Plasma treatment apparatus

Abstract

To make it easy to adjust plasma distribution in a plasma treatment apparatus with a plurality of electromagnetic wave supply parts.SOLUTION: A plasma treatment apparatus comprises: a treatment chamber having an upper opening; a dielectric top plate that partitions an inner space and an outer space of the treatment chamber to close the opening, and has a plurality of recesses formed on a surface facing the outer space; and a plurality of electromagnetic wave supply parts respectively having flat antennas, respectively installed in the plurality of recesses, and configured to supply electromagnetic waves into the treatment chamber. The antennas are disposed at bottom portions of the plurality of recesses.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, Patent Document 1 proposes a microwave introduction device that generates plasma from a processing gas by microwaves introduced into a processing vessel and performs plasma processing on a substrate. A conductive member that constitutes a top wall is disposed on the ceiling of the processing vessel. The conductive member has a number of openings, and a number of dielectric windows are fitted into the openings, and microwaves are introduced into the processing vessel through the dielectric windows. [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 a technique that can facilitate adjustment of plasma distribution in a plasma processing apparatus having a plurality of electromagnetic wave supply units. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a plasma processing apparatus comprising: a processing vessel having an opening at an upper portion; a dielectric top plate that separates an internal space and an external space of the processing vessel so as to cover the opening and has a plurality of recesses formed on its surface facing the external space; and a plurality of electromagnetic wave supply units each having a flat antenna and installed in each of the plurality of recesses and configured to supply electromagnetic waves into the processing vessel, the antennas being located at the bottom of the plurality of recesses. Effect of the Invention

[0006] According to one aspect, it is possible to easily adjust the plasma distribution in a plasma processing apparatus having a plurality of electromagnetic wave supply units. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to an embodiment; [Diagram 2] 3A and 3B are a cross-sectional view and a plan view of a dielectric top plate according to the first embodiment. [Diagram 3] 4A and 4B are diagrams showing a dielectric top plate and a first example of an electric field intensity distribution according to the first embodiment. [Figure 4] 11A and 11B are a cross-sectional view and a plan view of a dielectric top plate according to a second embodiment. [Diagram 5] FIG. 13 is a diagram showing a second example of a dielectric top plate and an electric field intensity distribution according to the second embodiment. [Figure 6] 13A and 13B are diagrams showing a third example of a dielectric top plate and an electric field intensity distribution according to the second embodiment. [Figure 7] 13A and 13B are a cross-sectional view and a plan view of a dielectric top plate according to a third embodiment. [Figure 8] FIG. 4 is a cross-sectional view of a dielectric top plate according to a reference example, a first embodiment, and a third embodiment. [Figure 9] 11A to 11C are diagrams showing examples of the results of electric field intensity distribution on the dielectric top plate according to the reference example, the first embodiment, and the third embodiment. [Figure 10] 6 is a graph showing an example of the results of the electric field intensity in the radial direction for each of the dielectric top plates according to the reference example, the first embodiment, and the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0009] [Plasma processing equipment] A configuration example of a plasma processing apparatus according to an embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus 1 according to an embodiment. The plasma processing apparatus 1 has a processing vessel 2 that accommodates a substrate W, for example a semiconductor wafer, and a dielectric top plate 11. The processing vessel 2 has an opening at the top and is substantially cylindrical. The processing vessel 2 is formed of a metal material such as aluminum and its alloy. The dielectric top plate 11 is provided to close the opening of the processing vessel 2, and separates the internal space of the processing vessel 2 from the external space. The internal space of the processing vessel 2 separated by the dielectric top plate 11 is a vacuum, and the external space is the atmosphere. The dielectric top plate 11 is formed of a dielectric material such as alumina (Al2O3). However, the dielectric top plate 11 is not limited to alumina. The surface of the dielectric top plate 11 that contacts the external space is covered with a metal (not shown).

[0010] Furthermore, the plasma processing apparatus 1 includes a gas supply unit 31 that supplies a processing gas into the processing vessel 2, an exhaust unit 4 that exhausts the inside of the processing vessel 2, and an electromagnetic wave supply unit 5 that introduces an electromagnetic wave into the processing vessel 2. In this embodiment, as an example of the electromagnetic wave, a microwave with a frequency of 860 MHz is applied. However, the electromagnetic wave is not limited to the microwave with a frequency of 860 MHz, and may be an electromagnetic wave with a frequency of 300 MHz to 300 GHz.

[0011] A plurality of electromagnetic wave supply units 5 are provided on the surface (upper surface) of the dielectric top plate 11 on the external space side of the processing vessel 2. The electromagnetic wave supply unit 5 has a coaxial waveguide 63 having an internal conductor 63a and an external conductor 63b arranged on the outer side of the internal conductor 63a. The tip of the internal conductor 63a is connected to an antenna 65 via a dielectric plate 64 having a conductor at its center. That is, the antenna 65 is provided at each end of the plurality of electromagnetic wave supply units 5.

[0012] The antenna 65 is made of metal and has a flat plate shape. A ring-shaped slot S is formed in the antenna 65. The antenna 65 has a radiation surface that radiates microwaves from the slot S. The dielectric plate 64 has a function of adjusting impedance.

[0013] The surface (top surface) of the dielectric top plate 11 facing the external space has a plurality of recesses 66. A plurality of electromagnetic wave supplying parts 5 are respectively disposed in the plurality of recesses 66 of the dielectric top plate 11. The antenna 65 is located at the bottoms 66a of the plurality of recesses 66.

[0014] The shape of the recess 66 in plan view is circular or similar to that of the antenna 65. For example, if the antenna 65 is circular (a perfect circle), the shape of the recess 66 in plan view may be similar to that of the antenna 65. For example, if the antenna 65 is elliptical, the shape of the recess 66 in plan view may be circular.

[0015] The microwave output unit 50 has a distributor (not shown) and distributes the microwaves by the distributor. The distributed microwaves are introduced into the electromagnetic wave supply unit 5 via the microwave introduction module 61 and propagate between the internal conductor 63a and the external conductor 63b. The radiation surface of the antenna 65 that radiates the microwaves is in contact with the bottom 66a of the recess 66. With this configuration, the electromagnetic wave supply unit 5 radiates the microwaves through the slots S of the antenna 65, and the microwaves are propagated inside the dielectric top plate 11 to supply them into the processing vessel 2. The gas is decomposed by the energy of the microwaves near the surface (lower surface) of the dielectric top plate 11 on the internal space side, generating plasma.

[0016] A mounting table 21 is disposed inside the processing vessel 2. The mounting table 21 has a mounting surface 21a, and a substrate W is placed on the mounting surface 21a. The mounting table 21 is supported by a support member 22 and is insulated by an insulating member 23 provided between the support member 22 and the processing vessel 2.

[0017] A plurality of exhaust ports 13a (two in FIG. 1 ) are formed in the bottom of the processing vessel 2. An exhaust device 4 is connected to the exhaust ports 13a via exhaust pipes 14. The exhaust device 4 reduces the pressure inside the processing vessel 2 to a desired pressure (vacuum). A transfer port 12a for transferring a substrate W or the like is formed in a sidewall of the processing vessel 2. When transferring a substrate W or the like, the transfer port 12a is opened and closed by a gate valve G.

[0018] The high frequency bias power supply 25 is connected to the mounting table 21 via a matching unit 24. The high frequency bias power supply 25 supplies high frequency power to the mounting table 21 in order to attract ions into the substrate W.

[0019] The dielectric top plate 11 has a plurality of gas holes 16a penetrating the region other than the recess 66 on the external space side in the thickness direction and configured to supply a processing gas into the processing vessel 2. The plurality of gas holes 16a are formed in the gas nozzle 16. The gas nozzle 16 is connected to a plurality of gas lines 32. The gas nozzle 16 is provided such that the tip of the gas nozzle 16 is located below the lower surface of the dielectric top plate 11. However, the tip of the gas nozzle 16 may be located at the same height as the lower surface of the dielectric top plate 11. The processing gas is supplied from the gas supply unit 31, passes through the gas line 32 and the plurality of gas nozzles 16, and is supplied into the processing vessel 2 from the plurality of gas holes 16a. In one example, the plurality of gas holes 16a are evenly arranged in the circumferential direction between the central electromagnetic wave supply unit 5 and the plurality of electromagnetic wave supply units 5 on the periphery.

[0020] The control unit 8 processes computer-executable instructions that cause the plasma processing apparatus 1 described in the present disclosure to perform operations. In one embodiment, a part or all of the control unit 8 may be included in the plasma processing apparatus 1. In one embodiment, the control unit 8 may be separate from the plasma processing apparatus 1 and communicably connected to the plasma processing apparatus 1. The control unit 8 may include a processing unit, a storage unit, and a communication interface. The control unit 8 is realized by, for example, a computer. The processing unit may be configured to perform various control operations by reading a program from the storage unit and executing the read program. This program may be stored in the storage unit in advance, or may be acquired via a medium when necessary. The acquired program is stored in the storage unit and is read from the storage unit by the processing unit and executed. The medium may be various computer-readable storage media, or may be a communication line connected to the communication interface. The processing unit may be a CPU (Central Processing Unit). The storage unit may include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface may communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

[0021] [Dielectric top plate] In some conventional plasma processing apparatuses, a conductive member is provided on the top plate instead of the dielectric top plate 11. In this case, the conductive member has a number of openings, each of which is fitted with a dielectric window, and microwaves are introduced into the processing vessel through the dielectric window.

[0022] In this configuration, plasma is generated locally under the dielectric window. Therefore, the distribution of the plasma can be adjusted by individually adjusting the intensity of the local plasma. In order to supply plasma uniformly onto the substrate, it is necessary to increase the distance (gap) from the dielectric window to the mounting table 21 and diffuse the plasma in the space between them, thereby supplying the plasma uniformly onto the substrate. Therefore, the distance (gap) must be increased to a certain extent, which hinders the miniaturization of the device. In addition, in this configuration, a gap may occur between the conductive member and the dielectric window, which may cause particles to be generated. Particles are particularly likely to be generated under low-pressure process conditions.

[0023] In contrast, in the plasma processing apparatus 1 according to this embodiment, the top wall of the processing vessel 2 is composed of a single dielectric top plate 11. This eliminates the gap and prevents particle generation. Furthermore, since microwaves can be supplied into the processing vessel 2 from the entire surface of the single dielectric top plate 11, the plasma can be diffused even if the distance (gap) is reduced, and the apparatus can be made more compact.

[0024] On the other hand, in the plasma processing apparatus 1 according to the present embodiment, a plurality of electromagnetic wave supply units 5 are used to adjust the distribution of plasma density. When a plurality of electromagnetic wave supply units 5 are mounted on a single dielectric top plate 11 in this manner, microwaves radiated from a single antenna 65 spread through the dielectric top plate 11. As a result, a problem occurs in that it becomes difficult to adjust the distribution of plasma by individually controlling each of the plurality of electromagnetic wave supply units 5. As a result, the uniformity of the plasma processing of the substrate W is affected.

[0025] Therefore, in the plasma processing apparatus 1 according to the embodiment, a plurality of recesses 66 in which the plurality of electromagnetic wave supply units 5 are respectively installed are formed on the upper surface of the dielectric top plate 11, that is, on the surface facing the external space of the processing vessel 2.

[0026] First Embodiment [Dielectric top plate] The dielectric top plate 11 according to the first embodiment will be described with reference to Fig. 2. Fig. 2(a) is a cross-sectional view of the periphery of the dielectric top plate 11 according to the first embodiment provided in the plasma processing apparatus 1 shown in Fig. 1. Fig. 2(b) is a plan view of the dielectric top plate 11 according to the first embodiment viewed from the lower surface side (bottom 66a). Fig. 2(a) is a cross-sectional view taken along the AA plane of Fig. 2(b).

[0027] 2(b), the dielectric top plate 11 according to the first embodiment has one recessed portion 66 in the center and six recessed portions 66 on the periphery, for a total of seven recessed portions 66. The area of ​​the dielectric top plate 11 other than the recessed portions 66 (hereinafter also referred to as the "flat portion") is of the same height. The bottom surface of the dielectric top plate 11 is flat with no irregularities.

[0028] The electromagnetic wave supply units 5 each have a flat antenna 65 at a tip (end). The antenna 65 has a ring-shaped slot S and has a radiation surface that radiates microwaves from the slot S. The antenna 65 is installed only in the recess 66. The antenna 65 is located at the bottom 66a of the recess 66, and the radiation surface of the antenna 65 is in contact with the bottom 66a. As shown in FIG. 2(b), the shape of the recess 66 in plan view is similar to that of the antenna 65. That is, the recess 66 and the antenna 65 are perfect circles, and the diameter of the recess 66 is larger than the diameter of the antenna 65.

[0029] 2(a), the thickness of the dielectric top plate 11 at the flat portion without the recess 66 is H1, the depth of the recess 66 is H2, and the thickness of the dielectric top plate 11 at the bottom 66a is H3. The thickness H1 is the vertical distance between the upper and lower surfaces of the dielectric top plate 11. The depth H2 is the vertical distance between the upper surface of the dielectric top plate 11 and the bottom 66a. The thickness H3 is the vertical distance between the lower surface of the dielectric top plate 11 and the bottom 66a.

[0030] The thickness H3 of the dielectric top plate 11 at the bottom portion 66a may be λ / 8 or less, where λ is the wavelength of the microwave propagating through the dielectric top plate 11. λ is the wavelength of the electromagnetic wave (microwave) in the dielectric top plate 11, λ0 is the free space wavelength of the electromagnetic wave (microwave) in a vacuum, and ε rWhen the relative dielectric constant of the dielectric top plate 11 is λ=λ0 / √ε r That is, the relative dielectric constant ε r Therefore, the wavelength λ of the microwave in the dielectric top plate 11 is shorter than the free space wavelength λ 0. The lower limit value of the thickness H3 of the dielectric top plate 11 at the bottom portion 66a is 5 mm in consideration of strength.

[0031] By making the thickness H3 of the dielectric top plate 11 at the bottom 66a of the recess 66 of the dielectric top plate 11 thinner than λ / 8, the proportion of microwaves that transmit in the horizontal direction (sideways) decreases, the electromagnetic field distribution can be localized, and the plasma distribution can be efficiently controlled.

[0032] That is, the microwaves are mainly radiated vertically from the slots S to the bottom 66a, and the proportion of the microwaves that are transmitted horizontally (laterally) is small. Therefore, the electromagnetic field of the microwaves radiated from the antenna 65 efficiently contributes to plasma generation in the vicinity of the lower surface of the dielectric top plate 11 below the recess 66. This makes it possible to localize the electromagnetic field distribution, and to efficiently control the plasma distribution.

[0033] Furthermore, the multiple gas holes 16a penetrate the flat portion of the dielectric top plate 11 and supply the processing gas into the processing vessel 2. The microwaves that enter the flat portion spread evenly within the flat portion. Furthermore, the recesses 66 reduce the rate at which the microwaves are transmitted in the horizontal (lateral) direction. This reduces the electric field strength within the flat portion, and by creating a gas flow path in this portion, it is possible to prevent plasma from being generated in the gas flow path and the gas from being decomposed before entering the processing vessel 2.

[0034] [Simulation 1] The configuration of the recess 66 of the dielectric top plate 11 according to the first embodiment and the results of simulation 1 of the electric field intensity distribution will be described with reference to Fig. 3. Fig. 3 is a diagram showing the dielectric top plate 11 according to the first embodiment and a first result of the electric field intensity distribution.

[0035] Fig. 3(a) is a reference example, and shows the electric field strength distribution at the interface between the plasma and the lower surface of the dielectric top plate 111 when a dielectric top plate 111 having a flat upper surface without a recess 66 is used. Figs. 3(b) to (d) show the electric field strength distribution at the interface between the plasma and the lower surface of the dielectric top plate 11 when a dielectric top plate 11 according to the first embodiment is used.

[0036] As a condition for simulation 1, microwaves with a frequency of 860 MHz are supplied from seven electromagnetic wave supply units 5. In the reference example of FIG. 3(a), the thickness H1 of the dielectric top plate 111 is set to 10 mm. In the first embodiment of FIG. 3(b), FIG. 3(c), and FIG. 3(d), the thickness H1 of the dielectric top plate 11 is set to 15 mm, 20 mm, and 30 mm, and the depth H2 of the recess 66 is set to 5 mm, 10 mm, and 20 mm. In addition, the thickness H3 of the dielectric top plate 11 at the bottom 66a is all set to 10 mm.

[0037] 3(a), the dielectric top plate 111 is flat and has no recesses. Therefore, the microwaves radiated from the slots S of the antenna 65 spread over the entire dielectric top plate 111. In the case of the dielectric top plate 111 of the reference example, even if the thickness H1 is changed to 20 mm or 30 mm, the microwaves spread over the entire dielectric top plate 111.

[0038] In contrast, in the first embodiment shown in Figures 3(b) to (d), the dielectric top plate 11 has a recess 66, and the thickness H3 of the dielectric top plate 11 at the bottom 66a is made thinner than λ / 8. This reduces the rate at which microwaves radiated to the bottom 66a are transmitted in the horizontal direction (lateral direction), and the microwaves are transmitted in the generally vertical direction, thereby increasing the electric field strength under the dielectric top plate 11 in which the recess 66 is formed in plan view. As a result, in the results of Simulation 1 shown in Figures 3(b) to (d), the electric field strength under the dielectric top plate 11 in which the recess 66 is formed is clearly higher than the electric field strength under the dielectric top plate 111 in which the recess 66 is not formed.

[0039] 3(b) to (d), it is found that the ratio of microwaves transmitted in the horizontal direction (lateral direction) can be reduced by making the thickness H3 of the dielectric top plate 11 at the bottom 66a of the recess 66 of the dielectric top plate 11 thinner than λ / 8. As a result, the electromagnetic field distribution can be localized under the dielectric top plate 11 where the recess 66 is formed, and the plasma distribution can be efficiently controlled.

[0040] <Second embodiment> [Dielectric top plate] The dielectric top plate 11A according to the second embodiment will be described with reference to Fig. 4. Fig. 4(a) is a cross-sectional view of the periphery of the dielectric top plate 11A according to the second embodiment included in the plasma processing apparatus 1 shown in Fig. 1. Fig. 4(b) is a plan view of the dielectric top plate 11A according to the second embodiment from the lower surface side (bottom 66Aa). Fig. 4(a) is a cross-sectional view taken along the plane BB in Fig. 4(b).

[0041] In the second embodiment, the shape of the concaves and convexes on the top surface of the dielectric top plate 11A is different from that of the top surface of the dielectric top plate 11 according to the first embodiment, and the other configurations are the same. As shown in FIG. 4(b), the dielectric top plate 11A according to the second embodiment has one electromagnetic wave supply unit 5 in the center and six on the periphery, and a convex portion indicated by a bank 67 is provided between adjacent electromagnetic wave supply units 5. The bank 67a between the electromagnetic wave supply units 5 on the periphery surrounding the electromagnetic wave supply unit 5 in the center is annular. The bank 67b between adjacent electromagnetic wave supply units 5 on the periphery is rod-shaped, connected to the bank 67a at the base end of the bank 67b, and extending radially outward from the bank 67a. The tip of the bank 67b is connected to a substantially annular bank 67c surrounding the electromagnetic wave supply unit 5 on the periphery. The banks 67a, 67b, and 67c are also collectively referred to as the bank 67.

[0042] By providing the banks 67 between the adjacent electromagnetic wave supply units 5 in this manner, the depressions other than the banks 67 on the external space side of the processing vessel 2 become the recesses 66A. The bottoms 66Aa of the recesses 66A of the dielectric top plate 11A are at the same height. The lower surface of the dielectric top plate 11A is flat without any irregularities.

[0043] The electromagnetic wave supply units 5 each have a flat antenna 65 at its tip (end). The antenna 65 has a ring-shaped slot S and has a radiation surface that radiates microwaves from the slot S. The antenna 65 is installed only inside the bank 67 (in the recess 66A). The antenna 65 is located at the bottom 66Aa of the recess 66A, and its radiation surface is in contact with the bottom 66Aa. As shown in FIG. 4(b), the recess 66A at the center of the dielectric top plate 11A is similar in shape to the electromagnetic wave supply unit 5, and the six recesses 66A on the periphery are roughly sector-shaped and partially recessed outward along the electromagnetic wave supply unit 5.

[0044] As shown in FIG. 4(a), the thickness of the dielectric top plate 11A at the portion where the bank 67 is present is H1, the height of the bank 67 is H4, and the thickness of the dielectric top plate 11A at the bottom 66Aa is H3. The thickness H1 is the vertical distance between the upper surface of the bank 67 of the dielectric top plate 11A and the lower surface of the dielectric top plate 11A. The height H4 of the bank 67 is the vertical distance between the upper surface of the bank 67 of the dielectric top plate 11A and the bottom 66Aa. The thickness H3 is the vertical distance between the lower surface of the dielectric top plate 11A and the bottom 66Aa. As shown in FIG. 4(a), the width of the banks 67a and 67b is D. The widths D of the banks 67a and 67b are the same. The width of the bank 67c is partially smaller than the width D along the electromagnetic wave supply unit 5. The heights H4 of the banks 67a, 67b, and 67c are the same.

[0045] The height H4 and width D of the bank 67 are within the range of λ / 4±λ / 8 (from λ / 8 to 3λ / 8) when the wavelength of the microwave propagating through the dielectric top plate 11A is λ. If the height H4 and width D of the bank 67 are λ / 4 for the microwaves incident on the bank 67 from the recess 66A, an effect similar to a choke is generated, and an effect of suppressing the microwaves that go beyond the bank 67 and go horizontally (sideways) is generated. However, even if the height H4 and width D of the bank 67 are deviated from λ / 4 by about ±λ / 8, the microwaves weaken each other. For this reason, if the height H4 and width D of the bank 67 are within the range of λ / 4±λ / 8, it is considered that the bank 67 functions as a choke and the microwaves do not propagate beyond the bank 67 to the adjacent recess 66A.

[0046] The upper and lower limits of the thickness H3 of the dielectric top plate 11A at the bottom portion 66Aa may be the same as the range of the thickness H3 of the dielectric top plate 11 according to the first embodiment.

[0047] [Simulation 2] The configuration of the banks 67 of the dielectric top plate 11A according to the second embodiment and the results of a second simulation of the electric field intensity distribution will be described with reference to Fig. 5. Fig. 5 is a diagram showing the dielectric top plate 11A according to the second embodiment and a second example of the electric field intensity distribution.

[0048] Fig. 5(a) is a reference example, and shows the electric field strength distribution at the interface between the plasma and the lower surface of the dielectric top plate 111 when a dielectric top plate 111 with a flat upper surface is used. Figs. 5(b) to (d) show the electric field strength distribution at the interface between the plasma and the lower surface of the dielectric top plate 11A when a dielectric top plate 11A according to the second embodiment is used.

[0049] The conditions for simulation 2 are that the width D of the bank is fixed and the height H4 of the bank 67 is variable. In addition, among the seven electromagnetic wave supply units 5, only the electromagnetic wave supply unit 5 at the center left end is turned off, and microwaves with a frequency of 860 MHz are supplied from the remaining six electromagnetic wave supply units 5. In the reference example of FIG. 5(a), the thickness H1 of the dielectric top plate 111 is set to 10 mm. In the second embodiment of FIG. 5(b), FIG. 5(c), and FIG. 5(d), the height H4 of the bank 67 is set to 20 mm, 30 mm, and 40 mm, and the width D of the bank 67 is all set to 30 mm. In addition, the thickness H3 of the dielectric top plate 11A at the bottom 66Aa is all set to 10 mm. The thickness H1 of the dielectric top plate 11A is set to 30 mm, 40 mm, and 50 mm.

[0050] 5(a), the dielectric top plate 111 is flat and has no recesses. Therefore, the microwaves radiated from the slots S of the antennas 65 of the six electromagnetic wave supply units 5 spread over the entire dielectric top plate 111, and it is not possible to prevent the microwaves from reaching the antenna 65 of the electromagnetic wave supply unit 5 at the center left end.

[0051] 5(b) to (d), the dielectric top plate 11A has a bank 67, and the height H4 and width D of the bank 67 are set to satisfy the condition within the range of λ / 4±λ / 8. This produces an effect similar to a choke in the bank 67, and produces an effect of suppressing microwaves that pass over the bank 67 and travel in the horizontal direction (sideways).

[0052] As a result, the results of simulation 2 shown in Figures 5(b) to (d) show that the microwaves radiated from the slots S of the antennas 65 of the six electromagnetic wave supply units 5 are prevented from leaking into the area of ​​the electromagnetic wave supply unit 5 at the left end of the center.

[0053] As other conditions for Simulation 2, the simulation was performed using dielectric top plate 11A, setting height H4 of banks 67 to 5 mm and 10 mm, and setting width D of banks 67 to 30 mm for all. Under these conditions, the choke-like function of banks 67 was low, and the effect of bouncing microwaves traveling horizontally (sideways) beyond banks 67 was low. This is thought to be because, under these conditions, height H4 and width D of banks 67 do not satisfy the condition of being within the range of λ / 4±λ / 8, respectively.

[0054] [Simulation 3] The configuration of the banks 67 of the dielectric top plate 11A according to the second embodiment and the results of a third simulation of the electric field intensity distribution will be described with reference to Fig. 6. Fig. 6 is a diagram showing the dielectric top plate 11A according to the second embodiment and a third example of the electric field intensity distribution.

[0055] The conditions for simulation 3 are that the height H4 of the bank is fixed and the width D of the bank 67 is variable. As in simulation 2, only the electromagnetic wave supply unit 5 at the center left end is turned off among the seven electromagnetic wave supply units 5, and microwaves with a frequency of 860 MHz are supplied from the remaining six electromagnetic wave supply units 5. In the second embodiment of Figures 6(a), 6(b), and 6(c), the heights H4 of the banks 67 are all set to 30 mm, and the widths D of the banks 67 are set to 40, 30, and 20 mm. The thicknesses H3 of the dielectric top plate 11A in the recesses 66A are all set to 10 mm. The thicknesses H1 of the dielectric top plate 11A are all set to 40 mm.

[0056] 6(a) to 6(c), the height H4 and width D of the bank 67 are set so as to satisfy the condition within the range of λ / 4±λ / 8. This produces an effect similar to a choke in the bank 67, and produces an effect of suppressing microwaves that pass over the bank 67 and travel in the horizontal direction (sideways).

[0057] As a result, the results of simulation 3 shown in Figures 6(a) to (c) show that the microwaves radiated from the slots S of the antennas 65 of the six electromagnetic wave supply units 5 are prevented from leaking into the area of ​​the electromagnetic wave supply unit 5 at the left end of the center.

[0058] As other conditions for Simulation 3, the simulation was performed using the dielectric top plate 11A, with the width D of the bank 67 set to 10 mm, and the height H4 of the bank 67 set to 30 mm. Under these conditions, the choke-like function of the bank 67 was low, and the effect of suppressing microwaves that pass over the bank 67 in the horizontal direction (sideways) was low. Similarly, the simulation was performed using the dielectric top plate 11A, with the width D of the bank 67 set to 20 mm, 30 mm, and 40 mm, and the height H4 of the bank 67 set to 40 mm. Under these conditions, the choke-like function of the bank 67 was also low, and the effect of suppressing microwaves that pass over the bank 67 in the horizontal direction (sideways) was low. This is thought to be because, under these conditions, the height H4 and width D of the bank 67 do not satisfy the condition within the range of λ / 4±λ / 8, respectively.

[0059] As described above, the dielectric top plate 11, 11A according to the first and second embodiments has the recesses 66, 66A on the upper surface thereof. This makes it possible to prevent the microwaves emitted from one antenna 65 from spreading outside the area of ​​the recesses 66 and 66A of the dielectric top plate 11, and to control the plasma distribution for each area.

[0060] <Third embodiment> [Dielectric top plate] The dielectric top plate 11B according to the third embodiment will be described with reference to Fig. 7. Fig. 7(a) is a cross-sectional view of the periphery of the dielectric top plate 11B according to the third embodiment included in the plasma processing apparatus 1 shown in Fig. 1. Fig. 7(b) is a plan view of the dielectric top plate 11B according to the third embodiment viewed from the lower surface side (bottom 66a). Fig. 7(a) is a view cut along the CC plane in Fig. 7(b).

[0061] As shown in Fig. 7(b), the dielectric top plate 11B according to the third embodiment has a total of seven recesses 66, one in the center and six on the periphery, similar to the dielectric top plate 11 according to the first embodiment (see Fig. 2(b)). Note that the area of ​​the dielectric top plate 11B other than the recesses 66 (hereinafter also referred to as the "flat portion") is of the same height. The bottom surface of the dielectric top plate 11B is flat with no irregularities.

[0062] The electromagnetic wave supply units 5 each have a flat antenna 65 at a tip (end). The antenna 65 has a ring-shaped slot S and has a radiation surface that radiates microwaves from the slot S. The antenna 65 is installed only in the recess 66. The antenna 65 is located at the bottom 66a of the recess 66, and the radiation surface of the antenna 65 is in contact with the bottom 66a. As shown in FIG. 7(b), the shape of the recess 66 in a plan view is similar to that of the antenna 65. That is, the recess 66 and the antenna 65 are perfect circles, and the diameter of the recess 66 is larger than the diameter of the antenna 65.

[0063] As shown in Fig. 7(a), the thickness of the dielectric top plate 11B at the flat portion without the recess 66 is H1, the depth of the recess 66 is H2, and the thickness of the dielectric top plate 11B at the bottom 66a is H3. The thickness H1 is the vertical distance between the upper and lower surfaces of the dielectric top plate 11B. The depth H2 is the vertical distance between the upper surface of the dielectric top plate 11B and the bottom 66a. The thickness H3 is the vertical distance between the lower surface of the dielectric top plate 11B and the bottom 66a.

[0064] The thickness H3 of the dielectric top plate 11B at the bottom portion 66a may be λ / 8 or less, where λ is the wavelength of the microwave propagating through the dielectric top plate 11B. λ is the wavelength of the electromagnetic wave (microwave) in the dielectric top plate 11B, λ0 is the free space wavelength of the electromagnetic wave (microwave) in a vacuum, and ε r When the relative dielectric constant of the dielectric top plate 11B is λ=λ0 / √ε r That is, the relative dielectric constant ε r As a result, the wavelength λ of the microwave in the dielectric top plate 11B is shorter than the free space wavelength λ 0. The lower limit value of the thickness H3 of the dielectric top plate 11B at the bottom portion 66a is 5 mm in consideration of strength.

[0065] By making the thickness H3 of the dielectric top plate 11B at the bottom 66a of the recess 66 of the dielectric top plate 11B thinner than λ / 8, the proportion of microwaves that transmit in the horizontal direction (sideways) decreases, the electromagnetic field distribution can be localized, and the plasma distribution can be efficiently controlled.

[0066] That is, the microwaves are mainly radiated vertically from the slots S to the bottom 66a, and the proportion of the microwaves that are transmitted horizontally (laterally) is small. Therefore, the electromagnetic field of the microwaves radiated from the antenna 65 efficiently contributes to plasma generation in the vicinity of the lower surface of the dielectric top plate 11B below the recess 66. This makes it possible to localize the electromagnetic field distribution and efficiently control the plasma distribution.

[0067] Furthermore, the multiple gas holes 16a penetrate the flat portion of the dielectric top plate 11B and supply the processing gas into the processing vessel 2. The microwaves that enter the flat portion spread evenly within the flat portion. Furthermore, the recesses 66 reduce the rate at which the microwaves are transmitted in the horizontal (lateral) direction. This reduces the electric field strength within the flat portion, and by creating a gas flow path in this portion, it is possible to prevent plasma from being generated in the gas flow path and the gas from being decomposed before entering the processing vessel 2.

[0068] Furthermore, the recess 66 of the dielectric top plate 11B is provided with a choke 70, which is a circular ring-shaped protrusion located on the outer periphery of the antenna 65. The choke 70 has a ring shape (circular ring shape) in a plan view, and is arranged so as to surround the outside of the antenna 65 in a plan view. The choke 70 has a rectangular cross section, and has an inner peripheral surface and an outer peripheral surface that are cylindrical surfaces, a bottom surface that is a circular ring-shaped flat surface connecting the lower end of the inner peripheral surface and the lower end of the outer peripheral surface, and an upper surface that is a circular ring-shaped flat surface connecting the upper end of the inner peripheral surface and the upper end of the outer peripheral surface. The choke 70 has a circular ring-shaped dielectric made of the same material as the dielectric top plate 11B (alumina Al2O3), etc., and a conductor (metal) that is provided on the surface of the dielectric and through which microwaves propagate. The conductor (metal) is provided so as to cover three surfaces of the choke 70, namely, the inner peripheral surface, the outer peripheral surface, and the upper surface. Furthermore, the shape of the inner circumferential surface of choke 70 in a plan view is similar to that of antenna 65, and the shape of the outer circumferential surface of choke 70 in a plan view is similar to that of recess 66. Furthermore, choke 70 is disposed in recess 66. That is, the inner diameter of choke 70 is larger than the diameter of antenna 65, and the outer diameter of choke 70 is smaller than the diameter of recess 66.

[0069] Here, the height of choke 70 is H5. The width of choke 70 is D5. The height H5 of choke 70 is preferably λ / 4. This allows the microwaves propagating through the bottom surface of choke 70 and the microwaves propagating through the inner peripheral surface, upper surface, and outer peripheral surface of choke 70 to weaken each other, thereby suppressing microwaves that pass over choke 70 and propagate horizontally (sideways). Note that the height H5 of choke 70 is not limited to this, and microwaves that pass over choke 70 and propagate horizontally (sideways) can be suppressed even within a range of λ / 4±λ / 8 (within a range of λ / 8 to 3λ / 8: λ / 8≦H5≦3λ / 8).

[0070] Moreover, it is preferable that width D5 of choke 70 is approximately the same as thickness H3 of dielectric top plate 11B at recess 66. This allows the microwaves propagating along the bottom surface of choke 70 and the microwaves propagating along the inner circumferential surface, upper surface, and outer circumferential surface of choke 70 to be branched into two and suitably cancel each other out. Specifically, it is preferable that width D5 of choke 70 is within a range of 0.5 to 2 times thickness H3 of dielectric top plate 11B at recess 66 (0.5×H3≦D5≦2×H3).

[0071] In the above description, the dielectric top plate 11B is provided with a separate annular dielectric (choke 70), but this is not limited to the above. A ring-shaped protrusion (corresponding to the choke 70) standing upright from the recess 66 of the dielectric top plate 11B may be formed integrally.

[0072] [Simulation 4] The results of Simulation 4 of the electric field intensity distribution of the dielectric top plate 11B according to the third embodiment will be described with reference to Figures 8 to 10. Figure 8 is a cross-sectional view of the dielectric top plate 111 according to the reference example, the dielectric top plate 11 according to the first embodiment, and the dielectric top plate 11B according to the third embodiment.

[0073] The dielectric top plate 111 according to the reference example shown in FIG. 8(a) does not have a recess 66, and the top surface is formed flat. The dielectric top plate 111 according to the reference example has a choke 70 on the top surface. The thickness H1 of the dielectric top plate 111 is 25 mm. The height H5 of the choke 70 is λ / 4 (in the case of Al2O3, λ0=340 mm, ε r ≒10, λ / 4=27mm).

[0074] The dielectric top plate 11 according to the first embodiment shown in Fig. 8(b) has a recess 66. Furthermore, the dielectric top plate 11 according to the first embodiment is not provided with a choke 70. The thickness H1 of the dielectric top plate 11 is 25 mm. The thickness H2 at the recess 66 is 10 mm (λ / 8 or less).

[0075] The dielectric top plate 11B according to the third embodiment shown in FIG. 8(c) has a recess 66. Furthermore, the dielectric top plate 11B according to the third embodiment has a choke 70 provided in the recess 66. The dielectric top plate 11B has a thickness H1 of 25 mm. The thickness H3 at the recess 66 is 10 mm (λ / 8 or less). Furthermore, the height H5 of the choke 70 is λ / 4.

[0076] Fig. 9 is a diagram showing an example of the electric field strength distribution in each of the dielectric top plate 111 according to the reference example, the dielectric top plate 11 according to the first embodiment, and the dielectric top plate 11B according to the third embodiment. Fig. 10 is a graph showing an example of the electric field strength in the radial direction in each of the dielectric top plate 111 according to the reference example, the dielectric top plate 11 according to the first embodiment, and the dielectric top plate 11B according to the third embodiment. In Fig. 10, the vertical axis indicates the electric field strength, and the horizontal axis indicates the radial position with the center position of the antenna 65 being 0 (zero).

[0077] The conditions for simulation 4 are that microwaves with a frequency of 860 MHz are supplied from the central electromagnetic wave supply unit 5 .

[0078] 9(a) and 10(a), no microwave shielding effect was observed even when chokes 70 were provided on the flat dielectric top plate 111 having no recesses. Specifically, the electric field strength at a radius R=175 [mm] was about 1 / 5 of the electric field strength directly below the antenna 65.

[0079] 9(b) and 10(b) according to the first embodiment, a microwave shielding effect was observed by providing an antenna 65 in a recess 66. Specifically, the electric field strength at a radius R=175 [mm] was about 1 / 9 of the electric field strength directly below the antenna 65.

[0080] 9(c) and 10(c) of the dielectric top plate 11B according to the third embodiment, a further microwave shielding effect was observed by providing an antenna 65 and a choke 70 in the recess 66. Specifically, the electric field strength at a radius R=175 [mm] was about 1 / 100 of the electric field strength directly below the antenna 65.

[0081] From the above results, it can be seen that in the third embodiment of Figures 9(c) and 10(c), the ratio of microwaves transmitted in the horizontal direction (lateral direction) can be reduced by making the thickness H3 of the dielectric top plate 11B at the bottom 66a of the recess 66 of the dielectric top plate 11B thinner than λ / 8 and providing a choke 70 in the recess 66. As a result, the electromagnetic field distribution can be localized under the dielectric top plate 11B where the recess 66 is formed, and the plasma distribution can be efficiently controlled.

[0082] The electric field strength of the microwaves propagating to the choke 70 arranged on the bottom 66a of the dielectric top plate 11B according to the third embodiment is greater than the electric field strength of the microwaves propagating to the choke 70 arranged on the top surface of the dielectric top plate 111 according to the reference example. Therefore, by providing the choke 70 on the bottom 66a where the electric field strength is greater, it is possible to suitably attenuate the microwaves transmitting in the horizontal direction.

[0083] As described above, according to the plasma processing apparatus 1 having the dielectric top plate 11, 11A, 11B of the first to third embodiments, the electric field strength distribution within the dielectric top plate generated by the microwaves supplied from the multiple electromagnetic wave supply units 5 can be localized, making it easy to adjust the plasma distribution.

[0084] In particular, by making the thickness H3 of the dielectric top plate 11 at the bottom 66a of the recess 66 in the first embodiment thinner than λ / 8, the proportion of microwaves that transmit in the horizontal direction (lateral direction) is reduced, the electromagnetic field distribution can be localized, and the plasma distribution can be efficiently controlled.

[0085] Furthermore, by setting the height H4 and width D of the bank 67 of the dielectric top plate 11A in the second embodiment to within the range of λ / 4±λ / 8, an effect similar to a choke is produced, and the microwaves radiated from the antenna 65 of one electromagnetic wave supply unit 5 can be efficiently prevented from leaking into the area of ​​an adjacent electromagnetic wave supply unit 5.

[0086] Furthermore, in the dielectric top plate 11B of the third embodiment, by providing a choke 70 in the recess 66, it is possible to efficiently prevent the microwaves radiated from the antenna 65 of one electromagnetic wave supply unit 5 from leaking into the area of ​​an adjacent electromagnetic wave supply unit 5.

[0087] Although the dielectric of the dielectric top plates 11, 11A, 11B and the choke 70 has been described as being alumina, the present invention is not limited to this and may be quartz (SiO2), silicon nitride (SiN), or the like.

[0088] The plasma processing apparatus according to the embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The matters described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0089] The above disclosed embodiments include, for example, the following aspects. (Appendix 1) A processing vessel having an opening at an upper portion; a dielectric top plate that divides an internal space and an external space of the processing vessel so as to cover the opening, the dielectric top plate having a plurality of recesses formed on a surface facing the external space; a plurality of electromagnetic wave supply units each having a flat antenna, each of which is installed in each of the plurality of recesses and configured to supply an electromagnetic wave into the processing vessel, the antenna being a plurality of electromagnetic wave supply units located at bottoms of the plurality of recesses; The plasma processing apparatus comprises: (Appendix 2) The thickness of the dielectric top plate in the plurality of recesses is λ / 8 or less, where λ is the wavelength of the electromagnetic wave propagating through the dielectric top plate. 2. The plasma processing apparatus according to claim 1. (Appendix 3) the dielectric top plate has a plurality of gas holes penetrating a region other than the plurality of recesses in a thickness direction and configured to supply a processing gas into the processing chamber; 3. The plasma processing apparatus according to claim 1 or 2. (Appendix 4) The planar shape of the plurality of recesses is similar to that of the antenna or is circular. 4. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus comprises: (Appendix 5) The dielectric top plate has banks between adjacent electromagnetic wave supply units, so that a plurality of recesses are formed surrounded by the banks. 4. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus comprises: (Appendix 6) The height and width of the bank are each within the range of λ / 4±λ / 8. 6. The plasma processing apparatus according to claim 5. (Appendix 7) The recess is provided with a protrusion located on an outer periphery of the antenna, The height of the convex portion is within the range of λ / 4±λ / 8. 3. The plasma processing apparatus according to claim 2. (Appendix 8) The protrusion surrounds the antenna in a plan view. 8. The plasma processing apparatus according to claim 7. (Appendix 9) The width of the convex portion is within a range of 0.5 to 2 times the thickness of the dielectric top plate at the concave portion. 9. The plasma processing apparatus according to claim 7 or 8. (Appendix 10) The recesses each have a circular shape in a plan view, The protrusion is provided for each of the plurality of recesses. 10. The plasma processing apparatus according to any one of claims 7 to 9. (Appendix 11) the antenna is provided at each end of the plurality of electromagnetic wave supply units, has a ring-shaped slot, and has a radiation surface that radiates electromagnetic waves from the slot; 7. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus comprises: (Appendix 12) The antenna radiates electromagnetic waves from the radiation surface, thereby making the electric field intensity of the plasma below the dielectric top plate on which the recess is formed in a plan view higher than the electric field intensity of the plasma below the dielectric top plate on which the recess is not formed. 12. The plasma processing apparatus according to claim 11. [Explanation of symbols]

[0090] 1. Plasma processing equipment 2. Treatment vessel 5 Electromagnetic wave supply section 11, 11A Dielectric top plate 16a Gas hole 65 Antenna 66, 66 recess 66a, 66Aa Bottom of recess 67 Bank

Claims

1. A processing vessel having an opening at an upper portion; a dielectric top plate that divides an internal space and an external space of the processing vessel so as to cover the opening, the dielectric top plate having a plurality of recesses formed on a surface facing the external space; a plurality of electromagnetic wave supply units each having a flat antenna, each of which is installed in each of the plurality of recesses and configured to supply an electromagnetic wave into the processing vessel, the antenna being a plurality of electromagnetic wave supply units located at bottoms of the plurality of recesses; The plasma processing apparatus comprises:

2. The thickness of the dielectric top plate at the plurality of recesses is λ / 8 or less, where λ is the wavelength of an electromagnetic wave propagating through the dielectric top plate. The plasma processing apparatus according to claim 1 .

3. the dielectric top plate has a plurality of gas holes penetrating a region other than the plurality of recesses in a thickness direction and configured to supply a processing gas into the processing chamber; The plasma processing apparatus according to claim 1 .

4. The planar shape of the plurality of recesses is similar to that of the antenna or is circular. The plasma processing apparatus according to any one of claims 1 to 3.

5. The dielectric top plate has banks between adjacent electromagnetic wave supply units, so that a plurality of recesses are formed surrounded by the banks. The plasma processing apparatus according to any one of claims 1 to 3.

6. The height and width of the bank are each within the range of λ / 4±λ / 8. The plasma processing apparatus according to claim 5 .

7. The recess is provided with a protrusion located on an outer periphery of the antenna, The height of the convex portion is within the range of λ / 4±λ / 8. The plasma processing apparatus according to claim 2 .

8. The protrusion surrounds the antenna in a plan view. The plasma processing apparatus according to claim 7 .

9. The width of the convex portion is within a range of 0.5 to 2 times the thickness of the dielectric top plate at the concave portion. The plasma processing apparatus according to claim 7 .

10. The recesses each have a circular shape in a plan view, The protrusion is provided for each of the plurality of recesses. The plasma processing apparatus according to claim 7 .

11. the antenna is provided at each end of the plurality of electromagnetic wave supply units, has a ring-shaped slot, and has a radiation surface that radiates electromagnetic waves from the slot; The plasma processing apparatus according to any one of claims 1 to 3.

12. The antenna radiates electromagnetic waves from the radiation surface, thereby making the electric field intensity of the plasma below the dielectric top plate on which the recess is formed in a plan view higher than the electric field intensity of the plasma below the dielectric top plate on which the recess is not formed. The plasma processing apparatus according to claim 11 .

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