JP2009099975A - Plasma processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slot antenna type microwave plasma processing device for controlling electric field distribution in the vicinity of a slot antenna and uniformly controlling plasma to be generated. <P>SOLUTION: The plasma processing device 100 includes a plurality of stubs 43 as a second waveguide for adjusting field distribution to be formed on a planar antenna plate 31 configuring a flat waveguide. The stubs 43 are provided so as to penetrate through a conductive cover member 34 on the upper part of slots 32 formed on the external periphery of the planar antenna plate 31. The stubs 43 are disposed symmetrically in their diameter direction with the center of the planar antenna plate 31 sandwiched. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus for processing an object to be processed by plasma generated by introducing a microwave to a processing container using a planar antenna having a plurality of slots.

  As a plasma processing apparatus that performs plasma processing such as oxidation processing and nitriding processing on an object to be processed such as a semiconductor wafer, a slot antenna is used to generate plasma by introducing, for example, a microwave with a frequency of 2.45 GHz into the processing container. There is known a plasma processing apparatus of the type to be used (for example, Patent Document 1 and Patent Document 2). In such a microwave plasma processing apparatus, it is possible to form surface wave plasma in a processing container by generating plasma having a high plasma density.

  In the slot antenna type plasma processing apparatus, even if apparatuses of the same specifications are operated under the same conditions, there is a slight difference in plasma distribution between the apparatuses. In addition, when there is a slot arrangement in the slot antenna, the shape of the microwave transmitting plate or the slow wave material, or a difference in material, there is a problem that a reflected wave is generated and a loss of microwave power occurs. Further, if it is attempted to change the conditions of the processing performed in the plasma processing apparatus, the plasma in the processing container tends to be unstable or non-uniform. In order to stabilize the plasma under the changed conditions, the slot arrangement and shape of the slot antenna, the shape of the microwave transmission plate, etc. must be changed, which requires major equipment modifications for each process. There was a problem. In particular, when processing a substrate such as a large semiconductor wafer, if the plasma becomes unstable or non-uniform in the processing vessel, non-uniform processing results are likely to occur within the surface of the substrate.

  In an electron cyclotron resonance (ECR) type microwave plasma processing apparatus, stubs are provided at predetermined intervals along a coaxial line coupled to a microwave power source for the purpose of uniformly distributing the microwave power near the periphery of the plasma forming unit. There has been a proposal to dispose (for example, Patent Document 3). Further, in a plasma processing apparatus using high-frequency power of 100 MHz to 1000 MHz, a stub that forms a capacitance and creates a resonance state between the upper surface of the antenna container and the rod is disposed on the upper surface of the antenna container having a radial rod. Technology has also been proposed (for example, Patent Document 4).

Japanese Patent Laid-Open No. 11-260594 JP 2001-223171 A Special Table 2000-514595 JP-A-11-297494

  Neither of the plasma processing apparatuses described in Patent Document 3 and Patent Document 4 is a slot antenna type plasma processing apparatus. Thus, in the slot antenna type microwave plasma processing apparatus, without changing the shape and arrangement of the slot, the technology for ensuring the uniformity of the plasma by a member that adjusts the electromagnetic field by the microwave, such as a stub, Until now, it has not been fully studied.

The present invention has been made in view of the above circumstances, and in a slot antenna type microwave plasma processing apparatus, by controlling the electric field distribution near the slot antenna and forming a uniform electric field distribution over the entire slot antenna, The purpose is to make the generated plasma uniform.

The plasma processing apparatus according to the present invention includes:
A processing container that can be evacuated to accommodate a workpiece;
A transmission plate that is airtightly attached to the upper opening of the processing vessel and transmits microwaves for plasma generation;
A planar antenna that has a plurality of slots formed through a flat substrate made of a conductive material and is arranged on the transmission plate to introduce microwaves into the processing container;
A conductive cover member covering the planar antenna from above;
A first waveguide provided through the conductive cover member and supplying microwaves from a microwave generation source to the planar antenna;
A plurality of second waveguides arranged above the outer periphery of the planar antenna, for adjusting the electric field distribution in the planar antenna;
It has.

  In the plasma processing apparatus according to the present invention, the second waveguide may be disposed within a range of 2 to 4.

  In the plasma processing apparatus according to the present invention, at least two of the second waveguides may be arranged symmetrically in the radial direction with the center of the planar antenna interposed therebetween.

  In the plasma processing apparatus according to the present invention, the second waveguide may be disposed above a line connecting the slots from the center of the planar antenna toward the radially outward direction.

  Further, in the plasma processing apparatus according to the present invention, the slots are concentrically arranged as a slot pair in the flat substrate, and the second waveguide has a diameter of the slot pair. It may be arranged above the inner slot in the direction or above the outer slot.

  In the plasma processing apparatus according to the present invention, the center of the second waveguide may be positioned so as to overlap the center of the opening of the slot.

  In the plasma processing apparatus according to the present invention, a part or the whole of the second waveguide may be constituted by a hollow member having a cavity inside inserted into the conductive cover member.

  In the plasma processing apparatus according to the present invention, a part or the whole of the second waveguide may be configured by an opening that penetrates the conductive cover member.

  In the plasma processing apparatus according to the present invention, a part or the whole of the second waveguide may be configured by a recess formed in the conductive cover member.

  In the plasma processing apparatus according to the present invention, the upper end portion of the second waveguide may be closed.

  The plasma processing apparatus according to the present invention may further include a retardation plate for adjusting a wavelength of a microwave supplied to the planar antenna on the planar antenna.

  According to the present invention, in a plasma processing apparatus including a planar antenna having a plurality of slots, a plurality of second waveguides for adjusting the electric field distribution in the planar antenna are provided in the flat waveguide configured by the planar antenna. By providing, the electric field strength in the planar antenna can be made uniform. As a result, the reflection coefficient (reflected wave) of the microwave to the first waveguide is suppressed, and the microwave absorption efficiency with respect to the plasma generated in the processing container can be increased. In addition, plasma can be stably generated in the processing container, and the plasma distribution can be made uniform. Therefore, even when the object to be processed is a large substrate, there is an effect that uniform processing can be performed in the surface.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a schematic configuration of a plasma processing apparatus 100 according to a first embodiment of the present invention. FIG. 2 is a plan view showing a planar antenna of the plasma processing apparatus 100 of FIG. FIG. 3 is a perspective view showing a schematic configuration of the upper surface of the plasma processing apparatus 100 of FIG. FIG. 4 is a diagram showing a schematic configuration example of a control system in the plasma processing apparatus 100 of FIG.

The plasma processing apparatus 100 generates plasma by introducing a microwave into a processing container using a planar antenna having a plurality of slot-shaped holes, particularly a RLSA (Radial Line Slot Antenna). It is configured as a plasma processing apparatus that can generate microwave-excited plasma having a density and a low electron temperature. In the plasma processing apparatus 100, processing with plasma having a plasma density of 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ and a low electron temperature of 0.7 to 2 eV is possible. Therefore, the plasma processing apparatus 100 can be suitably used in the manufacturing process of various semiconductor devices.

  The plasma processing apparatus 100 includes, as main components, an airtight processing container 1, a gas supply mechanism 18 for supplying gas into the processing container 1, and an exhaust mechanism for evacuating the processing container 1 under reduced pressure. An exhaust device 24, a microwave introduction mechanism 27 that is provided in the upper portion of the processing container 1 and introduces microwaves into the processing container 1, and a control unit 50 as a control unit that controls each component of the plasma processing apparatus 100. And. Note that the gas supply mechanism 18, the exhaust device 24, and the microwave introduction mechanism 27 constitute plasma generating means for generating plasma in the processing container 1.

  The processing container 1 is a substantially cylindrical container that is grounded. Note that the processing container 1 may be formed in a rectangular tube shape. The processing container 1 has a bottom wall 1a and a side wall 1b made of a material such as aluminum.

  Inside the processing container 1 is provided a mounting table 2 for horizontally supporting a silicon wafer (hereinafter simply referred to as “wafer”) W which is an object to be processed. The mounting table 2 is made of a material having high thermal conductivity, such as ceramics such as AlN. The mounting table 2 is supported by a cylindrical support member 3 extending upward from the center of the bottom of the exhaust chamber 11. The support member 3 is made of ceramics such as AlN, for example.

Further, the mounting table 2 is provided with a cover ring 4 that covers the outer edge portion thereof and guides the wafer W. The cover ring 4 is an annular member made of a material such as quartz, AlN, Al ₂ O ₃ , or SiN.

  In addition, a resistance heating type heater 5 as a temperature adjusting mechanism is embedded in the mounting table 2. The heater 5 is heated by the heater power supply 5a to heat the mounting table 2 and uniformly heats the wafer W, which is a substrate to be processed, with the heat.

  The mounting table 2 is provided with a thermocouple (TC) 6. By measuring the temperature with the thermocouple 6, the heating temperature of the wafer W can be controlled in a range from room temperature to 900 ° C., for example.

  The mounting table 2 is provided with wafer support pins (not shown) for supporting the wafer W and raising and lowering it. Each wafer support pin is provided so as to protrude and retract with respect to the surface of the mounting table 2.

  A cylindrical liner 7 made of quartz is provided on the inner periphery of the processing container 1. In addition, a quartz baffle plate 8 having a large number of exhaust holes 8 a is annularly provided on the outer peripheral side of the mounting table 2 in order to uniformly exhaust the inside of the processing container 1. The baffle plate 8 is supported by a plurality of support columns 9.

  A circular opening 10 is formed at a substantially central portion of the bottom wall 1 a of the processing container 1. An exhaust chamber 11 that communicates with the opening 10 and protrudes downward is provided on the bottom wall 1a. An exhaust pipe 12 is connected to the exhaust chamber 11 and is connected to an exhaust device 24 via the exhaust pipe 12.

  A metal plate 13 having a function as a lid (lid) for opening and closing the processing container 1 and having an opening is joined to the upper end of the processing container 1. The inner peripheral lower part of the plate 13 protrudes toward the inner side (inside the processing container space) to form an annular support part 13a.

  An annular gas introduction part 15 is provided on the side wall 1 b of the processing container 1. The gas introduction unit 15 is connected to a gas supply mechanism 18 that supplies an oxygen-containing gas and a plasma excitation gas. The gas introduction part 15 may be provided in a nozzle shape or a shower shape.

  Further, on the side wall 1b of the processing container 1, a loading / unloading port 16 for loading / unloading the wafer W between the plasma processing apparatus 100 and a transfer chamber (not shown) adjacent to the plasma processing apparatus 100, and the loading / unloading port 16 are provided. And a gate valve 17 for opening and closing.

The gas supply mechanism 18 includes, for example, a rare gas such as Ar, Kr, Xe, and He for plasma formation, a processing gas such as an oxygen gas in an oxidation process, a nitrogen gas in a nitriding process, a source gas in a CVD process, and a processing container It has a gas supply source (not shown) for supplying a purge gas such as N ₂ and Ar used for replacing the inner atmosphere, a cleaning gas such as ClF ₃ and NF ₃ used for cleaning the inside of the processing container 1, etc. ing. Each gas supply source includes a mass flow controller and an open / close valve (not shown) so that the supplied gas can be switched and the flow rate can be controlled.

  The exhaust device 24 as an exhaust mechanism includes a high-speed vacuum pump such as a turbo molecular pump. As described above, the exhaust device 24 is connected to the exhaust chamber 11 of the processing container 1 through the exhaust pipe 12. The gas in the processing container 1 flows uniformly into the space 11a of the exhaust chamber 11, and is further exhausted to the outside through the exhaust pipe 12 by operating the exhaust device 24 from the space 11a. Thereby, it is possible to depressurize the inside of the processing container 1 at a high speed, for example, to 0.133 Pa.

  Next, the configuration of the microwave introduction mechanism 27 will be described. The microwave introduction mechanism 27 includes, as main components, a transmission plate 28, a planar antenna plate 31, a slow wave plate 33, a conductive cover member 34, a waveguide 37 as a first waveguide, a matching circuit 38, and A microwave generator 39 is provided. In the plasma processing apparatus 100 according to the present embodiment, the second waveguide that adjusts the electric field distribution in the flat waveguide formed by the planar antenna plate 31 and the cover member 34 in the microwave introduction mechanism 27. At least one stub 43 as a tube is provided (two are illustrated in FIGS. 1 and 3).

The transmission plate 28 that transmits microwaves is provided on a support portion 13 a that protrudes toward the inner periphery of the plate 13. The transmission plate 28 is made of a dielectric, for example, ceramics such as quartz, Al ₂ O ₃ , and AlN. A gap between the transmission plate 28 and the support portion 13a is hermetically sealed through a seal member 29. Therefore, the inside of the processing container 1 is kept airtight.

  The planar antenna plate 31 is provided above the transmission plate 28 so as to face the mounting table 2. The planar antenna plate 31 has a disk shape. The shape of the planar antenna plate 31 is not limited to a disk shape, and may be a square plate shape, for example. The planar antenna plate 31 is locked to the upper end of the plate 13.

  As shown in FIG. 2, for example, the planar antenna plate 31 has a base material 31a and a large number of slots 32 formed through the base material 31a in a predetermined pattern. The base material 31a is made of, for example, a copper plate or an aluminum plate whose surface is plated with gold or silver. Each slot 32 has an elongated shape. In addition, the slots 32 are arranged concentrically in pairs with two slots 32 arranged so that their longitudinal directions are different. That is, a pair of a slot 32a whose longitudinal direction forms a predetermined first angle and a slot 32b whose longitudinal direction forms a predetermined second angle with respect to the radial direction of the base material 31a make a pair. None, and a plurality of slot pairs are arranged in one or more rows, preferably in a plurality of rows, concentrically in the circumferential direction of the base material 31a. In FIG. 2, the interval between adjacent pairs of slots formed concentrically is indicated by Δr. Note that the interval Δr can be appropriately adjusted by the arrangement of the slot pairs.

  Note that the arrangement and number of slots 32 of the planar antenna plate 31 shown in FIG. 2, the arrangement interval, the arrangement angle, and the like are merely examples. The length and arrangement interval of the slots 32 can be determined according to the wavelength (λg) of the microwave. For example, the slots 32 are preferably arranged so that the wavelength is from λg / 4 to λg. The slot 32 may have another shape such as a circular shape or an arc shape. Furthermore, the arrangement form of the slots 32 is not particularly limited, and the slots 32 may be arranged concentrically, for example, spirally, radially, or the like. When a substrate for a flat panel display such as a liquid crystal display or an organic EL display is used as a processing target, a plurality of slots can be arranged in a linear shape or a square spiral shape.

  A slow wave plate 33 made of a material having a dielectric constant larger than that of a vacuum is provided between the flat antenna plate 31 and the cover member 34 constituting the flat waveguide. The slow wave plate 33 is disposed so as to cover the planar antenna plate 31. Examples of the material of the slow wave plate 33 include quartz, polytetrafluoroethylene resin, and polyimide resin. The slow wave plate 33 has a function of adjusting the plasma by shortening the wavelength of the microwave because the wavelength of the microwave becomes longer in vacuum.

  The planar antenna plate 31 and the transmission plate 28 and the slow wave plate 33 and the planar antenna plate 31 may be brought into contact with or separated from each other, but are preferably brought into contact with each other.

  A cover member 34 having a function of forming a waveguide is provided on the upper portion of the processing container 1 so as to cover the planar antenna plate 31 and the slow wave plate 33. The cover member 34 is made of a metal material such as aluminum or stainless steel. The upper end of the plate 13 and the cover member 34 are sealed by a sealing member 35 such as a spiral shield ring having conductivity so that microwaves do not leak outside. The cover member 34 is formed with a cooling water flow path 34a. The cover member 34, the slow wave plate 33, the planar antenna plate 31 and the transmission plate 28 can be cooled by allowing cooling water to flow through the cooling water flow path 34a. By this cooling mechanism, the cover member 34, the slow wave plate 33, the planar antenna plate 31, the transmission plate 28, and the plate 13 are prevented from being deformed / damaged by the heat of the plasma. The cover member 34 is grounded.

  An opening 36 is formed in the center of the upper wall (ceiling) of the cover member 34, and the lower end of the waveguide 37 is connected to the opening 36. A microwave generator 39 that generates microwaves is connected to the other end of the waveguide 37 via a matching circuit 38.

  The waveguide 37 is connected to a coaxial waveguide 37a having a circular cross section extending upward from the opening 36 of the cover member 34, and an upper end portion of the coaxial waveguide 37a via a mode converter 40. And a rectangular waveguide 37b extending in the horizontal direction. The mode converter 40 has a function of converting the microwave propagating in the TE mode in the rectangular waveguide 37b into the TEM mode.

  An inner conductor 41 extends at the center of the coaxial waveguide 37a. The inner conductor 41 is connected and fixed to the center of the planar antenna plate 31 at its lower end. With such a structure, microwaves are efficiently and uniformly propagated radially and uniformly to the planar antenna plate 31 constituting a part of the flat waveguide through the inner conductor 41 of the coaxial waveguide 37a.

  As shown in FIG. 3, the stub 43 is a rectangular waveguide formed of a hollow tubular member having a rectangular shape in cross section. The stub 43 is made of a metal material such as aluminum or stainless steel. The stub 43 is provided in the vertical direction on the outer peripheral portion of the cover member 34. A lower portion of the stub 43 is inserted into the cover member 34 and penetrates the cover member 34. The upper part of the stub 43 is provided so as to protrude from the upper surface of the cover member 34. The shape, arrangement, number of arrangements, etc. of the stubs 43 in the plasma processing apparatus 100 of the present embodiment will be described in detail later.

  With the microwave introduction mechanism 27 having the above-described configuration, the microwave generated by the microwave generator 39 is propagated to the planar antenna plate 31 through the waveguide 37 and is processed through the slot 32 and the transmission plate 28. 1 is introduced. For example, 2.45 GHz is preferably used as the frequency of the microwave, and 8.35 GHz, 1.98 GHz, or the like can also be used.

  Each component of the plasma processing apparatus 100 is connected to and controlled by the controller 50. As shown in FIG. 4, the control unit 50 includes a process controller 51, which is a computer including a CPU, and a user interface 52 and a storage unit 53 connected to the process controller 51. In the plasma processing apparatus 100, the process controller 51 is a component related to process conditions such as temperature, gas flow rate, pressure, and microwave output (for example, the heater power supply 5a, the gas supply mechanism 18, the exhaust device 24, the microwave). The control means is connected to the generator 39 and the like, and controls them collectively.

  The user interface 52 includes a keyboard on which a process manager manages command input to manage the plasma processing apparatus 100, a display that visualizes and displays the operating status of the plasma processing apparatus 100, and the like. The storage unit 53 stores a recipe in which a control program (software) for realizing various processes executed by the plasma processing apparatus 100 under the control of the process controller 51 and processing condition data are recorded. Yes.

  Then, if necessary, an arbitrary recipe is called from the storage unit 53 by an instruction from the user interface 52 and is executed by the process controller 51, so that the processing container 1 of the plasma processing apparatus 100 is controlled under the control of the process controller 51. Desired processing. The recipe such as the control program and processing condition data may be stored in a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a flash memory, a DVD, or the like. It is also possible to transmit the data from other devices as needed via a dedicated line and use it online.

  In the plasma processing apparatus 100 configured in this way, damage-free plasma processing can be performed on the underlying film or the like at a low temperature of 800 ° C. or lower (particularly from about room temperature to 500 ° C.). In addition, since the plasma processing apparatus 100 is excellent in plasma uniformity, process uniformity can be realized.

Next, an example of a plasma processing procedure using the plasma processing apparatus 100 according to the present embodiment will be described. Here, a case where oxygen containing gas is used as the processing gas and the wafer surface is subjected to plasma oxidation processing will be described as an example.
First, for example, a command is input from the user interface 52 to perform plasma oxidation processing in the plasma processing apparatus 100. In response to this instruction, the process controller 51 reads the recipe stored in the storage unit 53. Then, from the process controller 51 to each end device of the plasma processing apparatus 100 such as the gas supply mechanism 18, the exhaust apparatus 24, the microwave generator 39, the heater power supply 5 a, etc., so that the plasma oxidation process is performed under conditions based on the recipe. A control signal is sent out.

  Then, the gate valve (not shown) is opened, and the wafer W is loaded into the processing container 1 from the loading / unloading port and mounted on the mounting table 2. Next, while evacuating the inside of the processing container 1, an inert gas and an oxygen-containing gas are introduced from the gas supply mechanism 18 into the processing container 1 through the gas introduction part 15 at a predetermined flow rate. Further, the inside of the processing container 1 is adjusted to a predetermined pressure by adjusting the exhaust amount and the gas supply amount.

Next, the power of the microwave generator 39 is turned on to generate microwaves. The generated microwave having a predetermined frequency, for example, 2.45 MHz, is guided to the rectangular waveguide 37b through the matching circuit 38. The microwave guided to the rectangular waveguide 37b passes through the coaxial waveguide 37a and is supplied to the planar antenna plate 31 constituting the flat waveguide. In other words, the microwave propagates in the TE mode in the rectangular waveguide 37b, and the TE mode microwave is converted into the TEM mode by the mode converter 40, and the planar waveguide plate 31 passes through the coaxial waveguide 37a. It is propagated towards. Then, the microwave is radiated into the processing container 1 (the space above the wafer W) through the transmission plate 28 from the slot 32 which is a hole formed through the planar antenna plate 31. The microwave output at this time is preferably in the range of 0.41 to 4.19 W / cm ² as the power density per cm ^{2 of the} transmission plate 28. The microwave output can be selected, for example, from the range of 500 to 5000 W so that the power density is within the above range according to the purpose.

An electromagnetic field is formed in the processing container 1 by the microwave radiated from the planar antenna plate 31 to the processing container 1 through the transmission plate 28, and the inert gas and the oxygen-containing gas are turned into plasma. The microwave-excited plasma has a high density of about 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ due to microwaves radiated from a large number of slots 32 of the planar antenna plate 31. The plasma has a low electron temperature of about 1.5 eV or less. The microwave-excited high-density plasma formed in this way has little plasma damage due to ions or the like on the underlying film. Then, the silicon surface of the wafer W is oxidized by the action of active species such as radicals or ions in the plasma, and a thin film of silicon oxide film SiO ₂ is formed.

  When a control signal for terminating the plasma process is sent from the process controller 51, the power of the microwave generator 39 is turned off (off), and the plasma oxidation process is terminated. Next, the supply of the processing gas from the gas supply mechanism 18 is stopped and the inside of the processing container 1 is evacuated. Then, the wafer W is unloaded from the processing container 1 and the plasma processing for one wafer W is completed.

  Next, the detailed structure of the stub 43 in the plasma processing apparatus 100 of this Embodiment is demonstrated. As shown in FIG. 5, in the present embodiment, at the outer periphery of the cover member 34, the lower part of the hollow tubular member 43 a having a rectangular cross section constituting the stub 43 is inserted into the opening 34 b provided in the cover member 34. Has been. The hollow tubular member 43 a having a hollow block shape penetrates the cover member 34 and reaches the upper surface of the slow wave plate 33. The lower end of the hollow tubular member 43 may be in contact with the slow wave material 33 or may be separated.

  In FIG. 5, the upper portion of the stub 43 is provided so as to protrude from the upper surface of the cover member 34, but it does not need to protrude. The height H of the stub 43 (that is, the length of the waveguide) is relative to the in-tube wavelength λg (= 154 mm) of the microwave propagating in the stub 43 so that a standing wave is generated by the microwave in the stub 43. It is preferable to adjust the height to be in the range of λg or less, for example, λg / 4 (= 38 mm), λg / 2 (= 77 mm), 3λg / 4 (= 15.5 mm), etc. Can do. The area of the cross section of the stub 43 can also be set according to the wavelength λg of the microwave propagating in the stub 43.

  The upper portion of the stub 43 may be closed by the lid body 44 as shown in FIG. 5, but may be in an open state, for example, as shown in FIG. In order to increase the absorption rate of the microwave to the plasma and suppress the reflection of the microwave to the waveguide 37, it is preferable to close the upper portion of the stub 43 as shown in FIG. The means for closing the upper portion of the stub 43 is not limited to the lid body 44, and the upper portion may be closed by integral molding, for example.

  Further, when the upper portion of the stub 43 is closed, a configuration having a movable lid portion (movable body) may be used instead of the lid body 44 as shown in FIG. 5 (not shown). Since the effective tube length of the stub 43 can be arbitrarily changed by using the movable lid portion, the height of the stub 43 can be adjusted substantially variably. Then, by adjusting the height of the stub 43 variably, the electric field strength in the transmission plate 28 can be easily controlled as shown in an experimental example described later. Therefore, it is advantageous to use a movable lid from the viewpoint of improving the uniformity of plasma and further improving the uniformity of processing within the wafer surface. In addition, there is no restriction | limiting in particular as a mechanism which makes a cover part movable up and down, For example, arbitrary mechanisms, such as a screw mechanism (refer FIG. 27) which can position a cover part by moving up and down, are employable.

  FIG. 7 to FIG. 9 show other configuration examples of the stub 43. FIG. 7 shows an aspect in which the upper part of the stub 43 is constituted by a hollow tubular member 43 a having a rectangular cross section, and the lower part of the stub 43 is constituted by a rectangular opening 34 b formed in the cover member 34. The hollow tubular member 43a is attached to the upper surface of the cover member 34 by an arbitrary fixing means (not shown) such as a screw. In the stub 43 shown in FIG. 7, the hollow portion of the hollow tubular member 43a and the opening 34b of the cover member 34 are aligned to form a waveguide in the vertical direction. In addition, also in the stub 43 shown in FIG. 7, deployment of the cover body 44 is arbitrary.

  FIG. 8 shows an aspect of the stub 43 configured by a rectangular opening 34 b formed in the cover member 34. In the stub 43 shown in FIG. 8, a waveguide is formed in the vertical direction only by the opening 34 b of the cover member 34. Accordingly, the height H of the stub 43 matches the thickness of the cover member 34. In addition, also in the stub 43 shown in FIG. 8, deployment of the cover body 44 is arbitrary.

  FIG. 9 shows an aspect of the stub 43 configured by the recess 34 c formed on the lower surface of the cover member 34. The recess 34 c is opened toward the slow wave plate 33 disposed below the cover member 34. In the stub 43 shown in FIG. 9, the waveguide is formed in the vertical direction only by the recess 34 c of the cover member 34. Therefore, the height H of the stub 43 is smaller than the thickness of the cover member 34.

  In the plasma processing apparatus 100 of the present embodiment, the plasma is uniformly generated in the processing chamber 1 and the uniformity of the processing in the vicinity of the central portion and the peripheral portion of the wafer W is ensured in the vicinity of the peripheral portion of the planar antenna plate 31. A stub 43 is disposed above the stub. As described above, the microwave generated by the microwave generator 39 is supplied to the central portion of the planar antenna plate 31 via the coaxial waveguide 37a, and is formed by the radial antenna plate 31 and the cover member 34. It propagates through the waveguide (flat waveguide). As the distance that the microwave propagates through the waveguide increases, the reflected wave increases and the standing wave attenuates. For this reason, the electric field generated by the microwave in the flat waveguide becomes strong at the central portion of the planar antenna plate 31 which is a portion where the microwave is introduced into the flat waveguide through the lower end portion of the coaxial waveguide 37a. In the vicinity of the peripheral edge of the planar antenna plate 31, there is a tendency to become weak. When the electric field distribution on the planar antenna plate 31 becomes non-uniform in this way, the reflection coefficient to the waveguide 37 increases and the efficiency of absorbing microwaves into the plasma decreases. That is, the effective power of the microwave introduced into the processing container 1 is reduced, and the power loss is increased. As a result, the plasma generated in the processing container 1 becomes non-uniform. In particular, when the processing container 1 is increased in size so as to process a large-diameter wafer W, this problem becomes apparent, and the plasma density in the vicinity of the side wall 1b of the processing container 1 decreases, so that the processing can be performed uniformly within the surface of the wafer W. It becomes difficult to do.

  From such a viewpoint, in order to efficiently supply microwaves into the processing container 1 and generate uniform plasma, the stub 43 is disposed above the outer peripheral portion (that is, near the peripheral portion) of the planar antenna plate 31. In addition, it is preferable to make the electric field distribution on the planar antenna plate 31 close to uniform. In particular, by arranging the stub 43 above the slot 32 formed on the outer peripheral portion of the planar antenna plate 31, microwaves are introduced into the stub 43 as compared with the case where the stub 43 is disposed elsewhere. It becomes easy. Then, nonuniform microwaves (reflected waves and standing waves) are absorbed by the stub 43, whereby a uniform electric field strength distribution can be formed on the planar antenna plate 31. Further, when the microwave (incident wave) incident from the center of the flat waveguide propagates radially outward of the planar antenna plate 31, the reflection of the microwave (reflected wave) at the outer peripheral portion of the flat waveguide. ) Can be prevented.

  In the present embodiment, it is preferable to arrange the stub 43 so that the hollow portion of the hollow tubular stub 43 overlaps the opening of the slot 32 formed in the outer peripheral portion of the planar antenna plate 31. Further, the stub 43 is positioned so that the hollow portion of the stub 43 is positioned above the center of the opening surface of the slot 32 formed on the outer periphery of the planar antenna plate 31 (hereinafter simply referred to as “the center of the slot 32”). More preferably, it is arranged. Further, the center of the opening surface of the stub 43 (hereinafter simply referred to as “the center of the stub 43”) is positioned on an arc connecting the center of the slot 32 formed in the outer peripheral portion of the planar antenna plate 31 in the circumferential direction. Is preferred. In particular, it is more preferable to arrange the stub 43 so that the center of the stub 43 overlaps the center of the slot 32 in the vicinity of the peripheral edge portion of the planar antenna plate 31. In addition, it is desirable to arrange the stub 43 so that the hollow portion of the stub 43 and the entire opening of the slot 32 overlap each other.

  Next, with reference to FIGS. 10 to 12, a preferred example of the arrangement position of the stub 43 in the radial direction of the planar antenna plate 31 will be described. 10 to 12 are explanatory diagrams showing the arrangement of the stubs 43 with respect to the positions of the slot pairs (slot 32a and slot 32b) arranged on the outermost periphery of the planar antenna plate 31. FIG. In each figure, the stub 43 is indicated by a virtual line.

The stub 43 is located between the outer peripheral end of the outer slot 32a and the inner peripheral end of the inner slot 32b in the pair of slots arranged on the outermost periphery of the planar antenna plate 31. It is preferable to arrange so that the center Os of is located. In other words, it signed a longitudinal outer ends of the plurality of slots 32a that are outside of the inner outermost slot pairs, a first virtual circle around the center O _A of the plane antenna plate 31, of the outermost slot pairs longitudinal bear inner end, a second imaginary circle centered on the center O _a of the plane antenna plate 31, surrounded by an annular region, the center of the stub 43 of the plurality of slots 32b on the inside It is preferable that the stub 43 is arranged such that Os is located and at least a part of at least one slot overlaps the stub 43 in plan view.

FIG. 10 shows that the center Os of the stub 43 is located on the arc R _32b in the circumferential direction connecting the centers O _32b of the inner slots 32b constituting the pair of slots arranged on the outermost periphery in the outer peripheral portion of the planar antenna plate 31. An example in which stubs 43 are arranged is shown. In FIG. 10, in particular, the center Os of the stub 43 is positioned so as to overlap the center O _{32b of the} slot 32b. Note that FIG. 10 shows a configuration example in which one entire slot 32b falls within a range that overlaps the stub 43. However, the present invention is not limited to this, and the entire plurality of slots 32b fall within the range that overlaps the stub 43. You may comprise so that it may enter (for example, two slots 32b enter the range which overlaps with the stub 43). Further, depending on the relative sizes of the slot 32b and the stub 43, a part of the slot 32b may be included in a range overlapping the stub 43 (for example, the slot 32b partially overlaps the stub 43). .

FIG. 11 shows the center Os of the stub 43 on the arc R _32a in the circumferential direction connecting the centers O _32a of the outer slots 32a constituting the slot pairs arranged on the outermost periphery in the outer peripheral portion of the planar antenna plate 31. The example which has arrange | positioned the stub 43 so that it may be located is shown. In FIG. 11, in particular, the center O _{32a of the} slot 32a is aligned with the center Os of the stub 43. Note that FIG. 11 shows a configuration example in which one entire slot 32a falls within a range that overlaps the stub 43. However, the present invention is not limited to this, and the entire plurality of slots 32a fall within the range that overlaps the stub 43. You may comprise so that it may enter (for example, the two slots 32a enter the range which overlaps with the stub 43). Further, depending on the relative sizes of the slot 32a and the stub 43, a part of the slot 32a may be included in a range overlapping the stub 43 (for example, the slot 32a partially overlaps the stub 43). .

As described above, the surface current generated on the base material 31a of the planar antenna plate 31 by the microwave propagated from the coaxial waveguide 37a to the center of the planar antenna plate 31 is directed toward the radially outward direction of the planar antenna plate 31. However, since it is blocked by the slot 32 on the way, an electric charge is induced at the edge of the slot 32. This electric charge becomes a new microwave generation source. Since electric charges are likely to be accumulated near the center of the slot 32 in the longitudinal direction, the electric field tends to concentrate at the center of the slot 32. In the example shown in FIG. 10 and FIG. 11, the stub 43 is disposed right above the centers O _32a and O _32b of the slots _32a and _32b to suppress the concentration of the electric field in the vicinity of the centers O _32a and O _{32b of the} slot 32. did.

As shown in FIG. 10 or FIG. 11, the stub is arranged so that the center Os of the stub 43 overlaps the center O _32a or O _32b of the slot 32a or 32b constituting the slot pair arranged on the outermost periphery of the planar antenna plate 31. By disposing 43, the lower slot 32 and the upper stub 43 can be opposed to each other with the slow wave plate 33 interposed therebetween. In FIG. 10 or FIG. 11, it is particularly desirable to arrange the stub 43 so that the hollow portion of the stub 43 and the entire opening of the slot 32 overlap each other. With the arrangement of the stub 43 as described above, the electric field near the slot 32 can be expanded upward. Thereby, the concentration and uneven distribution of the electric field on the planar antenna plate 31 are effectively suppressed. In this way, by arranging the stub 43 so that the center Os of the stub 43 overlaps the centers O _32a and O _32b of the slots 32a and 32b, the electric field distribution on the space inside the processing container 1 below the planar antenna plate 31. Can be adjusted uniformly to make the plasma in the processing container 1 uniform. The center Os of the stub 43 may be disposed between two slot pairs adjacent in the circumferential direction.

10 and 11, the centers O _32a and O _32b of the slot 32a or the slot 32b constituting the outermost peripheral slot pair are defined as the inner slot pair from the center O _A of the planar antenna plate 31. The slots 32c and 32d (only one pair is shown in FIGS. 10 to 12 but not necessarily a pair) are positioned on an extension line of the straight line X passing through the centers O _32c and O _32d .

FIG. 12 shows a case where perpendicular lines are drawn from the centers of the slots 32a and 32b in the direction perpendicular to the longitudinal direction of the slots 32a and 32b constituting the slot pairs arranged on the outermost periphery of the planar antenna plate 31, respectively. An example in which the center Os of the stub 43 is aligned with the intersection point I is shown. That is, the center Os of the stub 43 is overlapped with the intersection point I, and the stub 43 is arranged so that the stub 43 is positioned above the intersection point I. Incidentally, an arbitrary position on the arc R _I connecting the intersection I in the circumferential direction of the plane antenna plate 31, center Os of the stub 43 may be positioned. For example, the center Os of the stub 43 may be disposed between two adjacent slot pairs in the circumferential direction. FIG. 12 shows a configuration example in which almost the entire pair of slots 32 a and 32 b are within the range overlapping with the stub 43, but this is not limiting, and more slots are within the range overlapping with the stub 43. It may be configured such that a part of each of a plurality of slot pairs enters.

  Next, the influence of the three arrangements of the stubs 43 in the radial direction of the planar antenna plate 31 illustrated in FIGS. 10 to 12 on the microwave power and the electric field distribution supplied to the processing container 1 of the plasma processing apparatus 100. It was verified by simulation. The results are shown in Table 1.

<Simulation condition 1>
The simulation conditions are as follows.
Software used: COMSOL (trade name; manufactured by COMSOL)
Radial arrangement: An annular stub 43 was assumed, as schematically shown in FIG. Arc connecting the position of the half (D / 2) of the width D of the stub 43 on the circle ring, on the arc _{R 32 b} shown in FIG. 10, on the circular arc _{R I} shown in FIG. 12, and, in FIG. 11 They were set so as to be positioned on the indicated arc R _32a . Each arc having a radius (distance from the vertical axis passing through the center _{O A} of the plane antenna plate 31 in the horizontal direction), for example, an arc _{R 32 b} is 184 mm, the circular arc _{R I} is 200mm and the arc _{R 32a} is a 215 mm.
Stub: The height of the annular stub 43 was set to a height of 115.5 mm (3λ / 4) in the vertical direction from the upper surface of the slow wave plate 33 for each of the closed and opened ones.
Boundary condition: perfect conductor Electron density of plasma: 1 × 10 ¹² · cm ⁻³ was reached at a position 1 cm below the transmission plate 28, and the electron density was set below that.
Dielectric constant: Set to 4.2 (SiO ₂ ) and 1.0 (air).
Pressure: set to 13.3 Pa (100 mTorr).
Temperature: set to 500 ° C.
Transmission plate: set to a quartz arch shape.
Planar antenna plate: Two slots are formed in a C-shaped (L-shaped) pair to form a slot pair, and the slot pair is set to have a structure in which the slot pair is concentrically arranged around the inside and outside.

In the simulation, as shown in FIG. 13, the power (supply power) P _{S of} the microwave supplied from the microwave generator 39 to the waveguide 37 is introduced into the processing container 1 from the coaxial waveguide 37a. The net microwave power (introduction power) P _I , the microwave power (discharge power) P _O emitted from the stub 43 to the outside, and the plasma generated in the processing vessel 1 through the transmission plate 28 are absorbed. (Used) microwave power (absorption power) P _A , microwave power (loss power) P _L lost on the wall surface of the stub 43, microwave power reflected to the coaxial waveguide 37a ( for the reflected power) _{P R,} it was calculated balance of power by setting the supply power _{P S} to 2000 W. _{As P L = P I -P O -P} A, also calculated as _P R _{= P} S -P _I.

Table 1 in "arrangement D1", which corresponds to the position shown in FIG. 10, the distance from the center _{O A} of the plane antenna plate 31 to the center _{O 32 b} of the slot 32 b (184 mm), on the annular stub The alignment was performed so that the radii of 43 coincided. "Arrangement D2", which corresponds to the position shown in FIG. 12, the distance from the center O _A of the plane antenna plate 31 to the intersection point I (200 mm), as the radius of the stub 43 on the circular ring coincides Aligned. "Arrangement D3", which corresponds to the position shown in FIG. 11, the distance from the center _{O A} of the plane antenna plate 31 to the center _{O 32a} of the slot 32a (215 mm), the radius of the stub 43 on the circular ring Aligned to match. For comparison, a simulation was performed under the same conditions even when the stub 43 was not provided.

From Table 1, as compared with the case without the stub 43, the arrangement D1~D3 provided a stub 43, both overall absorption power P _A is larger when the top is the case was closed and opened, reflected power P _R is It turned out to be small. Therefore, it was shown that by providing the stub 43, the reflected wave in the waveguide is suppressed compared to the case where the stub 43 is not provided, and the microwave can be efficiently supplied into the processing container 1.

Further, when comparing the case where the upper part of the stub 43 is closed and the case where it is opened, the emission power _PO is larger in the latter (when opened) than in the former (when closed). it was found absorption power P _a is small. Therefore, it was shown that the microwave can be efficiently supplied into the processing container 1 by closing the upper portion of the stub 43.

Based on the above results, the arrangement of the stubs 43 was examined on the assumption that the upper part of the stubs 43 is closed. In Table 1, the absorption power _{P A,} the arrangement D1 is the largest and 700 W, then placed D3 was greater at 675 W. On the other hand, the arrangement D2 is absorbed power _{P A} is remained 307W.

The reflected power _{P R} of the microwaves reflected into the waveguide 37, disposed D1 is the smallest and 1278W, whereas arrangement D3 was 1304W then placed D2 is 1667W, arranged D1 and arranged There were more generations of reflected waves than D3.

Further, the cross section of the stub 43 (position 0.5 mm above the lower end), the upper surface of the slow wave plate 33, the central cross section of the slow wave plate 33 (position of thickness × ½), and the central cross section of the planar antenna plate 31. Surface (position of thickness × 1/2), cross section of transmission plate 28 (position 9 mm below upper end), lower surface of transmission plate 28 (flat portion), transmission plate 28 (including curved surface portion) and processing container The electric field distribution in the processing container 1 0.5 mm below the interface with the inner space 1 and the lower surface of the transmission plate 28 was imaged and analyzed. As a result, for example, the electric field distribution of the central cross section of the planar antenna plate 31 is uneven in the area around the inner peripheral slot pair in the arrangement D2, whereas in the arrangement D1 and the arrangement D3, the electric field distribution is flat. A strong electric field spread uniformly throughout the planar antenna plate 31 including not only the periphery of the slot pair on the inner peripheral side of the antenna plate 31 but also the area near the slot pair on the outer peripheral side (results not shown). The simulation results of the electric field distribution for other parts showed the same tendency. The partial electric field is strong, through the inner circumferential side of the slot pairs from the center O _A of the plane antenna plate 31, that tend to be formed radially in a radially outward direction to the outer peripheral side of the slot pairs were found.

  From the above simulation results, it was shown that the microwave can be efficiently supplied into the processing container 1 by providing the stub 43 for adjusting the electric field distribution generated on the planar antenna plate 31 constituting the flat waveguide.

  Moreover, it was shown that the microwave can be efficiently supplied into the processing container 1 by keeping the upper portion of the stub 43 closed, as compared with the case where the upper portion is opened.

The hollow portion of the annular stub 43 is preferably disposed so as to overlap the outermost slot pair, and is disposed so as to overlap the outer slot 32a or the inner slot 32b of the outermost slot pair. Has been shown to be more preferred. Particularly, the arrangement D1 (see FIG. 10) in which the center Os of the stub 43 is aligned with the center O _32b of the slot 32b inside the outermost slot pair of the planar antenna plate 31 as the place where the stub 43 is disposed. Then, it became clear that the arrangement D3 (see FIG. 11) in which the center Os of the stub 43 is aligned with the center O _32a of the outer slot 32a of the outermost peripheral slot pair is preferable.

Next, the number of stubs 43 installed will be described with reference to FIGS.
14 shows a state in which one hollow block stub 43 is arranged, FIG. 15 shows a state in which two hollow block stubs 43 are arranged, and FIG. 16 shows a state in which three hollow block stubs 43 are arranged. Are superimposed on the planar antenna plate 31, respectively. FIGS. 17 to 19 are modifications in the case where two stubs 43 shown in FIG. 15 are arranged. 14 to 19, only a part of the slot 32 of the planar antenna plate 31 is illustrated, and the slot 32 unnecessary for explanation is omitted. As shown in FIGS. 15 and 16, two or more stubs 43 are preferably arranged. In particular, as shown in FIG. 15, in the radial direction across the center O _A of the plane antenna plate 31, it is preferable to dispose the two stubs 43 in point symmetry. By arranging the two stubs 43 symmetrically in the radial direction of the planar antenna plate 31, the effect of making the electric field distribution near the planar antenna plate 31 uniform is the highest. Even if more stubs 43 are arranged than necessary, an improvement in the effect of uniforming the electric field distribution is not always obtained, and may be lowered. Arranging more stubs 43 than necessary increases the number of parts of the plasma processing apparatus 100 and increases the cost of the apparatus. Therefore, the number of stubs 43 disposed is preferably 2-6, and more preferably 2-4.

Further, the microwave is introduced from the coaxial waveguide 37a in the vicinity of the center O _A of the plane antenna plate 31, it becomes circularly polarized waveguide formed by the plane antenna plate 31 and the cover member 34 in the radially outward direction Propagating and generating surface currents radially along the slots 32 arranged radially. For this reason, when the slot pairs are arranged concentrically from the center of the planar antenna plate 31, it is preferable to arrange the stubs 43 along the rows formed by the slots 32 in the radially outward direction. In 14 to 16 for example, from the center _{O A} of the plane antenna plate 31, slot 32c, (although shown only one pair not necessarily pair) inner circumferential side of the slot pairs consisting 32d through the slots 32a, 32b A row formed by the slots 32 in the radially outward direction from the inner circumferential side to the outermost circumferential line is shown by the XX line connecting the outermost circumferential slot pairs. On the other hand, Y-Y line shown in FIGS. 14 to 16, from the center _{O A} of the plane antenna plate 31, inner slot pairs (slots 32c, 32d) is not through, the outermost slot pairs (slots 32a, 32b). The stub 43 may be arranged on either the XX line or the YY line, but is preferably arranged on the XX line. For example, when two stubs 43 are arranged on the YY line and compared with the case where two stubs 43 are arranged on the XX line as shown in FIG. More preferably, the two stubs 43 are arranged opposite to each other.

  Next, the effects of the three arrangements of the stubs 43 illustrated in FIGS. 14 to 16 on the microwave power and the electric field supplied to the processing container 1 of the plasma processing apparatus 100 were examined by simulation. The results are shown in Table 2.

<Simulation condition 2>
The simulation conditions are as follows.
Radial arrangement: one, two, or two stubs 43 so that the center of the hollow block-like stub 43 overlaps the center O _32b of the inner slot 32b in the outermost slot pair of the planar antenna plate 31 vertically It was set to arrange three (see FIG. 10, arrangement D1).
Stub: A rectangular shape in cross section with the upper part closed, and the length in the longitudinal direction was set to 100 mm, the width was 35 mm, and the height from the top surface of the slow wave plate was 115.5 mm (3λ / 4). Conditions other than those described above are the same as the simulation condition 1 and will not be described.

In the simulation, introduced power _{P I,} the absorbed power _{P A,} the loss power _{P L,} the reflected power _{P R,} and sets the supply power _{P S} in 2000W calculate the balance of the power (see FIG. 13). _{Incidentally,} the P _{L =} P I -P _A, was also calculated by _P R _{= P} S -P _I.

  “Number of installations N1” in Table 2 is one in which one stub 43 is arranged at the position shown in FIG. “Installation number N2” is obtained by disposing two stubs 43 at positions facing each other as shown in FIG. “Installation number N3” is obtained by arranging three stubs 43 at positions separated by 120 ° in the circumferential direction shown in FIG. For comparison, the simulation results for the case where the stub 43 is not provided are re-published.

In Table 2, the absorption power _{P A} is installed number N2 is the largest and 1559W, then installation speed N3 was greater at 882W. On the other hand, the installation number N1, the absorbed power _{P A} is 382W, the lowest in the case of providing a stub 43. The reflected power _{P R,} the installation number N2 is the smallest and 389 W, while the installation speed N3 was 1157W then placed number N1 is 1589W, the results inferior to the installation number N1 and installation speed N3 became.

  Further, the cross section of the stub 43 (position 0.5 mm above the lower end), the upper surface of the slow wave plate 33, the central cross section of the slow wave plate 33 (position of thickness × ½), and the central cross section of the planar antenna plate 31. Surface (thickness × 1/2 position), cross section of transmission plate 28 (position 9 mm below upper end), lower surface of transmission plate 28 (flat portion), and transmission plate 28 (including curved surface portion) and processing When the electric field distribution at the interface with the inner space of the container 1 was imaged and analyzed, it was confirmed that the installed number N2 and the installed number N3 were more evenly distributed than the installed number N1 (results) Is omitted).

From the above simulation results, it has been found that the number of stubs 43 provided is preferably a plurality, for example two or three, rather than one. In comparison with the results in Table 1, rather than making a stub 43 into an annular, who provided independently hollow block-shaped stub 43 into two or more circumferentially, absorption power P _A is much larger It has been found. Accordingly, by providing two or more stubs 43 above the planar antenna plate 31 constituting the flat waveguide, the electric field distribution generated on the planar antenna plate 31 is uniformly adjusted, and the processing container 1 can be efficiently introduced. It has been shown that microwaves can be supplied.

In the example shown in FIGS. 14 to 16, the hollow block-like stub 43 is disposed above the inner slot 32 b in the outermost peripheral slot pair. However, for example, as shown in FIG. 17, the stub 43 may be arranged above the intermediate position between the slot 32a and the slot 32b constituting the outermost peripheral slot pair. For example, as shown in FIG. 18, the stub 43 may be disposed above the outer slot 32a in the outermost slot pair. Furthermore, for example, as shown in FIG. 19, of the two opposite stubs 43, the one located above the inside of the slot 32b of the slot pairs on the outermost circumference, the other end, opposite side of the center O _A It may be arranged above the outer slot 32a of the outermost peripheral slot pair located at the position. 17 to 19 exemplify the case where two stubs 43 are arranged symmetrically in the radial direction of the planar antenna plate 31, but when one stub 43 is arranged (see FIG. 14), A similar arrangement is possible when three stubs 43 are arranged (see FIG. 16).

  Next, the influence of the arrangement and number of the stubs 43 on the microwave power and electric field supplied to the processing container 1 was examined in more detail by simulation. The results are shown in Table 3.

<Simulation condition 3>
The simulation conditions are as follows.
Circumferential arrangement: As shown in FIGS. 20 to 26, stubs 43 were arranged in seven arrangements / numbers, and simulations were performed. 20 to 26, the arrangement of the stubs 43 with respect to the planar antenna plate 31 is schematically shown. Line in each figure, the slot 32 is omitted, connecting the center _{O A} of the plane antenna plate 31, slot 32c on the inner circumferential side of the slot pairs, 32d and the outermost slot pairs of the slot 32a, the 32 b X- X represents the arrangement of the slots 32 in the radial direction.
Radial arrangement: The center of the stub 43 is set to overlap the center O _32b of the inner slot 32b in the outermost slot pair of the planar antenna plate 31 (see FIG. 10, arrangement D1).
Conditions other than the above are the same as the simulation condition 2 and will not be described.

In the simulation, introduced power _{P I,} the absorbed power _{P A,} the loss power _{P L,} the reflected power _{P R,} and sets the supply power _{P S} in 2000W calculates the over balance of each power. _{Incidentally,} the P _{L =} P I -P _A, was also calculated by _P R _{= P} S -P _I.

In “Arrangement C1” in Table 3, as shown in FIG. 20, two stubs 43 are arranged at positions facing each other on the line XX. In the “arrangement C2”, the two stubs 43 are arranged asymmetrically with respect to the center O _A of the planar antenna plate 31 as shown in FIG. Note that the two stubs 43 are arranged at positions 120 ° apart in the circumferential direction. In “Arrangement C3”, as shown in FIG. 22, the three stubs 43 are arranged at asymmetric positions. Of the three stubs 43, the two stubs 43 are arranged opposite to each other on the XX line as in the arrangement C1, but the remaining one stub 43 is shifted by an angle of 60 °. Only one is arranged on another XX line. In the “arrangement C4”, as shown in FIG. 23, four stubs 43 are separately arranged on two XX lines. These two line X-X intersect at the center O _A of the plane antenna plate 31 at an angle of 60 °. In the “arrangement C5”, as shown in FIG. 24, the four stubs 43 are arranged with their positions shifted by 90 ° in the circumferential direction. The four stubs 43 are arranged so as to face a position deviated from the XX line (on the YY line shown in FIGS. 14 to 19). As shown in FIG. 25, the “arrangement C6” is arranged so that the two stubs 43 face each other in the radial direction at a position off the XX line (on the YY line shown in FIGS. 14 to 19). It is set. In the “arrangement C7”, as shown in FIG. 26, the six stubs 43 are evenly arranged on the XX line whose positions are shifted by 60 ° in the circumferential direction. For comparison, the simulation results for the case where the stub 43 is not provided are also shown again.

From Table 3, any of the arrangements C1 to C7 was a better result than the case where the stub 43 was not arranged. Absorption power _{P A} is disposed C3 (FIG. 22) is the largest and 1605W, then placed C1 (FIG. 20) was almost the same value as 1559W. The arrangement C5 (FIG. 24), for the placement C6 (FIG. 25), disposed C3, greater absorption power _{P A} Following placement C1. On the other hand, placement C2, arranged C4, disposed C7 is arranged C1, arranged C3, smaller absorption power _{P A} than the arrangement C5 and placement C6. The two stubs 43, disposed and arranged asymmetrically in a radial direction across the center of the plane antenna plate 31 C2 (FIG. 21), the absorption power P _A is smaller, was the lowest results. Also, four stubs 43 arranged circumferentially 60 ° staggered C4 (Fig. 23), arranged to place six stubs 43 in the circumferential direction C7 (FIG. 26) is also expected absorption power _{P A} is smaller The effect was not obtained.

The reflected power _{P R,} arrangement C1, arranged C3, disposed C5 and arranged C6 were less good substantially equivalent. In contrast, placement C2, arranged C4 and placement C7 are reflected power _{P R} is arranged C1, arranged C3, larger than the arrangement C5 and placement C6, higher reflectance.

In the case where the stub 43 and the same number arranged, two at the stubs 43 and arranged C1 which is arranged to compare the arrangement C6, from the center O _A of the plane antenna plate 31, and slot pairs on the inner peripheral side, the outer peripheral side slot arranged and disposed stub 43 in X-X line connecting the pair radially outward C1 from the center O _a of the plane antenna plate 31, the position of the slot pairs on the inner peripheral side without passing the slot pairs on the outer peripheral side only Better results were obtained than the arrangement C6 in which the stub 43 was arranged on the YY line passing through the line. Further, in the comparison between the arrangement C4 in which the four stubs 43 are arranged and the arrangement C5, the arrangement C5 in which the stubs 43 are evenly arranged in the circumferential direction of the planar antenna plate 31 is remarkably superior.

  Further, the cross section of the stub 43 (position 0.5 mm above the lower end), the upper surface of the slow wave plate 33, the central cross section of the slow wave plate 33 (position of thickness × ½), and the central cross section of the planar antenna plate 31. Electric field distribution at the interface between the surface (position of thickness × 1/2), the cross section of the transmission plate 28 (position 9 mm below the upper end), and the transmission plate 28 (including the curved surface portion) and the space inside the processing container 1 As a result, it was confirmed that the arrangement C3 and the arrangement C1 have the most uniform electric field distribution, and then the arrangement C5 and the arrangement C6 have a good electric field distribution (results not shown).

From the above simulation results, the position to dispose the stub 43, from the center O _A of the plane antenna plate 31, and an inner peripheral side of the slot pairs, the outer peripheral side of the slot pairs and the connecting radially outward line (X- a position overlapping the X-ray), it is understood that it is preferable to arrange symmetrically about the center O _a. However, even when the arrangement is based on this rule, it has been shown that if the number of stubs 43 is increased, the efficiency of absorption of microwaves into the plasma decreases. Therefore, it was found that the number of stubs 43 installed is preferably in the range of 2-4.

Next, the state when the gas was introduced into the plasma processing apparatus 100 to generate plasma was simulated. The simulation conditions are as follows.
<Simulation condition 4>
Radial arrangement: assuming an annular stub 43, the position of the arc connecting the width D half (30 mm) of the stub 43 (D / 2) is horizontal from the vertical axis passing through the center O _A of the plane antenna plate 31 The direction was set to 184 mm (see FIG. 13).
Stub: The height of 115.5 mm (3λ / 4) from the upper surface of the wave retardation plate 33 was set for the one in which the upper part of the annular stub 43 was closed.

In the simulation condition 4, the power (absorbing power) P _A of the microwave is absorbed into the plasma in the processing chamber 1 through the transmitting plate 28, whereas if not provided a stub 43 was 641W, In the case where the stub 43 was provided, it was 1373W, which was greatly improved.

  Further, when the electron density and the electron temperature distribution of the plasma in the processing container 1 are imaged, the plasma electron temperature and the electron density are higher when the stub 43 is provided than when the stub 43 is not provided. It was confirmed that both of them spread uniformly over a wider range in the radial direction of the planar antenna plate 31 while maintaining a low electron temperature and high electron density state immediately below the transmission plate 28.

  Further, when the distribution of N radicals and N ions in the processing container 1 is imaged, when the stub 43 is provided, both the N radicals and N ions are directly below the transmission plate 28 as compared with the case where the stub 43 is not provided. Thus, it was confirmed that the flat antenna plate 31 spreads uniformly over a wide range in the radial direction.

  From the above simulation results, it was confirmed that the plasma can be made uniform in the processing container 1 by providing the stub 43.

  An experiment was conducted to prove that the in-plane uniformity of the treatment can be improved by adjusting the height of the stub. The experimental method and the results are described below.

  First, the configuration of the plasma processing apparatus used in the experiment will be described with reference to FIG. The plasma processing apparatus shown in FIG. 27 differs from the plasma processing apparatus shown in FIG. 1 only in the following points. First, a protrusion 28 a is provided at the center of the lower surface of the transmission plate 28. Further, instead of the cover ring 4, a cover 4a covering the entire surface of the mounting table 2 is provided, and the positioning of the wafer W is performed by a guide 4b provided on the upper surface of the cover 4a. Instead of the stub 43, four stubs 43A capable of changing the effective stub height are provided. A movable body 43a is provided inside the stub 43A, and the movable body 43a moves vertically by a bolt / nut structure (the detailed structure is not shown) by rotating the handle 43b. Can do. Since the movable body 43a determines the effective tube length of the stub similarly to the lid body 44 of the stub 43, the substantial stub height (H) can be changed by moving the movable body 43a up and down.

  As shown in FIG. 28, the base plate 31a of the planar antenna plate 31 is formed with 24 slot pairs on the outer peripheral portion and 8 slot pairs on the central portion. The base material 31a has an intermediate portion in which no slot 32 is formed between the outer peripheral portion and the central portion. The stubs 43A are arranged at intervals of 90 degrees on a pitch circle having a predetermined diameter. FIG. 28 shows the outline of the inner wall surface of the stub 43A. In plan view, the stubs 43A are arranged so that the centers of the four stubs overlap each other on the circumference connecting the centers of the inner slots (32b) of the slot pairs (32a, 32b) on the outer periphery of the planar antenna plate 31. And slots are arranged. In addition, on the line connecting the center of each slot of the inner peripheral slot pair (32c, 32d) and the center of the outer slot (32a) of the outer peripheral slot pair (32a, 32b) in the radially outward direction, The stub 43A and the slot are arranged such that the center of each of the four stubs 43A overlaps and at least one slot (32b) inside the outer peripheral slot pair (32a, 32b) is inside each stub 43A. Is arranged.

  The graph of FIG. 29 shows the relationship between the stub height H and the electric field strength of the top plate (transmission plate 28) below the stub when the microwave frequency is 2.45 GHz. From FIG. 29, within the range of stub height H of 20 to 60 mm, the electric field strength decreases as the stub height H increases, and the change in the electric field strength relative to the change in the stub height H becomes relatively gradual. You can see that Therefore, changing the stub height H in the range of 20 to 60 mm is suitable for fine adjustment of the electric field distribution.

  Although not shown in FIG. 29, the electric field strength periodically changes every time the stub height H changes by λ / 2 (λ is the wavelength in the tube).

[First experiment]
In the experiment, a semiconductor wafer having a 30 Å thick SiO ₂ thermal oxide film formed on the surface was prepared. This wafer was subjected to plasma nitridation using the microwave plasma processing apparatus described with reference to FIGS.

The process conditions in the first experiment are as follows.
Ar gas flow rate: 1000 mL / min (sccm)
N ₂ gas flow rate: 200 mL / min (sccm)
Process pressure: 25Pa
Microwave output: 1900 W (0.97 W / cm ² )
Wafer temperature: 500 ° C
Process time: 50 sec

  First, the height of all four stubs was set to 40 mm (that is, the median value of 20 to 60 mm), and plasma nitriding was performed. The nitrogen concentration was measured by XPS (X-ray Photoelectron Spectroscopy) at 25 locations on the processed wafer surface. The result is shown in the left column (“initial”) of the table of FIG. In this table, the stub height at each position is shown in the upper row, a map showing the nitrogen concentration distribution on the wafer is shown in the middle row, and the in-plane uniformity index of processing is shown in the lower row. A certain σ / AVE (that is, standard deviation of nitrogen concentration / average value of nitrogen concentration) and Range / 2AVE [that is, (maximum value of nitrogen concentration−minimum value of nitrogen concentration) / average value of nitrogen concentration × 2] are shown. Has been. Note that the stub position means that “1” is upward toward the paper surface in the map, “2” is left toward the paper surface in the map, “3” is downward toward the paper surface in the map, and “4”. Means each position on the right in the map (see also FIG. 28). In the middle map, the area where the nitrogen concentration is close to the average value is “0”, “+1, +2,...” According to the concentration level of the area where the nitrogen concentration is higher than that, and the area where the nitrogen concentration is lower than that. The values “−1, −2,...” Are assigned according to the density level.

  In accordance with the basic policy of reducing the height of the stub at the position corresponding to the region having a low nitrogen concentration and increasing the height of the stub at the position corresponding to the region having a high nitrogen concentration, each position as shown in STEPs 1-3. The table of FIG. 30 shows the process of increasing the in-plane uniformity of the nitrogen concentration by trial and error while changing the stub height. According to this table, it can be seen that the nitrogen concentration distribution can be changed by changing the electric field strength distribution by changing the height of the stub. In this first experiment, as shown in STEPs 1-3 of FIG. 30, by increasing the stub height at position 1 from 40 mm to 50 mm and decreasing the stub height at position 2 from 40 mm to 25 mm, Satisfactory in-plane uniformity was secured.

[Second experiment]
Next, using the same plasma processing apparatus as in the first experiment, a second experiment was performed under different process conditions described below.

The process conditions in the second experiment are as follows.
Ar gas flow rate: 750 mL / min (sccm)
N ₂ gas flow rate: 200 mL / min (sccm)
Process pressure: 25Pa
Microwave output: 2000 W (0.97 W / cm ² )
Wafer temperature: 500 ° C
Process time: 50 sec

  The result is shown in FIG. 31A is a map showing the initial nitrogen concentration, and FIG. 31B is a map showing the nitrogen concentration distribution at the end of adjustment. Description of the intermediate process of adjustment is omitted. The initial stub height was 30 mm at all positions 1, 2, 3, and 4. At this time, σ / AVE was 1.02, and Range / 2AVE was 1.99. In contrast, as a result of changing the stub height to 45 mm at position 1, 20 mm at position 2, 20 mm at position 3, and 45 mm at position 4, σ / AVE is 0.43, and Range / 2AVE is 1.03. As a result, a significant improvement in in-plane uniformity was confirmed. From the first and second experiments, it was confirmed that even if the process conditions are different, the nitrogen concentration distribution can be changed by changing the electric field strength distribution by changing the stub height.

  From the above experimental results, even when the process conditions such as pressure and microwave power change greatly, the electric field intensity distribution is changed by changing the stub height, and the in-plane of the wafer W is changed. It is understood that the nitrogen concentration distribution can be made uniform. Further, in the case where the slot arrangement is different, the shape of the top plate (transmission plate 28) is different, or there is a difference between chambers, the electric field strength can be adjusted by adjusting the stub height as in the above experimental example. By adjusting the above, uniform processing can be realized within the surface of the wafer W.

  As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible. For example, in the embodiment described above, the stub 43 is disposed so that the longitudinal direction of the stub 43 is orthogonal to the radial direction of the planar antenna plate 31, but the present invention is not limited to this. For example, as shown in FIG. 32, the stub 43 may be arranged so that the longitudinal direction of the slot 32 and the longitudinal direction of the stub 43 coincide. Further, the stub 43 is not limited to the slots 32a and 32b constituting the outermost peripheral slot pair of the planar antenna plate 31. For example, if the electric field is abnormally strong, the stub 43 may be located at any position on the planar antenna plate 31. You may arrange on top.

  Further, the shape of the horizontal cross section of the stub 43 is not limited to a rectangle, and may be, for example, a square or a circle (including an ellipse). Further, the stub 43 may be formed in an annularly continuous shape so as to surround the coaxial waveguide 37a.

  The plasma processing apparatus provided with the stub 43 of the present invention can be applied to, for example, a plasma oxidation processing apparatus, a plasma nitriding processing apparatus, a plasma CVD processing apparatus, a plasma etching processing apparatus, a plasma ashing processing apparatus, and the like. Furthermore, the plasma processing apparatus provided with the stub 43 of the present invention is not limited to processing a semiconductor wafer as an object to be processed. For example, a substrate for a flat panel display device such as a liquid crystal display device or an organic EL display device is processed. It can also be applied to a plasma processing apparatus as a body.

It is a schematic sectional drawing which shows an example of the plasma processing apparatus which concerns on embodiment of this invention. It is drawing which shows the structure of the planar antenna board in the plasma processing apparatus of FIG. It is a principal part perspective view which shows the structure of the upper part of the plasma processing apparatus of FIG. It is a block diagram which shows schematic structure of the control system of the plasma processing apparatus of FIG. It is principal part sectional drawing of the upper part of the plasma processing apparatus of FIG. 1 which shows the structural example of a stub. It is principal part sectional drawing of the upper part of the plasma processing apparatus which shows another structural example of a stub. It is principal part sectional drawing of the upper part of the plasma processing apparatus which shows another structural example of a stub. It is principal part sectional drawing of the upper part of the plasma processing apparatus which shows another structural example of a stub. It is principal part sectional drawing of the upper part of the plasma processing apparatus which shows another structural example of a stub. It is drawing explaining the arrangement position of the stub with respect to a slot. It is drawing explaining another example of the arrangement position of the stub with respect to a slot. It is drawing explaining the further another example of the arrangement position of the stub with respect to a slot. It is drawing used for description of the power balance of the microwave in simulation. It is drawing explaining the number of arrangement | positioning of the stub with respect to a planar antenna board. It is drawing explaining another example of the arrangement | positioning number of the stub with respect to a planar antenna board. It is drawing explaining the further another example of the arrangement | positioning number of the stub with respect to a planar antenna board. It is drawing explaining the example of arrangement | positioning of the stub with respect to a planar antenna board. It is drawing explaining another example of arrangement | positioning of the stub with respect to a planar antenna board. It is drawing explaining another example of arrangement | positioning of the stub with respect to a planar antenna board. It is drawing explaining the arrangement position and number of stubs in simulation. It is drawing explaining the arrangement position and number of stubs in simulation. It is drawing explaining the arrangement position and number of stubs in simulation. It is drawing explaining the arrangement position and number of stubs in simulation. It is drawing explaining the arrangement position and number of stubs in simulation. It is drawing explaining the arrangement position and number of stubs in simulation. It is drawing explaining the arrangement position and number of stubs in simulation. It is a schematic sectional drawing which shows the structure of the plasma processing apparatus used for experiment. It is a top view which shows the positional relationship of a stub and a slot in the plasma processing apparatus used for experiment. It is a graph which shows the relationship between stub height and the electric field strength of a top-plate part. It is a chart which shows the result of the 1st experiment. It is a figure which shows the result of a 2nd experiment. It is drawing explaining the modification of the arrangement position of the stub with respect to a slot.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Processing container, 2 ... Mounting stand, 3 ... Support member, 5 ... Heater, 12 ... Exhaust pipe, 15 ... Gas introduction part, 18 ... Gas supply mechanism, 19a ... Inert gas supply source, 19b ... Oxygen containing gas supply Source, 24 ... exhaust device, 27 ... microwave introduction mechanism, 28 ... transmission plate, 29 ... sealing member, 31 ... planar antenna plate, 32 ... slot, 37 ... waveguide, 37a ... coaxial waveguide, 37b ... rectangular Waveguide, 39 ... microwave generator, 43 ... stub, 50 ... control unit, 51 ... process controller, 52 ... user interface, 53 ... storage unit, 100 ... plasma processing apparatus, W ... semiconductor wafer (substrate)

Claims (11)

A processing container that can be evacuated to accommodate a workpiece;
A transmission plate that is airtightly attached to the upper opening of the processing vessel and transmits microwaves for plasma generation;
A planar antenna that has a plurality of slots formed through a flat substrate made of a conductive material and is arranged on the transmission plate to introduce microwaves into the processing container;
A conductive cover member covering the planar antenna from above;
A first waveguide provided through the conductive cover member and supplying microwaves from a microwave generation source to the planar antenna;
A plurality of second waveguides arranged above the outer periphery of the planar antenna, for adjusting the electric field distribution in the planar antenna;
A plasma processing apparatus comprising:   The plasma processing apparatus according to claim 1, wherein the second waveguide is disposed in a range of 2 to 4.   The plasma processing apparatus according to claim 2, wherein at least two of the second waveguides are arranged symmetrically in the radial direction with the center of the planar antenna interposed therebetween.   4. The plasma processing apparatus according to claim 3, wherein the second waveguide is disposed above a line connecting the slots from the center of the planar antenna in a radially outward direction.   The slots are concentrically arranged in a slot pair in the flat substrate, and the second waveguide is above or outside the radially inner slot of the slot pair. The plasma processing apparatus according to claim 4, wherein the plasma processing apparatus is disposed above the slot.   6. The plasma processing apparatus according to claim 5, wherein the center of the second waveguide is positioned so as to overlap the center of the opening of the slot.   7. A part of or the whole of the second waveguide is constituted by a hollow member having a cavity inside inserted into the conductive cover member. The plasma processing apparatus according to claim 1.   7. The plasma processing according to claim 3, wherein a part or the whole of the second waveguide is configured by an opening that penetrates the conductive cover member. 8. apparatus.   The plasma processing according to any one of claims 3 to 6, wherein a part or the whole of the second waveguide is configured by a recess formed in the conductive cover member. apparatus.   The plasma processing apparatus according to claim 1, wherein an upper end portion of the second waveguide is closed. 11. The plasma processing according to claim 1, further comprising a retardation plate for adjusting a wavelength of a microwave supplied to the planar antenna on the planar antenna. apparatus.

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