Plasma generator and cooling jacket

Abstract

To quickly operate a matching box of a plasma generator, which converts gas into plasma using microwaves, thereby reducing a burden on the matching box.SOLUTION: A plasma generator includes: a microwave generating source that generates microwaves; a cylindrical plasma generating tube in which gas to be plasmatized by the microwaves flows; a waveguide that transmits the microwaves generated from the microwave generating source to the plasma generating tube; a matching box that is provided in the waveguide between the microwave generating source and the plasma generating tube; a cooling jacket that is provided on an outer circumferential surface of the plasma generating tube and cools the plasma generating tube; and a cylindrical casing that houses the plasma generating tube and the cooling jacket. The cooling jacket extends along a direction of travel of the gas flowing through the plasma generating tube, and has three slits that allow microwaves to pass into the plasma generating tube, and a cooling channel that is provided between adjacent slits and through which a cooling fluid for cooling the plasma generating tube flows.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plasma generating device and a cooling jacket. [Background technology]

[0002] 2. Description of the Related Art Conventionally, when a plasma gas is used to process a workpiece or form a thin film, a plasma generating device is used to convert a predetermined gas into a plasma state using microwaves.

[0003] The plasma generating device may include a plasma generating tube through which a gas to be converted into plasma flows, and a microwave generating source that generates microwaves for converting the gas flowing through the plasma generating tube into plasma.

[0004] Heat is generated when gas is converted into plasma, and this heat can heat and damage the plasma generating tube. Therefore, some plasma generators of this type further include a cooling jacket to cool the plasma generating tube, as shown in Patent Document 1, for example. This cooling jacket is formed along the direction of gas flow through the plasma generating tube and has four or more slits through which microwaves irradiated from outside the plasma generating tube pass, and multiple cylindrical flow paths formed between adjacent slits through which a cooling fluid flows. With this configuration, microwaves generated from the microwave source pass through the slits to convert the gas flowing through the plasma generating tube into plasma, and the plasma generating tube is cooled by the cooling fluid flowing through the cylindrical flow paths, preventing damage to the plasma generating tube due to the heat generated during plasma generation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-205172 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, it was thought that increasing the number of slits in the cooling jacket would increase the area through which microwaves pass in the plasma generating tube, thereby enabling more efficient plasma generation.

[0007] On the other hand, for example, in a cooling jacket with eight slits, the resonant frequency of the cooling jacket and casing is at 4 GHz, as shown in Figure 6. Because this resonant frequency is different from the microwave frequency, it takes time to adjust the resonant impedance of the cooling jacket and casing to match the impedance of the microwave generation source, and this places a burden on the matching box when adjusting the match.

[0008] Therefore, a main object of the present invention is to quickly operate a matching box in a plasma generating device that converts gas into plasma using microwaves, thereby reducing the load on the matching box. [Means for solving the problem]

[0009] As a result of intensive research by the present inventors to solve the above problems, the present inventors discovered for the first time that if a cooling jacket has three slits, the resonant frequency of the cooling jacket and casing will be near the microwave frequency, and this led to the present invention.

[0010] That is, the plasma generator according to the present invention comprises a microwave generating source that generates microwaves, a cylindrical plasma generating tube through which a gas to be converted into plasma by the microwaves flows, a waveguide that connects the microwave generating source and the plasma generating tube and transmits the microwaves to the plasma generating tube, a matching box that is provided in the waveguide between the microwave generating source and the plasma generating tube, a cooling jacket that is provided on the outer peripheral surface of the plasma generating tube and cools the plasma generating tube, and a cylindrical casing that houses the plasma generating tube and the cooling jacket, wherein the cooling jacket extends along or at an angle to the traveling direction of the gas flowing through the plasma generating tube, and has three slits that allow the microwaves to pass into the plasma generating tube, and cooling flow paths that are formed between adjacent slits and through which a cooling fluid that cools the plasma generating tube flows.

[0011] In this plasma generator, the cooling jacket has three slits, so the resonant frequency of the cooling jacket and casing is around 2.45 GHz. As a result, the difference between the microwave frequency and the resonant frequency is smaller than in the past, which shortens the time required to adjust the resonant impedance of the cooling jacket and casing to match the impedance of the microwave generation source, and reduces the burden of matching adjustment using a matching box.

[0012] It is desirable that the slit extends along a direction perpendicular to or at an incline with respect to the vibration direction of the electric field of the microwave, that the cross section of the waveguide is rectangular, and that the long sides constituting the rectangular shape extend along or at an incline with respect to the direction in which the slit extends.

[0013] With this configuration, the slits are formed in a direction perpendicular to the vibration direction of the microwave electric field, and the long sides of the rectangular cross section of the waveguide are aligned along the direction in which the slits extend, so that microwave reflection at the cooling jacket is suppressed and the microwaves can pass through the slits efficiently. As a result, the microwaves are appropriately irradiated onto the plasma generating tube, and the gas flowing inside the plasma generating tube can be efficiently converted into plasma.

[0014] It is preferable that at least two of the three slits face toward the microwave generation source.

[0015] With this configuration, at least two slits face the microwave generation source, so microwaves generated from the microwave generation source are transmitted to the plasma generating tube more efficiently than when only one slit faces the microwave generation source, and as a result, the gas flowing inside the plasma generating tube can be efficiently converted into plasma.

[0016] In order to uniformly convert the gas flowing inside the plasma generating tube into plasma in the circumferential direction of the plasma generating tube, microwaves must also pass through from the side opposite the microwave generating source. Therefore, an example is one that further includes a reflector plate that is provided in the waveguide opposite the microwave generation source via the plasma generation tube and reflects microwaves from the microwave generation source toward the plasma generation tube, and at least one of the three slits is formed facing toward the reflector plate, and at least one other slit is formed facing toward the microwave generation source.

[0017] With this configuration, in the cooling jacket having three slits, one slit facing the reflector allows microwaves reflected from the reflector to pass into the plasma generating tube, and the other slit allows microwaves generated by the microwave generation source to pass into the plasma generating tube, so that the gas flowing inside can be uniformly converted into plasma in the circumferential direction of the plasma generating tube.

[0018] The casing preferably has an observation window formed therein for observing the internal state of the plasma generating tube.

[0019] With this configuration, by forming an observation window in the casing for observing the internal state of the plasma generating tube, it is possible to visually check the plasma generated inside the plasma generating tube through the observation window, and by installing a thermometer in the observation window, it is possible to check the temperature of the plasma generating tube. As a result, it is possible to prevent microwaves from being emitted to the outside while also being able to observe the internal state of the plasma generating tube.

[0020] The casing is preferably configured to be separable into a plurality of members.

[0021] With this configuration, the casing can be separated into a plurality of members, which makes it easy to attach, detach, and assemble the casing.

[0022] The plasma generating tube is preferably constructed from yttria, yttria-coated quartz, and / or sapphire tubes, or combinations thereof.

[0023] With this configuration, when a gas containing fluorine is converted into plasma, it is possible to prevent the generation of by-products.

[0024] It is preferable that the plasma generating device further comprises a plurality of plasma detecting units arranged opposite to the opening direction of the slit and detecting the emission intensity of the plasma generated inside the plasma generating tube.

[0025] With this configuration, the plurality of plasma detectors are arranged facing each other in the direction in which the slits are open, and the plurality of plasma detectors can detect the emission intensity of the plasma generated inside the plasma generating tube through the slits. The distribution state of the plasma inside the plasma generating tube can be determined based on the emission intensity of the plasma detected by the plurality of plasma detectors, and the user can detect a malfunction of the plasma lighting from the distribution state of the plasma.

[0026] Inside the plasma generating tube, the distribution of plasma is more uneven in the direction along the gas flow than in the direction intersecting the gas flow. Therefore, it is preferable that the plurality of plasma detectors are arranged along the direction of gas flow.

[0027] With this configuration, multiple plasma detection units are arranged along the direction of gas flow, making it possible to reliably know the distribution state of plasma in directions where the bias is likely to be large, and to reliably detect malfunctions in plasma lighting.

[0028] In order to detect plasma lighting failures in the state of plasma distribution inside the plasma generating tube along the direction of gas flow, it is important to detect the plasma emission intensity in the central part of the plasma generating tube. Therefore, it is preferable that the plurality of plasma detectors detect the emission intensity of the plasma at the top, the center and the bottom of the plasma generating tube in the direction of travel of the gas.

[0029] With this configuration, at least some of the plurality of plasma detection units detect the emission intensity of the plasma in the center of the plasma generating tube, making it possible to more reliably detect plasma lighting failures. In addition, the other plasma detectors detect the emission intensity of the plasma at the top and bottom of the plasma generating tube, so that the distribution state of the plasma throughout the inside of the plasma generating tube in the direction of gas flow can be accurately determined.

[0030] The cooling jacket is provided on the outer peripheral surface of a cylindrical plasma generating tube through which gas to be plasmatized by microwaves flows, and cools the plasma generating tube. The cooling jacket is characterized by having three slits formed along the direction of travel of the gas flowing through the plasma generating tube to allow the microwaves to pass through to the plasma generating tube, and a cooling flow path formed between adjacent slits, through which a cooling fluid for cooling the plasma generating tube flows.

[0031] With this configuration, it is possible to obtain the same effects as those of the above-mentioned plasma generating device.

[0032] The cooling jacket is provided on the outer peripheral surface of a cylindrical plasma generating tube through which gas to be plasmatized by microwaves flows, and cools the plasma generating tube, the cooling jacket extending along a direction perpendicular to the oscillation direction of the electric field of the microwaves or at an incline, and including slits that allow the microwaves to pass into the plasma generating tube, and a cooling flow path that is provided separately from the slits and through which a cooling fluid that cools the plasma generating tube flows, the slits extending along a direction perpendicular to the oscillation direction of the electric field of the microwaves or at an incline, the cross section of the waveguide being rectangular, and the long sides that make up the rectangular shape extending along the direction in which the slits extend or at an incline.

[0033] With this configuration, microwaves can be passed through the slits, thereby efficiently irradiating the plasma generating tube with microwaves. [Effects of the Invention]

[0034] According to the present invention configured as described above, in a plasma generating device that converts gas into plasma using microwaves, the matching box can be operated quickly, thereby reducing the load on the matching box. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a schematic diagram showing a plasma generation device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a front view of the plasma generating device according to the embodiment. [Figure 3] 2 is a cross-sectional view taken along line AA of the plasma generating device according to the embodiment. [Figure 4] 5 is a BB cross-sectional view of the plasma generation device according to the embodiment. [Figure 5] 1A is a schematic diagram of the casing attached to the device according to the embodiment, and FIG. 1B is a schematic diagram of the casing removed from the device according to the embodiment. [Figure 6] 10 is a measurement result showing the relationship between the number of slits and the resonance frequency. [Figure 7] 10 is a graph comparing the etching rate in a cooling jacket having three slits with the etching rate in a cooling jacket having eight slits. [Figure 8] 1A-1C show various embodiments of a cooling jacket having three slits. [Figure 9] FIG. 10 is a side view of a plasma generation device according to another embodiment. [Figure 10] FIG. 10 is a CC cross-sectional view of a plasma generation device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0036] An embodiment of a plasma generating device according to the present invention will be described below with reference to the drawings. Note that in all of the drawings shown below, some parts may be omitted or exaggerated for clarity. The same components are designated by the same reference numerals, and their descriptions will be omitted where appropriate.

[0037] The plasma generating device 100 according to this embodiment converts a gas into plasma by irradiating the gas with microwaves.

[0038] 1 or 3, the plasma generator 100 includes a microwave generation source 2 that generates microwaves, a plasma generating tube 3 through which gas to be converted into plasma by the microwaves flows, a waveguide 4 that transmits the microwaves, a reflector 5 that reflects the microwaves, a matching box 6 provided in the waveguide 4, a cooling jacket 7 that cools the plasma generating tube 3, and a casing 8 that houses the plasma generating tube 3 and the cooling jacket 7. Each part will be described below.

[0039] The microwave generation source 2 generates microwaves for converting the gas flowing through the plasma generating tube 3 into plasma. Specifically, the microwave generation source 2 is configured, for example, by a magnetron. The frequency of the microwaves generated by the microwave generation source 2 is, for example, 300 MHz to 300 GHz (preferably 2.45 GHz), the wavelength of the microwaves generated by the microwave generation source 2 is, for example, 1 mm to 1 m (preferably about 12 cm), and the oscillation output of the microwaves is, for example, 1 kW to 10 kW.

[0040] The plasma generating tube 3 is roughly cylindrical, and a gas to be converted into plasma by microwaves flows inside. The plasma generating tube 3 is made of, for example, yttria, but is not limited to this. For example, the plasma generating tube 3 may be made of yttria-coated quartz and / or sapphire tube, or a combination of these, in addition to yttria.

[0041] Here, if the direction of travel of the gas flowing inside the plasma generating tube 3 is defined as the up-down direction, the upper end of the plasma generating tube 3 is connected to a gas inlet port P1 through which a gas supply source (not shown) that supplies gas to be converted into plasma flows into the plasma generating tube 3, as shown in Figures 2 and 3. The gas supplied to the gas inlet port P1 flows inside the plasma generating tube 3, and the gas converted into plasma is discharged from the lower end of the plasma generating tube 3 into a processing chamber (not shown). Note that, hereinafter, the up-down direction will similarly refer to the direction of travel of the gas flowing inside the plasma generating tube 3.

[0042] The components of the gas supplied from the gas supply source are appropriately selected depending on the process to be performed in the process chamber (not shown), and may include, for example, SF, He, Ar, NF, H, O, N, NF, Cl, HCl, NH, CF, C, F, C, F, C, F, Cl, F, N, O, or H, O.

[0043] The waveguide 4 is, for example, a rectangular waveguide formed in the shape of a hollow square pillar, and transmits the microwaves generated from the microwave generation source 2 to the plasma generation tube 3. Specifically, the waveguide 4 faces the microwave generation source 2, connects the microwave generation source 2 to an opening 8a formed in the casing 8, and extends in a direction perpendicular to the up-down direction.

[0044] Furthermore, the waveguide 4 faces away from the microwave generating source 2 and extends in a direction perpendicular to the up-down direction from an opening 8b formed in the casing 8, and a reflector 5 is provided inside this waveguide 4. Specifically, the reflector 5 reflects the microwaves generated from the microwave generating source 2 toward the plasma generating tube 3, and has a reflecting surface 5a provided opposite the microwave generating source 2 across the plasma generating tube 3.

[0045] The surface opposite to the reflecting surface 5a is connected to a rod L that moves the reflecting plate 5 in a direction perpendicular to the up-down direction. The reflection position of the microwave is controlled by moving the rod L. The reflection position of the microwave is controlled by an actuator (not shown) so that a standing wave is formed in the waveguide 4.

[0046] The matching box 6 is provided in the waveguide 4 between the microwave source 2 and the plasma generating tube 3, and performs matching to match the resonant impedance of the cooling jacket 7 and the casing 8 to the impedance of the microwave source 2. Specifically, the matching box 6 has a plurality of stubs. Each stub is configured so that the amount of protrusion thereof into the internal space of the waveguide 4 can be adjusted, and by adjusting the protruding position of each stub with respect to a reference position, the impedance of the microwave source 2 and the resonant impedance of the cooling jacket 7 and the casing 8 are matched.

[0047] The cooling jacket 7 is hollow and cylindrical, and is provided on the outer circumferential surface of the plasma generating tube 3 to cool the plasma generating tube 3. Specifically, as shown in Fig. 3, the cooling jacket 7 extends in the vertical direction and includes three slits 71 that allow microwaves to pass through to the plasma generating tube 3, cooling channels 72 that are provided between adjacent slits 71 and through which a cooling fluid that cools the plasma generating tube 3 flows, and a heat conduction member 73 that is interposed between the cooling channels 72 and the plasma generating tube 3 and that conducts the cold air in the cooling channels 72 to the plasma generating tube 3. The upper and lower parts of the cooling jacket 7 are supported by an upper support member S1 and a lower support member S2, respectively.

[0048] The three slits 71 each have a roughly rectangular shape and penetrate from the outer peripheral surface to the inner peripheral surface of the cooling jacket 7. Here, one slit refers to a slit from the upper end to the lower end of the cooling jacket 7 when the cooling jacket 7 and the casing 8 resonate. By forming three slits 71 in the cooling jacket 7, the cooling jacket 7 and the casing 8 resonate near the frequency of the microwave source 2. In this embodiment, "near the frequency of the microwave source 2" refers to a frequency between 2.25 GHz and 2.65 GHz (more preferably, between 2.40 GHz and 2.50 GHz) when the frequency of the microwave source 2 is 2.45 GHz. Alternatively, when the frequency of the microwave source 2 is not 2.45 GHz, the frequency refers to a frequency between 90% and 110% (more preferably, between 97% and 103%) of the frequency of the microwave source 2.

[0049] In this embodiment, the three slits 71 are formed from the upper end to the lower end of the cooling jacket 7 and are arranged along the circumferential direction of the cooling jacket 7. Specifically, the electric field of the microwaves generated from the microwave generation source 2 oscillates in a direction perpendicular to the up-down direction, and each slit 71 extends in a direction perpendicular to the oscillation direction of the electric field of the microwaves. More specifically, the longitudinal direction of each slit 71 extends so as to be parallel to the long side of the rectangular shape constituting the waveguide 4. Note that the shape of each slit 71 is not limited to a rectangular shape and may be an elongated shape such as an elliptical shape. Furthermore, although each slit 71 has the same shape in this embodiment, the slits 71 may have different shapes, and the longitudinal lengths of each slit 71 may be different lengths.

[0050] 4, at least two of the three slits 71 face toward the microwave generation source 2. Specifically, as shown in FIG. 4, two of the three slits 71, slits 71a and 71b, face toward the microwave generation source 2, and the remaining slit 71c faces toward the reflecting surface 5a of the reflector 5. As a result, the slits 71a and 71b allow the microwaves generated from the microwave generation source 2 to pass directly to the plasma generating tube 3, and the slit 71c allows the microwaves generated from the microwave generation source 2 to pass through to the plasma generating tube 3 via the reflecting surface 5a.

[0051] Furthermore, beam-shaped regions 71z are formed between adjacent slits 71 so as to be parallel to each slit 71. The beam-shaped regions 71z are formed from the upper end to the lower end of the cooling jacket 7. A cooling flow path 72 is provided inside the beam-shaped regions 71z.

[0052] The cooling flow passages 72 are generally cylindrical and are formed in the up-down direction from the upper end to the lower end of the cooling jacket 7. Specifically, a plurality of cooling flow passages 72 are formed at generally equal intervals along the circumferential direction of the cooling jacket 7, and as shown in Fig. 4, eight cooling flow passages 72 are formed in this embodiment, but the number of cooling flow passages 72 is not particularly limited. Furthermore, in this embodiment, the cooling flow passages 72 are provided in all of the beam-shaped regions 71z to facilitate cooling of the plasma generating tube 3, but may be provided in only some of the beam-shaped regions 71z.

[0053] The lower end of the cooling flow path 72 is connected to a cooling fluid inlet port P2 that allows the cooling fluid to flow into the cooling flow path 72, and the upper end of the cooling flow path 72 is connected to a cooling fluid outlet port P3 that allows the cooling fluid to flow out of the cooling flow path 72. In other words, the direction in which the cooling fluid flows through the cooling flow path 72 is opposite to the direction in which the gas flows inside the plasma generating tube 3. As a result, inside the plasma generating tube 3, the downstream side tends to be more susceptible to heating due to the gas being converted into plasma than the upstream side, and since a cooling fluid with a lower temperature flows from the lower part of the cooling flow path 72, the cooling efficiency of the plasma generating tube 3 can be improved.

[0054] The heat conducting member 73 is provided between the inner peripheral surface of the beam-shaped region 71z and the outer peripheral surface of the plasma generating tube 3, in contact with each other. In this embodiment, the heat conducting member 73 is formed along the vertical direction from the upper end to the lower end of the cooling jacket 7, but the heat conducting member 73 may be provided along a part of the vertical direction. The material forming the heat conducting member 73 is, for example, an ultra-low hardness heat dissipation silicone pad.

[0055] The casing 8 is generally cylindrical and houses the plasma generating tube 3 and the cooling jacket 7 to block microwaves from radiating to the outside. The casing 8 is configured to be separable into multiple members. In this embodiment, as shown in FIG. 5 , the casing 8 is configured to be separable along the vertical direction into two members, a first half 81 and a second half 82, each of which is generally semi-cylindrical. Specifically, as shown in FIG. 5( a), the first half 81 and the second half 82 are fixed together with the plasma generating tube 3 and the cooling jacket 7 sandwiched therebetween, thereby housing the plasma generating tube 3 and the cooling jacket 7 in the casing 8. Then, as shown in FIG. 5( b), the first half 81 and the second half 82 are separated along the vertical direction to remove the casing 8.

[0056] The first half 81 has an opening 8a formed therein, which faces the microwave source 2 and is connected to the waveguide 4. The second half 82 has an opening 8b formed therein, which faces the reflector 5 and is connected to the waveguide 4.

[0057] Furthermore, the casing 8 is formed with an observation window W for observing the internal state of the plasma generating tube 3. Specifically, the observation window W is a through-hole formed penetrating from the outer peripheral surface to the inner peripheral surface of the casing 8. In this embodiment, a plurality of observation windows W are formed along the up-and-down direction of the casing 8. More specifically, the plurality of observation windows W are formed at approximately equal intervals from the top to the bottom of each of the first half 81 and the second half 82. Note that the number of observation windows W and the locations where they are formed are not particularly limited.

[0058] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the above and below-described aims, and all such modifications are included within the technical scope of the present invention.

[0059] <Example: Comparison of resonance frequencies> Next, with reference to FIG. 6, a description will be given of the measurement results comparing the resonance frequencies of a cooling jacket and casing having three slits with those of cooling jackets and casings having other numbers of slits.

[0060] Here, the resonance frequencies of the three and eight cooling jackets and the casing were measured using a network analyzer.

[0061] As a result, it was confirmed that the resonant frequency of the cooling jacket and casing for the cooling jacket with three slits was 2.40 GHz. On the other hand, it was confirmed that the resonant frequency of the cooling jacket and casing for the cooling jacket with four slits was near 2.76 GHz. Furthermore, it was confirmed that the resonant frequency of the cooling jacket and casing for the cooling jacket with eight slits was near 4.00 GHz. It is assumed that the resonant frequency of the cooling jacket and casing for the cooling jacket with one or two slits is lower than the resonant frequency of the cooling jacket with three slits, 2.40 GHz. Therefore, compared to cooling jackets with other numbers of slits, the cooling jacket with three slits has the smallest deviation between the resonant frequency of the cooling jacket and casing and the microwave frequency of 2.45 GHz, thereby reducing the burden of matching adjustment using a matching box.

[0062] <Example: Comparison of etching rates> Next, in a plasma generator equipped with a cooling jacket having three and eight slits, a gas (etching gas) for etching the wafer was supplied to the plasma generating tube while a microwave (frequency 2.45 GHz) was irradiated onto the plasma generating tube to convert the etching gas flowing through the plasma generating tube into plasma. The microwave was irradiated so that the vibration direction of the electric field was perpendicular to the height direction of the plasma generating tube (the length direction of the slits). A wafer was then etched using the converted gas, and the etching rate was measured under the following four conditions.

[0063] Condition 1: Etching gas pressure is 100 Pa, etching gas components and concentrations are 1400 sccm of SF6 and 400 sccm of O2, and microwave output is 1000 W. Condition 2: Etching gas pressure is 200 Pa, etching gas components and concentrations are 1400 sccm of SF6 and 400 sccm of O2, and microwave output is 1000 W. Condition 3: Etching gas pressure is 100 Pa, etching gas components and concentration are 1400 sccm of SF6, and microwave output is 1000 W. Condition 4: Etching gas pressure is 100 Pa, etching gas components and concentrations are 1400 sccm of SF6 and 400 sccm of O2, and microwave output is 500 W.

[0064] FIG. 7 is a graph showing the etching rates when wafers are etched under the above four conditions in cooling jackets with three and eight slits. Under condition 1, the etching rate of the plasma generator equipped with a cooling jacket having three slits was 330.1 nm / min, and the etching rate of the plasma generator equipped with a cooling jacket having eight slits was 385.5 nm / min. Under condition 2, the etching rate of the plasma generator equipped with a cooling jacket having three slits was 822.0 nm / min, and the etching rate of the plasma generator equipped with a cooling jacket having eight slits was 805.8 nm / min. Under condition 3, the etching rate of the plasma generator equipped with a cooling jacket having three slits was 617.0 nm / min, and the etching rate of the plasma generator equipped with a cooling jacket having eight slits was 570.0 nm / min. Under condition 4, the etching rate of the plasma generator equipped with a cooling jacket having three slits was 153.3 nm / min, and the etching rate of the plasma generator equipped with a cooling jacket having eight slits was 129.0 nm / min. Therefore, it was thought that increasing the number of slits in the cooling jacket would increase the etching rate, but it was found that under all conditions 1 to 4, there was no significant difference in etching rate between three and eight slits, confirming that plasma can be generated efficiently even in a plasma generating device equipped with a cooling jacket with three slits.

[0065] <Effects of this embodiment> According to the plasma generator 100 of this embodiment, the cooling jacket 7 has three slits 71, and therefore the resonant frequency of the cooling jacket 7 and the casing 8 is around 2.45 GHz. As a result, the deviation between the microwave frequency and the resonant frequency is smaller than in cooling jackets having other numbers of slits, so that it is possible to shorten the time required to adjust the resonant impedance of the cooling jacket 7 and the casing 8 to match the impedance of the microwave generation source 2, and reduce the burden on the matching box 6 when performing matching adjustment. Furthermore, since there is no large difference in etching rate between three and eight slits, plasma can be generated efficiently even in a plasma generating device equipped with a cooling jacket having three slits.

[0066] Furthermore, the slits 71 are formed in a direction perpendicular to the vibration direction of the microwave electric field, and the long sides of the rectangular cross section of the waveguide 4 are aligned along the direction in which the slits 71 extend, so that the microwaves are prevented from being reflected by the cooling jacket 7 and can pass efficiently through the slits 71. As a result, the microwaves are appropriately irradiated onto the plasma generating tube 3, and the gas flowing inside the plasma generating tube 3 can be efficiently converted into plasma.

[0067] Furthermore, because the two slits 71a and 71b face toward the microwave generation source 2, the microwaves generated from the microwave generation source 2 are transmitted more efficiently to the plasma generating tube 3 than when only one slit faces toward the microwave generation source 2. As a result, the gas flowing inside the plasma generating tube 3 can be efficiently converted into plasma. In addition, since one slit 71c is formed facing the reflector plate 5, the gas flowing inside the plasma generating tube 3 can be uniformly converted into plasma in the circumferential direction of the plasma generating tube 3.

[0068] Furthermore, for example, the plasma generated inside the plasma generating tube 3 can be visually observed through the observation window W, and the temperature of the plasma generating tube 3 can be confirmed by inserting a thermometer such as an optical fiber thermometer into the observation window W. As a result, it is possible to prevent microwaves from being emitted to the outside while also being able to observe the internal state of the plasma generating tube 3.

[0069] Furthermore, since the casing 8 is configured to be separable into a plurality of members, the casing 8 can be easily attached and detached.

[0070] Furthermore, since the plasma generating tube 3 is made of yttria, it is possible to prevent the generation of by-products when a gas containing fluorine is turned into plasma.

[0071] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0072] In the above embodiment, three slits 71 are formed from the upper end to the lower end of the cooling jacket 7 and are arranged along the circumferential direction of the cooling jacket 7. When the cooling jacket 7 and the casing 8 resonate near the frequency of the microwave generation source 2, one slit 71 may be divided into multiple slits as shown in Figures 8(b) to (d).

[0073] For example, as shown in FIG. 8(b), a single slit 71 may have a longitudinal component along the vertical direction and be divided into multiple pieces along the vertical direction. Also, as shown in FIG. 8(c), a single slit 71 may have a longitudinal component inclined with respect to the vertical direction and be divided into multiple pieces along the inclined longitudinal component. Furthermore, as shown in FIG. 8(d), a single slit 71 may be formed along an approximate imaginary straight line C inclined with respect to the vertical direction and be divided into multiple pieces along the approximate imaginary line C. In the case of FIG. 8(d), the divided slits 71 each have a longitudinal component along the vertical direction.

[0074] In the above embodiment, the three slits 71 are formed from the upper end to the lower end of the cooling jacket 7, but this is not limited to this. For example, if each slit 71 is formed from the upper end to a part of the lower end of the cooling jacket 7 and the cooling jacket 7 and the casing 8 resonate, it is said that three slits 71 are formed in Fig. 8(a).

[0075] In this case, as shown in Fig. 8(b), for example, the three slits 71 may each have a longitudinal component along the up-down direction and be arranged on a substantially straight line parallel to the longitudinal component of the slits 71. Alternatively, as shown in Fig. 8(c), for example, the three slits 71 may each have a longitudinal component inclined with respect to the up-down direction and be arranged on a substantially straight line parallel to the longitudinal component of the slits 71. Furthermore, as shown in Fig. 8(d), for example, the three slits 71 may each have a longitudinal component along the up-down direction and be arranged on a substantially imaginary line C inclined with respect to the up-down direction.

[0076] In the above embodiment, the slits 71 are formed so that their longitudinal direction is perpendicular to the vibration direction of the electric field of the microwave, but the slits 71 may have a vertical component in their longitudinal direction. That is, the longitudinal direction of the slits 71 may be inclined from the direction perpendicular to the vibration direction of the electric field of the microwave.

[0077] In the above embodiment, the two slits 71a and 71b face the microwave generation source 2, but the direction of each slit 71 is not limited to this. For example, all three slits 71 may face the microwave generation source 2, or only one slit 71 may face the microwave generation source 2.

[0078] In the above embodiment, the plasma generator 100 includes the reflector 5, but the reflector 5 may not be included.

[0079] In the above embodiment, the casing 8 has an observation window W formed therein, but the casing 8 does not necessarily have to have an observation window W formed therein.

[0080] In the above embodiment, the casing 8 was separable into two members, the first half 81 and the second half 82, but it may be separable into three or more members, or may be a single unit. Also, while the casing 8 was separable along the vertical direction, the direction in which the casing 8 can be separated is not limited to the vertical direction, and may be, for example, a direction perpendicular to the vertical direction or another direction.

[0081] 9 and 10, the plasma generator 100 may further include a plurality of plasma detectors 9 that detect the emission intensity of the plasma generated inside the plasma generating tube 3. Here, the plurality of plasma detectors 9 are arranged facing each other in the direction in which the slits 71 are open. More specifically, the plurality of plasma detectors 9 are provided on the outer peripheral surface of the casing 8 via an attachment member B that has a long component in the vertical direction.

[0082] The plasma detection unit 9 detects the emission intensity of the plasma in a predetermined region inside the plasma generating tube 3 through the slit 71. Here, the plasma detection unit 9 is, for example, a photodiode, and outputs an analog signal corresponding to the emission intensity of the plasma to a computing device (not shown). The plasma detection unit 9 may also include a filter for detecting the emission intensity of the plasma at a predetermined wavelength.

[0083] The arithmetic unit is a computer having a CPU, internal memory, input / output interface, etc., and may perform A / D conversion on the analog signal obtained by the plasma detection unit 9. The arithmetic unit may also display the plasma distribution state in real time on a display unit (not shown), such as a display.

[0084] 9, the plurality of plasma detectors 9 are arranged along the vertical direction of the plasma generating tube 3, i.e., along the direction of gas travel. Here, as shown in FIGS. 9 and 10, the plurality of plasma detectors 9 are arranged along the direction in which one slit 71 that opens toward the microwave generation source 2 extends. Note that, in order to detect the distribution state of plasma in a direction intersecting the direction of gas travel, the plurality of plasma detectors 9 may be arranged opposite each of the two slits 71 that open toward the microwave generation source 2.

[0085] The multiple plasma detection units 9 detect the emission intensity of plasma in different regions inside the plasma generating tube 3. Specifically, as shown in Fig. 9, three plasma detection units 9 detect the emission intensity of plasma in the upper part, central part, and lower part of the plasma generating tube 3 in the gas traveling direction. Note that, in order to detect the plasma distribution state more accurately, it is sufficient that at least one plasma detection unit 9 detects the emission intensity of plasma in the central part of the plasma generating tube 3. Furthermore, the number of plasma detection units 9 is at least two or more and is not limited to three.

[0086] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0087] 100 Plasma generator 2. Microwave Source 3. Plasma generating tube 4...Waveguide 5...Reflector 6...matching box 7. Cooling jacket 71 Slit 71z...beam area 72 Cooling channel 73 Heat conduction material 8 Casing 81...first half 82...Second half 9. Plasma detection unit W: Observation window

Claims

1. a microwave source that generates microwaves; a plasma generating tube having a cylindrical shape and through which a gas to be converted into plasma by the microwave flows; a waveguide that transmits the microwaves generated from the microwave generation source to the plasma generation tube; a matching box provided in the waveguide between the microwave generation source and the plasma generation tube; a cooling jacket provided on an outer peripheral surface of the plasma generating tube to cool the plasma generating tube; a cylindrical casing that houses the plasma generating tube and the cooling jacket; The cooling jacket is three slits extending along or obliquely to the direction of gas flow through the plasma generating tube, and allowing the microwaves to pass through the plasma generating tube; a cooling flow path provided between adjacent ones of the slits, through which a cooling fluid for cooling the plasma generating tube flows.

2. The slit extends along a direction perpendicular to or inclined to a vibration direction of the electric field of the microwave, 2. The plasma generator according to claim 1, wherein the waveguide has a rectangular cross section, and a long side of the rectangular cross section is aligned with or inclined to a direction in which the slit extends.

3. 3. The plasma generator according to claim 1, wherein at least two of the three slits face toward the microwave generation source.

4. a reflector that is provided in the waveguide opposite the microwave generation source with the plasma generation tube interposed therebetween and that reflects microwaves from the microwave generation source toward the plasma generation tube, 3. The plasma generating device according to claim 1, wherein at least one of the three slits is formed facing toward the reflector, and at least one other of the slits is formed facing toward the microwave generating source.

5. 5. The plasma generator according to claim 1, wherein the casing is provided with an observation window for observing an internal state of the plasma generating tube.

6. The plasma generator according to claim 5 , wherein the casing is configured to be separable into a plurality of members.

7. 7. The plasma generating device according to claim 1, wherein the plasma generating tube is made of yttria, yttria-coated quartz, and / or sapphire tube, or a combination thereof.

8. 8. The plasma generating device according to claim 1, further comprising a plurality of plasma detecting units arranged opposite to each other in a direction in which the slits are opened, and configured to detect the emission intensity of the plasma generated inside the plasma generating tube.

9. The plasma generation device according to claim 8 , wherein the plurality of plasma detection units are arranged along a direction in which the gas travels.

10. 10. The plasma generation device according to claim 9, wherein the plurality of plasma detection units detect the emission intensity of the plasma at an upper part of the plasma generation tube, a central part of the plasma generation tube, and a lower part of the plasma generation tube in the traveling direction of the gas.

11. A cooling jacket is provided on the outer circumferential surface of a cylindrical plasma generating tube through which a gas to be plasmatized by microwaves flows, and the cooling jacket cools the plasma generating tube, three slits extending along or obliquely to the direction of gas flow through the plasma generating tube, and allowing the microwaves to pass through the plasma generating tube; a cooling jacket including a cooling passage formed between adjacent ones of the slits, through which a cooling fluid for cooling the plasma generating tube flows.

12. A cooling jacket is provided on the outer circumferential surface of a cylindrical plasma generating tube through which a gas to be plasmatized by microwaves flows, and the cooling jacket cools the plasma generating tube, a slit extending in a direction perpendicular to or inclined to the vibration direction of the electric field of the microwave, and allowing the microwave to pass through to the plasma generating tube; a cooling flow path provided separately from the slit, through which a cooling fluid for cooling the plasma generating tube flows; The slit extends along a direction perpendicular to or inclined to a vibration direction of the electric field of the microwave, A cooling jacket, wherein the waveguide has a rectangular cross section, and the long sides of the rectangular cross section are aligned along the direction in which the slits extend or are inclined.

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