Electromagnetic wave supply mechanism and plasma processing apparatus

Abstract

To reduce reflected power when electromagnetic waves are branched and introduced into a plurality of locations.SOLUTION: An electromagnetic wave supply mechanism is an electromagnetic wave supply mechanism for supplying electromagnetic waves into a processing vessel that serves as a load, and includes a first branch circuit. The first branch circuit is provided downstream of a high-frequency power source configured to generate electromagnetic waves and is configured as a waveguide, and includes: a first waveguide having an input end; a plurality of second waveguides each having an output end; and a branch point where the first waveguide is branched into a plurality of second waveguides by n (n is an integer of 2 or more). Each output end is connected to a load or an input end of a second branch circuit that is the next branch circuit. In the first branch circuit, when the total number of output ends as viewed from the branch point is n, the lengths of the second waveguides from the branch point to the n output ends differ by m×λ / 2+(λ / 2) / n (m is 0 or a positive integer).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electromagnetic wave supply mechanism and a plasma processing apparatus. [Background technology]

[0002] The plasma processing apparatus disclosed in Patent Document 1 includes a processing vessel for accommodating a workpiece, a mounting table disposed inside the processing vessel and having a mounting surface on which the workpiece is placed, a gas supply mechanism for supplying a processing gas into the processing vessel, and a microwave introduction device for generating microwaves for generating plasma of the processing gas in the processing vessel and introducing the microwaves into the processing vessel. The microwave introduction device is disposed on the upper part of the processing vessel and includes a conductive member having a plurality of openings, and a plurality of microwave transmission windows that fit into the plurality of openings and transmit and introduce microwaves into the processing vessel. The plurality of microwave transmission windows are disposed on a single imaginary plane parallel to the mounting surface while being fitted into the plurality of openings, and include a first microwave transmission window and second and third microwave transmission windows adjacent to the first microwave transmission window. The first to third microwave-transparent windows are set and arranged so that the distance between the center point of the first microwave-transparent window and the center point of the second microwave-transparent window, and the distance between the center point of the first microwave-transparent window and the center point of the third microwave-transparent window are equal or approximately equal to each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-216745 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides an electromagnetic wave supply mechanism and a plasma processing apparatus capable of reducing reflected power when an electromagnetic wave is branched and introduced into a plurality of locations. [Means for solving the problem]

[0005] An electromagnetic wave supply mechanism according to an embodiment of the present disclosure is an electromagnetic wave supply mechanism for supplying electromagnetic waves into a processing vessel serving as a load, and includes a first branch circuit. The first branch circuit is provided downstream of a high-frequency power source configured to generate electromagnetic waves, and is configured as a waveguide, and includes a first waveguide having an input end, a plurality of second waveguides each having an output end, and a branch point that branches the first waveguide into a plurality of second waveguides by n (n is an integer of 2 or more). Each output end is connected to a load or an input end of a second branch circuit that is the next branch circuit. In the first branch circuit, when the total number of output ends as viewed from the branch point is n, the lengths of the second waveguides from the branch point to each of the n output ends differ by m×λ / 2+(λ / 2) / n (m is 0 or a positive integer). Effect of the Invention

[0006] According to the present disclosure, it is possible to reduce reflected power when an electromagnetic wave is branched and introduced into a plurality of locations. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of a plasma processing apparatus according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating an example of a ceiling wall of a processing vessel in this embodiment. [Diagram 3] FIG. 3 is a diagram illustrating an example of a branch circuit according to the present embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example in which branch circuits are connected in series in this embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a distribution model of a multi-port branch circuit. [Figure 6] FIG. 6 is a diagram illustrating an example of a composite model of a multi-port branch circuit. [Figure 7] FIG. 7 is a diagram illustrating an example of a propagation model of a multi-port branch circuit. [Figure 8] FIG. 8 is a diagram showing, in terms of complex space vectors, how the sum of the propagating waves from each port results in total reflection. [Figure 9] FIG. 9 is a diagram illustrating an example of a T-branch circuit model. [Figure 10] FIG. 10 is a diagram illustrating an example of a T-branch circuit model in this embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of a propagation condition in a T-branch circuit model. [Figure 12] FIG. 12 is a diagram showing an example of reflection in a T-branch circuit model. [Figure 13] FIG. 13 is a diagram showing an example of the allowable error of the difference in length of the second waveguide in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the disclosed electromagnetic wave supply mechanism and plasma processing apparatus will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to the following embodiments.

[0009] In a plasma processing apparatus, for example, when electromagnetic waves are introduced into a processing vessel from a plurality of transmission windows or a plurality of electrodes, the electromagnetic waves are supplied from a high-frequency power source to each transmission window or electrode through matching devices provided for each transmission window or electrode. For example, a variable capacitor or a variable inductor is used as the matching device, but the life span and matching time of the sliding parts become an issue. In response to this, it is conceivable to minimize the number of matching devices and consume the reflected power using an isolator. However, when the reflected power is large, the power loss due to the isolator becomes large, and the power consumption of the high-frequency power source becomes large. Therefore, in order to minimize the number of matching devices and reduce the power consumption of the high-frequency power source, it is expected to reduce the reflected power when the electromagnetic waves are branched and introduced into multiple locations.

[0010] [Configuration of Plasma Processing Apparatus 100] 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to an embodiment of the present disclosure. The plasma processing apparatus 100 shown in FIG. 1 includes a processing vessel 101, a mounting table 102, a gas supply mechanism 103, an exhaust device 104, a microwave introduction device 105, and a control unit 106. The processing vessel 101 accommodates a substrate W. The mounting table 102 mounts the substrate W. The gas supply mechanism 103 supplies gas into the processing vessel 101. The exhaust device 104 exhausts the inside of the processing vessel 101. The microwave introduction device 105 generates microwaves for generating plasma in the processing vessel 101, and introduces the microwaves into the processing vessel 101. The control unit 106 controls the operation of each unit of the plasma processing apparatus 100.

[0011] The processing vessel 101 is made of a metal material such as aluminum or an alloy thereof, has a substantially cylindrical shape, and has a plate-like top wall portion 111 and bottom wall portion 113, and a side wall portion 112 connecting them. The microwave introduction device 105 is provided on the upper part of the processing vessel 101, and functions as a plasma generating means that introduces electromagnetic waves (microwaves) into the processing vessel 101 to generate plasma. The microwave introduction device 105 will be described in detail later.

[0012] The top wall 111 has a plurality of openings into which a microwave radiation mechanism, an output end of a second waveguide, and a gas introduction section, which will be described later, of the microwave introduction device 105 are fitted. The side wall 112 has a transfer port 114 for transferring a substrate W, which is a substrate to be processed, between the side wall 112 and a transfer chamber (not shown) adjacent to the processing vessel 101. The transfer port 114 is adapted to be opened and closed by a gate valve 115. The bottom wall 113 is provided with an exhaust device 104. The exhaust device 104 is provided on an exhaust pipe 116 connected to the bottom wall 113, and includes a vacuum pump and a pressure control valve. The inside of the processing vessel 101 is exhausted through the exhaust pipe 116 by the vacuum pump of the exhaust device 104. The pressure inside the processing vessel 101 is controlled by a pressure control valve.

[0013] The mounting table 102 is disk-shaped and made of ceramics such as AlN. The mounting table 102 is supported by a cylindrical support member 120 and a base member 121 made of ceramics such as AlN, which extend upward from the center of the bottom of the processing vessel 101. A guide ring 181 for guiding the substrate W is provided on the outer edge of the mounting table 102. Furthermore, inside the mounting table 102, lifting pins (not shown) for lifting and lowering the substrate W are provided so as to be able to protrude and retract from the upper surface of the mounting table 102.

[0014] Furthermore, a resistance heating type heater 182 is embedded inside the mounting table 102, and this heater 182 heats the substrate W placed thereon via the mounting table 102 by being supplied with power from a heater power supply 183. A thermocouple (not shown) is inserted in the mounting table 102, and the heating temperature of the substrate W can be controlled to a predetermined temperature, for example, in the range of 300 to 1000° C., based on a signal from the thermocouple. Furthermore, an electrode 184 having a size approximately equal to that of the substrate W is embedded above the heater 182 in the mounting table 102, and a high frequency bias power supply 122 is electrically connected to this electrode 184. A high frequency bias for attracting ions is applied from this high frequency bias power supply 122 to the mounting table 102. Note that the high frequency bias power supply 122 may not be provided depending on the characteristics of the plasma processing.

[0015] The gas supply mechanism 103 is for introducing a plasma generating gas and a raw material gas for forming, for example, a graphene film (carbon-containing film) into the processing vessel 101, and has a plurality of gas introduction nozzles 123. The gas introduction nozzles 123 are fitted into openings formed in the ceiling wall 111 of the processing vessel 101. The gas introduction nozzles 123 are connected to a gas supply pipe 191. The gas supply pipe 191 is branched into five branch pipes 191a, 191b, 191c, 191d, and 191e. An Ar gas supply source 192, an O2 gas supply source 193, an N2 gas supply source 194, an H2 gas supply source 195, and a C2H2 gas supply source 196 are connected to the branch pipes 191a, 191b, 191c, 191d, and 191e. The Ar gas supply source 192 supplies Ar gas as a noble gas (rare gas) that is a plasma generating gas. The O2 gas supply source 193 supplies O2 gas as an oxidizing gas, which is a cleaning gas. The N2 gas supply source 194 supplies N2 gas used as a purge gas or the like. The H2 gas supply source 195 supplies H2 gas as a reducing gas. The C2H2 gas supply source 196 supplies acetylene (C2H2) gas as a carbon-containing gas, which is a film-forming raw material gas. The C2H2 gas supply source 196 may supply other carbon-containing gases, such as ethylene (C2H4).

[0016] Although not shown, the branch pipes 191a, 191b, 191c, 191d, and 191e are provided with mass flow controllers for flow rate control and valves before and after the mass flow controllers. It is also possible to adjust the dissociation of gases by providing a shower plate to supply C2H2 gas and H2 gas to a position close to the substrate W. The same effect can be obtained by extending the nozzles for supplying these gases downward.

[0017] As described above, the microwave introduction device 105 is provided above the processing vessel 101, and functions as a plasma generating means for generating plasma by introducing electromagnetic waves (microwaves) into the processing vessel 101. The microwave introduction device 105 is an example of an electromagnetic wave supply mechanism.

[0018] The microwave introduction device 105 has a top wall 111 of the processing container 101, a microwave output unit 130, and an antenna unit 140. The top wall 111 functions as a top plate. The microwave output unit 130 generates microwaves and distributes the microwaves to a plurality of paths before outputting them. The antenna unit 140 introduces the microwaves output from the microwave output unit 130 into the processing container 101.

[0019] The microwave output unit 130 has a microwave power supply, a microwave oscillator, an amplifier, and a distributor. The microwave oscillator is solid-state and oscillates (e.g., PLL oscillates) a microwave at, for example, 860 MHz. The frequency of the microwave is not limited to 860 MHz, and it is possible to use a frequency in the range of 700 MHz to 10 GHz, such as 2.45 GHz, 8.35 GHz, 5.8 GHz, and 1.98 GHz. The microwave oscillator can vary the oscillation frequency, for example, by frequency modulation. The amplifier amplifies the microwave oscillated by the microwave oscillator. The distributor distributes the microwave amplified by the amplifier to a plurality of paths. The distributor distributes the microwave while matching the impedance of the input side and the output side. The distributor distributes the microwave to, for example, one microwave radiation mechanism 143 and three branch circuits 150, which will be described later.

[0020] The antenna unit 140 has a microwave radiation mechanism 143 arranged at the center of the top wall 111, and a branch circuit 150. A plurality of output ends 155 of the second waveguides 152 constituting the branch circuit 150 are arranged on the same circumference so as to surround the periphery of the microwave radiation mechanism 143. As described later, the branch circuit 150 includes, for example, a first waveguide 151, two second waveguides 152, and a branch point 153 that branches the first waveguide 151 into two second waveguides 152. For example, three branch circuits 150 are arranged around the microwave radiation mechanism 143. That is, six output ends 155 of the second waveguides 152 are arranged around the microwave radiation mechanism 143. An amplifier unit 142 is provided between the microwave output unit 130 and the microwave radiation mechanism 143 and between the microwave output unit 130 and the branch circuit 150. The microwaves distributed by the distributor of the microwave output unit 130 are amplified by the amplifier unit 142. The microwaves output from the amplifier unit 142 are radiated into the processing vessel 101 from a microwave transmitting plate 163 of the antenna unit described later via a microwave radiation mechanism 143 and each branch circuit 150.

[0021] The amplifier unit 142 has a phase shifter, a variable gain amplifier, a main amplifier, and an isolator. The phase shifter changes the phase of the microwave. The variable gain amplifier adjusts the power level of the microwave input to the main amplifier. The main amplifier is configured as a solid-state amplifier. The isolator separates the reflected microwave reflected by the microwave radiation mechanism 143 and the branch circuit 150 and heading toward the main amplifier. A matching device may be provided between the amplifier unit 142 and the branch circuit 150.

[0022] A microwave transmitting plate 163 fitted in the ceiling wall 111 is provided on the lower surface side of the microwave radiation mechanism 143 and on the lower surface side of the output end 155 of the branch circuit 150, and its lower surface is exposed to the internal space of the processing vessel 101. The microwaves transmitted through the microwave transmitting plate 163 generate plasma in the space within the processing vessel 101.

[0023] FIG. 2 is a schematic diagram showing an example of the ceiling wall of the processing vessel in this embodiment. As shown in FIG. 2, in this embodiment, seven microwave transmitting plates 163 from which microwaves are radiated are provided and are evenly arranged in a hexagonal close-packed arrangement. That is, among the seven microwave transmitting plates 163, one corresponding to the microwave radiating mechanism 143 is arranged at the center of the ceiling wall 111, and the other six microwave transmitting plates 163 corresponding to each output end 155 are arranged around it. The six microwave transmitting plates 163 correspond to, for example, the six output ends 155 of the three branch circuits 150. These seven microwave transmitting plates 163 are arranged so that adjacent microwave transmitting plates 163 are equally spaced apart. In addition, the multiple gas introduction nozzles 123 of the gas supply mechanism 103 are arranged so as to surround the periphery of the central microwave transmitting plate 163. The number of microwave transmitting plates 163 from which microwaves are radiated is not limited to seven.

[0024] Returning to the explanation of Fig. 1, the control unit 106 is typically made up of a computer and controls each part of the plasma processing apparatus 100. The control unit 106 includes a storage unit that stores a process recipe, which is a process sequence and control parameters of the plasma processing apparatus 100, an input means, a display, etc., and is capable of performing a predetermined control according to a selected process recipe. For example, the control unit 106 controls each part of the plasma processing apparatus 100 so as to perform a film formation process.

[0025] [Structure of branch circuit 150] Next, the branch circuit 150 will be described in detail with reference to Fig. 3 and Fig. 4. Fig. 3 is a diagram showing a schematic example of a branch circuit in this embodiment. As shown in Fig. 3, the branch circuit 150 has a first waveguide 151, two second waveguides 152, and a branch point 153 that branches the first waveguide 151 into two second waveguides 152. The branch circuit 150 is provided downstream of the microwave output unit 130 (high frequency power source) and the amplifier unit 142, and is configured as a waveguide. The branch circuit 150 is configured, for example, of a coaxial cable, a waveguide, or the like.

[0026] The first waveguide 151 includes an input end 154. The input end 154 is connected to the amplifier unit 142. The second waveguide 152 is branched at a branch point 153 into two, which are the second waveguides 152a and 152b. A T-branch circuit model, which will be described later, is applied to the branch circuit 150 including the branch point 153. The second waveguides 152a and 152b include output ends 155a and 155b, respectively. The number of branches at the branch point 153 is not limited to two, and may be any n-branch (n is an integer of 2 or more). In the following description, when the second waveguides 152a and 152b and the output ends 155a and 155b are not distinguished from each other, they may simply be referred to as the second waveguide 152 and the output end 155.

[0027] The length of each of the multiple second waveguides 152 is set as follows. When the total number of output ends 155 as viewed from the branch point 153 is n, the lengths of the second waveguides 152 from the branch point 153 to each of the n output ends 155 are different by m×λ / 2+(λ / 2) / n, where λ is the wavelength of the microwave. Here, m is the number of revolutions in the Γ plane of the voltage reflection coefficient Γ as viewed from the branch point 153 to the load of the output end 155, and is 0 or a positive integer. For example, the second waveguides 152a and 152b shown in FIG. 3 are two-branched, so that when m=0, the lengths differ by λ / 4. The lengths of the first waveguide 151 and the second waveguide 152 are determined by the length of the central conductor in the case of a coaxial cable, and are determined by the length of the central axis of the waveguide in the case of a waveguide. In this way, when the lengths of the multiple second waveguides 152 are different, the second and subsequent second waveguides 152 have a bent structure, thereby making it possible to compact the branching circuit 150. For example, in the second waveguides 152a and 152b, the second waveguide 152b has a bent structure as shown in FIG.

[0028] In the branch circuit 150, microwaves 156 inputted from an input end 154 are evenly branched to second waveguides 152a and 152b at a branch point 153 via a first waveguide 151, and are outputted as microwaves 157a and 157b from output ends 155a and 155b, respectively. In the branch circuit 150, according to a T-branch circuit model described later, the first-order reflected waves cancel each other out, so that the reflected wave (voltage) to the input end 154 attenuates to the nth power (n=2) (reflection coefficient Γ n If we consider the reflected wave in terms of power, (reflection coefficient Γ n ) 2 Since the reflected power is attenuated by , it is possible to reduce the reflected power.

[0029] FIG. 4 is a diagram showing an example of the branch circuits connected in series in this embodiment. FIG. 4 shows a state in which the branch circuits 150a and 150b are connected in series to the output terminals 155a and 155b of the branch circuit 150, respectively. The branch circuits 150a and 150b have the same configuration as the branch circuit 150, that is, they are two-branch branch circuits. A microwave is input from the output terminal 155a of the branch circuit 150 to the input terminal 154a of the branch circuit 150a, and is evenly branched and output as microwaves 158a and 158b from the output terminals 155c and 155d, respectively. Similarly, a microwave is input from the output terminal 155b of the branch circuit 150 to the input terminal 154b of the branch circuit 150b, and is evenly branched and output as microwaves 158c and 158d from the output terminals 155e and 155f, respectively. In the example of FIG. 4, the microwave 156 is split into two parts by the branch circuits 150, 150a, and 150b in a tournament system. p The reflected wave is then branched into two waves, and output as microwaves 158a to 158d. At this time, the reflected wave has a reflection coefficient Γ n In the example of Figure 4, p=2, n=2 p If we consider the reflected wave in terms of power, (reflection coefficient Γ n ) 2 Since the reflected power is attenuated by , the reflected power can be further reduced. Also, the difference in length of the second waveguide 152 can be considered for each of the branch circuits 150, 150a, and 150b.

[0030] [Multi-port branch circuit model] Next, a model of a multi-port branch circuit will be described with reference to Fig. 5 to Fig. 8. Fig. 5 is a diagram showing an example of a distribution model of a multi-port branch circuit. Fig. 6 is a diagram showing an example of a synthesis model of a multi-port branch circuit. As shown in Fig. 5, when considering a branch circuit that equally distributes electromagnetic waves (traveling waves) in phase, in the case of n branches, the power is divided by 1 / n, and therefore the amplitudes (for example, voltage amplitudes) of the distributed electromagnetic waves (microwaves) are 1 / √n.

[0031] On the other hand, as shown in Figure 6, if an electromagnetic wave is input from the opposite direction to the same branch circuit, it will act as a combiner if it is a passive transmission line. In the case of n combination, the power is multiplied by n, so the amplitude of the combined electromagnetic wave will be √n. If all power is combined when all phases are aligned, the amplitude input from each port is multiplied by (√n) / n = 1 / √n and propagated. If we consider the relationship when all phases are aligned, with the propagation coefficient of one port being a and the propagation coefficient of the other port being b among the ports on the branch side, no reflected waves are generated at each port, so the relationship is as shown in the following equation (1), which can be transformed to equation (2).

[0032] a + (n - 1) × b = 0 (1) a = -(n-1)b (2)

[0033] Next, as a typical condition for realizing total reflection, we assume that the phases between the ports are shifted by 2π / n. Figure 7 shows an example of a propagation model of a multi-port branching circuit. As shown in Figure 7, the phases of the ports are e 0 , e i2π×1 / n , e i2π×2 / n , e i2π×3 / n , ,e i2π×(n-1) / n Since it is total reflection, the following formula (3) gives us formulas (4) and (5).

[0034] Σe i2π×k / n (k=0~n-1)=0 (3) 1+Σe i2π×k / n (k=1~n-1)=0 (4) Σe i2π×k / n(k=1~n-1)=-1 (5)

[0035] Since the sum of the propagating waves from each port is “1” (total reflection), the above equations (2) and (5) give the following equations (6) to (8), from which equation (9) can be obtained.

[0036] a+b×Σe i2π×k / n (k=1~n-1)=-(n-1)bb (6) -(n-1)bb=-nb (7) -nb=1 (8) b=-1 / n (9)

[0037] In other words, from the perspective of one port, the intrusion into another port is -1 / n×e iθ The reflection to the own port is (n-1) / n×e iθ Note that e iθ indicates that the phase is arbitrary.

[0038] Here, equation (3) will be explained using FIG. 8. FIG. 8 is a diagram showing, with complex space vectors, how the sum of the propagating waves from each port becomes total reflection. Graph 10 in FIG. 8 shows the complex space vectors for k=0 to n-1 in equation (3). The left side of equation (3) is equivalent to adding each complex space vector in order, in other words, as shown in graph 11, it is congruent with a regular n-gon with the same side length and equal interior angles, so it is "0".

[0039] [T-branch circuit model] Next, using Figs. 9 to 12, a T-branch circuit model, which is a two-port branch circuit, is used to calculate the reflection coefficient Γ n Next, we will explain the attenuation in (n=2). Fig. 9 is a diagram that shows a schematic example of a T-branch circuit model. Model 12 shown in Fig. 9 is a model in which the length from input terminal A to output terminals B and C is the same. In model 12, an electromagnetic wave (traveling wave) input from input terminal A is evenly branched to output terminals B and C. The reflected waves at output terminals B and C are in phase with each other, so they are combined at the branch point and return to input terminal A.

[0040] Fig. 10 is a diagram showing a schematic example of a T-branch circuit model in this embodiment. Model 13 shown in Fig. 10 is a model in which the waveguide on the output end B side of model 12 is extended by λ / 4, which is a length equivalent to (λ / 2) / n. In model 13, an electromagnetic wave (traveling wave) input from input end A is evenly branched to output ends B and C. The reflected wave at output end B has a long path length of λ / 2 on a round trip, so its phase is shifted by 180 degrees from the reflected wave at output end C. In other words, the reflected waves at output ends B and C have opposite phases and cancel each other out at the branch point.

[0041] FIG. 11 is a diagram showing an example of a propagation condition in a T-branch circuit model. Propagation condition 14 shown in FIG. 11 represents a voltage transmission coefficient 1 / √2 for evenly distributing power input from input terminal A with an amplitude (voltage amplitude) of "1". In other words, a voltage of "1 / √2" is output to output terminals B and C, respectively. Propagation condition 15 represents that when voltages (reflected waves) input from output terminals B and C with an amplitude of "1" are in phase, they are combined and a voltage with an amplitude of "√2" is output from input terminal A. Propagation condition 16 represents that when voltages (reflected waves) input from output terminal B with "1" and from output terminal C with "-1" (phase inversion) are in phase, they are combined (cancelled out) and a voltage of "0" is output from input terminal A.

[0042] When propagation conditions 14 to 16 are satisfied, the reflected wave is considered to propagate as shown in propagation conditions 17 and 18. In propagation condition 17, a voltage "1" input from output terminal B propagates "1 / √2" to input terminal A, is reflected at the branching point and returns "-1 / 2" to output terminal B, and propagates "1 / 2" to output terminal C. In propagation condition 18, a voltage "1" input from output terminal C propagates "1 / √2" to input terminal A, is reflected at the branching point and returns "-1 / 2" to output terminal C, and propagates "1 / 2" to output terminal B.

[0043] Fig. 12 is a diagram showing an example of reflection in a T-branch circuit model. Fig. 12 shows an example of reflection at output ends B and C in the case where the reflected wave propagates as shown in propagation conditions 17 and 18 in model 12. Note that output ends B and C are load ends, and reflect the electromagnetic wave with reflection coefficients Γ1 and Γ2, respectively. Also, in Fig. 12, the electromagnetic wave is expressed as a voltage amplitude.

[0044] An electromagnetic wave (traveling wave) input of "1" from input terminal A propagates to output terminals B and C as a wave multiplied by "1 / √2". The travelling wave is reflected at output terminals B and C with reflection coefficients Γ1 and Γ2, respectively, and becomes reflected waves with amplitudes of "1 / √2×Γ1" and "1 / √2×Γ2" respectively (first time in Figure 12). The first reflected wave is incident on the branching point in the opposite direction, so it is reflected toward output terminals B and C respectively. The reflected waves from the branching point toward output terminals B and C have amplitudes of "1 / √2×1 / 2×(Γ2-Γ1)" and "1 / √2×1 / 2×(Γ1-Γ2)" respectively. Furthermore, the reflected waves from the branching point toward output terminals B and C are reflected at output terminals B and C with reflection coefficients Γ1 and Γ2, respectively (second time in Figure 12). The second reflected wave has amplitudes of 1 / √2×1 / 2×(Γ2-Γ1)×Γ1 and 1 / √2×1 / 2×(Γ1-Γ2)×Γ2 at output terminals B and C, respectively. The second reflected wave enters the branching point in the opposite direction, so it is reflected toward output terminals B and C. The reflected waves from the branching point toward output terminals B and C have amplitudes of 1 / √2×1 / 2×(Γ2-Γ1)×-1 / 2×(Γ2+Γ1) and 1 / √2×1 / 2×(Γ1-Γ2)×-1 / 2×(Γ2+Γ1) (third time in Figure 12). Thereafter, reflection is repeated at output terminals B and C in the same way as the first two times.

[0045] First, find the reflected wave on the side of output terminal B. If the wave reflected for the second time at output terminal B is the reflected wave a, as shown in the following equation (10), the sum S of the reflected waves returning to the branch point from the second time onwards is given by the following equation (11).

[0046] a=1 / √2×1 / 2×(Γ2-Γ1)×Γ1 ···(10) S = a + a × (-1 / 2 × (Γ2 + Γ1)) +a×(-1 / 2×(Γ2+Γ1)) 2 +····(11)

[0047] Equations (12) and (13) are obtained by using a general method for finding the sum of an infinite series of equation (11).

[0048] SS×(-1 / 2×(Γ2+Γ1))=a ···(12) S=a / (1+1 / 2×(Γ1+Γ2)) ···(13)

[0049] By adding the first reflected wave “1 / √2×Γ1” to equation (13), the sum of the reflected waves Vs is given by the following equation (14).

[0050] Vs=1 / √2×Γ1 +(1 / √2×1 / 2×(Γ2-Γ1)×Γ1) / (1+1 / 2×(Γ1+Γ2)) (14)

[0051] As for the output terminal C side, as shown in FIG. 12, the reflection coefficient Γ1 and the reflection coefficient Γ2 can be interchanged and the result can be obtained in the same manner as the output terminal B side.

[0052] The composite wave Vr returning to the input terminal A is obtained by multiplying each reflected wave by “1 / √2” and adding them together as shown in the propagation conditions 17 and 18, and is expressed by the following equation (15).

[0053] Vr = (Γ1 + Γ2) / 2 -1 / 2×1 / 2×(Γ2-Γ1) 2 / (1+1 / 2×(Γ2+Γ1)) =(Γ1+Γ2) / 2-(Γ2-Γ1) 2 / (2+(Γ2+Γ1)) / 2 = ((Γ1+Γ2)-(Γ2-Γ1) 2 / (2+Γ2+Γ1)) / 2 =(Γ1+Γ2+2×Γ1×Γ2) / (2+Γ2+Γ1) ···(15)

[0054] Here, if the reflection coefficients are equal and in phase (Γ2=Γ1) to correspond to model 12, the reflected wave Vrc is given by the following equation (16), and the voltage standing wave ratio VSWRc in this case is given by the following equation (17).

[0055] Vrc = Γ1 (16) VSWRc=(1+Γ1) / (1-Γ1) ···(17)

[0056] Next, when the reflection coefficients are equal and in opposite phase (Γ2 = -Γ1) to correspond to model 13, the reflected wave Vra is given by the following equation (18), and the voltage standing wave ratio VSWRa in this case is given by the following equation (19). Note that the reflection coefficient Γ2 = -Γ1 indicates that the phase of the reflected wave at output terminal C is inverted from that at output terminal B.

[0057] Vra = -Γ1 2 (18) VSWRa = (1 + Γ1 2 ) / (1-Γ1 2 ) ···(19)

[0058] That is, in the model 13 corresponding to this embodiment, the reflected wave has a reflection coefficient Γ1 2 It can be seen that the decay rate is

[0059] [Tolerance of branch circuit 150] Next, the allowable error of the length of the second waveguide 152 in the branch circuit 150 will be described with reference to Fig. 13. Fig. 13 is a diagram showing an example of the allowable error of the difference in the length of the second waveguide in this embodiment. Graph 20 in Fig. 13 shows the relationship between the waveguide length (λ / 4) of the difference in the length of the second waveguide 152 and the reflection coefficient |Γ| when, for example, an electromagnetic wave of 2.45 GHz is input to the branch circuit 150. In addition, in graph 20, the reflection coefficient of the load at the output ends 155a and 155b is set to Γ1 = Γ2 = 0.3.

[0060] For example, when the insulator of the coaxial cable in the second waveguide 152 is polyethylene, the wavelength λ of the electromagnetic wave of 2.45 GHz is 122 mm, and the wavelength shortening rate is 0.66, so the phase rotates 360 degrees every 122 mm × 0.66 / 2 = 40.26 mm. That is, if the difference in length between the second waveguide 152a and the second waveguide 152b is λ / 4 = 20.13 mm, the phase rotates (inverts) 180 degrees between the output end 155a and the output end 155b. In the graph 20, for example, the range in which the reflection coefficient |Γ| is 0.1 or less is 20.13 mm ± 0.1 mm. In this embodiment, for example, the range in which the reflection coefficient |Γ| is 0.1 or less, which is estimated to be practically usable even without a matching device, is set as the allowable error. Here, the range in which the reflection coefficient |Γ| is 0.1 or less is the range in which the reflected power is 1% or less. In addition, since graph 20 is defined by a function that converts the phase difference between second waveguide 152a and second waveguide 152b into the waveguide length, the allowable error is proportional to the wavelength λ. Therefore, since the allowable error is ±1 mm when λ / 4=20.13 mm, it can be said that ±λ / 80.52 mm ≒ ±λ / 80 mm. In addition, in the case of n-branching, since the allowable error is also related to the number of branches, the allowable error can be expressed as ±λ / n / 40 mm.

[0061] In the above embodiment, the electromagnetic waves are supplied from the multiple output ends 155 to one processing vessel 101, but the present invention is not limited to this. For example, the electromagnetic waves may be supplied from each output end 155 of one branch circuit 150 to multiple processing vessels (different processing vessels) having the same reflection coefficient when they serve as loads.

[0062] In the above embodiment, the branch circuit 150 is a coaxial cable, but the present invention is not limited to this. For example, the same concept can be applied to a case where the branch circuit 150 is a waveguide.

[0063] As described above, according to this embodiment, the electromagnetic wave supply mechanism (microwave introduction device 105) is an electromagnetic wave supply mechanism for supplying electromagnetic waves into a processing vessel (for example, processing vessel 101) that serves as a load, and includes a first branch circuit (branch circuit 150). The first branch circuit is provided downstream of a high-frequency power source (microwave output unit 130) configured to generate electromagnetic waves, and is configured as a waveguide, and includes a first waveguide 151 having an input end 154, a plurality of second waveguides 152 each having an output end 155, and a branch point 153 that branches the first waveguide 151 into a plurality of second waveguides 152 by n (n is an integer of 2 or more). Each output end 155 is connected to a load or an input end (input ends 154a, 154b) of a second branch circuit (branch circuits 150a, 150b) that is the next branch circuit. In the first branch circuit, when the total number of output ends 155 seen from branch point 153 is n, the lengths of second waveguides 152 from branch point 153 to each of the n output ends 155 differ by m×λ / 2+(λ / 2) / n (m is 0 or a positive integer). As a result, it is possible to reduce reflected power when an electromagnetic wave is branched and introduced into a plurality of locations.

[0064] Moreover, according to the present embodiment, the second waveguides 152 have a bent structure with respect to the lengths of the second and subsequent second waveguides 152. As a result, the positions of the output ends 155 of the second and subsequent second waveguides 152 can be adjusted.

[0065] Moreover, according to this embodiment, a matching box is further connected between the high frequency power supply and the branch point 153. As a result, the reflected power can be further reduced.

[0066] Furthermore, according to this embodiment, the second branch circuit has the same configuration as the first branch circuit and is connected in series to the first branch circuit, which makes it possible to further reduce reflected power.

[0067] Furthermore, according to the present embodiment, the processing vessel is a plurality of processing vessels, and as a result, even when the electromagnetic wave is distributed to the plurality of processing vessels, the reflected power can be reduced.

[0068] Furthermore, according to this embodiment, each of the processing vessels has the same reflection coefficient when it acts as a load, so that reflected waves from each of the processing vessels can cancel each other out.

[0069] According to the present embodiment, the processing vessel is a single processing vessel, and electromagnetic waves are supplied from multiple locations in the single processing vessel into the single processing vessel, respectively. As a result, it is possible to reduce reflected power when the electromagnetic waves are branched and introduced into multiple locations.

[0070] Furthermore, according to the present embodiment, each of the multiple locations in one processing vessel has the same reflection coefficient when it acts as a load, so that reflected waves from different locations in one processing vessel can cancel each other out.

[0071] Moreover, according to this embodiment, the allowable error in length of each of the second waveguides 152 is set based on the wavelength of the electromagnetic wave in the waveguide and the n-branching of the branch point 153. As a result, it is possible to set the allowable error proportional to the wavelength of the electromagnetic wave.

[0072] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.

[0073] The present disclosure can also be configured as follows. (1) An electromagnetic wave supply mechanism for supplying electromagnetic waves into a processing vessel serving as a load, a first branching circuit provided downstream of a high frequency power source configured to generate the electromagnetic wave, configured as a waveguide, including a first waveguide having an input end, a plurality of second waveguides each having an output end, and a branch point that branches the first waveguide into a plurality of second waveguides by n (n is an integer of 2 or more); Each of the output terminals is connected to the load or an input terminal of a second branch circuit that is a next branch circuit; When the total number of the output ends as viewed from the branch point is n, the lengths of the second waveguide from the branch point to each of the n output ends differ by m×λ / 2+(λ / 2) / n (m is 0 or a positive integer), Electromagnetic wave supply mechanism. (2) The second waveguides have a bent structure with respect to the second and subsequent second waveguides, The electromagnetic wave supply mechanism described in (1) above. (3) A matching box is further connected between the high frequency power supply and the branch point. The electromagnetic wave supply mechanism according to (1) or (2). (4) The second branch circuit has the same configuration as the first branch circuit and is connected in series to the first branch circuit. The electromagnetic wave supply mechanism according to any one of (1) to (3). (5) The processing vessel is a plurality of processing vessels. The electromagnetic wave supply mechanism according to any one of (1) to (4). (6) Each of the plurality of processing vessels has the same reflection coefficient when serving as the load. The electromagnetic wave supply mechanism according to (5) above. (7) the processing vessel is a single processing vessel, and the electromagnetic waves are supplied into the single processing vessel from a plurality of locations in the single processing vessel, respectively; The electromagnetic wave supply mechanism according to any one of (1) to (4). (8) Each of the plurality of locations has the same reflection coefficient when it becomes the load. The electromagnetic wave supply mechanism according to (7) above. (9) The plurality of second waveguides each have a length tolerance set based on the wavelength of the electromagnetic wave in the waveguide and the n-branch at the branch point. The electromagnetic wave supply mechanism according to any one of (1) to (8). (10) A processing vessel; an electromagnetic wave supply mechanism configured to supply an electromagnetic wave into the processing vessel as a load; a radio frequency power source configured to generate the electromagnetic waves; Equipped with The electromagnetic wave supply mechanism includes: a first branching circuit provided downstream of the high frequency power source, configured as a waveguide, including a first waveguide having an input end, a plurality of second waveguides each having an output end, and a branch point that branches the first waveguide into a plurality of second waveguides by n (n is an integer of 2 or more); Each of the output terminals is connected to the load or an input terminal of a second branch circuit that is a next branch circuit; When the total number of the output ends as viewed from the branch point is n, the lengths of the second waveguide from the branch point to each of the n output ends differ by m×λ / 2+(λ / 2) / n (m is 0 or a positive integer), Plasma processing equipment. [Explanation of symbols]

[0074] 100 Plasma treatment device 101 Processing vessel 105 Microwave introduction device 130 Microwave output section 140 Antenna unit 143 Microwave Radiation Mechanism 150, 150a, 150b Branch circuits 151 First Waveguide 152,152a,152b 2nd waveguide 153 Branching Point 154, 154a, 154b input terminal 155, 155a~155d Output terminal

Claims

1. An electromagnetic wave supply mechanism for supplying electromagnetic waves into a processing vessel serving as a load, a first branching circuit provided downstream of a high frequency power source configured to generate the electromagnetic wave, configured as a waveguide, the first branching circuit including a first waveguide having an input end, a plurality of second waveguides each having an output end, and a branch point that branches the first waveguide into a plurality of second waveguides by n (n is an integer of 2 or more); Each of the output terminals is connected to the load or an input terminal of a second branch circuit that is a next branch circuit, When a total number of the output ends as viewed from the branch point is n, the lengths of the second waveguide from the branch point to each of the n output ends differ by m×λ / 2+(λ / 2) / n (m is 0 or a positive integer), Electromagnetic wave supply mechanism.

2. The second waveguides have a bent structure with respect to the second and subsequent second waveguides, 2. The electromagnetic wave supply mechanism according to claim 1.

3. A matching box is further connected between the high frequency power supply and the branch point.

3. The electromagnetic wave supply mechanism according to claim 1 or 2.

4. The second branch circuit has the same configuration as the first branch circuit and is connected in series to the first branch circuit.

3. The electromagnetic wave supply mechanism according to claim 1 or 2.

5. The processing vessel is a plurality of processing vessels.

3. The electromagnetic wave supply mechanism according to claim 1 or 2.

6. Each of the plurality of processing vessels has the same reflection coefficient when serving as the load.

6. The electromagnetic wave supply mechanism according to claim 5.

7. the processing vessel is a single processing vessel, and the electromagnetic waves are supplied into the single processing vessel from a plurality of locations in the single processing vessel, respectively; 3. The electromagnetic wave supply mechanism according to claim 1 or 2.

8. Each of the plurality of locations has the same reflection coefficient when it becomes the load.

8. The electromagnetic wave supply mechanism according to claim 7.

9. The plurality of second waveguides have respective lengths whose tolerance is set based on the wavelength of the electromagnetic wave in the waveguide and the n-branch of the branch point.

3. The electromagnetic wave supply mechanism according to claim 1 or 2.

10. A processing vessel; an electromagnetic wave supply mechanism configured to supply an electromagnetic wave into the processing vessel as a load; a radio frequency power source configured to generate the electromagnetic waves; Equipped with The electromagnetic wave supply mechanism includes: a first branching circuit provided downstream of the high frequency power source, configured as a waveguide, including a first waveguide having an input end, a plurality of second waveguides each having an output end, and a branch point that branches the first waveguide into a plurality of second waveguides by n (n is an integer of 2 or more); Each of the output terminals is connected to the load or an input terminal of a second branch circuit that is a next branch circuit, When a total number of the output ends as viewed from the branch point is n, the lengths of the second waveguide from the branch point to each of the n output ends differ by m×λ / 2+(λ / 2) / n (m is 0 or a positive integer), Plasma processing equipment.

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