Plasma processing equipment

Abstract

The load impedances of the multiple antenna sections are matched to be close to each other. [Solution] The plasma processing apparatus comprises a plasma processing chamber having a dielectric top plate and a plurality of antenna units that introduce electromagnetic waves to the dielectric top plate. Each of the plurality of antenna units has a power supply unit that supplies power of electromagnetic waves at a frequency assigned to each of the plurality of antenna units, a radiating unit located corresponding to the power supply unit that radiates power of electromagnetic waves, and a matching unit located between the power supply unit and the radiating unit that performs matching operations for electromagnetic waves at frequencies assigned to each of the plurality of antenna units. Adjacent antenna units are supplied with power of electromagnetic waves at different frequencies from each other.

Description

[Technical Field]

[0001] This disclosure relates to a plasma processing apparatus. [Background technology]

[0002] For example, Patent Document 1 discloses a plasma processing apparatus that introduces multiple microwaves into a processing vessel through a common microwave-transmitting member, and that effectively suppresses microwave interference inside the microwave-transmitting member. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-168186 [Overview of the project] [Problems that the invention aims to solve]

[0004] This disclosure provides a plasma processing apparatus capable of matching the load impedances of multiple antenna sections while keeping them close to each other. [Means for solving the problem]

[0005] One aspect of this disclosure provides a plasma processing apparatus. The plasma processing apparatus comprises a plasma processing chamber having a dielectric top plate and a plurality of antenna units that introduce electromagnetic waves to the dielectric top plate. Each of the plurality of antenna units has a power supply unit that supplies power of electromagnetic waves at a frequency assigned to each of the plurality of antenna units, a radiating unit located corresponding to the power supply unit that radiates power of electromagnetic waves, and a matching unit located between the power supply unit and the radiating unit that performs matching operations for electromagnetic waves at a frequency assigned to each of the plurality of antenna units. Adjacent antenna units are supplied with power of electromagnetic waves at different frequencies from each other. [Effects of the Invention]

[0006] According to this disclosure, the load impedances of multiple antenna sections can be matched while remaining close to each other. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to the embodiment. [Figure 2] Figure 2 shows an example of the configuration of the control unit. [Figure 3] Figure 3 shows an example of the configuration of multiple antenna units. [Figure 4] Figure 4 shows an example of the configuration of the matching section and the radiating section. [Figure 5] Figure 5 is a diagram illustrating the alignment state achieved by multiple alignment units. [Figure 6] Figure 6 shows an example of experimental results when microwaves of one or three frequencies were supplied to seven antenna sections, which are configured as multiple antenna sections. [Figure 7] Figure 7 shows an example of experimental results when microwaves of one or three frequencies were supplied to seven antenna sections, which are configured as multiple antenna sections. [Figure 8] Figure 8 shows an example of the arrangement of the seven antenna units used in the experiments in Figures 6 and 7. [Figure 9] Figure 9 shows the attenuation pattern of microwave power. [Figure 10] Figure 10 shows the change in the z-direction attenuation constant of the microwave electric field. [Figure 11] Figure 11 is a diagram illustrating the averaging time for the reflection coefficient. [Figure 12] Figure 12 shows an example of the microwave power frequencies to be allocated to multiple antenna sections. [Figure 13] Figure 13 shows an example of the microwave power frequencies to be assigned to multiple antenna sections. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the disclosed plasma processing apparatus will be described in detail based on the drawings. Note that the plasma processing apparatus according to the present disclosure is not limited by this embodiment, and the following embodiments can be appropriately combined within a range that does not conflict with each configuration and each processing content of the present disclosure. In addition, each figure referred to below is a schematic one for convenience of explanation. Therefore, details may be omitted, and the dimensional ratios do not necessarily match the actual ones.

[0009] The plasma processing apparatus according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic cross-sectional view showing an example of the plasma processing apparatus 1 according to the embodiment. FIG. 2 is a diagram showing an example of the configuration of the control unit 8. FIG. 3 is a diagram showing an example of the configuration of a plurality of antenna units 5. FIG. 4 is a diagram showing an example of the configuration of the matching unit 63B and the radiation unit 72.

[0010] The plasma processing apparatus 1 shown in FIG. 1 includes a plasma processing chamber 2, a gas supply mechanism 3, an exhaust device 4, a plurality of antenna units 5, and a control unit 8. The plasma processing apparatus 1 performs plasma processing on a substrate W such as a semiconductor wafer or a glass substrate. The plasma processing apparatus 1 may be a device that performs processes (plasma processing) such as film formation and etching on the substrate W by plasma.

[0011] The plasma processing chamber 2 has, for example, a substantially cylindrical shape with an open upper portion. The plasma processing chamber 2 is formed of a metal material such as aluminum and its alloy. The plasma processing chamber 2 includes a top wall 6, a bottom 13, and a side wall portion 12 that connects the top wall 6 and the bottom 13. The top wall 6 is formed of a single dielectric top plate 11 covered with a metal member. However, the top wall 6 may be formed of a plurality of dielectric top plates 11 located corresponding to each of the plurality of antenna units 5. The dielectric top plate 11 closes the upper opening of the plasma processing chamber 2. The dielectric top plate 11 has a plurality of recesses and constitutes microwave introduction portions 6A and 6B.

[0012] The side wall portion 12 has a loading / unloading port 12a for loading and unloading the substrate W between the plasma processing chamber 2 and a transfer chamber (not shown) adjacent to the plasma processing chamber 2. A gate valve G is disposed between the plasma processing chamber 2 and the transfer chamber (not shown). The gate valve G has a function of opening and closing the loading / unloading port 12a. The bottom portion 13 has a plurality (two in FIG. 1) of exhaust ports 13a. An exhaust pipe 14 connects the exhaust ports 13a and the exhaust device 4. The exhaust device 4 may have an APC valve and a high-speed vacuum pump. The exhaust device 4 controls the inside of the plasma processing chamber 2 to a desired pressure.

[0013] A mounting table 21 is disposed inside the plasma processing chamber 2. The mounting table 21 has a mounting surface 21a for mounting the substrate W. The mounting table 21 is supported on the bottom portion 13 via an insulating member 23 by a support member 22. A high-frequency bias power source 25 is connected to the mounting table 21 via a matching unit 24. The high-frequency bias power source 25 supplies high-frequency power for attracting ions to the substrate W. The matching unit 24 functions to match the impedance between the input side and the output side.

[0014] The gas supply mechanism 3 includes a gas supply source 31, a gas introduction portion 15, and a pipe 32 connecting the gas supply source 31 and the gas introduction portion 15. The gas introduction portion 15 penetrates the top wall 6. The gas introduction portion 15 has a plurality of nozzles 16 having a cylindrical shape. The plurality of nozzles 16 have gas holes 16a formed on their lower surfaces. The gas supply source 31 supplies, for example, a gas for plasma generation and a processing gas used for film formation processing, etching processing, and the like.

[0015] The control unit 8 controls each component of the plasma processing apparatus 1. The control unit 8 processes computer-executable instructions to be executed by the plasma processing apparatus 1. The control unit 8 may be configured to control each element of the plasma processing apparatus 1 to execute various processes. In one embodiment, part or all of the control unit 8 may be included in the plasma processing apparatus 1. As illustrated in FIG. 2, the control unit 8 may include a processing unit 81, a storage unit 82, and a communication interface 83.

[0016] The processing unit 81 may be configured to perform various control operations by reading a program from the storage unit 82 and executing the read program. This program may be stored in the storage unit 82 in advance, or it may be obtained via a medium when needed. The obtained program is stored in the storage unit 82 and read from the storage unit 82 and executed by the processing unit 81. The medium may be various storage media readable by a computer, or it may be a communication line connected to the communication interface 83. In the plasma processing apparatus 1, the processing unit 81 provides overall control of each component related to process conditions such as temperature, pressure, gas flow rate, high-frequency power for bias application, and microwave output. Each component may be, for example, a high-frequency bias power supply 25, a gas supply source 31, an exhaust device 4, or multiple antenna units 5. The processing unit 81 may also be a CPU (Central Processing Unit). The storage unit 82 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 83 communicates with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

[0017] <Multiple antenna sections> Returning to Figure 1, the multiple antenna units 5 are provided on the dielectric top plate 11 and function as plasma generation means for introducing microwaves into the plasma processing chamber 2 to generate plasma. In the example in Figure 3, there are five antenna units 5 (only one in the center and two on the outer periphery are shown in Figure 1), but this is not limited to this, and there may be two or more.

[0018] Each of the multiple antenna units 5 has a microwave output unit 50 that generates and outputs microwaves, and a microwave transmission unit 60 that transmits the microwaves output from the microwave output unit 50 to the plasma processing chamber 2. In this way, the multiple antenna units 5 introduce microwaves to the dielectric top plate 11. The microwaves pass through the dielectric top plate 11 and propagate as surface waves within the plasma processing chamber 2. Below the multiple antenna units 5, plasma is excited from the processing gas by the microwave power supplied to each of the multiple antenna units 5. Microwaves are an example of electromagnetic waves.

[0019] As shown in Figure 3, the microwave output unit 50 has a power supply unit 51. The power supply unit 51 includes power supply units 51A, 51Ba to 51Bd. The power supply unit 51 has a microwave oscillator 51a. Note that the microwave oscillator 51a is not shown in power supply units 51Ba to 51Bd. The power supply unit 51 may also have an amplifier, which is not shown.

[0020] The microwave transmission unit 60 includes an amplifier unit 62 that primarily amplifies and outputs microwaves, matching units 63A, 63Ba to 63Bd that adjust the impedance of the microwaves output from the amplifier unit 62, and a radiating unit 72. The radiating unit 72 has radiating sections 72A, 72Ba to 72Bd. A power supply unit 51 and a microwave transmission unit 60 are located correspondingly to each antenna unit 5.

[0021] The frequency of the microwave power allocated to each antenna unit 5 is pre-stored in, for example, the memory unit 82 as one of the parameters for setting the plasma processing conditions. The control unit 8 controls the power supply unit 51 based on the microwave power frequencies allocated to each antenna unit 5 so that adjacent antenna units 5 are supplied with microwave power of different frequencies. The microwave oscillator 51a of the power supply unit 51 oscillates microwaves (for example, PLL oscillation) at a frequency that satisfies the parameter conditions (for example, 860 MHz). Through this control, the power supply unit 51 outputs microwave power of the frequency allocated to its own antenna unit 5 to the microwave transmission unit 60.

[0022] The microwave transmission unit 60 transmits microwaves output from the power supply unit 51. As a result, the microwave transmission unit 60 radiates microwave power at the frequencies assigned to each of the five antenna units 5 from the radiating units 72A, 72Ba to 72Bd. The radiating units 72A, 72Ba to 72Bd also function as microwave slowing materials.

[0023] The configuration of the amplifier section 62 is identical in all cases. Multiple matching sections 63A, 63Ba to 63Bd are located between the amplifier section 62 and the radiating sections 72A, 72Ba to 72Bd, respectively. The amplifier section 62 includes a phase shifter 62A as a phase adjustment section that changes the phase of the microwave, and a variable gain amplifier 62B that adjusts the power level of the microwave input to the main amplifier 62C. Furthermore, the amplifier section 62 includes a main amplifier 62C configured as a solid-state amplifier, and an isolator 62D that separates reflected microwaves that are reflected by the slot antenna section of the microwave introduction section 6A or 6B and head toward the main amplifier 62C.

[0024] As shown in Figures 1 and 3, the matching sections 63A, 63Ba to 63Bd and the radiating sections 72A, 72Ba to 72Bd are provided in a one-to-one correspondence on the dielectric top plate 11. The center of the dielectric top plate 11 is provided with the matching section 63A and the radiating section 72A. The outer circumference of the dielectric top plate 11 is provided with four matching sections 63Ba to 63Bd (only two are shown in Figure 1) and four radiating sections 72Ba to 72Bd. Hereafter, the matching sections 63Ba to 63Bd arranged on the outer circumference will be collectively referred to as matching section 63B. Similarly, hereafter, the radiating sections 72Ba to 72Bd arranged on the outer circumference will be collectively referred to as radiating section 72B. The four matching sections 63B are evenly arranged around the matching section 63A at a 90-degree angle in the circumferential direction (see Figure 12(a)). Figure 4 shows a typical configuration of one matching section 63B located on the outer periphery of the dielectric top plate 11, but the matching section 63A located in the center of the dielectric top plate 11 has a similar configuration. Below, only the configuration of the matching section 63B will be described.

[0025] As shown in Figure 4, the matching unit 63B includes a slug tuner 64 for impedance matching, a main container 65 having a cylindrical shape extending in the vertical direction, and an inner conductor 66 extending in the same direction as the main container 65 within the main container 65. The main container 65 and the inner conductor 66 constitute a coaxial waveguide. The main container 65 constitutes the outer conductor of this coaxial waveguide. The inner conductor 66 has a rod-shaped or cylindrical shape. The space between the inner circumferential surface of the main container 65 and the outer circumferential surface of the inner conductor 66 forms a microwave transmission path 67 through which microwaves are transmitted.

[0026] The slug tuner 64 includes two slugs 69A and 69B arranged in a coaxial waveguide, an actuator 70 that operates the two slugs 69A and 69B, and a matching control unit 71 that controls the actuator 70. The slug tuner 64 further includes a detection unit 78 that detects the incident and reflected microwave waves. The detection unit 78 further has a function to separate the detected incident and reflected waves.

[0027] The slags 69A and 69B have a plate-like and annular shape and are placed between the inner circumferential surface of the main container 65 and the outer circumferential surface of the inner conductor 66. For example, dielectric materials formed from high-purity alumina with a relative permittivity of 10 are used for the slags 69A and 69B.

[0028] Based on commands from the matching control unit 71, the slug tuner 64 moves the slugs 69A and 69B vertically using the actuator 70. This allows the slug tuner 64 to adjust the impedance. For example, the matching control unit 71 may adjust the positions of the slugs 69A and 69B so that the impedance at the termination of the matching unit 63B becomes 50Ω.

[0029] The main amplifier 62C, the slug tuner 64, and the slot antenna section 74B on the dielectric top plate 11 are located in close proximity to each other. In particular, the slug tuner 64 and the slot antenna section 74B constitute a lumped-element circuit and function as a resonator. The slug tuner 64 performs impedance matching up to the slot antenna section 74B, thereby generating a uniform plasma.

[0030] As shown in Figures 1 and 4, the slots in the slot antenna sections 74A and 74B are formed as holes penetrating from the upper surface position in contact with the radiating sections 72A and 72B. In the matching sections 63A and 63B, the microwaves amplified by the main amplifier 62C are transmitted to the microwave introduction sections 6A and 6B through the microwave transmission path 67 between the inner surface of the main body container 65 and the outer surface of the inner conductor 66, and through the radiating sections 72A and 72B. In this embodiment, there is a microwave introduction section 6A located in the center of the dielectric top plate 11 and a microwave introduction section 6B located on the outer periphery of the dielectric top plate 11. The microwave introduction section 6A includes the slot antenna section 74A and a part of the dielectric top plate 11. The microwave introduction section 6B includes the slot antenna section 74B and a part of the dielectric top plate 11. The impedances of the microwave introduction section 6A and the microwave introduction section 6B are examples of the respective load impedances of the multiple antenna sections 5.

[0031] <alignment> Figure 5 is a diagram illustrating the alignment state provided by multiple alignment sections 63A and 63B. Figure 5(a) shows an example of a conventional alignment state provided by multiple alignment sections 63A and 63B, and Figure 5(b) shows an example of a conventional alignment state provided by multiple alignment sections 63A and 63B in the embodiment. The configuration of the multiple alignment sections 63A and 63B in the conventional configuration shown in Figure 5(a) and the embodiment shown in Figure 5(b) is the same.

[0032] As shown in Figure 5(a), the multiple matching units 63A and 63B are supplied with microwave power of the same frequency and phase from a single shared frequency oscillator. In other words, the power supply unit 51 and the matching units 63A and 63B are connected in a one-to-many relationship. The multiple matching units 63A and 63B match their impedances by moving their respective slugs 69A and 69B so that the reflected microwave power supplied to each unit is minimized.

[0033] The time it takes for slugs 69A and 69B to move to the matching position (hereinafter referred to as the matching time) is determined for each matching unit 63A and 63B according to the preset position (initial position) of slugs 69A and 69B. For this reason, the difference in matching times between multiple matching units 63A and 63B can be long, for example, on the order of seconds. In the example shown in Figure 5(a), suppose that matching unit 63B is matched before matching unit 63A. In this case, the matching unit 63B, which was matched first, is matched under the condition that the antinodes of the standing waves shown at points P1 and P2 are located on the dielectric top plate 11 below the matching unit 63B such that the microwave electric field is strongest on the dielectric top plate 11 below the matching unit 63B.

[0034] Microwave power is incident on the slot antenna section 74A connected to the matching section 63A from another slot antenna section 74B connected to the matching section 63B, passing through the dielectric top plate 11. Therefore, the distribution of standing waves that appear under the matching section 63B, which is matched first, becomes the reference, and in the matching section 63A, which is matched later, the standing waves that appear under that matching section 63A are matched under the condition that there are no antinodes of the standing waves, as shown at point P3. In this state, the plasma density under the dielectric top plate 11 of the slot antenna section 74A becomes low, while the plasma density under the dielectric top plate 11 of the slot antenna section 74B connected to the matching section 63B becomes high. As a result, the plasma density becomes non-uniform. Also, the value of the impedance (hereinafter also referred to as load impedance) in the matching section 63A at this time will be different from the value of the load impedance in the matching section 63B.

[0035] This phenomenon does not occur in plasma processing equipment where multiple slot antennas correspond to a single microwave source (a microwave source with a one-to-one power supply and matching unit). In such plasma processing equipment with multiple slot antennas for a single microwave source, the load impedance seen from the microwave source becomes the average impedance of the load impedances of each slot antenna. Therefore, as in the case of Figure 5(a), the load impedance seen from the microwave source is not directly related to the plasma density below the antenna.

[0036] In contrast, in this embodiment, the multiple power supply units 51 of the multiple antenna units 5 supply microwave power of different frequencies assigned to each antenna unit 5 to each antenna unit 5. Furthermore, the power supply units 51 supply microwave power of different frequencies to adjacent antenna units 5. The multiple matching units 63A and 63B shown in Figure 5(b) are supplied with microwave power of their respective assigned frequencies from the microwave oscillators 51a of the multiple power supply units 51, which are connected to each of the multiple matching units 63A and 63B on a one-to-one basis. Furthermore, adjacent multiple matching units 63A and 63B are supplied with microwave power of different frequencies. The multiple matching units 63A and 63B match their impedances so that the reflected wave power of microwaves of the frequency assigned to their own antenna unit 5 is minimized. As a result, the plasma processing apparatus 1 can be matched under the condition that the antinodes of standing waves occur on the dielectric top plate 11 beneath the matching units 63A and 63B.

[0037] Specifically, the matching control unit 71 performs the matching operation by moving the slags 69A and 69B within the coaxial waveguide (coaxial line) in relation to the microwaves of the frequency assigned to its own antenna unit 5. In other words, the matching control unit 71 only recognizes the microwave power of the frequency assigned to its own antenna unit 5. Therefore, the matching control unit 71 can ignore microwave power of other frequencies propagating from other antenna units 5 through the dielectric top plate 11 and match the microwaves of the frequency assigned to its own antenna unit 5. In other words, even if microwaves of different frequencies are incident on its own antenna unit from other antenna units 5, the matching state of its own antenna unit 5 is not affected by the microwaves coming from the other antenna units 5. As a result, the impedance can be matched so that the reflected microwave power is minimized at each antenna unit. This makes it possible to match the load impedances at each microwave input section 6A and 6B of multiple antenna units 5 so that they are close to each other.

[0038] Plasma of approximately the same density is generated under multiple antenna sections 5 within the plasma processing chamber 2, making the plasma uniform overall. In this embodiment, the matching sections 63A, 63Ba~63Bd of the multiple antenna sections 5 function as a detection circuit for reflected waves that respond only to the frequency of their own antenna section 5. As a result, the matching sections 63A, 63Ba~63Bd of each antenna section 5 can perform matching operations without being affected by microwaves from other antenna sections 5. This brings the impedances of the microwave introduction section 6A and microwave introduction section 6B closer together. Therefore, in this embodiment, the multiple antenna sections 5 can be matched while the load impedances of each antenna section 5 are close. As a result, the density of the plasma excited near the dielectric top plate 11 under the matching sections 63A, 63Ba~63Bd becomes uniform, and the plasma is generated uniformly. Note that if it is difficult to prepare oscillators of different frequencies for all antenna sections, since electromagnetic waves emitted from one antenna section mainly affect adjacent antenna sections, a similar effect can be obtained by making the frequencies of adjacent antenna sections different.

[0039] <Experimental Results> Referring to Figures 6 and 7, an example of experimental results regarding the plasma density distribution when microwaves of the same or different frequencies are supplied to multiple antenna units 5 will be explained. Figures 6 and 7 show an example of experimental results when microwaves of one or three frequencies are supplied to seven antenna units 5. Figure 8 shows an example of the arrangement of the seven antenna units used in the experiment in Figures 6 and 7. In this experiment, a plasma processing apparatus 1 was used, which had one antenna unit 5 (matching unit 63A) in the center and six antenna units 5 (matching units 63Ba to 63Bf) on the outer periphery.

[0040] Figures 6(a) and 7(a) show the experimental results when the plasma processing apparatus 1 supplied nitrogen gas and microwave power of one frequency (one type) to all antenna units 5 while controlling the pressure inside the plasma processing chamber 2 to 6 Pa. Figures 6(b) and 7(b) show the experimental results when the plasma processing apparatus 1 supplied nitrogen gas and microwave power of one frequency to all antenna units 5 while controlling the pressure inside the plasma processing chamber 2 to 20 Pa. In other words, in Figures 6(a), (b) and 7(a), (b), the power supply unit 51 supplied microwave power of the same frequency to the matching units 63A and 63B of the seven antenna units 5.

[0041] Figures 6(c) and 7(c) show the experimental results when the plasma processing apparatus 1 supplies nitrogen gas and microwave power of three different frequencies to the plasma processing chamber 2 while controlling the pressure inside the plasma processing chamber 2 to 6 Pa, and the entire antenna section 5 (matching section 63A, matching sections 63Ba to 63Bf) arranged in Figure 8. Figures 6(d) and 7(d) show the experimental results when the plasma processing apparatus 1 supplies nitrogen gas and microwave power of three different frequencies to the plasma processing chamber 2 while controlling the pressure inside the plasma processing chamber 2 to 20 Pa, and the entire antenna section 5 (matching section 63A, matching sections 63Ba to 63Bf) arranged in the same manner as in Figure 8. In other words, in Figures 6(c), (d) and 7(c), (d), the power supply unit 51 supplied microwave power of one frequency to the central matching unit 63A and two different frequencies alternately to the six outer matching units 63B, supplying a total of three frequencies of microwave power.

[0042] In Figure 6, the horizontal axis represents microwave power, and the vertical axis represents plasma density (uniformity). Figure 7 shows the plasma density distribution near the bottom surface of the dielectric top plate 11. Experimental results showed that when one type of microwave power was supplied to the central matching section 63A in Figure 8, and two different frequencies of microwave power were alternately supplied to the six matching sections 63Ba to 63Bf on the outer periphery, the plasma uniformity was better than when microwave power of the same frequency was supplied. In particular, the plasma density near the bottom surface of the dielectric top plate 11, as shown in Figures 7(a) and (b), tended to be lower on the right side of the paper than on the left side at all pressures, but there was almost no bias in the plasma density near the bottom surface of the dielectric top plate 11, as shown in Figures 7(c) and (d), indicating good plasma uniformity throughout the entire bottom surface of the dielectric top plate 11.

[0043] <Example of synchronized operation> An example of the matching operation performed by matching units 63A and 63B will be described. The detection unit 78 detects and separates the incident and reflected microwaves transmitted through the microwave transmission line 67. The matching units 63A and 63B perform the matching operation using, for example, the incident and reflected microwaves detected by the detection unit 78.

[0044] Specifically, the matching control unit 71 receives the incident wave signal and the reflected wave signal from the detection unit 78 and controls the amount of movement of the slugs 69A and 69B so that the reflected wave is minimized for the microwave incident wave of the frequency assigned to its own antenna unit. This allows the plasma processing apparatus 1 to match the load impedances of each of the multiple antenna units 5 while keeping them close together.

[0045] <Frequency Range> Next, the frequency range of the microwave power supplied to the multiple antenna units 5 will be described. In the following description, the center frequency, which is the frequency of the microwave power supplied to any of the multiple antenna units 5, is set as the reference frequency. Then, each power supply unit 51 of the multiple antenna units 5 supplies microwave power to its own antenna unit 5 at a frequency within the range of 95% to 105% of the center frequency. Any antenna unit 5 may be the central antenna unit 5 or any of the outer antenna units 5. Note that the center frequency may be the average value of different frequencies (for example, in the case of three frequencies, the average value of these three).

[0046] The frequency range of the microwaves supplied from the power supply unit 51 to each antenna unit 5 will be explained with reference to Figure 9. Figure 9 is a diagram showing the attenuation pattern of microwave power. In Figure 9, the lower surface of the dielectric top plate 11 is set to 0, and the depth direction of the plasma is set to the z direction.

[0047] The surface microwave waves propagate through the plasma beneath the dielectric top plate 11, attenuating as they go, and are consumed in the generation of the plasma. As shown in Figure 9, the absolute value of the microwave electric field |E| beneath the dielectric top plate 11 is given by E0exp(-αz). The attenuation constant α in the z direction, which is the imaginary part of the wave number in this equation, is a function of frequency and plasma density. E0 is the initial value of the microwave electric field at the lower surface of the dielectric top plate 11.

[0048] When the frequency of microwaves supplied by each power supply unit 51 of the multiple antenna units 5 changes, the attenuation pattern of the microwave electric field changes. The distribution of plasma density in the z direction near the substrate W is determined by the square of the electric field, i.e., α 2 It is proportional to the change in the square of the attenuation constant α (△α / α) if the distribution of plasma density in the z direction under multiple antenna sections 5 is within ±10% or less. 2 It would be good if it fell below 10%.

[0049] Based on the graph in Figure 10, (△α / α) 2 We found the value of △ω / ω at which the value is less than 10%. Figure 10 shows the change in the z-direction attenuation constant of the microwave electric field. In Figure 10, the horizontal axis represents the plasma density, and the vertical axis represents the change in the square of the z-direction attenuation constant of the microwave electric field (△α / α). 2 This figure shows the results of calculations using equations 3.10a and 3.10b from Guided-Wave-Produced Plasmas (Springer Series on Atoms + Plasmas, 24) by Yu. M. Aliev, H. Schluter, and A. Shivarova. Note that ω is the center frequency of the microwave power supplied to the multiple antenna sections 5. For example, the center frequency may be the frequency of the microwave power supplied to the central antenna section 5, or it may be the average value of the frequencies assigned to each of the multiple antenna sections 5. △ω is the difference between the frequency of the microwave power supplied to the multiple antenna sections 5 and the center frequency. In Figure 10, ω represents the frequency of the microwave power supplied to the central antenna section 5. △ω represents the difference between the frequency of the microwave power supplied to the central antenna section 5 and the frequency of the microwave power supplied to the outer antenna sections 5.

[0050] In the graphs of Figure 10(a) to (c), line A represents the imaginary part of the wave number (the attenuation constant α in the z direction), and line B represents the real part of the wave number. Therefore, when △ω / ω shown in Figure 10(a) from line A of the graph is equal to 0.1, the value shown by line A in the surface wave is (△α / α). 2The maximum value is approximately 35%. When Δω / ω shown in Fig. 10(b) is equal to 0.05, (Δα / α) indicated by line A in the surface wave 2 The maximum value is approximately 7%. When Δω / ω shown in Fig. 10(c) is equal to 0.01, (Δα / α) indicated by line A in the surface wave 2 The maximum value is approximately 0.2%. From the above, it can be seen that Δω / ω for which (Δα / α) 2 becomes 10% or less is ±5% or less.

[0051] If the values of the frequencies of the microwaves output from the respective power supply units 51 of the plurality of antenna units 5 differ too much, the difference in the surface wave resonance frequencies is large, and the z-direction distribution of the plasma density generated under the plurality of antenna units 5 changes. On the other hand, if the absolute value of the difference between the frequency of the microwave output from each power supply unit 51 and the center frequency is 5% or less, the plasma processing apparatus 1 can make the change amount (Δα / α) of the square of the attenuation constant α 2 10% or less. At this time, since the difference (variation) in the plasma density near the substrate W is considered to be ±10% or less, almost no non-uniformity of the plasma density due to the difference in the frequencies output from the respective power supply units 51 occurs. Therefore, taking the frequency of the microwave power supplied to any one of the plurality of antenna units 5 as the center frequency, the microwave power having a frequency within the range from 95% to 105% of the center frequency may be supplied to its own antenna unit 5. For example, when the center frequency of the microwave power is 860 MHz, the difference Δω from the center frequency is generally within the frequency range from approximately -40 MHz to +40 MHz. Therefore, if the frequency of the microwave power output from each power supply unit 51 is within the range of approximately 820 MHz to approximately 900 MHz when the center frequency is 860 MHz, no non-uniformity of the plasma density occurs. Note that at this time, it is not necessary to take any one of the frequencies of the microwave power output from the plurality of power supply units 51 as the center frequency.

[0052] <Average time t regarding reflection coefficient> Next, the averaging time t for the reflection coefficient will be explained. The matching control unit 71 may average the reflection coefficient values ​​of the microwave reflected waves detected by the detection unit 78 over a time longer than the time shown in Equation 1 below (averaging time t), and control the amount of movement of the slags 69A and 69B based on the averaged reflection coefficient values. t = 1 / (f max -f min )···(1) Note that in Equation 1, f max is equal to ω + △ω, and f min ω is equal to △ω.

[0053] The averaging time t shown in Equation 1 will be explained with reference to Figure 11. Figure 11 is a diagram illustrating the averaging time t with respect to the reflection coefficient. In Figure 11, the horizontal axis represents time (seconds), and the vertical axis represents the floating voltage. The floating voltage is the voltage at which the inflow of electrons and ions in the plasma is equal. There is a correlation between the floating voltage and the plasma density, and it can be assumed that when the floating voltage oscillates, the plasma density also oscillates.

[0054] When microwave power at a center frequency and a frequency with a difference of 100 kHz or 200 kHz from the center frequency is supplied to multiple antenna units 5, the floating voltage oscillates with a period Δf of 100 kHz or 200 kHz, as illustrated in Figure 11. This suggests that the plasma density is oscillating with a period Δf of 100 kHz or 200 kHz. The reflection coefficient is proportional to the plasma density. Therefore, the reflection coefficient is also assumed to be oscillating with a period Δf of 100 kHz or 200 kHz. The reflection coefficient is the value obtained by dividing the amplitude of the reflected microwave detected by the detection unit 78 by the amplitude of the incident wave. When microwave power of two or more frequencies is supplied to adjacent antenna units 5, the microwaves reinforce or cancel each other out, causing the plasma density to fluctuate, becoming stronger or weaker. As a result, the matching operation of the matching units 63A and 63B cannot keep up with the speed of this plasma density oscillation, which leads to a deterioration of the matching state.

[0055] To eliminate the influence of plasma density oscillations on the matching of matching units 63A and 63B, the matching control unit 71 calculates an averaging time t that is longer than one cycle of the floating voltage oscillation period Δf. In Figure 11, the averaging time t is longer than one cycle of the floating voltage oscillation period Δf when microwave power with a frequency difference of 200 kHz from the center frequency is supplied to multiple antenna units 5. Then, the matching control unit 71 calculates the average value of the reflection coefficient from the incident and reflected waves detected during the averaging time t. Based on the average value of the reflection coefficient, the matching control unit 71 controls the amount of movement of the slags 69A and 69B. In this way, the matching units 63A and 63B can stabilize their matching operation by reducing the oscillation of the reflection coefficient.

[0056] <Examples of frequencies to be assigned to the antenna section> Referring to Figures 12 and 13, an example of the frequency of microwave power to be assigned to multiple antenna units 5 will be described. Figures 12 and 13 are diagrams showing an example of the frequency of microwave power to be assigned to multiple antenna units 5.

[0057] Each of the multiple antenna units 5 has a power supply unit 51 that supplies microwave power at the frequency assigned to its respective antenna unit 5. The frequency of the microwave power assigned to each antenna unit 5 is stored, for example, in a storage unit 82.

[0058] Figure 12(a) schematically shows a matching unit 63A located at the center of five antenna sections 5 on the dielectric top plate 11, and matching units 63Ba to 63Bd located on the outer periphery. Each of the five antenna sections 5's power supply units 51 supplies microwave power of one frequency to the central matching unit 63A and two different frequencies alternately to the four outer matching units 63Ba to 63Bd. In the example shown in Figure 12(a), the power supply unit 51 of the central antenna section 5 supplies microwave power of the frequency XHz assigned to its own antenna section 5 to the matching unit 63A. Each of the outer antenna sections 5's power supply units 51 of the matching units 63Ba to 63Bd supplies microwave power of different frequencies X+AHz, X-AHz, X+AHz, and X-AHz between adjacent antenna sections 5, which are assigned to their respective antenna sections 5. As a result, adjacent antenna sections 5 are supplied with microwave power of different frequencies. For example, the matching sections of adjacent antenna sections 5 are: matching section 63A and matching section 63Ba, matching section 63A and matching section 63Bb, matching section 63A and matching section 63Bc, matching section 63A and matching section 63Bd, matching section 63Ba and matching section 63Bd, matching section 63Bd and matching section 63Bb, matching section 63Bb and matching section 63Bc, and matching section 63Bc and matching section 63Ba. As a result, matching sections 63A and 63Ba to 63Bd can perform matching operations for microwave frequencies assigned to their respective antenna sections 5.

[0059] Figure 12(b) schematically shows the central matching unit 63A and the outer matching units 63Ba to 63Bf of the seven antenna units 5. In the example shown in Figure 12(b), the power supply unit 51 of the central antenna unit 5 supplies microwave power at the frequency XHz assigned to its own antenna unit 5 to the matching unit 63A. Each power supply unit 51 of the outer antenna units 5 supplies microwave power at the frequencies X+AHz, X-AHz, X+AHz, X-AHz, X+AHz, and X-AHz, which are assigned to their respective antenna units 5, to the matching units 63Ba to 63Bf. As a result, adjacent antenna units 5 are supplied with microwave power of different frequencies, and the matching units 63A and 63Ba to 63Bf can perform matching operations for the microwave frequencies assigned to their respective antenna units 5.

[0060] Multiple antenna units 5 may be supplied with microwave power of different frequencies to the nearest adjacent antenna unit 5 (hereinafter referred to as the first adjacent antenna unit). Furthermore, the next adjacent antenna unit 5 (hereinafter referred to as the second adjacent antenna unit) may be supplied with microwave power of different or the same frequency. In other words, the distance between first adjacent antenna units is shorter than the distance between second adjacent antenna units.

[0061] Figures 13(a) to 13(c) are arrangement diagrams of the matching sections 63A and 63B of the multiple antenna sections 5, with the dielectric top plate 11 omitted. Figure 13(a) schematically shows the central matching section 63A and the outer matching sections 63Ba to 63Bf of the seven antenna sections 5, similar to Figure 12(b). Of the multiple antenna sections 5, the microwave interference between the first adjacent antenna sections (matching section 63A and matching section 63Bf, matching section 63Ba and matching section 63Bf, matching section 63Be and matching section 63Bf), indicated by solid arrows in Figure 13(a), is the strongest. Therefore, each power supply unit 51 of the first adjacent antenna section supplies microwave power of different frequencies to the first adjacent antenna section. The distance between the second adjacent antenna sections (matching section 63Bb and matching section 63Bf, matching section 63Bd and matching section 63Bf), indicated by dashed arrows in Figure 13(a), is longer than the distance between the first adjacent antenna sections. Therefore, microwave interference between the second adjacent antenna sections is weaker than microwave interference between the first adjacent antenna sections. Consequently, each power supply unit 51 of the second adjacent antenna section may supply microwave power of different frequencies to the second adjacent antenna section, or it may supply microwave power of the same frequency to the second adjacent antenna section.

[0062] Figure 13(b) schematically shows the central matching section 63A and the outer matching sections 63Ba to 63Bc of the four antenna sections 5. Of the multiple antenna sections 5, the microwave interference between the first adjacent antenna sections (matching section 63A and matching section 63Ba), indicated by the solid arrows in Figure 13(b), is the strongest. Therefore, each power supply unit 51 of the first adjacent antenna section supplies microwave power of different frequencies to the first adjacent antenna section. The microwave interference between the second adjacent antenna sections (matching section 63Ba and matching section 63Bb, and matching section 63Ba and matching section 63Bc), indicated by the dashed arrows in Figure 13(b), is weaker than the microwave interference between the first adjacent antenna sections. Therefore, each power supply unit 51 of the second adjacent antenna section may supply microwave power of different frequencies to the second adjacent antenna section, or may supply microwave power of the same frequency, depending on the degree of interference between the second adjacent antenna sections.

[0063] However, the space between the three outer antenna sections 5 constitutes the second adjacent antenna section. If microwave power of a different frequency is supplied only to the matching section 63Ba, and the same frequency of microwave power is supplied to both the matching section 63Ba and the matching section 63Bb, the plasma is likely to become non-uniform. In contrast, if the frequency of the microwave power supplied to the matching sections 63Ba to 63Bc is set to a single frequency, the plasma becomes more uniform. Furthermore, depending on the degree of interference between the second adjacent antenna sections, the frequencies of the microwave power supplied to the matching section 63A and 63Ba to 63Bc may all be different.

[0064] Figure 13(c) schematically shows the central matching section 63A and the outer matching sections 63Ba to 63Bd of the five antenna sections 5. Of the multiple antenna sections 5, the microwave interference between the first adjacent antenna sections (matching section 63A and matching section 63Bc), indicated by the solid arrows in Figure 13(c), is the strongest. Therefore, each power supply unit 51 of the first adjacent antenna section supplies microwave power of different frequencies to the first adjacent antenna section. The microwave interference between the second adjacent antenna sections (matching section 63Ba and matching section 63Bc, and matching section 63Bb and matching section 63Bc), indicated by the dashed arrows in Figure 13(c), is weaker than the microwave interference between the first adjacent antenna sections. Therefore, each power supply unit 51 of the second adjacent antenna section may supply microwave power of different frequencies to the second adjacent antenna section, or may supply microwave power of the same frequency, depending on the degree of interference between the second adjacent antenna sections.

[0065] The above-described antenna units 5 were explained in terms of interference with adjacent antenna units 5, with reference to an antenna unit 5 located in the center of the dielectric top plate 11 or one antenna unit 5 located on the outer periphery. However, the frequency of the microwave power supplied may be determined by similarly considering interference with adjacent antenna units 5 for other antenna units 5 located on the outer periphery of the dielectric top plate 11.

[0066] The microwave power at the center frequency does not necessarily have to be output from the antenna unit 5. Each of the multiple antenna units 5 only needs to be supplied with microwave power at a frequency within the range of 95% to 105% of the set center frequency. The frequencies of the microwave power supplied to the multiple antenna units 5 only need to be two or more different.

[0067] Furthermore, the plasma processing apparatus 1 is not limited to arranging the multiple antenna units 5 concentrically on the dielectric top plate 11; the objectives and effects of this invention can also be achieved by arranging them in a square shape or by arranging them biased to either the left or right side of the dielectric top plate 11. Also, while the plasma processing apparatus 1 arranges the multiple antenna units 5 in the center and on the outer periphery, it is not limited to this; multiple antenna units 5 may be arranged only on the outer periphery, or multiple antenna units may be arranged only in the center.

[0068] <Effects of the Embodiment> As described above, the plasma processing apparatus 1 according to this embodiment comprises a plasma processing chamber 2 having a dielectric top plate 11 and a plurality of antenna units 5 that introduce microwaves to the dielectric top plate 11. Each of the plurality of antenna units 5 has a power supply unit 51 that supplies microwave power at the frequency assigned to each of the plurality of antenna units 5, a radiating unit 72 located corresponding to the power supply unit 51 that radiates microwave power, and matching units 63A and 63B located between the power supply unit 51 and the radiating unit 72 that perform matching operations for the microwaves at the frequencies assigned to each antenna unit 5. In addition, adjacent antenna units 5 are supplied with microwave power at different frequencies from each other. With this configuration, each of the matching units 63A and 63B of the plurality of antenna units 5 matches the impedance so that the reflected wave power of the microwaves at the frequency assigned to its own antenna unit 5 is minimized. In this way, each of the matching units 63A and 63B of the plurality of antenna units 5 functions as a reflected wave detection circuit that responds only to the frequency of its own antenna unit 5. As a result, the matching units 63A and 63B of each antenna unit 5 can perform matching operations that minimize the reflected wave power of microwaves of a specific frequency without being affected by the matching operations of other antenna units 5 or microwaves from other antenna units 5. As a result, multiple antenna units 5 can be matched while keeping the load impedance of each antenna unit close. Thus, it becomes possible to generate a uniform plasma in a plasma processing apparatus 1 having multiple antenna units 5 on a dielectric top plate 11.

[0069] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0070] Furthermore, the following additional information is disclosed regarding the above embodiments. <Note> (1) A plasma processing chamber having a dielectric top plate, The dielectric top plate is equipped with a plurality of antenna units for introducing electromagnetic waves, Each of the multiple antenna sections is, A power supply unit that supplies power for the electromagnetic waves of the frequencies assigned to each of the multiple antenna units, A radiating unit located corresponding to the power supply unit and radiating the power of the electromagnetic waves, It has a matching unit located between the power supply unit and the radiating unit, which performs matching operations for the electromagnetic waves of the frequencies assigned to each of the antenna units, A plasma processing apparatus in which power from electromagnetic waves of different frequencies is supplied to adjacent antenna sections. (2) The plasma processing apparatus according to (1), wherein the power supply unit and the radiation unit are provided in a one-to-one correspondence. (3) The matching unit is The system includes a detection unit that detects the incident and reflected waves of the electromagnetic wave, The plasma processing apparatus according to (1) or (2), wherein the apparatus performs a matching operation so that the reflected wave detected by the detection unit is minimized with respect to the incident wave of the electromagnetic wave of the frequency assigned to its own antenna unit. (4) The aforementioned power supply unit is A plasma processing apparatus according to any one of (1) to (3), wherein the frequency of the electromagnetic wave power supplied to one of the plurality of antenna units is used as the center frequency, and the electromagnetic wave power supplied to the antenna unit itself is within the range of 95% to 105% of the center frequency. (5) The aforementioned center frequency is, The plasma processing apparatus according to (4), which is the average value of the frequencies assigned to each of the multiple antenna sections. (6) The matching unit includes a slug that can move within the coaxial waveguide, A plasma processing apparatus according to any one of (1) to (5), comprising a matching control unit that performs a matching operation by moving the slug with respect to the electromagnetic wave of the frequency assigned to its own antenna unit. (7) The matching unit is The system includes a detection unit that detects the incident and reflected waves of the electromagnetic wave, The matching control unit, The plasma processing apparatus according to (6), wherein the value of the reflection coefficient of the reflected wave detected by the detection unit is averaged over a time longer than the time t shown in the following equation 1, and the amount of slag movement is controlled based on the averaged value of the reflection coefficient. t=1 / (fmax-fmin)...Equation 1 (8) Among the multiple antenna units, power of electromagnetic waves of different frequencies is supplied to two or more of the closest adjacent antenna units. A plasma processing apparatus according to any one of (1) to (7), wherein power of electromagnetic waves of different or the same frequency is supplied to two or more adjacent antenna parts at a distance greater than the distance between the two or more adjacent antenna parts. [Explanation of Symbols]

[0071] 1: Plasma processing equipment 2: Plasma processing chamber 3: Gas supply mechanism 5: Antenna section 8: Control Unit 11: Dielectric top plate 51: Power supply section 50: Microwave output section 51a: Microwave Oscillator 60: Microwave transmission section 63A, 63B: Matching part 64: Slag Tuner 69A, 69B: Slag 70: Actuator 71: Matching Control Unit 72: Radiation section 78: Detection unit

Claims

1. A plasma processing chamber having a dielectric top plate, The dielectric top plate is equipped with a plurality of antenna units for introducing electromagnetic waves, Each of the multiple antenna sections is, A power supply unit that supplies power for the electromagnetic waves of the frequencies assigned to each of the multiple antenna units, A radiating unit located corresponding to the power supply unit and radiating the power of the electromagnetic waves, It has a matching unit located between the power supply unit and the radiating unit, which performs matching operations for the electromagnetic waves of the frequencies assigned to each of the antenna units, A plasma processing apparatus in which power from electromagnetic waves of different frequencies is supplied to adjacent antenna sections.

2. The plasma processing apparatus according to claim 1, wherein the power supply unit and the radiation unit are provided in a one-to-one correspondence.

3. The matching unit is The system includes a detection unit that detects the incident and reflected waves of the electromagnetic wave, The plasma processing apparatus according to claim 1, wherein the detection unit performs a matching operation so that the reflected wave detected by the detection unit is minimized with respect to the incident wave of the electromagnetic wave of the frequency assigned to the antenna unit itself.

4. The aforementioned power supply unit is The plasma processing apparatus according to claim 1, wherein the frequency of the electromagnetic wave power supplied to one of the plurality of antenna units is used as the center frequency, and the power of the electromagnetic wave within a range of 95% to 105% of the center frequency is supplied to the antenna unit itself.

5. The aforementioned center frequency is, The plasma processing apparatus according to claim 4, wherein the average value of the frequencies assigned to each of the multiple antenna sections.

6. The matching unit includes a slug that can move within the coaxial waveguide, The plasma processing apparatus according to claim 1, further comprising a matching control unit that performs a matching operation by moving the slug with respect to the electromagnetic wave of the frequency assigned to its own antenna unit.

7. The matching unit is The system includes a detection unit that detects the incident and reflected waves of the electromagnetic wave, The matching control unit, The plasma processing apparatus according to claim 6, wherein the value of the reflection coefficient of the reflected wave detected by the detection unit is averaged over a time longer than the time t shown in the following equation 1, and the amount of slag movement is controlled based on the averaged value of the reflection coefficient. t = 1 / (f ｍａｘ -f ｍｉｎ )・・・Form 1

8. Among the multiple antenna units, power of electromagnetic waves of different frequencies is supplied to two or more of the closest adjacent antenna units. The plasma processing apparatus according to claim 1, wherein power of electromagnetic waves of different or the same frequency is supplied to two or more adjacent antenna sections at a distance greater than the distance between the two or more adjacent antenna sections.

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