JP2012049353A - Plasma processing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide plasma processing equipment using a micro-wave, capable of improving uniformity of plasma processing.SOLUTION: Plasma processing equipment comprises: a processing chamber 114 of which inside is depressurized and exhausted; a substrate electrode 110 provided in the processing chamber 114, and on which a substrate 109 to be treated is placed; a plasma generator for generating plasma in the processing chamber 114 by using an electromagnetic wave for generating plasma; a supply system for supplying a processing gas into the processing chamber; and a vacuum exhaust system for exhausting the inside of the processing chamber, in which a traveling wave is excited into a ring-shaped cavity resonator 209 by controlling an amplitude and a phase difference of the electromagnetic wave for generating plasma branched to a linear wave guide tube 204 via a linear wave guide tube 201, a square wave guide tube 202 and a circular wave guide tube 203.

Description

  The present invention relates to a plasma processing apparatus for plasma processing a substrate to be processed.

  Substrates used in the manufacture of semiconductor devices such as semiconductor memories and logic LSIs tend to be increased in diameter to improve productivity, and the most advanced semiconductor devices such as semiconductor memories use a silicon substrate having a diameter of 300 mm. Has become the mainstream. Furthermore, there is an opinion that a silicon substrate with a diameter of 450 mm is necessary, and it is thought that the trend of increasing the substrate diameter will continue. Although a plasma processing apparatus is used in the manufacturing process of these semiconductor devices, it is necessary to perform uniform plasma processing on the substrate to be processed, and the technical difficulty associated with increasing the diameter of the substrate to be processed tends to increase. .

  In order to perform uniform plasma processing on the substrate to be processed, naturally the distribution of plasma characteristics such as plasma density and temperature near the substrate to be processed is important, and the plasma distribution is optimized from the viewpoint of uniform plasma processing. Technology to do is important.

  Plasma processing equipment that generates plasma using microwave power can generate high-density plasma even under low pressure, and can be easily controlled by adjusting the static magnetic field distribution by using it together with a static magnetic field. It is widely used for manufacturing the semiconductor device. In response to the above-mentioned trend of increasing the diameter of the substrate, it is important to control the plasma distribution in the microwave plasma processing apparatus.

  However, microwaves have a wavelength as short as several centimeters to several tens of centimeters, and the microwave distribution is easy to change with dimensions of the same order as the wavelength. The microwave distribution should be optimized to obtain a uniform plasma treatment over a wide range. Tend to be difficult.

  As a plasma source for generating plasma using a microwave, for example, there are the following conventional techniques. Patent Document 1 discloses an example using a cavity resonator in which rectangular waveguides are arranged in a ring shape in order to radiate plasma generation microwaves into a processing chamber. A slot antenna is disposed on the plasma processing chamber side of the cavity resonator, and plasma can be generated by efficiently radiating microwave power to the plasma processing chamber. In order to excite a ring-shaped cavity resonator, a rectangular waveguide is connected to supply microwaves.

  In Patent Document 2, in order to excite the ring-shaped cavity resonator in the prior art 1, the coaxial line is arranged coaxially with the ring-shaped cavity resonator and excited, thereby reducing the bias of the electromagnetic field in the cavity resonator. .

  First, referring to FIG. 11, a conventional etching apparatus described in Patent Document 2 will be briefly described.

  The electromagnetic wave generated by the high frequency power source 117 is transmitted to the coaxial line 101 by the coaxial waveguide converter 118 via the isolator 121 and the automatic matching machine 120 through the waveguide 119. A magnetron with an oscillation frequency of 2.45 GHz was used as the high frequency power source 117. Further, an electromagnetic wave is transmitted through the coaxial line 101, branched into a plurality of short coaxial lines 104 by a branch circuit 111 composed of a conductor 102 and a dielectric plate 103, and brought to a ring-shaped cavity resonator 105.

  A plurality of slots 106 are provided radially below the ring-shaped cavity resonator 105 and are radiated to the processing chamber 114 through the dielectric window 107 and the shower plate 108. Quartz was used as the material for the dielectric window 107 and the shower plate 108. The shower plate 108 is not shown in the drawing so that the processing gas supplied from the processing gas supply system (not shown) can be supplied into the processing chamber 114 in a shower shape through a minute gap between the dielectric window 107 and the shower plate 108. Many gas supply holes are provided.

  Further, a vacuum exhaust system (not shown) is connected to the processing chamber 114, and functions to evacuate the processing chamber 114 and maintain the processing chamber 114 at a predetermined pressure suitable for processing. A substrate electrode 110 for placing a substrate to be processed 109 is installed in the processing chamber 114. A bias power source 115 is connected to the substrate electrode 110 via an automatic matching machine 116, and a bias potential can be applied to the substrate 109 to be processed. The frequency of the bias power supply 115 is 400 kHz.

  A static magnetic field generating means 112 is provided around the processing chamber 114, and a static magnetic field can be applied to the processing chamber 114. The generation of a static magnetic field (0.0875 Tesla in the case of a frequency of 2.45 GHz) in the processing chamber 114 facilitates the generation of plasma even in a high vacuum region, and enables plasma processing in a wide pressure range. Can be possible. Further, by adjusting the distribution of the static magnetic field, it is possible to adjust the plasma distribution by controlling the position where the electron cyclotron resonance occurs and the diffusion of the plasma.

  Also, a static magnetic field generating means 113 is provided inside the ring of the ring-shaped cavity resonator 105, so that the controllable range of the static magnetic field can be expanded.

JP-A-9-270386 JP 2007-35411 A

Masamitsu Nakajima, Microwave Engineering, Morikita Publishing

  In the prior arts of Patent Documents 1 and 2, the electromagnetic field in the ring-shaped cavity resonator forms an electric field standing wave. FIG. 12 shows an example of the electric field strength distribution in the ring-shaped cavity resonator. A high electric field portion and a low electric field portion are shown as contour lines. In the example of FIG. 12, a standing wave of an electric field is formed, and there are eight abdominal portions with strong electric field strength and nodal portions with low electric field strength. The positions of these abdominal nodes are fixed, and it has been found that there is a problem that the strength of the electric field strength corresponding to the abdominal nodes in the cavity resonator is generated in the plasma processing chamber.

  Therefore, the plasma generated in the processing chamber 104 is also nonuniform. Due to this non-uniformity, the plasma processing of the dielectric window that transmits microwaves while holding the vacuum processing chamber hermetically increases locally, or adversely affects the uniformity of plasma processing performed on the substrate to be processed. It has been found that problems such as these may occur.

  The first problem to be solved by the present invention is to solve the non-uniformity caused by the standing wave generated in the ring-shaped cavity resonator.

  In the prior art of Patent Document 2, the coaxial line is used for exciting the ring-shaped cavity resonator, but it is found that there is a problem that the coaxial line is heated when high-power microwave power is applied. It was.

  The second problem to be solved by the present invention is to provide a plasma processing apparatus in which the prior art of Patent Document 2 is improved so as to enable high-power microwave power input.

  The third problem to be solved by the present invention is to cope with various shapes of substrates to be processed. In the prior arts of Patent Documents 1 and 2, a ring-shaped cavity resonator is used, which is suitable for plasma processing when the substrate to be processed is circular. However, in recent years, rectangular substrates are sometimes used in the field of manufacturing liquid crystal displays and the like. In this field, the size of the substrate is increasing mainly for the purpose of improving productivity. It is required to perform a uniform plasma treatment on these non-disc-shaped substrates.

  In response to the first problem, a plurality of places for exciting electromagnetic waves in the ring-shaped cavity resonator are prepared, the phase is optimized, and a traveling wave is excited in the ring-shaped resonator instead of a standing wave. The first problem of the invention can be solved.

  To solve the second problem, the second problem can be solved by using a structure composed of a circular waveguide and a rectangular waveguide instead of the coaxial line for exciting the ring-shaped cavity resonator.

  In response to the third problem, the cavity resonator is configured by combining a linear rectangular waveguide and an arc-shaped rectangular waveguide, thereby increasing the degree of freedom of arrangement of the plasma generation region, and It can cope with an increase in size.

  The plasma processing apparatus of the present invention includes a processing chamber in which the inside is evacuated, a substrate electrode provided in the processing chamber on which a substrate to be processed is disposed, and plasma generation for generating plasma by plasma generating electromagnetic waves in the processing chamber A plasma processing apparatus comprising: an apparatus; a supply system for supplying a processing gas into the processing chamber; and a vacuum exhaust system for exhausting the processing chamber, the plasma processing apparatus being installed concentrically with the introduction path of the plasma generating electromagnetic wave And a traveling wave in the right or left direction is excited by adjusting the amplitude and phase difference of the electromagnetic wave in the ring cavity.

  In the plasma processing apparatus of the present invention, the ring-shaped cavity resonator is further formed in an annular shape by connecting a plurality of linear waveguides and arc-shaped waveguides radially formed by the ring-shaped cavity resonator. A traveling wave in the right or left direction is excited in the ring-shaped cavity resonator by adjusting the amplitude and phase difference of the electromagnetic wave in the chamber.

  The plasma processing apparatus according to the present invention further adjusts the position of the dielectric plate arranged in the plurality of linear waveguides in adjusting the amplitude and phase difference of the plasma generating electromagnetic wave in the ring resonator. The phase is controlled by the above.

  In the plasma processing apparatus of the present invention, the adjustment of the amplitude and phase difference of the plasma generating electromagnetic wave in the ring resonator further changes the width of the plurality of linear waveguides formed radially. It is characterized by setting and adjusting the phase.

  The plasma processing apparatus of the present invention is further characterized in that the traveling wave is excited by supplying electromagnetic waves having phase differences to a plurality of feeding points.

  The plasma processing apparatus of the present invention further includes a plurality of linear waveguides, semicircular waveguides, and a plurality of linear waveguides formed radially by the ring-shaped cavity resonator. It is formed in an oval shape and adjusts the amplitude and phase difference of electromagnetic waves in the ring-shaped cavity resonator to excite a traveling wave in the right direction or the left direction in the ring-shaped cavity resonator.

  In the plasma processing apparatus of the present invention, the plasma generation electromagnetic wave introduction path is formed by connecting a rectangular waveguide, a square waveguide, and a circular waveguide, and is disposed below the circular waveguide. The plasma generating electromagnetic wave is branched into a plurality of linear waveguides formed radially by the tapered member formed.

  In addition, the plasma processing apparatus of the present invention generates a plasma by a plasma generating electromagnetic wave in the processing chamber, a processing chamber in which the inside is evacuated, a substrate electrode provided in the processing chamber and on which a substrate to be processed is disposed. A plasma processing apparatus, comprising: a plasma generation apparatus; a supply system for supplying a processing gas into the processing chamber; and a vacuum exhaust system for exhausting the processing chamber. The plasma processing apparatus is concentric with the introduction path of the plasma generating electromagnetic wave. A ring-shaped cavity resonator installed in the ring-shaped cavity resonator, wherein the ring-shaped cavity resonator is formed in an oval shape by connecting a semicircular waveguide and a plurality of linear waveguides. And

  The plasma processing apparatus of the present invention is further characterized in that the traveling wave is excited by supplying electromagnetic waves having phase differences to a plurality of feeding points.

  Further, the plasma processing apparatus of the present invention is further formed in an elliptical shape by connecting a plurality of linear waveguides and arc-shaped waveguides radially formed by the ring-shaped cavity resonator, By adjusting the amplitude and phase difference of the electromagnetic wave in the ring-shaped cavity, a traveling wave in the right or left direction is excited in the ring-shaped cavity.

  According to the present invention, exciting a traveling wave in a ring-shaped cavity resonator can prevent a spatial variation in plasma density caused by a standing wave, and can achieve uniform plasma processing.

  In addition, by using a three-dimensional circuit system mainly composed of a circular waveguide and a rectangular waveguide for excitation of the cavity resonator, compared to the excitation system using a coaxial line, the microwave power loss is reduced and the withstand voltage is improved. This has the effect of enabling high power input.

  In addition, the application of the present invention has an effect of increasing the degree of freedom of shape of the cavity resonator, so that uniform plasma processing can be easily performed on a large processing substrate and a plasma generation region can be set according to the shape of the processing substrate. There is an effect that the microwave power for plasma generation can be effectively used and the size of the apparatus can be reduced to the minimum necessary size.

  In addition, compared to the conventional technology, the plasma density distribution can be made uniform, the in-plane uniformity of the plasma treatment applied to the substrate to be processed is improved, and local wear due to the plasma nonuniformity of the microwave introduction window is reduced. Can be prevented. In addition, high-power microwaves can be input, and the search range for optimum process conditions can be expanded. It also has the effect of reducing energy consumption since the loss of microwave power is reduced.

FIG. 1 is an explanatory view of an etching apparatus according to Embodiment 1 of the present invention. FIG. 2 is a perspective view showing a converter for a rectangular waveguide and a circular waveguide TM01 mode. FIG. 3 is an explanatory view of the concept of exciting a traveling wave in the line at two feeding points. FIG. 4 is a perspective view showing a circuit branching from the circular waveguide TM01 mode to a plurality of rectangular waveguides. 5A and 5B are cross-sectional views showing a phase shifter, where FIG. 5A is a cross section perpendicular to the microwave transmission direction of the rectangular waveguide, and FIG. 5B is a cross section parallel to the microwave transmission direction of the rectangular waveguide. Is shown. FIG. 6 is an explanatory diagram showing the connection relationship between the rectangular waveguide and the ring-shaped cavity resonator. FIG. 7 is another explanatory diagram showing the connection relationship between the rectangular waveguide and the ring-shaped cavity resonator. FIG. 8 is a diagram showing a circular cavity resonator and an internal electric field strength distribution. FIG. 9 is a diagram showing an elliptical cavity resonator and an electric field intensity distribution inside. FIG. 10 is an explanatory view of an etching apparatus according to Embodiment 2 of the present invention. FIG. 11 is a schematic diagram of a configuration of an etching apparatus using a microwave of a conventional example. FIG. 12 is a diagram showing the electric field intensity distribution inside the conventional ring-shaped cavity resonator.

  A plasma etching apparatus using the present invention will be described below with reference to FIGS. 1 to 10 as an embodiment according to the present invention.

  As described above, in the conventional etching apparatus shown in FIG. 11, the electromagnetic wave generated by the high frequency power source 117 is transmitted by the waveguide 119 to the coaxial waveguide converter 118 via the isolator 121 and the automatic matching machine 120. 101. A magnetron with an oscillation frequency of 2.45 GHz was used as the high frequency power source 117. Further, an electromagnetic wave is transmitted through the coaxial line 101, branched into a plurality of short coaxial lines 104 by a branch circuit 111 composed of a conductor 102 and a dielectric plate 103, and brought to a ring-shaped cavity resonator 105.

  A plurality of slots 106 are provided radially below the ring-shaped cavity resonator 105 and are radiated to the processing chamber 114 through the dielectric window 107 and the shower plate 108. Quartz was used as the material for the dielectric window 107 and the shower plate 108. The shower plate 108 is not shown in the drawing so that the processing gas supplied from the processing gas supply system (not shown) can be supplied into the processing chamber 114 in a shower shape through a minute gap between the dielectric window 107 and the shower plate 108. Many gas supply holes are provided.

  Further, a vacuum evacuation system (not shown) is connected to the processing chamber 114 and functions to evacuate the processing chamber 114 and maintain the processing chamber at a predetermined pressure suitable for processing. A substrate electrode 110 for placing a substrate to be processed 109 is installed in the processing chamber 114. A bias power source 115 is connected to the substrate electrode 110 via an automatic matching machine 116, and a bias potential can be applied to the substrate 109 to be processed. The frequency of the bias power supply 115 is 400 kHz.

  A static magnetic field generating means 112 is provided around the processing chamber 114, and a static magnetic field can be applied to the processing chamber 114. The generation of a static magnetic field (0.0875 Tesla in the case of a frequency of 2.45 GHz) in the processing chamber 114 facilitates the generation of plasma even in a high vacuum region, and enables plasma processing in a wide pressure range. Can be possible. Further, by adjusting the distribution of the static magnetic field, it is possible to adjust the plasma distribution by controlling the position where the electron cyclotron resonance occurs and the diffusion of the plasma.

  Also, a static magnetic field generating means 113 is provided inside the ring of the ring-shaped cavity resonator 105, so that the controllable range of the static magnetic field can be expanded.

As described above, the etching apparatus shown in FIG. 11 has the following problems.
[Problem 1] The coaxial waveguide section may generate heat when a high output is applied.
[Problem 2] In some cases, non-uniform etching rates corresponding to the pattern of the electric field standing wave generated in the cavity resonator may occur.

  In response to Problem 1, the excitation structure of the ring cavity resonator was reviewed. First, a structure in which the coaxial waveguide is replaced with a circular waveguide was studied. In the examination, the characteristics of known microwave transmission lines such as a coaxial line, a circular waveguide, and a rectangular waveguide were confirmed by Non-Patent Document 1 described above.

  The fundamental mode of the coaxial waveguide has a radial electric field from the central axis, and is known to be similar to the TM01 mode of the circular waveguide. Similarly, the TM01 mode of a circular waveguide is similar to the TM11 mode of a rectangular waveguide.

  Therefore, it was decided to replace the coaxial waveguide with a circular waveguide operating in the TM01 mode. In the coaxial line, a large amount of current flows on the surface of the inner conductor, and there is a loss due to the surface resistance of the inner conductor.

  On the other hand, circular waveguides have no internal conductor and tend to have lower power loss than coaxial lines. FIG. 2 shows the result of studying the structure of a converter from a rectangular waveguide to a circular waveguide operating in the TM01 mode.

  As shown in FIG. 2, a rectangular waveguide 201 having a WRJ-2 standard (a cross section of 109.2 mm × 54.6 mm) was used. The waveguide 202 having a square cross section is converted to the TM11 mode of the rectangular waveguide 201, and further connected to the circular waveguide 203 to be converted to the TM01 mode of the circular waveguide 203.

  It is known that the lowest transmission mode of the circular waveguide 203 is a TE11 mode, then a TM01 mode, and then a TE21 mode. By setting the diameter of the circular waveguide 203 to 110 mm, which transmits the TM01 mode but does not transmit the TE21 mode, it is possible to prevent a higher order mode higher than the TM01 mode from being mixed.

  From the above examination, the connection relationship of the rectangular waveguide 201, the square waveguide 202, and the circular waveguide 203 was determined as shown in FIG. Further, the shape optimization is performed by simulating the microwave electromagnetic field using the overall length of the square waveguide 202 and the length of one side of the cross section (cross sectional shape) and the connection position of the square waveguide 202 and the rectangular waveguide 201 as parameters. Carried out.

  As an optimization criterion, the power output as the TM01 mode of the circular waveguide to the output port of the circular waveguide 203 of the incident power input from the input port of the rectangular waveguide 201 (hereinafter referred to as power transmission factor). Standard.

  The microwave electromagnetic field was simulated by numerically solving Maxwell's equations by the finite element method. As a result, the length of one side of the cross section of the square waveguide 202 is 109.2 mm, which is the same length as the long side of the cross section of the rectangular waveguide 201, and the total length of the square waveguide 202 is 1 in the rectangular waveguide TM11 mode. It was found that the power transmission rate was maximized by connecting the rectangular waveguide 201 corresponding to the wavelength of 200.6 mm to the center of the square waveguide 202.

  In the above, an example of examining the converter from the rectangular waveguide 201 to the TM01 mode of the circular waveguide 203 has been described. However, if the conversion efficiency is high and the breakdown voltage is not a problem, other types of converters can be used. It is.

  Next, improvement measures corresponding to Problem 2 were examined. In general, it is known that when waves traveling in opposite directions in a waveguide are superimposed, a standing wave having an abdominal node with electric field strength at a specific location can be formed. If the power or amplitude of both waves is the same, the electric field is always zero at the node position. If the power is different, the magnitude of the standing wave decreases, and if there is no power, the standing wave disappears. Therefore, in order to prevent the formation of standing waves, it is effective to eliminate one of the waves traveling in the opposite directions in the waveguide.

  In the case of a ring-shaped cavity, a standing wave is generated by superposition of waves propagating clockwise and counterclockwise in the ring. In the excitation method of the ring resonator according to Patent Document 2 of the conventional example shown in FIG. 12, since a clockwise and counterclockwise wave is excited simultaneously at each excitation point, a strong standing wave is excited.

  FIG. 12 illustrates an electric field standing wave pattern in the ring resonator. The magnitude of the electric field is displayed as a contour distribution. In the example of FIG. 12, waves for four wavelengths are included in the ring, and it can be seen that there are eight corresponding abdominal parts and node parts.

  In order to eliminate the clockwise or counterclockwise traveling wave, it was considered to supply power with a phase difference at two feeding points. The concept will be described with reference to FIG.

  It is assumed that the line A and the line B are connected to the line 1 at the feeding point A and the feeding point B, respectively. The wave sent from the line A to the line 1 via the feeding point A is divided into a wave traveling left (described as left A wave) and a wave traveling right (described as right A wave). Similarly, the wave sent from the line B passes through the feeding point B and becomes a wave traveling in the right direction (right B wave) and a wave traveling in the left direction (left B wave).

  For example, when only the traveling wave in the right direction is excited on the line 1, the left A wave and the left B wave cancel each other, and the right A wave and the right B wave do not cancel each other. In order for two waves to cancel each other, the amplitude is the same and the phase difference may be +180 degrees or -180 degrees. The phase of the left B wave at the feeding point A is the sum of the phase change that occurs between the feeding point B and the feeding point A and the phase at the time when the left B wave is supplied to the original feeding point B.

  Since the phase change that occurs from the feeding point B to the feeding point A is 360 degrees per wavelength in the line 1, it can be easily calculated from the proportional relationship. From the above, it is possible to cancel the traveling wave in the left direction by adjusting the phase difference of the left B wave with respect to the left A wave to ± 180 degrees at the feeding point A.

  For example, a case where a wave is supplied to the feeding point A at a phase of 0 degree, the distance between the feeding point A and the feeding point B is ¼ wavelength with respect to the wavelength of the line 1, and the phase at the feeding point B is 90 degrees. Think. In this case, the phase of the left B wave is 180 degrees at the feeding point A, and the left A wave is canceled if the amplitude is the same. On the other hand, the right A wave at the feeding point B has a phase of 90 degrees, which is the same as the phase of the right B wave of 90 degrees, and does not cancel each other.

  The case where the left traveling wave is canceled by the two feeding points A and B has been described above, but it is also possible to cancel the right traveling wave similarly by adjusting the amplitude and the phase difference. Similarly, when there are three or more feeding points, it is possible to cancel the traveling wave in either the right direction or the left direction. When adjusting so that three or more waves traveling in the same direction cancel each other, each wave is divided into two groups, and the overlapping wave of each group is considered, so that finally the case where there are two waves is obtained. I can do it.

  As a method for giving a phase difference, a method using a path length difference has been illustrated, but other known methods may be used. For example, it is known that the in-tube wavelength of the TE11 mode, which is the lowest-order mode of the rectangular waveguide, depends on the length of the long side, and the in-tube wavelength may be changed by this method to give a phase difference. In addition, it is possible to adjust the wavelength in the tube by loading a dielectric, and it is also possible to provide a phase difference by providing a discontinuous portion in the line.

  Next, a three-dimensional circuit branched from the circular waveguide TM01 mode was examined. The result of the examination is shown in FIG. FIG. 4 is a perspective view of a branch circuit that branches from the circular waveguide 203 into four rectangular waveguides 204, 205, 206, and 207.

  The microwave of the circular waveguide TM01 mode is incident from the upper port of the circular waveguide 203. A tapered member 208 is provided at the bottom of the circular waveguide 203 so that microwaves can be efficiently branched into the rectangular waveguides 204, 205, 206, and 207. The material of the three-dimensional circuit is preferably a metal having a high conductivity such as copper or aluminum in order to reduce the loss to the microwave. In order to further reduce the loss, the inner surface through which the microwave passes may be plated with, for example, silver as a material having higher conductivity. In this embodiment, it is made of aluminum.

  The rectangular waveguides 204 and 207 and the rectangular waveguides 205 and 206 are arranged on a straight line whose central axes are different from each other by 180 degrees. The TM01 mode of the circular waveguide 203 has a high degree of freedom in the arrangement direction of the rectangular waveguides 204, 205, 206, and 207 with respect to the central axis of the circular waveguide 203 because the electromagnetic field thereof does not change in the circumferential direction. That is, even if the directions of the rectangular waveguides 204, 205, 206, and 207 are changed, the branching ratio of the microwave power hardly changes. The rectangular waveguides 204, 205, 206, and 207 are sized to transmit only the TE11 mode, which is the lowest order mode of the rectangular waveguide.

  In order to optimize the above configuration, a microwave electromagnetic field simulation was performed. The simulation was performed by solving Maxwell's equation, which is a basic equation, by the finite element method. By adjusting the height of the tapered member 208 and the diameter of the bottom surface, it was confirmed that the power incident on the input port of the circular waveguide 203 was evenly distributed to each rectangular waveguide with little reflection. The case where there are four output waveguides has been described above, but the same applies to other numbers.

  As described above, in order to excite the traveling wave in the ring resonator, it is necessary to give a wave having a desired phase difference to a plurality of excitation locations. A phase shifter for controlling the phase applicable to the output side rectangular waveguide of the branch circuit shown in FIG. 4 was examined.

  As a phase shifter that can be installed in a rectangular waveguide, a known structure described in Non-Patent Document 1 was used. FIG. 5 shows an outline of the structure. 5A shows a cross section perpendicular to the microwave transmission direction of the rectangular waveguides 204 to 207, and FIG. 5B shows a cross section parallel to the microwave transmission direction.

  A dielectric plate 211 having a support bar 210 is loaded inside the rectangular waveguides 204 to 207. The position of the dielectric plate 211 in the X-axis direction in FIG. 5A can be adjusted by the support bar 210. In general, it is known that the wavelength of an electromagnetic wave in a dielectric is shortened according to the dielectric constant. In the TE11 mode, which is the lowest order mode of the rectangular waveguides 204 to 207, the magnitude of the electric field changes in the X-axis direction in FIG. It is known to be zero.

  Therefore, when the position of the dielectric plate 211 is adjusted, the influence on the electromagnetic field inside the rectangular waveguides 204 to 207 changes. When the dielectric plate 211 is in the vicinity of the tube wall, the wavelength shortening effect is small, and the waveguide When it is in the center, the wavelength shortening effect is maximized. When the wavelength in the rectangular waveguides 204 to 207 changes, the phase of the wave at the output end changes according to the wavelength. Therefore, the phase can be controlled by adjusting the position of the dielectric plate 211.

  In this embodiment, alumina ceramic is used as the material of the dielectric plate 211. Further, alumina ceramic is similarly used as the material of the support bar 210. However, when the influence of the reflected wave is small, it may be made of metal. Further, as the shape of the dielectric plate 211, a parallelogram shape was used as shown in FIG. By adopting the parallelogram shape, it is possible to prevent an abrupt change in the equivalent dielectric constant with respect to the traveling direction of the electromagnetic wave, so that the reflected wave from the dielectric plate 211 can be reduced. However, when the influence of this reflected wave is small, it may be a rectangle.

  In the example shown in FIG. 5, the support rod 210 shows an example in which the opposite tube wall of the waveguide penetrates, but it does not necessarily have to penetrate. By passing through the support bar 210, there is an effect of stabilizing the position of the dielectric plate 211, but the influence of the microwave power reflection by the support bar 210 is also increased. Alternatively, the length of the support rod 210 may be approximately halved so that only one side of the waveguide wall penetrates.

  In the conventional ring-shaped cavity resonator shown in FIG. 12, four wavelengths are included in 360 degrees of the entire circumference, and it can be seen that the path of one wavelength is 90 degrees. The line 1 in FIG. 3 corresponds to a ring-shaped cavity resonator. By providing a plurality of feed points in the ring-shaped cavity and adjusting the phase of the wave supplied to the feed point, the standing wave in the ring-shaped cavity is eliminated, and the traveling wave is clockwise or counterclockwise. I can do it.

  In this embodiment, the interval between the feeding points is 67.5 degrees. The phase difference due to propagation between the feeding points is 270 degrees at an angle corresponding to 3/4 wavelength as the path difference. Therefore, if a wave with a phase difference of −90 degrees is supplied to each feeding point, the total phase difference becomes 180 degrees, and a traveling wave can be excited in the ring resonator as described with reference to FIG. I can do it.

  FIG. 6 shows a connection relationship between the ring-shaped cavity resonator 209 and the exciting rectangular waveguides 204 to 207. A center axis of each of the rectangular waveguides 204 to 207 is indicated by a one-dot chain line. The feeding point is defined as the intersection of the inner surface of the ring resonator and the central axis of the rectangular waveguide.

  As shown in FIG. 6, the central axes of the rectangular waveguides 204 and 205 are arranged so as to intersect with an angle of 67.5 degrees. Each of the rectangular waveguides 204 to 207 is loaded with a movable phase adjusting dielectric plate 211 so that the phase of the microwave at the output end of each of the rectangular waveguides 204 to 207 can be adjusted.

  If the phase difference between the rectangular waveguide 204 and the rectangular waveguide 205 is adjusted to −90 degrees, a traveling wave can be excited in the ring-shaped cavity resonator. The rectangular waveguides 204 and 207 and the rectangular waveguides 205 and 206 are oriented in directions different from each other by 180 degrees. Since 90 degrees corresponds to one wavelength in the ring-shaped cavity, these two sets of rectangular waveguides excite positions different by two wavelengths. By increasing the number of feeding points necessary for exciting the traveling wave, the electric field distribution in the ring-shaped cavity resonator can be made more uniform.

  FIG. 7 shows another example of a ring-shaped cavity resonator and a rectangular waveguide for excitation. Only differences from the example shown in FIG. 6 will be described. In the example shown in FIG. 6, as described above, the dielectric plate 211 for phase adjustment is installed in each of the exciting rectangular waveguides 204 to 207, and each rectangular wave is guided by the position of the dielectric plate 211. The phase of the outputs of the tubes 204 to 207 could be adjusted.

  On the other hand, in another example shown in FIG. 7, the phase adjustment is performed by the width (d, D) of the rectangular waveguide. Compared with the example shown in FIG. 6, fine adjustment is difficult, but there is an advantage that the structure is simple. It is well known that the wavelength of the TE11 mode, which is the lowest order mode of a rectangular waveguide, is determined by the rectangular waveguide width (d, D), and is also described in Non-Patent Document 1. A desired phase difference can be given by adjusting the waveguide width (d, D).

  FIG. 1 is an explanatory view of an etching apparatus according to Embodiment 1 of the present invention. FIG. 1 shows the result of improving the prior art of Patent Document 2 shown in FIG.

  Description of common parts is omitted. A circular TM01 mode converter shown in FIG. 2 was used in place of the coaxial waveguide converter 118 of FIG. Thus, the coaxial waveguide 101 in FIG. The circular waveguide 203 has a diameter that does not transmit higher-order modes than the circular waveguide TM01 mode, as described with reference to FIG.

  A branch circuit shown in FIG. 5 was used in place of the branch circuit 111 shown in FIG. The phase shifter shown in FIG. 5 is used in the rectangular waveguides 204 to 208 of the branch circuit as shown in FIG. Instead of the phase shifter shown in FIG. 5, the phase may be adjusted using rectangular waveguides 204 to 208 having different widths as described in FIG. 7.

  Furthermore, as shown in FIG. 10, a cavity 1001 may be provided below the ring-shaped cavity resonator 105 and the radial slot 106. In addition to adjusting the microwave matching state by changing the height of the cavity 1001 to enable stable plasma generation, the microwave electromagnetic field that becomes stronger just below the slot by increasing the distance between the radial slot 106 and the dielectric window 107. Can be relaxed.

  In the example shown in FIGS. 1 and 10, an example in which the static magnetic field generating means 112 is provided is shown. However, if the plasma distribution adjustment effect by the electron cyclotron resonance phenomenon or the static magnetic field distribution adjustment is unnecessary, it may be omitted. good. By eliminating the static magnetic field generating means, there are effects of reducing the manufacturing cost of the apparatus and reducing the power consumption.

  FIG. 8 is a diagram showing a circular cavity resonator and an internal electric field strength distribution. In this embodiment, a clockwise traveling wave or a counterclockwise traveling wave is excited in a circular ring-shaped cavity resonator 209, thereby generating electric power generated in the conventional ring-shaped cavity resonator 209 in FIG. The non-uniformity of the distribution of the microwave electromagnetic field due to the abdomen and node of the field standing wave is alleviated.

  Next, the third problem, which is to cope with various substrate shapes, will be described. In order to perform uniform plasma processing on a substrate in response to an increase in the size of the substrate to be processed, it is necessary to generate uniform plasma within a range corresponding to the substrate dimensions. In Patent Documents 1 and 2, by adjusting the ring diameter of the ring-shaped cavity resonator in accordance with the diameter of the substrate to be processed, the plasma generation range can be adjusted, and the size can be increased. However, since the cavity resonator has a ring shape, there is a problem that it is difficult to cope with a case where the substrate to be processed has a non-circular shape such as a rectangle.

  To solve this problem, an elliptical cavity resonator in which a linear portion is added to a part of the ring-shaped cavity resonator 209 as shown in FIG. 9 can be used. A ring-shaped cavity resonator is divided into two on a semicircle, and a linear waveguide having a length that is an integral multiple of a half wavelength and a width that smoothly connects with the ring-shaped cavity resonator is connected. An elliptical ring-shaped cavity resonator 209 shown in FIG. 9 can be configured. FIG. 9 also shows the electric field intensity distribution in the cavity resonator.

  Similar to FIG. 11, the electric field intensity distribution is shown by the contour line distribution. According to the method described with reference to FIG. 3, it is possible to excite a clockwise traveling wave or a counterclockwise traveling wave in an elliptical cavity resonator as shown in the figure. If there is no problem in processing uniformity or the like in a state where a standing wave is excited, a standing wave may be used. The length of the added rectangular waveguide has a degree of freedom that is an integral multiple of a half wavelength, and can be freely selected according to the dimensions of the substrate to be processed.

  Similarly, a substantially rectangular cavity resonator can be formed by dividing the ring cavity resonator into four parts and connecting a linear waveguide between them. It is also possible to construct a cavity resonator with a more complicated arrangement by the same procedure.

  The present invention is not limited to the plasma etching apparatus shown in FIGS. 1 to 10, but can be applied to plasma etching apparatuses using other plasma generation methods. Further, for example, plasma CVD and plasma ashing can be applied as other plasma processing.

DESCRIPTION OF SYMBOLS 101 Coaxial line 102 Conductor 103 Dielectric board 104 Coaxial line 105 Ring-shaped cavity resonator 106 Radially several slots 107 Dielectric window 108 Shower plate 109 Substrate 110 Substrate electrode 111 Branch circuit 112 Static magnetic field generating means 113 Static magnetic field Generating means 114 processing chamber 115 bias power supply 116 automatic matching machine 117 high frequency power supply 118 coaxial waveguide converter 119 waveguide 120 automatic matching machine 121 isolator 201 rectangular waveguide 202 square waveguide 203 circular waveguide 204 rectangular Waveguide 205 Rectangular waveguide 206 Rectangular waveguide 207 Rectangular waveguide 208 Tapered member 209 Ring cavity resonator 210 Support bar 211 Movable phase adjusting dielectric plate 1001 Cavity

Claims (10)

A processing chamber in which the inside is evacuated,
A substrate electrode provided in the processing chamber and on which a substrate to be processed is disposed;
A plasma generator for generating plasma by plasma generating electromagnetic waves in the processing chamber;
A supply system for supplying a processing gas into the processing chamber;
In a plasma processing apparatus having a vacuum exhaust system for exhausting the processing chamber,
A ring-shaped cavity resonator installed concentrically with the introduction path of the plasma generating electromagnetic wave,
A plasma processing apparatus, wherein a traveling wave in a right direction or a left direction is excited by adjusting an amplitude and a phase difference of an electromagnetic wave in the ring cavity. The plasma processing apparatus according to claim 1,
The ring-shaped cavity is formed in an annular shape by connecting a plurality of linear waveguides and arc-shaped waveguides formed radially, and the amplitude and phase difference of electromagnetic waves in the ring-shaped cavity are determined. A plasma processing apparatus that adjusts and excites a traveling wave in a right direction or a left direction in the ring-shaped cavity resonator. The plasma processing apparatus according to claim 2, wherein
In adjusting the amplitude and phase difference of the plasma generating electromagnetic wave in the ring resonator, the phase is controlled by adjusting the position of a dielectric plate disposed in the plurality of linear waveguides. Plasma processing equipment. The plasma processing apparatus according to claim 2, wherein
In adjusting the amplitude and phase difference of the plasma generating electromagnetic wave in the ring resonator, the phase is adjusted by setting the widths of the plurality of linear waveguides formed radially to different values. A plasma processing apparatus. The plasma processing apparatus according to claim 2, wherein
The introduction path of the plasma generating electromagnetic wave is formed by connecting a rectangular waveguide, a square waveguide and a circular waveguide, and is formed radially by a tapered member disposed under the circular waveguide. A plasma processing apparatus, wherein the plasma generating electromagnetic wave is branched into a plurality of straight waveguides. The plasma processing apparatus according to claim 1,
A plasma processing apparatus, wherein the traveling wave is excited by supplying electromagnetic waves having phase differences to a plurality of feeding points. The plasma processing apparatus according to claim 1,
The ring-shaped cavity resonator is formed into an oval shape by connecting a plurality of linear waveguides, semicircular waveguides, and a plurality of linear waveguides formed radially. A plasma processing apparatus, wherein a traveling wave in a right direction or a left direction is excited in the ring-shaped cavity resonator by adjusting an amplitude and a phase difference of an electromagnetic wave in the cavity resonator. A processing chamber in which the inside is evacuated,
A substrate electrode provided in the processing chamber and on which a substrate to be processed is disposed;
A plasma generator for generating plasma by plasma generating electromagnetic waves in the processing chamber;
A supply system for supplying a processing gas into the processing chamber;
In a plasma processing apparatus having a vacuum exhaust system for exhausting the processing chamber,
A ring-shaped cavity resonator installed concentrically with the introduction path of the plasma generating electromagnetic wave,
The plasma processing apparatus, wherein the ring-shaped cavity resonator is formed in an oval shape by connecting a semicircular waveguide and a plurality of linear waveguides. The plasma processing apparatus according to claim 8, wherein
A plasma processing apparatus, wherein the traveling wave is excited by supplying electromagnetic waves having a phase difference to a plurality of feeding points. The plasma processing apparatus according to claim 8, wherein
The ring-shaped cavity resonator is formed in an elliptical shape by connecting a plurality of linear waveguides and arc-shaped waveguides formed radially, and the amplitude and level of electromagnetic waves in the ring-shaped cavity resonator are A plasma processing apparatus characterized by adjusting a phase difference to excite a traveling wave in a right direction or a left direction in the ring-shaped cavity resonator.

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