JP2018006256A - Microwave plasma processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve microwave radiation efficiency.SOLUTION: There is provide a microwave plasma processing device comprising a chamber for housing a substrate and a microwave radiation member for radiating a microwave in the chamber, and subjecting the substrate to plasma processing by surface wave plasma. The microwave radiation member comprises: a body part of metal; a slow wave member composed of a dielectric for transmitting a microwave and formed on the side into which a microwave in the body part is introduced; a resonance mechanism composed of a dielectric having lower relative permittivity than the slow wave member and arranged in at least an outer peripheral part or an inner peripheral part of the slow wave member in the body part; and a plurality of slots formed so that a longitudinal direction matches a magnetic field direction of the microwave on a lower surface of the slow wave member and radiating the microwave which propagated the slow wave metal and the resonance mechanism.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a microwave plasma processing apparatus.

  Compared with a parallel plate type plasma processing apparatus, the microwave plasma processing apparatus can uniformly form a surface wave plasma having a high density and a low electron temperature. In the microwave plasma processing apparatus, the microwave is radiated from the ceiling portion of the chamber into the chamber through a plurality of microwave introduction mechanisms. Surface wave plasma is generated on the surface on the chamber side by the radiated microwave, and the substrate is subjected to plasma treatment by the surface wave plasma (see, for example, Patent Documents 1 and 2). In Patent Documents 1 and 2, a microwave transmission window made of a dielectric is provided for each microwave introduction mechanism at the ceiling of the chamber, and the microwave is radiated into the chamber through the microwave transmission window.

International Publication No. 2008/013112 Pamphlet JP 2012-216745 A

  However, in such a configuration, depending on the configuration and arrangement of the microwave introduction mechanism, there may be a problem that the plasma does not spread sufficiently in the circumferential direction and the plasma becomes non-uniform.

  In view of the above problem, in one aspect, the present invention aims to increase the radiation efficiency of microwaves.

  In order to solve the above-described problem, according to one aspect, the substrate includes a chamber that accommodates the substrate and a microwave radiating member that radiates microwaves in the chamber, and the substrate is subjected to plasma processing by surface wave plasma. In the microwave plasma processing apparatus, the microwave radiating member is formed on a metal main body, a side into which the microwave is introduced in the main body, and a dielectric slow wave material that transmits microwaves. Disposed in at least one of an outer peripheral portion and an inner peripheral portion of the slow wave material in the main body portion, and having a dielectric resonance mechanism having a relative dielectric constant lower than that of the slow wave material, and a lower surface of the slow wave material. There is provided a microwave plasma processing apparatus having a direction aligned with a magnetic field direction of microwaves and having a plurality of slots for radiating microwaves propagated through the slow wave material and the resonance mechanism.

  According to one aspect, microwave radiation efficiency can be increased.

The figure which shows an example of the longitudinal cross-section of the microwave plasma processing apparatus which concerns on one Embodiment. The figure which shows an example of a structure of the microwave plasma source which concerns on one Embodiment. The enlarged view which shows an example of the microwave radiation member which concerns on one Embodiment. AA sectional drawing of FIG. AA sectional view of FIG. 3 (modification). BB sectional drawing of FIG. The figure for demonstrating distribution of the microwave electric power by the slow wave material which concerns on one Embodiment. The figure for demonstrating the effect of the dielectric material layer which concerns on one Embodiment. The figure for demonstrating the wavelength of the microwave which permeate | transmits the dielectric material from which a dielectric constant differs. The figure for demonstrating the relationship between the resonance mechanism which concerns on one Embodiment, and the radiation efficiency of a microwave. The figure which shows an example of the radiation efficiency by the resonance mechanism which concerns on one Embodiment. The figure which shows an example of the longitudinal cross-section of the microwave plasma processing apparatus which concerns on the modification 1 of one Embodiment. The figure which shows an example of the longitudinal cross-section of the microwave plasma processing apparatus which concerns on the modification 2 of one Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the substantially same structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Overall configuration of microwave plasma processing equipment]
FIG. 1 shows an example of a cross-sectional view of a microwave plasma processing apparatus 100 according to an embodiment of the present invention. FIG. 2 is a block diagram showing an example of the configuration of the microwave plasma source 2 used in the microwave plasma processing apparatus 100 of FIG.

  The microwave plasma processing apparatus 100 performs a predetermined plasma process on a semiconductor wafer W (hereinafter referred to as “wafer W”), which is an example of a substrate, by forming surface wave plasma using microwaves. As an example of the plasma process, a film forming process or an etching process is exemplified.

  The microwave plasma processing apparatus 100 includes a chamber 1 that accommodates a wafer W. The chamber 1 is a substantially cylindrical container made of a metal material such as aluminum or stainless steel, which is hermetically configured, and is grounded. The microwave plasma source 2 is provided so as to face the inside of the chamber 1 from an opening 1 a formed in the upper portion of the chamber 1. When microwaves are introduced into the chamber 1 by the microwave plasma source 2, surface wave plasma is formed in the chamber 1.

  A mounting table 11 on which a wafer W is mounted is provided in the chamber 1. The mounting table 11 is supported by a cylindrical support member 12 erected at the center of the bottom of the chamber 1 via an insulating member 12a. Examples of the material constituting the mounting table 11 and the support member 12 include metals such as aluminum whose surfaces are anodized (anodized) and insulating members (ceramics and the like) having high-frequency electrodes therein. The mounting table 11 may be provided with an electrostatic chuck for electrostatically attracting the wafer W, a temperature control mechanism, a gas flow path for supplying a heat transfer gas to the back surface of the wafer W, and the like.

  A high frequency bias power source 14 is electrically connected to the mounting table 11 via a matching unit 13. By supplying high-frequency power from the high-frequency bias power supply 14 to the mounting table 11, ions in the plasma are attracted to the wafer W side. Note that the high-frequency bias power source 14 may not be provided depending on the characteristics of the plasma processing.

  An exhaust pipe 15 is connected to the bottom of the chamber 1, and an exhaust device 16 including a vacuum pump is connected to the exhaust pipe 15. When the exhaust device 16 is operated, the inside of the chamber 1 is exhausted, and thereby the inside of the chamber 1 is depressurized at a high speed to a predetermined vacuum level. On the side wall of the chamber 1, a loading / unloading port 17 for loading / unloading the wafer W and a gate valve 18 for opening / closing the loading / unloading port 17 are provided.

  The microwave plasma source 2 includes a microwave output unit 30, a microwave transmission unit 40, and a microwave radiation member 50. The microwave output unit 30 outputs the microwaves distributed to a plurality of paths.

  The microwave transmission unit 40 transmits the microwave output from the microwave output unit 30. The peripheral microwave introduction mechanism 43a and the central microwave introduction mechanism 43b have a function of introducing the microwave output from the amplifier unit 42 into the microwave radiation member 50 and a function of matching impedance.

  The peripheral microwave introduction mechanism 43a and the center microwave introduction mechanism 43b arrange a cylindrical outer conductor 52 and a rod-shaped inner conductor 53 provided at the center thereof coaxially. Microwave power is supplied to the space between the outer conductor 52 and the inner conductor 53, and the microwave transmission path 44 through which the microwave propagates toward the microwave radiating member 50 is formed.

  The peripheral microwave introduction mechanism 43a and the central microwave introduction mechanism 43b are provided with a slag 61 and an impedance adjustment member 140 located at the tip thereof. By moving the slag 61, the impedance of the load (plasma) in the chamber 1 is matched with the characteristic impedance of the microwave power source in the microwave output unit 30. The impedance adjusting member 140 is formed of a dielectric, and adjusts the impedance of the microwave transmission path 44 by its relative dielectric constant.

  The microwave radiating member 50 is provided in a state of being hermetically sealed to a support ring 29 provided at the upper portion of the chamber 1, and radiates the microwave transmitted from the microwave transmission unit 40 into the chamber 1. The microwave radiation member 50 constitutes the ceiling portion of the chamber 1.

The microwave radiation member 50 is provided with a first gas introduction part 21 having a shower structure, and a first gas supply source 22 is connected to the first gas introduction part 21 via a gas supply pipe 111. The first gas supplied from the first gas supply source 22 is supplied into the chamber 1 through the first gas introduction unit 21 in a shower shape. The first gas introduction part 21 is an example of a first gas shower head that supplies a first gas at a first height from a plurality of gas holes formed in the ceiling part of the chamber 1. Examples of the first gas include plasma generation gas such as Ar gas, and gas that is desired to be decomposed with high energy such as O ₂ gas and N ₂ gas.

  The microwave radiating member 50 includes a main body 120, a slow wave material 121, a microwave transmitting member 122, a slot 123, a dielectric layer 124, and a dielectric resonance mechanism 129. In the present embodiment, the inside of the resonance mechanism 129 is filled with air. However, the inside of the resonance mechanism 129 may be filled with Teflon (registered trademark).

  The thickness of the resonance mechanism 129 is thinner than the thickness of the slow wave material 121. The slow wave material 121 was fitted in the main body part 120 by forming a space lower in height than the space in which the slow wave material 121 is fitted in the outer periphery of the slow wave material 121 inside the main body part 120. Sometimes the positioning of the slow wave material 121 and the formation of the space of the resonance mechanism 129 can be performed. The detailed structure of the microwave radiating member 50 will be described later.

A second gas introduction part 23 configured as a shower plate is horizontally provided in the chamber 1 at a position between the mounting table 11 and the microwave radiation member 50 in the chamber 1. The second gas introduction part 23 has a gas flow path 24 formed in a lattice shape and a large number of gas holes 25 formed in the gas flow path 24. A space 26 is formed. A gas supply pipe 27 extending outside the chamber 1 is connected to the gas flow path 24, and a second gas supply source 28 is connected to the gas supply pipe 27. A second gas such as SiH ₄ gas or C ₅ F ₈ gas is supplied from the second gas supply source 28 to be supplied without being decomposed as much as possible during plasma processing such as film formation or etching. It comes to be supplied. The second gas introduction unit 23 is an example of a second gas shower head that supplies the second gas from a plurality of gas holes at a second height that is lower than the first height at which the first gas is supplied. The first gas introduction unit 21 and the second gas introduction unit 23 are an example of a gas supply mechanism that supplies gas from the gas shower head into the chamber 1. In addition, as gas supplied from the 1st gas supply source 22 and the 2nd gas supply source 28, various gas according to the content of the plasma processing can be used.

  Each part of the microwave plasma processing apparatus 100 is controlled by the control device 3. The control device 3 includes a microprocessor 4, a ROM (Read Only Memory) 5, a RAM (Random Access Memory) 6, and the like. The ROM 5 and the RAM 6 store a process recipe that is a process sequence and control parameters of the microwave plasma processing apparatus 100. The microprocessor 4 is an example of a control unit that controls each unit of the microwave plasma processing apparatus 100 based on a process sequence and a process recipe. The control device 3 includes a touch panel 7, a display 8, and the like, and can perform input and display of results when performing predetermined control according to a process sequence and a process recipe.

  When performing plasma processing in the microwave plasma processing apparatus 100 having such a configuration, first, the wafer W is loaded into the chamber 1 from the opened gate valve 18 through the loading / unloading port 17 while being held on the transfer arm. Is done. The gate valve 18 is closed after the wafer W is loaded. The wafer W is transferred from the transfer arm to the pusher pin, and is placed on the placement table 11 when the pusher pin is lowered. The pressure in the chamber 1 is maintained at a predetermined degree of vacuum by the exhaust device 16. The first gas is introduced into the chamber 1 from the first gas introduction part 21 in a shower form, and the second gas is introduced into the chamber 1 from the second gas introduction part 23 in a shower form. Surface waves generated on the surface on the chamber side by the decomposition of the first and second gases by the microwaves radiated from the microwave radiation member 50 through the peripheral microwave introduction mechanism 43a and the central microwave introduction mechanism 43b. Plasma processing is performed on the wafer W by plasma.

(Microwave plasma source)
The microwave plasma source 2 includes a microwave output unit 30, a microwave transmission unit 40, and a microwave radiation member 50. As shown in FIG. 2, the microwave output unit 30 includes a microwave power supply 31, a microwave oscillator 32, an amplifier 33 that amplifies the oscillated microwave, and a distributor that distributes the amplified microwave into a plurality of parts. 34.

  The microwave oscillator 32 oscillates a microwave having a predetermined frequency (for example, 860 MHz), for example, by PLL (Phase Locked Loop). The distributor 34 distributes the microwave amplified by the amplifier 33 while matching the impedance between the input side and the output side so that the loss of the microwave does not occur as much as possible. As the microwave frequency, various frequencies in the range of 700 MHz to 3 GHz such as 915 MHz can be used in addition to 860 MHz.

  As illustrated in FIG. 1, the microwave transmission unit 40 includes a plurality of amplifier units 42, and a peripheral microwave introduction mechanism 43 a and a central microwave introduction mechanism 43 b provided corresponding to the amplifier unit 42. A plurality of (for example, six) peripheral microwave introduction mechanisms 43 a are provided along the circumferential direction on the peripheral portion of the microwave radiation member 50, and the central microwave introduction mechanism 43 b is the center of the microwave radiation member 50. One is provided on the part. The number of peripheral microwave introduction mechanisms 43a may be two or more, but is preferably three or more, for example, 3-6.

  As shown in FIG. 2, the amplifier unit 42 guides the microwave distributed by the distributor 34 to the peripheral microwave introduction mechanism 43a and the central microwave introduction mechanism 43b. The amplifier unit 42 includes a phase shifter 46, a variable gain amplifier 47, a main amplifier 48 constituting a solid state amplifier, and an isolator 49.

  The phase shifter 46 can modulate the radiation characteristic by changing the phase of the microwave. For example, by adjusting the phase of the microwaves introduced into the peripheral microwave introduction mechanism 43a and the central microwave introduction mechanism 43b, the directivity can be controlled to change the plasma distribution. Further, circularly polarized waves can be obtained by shifting the phase by 90 ° between adjacent microwave introduction mechanisms. The phase shifter 46 can be used for the purpose of spatial synthesis in the tuner by adjusting the delay characteristics between components in the amplifier. However, the phase shifter 46 may not be provided when such modulation of radiation characteristics and adjustment of delay characteristics between components in the amplifier are unnecessary.

  The variable gain amplifier 47 adjusts the power level of the microwave input to the main amplifier 48 and adjusts the plasma intensity. By changing the variable gain amplifier 47 for each antenna module, a distribution can be generated in the generated plasma.

  The main amplifier 48 constituting the solid state amplifier includes, for example, an input matching circuit, a semiconductor amplifying element, an output matching circuit, and a high Q resonance circuit. The isolator 49 separates the reflected microwaves that are reflected by the slot antenna portion and travel toward the main amplifier 48, and includes a circulator and a dummy load (coaxial terminator). The circulator guides the reflected microwave to the dummy load, and the dummy load converts the reflected microwave guided by the circulator into heat. The peripheral microwave introduction mechanism 43 a and the central microwave introduction mechanism 43 b introduce the microwave output from the amplifier unit 42 into the microwave radiation member 50.

(Microwave radiation member)
Next, the microwave radiation member 50 will be described with reference to FIGS. 3 and 4. FIG. 3 shows an example of a cross section showing the main part of the microwave radiation member 50. FIG. 4 shows an AA cross section of FIG.

  The microwave radiating member 50 radiates the microwave output from the microwave output unit 30 and transmitted through the microwave transmission unit 40 into the chamber 1. The microwave radiating member 50 has a metal main body 120. The main body 120 is preferably formed from a metal having high thermal conductivity such as aluminum or copper.

  The main body 120 has a peripheral portion where the peripheral microwave introduction mechanism 43a is disposed and a central portion where the central microwave introduction mechanism 43b is disposed. The peripheral portion corresponds to the peripheral region of the wafer W, and the central portion corresponds to the central region of the wafer.

In the upper part of the peripheral part of the main body part 120 (the side where the microwave in the main part 120 is introduced), the slow wave material 121 is disposed along the peripheral microwave introduction mechanism arrangement region including the arrangement part of the peripheral microwave introduction mechanism 43a. It is inserted. The slow wave material 121 is formed of a dielectric material that transmits microwaves. The slow wave material 121 has a relative dielectric constant greater than that of vacuum, and is formed of, for example, ceramics such as quartz and alumina (Al ₂ O ₃ ), fluorine resin such as polytetrafluoroethylene, and polyimide resin. obtain. That is, since the wavelength of the microwave becomes longer in vacuum, the slow wave material 121 is made of a material having a relative dielectric constant larger than that of the vacuum, thereby shortening the wavelength of the microwave and including the slot 123. It has a function to reduce the size.

  A ring-shaped microwave transmitting member 122 provided along the peripheral microwave introduction mechanism arrangement region is fitted on the lower surface (surface on the chamber 1 side) of the peripheral portion of the main body 120. A plurality of slots 123 and a dielectric layer 124 are vertically formed in a portion of the main body 120 between the slow wave material 121 and the microwave transmitting member 122.

The microwave transmitting member 122 is made of a dielectric material that is a material that transmits microwaves. The microwave transmitting member 122 is exposed to the chamber 1 in a ring shape and forms a uniform surface wave plasma in the circumferential direction. As a function. The microwave transmitting member 122 can be formed of, for example, ceramics such as quartz and alumina (Al ₂ O ₃ ), fluorine resin such as polytetrafluoroethylene, and polyimide resin, similarly to the slow wave material 121. In addition, the microwave transmission member 122 may be divided | segmented into plurality along the circumferential direction.

  As shown in FIG. 3, the slot 123 extends from a position in contact with the lower surface of the slow wave member 121 of the main body 120 to the upper surface of the dielectric layer 124, and radiates microwaves transmitted from the peripheral microwave introduction mechanism 43a. Determine characteristics. A region between the slow wave member 121 and the dielectric layer 124 of the main body 120 is a slot antenna unit including a slot 123.

  A cylindrical member 82 is provided on the bottom plate at the tip of the microwave transmission path 44. The slot 123 has a function of mode-converting microwaves transmitted as TEM waves from the peripheral microwave introduction mechanism 43a through the cylindrical member 82 into TE waves. The microwave radiated from the slot 123 is radiated into the chamber 1 through the dielectric layer 124 and the microwave transmitting member 122 in a single mode of TE wave.

  Referring to FIG. 4 showing the AA cross section of FIG. 3, the plurality of slots 123 are separated by the isolation portion 120 a of the main body 120 and are equally arranged in an arc shape on the circumference of the same diameter. The radiation characteristics of the microwave are determined by the shape and arrangement of the slots 123. The plurality of arc-shaped slots 123 are thus provided so that the overall shape is a circular shape, thereby making the electric field uniform. Can be dispersed.

  In this embodiment, as shown in FIGS. 3 and 4, a dielectric resonance mechanism 129 having a dielectric constant lower than that of the slow wave material 121 is formed on the outer periphery of the slow wave material 121. In this embodiment, the radiation efficiency of the microwave radiated from the slot 123 is enhanced by the function of the resonance mechanism 129. The function of the resonance mechanism 129 will be described later.

  FIG. 4 shows an example in which twelve arc-shaped slots 123 are provided in a line on the circumference. However, the shape and number of the slots 123 are not limited to this, and the size of the microwave transmitting member 122 and the microwaves are not limited thereto. It is set appropriately according to the wavelength. For example, FIG. 5 shows another example of the AA cross section of FIG. FIG. 5 shows an example in which six arc-shaped slots 123 are provided in a line on the circumference.

  The slot 123 may be in a vacuum or may be filled with a Teflon (registered trademark) dielectric. By filling the slot 123 with a dielectric, the effective wavelength of the microwave is shortened and the thickness of the slot can be reduced.

  The length of one slot 123 in the circumferential direction (longitudinal direction) is preferably slot λg / 2 from the viewpoint of increasing the electric field strength and obtaining good efficiency. Here, λg is the effective wavelength of the microwave and can be expressed by the following equation (1).

ε_ｓはスロット１２３に充填される誘電体の比誘電率であり、λは真空中のマイクロ波の波長である。また、λｃはカットオフ波長であり、ＴＥ０１モードで給電する場合、空洞共振器の長手方向の長さをａとして、
λ_ｃ＝２ａ
と表される。

ε _s is the dielectric constant of the dielectric filled in the slot 123, and λ is the wavelength of the microwave in vacuum. In addition, λc is a cutoff wavelength, and when power is supplied in the TE01 mode, the length in the longitudinal direction of the cavity resonator is a,
λ _c = 2a
It is expressed.

  Considering the fine adjustment component δ (including 0) for fine adjustment so that the uniformity of the electric field strength in the circumferential direction is high, the circumferential length of the slot 123 is preferably (λg / 2) −δ. .

  In addition, although the slot 123 is provided in the center of the radial direction of the slow wave material 121 and the microwave transmission member 122, the peripheral microwave introduction mechanism 43a is provided inside the radial direction center. This is because the electric field is evenly distributed between the inner side and the outer side in consideration of the difference in length between the inner circumference and the outer circumference of the slow wave material 121.

  Referring to FIG. 6 showing the BB cross section of FIG. 4, the dielectric layers 124 are provided in a one-to-one correspondence below the slots 123. In the example of FIG. 4, twelve dielectric layers 124 are provided for each of twelve slots 123. Adjacent dielectric layers 124 are separated by a separating portion 120 a of the metal main body 120. A single loop magnetic field can be formed in the dielectric layer 124 by the microwave radiated from the corresponding slot 123, so that coupling of the magnetic field loop does not occur in the microwave transmission member 122 below the dielectric layer 124. It has become. Thereby, the appearance of a plurality of surface wave modes can be prevented, and a single surface wave mode can be realized. The circumferential length of the dielectric layer 124 is preferably λg / 2 or less from the viewpoint of preventing the appearance of a plurality of surface wave modes. Further, the thickness of the dielectric layer 124 is preferably 1 to 5 mm.

  The dielectric layer 124 may be air (vacuum), or may be a dielectric material such as dielectric ceramics or resin. Examples of the dielectric material include fluorine such as quartz, ceramics, and polytetrafluoroethylene. A resin or a polyimide resin can be used. When the microwave plasma processing apparatus 100 processes a 300 mm wafer and uses alumina having a relative dielectric constant of about 10 as a dielectric in the microwave wavelength 860 MHz, the slow wave material 121, the microwave transmitting member 122, and the slot 123, An air layer (vacuum layer) can be suitably used as the dielectric layer 124.

  Returning to FIG. 3, a slow wave member 131 having a disk shape is fitted into the central microwave introduction mechanism arrangement region corresponding to the central microwave introduction mechanism 43 b in the upper part of the central portion of the main body 120, and the slow wave member 131 is inserted. A microwave transmitting member 132 having a disk shape is fitted into a portion corresponding to the above. A portion of the main body 120 between the slow wave member 131 and the microwave transmitting member 132 is a slot antenna portion having a slot 133. The shape and size of the slot 133 are appropriately adjusted so as to suppress the occurrence of mode jump and to obtain a uniform electric field strength. For example, the slot 133 may be formed in a ring shape. As a result, there is no seam between slots, a uniform electric field can be formed, and mode jumps are less likely to occur.

  Like the slot 123, the slot 133 is preferably filled with a dielectric. As the dielectric filled in the slot 133, the same one as that used for the slot 123 can be used. In addition, as the dielectric constituting the slow wave material 131 and the microwave transmission member 132, the same material as the above-described slow wave material 121 and the microwave transmission member 122 can be used.

  On the upper surface of the main body 120, a ring-shaped groove 126 is formed between the peripheral microwave introduction mechanism arrangement region and the central microwave introduction mechanism arrangement region. Thereby, the microwave interference between the peripheral microwave introduction mechanism 43a and the center microwave introduction mechanism 43b can be suppressed.

  The main body 120 is provided with the first gas introduction part 21 described above. The first gas introduction part 21 forms an annular shape between the peripheral part having the peripheral microwave introduction mechanism arrangement area and the central part having the central microwave introduction mechanism arrangement area, and is formed concentrically with the outer gas diffusion space 141. And an inner gas diffusion space 142. A gas introduction hole 143 connected to the upper surface of the main body 120 is formed on the upper surface of the outer gas diffusion space 141, and a plurality of gas holes 144 reaching the lower surface of the main body 120 are formed on the lower surface of the outer gas diffusion space 141. Is formed. On the other hand, a gas introduction hole 145 connected to the upper surface of the main body 120 is formed on the upper surface of the inner gas diffusion space 142, and a plurality of gas holes reaching the lower surface of the main body 120 are formed on the lower surface of the inner gas diffusion space 142. 146 is formed. A gas supply pipe 111 for supplying the first gas from the first gas supply source 22 is connected to the gas introduction holes 143 and 145.

(Distribution of microwave power)
FIG. 7 shows the arrangement of the slots 123 at the peripheral edge of the microwave radiating member 50 and the distribution of the microwave power. As shown in FIG. 7, the peripheral microwave introduction mechanism 43 a is disposed so as to straddle between the two slow wave members 121. That is, in the example of FIG. 4, the twelve slow wave members 121 are arranged so as to extend on both sides from positions corresponding to the six peripheral microwave introduction mechanisms 43a. In the example of FIG. 5, the six slow wave members 121 are arranged so as to extend to both sides from positions corresponding to the three peripheral microwave introduction mechanisms 43a.

  As described above, since the isolation portion 120a of the main body 120 is disposed immediately below the peripheral microwave introduction mechanism 43a, the microwave power transmitted through the peripheral microwave introduction mechanism 43a is separated by the isolation portion 120a. And is equally distributed to the slow wave members 121 on both sides thereof. As a result, microwaves with equally distributed power are radiated from the slots 123.

  A microwave transmitted as a TEM wave from the peripheral microwave introduction mechanism 43 a is mode-converted into a TE wave in the slot 123, and is radiated into the chamber 1 through the dielectric layer 124 and the microwave transmitting member 122.

(Dielectric layer)
When the microwave transmitting member 122 is disposed immediately below the plurality of slots 123 provided on the arc, as shown in FIG. 8A, the magnetic field H generated by the microwaves radiated from each slot 123 is In some cases, the wave transmitting member 122 is coupled. A plurality of surface wave modes appear by coupling or not coupling of the magnetic field by the microwave transmitting member 122. When a plurality of surface wave modes appear, a mode jump may occur during plasma processing, the plasma is not stable, and hinders uniform plasma processing on the wafer W.

  The appearance probability of the surface wave mode is determined by the microwave transmitting member factor (shape, material) and the slot factor (shape, size), and a single mode can be realized by adjusting these factors. However, the microwave transmitting member is designed in advance, and it is difficult to change it. For this reason, it is effective to adjust the slot factor.

  Therefore, in the present embodiment, as shown in FIG. 8B, a plurality of dielectric layers 124 are provided below the plurality of slots 123 so as to correspond to the slots 123, respectively. Thus, a single loop magnetic field can be generated in each dielectric layer 124 by the microwaves radiated from each slot 123. As a result, a magnetic field loop corresponding to the magnetic field loop of the dielectric layer 124 is formed in the microwave transmitting member 122, and magnetic field coupling can be prevented from occurring in the microwave transmitting member 122 (decoupling). For this reason, it is possible to prevent a plurality of surface wave modes from appearing due to the occurrence or non-occurrence of a magnetic field loop in the microwave transmitting member 122, and to realize a stable plasma process that does not cause a mode jump. Can do.

  In this case, since a plurality of modes are likely to occur if there are a plurality of standing waves “Hara” or “Bushi” in the dielectric layer 124, the circumferential length of the dielectric layer 124 is λg / 2 or less. It is preferable. In addition, since the plurality of slots 123 are arranged circumferentially, microwaves can be emitted circumferentially, and the uniformity of plasma in the circumferential direction can be improved.

(Resonance mechanism)
Next, the resonance mechanism 129 will be described with reference to FIGS. 9 and 10. FIG. 9 is a diagram for explaining the wavelengths of microwaves that pass through dielectrics having different relative dielectric constants. FIG. 10 is a diagram for explaining the relationship between the resonance mechanism 129 and the microwave radiation efficiency according to an embodiment.

In the present embodiment, the slow wave material 121 is formed of alumina (Al ₂ O ₃ ), and the resonance mechanism 129 is an air layer. The resonance mechanism 129 may be filled with Teflon (registered trademark). The resonance mechanism 129 may be a dielectric having a relative dielectric constant lower than that of the dielectric forming the slow wave material 121.

  As shown in FIG. 9, when two dielectrics having different relative dielectric constants are adjacent to each other, the wavelength of the microwave propagating through the two dielectrics is expressed by the above formula (1).

In the present embodiment, ε _s indicates the relative dielectric constant of alumina (Al ₂ O ₃ ). In the present embodiment, the slow wave material 121 is made of alumina, and the effective wavelength λg of the microwave in the slow wave material 121 is shorter than the effective wavelength λ of the microwave in the resonance mechanism 129.

  FIG. 10A schematically shows an example of the magnetic field H formed by the microwave propagating through the slow wave material 121 when there is no air layer of the resonance mechanism 129 on the outer peripheral portion of the slow wave material 121. Since the magnetic field H is formed on the metal surface, the magnetic field H at both ends of the slow wave material 121 is the strongest, and the magnetic field H at the center of the slow wave material 121 is the weakest.

At that time, the longitudinal direction of the slot 123 formed in the vicinity of the center of the slow wave material 121 is formed in alignment with the direction of the magnetic field H, and microwaves can be emitted. However, since the intensity H ₁ of the magnetic field H at the center of the slow wave material 121 is weaker than the maximum value of the intensity of the magnetic field H, the radiation efficiency of the microwave radiated from the slot 123 is lower than the maximum value. ing.

  On the other hand, if the slot 123 is formed at the end of the slow wave material 121, the microwave radiation efficiency can be increased. However, in this case, a plurality of surface wave modes are generated, and a single surface wave mode cannot be obtained.

On the other hand, FIG. 10B schematically shows an example of the magnetic field H formed by the microwave when the air layer of the resonance mechanism 129 exists on the outer peripheral portion of the slow wave material 121. Since the resonance mechanism 129 exists, the intensity H ₂ (> H ₁ ) of the magnetic field H at the position of the slot 123 is high. That is, by forming the resonance mechanism 129 on the outer periphery of the slow wave material 121, the radiation efficiency of microwaves radiated from the slot 123 formed near the center of the slow wave material 121 can be increased.

  The resonance mechanism 129 in the present embodiment uses a dielectric having a relative dielectric constant lower than that of the slow wave material 121. On the other hand, it is conceivable to simply spread the slow wave material 121 to the position of the resonance mechanism 129. However, if the slow wave material 121 is simply widened in this way, the width of the slow wave material 121 becomes wide and a plurality of surface wave modes may occur. For this reason, the resonance mechanism 129 needs to dispose a dielectric having a relative dielectric constant different from that of the slow wave material 121.

  Further, when the resonance mechanism 129 is formed of a dielectric having a relative dielectric constant higher than that of the slow wave material 121, the effective microwave wavelength λ in the resonance mechanism 129 is equal to the effective microwave wavelength λg in the slow wave material 121. Shorter than. In this case, a new surface wave mode may occur in the resonance mechanism 129, and it may be difficult to control to a single surface wave mode. Therefore, in the present embodiment, a dielectric having a relative dielectric constant lower than that of the slow wave plate 121 is disposed in the resonance mechanism 129. As a result, the surface wave mode can be unified and the microwave radiation efficiency can be increased.

  Further, when the effective wavelength λ of the microwave in the resonance mechanism 129 is shorter than the effective wavelength λg of the microwave in the slow wave material 121, an error in the width of the resonance mechanism 129 that may occur in machining when the slow wave plate 121 is assembled. On the other hand, since the effective wavelength λ of the microwave is short, a large error occurs in the propagation path of the microwave. As a result, the accuracy for improving the radiation efficiency in the slot 123 may not be obtained due to a dimensional error of the resonance mechanism 129 that may occur in machining.

  Therefore, in this embodiment, the resonance mechanism 129 is formed of a dielectric having a relative dielectric constant lower than that of the slow wave material 121. Thereby, the effective wavelength λ of the microwave in the resonance mechanism 129 is longer than the effective wavelength λg of the microwave in the slow wave material 121. As a result, in the present embodiment, the radiation efficiency in the slot 123 can be improved even when a dimensional error of, for example, about 1 mm occurs in the resonance mechanism 129 due to machining.

(Radiation efficiency)
The microwave radiation efficiency by the resonance mechanism 129 according to the present embodiment will be described with reference to FIG. FIG. 11A shows an example of the strength of the magnetic field of the microwave radiated from the slot 123 when the resonance mechanism 129 according to the present embodiment is formed on the outer peripheral portion of the slow wave material 121. FIG. 11B shows an example of the strength of the magnetic field of the microwave radiated from the slot 123 when the resonance mechanism 129 according to the present embodiment is not formed on the outer peripheral portion of the slow wave material 121.

  According to this result, when the resonance mechanism 129 is formed on the outer peripheral portion of the slow wave material 121, the magnetic field in the slot 123 portion is larger than when the resonance mechanism 129 is not formed on the outer peripheral portion of the slow wave material 121. You can see that it is getting stronger. Thereby, according to the resonance mechanism 129 which concerns on this embodiment, it was proved that the radiation efficiency of a microwave can be improved.

<Operation of plasma processing apparatus>
Next, the operation in the microwave plasma processing apparatus 100 configured as described above will be described.

  First, the wafer W is loaded into the chamber 1 and placed on the mounting table 11. Then, a plasma generation gas such as Ar gas or a gas to be decomposed with high energy is supplied as the first gas from the first gas supply source 22. The first gas is introduced into the chamber 1 from the first gas introduction part 21 of the microwave radiating member 50.

  The microwaves transmitted from the microwave output unit 30 through the plurality of amplifier units 42 and the plurality of microwave introduction mechanisms 43 a and 43 b of the microwave transmission unit 40 are radiated into the chamber 1 through the microwave radiation member 50. . The first gas is turned into plasma by the high electric field energy of the microwave radiated to the surface of the ceiling, and surface wave plasma is generated.

  A processing gas to be supplied from the second gas supply source 28 without being decomposed as much as possible is supplied as the second gas. The second gas is introduced into the chamber 1 via the second gas introduction part 23. The second gas introduced from the second gas introduction unit is excited by the plasma of the first gas. At this time, since the second gas introduction position is a position with lower energy away from the surface of the microwave radiation member 50, the second gas is excited in a state where unnecessary decomposition is suppressed. Then, plasma processing, for example, film formation processing or etching processing is performed on the wafer W by the plasma of the first gas and the second gas.

  At this time, the six peripheral microwave introduction mechanisms 43 a are oscillated from the microwave oscillator 32 of the microwave output unit 30, amplified by the amplifier 33, and then distributed into a plurality by the distributor 34. The microwave power passed is fed. The microwave power fed to the peripheral microwave introduction mechanism 43 a is transmitted through the microwave transmission path 44 and introduced into the peripheral portion of the microwave radiation member 50. At that time, the impedance is automatically matched by the slag 61, and the microwave is introduced with substantially no power reflection. The introduced microwave passes through the slow wave material 121 and is radiated into the chamber 1 through the slot 123 of the slot antenna unit and the microwave transmitting member 122, and on the lower surfaces of the microwave transmitting member 122 and the main body 120. A surface wave is formed in the corresponding portion, and surface wave plasma is generated in the portion immediately below the microwave radiating member 50 in the chamber 1 by this surface wave.

  At this time, the 12 arc-shaped slow wave members 121 are arranged so as to form a ring shape along the peripheral microwave introduction mechanism arrangement region. The twelve slow wave members 121 are separated by an isolation portion 120a that forms a part of the main body 120, and the peripheral microwave introduction mechanism 43a is disposed so as to straddle between the two slow wave members 121. Has been. That is, the twelve slow wave members 121 are arranged so as to extend to both sides from positions corresponding to the six peripheral microwave introduction mechanisms 43a. As described above, the isolation portion 120a of the main body 120 is disposed immediately below the peripheral microwave introduction mechanism 43a. For this reason, the microwave transmitted through the peripheral microwave introduction mechanism 43a is separated by the isolation portion 120a, and the electric field strength of the portion directly below the peripheral microwave introduction mechanism 43a where the microwave electric field is normally increased does not increase. It is equally distributed to the slow wave material 121 on both sides.

  Furthermore, by forming the resonance mechanism 129 on the outer peripheral portion of the slow wave material 121, the radiation efficiency of microwaves radiated from the slot 123 formed near the center of the slow wave material 121 can be increased.

  And a microwave is radiated | emitted from the slot 123 provided so that the whole shape might make a circumferential shape along the periphery microwave introduction | transduction mechanism arrangement | positioning area | region. Since the microwave transmitting member 122 is provided in a ring shape on the lower surface of the slot 123, the microwave power uniformly distributed by the slow wave material 121 is radiated uniformly in the slot 123, and further, the microwave transmitting member 122 Can be expanded in a circumferential shape. For this reason, a uniform microwave electric field can be formed directly below the microwave transmitting member 122 along the peripheral microwave introduction mechanism arrangement region, and a uniform surface wave plasma can be formed in the circumferential direction in the chamber 1. .

  Since the microwave power can be expanded in the circumferential direction in this way, the number of peripheral microwave introduction mechanisms 43a can be reduced from six to three, and the apparatus cost can be reduced.

  In addition, the number of surface wave modes can be reduced by adjusting the number, shape, and arrangement of the slots 123 arranged in the circumference, and the mode can be reduced by optimizing the number, shape, and arrangement of slots. The number can be two or even one. By reducing the number of surface wave modes in this way, stable plasma processing with few mode jumps can be performed. In addition, by adjusting the number, shape, arrangement, and the like of the slots 123 in this way, the interference of microwaves that penetrates microwaves from one peripheral microwave introduction mechanism 43a to another peripheral microwave introduction mechanism 43a is also suppressed. be able to.

  Furthermore, a ring-shaped groove 126 is formed on the upper surface of the main body 120 between the peripheral microwave introduction mechanism arrangement region and the central microwave introduction mechanism arrangement region. Thereby, the microwave interference and mode jump between the peripheral microwave introduction mechanism 43a and the center microwave introduction mechanism 43b can be suppressed.

  Further, a microwave is introduced from the central microwave introduction mechanism 43 b into the central portion of the microwave radiating member 50. The microwave introduced from the central microwave introduction mechanism 43b passes through the slow wave member 131 and is radiated into the chamber 1 through the slot 133 of the slot antenna part and the microwave transmitting member 132, and the central part in the chamber 1 is radiated. In addition, surface wave plasma is generated. For this reason, uniform plasma can be formed over the entire wafer arrangement region in the chamber 1.

  Further, the first gas introduction part 21 is provided in the microwave radiating member 50, and the first gas is supplied from the first gas supply source 22 to the upper surface region of the chamber 1 where the microwave is radiated. Thereby, the first gas can be excited with high energy, and the gas can be decomposed to form surface wave plasma. Further, by providing the second gas introduction part 23 at a position lower than the first gas introduction part 21 and supplying the second gas, the second gas is in a state in which unnecessary decomposition is suppressed by lower energy. It can be turned into plasma. Thereby, a preferable plasma state can be formed according to the required plasma treatment.

(Microwave plasma processing apparatus according to Modification 1)
Next, a microwave plasma processing apparatus 100 according to Modification 1 of the embodiment to which the resonance mechanism 129 described above is applied will be described with reference to FIG. FIG. 12 shows an example of a longitudinal section of the microwave plasma processing apparatus 100 according to the first modification of the present embodiment. The microwave plasma processing apparatus 100 according to the first modification differs from the microwave plasma processing apparatus 100 shown in FIG. 1 only in the mechanism of the second gas introduction unit 23. Therefore, only the mechanism of the second gas introduction unit 23 according to Modification 1 will be described here.

  In the present modification, the microwave radiating member 50 is provided with a second gas introduction portion 23 having a ring-shaped shower structure. In the second gas introduction part 23, a plurality of nozzles 23a extending downward from the ceiling part are evenly arranged. A second gas supply source 28 is connected to the second gas introduction part 23 via a gas supply pipe 112.

A second gas such as SiH ₄ gas or C ₅ F ₈ gas is supplied from the second gas supply source 28 to be supplied without being decomposed as much as possible during plasma processing such as film formation or etching. It comes to be supplied. The second gas passes through the nozzle 23 a extending from the ring-shaped shower structure toward the wafer W via the gas supply pipe 112 and is supplied to a position lower than the ceiling portion of the chamber 1. The second gas introduction unit 23 according to the modified example includes a second gas shower head that supplies the second gas from the plurality of gas holes at a second height that is lower than the first height that supplies the first gas. It is an example.

  Also in the modified example 1, by supplying the second gas to a position lower than the first gas introduction unit 21, the second gas can be turned into plasma in a state where unnecessary decomposition is suppressed by lower energy. it can. Thereby, a preferable plasma state can be formed according to the required plasma treatment.

(Microwave plasma processing apparatus according to Modification 2)
Next, a microwave plasma processing apparatus 100 according to Modification 2 of the embodiment will be described with reference to FIG. FIG. 13 shows an example of a longitudinal section of a microwave plasma processing apparatus 100 according to the second modification of the present embodiment.

  In the microwave plasma processing apparatus 100 according to the second modification, the central microwave introduction mechanism 43b is not provided, but the annular microwave radiation member 50 including the arrangement region of the peripheral microwave introduction mechanism 43a is provided. An electrically conductive shower head 150 having a size substantially the same as that of the wafer W is provided via an insulating member 151 at the inner central portion.

  The shower head 150 has a gas diffusion space 152 formed in a disc shape, a number of gas holes 153 formed so as to face the chamber 1 from the gas diffusion space 152, and a gas introduction hole 154. . A gas supply source 157 is connected to the gas introduction hole 154 via a gas supply pipe 158. A high frequency power source 156 for generating plasma is electrically connected to the shower head 150 via a matching unit 155. The mounting table 11 has a conductive portion and functions as a counter electrode of the shower head 150. A gas necessary for plasma processing is supplied from the gas supply source 157 into the chamber 1 through the gas supply pipe 158 and the shower head 150. By supplying high frequency power from the high frequency power source 156 to the shower head 150, a high frequency electric field is formed between the shower head 150 and the mounting table 11, and capacitively coupled plasma is formed in a space immediately above the wafer W.

  In the microwave plasma processing apparatus 100 having such a configuration, the configuration of the central portion is the same as that of a parallel plate type plasma etching apparatus that performs plasma etching on the wafer W. Therefore, for example, it can be used as a plasma etching apparatus that adjusts the plasma density at the periphery of the wafer with surface wave plasma using microwaves. It is also possible not to provide a mechanism for generating plasma at the center.

  As described above, according to the microwave plasma processing apparatus 100 according to the present embodiment and the first and second modifications, the resonance mechanism 129 is formed on the outer peripheral portion of the slow wave material 121. Thereby, it is possible to increase the radiation efficiency of the microwave while generating a single surface wave mode, and to generate uniform plasma. The resonance mechanism 129 is not limited to being formed on the outer peripheral portion of the slow wave material 121. The resonance mechanism 129 may be formed on at least one of the outer peripheral portion and the inner peripheral portion of the slow wave material 121.

  As described above, the microwave plasma processing apparatus has been described in the above embodiment. However, the microwave plasma processing apparatus according to the present invention is not limited to the above embodiment and the first and second modifications, and may be variously within the scope of the present invention. Modifications and improvements are possible. The matters described in the embodiment and the first and second modifications can be combined within a consistent range.

  For example, in the above embodiment and the first and second modifications, the configuration of the microwave output unit 30 and the microwave transmission unit 40 is not limited to the above embodiment, for example, the microwave radiated from the slot antenna unit. A phase shifter is not required when there is no need to perform wave directivity control or circular polarization.

  Further, in the above-described embodiment, an example in which a plurality of microwave introduction mechanisms are used when the microwave plasma source 2 is introduced into the microwave radiation member 50 has been described. However, in the present invention, it is only necessary to obtain a single surface wave mode when a surface wave plasma is generated by emitting microwaves from a plurality of circumferentially arranged slots, and there is only one microwave introduction mechanism. There may be, and the mode of microwave introduction is not limited. It is also possible not to provide a mechanism for generating plasma at the center.

  In the above-described embodiment, the film forming apparatus and the etching apparatus are exemplified as the plasma processing apparatus. Can also be used.

  The substrate is not limited to the wafer W, and may be another substrate such as an FPD (flat panel display) substrate typified by an LCD (liquid crystal display) substrate or a ceramic substrate.

DESCRIPTION OF SYMBOLS 1 Chamber 2 Microwave plasma source 3 Control apparatus 11 Mounting stand 21 1st gas introduction part 22 1st gas supply source 23 2nd gas introduction part 28 2nd gas supply source 30 Microwave output part 40 Microwave transmission part 43a Perimeter micro Wave introduction mechanism 43b Central microwave introduction mechanism 44 Microwave transmission path 50 Microwave radiation member 52 Outer conductor 53 Inner conductor 61 Slag 100 Microwave plasma processing apparatus 120 Main body 121 Slow wave material 122 Microwave transmission member 123 Slot 124 Dielectric Layer 129 Resonance mechanism 140 Impedance adjusting member

Claims (5)

A microwave plasma processing apparatus having a chamber for accommodating a substrate and a microwave radiating member for radiating microwaves in the chamber, and performing plasma processing on the substrate by surface wave plasma,
The microwave radiating member is
A metal body,
A dielectric slow wave material that is formed on the side of the main body where microwaves are introduced, and that transmits microwaves;
A dielectric resonance mechanism disposed in at least one of an outer peripheral portion and an inner peripheral portion of the slow wave material in the main body, and having a relative dielectric constant lower than that of the slow wave material;
A plurality of slots that radiate microwaves propagated through the slow wave material and the resonance mechanism, the longitudinal direction being aligned with the magnetic field direction of the microwave on the lower surface of the slow wave material,
A microwave plasma processing apparatus. The inside of the resonance mechanism is filled with air or Teflon (registered trademark).
The microwave plasma processing apparatus according to claim 1. The resonance mechanism is provided on an outer periphery of the slow wave material,
The microwave plasma processing apparatus according to claim 1 or 2. The thickness of the resonance mechanism is thinner than the thickness of the slow wave material,
The microwave plasma processing apparatus as described in any one of Claims 1-3. A gas supply mechanism for supplying gas into the chamber from a gas shower head;
The gas shower head is
A first gas shower head for supplying a first gas at a first height from a plurality of gas holes formed in the microwave radiation member;
A second gas shower head having a plurality of nozzles and supplying a second gas from the plurality of nozzles at a second height lower than a first height for supplying the first gas.
The microwave plasma processing apparatus as described in any one of Claims 1-4.

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