Apparatus for plasma processing

Abstract

The antenna includes an inner structure, an outer structure, and a plurality of interconnect structures coupling the inner structure to the outer structure, the plurality of interconnect structures being axially symmetric about a center of the antenna, and each interconnect structure having an azimuth component of at least 30 degrees.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority and the filing date of U.S. Non-Provisional Patent Application No. 17 / 649,823, filed February 3, 2022, the entirety of which is incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to semiconductor processing techniques and, in a particular embodiment, to an apparatus for emitting electromagnetic waves in a plasma processing system to process a substrate in the plasma processing system. [Background technology]

[0003] Plasma processing is widely used in the semiconductor industry in the manufacture and fabrication of high density microcircuits. In a plasma processing system, electromagnetic waves radiated into a plasma chamber generate an electromagnetic field. The generated electromagnetic field heats electrons in the chamber. The heated electrons ignite a plasma to process substrates in processes such as etching, deposition, oxidation, sputtering, etc. An antenna is used to generate the plasma in the plasma chamber and can be capacitively or inductively coupled to the plasma.

[0004] A non-uniform electromagnetic field in a plasma processing chamber results in a non-uniform plasma, which results in non-uniform processing of the substrate due to different portions of the substrate being processed with plasma of different densities. Therefore, an apparatus and system for improving the uniformity of the electromagnetic field in a plasma processing system is desirable. To reduce maintenance costs, an antenna that does not require calibration or adjustment to maintain the uniformity of the electromagnetic field is desirable. Summary of the Invention

[0005] In one embodiment, an antenna for plasma processing includes an inner structure, an outer structure, and a plurality of interconnect structures coupling the inner structure to the outer structure, the plurality of interconnect structures being axially symmetric about a center of the antenna, each interconnect structure having an azimuthal component of at least 30 degrees.

[0006] According to another embodiment, an antenna for plasma processing includes a conductive inner structure, a conductive outer structure, and a conductive interconnect structure coupling the conductive inner structure to the conductive outer structure, the conductive interconnect structure having a plurality of axially symmetric cutouts, each of the axially symmetric cutouts having a curved shape in a top view.

[0007] According to yet another embodiment, an apparatus for a plasma processing system includes a radiating structure coupleable to a current supply, the radiating structure being a conductive plate having a plurality of axially symmetric notches, the axially symmetric notches having respective azimuthal components of at least 30 degrees; a plasma chamber coupled to the radiating structure; and a dielectric structure disposed between the radiating structure and the plasma chamber.

[0008] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure, as claimed. [Brief description of the drawings]

[0009] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0010] [Figure 1] 1 is a diagram of a plasma processing system according to one embodiment. [Diagram 2] FIG. 2 is a perspective view of a radiating structure according to one embodiment. [Diagram 3] FIG. 2 is a perspective view of a radiating structure according to one embodiment. [Figure 4]FIG. 2 is a perspective view of a radiating structure according to one embodiment. [Diagram 5] FIG. 2 is a perspective view of a radiating structure according to one embodiment. [Figure 6] FIG. 2 is a perspective view of a radiating structure according to one embodiment. [Figure 7] FIG. 2 is a perspective view of a radiating structure according to one embodiment. [Figure 8] FIG. 2 is a top view of a radiating structure of one embodiment. [Figure 9] FIG. 2 is a top view of a radiating structure of one embodiment. [Figure 10] FIG. 1 is a schematic diagram of an inductively coupled plasma structure of one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Corresponding numerals and symbols in different drawings generally refer to corresponding parts unless otherwise indicated. The drawings are drawn to clearly show relevant aspects of the embodiments and are not necessarily drawn to scale. The edges of features drawn in the drawings do not necessarily indicate the ends of the extents of the features.

[0012] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Detailed descriptions of the making and use of various embodiments are provided below. It should be understood, however, that the various embodiments described herein may be applied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the various embodiments and should not be construed as limiting in scope.

[0013] References in the framework of this specification to "one embodiment" or "one embodiment" are intended to indicate that a particular configuration, structure, or feature described with respect to that embodiment is included in at least one embodiment. Thus, phrases such as "in one embodiment" or "in one embodiment" that may appear in one or more places in this specification do not necessarily refer to one and the same embodiment. Furthermore, particular features, structures, or features may be combined in any suitable manner in one or more embodiments.

[0014] Although aspects of the invention are described primarily in the context of radiative structures in plasma processing systems, aspects of the invention can be applied to fields other than the semiconductor industry as well. Plasmas can be used to treat and modify surface properties through functionalization. For example, plasmas can convert hydrophobic surfaces to hydrophilic surfaces to prepare surfaces for paint deposition. Furthermore, aspects of the invention are not limited to plasmas. For example, RF can be used to defrost frozen foods or to dry textiles, food, wood, etc. In these various instances, and across industries, a uniform oscillating magnetic field as disclosed herein is advantageous.

[0015] References used herein are provided merely for convenience and therefore do not define the scope of protection or the region of the embodiments. According to one or more embodiments of the present disclosure, the plasma generation system may include a radiating structure (also referred to as an antenna or plate antenna) that is a rigid unibody structure with discrete axial symmetry (e.g., n-fold symmetry for a rotation of an angle 360° / n around a central axis, where n is an integer). It is desirable to use a rigid unibody radiating structure to generate a uniform plasma field because the rigid unibody radiating structure maintains its shape and relative position with respect to the plasma generation system. This reduces the time required to orient or calibrate the radiating structure, thus saving the associated costs. In an embodiment, the unibody structure is a structure that is effectively a rigid unitary body. An example of a unibody structure is a structure machined from a single metal stock. However, the unibody structure may also be manufactured by joining sub-parts together using either physical or chemical methods to achieve a rigid unitary structure.

[0016] Figure 1 illustrates a diagram of a plasma processing system 100 in one embodiment. The plasma processing system 100 includes an RF source 102 (also referred to as an RF generator), a radiating structure 104, a plasma chamber 106, and an optional dielectric plate 114 (also referred to as a dielectric structure), which may (or may not) be arranged as shown in Figure 1. In some embodiments, the dielectric structure comprises air. Additionally, the plasma processing system 100 may include additional components not depicted in Figure 1.

[0017] In an embodiment, the RF source 102 includes an RF power supply that may include a generator circuit and a matching circuit (not shown). The RF source 102 is coupled to the radiating structure 104 via a feed structure 103. The RF source 102 feeds a traveling RF wave to the radiating structure 104. The traveling RF wave is transmitted (i.e., radiated) by the radiating structure 104 towards the plasma chamber 106.

[0018] In an embodiment, the feed structure 103 may include a transmission line such as a coaxial cable, an interface having conductive offsets 712 and 732 (see below and FIG. 7), or the like, or a combination thereof.

[0019] The plasma chamber 106 includes a substrate holder 108. As shown, a substrate 110 is placed on the substrate holder 108 to be processed. Optionally, the plasma chamber 106 may include a bias power supply 118 coupled to the substrate holder 108. The plasma chamber 106 may also include one or more pump outlets 116 for removing by-products from the plasma chamber 106 by selective control of gas flow rates therein. In an embodiment, the pump outlets 116 are located near (e.g., below / around) the substrate holder 108 and the substrate 110.

[0020] In an embodiment, the radiating structure 104 is separated from the plasma chamber 106 by a dielectric plate 114 made of a dielectric material. The dielectric plate 114 separates the low pressure environment in the plasma chamber 106 from the outside atmosphere. It should be understood that the radiating structure 104 can be located directly adjacent to the plasma chamber 106 or the radiating structure 104 can be separated from the plasma chamber 106 by air. In an embodiment, the dielectric plate 114 is selected to minimize reflection of RF waves from the plasma chamber 106. In another embodiment, the radiating structure 104 is embedded within the dielectric plate 114.

[0021] In one embodiment, the radiating structure 104 couples RF power from the RF source 102 into the plasma chamber 106 to process the substrate 110. Specifically, the radiating structure 104 radiates electromagnetic waves in response to a traveling RF wave being provided from the RF source 102. The radiated electromagnetic waves enter the plasma chamber 106 from the atmosphere side (i.e., the radiating structure 104 side) of the dielectric plate 114. The radiated electromagnetic waves generate an electromagnetic field in the plasma chamber 106. The generated electromagnetic field ignites and sustains a plasma 112 by transferring energy to free electrons in the plasma chamber 106. The plasma 112 can be used, for example, to selectively etch or deposit material on the substrate 110.

[0022] 1, the radiating structure 104 is shown as being external to the plasma chamber 106. However, in embodiments, the radiating structure 104 may be located inside the plasma chamber 106.

[0023] 2 illustrates a perspective view of a radiating structure 104 according to some embodiments. The radiating structure 104 may also be referred to as an antenna or an antenna plate.

[0024] To provide uniformity in the generated plasma, it is advantageous for the antenna of an inductively coupled plasma (ICP) or capacitively coupled plasma (CCP) system to have discrete axial symmetry.

[0025] In an embodiment, the radiating structure 104 is formed as having a rigid unibody structure. Thus, the radiating structures 104 can be manufactured with increased consistency in shape and size between different radiating structures 104.

[0026] For example, the radiating structure 104 can be machined from a single plate of conductive material, which can increase the repeatability of the process. For example, the radiating structure 104 may incur reduced distortion during installation, for example, in the plasma processing system 100, due to being a rigid unibody. This can reduce the time for calibration of the radiating structure 104 after installation.

[0027] In an embodiment, the radiating structure 104 is a conductive plate comprising copper, aluminum, iron, nickel, cobalt, etc., or combinations thereof.

[0028] In some embodiments, the radiating structure 104 has a vertical thickness of greater than 10 mm, which can help avoid deformation during installation.

[0029] In some embodiments, the conductive portion of the radiating structure 104 has a vertical thickness of less than 10 mm, for example in the range of 2 mm to 5 mm. In embodiments, the radiating structure 104 includes a conductive portion mounted on a support structure that is a dielectric material (e.g., plastic, etc.). For example, the radiating structure 104 may be a metal layer bonded to a PC board, where the PC board is the dielectric support structure. The support structure provides increased rigidity, which increases process repeatability and avoids deformation during installation.

[0030] In an embodiment, the support structure has a vertical thickness of at least 5 mm, for example in the range of 5 mm to 8 mm. The radiating structure 104 may be mechanically or chemically attached to the support structure. This may be advantageous to increase the repeatability of the manufacturing process of the radiating structure 104 while reducing costs. For example, the conductive portions of the radiating structure 104 may be formed using photographic techniques to achieve very high repeatability and precision, whereas a dielectric support structure (e.g., plastic) may have a greater vertical thickness and be manufactured with less precision than the conductive portions of the radiating structure.

[0031] In an embodiment, the radiating structure 104 includes an inner ring 210 (also referred to as the inner structure), an outer ring 230 (also referred to as the outer structure), and two spiral arms 220 (also referred to as the radiating elements or interconnect structures) between the inner ring 210 and the outer ring 230. The spiral arms 220 are separated by slits 250 (also referred to as cutouts or axially symmetric cutouts), which may be filled with air, vacuum, or a dielectric material.

[0032] 2, the spiral arm 220 includes two Archimedean spirals. It should be understood that the number of spiral arms and the type of spiral (e.g., Archimedean spiral) are non-limiting and additional spiral arms and types may be used as well.

[0033] In an embodiment, the spiral arms 220 generate a high density plasma 112 (see FIG. 1 above) with discrete axial symmetry and with azimuthal symmetry. The plasma 112 may be generated using a predominantly inductively coupled electric field or a predominantly capacitively coupled electric field. Inputs and outputs for generating electromagnetic fields are connected to the inner ring 210 and the outer ring 230. In an embodiment, one or more current supplies are connected to the inner ring 210 and one or more current supplies are connected to the outer ring 230.

[0034] For example, if the radiating structure 104 has two spiral arms 220 as shown in FIG. 2 , a first current supply is connected to the inner ring 210 where the first spiral arm 220 meets the inner ring 210, a second current supply is connected to the inner ring 210 where the second spiral arm 220 meets the inner ring 210, a third current supply is connected to the outer ring 230 where the first spiral arm 220 meets the outer ring 230, and a fourth current supply is connected to the outer ring 230 where the second spiral arm 220 meets the outer ring 230.

[0035] In one embodiment, the first current supply and the second current supply are driven (e.g., connected to respective current inputs) and the third current supply and the fourth current supply are connected to a reference ground, either directly or via a capacitor, which may be variable.

[0036] In one embodiment, the first and second current supplies are connected to a reference ground, either directly or through a capacitor that may be variable, and the third and fourth current supplies are driven (e.g. connected to their respective current inputs). In an embodiment, the relative phase of the current drives of the first and second current supplies to the third and fourth current supplies is 180°, whereas the amplitudes are the same. Such an embodiment increases the induced electric field generated by the radiating structure 104. In other embodiments, the relative phase and the relative amplitude have different values ​​in order to sinusoidally vary the charge on the radiating structure 104, and thus the capacitive coupling between the radiating structure and the plasma.

[0037] In one embodiment, the first and second current supplies are powered (e.g., connected to respective current inputs) and the third and fourth current supplies have no electrical connection, such that the inner ring 210 is coupled to the current inputs and the outer ring 230 has no electrical connection to the exterior of the radiating structure 104. Leaving the outer ring 230 without an electrical connection may be advantageous for ignition at low pressures.

[0038] In an embodiment, the slits 250 are wound continuously from the inner ring 210 to the outer ring 230. The slits 250 may have an azimuthal component of at least 30 degrees. In an embodiment, the slits 250 have the same shape and occupy the same volume. The length of the slits 250 may be less than 1 / 2 wavelength of the electromagnetic radiation generated by the radiating structure 104. For example, if the excitation frequency of the radiating structure 104 is in the range of 5 MHz to 100 MHz, the length of the slits 250 may be in the range of 20 m to 1 m. The length of the slits 250 may be smaller depending on the details of the circuit driving the radiating structure 104 (see below and FIG. 9). For example, with the addition of a capacitor at the end of the circuit driving the radiating structure 104, the length of the slits 250 may be 1 / 10 of the electromagnetic radiation generated by the radiating structure 104.

[0039] In embodiments, the slits 250 are separated from one another by the spiral arms 220, and the slits 250 do not connect to one another throughout the spiral arms 220, the inner ring 210, or the outer ring 230. In some embodiments, both ends of the slits 250 are closed. In other embodiments, at least one end of the slits 250 is open.

[0040] In some embodiments, attachment points 260 are located on the inner ring 210, the outer ring 230, or both. The attachment points 260 may be used to couple a power feed rod or an antenna support to the inner ring 210 or the outer ring 230. The attachment points 260 may be spaced equidistantly along the inner ring 210 and the outer ring 230, and equidistantly spaced from the inner and outer edges of the inner ring 210 or the outer ring 230, respectively. However, any suitable pattern for the attachment points 260 may be used. In other embodiments, the radiating structure 104 does not have attachment points and is secured to the antenna support or power feed rod by other means, such as by clamps, soldering, etc.

[0041] In an embodiment, the radiating structure 104 radiates an electromagnetic field towards the plasma chamber 106, which generates an azimuthally symmetric high density plasma 112 using primarily inductively coupled electric fields or primarily capacitively coupled electric fields (see FIG. 1 above).

[0042] In an embodiment, the radiating structure 104 includes helical arms 220 that create azimuthal symmetry as disclosed herein.

[0043] In an embodiment, the excitation frequency of the radiating structure 104 is in the radio frequency range (e.g., 10-400 MHz, e.g., 13 MHz), although this is not limiting and other frequency ranges may be contemplated as well (e.g., in the range of 5 MHz to 100 MHz). For example, the inventive aspects disclosed herein are equally applicable to applications in the microwave frequency range.

[0044] In an embodiment, the operating frequency of the radiating structure 104 is in the range of 5 to 100 megahertz (MHz). In an embodiment, the power delivered by the radiating structure 104 is in the range of 10 to 5000 watts (W), which is determined by various factors such as the distance from the radiating structure 104, the impedance value, etc.

[0045] In an embodiment, the radiating structure 104 includes a radiating element, such as a helical arm 220. The radiating element may be an element having discrete, axially symmetric arms electrically connected to the RF source 102.

[0046] In an embodiment, the radiating elements have the same shape and are arranged about a central axis such that there is N-fold symmetry upon rotation, where N is an integer greater than one.

[0047] In an embodiment, the elements of the radiating structure 104 in which the magnetic field is high and the elements of the radiating structure 104 in which the electric field is high are arranged around a central axis of symmetry. In an embodiment, the central axis of symmetry is perpendicular to the dielectric plate 114 (see FIG. 1 above). In an embodiment in which the dielectric plate 114 is disk-shaped, the central axis of symmetry passes through the center of the disk. The elements of the radiating structure 104 are arranged such that rotating all the elements around the axis of symmetry by an angle equal to 2π divided by an integer greater than 1 does not change the shape.

[0048] In an embodiment, the radiating structure 104 is a conductive planar closed ring structure having a plurality of spiral arms 220. The spiral arms 220 have n-fold symmetry about an axis passing through the center point 206 of the radiating structure 104. Although the number of spiral arms 220 is shown in FIG. 2 as being two, the number of spiral arms 220 is non-limiting and can be any number greater than one (e.g., between 2 and 16).

[0049] In an embodiment, the radiating structure 104 is a monolithic structure. In such an embodiment, the radiating structure 104 includes a closed inner ring 210 and a closed outer ring 230, which provide a mechanical connection to hold the helical arms 220 together into a single unit.

[0050] In an embodiment, the radiating structure 104 is a conductive plate with multiple axially symmetric spiral cutouts forming multiple spiral arms 220. In an embodiment in which the radiating structure 104 is formed from a conductive plate, assembly and mechanical misalignment of the radiating structure is minimized due to the typically tight tolerances in the fabrication and manufacturing of the radiating structure 104. Advantageously, such a structure provides a more robust and repeatable electromagnetic wave. Furthermore, the design of the radiating structure 104 provides scaling to address multiple radial zones for the generated electromagnetic field.

[0051] In an embodiment, the boundaries of the spiral arms 220 relative to the inner ring 210 are symmetric about the inner ring 210 and the boundaries of the spiral arms 220 relative to the outer ring 230 are symmetric about the outer ring 230 .

[0052] In an embodiment, each end of each spiral arm 220, measured from the center of each spiral arm 220, has a different radius.

[0053] In an embodiment, each spiral arm 220 has a linear distance between its ends. In such an embodiment, the linear distances of most of the spiral arms 220 are the same or similar length.

[0054] In an embodiment, the end points where each spiral arm 220 meets the outer ring 230 are disposed at different angles measured from the center point 206 of the radiating structure 104 to a tangent at the end point (ie, at the outer ring).

[0055] In an embodiment, the arrangement of the spiral arms 220 includes arranging the spiral arms 220 such that the shape of the spiral arms 220 does not change when all of the spiral arms 220 are rotated about an axis of symmetry through an angle equal to 2π divided by an integer greater than 2. In one exemplary embodiment, the integer is equal to 8.

[0056] In an embodiment, the radiating structure 104 is semi-axisymmetric.

[0057] As shown, the spiral arm 220 has a design corresponding to an Archimedean spiral forming a helical antenna. However, the design of the radiating structure 104 is not limiting. For example, in an embodiment, the spiral arm 220 may be in the shape of a logarithmic spiral forming a helical antenna.

[0058] In embodiments, the radiating structures disclosed herein provide a uniform electromagnetic field within the plasma chamber 106. The uniform electromagnetic field provides a uniform distribution of density of the plasma 112 and therefore uniform substrate processing in the plasma.

[0059] In an embodiment, the spiral arms 220 are geometrically wound in both radial and azimuth directions. In an embodiment, the spiral arms 220 are arranged in a nested manner.

[0060] In an embodiment, each of the spiral arms 220 has the same shape, length, and volume as the remainder of the spiral arms 220 .

[0061] The radiating structure 104 may be manufactured by one or more manufacturing techniques, such as machining, casting, etching, electroforming, 3D metal printing, or a combination thereof. Different manufacturing techniques may offer different advantages, such as the desired plate thickness, materials or coatings used, and properties, e.g., shape, weight, coefficient of thermal expansion, etc., of the radiating structure 104.

[0062] In some embodiments, the radiating structure 104 is manufactured by a machining process. Machining is used to cut a metal plate to a desired thickness and remove portions to form a desired pattern (e.g., the pattern of the radiating structure shown in Figures 2-6). In some embodiments, the radiating structure 104 formed by machining may have a thickness in the range of 2 mm to 20 mm, and the radiating structure 104 may be mounted on a dielectric support structure to provide increased mechanical rigidity.

[0063] In some embodiments, machining is used to form the radiating structure 104 from copper or a copper alloy. The use of copper or a copper alloy for the machining process allows for precise shapes and high conductivity, e.g., 4×10 7 S / m~6×10 7 A radiating structure 104 may be provided having a conductivity in the range of S / m or a conductivity in the range of 100% IACS to 50% IACS.

[0064] In some embodiments, machining is used to form the radiating structure 104 from aluminum or an aluminum alloy. Using aluminum or an aluminum alloy for the machining process can provide the radiating structure 104 with a precise shape and low weight due to the low density of aluminum. For example, the weight of the radiating structure 104 may be in the range of 2 kg to 4 kg, or the specific density of the radiating structure material may be in the range of 2.6 to 2.8.

[0065] In some embodiments, machining is used to form the radiating structure 104 from an iron-nickel alloy or an iron-nickel-cobalt alloy. By using an iron-nickel alloy or an iron-nickel-cobalt alloy for the machining process, the process allows for precise geometry and 10×10 -6 m / (mC)~15×10 -6 m / (mC) range or 0 / K~5×10 -6 The radiating structure 104 may be provided with a low coefficient of thermal expansion, such as a coefficient of thermal expansion in the range of 1 / K. Additionally, the use of iron-nickel or iron-nickel-cobalt alloys for the machining process may enable plating of the radiating structure 104, for example with a gold or silver coating, to be applied using a suitable technique, such as electroplating or electroless plating.

[0066] In some embodiments, the radiating structure 104 is manufactured by a casting process. Molten metal is poured into a mold having a desired pattern to form a radiating structure having a desired shape (e.g., the pattern of the radiating structure shown in Figures 2-6). Casting can be less expensive than other manufacturing techniques, such as machining, etching, electroforming, etc. In some embodiments, the radiating structure 104 formed by casting may have a thickness in the range of 3 mm to 25 mm, and the radiating structure 104 may be mounted on a dielectric support structure to provide increased mechanical rigidity.

[0067] In some embodiments, casting is used to form the radiating structure 104 from a copper alloy. Using a copper alloy for the casting process can provide the radiating structure 104 at a low cost and with high conductivity, such as that described above for radiating structures formed using machining in a copper alloy.

[0068] In some embodiments, casting is used to form the radiating structure 104 from an aluminum alloy. Using an aluminum alloy for the casting process can provide the radiating structure 104 at a low cost and with a low weight due to the low density of aluminum, such as the weights discussed above for radiating structures formed using machining of aluminum or aluminum alloys.

[0069] In some embodiments, casting is used to form the radiating structure 104 from an iron-nickel alloy or an iron-nickel-cobalt alloy. Using an iron-nickel alloy or an iron-nickel-cobalt alloy for the casting process can provide the radiating structure 104 at a low cost and with a low thermal expansion coefficient, such as those described above for a radiating structure formed using machining on an iron-nickel alloy or an iron-nickel-cobalt alloy. Additionally, using an iron-nickel alloy or an iron-nickel-cobalt alloy for the casting process can enable plating of the radiating structure 104, for example with a gold or silver coating, to be applied using a suitable technique, such as electroplating or electroless plating.

[0070] In some embodiments, the radiating structure 104 is fabricated by an etching process. A desired pattern (e.g., the pattern of the radiating structure shown in Figures 2-6) to form a radiating structure having a desired shape is printed (e.g., by exposure to light) onto a photoresist on a thin metal plate. The areas of the photoresist that were not exposed are removed to expose the regions of the metal plate, and then the exposed areas of the metal plate are removed with a suitable etchant (e.g., wet etching with an acidic solution). Etching can be useful for forming thinner radiating structures than other manufacturing techniques such as machining, casting, and electroforming. In some embodiments, the radiating structure 104 formed by etching may have a thickness in the range of 0.1 mm to 2 mm, and the radiating structure 104 may be mounted on a dielectric support structure to provide mechanical rigidity.

[0071] In some embodiments, etching is used to form the radiating structure 104 from a copper alloy. Using a copper alloy for the etching process can provide the radiating structure 104 with a thinner thickness and higher conductivity, such as that described above for radiating structures formed using machining in copper or copper alloys.

[0072] In some embodiments, etching is used to form the radiating structure 104 from an aluminum alloy. Using an aluminum alloy for the etching process can provide the radiating structure 104 with a thinner thickness and lower weight due to the low density of aluminum, such as the weights discussed above for radiating structures formed using machining in aluminum or aluminum alloys.

[0073] In some embodiments, etching is used to form the radiating structure 104 from an iron-nickel alloy or an iron-nickel-cobalt alloy. Using an iron-nickel alloy or an iron-nickel-cobalt alloy for the etching process can provide the radiating structure 104 with a thinner thickness and a lower thermal expansion coefficient, such as those described above for radiating structures formed using machining in an iron-nickel alloy or an iron-nickel-cobalt alloy. Additionally, using an iron-nickel alloy or an iron-nickel-cobalt alloy for the etching process can enable plating of the radiating structure 104, for example with a gold or silver coating, to be applied using a suitable technique, such as electroplating or electroless plating.

[0074] In some embodiments, the radiating structure 104 is fabricated by an electroforming process. In electroforming, a desired thickness of metal is electrodeposited on a conductive model having a desired shape (e.g., the pattern of the radiating structure shown in Figures 2-6). In some embodiments, the conductive model is formed by fabricating a desired shape from a non-conductive material (e.g., plastic, glass, etc.) and then depositing a conductive layer on the non-conductive material. The conductive layer can be chemically deposited using a vacuum deposition technique such as sputtering. After the desired thickness of metal is electrodeposited on the conductive model to form the radiating structure 104, the conductive model is removed from the electroformed radiating structure 104 using a mechanical or chemical separation method. In some embodiments, the radiating structure 104 formed by machining may have a thickness in the range of 0.1 mm to 3 mm, and the radiating structure 104 may be mounted on a dielectric support structure to provide increased mechanical rigidity.

[0075] In some embodiments, electroforming is used to form the radiating structure 104 using a copper alloy, which can provide the radiating structure 104 with thinner thicknesses, precise shapes, and high conductivity, such as those discussed above for radiating structures formed using machining in copper or copper alloys.

[0076] In some embodiments, electroforming is used to form the radiating structure 104 using an aluminum alloy, which can provide the radiating structure 104 with a smaller thickness, precise shape, and low weight due to the low density of aluminum, such as the weights discussed above for radiating structures formed using machining in aluminum or aluminum alloys.

[0077] In some embodiments, electroforming is used to form the radiating structure 104 using an iron-nickel or iron-nickel-cobalt alloy, which can provide the radiating structure 104 with a thinner thickness, precise shape, and low thermal expansion coefficient, such as those described above for radiating structures formed using machining into an iron-nickel or iron-nickel-cobalt alloy. Additionally, forming the iron-nickel or iron-nickel-cobalt alloy using an electroforming process can enable plating of the radiating structure 104, for example with a gold or silver coating, to be applied using a suitable technique, such as electroplating or electroless plating.

[0078] In some embodiments, the radiating structure 104 is manufactured by a 3D metal printing process. 3D metal printing can allow for complexity in the pattern of the radiating structure 104 without increasing costs, such as for creating cooling channels in the radiating structure 104.

[0079] The radiating structures of the present disclosure (e.g., radiating structure 104 as shown in FIG. 2) may be distinguished from other structures such as Faraday shields. Generally, a Faraday shield is composed of a metal plate with a slit (e.g., a slit with straight sidewalls) perpendicular to the radio frequency current element that may be located directly above the Faraday shield. The slit may extend from the center of the plate to the edge of the plate. The Faraday shield may be sandwiched between the powered portion of the antenna and the plasma to reduce the sheath electric field (electric field with polarization perpendicular to the sheath edge). To be effective, the Faraday shield is typically grounded and, unlike the radiating structures of the present disclosure, is generally not driven by an RF source.

[0080] As mentioned above, a typical Faraday cage has a straight slit that runs from the center of the Faraday cage to the edge of the Faraday cage. However, a radiating structure of the present disclosure (e.g., radiating structure 104) may have a slit 250 with curved sidewalls (see FIG. 2 above) that have a significant azimuthal component, such as an azimuthal component of at least 30 degrees. This azimuthal component may be a significant difference between a radiating structure of the present disclosure and a typical Faraday cage.

[0081] 3 shows a perspective view of a radiating structure 300 according to some embodiments. The radiating structure 300 comprises a central disk 310 (also referred to as an inner structure) at the center of the radiating structure 300 that connects to the helical arms 220. In some embodiments, the central disk 310 is connected to a single current supply, for example attached to the center 306 of the central disk 310.

[0082] FIG. 4 shows a perspective view of a radiating structure 400 according to some embodiments. In the radiating structure 400, the inner ring 410 and the outer ring 430 are separated by an additional slit 452, so that each spiral arm 220 is separate (electrically insulated) from each other. This may help to restrict current flow along each spiral arm 220 in a single azimuthal direction from one respective end of each spiral arm 220 to the respective opposite end, which may allow inductive coupling between the radiating structure 400 and the generated plasma 112 (see FIG. 1 above). Since the additional slit 452 separates the spiral arms 220 and the respective attached segments of the inner ring 410 and the outer ring 430 from each other, additional dielectric supports may be used to hold the radiating structure 400 together. For example, the slit 250 or the additional slit 452 may be filled with a dielectric material.

[0083] 5 shows a perspective view of a radiating structure 500 having an eight-fold symmetric configuration, according to some embodiments. The radiating structure 500 has eight spiral arms 220 extending between the inner ring 210 and the outer ring 230 of the radiating structure 500, and eight slits 250 between each of the spiral arms 220. In other embodiments, the radiating structure 500 may have any suitable number of spiral arms 220 and slits 250, for example, between 2 and 32 spiral arms 220 and slits 250. In an embodiment in which the generated plasma is used to process a substrate having a diameter of 300 mm, the number of spiral arms 220 is in the range of 2 to 16.

[0084] FIG. 6 illustrates a perspective view of a radiating structure 600 according to some embodiments. In the radiating structure 600, the inner ring 610 and the outer ring 630 are polygons with straight sides. In the example illustrated in FIG. 6, the inner ring 610 and the outer ring 630 are octagons each with eight sides, although the inner ring 610 and the outer ring 630 may each have any suitable number of sides, for example, between three and twelve sides. In some embodiments, the sides of the inner ring 610 and the outer ring 630. In other embodiments, the sides of the inner ring 610 and the outer ring 630 are curved.

[0085] In some embodiments, the radiating structure 600 has two spiral arms 220 and two slits 250 extending between the inner ring 610 and the outer ring 630. In other embodiments, the radiating structure 600 has any suitable number of spiral arms 220 and slits 250, for example, between 2 and 32 spiral arms 220 and slits 250. In some embodiments, the spiral arms 220 have curved sides. In other embodiments, the spiral arms 220 are comprised of a series of respective straight line segments arranged in a spiral pattern.

[0086] 7 shows a perspective view of a radiating structure 700 according to some embodiments. The spiral arms 220 of the radiating structure 700 lie in a separate plane from the inner ring 710 and the outer ring 730. In some embodiments, the inner ring 710 is connected to each spiral arm 220 by a respective conductive offset 712, and the outer ring 730 is connected to each spiral arm 220 by a respective conductive offset 732. In some embodiments, the inner ring 710 and the outer ring 730 lie in the same plane. In other embodiments, the inner ring 710 and the outer ring 730 lie in different planes from each other and different from the plane of the spiral arms 220.

[0087] FIG. 8 shows a top view of an embodiment of a radiating structure 800 having an inner radiating structure 802 and an outer radiating structure 804. The inner radiating structure 802 and the outer radiating structure 804 are concentric conductive ring structures with a helical cutout 850 separating the helical arms 820. The inner radiating structure 802 is located within the inner ring cutout of the outer radiating structure 804. In some embodiments, the inner radiating structure 802 is on the same plane as the outer radiating structure 804 and has the same center point 806. In other embodiments, the inner radiating structure 802 and the outer radiating structure 804 are on parallel planes with a separation distance, for example, in the range of 1 mm to 30 mm. A separation distance between the inner radiating structure 802 and the outer radiating structure 804 that is greater than 30 mm may be disadvantageous because the coupling between the plasma 112 and either the inner radiating structure 802 or the outer radiating structure 804, whichever is farther from the plasma 112 (see FIG. 1 above), is almost negligible.

[0088] Each of the inner radiating structure 802 and the outer radiating structure 804 forms a helical antenna. Although the inner radiating structure 802 and the outer radiating structure 804 are shown having eight helical arms 820 and eight helical cutouts 850, the inner radiating structure 802 and the outer radiating structure 804 may have any suitable number of helical arms 820 and helical cutouts 850. For example, the inner radiating structure 802 may have two helical arms 820 and two helical cutouts 850 (see FIG. 2 above), and the outer radiating structure 804 may have eight helical arms 820 and eight helical cutouts 850.

[0089] 9 shows a top view of an embodiment of a radiating structure 900 having eight spiral arms 920 at different radial angles, according to some embodiments. The radial angle of the spiral arm 920 is measured between a first line and a second line, where the first line is between the center point of the spiral arm 920 and the point where the spiral arm 920 meets the inner ring 210 (i.e., the tangent at the meet point), and the second line is a tangent to the inner ring 210 at the meet point.

[0090] In an embodiment, the respective radial angles of each spiral arm 920 are in the range of 30°-80°, which is advantageous for proper operation of the radiating structure 900 to generate an azimuthally symmetric high density plasma 112 (see FIG. 1 above). A radial angle of 30° or more can provide an azimuth component of the spiral arm 920 that is greater than the radial component of the spiral arm 920. This is advantageous for generating a toroidal plasma that is efficient for inductively coupled plasma because the toroidal plasma allows electrons to travel in a circular motion in the toroidal plasma, reducing electron loss at the walls of the chamber 106.

[0091] As shown in FIG. 9, four of the spiral arms 920 have a first radial angle, and four of the spiral arms 920 have a second radial angle that is greater than the first radial angle, with the spiral arms 920 having the first radial angle alternating with the spiral arms 920 having the second radial angle. It should be understood that FIG. 9 is an example, and the number of spiral arms 920, as well as the relative magnitude and distribution of the radial angles, are non-limiting. For example, the radiating structure 900 may have two spiral arms 920 with a first radial angle, two spiral arms 920 with a second radial angle that is greater than the first radial angle, and four spiral arms 920 with a third radial angle that is less than the first radial angle. In other embodiments, the radial angles of each of the spiral arms 920 are the same, as shown for the spiral arms shown in FIGS. 2-8.

[0092] Figure 10 shows a schematic diagram of an inductively coupled plasma structure 1000 of one embodiment. The inductively coupled plasma structure 1000 includes an RF source 1002, a capacitor 1004, and a radiating structure 104, which may (or may not) be arranged as shown in Figure 10. Here, the RF source 1002 is shown as an AC power source. In an embodiment, the RF source 1002 is configured to supply a traveling RF wave to the radiating structure 104. In an embodiment, one or more of the capacitors 1004 are variable (e.g., varactors).

[0093] In an embodiment, the matching network includes an RF source 1002 coupled to the inner ring 210 of the radiating structure 104 via a capacitor 1004, a connection of the RF source 1002 to the capacitor 1004 coupled to a reference ground via another capacitor 1004, and an outer ring 230 of the radiating structure 104 coupled to a common RF ground 1062 via a capacitor 904. The matching network transforms the impedance looking into the matching network connected to the chamber 106 (see FIG. 1 above) to the same impedance (e.g., 50 ohms impedance) as the RF generator (e.g., RF source 1002) and the transmission line between the RF source 902 and the radiating structure 104. This allows the RF source 1002 to efficiently couple power to the radiating structure 104. The capacitor 1004 can also reduce noise in the circuit.

[0094] In another embodiment, the RF source 1002 is coupled to the outer ring 230 through a capacitor 1004, and the inner ring 210 is coupled to one or more common RF grounds 1062 through one or more respective capacitors 1004. The configuration of the radiating structure 104 and feed network is non-limiting and the configuration shown in Figure 10 is provided as an example.

[0095]

[0023] Exemplary embodiments of the present disclosure are summarized herein. Other embodiments can be seen throughout this specification and the claims.

[0096] Example 1. An antenna for plasma processing, the antenna comprising an inner structure, an outer structure, and a plurality of interconnect structures coupling the inner structure to the outer structure, the plurality of interconnect structures being axially symmetric about a center of the antenna, each interconnect structure having an azimuthal component of at least 30 degrees.

[0097] Example 2. The antenna of example 1, wherein the antenna is capable of being inductively or capacitively coupled to a plasma chamber.

[0098] Example 3. The antenna of example 1, wherein the top view of the inner structure and the outer structure is a ring, a disk, a polygon, or a circle.

[0099] Example 4. The antenna of example 1, wherein the antenna is a rigid unibody structure.

[0100] Example 5. The antenna of example 1, wherein each interconnect structure of the plurality of interconnect structures is electrically isolated from other interconnect structures of the plurality of interconnect structures.

[0101] Example 6. A system including the antenna of Example 1, the system comprising a radio frequency (RF) generator, a feed structure coupling the RF generator to the antenna, and a plasma chamber coupled to the antenna.

[0102] Example 7. The antenna according to example 1, wherein the resonant frequency of the antenna is 5 to 100 megahertz (MHz).

[0103] Example 8. The antenna of example 7, wherein the length of the interconnect structure is less than 1 / 2 wavelength of the resonant frequency.

[0104] Example 9. The antenna of example 1, wherein the antenna comprises a plurality of radial zones.

[0105] Example 10. An antenna for plasma processing, the antenna comprising: a conductive inner structure, a conductive outer structure, and a conductive interconnect structure coupling the conductive inner structure to the conductive outer structure, the conductive interconnect structure having a plurality of axially symmetric notches, each of the axially symmetric notches having a curved shape in a top view.

[0106] Example 11. The antenna of example 10, wherein at least one of the conductive inner structure, the conductive outer structure, and the conductive interconnect structure are on different planes.

[0107] Example 12. The antenna of example 10, wherein one of the conductive inner structure or the conductive outer structure is coupled to a current source, and the other of the conductive inner structure or the conductive outer structure is coupled to ground.

[0108] Example 13. The antenna of example 10, wherein one of the conductive inner structure or the conductive outer structure is coupled to a current source, and the other of the conductive inner structure or the conductive outer structure has no electrical connection.

[0109] Example 14. The antenna of example 10, wherein the conductive inner structure is coupled to a first current source and the conductive outer structure is coupled to a second current source.

[0110] Example 15. An apparatus for a plasma processing system, the apparatus including: a radiating structure coupleable to a current supply, the radiating structure being a conductive plate having a plurality of axially symmetric notches, the axially symmetric notches having respective azimuthal components of at least 30 degrees; a plasma chamber coupled to the radiating structure; and a dielectric structure disposed between the radiating structure and the plasma chamber.

[0111] Example 16 The apparatus of example 15, wherein the axially symmetric cutout comprises a helical shape.

[0112] Example 17. The apparatus of example 15, wherein the axisymmetric cutout has an azimuthal component of at least 30 degrees.

[0113] Example 18. The apparatus of example 15, wherein the number of axially symmetric notches in the plurality of axially symmetric notches is in the range of 2 to 16.

[0114] Example 19. The apparatus of example 15, further comprising a radio frequency (RF) generator and a feed structure coupling the RF generator to the radiating structure.

[0115] Example 20. The apparatus of example 15, wherein the radiating structure has a vertical thickness of greater than 10 mm.

[0116] Example 21. The antenna of example 1, wherein each of the inner structure and the outer structure comprises a rigid ring structure.

[0117] Example 22. An antenna for plasma processing, the antenna comprising: a conductive inner structure; a conductive outer structure; and a plurality of spiral arms coupling the inner structure to the outer structure, the plurality of spiral arms being conductive, and each of the plurality of spiral arms having a respective dielectric region between adjacent spiral arms of the plurality of spiral arms.

[0118] Example 23. The antenna of example 22, wherein the plurality of spiral arms are part of a rigid unibody structure.

[0119] Example 24. The antenna of Example 22, wherein the number of spiral arms in the plurality of spiral arms is in the range of 2 to 16.

[0120] Example 25. An antenna for plasma processing, the antenna comprising an inner structure, an outer structure, and an interconnect structure coupling the inner structure to the outer structure, the interconnect structure comprising a first spiral notch and a second spiral notch, the first spiral notch and the second spiral notch being symmetrical about a centerline of the interconnect structure.

[0121] Example 26. The antenna of example 25, wherein the first spiral cutout and the second spiral cutout are separated by a dielectric material.

[0122] Example 27. An antenna for plasma processing, the antenna comprising an inner structure, an outer structure, and a plurality of interconnect structures coupling the inner structure to the outer structure, the plurality of interconnect structures being arranged in a spiral configuration.

[0123] Example 28. The antenna of Example 27, including the spiral configuration having a first end of each interconnect structure coupled to an inner ring structure and a second end of each interconnect structure coupled to an outer ring structure.

[0124] Example 29. The antenna of Example 28, wherein the first end of each interconnect structure and the second end of each interconnect structure are positioned at different angles measured from a center point of the antenna.

[0125] Example 30. The antenna of example 28, wherein each end of each interconnect structure has a different radius when measured from the center of each interconnect structure.

[0126] Example 31. The antenna of example 28, wherein each end of each interconnect structure has a different radial angle when measured from the center of each interconnect structure.

[0127] Example 32. The antenna of example 28, wherein the radial angles of each interconnect structure are symmetrical.

[0128] Example 33. An antenna as described in Example 28, wherein each interconnect structure has a linear distance between the ends of each interconnect structure, and the linear distances of the majority of the multiple interconnect structures are the same or similar length.

[0129] Example 34. An antenna as described in Example 28, wherein the interconnect structure is a helical element and the helical elements are arranged such that the shape of the helical elements does not change during rotation of all of the helical elements around the axis of symmetry by an angle equal to 2π divided by an integer greater than 2.

[0130] Example 35. The antenna of example 34, wherein the integer is equal to 8.

[0131] Example 36. The antenna of example 34, wherein the helical element has 2, 3, 4, 8, or 16-fold symmetry.

[0132] While the present disclosure has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present disclosure, will be apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover any such modifications or embodiments.

Claims

1. 1. An antenna for plasma processing, the antenna comprising: An inner structure; An outer structure; a plurality of interconnect structures coupling the inner structure to the outer structure, the plurality of interconnect structures being axially symmetric about a center of the antenna, each interconnect structure having an azimuth component of at least 30 degrees.

2. The antenna of claim 1 , wherein the antenna is inductively or capacitively coupleable to a plasma chamber.

3. 10. The antenna of claim 1, wherein a top view of the inner structure and the outer structure is a ring, a disk, a polygon, or a circle.

4. The antenna of claim 1 , wherein the antenna is a rigid unibody structure.

5. The antenna of claim 1 , wherein each interconnect structure of the plurality of interconnect structures is electrically isolated from other interconnect structures of the plurality of interconnect structures.

6. A system comprising the antenna of claim 1, the system comprising: a radio frequency (RF) generator; a feed structure coupling the RF generator to the antenna; a plasma chamber coupled to the antenna.

7. 10. The antenna of claim 1, wherein the resonant frequency of the antenna is between 5 and 100 megahertz (MHz).

8. The antenna of claim 7 , wherein the length of the interconnect structure is less than one-half wavelength of the resonant frequency.

9. The antenna of claim 1 , wherein the antenna comprises a plurality of radial zones.

10. 1. An antenna for plasma processing, the antenna comprising: a conductive inner structure; an electrically conductive outer structure; a conductive interconnect structure coupling the inner conductive structure to the outer conductive structure, the conductive interconnect structure having a plurality of axially symmetric cutouts, each of the axially symmetric cutouts having a curved shape in a top view.

11. The antenna of claim 10 , wherein at least one of the inner conductive structure, the outer conductive structure, and the conductive interconnect structure are on different planes.

12. 11. The antenna of claim 10, wherein one of the inner conductive structure or the outer conductive structure is coupled to a current source and the other of the inner conductive structure or the outer conductive structure is coupled to ground.

13. 11. The antenna of claim 10, wherein one of the inner conductive structure or the outer conductive structure is coupled to a current source, and the other of the inner conductive structure or the outer conductive structure has no electrical connections.

14. The antenna of claim 10 , wherein the inner conductive structure is coupled to a first current source and the outer conductive structure is coupled to a second current source.

15. 1. An apparatus for a plasma processing system, comprising: a radiating structure coupleable to a current supply, said radiating structure being a conductive plate having a plurality of axially symmetric cutouts, said cutouts having respective azimuthal components of at least 30 degrees; a plasma chamber coupled to the radiating structure; 11. An apparatus comprising: a dielectric structure, the dielectric structure being disposed between the radiating structure and the plasma chamber.

16. The apparatus of claim 15 , wherein the axially symmetric cutout comprises a helical shape.

17. The apparatus of claim 15 , wherein the axisymmetric cutout has an azimuthal component of at least 30 degrees.

18. The apparatus of claim 15, wherein a number of axially symmetric notches in the plurality of axially symmetric notches ranges from 2 to 16.

19. a radio frequency (RF) generator; 16. The apparatus of claim 15, further comprising a feed structure coupling the RF generator to the radiating structure.

20. The apparatus of claim 15 , wherein the radiating structure has a vertical thickness of greater than 10 mm.

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