Plasma processing equipment

Abstract

To avoid or suppress abnormal electric discharges in a mechanism that exhausts air from a side of a processing space.SOLUTION: There is provided, a plasma processing device comprising: a processing container; a placement table which is provided inside of the processing container; an upper electrode that faces a placement surface of the placement table and constitutes a top wall of the processing container, and which is supplied with RF electric power; and an exhaust duct that demarcates a processing space in the processing container together with the placement surface and the upper electrode. A radial cross section of an outer wall of the exhaust duct that faces the processing space is L-shaped, and the exhaust duct has an exhaust hole communicating with an internal exhaust path, the exhaust hole being constructed so that, with respect to lengths d, e of two sides of the L shape, a distance b from a corner of the L shape to the exhaust hole is within the length d and within the length e, the length d being 7 mm or greater, the length e being greater than or equal to the length d.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Techniques for suppressing abnormal discharge have been proposed for plasma processing apparatuses that apply high-frequency power. For example, Patent Document 1 provides a plasma processing apparatus that includes a processing vessel, a stage within the processing vessel on which a substrate is placed and which has a heater inside, and an annular member made of a dielectric material and spaced apart from the periphery of the stage, with annular grooves formed radially on the underside of the annular member. According to this technology, the grooves formed on the underside of the annular member spaced apart from the periphery of the stage distribute the electric field generated by the high-frequency waves passing through the annular member. This reduces the electric field strength in the gap between the stage and the annular member, thereby suppressing abnormal discharge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-147795 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can avoid or suppress abnormal discharge in a mechanism that exhausts air from the side of a processing space. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a processing vessel, a mounting table provided within the processing vessel, an upper electrode facing a mounting surface of the mounting table, constituting a ceiling wall of the processing vessel, and receiving RF power, and an exhaust duct defining a processing space within the processing vessel together with the mounting surface and the upper electrode, wherein a radial cross section of an outer wall of the exhaust duct facing the processing space is With respect to the processing space L-shaped I'm depressed The exhaust duct has an exhaust hole that communicates with an internal exhaust path, and the exhaust hole is configured so that the distance b from the corner of the L-shape to the exhaust hole is within the length d and the length e of the two sides of the L-shape, and the length d is 7 mm or more, and the length e is d or more. [Effects of the Invention]

[0006] According to one aspect, abnormal discharge can be avoided or suppressed in a mechanism for exhausting gas from the side of the processing space. [Brief explanation 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; [Figure 2] 10A and 10B are diagrams showing examples of results of an electric field simulation around an exhaust duct according to an embodiment in comparison with a reference example. [Figure 3] FIG. 2 is a diagram showing an example of an exhaust duct according to the embodiment. [Figure 4] 10A and 10B are diagrams showing examples of simulation results illustrating the relationship between the length of the outer wall of the exhaust duct and the electric field strength according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments 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 redundant explanations may be omitted.

[0009] In this specification, deviations in directions such as parallel, right angles, orthogonal, horizontal, vertical, up / down, left / right, etc. are permitted to the extent that they do not impair the effects of the embodiments. The shape of the corners is not limited to right angles and may be rounded like an arch. Parallel, right angles, orthogonal, horizontal, vertical, circular, and coincident may also include approximately parallel, approximately right angles, approximately orthogonal, approximately horizontal, approximately vertical, approximately circular, and approximately coincident.

[0010] [Plasma processing equipment] A plasma processing apparatus 100 according to one embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view showing an example of the plasma processing apparatus 100 according to one embodiment. The plasma processing apparatus 100 has a processing vessel 1. The processing vessel 1 has a vessel 12 and a lid 11, and the lid 11 is attached to the top opening of the bottomed vessel 12. The vessel 12 and the lid 11 are made of, for example, aluminum. The inner walls of the vessel 12 and the lid 11 may be coated with a ceramic film, such as aluminum oxide or yttrium oxide, that is resistant to corrosion by plasma.

[0011] A stage S is provided within the vessel 12. The stage S is formed in the shape of a flat disk, and its upper surface serves as a mounting surface Sa on which a substrate W, such as a wafer, is placed. The stage S is made of a dielectric material such as alumina (Al2O3). A heater 20 for heating the substrate W is embedded within the stage S. The heater 20 is formed, for example, of a sheet-like or plate-like resistance heating element, and generates heat when power is supplied from a power supply unit. This heats the mounting surface Sa of the stage S, thereby raising the temperature of the substrate W to a predetermined process temperature suitable for film formation. For example, the heater 20 heats the substrate W placed on the stage S to 100°C to 300°C.

[0012] Furthermore, a mesh-shaped metal electrode plate 21 is embedded in the stage S in parallel to the heater 20. The electrode plate 21 may be supplied with RF (radio frequency) bias power or may be connected to the ground. The stage S functions as a lower electrode facing the upper electrode 14.

[0013] The stage S is supported by a support portion 22 extending below the stage S. The support portion 22 penetrates the bottom of the container 12 and is supported by a lifting mechanism 35. The lifting mechanism 35 raises and lowers the support portion 22, thereby raising and lowering the stage S between a processing position (stage S position shown in FIG. 1) where the substrate W is processed and a transfer position (stage S position shown by the two-dot chain line in FIG. 1) where the substrate W is transferred. The lifting mechanism 35 also adjusts the distance (Gap) between the stage S and the upper electrode 14.

[0014] At the transfer position, the substrate W is transferred to and from an external transport mechanism via a loading / unloading port (not shown). Through holes are formed in the stage S, through which the shafts of the lifting pins 30 are inserted. When the stage S is moved from the processing position for the substrate W (see FIG. 1) to the transfer position for the substrate W (see the two-dot chain line in FIG. 1), the heads of the lifting pins 30 protrude from the mounting surface of the stage S. As a result, the heads of the lifting pins 30 support the substrate W from its underside, lift the substrate W from the mounting surface Sa of the stage S, and transfer the substrate W to and from the external transport mechanism.

[0015] Above the stage S and below the lid 11, an upper electrode 14, which functions as a showerhead, is supported by the lid 11 while being insulated from the lid 11. The upper electrode 14 is disk-shaped and made of a conductor such as aluminum. The upper electrode 14 is disposed facing the stage S, constitutes the ceiling wall of the processing vessel 1, and is supplied with RF power. The upper electrode 14 is provided with a number of gas supply holes 16. The supply and stop of the film formation gas output from the gas supply unit 15 and the gas flow rate are controlled by a valve V and a flow rate controller MFC, and the controlled gas is introduced into a gas inlet 18 via a gas line 17. The introduced gas passes through a through-hole 19 formed in the lid 11 and a flow path 24, and is introduced into the vessel 12 from the multiple gas supply holes 16.

[0016] An RF power supply 36 is connected to the upper electrode 14 via a matching box 37. RF power having a frequency of, for example, 13.56 MHz, of frequencies between 0.4 MHz and 2450 MHz, is supplied from the RF power supply 36 to the upper electrode 14. The film formation gas introduced into the vessel 12 is dissociated by the RF electric field, generating plasma. The plasma generated in the space between the upper electrode 14 and the stage S (hereinafter also referred to as the "processing space 10s") performs a film formation process on the substrate W on the stage S. The film formation process is an example of plasma processing, and the plasma processing may also be etching processing, etc.

[0017] A separation plate 47 is provided around the stage S, extending inward from the sidewall of the vessel 12 and separated from the stage S by a gap 44. The separation plate 47 is made of an insulating material such as alumina (Al2O3). The separation plate 47 is an annular member that, together with the stage S, separates the internal space of the processing vessel 1 into an upper space and a lower space. The outer periphery of the separation plate 47 is disposed on a step portion provided on the side surface of the vessel 12. The inner periphery of the separation plate 47 protrudes radially from the side surface of the vessel 12 toward the stage S. An insulating member 41 extends upward from the outer periphery of the separation plate 47 and covers the outer periphery of the sidewall, lid 11, and upper electrode 14 of the vessel 12 at a position higher than the stage S so as to surround the exhaust duct 40. With this configuration, the insulating member 41 and the separation plate 47 form an opening 43 that opens circumferentially around the entire circumference toward the processing space 10s. The exhaust duct 40 and the lid 11 are sealed with an O-ring 13. This seals the inside of the processing chamber 1, making it possible to maintain a vacuum state.

[0018] The insulating member 41 is made of ceramics such as alumina (Al2O3). An exhaust duct 40 is provided inside the insulating member 41 in close contact with the inner wall of the insulating member 41. The exhaust duct 40 is made of a metal such as aluminum and is connected to the ground. The exhaust duct 40 is an annular member formed in the circumferential direction around the entire circumference, and an exhaust path 42 is formed inside the circumferential direction.

[0019] The exhaust duct 40 is almost entirely covered with an insulating member, except for the outer walls 40a and 40b facing the processing space 10s. The horizontal and vertical outer walls 40a and 40b of the exhaust duct 40 facing the opening 43 are recessed outward. The mounting surface Sa of the stage S, the upper electrode 14, and the outer walls 40a and 40b of the exhaust duct 40 define the processing space 10s within the processing vessel 1.

[0020] With this configuration, an insulating member 41 is provided between the upper electrode 14 and the exhaust duct 40, and the upper electrode 14 is insulated from the exhaust duct 40 by the insulating member 41. A gap 46 is formed between the insulating member 41 and the upper electrode 14 (see FIG. 2(c)). Because the upper electrode 14 is made of metal and the insulating member 41 is made of ceramic, the gap 46 is provided to reduce friction and interference that occurs between the two members due to differences in thermal expansion.

[0021] The interface portion formed by the outer wall 41a of the insulating member 41 facing the processing space 10s and the outer wall 40a of the exhaust duct 40 is flat and stepless, and the exhaust duct 40 extends downward at a 90° angle at the intersection (corner) of the outer wall 40a and the outer wall 40b.

[0022] When the portion of exhaust duct 40 up to the height of outer wall 40b is defined as the lower portion and the portion above outer wall 40b is defined as the upper portion, the radial width of the lower portion of exhaust duct 40 is narrower than the radial width of the upper portion of exhaust duct 40. Exhaust duct 40 may also be shaped so that the radial width of the lower portion is wider than the radial width of the upper portion of exhaust duct 40.

[0023] Exhaust holes 51 are formed in exhaust duct 40, penetrating predetermined positions of outer walls 40a and 40b (see FIG. 3). A plurality of exhaust holes 51 are provided at equal intervals in the circumferential direction. Gas passing through exhaust path 42 is discharged by vacuum pump 45 from exhaust port 6 provided laterally from exhaust duct 40 to the outside of processing chamber 1.

[0024] The plasma processing apparatus 100 has a control unit 50. The control unit 50 may be a computer equipped with a processor, a storage unit such as a memory, an input device, a display device, a signal input / output interface, etc. The control unit 50 controls each unit of the plasma processing apparatus 100. An operator can use the input device in the control unit 50 to input commands and perform other operations to manage the plasma processing apparatus 100. The control unit 50 can also visualize and display the operating status of the plasma processing apparatus 100 using a display device. Furthermore, a control program and recipe data are stored in the storage unit. The control program is executed by the processor to perform various processes in the plasma processing apparatus 100. The processor executes the control program and controls each unit of the plasma processing apparatus 100 according to the recipe data.

[0025] [Abnormal discharge and countermeasures] Next, abnormal discharge and countermeasures therefor will be described with reference to Fig. 2. Fig. 2(c) shows an example result of an electric field simulation around the exhaust duct 40 according to the embodiment, compared with the reference examples of Figs. 2(a) and (b). Fig. 2(a) shows an example result of an electric field simulation around the exhaust mechanism 70 according to Reference Example 1. Fig. 2(b) shows an example result of an electric field simulation around the exhaust mechanism 71 according to Reference Example 2.

[0026] 1 is supplied to the upper electrode 14. As a result, an RF current flows between the upper electrode 14 and the stage S, which functions as a lower electrode, generating a strong electric field in the processing space 10s.

[0027] At the same time, RF power output from the RF power supply 36 flows over the surface of the metal lid 11 and the container 12 outside the upper electrode 14, and propagates through the insulating members. In Figures 2(a) to 2(c), 1500 W of RF power is supplied, flows over the surface of the lid 11, and propagates through the insulating members 63 (Figure 2(a)), 65 (Figure 2(b)), and 41 (Figure 2(c)). This generates an electric field within the insulating members 63, 65, and 41, which are made of ceramic. When the electric field becomes strong enough, the risk of abnormal discharge increases.

[0028] When the RF power is low, around 200 to 300 W, abnormal discharge does not occur in the exhaust mechanisms 70, 71 and exhaust duct 40. However, in recent years, there has been an increase in processes that supply high-power RF power of 1000 W or more. When such high-power RF power is supplied, a strong electric field is generated around the exhaust mechanisms 70, 71, which may cause abnormal discharge.

[0029] 2(a) to 2(c) show the results of a simulation performed under conditions in which an RF power of 1500 W at a frequency of 13.56 MHz is supplied to the upper electrode 14. In the exhaust mechanism 70 of Reference Example 1 shown in FIG. 2(a), an exhaust path 42 is formed in an insulating member 63 made of a ring-shaped ceramic. Also, an exhaust hole 62 is formed in the outer wall of the insulating member 63 facing the processing space 10s. The exhaust mechanism 70 does not have a metal exhaust duct 40.

[0030] The RF power flows on the surface of the metal lid 11 outside the upper electrode 14 and propagates through the insulating member 63. This generates an electric field inside the alumina insulating member 63 and in the exhaust path 42. The electric field is strong in region A where the exhaust hole 62 is formed near the opening 43. Abnormal discharge is likely to occur in region A where the electric field is strong.

[0031] In the configuration of the exhaust mechanism 70 of Reference Example 1 shown in FIG. 2(a), gas supplied through the gas supply holes 16 of the upper electrode 14 is converted into plasma in the processing space 10s, flows from the processing space 10s to the outer periphery, enters the insulating member 63 through the exhaust holes 62, and is exhausted through the exhaust path 42. At this time, abnormal discharge may occur in region A where the electric field is concentrated. Furthermore, abnormal discharge may occur in a portion of the insulating member 63 near region A where the electric field is strong. In particular, if the plasma generated in the processing space 10s enters the exhaust holes 62 and a strong electric field is generated near the exhaust holes 62 as shown in region A, abnormal discharge may occur at the exhaust holes 62. Therefore, it is necessary to weaken the electric field in region A near the exhaust holes 62.

[0032] 2(b) is composed of an alumina insulating member 65 and an aluminum exhaust duct 60. The insulating member 65 has an opening 43 that opens in the circumferential direction around the entire circumference toward the processing space 10s. The exhaust duct 60 is provided to cover the inner wall of the insulating member 65. The exhaust duct 60 has exhaust holes 61 formed toward the opening 43.

[0033] In this configuration, gas supplied through the gas supply holes 16 of the upper electrode 14 is converted into plasma in the processing space 10s, flows from the processing space 10s to the outer periphery, enters the exhaust duct 60 through the exhaust holes 61, and is exhausted through the exhaust path 42. At this time, abnormal discharge may occur in region B where the electric field is concentrated. Note that because the exhaust duct 60 is connected to the ground, the electric field in the exhaust duct 60 is zero. Therefore, abnormal discharge does not occur in the exhaust duct 60. On the other hand, if the plasma generated in the processing space 10s enters the exhaust holes 61 and a strong electric field is generated near the exhaust holes 61 as shown in region B, abnormal discharge will occur at the exhaust holes 61. Therefore, it is necessary to weaken the electric field in region B near the exhaust holes 61.

[0034] 2(c), the exhaust duct 40 has a recessed portion facing the opening 43, as compared to the exhaust duct 60 in FIG. 2(b). That is, the exhaust duct 40 is covered with an insulating member 41 and a separation plate 47, except for the outer walls 40a and 40b, and the outer walls 40a and 40b facing the processing space 10s are recessed in an L-shape. Exhaust holes 51 are formed in the corners (or near the corners) of the recessed outer walls 40a and 40b.

[0035] In this configuration, gas supplied through the gas supply holes 16 of the upper electrode 14 is converted into plasma in the processing space 10s, flows from the processing space 10s toward the outer periphery, enters the exhaust duct 40 through the exhaust holes 51, and is exhausted from the side of the vessel 12 through the exhaust path 42. The exhaust duct 40 is connected to the ground. Due to the shape of the recessed outer walls 40a and 40b, the recessed outer walls 40a and 40b form a region simply surrounded by ground potential on the processing space 10s side, preventing plasma from entering the exhaust holes 51. This weakens the electric field near the outer walls 40a and 40b. This weakens the electric field in region C near the exhaust holes 51 provided at the corners of the outer walls 40a and 40b, preventing abnormal discharge at the exhaust holes 51. Furthermore, because the exhaust duct 40 is connected to the ground, the electric field within the exhaust duct 40 is zero. Therefore, no abnormal discharge occurs within the exhaust duct 40. In particular, if the plasma generated in the processing space 10s enters the exhaust hole 51 and a strong electric field is generated near the exhaust hole 51, abnormal discharge occurs at the exhaust hole 51. However, with the configuration of the exhaust duct 40 according to this embodiment, the position of the exhaust hole 51 can be moved away from the plasma in the processing space 10s. Furthermore, the electric field can be weakened in the region C near the exhaust hole 51. This allows gas to be exhausted from the side of the processing vessel 1 while avoiding or suppressing abnormal discharge around the exhaust hole 51 and the exhaust duct 40. As a result, compared to when the exhaust duct is located at the bottom of the processing vessel 1, it is possible to improve the performance of the plasma and process while avoiding or suppressing abnormal discharge, and also to reduce the size of the processing vessel 1.

[0036] [Exhaust duct] The configuration of the exhaust duct 40 will be described in detail with reference to Figures 3 and 4. Figures 3(a) and 3(b) are diagrams showing an example of the exhaust duct 40 according to the embodiment. Figure 4 is a diagram showing an example of a simulation result showing the relationship between the length of the outer wall of the exhaust duct 40 according to the embodiment and the electric field strength.

[0037] 1 and 3(a), the outer walls 40a and 40b facing the processing space 10s are L-shaped, with a corner 40c formed by two sides of the outer walls 40a and 40b. The outer wall 40a is a horizontal surface, and the outer wall 40b is a vertical surface.

[0038] The angle θ (the angle of the corner 40c) is 90° or less. For example, the angle θ is 45°. The angle θ is preferably 30° or more and 90° or less. The reason why the angle θ is 30° or more and 90° or less is to prevent the exhaust hole 51 from being blocked by reaction products generated during film formation, to increase the efficiency when the reaction products are removed by cleaning, and to suppress the generation of particles.

[0039] The exhaust duct 40 has exhaust holes 51 that exhaust gas flowing from the processing space 10s. The exhaust holes 51 are configured such that, with respect to the lengths d and e of two sides of the outer walls 40a and 40b that form the L shape, a distance b from a corner 40c of the L shape to the inner wall of the exhaust holes 51 is within both lengths d and e.

[0040] Length d is 7 mm or more, and length e is d or more. The reason why length d is 7 mm or more will be explained with reference to FIG. 4. FIG. 4(a) shows an example of a simulation result showing the relationship between length d of outer wall 40a of exhaust duct 40 according to the embodiment and electric field intensity under the condition that RF power of 13.56 MHz and 1500 W is supplied to upper electrode 14. FIG. 4(b) shows the vertical axis of FIG. 4(a) in logarithmic (log) scale.

[0041] 4(a) and 4(b), the horizontal axis represents the length d of the outer wall 40a, and the vertical axis represents the electric field strength near the outer wall 40a and the outer wall 40b on the processing vessel 10s side. If the electric field strength is 30 V / m or less, abnormal discharge hardly occurs at the exhaust hole 51. From the results of the electric field simulation in FIG. 4(b), the length d of the outer wall 40a that can achieve an electric field strength of 30 V / m or less is calculated to be 7 mm or more.

[0042] As described above, in exhaust duct 40 according to this embodiment, distance b from L-shaped corner 40c to exhaust hole 51 is configured to be within length d (d≧7 mm) and also within length e. This allows the electric field at exhaust hole 51 to be roughly zero, and prevents abnormal discharge from occurring around exhaust hole 51 and exhaust duct 40.

[0043] As shown in FIG. 3(b), the outer walls 40a, 40b may be inclined at a corner 40c, and the corner 40c may be formed as a chamfered portion. Such a shape is also included in the shape in which the radial cross section of the outer walls 40a, 40b facing the processing space 10s of the exhaust duct 40 is L-shaped. The exhaust hole 51 penetrates at least one of the outer walls 40a, 40b, including the chamfered portion. In this case, the distance b from the corner 40c of the L-shape shown in FIG. 3(b) to the exhaust hole 51 is configured to be within the length d (d≧7 mm) and the length e of the outer wall 40a and the outer wall 40b shown in FIG. 3(b). Note that the angle θ of the corner 40c is not limited to 90°. Even if the angle θ is less than 90° (e.g., 45°), the radial cross section of the outer walls 40a, 40b facing the processing space 10s of the exhaust duct 40 is included in the shape in which the radial cross section is L-shaped.

[0044] The diameter of exhaust hole 51 is preferably 1 mm to 3 mm. If the diameter of exhaust hole 51 is larger than 3 mm, abnormal discharge is likely to occur, and if the diameter of exhaust hole 51 is smaller than 1 mm, exhaust hole 51 may be clogged with reaction products used in the film formation process performed in processing space 10s.

[0045] As described above, according to the plasma processing apparatus of this embodiment, it is possible to avoid or suppress abnormal discharge in the mechanism for exhausting gas from the side of the processing space.

[0046] The plasma processing apparatus according to the presently disclosed embodiments should be considered in all respects as illustrative and not restrictive. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The features 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.

[0047] In the above embodiment, the exhaust duct 40 has a shape in which the outer wall 40a protrudes inward at the upper part of the outer wall 40b, but this is not limiting. For example, the exhaust duct 40 may have a shape in which the outer wall 40a protrudes inward at the lower part of the outer wall 40b. [Explanation of symbols]

[0048] 1. Processing container 11 Lid 12 containers 14 Upper electrode 15 Gas supply section 16 Gas supply hole 36 RF power supply 40 Exhaust duct 41 Insulating material 42 Exhaust duct 44 Gap 45 Vacuum Pump 47 Separate version 50 control section 51 Exhaust hole 100 Plasma processing device S Stage

Claims

1. A processing vessel; a mounting table provided in the processing vessel; an upper electrode facing a mounting surface of the mounting table, constituting a ceiling wall of the processing vessel, and receiving RF power; an exhaust duct that, together with the mounting surface and the upper electrode, defines a processing space within the processing chamber; a radial cross section of an outer wall of the exhaust duct facing the processing space is recessed in an L-shape with respect to the processing space; the exhaust duct has an exhaust hole communicating with an internal exhaust path, and the exhaust hole is configured such that, with respect to lengths d and e of two sides of the L-shape, a distance b from a corner of the L-shape to the exhaust hole is within the lengths d and e, The length d is 7 mm or more, and the length e is d or more. Plasma processing equipment.

2. an insulating member is provided between the upper electrode and the exhaust duct; the insulating member insulates the upper electrode from the exhaust duct. The plasma processing apparatus according to claim 1 .

3. a surface formed by an outer wall of the insulating member facing the processing space and an outer wall of the exhaust duct is flat, and the corners are formed as chamfered portions that are chamfered with respect to the flat surface; The plasma processing apparatus according to claim 2 .

4. The exhaust hole penetrates at least one of the two sides or the chamfered portion. The plasma processing apparatus according to claim 3 .

5. There is no gap between the insulating member between the upper electrode and the exhaust duct and the exhaust duct, a gap is formed between the upper electrode and the insulating member between the upper electrode and the exhaust duct; 5. The plasma processing apparatus according to claim 2, wherein the plasma processing apparatus is a plasma processing apparatus.

6. The angle of the corner formed by the two sides is 90° or less. The plasma processing apparatus according to claim 1 .

7. The angle of the corner is equal to or greater than 30° and equal to or less than 90°. The plasma processing apparatus according to claim 6 .

8. The diameter of the exhaust hole is 1 mm to 3 mm. The plasma processing apparatus according to claim 1 .

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