Plasma source and plasma processing device

Abstract

To improve gas decomposition efficiency by facilitating plasma ignition.SOLUTION: A plasma source comprises: a plasma generation unit which includes a first wall including an opening and a second wall opposed to the first wall and constitutes a plasma generation space; a dielectric window which is provided on the first wall so as to close the opening and configured so as to transmit electromagnetic waves into the plasma generation space; and a protrusion which is provided on the second wall, protrudes from the second wall so as to be proximate to the dielectric window and includes a conductor in at least a portion. A gas hole which is opened toward the dielectric window is provided in the protrusion.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] It is important to use plasma to form films in order to obtain high-quality films at low temperatures. In recent years, there has been progress in thinning films, and plasma-assisted ALD (Atomic Layer Deposition) film formation has been adopted. While the use of plasma allows high-quality thin films to be obtained at low temperatures, electrical and physical damage to the film caused by the plasma can be an issue. To solve this problem, film formation using the ALD method using a remote source has been proposed.

[0003] For example, Patent Documents 1 and 2 disclose the configuration of a remote plasma processing apparatus having an ICP (Inductively Coupled Plasma) type remote plasma source. When an ICP type remote source is used as the remote source in this way, the stable range of plasma is narrow, and plasma ignition may not be easy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-150023 A [Patent Document 2] JP 2014-49529 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can facilitate plasma ignition and improve the efficiency of gas decomposition. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a plasma source comprising: a plasma generating section having a first wall with an opening and a second wall opposite the first wall, and constituting a plasma generation space; a dielectric window provided on the first wall so as to cover the opening and configured to transmit electromagnetic waves into the plasma generation space; and a protrusion provided on the second wall, protruding from the second wall so as to be close to the dielectric window, and including a conductor at least in part, wherein the protrusion has a gas hole opening toward the dielectric window. Effect of the Invention

[0007] According to one aspect, plasma ignition can be facilitated and gas decomposition efficiency can be improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional perspective view showing a plasma processing apparatus according to a first embodiment. [Diagram 2] FIG. 2 is an enlarged view of region A of the plasma source shown in FIG. [Diagram 3] FIG. 13 is a diagram showing an example of a simulation result of plasma electron density. [Figure 4] FIG. 2 is a perspective view showing a plasma source according to the first embodiment. [Diagram 5] FIG. 4 is a diagram showing an example of an electromagnetic wave supply unit. [Figure 6] 13A and 13B are diagrams showing modified examples of the protrusion portion. [Figure 7] FIG. 11 is a cross-sectional view showing a plasma processing apparatus according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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.

[0010] First Embodiment [Plasma processing equipment] A plasma processing apparatus 2 according to a first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a cross-sectional perspective view showing the plasma processing apparatus 2 according to the first embodiment. Fig. 2 is an enlarged view of an area A shown in Fig. 1.

[0011] The plasma processing apparatus 2 shown in FIG. 1 has a plasma source 1. The plasma source 1 is disposed on the upper part of the plasma processing apparatus 2 via a connecting part 23. The plasma source 1 has a first chamber 22, an electromagnetic wave supplying part 36, and a protruding part 24. The first chamber 22 is a flat rectangular container extending in the direction of an axis AX as the central axis of the plasma processing apparatus 2. The first chamber 22 and the electromagnetic wave supplying part 36 are an example of a plasma generating part. In the first embodiment, the plasma generating part is provided outside the plasma processing apparatus 2.

[0012] Among the walls constituting the first chamber 22, the two opposing walls having the largest area are referred to as the first wall 22a (see FIG. 4) and the second wall 22b. The first chamber 22 defines a plasma generating space 22d inside. An opening 22e is formed in the first wall 22a. The dielectric window 38 is made of ceramics (dielectric) such as alumina (Al2O3) and is configured to transmit electromagnetic waves such as microwaves. The dielectric window 38 is provided along the wall surface of the first wall 22a so as to close the opening 22e. The dielectric window 38 is provided at the tip of the electromagnetic wave supply unit 36 ​​and transmits the electromagnetic waves supplied from the electromagnetic wave supply unit 36 ​​to the plasma generating space 22d. The electromagnetic waves include microwaves. The frequency band of the microwaves is 300 MHz to 3 THz. The electromagnetic waves may include VHF waves having a frequency band of 150 MHz to 300 MHz.

[0013] The protrusion 24 is provided on the second wall 22b, protrudes from the second wall 22b so as to be close to the dielectric window 38, and includes a conductor at least in a portion thereof. The conductor functions as an electrode. The protrusion 24 is provided with a gas hole 24c that opens toward the dielectric window 38. The configuration and function of the protrusion 24 will be described later.

[0014] The gas hole 24c of the protrusion 24 is connected to a gas supply unit 50, and supplies the reducing gas from the gas supply unit 50 to the plasma generation space 22d. In the first chamber 22, the gas supplied from the gas hole 24c of the protrusion 24 is decomposed by the electric field of the electromagnetic wave supplied from the electromagnetic wave supply unit 36 ​​in the plasma generation space 22d to generate plasma. Radicals in the generated plasma are supplied to the plasma processing device 2 and used for processing the substrate W. The plasma processing device 2 has a second chamber 10. Note that processing gases other than the reducing gas may be supplied, for example, directly from the sidewall of the second chamber 10 to the processing chamber 30e.

[0015] In the embodiment, the second chamber 10 includes a chamber body 12. The chamber body 12 has a generally cylindrical shape and is open at the top. The chamber body 12 provides the sidewall and bottom of the second chamber 10. The chamber body 12 is made of a metal such as aluminum. The chamber body 12 is grounded.

[0016] The second chamber 10 further includes an upper wall 14. The upper wall 14 is made of a metal such as aluminum. The upper wall 14 closes an upper opening of the chamber body 12. The upper wall 14, together with the chamber body 12, is grounded.

[0017] The plasma processing apparatus 2 further includes a mounting table 18. The mounting table 18 is provided in the second chamber 10. The mounting table 18 is configured to support a substrate W mounted thereon. The substrate W is mounted on the mounting table 18 in a substantially horizontal state. The mounting table 18 may be supported by a support member 19. The support member 19 extends upward from the bottom of the second chamber 10. The mounting table 18 and the support member 19 may be formed of a dielectric material such as aluminum nitride.

[0018] The plasma processing apparatus 2 further includes a showerhead 20. The showerhead 20 is made of a metal such as aluminum. The showerhead 20 has a substantially disk shape and a hollow structure. The showerhead 20 shares an axis line AX as its central axis line. The showerhead 20 is provided above the mounting table 18 and below the upper wall 14. The showerhead 20 constitutes a ceiling portion that defines the internal space of the second chamber 10.

[0019] The second chamber 10 has a processing chamber 30e for processing a substrate between the shower head 20 and the mounting table 18. The substrate W is processed in the processing chamber 30e. The second chamber 10 has an axis line AX as its central axis line. The axis line AX is an axis line that extends vertically through the center of the second chamber 10.

[0020] The sidewall of the chamber body 12 provides a passage 12p. The substrate W passes through the passage 12p when being transferred between the inside and the outside of the second chamber 10. The passage 12p can be opened and closed by a gate valve 12v. The gate valve 12v is provided along the sidewall of the chamber body 12.

[0021] The bottom of the second chamber 10 provides an exhaust port 16a. The exhaust port 16a is connected to an exhaust system 16. The exhaust system 16 includes a pressure controller, such as an automatic pressure control valve, and a vacuum pump, such as a turbomolecular pump.

[0022] The showerhead 20 provides a diffusion chamber 30d therein. The showerhead 20 provides a plurality of gas through holes 20i penetrating the showerhead 20 in the thickness direction, and the plurality of gas through holes 20i open to the lower surface of the showerhead 20. The showerhead 20 forms a gas path for introducing gas from the diffusion chamber 30d through the plurality of gas through holes 20i into the processing chamber 30e. This allows radicals generated in the first chamber 22 and other gases, if necessary, to be introduced toward the processing chamber 30e. The mounting table 18 also functions as a lower electrode, and the showerhead 20 also functions as an upper electrode.

[0023] The periphery of the showerhead 20 is covered with a dielectric member 33 such as aluminum oxide. The periphery of the mounting table 18 is covered with a dielectric member 34 such as aluminum oxide. If high frequency power is not supplied to the showerhead 20, the dielectric member 33 does not have to be provided. However, it is preferable to provide the dielectric member 33 in order to define the area of ​​the showerhead 20 that functions as a counter electrode for the mounting table 18. It is also preferable to provide the dielectric member 33 in order to make the ratio of anodes and cathodes of the electrodes as equal as possible.

[0024] A high frequency power supply 60 is connected to the mounting table 18 via a matching device 61. The matching device 61 has an impedance matching circuit. The impedance matching circuit is configured to match the impedance of the load side (the mounting table 18 side) to the output impedance of the high frequency power supply 60. The frequency of the high frequency supplied from the high frequency power supply 60 is lower than the frequency of the VHF wave and the microwave supplied to the plasma source 1 described later, and is a frequency of 60 MHz or less. The frequency of the high frequency may be 13.56 MHz. The high frequency power supply 60 may be connected to the mounting table 18 or the shower head 20 via the matching device 61. The radicals transferred from the plasma source 1 to the plasma processing device 2 are dissociated again by the high frequency power applied in the plasma processing device 2, and are used for processing the substrate W.

[0025] [Plasma source] The plasma source 1 will be described in more detail with reference to Fig. 3 in addition to Fig. 1 and Fig. 2. Fig. 3 is a diagram showing an example of a simulation result of plasma electron density. The plasma source 1 has a connection part 23, which is fixed on an upper wall 14. A first chamber 22 is provided on the connection part 23, and radicals (active species) in the plasma generated in the first chamber 22 are supplied to the plasma processing device 2 via the connection part 23.

[0026] The connecting part 23 is a hollow member having a substantially cylindrical shape and made of a metal such as aluminum, and shares an axis line AX as its central axis line. The lower end of the connecting part 23 communicates with an opening formed in the center of the upper wall 14 of the second chamber 10.

[0027] The first chamber 22 is a flat rectangular waveguide centered on the axis AX. The upper end of the connecting part 23 expands in the width direction of the flat first chamber 22 and connects to the lower end of the first chamber 22. The first chamber 22 is configured to form a flat plasma generation space 22d therein. The first chamber 22 and the connecting part 23 are made of a conductor such as aluminum and have a ground potential.

[0028] Referring to FIG. 2, which is an enlarged view of region A in FIG. 1, the protruding portion 24 is cylindrical and is entirely formed of a dielectric material 24g such as alumina, AlN, or quartz. The protruding portion 24 penetrates the second wall 22b and protrudes from the second wall 22b. Inside the protruding portion 24, a gas hole 24c is formed penetrating the protruding portion 24. The gas hole 24c has a fine hole 24c1 and an expanded diameter portion 24c2 expanded from the fine hole 24c1, and an opening 24a at the tip of the gas hole 24c opens from the expanded diameter portion 24c2 toward the dielectric window 38. A reducing gas is supplied from the gas hole 24c into the plasma generating space 22d. This allows the protruding portion 24 to function as a gas nozzle. The function of the protruding portion 24 as a plasma ignition source will be described later.

[0029] The gas holes 24c of the protruding portion 24 eject gas toward the dielectric window 38. Therefore, by ejecting gas in the area where the energy of the electromagnetic waves is concentrated, the efficiency of decomposing the gas and the efficiency of generating radicals can be improved. e 1 is a diagram showing an example of a simulation result of the present disclosure. As a condition for the simulation of the present disclosure, argon gas was supplied from the gas hole 24c. A model was adopted in which the tip of the protruding part 24 does not protrude from the second wall 22b. The pressure in the plasma generation space 22d was set to 10 Pa, and microwaves with a frequency of 860 MHz were supplied from the dielectric window 38.

[0030] As a result of the simulation, as shown in FIG. 3, the plasma electron density N e The plasma electron density N e was higher near the center of the dielectric window 38 and decreased the further away from the center of the dielectric window 38. From the above results, it can be seen that the vicinity of the dielectric window 38 is a range where energy is concentrated.

[0031] 3, and gas is supplied from the tip of the protrusion 24 toward the dielectric window 38. As a result, the plasma electron density N e This allows the gas to be supplied to a region where the energy is concentrated near the dielectric window 38, thereby improving the efficiency of gas decomposition and the efficiency of radical generation.

[0032] The description will be continued with reference to the perspective view of the plasma source 1 according to the first embodiment in Fig. 4. The plasma source 1 has an electromagnetic wave supply unit 36 ​​connected to a first wall 22a of the first chamber 22. With reference to Figs. 1 and 4, two electromagnetic wave supply units 36 having centers on the axis line AX are arranged side by side in the longitudinal direction (vertical direction) of the first chamber 22 on the first wall 22a, which is one of the walls constituting the first chamber 22. The two electromagnetic wave supply units 36 have the same configuration.

[0033] The electromagnetic wave supplying unit 36 ​​has a dielectric window 38 at its tip and is configured to supply an electromagnetic wave into the first chamber 22 through the dielectric window 38. In this embodiment, microwaves are propagated from the microwave oscillator 40 through an input port to the electromagnetic wave supplying unit 36. The electromagnetic wave supplying unit 36 ​​has a coaxial waveguide structure and has an approximately cylindrical inner conductor 36a and an approximately cylindrical outer conductor 36b arranged concentrically around the inner conductor 36a. The microwaves propagate between the inner conductor 36a and the outer conductor 36b, pass through the approximately disk-shaped quartz member 37, and propagate to the dielectric window 38 through the slot S of the antenna 26 provided in the gap U (see FIG. 5) between the quartz member 37 and the dielectric window 38. Note that the space between the inner conductor 36a and the outer conductor 36b may be empty, or alumina or the like may be arranged. The microwaves pass through the dielectric window 38 and are radiated into the first chamber 22 from the opening 22e in the first wall 22a of the first chamber 22. The inner conductor 36a, the quartz member 37 and the dielectric window 38 are covered with the outer conductor 36b.

[0034] Fig. 5(a) shows the AA cross section of Fig. 4, being a plan view of the vicinity of the opening 22e of the first wall 22a from the inner wall side of the first wall 22a, and Fig. 5(b) shows a BB cross section passing through the center of the opening 22e shown in Fig. 5(a). As shown in Fig. 5(a), the conductor antenna 26 is in contact with the surface opposite to the surface of the dielectric window 38 exposed from the opening 22e, and a donut-shaped (annular) slot S is formed.

[0035] 5(b), the surface of the dielectric window 38 exposed from the opening 22e is circularly recessed in the central region 38a of the dielectric window 38, and the central region 38a is thinner than the peripheral region 38b of the dielectric window 38. This can improve the plasma ignition characteristics. However, the recess in the central region 38a is not necessary.

[0036] In this embodiment, two electromagnetic wave supply units 36 are arranged vertically on the first wall 22a, but three or more may be arranged, or only one may be arranged. The greater the number of electromagnetic wave supply units 36, the higher the radical generation efficiency and plasma generation efficiency.

[0037] With this configuration, the vicinity of the upper electromagnetic wave supply unit 36 ​​among the electromagnetic wave supply units 36 arranged in the vertical direction becomes a first dissociation area where dissociation of gas is promoted. Also, the vicinity of the lower electromagnetic wave supply unit 36 ​​becomes a second dissociation area where dissociation of gas is promoted. Since the gas dissociated in the first dissociation area is further dissociated in the second dissociation area, the degree of dissociation of gas increases vertically downward in the plasma generation space 22d in the first chamber 22. Therefore, high-density plasma is generated in the first chamber 22. As a result, the connecting unit 23 can supply sufficient radicals to the second chamber 10.

[0038] In this manner, radicals are supplied from the plasma source 1 to the processing chamber 30e between the mounting table 18 (lower electrode) and the shower head 20 (upper electrode), and the substrate W mounted on the mounting table 18 is processed. At this time, radicals flow from the plasma source 1 through the shower head 20 via a plurality of gas through holes 20i provided in the shower head 20, and are supplied to the processing chamber 30e. The radicals supplied to the processing chamber 30e may recombine during transfer to form gas. The radicals and the recombined gas are decomposed by the high-frequency power of the high-frequency power source 60, and the substrate W is subjected to processing such as film formation by the plasma generated thereby. By supplying radicals from the plasma source 1, even if the high-frequency power supplied from the high-frequency power source 60 is small and the frequency is relatively low, the gas can be sufficiently dissociated and the supply of radicals can be increased. This allows film formation on the substrate with little damage. Although not shown, gas that can be sufficiently dissociated only by the high-frequency power source 60 may be supplied directly to the shower head 20 without passing through the plasma source 1.

[0039] The control unit (control device) 90 may be a computer having a processor 91 and a memory 92. The control unit 90 includes an arithmetic unit, a storage unit, an input device, a display device, a signal input / output interface, and the like. The control unit 90 controls each part of the plasma processing device 2 including the plasma source 1. In the control unit 90, an operator can use the input device to input commands and the like to manage the plasma processing device 2. In addition, the control unit 90 can visualize and display the operating status of the plasma processing device 2 using the display device. Furthermore, the memory 92 of the control unit 90 stores a control program and recipe data. The control program is executed by the processor 91 of the control unit 90 to execute various processes in the plasma processing device 2. The processor 91 executes the control program and controls each part of the plasma processing device 2, so that various processes, for example, a plasma processing method, are executed in the plasma processing device 2 according to the recipe data.

[0040] When an ICP type remote source is used as the remote source, the stable range of plasma is narrow, and plasma ignition may not be easy. In contrast, according to the plasma processing apparatus 2 configured as described above, sufficient radicals can be supplied to the second chamber 10 using the plasma source 1 that generates plasma and activates gas using electromagnetic waves of a relatively high frequency, such as microwaves. This makes it possible to perform a process that causes less damage to the substrate W by using a remote plasma source that uses microwaves.

[0041] Furthermore, the plasma source 1 according to this embodiment has a protrusion 24. The protrusion 24 protrudes from the inner wall of the second wall 22b facing the dielectric window 38 in the first chamber 22 and is provided at a distance from the dielectric window 38.

[0042] The protrusion 24 includes a conductor at least in a part. In the protrusion 24 shown in FIG. 2, the conductor 24d is embedded in the dielectric 24g. The conductor 24d is made of a metal such as aluminum and functions as an internal electrode. The horizontal distance D (perpendicular to the axis AX) from the tip of the conductor 24d to the surface of the dielectric window 38 is a distance at which the electric field near the tip of the conductor 24d is sufficiently low, and the distance may be about 3 mm to 10 mm. However, it is more preferable to set the distance D to about 5 mm to 10 mm, since this can further suppress contamination, particles, and damage. The conductor 24d is donut-shaped (annular) and is embedded in the outer periphery of the enlarged diameter portion 24c2 near the end face of the gas hole 24c. The conductor 24d is covered by the dielectric 24g forming the protrusion 24 and is not exposed to the inner wall of the gas hole 24c.

[0043] In order to prevent abnormal discharge caused by surface waves of microwaves in gas hole 24c, gas hole 24c has enlarged diameter portion 24c2 at its tip, which enlarges from small hole 24c1 of gas hole 24c and opens toward dielectric window 38. Enlarged diameter portion 24c2 is cylindrical. Note that enlarged diameter portion 24c2 is not limited to a cylindrical shape, and may be a prismatic shape having a polygonal base such as a rectangle or pentagon.

[0044] The depth (length) of the expanded portion 24c2 from the tip of the gas hole 24c is 5 mm or more. The diameter of the small hole 24c1 of the gas hole 24c is smaller than 1 mm, for example, 0.3 mm. The diameter of the expanded portion 24c2 and the opening 24a is 3 mm or more and 1 / 8 of the surface wave wavelength λ of the microwave in the plasma or less.

[0045] The surface wave wavelength λ of microwaves in plasma is about 1 / 3 of the wavelength λ0 of microwaves in a vacuum. Since the wavelength λ0 used in microwave plasma processes is about 120 to 480 mm, the surface wave wavelength λ of microwaves in plasma is about 40 to 160 mm. Therefore, the diameter of the expanded diameter portion 24c2 and the opening 24a is 3 mm or more, and is about 5 to 20 mm, which is 1 / 8 of the surface wave wavelength λ of microwaves in plasma.

[0046] The technical meaning of the diameter of the enlarged diameter portion 24c2 and the opening 24a being 3 mm or more and 1 / 8 or less of the surface wave wavelength λ of the microwave in the plasma will be explained. For example, if the diameter of the enlarged diameter portion 24c2 and the opening 24a is 1 / 4 of the surface wave wavelength λ of the microwave in the plasma, the surface wave of the microwave stops at the opening 24a and cannot propagate beyond it. In other words, the enlarged diameter portion 24c2 and the opening 24a function to prevent the surface wave of the microwave from propagating beyond the opening. At this time, the surface wave of the microwave is totally reflected at the opening 24a, so that the electric field strength of the microwave becomes maximum near the opening 24a, and if it exceeds a critical value, an arc discharge occurs, which may result in abnormal discharge.

[0047] On the other hand, when the diameter of the opening 24a is 1 / 8 of the surface wave wavelength λ of the microwave in the plasma, the surface wave of the microwave can pass through the opening 24a. In this case, the surface wave of the microwave does not stop at the opening 24a, and the pressure difference between the internal pressure of the expanded diameter portion 24c2 and the pressure of the plasma generating space 22d is small. Therefore, the strong electric field of the microwave hardly penetrates into the inside of the expanded diameter portion 24c2, and the occurrence of abnormal discharge in the expanded diameter portion 24c2 can be prevented. Therefore, the diameter of the expanded diameter portion 24c2 and the opening 24a needs to be 1 / 8 of the surface wave wavelength λ of the microwave in the plasma, that is, 20 mm or less.

[0048] On the other hand, if the diameter of the opening 24a is smaller than 3 mm, the surface waves of the microwaves can pass through the opening 24a. However, the pressure difference between the internal pressure of the expanded diameter portion 24c2 and the pressure in the plasma generating space 22d becomes large. This makes it easier for abnormal discharge to occur in the expanded diameter portion 24c2. Therefore, the diameter of the opening 24a of the expanded diameter portion 24c2 is set to 3 mm or more. This makes it possible to prevent abnormal discharge from occurring at the tip of the gas hole 24c and its surroundings.

[0049] Next, the function of the protruding portion 24 as a plasma ignition source will be described. In plasma ignition using microwaves like the plasma source 1, the discharge electric field E bd The ignition performance is determined by the above.

[0050]

number

[0051] On the other hand, in a parallel plate type plasma processing apparatus such as the second chamber 10, a discharge voltage V V is generated between the lower electrode and the upper electrode by high frequency power according to Paschen's law, as shown in formula (2). bd The ignition performance is determined by the above.

[0052]

number

[0053] In formula (1), D and K are coefficients determined by the type of gas, p is the pressure in the chamber, and f is the frequency of the electromagnetic waves. m is a constant (approximately 0.5) determined by the type of gas. In formula (2), A and B are coefficients determined by the type of gas, p is the pressure in the chamber, d is the distance between the lower electrode and the upper electrode, and γ se is the secondary electron emission coefficient. The secondary electron emission coefficient is determined by the materials and surface conditions of the lower and upper electrodes.

[0054] In other words, Paschen's law does not hold for plasma ignition in the plasma source 1. Therefore, in the plasma source 1, the discharge voltage V bd In the plasma source 1, the discharge electric field E shown in equation (1) is not determined by bd Therefore, the protrusion 24 of the plasma source 1 has a shape and arrangement that is easy to ignite, which is specific to microwaves and VHF waves of 150 MHz or more, and makes it easy to ignite plasma in the first chamber 22.

[0055] When a microwave is radiated into the first chamber 22 while no plasma is being generated in the first chamber 22, the radiated microwave is reflected by the conductor 24d in the protrusion 24, and the reflected microwave wave returns to the first wall 22a. Then, a standing wave is generated between the incident microwave wave output from the dielectric window 38 and the reflected wave reflected by the protrusion 24. Since the first chamber 22 is flat and the space between the first wall 22a and the second wall 22b is narrow, a high electric field is generated in the first chamber 22, making it easy to ignite the plasma. On the other hand, after the plasma is ignited, the electric field between the protrusion 24 and the inner wall of the first wall 22a is not high.

[0056] From the above, the protrusion 24 is a passive ignition source, and no voltage is applied to itself, but the doughnut-shaped conductor 24d functions as an internal electrode and can reflect microwaves. The outer diameter of the conductor 24d is 10 mm or more and 28 mm or less.

[0057] The diameter of the opening 24a of the gas hole 24c is 3 mm or more and 1 / 8 of the surface wave wavelength λ of the microwave in the plasma or less, for example, 4 mm. Therefore, the lower limit of the outer diameter of the conductor 24d is set to 10 mm or more so that the conductor 24d functions as a passive ignition source while being large enough for the size of the opening 24a. Moreover, the upper limit of the outer diameter of the conductor 24d is preferably set to a size equal to or less than the inner diameter of the slot S provided for introducing the microwave, so as not to weaken the electric field strength and deteriorate the ignition ability. Therefore, the upper limit of the outer diameter of the conductor 24d is set to 28 mm or less.

[0058] (Modification of protrusion) The protrusion 24 is not limited to the configuration shown in FIG. 2. For example, a modified example of the protrusion 24 will be described with reference to FIG. 6. The protrusion 24 according to the modified example may be formed by forming the entire cylindrical shape of the conductor 24e, and the periphery of the conductor 24e may be covered with a dielectric 24f such as alumina. In this case, a gas hole 24c is formed inside the protrusion 24, and the gas hole 24c has a fine hole 24c1 and an expanded diameter portion 24c2, and the opening 24a at the tip of the gas hole 24c opens from the expanded diameter portion 24c2 toward the dielectric window 38. The size of the fine hole 24c1 and the expanded diameter portion 24c2 of the gas hole 24c is the same as that of the protrusion 24 in FIG. 2. The horizontal distance from the tip of the conductor 24e to the bottom surface of the dielectric window 38 is also the same as that of the conductor 24d in FIG. 2. By coating the conductor 24e with the dielectric 24f, the plasma resistance of the protrusion 24 can be increased and wear and deterioration due to the plasma can be suppressed. The modified configuration of the protrusion 24 also facilitates plasma ignition and improves the efficiency of decomposing gas. The tip of the protrusion 24 shown in Fig. 2 and Fig. 6 may have a rounded shape with chamfered corners.

[0059] The conductor 24d of the protruding portion 24 shown in FIG. 2 and the conductor 24e shown in FIG. 6 function as floating electrodes.

[0060] The distance between the inner walls of the first wall 22a and the second wall 22b is 10 to 100 times the skin depth of the plasma. The reason why the distance is in the range of 10 to 100 times is that the plasma conductivity shown below varies greatly with the plasma density. In the present embodiment, the distance between the inner walls of the first wall 22a and the second wall 22b is about 20 mm (see FIG. 1).

[0061] The value of the skin depth varies depending on (1) frequency, (2) electron density, and (3) the collision frequency of electrons and neutral particles. Here, the collision frequency of electrons and neutral particles (3) is determined by the gas species and electron temperature. The skin depth δ is calculated using formula (3). Skin depth δ = [2 / (ωμ0σ dc )] 1 / 2 (3) Here, ω is the power frequency, μ0 is the magnetic permeability of a vacuum, and σdc is the plasma conductivity. The plasma conductivity is calculated by equation (4). Plasma conductivity σ dc =e 2 n e / (mν m ) · · · (4) where e is the elementary charge, n e is the electron density, m is the mass of the electron, ν m is the electron-neutral collision frequency.

[0062] When the distance between the inner walls of the first wall 22a and the second wall 22b is 10 times the skin depth, the distance is about 20 mm when the microwave frequency is 800 MHz, about 28 mm when it is 400 MHz, and about 12 mm when it is 2.45 GHz. This makes it possible to realize a plasma source 1 with a low plasma electron temperature and high electron density. The pressure inside the first chamber 22 is used at 0.5 Torr or more.

[0063] According to the plasma source 1 of the first embodiment described above, by reducing the thickness of the first chamber 22 and providing the protruding portion 24, it is possible to facilitate plasma ignition, increase the plasma generation efficiency in the first chamber 22, and widen the stable range of plasma generation. In addition, by concentrating a high electron temperature and high electron density region in the region of the plasma generation space where the electromagnetic wave is supplied, it is possible to improve the gas decomposition efficiency and the radical generation efficiency. In particular, by injecting the reducing gas from the center of the protruding portion 24 and blowing it against the center of the dielectric window 38 where the energy of the electromagnetic wave is concentrated, it is possible to maximize the decomposition efficiency of the reducing gas.

[0064] <Second embodiment> [Plasma processing equipment] Next, a plasma processing apparatus 2 according to a second embodiment will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view showing the plasma processing apparatus 2 according to the second embodiment. The reference numerals attached to the respective parts in Fig. 7 that are the same as those attached to the respective parts in Fig. 1 indicate the same configuration.

[0065] In the second embodiment, the plasma source 1 is disposed at the top of the plasma processing apparatus 2. The plasma source 1 is provided integrally with the shower head 20, and the first chamber 22 in the first embodiment corresponds to the shower head 20 in the second embodiment. That is, the plasma source 1 has a diffusion chamber 30d in the shower head 20 as a plasma generation space, and has the diffusion chamber 30d, an electromagnetic wave supply unit 36, and a protruding portion 24. The diffusion chamber 30d and the electromagnetic wave supply unit 36 ​​are an example of a plasma generation unit. The plasma generation unit in the first embodiment is provided outside the plasma processing apparatus 2, but a part of the plasma generation unit in the second embodiment is provided inside the plasma processing apparatus 2.

[0066] If the two opposing walls having the largest area among the wall surfaces constituting the diffusion chamber 30d are defined as the first wall 22a and the second wall 22b, in the second embodiment, the upper wall of the shower head 20 is the first wall 22a, and the lower wall of the shower head 20 is the second wall 22b. An opening 22e is formed in the first wall 22a. The dielectric window 38 is provided in the first wall 22a so as to close the opening 22e, and transmits electromagnetic waves to the diffusion chamber 30d corresponding to the plasma generation space 22d. The dielectric window 38 is provided at the tip of the electromagnetic wave supply unit 36.

[0067] The protrusion 24 is provided on the second wall 22b, protrudes from the second wall 22b so as to be close to the dielectric window 38, and includes a conductor at least in a portion thereof. The configuration and function of the protrusion 24 may be any of the protrusions 24 shown in Fig. 2 and Fig. 6. The configuration and function of the protrusion 24 have been described above, so a description thereof will be omitted.

[0068] The gas holes of the protrusion 24 are connected to a gas supply unit 50, and supply the reducing gas from the gas supply unit 50 to the plasma generating space 22d. In the plasma generating space 22d, the reducing gas supplied from the gas holes of the protrusion 24 is decomposed by the electric field of the electromagnetic wave supplied from the electromagnetic wave supply unit 36 ​​to generate plasma. A plurality of gas through holes 20i are formed in the second wall 22b in the thickness direction of the second wall 22b and penetrate the second wall 22b. Radicals in the plasma generated in the plasma generating space 22d are supplied from the plurality of gas through holes 20i to the processing chamber 30e and are used to process the substrate W.

[0069] The plasma processing apparatus 2 has a second chamber 10. In the embodiment, the second chamber 10 includes a chamber body 12. The chamber body 12 has a substantially cylindrical shape and is open at the top. The chamber body 12 provides the sidewall and bottom of the second chamber 10. The chamber body 12 is made of a metal such as aluminum. The chamber body 12 is grounded.

[0070] The outer periphery of the showerhead 20 is covered with a dielectric member 33 such as aluminum oxide. The outer periphery of the mounting table 18 is covered with a dielectric member 34 such as aluminum oxide. The upper opening of the chamber body 12 is closed by the showerhead 20 and the member 33.

[0071] The plasma processing apparatus 2 further includes a mounting table 18. The mounting table 18 is provided in the second chamber 10. The mounting table 18 is configured to support a substrate W mounted thereon. The substrate W is mounted on the mounting table 18 in a substantially horizontal state.

[0072] A high frequency power supply 60 is connected to the mounting table 18 via a matching box 61. The bottom of the second chamber 10 is provided with an exhaust port 16a, which is connected to an exhaust device 16.

[0073] The thickness of the shower head 20 at the portion corresponding to the plasma generation space 22d is, for example, 20 mm. According to the plasma source 1 of the second embodiment described above, by reducing the thickness of the shower head 20 and providing the protruding portion 24, it is possible to facilitate plasma ignition, increase the plasma generation efficiency in the diffusion chamber 30d, and widen the stable range of plasma generation. In addition, by concentrating the high electron temperature and high electron density region in the region of the plasma generation space where the electromagnetic wave is supplied, it is possible to improve the gas decomposition efficiency and the radical generation efficiency. In particular, by injecting the reducing gas from the center of the protruding portion 24 and blowing it to the center of the dielectric window 38 where the energy is concentrated, it is possible to maximize the decomposition efficiency of the reducing gas.

[0074] The plasma source 1 and the plasma processing apparatus 2 according to the first and second embodiments can facilitate plasma ignition and improve the efficiency of gas decomposition.

[0075] The plasma source and plasma processing apparatus according to the presently disclosed embodiments should be considered in all respects as illustrative and not restrictive, and various modifications and improvements can be made thereto without departing from the spirit and scope of the appended claims.

[0076] By providing the protrusion 24, it is not necessary to move the alignment position, and the time to turn on the plasma can be shortened. This allows the gas to be replaced and plasma to be ignited quickly, making the configuration more suitable for the ALD (atomic layer deposition) process and improving productivity. However, it can also be applied to film formation by the CVD (Chemical Vapor Deposition) method. Substrate processing performed by the plasma processing apparatus disclosed in this specification includes, for example, film formation processing, etching processing, and the like. [Explanation of symbols]

[0077] 1. Plasma source 2. Plasma processing equipment 10 Second Chamber 20. Shower Head 22 First Chamber 22a 1st wall 22b 2nd wall 22d Plasma generation space 24 Protrusion 30e Processing Room 36 Electromagnetic wave supply section 38 Dielectric Window 90 Control section

Claims

1. a plasma generating section having a first wall with an opening and a second wall facing the first wall and constituting a plasma generating space; a dielectric window provided in the first wall so as to cover the opening and configured to transmit electromagnetic waves into the plasma generating space; a protrusion provided on the second wall, protruding from the second wall so as to be adjacent to the dielectric window, and including at least a portion of a conductor; A plasma source in which the protrusion is provided with a gas hole opening toward the dielectric window.

2. The end surface of the gas hole is expanded in diameter.

10. The plasma source of claim 1.

3. The protrusion is formed of a dielectric material. A plasma source according to claim 1 or 2.

4. The conductor is embedded in the dielectric. The plasma source of claim 3.

5. the conductor is embedded in the outer periphery of the gas hole near the end face of the gas hole and is not exposed to the gas hole; 5. The plasma source of claim 4.

6. The conductor is doughnut shaped. A plasma source according to any one of the preceding claims.

7. The outer diameter of the conductor is 10 mm or more and 28 mm or less.

7. The plasma source of claim 6.

8. The protrusion is formed of a conductor, and the conductor is covered with a dielectric. A plasma source according to claim 1 or 2.

9. The distance between the first wall and the second wall is 10 to 100 times the plasma skin depth. A plasma source according to any one of the preceding claims.

10. The plasma source is disposed on an upper portion of a plasma processing apparatus via a connecting portion; The plasma processing apparatus has a processing chamber for processing a substrate, the plasma generating unit is provided outside the plasma processing apparatus, and supplies plasma generated from the gas supplied from the gas hole by the electromagnetic wave to the processing chamber through the connecting unit. A plasma source according to any one of the preceding claims.

11. The second wall has a plurality of through holes formed therein. A plasma source according to any one of the preceding claims.

12. The plasma source is disposed at an upper portion of a plasma processing apparatus, The plasma processing apparatus has a processing chamber for processing a substrate, a plasma generating unit, a part of which is provided inside the plasma processing apparatus, generating plasma from the gas supplied from the gas hole by the electromagnetic wave, and supplying the plasma to the processing chamber from the plurality of through holes; 12. The plasma source of claim 11.

13. A plasma processing apparatus comprising the plasma source according to any one of claims 1 to 12.

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