Plasma processing apparatus

A plasma processing apparatus includes a processing container 53, a mounting table 61 arranged in the processing container 53 to support a wafer W, a sealing plate 55 opposed to the wafer W supported by the mounting table 61, an annular antenna 73 arranged on the sealing plate 55 and consisting of an annular waveguide to introduce a microwave into the processing container 53 through the sealing plate 55, the annular antenna 73 being arranged so that a plane containing an annular waveguide path defined by the annular waveguide is generally parallel with the sealing plate 55, a directional coupler 79 arranged on the periphery of the annular antenna 73, a propagation waveguide 81 connected to the directional coupler 79 and a microwave oscillator 83 connected to the propagation waveguide 81. Accordingly, it is possible to form an uniform microwave in the antenna, so that an uniform plasma can be produced in the processing container.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a plasma processing apparatus utilizing a high-frequency wave.

2. Description of the Related Art

Conventionally, there is known a plasma processing apparatus which includes an antenna consisting of an annular waveguide arranged on the upper face of a processing container to supply its interior with a microwave, as shown inFIG. 17(Japanese Patent Publication kokai No. 11-121196).

This plasma processing apparatus11has a processing container13on which an antenna15is mounted. The antenna15is formed by an annularly-curled waveguide having its end closed and has slots17. . . formed on the side of the processing container13. The other end of the antenna15is connected to a microwave oscillator19.

In the plasma processing apparatus11, the microwave from the microwave oscillator19is reflected on an end21of the antenna15to form a standing wave in the waveguide. Then, the microwave is emitted into the processing container13through the slots17. . . thereby to generate a plasma for processing.

While,FIG. 18shows another plasma processing apparatus31(Japanese Patent Publication kokai No. 5-34598) in which an antenna35in the form of an annular waveguide is wound around the outer periphery of a processing container33and also connected to a microwave oscillator39through a waveguide37. In operation, the microwave supplied from the microwave oscillator39is divided into left and right at a connecting part41between the waveguide37and the antenna35. Then, the so-divided microwaves meet again at a part43on the opposite side of the connecting part41and is reflected mutually to form a standing wave in the antenna35. Through slots45. . . formed on the inner side of the antenna35, the microwaves are emitted into the inside processing container33, so that the plasma is produced in the processing container33for processing.

Further,FIG. 19shows a plasma processing apparatus121(Japanese Patent Publication kokai No. 11-40397) which includes an antenna125consisting of an annular waveguide arranged on the upper face of a processing container123. The antenna125has a plurality of slots127. . . formed on the side of the processing container13. The upper face of the annular antenna125is connected to a waveguide129for supplying a microwave, perpendicularly. A convex ridge131is formed at a joint part between the waveguide129and the antenna125. The microwave propagated from the waveguide129is divided to two groups of microwaves at the convex ridge131. Then, the so-divided microwaves meet again on the opposite side of the joint part and is reflected mutually to form a standing wave in the antenna125. The plasma processing apparatus121is adapted so as to emit a microwave from the standing wave toward the processing container13.

In the above plasma processing apparatuses11,31,121each forming the standing wave in the antenna, however, the microwave has different intensities at each node and antinode of the standing wave. Thus, due to the positional relationship between node and antinode in the antenna, a problem arises in that the interior of the processing container has an electromagnetic field of uneven intensity. Additionally, if the position of each node of the standing wave is deviated from the slot of the antenna, the uniformity of electromagnetic field cannot be maintained in the processing container, causing a problem of impossibility to produce the plasma uniformly, hitherto.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problem, the object of the present invention is to provide a plasma processing apparatus which is capable of forming an uniform microwave in an antenna thereby to produce an uniform plasma in a processing container.

The first feature of the present invention resides in a plasma processing apparatus which comprises:a processing container in form of a cylinder with a bottom;a supporting unit disposed in the processing container to support an object to be processed;a dielectric window arranged in an opening of the processing container to close up the processing container in an air-tight manner, the dielectric window being made of dielectric allowing a high-frequency wave to permeate the dielectric window into an interior of the processing container;an annular waveguide shaped in form of a ring to introduce the high-frequency wave into the processing container through the dielectric window and also fitted to the dielectric window so that a plane containing an annular waveguide path of the annular waveguide extends along the dielectric window; anda traveling-wave generator arranged at the annular waveguide to produce a traveling wave in form of an endless ring in the annular waveguide.

The second feature of the present invention resides in that the traveling-wave generator includes:a high-frequency wave generator for supplying the high-frequency wave;a propagation waveguide tube connected to the high-frequency wave generator to propagate the high-frequency wave generated in the high-frequency wave generator; anda directional coupler arranged between the propagation waveguide and the annular waveguide to connect the propagation waveguide with the annular waveguide thereby to supply the annular waveguide with the high-frequency wave which has been propagated in the propagation waveguide, as the traveling wave.

The third feature of the present invention resides in that the annular waveguide has its circumferential length a natural number of times as long as a wave length in the annular waveguide.

The fourth feature of the present invention resides in that the traveling-wave generator has a multiphase high-frequency wave supplier for supplying several positions apart from each other in the circumferential direction of the annular waveguide with high-frequency waves whose phases are shifted from each other in the circumferential direction, whereby the supply of the high-frequency waves whose phases are shifted from each other in the circumferential direction of the annular waveguide allows the traveling wave to be generated in the annular waveguide.

The fifth feature of the present invention resides in that the multiphase high-frequency wave supplier comprises:a high-frequency wave generator for generating a high-frequency wave in TE11 mode;a cylindrical waveguide having its one end connected to the high-frequency wave generator;a circularly-polarized wave converter arranged in the middle of the cylindrical waveguide to rotate the high-frequency wave in TE11 mode being propagated in the cylindrical waveguide about an axis of the cylindrical waveguide; anda plurality of branch waveguides having respective one ends connected to an outer face of another end of the cylindrical waveguide at respective positions apart from each other in the circumferential direction of the cylindrical waveguide and also having the other ends connected to the annular waveguide at respective positions apart from each other in the circumferential direction of the annular waveguide.

The sixth feature of the present invention resides in that the multiphase high-frequency wave supplier comprises:a high-frequency wave generator for generating a high-frequency wave in TE11 mode in the waveguide;a plurality of branch waveguides having respective one ends connected to the waveguide and the other ends connected to the annular waveguide at respective positions apart from each other in the circumferential direction of the annular waveguide; andphase shifters arranged in the branch waveguides respectively to control respective phases of plural high-frequency waves divided by the branch waveguides so that a traveling wave is generated in the annular waveguide when the high-frequency waves are supplied into the annular waveguide.

The seventh feature of the present invention resides in that circumferential length of the annular waveguide is a natural number of times as long as a wave length in the annular waveguide.

The eighth feature of the present invention resides in that the waveguide to supply the annular waveguide with the high-frequency wave is shaped to be rectangular.

The ninth feature of the present invention resides in that the waveguide to supply the annular waveguide with the high-frequency wave is a coaxial waveguide.

The tenth feature of the present invention resides in that the plasma processing apparatus further comprises a gas supply tube for supplying the processing container with gas, wherein the gas supply tube has its opening connected to a part of the dielectric window surrounded by the annular waveguide.

The eleventh feature of the present invention resides in that the dielectric window is provided, at its part surrounded by the annular waveguide, with an opposing electrode arranged in opposition to the supporting unit.

The twelfth feature of the present invention resides in that the dielectric window is provided, at its part surrounded by the annular waveguide, with a leading end of a gas supply tube for supplying the processing container with gas, the leading end having an opening formed to supply the gas into the processing container and also providing an opposing electrode arranged in opposition to the supporting unit.

The thirteenth feature of the present invention resides in that the opposing electrode is grounded for earth.

The fourteenth feature of the present invention resides in that the opposing electrode is connected to a high-frequency power source.

The fifteenth feature of the present invention resides in that the annular waveguide is in form of a circular loop.

The sixteenth feature of the present invention resides in that the annular waveguide is in form of a rectangular loop.

The seventeenth feature of the present invention resides in that the high-frequency wave has a frequency from 200 MHz to 35 GHz.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference toFIGS. 1Ato16, embodiments of the present invention will be described below.

FIGS. 1A,1B,1C and2are structural views showing the plasma processing apparatus of the first embodiment. InFIG. 1A, this plasma etching apparatus51has a processing container53whose sidewall and bottom are made of conductive material, such as aluminum, and which is shaped to be a cylinder with bottom, as a whole. The ceiling part of the container53is opened, whereas it is sealed by a sealing plate55having a thickness to endure a vacuum pressure through a sealant, such as O-ring, in an air-tight manner. This sealing plate55is made from dielectric material exhibiting heat-resistance, microwave permeability and small dielectric loss, for example, silica glass, alumina, ceramics of aluminum nitride or the like. Owing to the provision of the sealing plate55, there is defined a processing space57in the processing container53. Fitted on the sealing plate55is a cover member59in the form of a circular lid of conductive material, which is fixed on the processing container53.

In the processing container53, a mounting table61is accommodated to mount a semiconductor wafer W as the object to be processed, thereon. The mounting table61is made of aluminum and also disposed on the bottom of the processing container53through an insulating member. The mounting table61is connected with a matching box65and a bias high-frequency source67through a power line63. The processing container53is provided, on a sidewall thereof, with a gas nozzle69of a silica pipe to introduce a processing gas into the container53. On the bottom of the processing container53, there are provided exhaust ports71,71communicated with a not-shown vacuum pump, allowing the interior of the processing container53to be evacuated to a predetermined pressure as occasion demands.

While, arranged on the upper face of the cover member59is an annular antenna73which introduces a microwave into the processing space57. The annular antenna73can be obtained by forming a waveguide having a rectangular section so as to be endless and annular. The antenna73is also arranged so that a plane containing an annular waveguide path defined by the annular waveguide is substantially parallel with the sealing plate55. In the pipe wall of the annular antenna73on the side of the processing space57, a plurality of slots75are formed to extend in a radial direction of the antenna, at intervals in the circumferential direction. Correspondingly, the cover member59has a plurality of openings77formed to correspond to the slots75, respectively.

On the outside face of the annular antenna73, a propagation waveguide81is connected tangential to the antenna73through a directional coupler79. The other end of the propagation waveguide81is connected to a microwave oscillator83for supplying the microwave. The directional coupler79operates to make the microwave, which has been propagated in the waveguide81from the microwave oscillator83in the direction of arrow A in the figure, propagate only in the direction of arrow B in the annular antenna73. Consequently, the microwave as a traveling wave is propagated in the annular antenna73in the form of an endless ring, only in the only one direction (the direction of arrow B). A microwave absorber85is detachably attached to the inside of an end of the propagation waveguide81on the side of the directional coupler79. The microwave absorber85operates to prevent the microwave propagated in the propagation waveguide81in the direction of arrow A from being reflected on the end of the propagation waveguide81into a standing wave, thereby to maintain a traveling wave. Note, it is also possible to change a traveling-wave mode to a standing-wave mode by replacing the microwave absorber by a microwave reflector. In such a constitution, the above annular antenna73, the directional coupler79and the propagation waveguide81constitute a ring resonator74. In the ring resonator74, it is preferable to employ a so-called “short-slot” hybrid having a degree of coupling 3 dB for the directional coupler79. In case of arranging a plurality of directional couplers in the circumferential direction of the above annular waveguide, a path length of waveguide between the adjoining directional couplers has only to be adjusted together with the adjustment in phases of the so-supplied microwaves so that a traveling wave can be formed in a single direction of the annular waveguide.

Next, the operation of the above-constructed apparatus of the embodiment will be described. First, through a not-shown gate valve, the semiconductor wafer W is accommodated in the processing container53by a transfer arm and successively mounted on the upper face of the mounting table61. Then, while maintaining the interior of the processing container53at a predetermined processing pressure, a processing gas under its flow control is supplied into the container through the gas nozzle69. Simultaneously, the microwave of e.g. 2.45 GHz as a high-frequency wave is introduced from the microwave oscillator83thereby producing a plasma for processing. In connection, if a bias high-frequency power is applied on the mounting table61, then a negative potential can be produced on the mounting table61, allowing an ion to be extracted from the plasma effectively.

In the above structure, the microwave supplied from the microwave oscillator83is propagated in the propagation waveguide81in the direction of arrow A and subsequently supplied into the annular antenna73at directional coupler79. Hereat, it is desirable that the microwave supplied from the microwave oscillator83to the annular antenna73has a frequency from 200 MHz to 35 GHz. In case of adopting the microwave of 200 MHz whose wave length is 1.47 m, the annular waveguide path of one wave length will have 46.8 cm in diameter, which is believed to be a maximum size in view of the dimension of a chamber defined therein. Alternatively, in case of the microwave of 35 GHz having 8.4 mm in wave length, the annular waveguide path of one wave length will have a minimum length under the present arrangement of slots by 0.8 mm in plate thickness, 2 mm in opening width and 2 mm in interval. Here, since the directional coupler79is arranged at the connecting part between the propagation waveguide81and the annular antenna73, the microwave propagated in the direction of arrow A in the propagation waveguide81is then propagated only in the direction of arrow B in the annular antenna73, producing a traveling wave rotating in the annular antenna73in the form of an endless ring. Then, the microwave being propagated as the traveling wave in the annular antenna73is emitted to the interior of the processing container53through the numerous slots75. Note, since the microwave traveling in the annular antenna73is not a standing wave but a traveling wave rotating in the annular antenna in the form of an endless ring, an electromagnetic field emitted from the slots75becomes uniform in the circumferential direction of the annular antenna73. Accordingly, it is possible to produce a remarkably uniform plasma in the processing container53, allowing an uniform processing to be applied on even a large-diameter wafer throughout.

According to the embodiment, since the plasma processing apparatus comprises the processing container53, the mounting table61disposed in the processing container53to support the wafer W, the sealing plate55opposing the wafer W supported by the mounting table61, the annular antenna73consisting of an annular waveguide to introduce the microwave into the processing container53through the sealing plate55and also having its plane containing an annular waveguide path arranged to be substantially parallel with the sealing plate55, the directional coupler79arranged in the periphery of the annular antenna73, the propagation waveguide81connected with the directional coupler79and the microwave oscillator83connected to the propagation waveguide81, it is possible to form a traveling wave in the from of an endless ring in the annular antenna73thereby to emit an electromagnetic field which is uniform in the circumferential direction, into the annular antenna73. Thus, it is possible to produce an uniform plasma in the processing container53, allowing an uniform processing to be applied on even a large-diameter wafer.

When it is required to alter the producing condition of plasma, there may be inclined an angle between a plane having the slots75of the annular antenna73formed therein and the sealing plate55. For example, when it is required to intensify the production of plasma at the center of the chamber, the plane having the slots75formed therein is inclined so as to direct the center of the chamber, as shown in FIG.1B. Conversely, when it is required to intensify the production of plasma at the periphery of the chamber, the plane having the slots75formed therein has only to be inclined so as to direct the periphery of the chamber.

FIG. 3is a view showing a plasma processing apparatus121in accordance with the second embodiment of the present invention. This plasma processing apparatus121is similar to the plasma processing apparatus51besides a gas supply tube123arranged at the center of the sealing plate55surrounded by the annular antenna73. This gas supply tube has a lower part funnel-shaped so as to gradually increase its diameter as approaching the lowermost end provided with a number of nozzles125. In this way, since the antenna73supplying the processing container53with the microwave is in the form of a circular loop, the gas supply tube123can be provided at the central opening of the antenna73. Accordingly, it is possible to supply the wafer W with reactive gas etc. uniformly, thereby preventing the uneven processing due to unequal gas supply.

FIG. 4is a view showing a plasma processing apparatus131in accordance with the third embodiment of the present invention. This plasma processing apparatus131is similar to the plasma processing apparatus51besides an opposing electrode133arranged at the center of the sealing plate55surrounded by the annular antenna73so as to oppose the mounting table61. The opposing electrode133is grounded for earthing. With this arrangement, it is possible to form a strong and uniform electromagnetic field between the mounting table61and the opposing electrode133, whereby ions can be extracted from the plasma effectively, accomplishing an uniform processing.

FIG. 5is a view showing a plasma processing apparatus141in accordance with the fourth embodiment of the present invention. This plasma processing apparatus141is similar to the plasma processing apparatus131of the third embodiment inFIG. 4besides a high-frequency source143in place of the earth for the opposing electrode133. In this way, since the opposing electrode133is connected to the high-frequency source143, it is possible to form a desired strong and uniform electromagnetic field between the mounting table61and the opposing electrode133. Therefore, it is possible to accomplish the extraction of ions from the plasma more effectively and also the uniform processing.

FIG. 6is a view showing the fifth embodiment of the present invention. A plasma processing apparatus151of this figure is similar to the same of the third embodiment except that the lower end of a gas supply tube is formed by an opposing electrode. The gas supply tube153has a cylindrical gas tube body155and a nozzle part157in the form of a hollow disc connected to the lower end of the tube body155. A plurality of nozzle orifices159. . . are formed on the underface of the nozzle part157opposed to the mounting table61. The gas supply tube153is made from conductor and also grounded through an earthing line. In the gas supply tube153constructed above, the processing gas passing through the gas tube body155is diffused in the radial direction at the nozzle part157and subsequently supplied into the processing container53through the nozzle orifices159uniformly. Further, since this gas supply tube is grounded for earthing, it also serves as an opposing electrode opposing the mounting table61. Alternatively, the gas supply tube may be separated from halfway through insulation so that the nozzle part is connected to the high-frequency source.

In this way, as the gas supply tube153of the plasma processing apparatus151has functions of supplying the processing gas and also providing an opposing electrode in opposition to the mounting table, it is possible to supply the wafer W with reactive gas etc. uniformly and also possible to form an uniform and strong electric field between the mounting table61and the opposing electrode153, whereby an uniform plasma can be produced.

FIGS. 7 and 8show the sixth embodiment of the present invention. A plasma processing apparatus91in these figures is similar to the plasma processing apparatus51ofFIGS. 1 and 2except that the propagation waveguide81is connected with the upper face of the annular antenna73in the form of a circular loop, through a directional coupler93.

The plasma processing apparatus91exhibits operation and effect similar to those of the plasma processing apparatus51.

FIG. 9shows the seventh embodiment of the present invention. In a plasma processing apparatus101, a power supply unit103is arranged on the annular antenna117on the processing container53. The power supply unit103has a cylindrical waveguide105. A not-shown microwave oscillator is connected to the cylindrical waveguide105to supply the microwave in TE11 mode. In the middle of the cylindrical waveguide105, a circularly-polarized wave converter107is arranged to rotate the so-supplied “TE11 mode” microwave about an axis of the cylindrical waveguide105. Connected to the outer face of the lower end of the cylindrical waveguide105are first to fourth branch waveguides109,111,113,115which project radially outward at intervals of 90 degrees around the axis of the waveguide105. After projecting radially outward, the first to the fourth branch waveguides109,111,113,115are respectively bent so as to extend downwardly. These first to fourth branch waveguides are finally connected to an annular antenna117in the form of a circular loop, at respective positions apart from each other by 90 degrees in the circumferential direction of the antenna117.

With the structure mentioned above, the “TE11 mode” microwave being propagated from the microwave oscillator (not shown) into the cylindrical waveguide105reaches the circularly-polarized wave converter107. By the circularly-polarized wave converter107, the “TE11 mode” microwave is rotated about the axis of the cylindrical waveguide105to reach the lowermost end of the cylindrical waveguide105. Hereat, the rotating “TE11 mode” microwave enters the first to the fourth branch waveguides109,111,113,115. Note, the microwave propagated in the cylindrical waveguide105is a rotating circularly-polarized wave and additionally, the first to the fourth branch waveguides109,1111113,115are connected to the outer face of the cylindrical waveguide105while being shifted from each other by 90 degrees in the circumferential direction of the waveguide. Therefore, the phases of respective microwaves entering the annular antenna117through the first to the fourth branch waveguides109,111,113,115are also shifted from each other by 90 degrees. Thus, the microwaves entering the annular antenna117forms a traveling wave rotating in the circumferential direction, as a whole. The “rotating” traveling wave formed in the annular antenna117is uniformly emitted into the processing container53through slots (not shown) formed on the underface of the antenna, thereby forming an uniform plasma.

In this way, according to this embodiment, the plasma processing apparatus includes the microwave oscillator oscillating the “TE11 mode” microwave, the cylindrical waveguide105connected to the microwave oscillator, the circularly-polarized wave converter107arranged in the middle of the cylindrical waveguide105to rotate the “TE11 mode” microwave, the first to the fourth branch waveguides109,111,113,115connected to the outer face of the lower end of the cylindrical waveguide105at intervals of 90 degrees around the axis of the waveguide105, the annular antenna117to which the first to the fourth branch waveguides are connected apart from each other by 90 degrees in the circumferential direction, and the process container52having the sealing plate provided with the annular antenna117. Therefore, it is possible to form the traveling wave rotating in the circumferential direction, in the annular antenna117. Thus, it is possible to provide the interior of the processing container117with an uniform electromagnetic field, whereby an uniform plasma can be produced. Therefore, it is possible to apply an uniform processing on even a large-diameter wafer.

FIGS. 10to14show the eighth embodiment of the present invention.FIG. 10is a perspective view of the embodiment, whileFIG. 11is a circuit diagram of the embodiment. In these figures, a plasma processing apparatus161has a waveguide163. This waveguide163includes a first rectangular waveguide167having a microwave introductory port165. The first rectangular waveguide167is divided into a second rectangular waveguide171, a third rectangular waveguide173and a first dummy load175by a first “magic” T member169. Further, the second rectangular waveguide171is divided into a fourth rectangular waveguide179, a fifth rectangular waveguide181and a second dummy load183by a second “magic” T member177. Also, the third rectangular waveguide173is divided into a sixth rectangular waveguide187, a seventh rectangular waveguide189and a third dummy load191by a third “magic” T member185.

Respective lower ends193. . . of the fourth rectangular waveguide179, the fifth rectangular waveguide181, the sixth rectangular waveguide187and the seventh rectangular waveguide189are all bent at right angles and connected to an annular antenna197through coaxial waveguides195, as shown in FIG.12. Connections of these four rectangular waveguides179,181,187,189with the annular antenna197are separated from each other by 90 degrees in the circumferential direction, as shown inFIGS. 10 and 11.

Additionally, as shown inFIG. 11, phase shifters199,201,203are interposed in the fourth rectangular waveguide179, the fifth rectangular waveguide181and the sixth rectangular waveguide187, respectively. These phase shifters199,201,203operate to shift respective phases of microwaves propagated in the respective waveguides by predetermined amounts thereby to shift the respective microwaves at a point of time reaching the annular antenna197successively. Consequently, as a whole, the phase shifters199,201,203serve to form a traveling wave in the annular antenna.

In the plasma processing apparatus161constructed above, the microwave introduced from a “TE10 mode” microwave generator (not shown) into the microwave introductory port is divided at the first “magic” T member and further divided, at the second and the third “magic” T members177,185, into four parts finally. In the so-divided microwaves, the microwaves propagated in the fourth rectangular waveguide179, the fifth rectangular waveguide181and the sixth rectangular waveguide187are adjusted in respective phases by the phase shifters199,201,203, so that the traveling wave is formed in the annular antenna197finally.

In this way, the plasma processing apparatus161includes the microwave generator for generating the “TE10 mode” microwave, the waveguide163having one end connected to the generator and other ends connected to the annular antenna163at respective positions apart from each other in the circumferential direction of the antenna163, and also the phase shifters199,201,203which are arranged in the branch waveguides of the above waveguide to adjust the phases of plural microwaves divided by the branch waveguides so that the traveling wave is produced in the annular antenna197when the so-divided microwaves are supplied into the annular antenna197. Therefore, it is possible to emit the uniform plasma into the processing container through the annular antenna197, whereby the inform plasma can be produced in the processing container.

Note, as shown inFIG. 12, although the fourth rectangular waveguide179, the fifth rectangular waveguide181, the sixth rectangular waveguide187and the seventh rectangular waveguide189are connected to the annular antenna197through the coaxial waveguides195in the eighth embodiment, the present invention is not limited to this arrangement only. For example, in the modification shown inFIG. 13, the rectangular waveguide179etc. is connected to the annular antenna197directly, while its connecting part is provided with a bump205allowing the microwave to be introduced into the annular antenna197.

Additionally, although three phase shifters199,201,203are provided in the eighth embodiment, it is not limited to this arrangement. For example, as shown inFIG. 14, if there is adopted an arrangement where four divided waveguides211are connected with the annular antenna197on consideration of basic characteristics of the “magic” T member, then the purpose of the invention could be attained by only providing two phase shifters213,214.

Note, in common with the seventh embodiment of FIG.9and the eighth embodiment ofFIG. 10, the plural waveguides are connected to the annular waveguide to provide it with multiphase microwaves, thereby producing the traveling wave in the annular waveguide. This arrangement is supported by the following condition.

Now, we study a case that one microwave supply port A303and another microwave supply port B305are arranged in an annular waveguide301, as shown in FIG.15.

It is assumed that the phase standard resides in the supply port A303where the phase is equal to zero. If the phase at the supply port B305has a delay of [−θt], then it can be conversely said that the phase at the supply port A303precedes the phase at the supply port B305by [θt] on the ground of the phase standard at the supply port B305. It is further assumed that a phase change amounts to [θL] at the supply port A under condition that the microwave is propagated in a waveguide path307between the supply port A and the supply port B.

Then, a condition allowing the microwave to be propagated from the supply port A to the supply port B is as follows:
−θt+θL=360°×N(note: N is zero or natural number)
θt+θL=180°×(2M+1) (note: M is zero or natural number)

From the above equations, there are established the following equations:
2θL=360°×N+180°×(2M+1)
θL=180°×N+90°×(2M+1)

This condition constitutes an arithmetical progression of 90° in initial value and 180° in difference. It doesn't matter which of the above values is selected as to the interval between the supply ports on the annular waveguide.

Additionally, in order that a phase of microwave supplied from the supply port A agrees with a phase of microwave again returning the supply port A after being propagated in the annular waveguide, its circumferential length has to be a natural number of times as long as a wave length in the annular waveguide. Note, in this specification, the above circumferential length designates a length of a center line403of the section of an annular waveguide401, as shown in FIG.16.

In order to establish a wave motion in the form of a standing wave in the annular waveguide, there is required a condition where the microwave is propagated in both directions between the supply port A and the supply port B. That is as follows:
−θt+θL=360°×N(note: N is zero or natural number)
θt+θL=180°×(2M+1) (note: M is zero or natural number)
2θL=360°×K(note: K is a natural number)
θL=180°×K

Further, the circumferential length of the annular waveguide has to be a natural number of times as long as a wave length in the waveguide.

The apparatus of the present invention is applicable for etching, ashing, CVD, change in the characters of membrane, etc.

Note, although the antenna in the form of a circular loop is adopted in the above embodiments, without limitation to this configuration, the antenna may be shaped to be rectangular or polygonal. Additionally, without limitation to the semiconductor wafer, a substrate for flat-panel display, such as LCD, may be adopted as an object to be processed.

As mentioned above, according to the present invention, the plasma processing apparatus comprises the processing container in form of a cylinder with a bottom, the supporting unit disposed in the processing container to support an object to be processed, the dielectric window arranged in an opening of the processing container to close up the processing container in an air-tight manner, the dielectric window having a dielectric body allowing a high-frequency wave to permeate an interior of the processing container, the annular waveguide shaped in form of a ring to introduce the high-frequency wave into the processing container through the dielectric window and also fitted to the dielectric window so that a plane containing an annular waveguide path of the annular waveguide extends along the dielectric window, and the traveling-wave generator arranged in the annular waveguide to produce a traveling wave in form of an endless ring in the annular waveguide. Accordingly, it is possible to form a traveling wave rotating in the annular waveguide, whereby an uniform electromagnetic field can be emitted into the processing container. Thus, it is possible to produce an uniform plasma in the processing container, allowing of the application of uniform processing on the object to be processed.