnetic field distribution in a multimode cavity (1 / 2 position in the height direction)” shown in “Summary: Historical background of research and development of microwave application to material processing” by Hideoki Fukushima, edited by the Editorial Committee for Latest Microwave Energy and Application Technology, published by Industrial Technology Service Center Co., Ltd., November 26, 2014, pp. 331-338. The plasma processing apparatus E disclosed in the present application outputs microwaves generated by a microwave output unit 1. The microwaves are output from the tip of the inner conductor 30 of the coaxial tube 3 via the waveguide 2, propagate through the dielectric 4, and become a single-mode or multimode standing wave. FIG. 5 and FIG. 6 conceptually show a standing wave generated in the dielectric 4 formed in a rectangular parallelepiped shape in a plan view. In the present application, the behavior illustrated in Fig. 5 is described as a single-mode standing wave, and the behavior illustrated in Fig. 6 is described as a multi-mode standing wave. When a dielectric 4 having an inclined surface, rather than a rectangular parallelepiped shape, is used, the microwaves undergo diffuse reflection inside, and therefore do not form standing waves aligned vertically and horizontally as illustrated in Fig. 5 and Fig. 6. When a dielectric 4 having a curved surface, such as a circle, is used, the microwaves do not form standing waves aligned vertically and horizontally.

[0030] FIG. 7 is a cross-sectional view showing an example of the structure of the dielectric 4 and the surrounding area of ​​the plasma generating unit U disclosed in the present application. FIG. 7 shows the behavior of microwaves in the dielectric 4 and plasma generated by the microwaves. As shown in FIG. 7, the insertion position of the tip of the inner conductor 30 inserted into the dielectric 4 is set at or near the node of a single-mode or multi-mode standing wave formed by the microwaves in the dielectric 4. By setting the insertion position of the tip of the inner conductor 30 in this manner, the microwaves propagate efficiently from the tip of the inner conductor 30 into the dielectric 4 to become a standing wave. The standing wave formed in the dielectric 4 forms plasma such as surface wave plasma or volume wave plasma on the lower surface (plasma surface) of the dielectric 4. By propagating the microwaves into the dielectric 4 to form a standing wave, the degree of freedom in designing the plasma generation surface of the dielectric 4 can be improved, and for example, the area of ​​the plasma generation surface can be expanded. In addition, the electric field intensity of the plasma surface acts in a uniform direction for plasma generation surfaces designed in various shapes, making it possible to aim for the formation of homogeneous plasma.

[0031] A description will be given of design examples of the shape of the dielectric 4 and the microwave wavelength to form the standing waves shown in Fig. 5 to Fig. 7. In the following description, the thickness of the dielectric 4 is defined as t, the short side of the rectangular top surface into which the inner conductor 30 is inserted as a, and the long side as b (see Fig. 4). The wavelength in a vacuum is defined as λ0, the wavelength in the dielectric 4 as λd, and the dielectric constant as ε.

[0032] When alumina having a dielectric constant ε=9.6 is used as the dielectric 4, the wavelength λd of the microwave (2.45 GHz) in the dielectric 4 is calculated as λd=39.3 mm using the following formula (1) assuming that λ0=122 mm.

[0033] λd=λ0 / (ε^1 / 2) Equation (1)

[0034] Moreover, the thickness t is preferably about 1 / 2 the microwave wavelength in the dielectric 4 in order to set it as the minimum thickness necessary for microwaves to propagate and form a standing wave. From λd=39.3 mm calculated using the above formula (1), the optimum value for thickness t is 17 mm to 19 mm. Note that, since the inner conductor 30 is inserted so that its tip is located at a position 1 / 2 the thickness t of the dielectric 4, the insertion depth of the inner conductor 30 is about 9 mm.

[0035] Similarly, when quartz glass with a dielectric constant ε=3.8 is used as the dielectric 4, λd=62.6 mm and t=30 mm to 32 mm. If the thickness t is equal to or greater than the wavelength of the microwave, irregular reflection occurs inside, and standing waves aligned vertically and horizontally are not formed. The insertion depth of the inner conductor 30 is about 15 mm.

[0036] The short side a and long side b of the rectangle constituting the upper surface of the dielectric 4 into which the tip of the inner conductor 30 is inserted are designed to be N times (N is a natural number) the 1 / 2 wavelength (λd / 2) of the microwave in the dielectric 4. That is, the microwave output section 1 outputs microwaves having a wavelength such that the short side a and long side b of the dielectric 4 are N times the 1 / 2 wavelength in the dielectric 4, whereby the plasma generating unit U can form a standing wave in the dielectric 4. For example, when the microwave is 2.45 GHz and alumina is used as the dielectric 4, the short side a and long side b are designed to be approximately 39 mm, 78 mm, 117 mm, 156 mm, and so on.

[0037] Similarly, when quartz glass is used as the dielectric 4, the short side a and long side b of the dielectric 4 are designed to be 62 mm, 124 mm, 186 mm, 248 mm, . . .

[0038] FIG. 8 is an explanatory diagram showing an example of the relationship between the inner conductor 30, the dielectric 4, and the standing wave included in the plasma generating unit U disclosed in the present application. FIG. 8 shows the outline of the standing wave and the position of the inner conductor 30 when the lengths of the short side a and long side b of the alumina dielectric 4 are 39 mm, 78 mm, 117 mm, and 156 mm. The positions of the inner conductor 30 when the lengths of the short side a (or long side b) are 39 mm, 78 mm, 117 mm, and 156 mm are 30A, 30B, 30C, and 30D, respectively. As illustrated in FIG. 8, the plasma generating unit U disclosed in the present application is designed so that the tip of the inner conductor 30 is located at a node of the standing wave. Note that FIG. 8 illustrates a series of examples in which the tip of the inner conductor 30 is located at a node of the standing wave formed in the center of the dielectric 4, but the tip of the inner conductor 30 may be located at a node off the center as long as it is a node of the standing wave.

[0039] A plasma generating method using the plasma processing apparatus E disclosed in the present application and configured as described above will be described with reference to Figures 1 to 7. First, the processing object W is carried into the processing chamber 5 of the plasma processing apparatus E on the transport conveyor 50 by the carry-in conveyor 52. After the processing object W is carried in, the carry-in gate 51 and the carry-out gate 53 are closed to seal the processing chamber 5. Next, the gas in the processing chamber 5 is sucked in through the gas exhaust part 57 by the pressure reducing part 56, and the processing chamber 5 is put into a reduced pressure state.

[0040] After the pressure inside the processing chamber 5 is reduced, a gas containing oxygen, hydrogen, argon, nitrogen, carbon fluoride, water vapor, or a mixture of these gases as its main components is supplied into the processing chamber 5 from the gas supply unit 55 as a processing gas.

[0041] After the processing chamber 5 is filled with the processing gas, the microwave output unit 1 outputs an oscillated microwave. The microwave output from the microwave output unit 1 is transmitted through the waveguide 2 and sent to the coaxial tube 3. The microwave is transmitted from the tip of the inner conductor 30 in the coaxial tube 3 to the dielectric 4, and forms a single-mode or aligned multi-mode standing wave spreading in the dielectric 4.

[0042] For example, when the plasma generating unit U generates surface wave plasma, the inside of the processing chamber 5 is depressurized to about 30 to 300 Pa. In the plasma generating unit U, the part with the highest electric field strength is converted into plasma, which becomes surface wave plasma. When the electron density of the plasma part becomes high density, the part cannot receive any more microwave power, so the plasma spreads and becomes surface wave plasma, resulting in homogenized plasma as a whole. In particular, the plasma generating unit U disclosed in the present application generates surface wave plasma by a standing wave generated in the dielectric 4, and therefore homogenized plasma is easily generated.

[0043] Furthermore, for example, when the plasma generating unit U generates volume wave plasma, the inside of the processing chamber 5 is depressurized to about 20 Pa or less. When the inside of the processing chamber 5 is depressurized to 20 Pa or less, plasma generated by a standing wave generated in the dielectric body 4 included in the plasma generating unit U diffuses in the processing chamber 5 and becomes volume wave plasma.

[0044] In the processing chamber 5, the processing object W placed on the transport conveyor 50 is transported by the transport conveyor 50 while being irradiated with plasma such as surface wave plasma or volume wave plasma generated on the lower surface of the dielectric body 4. When the processing object W is transported by the transport conveyor 50, the plasma processing for the processing object W is completed. After the plasma processing is completed, the processing gas is discharged and outside air is supplied, and then the discharge gate 53 opens, and the processing object W is handed over from the transport conveyor 50 to the discharge conveyor 54 and discharged by the discharge conveyor 54.

[0045] In this manner, the plasma processing apparatus E disclosed in the present application uses the plasma generating unit U to carry out the plasma generating method.

[0046] Also, for example, when the plasma generating unit U generates volume wave plasma, the inside of the processing chamber 5 is depressurized to about 20 Pa or less. When the inside of the processing chamber 5 is depressurized to 20 Pa or less, the plasma generated by the standing wave generated in the dielectric 4 provided in the plasma generating unit U diffuses in the processing chamber 5 and becomes volume wave plasma. The plasma generating unit U disclosed in the present application is designed to optimize various dimensions and shapes such as the general dimensions of the dielectric 4 and the dimensions of the opening 400 of the metal housing 40. By optimizing various dimensions and shapes, the plasma generating unit U disclosed in the present application has a small value such as 1.5 or less as the minimum value of VSWR (Voltage Standing Wave Ratio) for the microwave frequency. Also, for example, when the VSWR is 1.5, the reflectance is 4%. Even when generating such a volume wave plasma, the microwaves propagate to the end of the dielectric 4 and become standing waves, making it easier to homogenize the electric field strength on the plasma surface of the dielectric 4 and improving the degree of freedom in the shape of the plasma generation surface that generates plasma, for example, making it possible to increase the area of ​​the generation surface.

[0047] In the case of the volume wave plasma described above, the smaller the reflection at the dielectric 4, the smaller the burden on the isolator, and no matching device is required to return the reflection from the oscillator side of the microwave output unit 1 to the processing chamber 5. This is a particularly effective characteristic when a semiconductor oscillator is used to generate microwaves.

[0048] Next, the shape of the dielectric 4 in the plasma generating unit U disclosed in the present application and the influence of the metal housing 40 covering the dielectric 4 will be described using the results of a simulation. For the simulation, HFSS (High Frequency Structure Simulator) manufactured by Ansys was used. In the following simulations, the conditions are as follows. The dielectric 4 is made of alumina, and has an optimal shape and size for forming a standing wave. For the dielectric 4, similar results have been obtained when quartz glass is used. The conditions of the inner conductor 30 are set so that the position of the tip and the insertion depth are optimal. First, as Simulation Example 1, Simulation Examples 1.1 to 1.3 were performed. In Simulation Example 1 (Examples 1.1 to 1.3), the influence of the metal housing 40 covering the dielectric 4 was confirmed by simulation under the conditions optimized for forming a standing wave as described above for the dielectric 4 and the inner conductor 30. For the electric field strength, the calculation result is obtained when 1 w is input from the coaxial end face, and the maximum electric field strength level shown in dark color is 1000 V / m or 400 V / m. The electric field strength is displayed as the maximum value under the conditions. The following simulation examples are the results of simulating the electric field strength, and the plasma is indirectly estimated from the electric field strength.

[0049] <Simulation example 1.1> FIG. 9 is an explanatory diagram showing some of the conditions of the simulation in the plasma generating unit U disclosed in the present application. FIG. 10 is an example of the simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 9(a) shows a side view of the dielectric 4 defined as a condition, and FIG. 9(b) shows a bottom view of the dielectric 4. Simulation example 1.1 uses a dielectric 4 whose side and bottom are not covered with a metal housing 40 as an experimental condition. In addition, in order to keep the same conditions except that it is not covered with the metal housing 40, it is assumed that the metal housing 40 exists on the upper surface that functions as a cooling surface, and the region corresponding to the metal housing 40 on the side and bottom is defined as a reduced pressure space V and is shown by diagonal lines in the figure. The simulation result of the electric field intensity illustrated in FIG. 10 is a simulation result in which the electric field intensity at a position 2 mm below the lower surface of the dielectric 4 is shown in shades. As illustrated in FIG. 10, the standing wave spreads to a position corresponding to the end in the dielectric 4. When the dielectric 4 is not covered with the metal housing 40, a peak of the electric field intensity appears in the center, but the electric field intensity is low overall.

[0050] <Simulation example 1.2> FIG. 11 is an explanatory diagram showing some of the simulation conditions in the plasma generating unit U disclosed in the present application. FIG. 12 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 11(a) shows a side view of the dielectric 4 defined as a condition, and FIG. 11(b) shows a bottom view of the dielectric 4. In Simulation Example 1.2, the upper and side surfaces of the dielectric 4 are covered with a metal housing 40, but the entire lower surface is used as a plasma surface as shown as an opening 400, as an experimental condition. In addition, in the simulation setting, it is set that the reduced pressure space V is in contact with the opening 400, and is shown by diagonal lines in the figure. In the simulation result of the electric field intensity illustrated in FIG. 12, compared to Simulation Example 1.1, the electric field spreads over the entire dielectric 4, the electric field intensity in the center is strong, and the overall electric field intensity is homogenized.

[0051] <Simulation example 1.3> FIG. 13 is an explanatory diagram showing some of the simulation conditions in the plasma generating unit U of the present disclosure. FIG. 14 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U of the present disclosure. FIG. 13(a) shows a side view of the dielectric 4 defined as a condition, and FIG. 13(b) shows a bottom view of the dielectric 4. Simulation example 1.3 uses a metal housing 40 that covers the upper and side surfaces of the dielectric 4 and has a part of the lower surface open as a plasma surface as shown as an opening 400 as an experimental condition. The open plasma surface of the metal housing 40 in simulation example 1.3 is a narrower area than the plasma surface of the metal housing 40 in simulation example 1.2. In the simulation result of the electric field intensity illustrated in FIG. 14, the area with strong electric field intensity spreads over the entire plasma surface compared to simulation example 1.2.

[0052] From the simulation results of Simulation Example 1 above, the plasma generating unit U disclosed herein makes it possible to control the plasma generation area and electric field intensity by limiting the dimensions of the opening 400 of the metal housing 40, i.e., the dimensions of the plasma generating surface that contacts the reduced pressure space V in the processing chamber 5.

[0053] <Simulation example 2> The plasma generating unit U disclosed in the present application can be developed in various forms without being limited to the above simulation example. Simulation results in other forms are illustrated. FIG. 15 is an example of a simulation result of the electric field strength in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 15(a) shows the electric field strength in the dielectric 4 from a side view, and FIG. 15(b) shows it from a bottom view. Simulation example 2 is an example in which the length is further extended by using a long-sized dielectric 4, and the simulation results of the electric field strength are as shown in FIGS. 15(a) and (b). In simulation example 2, a simulation is performed under the condition that the long-sized dielectric 4 has a short side a=39 mm and a long side b=494 mm, and the results are shown. As illustrated in FIGS. 15(a) and (b), the plasma generating unit U disclosed in the present application can generate homogenized plasma by resonating the standing wave in the dielectric 4, even if the long-sized dielectric 4 is used.

[0054] <Simulation example 3> As shown in Simulation Example 2, the microwave propagates to the end of the long dielectric 4 and becomes a standing wave. Simulation Example 3 is a form in which a plurality of dielectrics 4 are arranged in series while considering the characteristics of such a standing wave. FIG. 16 is an explanatory diagram showing some of the conditions of the simulation in the plasma generating unit U disclosed in the present application. FIG. 17 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 16(a) shows a side view of the dielectric 4 defined as a condition, and FIG. 16(b) shows an enlarged view of a part of the dielectric 4 indicated by the circle in FIG. 16(a). Simulation Example 3 is a form in which a plurality of dielectrics 4 are arranged in series, and the dielectrics 4 are arranged with a gap therebetween as illustrated in FIG. 16. The simulation of Simulation Example 3 is a result in which a gap of 1 mm is opened and the space between them is defined as a reduced pressure space V. Even when multiple dielectrics 4 are arranged with gaps between them, by arranging the dielectrics 4 so that their lengths and nodes are located in the gaps and optimizing the design of the openings 400 in the metal housing 40, microwaves propagate to the tips of both dielectrics 4, resonate as a whole, and form standing waves, as shown in Fig. 17. In tests using an actual device, it was confirmed that operation was possible with a gap of 0.1 mm or less, and that a long plasma generating unit U could be realized by arranging multiple dielectrics 4.

[0055] <Simulation example 4> Simulation example 4 is a form in which a plurality of rectangular parallelepiped dielectrics 4 are arranged so that the propagation direction of the microwaves changes. FIG. 18 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. In simulation example 4 illustrated in FIG. 18, a long rectangular parallelepiped dielectric 4 is arranged at both ends of the other rectangular parallelepiped dielectric 4 so that the long side directions are perpendicular to each other, forming a U-shaped dielectric 4 as a whole. Even if the dielectric 4 has a bent shape as shown in Example 4, it is possible to propagate the microwave to the end and form a standing wave by adjusting the length of the dielectric 4 and the wavelength of the microwave and arranging the dielectric 4 so that the nodes are at the bent positions.

[0056] <Simulation example 5> Simulation example 5 is a form in which the position where the inner conductor 30 of the coaxial tube 3 is inserted is shifted from the center of gravity of the dielectric 4. FIG. 19 is an explanatory diagram showing an example of a simulation condition in the plasma generating unit U disclosed in the present application. FIG. 20 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 19 shows a side view of the dielectric 4 defined as a condition. As illustrated in FIG. 19, in the plasma generating unit U according to simulation example 5, the inner conductor 30 of the coaxial tube 3 is inserted near the end of the dielectric 4. As shown in FIG. 20, even when the inner conductor 30 is inserted near one end, the microwave propagates to the other end and forms a standing wave.

[0057] <Simulation example 6> Simulation example 6 is a form in which the inner conductor 30 of the coaxial tube 3 is inserted from an end of the dielectric 4 along the long side direction in Simulation example 5. FIG. 21 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 21(a) shows the electric field intensity in the dielectric 4 from a side view, and FIG. 21(b) shows the electric field intensity in the dielectric 4 from a bottom view. As shown in FIG. 21, even when the inner conductor 30 is inserted from one end so as to be parallel to the long side direction, microwaves propagate to the other end, forming standing waves.

[0058] <Simulation example 7> Simulation example 7 is a form in which the electric field strength is controlled by the shape of the opening 400 of the metal housing 40. FIG. 22 is an example of a simulation result of the electric field strength in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 22(a) shows the electric field strength in the dielectric 4 from a perspective from below, and FIG. 22(b) shows an enlarged part of FIG. 22(a). The plasma generating unit U according to Simulation example 7 aims to control the electric field strength by the shape of the opening 400 of the metal housing 40 and start the plasma lighting at low power. In the plasma generating unit U, total reflection occurs from the plasma generating unit U until the plasma lighting starts, which puts a strain on the isolator, so a characteristic that a high electric field is generated in a low power state is required. Specifically, as shown in FIG. 22, a small gap is provided at the peak of the standing wave, and the discharge is set to start there first. In a simulation under the conditions of Simulation Example 7 shown in Fig. 22, the plasma generating unit U produces an electric field of 200 V / cm with an input of 50 W, which is sufficient to start a discharge even under a reduced pressure of 100 Pa. In the plasma generating unit U, plasma is generated starting from the part where the discharge starts, and the generated plasma spreads throughout. Even when a gap is provided as shown in Fig. 22, no deterioration in the voltage standing wave ratio (VSWR) was observed.

[0059] <Simulation example 8> Simulation example 8 is a configuration in which a plurality of sets of a coaxial tube 3, a dielectric 4, and a metal housing 40 are arranged side by side. FIG. 23 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 23 is a bottom view of the dielectric 4. By arranging a plurality of plasma generating units U disclosed in the present application side by side, it is possible to generate plasma over a wide range. In the plasma generating unit U illustrated in FIG. 23, standing waves are generated in each of the plurality of dielectrics 4, but mutual interference can be prevented by inserting a metal plate between the dielectrics 4.

[0060] <Simulation Example 9> Simulation example 9 is a form in which a plurality of openings 400 are formed in the metal housing 40. FIG. 24 is an explanatory diagram showing some of the conditions of the simulation in the plasma generating unit U disclosed in the present application. FIG. 25 is an example of a simulation result of the electric field intensity in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 24(a) shows a side view of the dielectric 4 defined as a condition, and FIG. 24(b) shows a bottom view of the dielectric 4. Simulation example 9 is a form in which rectangular openings 400 are formed in four places on the lower surface of the metal housing 40, arranged in a matrix of two columns and two rows. The vertical and horizontal dimensions of each opening 400 are different. Even when a plurality of openings 400 are formed on the lower surface of the metal housing 40, standing waves are formed in the dielectric 4, as exemplified in FIG. 25, and plasma can be generated. The plasma generating unit U shown as simulation example 9 is capable of generating stable plasma that can respond to fluctuations in the wavelength of microwaves by making the plurality of openings 400 different in shape and size.

[0061] <Relationship between frequency and voltage standing wave ratio (VSWR)> Next, the relationship between frequency and VSWR in the plasma generating unit U disclosed in the present application will be described. FIG. 26 is a graph showing an example of the relationship between frequency and voltage standing wave ratio (VSWR) for a standing wave in the dielectric 4 in the plasma generating unit U disclosed in the present application. FIG. 26 shows the relationship between frequency and VSWR when designed to have a minimum value of VSWR of 1.5 or less in a model in which a microwave with a frequency of 2.45 GHz is propagated to form a standing wave in the dielectric 4 of the plasma generating unit U disclosed in the present application, which is exemplified as Simulation Example 9. FIG. 26 shows the relationship between frequency and VSWR, with the frequency of the microwave input to the dielectric 4 on the horizontal axis and VSWR on the vertical axis. By covering the dielectric 4 with a metal housing 40 and limiting the plasma generating surface by making a part of the metal housing 40 an opening 400, it becomes possible to control not only the plasma generating region and the electric field intensity but also the VSWR. In the simulation result shown in FIG. 26, the VSWR is suppressed to about 1.4 in the vicinity of 2.45 GHz. 26, it was confirmed that surface wave plasma was generated with a reflection rate of 18% (VSWR is 2.5) when the pressure in the processing chamber 5 was 120 Pa. It was also confirmed that volume wave plasma was generated with a reflection rate of 3% (VSWR is 1.4) when the pressure in the processing chamber 5 was 20 Pa.

[0062] As described above, in the plasma generating unit U disclosed in the present application, microwaves propagate through the dielectric 4, and the propagated microwaves generate standing waves. As a result, the plasma generating unit U disclosed in the present application has excellent effects, such as being able to construct a system that can improve the degree of freedom in designing the shape of the plasma generation surface, including enlarging the plasma generation area. Furthermore, the plasma generating unit U disclosed in the present application can propagate standing waves even when multiple dielectrics 4 are arranged closely to each other. Therefore, the plasma generating unit U disclosed in the present application has excellent effects, such as being able to generate plasma over a large area by arranging the dielectrics 4.

[0063] The present invention is not limited to the above-described embodiment, and can be implemented in various other forms. Therefore, the above-described embodiment is merely illustrative in all respects and should not be interpreted as being restrictive. The technical scope of the present invention is described by the claims, and is not restricted in any way by the text of the specification. Furthermore, all modifications and changes within the equivalent scope of the claims are within the scope of the present invention.

[0064] For example, in the above embodiment, a form applied to continuous processing in which plasma is irradiated onto the transported processing object W has been shown, but the present invention is not limited to this. Processing target W The present invention can be applied to various applications, such as batch processing in which a substrate is placed on the substrate and exposed to plasma. [Explanation of symbols]

[0065] E Plasma treatment equipment U Plasma Generation Unit W Processing target 1 Microwave output section 2 waveguide 3 coaxial tube 30 Inner conductor 4. Dielectrics 40 Metal case 400 opening 401 Supply port 402 Outlet 5 Processing Room 50 Transport Conveyor 51 Carry-in Gate 52 Incoming conveyor 53 Export Gate 54 Discharge Conveyor 55 Gas Supply Section 56 Pressure reducing section 57 Gas exhaust section V Decompression space

Claims

1. A plasma generating unit comprising a dielectric body into which a tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output unit is inserted, the plasma generating unit generating plasma by the microwaves transmitted by the coaxial tube, the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, the inner conductor is inserted such that a tip thereof is located at a node of a standing wave generated in the dielectric, A plasma is generated on the surface of the dielectric by the generated standing wave. A plasma generating unit characterized by:

2. A plasma generating unit comprising a dielectric body into which a tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output unit is inserted, the plasma generating unit generating plasma by the microwaves transmitted through the coaxial tube, The dielectric body has a rectangular parallelepiped shape, the inner conductor is inserted so as to be parallel to the shortest side of the dielectric; the dielectric body is formed in a shape and size such that a standing wave parallel to a long side or a short side of a surface perpendicular to an insertion direction of the inner conductor is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, A plasma is generated on the surface of the dielectric by the generated standing wave. A plasma generating unit characterized by:

3. A plasma generating unit as claimed in claim 2, The dielectric body having a rectangular parallelepiped shape is The length of the long side and short side of the surface into which the tip of the inner conductor is inserted is N times (N is a natural number of 2 or more) the half wavelength of the microwave propagating inside. A plasma generating unit characterized by:

4. 4. The plasma generating unit according to claim 3, a metal housing covering the dielectric and having a plurality of openings formed on one surface other than the surface into which the inner conductor is inserted; The dielectric material is The length of the inner conductor in the insertion direction is 17 to 19 mm and is formed using alumina or 30 to 32 mm and using quartz glass, The metal housing is A cooling surface is provided in contact with the dielectric material and cools the dielectric material. A plasma generating unit characterized by:

5. A plasma generating unit comprising a dielectric body into which a tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output unit is inserted, the plasma generating unit generating plasma by the microwaves transmitted through the coaxial tube, The dielectric body has a rectangular parallelepiped shape, the inner conductor is inserted so as to be parallel to the longest side of the dielectric; the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, A plasma is generated on the surface of the dielectric by the generated standing wave. A plasma generating unit characterized by:

6. A plasma generating unit comprising a dielectric body into which a tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output unit is inserted, the plasma generating unit generating plasma by the microwaves transmitted through the coaxial tube, The dielectric body is arranged in a plurality of spaces, the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, A plasma is generated on the surface of the dielectric by the generated standing wave. A plasma generating unit characterized by:

7. A plasma generating unit comprising a dielectric body into which a tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output unit is inserted, the plasma generating unit generating plasma by the microwaves transmitted through the coaxial tube, The dielectric body has a rectangular parallelepiped shape, the inner conductor is inserted so as to be parallel to the shortest side of the dielectric; the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, a metal housing covering the dielectric and having a plurality of openings formed on one surface other than the surface into which the inner conductor is inserted; A plasma is generated on the surface of the dielectric material exposed through the opening of the metal housing by the generated standing wave. A plasma generating unit characterized by:

8. A microwave power supply device comprising: a dielectric body into which a tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output unit is inserted; and a plasma generating unit that generates plasma by the microwaves transmitted by the coaxial tube; The plasma generating unit includes: a metal housing that covers the dielectric and has an opening at one end; the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, a processing chamber for accommodating the dielectric body covered with the metal housing; The generated standing wave radiates microwaves from the opening of the metal housing into the processing chamber, the pressure of which has been reduced to 30 to 300 Pa, thereby generating surface wave plasma on the surface of the dielectric.

2. A plasma processing apparatus comprising:

9. A microwave power supply device comprising: a dielectric body into which a tip of an inner conductor of a coaxial tube that transmits microwaves output from a microwave output unit is inserted; and a plasma generating unit that generates plasma by the microwaves transmitted by the coaxial tube; The plasma generating unit includes: a metal housing that covers the dielectric and has an opening at one end; the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, a processing chamber for accommodating the dielectric body covered with the metal housing; The generated standing wave radiates microwaves from the opening of the metal housing into the processing chamber, the pressure of which has been reduced to 20 Pa or less, thereby generating volume wave plasma on the surface of the dielectric material.

2. A plasma processing apparatus comprising:

10. The plasma processing apparatus according to claim 9, It is designed so that the minimum voltage standing wave ratio seen from the inner conductor through which the microwave is introduced is 1.5 or less.

2. A plasma processing apparatus comprising:

11. A plasma generation method using a microwave output unit that outputs a microwave of a predetermined wavelength, a coaxial tube that transmits the microwave output from the microwave output unit, and a dielectric body into which a tip of an inner conductor of the coaxial tube is inserted, the method generating plasma by the microwave transmitted through the coaxial tube, the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, the inner conductor is inserted such that a tip thereof is located at a node of a standing wave generated in the dielectric, A plasma is generated on the surface of the dielectric by the generated standing wave. A method for generating plasma.

12. A method for generating plasma using a microwave output unit which outputs microwaves of a predetermined wavelength, a coaxial tube which transmits the microwaves output from the microwave output unit, and a dielectric body into which a tip of an inner conductor of the coaxial tube is inserted, the method comprising the steps of: The dielectric body has a rectangular parallelepiped shape, the inner conductor is inserted so as to be parallel to the shortest side of the dielectric; the dielectric body is formed in a shape and size such that a standing wave parallel to a long side or a short side of a surface perpendicular to an insertion direction of the inner conductor is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, A plasma is generated on the surface of the dielectric by the generated standing wave. A method for generating plasma.

13. A method for generating plasma using a microwave output unit which outputs microwaves of a predetermined wavelength, a coaxial tube which transmits the microwaves output from the microwave output unit, and a dielectric body into which a tip of an inner conductor of the coaxial tube is inserted, the method comprising the steps of: The dielectric body has a rectangular parallelepiped shape, the inner conductor is inserted so as to be parallel to the longest side of the dielectric; the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, A plasma is generated on the surface of the dielectric by the generated standing wave. A method for generating plasma.

14. A method for generating plasma using a microwave output unit which outputs microwaves of a predetermined wavelength, a coaxial tube which transmits the microwaves output from the microwave output unit, and a dielectric body into which a tip of an inner conductor of the coaxial tube is inserted, the method comprising the steps of: The dielectric body is arranged in a plurality of spaces, the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, A plasma is generated on the surface of the dielectric by the generated standing wave. A method for generating plasma.

15. A method for generating plasma using a microwave output unit which outputs microwaves of a predetermined wavelength, a coaxial tube which transmits the microwaves output from the microwave output unit, and a dielectric body into which a tip of an inner conductor of the coaxial tube is inserted, the method comprising the steps of: The dielectric body has a rectangular parallelepiped shape, the inner conductor is inserted so as to be parallel to the shortest side of the dielectric; the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, The dielectric body is covered with a metal housing, the metal housing has a plurality of openings formed on one surface other than the surface into which the inner conductor is inserted, A plasma is generated on the surface of the dielectric material exposed through the opening of the metal housing by the generated standing wave. A method for generating plasma.

16. A method for generating plasma using a microwave output unit which outputs microwaves of a predetermined wavelength, a coaxial tube which transmits the microwaves output from the microwave output unit, and a dielectric body into which a tip of an inner conductor of the coaxial tube is inserted, the method comprising the steps of: The dielectric body is covered with a metal housing having a part opened, the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, The dielectric body covered with the metal housing is accommodated in a processing chamber, a microwave having a predetermined wavelength output from the microwave output unit propagates through the dielectric, generating a standing wave within the dielectric, The generated standing wave radiates microwaves from the opening of the metal housing into the processing chamber, the pressure of which has been reduced to 30 to 300 Pa, thereby generating plasma on the surface of the dielectric material. A method for generating plasma.

17. A method for generating plasma using a microwave output unit which outputs microwaves of a predetermined wavelength, a coaxial tube which transmits the microwaves output from said microwave output unit, and a dielectric body into which a tip of an inner conductor of said coaxial tube is inserted, said method comprising the steps of: The dielectric body is covered with a metal housing having a part opened, the dielectric body is formed in a shape and size such that a standing wave is generated therein by the microwave of a predetermined wavelength output from the microwave output portion propagating therethrough, The dielectric body covered with the metal housing is accommodated in a processing chamber, a microwave having a predetermined wavelength output from the microwave output unit propagates through the dielectric, generating a standing wave within the dielectric, The generated standing wave radiates microwaves from the opening of the metal housing into the processing chamber, the pressure of which has been reduced to 20 Pa or less, thereby generating volume wave plasma on the surface of the dielectric material. A method for generating plasma.

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