JPWO2010140526A1 - Plasma processing apparatus and power supply method for plasma processing apparatus - Google Patents

Abstract

A plasma processing apparatus that does not require a large-area dielectric to propagate a surface wave of a microwave is provided. A microwave plasma processing apparatus includes a microwave source that outputs a microwave, a rectangular waveguide that transmits the microwave output from the microwave source, and a microwave that is supplied via the rectangular waveguide. Gas is excited by the generated microwave energy to generate plasma, and the processing container 10 that performs plasma processing on the object to be processed in the decompressed processing chamber, and the metal slot antenna 32 in which a plurality of slots 32a are formed. And a dielectric member that is provided between the microwave source 40 and the processing container 10 and transmits microwaves, and propagates the microwave along the metal surface of the slot antenna 32 that forms the inner wall of the processing container 10. . Accordingly, a gas is excited by microwave energy to generate plasma, and the substrate G is subjected to plasma processing in the processing chamber. [Selection] Figure 1

Description

  The present invention relates to power supply of a plasma processing apparatus that excites a gas to plasma-treat a workpiece.

  Plasma generated by the energy supplied through the dielectric window includes electron cyclotron resonance plasma (ECP), helicon wave excitation plasma (HWP), and inductively coupled plasma (ICP: Inductive Plasma). Coupled Plasma), microwave excited surface wave plasma (SWP: Surface Wave Plasma), and the like. Among these, the microwave plasma processing apparatus has advantages such as no need for a magnetic field and easy generation of high-density plasma having a cutoff density (critical density of surface wave excitation) or higher.

  For example, Patent Document 1 discloses an RLSA (Radial Line Slot Antenna) apparatus which is one of microwave plasma processing apparatuses. In the RLSA apparatus, a disk-shaped dielectric window is provided on the ceiling surface of the processing chamber. The microwaves are passed through a number of slots (openings), are transmitted through a dielectric window, and are introduced into the processing chamber. When the electron density of plasma generated in the processing chamber exceeds the cut-off density, surface waves can be propagated in the radial direction and the azimuth direction along the boundary surface between the dielectric window and the plasma. While the surface wave propagates, a part of the surface wave is absorbed by the plasma as an evanescent wave. The electric field energy of the evanescent wave is used for plasma generation and maintenance. Hereinafter, the surface wave propagating along the boundary surface between the dielectric window and the plasma is also referred to as a dielectric surface wave (Dielectric Surface Wave).

  In Patent Document 1, the processing chamber is sealed from the outside air space by a large-area dielectric installed on the ceiling of the processing chamber to keep the processing chamber airtight.

JP 2008-13816 A

  However, the dielectric window has a large area and is not only difficult to manufacture but also expensive. Further, heating and cooling are repeated for each process, and each time the dielectric is stressed, there is a possibility that the dielectric breaks. Furthermore, the dielectric is sputtered mainly by ions in the plasma, and the dielectric pieces generated thereby cause vacuum contamination in the processing chamber, which may cause contamination.

  In contrast, if a metal antenna is installed on the ceiling, the sheath layer on the metal surface functions as a dielectric layer, and the surface wave propagates along the boundary surface between the sheath and the plasma, the ceiling Even if a large-area dielectric is not installed, the electric field energy of the microwave can be absorbed by the plasma.

  In order to solve the above problems, the present invention provides a plasma processing apparatus that does not require a large-area dielectric to propagate a microwave surface wave, and a power supply method using the plasma processing apparatus.

  That is, in order to solve the above problems, according to an aspect of the present invention, an electromagnetic wave source that outputs an electromagnetic wave, a waveguide that transmits the electromagnetic wave output from the electromagnetic wave source, and the waveguide A gas is excited by the energy of the supplied electromagnetic wave to generate plasma, and a processing container for performing plasma processing on the object to be processed in a decompressed processing chamber; a metal slot antenna having a plurality of slots; A plasma processing apparatus that is provided between an electromagnetic wave source and the processing container, and that propagates the electromagnetic wave along a metal surface of the slot antenna that forms an inner wall of the processing container. Is provided.

  According to this configuration, the dielectric member is provided between the electromagnetic wave source and the processing container. Thereby, the atmosphere side where the electromagnetic wave source is arrange | positioned and the pressure reduction side in a processing container can be interrupted | blocked. Further, the electromagnetic wave is transmitted through the waveguide while passing through the dielectric member and supplied to the processing chamber, and propagates as a surface wave on the boundary surface between the metal surface of the slot antenna forming the inner wall of the processing chamber and the plasma. . During propagation, part of the surface wave is absorbed by the plasma as an evanescent wave, and the electric field energy can be used to generate and maintain the plasma.

  According to this, it is not necessary to provide a large-area dielectric window facing the object to be processed on the ceiling surface of the processing chamber. Therefore, since there is no large-area dielectric above the object to be processed, it is possible to prevent the dielectric window from being sputtered and causing vacuum contamination in the processing chamber. Thereby, the problem of contamination can be avoided. Further, heating and cooling are repeated for each process, and the risk that the dielectric is stressed each time and the dielectric window is cracked can be avoided. Furthermore, the cost can be reduced by eliminating the need for an expensive large-area dielectric window. Further, by using the waveguide for electromagnetic wave transmission, the apparatus can be downsized and the cost can be reduced as compared with the case where the coaxial tube is used for electromagnetic wave transmission. Hereinafter, the surface wave propagating along the boundary surface between the metal surface of the slot antenna and the plasma is also referred to as a metal surface wave.

  The slot antenna may be provided adjacent to the waveguide, and the dielectric member may include a plurality of in-slot dielectric members that block the interior of the plurality of slots.

  One end of the in-slot dielectric member may protrude from the metal surface of the slot antenna toward the processing chamber.

  The protruding portion of at least one of the in-slot dielectric members may be chamfered.

  The protruding portion of the in-slot dielectric member has at least a portion whose outer surface is chamfered with respect to the center of the slot group and a portion whose inner surface is chamfered with respect to the center of the slot group. May be.

  The area ratio between the portion where the outer surface is chamfered with respect to the center of the slot group and the portion where the inner surface is chamfered with respect to the center of the slot group is such that the area ratio is transmitted through the dielectric member in each slot. You may form so that it may become a ratio according to the distribution ratio of the electromagnetic wave energy at the time of propagating on the metal surface of the slot antenna.

  The area of the portion where the outer surface is chamfered with respect to the center of the slot group may be larger than the area of the portion where the inner surface is chamfered with respect to the center of the slot group.

  The protruding portion of the in-slot dielectric member may be provided with an inclination.

  The dielectric member may include a dielectric window that closes at least a part of the waveguide.

  The dielectric window and the waveguide may maintain hermeticity in the processing chamber by cast-in.

  The in-slot dielectric member and the slot antenna may maintain the airtightness in the processing chamber by casting.

  The in-slot dielectric member and the slot antenna may maintain airtightness in the processing chamber by providing a sealing material between the in-slot dielectric member and the slot antenna.

  In order to solve the above problems, according to another aspect of the present invention, a step of outputting an electromagnetic wave from an electromagnetic wave source, a process of transmitting the output electromagnetic wave into a waveguide, and performing a plasma treatment with the electromagnetic wave source Transmitting electromagnetic waves to a dielectric member provided between the container, propagating the transmitted electromagnetic waves along a metal surface of the slot antenna forming an inner wall of a processing chamber of the processing container, and A plasma is generated by exciting a gas by energy of an electromagnetic wave propagated along a metal surface of a slot antenna to generate a plasma, and subjecting the object to be processed to plasma processing in the decompressed processing chamber, A method is provided.

  As described above, according to the present invention, the metal surface of the slot antenna that forms the inner wall of the processing chamber and the plasma can be formed by transmitting microwaves to the dielectric member in the slot without requiring a large-area dielectric window. Surface waves can be propagated to the boundary surface.

It is a longitudinal cross-sectional view (2-2 cross section of FIG. 2) of the plasma processing apparatus which concerns on 1st Embodiment of this invention. It is the figure which showed the ceiling surface (1-1 cross section of FIG. 1) of the plasma processing apparatus which concerns on the same embodiment. It is a figure (3-3 cross section of FIG. 2) for demonstrating the propagation of the microwave of the plasma processing apparatus which concerns on the same embodiment. It is a figure for demonstrating propagation of the microwave of the conventional plasma processing apparatus. The C surface formed in the dielectric material which concerns on the same embodiment is shown. It is the simulation result which showed the relationship between the width | variety of C surface, and electric power reflection. It is the figure which showed typically the relationship between the ratio of the width | variety of the outer side and inner C surface, and the distribution ratio of the energy of a microwave. It is the figure which showed typically the relationship between the ratio of the width | variety of the outer side and inner C surface, and the distribution ratio of the energy of a microwave. It is another example of C surface formed in the dielectric material member. It is another example of C surface formed in the dielectric material member. It is a schematic diagram of the longitudinal cross-section of the plasma processing apparatus which concerns on 2nd Embodiment of this invention. It is a schematic diagram of the longitudinal cross-section of the plasma processing apparatus which concerns on 3rd Embodiment of this invention. It is a schematic diagram of the longitudinal cross-section of the plasma processing apparatus which concerns on 4th Embodiment of this invention. It is the simulation result which showed the relationship between the width | variety of C surface, and radiation distance ratio. It is a figure for demonstrating the modification of a slot group. It is a figure for demonstrating the modification of a slot group. It is a figure for demonstrating the modification of a slot group.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the element which has substantially the same structure, the duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<First Embodiment>
First, a microwave plasma processing apparatus according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view (cross section 2-2 in FIG. 2) of a microwave plasma processing apparatus according to the present embodiment, and FIG. 2 is a view showing a ceiling surface of the microwave plasma processing apparatus (in FIG. 1). 1-1 cross-section). The microwave plasma processing apparatus 100 is an apparatus that generates plasma by exciting a desired gas with microwave energy, and performs plasma processing on a substrate in a processing chamber. The plasma processing includes all processing for processing the substrate G by the action of plasma, such as film formation processing and etching processing.

(Configuration of microwave plasma processing equipment)
The microwave plasma processing apparatus 100 includes a processing container 10 and a lid 20. The processing container 10 has a bottomed cubic shape whose upper part is opened. The processing chamber U is defined by the processing container 10 and the lid 20, and the airtightness of the processing chamber U is maintained by an O-ring 21 provided on the contact surface. The processing container 10 and the lid 20 are made of a metal such as aluminum, for example, and are electrically grounded.

  A susceptor 11 (mounting table) is provided at the center of the processing container 10, and a substrate G is placed on the susceptor 11. The susceptor 11 is made of, for example, aluminum nitride, and a power feeding unit 11a and a heater 11b are provided therein.

  A high frequency power source 12b is connected to the power supply unit 11a via a matching unit 12a (for example, a capacitor). In addition, a high-voltage DC power supply 13b is connected to the power supply unit 11a via a coil 13a. The matching unit 12a, the high-frequency power source 12b, the coil 13a, and the high-voltage DC power source 13b are provided outside the processing container 10. The high frequency power supply 12b and the high voltage DC power supply 13b are grounded.

  The power feeding unit 11a applies a predetermined bias voltage to the inside of the processing container 10 by the high frequency power output from the high frequency power source 12b. The power feeding unit 11a is configured to electrostatically attract the substrate G with a DC voltage output from the high-voltage DC power supply 13b. An AC power supply 14 provided outside the processing container 10 is connected to the heater 11b, and the substrate G is held at a predetermined temperature by an AC voltage output from the AC power supply 14.

  The bottom surface of the processing container 10 is opened in a cylindrical shape, and one end of a bellows 15 is attached to the outer peripheral edge thereof. The other end of the bellows 15 is fixed to the elevating plate 16. In this way, the opening at the bottom of the processing container 10 is sealed by the bellows 15 and the lifting plate 16.

  The susceptor 11 is supported by a cylinder 17 disposed on the elevating plate 16 and moves up and down integrally with the elevating plate 16 and the cylinder 17, thereby raising the susceptor 11 to a height corresponding to the processing process. It comes to adjust. A baffle plate 18 for controlling the gas flow in the processing chamber U to a preferable state is provided around the susceptor 11.

  A vacuum pump (not shown) provided outside the processing container 10 is provided at the bottom of the processing container 10. The vacuum pump discharges the gas in the processing container 10 through the gas discharge pipe 19 to reduce the pressure in the processing chamber U to a desired degree of vacuum.

  The lid 20 is provided with a rectangular rectangular waveguide 31 and a slot antenna 32. As shown in FIG. 2 on the apparatus ceiling surface, which is a cross section 1-1 in FIG. 1, six rectangular waveguides 31 are arranged in parallel inside the lid body 20. The rectangular waveguide 31 is one of transmission lines (waveguides) for transmitting microwaves output from the microwave source 40.

Returning to FIG. 1, the inside of the rectangular waveguide 31 is filled with a dielectric member 33 such as fluororesin (for example, Teflon (registered trademark)), alumina (Al ₂ O ₃ ), quartz, or the like. The dielectric member 33 controls the in-tube wavelength λg ₁ of the microwave that is transmitted through each rectangular waveguide 31 according to the formula λg ₁ = λc / (ε ₁ ) ^1/2 . Here, λc is the wavelength of free space, and ε ₁ is the dielectric constant of the dielectric member 33.

  Each rectangular waveguide 31 is opened at the top, and a movable portion 34 is inserted in the opening so as to be movable up and down. The movable portion 34 is made of a conductive material that is a non-magnetic material such as aluminum. An elevating mechanism 35 is provided outside the lid body 20 and on the upper surface of each movable portion 34 to move the movable portion 34 up and down. With this configuration, the height of the rectangular waveguide 31 can be changed by moving the movable portion 34 up and down up to the upper surface of the dielectric member 33.

  The slot antenna 32 is configured integrally with the lid 20 at the lower part of the rectangular waveguide 31. Slot antenna 32 The slot antenna 32 is made of a metal that is a non-magnetic material such as aluminum. The slot antenna 32 is provided with a slot group 32ag shown in FIG. 2 on the lower surface of each rectangular waveguide 31. The slot group 32ag is formed on the long-side surface (H surface) of the rectangular waveguide 31.

Each slot group 32ag is formed of four slots (openings) of slots 32a1 to 32a4 (hereinafter also referred to as slots 32a), and are arranged at equal intervals at a pitch of the guide wavelength λg _1/2 . The slots 32a1 to 32a4 are all equal in distance between adjacent slots facing the center of the slot group 32ag. The four slots 32a1 to 32a4 included in one slot group 32ag are arranged point-symmetrically. The rectangular waveguide 31 is constituted by a portion formed by digging a rectangular groove in the lid 20 and the upper surface of the slot antenna 32 as schematically shown in FIGS. 1 and 8A, for example.

As shown in FIG. 1, the interior of each slot 32a is filled with an in-slot dielectric member 36 made of a dielectric material such as fluororesin, alumina (Al ₂ O ₃ ), quartz, etc., thereby closing the slot 32a. Has been.

  3A shows a 3-3 cross section of FIG. As shown in FIG. 3A, the absolute value of the amplitude of the standing wave of the microwave formed in the internal space of the rectangular waveguide 31 is equal at the positions of the slots 32a1 and 32a3. The same applies to the slots 32a2 and 32a4 not shown in FIG. 3A. Accordingly, the absolute values of the amplitudes of the microwaves supplied from the slots 32a1 to 32a4 to the processing chamber among the microwaves transmitted through the rectangular waveguide 31 become equal. Therefore, when the in-slot dielectric member 36 has the same shape, the electric field strengths of the microwaves supplied from the slots 32a1 to 32a4 are substantially equal to each other and become a metal surface wave MSW (Metal Surface Wave) to form the metal surface of the slot antenna 32. Propagates the interface between the plasma and the plasma. During propagation, a uniform plasma can be generated with evenly distributed electric field energy.

In this embodiment, the gap between the slot internal dielectric 36 and the slot 32a is sealed with a large number of sealing materials, but the slot internal dielectric member 36 and the slot antenna 32 may be formed by casting. That is, the metal bath water of aluminum or aluminum alloy is poured around the alumina (dielectric member 36 in the slot) and cast. Details of cast-in are described in, for example, Japanese Patent Application Laid-Open No. 64-53761. As a result, the in-slot dielectric member 36 can be embedded in close contact with the slot 32a. As a result, the rectangular waveguide 31 and the like communicating with the atmosphere and the inside of the processing chamber in a vacuum state can be shut off. Thereby, the microwave can be transmitted through the in-slot dielectric member 36 while the process chamber U is kept airtight. At that time, the in-slot dielectric member 36 controls the in-tube wavelength λg ₂ of each slot 32 a according to the formula λg ₂ = λc / (ε ₂ ) ^1/2 . Here, ε ₂ is the dielectric constant of the in-slot dielectric member 36.

  During manufacturing, the in-slot dielectric member 36 and the slot antenna 32 may be integrally fired at a predetermined temperature. According to this, the in-slot dielectric member 36 and the slot antenna 32 are brought into close contact with each other by integral firing.

  As shown in FIG. 2, the three microwave sources 40 are connected to two rectangular waveguides 31 via Y branch tubes 41 (Y branched waveguides). In this way, the microwaves output from the three microwave sources 40 are transmitted to the six rectangular waveguides 31 in the lid 20 while being Y-branched by the Y branch tube 41. The microwave transmitted through the rectangular waveguide 31 is incident from the slot 32a, passes through the plurality of in-slot dielectric members 36, and is supplied into the processing chamber. The Y branch tube 41 is one of transmission lines (waveguides) for transmitting the microwave output from the microwave source 40.

  In the microwave plasma processing apparatus 100 according to the present embodiment, the dielectric for propagating the surface wave of the microwave is not provided on the lower surface of the slot antenna 32. Therefore, in the ceiling surface of the present apparatus shown in FIG. 2, the metal surface of the slot antenna 32 is exposed, and the end of the in-slot dielectric member 36 protrudes from the slot 32a.

  The gas supply source 42 shown in FIG. 1 is connected to the gas line Lin. As shown in the ceiling surface of FIG. 2, the gas line Lin is connected to a plurality of gas introduction pipes 43 provided at equal intervals. The gas supplied from the gas supply source 42 is introduced into the processing chamber while being diverted to the respective gas introduction pipes 43 via the gas line Lin.

  The cooling water pipe 44 is embedded in the lid 20 and is connected to a refrigerant supply source 45 disposed outside the apparatus. The cooling water supplied from the refrigerant supply source 45 circulates in the cooling water pipe 44 and returns to the refrigerant supply source 45, so that the lid 20 is maintained at a desired temperature.

  With the configuration described above, the microwaves output from the three microwave sources 40 shown in FIG. 2 are transmitted through the rectangular waveguide 31 and incident on the slots 32a of the slot antenna 32, and the in-slot dielectric member 36 is obtained. And is supplied into the processing chamber U. The gas supplied from the gas supply source 42 is excited by the electric field energy of the incident microwave, whereby plasma is generated above the substrate G, and plasma processing is performed on the substrate G.

(Microwave propagation)
Next, microwave propagation will be described with reference to FIG. 3A (section 3-3 in FIG. 2). 3A shows the propagation of microwaves in the microwave plasma processing apparatus 100 according to the present embodiment, and FIG. 3B shows the propagation of microwaves in the conventional microwave plasma processing apparatus 99.

  In the conventional microwave plasma processing apparatus 99, the slot antenna 32 is provided on the lower surface of the rectangular waveguide 31, and the slot antenna 32 is formed with a plurality of slots 32a. This is the same as the processing apparatus 100. In addition, the conventional microwave plasma processing apparatus 99 is provided with a large-area dielectric 90 in close contact with the lower surface of the slot antenna 32. The large-area dielectric 90 is fixed by a beam 91.

  According to the conventional microwave plasma processing apparatus 99, the microwave transmitted through the rectangular waveguide 31 passes through the slot 32a, passes through the large-area dielectric 90, and is supplied into the processing chamber. Furthermore, the microwave propagates along the surface of the large-area dielectric 90 and the plasma interface. During propagation, part of the microwave is absorbed by the plasma as an evanescent wave and used to maintain the plasma. In FIG. 3B, the surface wave of the microwave propagating along the surface of the large-area dielectric 90 and the plasma interface is schematically shown as a dielectric surface wave DSW.

  On the other hand, in the microwave plasma processing apparatus 100 according to the present embodiment, as shown in FIG. 3A, there is no dielectric on the lower surface of the slot antenna 32, and the slot antenna 32 is exposed on the ceiling surface. In this case, the microwave transmitted through the rectangular waveguide 31 enters the slot 32a, passes through the in-slot dielectric member 36, and is supplied into the processing chamber.

  The microwave supplied to the processing chamber propagates along the metal surface of the slot antenna 32 exposed to the ceiling surface and the plasma interface. During propagation, part of the microwave is absorbed by the plasma as an evanescent wave and used to maintain the plasma. In FIG. 3A, the surface wave of the microwave which propagates along the metal surface of the slot antenna 32 and the plasma boundary surface is schematically shown as the metal surface wave MSW.

(Relationship between metal surface wave propagation and frequency)
The dielectric constant of the plasma is represented by ε _r ′ −jε _r ″. Since there is a loss component in the dielectric constant of the plasma, the dielectric constant of the plasma is represented by a complex number. The absolute value of the dielectric constant of the plasma ε _r ′ Is usually smaller than −1, and the dielectric constant of plasma is expressed by the following equation (1).

ここで、ｋは波数、ｋ_０は真空中の波数、ωは金属表面波の周波数、ν_ｃは電子衝突周波数、ω_ｐｅは次式（３）で表される電子プラズマ周波数である。The propagation characteristics when microwaves are incident on the plasma are expressed by the following equation (2).

Here, k is the wave number, k ₀ is the wave number in vacuum, ω is the frequency of the metal surface wave, ν _c is the electron collision frequency, and ω _pe is the electron plasma frequency represented by the following equation (3).

ここで、ｅは素電荷、ｎ_ｅはプラズマの電子密度、ε_０は真空中の誘電率、ｍ_ｅは電子の質量である。

Here, e is the elementary charge, n _e the electron density of the plasma, epsilon ₀ is the dielectric constant, m _e in a vacuum is the electron mass.

ｋは波数である。The penetration length δ indicates how much the microwave can enter the plasma when the microwave is incident. Specifically, the distance that the microwave entered until the electric field intensity E of the microwave attenuated to 1 / e of the electric field intensity E ₀ at the plasma boundary surface is the penetration length δ. The approach length δ is expressed by the following equation (4).

k is the wave number.

When the electron density n _e is higher than the cut-off density n _c represented by the following formula (5), the microwave can not be propagated in the plasma were incident on the plasma microwave decays rapidly. In other words, if the electron density n _e is higher than the cut-off density n _c, the microwave is reflected in the vicinity of the plasma surface, it propagates the inner surface of the processing chamber as the surface waves.

According to equation (5), the cut-off density n _c is, omega is proportional to the square of the frequency of the MSW. This, in the case of using the microwave of the frequency of 915MHz indicates that stable plasma can be obtained even in the electron density n _e is about 1/7 for the case of using a microwave of 2.45GHz frequency . As a result, plasma is generated even at low energy, a process with very little damage is possible, and the process window can be widened.

For example, at a frequency of 915 MHz, the metal surface wave MSW propagates long on the inner surface of the processing chamber even in a low-density plasma whose electron density near the surface is about 1 × 10 ¹¹ cm ⁻³ . According to the equation (1), when the frequency is lowered, the real part ε _r ′ of the dielectric constant of the plasma is negatively increased and the plasma impedance is decreased. Therefore, the microwave electric field applied to the plasma becomes weaker than the microwave electric field applied to the sheath, and the loss of the microwave in the plasma is reduced, so that the attenuation amount of the metal surface wave MSW is reduced. Therefore, it is more preferable to supply a microwave of 1 to 2 GHz or less where the attenuation amount of the metal surface wave MSW is small.

  In the microwave plasma processing apparatus 100 shown in FIG. 1, the microwave emitted from the slot 32a propagates to the periphery of the substrate G along the inner wall of the processing container 10 (the metal surface of the slot antenna 32 and the metal side wall of the processing container). As a result, the plasma generated in the processing container 10 becomes non-uniform and the uniformity of the process deteriorates, or the gate valve that is opened and closed when the substrate G is carried into and out of the processing container 10, Detrimental effects such as deterioration of the susceptor 11 on which is placed. Therefore, when the metal surface wave MSW is not sufficiently attenuated while propagating along the metal surface of the slot antenna 32, a means for reflecting the metal surface wave MSW and preventing further propagation is required.

  Therefore, a substantially rectangular groove 50 is formed on the metal surface near the outer periphery of the slot antenna 32 forming the ceiling surface. The groove 50 is provided in the vicinity of the side wall of the processing vessel 10 at an equal interval from the side wall, and surrounds the slot 32 a formed in the ceiling surface and the hole of the gas introduction pipe 36. Thereby, the groove | channel 50 suppresses propagation of the metal surface wave MSW. The groove 50 may be provided on the inner surface of the processing container 10 other than the metal surface near the outer periphery of the slot antenna 32. Further, the propagation of the metal surface wave MSW may be suppressed by forming a metal protrusion instead of the groove 50, or the propagation of the metal surface wave MSW may be suppressed by forming the protrusion of the dielectric member. Good.

(Projection of dielectric member in slot)
In particular, as shown in FIG. 3A, one end of the in-slot dielectric member 36 protrudes from the lower surface of the slot antenna 32 (that is, the metal surface exposed to the processing chamber side) to the processing chamber side by about 1 mm to 5 mm. As a result, microwaves are easily emitted from the in-slot dielectric member 36.

(Chamfering of dielectric member)
Further, as shown in FIG. 4A, the protruding portion of the in-slot dielectric member 36 is chamfered. The chamfer (C surface: hamfer) is formed along the longitudinal direction of the in-slot dielectric member 36. The C surface of the in-slot dielectric member 36 includes a portion where the outer surface is chamfered with respect to the center of the slot group (outer taper) and a portion where the inner surface is chamfered with respect to the center of the slot group (inner Taper). The area of the outer taper OC is larger than the area of the inner taper IC.

  The chamfer of the outer taper of the in-slot dielectric member 36 may be formed only on the in-slot dielectric member 36 closest to the inner wall of the processing chamber.

(Microwave energy distribution)
The inventor performed a simulation on how the shape of the chamfered portion relates to the microwave energy output from the chamfered portion.

  In the simulation shown in FIG. 4B, the width in the short direction of the chamfered portion IC (inner taper) on the inner side with respect to the center of the slot group 32ag is a fixed value of 0.2 mm, and the outer side with respect to the center of the slot group 32ag. The width of the chamfered portion OC (outer taper) in the short direction was set to be variable, 0.2 mm, 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm.

As a result, when the dimensional ratio between the inner taper IC and the outer taper OC was the same (in the case of FIG. 5A), the power reflection ratio of the outer taper OC to the inner taper IC was 1.18 (e ⁻⁵ ). The power reflection ratio indicates the energy distribution ratio between the microwave reflected back by the inner taper IC and the microwave reflected back by the outer taper OC.

Further, according to the result of FIG. 4B, when the dimensional ratio of the outer taper OC to the inner taper IC is gradually increased, the power reflection ratio is gradually increased accordingly, and the dimension of the outer taper OC is reduced to 5 mm. In this case, the power reflection ratio reached 2.30 (e ⁻⁵ ).

When the dimension of the outer taper OC was 0.2 mm to 5 mm with respect to the dimension of the inner taper IC 0.2 mm, the power reflection ratio was as small as e ⁻⁵ in any case. Therefore, even if the inner taper IC and the outer taper OC are formed in the in-slot dielectric member 36, the microwave energy that is returned without being consumed for plasma generation is very small, and the in-slot dielectric member 36 has a tapered chamfer. It turns out that there is no problem in forming.

  Then, next, the inventor performed the simulation of the radiation distance ratio shown in FIG. Also here, the width in the short direction of the chamfered portion IC (inner taper in FIG. 9a) on the inner side with respect to the center of the slot group 32ag is a fixed value of 0.2 mm, The width in the short direction of the chamfered portion OC (outer taper in FIG. 9a) was variably set to 0.2 mm, 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm. The horizontal axis of the graph of FIG. 9c indicates the width of the outer taper, and the vertical axis indicates the radial distance ratio of the outer taper to the inner taper. The radiation distance ratio indicates the distance of plasma diffused on the outer taper side (corresponding to plasma intensity) to the distance of plasma diffused on the inner taper side (corresponding to plasma intensity).

  According to this, it can be seen that when both the inner taper IC and the outer taper OC have dimensions of 0.2 mm, the microwave energy output from the outer taper OC and the inner taper IC is equally divided. This state is schematically shown in FIG. 5A showing a cross section perpendicular to the longitudinal direction of the in-slot dielectric member 36.

  On the other hand, when the dimension of the inner taper IC is 0.2 mm and the dimension of the outer taper OC is 5 mm, the radiation distance ratio is the largest, and the microwave energy output from the outer taper OC is reduced from the inner taper IC. It was found that the energy can be distributed about 1.3 times the energy of the output microwave. This state is schematically shown in FIG. 5B.

  The plasma is preferably generated uniformly above the substrate G. Accordingly, when the dimensions of the OC of the inner taper IC and the outer taper are made equal, as shown in FIG. 11, the slot 32a has a distance Sa between the slots adjacent to the center direction C1 of the slot group 32ag and vice versa. It is desirable that the distance Sb between the adjacent slots with respect to the central direction C2 is approximately equal in the direction. Thereby, the distance between all the slots becomes equal, and the energy of the microwaves output from the outer taper OC and the inner taper IC is equally divided, so that uniform plasma can be generated. However, the dimensions of the waveguide for efficiently transmitting the microwave are determined by the standard, and the arrangement of the slots 32a is restricted by the dimensions of the waveguide. Therefore, in actuality, as shown in FIG. 12, the slot 32a must be disposed at a position close to the center of the slot group 32ag according to the dimension of the waveguide 31.

  Therefore, if the area of the outer taper OC is processed to be larger than the area of the inner taper IC and the microwave energy output from the outer taper OC is designed to be larger than the microwave energy output from the inner taper IC. Uniform plasma can be generated.

  In the case of the microwave plasma processing apparatus 100 according to the present embodiment, the inventor achieves a uniform plasma density distribution by setting the outer taper OC dimension and the inner taper IC dimension to “5: 0.2”. It was clarified by simulation that it was possible.

  As described above, according to the microwave plasma processing apparatus 100 according to the present embodiment, the dielectric window conventionally provided on the ceiling surface becomes unnecessary, which is advantageous in terms of contamination problems, maintenance, and cost. Device can be manufactured.

  In addition, by optimizing the shape of the protruding portion of the in-slot dielectric member 36 that closes the inside of the slot, the microscopically emitted from the lower part of the in-slot dielectric member 36 toward the metal surface of the slot antenna 32 is emitted. The distribution ratio of wave energy can be controlled.

  That is, the area ratio of the outer taper OC and the inner taper IC is determined and processed so that the distribution ratio of the microwave energy propagating on the metal surface of the slot antenna 32 becomes a desired ratio. Thereby, the energy amount of the microwave distributed to the outside with respect to the center of the slot group 32ag can be increased, and the uniformity of the plasma can be improved.

  In addition, the chamfered portion may be chamfered not only at the corner portion facing outward with respect to the center of the slot group 32ag and the corner portion facing inward with respect to the center of the slot group 32ag, but also at other corner portions. For example, as shown in FIG. 6, an outer taper OC and an inner taper IC may be provided on the side surface of the in-slot dielectric member 36. Also in this case, the outer taper OC is cut larger than the inner taper IC. By making the energy of the microwave output from the outer taper OC larger than that of the inner taper IC in this way, uniform plasma can be generated. As shown in FIG. 7, the shape may be a combination of the chamfer OC, IC of FIG. 4A and the outer taper OC, inner taper IC of FIG. Of course, in some cases, it is conceivable that the inner taper IC should be sharpened more than the outer taper OC.

  Further, the chamfer of the outer taper of the in-slot dielectric member 36 may be formed only on the in-slot dielectric member 36 closest to the inner wall of the processing chamber. Alternatively, the chamfer of the outer taper of the dielectric member 36 in the slot closest to the inner wall of the processing chamber may be formed to be larger than the chamfer of the outer taper of the other dielectric member 36 in the slot. The plasma is preferably generated uniformly above the substrate G. In general, however, the outer plasma tends to be less dense than the central plasma. This is because when the plasma diffuses to the inner wall side of the processing chamber, the plasma is consumed for a chemical reaction (recombination) occurring in the vicinity of the wall surface. Therefore, the area of the outer taper OC of the dielectric member 36 in the slot closest to the inner wall of the processing chamber is processed to be larger than the energy of the microwave output toward the inner wall side of the processing chamber where the plasma density tends to decrease. If designed to do so, uniform plasma can be generated.

  As described above, according to the microwave plasma processing apparatus 100 according to the first embodiment, uniform plasma can be generated without providing a large-area dielectric window below the slot antenna 32. In particular, by processing the protruding portion of the in-slot dielectric member 36 into an appropriate shape according to the configuration and process conditions of the microwave plasma processing apparatus 100, the distribution ratio of the microwave energy transmitted through the in-slot dielectric member 36 can be reduced. Can be controlled. As a result, the plasma density can be made uniform.

  In the first embodiment, the slot-side dielectric member 36 closes the inside of the slot, so that the waveguide-side atmosphere and the processing-vessel-side vacuum can be reduced without providing a large-area dielectric window below the slot antenna 32. Was shut off.

  On the other hand, by providing a dielectric between the microwave source 40 and the processing container 10 other than the inside of the slot, the atmosphere on the waveguide side and the vacuum on the processing container side may be shut off. . Also by this, the atmosphere on the waveguide side and the vacuum on the processing container side can be shut off without providing a large-area dielectric window below the slot antenna 32.

Second Embodiment
For example, in the second embodiment shown in FIG. 8A, the inter-waveguide dielectric member 200 is provided between the microwave source 40 and the processing vessel 10 and at the ends of the rectangular waveguide 31 and the Y branch tube 41. Each contact surface is sealed with a sealing material 205. As a result, the inside of the Y branch pipe 41 is in an atmospheric state, and the inside of the rectangular waveguide 31 is in a vacuum state (or a reduced pressure state). As a result, the inside of the processing container 10 can be kept airtight. Note that the inter-waveguide dielectric member 200 is not necessarily disposed at the ends of the rectangular waveguide 31 and the Y branch tube 41, and shuts off the atmosphere on the waveguide side and the vacuum on the processing vessel side. As described above, at least a part of the rectangular waveguide 31 or the Y branch tube 41 may be closed.

The inter-waveguide dielectric member 200 is preferably made of a material having a dielectric loss tangent (tan δ) of 0.0001 or less and a strength capable of withstanding a pressure difference between the atmosphere and vacuum. Examples of the inter-waveguide dielectric member 200 include alumina (Al ₂ O ₃ ), aluminum nitride (AlN), and yttria (Y ₂ O ₃ ). An example of the sealing material is an O-ring.

  In the present embodiment, the sealing material 205 is used for sealing, but the inter-waveguide dielectric member 200, the rectangular waveguide 31 and the Y branch pipe 41 shown by M in FIG. 8A are formed by casting. May be. That is, a metal bath of aluminum or aluminum alloy is poured around alumina (dielectric member 200 between waveguides) and cast. Thus, the inter-waveguide dielectric member 200, the rectangular waveguide 31 and the Y branch tube 41 are joined. Note that the cast-in manufacturing method can also be applied to the third and fourth embodiments described below.

  Even in the microwave plasma processing apparatus 100 according to the second embodiment, the waveguide-side atmosphere and the processing container-side can be formed by the inter-waveguide dielectric member 200 without providing a large-area dielectric under the slot antenna 32. The vacuum can be cut off. Thereby, a metal surface wave (MSW) can be propagated to the metal surface of the slot antenna 32 that forms the ceiling surface of the processing container. Furthermore, gas can be prevented from leaking to the microwave source 40. Further, in the first embodiment, a large number of sealing materials for sealing between the in-slot dielectric member 36 and the slot 32a are necessary. However, according to the second embodiment, the inter-waveguide dielectric member 200 Only one place needs to be sealed, and the number of sealing materials can be reduced.

<Third Embodiment>
In the second embodiment, since the inside of the rectangular waveguide 31 is vacuum, there is a possibility that electric discharge occurs in the waveguide. Therefore, in the third embodiment shown in FIG. 8B, in addition to the configuration of the second embodiment, the inside of the rectangular waveguide 31 is filled with a dielectric 210 made of fluororesin (eg, Teflon (registered trademark)). Thereby, abnormal discharge inside the rectangular waveguide 31 can be avoided.

  In the third embodiment, it is preferable to introduce an inert gas such as argon gas into the gap between the rectangular waveguide 31 and the dielectric 210. According to this, it is possible to prevent the processing gas from flowing back into the waveguide from the processing chamber side. On the other hand, even if argon gas leaks from the inside of the waveguide into the processing chamber, it is inactive and does not affect the process in the processing chamber.

<Fourth embodiment>
The fourth embodiment shown in FIG. 8C includes the inter-waveguide dielectric member 200 shown in the second embodiment and the in-slot dielectric member 36 shown in the first embodiment. Further, the rectangular waveguide 31 is provided. An insulating gas such as SF ₆ gas is introduced into the interior of the chamber. For example, SF ₆ gas has an insulation property about three times that of air. This also makes it possible to avoid abnormal discharge inside the rectangular waveguide 31.

The reason why the in-slot dielectric member 36 is embedded in the slot in the fourth embodiment is to avoid the adverse effect on the process when SF ₆ gas flows into the processing container. Also in the second and third embodiments, the in-slot dielectric member 36 may be embedded in the slot in addition to the inter-waveguide dielectric member 200.

  In the description of each of the above embodiments, the slot group is formed on the long side surface (H surface) of the waveguide. However, the rectangular slot is formed on the short side surface (E surface) of the waveguide. It may be formed. Also in this case, the slot interval is an integral multiple of the guide wavelength λg / 2.

  In the above embodiment, the operations of the respective units are related to each other, and can be replaced as a series of operations and a series of processes in consideration of the mutual relations. Thereby, embodiment of a plasma processing apparatus can be made into embodiment of the electric power feeding method of a plasma processing apparatus.

  Accordingly, there is provided a power supply method for a plasma processing apparatus for supplying an electromagnetic wave to a processing chamber in which plasma processing is performed, the step of outputting the electromagnetic wave from an electromagnetic wave source, and the step of transmitting the outputted electromagnetic wave to a waveguide. The transmitted electromagnetic wave is incident from a plurality of slots formed in a metal slot antenna and transmitted to a plurality of in-slot dielectric members closing the plurality of slots; and the transmitted electromagnetic wave is processed by the processing And propagating along the metal surface of the slot antenna that forms the inner wall of the chamber.

  As mentioned above, although preferred embodiment of this invention was described in detail, referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, the in-slot dielectric member 36 and the inter-waveguide dielectric member 200 described in the above embodiments are provided between the electromagnetic wave source and the processing container, and the atmosphere side where the electromagnetic wave source is disposed and the inside of the processing container. It is an example of the dielectric member which interrupts | blocks from the pressure reduction side. Therefore, the dielectric member according to the present invention may be provided at any position between the electromagnetic wave source and the processing container as long as it can block the atmosphere side where the electromagnetic wave source is disposed and the decompression side in the processing container. Good.

  The plasma processing apparatus according to the present invention is not limited to the rectangular microwave plasma processing apparatus described in the above embodiment, and can be used for a plasma processing apparatus that supplies power using a slot. For example, in the case of a cylindrical RLSA plasma processing apparatus, there is no need to provide a disk-shaped dielectric window on the ceiling surface, and the microwave transmitted through a radial line slot antenna without a dielectric window becomes a metal surface wave and is applied to the ceiling. It propagates on the metal surface that forms the inner wall.

  Further, the slot antenna according to the present invention is not limited to the arrangement of the slots 32a shown in FIG. 2, and may be arranged at a position where the phase and energy intensity of the microwaves supplied from the slots 32a into the processing chamber are substantially equal. it can.

  A specific modification of the slot position will be described with reference to FIG. In the present modification, the longitudinal direction of the plurality of slots 32a1 to 32a4 is inclined at 45 degrees with respect to the longitudinal direction of the rectangular waveguide 31, and the slot 32a1 and the slot 32a3, and the slot 32a2 and the slot 32a4 face each other. And it is formed into a mouth shape. The longitudinal direction of the slot 32a1 and the slot 32a3 is formed at a position inclined 45 degrees counterclockwise with respect to the longitudinal direction of the rectangular waveguide 31. The longitudinal direction of the slot 32a2 and the slot 32a4 is the same as that of the rectangular waveguide 31. It is formed at a position inclined 45 degrees clockwise with respect to the longitudinal direction.

  The distance between the slot 32a1 and the slot 32a3 and the distance between the slot 32a2 and the slot 32a4 are all equal. The slots 32a1 to 32a4 are all equal in distance between adjacent slots. The four slots 32a1 to 32a4 included in one slot group 32ag are arranged point-symmetrically. The slot group 32ag is formed with a pitch of the guide wavelength λg / 2.

  In this modification, the slots 32a1 to 32a4 are disposed at an inclination of 45 degrees with respect to the longitudinal direction of the rectangular waveguide 31, so that the microwaves supplied from the slots 32a1 to 32a4 are circularly polarized. While being supplied to the processing chamber. In the case of circular polarization, the generated electromagnetic field leaks from the slots 32 a 1 to 32 a 4 while rotating and is transmitted to the inside of the processing container 10.

  In addition to this, in the present modification, the slots 32 a 1 to 32 a 4 are disposed with an inclination of 45 degrees with respect to the longitudinal direction of the rectangular waveguide 31. Thereby, the metal surface wave MSW propagating on the ceiling surface propagates radially toward the direction of 45 degrees oblique to the longitudinal direction of the rectangular waveguide 31. As a result, since the metal surface wave MSW easily propagates in the angular direction of the ceiling surface of the processing chamber together with the chamfering effect of the in-slot dielectric member 36, more uniform plasma can be generated. Therefore, in order to generate uniform plasma, the slots 32a1 to 32a4 are inclined 45 degrees with respect to the longitudinal direction of the rectangular waveguide 31, and the slots 32a1 to 32a4 are inclined with respect to the longitudinal direction of the rectangular waveguide 31. It is more preferable to arrange them in parallel and vertically.

  The inclination angle of the plurality of slots 32a1 to 32a4 with respect to the longitudinal direction of the rectangular waveguide 31 may not be 45 degrees, and the longitudinal direction of the slots 32a1 and 32a3 is relative to the longitudinal direction of the rectangular waveguide 31. The slot 32a2 and the slot 32a4 are longitudinally inclined at α degrees (0 <α <90) and the longitudinal directions of the slots 32a2 and 32a4 are α degrees clockwise with respect to the longitudinal direction of the rectangular waveguide 31 (0 < α <90) It may be formed at an inclined position.

  Also in this case, since the slots 32a1 to 32a4 are inclined at an arbitrary angle with respect to the longitudinal direction of the rectangular waveguide 31, the microwaves supplied from the slots 32a1 to 32a4 into the processing chamber are circular. It is supplied to the processing chamber while being polarized.

  The microwave output from the microwave source 40 according to the present invention may be 896 MHz, 915 MHz, 922 MHz, 2.45 GHz, or the like. The microwave source 40 is an example of an electromagnetic wave source that outputs an electromagnetic wave for exciting plasma, and includes a magnetron and a high-frequency power source as long as the electromagnetic wave source outputs an electromagnetic wave of 100 MHz or higher.

Note that the size of the substrate G (glass substrate) may be 720 mm × 720 mm or more. For example, the G3 substrate size is 720 mm × 720 mm (dimension in the chamber: 400 mm × 500 mm), and the G4.5 substrate size is 730 mm × 920 mm. (Dimension in chamber: 1000 mm × 1190 mm), 1100 mm × 1300 mm in G5 substrate size (dimension in chamber: 1470 mm × 1590 mm). A microwave having a power of 1 to 8 W / cm ² is supplied into the processing chamber having the above size.

DESCRIPTION OF SYMBOLS 10 Processing container 20 Cover body 31 Waveguide 32 Slot antenna 32a Slot 36 In-slot dielectric member 40 Microwave source 43 Gas introduction pipe 50 Groove 100 Microwave plasma processing apparatus 200 Inter-waveguide dielectric member MSW Metal surface wave DSW Dielectric surface wave

Claims (13)

An electromagnetic wave source that outputs electromagnetic waves;
A waveguide for transmitting electromagnetic waves output from the electromagnetic wave source;
A processing vessel for generating a plasma by exciting a gas by the energy of electromagnetic waves supplied through the waveguide, and performing a plasma treatment on the object to be processed in a decompressed processing chamber;
A metal slot antenna formed with a plurality of slots;
A dielectric member provided between the electromagnetic wave source and the processing container and transmitting the electromagnetic wave;
The plasma processing apparatus which propagates the said electromagnetic wave along the metal surface of the said slot antenna which forms the inner wall of the said processing container. The slot antenna is provided adjacent to the waveguide;
The plasma processing apparatus according to claim 1, wherein the dielectric member includes a plurality of in-slot dielectric members that block the inside of the plurality of slots.   The plasma processing apparatus according to claim 2, wherein one end of the in-slot dielectric member protrudes toward the processing chamber from a metal surface of the slot antenna.   The plasma processing apparatus according to claim 3, wherein at least one of the in-slot dielectric members has a chamfered protruding portion.   The projecting portion of the in-slot dielectric member has at least a portion whose outer surface is chamfered with respect to the center of the slot group and a portion whose inner surface is chamfered with respect to the center of the slot group. 4. The plasma processing apparatus according to 4.   The area ratio between the portion where the outer surface is chamfered with respect to the center of the slot group and the portion where the inner surface is chamfered with respect to the center of the slot group is such that the area ratio is transmitted through the dielectric member in each slot. The plasma processing apparatus according to claim 5, wherein the plasma processing apparatus is formed so as to have a ratio according to a distribution ratio of electromagnetic wave energy when propagating on the metal surface of the slot antenna.   The plasma processing according to claim 6, wherein an area of a portion where the outer surface is chamfered with respect to the center of the slot group is larger than an area of a portion where the inner surface is chamfered with respect to the center of the slot group. apparatus.   The plasma processing apparatus according to claim 3, wherein the protruding portion of the in-slot dielectric member is provided with an inclination.   The plasma processing apparatus according to claim 1, wherein the dielectric member includes a dielectric window that closes at least a part of the waveguide.   The plasma processing apparatus according to claim 9, wherein the dielectric window and the waveguide maintain hermeticity in the processing chamber by cast-in.   3. The plasma processing apparatus according to claim 2, wherein the in-slot dielectric member and the slot antenna maintain hermeticity in the processing chamber by casting. 3.   The plasma processing apparatus according to claim 2, wherein the in-slot dielectric member and the slot antenna maintain airtightness in the processing chamber by providing a sealing material between the in-slot dielectric member and the slot antenna. Outputting electromagnetic waves from an electromagnetic wave source;
Transmitting the output electromagnetic wave into a waveguide, and transmitting the electromagnetic wave to a dielectric member provided between the electromagnetic wave source and a processing vessel for performing plasma processing;
Propagating the transmitted electromagnetic wave along a metal surface of the slot antenna forming an inner wall of a processing chamber of the processing container;
Exciting the gas with the energy of the electromagnetic wave propagated along the metal surface of the slot antenna to generate plasma, and subjecting the object to be processed to plasma processing in the reduced processing chamber;
A power supply method for a plasma processing apparatus including:

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