JP7749869B2 - Plasma processing equipment - Google Patents

Description

The present invention relates to an ECR (Electron Cyclotron Resonance) plasma processing apparatus using microwaves.

In recent years, the integration level of semiconductor devices has increased, requiring finer processing, or improved processing accuracy, while also making it more difficult to improve the uniformity of etching rates or the uniformity of critical dimensions (CD) across the wafer surface. Furthermore, the materials being etched have changed from single-layer films to multilayer films, and multi-step etching, in which the etching conditions are changed during the processing of each multilayer film, has become more common. In this case, factors that affect etching uniformity, etc., differ for each step, making it difficult to achieve uniform etching rates and axial symmetry at the completion of etching of each multilayer film.

One of the micro-etching techniques used in the semiconductor field is dry etching, with plasma-based dry etching being particularly common. Plasma uses collisions between electrons and the molecules or atoms of the process gas to excite them, generating ions and radicals. Plasma processing equipment achieves anisotropic etching with ions and isotropic etching with radicals. Electron cyclotron resonance (ECR) is one plasma source. Because ECR can generate high-density plasma, it is used to improve the voltage resistance of DRAM in semiconductor devices and to create high-capacity capacitors.

Figure 8 shows the configuration of a conventional ECR etching apparatus. 2.45 GHz microwaves emitted from a magnetron 72 propagate through an isolator 73, a rectangular waveguide 74, and a three-stub tuner 75 in TE10 mode, before being converted to TE11 mode by a circular-to-rectangular waveguide converter 76. The circular-to-rectangular waveguide converter 76 has a diameter of 90 mm so that the 2.45 GHz microwaves can pass through in the fundamental TE11 mode propagation mode. To generate axially symmetric microwave radiation, a quartz dielectric quarter-wave plate 8 is used to form circular polarization. By rotating the microwaves in the TE11 mode propagation mode over time, the microwave electric field distribution becomes axially symmetric and is radiated into the cavity 6. In order to propagate the microwave as a circularly polarized wave within the circular waveguide 5, the aforementioned quarter-wave plate 8 is inserted into the circular waveguide 5 at an angle of 45 degrees to the plane of polarization of the linearly polarized wave in the TE11 mode.

The circularly polarized microwaves entering the cavity 6 are introduced into the processing chamber 1 through a quartz window 13 and a shower plate 14 located at the top of the processing chamber 1, which is covered by an upper electromagnetic coil 9, a middle electromagnetic coil 10, and a lower electromagnetic coil 11. The electric field generated by the microwaves and the magnetic field formed perpendicular to the electric field cause electron cyclotron motion. When the microwave frequency is 2.45 GHz, electrons perpendicular to the magnetic field are deflected by the Lorentz force, gradually causing the electrons to undergo circular motion. The magnetic flux density B at this time is calculated using the formula fc = eB/2πme (e is the electron charge of 1.6×10 ⁻¹⁹ C, me is the electron mass of 9.1×10 ⁻³¹ Kg, and fc is 2.45 GHz). At 875 G, electron cyclotron resonance occurs, increasing the probability of collisions between electrons and gas molecules in the processing chamber 1. This enables high-density plasma to be generated even at low pressures.

The pressure in the processing chamber 1 is reduced to around 1 Pa during etching by a vacuum pump 17, and high-density plasma of 10 ¹¹ cm ^-3 or higher can be obtained in this pressure range. Furthermore, the RF power supply 16 applied to the substrate stage 15 allows for control of plasma formation and independent ion energy, enabling precise shape control. Furthermore, to improve the in-plane uniformity of the substrate w to be processed, a circularly polarized wave is introduced into the processing chamber 1 using a quarter-wave plate 8.

The axial ratio of the circularly polarized wave generated by the quarter-wave plate 8 of the prior art does not take into account reflection from the processing chamber 1, so when the plasma density in the processing chamber 1 reaches a certain value, a reflected wave is generated from the processing chamber 1. This reflected wave forms a standing wave with the incident wave, which hinders the rotation of the TE11 mode electric field in the circular waveguide 5 and reduces the axial ratio of the circularly polarized wave to be input into the processing chamber 1. The axial ratio is defined as the circularity of the circularly polarized wave, with 1 being the highest circularity.

To perform uniform plasma processing on the substrate w to be processed, the distribution of plasma characteristics such as plasma density and temperature near the substrate w to be processed is, of course, important, and technology to optimize the plasma distribution from the perspective of uniform plasma processing is important.

Plasma processing equipment that generates plasma using microwave power can generate high-density plasma even under low pressure, and when used in conjunction with a static magnetic field, the plasma distribution can be easily controlled by adjusting the static magnetic field distribution. These features make them widely used in the manufacture of semiconductor processing equipment. In response to the trend toward larger substrate diameters mentioned above, controlling the plasma distribution is also important in microwave plasma processing equipment. However, microwave wavelengths are short, ranging from a few centimeters to several dozen centimeters, and the electric field distribution of microwaves on semiconductor substrates with dimensions on the same order as the wavelength is prone to change. Therefore, optimizing the microwave distribution to achieve uniform plasma processing over a wide area presents a challenge.

In plasma sources that generate plasma using microwaves, examples of conventional technology that uses circularly polarized microwaves include the following prior art documents.

JP 2010-192750 A Japanese Patent Application Laid-Open No. 2003-188152 Japanese Patent Application Laid-Open No. 2006-339547

Michael A. Lieberman et. al, “Principles of Plasma Discharges and Materials Processing”John Wiley & Sons, Inc. (2005)

Etching of structural patterns in semiconductor devices, particularly the shape accuracy of gate processing, which governs the operating characteristics of semiconductor devices, and the uniformity of etching rates, are becoming increasingly stringent. To solve the aforementioned issues, numerous distribution control technologies for ECR plasma used in dry etching have been proposed.

In the prior art disclosed in Patent Document 1, a single-mode microwave such as TE10 is transmitted from a rectangular waveguide connected to a magnetron by inserting a 1/4λg waveplate (λg shown here is the wavelength of the electromagnetic wave in a φ90 mm circular waveguide at 2.45 GHz) into a circular waveguide connected to the rectangular waveguide. This creates a rotating TE11 mode electric field within the circular waveguide, which is then radiated into the processing chamber of a plasma processing device, thereby achieving a high etching rate uniformity. However, the phase plate in Patent Document 1 forms a 45° clockwise angle with the primary polarization plane, and can only radiate right-handed electromagnetic waves (hereinafter, right-handed electromagnetic waves will be referred to as R-waves and left-handed electromagnetic waves as L-waves) during the etching process.

As shown in Non-Patent Document 1, in a magnetic field B environment, the electromagnetic energy of R waves is continuously accelerated by the Lorentz force into electrons wrapped around the magnetic field lines, which makes it easier for the microwave energy to be absorbed by the electrons, increasing the electron temperature Te. This causes an electron-shelling effect on the top of fine patterns such as FinFETs in semiconductor device structures. As a result, the ion trajectories incident on the wall surfaces of the fins in the dense and sparse portions of the device pattern on the substrate are bent by the negative electric field of the electron-shelling effect, resulting in the formation of notches of varying degrees at the base of the fins of the FinFET.

In Patent Document 2, a cross slot is used at the connection between the rectangular and circular waveguides to radiate rotational TE11 mode electromagnetic waves into the circular waveguide. However, like Patent Document 1, Patent Document 2 can only radiate either R-waves or L-waves during the plasma processing process. Furthermore, because the dimensions and angle of the cross slot are designed according to specific process conditions, it cannot follow changes in impedance within the processing chamber, which can result in a decrease in the axial ratio of the radiated circularly polarized waves. Furthermore, when R-waves are selected, the electron temperature Te becomes too high as the input microwave power increases, and when L-waves are selected, plasma ignition becomes difficult.

Patent Document 3 connects two rectangular waveguides in an L shape, with a reflection suppression section at the right angle of the L shape that connects to a circular waveguide. By connecting different magnetrons to the input ends of each of the two rectangular waveguides, circularly polarized waves are combined in a combining chamber connected to the right angle of the L shape. Patent Document 3 does not mention radiating L waves into the reactor of a plasma processing device, but it is believed that adjusting the output phase of the two magnetrons makes it possible to provide R or L waves. However, because the two L-shaped rectangular waveguides mentioned above can propagate single-mode TE10 microwaves, they can also propagate reflected waves due to the plasma load within the processing chamber of the plasma processing device. Maintaining the axial ratio of the circularly polarized waves requires a three-stub tuner in the rectangular waveguide section. Furthermore, because TE10 mode propagates, reflected waves from the reactor also propagate within the rectangular waveguide. This causes the axial ratio of the circularly polarized waves radiated into the reactor to change depending on the process conditions of the plasma processing device.

A plasma processing apparatus according to one embodiment of the present invention comprises a processing chamber for performing plasma processing, a circular waveguide connected to the cavity of the processing chamber and capable of propagating microwave power in TE11 mode, 2n solid-state microwave sources, where n is a natural number greater than or equal to 2, a phase controller for controlling the phase of the microwave power output by each of the solid-state microwave sources, 2n coaxial-waveguide converters connected to each of the solid-state microwave sources and converting the microwave power from TEM mode to TE10 mode, and a polarization combining antenna having 2n cutoff waveguides connected to the circular waveguides on the same plane perpendicular to the axial direction of the circular waveguides, with the angle between adjacent cutoff waveguides in the axial direction being 180°/n. The 2n cutoff waveguides are connected to the 2n coaxial-waveguide converters in a one-to-one relationship, and in the cutoff waveguides, microwave power in TE10 mode is blocked and an evanescent field is excited toward the circular waveguide.

The present invention provides a microwave-based plasma processing apparatus that can suppress reflected waves, radiate circularly polarized waves with a high axial ratio, and selectively change the polarization radiation pattern. Other objectives and novel features will become apparent from the description of this specification and the accompanying drawings.

FIG. 1 is a diagram illustrating the configuration of an ECR plasma processing apparatus. 1 is a horizontal cross-sectional view of a polarization combining antenna according to a first embodiment. FIG. 1 is an explanatory diagram of the principle of R-wave coupling by phase control of a solid-state microwave source. FIG. 1 is an explanatory diagram of the principle of R-wave coupling by phase control of a solid-state microwave source. FIG. 1 is an explanatory diagram of the principle of R-wave coupling by phase control of a solid-state microwave source. 10A and 10B are diagrams showing the results of an electromagnetic field simulation of the electric field strength distribution in a circular waveguide according to the combination of the output phases of a solid-state microwave source. FIG. 10 is a horizontal cross-sectional view of the polarization combining antenna of the second embodiment. This is an example of a combination of polarizations emitted within an arbitrary fixed time period. 10 shows the results of a simulation of the change in the axial ratio in a circular waveguide due to differences in the reflection coefficient of the processing device. FIG. 1 is a diagram showing the configuration of a conventional ECR plasma processing apparatus.

Below, an embodiment of the present invention will be described using the drawings.

The configuration of Example 1 will be explained using Figures 1 to 4. Figure 1 shows the overall configuration of the ECR plasma processing apparatus of Example 1. Components common to Figure 8 are assigned the same reference numerals, and duplicate explanations will be omitted. The processing chamber 1 is a high-vacuum vessel depressurized to approximately 0.1 to 1 Pa by a vacuum pump 17. In this example, a phase controller 7 is provided, which can control the output phase and power ON/OFF operation of multiple solid-state microwave sources 2. Each of the multiple solid-state microwave sources 2 is connected to a coaxial-waveguide converter 3, and each of the coaxial-waveguide converters 3 is connected to a cutoff waveguide 4, and microwave power from the solid-state microwave source 2 is introduced from the coaxial-waveguide converter 3 to the cutoff waveguide 4.

To radiate microwaves into the cavity 6, a 90 mm diameter circular waveguide 5 capable of propagating 2.45 GHz TE11 mode microwaves is connected to multiple cutoff waveguides 4. Since the output frequency of the solid-state microwave source 2 is 2.45 GHz, the width of the cutoff waveguide 4 is 60 mm, and the length to the outermost periphery of the circular waveguide 5 (r = 45 mm) is 42.5 mm to block TE10 mode microwaves. The number of connected cutoff waveguides 4 is 2n (where n is a natural number greater than or equal to 2). A polarization combining antenna is formed at the connection between the circular waveguide 5 and multiple cutoff waveguides 4. The cutoff waveguide 4 is assumed to be a rectangular waveguide, but it may also be a circular waveguide.

Figure 2 shows a horizontal cross section of the polarization combining antenna of Example 1 (corresponding to the A-A cross section shown in Figure 1). The polarization combining antenna shown in Figure 2 has n=2 cutoff waveguides 4, i.e., four cutoff waveguides, each connected at 0°, 90°, 180°, and 270° directions on the same plane perpendicular to the axial direction of the circular waveguide 5. Depending on the direction, the cutoff waveguide 4 at 0° direction will be referred to as 4#1, the cutoff waveguide 4 at 90° direction as 4#2, the cutoff waveguide 4 at 180° direction as 4#3, and the cutoff waveguide 4 at 270° direction as 4#4. In addition, the points where the four cutoff waveguides 4#1, 4#2, 4#3, and 4#4 are connected to the coaxial waveguide converter 3 will be referred to as port 1, port 2, port 3, and port 4, respectively. Even when n≧3, the cutoff waveguides are connected on the same plane perpendicular to the axial direction of the circular waveguide 5 so that the angle between the axial directions of adjacent cutoff waveguides is 180°/n.

The coaxial-waveguide converters 3 and solid-state microwave sources 2 shown in Figure 1 are provided in sets of four, corresponding to the four cutoff waveguides 4. The output phases of the four solid-state microwave sources 2 are controlled to, for example, 0π, 1/2π, π, and 3/2π as shown in Figure 3A, and are introduced into the coaxial-waveguide converter 3, where they are converted from TEM mode to TE10 mode. Because TE10 mode microwaves are in the form of electromagnetic waves, they do not propagate within the cutoff waveguide 4. Instead, their microwave power excites an evanescent field toward the circular waveguide 5 within a certain distance of the cutoff waveguide 4. The excited evanescent field forms an electric field at the junction between the cutoff waveguide 4 and the circular waveguide 5 of the polarization combining antenna, thereby radiating electromagnetic waves back into the circular waveguide 5. The radiated electromagnetic waves are in TE11 mode, propagating within the circular waveguide 5. Since the TE11 mode electromagnetic wave from the circular waveguide 5 has the same frequency of 2.45 GHz as the frequency at which the electric field of the evanescent field is formed, the TE11 mode electromagnetic wave propagating through the circular waveguide 5 also has a frequency of 2.45 GHz.

As explained above, microwaves in TE11 mode are ultimately radiated from the circular waveguide 5 of the polarization combining antenna toward the cavity 6, but electromagnetic wave propagation from the microwave power source (wave source) is not directly utilized. The microwave power source (solid-state microwave source 2) in this embodiment is used solely to excite an evanescent field at the junction between the cutoff waveguide 4 and the circular waveguide 5.

Figures 3A-3C illustrate the principle of R-wave coupling using phase control of the solid-state microwave source of the present invention. Figure 3A shows an example in which four solid-state microwave sources 2 are controlled by a phase controller 7, with the phases to four cutoff waveguides 4#1, 4#2, 4#3, and 4#4 set to 0°, 90°, 180°, and 270°, respectively. As shown in Figure 3B, at time O1, an electric field in the -Ex direction is coupled by the output phases of ports 1 and 3. Similarly, as shown in Figure 3C, at time O2, an electric field in the +Ey direction is coupled by the output phases of ports 2 and 4. By controlling the phase difference between time O1 and time O2 to 1/2π, circularly polarized waves are radiated into the circular waveguide 5. The one-cycle timing chart in Figure 3A shows an example in which circularly polarized R-waves are synthesized by phase control of the output power from the solid-state microwave source 2.

Note that if the timing chart in Figure 3A is reversed, i.e., if the phases of the power supplied to cutoff waveguides 4#1, 4#2, 4#3, and 4#4 are set to 270°, 180°, 90°, and 0°, respectively, circularly polarized L-waves will be formed in circular waveguide 5. Furthermore, in Figure 3A, ports 1 and 3, and ports 2 and 4, respectively, excite evanescent fields at the same timing, but even with the phase combinations of ports 1 and 4 and ports 2 and 3, a rotating electric field, i.e., right-handed circularly polarized R-waves, can be coupled into circular waveguide 5. However, in this case, the radiated power will be half that of the phase combinations of ports 1 and 3 and ports 2 and 4 shown in Figure 3A.

Figure 4 shows the results of an electromagnetic field simulation of the electric field strength distribution within a circular waveguide depending on the combination of solid-state microwave source output phases. As shown in Figure 4, by controlling the microwave radiation phase of the solid-state microwave source 2 to the cutoff waveguides 4 connected to the four corners of the circular waveguide 5, circularly polarized R-waves and L-waves, as well as elliptically polarized waves at -45°, 45°, 90°, and 0° in the +Ey direction (clockwise around +Ey is positive, counterclockwise around +Ey is negative), are radiated into the circular waveguide 5, which then travels through the cavity 6 and enters the processing chamber 1. In this way, by controlling the spatial arrangement of the four cutoff waveguides 4 of the polarization combining antenna in Figure 2 and the output phase of the solid-state microwave source 2 with the phase controller 7 using the phase control in Figure 3, it is possible to adjust the circular polarization, elliptically polarized waves, and power of the electromagnetic waves radiated into the processing chamber 1, as shown in Figure 4.

The electromagnetic waves emitted from the circular waveguide 5 resonate in the cavity 6 of the plasma processing apparatus of this embodiment, passing through the quartz window 13 and shower plate 14 and supplying electromagnetic power to the processing chamber 1. At this time, a static magnetic field B (not shown) is formed within the processing chamber 1 by the upper electromagnetic coil 9, middle electromagnetic coil 10, and lower electromagnetic coil 11, and process gas G is supplied through the gas holes in the shower plate 14. Electrons wrapped around the magnetic field lines of the static magnetic field B are accelerated by the supplied electromagnetic waves, causing electron cyclotron resonance, which ultimately absorbs the electromagnetic wave power. A plasma ECR surface (resonance point) is formed at a location where the magnetic flux density is 875 G within the reduced-pressure vacuum vessel of the processing chamber 1, and the plasma expands and is generated over time.

The configuration of Example 2 will be explained using Figures 1, 2, and 5. In Example 1, the cutoff waveguide 4 of the polarization combining antenna is directly connected to the circular waveguide 5, so explaining the mechanism of R-wave formation, at the connection with the circular waveguide 5, the evanescent fields excited from ports 1 and 3 form an electric field in the ±Ex direction. On the other hand, an electric field in the ±Ey direction is formed at ports 2 and 4. Therefore, the TE11 mode, in which the electric field rotates, can be emitted from the circular waveguide 5. As can be seen in Figures 3B and 3C, the evanescent field excited in the cutoff waveguide 4 forms a linearly polarized wave within the circular waveguide 5, so the connection between the cutoff waveguide 4 and the circular waveguide 5 does not necessarily have to be limited to a circular shape.

For this reason, in Example 2, the connection portion with the four-way cutoff waveguide 4 is rectangular, which is easy to manufacture, and is connected to the circular waveguide 5, as shown in Figure 5. The microwaves propagating through the rectangular coupling portion 501 in Figure 5 are in TE10 mode, but since this behavior closely resembles the TE11 mode propagating through the circular waveguide 5 connected to the bottom of the rectangular coupling portion 501, there is no unnecessary reflection. Therefore, even when the rectangular coupling portion 501 in Figure 5 is provided, by controlling the phase of the solid-state microwave source 2, as in Example 1, it is possible to radiate circularly polarized waves, elliptically polarized waves, and power-adjustable microwaves to the processing chamber 1, as shown in Figure 4.

In consideration of the above, since the coupled electric field due to the evanescent field forms linear polarization in the ±Ex and ±Ey directions, the rectangular coupling section 501 in Figure 5 may be of any shape as long as the aforementioned linear polarization can be propagated.

The configuration of Example 3 is described using Figures 1 and 6. In conventional methods for radiating circularly polarized waves to a plasma processing apparatus, the incident and reflected waves are in the form of electromagnetic waves. Therefore, circular polarizers have been designed for the configuration with the highest circular polarization axial ratio among the plasma processing conditions, or for each target process. As a result, there is no selectivity for the circular polarization that can be radiated, and from the standpoint of ignition and plasma density, the apparatus is generally designed for R-wave circular polarization. In contrast, the axial ratio of the circular polarization that can be provided by the plasma processing apparatus of this example is almost independent of the process conditions. By controlling the output phase of the solid-state microwave source 2, R-wave, L-wave, and elliptical circular polarization can be selectively formed within the circular waveguide 5. Utilizing the above-described characteristics, Example 3 uses the phase controller 7 to control the output phase and ON/OFF combinations of the four solid-state microwave sources 2 during a fixed time t0, for example, as shown in Figure 6, allowing for the desired timing of a wide variety of microwave radiation forms, including R-wave radiation, L-wave radiation, and elliptical circular polarization.

Figure 7 shows the results of a simulation (using HFSS (High Frequency Simulation Software)) of the change in axial ratio within the circular waveguide due to differences in the reflection coefficient of the processing equipment for a comparative circularly polarized wave generator using a quarter-wave plate (see Figure 8) and the circularly polarized wave generator of this embodiment (see Figure 1). In this embodiment, the electromagnetic waves from the solid-state microwave source 2 are not directly emitted from the circular waveguide 5 of the polarization combining antenna, but rather the circularly polarized waves are indirectly introduced into the circular waveguide 5 by the evanescent field of the cutoff waveguide 4. Therefore, as shown in Figure 7, the system is less susceptible to reflected waves from the processing chamber 1 due to fluctuations in the plasma load caused by processing conditions during the plasma etching process or film formation, such as the material gas G and pressure, and therefore can radiate circularly polarized waves with a high axial ratio into the processing chamber 1 even if the plasma load fluctuates. As shown in FIG. 7, in the configuration of this embodiment, unlike the conventional quarter-phase plate microwave plasma processing apparatus, reflected waves can be suppressed without providing the waveguide with a three-stub tuner, which is a reflected wave control device (reflected waves are in the form of electromagnetic waves and cannot pass through the cutoff waveguide 4), and circularly polarized waves with a high axial ratio can be radiated.

Furthermore, by using phase combinations such as those shown in Figure 4, it is possible to radiate not only circularly polarized waves but also elliptically polarized waves with different directions by controlling the output phase of the solid-state microwave source 2, and the polarization radiation form can be selectively changed depending on the film distribution and etching rate on the substrate to be processed w. As mentioned above, R waves can continuously accelerate electrons in the direction of the magnetic field formed in the processing chamber 1, thereby achieving high plasma density. However, as the microwave supply power increases, the electron temperature Te increases, causing negative charge to accumulate at the top end of the fin of the FinFET, and the electron shielding effect makes precise control of the gate shape difficult.

In contrast, with the plasma processing apparatus of this embodiment, the electron temperature Te can be controlled by selectively switching between R and L waves using the phase controller 7, enabling precise processing of the gate shape of semiconductor devices. Furthermore, by selectively switching between R and L waves, the plasma absorption power of the plasma region formed within the processing chamber 1 can be adjusted globally or regionally, allowing for the control of the desired etching rate distribution depending on the application, such as the temperature distribution of the substrate support, as well as a uniform etching rate for the substrate w to be processed. While the example of etching has been described here, the same applies to film formation.

The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

1...Processing chamber 2...Solid-state microwave source 3...Coaxial waveguide converter 4...Cutoff waveguide 5...Circular waveguide 6...Cavity 7...Phase controller 9...Upper electromagnetic coil 10...Middle electromagnetic coil 11...Lower electromagnetic coil 12...Yoke 13...Quartz window 14...Shower plate 15...Substrate to be processed stage 16...RF power supply 17...Vacuum pump w...Substrate to be processed G...Material gas 501...Rectangular coupling section.

Claims (9)

a processing chamber for performing plasma processing;
a circular waveguide coupled to the cavity of the processing chamber and capable of propagating microwave power in TE11 mode;
2n solid-state microwave sources, where n is a natural number equal to or greater than 2;
a phase controller for controlling the phase of microwave power output by each of the solid-state microwave sources;
2n coaxial-waveguide converters connected to each of the solid-state microwave sources to convert the microwave power from a TEM mode to a TE10 mode;
a polarization combining antenna including 2n cutoff waveguides connected to the circular waveguide on the same plane perpendicular to the axial direction of the circular waveguide, wherein the angle between adjacent cutoff waveguides in the axial direction is 180°/n,
the 2n cutoff waveguides are connected to the 2n coaxial-waveguide converters in a one-to-one relationship;
In the cutoff waveguide, the microwave power in TE10 mode is cut off, and an evanescent field is excited toward the circular waveguide. In claim 1,
The evanescent field forms an electric field at a connection portion between the cutoff waveguide and the circular waveguide, and radiates microwave power in TE11 mode to the circular waveguide. In claim 1,
the 2n cutoff waveguides include a first cutoff waveguide and a second cutoff waveguide connected to the circular waveguide so as to face each other,
the 2n solid state microwave sources include a first solid state microwave source and a second solid state microwave source;
The phase controller causes the first solid-state microwave source connected to the first cutoff waveguide to generate microwaves that have an opposite phase to microwaves generated by the second solid-state microwave source connected to the second cutoff waveguide. In claim 3,
where n=2, the 2n cutoff waveguides include a third cutoff waveguide and a fourth cutoff waveguide connected to the circular waveguide so as to face each other, and the 2n solid-state microwave sources include a third solid-state microwave source and a fourth solid-state microwave source;
the phase controller causes the third solid-state microwave source connected to the third cutoff waveguide to generate microwaves that are 1/2π out of phase with respect to the microwaves generated by the first solid-state microwave source, and causes the fourth solid-state microwave source connected to the fourth cutoff waveguide to generate microwaves that are 4/2π out of phase with respect to the microwaves generated by the first solid-state microwave source. In claim 1,
A plasma processing apparatus in which n=2, and a connection portion between the 2n cutoff waveguides and the circular waveguide in the polarization combining antenna is rectangular. In claim 1,
The phase controller switches ON/OFF the phases of the microwaves generated by the 2n solid-state microwave sources and/or the outputs of the 2n solid-state microwave sources, thereby enabling switching of the microwave radiation form of the microwaves propagated through the circular waveguide and radiated into the processing chamber. In claim 6,
The phase controller switches ON/OFF the phases of the microwaves generated by the 2n solid-state microwave sources and/or the outputs of the 2n solid-state microwave sources, thereby coupling any one of right-handed circularly polarized microwaves, left-handed circularly polarized microwaves, and elliptically polarized microwaves of a predetermined direction contained in the same plane perpendicular to the axial direction of the circular waveguide into the circular waveguide. In claim 7,
A plasma processing apparatus that switches a microwave radiation form of microwaves radiated into the processing chamber during a plasma processing period in the processing chamber. In claim 8,
The plasma processing apparatus in the processing chamber is a plasma etching process or a film forming process.