JP2010140679A - Metal surface wave measuring device and metal surface wave measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure metal surface waves propagated between a metal face and plasma in a treatment vessel of a plasma treatment device. <P>SOLUTION: The metal surface wave measuring device 1000 is fitted to a plasma treatment device 2000 putting a substrate G by plasma treatment by exciting gas with electromagnetic waves for measuring metal surface waves propagated between metal and plasma in the treatment vessel. The metal surface wave measuring device 1000 is provided with probes 1005a, 1005b, 1005c formed of metal fitted in proximity to the plasma, and an oscilloscope 1030 electrically connected with the probes 1005a, 1005b, 1005c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a measurement apparatus for a plasma processing apparatus that excites a gas by electromagnetic waves to perform plasma processing on an object to be processed.

Among plasmas generated using electromagnetic waves, microwave plasma is generated by introducing microwaves into a processing chamber in a reduced pressure state through a dielectric plate. In the microwave plasma processing apparatus, plasma electron density n _e is higher than the cut-off density n _c, the microwave can not enter into the plasma propagates between the dielectric plate and the plasma. During propagation, part of the microwave is absorbed by the plasma as an evanescent wave and used to maintain the plasma. Thus, the microwave propagating between the dielectric plate and the plasma is called, for example, a dielectric surface wave.

However, when a low-frequency microwave is supplied to the plasma processing apparatus, not only the dielectric surface wave propagating between the dielectric plate and the plasma, but also the surface propagating between the metal surface of the processing vessel inner surface and the plasma. Waves (hereinafter referred to as metal surface waves (conductor surface waves)) are generated. MSW, the electron density of the plasma can not propagate lower than twice the cutoff density n _c. Since the cut-off density n _c is proportional to the square of the frequency of the electromagnetic wave, MSW low frequencies, can not propagate the electron density is not high. Furthermore, the metal surface wave has a characteristic that it is more difficult to attenuate as the frequency is lower.

At a frequency of 2450MHz, which is generally used in the generation of the plasma, not the value of the cut-off density _{n c} is 7.5 × ^{10 10 cm -3,} and the electron density of 1.5 × ¹⁰ 11 ^{cm -3} or more And metal surface waves do not propagate. For example, in a low density plasma with an electron density near the surface of about 1 × 10 ¹¹ cm ⁻³ , the metal surface wave does not propagate at all. Even when the electron density is higher, the propagation of metal surface waves is often not a problem because of the large attenuation. On the other hand, at a frequency of 915 MHz, for example, a metal surface wave propagates long on the inner surface of the processing chamber even in a low-density plasma having an electron density of about 1 × 10 ¹¹ cm ⁻³ near the surface.

  Therefore, when performing plasma processing using low-frequency electromagnetic waves, it is necessary to design an apparatus for controlling the propagation of not only dielectric surface waves but also metal surface waves. At that time, if there is an apparatus that directly measures the propagation state of the metal surface wave, the actual propagation state of the metal surface wave can be known, and the design of the plasma processing apparatus can be optimized based on the propagation state. As a result, a uniform plasma having a low electron temperature and a high electron density can be stably generated.

  Therefore, the present invention measures the propagation state of the metal surface wave propagating between the metal surface in the processing container of the plasma processing apparatus for plasma processing the object to be processed and the plasma.

  In order to solve the above problems, according to an aspect of the present invention, a plasma processing apparatus that plasmas a target object by exciting a gas with electromagnetic waves is provided between a metal member inside the processing container and the plasma. A metal surface wave measuring device for measuring a propagating metal surface wave, comprising: a probe made of metal provided in proximity to the metal member and plasma; and an electromagnetic wave measuring means electrically connected to the probe. A metal surface wave measuring device is provided.

  According to this, the propagation state of the metal surface wave can be accurately measured by the probe made of metal. The measurement result is transmitted to electromagnetic wave measurement means electrically connected to the probe. The electromagnetic wave measuring means measures, for example, the voltage amplitude, phase, waveform, spectrum, etc. of the metal surface wave based on the transmitted measurement result. In this way, by directly measuring the propagation state of the metal surface wave, the design of the plasma processing apparatus, particularly around the electrodes, can be optimized from the result. Thereby, plasma with low electron temperature, high electron density, and high uniformity can be generated using an optimized plasma processing apparatus. As a result, plasma processing with little damage can be performed.

  The metal member may be provided around the metal probe so as to be insulated from the metal probe via a first dielectric.

  A second dielectric may be provided between the probe and the plasma.

  The surface on the plasma side of the second dielectric and the metal surface on the plasma side inside the processing container in which the second dielectric is close may be disposed substantially on the same plane.

  A coaxial line may be provided between the probe and the electromagnetic wave measuring means.

  The electromagnetic wave measuring means may measure any one of voltage amplitude, phase, waveform, and spectrum based on the measurement result of the probe.

  A plurality of the probes are arranged, and the electromagnetic wave measuring means is based on the measurement results of the plurality of probes, and is based on at least one of a phase difference or an amplitude ratio, and at least a wavelength, a propagation constant, an attenuation constant, and a phase constant Either may be measured.

  In order to solve the above-described problem, according to another aspect of the present invention, a gas is excited by an electromagnetic wave to plasma an object to be processed. A method of measuring a propagating metal surface wave, wherein the metal surface wave is measured using a metal probe provided close to plasma, and the measurement result is an electromagnetic wave electrically connected to the probe. A metal surface wave measuring method is provided which is transmitted to a measuring means and measures at least one of an amplitude, a phase, a waveform and a spectrum of the voltage using the electromagnetic wave measuring means based on the transmitted measurement result.

  In the metal surface wave measurement method, based on the results of measurement using a plurality of the probes, the wavelength of the metal surface wave, the propagation constant, the attenuation constant, from at least one of the phase difference or the amplitude ratio using the electromagnetic wave measurement means, You may measure at least any one of a phase constant and a propagation constant.

  As described above, according to the present invention, it is possible to measure a metal surface wave that propagates between a metal surface in a processing container of a plasma processing apparatus that performs plasma processing on an object to be processed and plasma.

BEST MODE FOR CARRYING OUT THE INVENTION

(First embodiment)
Referring to the accompanying drawings, first, a plasma processing apparatus according to a first embodiment of the present invention, FIG. 1 (cross section OO in FIG. 2) schematically showing a vertical section of the apparatus and a processing container 2 will be described with reference to FIG. In the following description and the accompanying drawings, components having the same configuration and function are denoted by the same reference numerals, and redundant description is omitted.

(Configuration of plasma processing equipment)
(First embodiment)
First, the configuration of the microwave plasma processing apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 schematically shows a longitudinal sectional view of the apparatus. FIG. 1 shows a 2-OO′-2 cross section of FIG. FIG. 2 is a ceiling surface of the microwave plasma processing apparatus 10 and shows a cross section 1-1 of FIG. In the first embodiment, an upper gas shower plate is provided on the ceiling surface.

(Outline of microwave plasma processing equipment)
As shown in FIG. 1, the microwave plasma processing apparatus 10 includes a processing container 100 for plasma processing a glass substrate (hereinafter referred to as “substrate G”). The processing container 100 includes a container body 200 and a lid body 300. The container body 200 has a bottomed cubic shape with an upper portion opened, and the opening is closed by a lid 300. The lid body 300 includes an upper lid body 300a and a lower lid body 300b. An O-ring 205 is provided on a contact surface between the container main body 200 and the lower lid body 300b, whereby the container main body 200 and the lower lid body 300b are hermetically sealed to define a processing chamber. An O-ring 210 and an O-ring 215 are also provided on the contact surface between the upper lid body 300a and the lower lid body 300b, whereby the upper lid body 300a and the lower lid body 300b are sealed. The container body 200 and the lid body 300 are made of a metal such as an aluminum alloy, for example, and are electrically grounded.

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

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

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

  The metal cover 310 and the metal cover 320 are thicker by the thickness of the dielectric plate 305. According to such a shape, the height of the ceiling surface becomes substantially equal, and at the same time, the portion where the dielectric plate 305 is exposed and the shape of the recesses in the vicinity thereof all have the same pattern.

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

  The dielectric plate 305 and the metal electrode 310 are equally supported by the lid 300 from four locations by screws 325 (see FIG. 2). Similarly, the metal cover 320 and the side cover 350 are attached to the main body portion of the lid 300 with screws 325. A main gas flow path 330 is provided between the upper lid body 300a and the lower lid body 300b. The main gas channel 330 divides the gas into the first gas channel 325a provided in the plurality of screws 325. A narrow tube 335 that narrows the flow path is fitted into the inlet of the first gas flow path 325a. The thin tube 335 is made of ceramics or metal. A second gas flow path 310a1 is provided between the metal electrode 310 and the dielectric plate 305. Second gas flow paths 320 a 1 and 320 a 2 are also provided between the metal cover 320 and the lid 300 and between the side cover 350 and the lid 300. The front end surface of the screw 325 is flush with the lower surfaces of the metal electrode 310, the metal cover 320, and the side cover 350 so as not to disturb the plasma distribution. The first gas discharge holes 345a opened in the metal electrode 310 and the second gas discharge holes 345b1 and 345b2 opened in the metal cover 320 and the side cover 350 are opened downward at an equal pitch.

  The gas output from the gas supply source 905 passes through the first gas flow path 325a (branch gas flow path) from the main gas flow path 330, and the second gas flow path 310a1 and the metal cover 320 in the metal electrode 310. The first gas discharge hole 345a and the second gas discharge holes 345b1 and 345b2 are supplied to the processing chamber through the second gas flow paths 320a1 and 320a2 in the side cover 350. An O-ring 220 is provided on the contact surface between the lower lid 300 b and the dielectric plate 305 in the vicinity of the outer periphery of the first coaxial waveguide 610, and the atmosphere in the first coaxial waveguide 610 is placed inside the processing container 100. It is designed not to enter.

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

  An inner conductor 610a is inserted into the outer conductor 610b of the first coaxial waveguide formed by digging the lid 300. Similarly, the inner conductors 620a to 640a of the second to fourth coaxial waveguides are inserted into the outer conductors 620b to 640b of the second to fourth coaxial waveguides formed by digging the lid body 300, and the upper portions thereof Is covered with a lid cover 660. The inner conductor of each coaxial tube is made of copper with good thermal conductivity.

  Microwaves are supplied from the microwave source 900 and transmitted from the fourth coaxial waveguide 640 to the first coaxial waveguide 610 and the second coaxial waveguide 620 through the third coaxial waveguide 630. The surface of the dielectric plate 305 is covered with a metal film 305a except for a portion where the microwave is incident on the dielectric plate 305 from the first coaxial waveguide 610 and a portion where the microwave is emitted from the dielectric plate 305. Yes. Accordingly, the propagation of the microwave is not disturbed by the gap generated between the dielectric plate 305 and the adjacent member, and the microwave can be stably guided into the processing container.

  As shown in FIG. 2, the dielectric plate 305 is covered with the metal cover 320 and the inner wall of the processing vessel 100 in which the metal plate 310 and the dielectric plate 305 are not disposed one-on-one. (Including the inner wall of the processing container 100). The dielectric plate 305 and the inner wall of the processing vessel 100 in which the dielectric plate 305 is not disposed (including the inner wall of the processing vessel 100 covered with the metal cover 320) are substantially similar in shape or substantially The shape is symmetrical. According to such a configuration, electromagnetic waves are propagated along the metal surface exposed to the inside of the processing container 100, and are approximately evenly distributed from the dielectric plate 305 to the metal electrode side and the inner wall side (or the metal cover 320 and the side cover 350 side). Microwave power can be supplied.

  As a result, the microwave emitted from the dielectric plate 305 propagates on the surfaces of the metal electrode 310, the metal cover 320, and the side cover 350 while distributing the power in half as a surface wave. Hereinafter, the surface wave propagating between the metal surface on the inner surface of the processing vessel and the plasma is referred to as a metal surface wave. Thereby, a metal surface wave propagates to the entire ceiling surface, and uniform plasma is stably generated below the ceiling surface of the microwave plasma processing apparatus 10 according to the present embodiment.

  The side cover 350 is formed with an octagonal groove 340 so as to surround the entire eight dielectric plates 305, and metal surface waves propagating on the ceiling surface are prevented from propagating outside the groove 340. To do. A plurality of grooves 340 may be formed in multiple in parallel. A convex portion may be provided instead of the groove 340. The groove 340 and the convex part are examples of the propagation obstacle part.

  A region having the center point of the adjacent metal cover 320 around the metal electrode 310 as a center is hereinafter referred to as a cell Cel (see FIG. 2). On the ceiling surface, a cell Cel is defined as a unit, and the configuration of the same pattern is regularly arranged in an 8-cell Cel.

  The refrigerant supply source 910 is connected to the refrigerant pipe 910a inside the lid, and the refrigerant supplied from the refrigerant supply source 910 circulates in the refrigerant pipe 910a inside the lid and returns to the refrigerant supply source 910 again. The processing container 100 is kept at a desired temperature. A refrigerant pipe 910b passes through the inner conductor 640a of the fourth coaxial waveguide in the longitudinal direction. Heating of the internal conductor 640a is suppressed by passing the coolant through this flow path.

  It is desirable that there is no gap between the dielectric plate 305 and the lid 300 or between the dielectric plate 305 and the metal electrode 310. This is because if there is an uncontrolled gap, the wavelength of the microwave propagating through the dielectric plate 305 becomes unstable, which affects the plasma uniformity and the load impedance viewed from the coaxial tube. In addition, if there is a large gap (0.2 mm or more), there is a possibility of discharging in the gap. Therefore, when the nut 435 is tightened, the dielectric plate 305 and the lower lid 300b and the dielectric plate 305 and the metal electrode 310 are in close contact with each other.

  If the nut 435 is tightened with an excessive torque, the dielectric plate 305 may be stressed and cracked. In addition, even when the nut 435 is tightened, there is a risk of cracking due to stress when plasma is generated and the temperature of each part rises without cracking. For this reason, the metal electrode 310 can be lifted through the screw 325 with an appropriate force at all times (a force slightly larger than the force for crushing the O-ring 220 to bring the dielectric plate 305 and the lower lid 300b into close contact). A wave washer 430b having an optimal spring force is inserted between the nut 435 and the lower lid 300b. When the nut 435 is tightened, the deformation amount is constant without being tightened until the wave washer 430b becomes flat.

  A washer 430a is provided between the nut 435 and the wave washer 430b, but may or may not be present. Further, a washer 430c is provided between the wave washer 430b and the lower lid 300b. Normally, there is a gap between the screw 325 and the lid 300, and the gas in the main gas flow path 330 flows to the first gas flow path 310a through this gap. When this uncontrolled gas flow rate is large, there is a problem that the gas discharge from the first gas discharge hole 345a becomes non-uniform. For this reason, the gap between the washer 430c and the screw 325 is reduced, and the thickness of the washer 430c is increased to suppress the flow rate of the gas flowing through the outside of the screw 325.

<Measurement of metal surface waves>
As described above, MSW, plasma electron density n _e is unable to propagate less than twice the cutoff density n _c. Since the cut-off density n _c is proportional to the square of the frequency of the electromagnetic wave, MSW low frequencies, it is impossible to plasma electron density n _e is propagated not high. In addition, metal surface waves have a feature that they are less likely to attenuate as the frequency is lower.

In 2.45GHz frequency that is generally used to generate the plasma, the cut-off density _{n c} is 7.5 × ^{10 10 cm -3,} and the plasma electron density _{n e} is 1.5 × ¹⁰ 11 cm ^{- If} it is not ³ or more, the metal surface wave will not propagate. For example, in a low density plasma with an electron density near the surface of about 1 × 10 ¹¹ cm ⁻³ , the metal surface wave does not propagate at all. Even when the plasma electron density n _e is higher, the MSW for attenuation is large can not propagate so long.

On the other hand, for example, at a frequency of 915 MHz, the metal surface wave propagates long between the metal on the inner wall of the processing vessel and the plasma even in a low density plasma whose electron density near the surface is about 1 × 10 ¹¹ cm ⁻³ . Therefore, when low-frequency electromagnetic waves are supplied to the above-described microwave plasma processing apparatus 10, not only the dielectric surface wave propagates between the dielectric plate and the plasma, but also the metal surface of the inner wall of the processing vessel and the plasma. Metal surface waves propagate between them.

  The wavelength of the electromagnetic wave in free space is determined by the frequency of the electromagnetic wave output from the power source. However, the wavelength of the metal surface wave varies depending not only on the frequency but also on the thickness of the sheath and the plasma density. On the other hand, it is impossible to actually measure or accurately predict the width of the sheath. Therefore, the wavelength of the metal surface wave cannot be obtained immediately from the frequency of the microwave source, and it is necessary to actually measure it with the following metal surface wave measuring device. The measured wavelength of the metal surface wave is used to optimize the size and shape of the metal electrode 310 and the dielectric 305 when designing the microwave plasma processing apparatus 10. Therefore, the result of actual measurement by the metal surface wave measuring apparatus is very useful for designing the microwave plasma processing apparatus.

  Therefore, the inventors have devised a metal surface wave measuring device in order to measure the propagation state of the metal surface wave. FIG. 3 shows a metal surface wave measurement apparatus 1000 attached to a lid portion 2000a (here, an aluminum lid) of a microwave plasma processing apparatus 2000 for measurement.

(Microwave plasma processing equipment for measurement)
Before describing the internal configuration of the metal surface wave measuring apparatus 1000, a microwave plasma processing apparatus 2000 for measurement will be briefly described with reference to FIG. The ceiling surface of the microwave plasma processing apparatus 2000 (the surface on the plasma side of the lid portion 2000a) is a substantially square of 400 mm × 400 mm. There are no grooves or protrusions on the ceiling surface of the microwave plasma processing apparatus 2000 for measurement. If a propagation obstruction part that controls the propagation of the metal surface wave (the groove 340 or the convex part in the microwave plasma processing apparatus 10 that performs the plasma treatment described above) is provided, the metal surface wave is reflected at the propagation obstruction part. This is because the propagation of the metal surface wave is disturbed and the original propagation state of the metal surface wave cannot be measured accurately.

  A metal electrode 2005 is provided substantially at the center on the plasma side surface of the lid portion 2000a. The upper part of FIG. 5 is an enlarged view of the metal electrode 2005 and the lower surface around it, and the lower part of FIG. 5 shows a cross-sectional view thereof. The metal electrode 2005 is a plate-like member having a circular outer shape. The dielectric plate 2010 is a circular plate member having a diameter (110 mm) slightly larger than the diameter of the metal electrode 2005. Referring to the lower cross-sectional view of FIG. 5, the metal electrode 2005 and the dielectric plate 2010 are generally flat plate-like members provided with inclined portions at the end portions. The material is the same as the metal electrode 310 and dielectric 305 used in the microwave plasma processing apparatus 10 described above. Dielectric plate 2010 is sandwiched between metal electrode 2005 and lid portion 2000a. With this configuration, the dielectric plate 2010 is uniformly exposed on the outer periphery of the metal electrode 2005. The microwave transmitted through the first coaxial waveguide 610 is introduced into the processing container from the exposed portion of the dielectric plate 2010 and propagates through the metal surface in the processing container as a metal surface wave.

(Internal configuration of metal surface wave measuring device)
Next, the internal configuration of the metal surface wave measurement device 20 attached to the lid portion 2000a of the measurement microwave plasma processing device 2000 will be described with reference to FIG. 3 again. FIG. 3 shows a 3-3 cross section of FIG. The metal surface wave measuring device 20 includes a probe 1005c (inner conductor 1020a, third probe), a fixing member 1010 for fixing the probe 1005c, a plurality of screws 1015 for fixing the fixing member 1010 to the lid portion 2000a, a semi-rigid coaxial cable 1020, A coaxial cable 1025 and an oscilloscope 1030 are included.

  The semi-rigid coaxial cable 1020 has a metal inner conductor 1020a and an outer conductor 1020b, and a first dielectric 1020c is filled therebetween. The first dielectric 1020c is formed of Teflon (registered trademark). The semi-rigid coaxial cable 1020 is connected to the coaxial cable 1025 via a connector (not shown), and is further connected to the oscilloscope 1030. Since the coaxial cable 1025 is easy to bend, it is easier to use the coaxial cable 1025 provided between the semi-rigid coaxial cable 1020 and the oscilloscope 1030. However, the semi-rigid coaxial cable 1020 may be directly connected to the oscilloscope 1030. The coaxial cable 1025 and the semi-rigid coaxial cable 1020 are examples of coaxial lines provided between the probe 1005c and the oscilloscope 1030. Thereby, the oscilloscope 1030 is electrically connected to the probe 1005c.

  The outer conductor 1020b of the semi-rigid coaxial cable 1020 is a tubular member made of copper and is difficult to bend, whereas the outer conductor of the coaxial cable 1025 has a mesh shape and can be bent freely. Yes. The distal end of the outer conductor 1020b is inserted into the fixing member 1010, thereby fixing the semi-rigid coaxial cable 1020 to the fixing member 1010.

  The fixing member 1010 is made of copper. The fixing member 1010 has protruding portions at the upper part and the lower part. The upper protruding portion receives the outer conductor 1020b and fixes the probe 1005c. The lower protruding portion is inserted into the recess of the lid portion 2000a. The fixing member 1010 is fixed to the lid portion 2000a with a plurality of screws 1015. An O-ring 1035 is provided between the fixing member 1010 and the lid portion 2000a to block the vacuum in the processing chamber from the outside atmosphere.

  The inner conductor 1020a and the dielectric 1020c of the semi-rigid coaxial cable 1020 penetrate the fixing member 1010 in a state where the outer conductor 1020b does not exist. The inner conductor 1020a further extends to the inside of the lid portion 2000a. A second dielectric 1040 is interposed between the inner conductor 1020a and the plasma. Specifically, a hole is made in the approximate center of the second dielectric 1040, the internal conductor 1020a is inserted, and the tip of the internal conductor 1020a and the second dielectric 1040 are brought into close contact with each other. The second dielectric 1040 is made of quartz or ceramic. With this configuration, the inner conductor 1020a can function as a probe 1005c made of metal provided close to the plasma.

  An electric field of the metal surface wave TM is generated in the sheath near the tip of the probe 1005c in the height direction of the sheath. The microwave is transmitted to the oscilloscope 1030 from the coaxial cable 1025 by propagating through the lid 2000 and the metal surfaces of the fixing member 1010a and the outer conductor 1020b.

  Note that the probe 1005c may be provided in the metal member so as to be insulated from the metal member. For example, the outer conductor 1020b of the semi-rigid coaxial cable 1020 may be extended by the same length as the probe 1005c. In this case, the inner conductor 1020a becomes the probe 1005c, and the outer conductor 1020b becomes a metal member that propagates the metal surface wave.

  The tip of the probe 1005c should not be exposed from the second dielectric 1040 as shown in FIG. 3, but may be exposed. If the thickness of the second dielectric material from the tip of the probe 1005c to the plasma side surface of the second dielectric material 1040 is too thick, microwaves are difficult to enter, and if it is too thin, microwaves tend to enter too much. Note that the probe 1005c may be exposed to the plasma side without providing the second dielectric 1040.

  In this way, by providing the outer conductor 1020b that is hard to be bent of the semi-rigid coaxial cable 1020 between the coaxial cable 1025 and the fixing member 1010, the tip of the inner conductor 1020a is securely adhered to the second dielectric 1040, The probe 1005c is fixed so that a gap is generated between the inner conductor 1020a and the second dielectric 1040 and electrical connection does not deteriorate. However, the probe 1005c may be fixed using only the coaxial cable 1025 without using the semi-rigid coaxial cable 1020.

  The plasma-side surface 1040a of the second dielectric material 1040 and the plasma-side metal surface 2000a1 of the lid portion 2000a in which the second dielectric material 1040 is close to each other are disposed on substantially the same surface. This is to suppress the reflection of the metal surface wave and accurately measure the propagation state of the original metal surface wave without disturbing the propagation of the metal surface wave.

  In addition to the probe 1005c, the metal surface wave measuring device 20 is provided with probes 1005a (first probe) and 1005b (second probe). The probes 1005a to 1005c are connected to the channel 1 (ch. 1) to channel 3 (ch. 3). The metal surface wave measuring device 20 may perform measurement using only one probe, or may perform measurement using two or more probes.

  The oscilloscope 1030 (or the oscilloscope 1030 and a computer (not shown) connected to the oscilloscope 1030) is an example of an electromagnetic wave measurement unit that is electrically connected to the probe 1005c. Other examples of the electromagnetic wave measuring means include a voltmeter attached directly to a spectrum analyzer or a probe, for example. According to this, the voltage of the probe is directly measured using a voltmeter.

  When a metal surface wave is specified using a plurality of probes, at least one of the wavelength, propagation constant, attenuation constant, and phase constant of the metal surface wave is calculated from at least one of the phase difference and the amplitude ratio. In order to calculate the wavelength, propagation constant, attenuation constant, and phase constant of the metal surface wave, measurement values of two or more probes are required. On the other hand, the amplitude, phase, waveform, and spectrum of the voltage of the metal surface wave can be obtained based only on the measurement value of one probe.

(Measurement conditions for metal surface waves)
Next, after describing the measurement conditions of the metal surface wave TM, a method for calculating each parameter of the metal surface wave will be described. FIG. 4 shows the arrangement of three points of measurement probes 1005a1, 1005b1, and 1005c1, and the arrangement of three points of calibration probes 1005a2, 1005b2, and 1005c2.

  The measurement position was shifted by changing the angle from the center of the metal electrode 310 to each of the probes 1005a1, 1005b1, and 1005c1. This is to prevent measurement errors due to interference between measurements by the probes 1005a1, 1005b1, and 1005c1.

  Further, since there is a variation in the coupling degree of each probe and the transmission characteristics of the semi-rigid coaxial cable 1020 connected to each probe, calibration is required. Therefore, each probe 1005a2, 1005b2, 1005c2 is arranged at a position where the phase and amplitude of the metal surface wave TM are equal (for example, a position where the distance from the center of the metal electrode 310 to each probe is 100 mm), and a waveform observed by the oscilloscope 1030. The phase difference and the amplitude ratio were measured in advance.

  In actual measurement, the inventor made argon gas into plasma under a pressure of 0.5 Torr, directly measured the propagation state of the generated metal surface wave TM, and used the previously measured measurement value for calibration. Calibrated. FIG. 6 shows an example of a waveform after calibration of the metal surface wave TM directly measured by the probe 1005b (channel ch2). According to this, in the case of low density (when the power of the input microwave is 0.5 kW), the waveform of the metal surface wave TM is close to a sine curve, and only the fundamental wave component is included and no harmonic component is included. On the other hand, in the case of high density (when the power of the input microwave is 1 kW), the waveform of the metal surface wave TM is more complicated than the sine curve, and includes the fundamental wave component and the harmonic wave component. It was.

  As described above, some of the propagating metal surface waves contain a harmonic component and some do not. This difference is believed to be due to process conditions. For example, when high-power microwaves are supplied from the results shown in FIG. Further, when plasma is excited from an inert gas such as argon gas, harmonic components tend to enter.

  Even if a harmonic component is included in the metal surface wave, the propagation state of the metal surface wave does not basically deteriorate. However, whether or not the process conditions include harmonic components in the metal surface wave is valuable information useful for designing the size and shape of the microwave plasma processing apparatus 10 particularly around the metal electrode. Therefore, based on the measurement value from the probe of the metal surface wave measuring apparatus 20 described above, each parameter of the metal surface wave is calculated as follows using the electromagnetic wave measuring means.

(Calculation method for each parameter of metal surface wave)
The electric field intensity E (z) of the metal surface wave propagating in the z direction is expressed by the following equation.
E (z) = E ₀ e ^−γz = E ₀ e ^−αz e ^−jβz (1)
Here, γ is a propagation constant of the metal surface wave, α is an attenuation constant, and β is a phase constant. The amplitude ratio of the metal surface wave at the position z and the position z + Δz is A (A <1), and the phase difference is Δθ. From equation (1), the attenuation constant α and the phase constant β are expressed as follows using the amplitude ratio A and the phase difference Δθ.
α = −ln (A) / Δz (2)
β = Δθ / Δz (3)

Assuming that the wavelength of the metal surface wave is λ, from the relationship of β = 2π / λ,
λ = 2πΔz / Δθ (4)
It is expressed. By arranging two probes in the propagation direction of the metal surface wave and measuring their amplitude ratio, the attenuation constant α can be obtained from the equation (2). Similarly, by measuring these phase differences, the phase constant β can be obtained from the equation (3), and the wavelength λ can be obtained from the equation (4).

  Furthermore, more accurate measurement can be performed by arranging two or more probes and obtaining the amplitude ratio and phase difference between the probes. 8A to 8C show the results of calculating the wavelength from the phase difference of the metal surface wave based on the measurement results using the four probes 1005a, 1005b, 1005c, and 1005d shown in FIG. . The adjacent probes 1005a, 1005b, 1005c, and 1005d are arranged at equal intervals separated by Px in the X-axis direction and Py in the Y-axis direction. Here, Px and Py are both 5 mm.

  The plasma electron density and sheath width in FIG. 7 are appropriately set based on the actual plasma, and the wavelength of the metal surface wave obtained by calculation from the plasma electron density and sheath width and the micro output from each probe. The wavelength of the metal surface wave calculated from the wave phase difference was compared. In FIG. 8, the wavelength calculated from the phase difference between the channel ch1 and the channel ch2 of the oscilloscope 1030 connected to the probe 1005a and the probe 1005b is shown in the wavelength column of the probe 1 row. Channel ch1 and channel ch2 are connected to probe 1005a and probe 1005b. Similarly, the wavelength calculated from the phase difference between channel ch2 and channel ch3 is shown in the wavelength column of the probe 2 row, and the wavelength calculated from the phase difference between channel ch3 and channel ch4 is the wavelength of the probe 3 row. It is shown in the column.

  8A, 8B, and 8C, the wavelengths derived from the actually measured values of the channels ch1 to ch4 are almost the same length. From the above, it was proved that the measurement accuracy of the channels ch1 to 4 is generally good. Therefore, it is possible to perform measurement with higher accuracy by obtaining an average value of wavelengths derived from actually measured values of the channels ch1 to ch4. The amount of coupling is represented by 20 log (V2 / V1) [dB], where V1 is the microwave voltage applied to the sheath and V2 is the microwave voltage output from the probe. Instead of the above method of calculating the wavelength of the metal surface wave from the phase difference, the attenuation constant of the metal surface wave may be calculated from the amplitude ratio.

  As described above, according to the metal surface wave measurement device 20 according to the present embodiment, the amplitude, phase, and waveform of the voltage of the metal surface wave are measured by measuring the metal surface wave using one or more probes. The spectrum can be measured. Further, by measuring the metal surface wave using two or more probes, the wavelength, propagation constant, attenuation constant, and phase constant of the metal surface wave can be measured.

  In the above embodiment, the operations of the respective units are related to each other, and can be replaced as a series of operations in consideration of the relationship between each other. And by substituting in this way, embodiment of a metal surface wave measuring device can be made into embodiment of a metal surface wave measuring method.

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

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

  The shape of the metal electrode 310 is not limited to a square, and may be a triangle, a hexagon, or an octagon. In this case, the shape of the dielectric plate 305 and the metal cover 320 is the same as the shape of the metal electrode 310. The metal cover 320 may or may not be provided, but if the metal cover 320 is not provided, the gas flow path may be formed directly in the lid 300.

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

  In the plasma processing apparatus according to the present invention, any plasma processing such as film formation processing, diffusion processing, etching processing, and ashing processing can be performed.

It is a longitudinal cross-sectional view of the microwave plasma processing apparatus which concerns on one Embodiment of this invention. It is the figure which showed the ceiling surface of the microwave plasma processing apparatus which concerns on the same embodiment. It is a longitudinal section of a metal surface wave measuring device concerning one embodiment of the present invention. It is a figure for demonstrating the position of the probe (for measurement and calibration) attached to the plasma processing apparatus for measurement. It is the bottom view and sectional drawing of the metal electrode periphery of the plasma processing apparatus for measurement. It is the figure which showed an example of the waveform of the measured metal surface wave. It is a measurement model which showed the position of four probes. It is a table | surface of the result of having computed the wavelength of the metal surface wave from the phase difference of the metal surface wave measured using the measurement model of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Microwave plasma processing apparatus 100 Processing container 200 Container main body 300 Cover body 305 Dielectric board 310 Metal electrode 1000 Metal surface wave measuring apparatus 1005a, 1005b, 1005c, 1005d Probe 1010 Fixing member 1015 Screw 1020 Semi-rigid coaxial cable 1020a Inner conductor 1020b External Conductor 1020c First dielectric 1025 Coaxial cable 1030 Oscilloscope 1035 O-ring 1040 Second dielectric 2000 Microwave plasma processing apparatus 2000a Lid 2005 Metal electrode 2010 Dielectric TM Metal surface wave

Claims (9)

A metal surface wave measuring device that is provided in a plasma processing apparatus that plasmas a target object by exciting a gas with electromagnetic waves and that measures a metal surface wave propagating between a metal member inside the processing container and the plasma,
A probe made of metal provided close to the metal member and plasma;
A metal surface wave measuring device comprising: an electromagnetic wave measuring means electrically connected to the probe.   2. The metal surface according to claim 1, wherein the metal member is provided around the metal probe so as to be insulated from the metal probe via a first dielectric. 3. Wave measuring device.   The metal surface wave measuring device according to claim 1, wherein a second dielectric is provided between the probe and the plasma.   The plasma-side surface of the second dielectric and the plasma-side metal surface of the processing container in which the second dielectric is close to each other are disposed on substantially the same surface. Item 4. The metal surface wave measuring device according to any one of Items 1 to 3.   The metal surface wave measuring device according to claim 1, wherein a coaxial line is provided between the probe and the electromagnetic wave measuring means.   The metal surface wave measurement device according to claim 1, wherein the electromagnetic wave measurement unit measures any one of an amplitude, a phase, a waveform, and a spectrum of a voltage based on a measurement result of the probe. A plurality of the probes are arranged;
The electromagnetic wave measuring means measures at least one of a wavelength, a propagation constant, an attenuation constant, and a phase constant of a metal surface wave from at least one of a phase difference or an amplitude ratio based on measurement results of the plurality of probes. The metal surface wave measuring device according to claim 1. A method of measuring a metal surface wave propagating between a metal and plasma inside a processing vessel provided in a plasma processing apparatus that excites a gas by electromagnetic waves and plasma-treats an object to be processed,
Measure the metal surface wave using a probe made of metal provided close to the plasma,
Transmitting the measurement result to electromagnetic wave measuring means electrically connected to the probe,
A metal surface wave measuring method for measuring at least one of an amplitude, a phase, a waveform, and a spectrum of a voltage using the electromagnetic wave measuring unit based on the transmitted measurement result. Based on the results of measurement using a plurality of the probes, the electromagnetic wave measuring means is used to measure at least one of the wavelength, propagation constant, attenuation constant, and phase constant of the metal surface wave from at least one of the phase difference and the amplitude ratio. The metal surface wave measuring method according to claim 8, wherein:

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