JP2009301808A - Plasma processing apparatus, and plasma processing method - Google Patents

Abstract

A coaxial pipe distributor including a coaxial pipe extending non-vertically at a branching portion is provided.
A plasma processing apparatus 10 for plasma processing a target object by exciting a gas with a microwave, a processing container 100, a microwave source 900 for outputting a microwave, and a microwave output from the microwave source 900. A transmission line 900a for transmitting a wave, a plurality of dielectric plates 305 that are provided on the inner wall of the processing vessel 100 and emit microwaves into the processing vessel, and adjacent to the plurality of dielectric plates 305, a plurality of microwaves A plurality of first coaxial tubes 610 that transmit to the dielectric plate 305, and one or more stages of coaxial tube distribution that distribute and transmit the microwaves transmitted through the transmission line 900a to the plurality of first coaxial tubes 610. And a container 700. The coaxial pipe distributor 700 includes a second coaxial pipe 620 having an input part In and three or more third coaxial pipes 630 connected to the second coaxial pipe 620. Each extends non-perpendicular to the second coaxial waveguide 620.
[Selection] Figure 5

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for generating plasma using electromagnetic waves and performing plasma processing on an object to be processed. In particular, it relates to impedance matching of transmission lines.

  The area of glass substrates for flat panel displays and solar cells is increasing year by year, and substrate sizes exceeding 3 m square are already being put into practical use. The manufacture of flat panel displays and solar cells requires a plasma processing apparatus that can generate uniform and stable plasma over a wide area that exceeds the substrate size. Furthermore, as plasma processing is diversified as products become more sophisticated and multifunctional, apparatuses capable of handling a wide range of processing conditions are required. A microwave plasma apparatus is a promising candidate that satisfies these requirements.

  When the plasma is excited with microwave energy, a plasma with a low electron temperature is obtained because of the high frequency. When the electron temperature is low, the energy of ions incident on the substrate surface and the chamber inner surface is kept low, so that treatment without damage by ion irradiation or contamination by impurities can be performed. Furthermore, since excessive dissociation of the source gas can be suppressed and target radicals and ions can be generated, high-quality and high-speed processing can be performed.

  On the other hand, since the wavelength of the microwave is shorter than the substrate size, it is difficult to excite uniform plasma on a large area substrate. Moreover, since the cutoff density (proportional to the square of the frequency) is high, it is difficult to cope with a wide range of processing conditions. Therefore, the inventor proposed a cell division method that lowers the plasma excitation frequency and divides the plasma excitation area into cells to uniformly supply microwave power to each cell. It was possible to excite uniform and stable plasma (see, for example, Patent Document 1).

JP 2006-310794 A

  In this cell division method, the microwave power generated by one or two small number of microwave power supplies is evenly distributed and supplied to a maximum of a large number of cells. This requires a multistage distributor that transmits microwaves to all cells.

Normally, uniform plasma processing can be performed by making the plasma excitation region 60 mm to 80 mm larger than the substrate size. However, if the end coaxial tubes are connected to the distributor vertically at equal pitches, it is necessary to make the pitch of the end coaxial tubes approximately equal to an integral multiple of π rad in order to transmit microwaves of the same amplitude and phase to each cell. is there. According to this, the cell size is restricted by the in-tube wavelength of the microwave, and the cell size cannot be determined in accordance with the substrate size. Furthermore, the number of distributions that can constitute a practical distributor is limited. For example, a 2 ^m distributor (m is an integer) is easy to configure, but it may be difficult to create a practical distributor with other distribution numbers. For this reason, an apparatus will enlarge more than necessary. In addition, the plasma excitation region becomes larger than necessary, and in order to maintain the plasma, power more than that originally required for the process is consumed. Large equipment must handle extremely large microwave power, so optimizing the plasma excitation region according to the substrate size can save considerable power consumption, leading to cost reduction and effective use of resources. .

  In order to solve the above-mentioned problems, the present invention provides a coaxial pipe distributor including a coaxial pipe that extends non-vertically at a branch portion.

  That is, in order to solve the above-described problem, according to an aspect of the present invention, there is provided a plasma processing apparatus that plasmas a target object by exciting a gas with an electromagnetic wave, the processing container, and an electromagnetic wave source that outputs the electromagnetic wave A transmission line that transmits the electromagnetic wave output from the electromagnetic wave source, a plurality of dielectric plates that are provided on the inner wall of the processing container and emit the electromagnetic waves into the processing container, and adjacent to the plurality of dielectric plates A plurality of first coaxial tubes that transmit electromagnetic waves to the plurality of dielectric plates, and one or more stages that distribute and transmit the electromagnetic waves transmitted through the transmission line to the plurality of first coaxial tubes. A coaxial pipe distributor, and at least one of the coaxial pipe distributors includes a second coaxial pipe having an input portion and three or more third coaxial pipes connected to the second coaxial pipe. Each of the third coaxial pipes The plasma processing apparatus is provided with a portion for non-vertically oriented with respect to the second coaxial waveguide. Each of the third coaxial waveguides may be connected non-vertically to the second coaxial waveguide, or may be connected vertically and extend non-perpendicularly therefrom.

  According to this, at least one stage of the coaxial pipe distributor includes a second coaxial pipe and three or more third coaxial pipes, and each third coaxial pipe is connected to the second coaxial pipe. Stretch non-perpendicularly. As a result, the plasma excitation region can be determined in accordance with the substrate size without being restricted by the guide wavelength, so that the power consumption can be reduced. Moreover, it can avoid that the whole apparatus becomes larger than necessary. As an example of the shape of the third coaxial waveguide, a curved third coaxial waveguide is connected to the second coaxial waveguide, or a rod-shaped third coaxial tube is obliquely connected to the second coaxial waveguide. This is the case.

  Each third coaxial waveguide may have an impedance conversion mechanism. As a result, the impedance can be matched to the plasma as a load while being branched from the second coaxial waveguide to the third coaxial waveguide, and a high-power microwave can be transmitted.

  The number of connecting portions between the second coaxial waveguide and the third coaxial waveguide between the input portion of the second coaxial waveguide and the end of the second coaxial waveguide is 2 or less. preferable. This is because even if the frequency of the electromagnetic wave fluctuates, the balance of power supplied to the third coaxial waveguide is not easily lost.

  The electrical length between the connecting portions between the connecting portions of the second coaxial waveguide and the third coaxial waveguide where the input portion is not interposed may be approximately equal to an integral multiple of π rad. According to this, power can be evenly distributed from the second coaxial waveguide to the third coaxial waveguide. Further, when the electrical length between the connecting portions is approximately an integral multiple of 2π rad, the phase can be aligned with the amplitude.

  In the connecting portion between the second coaxial waveguide and the third coaxial waveguide, two of the third coaxial waveguides may be connected to the second coaxial waveguide. As a result, by reducing the number of connecting portions, it is possible to make it difficult for the balance of power supplied to the third coaxial waveguide to be lost even if the frequency of the electromagnetic wave fluctuates.

  The inner conductor of the third coaxial waveguide may be thinner than the inner conductor of the second coaxial waveguide. The outer conductor of the third coaxial waveguide may be thinner than the outer conductor of the second coaxial waveguide. This is to reduce disturbance in the transmission state of electromagnetic waves transmitted through the coaxial waveguide.

  The inner conductor and the outer conductor of the second coaxial waveguide are short-circuited at at least one end of the second coaxial waveguide, and the second coaxial tube is closest to the end from the end of the second coaxial waveguide. The electrical length to the connecting portion between the second coaxial waveguide and the third coaxial waveguide may be approximately equal to an odd multiple of π / 2 rad. According to this, the part from the end of the second coaxial waveguide to the connecting part does not exist for electromagnetic wave transmission, and the transmission line can be easily designed.

When the impedance of the first coaxial waveguide viewed from the plasma side is matched, the impedance of the third coaxial waveguide viewed from the connecting portion of the second coaxial waveguide and the third coaxial waveguide is R _r3 , which is generally resistive, is connected between the connecting portion and the third coaxial waveguide side, and is connected between the input portion of the second coaxial waveguide and one end of the second coaxial waveguide. the number of third coaxial waveguides N _s, when the characteristic impedance of the second coaxial waveguide was Z _c2, the characteristic impedance Z _c2 of the second coaxial waveguide may be generally equal to R _{r3 /} N _s . As a result, there is no reflection when viewed from the distributor input side, and a high-power microwave can be transmitted.

A fourth coaxial tube having a characteristic impedance of _Zc4 is connected to the input portion of the second coaxial waveguide, and when the impedance of the first coaxial waveguide viewed from the plasma side is matched, the second coaxial tube is matched. The impedance when the third coaxial waveguide side is viewed from the connection portion between the coaxial tube and the third coaxial waveguide is generally resistive, and the resistance when the third coaxial tube side is viewed from the connection portion is R. _r3, when the number of the third coaxial waveguides connected to the second coaxial waveguide was _{N t,} the characteristic impedance _{Z c4} is generally may be equal to _R r3 / _{N t.} As a result, there is no reflection when viewed from the distributor input side, and a high-power microwave can be transmitted.

  The electrical length of the third coaxial waveguide may be approximately π / 2 rad. As a result, the impedance when the third coaxial waveguide side is viewed from the connecting portion of the second and third coaxial waveguides can be made generally resistive.

  Of the inner conductor of the third coaxial waveguide, a connecting portion with the second coaxial waveguide may be thinner than other portions. The electrical length of the third coaxial waveguide can be adjusted by adjusting the thickness and length of the narrowed portion.

When the impedance viewed from the first coaxial waveguide viewed from the plasma side is matched, the impedance viewed from the output end of the third coaxial waveguide is generally resistive, and the impedance of the third coaxial waveguide is R _{r5 is} a resistance viewed from the output end to the output side, N _{s is} the number of third coaxial tubes connected between the input portion of the second coaxial waveguide and one end of the second coaxial waveguide, When the characteristic impedance of the second coaxial waveguide is Z _c2 , the characteristic impedance Z _c3 of the third coaxial waveguide may be approximately equal to (R _r5 × N _s × Z _c2 ) ^1/2 . As a result, there is no reflection when viewed from the input side of the coaxial waveguide distributor, and a high-power microwave can be transmitted.

A fourth coaxial waveguide having a characteristic impedance of _Zc4 is connected to the input portion of the second coaxial waveguide, and when the impedance of the first coaxial waveguide viewed from the plasma side is matched, the third coaxial tube is matched. The impedance viewed from the output end of the coaxial tube is generally resistive, and the resistance viewed from the output end of the third coaxial tube is connected to R _r5 , the second coaxial tube. When the number of third coaxial waveguides is N _t , the characteristic impedance Z _c3 of the third coaxial waveguide may be approximately equal to (R _r5 × N _t × Z _c4 ) ^1/2 . As a result, there is no reflection when viewed from the input side of the coaxial waveguide distributor, and a high-power microwave can be transmitted.

  The connecting portion between the output end of the third coaxial waveguide and the fifth coaxial waveguide may be a T-branch. At least one of the inner conductor of the third coaxial waveguide and the inner conductor of the fifth coaxial waveguide may be such that the connecting portion of the T branch is thinner than the other portion. At least one of the outer conductor of the third coaxial waveguide and the outer conductor of the fifth coaxial waveguide may be such that the branch portion of the T branch is thicker than the other portion.

  In the case where the third coaxial waveguide is provided with a thinned portion or a thickened portion, the electrical length of the third coaxial waveguide can be adjusted by adjusting the length or thickness. In the case of the fifth coaxial waveguide, the electrical length of the fifth coaxial waveguide can be adjusted by adjusting its length and thickness. Also, the characteristic impedances of the third coaxial tube and the fifth coaxial tube are usually greatly different. In the branch part, unnecessary reflection at the branch part can be suppressed by thinning the inner conductor of the fifth coaxial waveguide and providing a buffer part.

  Of the narrowed portion of the inner conductor of the fifth coaxial waveguide, the length of the portion from the T-branch connecting portion toward one branch destination and the portion from the T-branch connecting portion toward the other branch destination It may be different from the length. Thereby, the ratio of the electric power of the microwave supplied to the two branch destinations of the T branch can be adjusted.

  A plurality of metal electrodes that are electrically connected to an inner wall of the processing vessel and are adjacent to the plurality of dielectric plates on a one-to-one basis, wherein each dielectric plate includes the adjacent metal electrodes and the dielectric plates; Each of the dielectric plates and the inner wall of the processing vessel in which the dielectric plates are not arranged or the metal cover provided on the inner wall are substantially disposed between the inner walls of the processing vessel in which the dielectric plates are not arranged. It may be a similar shape or a substantially symmetric shape. Thereby, the electromagnetic wave power can be supplied from the dielectric plate to both sides almost uniformly.

  In order to solve the above problems, according to another aspect of the present invention, there is provided a plasma processing apparatus for plasma-treating an object to be processed by exciting a gas with an electromagnetic wave, a processing container, an electromagnetic wave source for outputting the electromagnetic wave, A transmission line that transmits the electromagnetic wave output from the electromagnetic wave source, a plurality of dielectric plates that are provided on the inner wall of the processing container and emit the electromagnetic waves into the processing container, and adjacent to the plurality of dielectric plates. A plurality of first coaxial tubes that transmit electromagnetic waves to the plurality of dielectric plates, and one or more stages that distribute and transmit the electromagnetic waves transmitted through the transmission line to the plurality of first coaxial tubes. A plasma processing apparatus is provided in which at least one of the coaxial tube distributors has different characteristic impedances between the input-side coaxial tube and the output-side coaxial tube.

  According to this, at least one of the coaxial tube distributors connects the coaxial tube on the input side and the coaxial tube on the output side by changing the characteristic impedance between the coaxial tube on the input side and the coaxial tube on the output side. Impedance matching can be achieved at the part. For example, the connecting portion of the input-side coaxial tube and the output-side coaxial tube has two branches, and the two-branch has twice the characteristic impedance of the input-side coaxial tube as the output-side coaxial tube. May be substantially equal to the characteristic impedance. According to this, a high-power microwave can be transmitted.

  Of the outer conductor of the coaxial tube on the output side constituting the two branches, the connecting part may be thicker than the other part. By suppressing the electrostatic capacitance between the inner conductor and the outer conductor at the branch portion, reflection at the branch portion can be reduced.

  In order to solve the above problems, according to another aspect of the present invention, a gas is introduced into a processing container, an electromagnetic wave is output from an electromagnetic wave source, the output electromagnetic wave is transmitted to a transmission line, and the transmission line The electromagnetic wave transmitted through the first coaxial waveguide is distributed to a plurality of first coaxial waveguides from one or more coaxial tube distributors, and the electromagnetic waves transmitted through the first coaxial waveguide are provided on the inner wall of the processing vessel. When the plurality of dielectric plates are emitted into the processing container and electromagnetic waves are transmitted to the coaxial tube distributor, at least one of the coaxial tube distributors has a second coaxial tube having an input portion and the first coaxial tube distributor. Including three or more third coaxial waveguides connected to the two coaxial waveguides, and transmitting electromagnetic waves to each third coaxial waveguide having a portion extending non-perpendicular to the second coaxial waveguide; Due to electromagnetic waves emitted into the processing vessel through the first coaxial waveguide. Plasma processing method for performing plasma processing on a processing target is provided to excite the gas.

  According to this, at least one stage of the coaxial pipe distributor is branched into three or more third coaxial pipes connected non-perpendicularly from the second coaxial pipe to the second coaxial pipe. Thereby, a microwave can be equally distributed to a plurality of cells determined according to the substrate size. As a result, the entire apparatus does not become larger than necessary, and the plasma excitation region does not become larger than necessary, so that power consumption can be reduced.

  In order to solve the above-described problem, according to another aspect of the present invention, gas is introduced into a processing container, an electromagnetic wave is output from an electromagnetic wave source, the output electromagnetic wave is transmitted to a transmission line, and one stage or Two or more stages of coaxial pipes are formed, and at least one of the coaxial pipe distributors having different characteristic impedances of the input side coaxial pipe and the output side coaxial pipe transmits the transmitted electromagnetic wave to the plurality of first coaxial pipes. The electromagnetic wave is transmitted to a plurality of dielectric plates adjacent to the plurality of first coaxial waveguides and provided on the inner wall of the processing container, and is transmitted from the plurality of dielectric plates into the processing container. There is provided a plasma processing method for emitting an electromagnetic wave, exciting a gas by the emitted electromagnetic wave, and plasma-treating an object to be processed in the processing container.

  According to this, by changing the characteristic impedance between the coaxial tube on the input side and the coaxial tube on the output side of the coaxial tube distributor, for example, the impedance is matched at the branching portion when transmitting the microwave while distributing it. be able to.

  As described above, according to the present invention, the plasma excitation region can be adjusted in accordance with the substrate size without being restricted by the wavelength in the tube by the coaxial tube distributor including the coaxial tube that extends non-vertically at the branch portion. Can be determined.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, the same reference numerals are given to the constituent elements having the same configuration and function, and redundant description is omitted.

(First embodiment)
First, an outline of the microwave plasma processing apparatus according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a ceiling surface of a microwave plasma processing apparatus according to this embodiment. 1 is a 2-2 cross section of FIG. FIG. 2 shows a part of a longitudinal section of the microwave plasma processing apparatus 10. FIG. 2 is a cross section taken along the line 1-O'-1 of FIG. FIG. 3 is an enlarged view of the region Ex in FIG.

(Outline of microwave plasma processing equipment)
As shown in FIG. 2, the microwave plasma processing apparatus 10 includes a processing container 100 for plasma processing a glass substrate (hereinafter referred to as “substrate G”). The processing container 100 includes a container body 200 and a lid body 300. The container body 200 has a bottomed cubic shape with an upper portion opened, and the opening is closed by a lid 300. The lid body 300 includes an upper lid body 300a and a lower lid body 300b. An O-ring 205 is provided on a contact surface between the container main body 200 and the lower lid body 300b, whereby the container main body 200 and the lower lid body 300b are hermetically sealed to define a processing chamber. An O-ring 210 and an O-ring 215 are also provided on the contact surface between the upper lid 300a and the lower lid 300b, so that the upper lid 300a and the lower lid 300b are sealed. The container body 200 and the lid body 300 are made of a metal such as an aluminum alloy, for example, and are electrically grounded.

  A susceptor 105 (stage) for placing the substrate G is provided inside the processing container 100. Susceptor 105 is made of, for example, aluminum nitride. The susceptor 105 is supported by a support 110, and a baffle plate 115 for controlling the gas flow in the processing chamber to a preferable state is provided around the susceptor 105. A gas exhaust pipe 120 is provided at the bottom of the processing container 100, and the gas in the processing container 100 is exhausted using a vacuum pump (not shown) provided outside the processing container 100.

  1 and 2, the dielectric plate 305, the metal electrode 310, and the metal cover 320 are regularly arranged on the ceiling surface of the processing container 100. A side cover 350 is provided around the metal electrode 310 and the metal cover 320. The dielectric plate 305, the metal electrode 310, and the metal cover 320 are substantially square plates with slightly rounded corners. In addition, a rhombus may be sufficient. In this specification, the metal electrode 310 refers to a flat plate provided adjacent to the dielectric plate 305 so that the dielectric plate 305 is substantially uniformly exposed from the outer edge of the metal electrode 310. As a result, the dielectric plate 305 is sandwiched between the inner wall of the lid 300 and the metal electrode 310. The metal electrode 310 is electrically connected to the inner wall of the processing container 100.

  Forty-eight dielectric plates 305 and metal electrodes 310 are arranged at an equal pitch at a position inclined approximately 45 ° with respect to the substrate G and the processing container 100. The pitch is determined such that the diagonal length of one dielectric plate 305 is 0.9 times or more the distance between the centers of adjacent dielectric plates 305. Thereby, the slightly cut corners of the dielectric plate 305 are arranged adjacent to each other.

  The metal cover 320 is thicker than the metal cover 320 by the thickness of the dielectric plate 320. According to such a shape, the height of the ceiling surface becomes substantially equal, and at the same time, the portion where the dielectric plate 305 is exposed and the shape of the recesses in the vicinity thereof all have the same pattern.

  The dielectric plate 305 is made of alumina, and the metal electrode 310, the metal cover 320, and the side cover 350 are made of an aluminum alloy. In this embodiment, the eight dielectric plates 305 and the metal electrodes 310 are arranged in six rows in eight rows. However, the present invention is not limited to this, and the increase in the number of the dielectric plates 305 and the metal electrodes 310 is also reduced. You can also.

  The dielectric plate 305 and the metal electrode 310 are equally supported from four places by screws 325 (see FIG. 3). As shown in FIG. 2, a main gas flow path 330 formed in a lattice shape in a direction perpendicular to the paper surface is provided between the upper lid body 300a and the lower lid body 300b. The main gas flow path 330 divides the gas into the gas flow paths 325 a provided in the plurality of screws 325. A narrow tube 335 for narrowing the flow path is fitted at the inlet of the gas flow path 325a. The thin tube 335 is made of ceramics or metal. A gas flow path 310 a is provided between the metal electrode 310 and the dielectric plate 305. A gas flow path 320 a is also provided between the metal cover 320 and the dielectric plate 305 and between the side cover 350 and the dielectric plate 305. The front end surface of the screw 325 is flush with the lower surfaces of the metal electrode 310, the metal cover 320, and the side cover 350 so as not to disturb the plasma distribution. The gas discharge holes 345a opened in the metal electrode 310 and the gas discharge holes 345b opened in the metal cover 320 and the side cover 350 are arranged at an equal pitch.

  The gas output from the gas supply source 905 passes through the gas flow path 325a (branch gas flow path) from the main gas flow path 330, and the first gas flow path 310a in the metal electrode 310, the metal cover 320, and the side cover. Through the second gas flow path 320a in 350, gas is supplied from the gas discharge holes 345a and 345b into the processing chamber. An O-ring 220 is provided on the contact surface between the lower lid 300 b and the dielectric plate 305 in the vicinity of the outer periphery of the first coaxial waveguide 610, and the atmosphere in the first coaxial waveguide 610 is placed inside the processing container 100. It is designed not to enter.

  In this way, by forming the gas shower plate on the metal surface of the ceiling portion, it has been possible to suppress the etching of the dielectric plate surface caused by ions in the plasma and the deposition of reaction products on the inner wall of the processing vessel, It is possible to reduce contamination and particles. Further, unlike a dielectric, a metal can be easily processed, so that the cost can be greatly reduced.

  The inner conductor 610a is inserted into the outer conductor 610b of the first coaxial waveguide formed by digging the lid 300. Similarly, the inner conductors 620a to 650a of the second to fifth coaxial waveguides are inserted into the outer conductors 620b to 650b of the second to fifth coaxial waveguides formed by digging in the same manner, and the upper portion thereof is the lid cover 660. Covered with. The inner conductor of each coaxial tube is made of copper with good thermal conductivity.

  The surface of the dielectric plate 305 shown in FIG. 2 is a metal film 305a except for a portion where the microwave is incident on the dielectric plate 305 from the first coaxial waveguide 610 and a portion where the microwave is emitted from the dielectric plate 305. It is covered with. Accordingly, the propagation of the microwave is not disturbed by the gap generated between the dielectric plate 305 and the adjacent member, and the microwave can be stably guided into the processing container.

  As shown in FIG. 1, the dielectric plate 305 is covered with the metal cover 320 (the metal cover 320 is covered with the metal plate 310 and the inner wall of the processing vessel 100 where the dielectric plate 305 is not disposed). (Including the inner wall of the processing container 100). The dielectric plate 305 and the inner wall of the processing vessel 100 in which the dielectric plate 305 is not disposed (including the inner wall of the processing vessel 100 covered with the metal cover 320) are substantially similar in shape or substantially The shape is symmetrical. Thereby, microwave power can be supplied from the dielectric plate to the metal electrode side and the inner wall side (metal cover 320 and side cover 350 side) substantially evenly. As a result, the microwave emitted from the dielectric plate 305 propagates on the surfaces of the metal electrode 310, the metal cover 320, and the side cover 350 while distributing the power in half as a surface wave. Hereinafter, the surface wave propagating between the metal surface on the inner surface of the processing container and the plasma is referred to as a conductor surface wave (metal surface wave). Thereby, the conductor surface wave propagates to the entire ceiling surface, and uniform plasma is stably generated below the ceiling surface of the microwave plasma processing apparatus 10 according to the present embodiment.

  An octagonal groove 340 is formed in the side cover 350 so as to surround the entire 48 dielectric plates 305, and the conductor surface wave propagating on the ceiling surface is prevented from propagating outside the groove 340. To do. A plurality of grooves 340 may be formed in multiple in parallel.

  A region having the center point of the adjacent metal cover 320 around the metal electrode 310 as a center is hereinafter referred to as a cell Cel (see FIG. 1). On the ceiling surface, 48 cells Cel are regularly arranged in the same pattern with the cell Cel as a unit. Note that the size of the cell Cel is not limited by the wavelength. This will be described later.

  The refrigerant supply source 910 is connected to the refrigerant pipe 910a inside the lid and the refrigerant pipe 910b of the inner conductor 620a of the second coaxial pipe, and the refrigerant supplied from the refrigerant supply source 910 passes through the refrigerant pipes 910a and 910b. By circulating and returning to the refrigerant supply source 910 again, heating of the lid 300 and the inner conductor is suppressed.

(Multiple branches: Symmetrical 8 branches)
Next, multi-branch (symmetric 8-branch) according to the present embodiment will be described with reference to FIGS. FIG. 4 is a schematic diagram of a branch circuit including the coaxial waveguide distributor 700. FIG. 5 shows a 3-3 cross section of FIG.

  The microwave source 900 is connected to the waveguide and transmits the microwave to the fourth coaxial waveguide 640 via the coaxial waveguide converter while being branched into three. The fourth coaxial waveguide 640 is bifurcated (T-branch) and connected to the second coaxial waveguide 620. A portion where the microwave is incident on the second coaxial waveguide 620 from the fourth coaxial waveguide 640 is hereinafter referred to as an input portion In of the second coaxial waveguide. The coaxial pipe distributor 700 is a multi-branch structure including a second coaxial pipe 620 having an input part In and a third coaxial pipe 630 that is connected to the second coaxial waveguide 620 at four positions and extends non-vertically. . In the connection portion between the second coaxial waveguide 620 and the third coaxial waveguide 630, two third coaxial waveguides 630 are connected to the second coaxial waveguide 620. In the present embodiment, eight third coaxial waveguides 630 are connected to the second coaxial waveguide 620. Each of the eight third coaxial waveguides 630 is T-branched to the fifth coaxial waveguide 650 and is connected to the first coaxial waveguide 610 at both ends of the fifth coaxial waveguide 650. It is connected to the dielectric plate 305 at the end of 610.

  As a result, the 915 MHz microwave output from one microwave source 900 is converted into an isolator, a directional coupler, a matching unit (not shown), a waveguide 3 distributor, and three coaxial waveguide converters. Then, the signal is transmitted through the fourth coaxial waveguide 640, and is transmitted while the power is evenly distributed by the coaxial waveguide distributor 700 including the second coaxial waveguide 620 and the eight third coaxial waveguides 630. The microwave transmitted through the third coaxial waveguide 630 is transmitted to the dielectric plate 305 through the fifth coaxial waveguide 650 and the first coaxial waveguide 610, and is exposed to the periphery of the metal electrode 310. To the processing container. In the present apparatus, three second coaxial waveguides 620 are arranged in parallel at an equal pitch.

  In the present embodiment, eight third coaxial waveguides 630 are connected to the second coaxial waveguide 620, but three or more third coaxial waveguides 630 are connected to the second coaxial waveguide 620. Just do it. The branch part formed in the coaxial waveguide distributor 700 according to the present embodiment is a symmetrical multi-branch. The symmetric multi-branch means that the number and connection position of the third coaxial waveguide 630 connected to one branch destination from the input portion In in the center of the inner conductor of the second coaxial waveguide is connected to the other branch destination. It is equal to the number and connection position of the three coaxial pipes 630, and refers to three or more branches having symmetry about the input part In.

  On the other hand, the branch portion formed in the coaxial waveguide distributor 700 according to the second embodiment to be described later is an asymmetric multi-branch. For example, as shown in FIGS. 8 and 9, the asymmetric multi-branch is the number of third coaxial waveguides 630 connected to one branch destination from the input portion In at the center of the inner conductor of the second coaxial waveguide. And the number of the third coaxial waveguides 630 connected to the other branch destination and the connecting position are equal to or more than three branches having no symmetry with respect to the input portion In.

As shown in FIG. 5, among the connection portions A _{1 to} A ₄ connecting the internal conductor 620 a and the internal conductor 630 a, the input portion In is the midpoint between the connection portion A ₂ and the connection portion A ₃ . Input In is not interposed, if the electrical length of and between the connecting portion A ₃ of the imaging section A ₁ and the connecting portion A ₂ and the connecting portion A ₄ is sufficient that the integral multiple of rad, all third The amplitudes of the microwaves transmitted to the coaxial tube 630 become equal. Furthermore, if these electrical length becomes an odd multiple of rad, the third coaxial tubes 630 are respectively connected to the connecting portion A ₁ and the connecting portion A _2, and a connecting portion A ₃ and the connecting portion A ₄ The phases of the microwaves transmitted to the third coaxial waveguides 630 respectively connected to each other are shifted by π rad. On the other hand, if these electrical lengths are an even multiple of πrad, that is, an integral multiple of 2πrad, the phases of the microwaves transmitted to all the third coaxial waveguides 630 are equal. In the present embodiment, since the phases need to be matched, these electrical lengths only have to be an integral multiple of 2π rad. In addition, since the propagation mode (TEM mode) is disturbed around the connecting portion, the electrical length changes. Therefore, in practice, the distance between the connecting portion A ₁ and the connecting portion A ₂ and the distance between the connecting portion A ₃ and the connecting portion A ₄ are the in-tube wavelength λg _{2 of} the second coaxial waveguide 620 = 327. It is set to be several mm longer than 6 mm.

  The structure of the coaxial waveguide distributor 700 will be described in more detail with reference to FIG. The second coaxial waveguide 620 is connected to the fourth coaxial waveguide 640 at the center thereof. From the input part In of the second coaxial waveguide 620 to the end of the second coaxial waveguide 620, the third coaxial waveguide 630 is connected to each end in two places, and is extended while being curved. Yes. The number of the third coaxial waveguides 630 connected between the input portion In of the second coaxial waveguide 620 and the end of the second coaxial waveguide 620 is preferably 2 or less. This is because the balance of power shared by the third coaxial waveguide 630 is not easily lost even if the frequency of the microwave fluctuates.

  The inner conductor 620a and the outer conductor 620b of the second coaxial waveguide are short-circuited at both ends of the second coaxial waveguide 620, and the second coaxial waveguide closest to the end from the end of the second coaxial waveguide 620. The electrical length to the connecting portion between 620 and the third coaxial waveguide 630 is approximately equal to an odd multiple (here, 1) of π / 2 rad. Thereby, during this period, one end can be regarded as a distributed constant line short-circuited. As described above, the distributed constant line having the electrical length of π / 2 rad with one end short-circuited appears to have an infinite impedance when viewed from the other end. Therefore, the portion from the end portion of the second coaxial waveguide 620 to the connecting portion does not exist for microwave transmission, and the transmission line can be easily designed.

  The fifth coaxial waveguide 650 is connected to the output end of the internal conductor 630a (the output side end of the rod 630a1), and has a T branch. The first coaxial waveguide 610 is connected to both ends of the fifth coaxial waveguide 650 perpendicularly toward the back side of the drawing. With the above configuration, the microwave is input from the input portion of the second coaxial waveguide 620 to the coaxial waveguide distributor 700, transmitted through the second coaxial waveguide 620, and branched into the third coaxial waveguide 630. It is distributed and discharged from the plurality of adjacent dielectric plates 305 through the fifth and first coaxial tubes 650 and 610 into the processing container.

(4th coaxial pipe and T branch)
6 is a cross-sectional view taken along the line 4-4 of FIG. 5 and shows a connecting portion between the fourth coaxial waveguide 640 and the second coaxial waveguide 620. FIG. The connecting portion between the fourth coaxial waveguide 640 and the second coaxial waveguide 620 is bifurcated into a T shape (T branch). The tip of the inner conductor 640a of the fourth coaxial waveguide has a pipe 705 shape, and the inner conductor 620a passes through the inside of the pipe 705. As a result, the inner conductor 640a of the fourth coaxial waveguide and the inner conductor 620a of the second coaxial waveguide are brought into close contact with each other. The microwave is transmitted from the fourth coaxial waveguide 640 to the second coaxial waveguide 620.

  A groove is formed in the outer peripheral portion of the inner conductor 620a on both sides of the fourth coaxial waveguide 640, and a dielectric ring 710 is fitted in the groove. A groove is also formed in the outer peripheral portion of the inner conductor 640a of the fourth coaxial waveguide, and a dielectric ring 715 is fitted in the groove. The dielectric rings 710 and 715 are made of Teflon (registered trademark). Thereby, the inner conductors 620a and 640a of the second and fourth coaxial waveguides are supported by the outer conductors 620b and 640b, respectively.

  The outer conductor 640b of the fourth coaxial waveguide passes through the second coaxial waveguide and protrudes while being rounded like a bowl outward from the outer conductor 620b of the second coaxial waveguide. In this way, among the outer conductors of the two-branch output-side coaxial pipe (here, the second coaxial pipe 620), the outer conductor of the branch part (connection part) is made thicker than the outer conductors of the other parts. Thus, the space between the inner conductor 620a and the outer conductor 620b of the second coaxial waveguide is enlarged at the connecting portion, and reflection when the microwave is transmitted through the branch portion is suppressed.

  On the contact surface between the pipe 705 portion of the internal conductor 640a and the internal conductor 620a, a shield spiral 720 is provided on the outside, and an O-ring 725 is provided on the inside. The shield spiral 720 is for improving the electrical connection between the inner conductor 620a of the second coaxial waveguide and the inner conductor 640a of the fourth coaxial waveguide, and the O-ring 725 is configured such that the refrigerant is externally supplied from the refrigerant passage 910b. This is to prevent leakage.

  The inner conductor 640a of the fourth coaxial waveguide is slidably connected in the longitudinal direction of the second coaxial waveguide 620. The inner conductor 630a of the third coaxial waveguide is screwed to the second coaxial waveguide 620, but may be slidably connected in the longitudinal direction of the second coaxial waveguide 620. This is because stress is not applied to each coaxial tube with respect to thermal expansion of the member due to heating.

(Characteristic impedance)
In the two-branch system, two output-side coaxial tubes are connected in parallel to the input-side coaxial tube, so to match the impedance between the input and output, the input-side coaxial tube's characteristic impedance is What is necessary is just to make it 1/2 of an impedance. In this embodiment, the characteristic impedance of the fourth coaxial waveguide 640 (input-side coaxial tube) is set to 30Ω, and the characteristic impedance of the second coaxial waveguide 620 (output-side coaxial tube) is set to 60Ω. A relationship is established. Therefore, it is possible to transmit a high-power microwave while suppressing reflection at the branch portion.

(Connection portion between the third coaxial waveguide and the second coaxial waveguide)
Referring to FIG. 2, in the inner conductor 630a of the third coaxial waveguide, the rod 630a1 is fixed to the inner conductor connecting plate 630a2 by a screw S. Thus, in the connection part of the 2nd coaxial waveguide 620 and the 3rd coaxial waveguide 630, the 3rd coaxial waveguide 630 (rod 630a1) is opposed and connected with respect to the 2nd coaxial waveguide 620. . Note that only one third coaxial pipe 630 may be connected at each branch portion, or two or more third coaxial pipes 630 may be connected. Further, the third coaxial waveguides 630 may be coupled to face each other as in the present embodiment, but may not be opposed to each other.

  Of the inner conductor 630a of the third coaxial waveguide, a portion connected to the inner conductor 620a of the second coaxial waveguide (portion of the inner conductor connecting plate 630a2) is thinner than the other portions. This is to reduce disturbance in the transmission state of the microwaves transmitted through the second coaxial waveguide. Furthermore, the electrical length of the third coaxial waveguide 630 can be adjusted by changing the length and thickness of the thinned portion. By making the inner conductor 630a of the third coaxial waveguide thinner than the inner conductor 620a of the second coaxial waveguide, or by making the outer conductor 630b of the third coaxial waveguide thinner than the outer conductor 620b of the second coaxial waveguide. The disturbance of the transmission state of the microwave is reduced. The inner conductor connecting plate 630a2 and the inner conductor 620a of the second coaxial waveguide are fixed by brazing or soldering. Note that the third coaxial waveguide 630 also functions as an impedance conversion mechanism, which will be described later.

(5th coaxial pipe and T branch)
Next, the structure of the T branch by the third and fifth coaxial waveguides 630 and 650 will be described with reference to FIG. The third coaxial waveguide 630 connects the second coaxial waveguide 620 and the fifth coaxial waveguide 650 while bending. The inner conductor 650a of the fifth coaxial waveguide is made of copper like the inner conductors 620a and 630a of the second and third coaxial waveguides. The connecting portions of the inner conductors 630a and 650a of the third and fifth coaxial waveguides are soldered or brazed in a state where the inner conductor 630a of the third coaxial waveguide is fitted in the recess of the inner conductor 650a of the fifth coaxial waveguide. It is fixed by attaching.

  Grooves are formed on both sides of the T-branch on the outer periphery of the inner conductor 650a of the fifth coaxial waveguide, and a dielectric ring 730 is fitted in the groove. Thereby, the inner conductor 650a of the fifth coaxial waveguide is supported by the outer conductor 650b. The inner conductor 650a of the fifth coaxial waveguide is also supported from the side by the dielectric rod 735. The dielectric rod 735 is inserted into a hole provided in the inner conductor 650a of the fifth coaxial waveguide, and fixes the inner conductor 610a of the first coaxial waveguide to the fifth coaxial waveguide 650. The dielectric ring 730 and the dielectric rod 735 are made of Teflon.

(Impedance conversion mechanism)
Next, the impedance conversion mechanism of the third coaxial waveguide will be described.

  In order to eliminate the reflection in the coaxial waveguide distributor 700, the impedance when the third coaxial waveguide side is viewed from the connecting portion of the second coaxial waveguide 620 and the third coaxial waveguide 630 is a real number having a desired value. Good. If the output side of the third coaxial waveguide 630 is matched, the electrical length of the third coaxial waveguide 630 is designed to be approximately π / 2 rad so that the third coaxial waveguide side is viewed from the connecting portion. Impedance can be a real number. Furthermore, by changing the characteristic impedance of the third coaxial waveguide, the impedance when the third coaxial waveguide side is viewed from the connecting portion can be set to a desired value.

  As shown in FIG. 2, in the inner conductor 630a of the third coaxial waveguide described above, the portion (the inner conductor connecting plate 630a2) connected to the inner conductor 620a of the second coaxial waveguide is the other portion (the rod 630a1 portion). It is getting thinner. Thus, the electrical length of the third coaxial waveguide 630 can be increased by making the inner conductor 630a of the third coaxial waveguide thin.

  Although not shown, the third coaxial pipe inner conductor 630a can also be reduced by thinning the connecting portion of the fifth coaxial waveguide inner conductor 650a or by increasing the thickness of the outer conductor 630b. The electrical length of the coaxial tube 630 can be increased.

  Further, the connection portion between the inner conductor 650a of the fifth coaxial waveguide 650a and the inner conductor 630a of the third coaxial waveguide is made thin like the constricted portion 650a1 in FIG. 7 or the outer conductor 650b is made thicker. The electrical length of the third coaxial waveguide 630 can be increased.

  As described above, it is possible to adjust the electrical length of the third coaxial waveguide by providing the third coaxial waveguide 630 with a thinned portion or a thickened portion and adjusting the length and thickness thereof. it can. Further, the electrical length of the connected coaxial pipe can be adjusted by adjusting the length and thickness of the coaxial pipe (here, the second and fifth coaxial pipes) connected to the third coaxial pipe. it can. By these adjusting means (impedance conversion mechanism), the cell pitch Pi1 (see FIG. 1) in the direction perpendicular to the second coaxial waveguide 620 can be determined relatively freely. Furthermore, by bending the third coaxial waveguide 630, the cell pitch Pi2 in the direction horizontal to the second coaxial waveguide 620 can be determined relatively freely.

  Thereby, the vertical and horizontal sizes of the cells can be freely determined according to the substrate size without being restricted by the wavelength in the tube of the microwave. Normally, uniform plasma processing can be performed if the plasma excitation area Ea is enlarged by about 60 mm to 80 mm with respect to the substrate size. Therefore, by setting the plasma excitation region Ea to a region that satisfies the above conditions and is slightly larger than the size of the glass substrate, the plasma excitation region does not become larger than necessary, and power consumption can be reduced. It is also possible to avoid the entire apparatus becoming larger than necessary.

(Impedance buffer)
The thicker the inner conductor, the smaller the characteristic impedance, and the thinner the inner conductor, the larger the characteristic impedance. Therefore, when the inner conductor 630a of the third coaxial waveguide having a different thickness and the inner conductor 650a between the fifth coaxial are directly connected, the characteristic impedance is greatly different, so that reflection is increased at the connection portion. Therefore, the constricted portion 650a1 of the connecting portion between the inner conductor 650a of the fifth coaxial waveguide and the inner conductor 630a of the third coaxial waveguide also has a function of reducing reflection. In this way, the constricted portion 650a1 serves as an impedance buffer portion, and can be connected while gradually changing the characteristic impedance, suppressing the reflection of the microwave, and the microwave on the left and right of the fifth coaxial waveguide 650. Can be made easier to enter. Furthermore, in accordance with the curved shape of the third coaxial tubes 630, as well as the thickness of the constricted portion 650A1, of the inner conductor 650a of the fifth coaxial waveguide from the midpoint R ₁ of the right waist of the length Lr and left By making the constriction length Ll different, it is possible to transmit microwaves of equal power to the left and right of the fifth coaxial waveguide 650.

  In the case of a symmetric multi-branch, the impedances viewed from both ends from the input part In of the second coaxial waveguide 620 can be matched, and the impedance viewed from the load side from the fourth coaxial waveguide 640 can be matched. You can also. As a result, there is no reflection when viewed from the input side of the coaxial waveguide distributor 700, and a high-power microwave can be transmitted. If the following conditions are satisfied, the impedance of the second coaxial waveguide 620 viewed from the load side can be matched.

That is, when the impedance of the third coaxial waveguide 610 viewed from the plasma side is matched, the impedance viewed from the output end of the third coaxial waveguide 630 is generally resistive, and the third coaxial waveguide 610 R _{r5 is} the resistance viewed from the output end of 630 and the number of the third coaxial waveguides 630 connected between the input portion of the second coaxial waveguide 620 and the end of the second coaxial waveguide 620. N _s , where the characteristic impedance of the second coaxial waveguide 620 is Z _c2 , the characteristic impedance Z _c3 of the third coaxial waveguide 630 is approximately equal to (R _r5 × N _s × Z _c2 ) ^1/2. The electrical length is π / 2 rad. For example, in the case of 8 branches shown in FIG. 4, two fifth coaxial waveguides 650 having a characteristic impedance of 30Ω are connected in parallel to the output end of the third coaxial waveguide 630. _r5 = 15Ω. If N _s = 4 and Z _c2 = 60Ω, Z _c3 may be set to 60Ω.

In addition, the impedance of the third coaxial waveguide side seen from the connection portion between the second coaxial waveguide 620 and the third coaxial waveguide 630 is generally resistive, and the second coaxial waveguide 620 and the third coaxial waveguide 630 are in resistance. The third coaxial _waveguide connected between the input portion In of the second coaxial waveguide 620 and one end of the second coaxial waveguide 620 is R _r3 when the third coaxial waveguide side is viewed from the connecting portion with R _r3 . 630 number of _{N s,} when the characteristic impedance of the second coaxial waveguide 620 and the _{Z c2,} to equalize the characteristic impedance _{Z c2} of the second coaxial waveguide 620 generally in _R r3 / _{N s.}

For example, in the case of eight branches shown in FIG. 4, R _r3 = 240 and Z _c2 = 240/4 = 60Ω, and the above relationship is satisfied.

(Second Embodiment: Asymmetric 6 branches)
Next, the branch circuit of the glass substrate for G4.5 concerning 2nd Embodiment is demonstrated, referring FIG.8 and FIG.9. FIG. 8 is a schematic diagram of a branch circuit including the coaxial waveguide distributor 700 according to this embodiment. FIG. 9 shows a ceiling surface of the microwave plasma processing apparatus 10 according to the present embodiment. In the present embodiment, the coaxial pipe is multi-branched with six asymmetric branches. The size of the glass substrate for G4.5 is 730 × 920 mm.

  In the present embodiment, as illustrated in FIG. 8, the transmission line 900a includes a waveguide, a coaxial waveguide converter, and a plurality of coaxial tubes. Microwaves output from one microwave source 900 are transmitted to the coaxial waveguide converter while being branched into three by the waveguide, and are transmitted to the coaxial tube distributor 700 via the fourth coaxial tube 640. . The coaxial pipe distributor 700 has a multi-branch structure including a third coaxial pipe 630 that is asymmetrically branched into six second coaxial pipes 620 having an input part In.

As shown in FIG. 9, the number of cells is uniformly arranged in a total of 36 cells in six rows in the substrate longitudinal direction and the substrate short direction. Input unit In the middle of the connecting portion _{A 2} and the connecting portion _{A 3,} is the midpoint of the connecting portion _{A 4} and young properly connecting portion _{A 3.} As described above, in the case of a symmetric multi-branch, impedances viewed from both ends from the input part In of the second coaxial waveguide 620 can be matched, and the load side can be viewed from the fourth coaxial waveguide 640. The impedance can be matched.

  However, in the case of asymmetric multi-branch, if the impedances viewed from both ends from the input part In of the second coaxial waveguide 620 are matched, the microwave power transmitted to the left and right becomes equal. The power of the microwave to be supplied is different on the left and right. For this reason, the impedance of the second coaxial waveguide 620 as viewed from both ends from the input portion In cannot be matched. However, if the following conditions are satisfied, the impedance of the fourth coaxial waveguide 640 viewed from the load side can be matched. As a result, high-power microwaves can be transmitted.

That is, when the fourth coaxial waveguide 640 having a characteristic impedance of _Zc4 is connected to the input portion In of the second coaxial waveguide 620 and the impedance of the first coaxial waveguide 610 viewed from the plasma side is matched. The impedance viewed from the output end of the third coaxial waveguide 630 is generally resistive, and the resistance viewed from the output end of the third coaxial waveguide 630 is R _r5 , the second coaxial waveguide 620. And the characteristic impedance Z _c3 of the third coaxial waveguide 630 is approximately equal to (R _r5 × N _t × Z _c4 ) ^1/2 , where N _t is the number of the third coaxial waveguides 630 connected to The electrical length is π / 2 rad. For example, in the case of the six branches shown in FIG. 8, two fifth coaxial waveguides 650 having a characteristic impedance of 30Ω are connected in parallel to the output end of the third coaxial waveguide 630. _r5 = 15Ω. Further, if N _t = 6, Z _c4 = 30Ω, Z _c3 may be set to 52Ω.

Further, the impedance of the third coaxial waveguide side viewed from the connection portion of the second coaxial waveguide 620 and the third coaxial waveguide 630 is generally resistive, and the third coaxial waveguide side is viewed from the connection portion. When the resistance is R _r3 and the number of the third coaxial waveguides 630 connected to the second coaxial waveguide 620 is N _t , the characteristic impedance Z _c4 is made approximately equal to R _r3 / N _t .

For example, in the case of 6 branches shown in FIG. 8, R _r3 = 180, Z _c4 = 180/6 = 30Ω, and the above relationship is satisfied.

In the case of the symmetric multi-branch, since the impedances viewed from both ends from the input part of the second coaxial waveguide 620 can be matched, there is no standing wave at the connection parts A _{2 to} A _3. The interval between the connecting portions A _{2 to} A ₃ was arbitrary. On the other hand, in the case of an asymmetric branch, the portion of the connecting portion A ₂ to A ₃ have generated a standing wave, the electrical length between the connecting portions A ₂ to A _3, at the integer multiples (the embodiment of 2πrad 1 times).

However, when the coaxial tube is connected to the input part, the propagation mode is disturbed around the connection part, so that the electrical length changes. In order to correct this deviation in electrical length, a dielectric ring 710 made of Teflon is provided between the input portion In and the connecting portion A ₂ and between the input portion and the connecting portion A ₃ . By optimizing the thickness, position, and dielectric constant of the dielectric ring 710, microwaves having the same amplitude and phase can be transmitted to the branch destination even in asymmetric multi-branching.

(Third embodiment)
Next, the branch circuit of the glass substrate for G10 concerning 3rd Embodiment is demonstrated, referring FIG.10 and FIG.11. FIG. 10 is a schematic diagram of a branch circuit including the coaxial waveguide distributor 700. FIG. 11 shows a waveguide distributor 850 mounted on a microwave plasma processing apparatus. In this embodiment, the coaxial pipe is multi-branched with eight symmetrical branches. The size of the glass substrate for G10 is 2880 × 3080 mm.

  The waveguide distributor 850 has a tournament type 2 × 2 × 2 branch formed in a planar shape. A waveguide 850 branches symmetrically on both sides with respect to the microwave source 900 and the tuner. Since it is configured in a planar shape, the thickness of the waveguide 850 (the length in the direction perpendicular to the paper surface of FIG. 11) is thin and can be easily placed on the apparatus.

  The number of cells is equally arranged in a total of 256 cells in 16 rows in the substrate longitudinal direction and the substrate short direction. Eight branches of coaxial pipe symmetry are arranged in two rows in the horizontal direction and eight rows in the vertical direction.

(Modification of impedance conversion mechanism)
Next, a modification of the impedance conversion mechanism will be briefly described with reference to FIG. As shown in FIG. 5, the third coaxial waveguide 630 according to each of the above-described embodiments is curved, whereas the third coaxial waveguide 630 according to this modification has a rod shape, and the second Are connected obliquely to the coaxial tube. This also allows the third coaxial waveguide 630 to function as an impedance conversion mechanism, thereby suppressing reflection when viewed from the distributor input side and transmitting a high-power microwave.

(Fourth embodiment: modification of coaxial pipe distributor)
Finally, a modification of the coaxial waveguide distributor 700 according to the fourth embodiment will be briefly described with reference to FIGS. 13 to 15. FIG. 13 is a cross-sectional view of the microwave plasma processing apparatus according to the present embodiment. FIG. 13 shows an 8-OO′-8 cross section of FIG. FIG. 14 shows a 6-6 cross section of FIG. FIG. 15 shows a 7-7 cross section of FIG. The microwave plasma processing apparatus 10 according to the fourth embodiment is for a semiconductor substrate having a wafer size of 300 mm in diameter.

  In the present embodiment, the fourth coaxial waveguide 640 is T-branched to the third coaxial waveguide 630 (rod 630a1 and internal conductor connecting plate 630a2), and the third coaxial waveguide 630 is the fifth coaxial waveguide 650. T-branch to The branch portion of the third coaxial waveguide 630 has a narrower portion 630a11 that is narrower than the other portions. The T branch from the third coaxial waveguide 630 to the fifth coaxial waveguide 650 is basically the same as the T branch of FIG. 5, and the third coaxial waveguide 630 performs impedance conversion. However, in this embodiment, the third coaxial waveguide 630 is not curved, and the inner conductor 630a of the third coaxial waveguide is vertically connected to the inner conductor 650 of the fifth coaxial waveguide.

  Two fifth coaxial waveguides 650 having a characteristic impedance of 30Ω are connected in parallel to the output end of the third coaxial waveguide. Therefore, when the impedance of the first coaxial waveguide 610 viewed from the plasma side is matched, the impedance viewed from the output end of the third coaxial waveguide 630 is 30/2 = 15Ω. On the other hand, the characteristic impedance of the fourth coaxial waveguide 640 is 50Ω. Therefore, if the impedance when the third coaxial waveguide side is viewed from the connecting portion of the fourth coaxial waveguide and the third coaxial waveguide is 50 × 2 = 100Ω, the reflection in the distributor is eliminated and the high power micro Can transmit waves. The impedance conversion from 15Ω to 100Ω is performed by a third coaxial waveguide having an electrical length of π / 2 rad.

  In the present embodiment, a constricted portion 630a11 is provided on the inner conductor 630a side of the connecting portion. The electrical length of the third coaxial waveguide 630 is adjusted by the diameter and length of the constricted portion 630a11.

  Note that, in the outer conductor of the output-side coaxial tube that constitutes the two branches (the outer conductor 650b of the fifth coaxial tube in FIG. 15), the connecting portion may be thicker than the other portions.

  According to the microwave plasma processing apparatus 10 according to the first to third embodiments and the modification described above, at least one stage of the coaxial tube distributor 700 is connected to the second coaxial tube 620 through the second coaxial tube. The multi-branch branches into three or more third coaxial pipes 630 that are non-perpendicularly connected to the pipe 620. The third coaxial waveguide 630 has a mechanism for adjusting the characteristic impedance, and the characteristic impedance on the input side (electromagnetic wave source side) of the third coaxial waveguide 630 is set to the output side (plasma side) of the third coaxial waveguide 630. Can be matched to the characteristic impedance. As a result, microwave transmission efficiency can be improved.

  Further, according to the microwave plasma processing apparatus 10 according to the fourth embodiment, at least one stage of the coaxial tube distributor 700 is branched due to the difference in characteristic impedance between the input-side coaxial tube and the output-side coaxial tube. Impedance can be matched at the part. As a result, a high-power microwave can be transmitted.

  In each of the embodiments described above, the microwave source 900 that outputs a microwave of 915 MHz has been described. However, a microwave source that outputs a microwave of 896 MHz, 922 MHz, 2.45 GHz, or the like may be used. The microwave source is an example of an electromagnetic wave source that generates an electromagnetic wave for exciting plasma, and includes a magnetron and a high-frequency power source as long as the electromagnetic wave source outputs an electromagnetic wave of 100 MHz or higher.

  Further, the shape of the metal electrode 310 is not limited to a quadrangular shape, and may be a triangular shape, a hexagonal shape, or an octagonal shape. In this case, the shape of the dielectric plate 305 and the metal cover 320 is the same as the shape of the metal electrode 310. The metal cover 320 and the side cover may or may not be present. When there is no metal cover 320, a gas flow path is formed directly in the lid 300. Further, there may be no gas discharge hole, no gas discharge function, or a lower shower may be provided. The number of metal electrodes 310 and dielectric plates 305 is not limited to eight, and may be one or more.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, the impedance conversion mechanism of the third coaxial waveguide 630 includes a mechanism extending non-perpendicularly from the second coaxial waveguide 620, an inner conductor 620a of the second coaxial waveguide, and an inner conductor 630a of the third coaxial waveguide. An impedance conversion mechanism made of a dielectric such as Teflon may be combined in between.

  In the present invention, if at least one stage of the coaxial waveguide distributor 700 includes the second coaxial waveguide 620 and three or more third coaxial waveguides 630, other transmission lines are included. Also good. In addition, each third coaxial waveguide 630 extends in a curved manner even if it extends obliquely from the second coaxial waveguide 620 as long as it extends non-perpendicularly with respect to the second coaxial waveguide. Or other shapes.

  The plasma processing apparatus is not limited to the above-described microwave plasma processing apparatus, and may be any apparatus that finely processes an object to be processed by plasma, such as a film formation process, a diffusion process, an etching process, an ashing process, or a plasma doping process.

  Further, for example, the plasma processing apparatus according to the present invention can process a large-area glass substrate, a circular silicon wafer, and a square SOI (Silicon On Insulator) substrate.

It is the figure which showed the ceiling surface of the microwave plasma processing apparatus which concerns on 1st Embodiment (2-2 cross section of FIG. 2). It is 1-O-O'-1 sectional drawing of FIG. It is an enlarged view of the area | region Ex of FIG. It is the figure which showed the branch circuit concerning the embodiment. FIG. 3 is a cross-sectional view taken along the line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along 4-4 in FIG. 5. It is a figure for demonstrating the function of an impedance converter. It is the figure which showed the branch circuit concerning 2nd Embodiment. It is the figure which showed the cut surface of the cover body which concerns on the same embodiment. It is the figure which showed the branch circuit concerning 3rd Embodiment. It is the figure which showed typically the waveguide branch and coaxial tube multi-branch concerning the embodiment. It is the figure which showed the coaxial pipe distributor concerning a modification. It is a longitudinal cross-sectional view of the microwave plasma processing apparatus concerning 4th Embodiment. It is 6-6 sectional drawing of FIG. It is 7-7 sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Microwave plasma processing apparatus 100 Processing container 300 Cover body 305 Dielectric board 310 Metal electrode 320 Metal cover 350 Side cover 610 1st coaxial tube 620 2nd coaxial tube 630 3rd coaxial tube 630a1 Rod 630a11, 650a1 Constriction part 630a2 Inner conductor connecting plate 640 Fourth coaxial tube 650 Fifth coaxial tube 700 Coaxial tube distributor 705 Dielectric ring 900 Microwave source Cel Unit cell

Claims (27)

A plasma processing apparatus that plasmas a target object by exciting a gas with electromagnetic waves,
A processing vessel;
An electromagnetic wave source that outputs electromagnetic waves;
A transmission line for transmitting electromagnetic waves output from the electromagnetic wave source;
A plurality of dielectric plates provided on the inner wall of the processing container and emitting electromagnetic waves into the processing container;
A plurality of first coaxial waveguides adjacent to the plurality of dielectric plates and transmitting electromagnetic waves to the plurality of dielectric plates;
One or two or more stages of coaxial pipe distributors for distributing and transmitting electromagnetic waves transmitted through the transmission line to the plurality of first coaxial pipes,
At least one stage of the coaxial pipe distributor includes a second coaxial pipe having an input portion and three or more third coaxial pipes connected to the second coaxial pipe,
Each of the third coaxial waveguides is a plasma processing apparatus having a portion extending non-perpendicular to the second coaxial waveguide.   The plasma processing apparatus according to claim 1, wherein each third coaxial waveguide has an impedance conversion mechanism.   The number of connecting portions between the second coaxial waveguide and the third coaxial waveguide between the input portion of the second coaxial waveguide and the end of the second coaxial waveguide is 2 or less. The plasma processing apparatus according to claim 1.   4. The electrical length between the connecting portions between the connecting portions of the second coaxial waveguide and the third coaxial waveguide where the input portion is not interposed is approximately equal to an integral multiple of π rad. The plasma processing apparatus described.   5. The plasma processing according to claim 4, wherein an electrical length between connection portions between the connection portions of the second coaxial waveguide and the third coaxial waveguide not including the input portion is approximately equal to an integral multiple of 2π rad. apparatus.   6. The connection portion between the second coaxial waveguide and the third coaxial waveguide, wherein the third coaxial waveguide is connected to the second coaxial waveguide two by two. The plasma processing apparatus described in 1.   The plasma processing apparatus according to claim 1, wherein the third coaxial waveguide is curved.   The plasma processing apparatus according to claim 1, wherein the third coaxial waveguide is obliquely connected to the second coaxial waveguide.   The plasma processing apparatus according to claim 1, wherein an inner conductor of the third coaxial waveguide is thinner than an inner conductor of the second coaxial waveguide.   The plasma processing apparatus according to claim 1, wherein an outer conductor of the third coaxial waveguide is thinner than an outer conductor of the second coaxial waveguide. The inner conductor and the outer conductor of the second coaxial waveguide are short-circuited at at least one end of the second coaxial waveguide,
The electrical length from the end of the second coaxial waveguide to the connecting portion between the second coaxial waveguide and the third coaxial waveguide closest to the end is approximately equal to an odd multiple of π / 2 rad. The plasma processing apparatus described in any one of 1-10. When the impedance of the first coaxial waveguide viewed from the plasma side is matched, the impedance of the third coaxial waveguide viewed from the connecting portion of the second coaxial waveguide and the third coaxial waveguide is Is generally resistant,
The resistance of the third coaxial waveguide connected from the input portion of the second coaxial waveguide to one end of the second coaxial waveguide is R _r3 when the third coaxial waveguide is seen from the coupling portion. the number _{N s,} the characteristic impedance of the second coaxial waveguide when the _{Z c2,} to one of the characteristic impedance _{Z c2} of the second coaxial waveguide is approximately _R r3 / _{N s} equal claims 1 to 11 The plasma processing apparatus described. A fourth coaxial tube having a characteristic impedance of _Zc4 is connected to the input portion of the second coaxial waveguide, and when the impedance of the first coaxial waveguide viewed from the plasma side is matched, the second coaxial tube is matched. The impedance when the third coaxial waveguide side is viewed from the connecting portion of the coaxial coaxial tube and the third coaxial waveguide is generally resistive.
The characteristic impedance Z _c4 is approximately R, where R _{r3 is} the resistance when the third coaxial waveguide side is viewed from the connecting portion, and N _t is the number of the third coaxial waveguides connected to the second coaxial waveguide. _The plasma processing apparatus according to claim 1, which is equal to _{r 3} / N _t .   The plasma processing apparatus according to claim 1, wherein an electrical length of the third coaxial waveguide is approximately π / 2 rad.   The plasma processing apparatus according to claim 1, wherein, of the inner conductor of the third coaxial waveguide, a connection portion with the second coaxial waveguide is thinner than other portions. When the impedance viewed from the first coaxial waveguide viewed from the plasma side is matched, the impedance viewed from the output end of the third coaxial waveguide is generally resistive, and the impedance of the third coaxial waveguide is R _{r5 is} a resistance viewed from the output end to the output side, N _{s is} the number of third coaxial tubes connected between the input portion of the second coaxial waveguide and one end of the second coaxial waveguide, when the characteristic impedance of the second coaxial tube was _{Z c2,} the third characteristic impedance _{Z c3} of the coaxial tube is generally _{(R r5 × N s × Z} c2) 1/2 is equal claim 14 or claim The plasma processing apparatus according to any one of 15. A fourth coaxial waveguide having a characteristic impedance of _Zc4 is connected to the input portion of the second coaxial waveguide, and when the impedance of the first coaxial waveguide viewed from the plasma side is matched, the third coaxial tube is matched. The impedance viewed from the output end of the coaxial tube is generally resistive, and the resistance viewed from the output end of the third coaxial tube is connected to R _r5 , the second coaxial tube. the third number of coaxial tubes when the _{N t,} the third characteristic impedance _{Z c3} of the coaxial tube is generally _{(R r5 × N t × Z} c4) 1/2 is equal claim 14 or claim 15 The plasma processing apparatus described in any one of.   The plasma processing apparatus according to claim 1, wherein a connecting portion between the output end of the third coaxial waveguide and the fifth coaxial waveguide is a T branch.   19. The plasma processing apparatus according to claim 18, wherein at least one of the inner conductor of the third coaxial waveguide and the inner conductor of the fifth coaxial waveguide has a narrower T-branch connecting portion than other portions.   Of the narrowed portion of the inner conductor of the fifth coaxial waveguide, the length of the portion from the T-branch connecting portion toward one branch destination and the portion from the T-branch connecting portion toward the other branch destination The plasma processing apparatus according to claim 19, wherein the plasma processing apparatus is different from the length.   The outer conductor of the third coaxial waveguide or the outer conductor of the fifth coaxial waveguide is described in any one of claims 18 to 20, wherein the branch portion of the T branch is thicker than the other portion. Plasma processing equipment. A plurality of metal electrodes that are electrically connected to the inner wall of the processing vessel and are adjacent to the plurality of dielectric plates on a one-to-one basis;
Each dielectric plate is exposed from between the adjacent metal electrodes and the inner wall of the processing vessel in which each dielectric plate is not disposed,
When each dielectric plate is arranged, the inner wall of the processing vessel in which each dielectric plate is not arranged or the metal cover provided on the inner wall is substantially similar in shape, or substantially The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus has a symmetrical shape. A plasma processing apparatus that plasmas a target object by exciting a gas with electromagnetic waves,
A processing vessel;
An electromagnetic wave source that outputs electromagnetic waves;
A transmission line for transmitting electromagnetic waves output from the electromagnetic wave source;
A plurality of dielectric plates provided on the inner wall of the processing container and emitting electromagnetic waves into the processing container;
A plurality of first coaxial waveguides adjacent to the plurality of dielectric plates and transmitting electromagnetic waves to the plurality of dielectric plates;
One or two or more stages of coaxial pipe distributors for distributing and transmitting electromagnetic waves transmitted through the transmission line to the plurality of first coaxial pipes,
At least one of the coaxial tube distributors is a plasma processing apparatus in which characteristic impedances of an input-side coaxial tube and an output-side coaxial tube are different. The connecting portion between the input-side coaxial tube and the output-side coaxial tube has two branches,
24. The plasma processing apparatus according to claim 23, wherein in the two branches, twice the characteristic impedance of the input-side coaxial tube is substantially equal to the characteristic impedance of the output-side coaxial tube.   25. The plasma processing apparatus according to claim 24, wherein, of the outer conductors of the output-side coaxial tube constituting the two branches, the connecting portion is thicker than the other portions. Introducing gas into the processing vessel,
Output electromagnetic waves from an electromagnetic source,
Transmit the output electromagnetic wave to the transmission line,
The electromagnetic wave transmitted through the transmission line is distributed from a single stage or two or more stages of coaxial pipe distributors to a plurality of first coaxial pipes, and transmitted.
The electromagnetic wave transmitted through the first coaxial waveguide is emitted into the processing container from a plurality of dielectric plates provided on the inner wall of the processing container,
When transmitting electromagnetic waves to the coaxial tube distributor, at least one of the coaxial tube distributors has a second coaxial tube having an input portion and three or more third coaxials connected to the second coaxial tube. An electromagnetic wave is transmitted to each third coaxial waveguide having a portion extending non-perpendicular to the second coaxial waveguide, and is emitted into the processing container via the first coaxial waveguide. A plasma processing method for plasma processing a target object by exciting the gas with an electromagnetic wave. Introducing gas into the processing vessel,
Output electromagnetic waves from an electromagnetic source,
Transmit the output electromagnetic wave to the transmission line,
One or two or more stages of coaxial tubes are formed, and at least in one of the stages, the transmitted electromagnetic waves are transmitted through a plurality of first electromagnetic waves by coaxial tube distributors having different characteristic impedances between the input-side coaxial tube and the output-side coaxial tube. Distribute and transmit to the coaxial pipe
Transmitting electromagnetic waves to a plurality of dielectric plates adjacent to the plurality of first coaxial tubes and provided on the inner wall of the processing vessel,
An electromagnetic wave is emitted from the plurality of dielectric plates into the processing container,
A plasma processing method in which a gas is excited by the emitted electromagnetic wave to plasma-treat an object to be processed in the processing container.

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