Methods and systems for plasma processing

Abstract

A resonant antenna system for a plasma processing tool includes a resonant antenna coupled to an RF source at a first point on the resonant antenna, a current balancing circuit coupled to the resonant antenna at a second point on the resonant antenna, a first current sensor coupled between the RF source and the resonant antenna, and a second current sensor coupled between the current balancing circuit and the resonant antenna. The current balancing circuit includes a variable component. The current balancing circuit is further coupled to a ground terminal.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to and benefit of the filing date of U.S. Nonprovisional Patent Application No. 18 / 298,829, filed on 11 April 2023, which is incorporated herein by reference in its entirety.

[0002] This disclosure generally relates to semiconductor processing technology, and in specific embodiments, to methods and systems for plasma processing. [Background technology]

[0003] Plasma processing is widely used in the semiconductor industry for the manufacturing and fabrication of high-density microcircuits. In a plasma processing system, electromagnetic waves emitted into a plasma chamber generate an electromagnetic field within the chamber. This generated electromagnetic field heats the electrons in the chamber. The heated electrons ignite the plasma, which then processes the substrate in processes such as etching, deposition, oxidation, and sputtering. [Overview of the project] [Problems that the invention aims to solve]

[0004] The non-uniform electromagnetic field within the plasma processing chamber results in non-uniform processing of the substrate because different parts of the substrate are processed by plasma with varying densities. Apparatus and systems that allow for control of plasma uniformity and thus lead to better etching and deposition processes are desirable. [Means for solving the problem]

[0005] According to one embodiment, a resonator antenna system for a plasma processing tool includes a resonator antenna coupled to an RF source at a first point on the resonator antenna, a current balance circuit coupled to the resonator antenna at a second point on the resonator antenna, the current balance circuit including a first variable component and further coupled to a ground terminal, a first current sensor coupled between the RF source and the resonator antenna, and a second current sensor coupled between the current balance circuit and the resonator antenna.

[0006] According to one embodiment, a method for plasma processing includes supplying power from an RF source to a resonator antenna, wherein the resonator antenna is above a plasma chamber and the RF source is coupled to the resonator antenna via a first current sensor and the resonator antenna is coupled to a ground terminal via a second current sensor; measuring a first current using the first current sensor and measuring a second current using the second current sensor; adjusting a variable component of the current balance circuit based on a difference between the first current and the second current, wherein the current balance circuit is coupled between the second current sensor and the ground terminal; and performing plasma processing in the plasma chamber using the plasma generated by the resonator antenna.

[0007] According to yet another embodiment, a plasma processing system includes a plasma processing chamber and a resonator antenna outside the plasma processing chamber, the resonator antenna being coupled to an RF power source at a first point on the resonator antenna, the matching circuit and the first current sensor being coupled between the RF power source and the first point, the resonator antenna having a ground terminal coupled to a second point on the resonator antenna, the length of the resonator antenna from the second point to the end of the resonator antenna being equal to a quarter wavelength of the operating frequency of the resonator antenna, and the second current sensor and the filter circuit being coupled between the second point and the ground terminal.

[0008] It should be understood that both the foregoing summary and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed present disclosure.

[0009] To fully understand the present invention and its advantages, refer hereto to the following description, which should be read in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a plasma processing system according to several embodiments. [Figure 2] This is a diagram of a matching circuit according to several embodiments. [Figure 3] This is a diagram of a resonant antenna according to several embodiments. [Figure 4] This is a schematic diagram of a current balancing circuit according to several embodiments. [Figure 5A] This is a schematic diagram of a current-balancing circuit according to several other embodiments. [Figure 5B] This is a schematic diagram of a current-balancing circuit according to several other embodiments. [Figure 5C] This is a schematic diagram of a current-balancing circuit according to several other embodiments. [Figure 5D] This is a schematic diagram of a current-balancing circuit according to several other embodiments. [Figure 5E] This is a schematic diagram of a current-balancing circuit according to several other embodiments. [Figure 5F] This is a schematic diagram of a current-balancing circuit according to several other embodiments. [Figure 6] This figure shows graphs of experimental results related to current balancing circuits in several embodiments. [Figure 7] This is a process flowchart diagram of a method for achieving current balance according to several embodiments. [Figure 8] This is a process flowchart diagram of a method for plasma processing according to several embodiments. [Modes for carrying out the invention]

[0011] Corresponding numbers and symbols in different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate relevant aspects of the embodiments and are not necessarily drawn to scale. The edges of features depicted in the figures do not necessarily indicate the end of the feature's extent.

[0012] The creation and use of various embodiments will be discussed in detail below. However, it should be recognized that the various embodiments described herein are applicable to a wide variety of specific situations. The specific embodiments discussed are merely illustrative of specific methods for creating and using various embodiments and should not be construed as limiting.

[0013] While aspects of the present invention are described primarily in relation to resonant structures in plasma processing systems, aspects of the present invention may also be applicable to fields other than the semiconductor industry. Plasma can be used for processing and modifying surface properties by functional group addition. For example, to treat a surface for paint deposition, plasma can convert a hydrophobic surface to a hydrophilic surface. Furthermore, aspects of the present invention are not limited to plasma. For example, RF can be used to thaw frozen foods or to dry textiles, food, wood, etc. In these various examples and across several industries, a uniformly generated plasma, as disclosed herein, is advantageous.

[0014] In various embodiments, the arrangement of various components is shown symmetrically, for example, to provide uniformity within the system. However, it should be understood that such symmetry is not required, and asymmetrical configurations can be intentionally introduced, for example, to compensate for non-uniformity within the system or to generate a skew chamber effect.

[0015] According to one or more embodiments of the present disclosure, the application relates to current balancing circuits and methods for balancing coil currents for plasma uniformity control. Generally, a radiating antenna (e.g., a dipole resonator or resonant coil) is used to radiate RF waves that generate an electromagnetic field within a plasma chamber. The electromagnetic field ignites and maintains the plasma within the plasma chamber. The uniformity of the plasma distribution may depend on the uniformity of the electromagnetic field. Achieving plasma uniformity can benefit from additional tuning mechanisms to deliver a uniform electromagnetic field to the plasma chamber, thereby generating a uniform plasma within the chamber, for example, for deposition or etching processes performed on a wafer within the plasma chamber. In particular, different coil sections of a resonant antenna may carry different amounts of current due to, for example, operating conditions, non-uniform loading to different coil sections, asymmetry of the plasma chamber, or other components such as absorbing coils that affect the current density. To compensate for the unbalanced amounts of current in different coil sections, a current balancing circuit may be coupled between the resonant antenna and the ground feed of the resonant source. A current balancing circuit provides a mechanism for regulating the current balance between different sections of a resonator coil (e.g., an inner coil section and an outer coil section), thereby delivering a balanced electromagnetic field to a plasma chamber. Plasma uniformity within the plasma chamber can be regulated by adjusting the current ratio between the resonator coil sections. This can be achieved by adjusting variable settings (e.g., capacitance, inductance, or resistance) in the current balancing circuit. This disclosure includes embodiments of current balancing circuits and control algorithms for operating systems having current balancing circuits to balance currents in different coil segments.

[0016] Embodiments of this disclosure will be described in reference to the attached drawings. One embodiment of a plasma processing system having a matching circuit and a resonant antenna will be described with reference to Figures 1 to 3. One embodiment of a current balancing circuit will be described with reference to Figure 4. Other embodiments of current balancing circuits will be described with reference to Figures 5A to 5F. Experimental results relating to the current balancing circuit will be described with reference to Figure 6. One embodiment of a method for achieving current balancing will be described with reference to Figure 7. One embodiment of a method for plasma processing will be described with reference to Figure 8.

[0017] Figure 1 shows a diagram of one embodiment of the plasma processing system 100, according to several embodiments. The plasma processing system 100 includes a matching circuit 200, a resonant antenna 102 (also called a resonant coil or dipole resonator), a housing structure 104, a plasma processing chamber 106, and optionally a dielectric plate 114, which may (or may not) be arranged as shown in Figure 1. Furthermore, the plasma processing system 100 may include additional components not shown in Figure 1.

[0018] In various embodiments, the resonant antenna 102 is coupled to an RF source 101 via a matching circuit 200. The RF source 101 includes an RF power supply, which may include a generator circuit. The RF source 101 supplies forward RF waves to the resonant antenna 102, which are radiated toward the plasma processing chamber 106. Throughout this specification, the RF source 101 may also be referred to as a power supply or RF source.

[0019] The RF source 101 is coupled to a matching circuit 200, which is coupled to a resonant antenna 102 via a power transmission line such as a coaxial cable. The RF source 101 may be used to supply RF power to the resonant antenna 102 as a continuous wave (CW). In one embodiment, the RF source 101 may be used to supply pulse-modulated RF power to the resonant antenna 102. The RF source 101 may supply pulse-modulated RF power to the resonant antenna 102 at a modulation frequency in the range of 10 Hz to 1000 kHz. Furthermore, the RF source 101 may supply pulse-modulated RF power to the RF source 101 at a duty cycle in the range of 10% to 90%.

[0020] In some embodiments, the RF source 101 includes an IV sensor (also called a current-voltage (IV) probe). The IV sensor measures the total impedance Z of the load coupled to the RF source 101. load Furthermore, feedback regarding power and impedance matching, such as the phase φ of the RF power, can be provided to the controller (see Figure 4 below). The IV sensor may include a current sensor and a voltage sensor. In some embodiments, the IV sensor has broadband performance over a frequency range of, for example, 0.307 MHz to 252 MHz. However, any suitable IV sensor can be used, including IV sensors that do not have broadband performance.

[0021] The plasma processing chamber 106 may be, for example, a medium frequency (MF) or high frequency (HF) plasma chamber. The plasma processing chamber 106 may include a vacuum chamber. In some embodiments, the plasma processing chamber 106 is configured to operate the plasma 115 at a first resonant frequency, the first resonant frequency being in the range of about 1 MHz to about 27 MHz. For example, the plasma processing chamber 106 may be configured to operate the plasma 115 at frequencies of 1 MHz or higher, 13.56 MHz or higher, 27 MHz or higher, etc.

[0022] In various embodiments, the plasma processing chamber 106 includes a substrate holder 108 (e.g., a chuck). As shown, the substrate 110 is placed on the substrate holder 108 for processing. Optionally, the plasma processing chamber 106 may include a bias power supply 118 coupled to the substrate holder 108. The plasma processing chamber 106 may also include one or more pump outlets 116 for removing by-products from the plasma processing chamber 106 by selective control of the internal gas flow rate. In various embodiments, the pump outlets 116 are located near the substrate holder 108 and the substrate 110 (e.g., below / around their periphery). In various embodiments, the plasma processing chamber 106 may include additional substrate holders (not shown). In various embodiments, the arrangement of the substrate holders 108 may differ from that shown in Figure 1. Thus, the number and location of the substrate holders 108 are not limiting.

[0023] In various embodiments, the resonant antenna 102 radiates an electromagnetic field toward the plasma processing chamber 106. The radiated electromagnetic field generates an azimuthal-symmetric, high-density plasma within the plasma generation region 112, accompanied by a low-capacitive coupling electric field. In various embodiments, the resonant antenna 102 is an inductively coupled antenna, such as a planar coil wound on a flat helix (i.e., a stovetop antenna). In one embodiment, the resonant antenna 102 includes an arm connected to a capacitive structure that generates azimuthal symmetry. In various embodiments, the excitation frequency of the resonant antenna 102 is within the radio frequency range (10 to 400 MHz), but this is not limiting, and other frequency ranges may be envisioned as well. For example, aspects of the present invention disclosed herein are equally applicable to applications in the microwave frequency range.

[0024] In various embodiments, the resonant antenna 102 includes a resonant element. The resonant element may be an arm electrically connected to a capacitive structure. The arm and the capacitive structure resonate with electromagnetic waves supplied from the RF source 101.

[0025] In various embodiments, the resonant element maintains a standing electromagnetic wave. The resonant element is positioned close to and parallel to the dielectric plate 114 so that the oscillating magnetic field from the resonant element penetrates into the plasma processing chamber 106. The time-varying magnetic field induces a time-varying electric field that transfers energy to the plasma electrons.

[0026] In various embodiments, the RF source 101 couples energy to the interface of the resonant antenna 102 to generate standing electromagnetic waves from the resonant antenna 102. In embodiments, the RF source 101 is coupled to the interface via a transmission line. It is desirable that the interface maintains the same or higher symmetry as the elements of the resonant antenna 102 under rotation around the axis of symmetry.

[0027] Furthermore, a housing structure 104 surrounding the resonant antenna 102 is shown. The housing structure 104 is a conductive structure that is electrically coupled to and thus RF-grounded to the RF ground of the RF source 101. In various embodiments, the housing structure 104 includes an opening for coupling an RF feed path from the RF source 101 to the resonant antenna 102 and for coupling the resonant antenna 102 to the ground terminal.

[0028] In various embodiments, the housing structure 104 is positioned adjacent to the top of the plasma processing chamber 106, thereby sandwiching the dielectric plate 114 between the housing structure 104 and the plasma processing chamber 106. Thus, the resonant antenna 102 generates electromagnetic waves that radiate through the dielectric plate 114 toward the plasma processing chamber 106.

[0029] In various embodiments, the resonant antenna 102 is located outside the plasma processing chamber 106 and is isolated from the plasma processing chamber 106 by a dielectric plate 114, typically made of a dielectric material. The dielectric plate 114 isolates the low-pressure environment inside the plasma processing chamber 106 from the external atmosphere. It should be understood that the resonant antenna 102 may be positioned directly adjacent to the dielectric plate 114. In various embodiments, the resonant antenna 102 is isolated from the plasma processing chamber 106 by air. In various embodiments, the properties of the dielectric plate 114 are selected to minimize the reflection of RF waves from the plasma processing chamber 106. In other embodiments, the resonant antenna 102 is embedded inside the dielectric plate 114. In various embodiments, the dielectric plate 114 is in the shape of a disk.

[0030] The dielectric plate 114 includes a first outer surface and a second outer surface. The first outer surface faces the plasma processing chamber 106. The second outer surface faces the resonator antenna 102. The second outer surface is located vertically above the first outer surface.

[0031] In one embodiment, a resonant antenna 102 couples RF power from an RF source 101 to a plasma processing chamber 106 for processing a substrate 110. Specifically, the resonant antenna 102 radiates electromagnetic waves in response to forward RF waves being supplied from the RF source 101. The radiated electromagnetic waves penetrate into the plasma processing chamber 106 from the atmosphere side (i.e., the resonant antenna 102 side) of the dielectric plate 114. The radiated electromagnetic waves generate an electromagnetic field within the plasma processing chamber 106. The generated electromagnetic field ignites and maintains the plasma in the plasma generation region 112 by transferring energy to free electrons within the plasma processing chamber 106. The generated plasma can be used, for example, to selectively etch or deposit a material on the substrate 110. Plasma processes may include etching processes such as reactive ion etching (RIE) processes and atomic layer etching (ALE) processes, and deposition processes such as plasma physical deposition (PVD) processes, plasma chemical deposition (CVD) processes, and atomic layer deposition (ALD) processes.

[0032] In various embodiments, the plasma generation region 112 is located directly below the portion of the dielectric plate 114 closest to the plasma processing chamber 106. In various embodiments, the uppermost surface of the plasma generation region 112 corresponds to the plane on which the outer surface of the dielectric plate 114 faces the plasma processing chamber 106.

[0033] In Figure 1, the resonant antenna 102 is located outside the plasma processing chamber 106. However, in various embodiments, the resonant antenna 102 may be located inside the plasma processing chamber 106. In such embodiments, the plasma generation region 112 is located directly below the portion of the resonant antenna 102 closest to the plasma processing chamber 106.

[0034] Figure 2 shows an exemplary matching circuit 200 according to several embodiments. The impedance associated with the plasma generated in the plasma processing chamber 106 corresponds to the load on the operating radiating resonant antenna 102. The impedance of the plasma can react based on, for example, changes in pressure, temperature, or operating conditions. Typically, a matching circuit (automatic or manual) coupled to the radiating antenna is used to minimize losses (i.e., reflected power) in response to changes in load conditions. The matching circuit 200 (also called a matching network or impedance matching network) is coupled between the RF source 101 and the resonant antenna 102. When forward power is radio waved from the RF source 101 to the resonant antenna 102, some reflected power may be reflected back due to impedance mismatch between the plasma processing chamber 106 and the RF source 101. The matching circuit 200 is used to reduce reflected power by converting the impedance seen by the matching circuit 200 (in other words, the impedance of the transmission line, the plasma processing chamber 106, and the resonant antenna 102) to the same impedance as the RF source 101 and any intermediate transmission line. This improves the efficiency of supplying power to the plasma processing chamber 106.

[0035] An exemplary matching circuit 212 includes a variable capacitor 204 coupled between the RF source 101 and ground, a variable capacitor 206 coupled to the node between the RF source 101 and the variable capacitor 204, and optionally an inductor 208 coupled between the variable capacitor 206 and the resonant antenna 102. The inductor 208 may be selectively included to achieve a matching impedance over a specific frequency range in order to achieve broadband RF performance. The variable capacitors 204 and 206 may include moving parts, such as motors, that control the relative position of the parallel plates of the variable capacitors 204 and 206, thereby controlling their respective capacitances.

[0036] It should be understood that the matching circuit 200 is shown in Figure 2 as a non-limiting example of an impedance matching network. Any suitable matching circuit 200, including any suitable combination of impedance-adjustable variable components (e.g., variable or fixed capacitors, variable or fixed inductors, variable or fixed resistors, etc., or combinations thereof), is within the scope of the disclosed embodiments.

[0037] Figure 3 shows a resonator antenna 102 according to several embodiments. In some embodiments, the resonator antenna 102 is a planar coil designed to be a half-wavelength dipole antenna, where the total length of the resonator antenna 102 is equal to half a wavelength at the operating frequency (e.g., the first resonant frequency). As an example, the resonator antenna 102 may be a flat coil antenna or stovetop antenna made of a conductive material, such as a coil of copper tubing. However, any suitable material and shape can be used for the resonator antenna 102. Because it includes a resonator antenna 102, the plasma processing system 100 may also be called a resonator antenna system.

[0038] The RF source 101 can be coupled to the resonant antenna 102 at a first point 122 on the resonant antenna 102 (for example, via a matching circuit 200). In addition, the resonant antenna 102 can be connected to ground 120 (also called ground terminal 120, as it is a terminal of a circuit coupled to electrical ground) at a second point 124 on the resonant antenna 102. The length of the resonant antenna 102 from the second point 124 to each end of the resonant antenna 102 may be equal to a quarter wavelength at the operating frequency (e.g., the first resonant frequency).

[0039] Since the resonant antenna 102 operates by resonating with the plasma generated by ignition in the plasma processing chamber 106, the only connection to ground 120 may pass through a second point 124, and each end of the resonant antenna 102 (in other words, the inner end and the outer end) may be left electrically floating. This configuration distinguishes the resonant antenna 102 from various RF plasma excitation coils that are coupled to ground at both ends of the coil via, for example, capacitors that may have varying capacitances.

[0040] Furthermore, an absorption coil 128 may be located near the resonant antenna 102. The absorption coil 128 is part of an induction loop that can adjust the resonant frequency of the resonant antenna 102, for example, by changing the effective inductance of the resonant antenna 102 through mutual induction. In the example illustrated in Figure 3, the absorption coil 128 is in the same plane as the coil of the resonant antenna 102 and is a loop of conductive material surrounded by the coil of the resonant antenna 102. However, the absorption coil 128 may have any suitable shape and position relative to the resonant antenna 102. The absorption coil 128 may be coupled to ground at both ends, or at one or both ends via their respective capacitors. A switch (e.g., a suitable MOSFET device) may be coupled between the ends of the absorption coil 128 and ground. By opening and closing the switch, the induction loop can be opened or closed, thereby adjusting the amount of magnetic field absorbed and, preferably, changing the resonant frequency of the resonant antenna 102 to affect or control the plasma process.

[0041] The absorption coil 128 may draw power unevenly from different coil segments, or due to other factors such as operating conditions, uneven loading of different coil sections, or asymmetry of the resonant antenna 102 or the plasma processing chamber 106, the amount of current flowing through different segments of the resonant antenna 102 may differ while the RF source 101 is supplying power. This can result in undesirable non-uniformity in the plasma generated in the plasma processing chamber 106. Unbalanced currents can be addressed by a current balancing circuit coupled between the resonant antenna 102 and ground 120.

[0042] Figure 4 shows a schematic diagram of an exemplary current balancing circuit 300 coupled between the resonant antenna 102 and ground 120, according to several embodiments. The current balancing circuit provides a mechanism for regulating the current balance between different sections of the resonant antenna 102 (e.g., an inner coil section 102A and an outer coil section 102B), thereby delivering a balanced electromagnetic field to the plasma chamber. As shown in Figure 4, the resonant antenna 102 can be divided into an inner coil section 102A and an outer coil section 102B on either side of a first point 122. Both the inner coil section 102A and the outer coil section 102B receive RF power from the RF source 101 at the first point 122. The inner coil section 102A and the outer coil section 102B are shown having, respectively, inductors and resistors in series, representing the respective inductances and resistances of the inner coil section 102A and the outer coil section 102B.

[0043] Due to various factors (for example, asymmetry of the absorption coil 128, the plasma processing chamber 106, or the structure of the resonant antenna 102), the currents flowing through the inner coil section 102A and the outer coil section 102B may differ. This is because the current I flowing into the resonant antenna 102 at the first point 122 in However, at the second point 124, the current I flowing out from the resonant antenna 102 outThis corresponds to being different. This is because according to Ohm's law, the current flowing into any junction in an electrical circuit is equal to the current flowing out of the junction. Current I in and I out can be balanced by coupling a current balance circuit 300 between the second point 124 and the ground 120. The current balance circuit 300 changes the impedance between the second point 124 and the ground 120, thereby making the absolute value of the difference between I in and I out (|I in -I out |) adjustable within a tolerance of 0 A to 0.2 A. This balances the currents flowing through the inner coil section 102A and the outer coil section 102B, which can be advantageous for achieving plasma uniformity.

[0044] The exemplary current balance circuit 300 shown in FIG. 4 includes a loop having an inductor 304 and a variable capacitor 312. When the capacitance of the variable capacitor 312 (also referred to as the balancing capacitance C BAL ) is changed, the impedance between the second point 124 and the ground 120 is changed, thereby bringing I out closer to I in . For example, the variable capacitor 312 can include a plurality of switch-capacitor networks connected in parallel. Each switch-capacitor network includes a capacitor and a switch connected in series. By controlling the on and off of the switches of the plurality of switch-capacitor networks, the capacitance of the variable capacitor 312 changes accordingly. Alternatively, the variable capacitor 312 can have its capacitance changed by mechanical movement. For example, the distance and / or overlapping area of the two plates of the variable capacitor 312 can be adjustable by an appropriate mechanical structure. In some embodiments, the variable capacitor 312 can vary within a range of 200 pF to 500 pF. In other embodiments, any other acceptable method for changing the capacitance of the variable capacitor 312 can be utilized.

[0045] In some embodiments, the current balancing circuit 300 is implemented in the same apparatus as the matching circuit 200. However, the current balancing circuit 300 is electrically isolated from the matching circuit 200, as it is coupled between the ground 120 and the resonant antenna 102, and the matching circuit is coupled between the RF source 101 and the resonant antenna 102. In other embodiments, the current balancing circuit 300 is implemented in any other suitable location.

[0046] The exemplary current-balancing circuit 300 is only one possible current-balancing circuit 300 that may be used. Any suitable filter circuit or resonant filter circuit (e.g., an LC or RLC circuit) having one or more variable components can be used as the current-balancing circuit 300. Figures 5A to 5F below illustrate this. in and I out Other exemplary current balancing circuits that can be used to balance the currents are shown.

[0047] current I in and I out To measure, the first current sensor 310 is coupled between the first point 122 and the RF source 101 (for example, between the first point 122 and the matching circuit 200), and the second current sensor 320 is coupled between the second point 124 and the current balancing circuit 300. The first current sensor 310 is I in The second current sensor 320 measures I out Measure.

[0048] Controller 400 may be used to automate the operation of the current balancing circuit 300. Controller 400 controls the first current sensor 310 (e.g., I in The value of (I) and the second current sensor 320 (for example, I out It receives an input from the value of and adjusts the impedance of the current balancing circuit 300 (for example, by changing the capacitance of the variable capacitor 312), I in and I outIt is configured to balance the two. In some embodiments, the controller 400 is further configured to automate the operation of the plasma processing system 100. Thus, the controller 400 may be further configured to receive measurements from the IV sensor of the RF source 101, adjust the output of the RF source 101, and adjust various variable components of the matching circuit 200. In some embodiments, the controller 400 includes a programmable processor, a microprocessor, or a computer. Although the controller 400 is shown as a single element for illustrative purposes, the controller 400 may include multiple elements. The controller 400 may be programmable by instructions stored in software, firmware, hardware, or a combination thereof.

[0049] Figures 5A to 5F show various examples of current balancing circuits. Figure 5A shows a current changing circuit 300A comprising a capacitor 302, a variable inductor 314, and a resistor 306. Figure 5B shows a current balancing circuit 300B comprising a capacitor 302, an inductor 304, and a variable resistor 316. Figure 5C shows a current balancing circuit 300C comprising a variable capacitor 312, a variable inductor 314, and a resistor 306. Figure 5D shows a current balancing circuit 300D comprising a capacitor 302, a variable inductor 314, and a variable resistor 316. Figure 5E shows a current balancing circuit 300E comprising a variable capacitor 312, an inductor 304, and a variable resistor 316. Figure 5F shows a current balancing circuit 300D comprising a variable capacitor 312, a variable inductor 314, and a variable resistor 316. Any of the current balancing circuits in Figures 5A to 5F, or any combination thereof, can be used as current balancing circuit 300 (see Figure 4 above), and any of the variable components of the current balancing circuits in Figures 5A to 5F is I in and I outThe current can be controlled by the controller 400 to balance the current. Furthermore, the current balancing circuit may include two or more fixed capacitors, variable capacitors, fixed inductors, variable inductors, fixed resistors, variable resistors, diodes, transistors, etc., or combinations thereof, coupled together in series and / or parallel. Any and all such suitable current balancing circuits having one or more variable components are within the scope of the disclosed embodiments.

[0050] Figure 6 shows a graph illustrating experimental results for a current-balanced circuit. The experimental results in Figure 6 were obtained from a plasma processing system having an Ar-filled plasma chamber at a pressure of 10 mT, which supplied RF power to a resonant antenna at a frequency of 26.95 MHz with a power output of 300 W. Current I in and I out This is plotted against the capacitance of the variable capacitor 312 (see Figure 4 above). As shown in Figure 6, the current I in and I out The matching value for this is the matching capacitance C of the variable capacitor 312, which is approximately 280pF. match This will be achieved.

[0051] Figure 7 shows a process flowchart of Method 500 for achieving current balance in a resonant antenna system according to several embodiments. Method 500 involves detecting current imbalances, for example, by having a controller 400 perform a certain interval in and I out This can be performed during the plasma process by checking it.

[0052] In step 502, the controller 400 receives current from current sensors 310 and 320 as described above with respect to Figure 4. in and I out Read out. Next, in step 504, controller 400 |I in -I out |Checks whether it is within a specified tolerance (for example, in the range of 0A to 0.1A). in -I outIf | is not within the specified tolerance, method 500 proceeds to step 506. in -I out If | is within a specified tolerance, method 500 proceeds to step 520.

[0053] In step 506, the controller 400 controls the balance capacitance C of the capacitor in the current balance circuit (e.g., the variable capacitor 312 in the exemplary current balance circuit 300) as described above with respect to Figure 4. BAL This modifies the adjustable parameters of the current balancing circuit. However, instead of capacitance, the controller 400 can change any adjustable parameter of the current balancing circuit (e.g., capacitance, inductance, resistance, etc., or a combination thereof).

[0054] Next, in step 508, the controller, as described above with respect to Figure 1, receives the total impedance Z of the load coupled to the RF source 101 from the IV sensor, which is part of the RF source 101. load The total impedance (for example, the total impedance of the matching circuit 200, the resonant antenna 102, the current balancing circuit 300, and the current sensors 310 and 320) and the phase φ of the RF power are read. Total impedance Z load This may be useful for adjusting the impedance of the matching circuit 200 to reduce reflected power.

[0055] In the subsequent step 510, the equilibrium capacitance C BALAfter the changes have been made (see step 506 above), the controller 400 checks whether the phase φ is less than, for example, ±5° (±5° is included as an example, but the controller may also check whether the phase φ is less than ±2°, less than ±1°, or less than ±10°). If the phase φ is greater than or equal to ±5°, the method proceeds to step 512, where the controller instructs the RF source 101 to change the RF generation frequency. The method then returns to step 510 and checks again whether the phase φ is less than ±5°. If the controller finds that the phase φ is less than ±5°, the method proceeds to step 514.

[0056] In step 514, controller 400 |I in -I out | (For example, the equilibrium capacitance C) BAL Check if it has decreased (by changing adjustable parameters such as |I in -I out If | does not decrease, proceed to step 516. in -I out If | decreases, proceed to step 518.

[0057] In step 516, the controller 400 adjusts the adjustable parameters (e.g., the equilibrium capacitance C) BAL ) is changed in the opposite direction to the change made in the previous step 506. Then the method returns to step 504, and the controller 400 is |I in -I out Check again whether | is within the specified tolerance.

[0058] In step 518, the controller 400 adjusts the adjustable parameters (e.g., equilibrium capacitance C) BAL ) is changed in the same direction as it was changed in the previous step 506. Then the method returns to step 504, and the controller 400 is |I in -I outCheck again whether | is within the specified tolerance.

[0059] In step 520, controller 400 |I in -I out After discovering that | is within the predetermined tolerance, impedance matching is achieved by the current balancing circuit 300, and the currents in the inner coil section 102A and the outer coil section 102B are approximately equal (see Figure 4 above), which may be advantageous for achieving plasma uniformity. The controller 400 controls | while the plasma process is continuing. in and I out The system may continue to monitor the current imbalance, and if another current imbalance is detected, method 500 may be performed again.

[0060] Figure 8 is a process flowchart of Method 600 for a plasma process according to several embodiments. In step 602, as described above with respect to Figure 1, the resonant antenna 102 is powered by the RF source 101. The resonant antenna 102 is located above the plasma chamber (e.g., the plasma processing chamber 106). As described above with respect to Figure 4, the RF source 101 is coupled to the resonant antenna 102 through a first current sensor 310, and the resonant antenna 102 is coupled to a ground terminal 120 through a second current sensor 320.

[0061] In step 604, as described above with respect to Figure 4, the first current sensor 310 detects the first current (for example, I in The second current sensor 320 measures the second current (for example, I out ) is measured. In step 606, as described above with respect to Figure 4, the variable components of the current balancing circuit 300 (e.g., variable capacitor 312) are adjusted based on the difference between the first current and the second current. The current balancing circuit 300 is coupled between the second current sensor 320 and the ground terminal 120.

[0062] In step 608, a plasma process is carried out in the plasma chamber using the plasma generated by the resonant antenna 102, as described above with respect to Figure 1. While the plasma process continues, the first current sensor 310 and the second current sensor 320 may continue to monitor the first and second currents, as in step 604, and method 600 returns to step 606, and may readjust the variable components if an imbalance between the first and second currents is detected again, as described above with respect to step 520 in Figure 7.

[0063] Exemplary embodiments of the present invention are described below. Other embodiments can also be understood from the entirety of this specification and the claims submitted herein. [Examples]

[0064] Example 1. A resonant antenna system for a plasma processing tool, comprising: a resonant antenna coupled to an RF source at a first point on the resonant antenna; a current balancing circuit coupled to the resonant antenna at a second point on the resonant antenna, the current balancing circuit including a first variable component and further coupled to a ground terminal; a first current sensor coupled between the RF source and the resonant antenna; and a second current sensor coupled between the current balancing circuit and the resonant antenna.

[0065] Embodiment 2. The resonant antenna system according to Embodiment 1, further comprising a first current sensor, a second current sensor, and a controller coupled to the first variable component, wherein the controller is configured to balance a first current measured by the first current sensor and a second current measured by the second current sensor by adjusting the parameters of the first variable component.

[0066] Example 3. The resonant antenna system according to Example 1 or 2, wherein the first variable component is a variable capacitor.

[0067] Example 4. The resonant antenna system according to Example 1 or 2, wherein the first variable component is a variable inductor.

[0068] Example 5. The resonant antenna system according to Example 1 or 2, wherein the first variable component is a variable resistor.

[0069] Example 6. The resonant antenna system according to any one of Examples 1 to 5, wherein the current balancing circuit further comprises a second variable component, the second variable component being of a different type from the first variable component.

[0070] Example 7. A resonant antenna system according to any one of Examples 1 to 6, wherein the resonant antenna is a flat coil antenna.

[0071] Example 8. The resonant antenna system according to Example 7, further comprising an absorbing coil surrounded by a resonant antenna.

[0072] Example 9. A resonant antenna system according to any one of Examples 1 to 8, wherein the inner and outer ends of the resonant antenna are electrically floating.

[0073] Example 10. A resonant antenna system according to any one of Examples 1 to 9, wherein the frequency of the RF source is at least 13.56 MHz.

[0074] Example 11. A resonant antenna system according to any one of Examples 1 to 10, wherein the RF source is pulse-modulated in the frequency range of 10 Hz to 1000 kHz.

[0075] Example 12. A resonant antenna system according to any one of Examples 1 to 11, wherein the RF source is pulse-modulated with a duty cycle in the range of 10% to 90%.

[0076] Example 13. A resonant antenna system according to any one of Examples 1 to 12, further comprising a matching circuit coupled between an RF source and a first current sensor, wherein the matching circuit is separate from the current balancing circuit.

[0077] Example 14. A method for plasma processing, comprising the steps of: supplying power to a resonant antenna with an RF source, wherein the resonant antenna is located above a plasma chamber, the RF source is coupled to the resonant antenna via a first current sensor, and the resonant antenna is coupled to a ground terminal via a second current sensor; measuring a first current using the first current sensor and measuring a second current using the second current sensor; adjusting a variable component of a current balancing circuit based on the difference between the first current and the second current, wherein the current balancing circuit is coupled between the second current sensor and a ground terminal; and performing plasma processing in a plasma chamber using plasma generated by the resonant antenna.

[0078] Example 15. The method according to Example 14, wherein the variable component is a variable capacitor.

[0079] Example 16. The method according to Example 14 or 15, wherein, after adjusting the variable components, the difference between the first current and the second current is less than 0.1A.

[0080] Example 17. A plasma processing system comprising a plasma processing chamber, a resonant antenna outside the plasma processing chamber, coupled to an RF source at a first point on the resonant antenna, with a matching circuit and a first current sensor coupled between the RF source and the first point, and a ground terminal coupled to a second point on the resonant antenna, wherein the length of the resonant antenna from the second point to the end of the resonant antenna is equal to 1 / 4 wavelength of the operating frequency of the resonant antenna, and a second current sensor and a filter circuit coupled between the second point and the ground terminal.

[0081] Example 18. The plasma processing system according to Example 17, wherein the filter circuit is an LC circuit.

[0082] Example 19. The plasma processing system according to Example 18, wherein the LC circuit includes a variable capacitor and a fixed inductor.

[0083] Example 20. The plasma processing system according to Example 18, wherein the LC circuit includes a variable inductor and a fixed capacitor.

[0084] Although the present invention has been described with reference to exemplary embodiments, this specification is not intended to be constrained. By reference to this specification, various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications or embodiments.

Claims

1. A resonant antenna system for plasma processing tools, The resonant antenna is coupled to an RF source at a first point on the resonant antenna, A current balancing circuit coupled to the resonant antenna at a second point on the resonant antenna, comprising a first variable component and further coupled to a ground terminal, A first current sensor coupled between the RF source and the resonant antenna, A second current sensor coupled between the current balancing circuit and the resonant antenna, A resonant antenna system equipped with a resonant tube.

2. The resonant antenna system according to claim 1, further comprising the first current sensor, the second current sensor, and a controller coupled to the first variable component, wherein the controller is configured to balance a first current measured by the first current sensor and a second current measured by the second current sensor by adjusting the parameters of the first variable component.

3. The resonant antenna system according to claim 1, wherein the first variable component is a variable capacitor.

4. The resonant antenna system according to claim 1, wherein the first variable component is a variable inductor.

5. The resonant antenna system according to claim 1, wherein the first variable component is a variable resistor.

6. The resonator antenna system according to claim 1, wherein the current balancing circuit further comprises a second variable component, the second variable component being of a different type from the first variable component.

7. The resonant antenna system according to claim 1, wherein the resonant antenna is a flat coil antenna.

8. The resonant antenna system according to claim 7, further comprising an absorbing coil surrounded by the resonant antenna.

9. The resonant antenna system according to claim 1, wherein the inner and outer ends of the resonant antenna are electrically levitating.

10. The resonant antenna system according to claim 1, wherein the frequency of the RF source is at least 13.56 MHz.

11. The resonant antenna system according to claim 1, wherein the RF source is pulse-modulated in a frequency range of 10 Hz to 1000 kHz.

12. The resonant antenna system according to claim 1, wherein the RF source is pulse-modulated with a duty cycle in the range of 10% to 90%.

13. The resonant antenna system according to claim 1, further comprising a matching circuit coupled between the RF source and the first current sensor, wherein the matching circuit is separate from the current balancing circuit.

14. A method for plasma processing, A step of supplying power to a resonant antenna with an RF source, wherein the resonant antenna is located above the plasma chamber, the RF source is coupled to the resonant antenna via a first current sensor, and the resonant antenna is coupled to a ground terminal via a second current sensor. The steps include measuring a first current using the first current sensor and measuring a second current using the second current sensor, A step of adjusting the variable components of a current balancing circuit based on the difference between the first current and the second current, wherein the current balancing circuit is coupled between the second current sensor and the ground terminal. The steps include: performing plasma processing in the plasma chamber using the plasma generated by the resonant antenna; A method that includes this.

15. The method according to claim 14, wherein the variable component is a variable capacitor.

16. The method according to claim 14, wherein, after adjusting the variable component, the difference between the first current and the second current becomes less than 0.1 A.

17. A plasma processing system, Plasma processing chamber and A resonant antenna outside the plasma processing chamber, coupled to an RF source at a first point on the resonant antenna, and a matching circuit and a first current sensor coupled between the RF source and the first point, A grounding terminal connected to a second point on the resonant antenna, wherein the length of the resonant antenna from the second point to the end of the resonant antenna is equal to 1 / 4 wavelength of the operating frequency of the resonant antenna, and a second current sensor and filter circuit are connected between the second point and the grounding terminal. A plasma processing system equipped with [the following features].

18. The plasma processing system according to claim 17, wherein the filter circuit is an LC circuit.

19. The plasma processing system according to claim 18, wherein the LC circuit comprises a variable capacitor and a fixed inductor.

20. The plasma processing system according to claim 18, wherein the LC circuit comprises a variable inductor and a fixed capacitor.

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