JP2023013151A - Plasma applicator and plasma processing apparatus - Google Patents

Abstract

To provide a plasma applicator and a plasma processing apparatus that provide uniform time average values of electric field strength distribution and can uniformize instantaneous plasma distribution.SOLUTION: A plasma applicator 1 comprises: a wave guide 11 which has a slot and into which a micro wave is to be introduced; a plurality of variable impedance elements 12a that are provided inside the wave guide and are arranged along a tube axis of the wave guide; and a switching element 13a that is electrically connected to each of the variable impedance elements and can electrically switch a magnitude of impedance of each of the plurality of variable impedance elements.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to plasma applicators and plasma processing apparatuses.

Plasma processing is utilized, for example, in manufacturing microstructures. For example, various processes such as etching and ashing are performed in the manufacture of semiconductor devices, flat panel displays, photomasks, and the like.
Further, in recent years, atmospheric pressure plasma processing, in which plasma processing is performed in an atmosphere higher than the atmospheric pressure, and in-liquid plasma processing, in which plasma processing is performed in a liquid, have been performed.

In such plasma processing, microwaves may be used to generate plasma. High-density plasma can be easily generated by using microwaves. For example, plasma applicators have been proposed that have waveguides with slots into which microwaves are introduced.

In such plasma applicators, one end of the waveguide is closed. Therefore, the traveling wave propagating inside the waveguide and the reflected wave reflected by the end face of the waveguide overlap to form a standing wave (standing wave) inside the waveguide. However, when a standing wave is formed, the standing wave has a portion with high electric field strength and a portion with low electric field strength in the direction along the tube axis of the waveguide (the direction in which the waveguide extends). will occur. If the microwave radiated to the outside of the slot has a high electric field strength portion and a low electric field strength portion, the density of the generated plasma becomes uneven. If the density of plasma becomes non-uniform, it becomes difficult to perform uniform processing.

Therefore, a technique has been proposed in which a reflector that moves in the direction along the waveguide axis is provided at the end of the waveguide. (See Patent Document 1, for example)
If a reflector that moves in the direction along the tube axis of the waveguide is provided, the position where the traveling wave is reflected by the reflector changes, so the phase of the reflected wave can be changed. If the phase of the reflected wave changes, the maximum electric field strength position of the standing wave can be moved. For example, if the reflector is reciprocated at a predetermined speed, the maximum electric field strength position of the standing wave reciprocates at the same speed. Therefore, even if the standing wave has a portion with a high electric field intensity and a portion with a low electric field intensity, the electric field intensity can be made uniform in terms of time average. Therefore, the density of the plasma generated by the microwaves emitted from the waveguide is also made uniform in terms of time average.

However, when a semiconductor wafer is processed to manufacture an electronic device, if the change in electric field intensity is slow, even if the plasma is uniform over time, it is non-uniform when viewed instantaneously. As a result, the wafer is instantaneously non-uniformly charged (charged up), and a strong current instantaneously flows between regions with different degrees of charging. As a result, electrical damage occurs to the electronic devices in the wafer. Therefore, the plasma is required not only to have high time-average uniformity, but also to have high uniformity in instantaneous density distribution. That is, it is required that the plasma be uniform and that the plasma density be free from local fluctuations.
If the electric field intensity changes slowly, the plasma distribution will fluctuate according to the electric field intensity distribution, and the instantaneous plasma distribution will not be uniform. Therefore, in a plasma applicator in which the electric field intensity changes slowly, even if the electric field intensity distribution can be made uniform in terms of the time average, the instantaneous electric field intensity distribution remains uneven, reflecting the standing wave.

To eliminate instantaneous plasma distribution irregularities, the electric field fluctuations must be faster than the plasma response time. The plasma response time is several ms (milliseconds). Therefore, it is difficult to move the reflector to an arbitrary position at high speed within several milliseconds by a mechanical method. As a result, the instantaneous plasma distribution remains uneven, the wafer is non-uniformly charged, and the device is electrically damaged. Therefore, there has been a demand for the development of a technique capable of achieving instantaneous plasma distribution uniformity (suppression to prevent unevenness).

Japanese Unexamined Patent Application Publication No. 2001-203099

The problem to be solved by the present invention is to provide a plasma applicator and a plasma processing apparatus that have a uniform time-averaged electric field strength distribution and that can achieve a uniform instantaneous plasma distribution. .

A plasma applicator according to an embodiment includes a waveguide having a slot into which microwaves are introduced, and a plurality of variable impedances provided inside the waveguide and arranged along the tube axis of the waveguide. and a switching element electrically connected to each of the plurality of variable impedance elements and capable of electrically switching between high and low impedance of each of the plurality of variable impedance elements.

According to the embodiments of the present invention, there are provided a plasma applicator and a plasma processing apparatus that have a uniform time-averaged electric field strength distribution and can achieve uniform instantaneous plasma distribution.

1 is a schematic cross-sectional view for illustrating a plasma processing apparatus according to an embodiment; FIG. 1 is a schematic plan view for illustrating a plasma processing apparatus according to an embodiment; FIG. FIG. 4 is a schematic cross-sectional view for illustrating a waveguide according to a comparative example; FIG. 5 is a schematic cross-sectional view for illustrating a waveguide according to another comparative example; FIG. 5 is a schematic cross-sectional view for illustrating a waveguide according to another comparative example; It is a schematic cross section for illustrating the plasma processing apparatus which concerns on other embodiment. FIG. 10 is a schematic plan view for illustrating a plasma processing apparatus according to another embodiment; (a) It is a schematic cross section for illustrating the plasma processing apparatus which concerns on other embodiment. (b) A schematic plan view for illustrating a plasma processing apparatus according to another embodiment.

Hereinafter, embodiments will be illustrated with reference to the drawings. In addition, in each drawing, the same reference numerals are given to the same constituent elements, and detailed description thereof will be omitted as appropriate.

FIG. 1 is a schematic cross-sectional view for illustrating a plasma processing apparatus 100 according to this embodiment.
FIG. 2 is a schematic plan view for illustrating the plasma processing apparatus 100 according to this embodiment.
A plasma processing apparatus 100 illustrated in FIGS. 1 and 2 is a plasma processing apparatus that performs plasma processing in the atmosphere. That is, the plasma processing apparatus 100 is an example of an atmospheric pressure plasma processing apparatus that performs plasma processing in an atmosphere higher than the atmospheric pressure.

As shown in FIGS. 1 and 2, the plasma processing apparatus 100 is provided with, for example, a plasma applicator 1, a power supply 2, a microwave generator 3, a mounting section 4, and a controller 5. FIG.
The plasma applicator 1 has, for example, a waveguide 11, a reflector section 12 and a switching section 13. FIG.

A microwave is introduced into the waveguide 11 . For example, the waveguide 11 has a tubular shape extending in one direction. One end of waveguide 11 is open. The other end of waveguide 11 is closed. For example, a microwave generator 3 to be described later is connected to the opening of the waveguide 11 . The internal space of the waveguide 11 becomes a space in which microwaves propagate.

The cross-sectional shape of the waveguide 11 is not particularly limited. The cross-sectional shape of the waveguide 11 can be, for example, rectangular, circular, or the like. The cross-sectional shape of the waveguide 11 illustrated in FIG. 1 is rectangular. One side surface of the waveguide 11, which has a square cross-section and is parallel to the tube axis, is a plane (H plane) perpendicular to the electric field direction of the microwave. A plane (E plane) parallel to the tube axis and perpendicular to the H plane is a plane parallel to the electric field direction of the microwave M. In the case of a general waveguide, the plane (end face) perpendicular to the tube axis is the reflecting plane (short-circuit plane; R plane). A later-described reflecting portion 12 provided inside the wave tube 11 functions as an R surface.

A slot 11a is formed on one H surface. The slot 11 a penetrates between the outer wall and the inner wall of the waveguide 11 . At least one slot 11a can be provided. When providing one slot 11a, the slot 11a extending in the direction in which the waveguide 11 extends can be provided. When a plurality of slots 11a are provided, the plurality of slots 11a can be arranged side by side in the direction in which the waveguide 11 extends so that the plurality of slots 11a draw a straight line. In the direction along the tube axis of the waveguide 11, the slots 11a are provided between the opening of the waveguide 11 and the plurality of variable impedance elements 12a.
The extending direction (longitudinal direction) of the slot 11a, the extending direction of the waveguide 11, and the direction along the tube axis of the waveguide 11 are all the same direction.

The waveguide 11 is made of a material that easily reflects microwaves, such as an aluminum alloy.

A window 11b covering the slot 11a can also be provided on the outer surface of the waveguide 11 or the like. The window 11b has a plate shape and is made of a material that transmits microwaves. Window 11b may be formed from a dielectric material such as quartz, for example.

Here, a standing wave formed inside the waveguide 11 will be described.
As described above, in the case of a general waveguide, the plane (end face) perpendicular to the tube axis is the reflecting plane (R plane). Therefore, the traveling wave propagating inside the waveguide is reflected by the end face of the waveguide. A reflected wave reflected by the end face of the waveguide propagates inside the waveguide in a direction opposite to that of the traveling wave.

FIG. 3 is a schematic cross-sectional view for illustrating a waveguide 211 according to a comparative example.
The waveguide 211 is a waveguide having a rectangular cross section. As shown in FIG. 3, microwaves are introduced into the waveguide 211 from the open end of the waveguide 211 . The microwave introduced into the waveguide 211 becomes a traveling wave that travels toward the end surface (R surface) of the waveguide 211 . The traveling wave is reflected by the R surface and becomes a reflected wave propagating inside the waveguide 211 in the direction opposite to the traveling wave.

In this case, the traveling wave and the reflected wave have the same wavelength, period (frequency or frequency), amplitude, and speed, but travel in opposite directions. Therefore, inside the waveguide 211, the traveling wave and the reflected wave overlap to form a standing wave. When a standing wave is formed, the electric field strength distribution 210 is as shown in FIG. Therefore, in the direction along the tube axis of the waveguide 211, a portion 210a with high electric field strength and a portion 210b with low electric field strength are generated. In addition, since the standing wave is a wave that does not advance and appears to stop and vibrate, the portion 210a with high electric field strength and the portion 210b with low electric field strength remain at the same position.

If the portion 210a with high electric field strength and the portion 210b with low electric field strength remain at the same position, the energy of microwaves radiated from slot 211a becomes uneven as shown in FIG. If the microwave energy is uneven, the density of the plasma generated outside the slot 211a becomes non-uniform. If the density of plasma becomes non-uniform, it becomes difficult to perform uniform processing.

FIG. 4 is a schematic cross-sectional view for illustrating a waveguide 311 according to another comparative example.
The waveguide 311 is a waveguide having a rectangular cross section. As shown in FIG. 4, microwaves are introduced into the waveguide 311 from the open end of the waveguide 311 . The microwave introduced into the waveguide 311 becomes a traveling wave traveling toward the R plane. The traveling wave is reflected by the R surface and becomes a reflected wave propagating inside the waveguide 311 in the opposite direction to the traveling wave. Therefore, in the waveguide 311 as well, the traveling wave and the reflected wave overlap to form a standing wave, as in the waveguide 211 described above. When a standing wave is formed, the electric field strength distribution 310 is as shown in FIG.

However, in the case of the waveguide 311, a reflector 311b is provided at the end of the waveguide 311 opposite to the opening side. In the direction along the tube axis of waveguide 311, the position of reflector 311b is movable. For example, the reflecting plate 311b can be reciprocated in the direction along the tube axis of the waveguide 311 using a driving device such as a solenoid or a motor. If the position of the reflecting plate 311b changes in the direction along the tube axis of the waveguide 311, the position where the traveling wave is reflected changes, so the phase of the reflected wave can be changed. If the phase of the reflected wave changes, the maximum electric field strength position of the standing wave can be moved as shown in FIG.

For example, if the reflecting plate 311b is reciprocated at a predetermined speed, the position of the maximum electric field intensity of the standing wave reciprocates at the same speed. Therefore, even if the standing wave has a portion with a high electric field intensity and a portion with a low electric field intensity, the electric field intensity can be made uniform in terms of time average. As a result, non-uniform density of plasma generated outside the slot 311a can be suppressed.

FIG. 5 is a schematic cross-sectional view for illustrating a waveguide 411 according to another comparative example.
The waveguide 411 is a waveguide having a rectangular cross section. As shown in FIG. 5, microwaves are introduced into the waveguide 411 from the open end of the waveguide 411 . The microwave introduced into the waveguide 411 becomes a traveling wave directed toward the R plane. The traveling wave is reflected by the R surface and becomes a reflected wave propagating inside the waveguide 411 in the opposite direction to the traveling wave. Therefore, in the waveguide 411 as well, the traveling wave and the reflected wave overlap to form a standing wave, as in the waveguide 211 described above. When a standing wave is formed, the electric field strength distribution 410 is as shown in FIG.

However, in the case of the waveguide 411, a plurality of reflectors 411b are provided near the end of the waveguide 411 opposite to the opening side. A plurality of reflectors 411b are arranged side by side in the direction along the tube axis of waveguide 411 . Each of the multiple reflectors 411 b is movable in a direction perpendicular to the tube axis of the waveguide 411 . For example, one reflector 411b selected from the plurality of reflectors 411b is inserted into the waveguide 411 or pulled out from the waveguide 411 using a drive device such as a solenoid or a motor. be able to. For example, the plurality of reflectors 411b can be sequentially inserted into the waveguide 411 or pulled out from the waveguide 411 sequentially.

By doing so, the position at which the traveling wave is reflected changes in the direction along the tube axis of the waveguide 411, so that the phase of the reflected wave can be changed. If the phase of the reflected wave changes, the maximum electric field strength position of the standing wave can be moved as shown in FIG. Therefore, even if the standing wave has a portion with a high electric field intensity and a portion with a low electric field intensity, the electric field intensity can be made uniform in terms of time average.
As a result, non-uniform density of plasma generated outside the slot 411a can be suppressed.

Here, if the moving speed of the reflectors 311b and 411b described above increases, the moving speed of the maximum electric field strength position of the standing wave also increases. Therefore, the variation speed of the electric field strength distribution also increases.
In this case, if the fluctuation of the electric field strength distribution becomes faster than the response speed of the plasma, it is possible to suppress the instantaneous non-uniformity of the plasma density distribution.

4 and 5, however, since the reflectors 311b and 411b are mechanically moved, there is a limit to increasing the moving speed of the reflectors 311b and 411b.

Therefore, as shown in FIG. 1, the plasma applicator 1 according to the present embodiment is provided with a reflecting section 12 and a switching section 13 .
Each of the multiple reflectors 12 has a variable impedance element 12a, a conductor 12b, and a conductor 12c.
A plurality of variable impedance elements 12a are provided inside the waveguide 11 and near the end of the waveguide 11 opposite to the opening side. A plurality of variable impedance elements 12 a are arranged side by side in the direction along the tube axis of the waveguide 11 .

As will be described later, when the switching element 13a is turned on, the reflecting portion 12 becomes a reflecting surface (R surface). Therefore, considering the control of the phase of the reflected wave, it is preferable to arrange the plurality of variable impedance elements 12a at regular intervals.

In addition, (m-1) or more variable impedance elements 12a are arranged at intervals L in the direction along the tube axis of the waveguide 11 so that the comb of the standing wave can be moved at equal intervals in m stages. , where λ is the wavelength of the microwave in the waveguide 11, the interval L preferably satisfies the following equation.
L=(n+1/m)×(λ/2)
Note that n is either 0, 1, or 2.
m is an integer of 2 or more.
By setting the interval L in this way, it is possible to improve the controllability of the phase of the reflected wave.

The variable impedance element 12a can be, for example, a PIN diode (p-intrinsic-n Diode). When a positive voltage above a certain level is applied to the anode terminal of the PIN diode, a direct current flows through the PIN diode and the impedance of the PIN diode to microwaves decreases. When no voltage is applied, almost no direct current flows through the PIN diode and the impedance of the PIN diode is high. Therefore, PIN diodes are preferred as variable impedance elements. Since the PIN diode has an anode and a cathode, the following description will also use a different expression. However, the variable impedance element is not necessarily limited to an element with distinguishable anode and cathode.
Further, the position of the variable impedance element 12a in the cross section of the waveguide 11 orthogonal to the tube axis is not particularly limited. However, considering the controllability of the phase of the reflected wave, it is preferable to provide the variable impedance element 12a at the position of the tube axis of the waveguide 11 (the center of the cross section) or in the vicinity of the tube axis.

One end of the conductor 12b is electrically connected to the anode side of the variable impedance element 12a. The other end of the conductor 12b is electrically connected to the power supply 2 via the switching section 13 (switching element 13a). The conductor 12b can be, for example, a wire containing metal such as copper or aluminum.

One end of the conductor 12c is electrically connected to the cathode side of the variable impedance element 12a. The other end of the conductor 12c is electrically connected to ground or the negative electrode side of the power supply 2 . The conductor 12c illustrated in FIG. 1 is electrically connected to the waveguide 11 which is grounded. The conductor 12c can be, for example, a wire containing metal such as copper or aluminum.

The switching unit 13 is provided outside the waveguide 11 . The switching unit 13 has a plurality of switching elements 13a. The switching section 13 is electrically connected to each of the plurality of variable impedance elements 12a. For example, one switching element 13a is electrically connected to a set of variable impedance element 12a, conductor 12b, and conductor 12c. The switching element 13a can be, for example, a transistor or the like.
As will be described later, the switching unit 13 can electrically switch the impedance level of each of the plurality of variable impedance elements 12a.

The power supply 2 is provided outside the waveguide 11 . The power supply 2 can be, for example, a DC power supply. The power supply 2 is electrically connected to the switching elements 13a. For example, the positive electrode of the power supply 2 is electrically connected to a plurality of reflectors 12 (variable impedance elements 12a) via a switching section 13 (switching element 13a). If the cathode side of the variable impedance element 12a is not grounded, the negative electrode of the power supply 2 and the cathode side of the variable impedance element 12a can be electrically connected via the conductor 12c.

The microwave generator 3 is provided outside the waveguide 11 . The microwave generator 3 can be connected to the opening side of the waveguide 11, for example. The microwave generator 3 introduces microwaves into the waveguide 11 . The microwave generator 3 can be, for example, a magnetron. The microwave generator 3 generates microwaves with a frequency of 1 GHz to 50 GHz (eg, 2.45 GHz), for example.

The mounting portion 4 is provided outside the waveguide 11 . A workpiece 200 is placed on the upper surface of the placing section 4 . The upper surface of the mounting portion 4 faces the slot 11 a of the waveguide 11 . A space between the side of the waveguide 11 on which the slot 11a is provided and the upper surface of the mounting portion 4 is a region where the plasma P is generated. In addition, means for holding the work 200 can be appropriately provided on the placing section 4 . Means for holding the workpiece 200 are, for example, an electrostatic chuck, a vacuum chuck, a mechanical chuck, or the like.

As shown in FIG. 2 , the mounting section 4 passes below the plasma applicator 1 .
The work 200 is not particularly limited as long as it is a target of plasma processing. Work 200 can be, for example, a semiconductor wafer, a glass substrate, or the like.

Controller 5 is provided outside waveguide 11 . The controller 5 has, for example, an arithmetic unit such as a CPU (Central Processing Unit) and a storage unit such as a memory. For example, the controller 5 can be a computer or the like. For example, the arithmetic unit controls the operation of each element provided in the plasma processing apparatus 100 based on the control program stored in the storage unit.

Next, operation of the plasma processing apparatus 100 will be described.
The controller 5 controls the microwave generator 3 to generate microwaves. The generated microwave is introduced into the waveguide 11 through the opening of the waveguide 11 . A microwave introduced into the waveguide 11 propagates toward the plurality of reflecting portions 12 .

The controller 5 controls the power supply 2 to apply voltage to the plurality of variable impedance elements (PIN diodes) 12a through the switching elements 13a.
In addition, the controller 5 controls the switching section 13 to change the positions at which the microwaves propagating toward the plurality of reflecting sections 12 are reflected.
For example, the controller 5 controls multiple switching elements 13a.
The controller 5 turns on one of the plurality of switching elements 13a and turns off the remaining switching elements 13a.
The controller 5 selects the switching element 13a to be turned on to change the position where the microwave is reflected.
The controller 5 switches the ON state and the OFF state of the plurality of switching elements 13a to move the position where the microwave is reflected.

Next, switching of the plurality of switching elements 13a will be further described.
Since voltage is applied to the plurality of switching elements 13a, current flows through the variable impedance element 12a, the conductor 12b, and the conductor 12c electrically connected to the switching element 13a in the ON state. Since the variable impedance element 12a through which the current flows becomes a conductor, it can reflect incident microwaves.

On the other hand, no current flows through the switching element 13a in the OFF state. Therefore, no current flows through the variable impedance element 12a, the conductor 12b, and the conductor 12c, which are electrically connected to the switching element 13a in the OFF state. The variable impedance element 12a, through which no current flows, is a nonconductor, so that incident microwaves can be transmitted.

Therefore, the controller 5 can change the position of the reflecting surface (R surface) (the position at which microwaves are reflected) by selecting the switching element 13a to be turned on. For example, by sequentially switching the ON state and the OFF state of the plurality of switching elements 13a, the plurality of reflecting portions 12 arranged in the direction along the tube axis of the waveguide 11 can be sequentially switched between conducting and non-conducting. can be done. By sequentially switching between conducting and non-conducting the plurality of reflecting portions 12, the positions of the reflecting surfaces can be changed sequentially. By sequentially changing the position of the reflecting surface, the phase of the reflected wave is sequentially changed, so that the maximum electric field strength position 110 of the standing wave can be moved as shown in FIG.

Therefore, even if the standing wave has a portion with a high electric field intensity and a portion with a low electric field intensity, the electric field intensity can be made uniform in terms of time average.
Further, by switching the ON state and OFF state of the plurality of switching elements 13a, the position of the reflecting surface can be sequentially changed. Therefore, the moving speed of the reflecting surface can be increased compared to the case of mechanically moving the reflecting plate described above. As the moving speed of the reflecting surface increases, the moving speed of the maximum electric field strength position 110 of the standing wave also increases. Therefore, the plasma density does not correspond to the fluctuation of the electric field intensity distribution, and is determined by the time-averaged amplitude distribution of the electric field intensity, thereby suppressing the unevenness of the plasma density distribution.

When switching the ON state and the OFF state of the plurality of switching elements 13 a , the switching elements 13 a can be sequentially switched in the direction along the tube axis of the waveguide 11 . Also, switching of the switching elements 13a can be performed at a predetermined number in the direction along the tube axis of the waveguide 11 . For example, switching of the switching elements 13a can be performed alternately.

Microwaves propagating inside the waveguide 11 are radiated to the outside of the waveguide 11 through the slots 11a. Plasma P is excited outside the waveguide 11 in the vicinity of the slot 11a by the microwave radiated to the outside of the waveguide 11 . As described above, since the electric field intensity of the microwaves radiated to the outside of the waveguide 11 is uniformed when viewed on a time average basis, the density of the generated plasma P is also when viewed on a time average basis. become uniform. Furthermore, by performing the switching sufficiently quickly (faster than the response of the plasma P), fluctuations in the plasma density distribution are also suppressed, and the plasma P without unevenness is obtained.

Air contained in the region where the plasma P is generated is excited and activated by the plasma P to generate plasma products such as radicals and ions. The generated plasma product reaches the surface of the workpiece 200, whereby the workpiece 200 is subjected to plasma processing.

In order to achieve a high processing speed, the distance between the placement section 4 and the waveguide 11 is shortened. Therefore, the plasma P and the plasma products reach the workpiece 200 more easily. In addition, it is possible to suppress diffusion of plasma products to the outside. However, when the distance between the mounting portion 4 and the waveguide 11 is shortened in a state where the density of the plasma P is uneven, uneven processing tends to occur.

As described above, according to the plasma processing apparatus 100 of the present embodiment, the moving speed of the maximum electric field strength position 110 of the standing wave can be increased, so the density of the plasma P can be made uniform. . Therefore, even if the distance between the mounting portion 4 and the waveguide 11 is shortened, it is possible to suppress the occurrence of processing unevenness. The distance between the mounting portion 4 and the waveguide 11 is preferably several tens of μm or more and several mm or less. In particular, in a pressure atmosphere of several hundred Pa or more, or in a liquid plasma described later, diffusion of electrons weakens, and the plasma approaches and concentrates on the slots 11a. Therefore, it is preferable to bring the mounting portion 4 as close to the waveguide 11 as possible.

FIG. 6 is a schematic cross-sectional view for illustrating a plasma processing apparatus 100a according to another embodiment.
FIG. 7 is a schematic plan view for illustrating a plasma processing apparatus 100a according to another embodiment.
As shown in FIGS. 6 and 7, the plasma processing apparatus 100a includes, for example, a plasma applicator 1, a power supply 2, a microwave generator 3, a mounting section 4, a controller 5, a chamber 6, and a gas supply section 7. is provided.

The chamber 6 can be, for example, a container having an airtight structure. A mounting portion 4 can be provided on the bottom surface inside the chamber 6 . The mounting section 4 is rotated by the driving section 4a. A plasma applicator 1 can be provided on the ceiling surface outside the chamber 6 . The chamber 6 can be made of metal such as an aluminum alloy, for example.

As shown in FIG. 7, the slot 11a of the plasma applicator 1 of the plasma processing apparatus 100a has a length of the waveguide 11 in a direction parallel to the tube axis (hereinafter simply referred to as the length of the slot 11a). shorter than the plasma applicator 1 of the processing apparatus 100; When the work 200 is polygonal, the length of the slot 11a is less than or equal to the length of the line connecting the rotation center of the work 200 and the corners of the outer periphery. When the workpiece 200 is circular, the length of the slot 11a is equal to or shorter than the length of the line connecting the center of rotation of the workpiece 200 and a point on the circumference.

Further, the rotational speed increases from the center of rotation of the workpiece 200 toward the outer circumference. Therefore, it is preferable that the slot 11a has a shape in which the width increases from the rotation center of the workpiece 200 toward the outer circumference. For example, it is preferable to form the slot 11a into a sector shape.
Alternatively, it may have a curved shape in which the curvature gradually increases from the rotation center side toward the outer peripheral side. More specifically, the portion closest to the center is formed along the radial direction, and the portion closest to the outer periphery is formed in a curved shape in which the curvature gradually increases from the rotation center side along the direction perpendicular to the radial direction. be. With such a shape as well, the length over which an arbitrary point on the surface of the rotating work 200 passes through the slot can be made longer toward the outer periphery, so that an effect similar to that of the fan shape can be obtained.

The gas supply unit 7 supplies the gas G to the space between the mounting unit 4 and the waveguide 11 inside the chamber 6 .
The gas supply section 7 has, for example, a nozzle 7a, a gas source 7b, and a gas control section 7c. Nozzles 7a can be provided, for example, on the sidewalls of chamber 6 .
A gas source 7 b is provided outside the chamber 6 . The gas source 7b can be a high-pressure cylinder containing the gas G, or a factory pipe for supplying the gas G, or the like.
The gas controller 7c is connected via a pipe between the nozzle 7a and the gas source 7b. The gas control unit 7c controls, for example, at least one of the flow rate and pressure of the gas G supplied to the nozzle 7a. The gas control unit 7c can also switch between starting the supply of the gas G and stopping the supply of the gas G. FIG. The gas control unit 7c can be, for example, an MFC (Mass Flow Controller).

The gas G can be appropriately selected according to the type of plasma processing, the material of the surface of the workpiece 200, and the like. The gas G is, for example, a gas containing fluorine atoms, a gas containing oxygen atoms, or the like.

The plasma processing apparatus 100a can be a plasma processing apparatus that performs plasma processing in an atmosphere with a wide range of gas pressures (several hundred mPa to several atmospheres). In particular, in the case of atmospheric pressure, there is no need for an exhaust section for decompressing the interior of the chamber 6 to a predetermined pressure.

The plasma processing apparatus 100a according to this embodiment has the same actions and effects as the plasma processing apparatus 100 described above.
Moreover, since the gas supply unit 7 is provided, various gases can be used as required. In this case, since the chamber 6 is provided, highly reactive gas such as gas containing fluorine atoms can be prevented from diffusing around the plasma processing apparatus 100a.
Therefore, it is possible to diversify the components of the plasma product and, in turn, diversify the plasma processing.
Further, by making the mounting part 4 rotatable, the plasma applicator 1 can be made smaller than the plasma processing apparatus 100 described above.
It should be noted that the plasma processing apparatus 100a may be provided with an exhaust section to perform the plasma processing in a reduced pressure atmosphere.

FIG. 8A is a schematic cross-sectional view illustrating a plasma processing apparatus 100b according to another embodiment.
FIG. 8B is a schematic plan view for illustrating a plasma processing apparatus 100b according to another embodiment.
The plasma processing apparatus 100b is an example of an in-liquid plasma processing apparatus that performs plasma processing in a liquid.
As shown in FIGS. 8A and 8B, the plasma processing apparatus 100b includes, for example, a plasma applicator 1, a power supply 2, a microwave generator 3, a controller 5, a chamber 8, and a transporter 9. is provided.

Chamber 8 can be, for example, a container having a liquid-tight structure. The chamber 8 can be provided with a loading port (not shown) for loading the work 200 and a loading port (not shown) for loading the work 200 out.

The interior of chamber 8 is filled with liquid 300 . Liquid 300 is not particularly limited. The liquid 300 can be, for example, water, an organic solvent such as alcohol, or a chemical solution.

The transfer section 9 is provided inside the chamber 8 . The transport unit 9 transports the workpiece 200 in the liquid 300 to a predetermined position. The transport unit 9 can be, for example, a conveyor.

In the plasma processing apparatus 100b, plasma processing can be performed as follows.
For example, the workpiece 200 is carried into the liquid inside the chamber 8 through the inlet port by a loading device (not shown). The transport unit 9 transports the workpiece 200 in the liquid to a position facing the slot 11a.

Plasma applicator 1 radiates microwaves to liquid 300 through slot 11a. At this time, the plurality of reflecting portions 12 and switching portions 13 make the electric field intensity uniform when viewed on a time average basis.

When microwaves are radiated to the liquid 300, the liquid 300 is heated to generate bubbles 300a. Plasma is generated when the microwave is incident on the bubble 300a, and plasma products are generated by the plasma. For example, the vapor or gas contained in the bubble 300a, the liquid 300 at the interface between the bubble 300a and the liquid 300, or the substances contained in the liquid 300 are excited and activated by the plasma to generate neutral active species, ions, or the like. Plasma products such as charged particles such as electrons are generated.

The generated plasma products diffuse into the liquid 300 , and the work 200 is plasma-treated by the plasma products diffused into the liquid 300 .

The transport unit 9 transports the plasma-treated work 200 to the position of the carry-out port. The work 200 transported to the position of the carry-out port is carried out of the chamber 8 by a carry-out device (not shown).

In the above, the liquid 300 is heated to boil the liquid 300 to generate the bubbles 300a, but the present invention is not limited to this. For example, the pressure of the liquid 300 may be reduced to generate bubbles 300a. Alternatively, gas may be supplied to the liquid 300 to generate the bubbles 300a.

Moreover, in the above description, the case where the work 200 is plasma-treated by the plasma products is exemplified, but the liquid 300 can also be plasma-treated by the plasma products. For example, impurities, bacteria, viruses, etc. contained in the liquid 300 can be decomposed or rendered harmless by plasma products.

The embodiments have been illustrated above. However, the invention is not limited to these descriptions.
Appropriate design changes made by those skilled in the art with respect to the above embodiments are also included in the scope of the present invention as long as they have the features of the present invention.
For example, the shape, size, material, arrangement, etc. of the elements provided in the plasma processing apparatus and plasma applicator are not limited to those illustrated and can be changed as appropriate. Moreover, each element provided in each of the above-described embodiments can be combined as much as possible, and a combination thereof is also included in the scope of the present invention as long as it includes the features of the present invention.

1 plasma applicator, 2 power supply, 3 microwave generator, 5 controller, 11 waveguide, 11a slot, 11b window, 12 reflector, 12a variable impedance element, 12b conductor, 12c conductor, 13 switching section, 13a switching element , 100 plasma processing apparatus 100a plasma processing apparatus 100b plasma processing apparatus 110 position of maximum electric field strength of standing wave 200 workpiece 300 liquid 300a bubble

Claims (6)

a waveguide having slots and into which microwaves are introduced;
a plurality of variable impedance elements provided inside the waveguide and arranged along the tube axis of the waveguide;
a switching element electrically connected to each of the plurality of variable impedance elements and capable of electrically switching between high and low impedance of each of the plurality of variable impedance elements;
Plasma applicator with 2. The method according to claim 1, wherein (m−1) or more of said variable impedance elements are arranged at regular intervals in the direction along the waveguide axis of said waveguide, and said intervals between said variable impedance elements satisfy the following equation: plasma applicator.
L=(n+1/m)×(λ/2)
L is the spacing of the variable impedance elements.
n is 0, 1, or 2;
m is an integer of 2 or more.
λ is the wavelength of the microwave in the waveguide. one end of the waveguide is open,
3. The plasma applicator according to claim 1, wherein said slot is provided between said opening and said plurality of variable impedance elements in a direction along the tube axis of said waveguide. A plasma applicator according to any one of claims 1 to 3;
a microwave generator that introduces microwaves into a waveguide provided in the plasma applicator;
a power supply electrically connected to a plurality of switching elements provided in the plasma applicator;
a controller that controls the plurality of switching elements;
with
The controller is
setting one of the plurality of switching elements to an ON state;
A plasma processing apparatus in which the remaining switching elements are turned off. 5. The plasma processing apparatus according to claim 4, wherein the controller changes the position where the microwave is reflected by selecting the switching element to be turned on. 6. The plasma processing apparatus according to claim 4, wherein the controller moves the position where the microwave is reflected by switching the ON state and the OFF state of the plurality of switching elements.

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