High Current Ribbon Inductor

Abstract

A method for forming a high current inductor utilizes a solid core material to form a ribbon inductor. In some embodiments, the method includes forming a central opening longitudinally through the solid core conductive material, the solid core conductive material having an outer diameter, the central opening forming an inner diameter of the solid core conductive material, a difference between the outer diameter and the inner diameter being a thickness of the ribbon conductor of the high current inductor, and removing a spiral portion of the solid core conductive material to form the ribbon conductor of the high current inductor, the width of the spiral portion forming a gap spacing between windings of the ribbon conductor.

Description

Technical Field

[0001] Embodiments of the present principle generally relate to semiconductor manufacturing.

Background Art

[0002] Inductors are used to assist in adjusting the load on high-power frequency generators that supply power to processing chambers in semiconductor production, along with other electronic elements such as capacitors. A matching network enables maximum power transfer between the generator and the processing chamber by maintaining an optimal load as seen from the generator. By automatically adjusting the matching impedance between the generator and the processing chamber, the matching network ensures maximum power transfer for different frequencies and different chamber loads. The inventors have noticed that during operation, the inductor in the matching network becomes very hot when exposed to high-current loads, thereby causing thermal / melting damage to the surrounding materials.

[0003] Therefore, the inventors have provided a method and apparatus for forming an inductor with excellent current handling capabilities.

Summary of the Invention

[0004] A method and apparatus for forming a high-current inductor are provided herein.

[0005] In some embodiments, a method for forming a high-current inductor includes forming a central opening that longitudinally penetrates a solid-core conductive material, wherein the solid-core conductive material has an outer diameter, the central opening forms the inner diameter of the solid-core conductive material, and the difference between the outer diameter and the inner diameter is the thickness of the ribbon conductor of the high-current inductor; and removing the spiral portion of the solid-core conductive material to form the ribbon conductor of the high-current inductor, wherein the width of the spiral portion forms a gap spacing between the windings of the ribbon conductor.

[0006] In some embodiments, the method includes: the thickness of the ribbon conductor of the high-current inductor being from about 0.060 inches to about 0.250 inches; the gap spacing being from about 0.250 inches to about 1.0 inch; the high-current inductor having an inductance of from about 50 nH to about 1000 nH; the high-current inductor having a length of from about 2 inches to about 20 inches; the inner diameter being from about 0.5 inches to about 5.0 inches; the outer diameter being from about 0.55 inches to about 5.25 inches; the solid-core conductive material being copper; the copper being silver-plated; placing an insert inside the high-current inductor; the insert having a second outer diameter substantially equal to the inner diameter; the insert being hollow and formed from a material having high thermal conductivity and low dielectric constant; the insert being configured to extract heat from the high-current inductor to the inner surface of the insert, and , said a coolant to flow do being configured to be able to flow over the entire inner surface; the high-current inductor operating at a power greater than 0 kilowatts and up to about 10 kilowatts; the high-current inductor operating at a frequency of from 1 MHz to about 300 MHz; and / or the high-current inductor having an inductance tolerance of less than 5%.

[0007] In some embodiments, the non-transitory computer-readable medium stores instructions that, when executed, cause a method for forming a high-current inductor, the method comprising: forming a central opening that longitudinally penetrates a solid-core conductive material, the solid-core conductive material having an outer diameter, the central opening forming an inner diameter of the solid-core conductive material, the difference between the outer diameter and the inner diameter being the thickness of the ribbon conductor of the high-current inductor; and removing a helical portion of the solid-core conductive material to form a ribbon conductor of the high-current inductor, the width of the helical portion forming a gap spacing between the turns of the ribbon conductor. In some embodiments, the non-transitory computer-readable medium can further include that the high-current inductor has an inductance of about 50 nH to about 1000 nH with an inductive tolerance of less than about 5%.

[0008] In some embodiments, an apparatus for providing inductance is a high-current inductor having a monolithic ribbon conductor formed by removing a central portion and a helical portion from a solid-core conductive material, the monolithic ribbon conductor having a helical shape, and can include one or more electrical connection points on a first end of the monolithic ribbon conductor and on a second end of the monolithic ribbon conductor. The high-current inductor is configured to operate with a current of up to 200 amperes or more and has an inductive tolerance of less than about 5%. In some embodiments, the apparatus can further include that the solid-core conductive material is copper, the high-current inductor is configured to operate with a power of 0 kilowatts to about 10 kilowatts or more, and / or the inductive value of the high-current inductor is in the range of about 50 nH to about 1000 nH.

[0009] Other further embodiments are disclosed below.

[0010] Embodiments of the present principle have been briefly summarized above and will be described in more detail below, but can be understood by referring to exemplary embodiments of the principle shown in the accompanying drawings. However, the accompanying drawings show only typical embodiments of the principle, and therefore, since the present principle may admit other equally effective embodiments, it should not be regarded as limiting the scope.

Brief Description of the Drawings

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Modes for Carrying Out the Invention

[0012] For ease of understanding, wherever possible, the same reference numbers are used to denote the same elements common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated into other embodiments without further elaboration.

[0013] This method and apparatus enable the formation of a ribbon inductor for high-power and high-current applications that can be produced with small inductance variations. The inductor is an important circuit component of a high-power RF impedance matching network used in semiconductor processing chambers and other high-power applications. The technology of this principle creates a ribbon inductor that enables the design of a high-power 10 kW RF matching network. Instead of fabricating the inductor using a lathe or coil winding machine with magnet wire, the ribbon inductor of this principle can be machined from a solid cylinder of conductive material. The resulting ribbon inductor can handle very high power (about 10 kW or more) and high current (about 200 A or more) with small inductance variations from one inductor to another, which is important in RF impedance matching network applications for filtering and impedance tuning purposes. Due to the small inductance variations, manufacturers can produce products with tighter tolerances and reproducible performance from product to product. Another advantage of this principle is an inductor that has an operating temperature up to 50% lower than conventional wound inductors.

[0014] Conventional inductors are manufactured using magnet wire or tubing and are wound on a lathe or coil winder. Conventional inductors cannot be used for high-current and high-power applications because the cross-sectional area of the wire or tubing used for winding is small, thereby increasing the resistance of the wire or tubing to high levels of current. When a high level of current is applied to a conventional inductor, significant heat is generated within the winding due to electrical resistance, leading to failures such as insulation breakdown (short circuit between wires) and thermal damage to surrounding components. The inventors have found that in conventional wound inductors, the windings between the turns always have some variation, which causes variation in the overall inductance value during the manufacture of the inductor. The inventors have also found that conventional wound inductors cannot carry high currents because the surface area of the wire or tubing used in conventional wound inductors is small. The inventors have discovered that the ribbon inductor of this principle can produce much higher power and higher current inductors within the same geometric volume as conventional low-power and low-current wound inductors while dramatically improving power handling and performance. The ribbon inductor of this principle can also be produced such that the variation in inductance between inductors is very small, making it possible to manufacture products with tight tolerances to obtain reproducible performance throughout a product line or within a product (e.g., a process chamber with multiple RF impedance matching networks).

[0015] FIG. 1 is a method 100 of forming a high power inductor. FIGS. 2-8 can be referred to in explaining method 100. In block 102, a central opening 302 is formed in the solid core conductive material 202. The solid core conductive material 202 can include a copper material or the like with a high conductivity (and low resistance to reduce heat problems), as shown in FIG. 200 of FIG. 2. The solid core conductive material 202 can have a length 206 of about 2 inches to about 20 inches. The solid core conductive material 202 can have an outer diameter (OD) 204 of about 0.55 inches to about 5.25 inches. The central opening 302 shown in FIG. 300 of FIG. 3 has an inner diameter (ID) 304 of about 0.5 inches to about 5.0 inches. The wall or coil thickness 306 is about 0.060 inches to about 0.250 inches. The central opening can be formed by drilling or cutting the solid core conductive material 202 from end to end, as shown in FIG. 3.

[0016] In block 104, the helical portion 402 of the solid core conductive material 202 is removed to form the ribbon conductor 512 (see FIG. 5). The helical portion 402 shown in FIG. 400 of FIG. 4 extends around the solid core conductive material 202 from the top 408 of the solid core conductive material 202 to the bottom 410 of the solid core conductive material 202 (over a length 206). The thickness of the helical portion 402 is the same as the coil thickness 306. The width 404 of the helical portion or "gap spacing" may be from about 0.250 inches to about 1.0 inches. The width 404 of the helical portion becomes the gap spacing 514 between the ribbon conductor windings after the helical portion 402 is removed (see FIG. 5). The gap spacing 514 between the turns determines at which frequency the self-capacitance of the inductor becomes like that of a transmission line (the inductor stops behaving like an inductor and instead behaves like a capacitor). In some embodiments, the gap spacing 514 is adjusted to increase the resonance cut-off frequency, which is much higher than the operating frequency, in order to control the self-capacitance point (the larger the gap spacing, the higher the resonance frequency). For example, when the matching network frequency is 40 MHz, by adjusting the gap spacing 514, the resonance cut-off frequency can be designed to be 80 MHz or higher. Further, the gap spacing 514 is generally much larger than that of a conventional wound inductor, thereby reducing the parasitic capacitance.

[0017] The coil pitch 416 can be appropriately controlled during manufacturing, thereby significantly reducing inductance variations. The coil pitch 416 is the distance between winding centers of the ribbon conductor measured between the turns. The coil pitch 416 can be adjusted to increase or decrease the number of turns in an inductor over a given length. The higher the operating frequency, the fewer turns are required in the inductor. In some embodiments, the resulting ribbon inductor can operate at 1 MHz to 300 MHz. In some embodiments, the resulting ribbon inductor can operate at 27 MHz to 200 MHz. The helical portion 402 can be removed by a cutting process or by an automated computer control process such as a computer numerical control (CNC) process. The width 406 of the ribbon conductor can be from about 0.5 inches to about 4.0 inches and can be adjusted based on the desired current value flowing through the ribbon conductor (the wider the ribbon width, the larger the current that becomes possible).

[0018] Embodiments according to this principle can be implemented in hardware, firmware, software, or any combination thereof. Further, embodiments can be implemented as instructions stored using one or more computer-readable media that can be read and executed by one or more processors. A computer-readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing platform, or a "virtual machine" running on one or more computing platforms). For example, a computer-readable medium can include any suitable form of volatile or non-volatile memory. In some embodiments, the computer-readable medium can include a non-transitory computer-readable medium.

[0019] Since the surface area of the ribbon conductor 512 is large, a very high current (for example, 200 A or more) can flow through the ribbon conductor 512, and better heat dissipation is also possible. After the removal of the spiral portion 402, the ribbon conductor 512 that also forms the basis of the ribbon inductor 516 is formed. The ribbon conductor 512 is formed from the spiral-shaped solid core conductive material 202. The ribbon conductor 512 is a "monolithic ribbon conductor" in that it is rigid and formed from a single material. In FIG. 500 of FIG. 5, the ribbon inductor 516 is undergoing some additional processing to shape the first end 504A and the second end 504B. The line 502 indicates the start / end point of the winding. In the example of FIG. 5, the ribbon inductor 516 is formed of three windings. The first winding starts at the first end 504A and ends at the first winding end 508. The second winding starts at the first winding end 508 and ends at the second winding end 510. The third winding starts at the second winding end 510 and ends at the second end 504B. In some embodiments, an inductance value of about 50 nH to about 1000 nH can be obtained based on parameters such as, for example, but not limited to, the number of windings (for example, coil pitch), length, gap spacing, thickness, and diameter of the ribbon inductor 516. In some embodiments, the ribbon inductor 516 may be silver-plated. Silver plating prevents the oxidation of the copper material. Copper oxide has lower conductivity than copper, thereby reducing the conductivity of copper. Silver forms silver oxide with high conductivity and increases the conductivity of the silver-plated copper ribbon inductor.

[0020] The machining process used in this principle to form a ribbon inductor enables a high precision that results in an inductance value that is reproducible throughout the inductor production process, which cannot be obtained with conventional wound inductors. By forming a ribbon inductor using a solid core material, the ribbon inductor becomes structurally more rigid and has less change in inductance value over a given current range and / or temperature range than conventional wound inductors. Using the forming method of this principle, a manufacturing tolerance of less than 5% of the inductance value can be obtained. Further, the inventors have found that machining an inductor from a solid core material removes the internal stresses caused by winding wires or tubes as seen in conventional wound inductors, reducing failures caused by fatigue or increased resistance caused by additional internal stresses.

[0021] In optional block 106, one or more electrical connection points can be formed at one or more ends of the ribbon inductor 516. In some embodiments, one or more fastening points 506 can be formed at the first end 504A and / or the second end 504B. The one or more fastening points 506 can be holes or other mounts that allow an electrical connection (electrical connection point) to be made at the end of the ribbon inductor 516 to pass current through the ribbon inductor 516. In optional block 108, an insert 602, such as a tubular structure, may be positioned inside the ribbon inductor 516 as shown in FIG. 600 of FIG. 6. In some embodiments, the insert 602 can function as a structural support that facilitates maintaining the shape of the ribbon inductor 516 by air cooling. In some embodiments, the insert 602 can alternatively, or in conjunction with providing support, function to provide a cooling path that aids in cooling the operating ribbon inductor 516 to further increase the current-carrying capacity of the ribbon inductor 516.

[0022] For example, as shown in FIG. 700 of FIG. 7, a cooling tube 702 is inserted into the ribbon inductor 516. A cooling line 706 is connected between the heat exchanger system 704 to allow a cooling fluid to flow through the cooling tube 702 and reduce the temperature of the operating ribbon inductor 516. In some embodiments, the cooling tube 702 is a high thermal conductivity insulator (electrical insulator) having a low dielectric constant. In some embodiments, as shown in FIG. 800 of FIG. 8, the cooling fluid can also be flowed inside the ribbon inductor. In some embodiments, a rectangular tube 802 having an internal opening 804 can be used to form the ribbon inductor. Next, the ribbon inductor can be formed by winding the rectangular tube 802 around a cylinder to form the winding of the ribbon inductor. In some embodiments, the rectangular tube 802 can be formed into a ribbon inductor as shown in FIG. 5 by varying the gap spacing and the number of windings to form a specific inductance value at a specific operating frequency as described above. The value obtained by subtracting the internal opening 804 from the cross-sectional area of the rectangular tube 802 determines the effective cross-sectional area of the ribbon inductor, which can also be adjusted to increase the current carrying capacity. Since the inside of the ribbon inductor is hollow, a coolant can be flowed inside the ribbon inductor to control the temperature of the ribbon inductor. The ribbon inductor formed from the rectangular tube 802 may be used in a cooling system as described with respect to FIG. 7, in which case the coolant flows through the internal opening 804 and inside the rectangular tube 802. In some embodiments, an insert 602 can be used to perform additional cooling by circulating an additional coolant through the insert 602 and the rectangular tube 802. Cooling of the inductor controls the amount of expansion and contraction of the inductor, which can cause performance variations such as, but not limited to, variations in inductive values and current carrying capacity.

[0023] In some embodiments, the ribbon inductor 916 may be used in the semiconductor processing system 900 of FIG. 9 as part of the RF impedance matching network 904. The RF impedance matching network 904 is electrically connected between the RF power source 906 and the processing chamber 902 to automatically match the impedance between the RF power source 906 and the processing chamber 902. In some embodiments, the RF power source 906 can operate in a frequency range of about 10 MHz to about 200 MHz. By matching the impedance, the RF impedance matching network 904 maximizes the power transfer from the RF power source 906 and the processing chamber 902 for optimal operating efficiency. In some embodiments, the ribbon inductor 916 can be used in the RF impedance matching network 904 to optimize the power efficiency of the plasma chamber. The ribbon inductor 916 is important for filtering and impedance adjustment purposes. The ribbon inductor of this principle with small inductance variation is suitable for use in high-power (10 kW or more) RF matching networks. Since the ribbon inductor of this principle is more stable and accurate than conventional wound inductors, when used in an RF impedance matching network, due to the small variation in inductance value over the operating range of the RF impedance matching network, the performance of the RF impedance matching network is improved. Since the inductance value of the RF impedance matching network is stable, it is not necessary to constantly compensate for the change in inductance value due to changes in temperature, frequency, and / or voltage and current, and the vibration during impedance matching is reduced. Furthermore, the ribbon inductor of this principle advantageously reduces power loss. Because of its large surface area, it has a high cooling effect and also helps to reduce RF power loss due to the skin effect. Another advantage is that the variation between the inductance values of the ribbon inductors is reduced. Because of the small inductance variation, the ribbon inductor can improve the consistency of the system in mass production.

[0024] In some embodiments, the controller 908 can be used in the semiconductor processing system 900. The controller 908 controls the operation of the semiconductor processing system 900 by using direct control or by controlling a computer (or controller) associated with the devices of the semiconductor processing system 900. During operation, the controller 908 enables data collection and feedback from each device and system to optimize the performance of the semiconductor processing system 900. The controller 908 enables, for example, monitoring of the impedance matching process for collecting data. Using the ribbon inductor of the present principle reduces the variation of parameters recognized by the controller 908 and the drift of the impedance matching process. The controller 908 generally includes a central processing unit (CPU) 910, a memory 912, and a support circuit 914. The CPU 910 may be any form of general-purpose computer processor that can be used in an industrial environment. The support circuit 914 is coupled to the CPU 910 in a conventional manner and can include a cache, a clock circuit, an input / output subsystem, a power supply, and the like. Software routines, such as the methods described below, may be stored in the memory 912 and, when executed by the CPU 910, can convert the CPU 910 into a special-purpose computer (controller 908). The software routines may also be stored and / or executed by a second controller (not shown) located remotely from the semiconductor processing system 900.

[0025] Memory 912 is in the form of a computer-readable storage medium that includes instructions for facilitating the operation of semiconductor processes and devices when executed by CPU 910. The instructions in memory 912 are in the form of program products such as programs that implement process recipes, optimization of power transfer, impedance matching control, etc. The program code may conform to any one of a number of different programming languages. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use in a computer system. The program of the program product defines the functionality of the aspects (including the methods described herein). Exemplary computer-readable storage media include non-writable storage media in which information is permanently stored (e.g., CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips, or read-only memory devices in a computer such as any type of solid-state non-volatile semiconductor memory), writable storage media in which changeable information is stored (e.g., floppy disks in a diskette drive or hard disk drive, or any type of solid-state random access semiconductor memory), but are not limited thereto. Such computer-readable storage media are aspects of the present principles when transmitting computer-readable instructions that direct the functionality of the methods described herein.

[0026] The foregoing is directed to embodiments of the present principles, but other and further embodiments of the present principles may be devised without departing from the basic scope thereof.

Claims

1. A method for forming a high-current inductor, comprising: forming a central opening that longitudinally penetrates a conductive material, wherein the conductive material has an outer diameter, the central opening forms an inner diameter of the conductive material, and a difference between the outer diameter and the inner diameter is a thickness of a ribbon conductor of the high-current inductor; removing a spiral portion of the conductive material so as to form the ribbon conductor of the high-current inductor, wherein a width of the ribbon conductor is from 12.7 mm to 101.6 mm (0.5 inch to 4.0 inches), and a width of the spiral portion forms a gap spacing between turns of the ribbon conductor; after removing the spiral portion, disposing an insert inside the high-current inductor; and the insert has a second outer diameter that is substantially equal to the inner diameter; the insert is hollow and is formed of a material having a high thermal conductivity and a low dielectric constant, the insert is configured to extract heat from the high-current inductor to an inner surface of the insert, and the insert is configured to allow a coolant to flow across the entire inner surface.

2. The method according to claim 1, wherein the thickness of the ribbon conductor of the high-current inductor is from about 1.524 mm to about 6.35 mm (about 0.060 inch to about 0.250 inch).

3. The method according to claim 1, wherein the gap spacing is from about 6.35 mm to about 25.4 mm (about 0.250 inch to about 1.0 inch).

4. The method according to claim 1, wherein the high-current inductor has an inductance of from about 50 nH to about 1000 nH.

5. The method according to claim 1, wherein the high-current inductor has a length of from about 50.8 mm to about 508 mm (about 2 inches to about 20 inches).

6. The method according to claim 1, wherein the inner diameter is from about 12.7 mm to about 127 mm (about 0.5 inch to about 5.0 inches).

7. The method according to claim 1, wherein the outer diameter is from about 13.97 mm to about 133.35 mm (about 0.55 inch to about 5.25 inches).

8. The method according to claim 1, wherein the conductive material is copper.

9. The method according to claim 8, wherein the copper is silver-plated.

10. The method according to claim 1, wherein the high-current inductor operates at a power greater than 0 kilowatts and up to about 10 kilowatts.

11. The method according to claim 1, wherein the high-current inductor operates at a frequency of 1 MHz to about 300 MHz.

12. The method according to claim 1, wherein the high-current inductor has an inductance tolerance of less than 5%.

13. A non-transitory computer-readable medium storing instructions that, when executed, cause a method for forming a high-current inductor, the method comprising: forming a central opening that longitudinally penetrates a conductive material, the conductive material having an outer diameter, the central opening forming an inner diameter of the conductive material, and a difference between the outer diameter and the inner diameter being a thickness of a ribbon conductor of the high-current inductor; removing a helical portion of the conductive material to form the ribbon conductor of the high-current inductor, the width of the ribbon conductor being 12.7 mm to 101.6 mm (0.5 inch to 4.0 inches), and the width of the helical portion forming a gap spacing between turns of the ribbon conductor; after removing the helical portion, disposing an insert inside the high-current inductor; and the insert having a second outer diameter that is approximately equal to the inner diameter; the insert is hollow and is formed of a material having a high thermal conductivity and a low dielectric constant, the insert being configured to extract heat from the high-current inductor to an inner surface of the insert and to allow a coolant to flow across the entire inner surface.

14. The non-transitory computer-readable medium according to claim 13, wherein the high-current inductor has an inductance of about 50 nH to about 1000 nH with an inductance tolerance of less than about 5%.

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