JP2019046787A - Plasma probe apparatus and plasma processing apparatus - Google Patents

Abstract

To provide a plasma probe apparatus that avoids the entry of gas.SOLUTION: A plasma probe apparatus includes an antenna unit attached to an opening formed in a wall or a mounting table of a processing container via a seal member for sealing between a vacuum space and an atmosphere space, an electrode connected to the antenna unit, and a dielectric support portion formed of a dielectric body and supporting the antenna portion from the periphery. Facing surfaces of the antenna unit and the wall or the mounting table are separated at a predetermined width, and the surface of the antenna unit exposed from the opening is recessed relative to the wall in which the opening is formed or the surface on the plasma generation space side of the mounting table.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a plasma probe apparatus and a plasma processing apparatus.

  Conventionally, a probe for measuring the state of plasma is inserted into the chamber, and the state of plasma is measured by supplying measurement power from the measurement power supply into the chamber (for example, See Patent Documents 1 to 3). For example, the probe disclosed in Patent Document 1 includes an antenna for emitting power, a coaxial cable for transmitting measurement power, and a dielectric tube whose tip is closed, and is in the dielectric tube. The antenna and the coaxial cable are connected to each other and inserted. The behavior of the plasma when generating the plasma is sensed by the arranged probe.

JP 2004-55324 A JP, 2005-277397, A Japanese Patent Laid-Open No. 6-68825

  However, in the conventional probe structure, the probe is disposed along the wall of the chamber or on the side of the plasma generation space with respect to the wall of the chamber. For this reason, gas, products generated during plasma processing, etc. are easily introduced into the gap formed between the probe disposed facing the plasma generation space and the chamber wall, which causes particles to be generated.

  Further, in the conventional probe structure, there is a concern that the gas may intrude into the inside of the probe, and the performance deterioration due to the corrosion inside the probe and the deposition residue may occur.

  It is an object of the present invention, in one aspect, to provide a plasma probe apparatus that avoids the entry of gas.

  In order to solve the above problems, according to one aspect, an antenna unit attached to an opening formed in a wall of a processing container or a mounting table via a seal member that seals between a vacuum space and an atmospheric space An electrode connected to the antenna unit, and a dielectric support unit formed of a dielectric and supporting the antenna unit from the periphery, and the opposing surface of the antenna unit and the wall or the mounting table is A plasma probe apparatus, which is separated by a predetermined width and exposed from the opening, is recessed with respect to the wall on which the opening is formed or the surface on the plasma generating space side of the mounting table. Provided.

  According to another aspect, there is provided a plasma processing apparatus comprising: a plurality of microwave radiation mechanisms for radiating microwaves output from an output section of a microwave plasma source into a processing container; and a plasma probe apparatus, wherein the plasma The probe apparatus includes an antenna unit attached to an opening formed in a wall or a mounting table of the processing container via a seal member for sealing between a vacuum space and an atmosphere space, and an electrode connected to the antenna unit And a dielectric support portion formed of a dielectric and supporting the antenna portion from the periphery, separating the facing surface of the antenna portion and the wall or the mounting table by a predetermined width, and the opening portion There is provided a plasma processing apparatus, wherein the surface of the antenna portion exposed from the surface is recessed relative to the wall on which the opening is formed or the surface on the plasma generation space side of the mounting table. .

  According to one aspect, it is possible to provide a plasma probe apparatus that avoids the ingress of gas.

The figure which shows an example of the microwave plasma processing apparatus which concerns on one Embodiment. The figure which shows an example of the inner wall of the ceiling part of the microwave plasma processing apparatus which concerns on one Embodiment. The figure which shows an example of a structure of the plasma probe apparatus which concerns on one Embodiment. The figure which shows an example of arrangement | positioning of the plasma probe apparatus which concerns on one Embodiment. The figure which shows an example of arrangement | positioning of the plasma probe apparatus which concerns on one Embodiment. The figure which shows an example of the measurement result by the plasma probe apparatus which concerns on one Embodiment. The figure which shows an example of the power dependence of plasma electron temperature by the probe measurement which concerns on one Embodiment. The figure which shows an example of the power dependence of plasma electron density by the probe measurement which concerns on one Embodiment. The figure which shows an example of a structure of the plasma probe apparatus which concerns on the modification of one Embodiment. The figure which shows an example of a structure of the plasma probe apparatus which concerns on the modification of one Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and the drawings, substantially the same configuration is given the same reference numeral to omit redundant description.

[Microwave plasma processing system]
FIG. 1 shows an example of a cross-sectional view of a microwave plasma processing apparatus 100 according to an embodiment of the present invention. The microwave plasma processing apparatus 100 has a processing container (chamber) 1 for containing a semiconductor wafer W (hereinafter, referred to as “wafer W”). The microwave plasma processing apparatus 100 is an example of a plasma processing apparatus that performs predetermined plasma processing on the wafer W by surface wave plasma formed on the inner wall surface of the ceiling portion of the processing container 1 by microwaves. As the predetermined plasma treatment, film formation treatment, etching treatment, ashing treatment and the like are exemplified.

  The microwave plasma processing apparatus 100 includes a processing vessel 1, a microwave plasma source 2, and a control device 3. The processing container 1 is a substantially cylindrical container made of a metal material such as aluminum or stainless steel which is airtightly configured, and is grounded.

  The processing container 1 has a main body 10, and forms a plasma processing space inside. The main body unit 10 is a disk-shaped top plate that constitutes a ceiling portion of the processing container 1. A support ring 129 is provided on the contact surface between the processing container 1 and the main body 10, whereby the inside of the processing container 1 is airtightly sealed. The main body 10 is formed of a metal material such as aluminum or stainless steel.

  The microwave plasma source 2 has a microwave output unit 30, a microwave transmission unit 40, and a microwave radiation mechanism 50. The microwave output unit 30 outputs microwaves by distributing to a plurality of paths. The microwaves are introduced into the processing vessel 1 through the microwave transmission unit 40 and the microwave radiation mechanism 50. The gas supplied into the processing container 1 is excited by the electric field of the introduced microwave, thereby forming a surface wave plasma.

  A mounting table 11 for mounting the wafer W is provided in the processing container 1. The mounting table 11 is supported by a cylindrical support member 12 erected at the center of the bottom of the processing container 1 via an insulating member 12 a. As a material which comprises the mounting base 11 and the supporting member 12, metal, such as aluminum etc. which carried out the alumite process (anodizing process) of the surface, and the insulation members (ceramics etc.) which had the electrode for high frequencies inside are illustrated. The mounting table 11 may be provided with an electrostatic chuck for electrostatically attracting the wafer W, a temperature control mechanism, a gas flow path for supplying a heat transfer gas to the back surface of the wafer W, and the like.

  A high frequency bias power supply 14 is connected to the mounting table 11 via a matching unit 13. The supply of high frequency power from the high frequency bias power supply 14 to the mounting table 11 causes ions in the plasma to be drawn to the wafer W side. The high frequency bias power supply 14 may not be provided depending on the characteristics of the plasma processing.

  An exhaust pipe 15 is connected to the bottom of the processing container 1, and an exhaust device 16 including a vacuum pump is connected to the exhaust pipe 15. When the exhaust device 16 is operated, the inside of the processing container 1 is exhausted, whereby the inside of the processing container 1 is rapidly depressurized to a predetermined degree of vacuum. A loading / unloading port 17 for loading / unloading the wafer W and a gate valve 18 for opening / closing the loading / unloading port 17 are provided on the side wall of the processing container 1.

  The microwave transmission unit 40 transmits the microwaves output from the microwave output unit 30. Referring to FIG. 2 which shows the A-A cross section of FIG. 1, the central microwave introducing part 43b in the microwave transmission part 40 is disposed at the center of the main body part 10, and the six peripheral microwave introducing parts 43a are main body It is arranged at equal intervals in the circumferential direction around the portion 10. The central microwave introducing portion 43 b and the six peripheral microwave introducing portions 43 a are provided correspondingly to each other, and the function and impedance for introducing the microwave output from the amplifier unit 42 shown in FIG. 1 into the microwave radiation mechanism 50 Have the ability to match. Hereinafter, the peripheral microwave introduction unit 43a and the central microwave introduction unit 43b are collectively referred to as the microwave introduction unit 43.

  As shown in FIGS. 1 and 2, the six dielectric layers 123 are disposed inside the main body 10 below the six peripheral microwave introduction parts 43a. In addition, one dielectric layer 133 is disposed inside the main body 10 below the central microwave introducing portion 43 b. The number of peripheral microwave introduction parts 43a and dielectric layers 123 is not limited to six, and may be two or more. However, the number of the peripheral microwave introduction parts 43a and 123 is preferably three or more, and may be, for example, three to six.

The microwave radiation mechanism 50 shown in FIG. 1 has dielectric top plates 121 and 131, slots 122 and 132, and dielectric layers 123 and 133. The dielectric top plates 121 and 131 are formed of a disk-like dielectric that transmits microwaves, and are disposed on the top surface of the main body portion 10. The dielectric top plates 121 and 131 are formed of, for example, a ceramic such as quartz or alumina (Al ₂ O ₃ ), a fluorine-based resin such as polytetrafluoroethylene, or a polyimide-based resin having a dielectric constant larger than that of vacuum. There is. Thus, the wavelength of the microwaves transmitted through the dielectric top plates 121 and 131 is made shorter than the wavelength of the microwaves propagating in the vacuum to make the antenna including the slots 122 and 132 smaller.

Below the dielectric top plates 121 and 131, the dielectric layers 123 and 133 are in contact with the back surface of the opening of the main body portion 10 through the slots 122 and 132 formed in the main body portion 10. The dielectric layers 123 and 133 are formed of, for example, a ceramic such as quartz or alumina (Al ₂ O ₃ ), a fluorine-based resin such as polytetrafluoroethylene, or a polyimide-based resin. The dielectric layers 123 and 133 are provided at positions recessed from the ceiling surface by the thickness of the opening formed in the main body portion 10, and function as dielectric windows for supplying microwaves to the plasma generation space U.

  The peripheral microwave introducing portion 43a and the central microwave introducing portion 43b coaxially arrange the cylindrical outer conductor 52 and the rod-like inner conductor 53 provided at the center thereof. The microwave power is supplied between the outer conductor 52 and the inner conductor 53, and the microwave transmission path 44 in which the microwaves propagate toward the microwave radiation mechanism 50 is formed.

  A slug 54 and an impedance adjusting member 140 located at the tip of the peripheral microwave introducing portion 43 a and the central microwave introducing portion 43 b are provided. By moving the slag 54, the impedance of the load (plasma) in the processing vessel 1 is matched to the characteristic impedance of the microwave power source in the microwave output unit 30. The impedance adjustment member 140 is formed of a dielectric, and adjusts the impedance of the microwave transmission line 44 by its relative dielectric constant.

The main body unit 10 is provided with a gas introducing unit 21 having a shower structure. The gas supplied from the gas supply source 22 is supplied from the gas diffusion chamber 62 through the gas introduction portion 21 via the gas supply pipe 111 into the processing container 1 in a shower shape. The gas introduction unit 21 is an example of a gas shower head that supplies gas from a plurality of gas supply holes 60 formed in the ceiling wall of the processing container 1. Examples of the gas include a gas for plasma generation such as Ar gas, a gas desired to be decomposed with high energy such as O ₂ gas and N ₂ gas, and a processing gas such as silane gas.

  Each part of the microwave plasma processing apparatus 100 is controlled by the control device 3. The control device 3 includes a microprocessor 4, a read only memory (ROM) 5, and a random access memory (RAM) 6. The ROM 5 and the RAM 6 store a process sequence which is a process sequence and control parameters of the microwave plasma processing apparatus 100. The microprocessor 4 is an example of a control unit that controls each unit of the microwave plasma processing apparatus 100 based on a process sequence and a process recipe. In addition, the control device 3 has a touch panel 7 and a display 8, and can perform input when performing predetermined control in accordance with the process sequence and the process recipe, and display of the result.

  When plasma processing is performed in the microwave plasma processing apparatus 100 having such a configuration, the wafer W is first held from the opened gate valve 18 through the loading / unloading port 17 into the processing container 1 while being held on the transfer arm. It is carried in. The gate valve 18 is closed after the wafer W is loaded. When the wafer W is transported to the upper side of the mounting table 11, the wafer W is transferred from the transfer arm to the pusher pin, and the wafer W is mounted on the mounting table 11 by lowering the pusher pin. The pressure inside the processing container 1 is maintained at a predetermined degree of vacuum by the exhaust device 16. A processing gas is introduced into the processing container 1 from the gas introduction unit 21 in the form of a shower. The microwaves radiated from the microwave radiation mechanism 50 through the peripheral microwave introduction part 43a and the central microwave introduction part 43b propagate on the inner surface of the ceiling wall. The gas is excited by the electric field of the microwaves that propagate as surface waves, and the wafer W is subjected to plasma processing by surface wave plasma generated in the plasma generation space U under the ceiling wall on the processing container 1 side.

[Plasma probe device]
A plurality of openings 1 b are formed in the circumferential direction on the side wall of the processing container 1, and a plurality of plasma probe devices 70 are attached. However, the number of plasma probe devices 70 attached to the processing container 1 may be one. The plasma probe device 70 senses the plasma generated in the plasma generation space U. Based on the sensing result, for example, the plasma electron temperature _Te and the plasma electron density _Ne can be calculated to estimate the behavior of the plasma.

  The plasma probe device 70 is connected to the monitor device 80 outside the microwave plasma processing apparatus 100. The monitor device 80 has a signal transmitter and outputs a signal of a predetermined frequency emitted by the signal transmitter. The signal is transmitted through the coaxial cable 81, transmitted to the plasma probe device 70, and transmitted from the antenna unit 71 at the tip of the plasma probe device 70 to plasma.

The plasma probe device 70 detects the current value of the signal reflected from the plasma side in response to the signal transmitted to the plasma side, and sends it to the monitor device 80. The current value of the detected signal is transmitted from the monitoring device 80 to the control device 3 and is subjected to FFT (frequency) analysis by the microprocessor 4 of the control device 3. Thereby, the plasma electron temperature _Te and the plasma electron density _Ne are calculated.

[Configuration of plasma probe device]
Next, an example of the configuration of the plasma probe device 70 will be described with reference to FIG. FIG. 3 is a view showing an example of the configuration of a plasma probe apparatus 70 according to an embodiment. The plasma probe apparatus 70 includes an antenna unit 71 attached to the opening 1 b formed in the side wall of the processing container 1 via an O-ring 73, an electrode 72 connected to the antenna unit 71, and the antenna unit 71 from the periphery. And a dielectric support 74 for supporting.

  The antenna unit 71 is provided at the tip of the plasma probe device 70. In the present embodiment, the tip of the antenna unit 71 is a disk-like member 71 a, and is disposed so as to close the opening of the opening 1 b via the O-ring 73. The O-ring 73 is formed of a dielectric such as resin. However, the tip of the antenna unit 71 is not limited to the disk shape, and may be, for example, a rectangular shape.

  The enlarged view of the opposing surface of the antenna part 71 (disk-shaped member 71a) of the periphery of the O-ring 73 and the wall of the processing container 1 is shown on the lower side of FIG. The tip end surface of the antenna unit 71 and the back surface near the opening 1 b of the wall of the processing container 1 are separated, and a gap 1 d of a predetermined width is formed.

  As described above, if the gap 1 d is not formed between the tip end surface of the antenna unit 71 and the wall of the processing container 1, the antenna unit 71 is DC-connected to the wall of the processing container 1. Then, the current of the signal transmitted from the monitoring device 80 flows to the wall of the processing vessel 1, and the ratio of the current flowing to the plasma becomes low. As a result, the antenna unit 71 does not function as an antenna of the plasma probe device 70. For this reason, a gap 1d of a predetermined width is formed on the tip surface of the antenna unit 71 and the back surface near the opening 1b of the wall of the processing container 1. The current of the signal flowing from the antenna unit 71 to the wall of the processing container 1 is referred to as “floating current”.

  Even when the alternating current flows to the wall side of the processing container 1, the antenna unit 71 functions as an antenna of the plasma probe device 70. However, in order to increase the sensitivity of the plasma probe apparatus 70, it is preferable that the floating current does not flow to the wall side of the processing vessel 1 including not only direct current but also alternating current.

  On the other hand, if the gap 1d is too wide, gas or plasma enters the gap 1d, causing problems of corrosion due to plasma, particles due to gas intrusion and abnormal discharge. Therefore, the gap 1 d is a space large enough to prevent the antenna portion 71 from being connected to the wall of the processing container 1 in a DC manner, and is designed to be narrow enough not to allow plasma or gas to enter.

  The antenna unit 71 is disposed at a position recessed from the inner wall surface of the processing container 1 in which the opening 1 b is formed, and the surface of the antenna unit 71 is exposed to the plasma generation space U at a recessed position from the inner wall surface. . By denting the surface of the antenna unit 71, the position where the gap 1d between the antenna unit 71 serving as a particle generation source and the wall of the processing container 1 is provided is separated from the wafer W. Thereby, generation of particles and intrusion of gas into the plasma probe device 70 can be prevented, the influence of the particles on the characteristics of plasma processing can be reduced, and corrosion of the plasma probe device 70 by plasma can be reduced. In addition, the surface of the antenna unit 71 is recessed without being at the same height as the inner wall surface of the processing container 1, thereby making it difficult to cause mode jump of surface wave plasma propagating in the inner wall surface of the processing container 1 and causing abnormal discharge. It can be avoided.

In addition, at least the region from the opening 1 b to the O-ring 73, which is the surface (tip surface) of the antenna unit 71, is covered with the insulator film 76 by thermal spraying of Y ₂ O ₃ . In addition, the region from the side surface of the opening 1b to the O-ring 73, which is a wall surface of the processing container 1 and passes through the back surface of the opening 1b, is covered with the insulator 1c by thermal spraying of Y ₂ O ₃ .

  As a result, it is possible to prevent direct current from flowing from the antenna unit 71 to the wall side of the processing container 1. In addition, plasma resistance can be enhanced. When the surface on the air side of the O-ring 73 of the antenna unit 71 and the inner wall surface of the processing container 1 are coated with the film 77 of an insulator, the plasma resistance is further improved, which is more preferable. The insulator films 76, 77, 1c may be formed by anodizing.

  The O-ring 73 seals between the vacuum space on the opening 1 b side and the atmospheric space on the mounting side of the plasma probe device 70. The O-ring 73 is an example of a seal member that seals between the vacuum space and the atmosphere space.

  As described above, in the present embodiment, the O-ring 73 is pressed against the back surface of the wall of the processing container 1 near the opening 1 b at the front end surface of the antenna unit 71 to seal the vacuum space and the atmosphere space. The gas hardly enters the gap between the antenna unit 71 and the wall of the processing container 1. Thereby, generation of particles can be reduced.

  In addition, if a corrosive gas enters the gap between the antenna unit 71 and the wall of the processing container 1, the antenna unit 71 is corroded and the performance of the plasma probe device 70 is degraded. From the above, when the plasma probe device 70 is disposed in the opening 1 b of the processing container 1, the vacuum seal by the O-ring 73 is further reduced as much as possible so that the gas does not enter the back side of the plasma probe device 70. It is done around the opening.

  As for the size of the opening 1b, the wider the opening, the higher the ratio of the current of the signal transmitted from the monitor device 80 to the plasma without being a floating current, so the sensitivity of the antenna unit 71 is improved. On the other hand, the wider the opening is, the easier it is for plasma and gas to intrude into the antenna unit 71 side, so that the antenna unit 71 is corroded by corrosion resistant gas and plasma, which lowers the performance of the plasma probe device 70 or abnormality. Discharge may occur. In addition, if the sensitivity of the plasma probe device 70 is too good, for example, reaction products generated in plasma processing adhere to the surface of the plasma probe device 70 etc. Measurement results are affected. As a result, the state of the plasma may not be measured accurately. Therefore, in consideration of the sensitivity of the antenna unit 71 and the penetration of gas or plasma, the opening of the opening 1 b is designed to an appropriate value within a range where the state of plasma can be measured with high accuracy. Further, the shape of the opening 1 b may be a circle, a rectangle, or another shape.

  The electrode 72 is inserted into the antenna unit 71, measures a current value indicating the state of plasma, and transmits it to the monitor device 80. The dielectric support portion 74 may be made of, for example, PTFE (polytetrafluoroethylene). The dielectric support portion 74 is an example of a fixing member that surrounds the antenna portion 71 and fixes the antenna portion 71 and the O-ring 73. The dielectric support portion 74 is fixed by screwing a metal member 1a such as aluminum to the wall of the processing container 1 with the antenna portion 71 and the O-ring 73 fixed in the vicinity of the opening 1b.

  In the present embodiment, the dielectric support portion 74 is separated into the two dielectric support parts 74a and 74b, but is not limited to this and may be integrated. Also, for example, the dielectric support portion 74 may be only the dielectric support part 74 a that fixes the disk-shaped member 71 a of the antenna portion 71 from the outer peripheral side. In this case, the antenna portion 71, the dielectric support part 74a and the O-ring 73 are fixed by the member 1a. In this case, the dielectric support part 74b may be a space or may be filled with PTFE.

  The ratio of the length C of the dielectric support portion 74 in the depth direction to the diameter B of the disk-like member 71a in FIG. 3 is about 1/2, specifically, any value in the range of 0.44 to 0.54. Is formed. If the diameter B and the length C are small or the ratio thereof is not appropriate, the current from the electrode 72 does not reach the plasma through the antenna portion 71, and the sensitivity becomes worse. Therefore, by setting the length B and the length C within the predetermined range, it is possible to provide the plasma probe device 70 with high sensitivity.

  In order to improve the sensitivity of the plasma probe apparatus 70, it is necessary to minimize the floating current flowing from the antenna unit 71 to the wall of the processing vessel 1. That is, the sensitivity of the plasma probe apparatus 70 is improved as the ratio of the current flowing in the plasma to the floating current is increased. Therefore, in order to increase the ratio of the current flowing in the plasma to the floating current, it is preferable that the surface area of the antenna portion 71 exposed to the opening 1 b be large.

  Therefore, in the present embodiment, at least one of the concave portion and the convex portion may be formed in the region of the tip surface of the antenna portion 71 which is exposed from the opening 1b. Alternatively, the distal end surface of the antenna unit 71 may be curved in a concave or convex shape. Thereby, the surface area of the antenna unit 71 can be increased. As a result, even when a signal of the same power is transmitted from the monitoring device 80, the current flowing to the plasma can be increased, and the sensitivity of the plasma probe device 70 can be further improved.

[Placement of plasma probe device]
Next, an example of the arrangement of the plasma probe device 70 will be described with reference to FIG. FIG. 4 is a view showing an example of the arrangement of the plasma probe device 70 with respect to the microwave plasma processing apparatus 100 according to the present embodiment. In the microwave plasma processing apparatus 100 according to the present embodiment, a part of the side wall of the processing container 1 is separated in a ring shape, and a plurality of openings 1 b are formed at equal intervals in the circumferential direction. The plasma probe apparatus 70 is attached to each through the O-ring 73. From the plurality of openings 1 b, a film 76 of an insulator of Y ₂ O ₃ for coating the antenna unit 71 is exposed on the plasma generation space side. The opening 1 b may be a slit provided in plural on the wall of the processing container 1. The opening 1 b may be formed in the side wall of the processing container 1 without separating the side wall in a ring shape.

  In the present embodiment, the plurality of openings 1b are provided in the circumferential direction of the side wall of the processing container 1, and the antenna portion 71 is pressed by the dielectric support parts 74a through the O-ring 73 in each opening 1b. Each plasma probe device 70 is attached. However, the member on which the plasma probe device 70 is disposed is not limited to the side wall of the processing container 1, and can be attached to at least one of the ceiling wall of the processing container 1 or the outer peripheral portion of the mounting table 11.

  For example, as shown in FIG. 5, a plurality of openings 1b are formed at equal intervals in, for example, the circumferential direction at the outer peripheral portion of the mounting table 11, and a plurality of plasma probe devices 70 are attached to the openings 1b. It is also good.

Further, a plurality of openings 1 b may be formed, for example, in the circumferential direction on the ceiling wall of the processing container 1, that is, the main body 10, and a plurality of plasma probe devices 70 may be attached to the openings 1 b. When the plasma probe device 70 is attached to the ceiling wall, Al ₂ O ₃ may be used instead of Y ₂ O _{3 as} the insulator film for coating the antenna unit 71.

[Measurement of plasma probe device]
An example of the result of measuring the state of plasma generated by the microwave plasma processing apparatus 100 by the plasma probe apparatus 70 of the present embodiment described above is shown in FIG. The current value I shown in the graph of the current measurement result on the upper side of FIG. 6 is transferred from the plasma probe device 70 to the control device 3 via the monitor device 80 and is FFT (Fourier Transform) by the microprocessor 4 of the control device 3 . As a result, as shown in the lower graph of FIG. 6, the amplitude component for each frequency is converted.

  In a plasma, current flows exponentially with respect to a predetermined voltage. The measured current value includes the component of the fundamental wave having the fundamental frequency, and harmonic components such as the first harmonic whose wavelength is twice that of the fundamental wave and the second harmonic whose wavelength is three times. ing. Therefore, plasma electron density and plasma electron temperature can be calculated by using the peak of the amplitude of the fundamental wave and the harmonics by FFT. In the graph after FFT, “1 ω” indicates the component of the fundamental wave, “2 ω” indicates the component of the first harmonic, and “3 ω” indicates the component of the second harmonic.

[Measurement of plasma electron density Ne / plasma probe device]
The control device 3 calculates the plasma electron density Ne and the plasma electron temperature Te using the amplitudes of the fundamental wave and the harmonics after the FFT of the current value measured by the plasma probe device 70. An example of the calculation method will be briefly described. When an alternating current is applied to the electrode 72 of the plasma probe device 70, a probe current _ipr shown in the equation (1) flows in the antenna unit 71.

ここで、ｅは電子素量、ｎ_ｓはプラズマシース表面の電子密度、

Here, e is an electron elementary quantity, n _s is the electron density of the plasma sheath surface,

は電子の平均速度、Ａはアンテナ部７１のプラズマに接している面積（つまり、開口部１ｂの面積）、Ｖ_Ｂｉａｓはプローブ印加電圧、Φ_ｐはプラズマ電位、Ｔ_ｅはプラズマの電子温度、ｕ_Ｂはボーム速度である。また、Ｖ_ｄｃは自己バイアス電圧、Ｖ_０はモニタ装置８０からプラズマプローブ装置７０に印加する交流電圧（例えば、４Ｖ〜５Ｖ）である。（１）式を第１種変形ベッセル関数Ｉ_ｋを用いて変形し、プローブ電流ｉ_ｐｒを（２）式のようにＤＣ成分とＡＣ成分に分離する。

Is the average velocity of electrons, A is the area of the antenna 71 in contact with the plasma (that is, the area of the opening 1b), V _Bias is the voltage applied to the probe, _{p p} is the plasma potential, T _e is the electron temperature of the plasma, u _B is Baume velocity. Further, V _dc is a self bias voltage, and V ₀ is an alternating voltage (for example, 4 V to ₅ V) applied from the monitor 80 to the plasma probe 70. The equation (1) is transformed using the first modified Bessel function I _k to separate the probe current _ip r into a DC component and an AC component as in equation (2).

（２）式の右辺の上段の項は、プローブ電流ｉ_ｐｒのＤＣ成分であり、（２）式の右辺の下段の項は、ｃｏｓ（ｋωｔ）に変数を掛け合わせたプローブ電流ｉ_ｐｒのＡＣ成分である。プローブ電流ｉ_ｐｒのＤＣ成分は、アンテナ部７１とプラズマとの間に流れる直流電流を示す。本実施形態に係るプラズマプローブ装置７０の構成では、アンテナ部７１と同軸ケーブル８１とは、ブロッキングコンデンサによりＤＣ的に接続されていないため、（２）式のプローブ電流ｉ_ｐｒのＤＣ成分は０とする。その結果、（３）式が導かれる。

(2) upper section of the right side of a DC component of the probe current _{i pr,} (2) is the lower section of the right side, cos (Keiomegati) probe current multiplied by the variable _{i pr} AC of It is an ingredient. The DC component of the probe current _ipr indicates a direct current flowing between the antenna unit 71 and the plasma. In the configuration of the plasma probe apparatus 70 according to the present embodiment, the antenna component 71 and the coaxial cable 81 are not connected in a DC manner by a blocking capacitor, so the DC component of the probe current _{ipr in} equation (2) is 0. Do. As a result, equation (3) is derived.

（３）式をフーリエ級数展開すると（４）式が得られる。

Fourier series expansion of equation (3) gives equation (4).

（４）式の左辺は、実測値であり、基本波（１ω）の電流ｉ_１ωの振幅との第１高調波（２ω）の電流ｉ_２ωの振幅との比を示す。
（４）式の右辺は、プローブ電流を第１種変形ベッセル関数で展開したときの基本波と第１高調波との比を示す。

The left side of the equation (4) is an actual measurement value and represents a _ratio of the amplitude of the current i _1ω of the fundamental wave (1ω) to the amplitude of the current i _2ω of the first harmonic (2ω).
The right side of the equation (4) represents the ratio of the fundamental wave to the first harmonic when the probe current is expanded by the first modified Bessel function.

Therefore, (4) from the equation, was calculated by FFT, can be calculated and the amplitude ratio of the amplitude and the first harmonic of the fundamental wave (1Omega) (2 [omega), the plasma electron temperature T _e from the ratio of the measured value. V ₀ is a monitor voltage (for example, 4 V).

Further, the DC component of the current i _1ω in the fundamental wave (1ω) is shown in equation (5). Equation (5) is 0 because it is a DC component of the current i 1 _ω .

電流ｉ_１ωのＡＣ成分を（６）式に示す。

The AC component of the current i _1ω is shown in equation (6).

（６）を用いて算出した基本波（１ω）における電流ｉ_１ωの絶対値を（７）式に代入することで、プラズマ中のイオン密度ｎ_ｉが算出される。イオン密度ｎ_ｉはプラズマ電子密度Ｎ_ｅに等しい。以上から、プラズマ電子密度Ｎ_ｅが算出される。

The ion density n _i in the plasma is calculated by substituting the absolute value of the current i _1ω in the fundamental wave (1ω) calculated using (6) into the equation (7). The ion density n _i is equal to the plasma electron density N _e . From the above, the plasma electron density _Ne is calculated.

The graph of FIG. 7 is an example of the result of comparing the power dependency of the plasma electron density N _e measured by the plasma probe apparatus 70 according to the present embodiment with the plasma electron density N _e measured by the Langmuir probe of the comparative example. is there. According to the graph, and when measured by a plasma probe device 70 according to the present embodiment, in the case of measuring by a Langmuir probe, power dependence of the plasma electron density N _e it is seen that substantially match.

The graph of FIG. 8 is an example of the result of comparing the power dependency of the plasma electron temperature T _e measured by the plasma probe apparatus 70 according to the present embodiment with the plasma electron temperature T _e measured by the Langmuir probe of the comparative example. is there. According to the graph, and when measured by a plasma probe device 70 according to the present embodiment, in the case of measuring by a Langmuir probe, power dependence of the plasma electron temperature T _e it is seen that substantially match.

  That is, the measurement result of the electrical specification of the plasma shows almost the same characteristic between the plasma probe device 70 according to the present embodiment and the Langmuir probe, and the plasma probe device 70 according to the present embodiment is similar to the Langmuir probe. It has been confirmed that it works. In addition, an example of the electric specific measurement of the plasma by a Langmuir probe is shown by Unexamined-Japanese-Patent No. 2009-194032.

  As described above, according to the plasma probe device 70 of the present embodiment, the gap 1 d which can prevent the generation of the floating current while preventing the gas from invading the inside of the plasma probe device 70 is provided. An antenna structure is provided. This improves measurement sensitivity and enables reliable measurement of plasma. Further, the structure in which the gas does not intrude can reduce the corrosion of the plasma probe device 70 due to plasma, and can prevent the performance of the plasma probe device 70 from being deteriorated.

[Modification]
If noise is large with respect to the current flowing between the antenna unit 71 and the plasma measured by the plasma probe device 70, the accuracy of the remaining signal obtained by removing the noise component from the signal is degraded. For example, as the floating current increases, the measurement sensitivity and accuracy of the signal measured by the plasma probe device 70 deteriorate.

  The O-ring 73 is considered electrically as a capacitance. When the O-ring 73 separates the metal of the side wall of the processing container 1 and the tip of the antenna portion 71 so as not to electrically connect the metals, the metals form a seal when sealing between the vacuum space and the atmosphere space. Adjacent, the leakage current (floating current) becomes large. As a result, the measurement sensitivity and measurement accuracy of the plasma probe device 70 may not be sufficiently obtained.

  So, in the plasma probe apparatus 70 concerning the modification of one Embodiment, it has the structure which can make generation | occurrence | production of a floating current zero substantially. A plasma probe apparatus 70 according to a modification of the embodiment will be described with reference to FIGS. 9 and 10.

  As shown in FIG. 9A, the plasma probe apparatus 70 according to the modification has an antenna portion 71, an electrode 75, and a dielectric support portion 74. The antenna unit 71 is attached to the opening 1 b formed in the side wall of the processing container 1 via the O-ring 73. The electrode 75 is embedded in the disk-shaped member 71 a at the tip of the antenna unit 71. The dielectric support portion 74 supports the antenna portion 71 from the periphery.

  In the plasma probe device 70 according to the modification, the disk-shaped member 71 a at the tip of the antenna unit 71 is formed of a dielectric. For example, the discoid member 71a may be formed of ceramics such as alumina. Therefore, the electrode 75 is embedded in the ceramic discoid member 71a so that the electrode 75 is not exposed in the vicinity of the surface 71a1 of the discoid member 71a exposed from the opening 1b. Thereby, since the electrode 75 is not exposed from the opening part 1b, generation | occurrence | production of a contamination can be prevented.

  Moreover, in the plasma probe apparatus 70 concerning a modification, a clearance gap is not provided between the side wall of the processing container 1 by which the O-ring 73 is arrange | positioned, and the disk shaped member 71a. This is because the side wall of the processing vessel 1 is metal and the disc-like member 71a is ceramic, so that both members do not conduct electricity. Therefore, the side wall of the processing container 1 and the disk-like member 71a can be electrically disconnected without providing a gap. Thus, the floating current leaking from the vicinity of the O-ring 73 can be reduced to almost zero, and the measurement sensitivity and accuracy of the plasma probe device 70 can be improved.

  In order to increase the measurement sensitivity of the plasma probe device 70, the area of the electrode 75 should be as large as possible. On the other hand, in order to obtain predetermined probe characteristics, it is preferable that the electrode 75 and the metal on the side wall of the processing container 1 do not overlap.

  Therefore, as shown in FIG. 9 (b), which is a view obtained by cutting FIG. 9 (a) along the B-B plane, the electrode 75 is separated by a distance W of about 2 to 3 mm from the edge of the opening 1b. It is preferable to make it circular. Furthermore, the electrode 75 is preferably in the form of a mesh.

  The opening 1 b is not limited to a circular shape, and may be a rectangle or another shape. The shape of the electrode 75 is preferably the same as or similar to the shape of the opening 1 b. That is, the shape of the electrode 75 is preferably rectangular if the opening 1 b is rectangular. Further, the electrode 75 is preferably formed inside the opening 1b, and the size thereof is preferably 2 mm or more away from the opening 1b.

With such a configuration, the capacitance between the plasma probe device 70 and the wall of the processing vessel 1 can be reduced, and the floating current can be significantly reduced. Furthermore, since the surface 71a1 of the disk-like member 71a exposed from the opening 1b is made of ceramics, the corrosion resistance by the processing gas can be improved. Therefore, coating of a Y ₂ O ₃ film or the like is not necessary on the surface 71 a 1 of the disk-like member 71 a exposed from the opening 1 b. In addition, in such a configuration, the possibility of abnormal discharge between the metal of the side wall of the processing vessel 1 and the ceramic of the disk-shaped member 71a can be extremely reduced. The electrode 75 can be embedded in a disk-shaped member 71a formed of a ceramic and integrally sintered.

  The surface 71a1 of the disk-shaped member 71a may be disposed at a position recessed from the surface on the plasma generation space side of the wall in which the opening 1b is formed. In addition, the surface 71a1 may be curved in a convex or concave shape.

  Further, as shown in FIG. 10A, the surface 71a1 of the disk-shaped member 71a may be in the same plane as the wall surface of the processing container 1 in which the opening 1b is formed. Further, as shown in FIG. 10 (b), the disk-like member 71a may be provided with a protrusion 71a2 which protrudes from the opening 1b. Also by this, the measurement sensitivity and accuracy of the plasma probe device 70 can be improved. Furthermore, since the disk-like member 71a is formed of a ceramic, the possibility of abnormal discharge is extremely small even if the protrusion 71a2 is provided. .

  As mentioned above, although the plasma probe apparatus and the plasma processing apparatus were explained by the above-mentioned embodiment, the plasma probe apparatus and plasma processing apparatus concerning the present invention are not limited to the above-mentioned embodiment, and various modification within the scope of the present invention And improvements are possible. Matters described in the above plurality of embodiments can be combined without contradiction.

  The substrate processing apparatus according to the present invention is applicable to any type of capacitively coupled plasma (CCP), inductively coupled plasma (ICP), radial line slot antenna, electron cyclotron resonance plasma (ECR), and Helicon Wave Plasma (HWP). .

  In the present specification, the semiconductor wafer W has been described as an example of the substrate. However, the substrate is not limited to this, and may be various substrates used for LCD (Liquid Crystal Display), FPD (Flat Panel Display), a CD substrate, a printed substrate, and the like.

DESCRIPTION OF SYMBOLS 1 processing container 1b opening part 2 microwave plasma source 3 control apparatus 10 main-body part 11 mounting base 14 high frequency bias power supply 21 gas introduction part 22 gas supply source 30 microwave output part 40 microwave transmission part 43a peripheral microwave introduction part 43b center Microwave introduction portion 44 Microwave transmission line 50 Microwave radiation mechanism 52 Outer conductor 53 Inner conductor 54 Slag 60 Gas supply hole 62 Gas diffusion chamber 70 Plasma probe device 71 Antenna portion 71a Disc-like member 72, 75 Electrode 73 O ring 74 dielectric Body support 76, 77, 1c Insulator film 80 Monitor device 100 Microwave plasma processing device 121, 131 Dielectric top plate 122, 132 Slot 123, 133 Dielectric layer 140 Impedance adjustment member U Plasma generation space

Claims (14)

An antenna unit attached to an opening formed in a wall or a mounting table of the processing container via a seal member for sealing between a vacuum space and an atmosphere space;
An electrode connected to the antenna unit;
A dielectric support formed of a dielectric and supporting the antenna unit from the periphery;
The facing surface of the antenna unit and the wall or the mounting table is separated by a predetermined width, and the surface of the antenna unit exposed from the opening corresponds to the plasma of the mounting table or the wall on which the opening is formed. It is recessed than the surface on the generation space side,
Plasma probe device. The tip portion of the antenna portion is disk-shaped, and the dimension in the depth direction of the dielectric support portion with respect to the diameter of the tip portion is formed to any value in the range of 0.44 to 0.54.
The plasma probe device according to claim 1. At least one of a concave portion and a convex portion is formed on the tip end surface of the antenna unit.
The plasma probe device according to claim 1. The tip surface of the antenna unit is curved in a concave or convex shape,
The plasma probe device according to any one of claims 1 to 3. A region from at least the opening to the seal member of the tip end surface of the antenna unit and the wall or the surface of the mounting table around the opening is covered with a Y ₂ O ₃ film ,
The plasma probe device according to any one of claims 1 to 4. The dielectric support is formed of PTFE (polytetrafluoroethylene).
The plasma probe device according to any one of claims 1 to 5. A plurality of the antenna units are attached to the plurality of circumferentially arranged openings via the seal member.
The plasma probe device according to any one of claims 1 to 6. The plurality of openings are equally spaced in the circumferential direction and have a slit shape.
The plasma probe device according to any one of claims 1 to 7. The plurality of openings are provided on at least one of a side wall of the processing container, a ceiling wall of the processing container, and an outer peripheral portion of the mounting table.
The plasma probe device according to any one of claims 1 to 8. A plasma processing apparatus comprising: a plurality of microwave radiation mechanisms for radiating microwaves output from an output unit of a microwave plasma source into a processing container; and a plasma probe device,
The plasma probe apparatus
An antenna unit attached to an opening formed in a wall or a mounting table of the processing container via a seal member for sealing between a vacuum space and an atmosphere space;
An electrode connected to the antenna unit;
A dielectric support formed of a dielectric and supporting the antenna unit from the periphery;
The facing surface of the antenna unit and the wall or the mounting table is separated by a predetermined width, and the surface of the antenna unit exposed from the opening corresponds to the plasma of the mounting table or the wall on which the opening is formed. It is recessed than the surface on the generation space side,
Plasma processing equipment. Having a plurality of said plasma probe devices,
A plurality of the antenna units are attached to the plurality of circumferentially arranged openings via the seal member.
The plasma processing apparatus according to claim 10. A dielectric antenna unit attached to an opening formed in a wall or mounting table of the processing container via a seal member that seals between a vacuum space and an atmospheric space;
An electrode embedded in the antenna unit;
And a dielectric support portion of dielectric material supported from the periphery of the antenna portion,
The electrode is formed inside the opening.
Plasma probe device. The electrode is at least 2 mm away from the opening.
The plasma probe device according to claim 12. The surface of the antenna portion exposed from the opening is recessed with respect to the wall on which the opening is formed or the surface on the plasma generation space side of the mounting table, or the same surface as the surface Also has a protruding projection,
The plasma probe device according to claim 12 or 13.

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