Plasma processing apparatus and microwave radiation source

Abstract

To prevent the occurrence of contamination near an opening that radiates a microwave.SOLUTION: There is provided a plasma processing apparatus comprising a processing container that has an opening in a top wall, and a microwave radiation source. The microwave radiation source has a slot antenna that has slots and radiates microwaves from the slots, and a transmission window that closes the opening and radiates the microwaves to the inside of the processing container from the slots. The transmission window has a first surface having a vertical suspension part that is vertically suspended to cover a side wall of the opening, and a second surface that is an opposite surface of the first surface and faces the slot antenna with a gap therebetween.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] For example, Patent Document 1 proposes a plasma processing apparatus in which the underside of a transmission window provided at an opening in the ceiling wall of a processing vessel is smooth, and the underside of the ceiling wall has a convex portion through which the surface waves of microwaves radiated from a microwave radiating member propagate.

[0003] Patent Document 2 proposes a plasma processing apparatus comprising a mounting table on which a wafer is placed within a chamber, a planar antenna member having a plurality of microwave transmission holes for introducing microwaves into the chamber, and a transmission plate that partitions a plasma processing space formed between the mounting table and the planar antenna member, and a convex portion is formed on the underside of the transmission plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-106358 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-294924 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can suppress the occurrence of contamination near an opening that radiates microwaves. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a plasma processing apparatus including a processing vessel having an opening in a top wall thereof, and a microwave radiation source, wherein the microwave radiation source includes a slot having a slot antenna for radiating microwaves from the slot, and a transmission window for closing the opening and radiating the microwaves from the slot into the processing vessel, the transmission window including a first surface having a hanging portion hanging down to cover a side wall of the opening, and a second surface opposite the first surface and facing the slot antenna across a gap. death , The second surface has a convex portion that contacts the center of the slot antenna, and is configured to face the slot antenna across the gap on the surface excluding the convex portion, and the outer periphery of the convex portion has a dimension that is equal to or smaller than the effective wavelength λ of the microwave. g is half of A plasma processing apparatus is provided. [Effects of the Invention]

[0007] According to one aspect, it is possible to suppress the occurrence of contamination near the opening through which microwaves are radiated. [Brief explanation of the drawings]

[0008] [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 an example of the configuration and alignment position of a transmission window according to a reference example. [Figure 3] 3A and 3B are diagrams showing an example of the configuration and alignment position of a transmission window according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of an experimental result of the number of contaminations in the configuration of the transmission window according to the first embodiment. [Figure 5] 10A and 10B are diagrams showing an example of the configuration and alignment position of a transmission window according to the second embodiment. [Figure 6] FIG. 10 is a diagram showing an example of experimental results of ignition performance in the configurations of the transmission windows of the second and third embodiments and the reference example. [Figure 7] FIG. 10 is a diagram showing an example of the configuration of a microwave radiation source according to a third embodiment. [Figure 8] 10A and 10B are diagrams showing an example of the configuration and alignment position of a transmission window according to the third embodiment. [Figure 9]FIG. 11 is a diagram showing an example of the results of an electromagnetic field simulation for the transmission window according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 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.

[0011] [Plasma processing equipment] An example of a plasma processing apparatus according to an embodiment will be described. Fig. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus 100 according to an embodiment. The plasma processing apparatus 100 includes a processing chamber 101, a mounting table 102, a gas supply unit 103, an exhaust unit 104, a microwave radiation source 140, and a control unit 106.

[0012] The processing vessel 101 is made of a metal material, for example, aluminum whose surface is coated with yttria (Y2O3) or the like, and has a cylindrical vessel body 112 with a bottom and a ceiling wall 111. The top of the vessel body 112 is open, and the opening is closed by the disk-shaped ceiling wall 111. This keeps the plasma processing space U in the processing vessel 101 airtight. A mounting table 102 is disposed at the bottom of the processing vessel 101.

[0013] The mounting table 102 is disk-shaped and made of, for example, a metal material such as aluminum whose surface has been anodized, or a ceramic material such as aluminum nitride (AlN). A substrate W, for example, a semiconductor wafer, is placed on the mounting table 102. The mounting table 102 is supported by, for example, a metal support member 120 that extends upward from the bottom of the container body 112 via an insulating member 121.

[0014] Furthermore, inside the mounting table 102, lifting pins (not shown) for lifting and lowering the substrate W are provided so as to be protrudable and retractable relative to the upper surface of the mounting table 102. Furthermore, a heater 126 is provided inside the mounting table 102 as a heating means. The heater 126 generates heat when power is supplied from a heater power supply 127. The output of the heater 126 is controlled by a temperature signal from a sensor (e.g., a thermocouple, not shown) provided near the upper surface of the mounting table 102, thereby heating and controlling the substrate W to a predetermined temperature.

[0015] A high-frequency power supply 122 is electrically connected to the mounting table 102. If the mounting table 102 is made of ceramic, an electrode is provided on the mounting table 102 and the high-frequency power supply 122 is electrically connected to the electrode. The high-frequency power supply 122 applies high-frequency power as bias power to the mounting table 102. The frequency of the high-frequency power applied by the high-frequency power supply 122 is preferably in the range of 0.4 to 27.12 MHz.

[0016] An exhaust pipe 116 is provided at the bottom of the vessel body 112, and an exhaust device 104 is connected to the exhaust pipe 116. The exhaust device 104 includes a vacuum pump, a pressure control valve, etc., and the inside of the processing vessel 101 is evacuated by the vacuum pump via the exhaust pipe 116, and controlled to a desired vacuum state. The pressure inside the processing vessel 101 is controlled by a pressure control valve based on the value of a pressure gauge (not shown). A load / unload port 114 is provided on a side wall of the vessel body 112, for loading / unloading a substrate W between the processing vessel 101 and a transfer chamber (not shown) adjacent to the processing vessel 101. When loading / unloading the substrate W, the load / unload port 114 is opened by a gate valve 115 provided along the side wall of the vessel body 112.

[0017] The top wall 111 has a plurality of openings for arranging the microwave radiation source 140 and the gas introduction pipe 123. The gas supply unit 103 has a plurality of gas introduction pipes 123, a gas supply pipe 124, and a gas supply source 125. The plurality of gas introduction pipes 123 are arranged in a plurality of openings formed around the microwave radiation source 140 in the center of the top wall 111. The plurality of gas introduction pipes 123 are connected to the gas supply source 125 via the gas supply pipe 124.

[0018] The gas supply source 125 supplies various processing gases. The gas supply pipe 124 is provided with a valve for controlling start and stop of the supply of the processing gas and a flow regulator for adjusting the flow rate of the processing gas.

[0019] The microwave radiation sources 140 are arranged at six openings (only two are shown in FIG. 1 ) on the periphery of the top wall 111 and at one opening in the center of the top wall 111. That is, in this embodiment, the seven microwave radiation sources 140 are arranged above the top wall 111 so that each is inserted into an opening in the top wall 111. However, the number and arrangement of the microwave radiation sources 140 are not limited to this, and for example, only one microwave radiation source may be arranged in the center of the top wall 111, or multiple microwave radiation sources 140 may be arranged only on the periphery of the top wall 111.

[0020] The microwave radiation source 140 is connected to the microwave output unit 130 via the amplifier unit 142. The microwave output unit 130 generates microwaves and distributes the microwaves to each amplifier unit 142. Each amplifier unit 142 mainly amplifies the distributed microwaves and outputs them to each microwave radiation source 140.

[0021] The microwave radiation source 140 includes an antenna module 143, a slot antenna 144, and a transmission window 145. The antenna module 143 is a coaxial waveguide having an inner conductor 143a and an outer conductor 143b arranged concentrically around the inner conductor 143a, and microwaves propagate through the space between the inner conductor 143a and the outer conductor 143b. Annular dielectric members M1 and M2 are provided above and below the space between the inner conductor 143a and the outer conductor 143b. The dielectric member M1 is disposed above the dielectric member M2. The dielectric members M1 and M2 are movable up and down, thereby adjusting the impedance. The configuration of the transmission window 145 will be described later in the order of the first, second, and third embodiments.

[0022] The tip of the outer conductor 143b (the tip of the antenna module 143) has an expanded diameter. A disk-shaped slot antenna 144 is fitted into the expanded diameter interior of the outer conductor 143b. The outer conductor 143b and the slot antenna 144 are provided on the upper part (exterior) of the top wall 111. The inner conductor 143a abuts against the center of the upper surface of the slot antenna 144. The slot antenna 144 has an arc-shaped or annular slot S around the center of the slot antenna 144 (see Figure 7(b)). The slot antenna 144 functions as an antenna that radiates microwaves from the slot S. Note that the slot S may be formed in an arc-shaped or annular shape around the center of the slot antenna 144.

[0023] A transmission window 145 is provided below the slot antenna 144, through which the microwaves emitted from the slot S are radiated into the processing vessel 101. The transmission window 145 is disposed inside an opening provided in the top wall 111 and closes the opening. The transmission window 145 is made of a dielectric material such as alumina (Al2O3), and transmits microwaves. In this manner, the microwave radiation source 140 radiates microwaves into the processing vessel 101.

[0024] The control unit 106 is, for example, a computer having a controller 106a and a memory 106b. The control unit 106 may also have an input device, a display device, etc. The controller 106a controls each unit of the plasma processing apparatus 100. The controller 106a allows an operator to input commands, etc., to manage the plasma processing apparatus 100 using the input device. The controller 106a can also visualize and display the operating status of the plasma processing apparatus 100 using the display device. Furthermore, the memory 106b stores a control program and recipe data for the controller 106a to control various processes performed in the plasma processing apparatus 100. The controller 106a executes the control program and controls each unit of the plasma processing apparatus 100 according to the recipe data, thereby performing substrate processing, such as film formation, using the plasma processing apparatus 100.

[0025] First Embodiment [Transparent window] Next, the configuration of the transmissive window 145 according to the first embodiment will be described in detail with reference to Fig. 2 and Fig. 3. Fig. 2(a) is a diagram showing the configuration of a transmissive window 145' according to a reference example. Fig. 3(a) is a diagram showing the configuration of the transmissive window 145 according to the first embodiment.

[0026] In both the reference example of FIG. 2(a) and the first embodiment of FIG. 3(a), the slot antenna 144 and the transmission window 145' and transmission window 145 are disk-shaped and have the same diameter. That is, the positions of the side walls of the slot antenna 144 and the transmission window 145' coincide, and the positions of the side walls of the slot antenna 144 and the transmission window 145 coincide. However, having the same diameter is not an essential condition. The side wall 111a1 of the opening in the top wall 111 is exposed.

[0027] In the transmission window 145' of the reference example in FIG. 2(a), both the bottom surface 145'L and the top surface 145'U are flat, and the top surface 145'U of the transmission window 145' is in contact with the slot antenna 144. The thickness of the transmission window 145' is constant. On the other hand, in the transmission window 145 of the first embodiment in FIG. 3(a), a first surface 145L, which is the bottom surface of the transmission window 145, has a hanging portion 145a that hangs down so as to cover a side wall 111a1 of the opening in the top wall 111. The thickness of the transmission window 145 is constant except for the hanging portion 145a. A second surface 145U, which is the top surface of the transmission window 145, is flat and in contact with the slot antenna 144. The hanging portion 145a is formed inside the side wall of the transmission window 145.

[0028] 2(a), an electric field due to electromagnetic waves emitted from the transmission window 145' is concentrated at or near the corners of the sidewall 111a1 of the opening in the ceiling wall 111, resulting in a high electric field near the opening of the ceiling wall 111 and damaging the ceiling wall 111. This damage wears away the sprayed yttria film on the surface of the ceiling wall 111, and the aluminum inside is exposed to plasma and scraped off, resulting in contamination with yttrium and aluminum. This metal contamination inside the processing vessel 101 has been a problem.

[0029] To avoid damage and contamination at or near the corners of the sidewall 111a1 of the opening in the top wall 111, the transmission window 145 of the first embodiment shown in FIG. 3(a) is provided with a hanging portion 145a that hangs down to cover the sidewall 111a1 of the opening. The hanging portion 145a covers the sidewall 111a1 of the opening around the entire periphery, on the outer periphery side of the slot S. The height of the end 145a1 of the hanging portion 145 matches the height of the end of the opening. That is, the end of the opening and the end 145a1 of the hanging portion 145a match the height of the underside 111a of the top wall 111.

[0030] This allows the hanging portion 145a to avoid electric field concentration at the corners of the sidewall 111a1 of the opening and the vicinity thereof, and prevents or suppresses damage to the vicinity of the opening of the top wall 111. This reduces the occurrence of metal contamination.

[0031] FIG. 4 shows an example of experimental results comparing the number of yttrium (Y) particles precipitated as metal contamination in the yttria sprayed film applied to the surface of the ceiling wall 111 when the transmission window 145 of the first embodiment is used and when the transmission window 145′ of the reference example is used.

[0032] 4, in the cases of N2 gas, NH3 gas, and NF3 / Ar / He mixed gas, the number of contaminations when plasma was generated using the transmission window 145 of the first embodiment was lower than when the transmission window 145' of the reference example was used. When plasma of N2 gas and NH3 gas was generated, the pressure inside the processing vessel 101 was controlled to 20 Pa. When plasma of NF3 / Ar / He mixed gas was generated, the pressure inside the processing vessel 101 was controlled to 20 Pa and 100 Pa. In either case, the use of the configuration of the transmission window 145 of the first embodiment was able to reduce the occurrence of metal contamination compared to the reference example.

[0033] However, in the transmission window 145 of the first embodiment shown in Figure 3(a), the shape of the transmission window is changed by providing the hanging portion 145a, which results in a narrower range of plasma usage conditions (process usage conditions) compared to the transmission window 145' of the reference example shown in Figure 2(a). This result will be explained using Figures 2(b)(c) and 3(b)(c). The thickness of the transmission window 145' is 10 mm, and the thickness of the transmission window 145 is 10 mm excluding the hanging portion 145a.

[0034] 2(b) and 3(b), the horizontal axis shows the power (W) of the microwaves input through the transmission windows 145 and 145′ when the pressure inside the processing vessel 101 is controlled to 6 Pa, 10 Pa, 20 Pa, 50 Pa, and 100 Pa. The vertical axis shows the alignment positions (mm) of the dielectric members M1 and M2 when the Ar gas plasma is generated.

[0035] 2(c) and 3(c), the horizontal axis shows the power (W) of the microwaves input through the transmission windows 145 and 145′ when the pressure inside the processing vessel 101 is controlled to 6 Pa, 10 Pa, 20 Pa, 50 Pa, and 100 Pa. The vertical axis shows the alignment positions (mm) of the dielectric members M1 and M2 when N2 gas plasma is generated.

[0036] As a result of the experiment, when the transmission window 145' of the reference example was used, the alignment positions of the dielectric members M1 and M2 did not change substantially even when the microwave power and pressure were changed, as shown in Figures 2(b) and 2(c). This indicates that the plasma is stable. In other words, this indicates that the plasma can be used under a wide range of conditions.

[0037] In contrast, when the transmission window 145 of the first embodiment was used, the alignment positions of the dielectric members M1 and M2 changed and variations occurred when the microwave power and pressure were changed, as shown in Figures 3(b) and 3(c). This indicates that the plasma is unstable. In other words, this indicates that the plasma usage conditions are narrow.

[0038] Furthermore, when the distance from the bottom surface of the dielectric member M2 to the top surface of the slot antenna 144 is D (see FIGS. 1 and 7(a)), if the distance D at the matching position of the dielectric member M2 is less than 10 mm, there is a possibility of contact because the distance from the dielectric member M2 to the slot antenna 144 is too short. In other words, this indicates that the dielectric member M2 cannot be moved any further toward the slot antenna 144, and matching cannot be achieved. In other words, this indicates that the conditions for using the plasma are narrow.

[0039] In this regard, when the transmission window 145' of the reference example was used, the alignment position (distance D) of the dielectric member M2 exceeded 10 mm, as shown in Fig. 2(b). In contrast, when the transmission window 145 of the first embodiment was used, the alignment position (distance D) of the dielectric member M2 fell below 10 mm, as shown in Fig. 3(b). From the above, with the transmission window 145 of the first embodiment shown in Fig. 3(a), the plasma became unstable compared to the transmission window 145' of the reference example shown in Fig. 2(a), and the plasma usage conditions were narrower.

[0040] Therefore, the shape of the transmission window 145 has been improved so that the plasma usage conditions are broader than when the transmission window 145 of the first embodiment is used, while at the same time, damage to the ceiling wall 111 is avoided and the occurrence of contamination can be suppressed. The configuration of the improved transmission window 145 of the second embodiment will be described with reference to FIG. 5.

[0041] Second Embodiment [Transparent window] 5(a) is a diagram showing an example of the configuration and alignment position of the transmission window 145 according to the second embodiment. The transmission window 145 of the second embodiment has basically the same configuration as that of the first embodiment, and the following will describe configurations that are different from those of the transmission window 145 of the first embodiment, and will not describe the same configurations.

[0042] The transmissive window 145 according to the second embodiment has a first surface 145L having a hanging portion 145a that hangs down to cover the side wall 111a1 of the opening, and a second surface 145U that is the opposite surface of the first surface 145L and faces the slot antenna 144 across a gap K. The slot antenna 144 and the second surface 145U are not in contact with each other, and a gap K of 2 mm exists between them in the vertical direction. The thickness of the transmissive window 145 is 8 mm excluding the hanging portion 145a. However, the gap K may be 2 mm or less in the vertical direction.

[0043] 5(b) and 5(c) show, on the horizontal axis, the power of the microwave input through the transmission window 145 of the second embodiment when the pressure inside the processing vessel 101 is controlled to 6 Pa, 10 Pa, 20 Pa, 50 Pa, and 100 Pa. Also, on the vertical axis, FIG. 5(b) shows the alignment positions of the dielectric members M1 and M2 when Ar gas plasma is generated, and FIG. 5(c) shows the alignment positions of the dielectric members M1 and M2 when N2 gas plasma is generated.

[0044] As a result of the experiment, when the transmission window 145 of the second embodiment was used and Ar gas plasma was generated as shown in Fig. 5(b), the alignment position of the dielectric member M1 remained almost unchanged even when the microwave power and pressure were changed. Although there was some variation in the alignment position of the dielectric member M2, the alignment position of the dielectric member M2 (distance D: see Fig. 7(a)) exceeded 10 mm. This indicates that the plasma was stable.

[0045] As shown in Figure 5(c), when plasma of N2 gas was generated, the alignment position of the dielectric members M1 and M2 remained almost unchanged even when the microwave power and pressure were changed. This indicates that the plasma is stable. In other words, this indicates that the plasma can be used under a wide range of conditions.

[0046] From the above, when the transmission window 145 of the second embodiment is used, the plasma can be stabilized and the plasma use conditions can be broadened compared to when the transmission window 145 of the first embodiment is used. Therefore, with the transmission window 145 of the second embodiment, it is possible to prevent or suppress damage to the ceiling wall 111 and reduce the occurrence of metal contamination while maintaining a wide range of plasma use conditions.

[0047] On the other hand, in the experimental results of plasma ignition performance, when the transmission window 145 of the second embodiment was used, the plasma ignition performance was worse than when the transmission window 145' of the reference example was used. Fig. 6 is a diagram showing an example of the experimental results of ignition performance for the transmission window configurations of the second and third embodiments and the reference example.

[0048] Figure 6(a) shows the state of plasma ignition when Ar gas plasma was generated. Figure 6(b) shows the state of plasma ignition when N gas plasma was generated. Plasma ignition was judged visually.

[0049] In this experiment, when the transmission window 145' according to the reference example was used in FIG. 6(1), and when the transmission window 145 according to the second embodiment was used in FIG. 6(2), ignition was indicated by a circle (◯) for each pressure and microwave power, and when ignition was not achieved by a cross (×) for each pressure and microwave power. The case where the transmission window 145 according to the second embodiment was used in FIG. 6(3) will be described later. When the transmission window 145 according to the second embodiment in FIG. 6(2) was used, the plasma ignition performance was worse in both FIGS. 6(a) and 6(b) than when the transmission window 145' according to the reference example shown in FIG. 6(1) was used.

[0050] Therefore, further improvements were made to the shape of the transmission window 145 so that damage to the ceiling wall 111 can be avoided and the occurrence of metal contamination can be suppressed while maintaining the plasma usage conditions and plasma ignition performance. The configuration of the improved transmission window 145 of the third embodiment will be described with reference to FIGS. 7 and 8.

[0051] <Third embodiment> [Transparent window] Fig. 7 is a cross-sectional schematic diagram showing an example of a microwave radiation source 140 including a transmission window 145 according to the third embodiment. Fig. 8 is a diagram showing an example of the configuration and alignment position of the transmission window 145 according to the third embodiment. The transmission window 145 of the third embodiment has basically the same configuration as the transmission window 145 of the second embodiment, and the following will describe configurations that are different from the transmission window 145 of the second embodiment, and will not describe the same configurations.

[0052] As shown in FIGS. 7(a) and 8(a), the transmission window 145 according to the third embodiment has a first surface 145L having a hanging portion 145a that hangs down to cover the sidewall 111a1 of the opening. The transmission window 145 also has a second surface 145U that is opposite the first surface 145L and faces the slot antenna 144 across a gap K. The second surface 145U has a protruding portion 145c that contacts the center of the slot antenna 144, and is configured to face the slot antenna 144 across the gap K on the surface excluding the protruding portion 145c. In other words, the second surface 145U does not contact the slot antenna 144 except for the protruding portion 145c, and a gap K of 2 mm exists between them in the vertical direction. The thickness of the transmission window 145 is 8 mm, excluding the hanging portion 145a.

[0053] Fig. 7(b) shows the positional relationship between the second surface 145U of the transmission window 145 and the back surface of the slot antenna 144 facing the second surface 145U, and Fig. 7(c) shows the second surface 145U. As shown in Fig. 7(b), in the present disclosure, the slot S of the slot antenna 144 is an annular opening having a predetermined inner diameter and outer diameter from the center CT. The area inside the inner diameter of the slot S is the center of the slot antenna 144, which has a contact portion with the protrusion 145c.

[0054] For example, in the present disclosure, the protrusion 145c has a cylindrical shape with a radius R and a height of 2 mm from the center of the transmission window 145. The upper surface of the protrusion 145c is the surface that contacts the slot antenna 144, and is a circle with a diameter (2R) that is smaller than the inner diameter (inner diameter) of the slot S. In this case, as shown in FIG. 7(b), the protrusion 145c is away from the slot S and contacts the center of the slot antenna 144.

[0055] However, the present disclosure is not limited to this, and the upper surface of the protrusion 145c may be a circle with a diameter (2R) equal to or smaller than the inner diameter of the slot S. For example, the diameter of the upper surface of the protrusion 145c may be the same as the inner diameter of the slot S. In this case, the upper surface of the protrusion 145c does not overlap the interior of the slot S. In other words, the upper surface of the protrusion 145c cannot be seen through the slot S. On the other hand, if the diameter of the upper surface of the protrusion 145c is larger than the inner diameter of the slot S, the upper surface of the protrusion 145c will overlap the interior of the slot S, which is not permitted. Also, in the present disclosure, the height of the protrusion is 2 mm, but it may be 2 mm or less.

[0056] 8(b) and 8(c) show the microwave power input through the transmission window 145 of the third embodiment on the horizontal axis when the pressure inside the processing chamber 101 is controlled to 6 Pa, 10 Pa, 20 Pa, 50 Pa, and 100 Pa. Also, FIG. 8(b) shows the alignment positions of the dielectric members M1 and M2 on the vertical axis when Ar gas plasma is generated, and FIG. 8(c) shows the alignment positions of the dielectric members M1 and M2 on the vertical axis when N gas plasma is generated.

[0057] As a result of the experiment, when the transmission window 145 of the third embodiment was used, the alignment position of the dielectric members M1 and M2 remained almost unchanged even when the microwave power and pressure were changed, regardless of whether plasma was generated using Ar gas or N2 gas, as shown in Figures 8(b) and (c). This indicates that the plasma is stable. In other words, this indicates that the plasma can be used under a wide range of conditions. Furthermore, when the transmission window 145 of the third embodiment was used, the alignment position (distance D) of the dielectric member M2 exceeded 10 mm, as shown in Figure 8(b). This indicates that the plasma is stable.

[0058] Furthermore, the experimental results of plasma ignition performance are shown in Fig. 6. When the transmission window 145 according to the third embodiment shown in Fig. 6(3) was used, the plasma ignition performance was improved for both gases shown in Fig. 6(a) and (b) compared to when the transmission window 145 according to the second embodiment shown in Fig. 6(2) was used. When the transmission window 145 according to the third embodiment shown in Fig. 6(3) was used, the plasma ignition performance was improved to the same level as when the transmission window 145' according to the reference example shown in Fig. 6(1) was used.

[0059] From the above, when the transmission window 145 of the third embodiment is used, the plasma can be stabilized and the conditions for using the plasma can be broadened, similarly to when the transmission window 145 of the second embodiment is used.

[0060] In addition, the transmission window 145 of the third embodiment can improve the plasma ignition performance compared to the case where the transmission window 145 of the second embodiment is used. As described above, the transmission window 145 of the third embodiment can avoid damage to the ceiling wall 111 and suppress the occurrence of metal contamination while maintaining the plasma usage conditions and plasma ignition performance.

[0061] The reason why the configuration of the transmission window 145 according to the third embodiment can improve plasma ignition performance will be described with reference to FIG. 9. FIG. 9 is a diagram showing an example of the results of an electromagnetic field simulation performed when microwaves of a predetermined power are radiated from the microwave radiation source 140 using the transmission window 145 according to the third embodiment. In FIG. 9(a), R indicates the radius of the convex portion 145c. r indicates the distance from the center of the transmission window 145. The center of the transmission window 145 is equal to the center CT of the slot antenna 144 shown in FIG. 7(b).

[0062] The conditions for the electromagnetic field simulation were that the transmission window 145 was made of alumina (Al2O3), no gas was supplied into the processing vessel 101, and the gap K was filled with the atmosphere (air). The frequency of the microwaves supplied from the microwave radiation source 140 was set to 860 MHz, and the microwave power was set to 500 W. The gap K was set to 2 mm, and the thickness of the transmission window 145 was set to 8 mm excluding the hanging portion 145a.

[0063] The results are shown in Figures 9(b) and 9(c). The horizontal axis of Figure 9(b) is the distance r (mm) from the central axis Ax of the transmission window 145 shown in Figure 9(a), and the vertical axis is the electric field strength (V / m) generated by the radiated microwaves. Figure 9(b) plots the maximum electric field strength (maximum electric field value) at the distance r from the center of the transmission window 145 when the radius R of the convex portion 145c (see Figures 9(a) and 7(c)) is 5 mm (R5), 8 mm (R8), 14 mm (R14), 19 mm (R19), and 24 mm (R24). Figure 9(c) is a table showing the maximum electric field value, regardless of the distance r, when the radius R of the convex portion 145c is 0 mm, 5 mm, 8 mm, 14 mm, 19 mm, and 24 mm. The radius R of the convex portion 145c being 0 mm indicates that the shape of the transmissive window 145 according to the second embodiment does not have the convex portion 145c.

[0064] The above results show that the presence of the protrusions 145c increases the maximum electric field value. When the radius R of the protrusions 145c is 8 mm, i.e., when the diameter φ of the protrusions 145c is 16 mm, the maximum electric field value of the radiated microwaves can be obtained. The larger the maximum electric field value, the better the plasma ignition performance. Therefore, by providing the protrusions 145c on the transmission window 145, the plasma ignition performance can be improved compared to the transmission window 145 according to the second embodiment, in which the transmission window 145 does not have the protrusions 145c.

[0065] In other words, according to the third embodiment of the transmission window 145, by providing the hanging portion 145a and the protruding portion 145c at predetermined positions on the transmission window 145, it is possible to avoid damage to the ceiling wall 111 and suppress the occurrence of metal contamination while maintaining the plasma usage conditions and plasma ignition performance.

[0066] The electric field intensity can be maximized by setting the outer circumferential dimension of the protrusion 145c to about half the effective wavelength of the microwave. The wavelength λ0 in a vacuum of a microwave with a frequency of 860 MHz is 348 mm. In this case, the effective wavelength of the microwave at the transmission window 145 is λ g Then, equation (1) holds.

[0067]

number

[0068] When the transmission window 145 is made of alumina, the relative dielectric constant ε r is approximately 10. Substituting this into equation (1), equation (2) gives half the effective wavelength of the microwave (λ g / 2) is calculated to be approximately 55.

[0069]

number

[0070] When the diameter φ of the convex portion 145c of the transmission window 145 is 16 mm (when the radius R is 8 mm), the outer periphery 2πR of the convex portion 145c is calculated to be approximately 50 from equation (3).

[0071] Outer circumference 2πR=2×3.14×8≒50...Equation (3)

[0072] The outer periphery of the protrusion 145c is set to the effective wavelength λ of the microwave. g Half the effective wavelength λ g The reason why the electric field strength can be maximized when the relative dielectric constant ε r This is because the electric field is strengthened at the boundary between the different surfaces, and the outer periphery of the protrusion 145c is effective in increasing the electric field strength.

[0073] Relative permittivity ε r In the case of the top wall 111, the boundary portion where the difference is made refers to the outer periphery of the alumina protrusion 145c, which is the boundary with the air layer of the gap K, and in the case of the slot S, refers to the boundary portion between the slot S, which is air, and the slot antenna 144, which is aluminum. Therefore, the outer periphery dimension of the slot S is set to the effective wavelength λ of the microwave. g Half the effective wavelength λ g 7(b) in the slot antenna 144, the strength of the magnetic field H and the electric field E generated at the boundary between the slot S and the slot antenna 144 shown in FIG. 7(b) can be maximized.

[0074] The outer circumferential dimension of the protrusion 145c is a parameter that maximizes the strength of the electric field E. The magnetic field H in FIG. 7(c) is generated by adjusting the outer circumferential dimension of the protrusion 145c to the effective wavelength λ of the microwave. g Half the effective wavelength λ g , the strength of the magnetic field H and the electric field E generated at the outer periphery (boundary) of the convex portion 145c can be maximized. g Half the effective wavelength λ g "Approaching half of λ" means roughly g / 2±λ g This is about / 10.

[0075] As described above, the plasma processing apparatus 100 and microwave radiation source 140 of this embodiment can suppress the occurrence of contamination due to damage to the opening that radiates microwaves.

[0076] In particular, when the transmission window 145 of the third embodiment is used, the plasma can be stabilized in the same way as when the transmission window 145 of the second embodiment is used, the plasma usage conditions can be broadened, and further, the plasma ignition ability can be improved compared to the transmission window 145 of the second embodiment.

[0077] 4, the number of yttrium (Y) particles precipitated as contamination when the transmission window 145 of the first embodiment was used was reduced compared to when the transmission window 145' of the reference example was used. Although not shown, the number of yttrium (Y) particles precipitated as contamination when the transmission window 145 of the second and third embodiments was used was also reduced compared to when the transmission window 145' of the reference example was used.

[0078] The plasma processing apparatus 100 and microwave radiation source 140 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 without contradiction, and can be combined without contradiction. [Explanation of symbols]

[0079] 100 Plasma processing device 101 Processing container 102 Mounting table 103 Gas Supply Unit 106 Control Unit 111 Ceiling wall 140 Microwave Radiation Source 144 Slot Antenna 145 Transparent window 145a hanging part 145c convex part 145L 1st page 145U 2nd side

Claims

1. A plasma processing apparatus including a processing vessel having an opening in a top wall and a microwave radiation source, The microwave radiation source a slot antenna having a slot and radiating microwaves from the slot; a transmission window that closes the opening and radiates microwaves from the slot into the processing vessel, The transmission window is a first surface having a hanging portion that hangs down so as to cover a side wall of the opening, and a second surface that is the opposite surface of the first surface and faces the slot antenna across a gap, the second surface has a protruding portion that contacts the center of the slot antenna, and is configured to face the slot antenna across the gap on a surface excluding the protruding portion, The plasma processing apparatus, wherein the outer periphery of the convex portion is half the effective wavelength λ g of the microwave.

2. The slot is formed in an arc or an annular shape around the center portion, The contact surface of the protrusion is a circle having a diameter equal to or smaller than the inner diameter of the slot, and does not overlap the inside of the slot. The plasma processing apparatus according to claim 1 .

3. The contact surface of the protrusion is a circle having a diameter smaller than the inner diameter of the slot, and is in contact with the center portion away from the slot. The plasma processing apparatus according to claim 2 .

4. The height of the convex portion is 2 mm or less. The plasma processing apparatus according to any one of claims 1 to 3.

5. The height of the end of the hanging portion is the same as the height of the end of the opening. The plasma processing apparatus according to any one of claims 1 to 4.

6. The hanging portion is formed on the outer circumferential side of the slot along the entire periphery of the side wall of the opening. The plasma processing apparatus according to any one of claims 1 to 5.

7. the hanging portion is formed inside the side wall of the transmission window, The plasma processing apparatus according to any one of claims 1 to 6.

8. A microwave radiation source for use in a plasma processing apparatus having a processing vessel with an opening in a top wall, a slot antenna having a slot and radiating microwaves from the slot; a transmission window that closes the opening and radiates microwaves from the slot into the processing vessel, The transmission window is a first surface having a hanging portion that hangs down so as to cover a side wall of the opening, and a second surface that is the opposite surface of the first surface and faces the slot antenna across a gap, the second surface has a convex portion that contacts the center of the slot antenna, and is configured to face the slot antenna across the gap on a surface excluding the convex portion, A microwave radiation source, wherein the outer periphery of the convex portion is half the effective wavelength λ g of the microwave.

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