Plasma source and plasma processing device

Abstract

The present application provides a plasma source and a plasma processing device, which can easily ignite plasma and improve the decomposition efficiency of gas. The plasma source comprises: a plasma generation part comprising a first wall with an opening and a second wall opposite to the first wall, and constituting a plasma generation space; a dielectric window provided on the first wall in a manner of closing the opening, and configured to enable electromagnetic waves to be transmitted to the plasma generation space; and a protruding part provided on the second wall, protruding from the second wall in a manner of being close to the dielectric window, and at least partially comprising a conductor, and a gas hole is provided on the protruding part and opens towards the dielectric window.

Description

Technical Field

[0001] This invention relates to plasma sources and plasma processing apparatus. Background Technology

[0002] To obtain high-quality films at low temperatures, plasma deposition is crucial. In recent years, with the continuous development of thin-film deposition technology, plasma-based ALD (Atomic Layer Deposition) methods have been adopted. While plasma enables the production of high-quality films at low temperatures, it also presents challenges due to electrical and physical damage caused by the plasma. To address this issue, techniques using remote plasma sources for ALD have been proposed.

[0003] For example, Patent Documents 1 and 2 disclose the structure of a remote plasma processing device having an ICP (Inductively Coupled Plasma) type remote plasma source. When using an ICP type remote plasma source as such, there are issues with a narrow plasma stability range and difficulty in igniting the plasma.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-150023

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-49529 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] This invention provides a technique that enables easy plasma ignition and improves the efficiency of gas decomposition.

[0010] Technical solutions for solving technical problems

[0011] According to one aspect of the present invention, a plasma source is provided, comprising: a plasma generating section including a first wall having an opening and a second wall opposite to the first wall, forming a plasma generating space; a dielectric window disposed on the first wall in a manner that closes the opening, configured to allow electromagnetic waves to be transmitted into the plasma generating space; and a protrusion disposed on the second wall, protruding from the second wall near the dielectric window, and at least a portion comprising a conductor, wherein the protrusion is provided with an air hole facing the opening of the dielectric window.

[0012] Invention Effects

[0013] According to one aspect of the present invention, plasma ignition can be easily performed, thereby improving the gas decomposition efficiency. Attached Figure Description

[0014] Figure 1 This is a cross-sectional perspective view of the plasma processing apparatus according to the first embodiment.

[0015] Figure 2 yes Figure 1 An enlarged view of region A of the plasma source shown.

[0016] Figure 3 This is a graph representing one example of the simulation results for plasma electron density.

[0017] Figure 4 This is a perspective view of the plasma source according to the first embodiment.

[0018] Figure 5 This is a diagram illustrating one example of an electromagnetic wave supply unit.

[0019] Figure 6 This is a diagram showing a variation of the protrusion.

[0020] Figure 7 This is a cross-sectional view showing the plasma processing apparatus of the second embodiment.

[0021] Explanation of reference numerals in the attached figures

[0022] 1. Plasma Source

[0023] 2. Plasma processing device

[0024] 10 Second Chamber

[0025] 20 spray heads

[0026] 22 First Chamber

[0027] 22a First Wall

[0028] 22b Second Wall

[0029] 22d Plasma Generation Space

[0030] 24. Protrusion

[0031] 30e processing room

[0032] 36 Electromagnetic Wave Supply Department

[0033] 38 Dielectric window

[0034] 90. Control Department. Detailed Implementation

[0035] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The same reference numerals are used to label the same components in each drawing, and sometimes repeated descriptions are omitted.

[0036] <First Implementation>

[0037] [Plasma Processing Device]

[0038] Reference Figure 1 and Figure 2 The plasma processing apparatus 2 of the first embodiment will be described. Figure 1 This is a cross-sectional perspective view of the plasma processing apparatus 2 according to the first embodiment. Figure 2 yes Figure 1 An enlarged view of region A shown.

[0039] Figure 1 The plasma processing apparatus 2 shown includes a plasma source 1. The plasma source 1 is disposed on the upper part of the plasma processing apparatus 2 via a connecting portion 23. The plasma source 1 includes a first chamber 22, an electromagnetic wave supply portion 36, and a protrusion 24. The first chamber 22 is a flat rectangular container extending along the central axis of the plasma processing apparatus 2, i.e., axis AX. The first chamber 22 and the electromagnetic wave supply portion 36 are an example of a plasma generation portion. In a first embodiment, the plasma generation portion is disposed outside the plasma processing apparatus 2.

[0040] The two opposing walls with the largest area in the first chamber 22 are referred to as the first wall 22a (see reference). Figure 4 The first chamber 22 forms a plasma generation space 22d. An opening 22e is formed in the first wall 22a. A dielectric window 38 is formed of a ceramic (dielectric) such as alumina (Al2O3) and is configured to allow electromagnetic waves such as microwaves to pass through. The dielectric window 38 is provided along the wall surface of the first wall 22a in a manner that closes the opening 22e. The dielectric window 38 is provided at the front end of the electromagnetic wave supply unit 36, so that the electromagnetic waves supplied from the electromagnetic wave supply unit 36 ​​are transmitted into the plasma generation space 22d. The electromagnetic waves include microwaves. The frequency band of the microwaves is 300MHz to 3THz. The electromagnetic waves may include VHF waves with a frequency band of 150MHz to 300MHz.

[0041] A protrusion 24 is provided on the second wall 22b, protruding from the second wall 22b close to the dielectric window 38, and at least a portion of it contains a conductor. The conductor functions as an electrode. An air hole 24c is provided in the protrusion 24, opening toward the dielectric window 38. The structure and function of the protrusion 24 will be described later.

[0042] The vent 24c of the protrusion 24 is connected to the gas supply unit 50, supplying reducing gas from the gas supply unit 50 to the plasma generation space 22d. In the first chamber 22, plasma is generated in the plasma generation space 22d by decomposing the gas supplied from the vent 24c of the protrusion 24 using the electric field of the electromagnetic waves supplied from the electromagnetic wave supply unit 36. The free radicals in the generated plasma are supplied to the plasma processing apparatus 2 for processing the substrate W. The plasma processing apparatus 2 has a second chamber 10. In addition, processing gases other than reducing gas can be supplied directly to the processing chamber 30e from the side wall of the second chamber 10, for example.

[0043] In one embodiment, the second chamber 10 includes a chamber body 12. The chamber body 12 has a generally cylindrical shape and an opening at its upper portion. The chamber body 12 provides the sidewalls and bottom of the second chamber 10. The chamber body 12 is formed of a metal such as aluminum. The chamber body 12 is grounded.

[0044] The second chamber 10 also includes an upper wall 14. The upper wall 14 is formed of a metal such as aluminum. The upper wall 14 closes the opening at the top of the chamber body 12. The upper wall 14 and the chamber body 12 are grounded together.

[0045] The plasma processing apparatus 2 also includes a stage 18. The stage 18 is disposed within the second chamber 10. The stage 18 is configured to support a substrate W placed thereon. The substrate W is placed on the stage 18 in a generally horizontal state. The stage 18 can be supported by a support member 19. The support member 19 extends upward from the bottom of the second chamber 10. The stage 18 and the support member 19 can be formed of a dielectric such as aluminum nitride.

[0046] The plasma processing apparatus 2 also includes a spray head 20. The spray head 20 is formed of a metal such as aluminum. The spray head 20 has a generally disc-shaped shape and a hollow structure. The spray head 20 shares a common axis AX as its central axis. The spray head 20 is positioned above the stage 18 and below the upper wall 14. The spray head 20 forms the top that divides the internal space of the second chamber 10.

[0047] The second chamber 10 has a processing chamber 30e for processing the substrate between the spray head 20 and the stage 18. The substrate W is processed in the processing chamber 30e. The second chamber 10 has an axis AX as its central axis. The axis AX is an axis extending vertically from the center of the second chamber 10.

[0048] The sidewall of the chamber body 12 provides a passage 12p. The substrate W passes through the passage 12p when it is transported between the inside and outside of the second chamber 10. The passage 12p can be opened and closed by a gate 12v. The gate 12v is disposed along the sidewall of the chamber body 12.

[0049] The bottom of the second chamber 10 provides an exhaust port 16a. The exhaust port 16a is connected to an exhaust device 16. The exhaust device 16 includes a pressure controller such as an automatic pressure control valve and a vacuum pump such as a turbomolecular pump.

[0050] The spray head 20 provides a diffusion chamber 30d internally. The spray head 20 is provided with a plurality of gas through-holes 20i extending through the spray head 20 in the thickness direction, opening on the lower surface of the spray head 20. The spray head 20 forms a gas path that introduces gas from the diffusion chamber 30d through the plurality of gas through-holes 20i into the processing chamber 30e. Thus, free radicals generated in the first chamber 22, as well as other gases used as needed, can be introduced into the processing chamber 30e. The stage 18 also functions as a lower electrode, and the spray head 20 also functions as an upper electrode.

[0051] The outer periphery of the spray head 20 is covered by a dielectric component 33 such as alumina. The outer periphery of the mounting stage 18 is covered by a dielectric component 34 such as alumina. If a high frequency is not supplied to the spray head 20, the dielectric component 33 may not be provided. However, in order to define the area of ​​the spray head 20 that functions as the opposite electrode of the mounting stage 18, it is preferable to provide the dielectric component 33. Furthermore, it is also preferable to provide the dielectric component 33 to make the ratio of the anode to the cathode of the electrodes as even as possible.

[0052] The mounting stage 18 is connected to the high-frequency power supply 60 via a matching adapter 61. The matching adapter 61 has an impedance matching circuit. The impedance matching circuit is configured to match the impedance on the load side (the mounting stage 18 side) with the output impedance of the high-frequency power supply 60. The high-frequency power supplied from the high-frequency power supply 60 has a frequency lower than the VHF wave and microwave frequency supplied to the plasma source 1 (described later), specifically a frequency below 60 MHz. The high-frequency frequency can be 13.56 MHz. Furthermore, the high-frequency power supply 60 can be connected to the mounting stage 18 or the spray head 20 via the matching adapter 61. The free radicals supplied from the plasma source 1 to the plasma processing apparatus 2 are re-dissociated under the action of the high-frequency electrical power applied within the plasma processing apparatus 2, and used for the processing of the substrate W.

[0053] [Plasma Source]

[0054] For plasma source 1, in addition to Figure 1 and Figure 2 In addition, refer to Figure 3 To provide a more detailed explanation. Figure 3This is a diagram illustrating one example of the simulation results for plasma electron density. The plasma source 1 has a connecting portion 23, which is fixed to the upper wall 14. A first chamber 22 is provided on the connecting portion 23, and the structure is configured such that free radicals (active substances) in the plasma generated in the first chamber 22 are supplied to the plasma processing device 2 via the connecting portion 23.

[0055] The connecting part 23 is a hollow, roughly cylindrical component made of a metal such as aluminum, sharing a common axis AX as its central axis. 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.

[0056] The first chamber 22 is a flat rectangular waveguide centered on axis AX. The upper end of the connecting portion 23 extends 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 inside. The first chamber 22 and the connecting portion 23 are made of conductors such as aluminum and have a ground potential.

[0057] Reference will Figure 1 Region A magnified Figure 2 As can be seen, the protrusion 24 is cylindrical and is formed entirely of dielectric materials 24g such as alumina, AlN, and quartz. The protrusion 24 penetrates the second wall 22b and protrudes from it. An air hole 24c is formed inside the protrusion 24, penetrating it. The air hole 24c has a fine hole 24c1 and an enlarged portion 24c2 formed by expanding the diameter of the fine hole 24c1. The opening 24a at the front end of the air hole 24c opens towards the dielectric window 38 from the enlarged portion 24c2. Reducing gas is supplied to the plasma generation space 22d through the air hole 24c. Thus, the protrusion 24 functions as a gas nozzle. The function of the protrusion 24 as a plasma ignition source will be explained later.

[0058] The vent 24c of the protrusion 24 ejects gas toward the dielectric window 38. Therefore, by ejecting gas into the area where electromagnetic wave energy is concentrated, the gas decomposition efficiency and free radical generation efficiency can be improved. Figure 3 N represents the plasma electron density within the plasma generation space 22d. e The figure shows one example of the simulation results. Argon gas was supplied from the vent 24c as the simulation conditions of this invention. The front end of the protrusion 24 was designed not to protrude from the second wall 22b. The pressure of the plasma generation space 22d was set to 10 Pa, and microwaves at a frequency of 860 MHz were supplied from the dielectric window 38.

[0059] The simulation results are as follows Figure 3 As shown, the plasma electron density N in the plasma generation space 22d near the dielectric window 38 eIncreases. Plasma electron density N e The higher the energy level is near the center of dielectric window 38, the lower the energy level is further away from the center of dielectric window 38. Based on the above results, it can be concluded that the vicinity of dielectric window 38 is the area where energy is concentrated.

[0060] Therefore, in this embodiment, the protrusion 24 is directed towards... Figure 3 The arrow points outwards, supplying gas from the front end of the protrusion 24 to the dielectric window 38. This allows for the supply of plasma electron density N to the plasma generation space 22d. e The gas is supplied to a region with high energy concentration. Therefore, by injecting gas into the energy-concentrated area near the dielectric window 38, the gas decomposition efficiency and free radical generation efficiency can be improved.

[0061] Furthermore, referring to Figure 4 The description will continue with a perspective view of the plasma source 1 according to the first embodiment. The plasma source 1 has an electromagnetic wave supply unit 36 ​​connected to the first wall 22a of the first chamber 22. (Refer to...) Figure 1 and Figure 4 It can be seen that in the first wall 22a that constitutes the first chamber 22, two electromagnetic wave supply units 36, with their centers located on the axis AX, are arranged longitudinally along the length direction (longitudinal direction) of the first chamber 22. The two electromagnetic wave supply units 36 have the same structure.

[0062] The electromagnetic wave supply unit 36 ​​has a dielectric window 38 at its front end, configured to supply electromagnetic waves into the first chamber 22 through the dielectric window 38. In this embodiment, microwaves propagate from the microwave oscillator 40 to the electromagnetic wave supply unit 36 ​​via the input port. The electromagnetic wave supply unit 36 ​​has a coaxial waveguide structure, including a generally cylindrical inner conductor 36a and a generally cylindrical outer conductor 36b arranged concentrically around the inner conductor 36a. Microwaves propagate between the inner conductor 36a and the outer conductor 36b and pass through a generally disk-shaped quartz component 37, passing through the gap U (see reference ) provided between the quartz component 37 and the dielectric window 38. Figure 5 The microwave propagates through the slot S on the antenna 26 in the first chamber 22 and into the dielectric window 38. Furthermore, there may be a space between the inner conductor 36a and the outer conductor 36b, or it may be filled with aluminum oxide or the like. The microwave transmits through the dielectric window 38 and radiates into the first chamber 22 from the opening 22e of the first wall 22a. Moreover, the inner conductor 36a, the quartz component 37, and the dielectric window 38 are covered by the outer conductor 36b.

[0063] Figure 5 (a) indicates Figure 4 Section AA is a view taken from the inner wall side of the first wall 22a, showing the area near the opening 22e of the first wall 22a. Figure 5 (b) indicates through Figure 5 (a) is a diagram of the BB section at the center of opening 22e. Figure 5 As shown in (a), the conductor antenna 26 contacts the opposite side of the surface of the dielectric window 38 exposed from the opening 22e, forming a ring-shaped (annular) groove S.

[0064] In addition, such as Figure 5 As shown in (b), the surface of the dielectric window 38 exposed from the opening 22e has a circular recess in the central region 38a of the dielectric window 38, and the central region 38a is thinner than the outer peripheral region 38b of the dielectric window 38. This improves the plasma ignition characteristics. However, the recess in the central region 38a may not be present.

[0065] In this embodiment, two electromagnetic wave supply units 36 are arranged longitudinally on the first wall 22a, but three or more may also be arranged, or only one may be arranged. The more electromagnetic wave supply units 36 there are, the higher the free radical generation efficiency and plasma generation efficiency.

[0066] With this structure, the area near the upper electromagnetic wave supply section 36 of the vertically arranged electromagnetic wave supply section 36 becomes a first dissociation region that promotes gas dissociation. Conversely, the area near the lower electromagnetic wave supply section 36 becomes a second dissociation region that promotes gas dissociation. Since the gas dissociated in the first dissociation region further dissociates in the second dissociation region, the degree of gas dissociation increases vertically towards the lower part of the plasma generation space 22d within the first chamber 22. Therefore, a high-density plasma can be generated in the first chamber 22. Consequently, the connecting section 23 can supply sufficient free radicals to the second chamber 10.

[0067] In this manner, free radicals are supplied from plasma source 1 to the processing chamber 30e between the stage 18 (lower electrode) and the spray head 20 (upper electrode) to process the substrate W placed on the stage 18. During this process, free radicals flow from plasma source 1 through multiple gas through-holes 20i provided in the spray head 20 and are supplied to the processing chamber 30e. Sometimes, the free radicals supplied to the processing chamber 30e recombine to form gas during transport. The high-frequency power of the high-frequency power supply 60 is used to decompose the free radicals and the resulting gas, and the plasma generated is used to perform film deposition and other treatments on the substrate W. By supplying free radicals from plasma source 1, even if the high frequency supplied from the high-frequency power supply 60 is relatively low, gas dissociation can be sufficiently advanced, thus improving the supply of free radicals. Therefore, substrate film deposition with less damage can be performed. Furthermore, although not shown in the figure, gases that can be sufficiently dissociated using only the high-frequency power supply 60 can be supplied directly to the spray head 20 without passing through plasma source 1.

[0068] The control unit (control device) 90 may be a computer including a processor 91 and a memory 92. The control unit 90 includes an arithmetic unit, a storage unit, an input device, a display device, and a signal input / output interface. The control unit 90 controls each part of the plasma processing apparatus 2, which includes the plasma source 1. In the control unit 90, the operator can use the input device to input commands for managing the plasma processing apparatus 2. Furthermore, the control unit 90 can visually display the operating status of the plasma processing apparatus 2 using the display device. The memory 92 of the control unit 90 stores control programs and scheme data. The control programs are executed by the processor 91 of the control unit 90 to perform various processes in the plasma processing apparatus 2. The processor 91 executes the control programs to control each part of the plasma processing apparatus 2, thereby executing various processes, such as plasma processing methods, in the plasma processing apparatus 2 according to the scheme data.

[0069] When using an ICP-type remote plasma source, there are issues such as a narrow plasma stability range and difficulty in plasma ignition. To address this, the plasma processing apparatus 2 with the above structure utilizes a plasma source 1 that generates plasma and activates gas using relatively high-frequency electromagnetic waves such as microwaves, supplying sufficient free radicals to the second chamber 10. Therefore, a process with less damage to the substrate W can be performed using a microwave-based remote plasma source.

[0070] The plasma source 1 in this embodiment also has a protrusion 24. The protrusion 24 protrudes from the inner wall of the second wall 22b opposite to the dielectric window 38 in the first chamber 22 and is provided at a distance from the dielectric window 38.

[0071] At least a portion of the protrusion 24 contains a conductor. Figure 2 In the protrusion 24 shown, a conductor 24d is embedded in the dielectric 24g. The conductor 24d is formed of a metal such as aluminum and functions as an internal electrode. The distance D from the front end of the conductor 24d to the surface of the dielectric window 38 in the horizontal direction (perpendicular to the axis AX) is a distance that can make the electric field near the front end of the conductor 24d sufficiently low, and a distance of about 3mm to 10mm is sufficient. However, it is more preferable if the distance D is about 5mm to 10mm to further suppress contaminants, particles, and damage. The conductor 24d is annular in shape and is embedded near the end face of the pore 24c, located on the outer periphery of the enlarged diameter portion 24c2. The conductor 24d is covered by the dielectric 24g that forms the protrusion 24 and is not exposed on the inner wall of the pore 24c.

[0072] To prevent abnormal discharge caused by surface waves of microwaves in the vent 24c, the vent 24c has an enlarged diameter portion 24c2 at its front end, which expands from the fine hole 24c1 of the vent 24c and opens toward the dielectric window 38. The enlarged diameter portion 24c2 is cylindrical. In addition, the enlarged diameter portion 24c2 is not limited to a cylindrical shape, but can also be a prism shape with a polygonal base such as a quadrilateral or pentagon.

[0073] The depth (length) of the expanded diameter portion 24c2 from the tip of the vent 24c is 5 mm or more. The diameter of the fine hole 24c1 of the vent 24c is less than 1 mm, for example, 0.3 mm. The diameter of the expanded diameter portion 24c2 and the opening portion 24a is 3 mm or more, and is less than 1 / 8 of the surface wave wavelength λ of microwaves in plasma.

[0074] The surface wave wavelength λ of microwaves in plasma is about one-third of the microwave wavelength λ0 in vacuum. Since the wavelength λ0 used in microwave plasma processes is approximately 120–480 mm, the surface wave wavelength λ of microwaves in plasma is approximately 40–160 mm. Therefore, the diameters of the expanded section 24c2 and the opening 24a are 3 mm or more, and are about one-eighth of the surface wave wavelength λ of microwaves in plasma, i.e., approximately 5–20 mm.

[0075] The technical meaning of having a diameter of 3 mm or more for the expanded diameter portion 24c2 and an opening portion 24a that is less than 1 / 8 of the surface wave wavelength λ of microwaves in plasma will be explained. For example, when the diameter of the expanded diameter portion 24c2 and the opening portion 24a is 1 / 4 of the surface wave wavelength λ of microwaves in plasma, the surface wave of the microwave will stop at the opening portion 24a and cannot propagate forward. That is, the expanded diameter portion 24c2 and the opening portion 24a function in a way that prevents the surface wave of the microwave from propagating forward from the opening. At this time, the surface wave of the microwave will be totally reflected at the opening portion 24a. Therefore, the electric field strength of the microwave becomes maximum near the opening portion 24a. If it exceeds a critical value, an arc discharge will occur, resulting in an abnormal discharge.

[0076] In this case, when the diameter of the opening 24a is 1 / 8 of the surface wave wavelength λ of the microwaves in the plasma, the surface waves of the microwaves can pass through the opening 24a. At this time, the surface waves of the microwaves do not stop at the opening 24a, and the pressure difference between the internal pressure of the expanded diameter section 24c2 and the pressure of the plasma generation space 22d is small. Therefore, the strong electric field of the microwaves hardly penetrates the interior of the expanded diameter section 24c2, preventing abnormal discharges from occurring in the expanded diameter section 24c2. Therefore, the diameters of the expanded diameter section 24c2 and the opening 24a need to be less than 1 / 8 of the surface wave wavelength λ of the microwaves in the plasma, i.e., less than 20 mm.

[0077] On the other hand, when the diameter of the opening 24a is less than 3 mm, the surface waves of microwaves can pass through the opening 24a. However, the pressure difference between the internal pressure of the expanded diameter section 24c2 and the pressure of the plasma generation space 22d increases. Therefore, abnormal discharge is easily generated in the expanded diameter section 24c2. Thus, the diameter of the opening 24a of the expanded diameter section 24c2 is 3 mm or more. This prevents abnormal discharge from occurring at the tip and around the vent 24c.

[0078] Next, the function of the protrusion 24 as a plasma ignition source will be explained. In plasma ignition using microwaves, such as plasma source 1, the discharge electric field E shown in equation (1) bd It determines the ignition performance.

[0079]

[0080] In this regard, in a parallel-plate type plasma processing device such as the second chamber 10, the discharge voltage V, as shown in equation (2), is obtained by discharging high-frequency electrical power between the lower and upper electrodes, according to Paschen's law. bd It determines the ignition performance.

[0081]

[0082] In equation (1), D and K are coefficients determined by the type of gas, p is the pressure inside the chamber, and f is the frequency of the electromagnetic wave. m is a constant (approximately 0.5) determined by the type of gas. In equation (2), A and B are coefficients determined by the type of gas, p is the pressure inside the chamber, d is the distance between the lower and upper electrodes, and γ... se It 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.

[0083] That is, in plasma source 1, Paschen's law does not hold for plasma ignition. Therefore, in plasma source 1, the ignition performance is not determined by the discharge voltage V shown in equation (2). bd Decision. In plasma source 1, if the discharge electric field E shown in equation (1) is enhanced... bd Ignition then becomes easier. Therefore, the protrusion 24 included in the plasma source 1 has a shape and configuration that facilitates ignition of microwaves and VHF waves above 150 MHz, making plasma ignition easy in the first chamber 22.

[0084] When no plasma is generated in the first chamber 22, when microwaves are radiated into the first chamber 22, the radiated microwaves are reflected by the conductor 24d within the protrusion 24, and the reflected microwave wave returns to the first wall 22a. Thus, 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. The first chamber 22 is flat, and the space between the first wall 22a and the second wall 22b is narrow, therefore a high electric field is generated within the first chamber 22, facilitating plasma ignition. On the other hand, after plasma ignition, the electric field between the protrusion 24 and the inner wall of the first wall 22a does not increase.

[0085] Based on the above, the protrusion 24 is a passive ignition source. Although it does not apply voltage itself, the annular conductor 24d functions as an internal electrode, reflecting microwaves. The outer diameter of the conductor 24d is between 10 mm and 28 mm.

[0086] The diameter of the opening 24a of the vent 24c is 3 mm or more, and is less than 1 / 8 of the surface wave wavelength λ of the microwave in the plasma, for example, 4 mm. Therefore, the lower limit of the outer diameter of the conductor 24d is a sufficiently large size relative to the size of the opening 24a, and is 10 mm or more in order to function as a passive ignition source. Furthermore, the upper limit of the outer diameter of the conductor 24d is preferably less than or equal to the inner diameter of the groove S provided for microwave introduction, so as not to weaken the electric field strength and deteriorate the ignition performance. Therefore, the upper limit of the outer diameter of the conductor 24d is 28 mm or less.

[0087] (Example of a variation of a protrusion)

[0088] Protrusion 24 is not limited to Figure 2 The structure shown. For example, refer to... Figure 6 A modified example of the protrusion 24 will be described. In this modified example, the protrusion 24 can be formed into a cylindrical integral shape by the conductor 24e, and the conductor 24e is surrounded by a dielectric 24f such as alumina. In this case, a pore 24c is also formed inside the protrusion 24. The pore 24c includes a fine hole 24c1 and an enlarged diameter portion 24c2. The opening 24a at the front end of the pore 24c opens from the enlarged diameter portion 24c2 toward the dielectric window 38. The dimensions of the fine hole 24c1 and the enlarged diameter portion 24c2 of the pore 24c are similar to... Figure 2 The dimensions of the protrusion 24 are the same. The horizontal distance from the front end of the conductor 24e to the bottom surface of the dielectric window 38 is also the same. Figure 2The situation is the same for conductor 24d. By coating conductor 24e with dielectric 24f, the plasma resistance of protrusion 24 can be improved, suppressing consumption and degradation caused by plasma. The modified structure of protrusion 24 also allows for easy plasma ignition, improving gas decomposition efficiency. Furthermore, Figure 2 and Figure 6 The shape of the front end of the protrusion 24 shown can also be a rounded shape obtained by chamfering the diagonal.

[0089] In addition, the protrusion 24 Figure 2 The conductor 24d shown and Figure 6 The conductor 24e shown functions as a floating electrode.

[0090] 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. This distance is in the range of 10 to 100 times because the plasma conductivity varies significantly with plasma density, as shown below. In this embodiment, the distance between the inner walls of the first wall 22a and the second wall 22b is approximately 20 mm (see reference). Figure 1 ).

[0091] The skin depth varies based on (1) frequency, (2) electron density, and (3) collision frequency between electrons and neutral particles. Here, the collision frequency between electrons and neutral particles in (3) is determined by the gas type and electron temperature. The skin depth δ is calculated using equation (3).

[0092] Skin depth δ=[2 / (ωμoσdc)] 1 / 2 …(3)

[0093] Here, ω is the power supply frequency, μ0 is the permeability of free space, and σ dc Let be the plasma conductivity. The plasma conductivity is calculated using equation (4).

[0094] Plasma conductivity σdc=e 2 n e / (mνm)…(4)

[0095] Here, e is the elementary charge, and n e Let m be the electron density, and ν be the mass of an electron. m The collision frequency between electrons and neutral particles.

[0096] When the distance between the inner walls of the first wall 22a and the second wall 22b is set to 10 times the skin depth, this distance is approximately 20 mm at a microwave frequency of 800 MHz, approximately 28 mm at 400 MHz, and approximately 12 mm at 2.45 GHz. This enables the realization of a plasma source 1 with low electron temperature and high electron density. Furthermore, the pressure within the first chamber 22 is maintained at 0.5 Torr or higher.

[0097] The plasma source 1 of the first embodiment described above, by thinning the thickness of the first chamber 22 and providing the protrusion 24, facilitates plasma ignition, improves plasma generation efficiency in the first chamber 22, and expands the stable range of plasma generation. Furthermore, by concentrating the high electron temperature and high electron density regions in the region supplied with electromagnetic waves within the plasma generation space, the gas decomposition efficiency and free radical generation efficiency can be improved. In particular, by injecting reducing gas from the center of the protrusion 24 and blowing the reducing gas towards the center of the dielectric window 38 where electromagnetic wave energy is concentrated, the decomposition efficiency of the reducing gas can be maximized.

[0098] <Second Implementation>

[0099] [Plasma Processing Device]

[0100] Next, refer to Figure 7 The plasma processing apparatus 2 of the second embodiment will be described. Figure 7 This is a cross-sectional view showing the plasma processing apparatus 2 according to the second embodiment. Figure 7 The annotations of each part of the attached drawings and Figure 1 When the reference numerals on different parts of an image are the same, they indicate that the parts have the same structure.

[0101] In the second embodiment, the plasma source 1 is disposed on the upper part of the plasma processing apparatus 2. The plasma source 1 and the spray head 20 are integrated, and the first chamber 22 of the first embodiment corresponds to the spray head 20 in the second embodiment. That is, the plasma source 1 uses the diffusion chamber 30d inside the spray head 20 as a plasma generation space, and has a diffusion chamber 30d, an electromagnetic wave supply section 36, and a protrusion 24. The diffusion chamber 30d and the electromagnetic wave supply section 36 are examples of plasma generation sections. The plasma generation section of the first embodiment is disposed outside the plasma processing apparatus 2, but a portion of the plasma generation section of the second embodiment is disposed inside the plasma processing apparatus 2.

[0102] If we define the two opposing walls with the largest area constituting the diffusion chamber 30d as the first wall 22a and the second wall 22b, then in the second embodiment, the upper wall of the spray head 20 is the first wall 22a, and the lower wall of the spray head 20 is the second wall 22b. An opening 22e is formed in the first wall 22a. A dielectric window 38 is provided in the first wall 22a to close the opening 22e, allowing electromagnetic waves to be transmitted into the diffusion chamber 30d corresponding to the plasma generation space 22d. The dielectric window 38 is provided at the front end of the electromagnetic wave supply unit 36.

[0103] The protrusion 24 is disposed on the second wall 22b, protruding from the second wall 22b near the dielectric window 38, and at least a portion of it contains a conductor. The structure and function of the protrusion 24 may be... Figure 2 and Figure 6 Any of the protrusions 24 shown. The structure and function of the protrusions 24 have been described above, so the explanation is omitted.

[0104] The vent of the protrusion 24 is connected to the gas supply section 50, supplying reducing gas from the gas supply section 50 to the plasma generation space 22d. In the plasma generation space 22d, the reducing gas supplied from the vent of the protrusion 24 is decomposed using the electric field of the electromagnetic waves supplied from the electromagnetic wave supply section 36 to generate plasma. Multiple gas through-holes 20i are formed in the thickness direction of the second wall 22b and penetrate the second wall 22b. Free radicals in the plasma generated in the plasma generation space 22d are supplied to the processing chamber 30e through the multiple gas through-holes 20i for processing the substrate W.

[0105] The plasma processing apparatus 2 has a second chamber 10. In one embodiment, the second chamber 10 includes a chamber body 12. The chamber body 12 has a generally cylindrical shape and an opening at its upper part. The chamber body 12 provides the sidewalls and bottom of the second chamber 10. The chamber body 12 is formed of a metal such as aluminum. The chamber body 12 is grounded.

[0106] The outer periphery of the spray head 20 is covered by a component 33, which is a dielectric material such as alumina. The outer periphery of the platform 18 is covered by a component 34, which is a dielectric material such as alumina. The opening at the top of the chamber body 12 is closed by the spray head 20 and the component 33.

[0107] The plasma processing apparatus 2 also includes a stage 18. The stage 18 is disposed within the second chamber 10. The stage 18 is configured to support a substrate W placed thereon. The substrate W is placed on the stage 18 in a substantially horizontal state.

[0108] The stage 18 is connected to the high-frequency power supply 60 via a matching device 61. The bottom of the second chamber 10 is provided with an exhaust port 16a, which is connected to the exhaust device 16.

[0109] The thickness of the portion of the spray head 20 corresponding to the plasma generation space 22d is, for example, 20 mm. Using the plasma source 1 of the second embodiment described above, by thinning the thickness of the spray head 20 and providing the protrusion 24, plasma ignition can be easily performed, improving the plasma generation efficiency in the diffusion chamber 30d and expanding the stable range of plasma generation. Furthermore, by concentrating the high electron temperature and high electron density regions in the region supplied with electromagnetic waves within the plasma generation space, the gas decomposition efficiency and free radical generation efficiency can be improved. In particular, by injecting reducing gas from the center of the protrusion 24 and blowing the reducing gas towards the center of the energy-concentrated dielectric window 38, the decomposition efficiency of the reducing gas can be maximized.

[0110] By employing the plasma source 1 and plasma processing device 2 of the first and second embodiments, plasma ignition can be easily performed, thereby improving the gas decomposition efficiency.

[0111] It should be understood that the plasma source and plasma processing apparatus of the embodiments disclosed herein are illustrative in all respects and are not restrictive. The embodiments can be modified and improved in various ways without departing from the scope and spirit of the present invention (claims).

[0112] By providing the protrusion 24, the time required for plasma generation (ON) can be shortened without moving the matching position. This allows for rapid plasma ignition by changing the gas, making it a more suitable structure for ALD (atomic layer deposition) processes and improving production efficiency. However, it can also be applied to film deposition based on CVD (chemical vapor deposition) methods. Examples of substrate processing performed by the plasma processing apparatus disclosed in this specification include film deposition and etching processes.

Claims

1. A plasma source, characterized in that, include: The plasma generation unit includes a first wall with an opening and a second wall opposite to the first wall, and forms a plasma generation space; A dielectric window, which is disposed on the first wall in a manner that closes the opening, is configured to allow electromagnetic waves to be transmitted into the plasma generation space; as well as A protrusion, disposed on the second wall, projecting from the second wall near the dielectric window, and at least a portion comprising a conductor. The protrusion is provided with an air hole that opens toward the dielectric window.

2. The plasma source according to claim 1, characterized in that: The end face of the pore is enlarged.

3. The plasma source according to claim 1, characterized in that: The protrusion is formed of a dielectric.

4. The plasma source according to claim 3, characterized in that: The conductor is embedded in the dielectric.

5. The plasma source according to claim 4, characterized in that: The conductor is embedded in the outer periphery of the pore near the end face of the pore, and is not exposed in the pore.

6. The plasma source according to any one of claims 1 to 5, characterized in that: The conductor is in the shape of a ring.

7. The plasma source according to claim 6, characterized in that: The outer diameter of the conductor is 10 mm or more and 28 mm or less.

8. The plasma source according to claim 1 or 2, characterized in that: The protrusion is formed of a conductor, which is surrounded by a dielectric.

9. The plasma source according to any one of claims 1 to 5, characterized in that: The distance between the first wall and the second wall is 10 to 100 times the plasma skin depth.

10. The plasma source according to any one of claims 1 to 5, characterized in that: The plasma source is disposed on the upper part of the plasma processing device via a connecting part. The plasma processing device has a processing chamber for processing the substrate. The plasma generation unit is located outside the plasma processing device, and supplies plasma generated from gas supplied from the vent using electromagnetic waves to the processing chamber through the connecting part.

11. The plasma source according to any one of claims 1 to 5, characterized in that: Multiple through holes are formed in the second wall.

12. The plasma source according to claim 11, characterized in that: The plasma source is located at the top of the plasma processing device. The plasma processing device has a processing chamber for processing the substrate. A portion of the plasma generation unit is located inside the plasma processing device, and plasma generated from gas supplied from the vent using electromagnetic waves is supplied to the processing chamber through the plurality of through holes.

13. A plasma processing apparatus, characterized in that: The plasma source includes any one of claims 1 to 12.

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