Patent Application
20230238217
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-008793, filed on Jan. 24, 2022, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a plasma processing apparatus.
Patent Document 1 discloses a plasma processing apparatus including an antenna that emits microwaves into a processing chamber and a dielectric member that transmits therethrough the microwaves emitted from the antenna to form surface waves. In addition, Patent Document 1 proposes that a length of a closed circuit, through which a surface current and a displacement current flow, is set to nλ0±δ (where n is a positive integer, λ0 is a wavelength of microwaves, and δ is a fine adjustment component (including zero)). Thus, since the surface current may be increased and a plasma absorption efficiency is increased, a rate of increase in electron density caused by an increased input power may rise.
Patent Document 2 discloses a plasma processing apparatus including a processing chamber, a dielectric window having a flat plate shape, an induction coil, a plate electrode, a radio frequency power supply, a gas supply device, and a sample table on which a sample is placed. A dielectric of a high permittivity material is provided between the dielectric window and a processing gas supply plate, so that a generated electric field is absorbed by the dielectric of the high permittivity material. Therefore, an effective voltage value is reduced, and the distribution of electric field becomes non-uniform. By forming a notch in a Faraday shield on the top of the dielectric window in order to prevent the occurrence above, the electric field immediately below the notch may be weakened, which makes the distribution of electric field uniform.
According to an embodiment of the present disclosure, a plasma processing apparatus includes: a processing container; a ceiling plate that constitutes a ceiling wall of the processing container, is formed of a first dielectric, and has an opening formed in the first dielectric; at least one transmissive window disposed in the opening and formed of a second dielectric having a second permittivity greater than a first permittivity of the first dielectric; and at least one electromagnetic wave supplier configured to supply electromagnetic waves toward the at least one transmissive window.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure.
Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same components will be denoted by the same reference numerals, and redundant explanations thereof may be omitted. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.
In this specification, in the directions of parallel, right angle, orthogonal, horizontal, vertical, up/down, left/right, and the like, a deviation that does not impair the effect of an embodiment is allowed. The shape of a corner is not limited to a right angle but may be rounded in an arch shape. The terms parallel, right-angled, orthogonal, horizontal, vertical, circular, cylindrical, disk, and coincident may include approximately parallel, approximately right-angled, approximately orthogonal, approximately horizontal, approximately vertical, approximately circular, approximately cylindrical, approximately disk, and approximately coincident.
First, a configuration example of a plasma processing apparatus 100 according to an embodiment will be described with reference to
The plasma processing apparatus 100 performs, for example, a plasma processing, such as an etching processing or a film forming processing, on a substrate W used as example of a wafer. The plasma processing apparatus 100 includes a processing container 1 that is configured in an airtight manner and is made of a metal such as aluminum or stainless steel, and the microwave plasma source 2 that is configured to form microwave plasma inside the processing container 1. The processing container 1 has a cylindrical shape and is grounded. The top of the processing container 1 forms an opening, and a support ring 29 is provided to surround the opening. The microwave plasma source 2 is provided to face an interior of the processing container 1 from the opening.
A stage 11 for horizontally supporting the substrate W is provided inside the processing container 1 so as to be supported by a cylindrical support member 12 that is erected at the center of the bottom of the processing container 1 via an insulating member 12a interposed between the support member 12 and the bottom of the processing container 1. An example of a material constituting the stage 11 and the support member 12 may include aluminum whose surface is alumite-treated (anodized).
Further, although not illustrated, the stage 11 is provided with an electrostatic chuck for electrostatically attracting the substrate W, a temperature control mechanism, a heat-transfer-gas flow path for supplying a heat transfer gas to a back surface of the substrate W, lifting pins configured to move up and down so as to transfer the substrate W, and the like. Furthermore, a radio-frequency bias power supply 14 is electrically connected to the stage 11 via a matcher 13. When radio frequency power is supplied from the radio-frequency bias power supply 14 to the stage 11, ions in plasma are drawn to the side of the substrate W.
An exhaust pipe 15 is connected to the bottom of the processing container 1, and an exhaust device 16 including a vacuum pump is connected to the exhaust pipe 15. The interior of the processing container 1 is exhausted by operating the exhaust device 16, so that the interior of the processing container 1 may be rapidly reduced in pressure to a predetermined degree of vacuum. Further, a sidewall of the processing container 1 is provided with a loading/unloading port 17 for loading and unloading the substrate W therethrough, and a gate valve 18 that opens and closes the loading/unloading port 17.
The ceiling plate 111 closes the opening formed in the top of the processing container 1 while being supported by the support ring 29 at the top of the processing container 1. As a result, a ceiling wall of the processing container 1 is constituted with the ceiling plate 111, and the processing container 1 and the ceiling plate 111 define a plasma generation space U. The ceiling plate 111 is formed of a dielectric with high plasma resistance. This makes it possible to avoid damage to the ceiling plate 111 due to microwaves emitted from the microwave plasma source 2 and, as a result, may prevent generation of particles or contamination.
The ceiling plate 111 has a disk shape (circular flat plate shape) and is formed of a dielectric (hereinafter also referred to as “first dielectric”). The first dielectric includes a plurality of openings 111b. A transmissive window 112 is formed of a dielectric (hereinafter also referred to as “second dielectric”) having a permittivity greater than that of the first dielectric, and is fitted into each opening 111b.
A thickness of the second dielectric forming the transmissive window 112 is the same as that of the first dielectric forming the ceiling plate 111. That is, a surface of the second dielectric exposed to the plasma generation space U (that is, a lower surface 111a) is flush with a surface of the first dielectric that is adjacent to the second dielectric and is exposed to the plasma generation space U. However, the entire surface of the first dielectric exposed to the plasma generation space U may not be a flat surface. For example, a recess or the like may be formed in a surface of the first dielectric other than the surface adjacent to the second dielectric. Further, a surface of the second dielectric opposite to the surface exposed to the plasma generation space U is flush with a surface of the first dielectric opposite to the surface that is adjacent to the second dielectric and is exposed to the plasma generation space U.
The permittivity of the second dielectric is greater than that of the first dielectric. Accordingly, the transmissive window 112 functions to confine the electromagnetic field of microwaves inside the second dielectric when transmitting the microwaves therethrough. For example, the first dielectric may be alumina (Al2O3) having a permittivity of about 9.6, or quartz having a permittivity of about 3.7 to 4, and the second dielectric may be a high permittivity material such as zirconia having a permittivity of 30. Ranges of a radius and an available permittivity of the second dielectric will be described later.
The microwave plasma source 2 is disposed on the top of the ceiling plate 111. In detail, an electromagnetic wave supplier 43 included in the microwave plasma source 2 is disposed on the top of the transmissive window 112 formed of the second dielectric. With such a configuration, the electromagnetic wave supplier 43 supplies microwaves, which are an example of electromagnetic waves, toward the transmissive window 112.
The periphery of the ceiling plate 111 is covered with a backing member 110 made of a metal such as aluminum, except for the lower surface 111a and a portion supported by the support ring 29. An airtight seal is provided between the support ring 29 and the backing member 110.
As illustrated in
As illustrated in
The microwave oscillator 32 oscillates microwaves having a predetermined frequency (for example, 915 MHz) in, for example, a phase locked loop (PLL) manner. The distributor 34 distributes the microwaves amplified by the amplifier 33 while taking impedance matching between the input side and the output side such that a loss of microwaves occurs as little as possible. In addition, the frequency of microwaves may be 700 MHz or more and 3 GHz or less, in addition to 915 MHz.
A plurality of antenna modules 41 are provided to guide the microwaves distributed by the distributor 34 into the processing container 1. Each antenna module 41 includes an amplifier part 42 that mainly amplifies the distributed microwaves, and the electromagnetic wave supplier 43. Further, the electromagnetic wave supplier 43 includes a tuner 60 (see
The amplifier part 42 includes a phase shifter 46, a variable gain amplifier 47, a main amplifier 48 that configures a solid state amplifier, and an isolator 49. The phase shifter 46 is configured to vary a phase of microwaves and may modulate the characteristics of emission by adjusting the phase of microwaves. For example, under the control of a controller 120, the phase shifter 46 adjusts the phase of microwaves for each antenna module to control directivity and change a distribution of plasma. Further, circularly polarized waves may be obtained by shifting the phase by 90 degrees in adjacent antenna modules. Further, the phase shifter 46 may be used for the purpose of spatial synthesis in the tuner by adjusting the characteristics of delay between components in the amplifier. However, the phase shifter 46 may be omitted when such modulation of the characteristics of emission or such adjustment of the characteristics of delay between components in the amplifier is unnecessary.
The variable gain amplifier 47 is an amplifier for adjusting a change in individual antenna modules or adjusting the intensity of plasma by adjusting a power level of microwaves input to the main amplifier 48. Varying the variable gain amplifier 47 for each antenna module may create a distribution of plasma being generated.
The main amplifier 48 that configures a solid state amplifier may be configured to include, for example, an input matching circuit, a semiconductor amplifying element, an output matching circuit, and a high-Q resonance circuit. The isolator 49 separates reflected microwaves that are reflected by the antenna part 113 and directed toward the main amplifier 48, and includes a circulator and a dummy load (coaxial terminator). The circulator guides the microwaves reflected by the antenna part 113 to the dummy load. The dummy load converts the reflected microwaves guided by the circulator into heat.
Next, returning to
The waveguide 44 is configured by coaxially arranging a cylindrical outer conductor 43b and a rod-shaped inner conductor 43a provided at the center of the outer conductor 43b. The antenna part 113 is provided at the tip of the waveguide 44. In the waveguide 44, the inner conductor 43a is on a power supply side and the outer conductor 43b is on a ground side.
Microwave power is supplied to a space between the outer conductor 43b and the inner conductor 43a. Then, the microwave power propagates toward the antenna part 113. Further, the tuner 60 is provided in the waveguide 44. The tuner 60 matches an impedance of load (plasma) inside the processing container 1 with a characteristic impedance of the microwave power supply in the microwave output part 30. Specifically, the tuner 60 achieves impedance matching by vertically moving two slags 61a and 61b between the outer conductor 43b and the inner conductor 43a.
The first dielectric forming the ceiling plate 111 includes a plurality of through-holes. In one example, when the lower surface 111a of the ceiling plate 111 is divided into a central portion, which is a region including the center of the lower surface 111a, and an outer peripheral portion, which is a region around the central portion, as illustrated in
As illustrated in
A processing gas is supplied from the gas supplier 27 and is introduced into the processing container 1 from the plurality of gas supply pipes 114 through the gas supply line 28. The introduced processing gas is excited in the plasma generation space U by surface waves of the microwaves introduced into the processing container 1 from the microwave plasma source 2, thereby forming plasma of the processing gas.
One or a plurality of electromagnetic wave suppliers 43 and transmissive windows 112 are provided in the same number.
In the related art, a ceiling plate of the plasma processing apparatus 100 is made of a metal such as aluminum and has a structure in which a transmissive window of a dielectric is disposed in an opening of the ceiling plate. In this case, when microwaves propagate through the transmissive window, the microwaves also propagate to a metal surface of the ceiling plate near the transmissive window, so that the electric field becomes stronger especially, for example, at the corners of the metal surface of the ceiling plate, which causes damage to the ceiling plate. This may cause particles or contamination due to the peel-off of a metal. As a way of eliminating the generation of particles and the like, there may be a method of forming the entire surface of the ceiling plate 111 with a dielectric material such as alumina having high plasma resistance.
However, in the configuration of the ceiling plate 111 according to the reference example, the electromagnetic field of microwaves transmitted through the dielectric material is diffused radially in the ceiling plate 111, which makes it difficult to locally generate plasma at a desired position as illustrated in
Hereinafter, the local plasma generation will be described by taking, as an example, the plasma processing apparatus 100 in which the first dielectric of the ceiling plate 111 is formed of alumina and the second dielectric of the transmissive window 112, on which the electric field of microwaves is to be concentrated, is formed of zirconia as a high permittivity material. However, the materials of the first dielectric and the second dielectric are not limited thereto. Thus, the electromagnetic field of microwaves may be confined in the transmissive window 112 of the high permittivity material by embedding the second dielectric, which is a higher permittivity material than the first dielectric, in the ceiling plate 111. Thus, it is possible to provide the plasma processing apparatus 100 capable of concentrating the electric field of microwaves immediately below the transmissive window 112, thereby locally generating plasma below the transmissive window 112 (see
A simulation result for obtaining appropriate values for ranges of the radius r and the permittivity εr of the second dielectric of the transmissive window 112 will be described with reference to
(2) illustrated in
The horizontal axis in
The vertical axis in
In the simulation result of
As a result, in the configuration of the ceiling plate 111 according to the present embodiment, the electromagnetic field of microwaves may be confined in the transmissive window 112 by embedding the transmissive window 112, which is formed of the second dielectric of a high permittivity material, in the ceiling plate 111. Thus, it is possible to prevent the electromagnetic field of microwaves supplied from the electromagnetic wave supplier 43 from leaking to the side of the ceiling plate 111 closer to the outer edge than the transmissive window 112.
Next, a result of the microwave propagation preventing effect when the radius r of the second dielectric is variably set will be described with reference to
According to this, it can be seen that the distribution of electric field changes depending on the radius r of the second dielectric of the transmissive window 112. However, in both cases where the radius r is 50 mm and 70 mm, the electric field is highly distributed in the second dielectric but is remarkably less at the outer edge by embedding the transmissive window 112 of the second dielectric in the ceiling plate 111. That is, it was possible to confine the electromagnetic field of microwaves in the second dielectric. For example, when the radius r of the second dielectric is 50 mm, the electric field intensity in the second dielectric having a diameter of 100 mm was high (in the range of 150 mm to 250 mm), and it was possible to reduce the electric field intensity in the first dielectric at the outer edge beyond 250 mm. Similarly, when the radius r of the second dielectric is 70 mm, the electric field intensity in the second dielectric having a diameter of 140 mm was high (in the range of 130 mm to 270 mm), and it was possible to reduce the electric field intensity in the first dielectric at the outer edge beyond 270 mm.
In this way, the electromagnetic field of microwaves supplied from the electromagnetic wave supplier 43 may be prevented from leaking to the side of the ceiling plate 111 of the first dielectric closer to the outer edge than the transmissive window 112. As will be understood from the above description, when a plurality of transmissive windows 112 are arranged in the ceiling plate 111, there is no influence of microwaves transmitted through adjacent transmissive windows 112 since electromagnetic waves may be confined in the high permittivity material of each transmissive window 112. Thus, the adjacent transmissive windows 112 need not be in contact with each other by interposing the first dielectric therebetween, and the thickness of the first dielectric provided between the adjacent transmissive windows 112 does not matter. That is, when the plurality of transmissive windows 112 are provided in the openings 111b of the ceiling plate 111, the thickness of the first dielectric of the ceiling plate 111 between the plurality of transmissive windows 112 may be a thin film.
Next, a simulation result for obtaining an appropriate value of the radius r of the second dielectric will be described with reference to
λ indicated on the horizontal axis in
The higher the permittivity εr, the shorter the effective wavelength λ of microwaves propagated in the second dielectric. In the case of the titanium oxide, the effective wavelength λ of microwaves in the second dielectric was 34.9 mm. According to the simulation result of
As will be understood from the above description, when the radius r of the second dielectric satisfies the condition of λ/2≤r≤3λ/2 based on the simulation result of
According to this, when the permittivity εr of the second dielectric constituting the transmissive window 112 is 30 or more, the electromagnetic field of microwaves may be further confined in the transmissive window 112, compared to when the permittivity εr of the second dielectric is 20. Thus, it is possible to prevent the electromagnetic field from being diffused to the outer edge outside the transmissive window 112, and thus, to locally generate plasma below the transmissive window 112 by concentrating the electric field below the transmissive window 112.
Accordingly, from the simulation result of
The second dielectric of the transmissive window 112 may be a high permittivity material having a permittivity of 30 or more and 100 or less. Thus, the second dielectric of the transmissive window 112 may be zirconia having a permittivity of 30, or titanium oxide having a permittivity of 100. Sapphire may be used for the second dielectric of the transmissive window 112 depending on the first dielectric.
Furthermore, specifically, the permittivity εr of the second dielectric of the transmissive window 112 may be 3 times or more and 4 times or less than the permittivity of the first dielectric of the ceiling plate 111 since this range may further sufficiently prevent the electromagnetic field from being diffused to the outer edge outside the transmissive window 112. Thus, the transmissive window 112 may be formed of zirconia having a permittivity of 30 to 40.
As described above, according to the plasma processing apparatus 100 of the present embodiment, the transmissive window 112 made of a high permittivity material is provided at a location where the electric field is to be concentrated in the ceiling plate 111 constituting the ceiling wall of the processing container 1. That is, the second dielectric of the transmissive window 112 is formed of a high permittivity material having a higher permittivity than the permittivity of the first dielectric of the ceiling plate 111. Thus, it is possible to confine the electric field of microwaves in the transmissive window 112, and thus, to prevent the propagation of microwaves outward of the transmissive window 112. Accordingly, it is possible to reduce the electric field intensity at the outer edge outside the transmissive window 112.
According to the present disclosure in some embodiments, it is possible to prevent electromagnetic waves from propagating inside a ceiling plate that constitutes a ceiling wall of a processing container included in a plasma processing apparatus.
The plasma processing apparatus according to the embodiments disclosed herein should be considered to be exemplary and not limitative in all respects. The embodiments may be modified and improved in various forms without departing from the scope of the appended claims and gist thereof. The matters described in the above multiple embodiments may have other configurations to the extent that they are not contradictory, and may be combined to the extent that they are not contradictory.
The plasma processing apparatus of the present disclosure may be applied to a radial line slot antenna apparatus.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-008793 | Jan 2022 | JP | national |
